uboot/README
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   1# SPDX-License-Identifier: GPL-2.0+
   2#
   3# (C) Copyright 2000 - 2013
   4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   5
   6Summary:
   7========
   8
   9This directory contains the source code for U-Boot, a boot loader for
  10Embedded boards based on PowerPC, ARM, MIPS and several other
  11processors, which can be installed in a boot ROM and used to
  12initialize and test the hardware or to download and run application
  13code.
  14
  15The development of U-Boot is closely related to Linux: some parts of
  16the source code originate in the Linux source tree, we have some
  17header files in common, and special provision has been made to
  18support booting of Linux images.
  19
  20Some attention has been paid to make this software easily
  21configurable and extendable. For instance, all monitor commands are
  22implemented with the same call interface, so that it's very easy to
  23add new commands. Also, instead of permanently adding rarely used
  24code (for instance hardware test utilities) to the monitor, you can
  25load and run it dynamically.
  26
  27
  28Status:
  29=======
  30
  31In general, all boards for which a configuration option exists in the
  32Makefile have been tested to some extent and can be considered
  33"working". In fact, many of them are used in production systems.
  34
  35In case of problems see the CHANGELOG file to find out who contributed
  36the specific port. In addition, there are various MAINTAINERS files
  37scattered throughout the U-Boot source identifying the people or
  38companies responsible for various boards and subsystems.
  39
  40Note: As of August, 2010, there is no longer a CHANGELOG file in the
  41actual U-Boot source tree; however, it can be created dynamically
  42from the Git log using:
  43
  44        make CHANGELOG
  45
  46
  47Where to get help:
  48==================
  49
  50In case you have questions about, problems with or contributions for
  51U-Boot, you should send a message to the U-Boot mailing list at
  52<u-boot@lists.denx.de>. There is also an archive of previous traffic
  53on the mailing list - please search the archive before asking FAQ's.
  54Please see http://lists.denx.de/pipermail/u-boot and
  55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
  56
  57
  58Where to get source code:
  59=========================
  60
  61The U-Boot source code is maintained in the Git repository at
  62git://www.denx.de/git/u-boot.git ; you can browse it online at
  63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
  64
  65The "snapshot" links on this page allow you to download tarballs of
  66any version you might be interested in. Official releases are also
  67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
  68directory.
  69
  70Pre-built (and tested) images are available from
  71ftp://ftp.denx.de/pub/u-boot/images/
  72
  73
  74Where we come from:
  75===================
  76
  77- start from 8xxrom sources
  78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
  79- clean up code
  80- make it easier to add custom boards
  81- make it possible to add other [PowerPC] CPUs
  82- extend functions, especially:
  83  * Provide extended interface to Linux boot loader
  84  * S-Record download
  85  * network boot
  86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
  87- create ARMBoot project (http://sourceforge.net/projects/armboot)
  88- add other CPU families (starting with ARM)
  89- create U-Boot project (http://sourceforge.net/projects/u-boot)
  90- current project page: see http://www.denx.de/wiki/U-Boot
  91
  92
  93Names and Spelling:
  94===================
  95
  96The "official" name of this project is "Das U-Boot". The spelling
  97"U-Boot" shall be used in all written text (documentation, comments
  98in source files etc.). Example:
  99
 100        This is the README file for the U-Boot project.
 101
 102File names etc. shall be based on the string "u-boot". Examples:
 103
 104        include/asm-ppc/u-boot.h
 105
 106        #include <asm/u-boot.h>
 107
 108Variable names, preprocessor constants etc. shall be either based on
 109the string "u_boot" or on "U_BOOT". Example:
 110
 111        U_BOOT_VERSION          u_boot_logo
 112        IH_OS_U_BOOT            u_boot_hush_start
 113
 114
 115Versioning:
 116===========
 117
 118Starting with the release in October 2008, the names of the releases
 119were changed from numerical release numbers without deeper meaning
 120into a time stamp based numbering. Regular releases are identified by
 121names consisting of the calendar year and month of the release date.
 122Additional fields (if present) indicate release candidates or bug fix
 123releases in "stable" maintenance trees.
 124
 125Examples:
 126        U-Boot v2009.11     - Release November 2009
 127        U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
 128        U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
 129
 130
 131Directory Hierarchy:
 132====================
 133
 134/arch                   Architecture specific files
 135  /arc                  Files generic to ARC architecture
 136  /arm                  Files generic to ARM architecture
 137  /m68k                 Files generic to m68k architecture
 138  /microblaze           Files generic to microblaze architecture
 139  /mips                 Files generic to MIPS architecture
 140  /nds32                Files generic to NDS32 architecture
 141  /nios2                Files generic to Altera NIOS2 architecture
 142  /openrisc             Files generic to OpenRISC architecture
 143  /powerpc              Files generic to PowerPC architecture
 144  /riscv                Files generic to RISC-V architecture
 145  /sandbox              Files generic to HW-independent "sandbox"
 146  /sh                   Files generic to SH architecture
 147  /x86                  Files generic to x86 architecture
 148/api                    Machine/arch independent API for external apps
 149/board                  Board dependent files
 150/cmd                    U-Boot commands functions
 151/common                 Misc architecture independent functions
 152/configs                Board default configuration files
 153/disk                   Code for disk drive partition handling
 154/doc                    Documentation (don't expect too much)
 155/drivers                Commonly used device drivers
 156/dts                    Contains Makefile for building internal U-Boot fdt.
 157/examples               Example code for standalone applications, etc.
 158/fs                     Filesystem code (cramfs, ext2, jffs2, etc.)
 159/include                Header Files
 160/lib                    Library routines generic to all architectures
 161/Licenses               Various license files
 162/net                    Networking code
 163/post                   Power On Self Test
 164/scripts                Various build scripts and Makefiles
 165/test                   Various unit test files
 166/tools                  Tools to build S-Record or U-Boot images, etc.
 167
 168Software Configuration:
 169=======================
 170
 171Configuration is usually done using C preprocessor defines; the
 172rationale behind that is to avoid dead code whenever possible.
 173
 174There are two classes of configuration variables:
 175
 176* Configuration _OPTIONS_:
 177  These are selectable by the user and have names beginning with
 178  "CONFIG_".
 179
 180* Configuration _SETTINGS_:
 181  These depend on the hardware etc. and should not be meddled with if
 182  you don't know what you're doing; they have names beginning with
 183  "CONFIG_SYS_".
 184
 185Previously, all configuration was done by hand, which involved creating
 186symbolic links and editing configuration files manually. More recently,
 187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
 188allowing you to use the "make menuconfig" command to configure your
 189build.
 190
 191
 192Selection of Processor Architecture and Board Type:
 193---------------------------------------------------
 194
 195For all supported boards there are ready-to-use default
 196configurations available; just type "make <board_name>_defconfig".
 197
 198Example: For a TQM823L module type:
 199
 200        cd u-boot
 201        make TQM823L_defconfig
 202
 203Note: If you're looking for the default configuration file for a board
 204you're sure used to be there but is now missing, check the file
 205doc/README.scrapyard for a list of no longer supported boards.
 206
 207Sandbox Environment:
 208--------------------
 209
 210U-Boot can be built natively to run on a Linux host using the 'sandbox'
 211board. This allows feature development which is not board- or architecture-
 212specific to be undertaken on a native platform. The sandbox is also used to
 213run some of U-Boot's tests.
 214
 215See board/sandbox/README.sandbox for more details.
 216
 217
 218Board Initialisation Flow:
 219--------------------------
 220
 221This is the intended start-up flow for boards. This should apply for both
 222SPL and U-Boot proper (i.e. they both follow the same rules).
 223
 224Note: "SPL" stands for "Secondary Program Loader," which is explained in
 225more detail later in this file.
 226
 227At present, SPL mostly uses a separate code path, but the function names
 228and roles of each function are the same. Some boards or architectures
 229may not conform to this.  At least most ARM boards which use
 230CONFIG_SPL_FRAMEWORK conform to this.
 231
 232Execution typically starts with an architecture-specific (and possibly
 233CPU-specific) start.S file, such as:
 234
 235        - arch/arm/cpu/armv7/start.S
 236        - arch/powerpc/cpu/mpc83xx/start.S
 237        - arch/mips/cpu/start.S
 238
 239and so on. From there, three functions are called; the purpose and
 240limitations of each of these functions are described below.
 241
 242lowlevel_init():
 243        - purpose: essential init to permit execution to reach board_init_f()
 244        - no global_data or BSS
 245        - there is no stack (ARMv7 may have one but it will soon be removed)
 246        - must not set up SDRAM or use console
 247        - must only do the bare minimum to allow execution to continue to
 248                board_init_f()
 249        - this is almost never needed
 250        - return normally from this function
 251
 252board_init_f():
 253        - purpose: set up the machine ready for running board_init_r():
 254                i.e. SDRAM and serial UART
 255        - global_data is available
 256        - stack is in SRAM
 257        - BSS is not available, so you cannot use global/static variables,
 258                only stack variables and global_data
 259
 260        Non-SPL-specific notes:
 261        - dram_init() is called to set up DRAM. If already done in SPL this
 262                can do nothing
 263
 264        SPL-specific notes:
 265        - you can override the entire board_init_f() function with your own
 266                version as needed.
 267        - preloader_console_init() can be called here in extremis
 268        - should set up SDRAM, and anything needed to make the UART work
 269        - these is no need to clear BSS, it will be done by crt0.S
 270        - must return normally from this function (don't call board_init_r()
 271                directly)
 272
 273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
 274this point the stack and global_data are relocated to below
 275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
 276memory.
 277
 278board_init_r():
 279        - purpose: main execution, common code
 280        - global_data is available
 281        - SDRAM is available
 282        - BSS is available, all static/global variables can be used
 283        - execution eventually continues to main_loop()
 284
 285        Non-SPL-specific notes:
 286        - U-Boot is relocated to the top of memory and is now running from
 287                there.
 288
 289        SPL-specific notes:
 290        - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
 291                CONFIG_SPL_STACK_R_ADDR points into SDRAM
 292        - preloader_console_init() can be called here - typically this is
 293                done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
 294                spl_board_init() function containing this call
 295        - loads U-Boot or (in falcon mode) Linux
 296
 297
 298
 299Configuration Options:
 300----------------------
 301
 302Configuration depends on the combination of board and CPU type; all
 303such information is kept in a configuration file
 304"include/configs/<board_name>.h".
 305
 306Example: For a TQM823L module, all configuration settings are in
 307"include/configs/TQM823L.h".
 308
 309
 310Many of the options are named exactly as the corresponding Linux
 311kernel configuration options. The intention is to make it easier to
 312build a config tool - later.
 313
 314- ARM Platform Bus Type(CCI):
 315                CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
 316                provides full cache coherency between two clusters of multi-core
 317                CPUs and I/O coherency for devices and I/O masters
 318
 319                CONFIG_SYS_FSL_HAS_CCI400
 320
 321                Defined For SoC that has cache coherent interconnect
 322                CCN-400
 323
 324                CONFIG_SYS_FSL_HAS_CCN504
 325
 326                Defined for SoC that has cache coherent interconnect CCN-504
 327
 328The following options need to be configured:
 329
 330- CPU Type:     Define exactly one, e.g. CONFIG_MPC85XX.
 331
 332- Board Type:   Define exactly one, e.g. CONFIG_MPC8540ADS.
 333
 334- 85xx CPU Options:
 335                CONFIG_SYS_PPC64
 336
 337                Specifies that the core is a 64-bit PowerPC implementation (implements
 338                the "64" category of the Power ISA). This is necessary for ePAPR
 339                compliance, among other possible reasons.
 340
 341                CONFIG_SYS_FSL_TBCLK_DIV
 342
 343                Defines the core time base clock divider ratio compared to the
 344                system clock.  On most PQ3 devices this is 8, on newer QorIQ
 345                devices it can be 16 or 32.  The ratio varies from SoC to Soc.
 346
 347                CONFIG_SYS_FSL_PCIE_COMPAT
 348
 349                Defines the string to utilize when trying to match PCIe device
 350                tree nodes for the given platform.
 351
 352                CONFIG_SYS_FSL_ERRATUM_A004510
 353
 354                Enables a workaround for erratum A004510.  If set,
 355                then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
 356                CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
 357
 358                CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
 359                CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
 360
 361                Defines one or two SoC revisions (low 8 bits of SVR)
 362                for which the A004510 workaround should be applied.
 363
 364                The rest of SVR is either not relevant to the decision
 365                of whether the erratum is present (e.g. p2040 versus
 366                p2041) or is implied by the build target, which controls
 367                whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
 368
 369                See Freescale App Note 4493 for more information about
 370                this erratum.
 371
 372                CONFIG_A003399_NOR_WORKAROUND
 373                Enables a workaround for IFC erratum A003399. It is only
 374                required during NOR boot.
 375
 376                CONFIG_A008044_WORKAROUND
 377                Enables a workaround for T1040/T1042 erratum A008044. It is only
 378                required during NAND boot and valid for Rev 1.0 SoC revision
 379
 380                CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
 381
 382                This is the value to write into CCSR offset 0x18600
 383                according to the A004510 workaround.
 384
 385                CONFIG_SYS_FSL_DSP_DDR_ADDR
 386                This value denotes start offset of DDR memory which is
 387                connected exclusively to the DSP cores.
 388
 389                CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
 390                This value denotes start offset of M2 memory
 391                which is directly connected to the DSP core.
 392
 393                CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
 394                This value denotes start offset of M3 memory which is directly
 395                connected to the DSP core.
 396
 397                CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
 398                This value denotes start offset of DSP CCSR space.
 399
 400                CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
 401                Single Source Clock is clocking mode present in some of FSL SoC's.
 402                In this mode, a single differential clock is used to supply
 403                clocks to the sysclock, ddrclock and usbclock.
 404
 405                CONFIG_SYS_CPC_REINIT_F
 406                This CONFIG is defined when the CPC is configured as SRAM at the
 407                time of U-Boot entry and is required to be re-initialized.
 408
 409                CONFIG_DEEP_SLEEP
 410                Indicates this SoC supports deep sleep feature. If deep sleep is
 411                supported, core will start to execute uboot when wakes up.
 412
 413- Generic CPU options:
 414                CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
 415
 416                Defines the endianess of the CPU. Implementation of those
 417                values is arch specific.
 418
 419                CONFIG_SYS_FSL_DDR
 420                Freescale DDR driver in use. This type of DDR controller is
 421                found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
 422                SoCs.
 423
 424                CONFIG_SYS_FSL_DDR_ADDR
 425                Freescale DDR memory-mapped register base.
 426
 427                CONFIG_SYS_FSL_DDR_EMU
 428                Specify emulator support for DDR. Some DDR features such as
 429                deskew training are not available.
 430
 431                CONFIG_SYS_FSL_DDRC_GEN1
 432                Freescale DDR1 controller.
 433
 434                CONFIG_SYS_FSL_DDRC_GEN2
 435                Freescale DDR2 controller.
 436
 437                CONFIG_SYS_FSL_DDRC_GEN3
 438                Freescale DDR3 controller.
 439
 440                CONFIG_SYS_FSL_DDRC_GEN4
 441                Freescale DDR4 controller.
 442
 443                CONFIG_SYS_FSL_DDRC_ARM_GEN3
 444                Freescale DDR3 controller for ARM-based SoCs.
 445
 446                CONFIG_SYS_FSL_DDR1
 447                Board config to use DDR1. It can be enabled for SoCs with
 448                Freescale DDR1 or DDR2 controllers, depending on the board
 449                implemetation.
 450
 451                CONFIG_SYS_FSL_DDR2
 452                Board config to use DDR2. It can be enabled for SoCs with
 453                Freescale DDR2 or DDR3 controllers, depending on the board
 454                implementation.
 455
 456                CONFIG_SYS_FSL_DDR3
 457                Board config to use DDR3. It can be enabled for SoCs with
 458                Freescale DDR3 or DDR3L controllers.
 459
 460                CONFIG_SYS_FSL_DDR3L
 461                Board config to use DDR3L. It can be enabled for SoCs with
 462                DDR3L controllers.
 463
 464                CONFIG_SYS_FSL_DDR4
 465                Board config to use DDR4. It can be enabled for SoCs with
 466                DDR4 controllers.
 467
 468                CONFIG_SYS_FSL_IFC_BE
 469                Defines the IFC controller register space as Big Endian
 470
 471                CONFIG_SYS_FSL_IFC_LE
 472                Defines the IFC controller register space as Little Endian
 473
 474                CONFIG_SYS_FSL_IFC_CLK_DIV
 475                Defines divider of platform clock(clock input to IFC controller).
 476
 477                CONFIG_SYS_FSL_LBC_CLK_DIV
 478                Defines divider of platform clock(clock input to eLBC controller).
 479
 480                CONFIG_SYS_FSL_PBL_PBI
 481                It enables addition of RCW (Power on reset configuration) in built image.
 482                Please refer doc/README.pblimage for more details
 483
 484                CONFIG_SYS_FSL_PBL_RCW
 485                It adds PBI(pre-boot instructions) commands in u-boot build image.
 486                PBI commands can be used to configure SoC before it starts the execution.
 487                Please refer doc/README.pblimage for more details
 488
 489                CONFIG_SPL_FSL_PBL
 490                It adds a target to create boot binary having SPL binary in PBI format
 491                concatenated with u-boot binary.
 492
 493                CONFIG_SYS_FSL_DDR_BE
 494                Defines the DDR controller register space as Big Endian
 495
 496                CONFIG_SYS_FSL_DDR_LE
 497                Defines the DDR controller register space as Little Endian
 498
 499                CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
 500                Physical address from the view of DDR controllers. It is the
 501                same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
 502                it could be different for ARM SoCs.
 503
 504                CONFIG_SYS_FSL_DDR_INTLV_256B
 505                DDR controller interleaving on 256-byte. This is a special
 506                interleaving mode, handled by Dickens for Freescale layerscape
 507                SoCs with ARM core.
 508
 509                CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
 510                Number of controllers used as main memory.
 511
 512                CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
 513                Number of controllers used for other than main memory.
 514
 515                CONFIG_SYS_FSL_HAS_DP_DDR
 516                Defines the SoC has DP-DDR used for DPAA.
 517
 518                CONFIG_SYS_FSL_SEC_BE
 519                Defines the SEC controller register space as Big Endian
 520
 521                CONFIG_SYS_FSL_SEC_LE
 522                Defines the SEC controller register space as Little Endian
 523
 524- MIPS CPU options:
 525                CONFIG_SYS_INIT_SP_OFFSET
 526
 527                Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
 528                pointer. This is needed for the temporary stack before
 529                relocation.
 530
 531                CONFIG_SYS_MIPS_CACHE_MODE
 532
 533                Cache operation mode for the MIPS CPU.
 534                See also arch/mips/include/asm/mipsregs.h.
 535                Possible values are:
 536                        CONF_CM_CACHABLE_NO_WA
 537                        CONF_CM_CACHABLE_WA
 538                        CONF_CM_UNCACHED
 539                        CONF_CM_CACHABLE_NONCOHERENT
 540                        CONF_CM_CACHABLE_CE
 541                        CONF_CM_CACHABLE_COW
 542                        CONF_CM_CACHABLE_CUW
 543                        CONF_CM_CACHABLE_ACCELERATED
 544
 545                CONFIG_SYS_XWAY_EBU_BOOTCFG
 546
 547                Special option for Lantiq XWAY SoCs for booting from NOR flash.
 548                See also arch/mips/cpu/mips32/start.S.
 549
 550                CONFIG_XWAY_SWAP_BYTES
 551
 552                Enable compilation of tools/xway-swap-bytes needed for Lantiq
 553                XWAY SoCs for booting from NOR flash. The U-Boot image needs to
 554                be swapped if a flash programmer is used.
 555
 556- ARM options:
 557                CONFIG_SYS_EXCEPTION_VECTORS_HIGH
 558
 559                Select high exception vectors of the ARM core, e.g., do not
 560                clear the V bit of the c1 register of CP15.
 561
 562                COUNTER_FREQUENCY
 563                Generic timer clock source frequency.
 564
 565                COUNTER_FREQUENCY_REAL
 566                Generic timer clock source frequency if the real clock is
 567                different from COUNTER_FREQUENCY, and can only be determined
 568                at run time.
 569
 570- Tegra SoC options:
 571                CONFIG_TEGRA_SUPPORT_NON_SECURE
 572
 573                Support executing U-Boot in non-secure (NS) mode. Certain
 574                impossible actions will be skipped if the CPU is in NS mode,
 575                such as ARM architectural timer initialization.
 576
 577- Linux Kernel Interface:
 578                CONFIG_CLOCKS_IN_MHZ
 579
 580                U-Boot stores all clock information in Hz
 581                internally. For binary compatibility with older Linux
 582                kernels (which expect the clocks passed in the
 583                bd_info data to be in MHz) the environment variable
 584                "clocks_in_mhz" can be defined so that U-Boot
 585                converts clock data to MHZ before passing it to the
 586                Linux kernel.
 587                When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
 588                "clocks_in_mhz=1" is automatically included in the
 589                default environment.
 590
 591                CONFIG_MEMSIZE_IN_BYTES         [relevant for MIPS only]
 592
 593                When transferring memsize parameter to Linux, some versions
 594                expect it to be in bytes, others in MB.
 595                Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
 596
 597                CONFIG_OF_LIBFDT
 598
 599                New kernel versions are expecting firmware settings to be
 600                passed using flattened device trees (based on open firmware
 601                concepts).
 602
 603                CONFIG_OF_LIBFDT
 604                 * New libfdt-based support
 605                 * Adds the "fdt" command
 606                 * The bootm command automatically updates the fdt
 607
 608                OF_TBCLK - The timebase frequency.
 609                OF_STDOUT_PATH - The path to the console device
 610
 611                boards with QUICC Engines require OF_QE to set UCC MAC
 612                addresses
 613
 614                CONFIG_OF_BOARD_SETUP
 615
 616                Board code has addition modification that it wants to make
 617                to the flat device tree before handing it off to the kernel
 618
 619                CONFIG_OF_SYSTEM_SETUP
 620
 621                Other code has addition modification that it wants to make
 622                to the flat device tree before handing it off to the kernel.
 623                This causes ft_system_setup() to be called before booting
 624                the kernel.
 625
 626                CONFIG_OF_IDE_FIXUP
 627
 628                U-Boot can detect if an IDE device is present or not.
 629                If not, and this new config option is activated, U-Boot
 630                removes the ATA node from the DTS before booting Linux,
 631                so the Linux IDE driver does not probe the device and
 632                crash. This is needed for buggy hardware (uc101) where
 633                no pull down resistor is connected to the signal IDE5V_DD7.
 634
 635                CONFIG_MACH_TYPE        [relevant for ARM only][mandatory]
 636
 637                This setting is mandatory for all boards that have only one
 638                machine type and must be used to specify the machine type
 639                number as it appears in the ARM machine registry
 640                (see http://www.arm.linux.org.uk/developer/machines/).
 641                Only boards that have multiple machine types supported
 642                in a single configuration file and the machine type is
 643                runtime discoverable, do not have to use this setting.
 644
 645- vxWorks boot parameters:
 646
 647                bootvx constructs a valid bootline using the following
 648                environments variables: bootdev, bootfile, ipaddr, netmask,
 649                serverip, gatewayip, hostname, othbootargs.
 650                It loads the vxWorks image pointed bootfile.
 651
 652                Note: If a "bootargs" environment is defined, it will overwride
 653                the defaults discussed just above.
 654
 655- Cache Configuration:
 656                CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
 657                CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
 658                CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
 659
 660- Cache Configuration for ARM:
 661                CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
 662                                      controller
 663                CONFIG_SYS_PL310_BASE - Physical base address of PL310
 664                                        controller register space
 665
 666- Serial Ports:
 667                CONFIG_PL010_SERIAL
 668
 669                Define this if you want support for Amba PrimeCell PL010 UARTs.
 670
 671                CONFIG_PL011_SERIAL
 672
 673                Define this if you want support for Amba PrimeCell PL011 UARTs.
 674
 675                CONFIG_PL011_CLOCK
 676
 677                If you have Amba PrimeCell PL011 UARTs, set this variable to
 678                the clock speed of the UARTs.
 679
 680                CONFIG_PL01x_PORTS
 681
 682                If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
 683                define this to a list of base addresses for each (supported)
 684                port. See e.g. include/configs/versatile.h
 685
 686                CONFIG_SERIAL_HW_FLOW_CONTROL
 687
 688                Define this variable to enable hw flow control in serial driver.
 689                Current user of this option is drivers/serial/nsl16550.c driver
 690
 691- Console Baudrate:
 692                CONFIG_BAUDRATE - in bps
 693                Select one of the baudrates listed in
 694                CONFIG_SYS_BAUDRATE_TABLE, see below.
 695
 696- Autoboot Command:
 697                CONFIG_BOOTCOMMAND
 698                Only needed when CONFIG_BOOTDELAY is enabled;
 699                define a command string that is automatically executed
 700                when no character is read on the console interface
 701                within "Boot Delay" after reset.
 702
 703                CONFIG_RAMBOOT and CONFIG_NFSBOOT
 704                The value of these goes into the environment as
 705                "ramboot" and "nfsboot" respectively, and can be used
 706                as a convenience, when switching between booting from
 707                RAM and NFS.
 708
 709- Pre-Boot Commands:
 710                CONFIG_PREBOOT
 711
 712                When this option is #defined, the existence of the
 713                environment variable "preboot" will be checked
 714                immediately before starting the CONFIG_BOOTDELAY
 715                countdown and/or running the auto-boot command resp.
 716                entering interactive mode.
 717
 718                This feature is especially useful when "preboot" is
 719                automatically generated or modified. For an example
 720                see the LWMON board specific code: here "preboot" is
 721                modified when the user holds down a certain
 722                combination of keys on the (special) keyboard when
 723                booting the systems
 724
 725- Serial Download Echo Mode:
 726                CONFIG_LOADS_ECHO
 727                If defined to 1, all characters received during a
 728                serial download (using the "loads" command) are
 729                echoed back. This might be needed by some terminal
 730                emulations (like "cu"), but may as well just take
 731                time on others. This setting #define's the initial
 732                value of the "loads_echo" environment variable.
 733
 734- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
 735                CONFIG_KGDB_BAUDRATE
 736                Select one of the baudrates listed in
 737                CONFIG_SYS_BAUDRATE_TABLE, see below.
 738
 739- Removal of commands
 740                If no commands are needed to boot, you can disable
 741                CONFIG_CMDLINE to remove them. In this case, the command line
 742                will not be available, and when U-Boot wants to execute the
 743                boot command (on start-up) it will call board_run_command()
 744                instead. This can reduce image size significantly for very
 745                simple boot procedures.
 746
 747- Regular expression support:
 748                CONFIG_REGEX
 749                If this variable is defined, U-Boot is linked against
 750                the SLRE (Super Light Regular Expression) library,
 751                which adds regex support to some commands, as for
 752                example "env grep" and "setexpr".
 753
 754- Device tree:
 755                CONFIG_OF_CONTROL
 756                If this variable is defined, U-Boot will use a device tree
 757                to configure its devices, instead of relying on statically
 758                compiled #defines in the board file. This option is
 759                experimental and only available on a few boards. The device
 760                tree is available in the global data as gd->fdt_blob.
 761
 762                U-Boot needs to get its device tree from somewhere. This can
 763                be done using one of the three options below:
 764
 765                CONFIG_OF_EMBED
 766                If this variable is defined, U-Boot will embed a device tree
 767                binary in its image. This device tree file should be in the
 768                board directory and called <soc>-<board>.dts. The binary file
 769                is then picked up in board_init_f() and made available through
 770                the global data structure as gd->fdt_blob.
 771
 772                CONFIG_OF_SEPARATE
 773                If this variable is defined, U-Boot will build a device tree
 774                binary. It will be called u-boot.dtb. Architecture-specific
 775                code will locate it at run-time. Generally this works by:
 776
 777                        cat u-boot.bin u-boot.dtb >image.bin
 778
 779                and in fact, U-Boot does this for you, creating a file called
 780                u-boot-dtb.bin which is useful in the common case. You can
 781                still use the individual files if you need something more
 782                exotic.
 783
 784                CONFIG_OF_BOARD
 785                If this variable is defined, U-Boot will use the device tree
 786                provided by the board at runtime instead of embedding one with
 787                the image. Only boards defining board_fdt_blob_setup() support
 788                this option (see include/fdtdec.h file).
 789
 790- Watchdog:
 791                CONFIG_WATCHDOG
 792                If this variable is defined, it enables watchdog
 793                support for the SoC. There must be support in the SoC
 794                specific code for a watchdog. For the 8xx
 795                CPUs, the SIU Watchdog feature is enabled in the SYPCR
 796                register.  When supported for a specific SoC is
 797                available, then no further board specific code should
 798                be needed to use it.
 799
 800                CONFIG_HW_WATCHDOG
 801                When using a watchdog circuitry external to the used
 802                SoC, then define this variable and provide board
 803                specific code for the "hw_watchdog_reset" function.
 804
 805                CONFIG_AT91_HW_WDT_TIMEOUT
 806                specify the timeout in seconds. default 2 seconds.
 807
 808- Real-Time Clock:
 809
 810                When CONFIG_CMD_DATE is selected, the type of the RTC
 811                has to be selected, too. Define exactly one of the
 812                following options:
 813
 814                CONFIG_RTC_PCF8563      - use Philips PCF8563 RTC
 815                CONFIG_RTC_MC13XXX      - use MC13783 or MC13892 RTC
 816                CONFIG_RTC_MC146818     - use MC146818 RTC
 817                CONFIG_RTC_DS1307       - use Maxim, Inc. DS1307 RTC
 818                CONFIG_RTC_DS1337       - use Maxim, Inc. DS1337 RTC
 819                CONFIG_RTC_DS1338       - use Maxim, Inc. DS1338 RTC
 820                CONFIG_RTC_DS1339       - use Maxim, Inc. DS1339 RTC
 821                CONFIG_RTC_DS164x       - use Dallas DS164x RTC
 822                CONFIG_RTC_ISL1208      - use Intersil ISL1208 RTC
 823                CONFIG_RTC_MAX6900      - use Maxim, Inc. MAX6900 RTC
 824                CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
 825                CONFIG_SYS_RV3029_TCR   - enable trickle charger on
 826                                          RV3029 RTC.
 827
 828                Note that if the RTC uses I2C, then the I2C interface
 829                must also be configured. See I2C Support, below.
 830
 831- GPIO Support:
 832                CONFIG_PCA953X          - use NXP's PCA953X series I2C GPIO
 833
 834                The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
 835                chip-ngpio pairs that tell the PCA953X driver the number of
 836                pins supported by a particular chip.
 837
 838                Note that if the GPIO device uses I2C, then the I2C interface
 839                must also be configured. See I2C Support, below.
 840
 841- I/O tracing:
 842                When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
 843                accesses and can checksum them or write a list of them out
 844                to memory. See the 'iotrace' command for details. This is
 845                useful for testing device drivers since it can confirm that
 846                the driver behaves the same way before and after a code
 847                change. Currently this is supported on sandbox and arm. To
 848                add support for your architecture, add '#include <iotrace.h>'
 849                to the bottom of arch/<arch>/include/asm/io.h and test.
 850
 851                Example output from the 'iotrace stats' command is below.
 852                Note that if the trace buffer is exhausted, the checksum will
 853                still continue to operate.
 854
 855                        iotrace is enabled
 856                        Start:  10000000        (buffer start address)
 857                        Size:   00010000        (buffer size)
 858                        Offset: 00000120        (current buffer offset)
 859                        Output: 10000120        (start + offset)
 860                        Count:  00000018        (number of trace records)
 861                        CRC32:  9526fb66        (CRC32 of all trace records)
 862
 863- Timestamp Support:
 864
 865                When CONFIG_TIMESTAMP is selected, the timestamp
 866                (date and time) of an image is printed by image
 867                commands like bootm or iminfo. This option is
 868                automatically enabled when you select CONFIG_CMD_DATE .
 869
 870- Partition Labels (disklabels) Supported:
 871                Zero or more of the following:
 872                CONFIG_MAC_PARTITION   Apple's MacOS partition table.
 873                CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
 874                CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
 875                                       bootloader.  Note 2TB partition limit; see
 876                                       disk/part_efi.c
 877                CONFIG_SCSI) you must configure support for at
 878                least one non-MTD partition type as well.
 879
 880- IDE Reset method:
 881                CONFIG_IDE_RESET_ROUTINE - this is defined in several
 882                board configurations files but used nowhere!
 883
 884                CONFIG_IDE_RESET - is this is defined, IDE Reset will
 885                be performed by calling the function
 886                        ide_set_reset(int reset)
 887                which has to be defined in a board specific file
 888
 889- ATAPI Support:
 890                CONFIG_ATAPI
 891
 892                Set this to enable ATAPI support.
 893
 894- LBA48 Support
 895                CONFIG_LBA48
 896
 897                Set this to enable support for disks larger than 137GB
 898                Also look at CONFIG_SYS_64BIT_LBA.
 899                Whithout these , LBA48 support uses 32bit variables and will 'only'
 900                support disks up to 2.1TB.
 901
 902                CONFIG_SYS_64BIT_LBA:
 903                        When enabled, makes the IDE subsystem use 64bit sector addresses.
 904                        Default is 32bit.
 905
 906- SCSI Support:
 907                CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
 908                CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
 909                CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
 910                maximum numbers of LUNs, SCSI ID's and target
 911                devices.
 912
 913                The environment variable 'scsidevs' is set to the number of
 914                SCSI devices found during the last scan.
 915
 916- NETWORK Support (PCI):
 917                CONFIG_E1000
 918                Support for Intel 8254x/8257x gigabit chips.
 919
 920                CONFIG_E1000_SPI
 921                Utility code for direct access to the SPI bus on Intel 8257x.
 922                This does not do anything useful unless you set at least one
 923                of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
 924
 925                CONFIG_E1000_SPI_GENERIC
 926                Allow generic access to the SPI bus on the Intel 8257x, for
 927                example with the "sspi" command.
 928
 929                CONFIG_EEPRO100
 930                Support for Intel 82557/82559/82559ER chips.
 931                Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
 932                write routine for first time initialisation.
 933
 934                CONFIG_TULIP
 935                Support for Digital 2114x chips.
 936                Optional CONFIG_TULIP_SELECT_MEDIA for board specific
 937                modem chip initialisation (KS8761/QS6611).
 938
 939                CONFIG_NATSEMI
 940                Support for National dp83815 chips.
 941
 942                CONFIG_NS8382X
 943                Support for National dp8382[01] gigabit chips.
 944
 945- NETWORK Support (other):
 946
 947                CONFIG_DRIVER_AT91EMAC
 948                Support for AT91RM9200 EMAC.
 949
 950                        CONFIG_RMII
 951                        Define this to use reduced MII inteface
 952
 953                        CONFIG_DRIVER_AT91EMAC_QUIET
 954                        If this defined, the driver is quiet.
 955                        The driver doen't show link status messages.
 956
 957                CONFIG_CALXEDA_XGMAC
 958                Support for the Calxeda XGMAC device
 959
 960                CONFIG_LAN91C96
 961                Support for SMSC's LAN91C96 chips.
 962
 963                        CONFIG_LAN91C96_USE_32_BIT
 964                        Define this to enable 32 bit addressing
 965
 966                CONFIG_SMC91111
 967                Support for SMSC's LAN91C111 chip
 968
 969                        CONFIG_SMC91111_BASE
 970                        Define this to hold the physical address
 971                        of the device (I/O space)
 972
 973                        CONFIG_SMC_USE_32_BIT
 974                        Define this if data bus is 32 bits
 975
 976                        CONFIG_SMC_USE_IOFUNCS
 977                        Define this to use i/o functions instead of macros
 978                        (some hardware wont work with macros)
 979
 980                        CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
 981                        Define this if you have more then 3 PHYs.
 982
 983                CONFIG_FTGMAC100
 984                Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
 985
 986                        CONFIG_FTGMAC100_EGIGA
 987                        Define this to use GE link update with gigabit PHY.
 988                        Define this if FTGMAC100 is connected to gigabit PHY.
 989                        If your system has 10/100 PHY only, it might not occur
 990                        wrong behavior. Because PHY usually return timeout or
 991                        useless data when polling gigabit status and gigabit
 992                        control registers. This behavior won't affect the
 993                        correctnessof 10/100 link speed update.
 994
 995                CONFIG_SH_ETHER
 996                Support for Renesas on-chip Ethernet controller
 997
 998                        CONFIG_SH_ETHER_USE_PORT
 999                        Define the number of ports to be used
1000
1001                        CONFIG_SH_ETHER_PHY_ADDR
1002                        Define the ETH PHY's address
1003
1004                        CONFIG_SH_ETHER_CACHE_WRITEBACK
1005                        If this option is set, the driver enables cache flush.
1006
1007- PWM Support:
1008                CONFIG_PWM_IMX
1009                Support for PWM module on the imx6.
1010
1011- TPM Support:
1012                CONFIG_TPM
1013                Support TPM devices.
1014
1015                CONFIG_TPM_TIS_INFINEON
1016                Support for Infineon i2c bus TPM devices. Only one device
1017                per system is supported at this time.
1018
1019                        CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1020                        Define the burst count bytes upper limit
1021
1022                CONFIG_TPM_ST33ZP24
1023                Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1024
1025                        CONFIG_TPM_ST33ZP24_I2C
1026                        Support for STMicroelectronics ST33ZP24 I2C devices.
1027                        Requires TPM_ST33ZP24 and I2C.
1028
1029                        CONFIG_TPM_ST33ZP24_SPI
1030                        Support for STMicroelectronics ST33ZP24 SPI devices.
1031                        Requires TPM_ST33ZP24 and SPI.
1032
1033                CONFIG_TPM_ATMEL_TWI
1034                Support for Atmel TWI TPM device. Requires I2C support.
1035
1036                CONFIG_TPM_TIS_LPC
1037                Support for generic parallel port TPM devices. Only one device
1038                per system is supported at this time.
1039
1040                        CONFIG_TPM_TIS_BASE_ADDRESS
1041                        Base address where the generic TPM device is mapped
1042                        to. Contemporary x86 systems usually map it at
1043                        0xfed40000.
1044
1045                CONFIG_TPM
1046                Define this to enable the TPM support library which provides
1047                functional interfaces to some TPM commands.
1048                Requires support for a TPM device.
1049
1050                CONFIG_TPM_AUTH_SESSIONS
1051                Define this to enable authorized functions in the TPM library.
1052                Requires CONFIG_TPM and CONFIG_SHA1.
1053
1054- USB Support:
1055                At the moment only the UHCI host controller is
1056                supported (PIP405, MIP405); define
1057                CONFIG_USB_UHCI to enable it.
1058                define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1059                and define CONFIG_USB_STORAGE to enable the USB
1060                storage devices.
1061                Note:
1062                Supported are USB Keyboards and USB Floppy drives
1063                (TEAC FD-05PUB).
1064
1065                CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1066                txfilltuning field in the EHCI controller on reset.
1067
1068                CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1069                HW module registers.
1070
1071- USB Device:
1072                Define the below if you wish to use the USB console.
1073                Once firmware is rebuilt from a serial console issue the
1074                command "setenv stdin usbtty; setenv stdout usbtty" and
1075                attach your USB cable. The Unix command "dmesg" should print
1076                it has found a new device. The environment variable usbtty
1077                can be set to gserial or cdc_acm to enable your device to
1078                appear to a USB host as a Linux gserial device or a
1079                Common Device Class Abstract Control Model serial device.
1080                If you select usbtty = gserial you should be able to enumerate
1081                a Linux host by
1082                # modprobe usbserial vendor=0xVendorID product=0xProductID
1083                else if using cdc_acm, simply setting the environment
1084                variable usbtty to be cdc_acm should suffice. The following
1085                might be defined in YourBoardName.h
1086
1087                        CONFIG_USB_DEVICE
1088                        Define this to build a UDC device
1089
1090                        CONFIG_USB_TTY
1091                        Define this to have a tty type of device available to
1092                        talk to the UDC device
1093
1094                        CONFIG_USBD_HS
1095                        Define this to enable the high speed support for usb
1096                        device and usbtty. If this feature is enabled, a routine
1097                        int is_usbd_high_speed(void)
1098                        also needs to be defined by the driver to dynamically poll
1099                        whether the enumeration has succeded at high speed or full
1100                        speed.
1101
1102                        CONFIG_SYS_CONSOLE_IS_IN_ENV
1103                        Define this if you want stdin, stdout &/or stderr to
1104                        be set to usbtty.
1105
1106                If you have a USB-IF assigned VendorID then you may wish to
1107                define your own vendor specific values either in BoardName.h
1108                or directly in usbd_vendor_info.h. If you don't define
1109                CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1110                CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1111                should pretend to be a Linux device to it's target host.
1112
1113                        CONFIG_USBD_MANUFACTURER
1114                        Define this string as the name of your company for
1115                        - CONFIG_USBD_MANUFACTURER "my company"
1116
1117                        CONFIG_USBD_PRODUCT_NAME
1118                        Define this string as the name of your product
1119                        - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1120
1121                        CONFIG_USBD_VENDORID
1122                        Define this as your assigned Vendor ID from the USB
1123                        Implementors Forum. This *must* be a genuine Vendor ID
1124                        to avoid polluting the USB namespace.
1125                        - CONFIG_USBD_VENDORID 0xFFFF
1126
1127                        CONFIG_USBD_PRODUCTID
1128                        Define this as the unique Product ID
1129                        for your device
1130                        - CONFIG_USBD_PRODUCTID 0xFFFF
1131
1132- ULPI Layer Support:
1133                The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1134                the generic ULPI layer. The generic layer accesses the ULPI PHY
1135                via the platform viewport, so you need both the genric layer and
1136                the viewport enabled. Currently only Chipidea/ARC based
1137                viewport is supported.
1138                To enable the ULPI layer support, define CONFIG_USB_ULPI and
1139                CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1140                If your ULPI phy needs a different reference clock than the
1141                standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1142                the appropriate value in Hz.
1143
1144- MMC Support:
1145                The MMC controller on the Intel PXA is supported. To
1146                enable this define CONFIG_MMC. The MMC can be
1147                accessed from the boot prompt by mapping the device
1148                to physical memory similar to flash. Command line is
1149                enabled with CONFIG_CMD_MMC. The MMC driver also works with
1150                the FAT fs. This is enabled with CONFIG_CMD_FAT.
1151
1152                CONFIG_SH_MMCIF
1153                Support for Renesas on-chip MMCIF controller
1154
1155                        CONFIG_SH_MMCIF_ADDR
1156                        Define the base address of MMCIF registers
1157
1158                        CONFIG_SH_MMCIF_CLK
1159                        Define the clock frequency for MMCIF
1160
1161                CONFIG_SUPPORT_EMMC_BOOT
1162                Enable some additional features of the eMMC boot partitions.
1163
1164- USB Device Firmware Update (DFU) class support:
1165                CONFIG_DFU_OVER_USB
1166                This enables the USB portion of the DFU USB class
1167
1168                CONFIG_DFU_MMC
1169                This enables support for exposing (e)MMC devices via DFU.
1170
1171                CONFIG_DFU_NAND
1172                This enables support for exposing NAND devices via DFU.
1173
1174                CONFIG_DFU_RAM
1175                This enables support for exposing RAM via DFU.
1176                Note: DFU spec refer to non-volatile memory usage, but
1177                allow usages beyond the scope of spec - here RAM usage,
1178                one that would help mostly the developer.
1179
1180                CONFIG_SYS_DFU_DATA_BUF_SIZE
1181                Dfu transfer uses a buffer before writing data to the
1182                raw storage device. Make the size (in bytes) of this buffer
1183                configurable. The size of this buffer is also configurable
1184                through the "dfu_bufsiz" environment variable.
1185
1186                CONFIG_SYS_DFU_MAX_FILE_SIZE
1187                When updating files rather than the raw storage device,
1188                we use a static buffer to copy the file into and then write
1189                the buffer once we've been given the whole file.  Define
1190                this to the maximum filesize (in bytes) for the buffer.
1191                Default is 4 MiB if undefined.
1192
1193                DFU_DEFAULT_POLL_TIMEOUT
1194                Poll timeout [ms], is the timeout a device can send to the
1195                host. The host must wait for this timeout before sending
1196                a subsequent DFU_GET_STATUS request to the device.
1197
1198                DFU_MANIFEST_POLL_TIMEOUT
1199                Poll timeout [ms], which the device sends to the host when
1200                entering dfuMANIFEST state. Host waits this timeout, before
1201                sending again an USB request to the device.
1202
1203- Journaling Flash filesystem support:
1204                CONFIG_JFFS2_NAND
1205                Define these for a default partition on a NAND device
1206
1207                CONFIG_SYS_JFFS2_FIRST_SECTOR,
1208                CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1209                Define these for a default partition on a NOR device
1210
1211- Keyboard Support:
1212                See Kconfig help for available keyboard drivers.
1213
1214                CONFIG_KEYBOARD
1215
1216                Define this to enable a custom keyboard support.
1217                This simply calls drv_keyboard_init() which must be
1218                defined in your board-specific files. This option is deprecated
1219                and is only used by novena. For new boards, use driver model
1220                instead.
1221
1222- Video support:
1223                CONFIG_FSL_DIU_FB
1224                Enable the Freescale DIU video driver.  Reference boards for
1225                SOCs that have a DIU should define this macro to enable DIU
1226                support, and should also define these other macros:
1227
1228                        CONFIG_SYS_DIU_ADDR
1229                        CONFIG_VIDEO
1230                        CONFIG_CFB_CONSOLE
1231                        CONFIG_VIDEO_SW_CURSOR
1232                        CONFIG_VGA_AS_SINGLE_DEVICE
1233                        CONFIG_VIDEO_LOGO
1234                        CONFIG_VIDEO_BMP_LOGO
1235
1236                The DIU driver will look for the 'video-mode' environment
1237                variable, and if defined, enable the DIU as a console during
1238                boot.  See the documentation file doc/README.video for a
1239                description of this variable.
1240
1241- LCD Support:  CONFIG_LCD
1242
1243                Define this to enable LCD support (for output to LCD
1244                display); also select one of the supported displays
1245                by defining one of these:
1246
1247                CONFIG_ATMEL_LCD:
1248
1249                        HITACHI TX09D70VM1CCA, 3.5", 240x320.
1250
1251                CONFIG_NEC_NL6448AC33:
1252
1253                        NEC NL6448AC33-18. Active, color, single scan.
1254
1255                CONFIG_NEC_NL6448BC20
1256
1257                        NEC NL6448BC20-08. 6.5", 640x480.
1258                        Active, color, single scan.
1259
1260                CONFIG_NEC_NL6448BC33_54
1261
1262                        NEC NL6448BC33-54. 10.4", 640x480.
1263                        Active, color, single scan.
1264
1265                CONFIG_SHARP_16x9
1266
1267                        Sharp 320x240. Active, color, single scan.
1268                        It isn't 16x9, and I am not sure what it is.
1269
1270                CONFIG_SHARP_LQ64D341
1271
1272                        Sharp LQ64D341 display, 640x480.
1273                        Active, color, single scan.
1274
1275                CONFIG_HLD1045
1276
1277                        HLD1045 display, 640x480.
1278                        Active, color, single scan.
1279
1280                CONFIG_OPTREX_BW
1281
1282                        Optrex   CBL50840-2 NF-FW 99 22 M5
1283                        or
1284                        Hitachi  LMG6912RPFC-00T
1285                        or
1286                        Hitachi  SP14Q002
1287
1288                        320x240. Black & white.
1289
1290                CONFIG_LCD_ALIGNMENT
1291
1292                Normally the LCD is page-aligned (typically 4KB). If this is
1293                defined then the LCD will be aligned to this value instead.
1294                For ARM it is sometimes useful to use MMU_SECTION_SIZE
1295                here, since it is cheaper to change data cache settings on
1296                a per-section basis.
1297
1298
1299                CONFIG_LCD_ROTATION
1300
1301                Sometimes, for example if the display is mounted in portrait
1302                mode or even if it's mounted landscape but rotated by 180degree,
1303                we need to rotate our content of the display relative to the
1304                framebuffer, so that user can read the messages which are
1305                printed out.
1306                Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1307                initialized with a given rotation from "vl_rot" out of
1308                "vidinfo_t" which is provided by the board specific code.
1309                The value for vl_rot is coded as following (matching to
1310                fbcon=rotate:<n> linux-kernel commandline):
1311                0 = no rotation respectively 0 degree
1312                1 = 90 degree rotation
1313                2 = 180 degree rotation
1314                3 = 270 degree rotation
1315
1316                If CONFIG_LCD_ROTATION is not defined, the console will be
1317                initialized with 0degree rotation.
1318
1319                CONFIG_LCD_BMP_RLE8
1320
1321                Support drawing of RLE8-compressed bitmaps on the LCD.
1322
1323                CONFIG_I2C_EDID
1324
1325                Enables an 'i2c edid' command which can read EDID
1326                information over I2C from an attached LCD display.
1327
1328- Splash Screen Support: CONFIG_SPLASH_SCREEN
1329
1330                If this option is set, the environment is checked for
1331                a variable "splashimage". If found, the usual display
1332                of logo, copyright and system information on the LCD
1333                is suppressed and the BMP image at the address
1334                specified in "splashimage" is loaded instead. The
1335                console is redirected to the "nulldev", too. This
1336                allows for a "silent" boot where a splash screen is
1337                loaded very quickly after power-on.
1338
1339                CONFIG_SPLASHIMAGE_GUARD
1340
1341                If this option is set, then U-Boot will prevent the environment
1342                variable "splashimage" from being set to a problematic address
1343                (see doc/README.displaying-bmps).
1344                This option is useful for targets where, due to alignment
1345                restrictions, an improperly aligned BMP image will cause a data
1346                abort. If you think you will not have problems with unaligned
1347                accesses (for example because your toolchain prevents them)
1348                there is no need to set this option.
1349
1350                CONFIG_SPLASH_SCREEN_ALIGN
1351
1352                If this option is set the splash image can be freely positioned
1353                on the screen. Environment variable "splashpos" specifies the
1354                position as "x,y". If a positive number is given it is used as
1355                number of pixel from left/top. If a negative number is given it
1356                is used as number of pixel from right/bottom. You can also
1357                specify 'm' for centering the image.
1358
1359                Example:
1360                setenv splashpos m,m
1361                        => image at center of screen
1362
1363                setenv splashpos 30,20
1364                        => image at x = 30 and y = 20
1365
1366                setenv splashpos -10,m
1367                        => vertically centered image
1368                           at x = dspWidth - bmpWidth - 9
1369
1370- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1371
1372                If this option is set, additionally to standard BMP
1373                images, gzipped BMP images can be displayed via the
1374                splashscreen support or the bmp command.
1375
1376- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1377
1378                If this option is set, 8-bit RLE compressed BMP images
1379                can be displayed via the splashscreen support or the
1380                bmp command.
1381
1382- Compression support:
1383                CONFIG_GZIP
1384
1385                Enabled by default to support gzip compressed images.
1386
1387                CONFIG_BZIP2
1388
1389                If this option is set, support for bzip2 compressed
1390                images is included. If not, only uncompressed and gzip
1391                compressed images are supported.
1392
1393                NOTE: the bzip2 algorithm requires a lot of RAM, so
1394                the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1395                be at least 4MB.
1396
1397- MII/PHY support:
1398                CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1399
1400                The clock frequency of the MII bus
1401
1402                CONFIG_PHY_RESET_DELAY
1403
1404                Some PHY like Intel LXT971A need extra delay after
1405                reset before any MII register access is possible.
1406                For such PHY, set this option to the usec delay
1407                required. (minimum 300usec for LXT971A)
1408
1409                CONFIG_PHY_CMD_DELAY (ppc4xx)
1410
1411                Some PHY like Intel LXT971A need extra delay after
1412                command issued before MII status register can be read
1413
1414- IP address:
1415                CONFIG_IPADDR
1416
1417                Define a default value for the IP address to use for
1418                the default Ethernet interface, in case this is not
1419                determined through e.g. bootp.
1420                (Environment variable "ipaddr")
1421
1422- Server IP address:
1423                CONFIG_SERVERIP
1424
1425                Defines a default value for the IP address of a TFTP
1426                server to contact when using the "tftboot" command.
1427                (Environment variable "serverip")
1428
1429                CONFIG_KEEP_SERVERADDR
1430
1431                Keeps the server's MAC address, in the env 'serveraddr'
1432                for passing to bootargs (like Linux's netconsole option)
1433
1434- Gateway IP address:
1435                CONFIG_GATEWAYIP
1436
1437                Defines a default value for the IP address of the
1438                default router where packets to other networks are
1439                sent to.
1440                (Environment variable "gatewayip")
1441
1442- Subnet mask:
1443                CONFIG_NETMASK
1444
1445                Defines a default value for the subnet mask (or
1446                routing prefix) which is used to determine if an IP
1447                address belongs to the local subnet or needs to be
1448                forwarded through a router.
1449                (Environment variable "netmask")
1450
1451- Multicast TFTP Mode:
1452                CONFIG_MCAST_TFTP
1453
1454                Defines whether you want to support multicast TFTP as per
1455                rfc-2090; for example to work with atftp.  Lets lots of targets
1456                tftp down the same boot image concurrently.  Note: the Ethernet
1457                driver in use must provide a function: mcast() to join/leave a
1458                multicast group.
1459
1460- BOOTP Recovery Mode:
1461                CONFIG_BOOTP_RANDOM_DELAY
1462
1463                If you have many targets in a network that try to
1464                boot using BOOTP, you may want to avoid that all
1465                systems send out BOOTP requests at precisely the same
1466                moment (which would happen for instance at recovery
1467                from a power failure, when all systems will try to
1468                boot, thus flooding the BOOTP server. Defining
1469                CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1470                inserted before sending out BOOTP requests. The
1471                following delays are inserted then:
1472
1473                1st BOOTP request:      delay 0 ... 1 sec
1474                2nd BOOTP request:      delay 0 ... 2 sec
1475                3rd BOOTP request:      delay 0 ... 4 sec
1476                4th and following
1477                BOOTP requests:         delay 0 ... 8 sec
1478
1479                CONFIG_BOOTP_ID_CACHE_SIZE
1480
1481                BOOTP packets are uniquely identified using a 32-bit ID. The
1482                server will copy the ID from client requests to responses and
1483                U-Boot will use this to determine if it is the destination of
1484                an incoming response. Some servers will check that addresses
1485                aren't in use before handing them out (usually using an ARP
1486                ping) and therefore take up to a few hundred milliseconds to
1487                respond. Network congestion may also influence the time it
1488                takes for a response to make it back to the client. If that
1489                time is too long, U-Boot will retransmit requests. In order
1490                to allow earlier responses to still be accepted after these
1491                retransmissions, U-Boot's BOOTP client keeps a small cache of
1492                IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1493                cache. The default is to keep IDs for up to four outstanding
1494                requests. Increasing this will allow U-Boot to accept offers
1495                from a BOOTP client in networks with unusually high latency.
1496
1497- DHCP Advanced Options:
1498                You can fine tune the DHCP functionality by defining
1499                CONFIG_BOOTP_* symbols:
1500
1501                CONFIG_BOOTP_NISDOMAIN
1502                CONFIG_BOOTP_BOOTFILESIZE
1503                CONFIG_BOOTP_SEND_HOSTNAME
1504                CONFIG_BOOTP_NTPSERVER
1505                CONFIG_BOOTP_TIMEOFFSET
1506                CONFIG_BOOTP_VENDOREX
1507                CONFIG_BOOTP_MAY_FAIL
1508
1509                CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1510                environment variable, not the BOOTP server.
1511
1512                CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1513                after the configured retry count, the call will fail
1514                instead of starting over.  This can be used to fail over
1515                to Link-local IP address configuration if the DHCP server
1516                is not available.
1517
1518                CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1519                to do a dynamic update of a DNS server. To do this, they
1520                need the hostname of the DHCP requester.
1521                If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1522                of the "hostname" environment variable is passed as
1523                option 12 to the DHCP server.
1524
1525                CONFIG_BOOTP_DHCP_REQUEST_DELAY
1526
1527                A 32bit value in microseconds for a delay between
1528                receiving a "DHCP Offer" and sending the "DHCP Request".
1529                This fixes a problem with certain DHCP servers that don't
1530                respond 100% of the time to a "DHCP request". E.g. On an
1531                AT91RM9200 processor running at 180MHz, this delay needed
1532                to be *at least* 15,000 usec before a Windows Server 2003
1533                DHCP server would reply 100% of the time. I recommend at
1534                least 50,000 usec to be safe. The alternative is to hope
1535                that one of the retries will be successful but note that
1536                the DHCP timeout and retry process takes a longer than
1537                this delay.
1538
1539 - Link-local IP address negotiation:
1540                Negotiate with other link-local clients on the local network
1541                for an address that doesn't require explicit configuration.
1542                This is especially useful if a DHCP server cannot be guaranteed
1543                to exist in all environments that the device must operate.
1544
1545                See doc/README.link-local for more information.
1546
1547 - MAC address from environment variables
1548
1549                FDT_SEQ_MACADDR_FROM_ENV
1550
1551                Fix-up device tree with MAC addresses fetched sequentially from
1552                environment variables. This config work on assumption that
1553                non-usable ethernet node of device-tree are either not present
1554                or their status has been marked as "disabled".
1555
1556 - CDP Options:
1557                CONFIG_CDP_DEVICE_ID
1558
1559                The device id used in CDP trigger frames.
1560
1561                CONFIG_CDP_DEVICE_ID_PREFIX
1562
1563                A two character string which is prefixed to the MAC address
1564                of the device.
1565
1566                CONFIG_CDP_PORT_ID
1567
1568                A printf format string which contains the ascii name of
1569                the port. Normally is set to "eth%d" which sets
1570                eth0 for the first Ethernet, eth1 for the second etc.
1571
1572                CONFIG_CDP_CAPABILITIES
1573
1574                A 32bit integer which indicates the device capabilities;
1575                0x00000010 for a normal host which does not forwards.
1576
1577                CONFIG_CDP_VERSION
1578
1579                An ascii string containing the version of the software.
1580
1581                CONFIG_CDP_PLATFORM
1582
1583                An ascii string containing the name of the platform.
1584
1585                CONFIG_CDP_TRIGGER
1586
1587                A 32bit integer sent on the trigger.
1588
1589                CONFIG_CDP_POWER_CONSUMPTION
1590
1591                A 16bit integer containing the power consumption of the
1592                device in .1 of milliwatts.
1593
1594                CONFIG_CDP_APPLIANCE_VLAN_TYPE
1595
1596                A byte containing the id of the VLAN.
1597
1598- Status LED:   CONFIG_LED_STATUS
1599
1600                Several configurations allow to display the current
1601                status using a LED. For instance, the LED will blink
1602                fast while running U-Boot code, stop blinking as
1603                soon as a reply to a BOOTP request was received, and
1604                start blinking slow once the Linux kernel is running
1605                (supported by a status LED driver in the Linux
1606                kernel). Defining CONFIG_LED_STATUS enables this
1607                feature in U-Boot.
1608
1609                Additional options:
1610
1611                CONFIG_LED_STATUS_GPIO
1612                The status LED can be connected to a GPIO pin.
1613                In such cases, the gpio_led driver can be used as a
1614                status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1615                to include the gpio_led driver in the U-Boot binary.
1616
1617                CONFIG_GPIO_LED_INVERTED_TABLE
1618                Some GPIO connected LEDs may have inverted polarity in which
1619                case the GPIO high value corresponds to LED off state and
1620                GPIO low value corresponds to LED on state.
1621                In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1622                with a list of GPIO LEDs that have inverted polarity.
1623
1624- I2C Support:  CONFIG_SYS_I2C
1625
1626                This enable the NEW i2c subsystem, and will allow you to use
1627                i2c commands at the u-boot command line (as long as you set
1628                CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1629                based realtime clock chips or other i2c devices. See
1630                common/cmd_i2c.c for a description of the command line
1631                interface.
1632
1633                ported i2c driver to the new framework:
1634                - drivers/i2c/soft_i2c.c:
1635                  - activate first bus with CONFIG_SYS_I2C_SOFT define
1636                    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1637                    for defining speed and slave address
1638                  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1639                    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1640                    for defining speed and slave address
1641                  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1642                    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1643                    for defining speed and slave address
1644                  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1645                    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1646                    for defining speed and slave address
1647
1648                - drivers/i2c/fsl_i2c.c:
1649                  - activate i2c driver with CONFIG_SYS_I2C_FSL
1650                    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1651                    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1652                    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1653                    bus.
1654                  - If your board supports a second fsl i2c bus, define
1655                    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1656                    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1657                    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1658                    second bus.
1659
1660                - drivers/i2c/tegra_i2c.c:
1661                  - activate this driver with CONFIG_SYS_I2C_TEGRA
1662                  - This driver adds 4 i2c buses with a fix speed from
1663                    100000 and the slave addr 0!
1664
1665                - drivers/i2c/ppc4xx_i2c.c
1666                  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1667                  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1668                  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1669
1670                - drivers/i2c/i2c_mxc.c
1671                  - activate this driver with CONFIG_SYS_I2C_MXC
1672                  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1673                  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1674                  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1675                  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1676                  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1677                  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1678                  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1679                  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1680                  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1681                  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1682                  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1683                  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1684                If those defines are not set, default value is 100000
1685                for speed, and 0 for slave.
1686
1687                - drivers/i2c/rcar_i2c.c:
1688                  - activate this driver with CONFIG_SYS_I2C_RCAR
1689                  - This driver adds 4 i2c buses
1690
1691                  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1692                  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1693                  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1694                  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1695                  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1696                  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1697                  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1698                  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1699                  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1700
1701                - drivers/i2c/sh_i2c.c:
1702                  - activate this driver with CONFIG_SYS_I2C_SH
1703                  - This driver adds from 2 to 5 i2c buses
1704
1705                  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1706                  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1707                  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1708                  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1709                  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1710                  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1711                  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1712                  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1713                  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1714                  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1715                  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1716
1717                - drivers/i2c/omap24xx_i2c.c
1718                  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1719                  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1720                  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1721                  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1722                  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1723                  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1724                  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1725                  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1726                  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1727                  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1728                  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1729
1730                - drivers/i2c/zynq_i2c.c
1731                  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1732                  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1733                  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1734
1735                - drivers/i2c/s3c24x0_i2c.c:
1736                  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1737                  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1738                    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1739                    with a fix speed from 100000 and the slave addr 0!
1740
1741                - drivers/i2c/ihs_i2c.c
1742                  - activate this driver with CONFIG_SYS_I2C_IHS
1743                  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1744                  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1745                  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1746                  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1747                  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1748                  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1749                  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1750                  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1751                  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1752                  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1753                  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1754                  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1755                  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1756                  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1757                  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1758                  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1759                  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1760                  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1761                  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1762                  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1763                  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1764
1765                additional defines:
1766
1767                CONFIG_SYS_NUM_I2C_BUSES
1768                Hold the number of i2c buses you want to use.
1769
1770                CONFIG_SYS_I2C_DIRECT_BUS
1771                define this, if you don't use i2c muxes on your hardware.
1772                if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1773                omit this define.
1774
1775                CONFIG_SYS_I2C_MAX_HOPS
1776                define how many muxes are maximal consecutively connected
1777                on one i2c bus. If you not use i2c muxes, omit this
1778                define.
1779
1780                CONFIG_SYS_I2C_BUSES
1781                hold a list of buses you want to use, only used if
1782                CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1783                a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1784                CONFIG_SYS_NUM_I2C_BUSES = 9:
1785
1786                 CONFIG_SYS_I2C_BUSES   {{0, {I2C_NULL_HOP}}, \
1787                                        {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1788                                        {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1789                                        {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1790                                        {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1791                                        {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1792                                        {1, {I2C_NULL_HOP}}, \
1793                                        {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1794                                        {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1795                                        }
1796
1797                which defines
1798                        bus 0 on adapter 0 without a mux
1799                        bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1800                        bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1801                        bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1802                        bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1803                        bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1804                        bus 6 on adapter 1 without a mux
1805                        bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1806                        bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1807
1808                If you do not have i2c muxes on your board, omit this define.
1809
1810- Legacy I2C Support:
1811                If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1812                then the following macros need to be defined (examples are
1813                from include/configs/lwmon.h):
1814
1815                I2C_INIT
1816
1817                (Optional). Any commands necessary to enable the I2C
1818                controller or configure ports.
1819
1820                eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=  PB_SCL)
1821
1822                I2C_ACTIVE
1823
1824                The code necessary to make the I2C data line active
1825                (driven).  If the data line is open collector, this
1826                define can be null.
1827
1828                eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1829
1830                I2C_TRISTATE
1831
1832                The code necessary to make the I2C data line tri-stated
1833                (inactive).  If the data line is open collector, this
1834                define can be null.
1835
1836                eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1837
1838                I2C_READ
1839
1840                Code that returns true if the I2C data line is high,
1841                false if it is low.
1842
1843                eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1844
1845                I2C_SDA(bit)
1846
1847                If <bit> is true, sets the I2C data line high. If it
1848                is false, it clears it (low).
1849
1850                eg: #define I2C_SDA(bit) \
1851                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1852                        else    immr->im_cpm.cp_pbdat &= ~PB_SDA
1853
1854                I2C_SCL(bit)
1855
1856                If <bit> is true, sets the I2C clock line high. If it
1857                is false, it clears it (low).
1858
1859                eg: #define I2C_SCL(bit) \
1860                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1861                        else    immr->im_cpm.cp_pbdat &= ~PB_SCL
1862
1863                I2C_DELAY
1864
1865                This delay is invoked four times per clock cycle so this
1866                controls the rate of data transfer.  The data rate thus
1867                is 1 / (I2C_DELAY * 4). Often defined to be something
1868                like:
1869
1870                #define I2C_DELAY  udelay(2)
1871
1872                CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1873
1874                If your arch supports the generic GPIO framework (asm/gpio.h),
1875                then you may alternatively define the two GPIOs that are to be
1876                used as SCL / SDA.  Any of the previous I2C_xxx macros will
1877                have GPIO-based defaults assigned to them as appropriate.
1878
1879                You should define these to the GPIO value as given directly to
1880                the generic GPIO functions.
1881
1882                CONFIG_SYS_I2C_INIT_BOARD
1883
1884                When a board is reset during an i2c bus transfer
1885                chips might think that the current transfer is still
1886                in progress. On some boards it is possible to access
1887                the i2c SCLK line directly, either by using the
1888                processor pin as a GPIO or by having a second pin
1889                connected to the bus. If this option is defined a
1890                custom i2c_init_board() routine in boards/xxx/board.c
1891                is run early in the boot sequence.
1892
1893                CONFIG_I2C_MULTI_BUS
1894
1895                This option allows the use of multiple I2C buses, each of which
1896                must have a controller.  At any point in time, only one bus is
1897                active.  To switch to a different bus, use the 'i2c dev' command.
1898                Note that bus numbering is zero-based.
1899
1900                CONFIG_SYS_I2C_NOPROBES
1901
1902                This option specifies a list of I2C devices that will be skipped
1903                when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1904                is set, specify a list of bus-device pairs.  Otherwise, specify
1905                a 1D array of device addresses
1906
1907                e.g.
1908                        #undef  CONFIG_I2C_MULTI_BUS
1909                        #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1910
1911                will skip addresses 0x50 and 0x68 on a board with one I2C bus
1912
1913                        #define CONFIG_I2C_MULTI_BUS
1914                        #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1915
1916                will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1917
1918                CONFIG_SYS_SPD_BUS_NUM
1919
1920                If defined, then this indicates the I2C bus number for DDR SPD.
1921                If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1922
1923                CONFIG_SYS_RTC_BUS_NUM
1924
1925                If defined, then this indicates the I2C bus number for the RTC.
1926                If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1927
1928                CONFIG_SOFT_I2C_READ_REPEATED_START
1929
1930                defining this will force the i2c_read() function in
1931                the soft_i2c driver to perform an I2C repeated start
1932                between writing the address pointer and reading the
1933                data.  If this define is omitted the default behaviour
1934                of doing a stop-start sequence will be used.  Most I2C
1935                devices can use either method, but some require one or
1936                the other.
1937
1938- SPI Support:  CONFIG_SPI
1939
1940                Enables SPI driver (so far only tested with
1941                SPI EEPROM, also an instance works with Crystal A/D and
1942                D/As on the SACSng board)
1943
1944                CONFIG_SOFT_SPI
1945
1946                Enables a software (bit-bang) SPI driver rather than
1947                using hardware support. This is a general purpose
1948                driver that only requires three general I/O port pins
1949                (two outputs, one input) to function. If this is
1950                defined, the board configuration must define several
1951                SPI configuration items (port pins to use, etc). For
1952                an example, see include/configs/sacsng.h.
1953
1954                CONFIG_HARD_SPI
1955
1956                Enables a hardware SPI driver for general-purpose reads
1957                and writes.  As with CONFIG_SOFT_SPI, the board configuration
1958                must define a list of chip-select function pointers.
1959                Currently supported on some MPC8xxx processors.  For an
1960                example, see include/configs/mpc8349emds.h.
1961
1962                CONFIG_SYS_SPI_MXC_WAIT
1963                Timeout for waiting until spi transfer completed.
1964                default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1965
1966- FPGA Support: CONFIG_FPGA
1967
1968                Enables FPGA subsystem.
1969
1970                CONFIG_FPGA_<vendor>
1971
1972                Enables support for specific chip vendors.
1973                (ALTERA, XILINX)
1974
1975                CONFIG_FPGA_<family>
1976
1977                Enables support for FPGA family.
1978                (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1979
1980                CONFIG_FPGA_COUNT
1981
1982                Specify the number of FPGA devices to support.
1983
1984                CONFIG_SYS_FPGA_PROG_FEEDBACK
1985
1986                Enable printing of hash marks during FPGA configuration.
1987
1988                CONFIG_SYS_FPGA_CHECK_BUSY
1989
1990                Enable checks on FPGA configuration interface busy
1991                status by the configuration function. This option
1992                will require a board or device specific function to
1993                be written.
1994
1995                CONFIG_FPGA_DELAY
1996
1997                If defined, a function that provides delays in the FPGA
1998                configuration driver.
1999
2000                CONFIG_SYS_FPGA_CHECK_CTRLC
2001                Allow Control-C to interrupt FPGA configuration
2002
2003                CONFIG_SYS_FPGA_CHECK_ERROR
2004
2005                Check for configuration errors during FPGA bitfile
2006                loading. For example, abort during Virtex II
2007                configuration if the INIT_B line goes low (which
2008                indicated a CRC error).
2009
2010                CONFIG_SYS_FPGA_WAIT_INIT
2011
2012                Maximum time to wait for the INIT_B line to de-assert
2013                after PROB_B has been de-asserted during a Virtex II
2014                FPGA configuration sequence. The default time is 500
2015                ms.
2016
2017                CONFIG_SYS_FPGA_WAIT_BUSY
2018
2019                Maximum time to wait for BUSY to de-assert during
2020                Virtex II FPGA configuration. The default is 5 ms.
2021
2022                CONFIG_SYS_FPGA_WAIT_CONFIG
2023
2024                Time to wait after FPGA configuration. The default is
2025                200 ms.
2026
2027- Configuration Management:
2028                CONFIG_BUILD_TARGET
2029
2030                Some SoCs need special image types (e.g. U-Boot binary
2031                with a special header) as build targets. By defining
2032                CONFIG_BUILD_TARGET in the SoC / board header, this
2033                special image will be automatically built upon calling
2034                make / buildman.
2035
2036                CONFIG_IDENT_STRING
2037
2038                If defined, this string will be added to the U-Boot
2039                version information (U_BOOT_VERSION)
2040
2041- Vendor Parameter Protection:
2042
2043                U-Boot considers the values of the environment
2044                variables "serial#" (Board Serial Number) and
2045                "ethaddr" (Ethernet Address) to be parameters that
2046                are set once by the board vendor / manufacturer, and
2047                protects these variables from casual modification by
2048                the user. Once set, these variables are read-only,
2049                and write or delete attempts are rejected. You can
2050                change this behaviour:
2051
2052                If CONFIG_ENV_OVERWRITE is #defined in your config
2053                file, the write protection for vendor parameters is
2054                completely disabled. Anybody can change or delete
2055                these parameters.
2056
2057                Alternatively, if you define _both_ an ethaddr in the
2058                default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2059                Ethernet address is installed in the environment,
2060                which can be changed exactly ONCE by the user. [The
2061                serial# is unaffected by this, i. e. it remains
2062                read-only.]
2063
2064                The same can be accomplished in a more flexible way
2065                for any variable by configuring the type of access
2066                to allow for those variables in the ".flags" variable
2067                or define CONFIG_ENV_FLAGS_LIST_STATIC.
2068
2069- Protected RAM:
2070                CONFIG_PRAM
2071
2072                Define this variable to enable the reservation of
2073                "protected RAM", i. e. RAM which is not overwritten
2074                by U-Boot. Define CONFIG_PRAM to hold the number of
2075                kB you want to reserve for pRAM. You can overwrite
2076                this default value by defining an environment
2077                variable "pram" to the number of kB you want to
2078                reserve. Note that the board info structure will
2079                still show the full amount of RAM. If pRAM is
2080                reserved, a new environment variable "mem" will
2081                automatically be defined to hold the amount of
2082                remaining RAM in a form that can be passed as boot
2083                argument to Linux, for instance like that:
2084
2085                        setenv bootargs ... mem=\${mem}
2086                        saveenv
2087
2088                This way you can tell Linux not to use this memory,
2089                either, which results in a memory region that will
2090                not be affected by reboots.
2091
2092                *WARNING* If your board configuration uses automatic
2093                detection of the RAM size, you must make sure that
2094                this memory test is non-destructive. So far, the
2095                following board configurations are known to be
2096                "pRAM-clean":
2097
2098                        IVMS8, IVML24, SPD8xx,
2099                        HERMES, IP860, RPXlite, LWMON,
2100                        FLAGADM
2101
2102- Access to physical memory region (> 4GB)
2103                Some basic support is provided for operations on memory not
2104                normally accessible to U-Boot - e.g. some architectures
2105                support access to more than 4GB of memory on 32-bit
2106                machines using physical address extension or similar.
2107                Define CONFIG_PHYSMEM to access this basic support, which
2108                currently only supports clearing the memory.
2109
2110- Error Recovery:
2111                CONFIG_NET_RETRY_COUNT
2112
2113                This variable defines the number of retries for
2114                network operations like ARP, RARP, TFTP, or BOOTP
2115                before giving up the operation. If not defined, a
2116                default value of 5 is used.
2117
2118                CONFIG_ARP_TIMEOUT
2119
2120                Timeout waiting for an ARP reply in milliseconds.
2121
2122                CONFIG_NFS_TIMEOUT
2123
2124                Timeout in milliseconds used in NFS protocol.
2125                If you encounter "ERROR: Cannot umount" in nfs command,
2126                try longer timeout such as
2127                #define CONFIG_NFS_TIMEOUT 10000UL
2128
2129- Command Interpreter:
2130                CONFIG_SYS_PROMPT_HUSH_PS2
2131
2132                This defines the secondary prompt string, which is
2133                printed when the command interpreter needs more input
2134                to complete a command. Usually "> ".
2135
2136        Note:
2137
2138                In the current implementation, the local variables
2139                space and global environment variables space are
2140                separated. Local variables are those you define by
2141                simply typing `name=value'. To access a local
2142                variable later on, you have write `$name' or
2143                `${name}'; to execute the contents of a variable
2144                directly type `$name' at the command prompt.
2145
2146                Global environment variables are those you use
2147                setenv/printenv to work with. To run a command stored
2148                in such a variable, you need to use the run command,
2149                and you must not use the '$' sign to access them.
2150
2151                To store commands and special characters in a
2152                variable, please use double quotation marks
2153                surrounding the whole text of the variable, instead
2154                of the backslashes before semicolons and special
2155                symbols.
2156
2157- Command Line Editing and History:
2158                CONFIG_CMDLINE_PS_SUPPORT
2159
2160                Enable support for changing the command prompt string
2161                at run-time. Only static string is supported so far.
2162                The string is obtained from environment variables PS1
2163                and PS2.
2164
2165- Default Environment:
2166                CONFIG_EXTRA_ENV_SETTINGS
2167
2168                Define this to contain any number of null terminated
2169                strings (variable = value pairs) that will be part of
2170                the default environment compiled into the boot image.
2171
2172                For example, place something like this in your
2173                board's config file:
2174
2175                #define CONFIG_EXTRA_ENV_SETTINGS \
2176                        "myvar1=value1\0" \
2177                        "myvar2=value2\0"
2178
2179                Warning: This method is based on knowledge about the
2180                internal format how the environment is stored by the
2181                U-Boot code. This is NOT an official, exported
2182                interface! Although it is unlikely that this format
2183                will change soon, there is no guarantee either.
2184                You better know what you are doing here.
2185
2186                Note: overly (ab)use of the default environment is
2187                discouraged. Make sure to check other ways to preset
2188                the environment like the "source" command or the
2189                boot command first.
2190
2191                CONFIG_DELAY_ENVIRONMENT
2192
2193                Normally the environment is loaded when the board is
2194                initialised so that it is available to U-Boot. This inhibits
2195                that so that the environment is not available until
2196                explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2197                this is instead controlled by the value of
2198                /config/load-environment.
2199
2200- Serial Flash support
2201                Usage requires an initial 'sf probe' to define the serial
2202                flash parameters, followed by read/write/erase/update
2203                commands.
2204
2205                The following defaults may be provided by the platform
2206                to handle the common case when only a single serial
2207                flash is present on the system.
2208
2209                CONFIG_SF_DEFAULT_BUS           Bus identifier
2210                CONFIG_SF_DEFAULT_CS            Chip-select
2211                CONFIG_SF_DEFAULT_MODE          (see include/spi.h)
2212                CONFIG_SF_DEFAULT_SPEED         in Hz
2213
2214
2215- TFTP Fixed UDP Port:
2216                CONFIG_TFTP_PORT
2217
2218                If this is defined, the environment variable tftpsrcp
2219                is used to supply the TFTP UDP source port value.
2220                If tftpsrcp isn't defined, the normal pseudo-random port
2221                number generator is used.
2222
2223                Also, the environment variable tftpdstp is used to supply
2224                the TFTP UDP destination port value.  If tftpdstp isn't
2225                defined, the normal port 69 is used.
2226
2227                The purpose for tftpsrcp is to allow a TFTP server to
2228                blindly start the TFTP transfer using the pre-configured
2229                target IP address and UDP port. This has the effect of
2230                "punching through" the (Windows XP) firewall, allowing
2231                the remainder of the TFTP transfer to proceed normally.
2232                A better solution is to properly configure the firewall,
2233                but sometimes that is not allowed.
2234
2235- Show boot progress:
2236                CONFIG_SHOW_BOOT_PROGRESS
2237
2238                Defining this option allows to add some board-
2239                specific code (calling a user-provided function
2240                "show_boot_progress(int)") that enables you to show
2241                the system's boot progress on some display (for
2242                example, some LED's) on your board. At the moment,
2243                the following checkpoints are implemented:
2244
2245
2246Legacy uImage format:
2247
2248  Arg   Where                   When
2249    1   common/cmd_bootm.c      before attempting to boot an image
2250   -1   common/cmd_bootm.c      Image header has bad     magic number
2251    2   common/cmd_bootm.c      Image header has correct magic number
2252   -2   common/cmd_bootm.c      Image header has bad     checksum
2253    3   common/cmd_bootm.c      Image header has correct checksum
2254   -3   common/cmd_bootm.c      Image data   has bad     checksum
2255    4   common/cmd_bootm.c      Image data   has correct checksum
2256   -4   common/cmd_bootm.c      Image is for unsupported architecture
2257    5   common/cmd_bootm.c      Architecture check OK
2258   -5   common/cmd_bootm.c      Wrong Image Type (not kernel, multi)
2259    6   common/cmd_bootm.c      Image Type check OK
2260   -6   common/cmd_bootm.c      gunzip uncompression error
2261   -7   common/cmd_bootm.c      Unimplemented compression type
2262    7   common/cmd_bootm.c      Uncompression OK
2263    8   common/cmd_bootm.c      No uncompress/copy overwrite error
2264   -9   common/cmd_bootm.c      Unsupported OS (not Linux, BSD, VxWorks, QNX)
2265
2266    9   common/image.c          Start initial ramdisk verification
2267  -10   common/image.c          Ramdisk header has bad     magic number
2268  -11   common/image.c          Ramdisk header has bad     checksum
2269   10   common/image.c          Ramdisk header is OK
2270  -12   common/image.c          Ramdisk data   has bad     checksum
2271   11   common/image.c          Ramdisk data   has correct checksum
2272   12   common/image.c          Ramdisk verification complete, start loading
2273  -13   common/image.c          Wrong Image Type (not PPC Linux ramdisk)
2274   13   common/image.c          Start multifile image verification
2275   14   common/image.c          No initial ramdisk, no multifile, continue.
2276
2277   15   arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2278
2279  -30   arch/powerpc/lib/board.c        Fatal error, hang the system
2280  -31   post/post.c             POST test failed, detected by post_output_backlog()
2281  -32   post/post.c             POST test failed, detected by post_run_single()
2282
2283   34   common/cmd_doc.c        before loading a Image from a DOC device
2284  -35   common/cmd_doc.c        Bad usage of "doc" command
2285   35   common/cmd_doc.c        correct usage of "doc" command
2286  -36   common/cmd_doc.c        No boot device
2287   36   common/cmd_doc.c        correct boot device
2288  -37   common/cmd_doc.c        Unknown Chip ID on boot device
2289   37   common/cmd_doc.c        correct chip ID found, device available
2290  -38   common/cmd_doc.c        Read Error on boot device
2291   38   common/cmd_doc.c        reading Image header from DOC device OK
2292  -39   common/cmd_doc.c        Image header has bad magic number
2293   39   common/cmd_doc.c        Image header has correct magic number
2294  -40   common/cmd_doc.c        Error reading Image from DOC device
2295   40   common/cmd_doc.c        Image header has correct magic number
2296   41   common/cmd_ide.c        before loading a Image from a IDE device
2297  -42   common/cmd_ide.c        Bad usage of "ide" command
2298   42   common/cmd_ide.c        correct usage of "ide" command
2299  -43   common/cmd_ide.c        No boot device
2300   43   common/cmd_ide.c        boot device found
2301  -44   common/cmd_ide.c        Device not available
2302   44   common/cmd_ide.c        Device available
2303  -45   common/cmd_ide.c        wrong partition selected
2304   45   common/cmd_ide.c        partition selected
2305  -46   common/cmd_ide.c        Unknown partition table
2306   46   common/cmd_ide.c        valid partition table found
2307  -47   common/cmd_ide.c        Invalid partition type
2308   47   common/cmd_ide.c        correct partition type
2309  -48   common/cmd_ide.c        Error reading Image Header on boot device
2310   48   common/cmd_ide.c        reading Image Header from IDE device OK
2311  -49   common/cmd_ide.c        Image header has bad magic number
2312   49   common/cmd_ide.c        Image header has correct magic number
2313  -50   common/cmd_ide.c        Image header has bad     checksum
2314   50   common/cmd_ide.c        Image header has correct checksum
2315  -51   common/cmd_ide.c        Error reading Image from IDE device
2316   51   common/cmd_ide.c        reading Image from IDE device OK
2317   52   common/cmd_nand.c       before loading a Image from a NAND device
2318  -53   common/cmd_nand.c       Bad usage of "nand" command
2319   53   common/cmd_nand.c       correct usage of "nand" command
2320  -54   common/cmd_nand.c       No boot device
2321   54   common/cmd_nand.c       boot device found
2322  -55   common/cmd_nand.c       Unknown Chip ID on boot device
2323   55   common/cmd_nand.c       correct chip ID found, device available
2324  -56   common/cmd_nand.c       Error reading Image Header on boot device
2325   56   common/cmd_nand.c       reading Image Header from NAND device OK
2326  -57   common/cmd_nand.c       Image header has bad magic number
2327   57   common/cmd_nand.c       Image header has correct magic number
2328  -58   common/cmd_nand.c       Error reading Image from NAND device
2329   58   common/cmd_nand.c       reading Image from NAND device OK
2330
2331  -60   common/env_common.c     Environment has a bad CRC, using default
2332
2333   64   net/eth.c               starting with Ethernet configuration.
2334  -64   net/eth.c               no Ethernet found.
2335   65   net/eth.c               Ethernet found.
2336
2337  -80   common/cmd_net.c        usage wrong
2338   80   common/cmd_net.c        before calling net_loop()
2339  -81   common/cmd_net.c        some error in net_loop() occurred
2340   81   common/cmd_net.c        net_loop() back without error
2341  -82   common/cmd_net.c        size == 0 (File with size 0 loaded)
2342   82   common/cmd_net.c        trying automatic boot
2343   83   common/cmd_net.c        running "source" command
2344  -83   common/cmd_net.c        some error in automatic boot or "source" command
2345   84   common/cmd_net.c        end without errors
2346
2347FIT uImage format:
2348
2349  Arg   Where                   When
2350  100   common/cmd_bootm.c      Kernel FIT Image has correct format
2351 -100   common/cmd_bootm.c      Kernel FIT Image has incorrect format
2352  101   common/cmd_bootm.c      No Kernel subimage unit name, using configuration
2353 -101   common/cmd_bootm.c      Can't get configuration for kernel subimage
2354  102   common/cmd_bootm.c      Kernel unit name specified
2355 -103   common/cmd_bootm.c      Can't get kernel subimage node offset
2356  103   common/cmd_bootm.c      Found configuration node
2357  104   common/cmd_bootm.c      Got kernel subimage node offset
2358 -104   common/cmd_bootm.c      Kernel subimage hash verification failed
2359  105   common/cmd_bootm.c      Kernel subimage hash verification OK
2360 -105   common/cmd_bootm.c      Kernel subimage is for unsupported architecture
2361  106   common/cmd_bootm.c      Architecture check OK
2362 -106   common/cmd_bootm.c      Kernel subimage has wrong type
2363  107   common/cmd_bootm.c      Kernel subimage type OK
2364 -107   common/cmd_bootm.c      Can't get kernel subimage data/size
2365  108   common/cmd_bootm.c      Got kernel subimage data/size
2366 -108   common/cmd_bootm.c      Wrong image type (not legacy, FIT)
2367 -109   common/cmd_bootm.c      Can't get kernel subimage type
2368 -110   common/cmd_bootm.c      Can't get kernel subimage comp
2369 -111   common/cmd_bootm.c      Can't get kernel subimage os
2370 -112   common/cmd_bootm.c      Can't get kernel subimage load address
2371 -113   common/cmd_bootm.c      Image uncompress/copy overwrite error
2372
2373  120   common/image.c          Start initial ramdisk verification
2374 -120   common/image.c          Ramdisk FIT image has incorrect format
2375  121   common/image.c          Ramdisk FIT image has correct format
2376  122   common/image.c          No ramdisk subimage unit name, using configuration
2377 -122   common/image.c          Can't get configuration for ramdisk subimage
2378  123   common/image.c          Ramdisk unit name specified
2379 -124   common/image.c          Can't get ramdisk subimage node offset
2380  125   common/image.c          Got ramdisk subimage node offset
2381 -125   common/image.c          Ramdisk subimage hash verification failed
2382  126   common/image.c          Ramdisk subimage hash verification OK
2383 -126   common/image.c          Ramdisk subimage for unsupported architecture
2384  127   common/image.c          Architecture check OK
2385 -127   common/image.c          Can't get ramdisk subimage data/size
2386  128   common/image.c          Got ramdisk subimage data/size
2387  129   common/image.c          Can't get ramdisk load address
2388 -129   common/image.c          Got ramdisk load address
2389
2390 -130   common/cmd_doc.c        Incorrect FIT image format
2391  131   common/cmd_doc.c        FIT image format OK
2392
2393 -140   common/cmd_ide.c        Incorrect FIT image format
2394  141   common/cmd_ide.c        FIT image format OK
2395
2396 -150   common/cmd_nand.c       Incorrect FIT image format
2397  151   common/cmd_nand.c       FIT image format OK
2398
2399- Standalone program support:
2400                CONFIG_STANDALONE_LOAD_ADDR
2401
2402                This option defines a board specific value for the
2403                address where standalone program gets loaded, thus
2404                overwriting the architecture dependent default
2405                settings.
2406
2407- Frame Buffer Address:
2408                CONFIG_FB_ADDR
2409
2410                Define CONFIG_FB_ADDR if you want to use specific
2411                address for frame buffer.  This is typically the case
2412                when using a graphics controller has separate video
2413                memory.  U-Boot will then place the frame buffer at
2414                the given address instead of dynamically reserving it
2415                in system RAM by calling lcd_setmem(), which grabs
2416                the memory for the frame buffer depending on the
2417                configured panel size.
2418
2419                Please see board_init_f function.
2420
2421- Automatic software updates via TFTP server
2422                CONFIG_UPDATE_TFTP
2423                CONFIG_UPDATE_TFTP_CNT_MAX
2424                CONFIG_UPDATE_TFTP_MSEC_MAX
2425
2426                These options enable and control the auto-update feature;
2427                for a more detailed description refer to doc/README.update.
2428
2429- MTD Support (mtdparts command, UBI support)
2430                CONFIG_MTD_UBI_WL_THRESHOLD
2431                This parameter defines the maximum difference between the highest
2432                erase counter value and the lowest erase counter value of eraseblocks
2433                of UBI devices. When this threshold is exceeded, UBI starts performing
2434                wear leveling by means of moving data from eraseblock with low erase
2435                counter to eraseblocks with high erase counter.
2436
2437                The default value should be OK for SLC NAND flashes, NOR flashes and
2438                other flashes which have eraseblock life-cycle 100000 or more.
2439                However, in case of MLC NAND flashes which typically have eraseblock
2440                life-cycle less than 10000, the threshold should be lessened (e.g.,
2441                to 128 or 256, although it does not have to be power of 2).
2442
2443                default: 4096
2444
2445                CONFIG_MTD_UBI_BEB_LIMIT
2446                This option specifies the maximum bad physical eraseblocks UBI
2447                expects on the MTD device (per 1024 eraseblocks). If the
2448                underlying flash does not admit of bad eraseblocks (e.g. NOR
2449                flash), this value is ignored.
2450
2451                NAND datasheets often specify the minimum and maximum NVM
2452                (Number of Valid Blocks) for the flashes' endurance lifetime.
2453                The maximum expected bad eraseblocks per 1024 eraseblocks
2454                then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2455                which gives 20 for most NANDs (MaxNVB is basically the total
2456                count of eraseblocks on the chip).
2457
2458                To put it differently, if this value is 20, UBI will try to
2459                reserve about 1.9% of physical eraseblocks for bad blocks
2460                handling. And that will be 1.9% of eraseblocks on the entire
2461                NAND chip, not just the MTD partition UBI attaches. This means
2462                that if you have, say, a NAND flash chip admits maximum 40 bad
2463                eraseblocks, and it is split on two MTD partitions of the same
2464                size, UBI will reserve 40 eraseblocks when attaching a
2465                partition.
2466
2467                default: 20
2468
2469                CONFIG_MTD_UBI_FASTMAP
2470                Fastmap is a mechanism which allows attaching an UBI device
2471                in nearly constant time. Instead of scanning the whole MTD device it
2472                only has to locate a checkpoint (called fastmap) on the device.
2473                The on-flash fastmap contains all information needed to attach
2474                the device. Using fastmap makes only sense on large devices where
2475                attaching by scanning takes long. UBI will not automatically install
2476                a fastmap on old images, but you can set the UBI parameter
2477                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2478                that fastmap-enabled images are still usable with UBI implementations
2479                without fastmap support. On typical flash devices the whole fastmap
2480                fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2481
2482                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2483                Set this parameter to enable fastmap automatically on images
2484                without a fastmap.
2485                default: 0
2486
2487                CONFIG_MTD_UBI_FM_DEBUG
2488                Enable UBI fastmap debug
2489                default: 0
2490
2491- SPL framework
2492                CONFIG_SPL
2493                Enable building of SPL globally.
2494
2495                CONFIG_SPL_LDSCRIPT
2496                LDSCRIPT for linking the SPL binary.
2497
2498                CONFIG_SPL_MAX_FOOTPRINT
2499                Maximum size in memory allocated to the SPL, BSS included.
2500                When defined, the linker checks that the actual memory
2501                used by SPL from _start to __bss_end does not exceed it.
2502                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2503                must not be both defined at the same time.
2504
2505                CONFIG_SPL_MAX_SIZE
2506                Maximum size of the SPL image (text, data, rodata, and
2507                linker lists sections), BSS excluded.
2508                When defined, the linker checks that the actual size does
2509                not exceed it.
2510
2511                CONFIG_SPL_TEXT_BASE
2512                TEXT_BASE for linking the SPL binary.
2513
2514                CONFIG_SPL_RELOC_TEXT_BASE
2515                Address to relocate to.  If unspecified, this is equal to
2516                CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2517
2518                CONFIG_SPL_BSS_START_ADDR
2519                Link address for the BSS within the SPL binary.
2520
2521                CONFIG_SPL_BSS_MAX_SIZE
2522                Maximum size in memory allocated to the SPL BSS.
2523                When defined, the linker checks that the actual memory used
2524                by SPL from __bss_start to __bss_end does not exceed it.
2525                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2526                must not be both defined at the same time.
2527
2528                CONFIG_SPL_STACK
2529                Adress of the start of the stack SPL will use
2530
2531                CONFIG_SPL_PANIC_ON_RAW_IMAGE
2532                When defined, SPL will panic() if the image it has
2533                loaded does not have a signature.
2534                Defining this is useful when code which loads images
2535                in SPL cannot guarantee that absolutely all read errors
2536                will be caught.
2537                An example is the LPC32XX MLC NAND driver, which will
2538                consider that a completely unreadable NAND block is bad,
2539                and thus should be skipped silently.
2540
2541                CONFIG_SPL_RELOC_STACK
2542                Adress of the start of the stack SPL will use after
2543                relocation.  If unspecified, this is equal to
2544                CONFIG_SPL_STACK.
2545
2546                CONFIG_SYS_SPL_MALLOC_START
2547                Starting address of the malloc pool used in SPL.
2548                When this option is set the full malloc is used in SPL and
2549                it is set up by spl_init() and before that, the simple malloc()
2550                can be used if CONFIG_SYS_MALLOC_F is defined.
2551
2552                CONFIG_SYS_SPL_MALLOC_SIZE
2553                The size of the malloc pool used in SPL.
2554
2555                CONFIG_SPL_OS_BOOT
2556                Enable booting directly to an OS from SPL.
2557                See also: doc/README.falcon
2558
2559                CONFIG_SPL_DISPLAY_PRINT
2560                For ARM, enable an optional function to print more information
2561                about the running system.
2562
2563                CONFIG_SPL_INIT_MINIMAL
2564                Arch init code should be built for a very small image
2565
2566                CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2567                Partition on the MMC to load U-Boot from when the MMC is being
2568                used in raw mode
2569
2570                CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2571                Sector to load kernel uImage from when MMC is being
2572                used in raw mode (for Falcon mode)
2573
2574                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2575                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2576                Sector and number of sectors to load kernel argument
2577                parameters from when MMC is being used in raw mode
2578                (for falcon mode)
2579
2580                CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2581                Partition on the MMC to load U-Boot from when the MMC is being
2582                used in fs mode
2583
2584                CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2585                Filename to read to load U-Boot when reading from filesystem
2586
2587                CONFIG_SPL_FS_LOAD_KERNEL_NAME
2588                Filename to read to load kernel uImage when reading
2589                from filesystem (for Falcon mode)
2590
2591                CONFIG_SPL_FS_LOAD_ARGS_NAME
2592                Filename to read to load kernel argument parameters
2593                when reading from filesystem (for Falcon mode)
2594
2595                CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2596                Set this for NAND SPL on PPC mpc83xx targets, so that
2597                start.S waits for the rest of the SPL to load before
2598                continuing (the hardware starts execution after just
2599                loading the first page rather than the full 4K).
2600
2601                CONFIG_SPL_SKIP_RELOCATE
2602                Avoid SPL relocation
2603
2604                CONFIG_SPL_NAND_BASE
2605                Include nand_base.c in the SPL.  Requires
2606                CONFIG_SPL_NAND_DRIVERS.
2607
2608                CONFIG_SPL_NAND_DRIVERS
2609                SPL uses normal NAND drivers, not minimal drivers.
2610
2611                CONFIG_SPL_NAND_IDENT
2612                SPL uses the chip ID list to identify the NAND flash.
2613                Requires CONFIG_SPL_NAND_BASE.
2614
2615                CONFIG_SPL_NAND_ECC
2616                Include standard software ECC in the SPL
2617
2618                CONFIG_SPL_NAND_SIMPLE
2619                Support for NAND boot using simple NAND drivers that
2620                expose the cmd_ctrl() interface.
2621
2622                CONFIG_SPL_UBI
2623                Support for a lightweight UBI (fastmap) scanner and
2624                loader
2625
2626                CONFIG_SPL_NAND_RAW_ONLY
2627                Support to boot only raw u-boot.bin images. Use this only
2628                if you need to save space.
2629
2630                CONFIG_SPL_COMMON_INIT_DDR
2631                Set for common ddr init with serial presence detect in
2632                SPL binary.
2633
2634                CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2635                CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2636                CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2637                CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2638                CONFIG_SYS_NAND_ECCBYTES
2639                Defines the size and behavior of the NAND that SPL uses
2640                to read U-Boot
2641
2642                CONFIG_SPL_NAND_BOOT
2643                Add support NAND boot
2644
2645                CONFIG_SYS_NAND_U_BOOT_OFFS
2646                Location in NAND to read U-Boot from
2647
2648                CONFIG_SYS_NAND_U_BOOT_DST
2649                Location in memory to load U-Boot to
2650
2651                CONFIG_SYS_NAND_U_BOOT_SIZE
2652                Size of image to load
2653
2654                CONFIG_SYS_NAND_U_BOOT_START
2655                Entry point in loaded image to jump to
2656
2657                CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2658                Define this if you need to first read the OOB and then the
2659                data. This is used, for example, on davinci platforms.
2660
2661                CONFIG_SPL_RAM_DEVICE
2662                Support for running image already present in ram, in SPL binary
2663
2664                CONFIG_SPL_PAD_TO
2665                Image offset to which the SPL should be padded before appending
2666                the SPL payload. By default, this is defined as
2667                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2668                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2669                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2670
2671                CONFIG_SPL_TARGET
2672                Final target image containing SPL and payload.  Some SPLs
2673                use an arch-specific makefile fragment instead, for
2674                example if more than one image needs to be produced.
2675
2676                CONFIG_SPL_FIT_PRINT
2677                Printing information about a FIT image adds quite a bit of
2678                code to SPL. So this is normally disabled in SPL. Use this
2679                option to re-enable it. This will affect the output of the
2680                bootm command when booting a FIT image.
2681
2682- TPL framework
2683                CONFIG_TPL
2684                Enable building of TPL globally.
2685
2686                CONFIG_TPL_PAD_TO
2687                Image offset to which the TPL should be padded before appending
2688                the TPL payload. By default, this is defined as
2689                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2690                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2691                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2692
2693- Interrupt support (PPC):
2694
2695                There are common interrupt_init() and timer_interrupt()
2696                for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2697                for CPU specific initialization. interrupt_init_cpu()
2698                should set decrementer_count to appropriate value. If
2699                CPU resets decrementer automatically after interrupt
2700                (ppc4xx) it should set decrementer_count to zero.
2701                timer_interrupt() calls timer_interrupt_cpu() for CPU
2702                specific handling. If board has watchdog / status_led
2703                / other_activity_monitor it works automatically from
2704                general timer_interrupt().
2705
2706
2707Board initialization settings:
2708------------------------------
2709
2710During Initialization u-boot calls a number of board specific functions
2711to allow the preparation of board specific prerequisites, e.g. pin setup
2712before drivers are initialized. To enable these callbacks the
2713following configuration macros have to be defined. Currently this is
2714architecture specific, so please check arch/your_architecture/lib/board.c
2715typically in board_init_f() and board_init_r().
2716
2717- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2718- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2719- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2720- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2721
2722Configuration Settings:
2723-----------------------
2724
2725- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2726                Optionally it can be defined to support 64-bit memory commands.
2727
2728- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2729                undefine this when you're short of memory.
2730
2731- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2732                width of the commands listed in the 'help' command output.
2733
2734- CONFIG_SYS_PROMPT:    This is what U-Boot prints on the console to
2735                prompt for user input.
2736
2737- CONFIG_SYS_CBSIZE:    Buffer size for input from the Console
2738
2739- CONFIG_SYS_PBSIZE:    Buffer size for Console output
2740
2741- CONFIG_SYS_MAXARGS:   max. Number of arguments accepted for monitor commands
2742
2743- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2744                the application (usually a Linux kernel) when it is
2745                booted
2746
2747- CONFIG_SYS_BAUDRATE_TABLE:
2748                List of legal baudrate settings for this board.
2749
2750- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2751                Begin and End addresses of the area used by the
2752                simple memory test.
2753
2754- CONFIG_SYS_MEMTEST_SCRATCH:
2755                Scratch address used by the alternate memory test
2756                You only need to set this if address zero isn't writeable
2757
2758- CONFIG_SYS_MEM_RESERVE_SECURE
2759                Only implemented for ARMv8 for now.
2760                If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2761                is substracted from total RAM and won't be reported to OS.
2762                This memory can be used as secure memory. A variable
2763                gd->arch.secure_ram is used to track the location. In systems
2764                the RAM base is not zero, or RAM is divided into banks,
2765                this variable needs to be recalcuated to get the address.
2766
2767- CONFIG_SYS_MEM_TOP_HIDE:
2768                If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2769                this specified memory area will get subtracted from the top
2770                (end) of RAM and won't get "touched" at all by U-Boot. By
2771                fixing up gd->ram_size the Linux kernel should gets passed
2772                the now "corrected" memory size and won't touch it either.
2773                This should work for arch/ppc and arch/powerpc. Only Linux
2774                board ports in arch/powerpc with bootwrapper support that
2775                recalculate the memory size from the SDRAM controller setup
2776                will have to get fixed in Linux additionally.
2777
2778                This option can be used as a workaround for the 440EPx/GRx
2779                CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2780                be touched.
2781
2782                WARNING: Please make sure that this value is a multiple of
2783                the Linux page size (normally 4k). If this is not the case,
2784                then the end address of the Linux memory will be located at a
2785                non page size aligned address and this could cause major
2786                problems.
2787
2788- CONFIG_SYS_LOADS_BAUD_CHANGE:
2789                Enable temporary baudrate change while serial download
2790
2791- CONFIG_SYS_SDRAM_BASE:
2792                Physical start address of SDRAM. _Must_ be 0 here.
2793
2794- CONFIG_SYS_FLASH_BASE:
2795                Physical start address of Flash memory.
2796
2797- CONFIG_SYS_MONITOR_BASE:
2798                Physical start address of boot monitor code (set by
2799                make config files to be same as the text base address
2800                (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2801                CONFIG_SYS_FLASH_BASE when booting from flash.
2802
2803- CONFIG_SYS_MONITOR_LEN:
2804                Size of memory reserved for monitor code, used to
2805                determine _at_compile_time_ (!) if the environment is
2806                embedded within the U-Boot image, or in a separate
2807                flash sector.
2808
2809- CONFIG_SYS_MALLOC_LEN:
2810                Size of DRAM reserved for malloc() use.
2811
2812- CONFIG_SYS_MALLOC_F_LEN
2813                Size of the malloc() pool for use before relocation. If
2814                this is defined, then a very simple malloc() implementation
2815                will become available before relocation. The address is just
2816                below the global data, and the stack is moved down to make
2817                space.
2818
2819                This feature allocates regions with increasing addresses
2820                within the region. calloc() is supported, but realloc()
2821                is not available. free() is supported but does nothing.
2822                The memory will be freed (or in fact just forgotten) when
2823                U-Boot relocates itself.
2824
2825- CONFIG_SYS_MALLOC_SIMPLE
2826                Provides a simple and small malloc() and calloc() for those
2827                boards which do not use the full malloc in SPL (which is
2828                enabled with CONFIG_SYS_SPL_MALLOC_START).
2829
2830- CONFIG_SYS_NONCACHED_MEMORY:
2831                Size of non-cached memory area. This area of memory will be
2832                typically located right below the malloc() area and mapped
2833                uncached in the MMU. This is useful for drivers that would
2834                otherwise require a lot of explicit cache maintenance. For
2835                some drivers it's also impossible to properly maintain the
2836                cache. For example if the regions that need to be flushed
2837                are not a multiple of the cache-line size, *and* padding
2838                cannot be allocated between the regions to align them (i.e.
2839                if the HW requires a contiguous array of regions, and the
2840                size of each region is not cache-aligned), then a flush of
2841                one region may result in overwriting data that hardware has
2842                written to another region in the same cache-line. This can
2843                happen for example in network drivers where descriptors for
2844                buffers are typically smaller than the CPU cache-line (e.g.
2845                16 bytes vs. 32 or 64 bytes).
2846
2847                Non-cached memory is only supported on 32-bit ARM at present.
2848
2849- CONFIG_SYS_BOOTM_LEN:
2850                Normally compressed uImages are limited to an
2851                uncompressed size of 8 MBytes. If this is not enough,
2852                you can define CONFIG_SYS_BOOTM_LEN in your board config file
2853                to adjust this setting to your needs.
2854
2855- CONFIG_SYS_BOOTMAPSZ:
2856                Maximum size of memory mapped by the startup code of
2857                the Linux kernel; all data that must be processed by
2858                the Linux kernel (bd_info, boot arguments, FDT blob if
2859                used) must be put below this limit, unless "bootm_low"
2860                environment variable is defined and non-zero. In such case
2861                all data for the Linux kernel must be between "bootm_low"
2862                and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2863                variable "bootm_mapsize" will override the value of
2864                CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2865                then the value in "bootm_size" will be used instead.
2866
2867- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2868                Enable initrd_high functionality.  If defined then the
2869                initrd_high feature is enabled and the bootm ramdisk subcommand
2870                is enabled.
2871
2872- CONFIG_SYS_BOOT_GET_CMDLINE:
2873                Enables allocating and saving kernel cmdline in space between
2874                "bootm_low" and "bootm_low" + BOOTMAPSZ.
2875
2876- CONFIG_SYS_BOOT_GET_KBD:
2877                Enables allocating and saving a kernel copy of the bd_info in
2878                space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2879
2880- CONFIG_SYS_MAX_FLASH_BANKS:
2881                Max number of Flash memory banks
2882
2883- CONFIG_SYS_MAX_FLASH_SECT:
2884                Max number of sectors on a Flash chip
2885
2886- CONFIG_SYS_FLASH_ERASE_TOUT:
2887                Timeout for Flash erase operations (in ms)
2888
2889- CONFIG_SYS_FLASH_WRITE_TOUT:
2890                Timeout for Flash write operations (in ms)
2891
2892- CONFIG_SYS_FLASH_LOCK_TOUT
2893                Timeout for Flash set sector lock bit operation (in ms)
2894
2895- CONFIG_SYS_FLASH_UNLOCK_TOUT
2896                Timeout for Flash clear lock bits operation (in ms)
2897
2898- CONFIG_SYS_FLASH_PROTECTION
2899                If defined, hardware flash sectors protection is used
2900                instead of U-Boot software protection.
2901
2902- CONFIG_SYS_DIRECT_FLASH_TFTP:
2903
2904                Enable TFTP transfers directly to flash memory;
2905                without this option such a download has to be
2906                performed in two steps: (1) download to RAM, and (2)
2907                copy from RAM to flash.
2908
2909                The two-step approach is usually more reliable, since
2910                you can check if the download worked before you erase
2911                the flash, but in some situations (when system RAM is
2912                too limited to allow for a temporary copy of the
2913                downloaded image) this option may be very useful.
2914
2915- CONFIG_SYS_FLASH_CFI:
2916                Define if the flash driver uses extra elements in the
2917                common flash structure for storing flash geometry.
2918
2919- CONFIG_FLASH_CFI_DRIVER
2920                This option also enables the building of the cfi_flash driver
2921                in the drivers directory
2922
2923- CONFIG_FLASH_CFI_MTD
2924                This option enables the building of the cfi_mtd driver
2925                in the drivers directory. The driver exports CFI flash
2926                to the MTD layer.
2927
2928- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2929                Use buffered writes to flash.
2930
2931- CONFIG_FLASH_SPANSION_S29WS_N
2932                s29ws-n MirrorBit flash has non-standard addresses for buffered
2933                write commands.
2934
2935- CONFIG_SYS_FLASH_QUIET_TEST
2936                If this option is defined, the common CFI flash doesn't
2937                print it's warning upon not recognized FLASH banks. This
2938                is useful, if some of the configured banks are only
2939                optionally available.
2940
2941- CONFIG_FLASH_SHOW_PROGRESS
2942                If defined (must be an integer), print out countdown
2943                digits and dots.  Recommended value: 45 (9..1) for 80
2944                column displays, 15 (3..1) for 40 column displays.
2945
2946- CONFIG_FLASH_VERIFY
2947                If defined, the content of the flash (destination) is compared
2948                against the source after the write operation. An error message
2949                will be printed when the contents are not identical.
2950                Please note that this option is useless in nearly all cases,
2951                since such flash programming errors usually are detected earlier
2952                while unprotecting/erasing/programming. Please only enable
2953                this option if you really know what you are doing.
2954
2955- CONFIG_SYS_RX_ETH_BUFFER:
2956                Defines the number of Ethernet receive buffers. On some
2957                Ethernet controllers it is recommended to set this value
2958                to 8 or even higher (EEPRO100 or 405 EMAC), since all
2959                buffers can be full shortly after enabling the interface
2960                on high Ethernet traffic.
2961                Defaults to 4 if not defined.
2962
2963- CONFIG_ENV_MAX_ENTRIES
2964
2965        Maximum number of entries in the hash table that is used
2966        internally to store the environment settings. The default
2967        setting is supposed to be generous and should work in most
2968        cases. This setting can be used to tune behaviour; see
2969        lib/hashtable.c for details.
2970
2971- CONFIG_ENV_FLAGS_LIST_DEFAULT
2972- CONFIG_ENV_FLAGS_LIST_STATIC
2973        Enable validation of the values given to environment variables when
2974        calling env set.  Variables can be restricted to only decimal,
2975        hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2976        the variables can also be restricted to IP address or MAC address.
2977
2978        The format of the list is:
2979                type_attribute = [s|d|x|b|i|m]
2980                access_attribute = [a|r|o|c]
2981                attributes = type_attribute[access_attribute]
2982                entry = variable_name[:attributes]
2983                list = entry[,list]
2984
2985        The type attributes are:
2986                s - String (default)
2987                d - Decimal
2988                x - Hexadecimal
2989                b - Boolean ([1yYtT|0nNfF])
2990                i - IP address
2991                m - MAC address
2992
2993        The access attributes are:
2994                a - Any (default)
2995                r - Read-only
2996                o - Write-once
2997                c - Change-default
2998
2999        - CONFIG_ENV_FLAGS_LIST_DEFAULT
3000                Define this to a list (string) to define the ".flags"
3001                environment variable in the default or embedded environment.
3002
3003        - CONFIG_ENV_FLAGS_LIST_STATIC
3004                Define this to a list (string) to define validation that
3005                should be done if an entry is not found in the ".flags"
3006                environment variable.  To override a setting in the static
3007                list, simply add an entry for the same variable name to the
3008                ".flags" variable.
3009
3010        If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3011        regular expression. This allows multiple variables to define the same
3012        flags without explicitly listing them for each variable.
3013
3014- CONFIG_ENV_ACCESS_IGNORE_FORCE
3015        If defined, don't allow the -f switch to env set override variable
3016        access flags.
3017
3018- CONFIG_USE_STDINT
3019        If stdint.h is available with your toolchain you can define this
3020        option to enable it. You can provide option 'USE_STDINT=1' when
3021        building U-Boot to enable this.
3022
3023The following definitions that deal with the placement and management
3024of environment data (variable area); in general, we support the
3025following configurations:
3026
3027- CONFIG_BUILD_ENVCRC:
3028
3029        Builds up envcrc with the target environment so that external utils
3030        may easily extract it and embed it in final U-Boot images.
3031
3032BE CAREFUL! The first access to the environment happens quite early
3033in U-Boot initialization (when we try to get the setting of for the
3034console baudrate). You *MUST* have mapped your NVRAM area then, or
3035U-Boot will hang.
3036
3037Please note that even with NVRAM we still use a copy of the
3038environment in RAM: we could work on NVRAM directly, but we want to
3039keep settings there always unmodified except somebody uses "saveenv"
3040to save the current settings.
3041
3042BE CAREFUL! For some special cases, the local device can not use
3043"saveenv" command. For example, the local device will get the
3044environment stored in a remote NOR flash by SRIO or PCIE link,
3045but it can not erase, write this NOR flash by SRIO or PCIE interface.
3046
3047- CONFIG_NAND_ENV_DST
3048
3049        Defines address in RAM to which the nand_spl code should copy the
3050        environment. If redundant environment is used, it will be copied to
3051        CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3052
3053Please note that the environment is read-only until the monitor
3054has been relocated to RAM and a RAM copy of the environment has been
3055created; also, when using EEPROM you will have to use env_get_f()
3056until then to read environment variables.
3057
3058The environment is protected by a CRC32 checksum. Before the monitor
3059is relocated into RAM, as a result of a bad CRC you will be working
3060with the compiled-in default environment - *silently*!!! [This is
3061necessary, because the first environment variable we need is the
3062"baudrate" setting for the console - if we have a bad CRC, we don't
3063have any device yet where we could complain.]
3064
3065Note: once the monitor has been relocated, then it will complain if
3066the default environment is used; a new CRC is computed as soon as you
3067use the "saveenv" command to store a valid environment.
3068
3069- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3070                Echo the inverted Ethernet link state to the fault LED.
3071
3072                Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3073                      also needs to be defined.
3074
3075- CONFIG_SYS_FAULT_MII_ADDR:
3076                MII address of the PHY to check for the Ethernet link state.
3077
3078- CONFIG_NS16550_MIN_FUNCTIONS:
3079                Define this if you desire to only have use of the NS16550_init
3080                and NS16550_putc functions for the serial driver located at
3081                drivers/serial/ns16550.c.  This option is useful for saving
3082                space for already greatly restricted images, including but not
3083                limited to NAND_SPL configurations.
3084
3085- CONFIG_DISPLAY_BOARDINFO
3086                Display information about the board that U-Boot is running on
3087                when U-Boot starts up. The board function checkboard() is called
3088                to do this.
3089
3090- CONFIG_DISPLAY_BOARDINFO_LATE
3091                Similar to the previous option, but display this information
3092                later, once stdio is running and output goes to the LCD, if
3093                present.
3094
3095- CONFIG_BOARD_SIZE_LIMIT:
3096                Maximum size of the U-Boot image. When defined, the
3097                build system checks that the actual size does not
3098                exceed it.
3099
3100Low Level (hardware related) configuration options:
3101---------------------------------------------------
3102
3103- CONFIG_SYS_CACHELINE_SIZE:
3104                Cache Line Size of the CPU.
3105
3106- CONFIG_SYS_CCSRBAR_DEFAULT:
3107                Default (power-on reset) physical address of CCSR on Freescale
3108                PowerPC SOCs.
3109
3110- CONFIG_SYS_CCSRBAR:
3111                Virtual address of CCSR.  On a 32-bit build, this is typically
3112                the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3113
3114- CONFIG_SYS_CCSRBAR_PHYS:
3115                Physical address of CCSR.  CCSR can be relocated to a new
3116                physical address, if desired.  In this case, this macro should
3117                be set to that address.  Otherwise, it should be set to the
3118                same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3119                is typically relocated on 36-bit builds.  It is recommended
3120                that this macro be defined via the _HIGH and _LOW macros:
3121
3122                #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3123                        * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3124
3125- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3126                Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.  This value is typically
3127                either 0 (32-bit build) or 0xF (36-bit build).  This macro is
3128                used in assembly code, so it must not contain typecasts or
3129                integer size suffixes (e.g. "ULL").
3130
3131- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3132                Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3133                used in assembly code, so it must not contain typecasts or
3134                integer size suffixes (e.g. "ULL").
3135
3136- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3137                If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3138                forced to a value that ensures that CCSR is not relocated.
3139
3140- Floppy Disk Support:
3141                CONFIG_SYS_FDC_DRIVE_NUMBER
3142
3143                the default drive number (default value 0)
3144
3145                CONFIG_SYS_ISA_IO_STRIDE
3146
3147                defines the spacing between FDC chipset registers
3148                (default value 1)
3149
3150                CONFIG_SYS_ISA_IO_OFFSET
3151
3152                defines the offset of register from address. It
3153                depends on which part of the data bus is connected to
3154                the FDC chipset. (default value 0)
3155
3156                If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3157                CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3158                default value.
3159
3160                if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3161                fdc_hw_init() is called at the beginning of the FDC
3162                setup. fdc_hw_init() must be provided by the board
3163                source code. It is used to make hardware-dependent
3164                initializations.
3165
3166- CONFIG_IDE_AHB:
3167                Most IDE controllers were designed to be connected with PCI
3168                interface. Only few of them were designed for AHB interface.
3169                When software is doing ATA command and data transfer to
3170                IDE devices through IDE-AHB controller, some additional
3171                registers accessing to these kind of IDE-AHB controller
3172                is required.
3173
3174- CONFIG_SYS_IMMR:      Physical address of the Internal Memory.
3175                DO NOT CHANGE unless you know exactly what you're
3176                doing! (11-4) [MPC8xx systems only]
3177
3178- CONFIG_SYS_INIT_RAM_ADDR:
3179
3180                Start address of memory area that can be used for
3181                initial data and stack; please note that this must be
3182                writable memory that is working WITHOUT special
3183                initialization, i. e. you CANNOT use normal RAM which
3184                will become available only after programming the
3185                memory controller and running certain initialization
3186                sequences.
3187
3188                U-Boot uses the following memory types:
3189                - MPC8xx: IMMR (internal memory of the CPU)
3190
3191- CONFIG_SYS_GBL_DATA_OFFSET:
3192
3193                Offset of the initial data structure in the memory
3194                area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3195                CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3196                data is located at the end of the available space
3197                (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3198                GENERATED_GBL_DATA_SIZE), and the initial stack is just
3199                below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3200                CONFIG_SYS_GBL_DATA_OFFSET) downward.
3201
3202        Note:
3203                On the MPC824X (or other systems that use the data
3204                cache for initial memory) the address chosen for
3205                CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3206                point to an otherwise UNUSED address space between
3207                the top of RAM and the start of the PCI space.
3208
3209- CONFIG_SYS_SCCR:      System Clock and reset Control Register (15-27)
3210
3211- CONFIG_SYS_OR_TIMING_SDRAM:
3212                SDRAM timing
3213
3214- CONFIG_SYS_MAMR_PTA:
3215                periodic timer for refresh
3216
3217- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3218  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3219  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3220  CONFIG_SYS_BR1_PRELIM:
3221                Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3222
3223- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3224  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3225  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3226                Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3227
3228- CONFIG_PCI_ENUM_ONLY
3229                Only scan through and get the devices on the buses.
3230                Don't do any setup work, presumably because someone or
3231                something has already done it, and we don't need to do it
3232                a second time.  Useful for platforms that are pre-booted
3233                by coreboot or similar.
3234
3235- CONFIG_PCI_INDIRECT_BRIDGE:
3236                Enable support for indirect PCI bridges.
3237
3238- CONFIG_SYS_SRIO:
3239                Chip has SRIO or not
3240
3241- CONFIG_SRIO1:
3242                Board has SRIO 1 port available
3243
3244- CONFIG_SRIO2:
3245                Board has SRIO 2 port available
3246
3247- CONFIG_SRIO_PCIE_BOOT_MASTER
3248                Board can support master function for Boot from SRIO and PCIE
3249
3250- CONFIG_SYS_SRIOn_MEM_VIRT:
3251                Virtual Address of SRIO port 'n' memory region
3252
3253- CONFIG_SYS_SRIOn_MEM_PHYS:
3254                Physical Address of SRIO port 'n' memory region
3255
3256- CONFIG_SYS_SRIOn_MEM_SIZE:
3257                Size of SRIO port 'n' memory region
3258
3259- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3260                Defined to tell the NAND controller that the NAND chip is using
3261                a 16 bit bus.
3262                Not all NAND drivers use this symbol.
3263                Example of drivers that use it:
3264                - drivers/mtd/nand/ndfc.c
3265                - drivers/mtd/nand/mxc_nand.c
3266
3267- CONFIG_SYS_NDFC_EBC0_CFG
3268                Sets the EBC0_CFG register for the NDFC. If not defined
3269                a default value will be used.
3270
3271- CONFIG_SPD_EEPROM
3272                Get DDR timing information from an I2C EEPROM. Common
3273                with pluggable memory modules such as SODIMMs
3274
3275  SPD_EEPROM_ADDRESS
3276                I2C address of the SPD EEPROM
3277
3278- CONFIG_SYS_SPD_BUS_NUM
3279                If SPD EEPROM is on an I2C bus other than the first
3280                one, specify here. Note that the value must resolve
3281                to something your driver can deal with.
3282
3283- CONFIG_SYS_DDR_RAW_TIMING
3284                Get DDR timing information from other than SPD. Common with
3285                soldered DDR chips onboard without SPD. DDR raw timing
3286                parameters are extracted from datasheet and hard-coded into
3287                header files or board specific files.
3288
3289- CONFIG_FSL_DDR_INTERACTIVE
3290                Enable interactive DDR debugging. See doc/README.fsl-ddr.
3291
3292- CONFIG_FSL_DDR_SYNC_REFRESH
3293                Enable sync of refresh for multiple controllers.
3294
3295- CONFIG_FSL_DDR_BIST
3296                Enable built-in memory test for Freescale DDR controllers.
3297
3298- CONFIG_SYS_83XX_DDR_USES_CS0
3299                Only for 83xx systems. If specified, then DDR should
3300                be configured using CS0 and CS1 instead of CS2 and CS3.
3301
3302- CONFIG_RMII
3303                Enable RMII mode for all FECs.
3304                Note that this is a global option, we can't
3305                have one FEC in standard MII mode and another in RMII mode.
3306
3307- CONFIG_CRC32_VERIFY
3308                Add a verify option to the crc32 command.
3309                The syntax is:
3310
3311                => crc32 -v <address> <count> <crc32>
3312
3313                Where address/count indicate a memory area
3314                and crc32 is the correct crc32 which the
3315                area should have.
3316
3317- CONFIG_LOOPW
3318                Add the "loopw" memory command. This only takes effect if
3319                the memory commands are activated globally (CONFIG_CMD_MEMORY).
3320
3321- CONFIG_MX_CYCLIC
3322                Add the "mdc" and "mwc" memory commands. These are cyclic
3323                "md/mw" commands.
3324                Examples:
3325
3326                => mdc.b 10 4 500
3327                This command will print 4 bytes (10,11,12,13) each 500 ms.
3328
3329                => mwc.l 100 12345678 10
3330                This command will write 12345678 to address 100 all 10 ms.
3331
3332                This only takes effect if the memory commands are activated
3333                globally (CONFIG_CMD_MEMORY).
3334
3335- CONFIG_SKIP_LOWLEVEL_INIT
3336                [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3337                low level initializations (like setting up the memory
3338                controller) are omitted and/or U-Boot does not
3339                relocate itself into RAM.
3340
3341                Normally this variable MUST NOT be defined. The only
3342                exception is when U-Boot is loaded (to RAM) by some
3343                other boot loader or by a debugger which performs
3344                these initializations itself.
3345
3346- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3347                [ARM926EJ-S only] This allows just the call to lowlevel_init()
3348                to be skipped. The normal CP15 init (such as enabling the
3349                instruction cache) is still performed.
3350
3351- CONFIG_SPL_BUILD
3352                Modifies the behaviour of start.S when compiling a loader
3353                that is executed before the actual U-Boot. E.g. when
3354                compiling a NAND SPL.
3355
3356- CONFIG_TPL_BUILD
3357                Modifies the behaviour of start.S  when compiling a loader
3358                that is executed after the SPL and before the actual U-Boot.
3359                It is loaded by the SPL.
3360
3361- CONFIG_SYS_MPC85XX_NO_RESETVEC
3362                Only for 85xx systems. If this variable is specified, the section
3363                .resetvec is not kept and the section .bootpg is placed in the
3364                previous 4k of the .text section.
3365
3366- CONFIG_ARCH_MAP_SYSMEM
3367                Generally U-Boot (and in particular the md command) uses
3368                effective address. It is therefore not necessary to regard
3369                U-Boot address as virtual addresses that need to be translated
3370                to physical addresses. However, sandbox requires this, since
3371                it maintains its own little RAM buffer which contains all
3372                addressable memory. This option causes some memory accesses
3373                to be mapped through map_sysmem() / unmap_sysmem().
3374
3375- CONFIG_X86_RESET_VECTOR
3376                If defined, the x86 reset vector code is included. This is not
3377                needed when U-Boot is running from Coreboot.
3378
3379- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3380                Option to disable subpage write in NAND driver
3381                driver that uses this:
3382                drivers/mtd/nand/davinci_nand.c
3383
3384Freescale QE/FMAN Firmware Support:
3385-----------------------------------
3386
3387The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3388loading of "firmware", which is encoded in the QE firmware binary format.
3389This firmware often needs to be loaded during U-Boot booting, so macros
3390are used to identify the storage device (NOR flash, SPI, etc) and the address
3391within that device.
3392
3393- CONFIG_SYS_FMAN_FW_ADDR
3394        The address in the storage device where the FMAN microcode is located.  The
3395        meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3396        is also specified.
3397
3398- CONFIG_SYS_QE_FW_ADDR
3399        The address in the storage device where the QE microcode is located.  The
3400        meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3401        is also specified.
3402
3403- CONFIG_SYS_QE_FMAN_FW_LENGTH
3404        The maximum possible size of the firmware.  The firmware binary format
3405        has a field that specifies the actual size of the firmware, but it
3406        might not be possible to read any part of the firmware unless some
3407        local storage is allocated to hold the entire firmware first.
3408
3409- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3410        Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3411        normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3412        virtual address in NOR flash.
3413
3414- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3415        Specifies that QE/FMAN firmware is located in NAND flash.
3416        CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3417
3418- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3419        Specifies that QE/FMAN firmware is located on the primary SD/MMC
3420        device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3421
3422- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3423        Specifies that QE/FMAN firmware is located in the remote (master)
3424        memory space.   CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3425        can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3426        window->master inbound window->master LAW->the ucode address in
3427        master's memory space.
3428
3429Freescale Layerscape Management Complex Firmware Support:
3430---------------------------------------------------------
3431The Freescale Layerscape Management Complex (MC) supports the loading of
3432"firmware".
3433This firmware often needs to be loaded during U-Boot booting, so macros
3434are used to identify the storage device (NOR flash, SPI, etc) and the address
3435within that device.
3436
3437- CONFIG_FSL_MC_ENET
3438        Enable the MC driver for Layerscape SoCs.
3439
3440Freescale Layerscape Debug Server Support:
3441-------------------------------------------
3442The Freescale Layerscape Debug Server Support supports the loading of
3443"Debug Server firmware" and triggering SP boot-rom.
3444This firmware often needs to be loaded during U-Boot booting.
3445
3446- CONFIG_SYS_MC_RSV_MEM_ALIGN
3447        Define alignment of reserved memory MC requires
3448
3449Reproducible builds
3450-------------------
3451
3452In order to achieve reproducible builds, timestamps used in the U-Boot build
3453process have to be set to a fixed value.
3454
3455This is done using the SOURCE_DATE_EPOCH environment variable.
3456SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3457option for U-Boot or an environment variable in U-Boot.
3458
3459SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3460
3461Building the Software:
3462======================
3463
3464Building U-Boot has been tested in several native build environments
3465and in many different cross environments. Of course we cannot support
3466all possibly existing versions of cross development tools in all
3467(potentially obsolete) versions. In case of tool chain problems we
3468recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3469which is extensively used to build and test U-Boot.
3470
3471If you are not using a native environment, it is assumed that you
3472have GNU cross compiling tools available in your path. In this case,
3473you must set the environment variable CROSS_COMPILE in your shell.
3474Note that no changes to the Makefile or any other source files are
3475necessary. For example using the ELDK on a 4xx CPU, please enter:
3476
3477        $ CROSS_COMPILE=ppc_4xx-
3478        $ export CROSS_COMPILE
3479
3480Note: If you wish to generate Windows versions of the utilities in
3481      the tools directory you can use the MinGW toolchain
3482      (http://www.mingw.org).  Set your HOST tools to the MinGW
3483      toolchain and execute 'make tools'.  For example:
3484
3485       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3486
3487      Binaries such as tools/mkimage.exe will be created which can
3488      be executed on computers running Windows.
3489
3490U-Boot is intended to be simple to build. After installing the
3491sources you must configure U-Boot for one specific board type. This
3492is done by typing:
3493
3494        make NAME_defconfig
3495
3496where "NAME_defconfig" is the name of one of the existing configu-
3497rations; see boards.cfg for supported names.
3498
3499Note: for some board special configuration names may exist; check if
3500      additional information is available from the board vendor; for
3501      instance, the TQM823L systems are available without (standard)
3502      or with LCD support. You can select such additional "features"
3503      when choosing the configuration, i. e.
3504
3505      make TQM823L_defconfig
3506        - will configure for a plain TQM823L, i. e. no LCD support
3507
3508      make TQM823L_LCD_defconfig
3509        - will configure for a TQM823L with U-Boot console on LCD
3510
3511      etc.
3512
3513
3514Finally, type "make all", and you should get some working U-Boot
3515images ready for download to / installation on your system:
3516
3517- "u-boot.bin" is a raw binary image
3518- "u-boot" is an image in ELF binary format
3519- "u-boot.srec" is in Motorola S-Record format
3520
3521By default the build is performed locally and the objects are saved
3522in the source directory. One of the two methods can be used to change
3523this behavior and build U-Boot to some external directory:
3524
35251. Add O= to the make command line invocations:
3526
3527        make O=/tmp/build distclean
3528        make O=/tmp/build NAME_defconfig
3529        make O=/tmp/build all
3530
35312. Set environment variable KBUILD_OUTPUT to point to the desired location:
3532
3533        export KBUILD_OUTPUT=/tmp/build
3534        make distclean
3535        make NAME_defconfig
3536        make all
3537
3538Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3539variable.
3540
3541User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3542setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3543For example to treat all compiler warnings as errors:
3544
3545        make KCFLAGS=-Werror
3546
3547Please be aware that the Makefiles assume you are using GNU make, so
3548for instance on NetBSD you might need to use "gmake" instead of
3549native "make".
3550
3551
3552If the system board that you have is not listed, then you will need
3553to port U-Boot to your hardware platform. To do this, follow these
3554steps:
3555
35561.  Create a new directory to hold your board specific code. Add any
3557    files you need. In your board directory, you will need at least
3558    the "Makefile" and a "<board>.c".
35592.  Create a new configuration file "include/configs/<board>.h" for
3560    your board.
35613.  If you're porting U-Boot to a new CPU, then also create a new
3562    directory to hold your CPU specific code. Add any files you need.
35634.  Run "make <board>_defconfig" with your new name.
35645.  Type "make", and you should get a working "u-boot.srec" file
3565    to be installed on your target system.
35666.  Debug and solve any problems that might arise.
3567    [Of course, this last step is much harder than it sounds.]
3568
3569
3570Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3571==============================================================
3572
3573If you have modified U-Boot sources (for instance added a new board
3574or support for new devices, a new CPU, etc.) you are expected to
3575provide feedback to the other developers. The feedback normally takes
3576the form of a "patch", i. e. a context diff against a certain (latest
3577official or latest in the git repository) version of U-Boot sources.
3578
3579But before you submit such a patch, please verify that your modifi-
3580cation did not break existing code. At least make sure that *ALL* of
3581the supported boards compile WITHOUT ANY compiler warnings. To do so,
3582just run the buildman script (tools/buildman/buildman), which will
3583configure and build U-Boot for ALL supported system. Be warned, this
3584will take a while. Please see the buildman README, or run 'buildman -H'
3585for documentation.
3586
3587
3588See also "U-Boot Porting Guide" below.
3589
3590
3591Monitor Commands - Overview:
3592============================
3593
3594go      - start application at address 'addr'
3595run     - run commands in an environment variable
3596bootm   - boot application image from memory
3597bootp   - boot image via network using BootP/TFTP protocol
3598bootz   - boot zImage from memory
3599tftpboot- boot image via network using TFTP protocol
3600               and env variables "ipaddr" and "serverip"
3601               (and eventually "gatewayip")
3602tftpput - upload a file via network using TFTP protocol
3603rarpboot- boot image via network using RARP/TFTP protocol
3604diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3605loads   - load S-Record file over serial line
3606loadb   - load binary file over serial line (kermit mode)
3607md      - memory display
3608mm      - memory modify (auto-incrementing)
3609nm      - memory modify (constant address)
3610mw      - memory write (fill)
3611cp      - memory copy
3612cmp     - memory compare
3613crc32   - checksum calculation
3614i2c     - I2C sub-system
3615sspi    - SPI utility commands
3616base    - print or set address offset
3617printenv- print environment variables
3618setenv  - set environment variables
3619saveenv - save environment variables to persistent storage
3620protect - enable or disable FLASH write protection
3621erase   - erase FLASH memory
3622flinfo  - print FLASH memory information
3623nand    - NAND memory operations (see doc/README.nand)
3624bdinfo  - print Board Info structure
3625iminfo  - print header information for application image
3626coninfo - print console devices and informations
3627ide     - IDE sub-system
3628loop    - infinite loop on address range
3629loopw   - infinite write loop on address range
3630mtest   - simple RAM test
3631icache  - enable or disable instruction cache
3632dcache  - enable or disable data cache
3633reset   - Perform RESET of the CPU
3634echo    - echo args to console
3635version - print monitor version
3636help    - print online help
3637?       - alias for 'help'
3638
3639
3640Monitor Commands - Detailed Description:
3641========================================
3642
3643TODO.
3644
3645For now: just type "help <command>".
3646
3647
3648Environment Variables:
3649======================
3650
3651U-Boot supports user configuration using Environment Variables which
3652can be made persistent by saving to Flash memory.
3653
3654Environment Variables are set using "setenv", printed using
3655"printenv", and saved to Flash using "saveenv". Using "setenv"
3656without a value can be used to delete a variable from the
3657environment. As long as you don't save the environment you are
3658working with an in-memory copy. In case the Flash area containing the
3659environment is erased by accident, a default environment is provided.
3660
3661Some configuration options can be set using Environment Variables.
3662
3663List of environment variables (most likely not complete):
3664
3665  baudrate      - see CONFIG_BAUDRATE
3666
3667  bootdelay     - see CONFIG_BOOTDELAY
3668
3669  bootcmd       - see CONFIG_BOOTCOMMAND
3670
3671  bootargs      - Boot arguments when booting an RTOS image
3672
3673  bootfile      - Name of the image to load with TFTP
3674
3675  bootm_low     - Memory range available for image processing in the bootm
3676                  command can be restricted. This variable is given as
3677                  a hexadecimal number and defines lowest address allowed
3678                  for use by the bootm command. See also "bootm_size"
3679                  environment variable. Address defined by "bootm_low" is
3680                  also the base of the initial memory mapping for the Linux
3681                  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3682                  bootm_mapsize.
3683
3684  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3685                  This variable is given as a hexadecimal number and it
3686                  defines the size of the memory region starting at base
3687                  address bootm_low that is accessible by the Linux kernel
3688                  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3689                  as the default value if it is defined, and bootm_size is
3690                  used otherwise.
3691
3692  bootm_size    - Memory range available for image processing in the bootm
3693                  command can be restricted. This variable is given as
3694                  a hexadecimal number and defines the size of the region
3695                  allowed for use by the bootm command. See also "bootm_low"
3696                  environment variable.
3697
3698  updatefile    - Location of the software update file on a TFTP server, used
3699                  by the automatic software update feature. Please refer to
3700                  documentation in doc/README.update for more details.
3701
3702  autoload      - if set to "no" (any string beginning with 'n'),
3703                  "bootp" will just load perform a lookup of the
3704                  configuration from the BOOTP server, but not try to
3705                  load any image using TFTP
3706
3707  autostart     - if set to "yes", an image loaded using the "bootp",
3708                  "rarpboot", "tftpboot" or "diskboot" commands will
3709                  be automatically started (by internally calling
3710                  "bootm")
3711
3712                  If set to "no", a standalone image passed to the
3713                  "bootm" command will be copied to the load address
3714                  (and eventually uncompressed), but NOT be started.
3715                  This can be used to load and uncompress arbitrary
3716                  data.
3717
3718  fdt_high      - if set this restricts the maximum address that the
3719                  flattened device tree will be copied into upon boot.
3720                  For example, if you have a system with 1 GB memory
3721                  at physical address 0x10000000, while Linux kernel
3722                  only recognizes the first 704 MB as low memory, you
3723                  may need to set fdt_high as 0x3C000000 to have the
3724                  device tree blob be copied to the maximum address
3725                  of the 704 MB low memory, so that Linux kernel can
3726                  access it during the boot procedure.
3727
3728                  If this is set to the special value 0xFFFFFFFF then
3729                  the fdt will not be copied at all on boot.  For this
3730                  to work it must reside in writable memory, have
3731                  sufficient padding on the end of it for u-boot to
3732                  add the information it needs into it, and the memory
3733                  must be accessible by the kernel.
3734
3735  fdtcontroladdr- if set this is the address of the control flattened
3736                  device tree used by U-Boot when CONFIG_OF_CONTROL is
3737                  defined.
3738
3739  i2cfast       - (PPC405GP|PPC405EP only)
3740                  if set to 'y' configures Linux I2C driver for fast
3741                  mode (400kHZ). This environment variable is used in
3742                  initialization code. So, for changes to be effective
3743                  it must be saved and board must be reset.
3744
3745  initrd_high   - restrict positioning of initrd images:
3746                  If this variable is not set, initrd images will be
3747                  copied to the highest possible address in RAM; this
3748                  is usually what you want since it allows for
3749                  maximum initrd size. If for some reason you want to
3750                  make sure that the initrd image is loaded below the
3751                  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3752                  variable to a value of "no" or "off" or "0".
3753                  Alternatively, you can set it to a maximum upper
3754                  address to use (U-Boot will still check that it
3755                  does not overwrite the U-Boot stack and data).
3756
3757                  For instance, when you have a system with 16 MB
3758                  RAM, and want to reserve 4 MB from use by Linux,
3759                  you can do this by adding "mem=12M" to the value of
3760                  the "bootargs" variable. However, now you must make
3761                  sure that the initrd image is placed in the first
3762                  12 MB as well - this can be done with
3763
3764                  setenv initrd_high 00c00000
3765
3766                  If you set initrd_high to 0xFFFFFFFF, this is an
3767                  indication to U-Boot that all addresses are legal
3768                  for the Linux kernel, including addresses in flash
3769                  memory. In this case U-Boot will NOT COPY the
3770                  ramdisk at all. This may be useful to reduce the
3771                  boot time on your system, but requires that this
3772                  feature is supported by your Linux kernel.
3773
3774  ipaddr        - IP address; needed for tftpboot command
3775
3776  loadaddr      - Default load address for commands like "bootp",
3777                  "rarpboot", "tftpboot", "loadb" or "diskboot"
3778
3779  loads_echo    - see CONFIG_LOADS_ECHO
3780
3781  serverip      - TFTP server IP address; needed for tftpboot command
3782
3783  bootretry     - see CONFIG_BOOT_RETRY_TIME
3784
3785  bootdelaykey  - see CONFIG_AUTOBOOT_DELAY_STR
3786
3787  bootstopkey   - see CONFIG_AUTOBOOT_STOP_STR
3788
3789  ethprime      - controls which interface is used first.
3790
3791  ethact        - controls which interface is currently active.
3792                  For example you can do the following
3793
3794                  => setenv ethact FEC
3795                  => ping 192.168.0.1 # traffic sent on FEC
3796                  => setenv ethact SCC
3797                  => ping 10.0.0.1 # traffic sent on SCC
3798
3799  ethrotate     - When set to "no" U-Boot does not go through all
3800                  available network interfaces.
3801                  It just stays at the currently selected interface.
3802
3803  netretry      - When set to "no" each network operation will
3804                  either succeed or fail without retrying.
3805                  When set to "once" the network operation will
3806                  fail when all the available network interfaces
3807                  are tried once without success.
3808                  Useful on scripts which control the retry operation
3809                  themselves.
3810
3811  npe_ucode     - set load address for the NPE microcode
3812
3813  silent_linux  - If set then Linux will be told to boot silently, by
3814                  changing the console to be empty. If "yes" it will be
3815                  made silent. If "no" it will not be made silent. If
3816                  unset, then it will be made silent if the U-Boot console
3817                  is silent.
3818
3819  tftpsrcp      - If this is set, the value is used for TFTP's
3820                  UDP source port.
3821
3822  tftpdstp      - If this is set, the value is used for TFTP's UDP
3823                  destination port instead of the Well Know Port 69.
3824
3825  tftpblocksize - Block size to use for TFTP transfers; if not set,
3826                  we use the TFTP server's default block size
3827
3828  tftptimeout   - Retransmission timeout for TFTP packets (in milli-
3829                  seconds, minimum value is 1000 = 1 second). Defines
3830                  when a packet is considered to be lost so it has to
3831                  be retransmitted. The default is 5000 = 5 seconds.
3832                  Lowering this value may make downloads succeed
3833                  faster in networks with high packet loss rates or
3834                  with unreliable TFTP servers.
3835
3836  tftptimeoutcountmax   - maximum count of TFTP timeouts (no
3837                  unit, minimum value = 0). Defines how many timeouts
3838                  can happen during a single file transfer before that
3839                  transfer is aborted. The default is 10, and 0 means
3840                  'no timeouts allowed'. Increasing this value may help
3841                  downloads succeed with high packet loss rates, or with
3842                  unreliable TFTP servers or client hardware.
3843
3844  vlan          - When set to a value < 4095 the traffic over
3845                  Ethernet is encapsulated/received over 802.1q
3846                  VLAN tagged frames.
3847
3848  bootpretryperiod      - Period during which BOOTP/DHCP sends retries.
3849                  Unsigned value, in milliseconds. If not set, the period will
3850                  be either the default (28000), or a value based on
3851                  CONFIG_NET_RETRY_COUNT, if defined. This value has
3852                  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3853
3854The following image location variables contain the location of images
3855used in booting. The "Image" column gives the role of the image and is
3856not an environment variable name. The other columns are environment
3857variable names. "File Name" gives the name of the file on a TFTP
3858server, "RAM Address" gives the location in RAM the image will be
3859loaded to, and "Flash Location" gives the image's address in NOR
3860flash or offset in NAND flash.
3861
3862*Note* - these variables don't have to be defined for all boards, some
3863boards currently use other variables for these purposes, and some
3864boards use these variables for other purposes.
3865
3866Image               File Name        RAM Address       Flash Location
3867-----               ---------        -----------       --------------
3868u-boot              u-boot           u-boot_addr_r     u-boot_addr
3869Linux kernel        bootfile         kernel_addr_r     kernel_addr
3870device tree blob    fdtfile          fdt_addr_r        fdt_addr
3871ramdisk             ramdiskfile      ramdisk_addr_r    ramdisk_addr
3872
3873The following environment variables may be used and automatically
3874updated by the network boot commands ("bootp" and "rarpboot"),
3875depending the information provided by your boot server:
3876
3877  bootfile      - see above
3878  dnsip         - IP address of your Domain Name Server
3879  dnsip2        - IP address of your secondary Domain Name Server
3880  gatewayip     - IP address of the Gateway (Router) to use
3881  hostname      - Target hostname
3882  ipaddr        - see above
3883  netmask       - Subnet Mask
3884  rootpath      - Pathname of the root filesystem on the NFS server
3885  serverip      - see above
3886
3887
3888There are two special Environment Variables:
3889
3890  serial#       - contains hardware identification information such
3891                  as type string and/or serial number
3892  ethaddr       - Ethernet address
3893
3894These variables can be set only once (usually during manufacturing of
3895the board). U-Boot refuses to delete or overwrite these variables
3896once they have been set once.
3897
3898
3899Further special Environment Variables:
3900
3901  ver           - Contains the U-Boot version string as printed
3902                  with the "version" command. This variable is
3903                  readonly (see CONFIG_VERSION_VARIABLE).
3904
3905
3906Please note that changes to some configuration parameters may take
3907only effect after the next boot (yes, that's just like Windoze :-).
3908
3909
3910Callback functions for environment variables:
3911---------------------------------------------
3912
3913For some environment variables, the behavior of u-boot needs to change
3914when their values are changed.  This functionality allows functions to
3915be associated with arbitrary variables.  On creation, overwrite, or
3916deletion, the callback will provide the opportunity for some side
3917effect to happen or for the change to be rejected.
3918
3919The callbacks are named and associated with a function using the
3920U_BOOT_ENV_CALLBACK macro in your board or driver code.
3921
3922These callbacks are associated with variables in one of two ways.  The
3923static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3924in the board configuration to a string that defines a list of
3925associations.  The list must be in the following format:
3926
3927        entry = variable_name[:callback_name]
3928        list = entry[,list]
3929
3930If the callback name is not specified, then the callback is deleted.
3931Spaces are also allowed anywhere in the list.
3932
3933Callbacks can also be associated by defining the ".callbacks" variable
3934with the same list format above.  Any association in ".callbacks" will
3935override any association in the static list. You can define
3936CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3937".callbacks" environment variable in the default or embedded environment.
3938
3939If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3940regular expression. This allows multiple variables to be connected to
3941the same callback without explicitly listing them all out.
3942
3943The signature of the callback functions is:
3944
3945    int callback(const char *name, const char *value, enum env_op op, int flags)
3946
3947* name - changed environment variable
3948* value - new value of the environment variable
3949* op - operation (create, overwrite, or delete)
3950* flags - attributes of the environment variable change, see flags H_* in
3951  include/search.h
3952
3953The return value is 0 if the variable change is accepted and 1 otherwise.
3954
3955Command Line Parsing:
3956=====================
3957
3958There are two different command line parsers available with U-Boot:
3959the old "simple" one, and the much more powerful "hush" shell:
3960
3961Old, simple command line parser:
3962--------------------------------
3963
3964- supports environment variables (through setenv / saveenv commands)
3965- several commands on one line, separated by ';'
3966- variable substitution using "... ${name} ..." syntax
3967- special characters ('$', ';') can be escaped by prefixing with '\',
3968  for example:
3969        setenv bootcmd bootm \${address}
3970- You can also escape text by enclosing in single apostrophes, for example:
3971        setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3972
3973Hush shell:
3974-----------
3975
3976- similar to Bourne shell, with control structures like
3977  if...then...else...fi, for...do...done; while...do...done,
3978  until...do...done, ...
3979- supports environment ("global") variables (through setenv / saveenv
3980  commands) and local shell variables (through standard shell syntax
3981  "name=value"); only environment variables can be used with "run"
3982  command
3983
3984General rules:
3985--------------
3986
3987(1) If a command line (or an environment variable executed by a "run"
3988    command) contains several commands separated by semicolon, and
3989    one of these commands fails, then the remaining commands will be
3990    executed anyway.
3991
3992(2) If you execute several variables with one call to run (i. e.
3993    calling run with a list of variables as arguments), any failing
3994    command will cause "run" to terminate, i. e. the remaining
3995    variables are not executed.
3996
3997Note for Redundant Ethernet Interfaces:
3998=======================================
3999
4000Some boards come with redundant Ethernet interfaces; U-Boot supports
4001such configurations and is capable of automatic selection of a
4002"working" interface when needed. MAC assignment works as follows:
4003
4004Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4005MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4006"eth1addr" (=>eth1), "eth2addr", ...
4007
4008If the network interface stores some valid MAC address (for instance
4009in SROM), this is used as default address if there is NO correspon-
4010ding setting in the environment; if the corresponding environment
4011variable is set, this overrides the settings in the card; that means:
4012
4013o If the SROM has a valid MAC address, and there is no address in the
4014  environment, the SROM's address is used.
4015
4016o If there is no valid address in the SROM, and a definition in the
4017  environment exists, then the value from the environment variable is
4018  used.
4019
4020o If both the SROM and the environment contain a MAC address, and
4021  both addresses are the same, this MAC address is used.
4022
4023o If both the SROM and the environment contain a MAC address, and the
4024  addresses differ, the value from the environment is used and a
4025  warning is printed.
4026
4027o If neither SROM nor the environment contain a MAC address, an error
4028  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4029  a random, locally-assigned MAC is used.
4030
4031If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4032will be programmed into hardware as part of the initialization process.  This
4033may be skipped by setting the appropriate 'ethmacskip' environment variable.
4034The naming convention is as follows:
4035"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4036
4037Image Formats:
4038==============
4039
4040U-Boot is capable of booting (and performing other auxiliary operations on)
4041images in two formats:
4042
4043New uImage format (FIT)
4044-----------------------
4045
4046Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4047to Flattened Device Tree). It allows the use of images with multiple
4048components (several kernels, ramdisks, etc.), with contents protected by
4049SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4050
4051
4052Old uImage format
4053-----------------
4054
4055Old image format is based on binary files which can be basically anything,
4056preceded by a special header; see the definitions in include/image.h for
4057details; basically, the header defines the following image properties:
4058
4059* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4060  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4061  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4062  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4063  INTEGRITY).
4064* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4065  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4066  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4067* Compression Type (uncompressed, gzip, bzip2)
4068* Load Address
4069* Entry Point
4070* Image Name
4071* Image Timestamp
4072
4073The header is marked by a special Magic Number, and both the header
4074and the data portions of the image are secured against corruption by
4075CRC32 checksums.
4076
4077
4078Linux Support:
4079==============
4080
4081Although U-Boot should support any OS or standalone application
4082easily, the main focus has always been on Linux during the design of
4083U-Boot.
4084
4085U-Boot includes many features that so far have been part of some
4086special "boot loader" code within the Linux kernel. Also, any
4087"initrd" images to be used are no longer part of one big Linux image;
4088instead, kernel and "initrd" are separate images. This implementation
4089serves several purposes:
4090
4091- the same features can be used for other OS or standalone
4092  applications (for instance: using compressed images to reduce the
4093  Flash memory footprint)
4094
4095- it becomes much easier to port new Linux kernel versions because
4096  lots of low-level, hardware dependent stuff are done by U-Boot
4097
4098- the same Linux kernel image can now be used with different "initrd"
4099  images; of course this also means that different kernel images can
4100  be run with the same "initrd". This makes testing easier (you don't
4101  have to build a new "zImage.initrd" Linux image when you just
4102  change a file in your "initrd"). Also, a field-upgrade of the
4103  software is easier now.
4104
4105
4106Linux HOWTO:
4107============
4108
4109Porting Linux to U-Boot based systems:
4110---------------------------------------
4111
4112U-Boot cannot save you from doing all the necessary modifications to
4113configure the Linux device drivers for use with your target hardware
4114(no, we don't intend to provide a full virtual machine interface to
4115Linux :-).
4116
4117But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4118
4119Just make sure your machine specific header file (for instance
4120include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4121Information structure as we define in include/asm-<arch>/u-boot.h,
4122and make sure that your definition of IMAP_ADDR uses the same value
4123as your U-Boot configuration in CONFIG_SYS_IMMR.
4124
4125Note that U-Boot now has a driver model, a unified model for drivers.
4126If you are adding a new driver, plumb it into driver model. If there
4127is no uclass available, you are encouraged to create one. See
4128doc/driver-model.
4129
4130
4131Configuring the Linux kernel:
4132-----------------------------
4133
4134No specific requirements for U-Boot. Make sure you have some root
4135device (initial ramdisk, NFS) for your target system.
4136
4137
4138Building a Linux Image:
4139-----------------------
4140
4141With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4142not used. If you use recent kernel source, a new build target
4143"uImage" will exist which automatically builds an image usable by
4144U-Boot. Most older kernels also have support for a "pImage" target,
4145which was introduced for our predecessor project PPCBoot and uses a
4146100% compatible format.
4147
4148Example:
4149
4150        make TQM850L_defconfig
4151        make oldconfig
4152        make dep
4153        make uImage
4154
4155The "uImage" build target uses a special tool (in 'tools/mkimage') to
4156encapsulate a compressed Linux kernel image with header  information,
4157CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4158
4159* build a standard "vmlinux" kernel image (in ELF binary format):
4160
4161* convert the kernel into a raw binary image:
4162
4163        ${CROSS_COMPILE}-objcopy -O binary \
4164                                 -R .note -R .comment \
4165                                 -S vmlinux linux.bin
4166
4167* compress the binary image:
4168
4169        gzip -9 linux.bin
4170
4171* package compressed binary image for U-Boot:
4172
4173        mkimage -A ppc -O linux -T kernel -C gzip \
4174                -a 0 -e 0 -n "Linux Kernel Image" \
4175                -d linux.bin.gz uImage
4176
4177
4178The "mkimage" tool can also be used to create ramdisk images for use
4179with U-Boot, either separated from the Linux kernel image, or
4180combined into one file. "mkimage" encapsulates the images with a 64
4181byte header containing information about target architecture,
4182operating system, image type, compression method, entry points, time
4183stamp, CRC32 checksums, etc.
4184
4185"mkimage" can be called in two ways: to verify existing images and
4186print the header information, or to build new images.
4187
4188In the first form (with "-l" option) mkimage lists the information
4189contained in the header of an existing U-Boot image; this includes
4190checksum verification:
4191
4192        tools/mkimage -l image
4193          -l ==> list image header information
4194
4195The second form (with "-d" option) is used to build a U-Boot image
4196from a "data file" which is used as image payload:
4197
4198        tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4199                      -n name -d data_file image
4200          -A ==> set architecture to 'arch'
4201          -O ==> set operating system to 'os'
4202          -T ==> set image type to 'type'
4203          -C ==> set compression type 'comp'
4204          -a ==> set load address to 'addr' (hex)
4205          -e ==> set entry point to 'ep' (hex)
4206          -n ==> set image name to 'name'
4207          -d ==> use image data from 'datafile'
4208
4209Right now, all Linux kernels for PowerPC systems use the same load
4210address (0x00000000), but the entry point address depends on the
4211kernel version:
4212
4213- 2.2.x kernels have the entry point at 0x0000000C,
4214- 2.3.x and later kernels have the entry point at 0x00000000.
4215
4216So a typical call to build a U-Boot image would read:
4217
4218        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4219        > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4220        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4221        > examples/uImage.TQM850L
4222        Image Name:   2.4.4 kernel for TQM850L
4223        Created:      Wed Jul 19 02:34:59 2000
4224        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4225        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4226        Load Address: 0x00000000
4227        Entry Point:  0x00000000
4228
4229To verify the contents of the image (or check for corruption):
4230
4231        -> tools/mkimage -l examples/uImage.TQM850L
4232        Image Name:   2.4.4 kernel for TQM850L
4233        Created:      Wed Jul 19 02:34:59 2000
4234        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4235        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4236        Load Address: 0x00000000
4237        Entry Point:  0x00000000
4238
4239NOTE: for embedded systems where boot time is critical you can trade
4240speed for memory and install an UNCOMPRESSED image instead: this
4241needs more space in Flash, but boots much faster since it does not
4242need to be uncompressed:
4243
4244        -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4245        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4246        > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4247        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4248        > examples/uImage.TQM850L-uncompressed
4249        Image Name:   2.4.4 kernel for TQM850L
4250        Created:      Wed Jul 19 02:34:59 2000
4251        Image Type:   PowerPC Linux Kernel Image (uncompressed)
4252        Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4253        Load Address: 0x00000000
4254        Entry Point:  0x00000000
4255
4256
4257Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4258when your kernel is intended to use an initial ramdisk:
4259
4260        -> tools/mkimage -n 'Simple Ramdisk Image' \
4261        > -A ppc -O linux -T ramdisk -C gzip \
4262        > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4263        Image Name:   Simple Ramdisk Image
4264        Created:      Wed Jan 12 14:01:50 2000
4265        Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4266        Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4267        Load Address: 0x00000000
4268        Entry Point:  0x00000000
4269
4270The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4271option performs the converse operation of the mkimage's second form (the "-d"
4272option). Given an image built by mkimage, the dumpimage extracts a "data file"
4273from the image:
4274
4275        tools/dumpimage -i image -T type -p position data_file
4276          -i ==> extract from the 'image' a specific 'data_file'
4277          -T ==> set image type to 'type'
4278          -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4279
4280
4281Installing a Linux Image:
4282-------------------------
4283
4284To downloading a U-Boot image over the serial (console) interface,
4285you must convert the image to S-Record format:
4286
4287        objcopy -I binary -O srec examples/image examples/image.srec
4288
4289The 'objcopy' does not understand the information in the U-Boot
4290image header, so the resulting S-Record file will be relative to
4291address 0x00000000. To load it to a given address, you need to
4292specify the target address as 'offset' parameter with the 'loads'
4293command.
4294
4295Example: install the image to address 0x40100000 (which on the
4296TQM8xxL is in the first Flash bank):
4297
4298        => erase 40100000 401FFFFF
4299
4300        .......... done
4301        Erased 8 sectors
4302
4303        => loads 40100000
4304        ## Ready for S-Record download ...
4305        ~>examples/image.srec
4306        1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4307        ...
4308        15989 15990 15991 15992
4309        [file transfer complete]
4310        [connected]
4311        ## Start Addr = 0x00000000
4312
4313
4314You can check the success of the download using the 'iminfo' command;
4315this includes a checksum verification so you can be sure no data
4316corruption happened:
4317
4318        => imi 40100000
4319
4320        ## Checking Image at 40100000 ...
4321           Image Name:   2.2.13 for initrd on TQM850L
4322           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4323           Data Size:    335725 Bytes = 327 kB = 0 MB
4324           Load Address: 00000000
4325           Entry Point:  0000000c
4326           Verifying Checksum ... OK
4327
4328
4329Boot Linux:
4330-----------
4331
4332The "bootm" command is used to boot an application that is stored in
4333memory (RAM or Flash). In case of a Linux kernel image, the contents
4334of the "bootargs" environment variable is passed to the kernel as
4335parameters. You can check and modify this variable using the
4336"printenv" and "setenv" commands:
4337
4338
4339        => printenv bootargs
4340        bootargs=root=/dev/ram
4341
4342        => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4343
4344        => printenv bootargs
4345        bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4346
4347        => bootm 40020000
4348        ## Booting Linux kernel at 40020000 ...
4349           Image Name:   2.2.13 for NFS on TQM850L
4350           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4351           Data Size:    381681 Bytes = 372 kB = 0 MB
4352           Load Address: 00000000
4353           Entry Point:  0000000c
4354           Verifying Checksum ... OK
4355           Uncompressing Kernel Image ... OK
4356        Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
4357        Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4358        time_init: decrementer frequency = 187500000/60
4359        Calibrating delay loop... 49.77 BogoMIPS
4360        Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4361        ...
4362
4363If you want to boot a Linux kernel with initial RAM disk, you pass
4364the memory addresses of both the kernel and the initrd image (PPBCOOT
4365format!) to the "bootm" command:
4366
4367        => imi 40100000 40200000
4368
4369        ## Checking Image at 40100000 ...
4370           Image Name:   2.2.13 for initrd on TQM850L
4371           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4372           Data Size:    335725 Bytes = 327 kB = 0 MB
4373           Load Address: 00000000
4374           Entry Point:  0000000c
4375           Verifying Checksum ... OK
4376
4377        ## Checking Image at 40200000 ...
4378           Image Name:   Simple Ramdisk Image
4379           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4380           Data Size:    566530 Bytes = 553 kB = 0 MB
4381           Load Address: 00000000
4382           Entry Point:  00000000
4383           Verifying Checksum ... OK
4384
4385        => bootm 40100000 40200000
4386        ## Booting Linux kernel at 40100000 ...
4387           Image Name:   2.2.13 for initrd on TQM850L
4388           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4389           Data Size:    335725 Bytes = 327 kB = 0 MB
4390           Load Address: 00000000
4391           Entry Point:  0000000c
4392           Verifying Checksum ... OK
4393           Uncompressing Kernel Image ... OK
4394        ## Loading RAMDisk Image at 40200000 ...
4395           Image Name:   Simple Ramdisk Image
4396           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4397           Data Size:    566530 Bytes = 553 kB = 0 MB
4398           Load Address: 00000000
4399           Entry Point:  00000000
4400           Verifying Checksum ... OK
4401           Loading Ramdisk ... OK
4402        Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
4403        Boot arguments: root=/dev/ram
4404        time_init: decrementer frequency = 187500000/60
4405        Calibrating delay loop... 49.77 BogoMIPS
4406        ...
4407        RAMDISK: Compressed image found at block 0
4408        VFS: Mounted root (ext2 filesystem).
4409
4410        bash#
4411
4412Boot Linux and pass a flat device tree:
4413-----------
4414
4415First, U-Boot must be compiled with the appropriate defines. See the section
4416titled "Linux Kernel Interface" above for a more in depth explanation. The
4417following is an example of how to start a kernel and pass an updated
4418flat device tree:
4419
4420=> print oftaddr
4421oftaddr=0x300000
4422=> print oft
4423oft=oftrees/mpc8540ads.dtb
4424=> tftp $oftaddr $oft
4425Speed: 1000, full duplex
4426Using TSEC0 device
4427TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4428Filename 'oftrees/mpc8540ads.dtb'.
4429Load address: 0x300000
4430Loading: #
4431done
4432Bytes transferred = 4106 (100a hex)
4433=> tftp $loadaddr $bootfile
4434Speed: 1000, full duplex
4435Using TSEC0 device
4436TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4437Filename 'uImage'.
4438Load address: 0x200000
4439Loading:############
4440done
4441Bytes transferred = 1029407 (fb51f hex)
4442=> print loadaddr
4443loadaddr=200000
4444=> print oftaddr
4445oftaddr=0x300000
4446=> bootm $loadaddr - $oftaddr
4447## Booting image at 00200000 ...
4448   Image Name:   Linux-2.6.17-dirty
4449   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4450   Data Size:    1029343 Bytes = 1005.2 kB
4451   Load Address: 00000000
4452   Entry Point:  00000000
4453   Verifying Checksum ... OK
4454   Uncompressing Kernel Image ... OK
4455Booting using flat device tree at 0x300000
4456Using MPC85xx ADS machine description
4457Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4458[snip]
4459
4460
4461More About U-Boot Image Types:
4462------------------------------
4463
4464U-Boot supports the following image types:
4465
4466   "Standalone Programs" are directly runnable in the environment
4467        provided by U-Boot; it is expected that (if they behave
4468        well) you can continue to work in U-Boot after return from
4469        the Standalone Program.
4470   "OS Kernel Images" are usually images of some Embedded OS which
4471        will take over control completely. Usually these programs
4472        will install their own set of exception handlers, device
4473        drivers, set up the MMU, etc. - this means, that you cannot
4474        expect to re-enter U-Boot except by resetting the CPU.
4475   "RAMDisk Images" are more or less just data blocks, and their
4476        parameters (address, size) are passed to an OS kernel that is
4477        being started.
4478   "Multi-File Images" contain several images, typically an OS
4479        (Linux) kernel image and one or more data images like
4480        RAMDisks. This construct is useful for instance when you want
4481        to boot over the network using BOOTP etc., where the boot
4482        server provides just a single image file, but you want to get
4483        for instance an OS kernel and a RAMDisk image.
4484
4485        "Multi-File Images" start with a list of image sizes, each
4486        image size (in bytes) specified by an "uint32_t" in network
4487        byte order. This list is terminated by an "(uint32_t)0".
4488        Immediately after the terminating 0 follow the images, one by
4489        one, all aligned on "uint32_t" boundaries (size rounded up to
4490        a multiple of 4 bytes).
4491
4492   "Firmware Images" are binary images containing firmware (like
4493        U-Boot or FPGA images) which usually will be programmed to
4494        flash memory.
4495
4496   "Script files" are command sequences that will be executed by
4497        U-Boot's command interpreter; this feature is especially
4498        useful when you configure U-Boot to use a real shell (hush)
4499        as command interpreter.
4500
4501Booting the Linux zImage:
4502-------------------------
4503
4504On some platforms, it's possible to boot Linux zImage. This is done
4505using the "bootz" command. The syntax of "bootz" command is the same
4506as the syntax of "bootm" command.
4507
4508Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4509kernel with raw initrd images. The syntax is slightly different, the
4510address of the initrd must be augmented by it's size, in the following
4511format: "<initrd addres>:<initrd size>".
4512
4513
4514Standalone HOWTO:
4515=================
4516
4517One of the features of U-Boot is that you can dynamically load and
4518run "standalone" applications, which can use some resources of
4519U-Boot like console I/O functions or interrupt services.
4520
4521Two simple examples are included with the sources:
4522
4523"Hello World" Demo:
4524-------------------
4525
4526'examples/hello_world.c' contains a small "Hello World" Demo
4527application; it is automatically compiled when you build U-Boot.
4528It's configured to run at address 0x00040004, so you can play with it
4529like that:
4530
4531        => loads
4532        ## Ready for S-Record download ...
4533        ~>examples/hello_world.srec
4534        1 2 3 4 5 6 7 8 9 10 11 ...
4535        [file transfer complete]
4536        [connected]
4537        ## Start Addr = 0x00040004
4538
4539        => go 40004 Hello World! This is a test.
4540        ## Starting application at 0x00040004 ...
4541        Hello World
4542        argc = 7
4543        argv[0] = "40004"
4544        argv[1] = "Hello"
4545        argv[2] = "World!"
4546        argv[3] = "This"
4547        argv[4] = "is"
4548        argv[5] = "a"
4549        argv[6] = "test."
4550        argv[7] = "<NULL>"
4551        Hit any key to exit ...
4552
4553        ## Application terminated, rc = 0x0
4554
4555Another example, which demonstrates how to register a CPM interrupt
4556handler with the U-Boot code, can be found in 'examples/timer.c'.
4557Here, a CPM timer is set up to generate an interrupt every second.
4558The interrupt service routine is trivial, just printing a '.'
4559character, but this is just a demo program. The application can be
4560controlled by the following keys:
4561
4562        ? - print current values og the CPM Timer registers
4563        b - enable interrupts and start timer
4564        e - stop timer and disable interrupts
4565        q - quit application
4566
4567        => loads
4568        ## Ready for S-Record download ...
4569        ~>examples/timer.srec
4570        1 2 3 4 5 6 7 8 9 10 11 ...
4571        [file transfer complete]
4572        [connected]
4573        ## Start Addr = 0x00040004
4574
4575        => go 40004
4576        ## Starting application at 0x00040004 ...
4577        TIMERS=0xfff00980
4578        Using timer 1
4579          tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4580
4581Hit 'b':
4582        [q, b, e, ?] Set interval 1000000 us
4583        Enabling timer
4584Hit '?':
4585        [q, b, e, ?] ........
4586        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4587Hit '?':
4588        [q, b, e, ?] .
4589        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4590Hit '?':
4591        [q, b, e, ?] .
4592        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4593Hit '?':
4594        [q, b, e, ?] .
4595        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4596Hit 'e':
4597        [q, b, e, ?] ...Stopping timer
4598Hit 'q':
4599        [q, b, e, ?] ## Application terminated, rc = 0x0
4600
4601
4602Minicom warning:
4603================
4604
4605Over time, many people have reported problems when trying to use the
4606"minicom" terminal emulation program for serial download. I (wd)
4607consider minicom to be broken, and recommend not to use it. Under
4608Unix, I recommend to use C-Kermit for general purpose use (and
4609especially for kermit binary protocol download ("loadb" command), and
4610use "cu" for S-Record download ("loads" command).  See
4611http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4612for help with kermit.
4613
4614
4615Nevertheless, if you absolutely want to use it try adding this
4616configuration to your "File transfer protocols" section:
4617
4618           Name    Program                      Name U/D FullScr IO-Red. Multi
4619        X  kermit  /usr/bin/kermit -i -l %l -s   Y    U    Y       N      N
4620        Y  kermit  /usr/bin/kermit -i -l %l -r   N    D    Y       N      N
4621
4622
4623NetBSD Notes:
4624=============
4625
4626Starting at version 0.9.2, U-Boot supports NetBSD both as host
4627(build U-Boot) and target system (boots NetBSD/mpc8xx).
4628
4629Building requires a cross environment; it is known to work on
4630NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4631need gmake since the Makefiles are not compatible with BSD make).
4632Note that the cross-powerpc package does not install include files;
4633attempting to build U-Boot will fail because <machine/ansi.h> is
4634missing.  This file has to be installed and patched manually:
4635
4636        # cd /usr/pkg/cross/powerpc-netbsd/include
4637        # mkdir powerpc
4638        # ln -s powerpc machine
4639        # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4640        # ${EDIT} powerpc/ansi.h        ## must remove __va_list, _BSD_VA_LIST
4641
4642Native builds *don't* work due to incompatibilities between native
4643and U-Boot include files.
4644
4645Booting assumes that (the first part of) the image booted is a
4646stage-2 loader which in turn loads and then invokes the kernel
4647proper. Loader sources will eventually appear in the NetBSD source
4648tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4649meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4650
4651
4652Implementation Internals:
4653=========================
4654
4655The following is not intended to be a complete description of every
4656implementation detail. However, it should help to understand the
4657inner workings of U-Boot and make it easier to port it to custom
4658hardware.
4659
4660
4661Initial Stack, Global Data:
4662---------------------------
4663
4664The implementation of U-Boot is complicated by the fact that U-Boot
4665starts running out of ROM (flash memory), usually without access to
4666system RAM (because the memory controller is not initialized yet).
4667This means that we don't have writable Data or BSS segments, and BSS
4668is not initialized as zero. To be able to get a C environment working
4669at all, we have to allocate at least a minimal stack. Implementation
4670options for this are defined and restricted by the CPU used: Some CPU
4671models provide on-chip memory (like the IMMR area on MPC8xx and
4672MPC826x processors), on others (parts of) the data cache can be
4673locked as (mis-) used as memory, etc.
4674
4675        Chris Hallinan posted a good summary of these issues to the
4676        U-Boot mailing list:
4677
4678        Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4679        From: "Chris Hallinan" <clh@net1plus.com>
4680        Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4681        ...
4682
4683        Correct me if I'm wrong, folks, but the way I understand it
4684        is this: Using DCACHE as initial RAM for Stack, etc, does not
4685        require any physical RAM backing up the cache. The cleverness
4686        is that the cache is being used as a temporary supply of
4687        necessary storage before the SDRAM controller is setup. It's
4688        beyond the scope of this list to explain the details, but you
4689        can see how this works by studying the cache architecture and
4690        operation in the architecture and processor-specific manuals.
4691
4692        OCM is On Chip Memory, which I believe the 405GP has 4K. It
4693        is another option for the system designer to use as an
4694        initial stack/RAM area prior to SDRAM being available. Either
4695        option should work for you. Using CS 4 should be fine if your
4696        board designers haven't used it for something that would
4697        cause you grief during the initial boot! It is frequently not
4698        used.
4699
4700        CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4701        with your processor/board/system design. The default value
4702        you will find in any recent u-boot distribution in
4703        walnut.h should work for you. I'd set it to a value larger
4704        than your SDRAM module. If you have a 64MB SDRAM module, set
4705        it above 400_0000. Just make sure your board has no resources
4706        that are supposed to respond to that address! That code in
4707        start.S has been around a while and should work as is when
4708        you get the config right.
4709
4710        -Chris Hallinan
4711        DS4.COM, Inc.
4712
4713It is essential to remember this, since it has some impact on the C
4714code for the initialization procedures:
4715
4716* Initialized global data (data segment) is read-only. Do not attempt
4717  to write it.
4718
4719* Do not use any uninitialized global data (or implicitly initialized
4720  as zero data - BSS segment) at all - this is undefined, initiali-
4721  zation is performed later (when relocating to RAM).
4722
4723* Stack space is very limited. Avoid big data buffers or things like
4724  that.
4725
4726Having only the stack as writable memory limits means we cannot use
4727normal global data to share information between the code. But it
4728turned out that the implementation of U-Boot can be greatly
4729simplified by making a global data structure (gd_t) available to all
4730functions. We could pass a pointer to this data as argument to _all_
4731functions, but this would bloat the code. Instead we use a feature of
4732the GCC compiler (Global Register Variables) to share the data: we
4733place a pointer (gd) to the global data into a register which we
4734reserve for this purpose.
4735
4736When choosing a register for such a purpose we are restricted by the
4737relevant  (E)ABI  specifications for the current architecture, and by
4738GCC's implementation.
4739
4740For PowerPC, the following registers have specific use:
4741        R1:     stack pointer
4742        R2:     reserved for system use
4743        R3-R4:  parameter passing and return values
4744        R5-R10: parameter passing
4745        R13:    small data area pointer
4746        R30:    GOT pointer
4747        R31:    frame pointer
4748
4749        (U-Boot also uses R12 as internal GOT pointer. r12
4750        is a volatile register so r12 needs to be reset when
4751        going back and forth between asm and C)
4752
4753    ==> U-Boot will use R2 to hold a pointer to the global data
4754
4755    Note: on PPC, we could use a static initializer (since the
4756    address of the global data structure is known at compile time),
4757    but it turned out that reserving a register results in somewhat
4758    smaller code - although the code savings are not that big (on
4759    average for all boards 752 bytes for the whole U-Boot image,
4760    624 text + 127 data).
4761
4762On ARM, the following registers are used:
4763
4764        R0:     function argument word/integer result
4765        R1-R3:  function argument word
4766        R9:     platform specific
4767        R10:    stack limit (used only if stack checking is enabled)
4768        R11:    argument (frame) pointer
4769        R12:    temporary workspace
4770        R13:    stack pointer
4771        R14:    link register
4772        R15:    program counter
4773
4774    ==> U-Boot will use R9 to hold a pointer to the global data
4775
4776    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4777
4778On Nios II, the ABI is documented here:
4779        http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4780
4781    ==> U-Boot will use gp to hold a pointer to the global data
4782
4783    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4784    to access small data sections, so gp is free.
4785
4786On NDS32, the following registers are used:
4787
4788        R0-R1:  argument/return
4789        R2-R5:  argument
4790        R15:    temporary register for assembler
4791        R16:    trampoline register
4792        R28:    frame pointer (FP)
4793        R29:    global pointer (GP)
4794        R30:    link register (LP)
4795        R31:    stack pointer (SP)
4796        PC:     program counter (PC)
4797
4798    ==> U-Boot will use R10 to hold a pointer to the global data
4799
4800NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4801or current versions of GCC may "optimize" the code too much.
4802
4803On RISC-V, the following registers are used:
4804
4805        x0: hard-wired zero (zero)
4806        x1: return address (ra)
4807        x2:     stack pointer (sp)
4808        x3:     global pointer (gp)
4809        x4:     thread pointer (tp)
4810        x5:     link register (t0)
4811        x8:     frame pointer (fp)
4812        x10-x11:        arguments/return values (a0-1)
4813        x12-x17:        arguments (a2-7)
4814        x28-31:  temporaries (t3-6)
4815        pc:     program counter (pc)
4816
4817    ==> U-Boot will use gp to hold a pointer to the global data
4818
4819Memory Management:
4820------------------
4821
4822U-Boot runs in system state and uses physical addresses, i.e. the
4823MMU is not used either for address mapping nor for memory protection.
4824
4825The available memory is mapped to fixed addresses using the memory
4826controller. In this process, a contiguous block is formed for each
4827memory type (Flash, SDRAM, SRAM), even when it consists of several
4828physical memory banks.
4829
4830U-Boot is installed in the first 128 kB of the first Flash bank (on
4831TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4832booting and sizing and initializing DRAM, the code relocates itself
4833to the upper end of DRAM. Immediately below the U-Boot code some
4834memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4835configuration setting]. Below that, a structure with global Board
4836Info data is placed, followed by the stack (growing downward).
4837
4838Additionally, some exception handler code is copied to the low 8 kB
4839of DRAM (0x00000000 ... 0x00001FFF).
4840
4841So a typical memory configuration with 16 MB of DRAM could look like
4842this:
4843
4844        0x0000 0000     Exception Vector code
4845              :
4846        0x0000 1FFF
4847        0x0000 2000     Free for Application Use
4848              :
4849              :
4850
4851              :
4852              :
4853        0x00FB FF20     Monitor Stack (Growing downward)
4854        0x00FB FFAC     Board Info Data and permanent copy of global data
4855        0x00FC 0000     Malloc Arena
4856              :
4857        0x00FD FFFF
4858        0x00FE 0000     RAM Copy of Monitor Code
4859        ...             eventually: LCD or video framebuffer
4860        ...             eventually: pRAM (Protected RAM - unchanged by reset)
4861        0x00FF FFFF     [End of RAM]
4862
4863
4864System Initialization:
4865----------------------
4866
4867In the reset configuration, U-Boot starts at the reset entry point
4868(on most PowerPC systems at address 0x00000100). Because of the reset
4869configuration for CS0# this is a mirror of the on board Flash memory.
4870To be able to re-map memory U-Boot then jumps to its link address.
4871To be able to implement the initialization code in C, a (small!)
4872initial stack is set up in the internal Dual Ported RAM (in case CPUs
4873which provide such a feature like), or in a locked part of the data
4874cache. After that, U-Boot initializes the CPU core, the caches and
4875the SIU.
4876
4877Next, all (potentially) available memory banks are mapped using a
4878preliminary mapping. For example, we put them on 512 MB boundaries
4879(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4880on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4881programmed for SDRAM access. Using the temporary configuration, a
4882simple memory test is run that determines the size of the SDRAM
4883banks.
4884
4885When there is more than one SDRAM bank, and the banks are of
4886different size, the largest is mapped first. For equal size, the first
4887bank (CS2#) is mapped first. The first mapping is always for address
48880x00000000, with any additional banks following immediately to create
4889contiguous memory starting from 0.
4890
4891Then, the monitor installs itself at the upper end of the SDRAM area
4892and allocates memory for use by malloc() and for the global Board
4893Info data; also, the exception vector code is copied to the low RAM
4894pages, and the final stack is set up.
4895
4896Only after this relocation will you have a "normal" C environment;
4897until that you are restricted in several ways, mostly because you are
4898running from ROM, and because the code will have to be relocated to a
4899new address in RAM.
4900
4901
4902U-Boot Porting Guide:
4903----------------------
4904
4905[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4906list, October 2002]
4907
4908
4909int main(int argc, char *argv[])
4910{
4911        sighandler_t no_more_time;
4912
4913        signal(SIGALRM, no_more_time);
4914        alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4915
4916        if (available_money > available_manpower) {
4917                Pay consultant to port U-Boot;
4918                return 0;
4919        }
4920
4921        Download latest U-Boot source;
4922
4923        Subscribe to u-boot mailing list;
4924
4925        if (clueless)
4926                email("Hi, I am new to U-Boot, how do I get started?");
4927
4928        while (learning) {
4929                Read the README file in the top level directory;
4930                Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4931                Read applicable doc/*.README;
4932                Read the source, Luke;
4933                /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4934        }
4935
4936        if (available_money > toLocalCurrency ($2500))
4937                Buy a BDI3000;
4938        else
4939                Add a lot of aggravation and time;
4940
4941        if (a similar board exists) {   /* hopefully... */
4942                cp -a board/<similar> board/<myboard>
4943                cp include/configs/<similar>.h include/configs/<myboard>.h
4944        } else {
4945                Create your own board support subdirectory;
4946                Create your own board include/configs/<myboard>.h file;
4947        }
4948        Edit new board/<myboard> files
4949        Edit new include/configs/<myboard>.h
4950
4951        while (!accepted) {
4952                while (!running) {
4953                        do {
4954                                Add / modify source code;
4955                        } until (compiles);
4956                        Debug;
4957                        if (clueless)
4958                                email("Hi, I am having problems...");
4959                }
4960                Send patch file to the U-Boot email list;
4961                if (reasonable critiques)
4962                        Incorporate improvements from email list code review;
4963                else
4964                        Defend code as written;
4965        }
4966
4967        return 0;
4968}
4969
4970void no_more_time (int sig)
4971{
4972      hire_a_guru();
4973}
4974
4975
4976Coding Standards:
4977-----------------
4978
4979All contributions to U-Boot should conform to the Linux kernel
4980coding style; see the kernel coding style guide at
4981https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4982script "scripts/Lindent" in your Linux kernel source directory.
4983
4984Source files originating from a different project (for example the
4985MTD subsystem) are generally exempt from these guidelines and are not
4986reformatted to ease subsequent migration to newer versions of those
4987sources.
4988
4989Please note that U-Boot is implemented in C (and to some small parts in
4990Assembler); no C++ is used, so please do not use C++ style comments (//)
4991in your code.
4992
4993Please also stick to the following formatting rules:
4994- remove any trailing white space
4995- use TAB characters for indentation and vertical alignment, not spaces
4996- make sure NOT to use DOS '\r\n' line feeds
4997- do not add more than 2 consecutive empty lines to source files
4998- do not add trailing empty lines to source files
4999
5000Submissions which do not conform to the standards may be returned
5001with a request to reformat the changes.
5002
5003
5004Submitting Patches:
5005-------------------
5006
5007Since the number of patches for U-Boot is growing, we need to
5008establish some rules. Submissions which do not conform to these rules
5009may be rejected, even when they contain important and valuable stuff.
5010
5011Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5012
5013Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5014see https://lists.denx.de/listinfo/u-boot
5015
5016When you send a patch, please include the following information with
5017it:
5018
5019* For bug fixes: a description of the bug and how your patch fixes
5020  this bug. Please try to include a way of demonstrating that the
5021  patch actually fixes something.
5022
5023* For new features: a description of the feature and your
5024  implementation.
5025
5026* A CHANGELOG entry as plaintext (separate from the patch)
5027
5028* For major contributions, add a MAINTAINERS file with your
5029  information and associated file and directory references.
5030
5031* When you add support for a new board, don't forget to add a
5032  maintainer e-mail address to the boards.cfg file, too.
5033
5034* If your patch adds new configuration options, don't forget to
5035  document these in the README file.
5036
5037* The patch itself. If you are using git (which is *strongly*
5038  recommended) you can easily generate the patch using the
5039  "git format-patch". If you then use "git send-email" to send it to
5040  the U-Boot mailing list, you will avoid most of the common problems
5041  with some other mail clients.
5042
5043  If you cannot use git, use "diff -purN OLD NEW". If your version of
5044  diff does not support these options, then get the latest version of
5045  GNU diff.
5046
5047  The current directory when running this command shall be the parent
5048  directory of the U-Boot source tree (i. e. please make sure that
5049  your patch includes sufficient directory information for the
5050  affected files).
5051
5052  We prefer patches as plain text. MIME attachments are discouraged,
5053  and compressed attachments must not be used.
5054
5055* If one logical set of modifications affects or creates several
5056  files, all these changes shall be submitted in a SINGLE patch file.
5057
5058* Changesets that contain different, unrelated modifications shall be
5059  submitted as SEPARATE patches, one patch per changeset.
5060
5061
5062Notes:
5063
5064* Before sending the patch, run the buildman script on your patched
5065  source tree and make sure that no errors or warnings are reported
5066  for any of the boards.
5067
5068* Keep your modifications to the necessary minimum: A patch
5069  containing several unrelated changes or arbitrary reformats will be
5070  returned with a request to re-formatting / split it.
5071
5072* If you modify existing code, make sure that your new code does not
5073  add to the memory footprint of the code ;-) Small is beautiful!
5074  When adding new features, these should compile conditionally only
5075  (using #ifdef), and the resulting code with the new feature
5076  disabled must not need more memory than the old code without your
5077  modification.
5078
5079* Remember that there is a size limit of 100 kB per message on the
5080  u-boot mailing list. Bigger patches will be moderated. If they are
5081  reasonable and not too big, they will be acknowledged. But patches
5082  bigger than the size limit should be avoided.
5083