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_XWAY_SWAP_BYTES
 532
 533                Enable compilation of tools/xway-swap-bytes needed for Lantiq
 534                XWAY SoCs for booting from NOR flash. The U-Boot image needs to
 535                be swapped if a flash programmer is used.
 536
 537- ARM options:
 538                CONFIG_SYS_EXCEPTION_VECTORS_HIGH
 539
 540                Select high exception vectors of the ARM core, e.g., do not
 541                clear the V bit of the c1 register of CP15.
 542
 543                COUNTER_FREQUENCY
 544                Generic timer clock source frequency.
 545
 546                COUNTER_FREQUENCY_REAL
 547                Generic timer clock source frequency if the real clock is
 548                different from COUNTER_FREQUENCY, and can only be determined
 549                at run time.
 550
 551- Tegra SoC options:
 552                CONFIG_TEGRA_SUPPORT_NON_SECURE
 553
 554                Support executing U-Boot in non-secure (NS) mode. Certain
 555                impossible actions will be skipped if the CPU is in NS mode,
 556                such as ARM architectural timer initialization.
 557
 558- Linux Kernel Interface:
 559                CONFIG_CLOCKS_IN_MHZ
 560
 561                U-Boot stores all clock information in Hz
 562                internally. For binary compatibility with older Linux
 563                kernels (which expect the clocks passed in the
 564                bd_info data to be in MHz) the environment variable
 565                "clocks_in_mhz" can be defined so that U-Boot
 566                converts clock data to MHZ before passing it to the
 567                Linux kernel.
 568                When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
 569                "clocks_in_mhz=1" is automatically included in the
 570                default environment.
 571
 572                CONFIG_MEMSIZE_IN_BYTES         [relevant for MIPS only]
 573
 574                When transferring memsize parameter to Linux, some versions
 575                expect it to be in bytes, others in MB.
 576                Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
 577
 578                CONFIG_OF_LIBFDT
 579
 580                New kernel versions are expecting firmware settings to be
 581                passed using flattened device trees (based on open firmware
 582                concepts).
 583
 584                CONFIG_OF_LIBFDT
 585                 * New libfdt-based support
 586                 * Adds the "fdt" command
 587                 * The bootm command automatically updates the fdt
 588
 589                OF_TBCLK - The timebase frequency.
 590                OF_STDOUT_PATH - The path to the console device
 591
 592                boards with QUICC Engines require OF_QE to set UCC MAC
 593                addresses
 594
 595                CONFIG_OF_BOARD_SETUP
 596
 597                Board code has addition modification that it wants to make
 598                to the flat device tree before handing it off to the kernel
 599
 600                CONFIG_OF_SYSTEM_SETUP
 601
 602                Other code has addition modification that it wants to make
 603                to the flat device tree before handing it off to the kernel.
 604                This causes ft_system_setup() to be called before booting
 605                the kernel.
 606
 607                CONFIG_OF_IDE_FIXUP
 608
 609                U-Boot can detect if an IDE device is present or not.
 610                If not, and this new config option is activated, U-Boot
 611                removes the ATA node from the DTS before booting Linux,
 612                so the Linux IDE driver does not probe the device and
 613                crash. This is needed for buggy hardware (uc101) where
 614                no pull down resistor is connected to the signal IDE5V_DD7.
 615
 616                CONFIG_MACH_TYPE        [relevant for ARM only][mandatory]
 617
 618                This setting is mandatory for all boards that have only one
 619                machine type and must be used to specify the machine type
 620                number as it appears in the ARM machine registry
 621                (see http://www.arm.linux.org.uk/developer/machines/).
 622                Only boards that have multiple machine types supported
 623                in a single configuration file and the machine type is
 624                runtime discoverable, do not have to use this setting.
 625
 626- vxWorks boot parameters:
 627
 628                bootvx constructs a valid bootline using the following
 629                environments variables: bootdev, bootfile, ipaddr, netmask,
 630                serverip, gatewayip, hostname, othbootargs.
 631                It loads the vxWorks image pointed bootfile.
 632
 633                Note: If a "bootargs" environment is defined, it will overwride
 634                the defaults discussed just above.
 635
 636- Cache Configuration:
 637                CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
 638                CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
 639                CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
 640
 641- Cache Configuration for ARM:
 642                CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
 643                                      controller
 644                CONFIG_SYS_PL310_BASE - Physical base address of PL310
 645                                        controller register space
 646
 647- Serial Ports:
 648                CONFIG_PL010_SERIAL
 649
 650                Define this if you want support for Amba PrimeCell PL010 UARTs.
 651
 652                CONFIG_PL011_SERIAL
 653
 654                Define this if you want support for Amba PrimeCell PL011 UARTs.
 655
 656                CONFIG_PL011_CLOCK
 657
 658                If you have Amba PrimeCell PL011 UARTs, set this variable to
 659                the clock speed of the UARTs.
 660
 661                CONFIG_PL01x_PORTS
 662
 663                If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
 664                define this to a list of base addresses for each (supported)
 665                port. See e.g. include/configs/versatile.h
 666
 667                CONFIG_SERIAL_HW_FLOW_CONTROL
 668
 669                Define this variable to enable hw flow control in serial driver.
 670                Current user of this option is drivers/serial/nsl16550.c driver
 671
 672- Console Baudrate:
 673                CONFIG_BAUDRATE - in bps
 674                Select one of the baudrates listed in
 675                CONFIG_SYS_BAUDRATE_TABLE, see below.
 676
 677- Autoboot Command:
 678                CONFIG_BOOTCOMMAND
 679                Only needed when CONFIG_BOOTDELAY is enabled;
 680                define a command string that is automatically executed
 681                when no character is read on the console interface
 682                within "Boot Delay" after reset.
 683
 684                CONFIG_RAMBOOT and CONFIG_NFSBOOT
 685                The value of these goes into the environment as
 686                "ramboot" and "nfsboot" respectively, and can be used
 687                as a convenience, when switching between booting from
 688                RAM and NFS.
 689
 690- Pre-Boot Commands:
 691                CONFIG_PREBOOT
 692
 693                When this option is #defined, the existence of the
 694                environment variable "preboot" will be checked
 695                immediately before starting the CONFIG_BOOTDELAY
 696                countdown and/or running the auto-boot command resp.
 697                entering interactive mode.
 698
 699                This feature is especially useful when "preboot" is
 700                automatically generated or modified. For an example
 701                see the LWMON board specific code: here "preboot" is
 702                modified when the user holds down a certain
 703                combination of keys on the (special) keyboard when
 704                booting the systems
 705
 706- Serial Download Echo Mode:
 707                CONFIG_LOADS_ECHO
 708                If defined to 1, all characters received during a
 709                serial download (using the "loads" command) are
 710                echoed back. This might be needed by some terminal
 711                emulations (like "cu"), but may as well just take
 712                time on others. This setting #define's the initial
 713                value of the "loads_echo" environment variable.
 714
 715- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
 716                CONFIG_KGDB_BAUDRATE
 717                Select one of the baudrates listed in
 718                CONFIG_SYS_BAUDRATE_TABLE, see below.
 719
 720- Removal of commands
 721                If no commands are needed to boot, you can disable
 722                CONFIG_CMDLINE to remove them. In this case, the command line
 723                will not be available, and when U-Boot wants to execute the
 724                boot command (on start-up) it will call board_run_command()
 725                instead. This can reduce image size significantly for very
 726                simple boot procedures.
 727
 728- Regular expression support:
 729                CONFIG_REGEX
 730                If this variable is defined, U-Boot is linked against
 731                the SLRE (Super Light Regular Expression) library,
 732                which adds regex support to some commands, as for
 733                example "env grep" and "setexpr".
 734
 735- Device tree:
 736                CONFIG_OF_CONTROL
 737                If this variable is defined, U-Boot will use a device tree
 738                to configure its devices, instead of relying on statically
 739                compiled #defines in the board file. This option is
 740                experimental and only available on a few boards. The device
 741                tree is available in the global data as gd->fdt_blob.
 742
 743                U-Boot needs to get its device tree from somewhere. This can
 744                be done using one of the three options below:
 745
 746                CONFIG_OF_EMBED
 747                If this variable is defined, U-Boot will embed a device tree
 748                binary in its image. This device tree file should be in the
 749                board directory and called <soc>-<board>.dts. The binary file
 750                is then picked up in board_init_f() and made available through
 751                the global data structure as gd->fdt_blob.
 752
 753                CONFIG_OF_SEPARATE
 754                If this variable is defined, U-Boot will build a device tree
 755                binary. It will be called u-boot.dtb. Architecture-specific
 756                code will locate it at run-time. Generally this works by:
 757
 758                        cat u-boot.bin u-boot.dtb >image.bin
 759
 760                and in fact, U-Boot does this for you, creating a file called
 761                u-boot-dtb.bin which is useful in the common case. You can
 762                still use the individual files if you need something more
 763                exotic.
 764
 765                CONFIG_OF_BOARD
 766                If this variable is defined, U-Boot will use the device tree
 767                provided by the board at runtime instead of embedding one with
 768                the image. Only boards defining board_fdt_blob_setup() support
 769                this option (see include/fdtdec.h file).
 770
 771- Watchdog:
 772                CONFIG_WATCHDOG
 773                If this variable is defined, it enables watchdog
 774                support for the SoC. There must be support in the SoC
 775                specific code for a watchdog. For the 8xx
 776                CPUs, the SIU Watchdog feature is enabled in the SYPCR
 777                register.  When supported for a specific SoC is
 778                available, then no further board specific code should
 779                be needed to use it.
 780
 781                CONFIG_HW_WATCHDOG
 782                When using a watchdog circuitry external to the used
 783                SoC, then define this variable and provide board
 784                specific code for the "hw_watchdog_reset" function.
 785
 786                CONFIG_AT91_HW_WDT_TIMEOUT
 787                specify the timeout in seconds. default 2 seconds.
 788
 789- Real-Time Clock:
 790
 791                When CONFIG_CMD_DATE is selected, the type of the RTC
 792                has to be selected, too. Define exactly one of the
 793                following options:
 794
 795                CONFIG_RTC_PCF8563      - use Philips PCF8563 RTC
 796                CONFIG_RTC_MC13XXX      - use MC13783 or MC13892 RTC
 797                CONFIG_RTC_MC146818     - use MC146818 RTC
 798                CONFIG_RTC_DS1307       - use Maxim, Inc. DS1307 RTC
 799                CONFIG_RTC_DS1337       - use Maxim, Inc. DS1337 RTC
 800                CONFIG_RTC_DS1338       - use Maxim, Inc. DS1338 RTC
 801                CONFIG_RTC_DS1339       - use Maxim, Inc. DS1339 RTC
 802                CONFIG_RTC_DS164x       - use Dallas DS164x RTC
 803                CONFIG_RTC_ISL1208      - use Intersil ISL1208 RTC
 804                CONFIG_RTC_MAX6900      - use Maxim, Inc. MAX6900 RTC
 805                CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
 806                CONFIG_SYS_RV3029_TCR   - enable trickle charger on
 807                                          RV3029 RTC.
 808
 809                Note that if the RTC uses I2C, then the I2C interface
 810                must also be configured. See I2C Support, below.
 811
 812- GPIO Support:
 813                CONFIG_PCA953X          - use NXP's PCA953X series I2C GPIO
 814
 815                The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
 816                chip-ngpio pairs that tell the PCA953X driver the number of
 817                pins supported by a particular chip.
 818
 819                Note that if the GPIO device uses I2C, then the I2C interface
 820                must also be configured. See I2C Support, below.
 821
 822- I/O tracing:
 823                When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
 824                accesses and can checksum them or write a list of them out
 825                to memory. See the 'iotrace' command for details. This is
 826                useful for testing device drivers since it can confirm that
 827                the driver behaves the same way before and after a code
 828                change. Currently this is supported on sandbox and arm. To
 829                add support for your architecture, add '#include <iotrace.h>'
 830                to the bottom of arch/<arch>/include/asm/io.h and test.
 831
 832                Example output from the 'iotrace stats' command is below.
 833                Note that if the trace buffer is exhausted, the checksum will
 834                still continue to operate.
 835
 836                        iotrace is enabled
 837                        Start:  10000000        (buffer start address)
 838                        Size:   00010000        (buffer size)
 839                        Offset: 00000120        (current buffer offset)
 840                        Output: 10000120        (start + offset)
 841                        Count:  00000018        (number of trace records)
 842                        CRC32:  9526fb66        (CRC32 of all trace records)
 843
 844- Timestamp Support:
 845
 846                When CONFIG_TIMESTAMP is selected, the timestamp
 847                (date and time) of an image is printed by image
 848                commands like bootm or iminfo. This option is
 849                automatically enabled when you select CONFIG_CMD_DATE .
 850
 851- Partition Labels (disklabels) Supported:
 852                Zero or more of the following:
 853                CONFIG_MAC_PARTITION   Apple's MacOS partition table.
 854                CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
 855                CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
 856                                       bootloader.  Note 2TB partition limit; see
 857                                       disk/part_efi.c
 858                CONFIG_SCSI) you must configure support for at
 859                least one non-MTD partition type as well.
 860
 861- IDE Reset method:
 862                CONFIG_IDE_RESET_ROUTINE - this is defined in several
 863                board configurations files but used nowhere!
 864
 865                CONFIG_IDE_RESET - is this is defined, IDE Reset will
 866                be performed by calling the function
 867                        ide_set_reset(int reset)
 868                which has to be defined in a board specific file
 869
 870- ATAPI Support:
 871                CONFIG_ATAPI
 872
 873                Set this to enable ATAPI support.
 874
 875- LBA48 Support
 876                CONFIG_LBA48
 877
 878                Set this to enable support for disks larger than 137GB
 879                Also look at CONFIG_SYS_64BIT_LBA.
 880                Whithout these , LBA48 support uses 32bit variables and will 'only'
 881                support disks up to 2.1TB.
 882
 883                CONFIG_SYS_64BIT_LBA:
 884                        When enabled, makes the IDE subsystem use 64bit sector addresses.
 885                        Default is 32bit.
 886
 887- SCSI Support:
 888                CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
 889                CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
 890                CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
 891                maximum numbers of LUNs, SCSI ID's and target
 892                devices.
 893
 894                The environment variable 'scsidevs' is set to the number of
 895                SCSI devices found during the last scan.
 896
 897- NETWORK Support (PCI):
 898                CONFIG_E1000
 899                Support for Intel 8254x/8257x gigabit chips.
 900
 901                CONFIG_E1000_SPI
 902                Utility code for direct access to the SPI bus on Intel 8257x.
 903                This does not do anything useful unless you set at least one
 904                of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
 905
 906                CONFIG_E1000_SPI_GENERIC
 907                Allow generic access to the SPI bus on the Intel 8257x, for
 908                example with the "sspi" command.
 909
 910                CONFIG_EEPRO100
 911                Support for Intel 82557/82559/82559ER chips.
 912                Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
 913                write routine for first time initialisation.
 914
 915                CONFIG_TULIP
 916                Support for Digital 2114x chips.
 917                Optional CONFIG_TULIP_SELECT_MEDIA for board specific
 918                modem chip initialisation (KS8761/QS6611).
 919
 920                CONFIG_NATSEMI
 921                Support for National dp83815 chips.
 922
 923                CONFIG_NS8382X
 924                Support for National dp8382[01] gigabit chips.
 925
 926- NETWORK Support (other):
 927
 928                CONFIG_DRIVER_AT91EMAC
 929                Support for AT91RM9200 EMAC.
 930
 931                        CONFIG_RMII
 932                        Define this to use reduced MII inteface
 933
 934                        CONFIG_DRIVER_AT91EMAC_QUIET
 935                        If this defined, the driver is quiet.
 936                        The driver doen't show link status messages.
 937
 938                CONFIG_CALXEDA_XGMAC
 939                Support for the Calxeda XGMAC device
 940
 941                CONFIG_LAN91C96
 942                Support for SMSC's LAN91C96 chips.
 943
 944                        CONFIG_LAN91C96_USE_32_BIT
 945                        Define this to enable 32 bit addressing
 946
 947                CONFIG_SMC91111
 948                Support for SMSC's LAN91C111 chip
 949
 950                        CONFIG_SMC91111_BASE
 951                        Define this to hold the physical address
 952                        of the device (I/O space)
 953
 954                        CONFIG_SMC_USE_32_BIT
 955                        Define this if data bus is 32 bits
 956
 957                        CONFIG_SMC_USE_IOFUNCS
 958                        Define this to use i/o functions instead of macros
 959                        (some hardware wont work with macros)
 960
 961                        CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
 962                        Define this if you have more then 3 PHYs.
 963
 964                CONFIG_FTGMAC100
 965                Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
 966
 967                        CONFIG_FTGMAC100_EGIGA
 968                        Define this to use GE link update with gigabit PHY.
 969                        Define this if FTGMAC100 is connected to gigabit PHY.
 970                        If your system has 10/100 PHY only, it might not occur
 971                        wrong behavior. Because PHY usually return timeout or
 972                        useless data when polling gigabit status and gigabit
 973                        control registers. This behavior won't affect the
 974                        correctnessof 10/100 link speed update.
 975
 976                CONFIG_SH_ETHER
 977                Support for Renesas on-chip Ethernet controller
 978
 979                        CONFIG_SH_ETHER_USE_PORT
 980                        Define the number of ports to be used
 981
 982                        CONFIG_SH_ETHER_PHY_ADDR
 983                        Define the ETH PHY's address
 984
 985                        CONFIG_SH_ETHER_CACHE_WRITEBACK
 986                        If this option is set, the driver enables cache flush.
 987
 988- PWM Support:
 989                CONFIG_PWM_IMX
 990                Support for PWM module on the imx6.
 991
 992- TPM Support:
 993                CONFIG_TPM
 994                Support TPM devices.
 995
 996                CONFIG_TPM_TIS_INFINEON
 997                Support for Infineon i2c bus TPM devices. Only one device
 998                per system is supported at this time.
 999
1000                        CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1001                        Define the burst count bytes upper limit
1002
1003                CONFIG_TPM_ST33ZP24
1004                Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1005
1006                        CONFIG_TPM_ST33ZP24_I2C
1007                        Support for STMicroelectronics ST33ZP24 I2C devices.
1008                        Requires TPM_ST33ZP24 and I2C.
1009
1010                        CONFIG_TPM_ST33ZP24_SPI
1011                        Support for STMicroelectronics ST33ZP24 SPI devices.
1012                        Requires TPM_ST33ZP24 and SPI.
1013
1014                CONFIG_TPM_ATMEL_TWI
1015                Support for Atmel TWI TPM device. Requires I2C support.
1016
1017                CONFIG_TPM_TIS_LPC
1018                Support for generic parallel port TPM devices. Only one device
1019                per system is supported at this time.
1020
1021                        CONFIG_TPM_TIS_BASE_ADDRESS
1022                        Base address where the generic TPM device is mapped
1023                        to. Contemporary x86 systems usually map it at
1024                        0xfed40000.
1025
1026                CONFIG_TPM
1027                Define this to enable the TPM support library which provides
1028                functional interfaces to some TPM commands.
1029                Requires support for a TPM device.
1030
1031                CONFIG_TPM_AUTH_SESSIONS
1032                Define this to enable authorized functions in the TPM library.
1033                Requires CONFIG_TPM and CONFIG_SHA1.
1034
1035- USB Support:
1036                At the moment only the UHCI host controller is
1037                supported (PIP405, MIP405); define
1038                CONFIG_USB_UHCI to enable it.
1039                define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1040                and define CONFIG_USB_STORAGE to enable the USB
1041                storage devices.
1042                Note:
1043                Supported are USB Keyboards and USB Floppy drives
1044                (TEAC FD-05PUB).
1045
1046                CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1047                txfilltuning field in the EHCI controller on reset.
1048
1049                CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1050                HW module registers.
1051
1052- USB Device:
1053                Define the below if you wish to use the USB console.
1054                Once firmware is rebuilt from a serial console issue the
1055                command "setenv stdin usbtty; setenv stdout usbtty" and
1056                attach your USB cable. The Unix command "dmesg" should print
1057                it has found a new device. The environment variable usbtty
1058                can be set to gserial or cdc_acm to enable your device to
1059                appear to a USB host as a Linux gserial device or a
1060                Common Device Class Abstract Control Model serial device.
1061                If you select usbtty = gserial you should be able to enumerate
1062                a Linux host by
1063                # modprobe usbserial vendor=0xVendorID product=0xProductID
1064                else if using cdc_acm, simply setting the environment
1065                variable usbtty to be cdc_acm should suffice. The following
1066                might be defined in YourBoardName.h
1067
1068                        CONFIG_USB_DEVICE
1069                        Define this to build a UDC device
1070
1071                        CONFIG_USB_TTY
1072                        Define this to have a tty type of device available to
1073                        talk to the UDC device
1074
1075                        CONFIG_USBD_HS
1076                        Define this to enable the high speed support for usb
1077                        device and usbtty. If this feature is enabled, a routine
1078                        int is_usbd_high_speed(void)
1079                        also needs to be defined by the driver to dynamically poll
1080                        whether the enumeration has succeded at high speed or full
1081                        speed.
1082
1083                        CONFIG_SYS_CONSOLE_IS_IN_ENV
1084                        Define this if you want stdin, stdout &/or stderr to
1085                        be set to usbtty.
1086
1087                If you have a USB-IF assigned VendorID then you may wish to
1088                define your own vendor specific values either in BoardName.h
1089                or directly in usbd_vendor_info.h. If you don't define
1090                CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1091                CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1092                should pretend to be a Linux device to it's target host.
1093
1094                        CONFIG_USBD_MANUFACTURER
1095                        Define this string as the name of your company for
1096                        - CONFIG_USBD_MANUFACTURER "my company"
1097
1098                        CONFIG_USBD_PRODUCT_NAME
1099                        Define this string as the name of your product
1100                        - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1101
1102                        CONFIG_USBD_VENDORID
1103                        Define this as your assigned Vendor ID from the USB
1104                        Implementors Forum. This *must* be a genuine Vendor ID
1105                        to avoid polluting the USB namespace.
1106                        - CONFIG_USBD_VENDORID 0xFFFF
1107
1108                        CONFIG_USBD_PRODUCTID
1109                        Define this as the unique Product ID
1110                        for your device
1111                        - CONFIG_USBD_PRODUCTID 0xFFFF
1112
1113- ULPI Layer Support:
1114                The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1115                the generic ULPI layer. The generic layer accesses the ULPI PHY
1116                via the platform viewport, so you need both the genric layer and
1117                the viewport enabled. Currently only Chipidea/ARC based
1118                viewport is supported.
1119                To enable the ULPI layer support, define CONFIG_USB_ULPI and
1120                CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1121                If your ULPI phy needs a different reference clock than the
1122                standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1123                the appropriate value in Hz.
1124
1125- MMC Support:
1126                The MMC controller on the Intel PXA is supported. To
1127                enable this define CONFIG_MMC. The MMC can be
1128                accessed from the boot prompt by mapping the device
1129                to physical memory similar to flash. Command line is
1130                enabled with CONFIG_CMD_MMC. The MMC driver also works with
1131                the FAT fs. This is enabled with CONFIG_CMD_FAT.
1132
1133                CONFIG_SH_MMCIF
1134                Support for Renesas on-chip MMCIF controller
1135
1136                        CONFIG_SH_MMCIF_ADDR
1137                        Define the base address of MMCIF registers
1138
1139                        CONFIG_SH_MMCIF_CLK
1140                        Define the clock frequency for MMCIF
1141
1142                CONFIG_SUPPORT_EMMC_BOOT
1143                Enable some additional features of the eMMC boot partitions.
1144
1145- USB Device Firmware Update (DFU) class support:
1146                CONFIG_DFU_OVER_USB
1147                This enables the USB portion of the DFU USB class
1148
1149                CONFIG_DFU_MMC
1150                This enables support for exposing (e)MMC devices via DFU.
1151
1152                CONFIG_DFU_NAND
1153                This enables support for exposing NAND devices via DFU.
1154
1155                CONFIG_DFU_RAM
1156                This enables support for exposing RAM via DFU.
1157                Note: DFU spec refer to non-volatile memory usage, but
1158                allow usages beyond the scope of spec - here RAM usage,
1159                one that would help mostly the developer.
1160
1161                CONFIG_SYS_DFU_DATA_BUF_SIZE
1162                Dfu transfer uses a buffer before writing data to the
1163                raw storage device. Make the size (in bytes) of this buffer
1164                configurable. The size of this buffer is also configurable
1165                through the "dfu_bufsiz" environment variable.
1166
1167                CONFIG_SYS_DFU_MAX_FILE_SIZE
1168                When updating files rather than the raw storage device,
1169                we use a static buffer to copy the file into and then write
1170                the buffer once we've been given the whole file.  Define
1171                this to the maximum filesize (in bytes) for the buffer.
1172                Default is 4 MiB if undefined.
1173
1174                DFU_DEFAULT_POLL_TIMEOUT
1175                Poll timeout [ms], is the timeout a device can send to the
1176                host. The host must wait for this timeout before sending
1177                a subsequent DFU_GET_STATUS request to the device.
1178
1179                DFU_MANIFEST_POLL_TIMEOUT
1180                Poll timeout [ms], which the device sends to the host when
1181                entering dfuMANIFEST state. Host waits this timeout, before
1182                sending again an USB request to the device.
1183
1184- Journaling Flash filesystem support:
1185                CONFIG_JFFS2_NAND
1186                Define these for a default partition on a NAND device
1187
1188                CONFIG_SYS_JFFS2_FIRST_SECTOR,
1189                CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1190                Define these for a default partition on a NOR device
1191
1192- Keyboard Support:
1193                See Kconfig help for available keyboard drivers.
1194
1195                CONFIG_KEYBOARD
1196
1197                Define this to enable a custom keyboard support.
1198                This simply calls drv_keyboard_init() which must be
1199                defined in your board-specific files. This option is deprecated
1200                and is only used by novena. For new boards, use driver model
1201                instead.
1202
1203- Video support:
1204                CONFIG_FSL_DIU_FB
1205                Enable the Freescale DIU video driver.  Reference boards for
1206                SOCs that have a DIU should define this macro to enable DIU
1207                support, and should also define these other macros:
1208
1209                        CONFIG_SYS_DIU_ADDR
1210                        CONFIG_VIDEO
1211                        CONFIG_CFB_CONSOLE
1212                        CONFIG_VIDEO_SW_CURSOR
1213                        CONFIG_VGA_AS_SINGLE_DEVICE
1214                        CONFIG_VIDEO_LOGO
1215                        CONFIG_VIDEO_BMP_LOGO
1216
1217                The DIU driver will look for the 'video-mode' environment
1218                variable, and if defined, enable the DIU as a console during
1219                boot.  See the documentation file doc/README.video for a
1220                description of this variable.
1221
1222- LCD Support:  CONFIG_LCD
1223
1224                Define this to enable LCD support (for output to LCD
1225                display); also select one of the supported displays
1226                by defining one of these:
1227
1228                CONFIG_ATMEL_LCD:
1229
1230                        HITACHI TX09D70VM1CCA, 3.5", 240x320.
1231
1232                CONFIG_NEC_NL6448AC33:
1233
1234                        NEC NL6448AC33-18. Active, color, single scan.
1235
1236                CONFIG_NEC_NL6448BC20
1237
1238                        NEC NL6448BC20-08. 6.5", 640x480.
1239                        Active, color, single scan.
1240
1241                CONFIG_NEC_NL6448BC33_54
1242
1243                        NEC NL6448BC33-54. 10.4", 640x480.
1244                        Active, color, single scan.
1245
1246                CONFIG_SHARP_16x9
1247
1248                        Sharp 320x240. Active, color, single scan.
1249                        It isn't 16x9, and I am not sure what it is.
1250
1251                CONFIG_SHARP_LQ64D341
1252
1253                        Sharp LQ64D341 display, 640x480.
1254                        Active, color, single scan.
1255
1256                CONFIG_HLD1045
1257
1258                        HLD1045 display, 640x480.
1259                        Active, color, single scan.
1260
1261                CONFIG_OPTREX_BW
1262
1263                        Optrex   CBL50840-2 NF-FW 99 22 M5
1264                        or
1265                        Hitachi  LMG6912RPFC-00T
1266                        or
1267                        Hitachi  SP14Q002
1268
1269                        320x240. Black & white.
1270
1271                CONFIG_LCD_ALIGNMENT
1272
1273                Normally the LCD is page-aligned (typically 4KB). If this is
1274                defined then the LCD will be aligned to this value instead.
1275                For ARM it is sometimes useful to use MMU_SECTION_SIZE
1276                here, since it is cheaper to change data cache settings on
1277                a per-section basis.
1278
1279
1280                CONFIG_LCD_ROTATION
1281
1282                Sometimes, for example if the display is mounted in portrait
1283                mode or even if it's mounted landscape but rotated by 180degree,
1284                we need to rotate our content of the display relative to the
1285                framebuffer, so that user can read the messages which are
1286                printed out.
1287                Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1288                initialized with a given rotation from "vl_rot" out of
1289                "vidinfo_t" which is provided by the board specific code.
1290                The value for vl_rot is coded as following (matching to
1291                fbcon=rotate:<n> linux-kernel commandline):
1292                0 = no rotation respectively 0 degree
1293                1 = 90 degree rotation
1294                2 = 180 degree rotation
1295                3 = 270 degree rotation
1296
1297                If CONFIG_LCD_ROTATION is not defined, the console will be
1298                initialized with 0degree rotation.
1299
1300                CONFIG_LCD_BMP_RLE8
1301
1302                Support drawing of RLE8-compressed bitmaps on the LCD.
1303
1304                CONFIG_I2C_EDID
1305
1306                Enables an 'i2c edid' command which can read EDID
1307                information over I2C from an attached LCD display.
1308
1309- Splash Screen Support: CONFIG_SPLASH_SCREEN
1310
1311                If this option is set, the environment is checked for
1312                a variable "splashimage". If found, the usual display
1313                of logo, copyright and system information on the LCD
1314                is suppressed and the BMP image at the address
1315                specified in "splashimage" is loaded instead. The
1316                console is redirected to the "nulldev", too. This
1317                allows for a "silent" boot where a splash screen is
1318                loaded very quickly after power-on.
1319
1320                CONFIG_SPLASHIMAGE_GUARD
1321
1322                If this option is set, then U-Boot will prevent the environment
1323                variable "splashimage" from being set to a problematic address
1324                (see doc/README.displaying-bmps).
1325                This option is useful for targets where, due to alignment
1326                restrictions, an improperly aligned BMP image will cause a data
1327                abort. If you think you will not have problems with unaligned
1328                accesses (for example because your toolchain prevents them)
1329                there is no need to set this option.
1330
1331                CONFIG_SPLASH_SCREEN_ALIGN
1332
1333                If this option is set the splash image can be freely positioned
1334                on the screen. Environment variable "splashpos" specifies the
1335                position as "x,y". If a positive number is given it is used as
1336                number of pixel from left/top. If a negative number is given it
1337                is used as number of pixel from right/bottom. You can also
1338                specify 'm' for centering the image.
1339
1340                Example:
1341                setenv splashpos m,m
1342                        => image at center of screen
1343
1344                setenv splashpos 30,20
1345                        => image at x = 30 and y = 20
1346
1347                setenv splashpos -10,m
1348                        => vertically centered image
1349                           at x = dspWidth - bmpWidth - 9
1350
1351- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1352
1353                If this option is set, additionally to standard BMP
1354                images, gzipped BMP images can be displayed via the
1355                splashscreen support or the bmp command.
1356
1357- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1358
1359                If this option is set, 8-bit RLE compressed BMP images
1360                can be displayed via the splashscreen support or the
1361                bmp command.
1362
1363- Compression support:
1364                CONFIG_GZIP
1365
1366                Enabled by default to support gzip compressed images.
1367
1368                CONFIG_BZIP2
1369
1370                If this option is set, support for bzip2 compressed
1371                images is included. If not, only uncompressed and gzip
1372                compressed images are supported.
1373
1374                NOTE: the bzip2 algorithm requires a lot of RAM, so
1375                the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1376                be at least 4MB.
1377
1378- MII/PHY support:
1379                CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1380
1381                The clock frequency of the MII bus
1382
1383                CONFIG_PHY_RESET_DELAY
1384
1385                Some PHY like Intel LXT971A need extra delay after
1386                reset before any MII register access is possible.
1387                For such PHY, set this option to the usec delay
1388                required. (minimum 300usec for LXT971A)
1389
1390                CONFIG_PHY_CMD_DELAY (ppc4xx)
1391
1392                Some PHY like Intel LXT971A need extra delay after
1393                command issued before MII status register can be read
1394
1395- IP address:
1396                CONFIG_IPADDR
1397
1398                Define a default value for the IP address to use for
1399                the default Ethernet interface, in case this is not
1400                determined through e.g. bootp.
1401                (Environment variable "ipaddr")
1402
1403- Server IP address:
1404                CONFIG_SERVERIP
1405
1406                Defines a default value for the IP address of a TFTP
1407                server to contact when using the "tftboot" command.
1408                (Environment variable "serverip")
1409
1410                CONFIG_KEEP_SERVERADDR
1411
1412                Keeps the server's MAC address, in the env 'serveraddr'
1413                for passing to bootargs (like Linux's netconsole option)
1414
1415- Gateway IP address:
1416                CONFIG_GATEWAYIP
1417
1418                Defines a default value for the IP address of the
1419                default router where packets to other networks are
1420                sent to.
1421                (Environment variable "gatewayip")
1422
1423- Subnet mask:
1424                CONFIG_NETMASK
1425
1426                Defines a default value for the subnet mask (or
1427                routing prefix) which is used to determine if an IP
1428                address belongs to the local subnet or needs to be
1429                forwarded through a router.
1430                (Environment variable "netmask")
1431
1432- Multicast TFTP Mode:
1433                CONFIG_MCAST_TFTP
1434
1435                Defines whether you want to support multicast TFTP as per
1436                rfc-2090; for example to work with atftp.  Lets lots of targets
1437                tftp down the same boot image concurrently.  Note: the Ethernet
1438                driver in use must provide a function: mcast() to join/leave a
1439                multicast group.
1440
1441- BOOTP Recovery Mode:
1442                CONFIG_BOOTP_RANDOM_DELAY
1443
1444                If you have many targets in a network that try to
1445                boot using BOOTP, you may want to avoid that all
1446                systems send out BOOTP requests at precisely the same
1447                moment (which would happen for instance at recovery
1448                from a power failure, when all systems will try to
1449                boot, thus flooding the BOOTP server. Defining
1450                CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1451                inserted before sending out BOOTP requests. The
1452                following delays are inserted then:
1453
1454                1st BOOTP request:      delay 0 ... 1 sec
1455                2nd BOOTP request:      delay 0 ... 2 sec
1456                3rd BOOTP request:      delay 0 ... 4 sec
1457                4th and following
1458                BOOTP requests:         delay 0 ... 8 sec
1459
1460                CONFIG_BOOTP_ID_CACHE_SIZE
1461
1462                BOOTP packets are uniquely identified using a 32-bit ID. The
1463                server will copy the ID from client requests to responses and
1464                U-Boot will use this to determine if it is the destination of
1465                an incoming response. Some servers will check that addresses
1466                aren't in use before handing them out (usually using an ARP
1467                ping) and therefore take up to a few hundred milliseconds to
1468                respond. Network congestion may also influence the time it
1469                takes for a response to make it back to the client. If that
1470                time is too long, U-Boot will retransmit requests. In order
1471                to allow earlier responses to still be accepted after these
1472                retransmissions, U-Boot's BOOTP client keeps a small cache of
1473                IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1474                cache. The default is to keep IDs for up to four outstanding
1475                requests. Increasing this will allow U-Boot to accept offers
1476                from a BOOTP client in networks with unusually high latency.
1477
1478- DHCP Advanced Options:
1479                You can fine tune the DHCP functionality by defining
1480                CONFIG_BOOTP_* symbols:
1481
1482                CONFIG_BOOTP_NISDOMAIN
1483                CONFIG_BOOTP_BOOTFILESIZE
1484                CONFIG_BOOTP_SEND_HOSTNAME
1485                CONFIG_BOOTP_NTPSERVER
1486                CONFIG_BOOTP_TIMEOFFSET
1487                CONFIG_BOOTP_VENDOREX
1488                CONFIG_BOOTP_MAY_FAIL
1489
1490                CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1491                environment variable, not the BOOTP server.
1492
1493                CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1494                after the configured retry count, the call will fail
1495                instead of starting over.  This can be used to fail over
1496                to Link-local IP address configuration if the DHCP server
1497                is not available.
1498
1499                CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1500                to do a dynamic update of a DNS server. To do this, they
1501                need the hostname of the DHCP requester.
1502                If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1503                of the "hostname" environment variable is passed as
1504                option 12 to the DHCP server.
1505
1506                CONFIG_BOOTP_DHCP_REQUEST_DELAY
1507
1508                A 32bit value in microseconds for a delay between
1509                receiving a "DHCP Offer" and sending the "DHCP Request".
1510                This fixes a problem with certain DHCP servers that don't
1511                respond 100% of the time to a "DHCP request". E.g. On an
1512                AT91RM9200 processor running at 180MHz, this delay needed
1513                to be *at least* 15,000 usec before a Windows Server 2003
1514                DHCP server would reply 100% of the time. I recommend at
1515                least 50,000 usec to be safe. The alternative is to hope
1516                that one of the retries will be successful but note that
1517                the DHCP timeout and retry process takes a longer than
1518                this delay.
1519
1520 - Link-local IP address negotiation:
1521                Negotiate with other link-local clients on the local network
1522                for an address that doesn't require explicit configuration.
1523                This is especially useful if a DHCP server cannot be guaranteed
1524                to exist in all environments that the device must operate.
1525
1526                See doc/README.link-local for more information.
1527
1528 - MAC address from environment variables
1529
1530                FDT_SEQ_MACADDR_FROM_ENV
1531
1532                Fix-up device tree with MAC addresses fetched sequentially from
1533                environment variables. This config work on assumption that
1534                non-usable ethernet node of device-tree are either not present
1535                or their status has been marked as "disabled".
1536
1537 - CDP Options:
1538                CONFIG_CDP_DEVICE_ID
1539
1540                The device id used in CDP trigger frames.
1541
1542                CONFIG_CDP_DEVICE_ID_PREFIX
1543
1544                A two character string which is prefixed to the MAC address
1545                of the device.
1546
1547                CONFIG_CDP_PORT_ID
1548
1549                A printf format string which contains the ascii name of
1550                the port. Normally is set to "eth%d" which sets
1551                eth0 for the first Ethernet, eth1 for the second etc.
1552
1553                CONFIG_CDP_CAPABILITIES
1554
1555                A 32bit integer which indicates the device capabilities;
1556                0x00000010 for a normal host which does not forwards.
1557
1558                CONFIG_CDP_VERSION
1559
1560                An ascii string containing the version of the software.
1561
1562                CONFIG_CDP_PLATFORM
1563
1564                An ascii string containing the name of the platform.
1565
1566                CONFIG_CDP_TRIGGER
1567
1568                A 32bit integer sent on the trigger.
1569
1570                CONFIG_CDP_POWER_CONSUMPTION
1571
1572                A 16bit integer containing the power consumption of the
1573                device in .1 of milliwatts.
1574
1575                CONFIG_CDP_APPLIANCE_VLAN_TYPE
1576
1577                A byte containing the id of the VLAN.
1578
1579- Status LED:   CONFIG_LED_STATUS
1580
1581                Several configurations allow to display the current
1582                status using a LED. For instance, the LED will blink
1583                fast while running U-Boot code, stop blinking as
1584                soon as a reply to a BOOTP request was received, and
1585                start blinking slow once the Linux kernel is running
1586                (supported by a status LED driver in the Linux
1587                kernel). Defining CONFIG_LED_STATUS enables this
1588                feature in U-Boot.
1589
1590                Additional options:
1591
1592                CONFIG_LED_STATUS_GPIO
1593                The status LED can be connected to a GPIO pin.
1594                In such cases, the gpio_led driver can be used as a
1595                status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1596                to include the gpio_led driver in the U-Boot binary.
1597
1598                CONFIG_GPIO_LED_INVERTED_TABLE
1599                Some GPIO connected LEDs may have inverted polarity in which
1600                case the GPIO high value corresponds to LED off state and
1601                GPIO low value corresponds to LED on state.
1602                In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1603                with a list of GPIO LEDs that have inverted polarity.
1604
1605- I2C Support:  CONFIG_SYS_I2C
1606
1607                This enable the NEW i2c subsystem, and will allow you to use
1608                i2c commands at the u-boot command line (as long as you set
1609                CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1610                based realtime clock chips or other i2c devices. See
1611                common/cmd_i2c.c for a description of the command line
1612                interface.
1613
1614                ported i2c driver to the new framework:
1615                - drivers/i2c/soft_i2c.c:
1616                  - activate first bus with CONFIG_SYS_I2C_SOFT define
1617                    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1618                    for defining speed and slave address
1619                  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1620                    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1621                    for defining speed and slave address
1622                  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1623                    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1624                    for defining speed and slave address
1625                  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1626                    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1627                    for defining speed and slave address
1628
1629                - drivers/i2c/fsl_i2c.c:
1630                  - activate i2c driver with CONFIG_SYS_I2C_FSL
1631                    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1632                    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1633                    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1634                    bus.
1635                  - If your board supports a second fsl i2c bus, define
1636                    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1637                    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1638                    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1639                    second bus.
1640
1641                - drivers/i2c/tegra_i2c.c:
1642                  - activate this driver with CONFIG_SYS_I2C_TEGRA
1643                  - This driver adds 4 i2c buses with a fix speed from
1644                    100000 and the slave addr 0!
1645
1646                - drivers/i2c/ppc4xx_i2c.c
1647                  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1648                  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1649                  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1650
1651                - drivers/i2c/i2c_mxc.c
1652                  - activate this driver with CONFIG_SYS_I2C_MXC
1653                  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1654                  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1655                  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1656                  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1657                  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1658                  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1659                  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1660                  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1661                  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1662                  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1663                  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1664                  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1665                If those defines are not set, default value is 100000
1666                for speed, and 0 for slave.
1667
1668                - drivers/i2c/rcar_i2c.c:
1669                  - activate this driver with CONFIG_SYS_I2C_RCAR
1670                  - This driver adds 4 i2c buses
1671
1672                  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1673                  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1674                  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1675                  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1676                  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1677                  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1678                  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1679                  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1680                  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1681
1682                - drivers/i2c/sh_i2c.c:
1683                  - activate this driver with CONFIG_SYS_I2C_SH
1684                  - This driver adds from 2 to 5 i2c buses
1685
1686                  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1687                  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1688                  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1689                  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1690                  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1691                  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1692                  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1693                  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1694                  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1695                  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1696                  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1697
1698                - drivers/i2c/omap24xx_i2c.c
1699                  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1700                  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1701                  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1702                  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1703                  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1704                  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1705                  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1706                  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1707                  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1708                  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1709                  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1710
1711                - drivers/i2c/zynq_i2c.c
1712                  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1713                  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1714                  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1715
1716                - drivers/i2c/s3c24x0_i2c.c:
1717                  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1718                  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1719                    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1720                    with a fix speed from 100000 and the slave addr 0!
1721
1722                - drivers/i2c/ihs_i2c.c
1723                  - activate this driver with CONFIG_SYS_I2C_IHS
1724                  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1725                  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1726                  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1727                  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1728                  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1729                  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1730                  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1731                  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1732                  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1733                  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1734                  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1735                  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1736                  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1737                  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1738                  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1739                  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1740                  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1741                  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1742                  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1743                  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1744                  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1745
1746                additional defines:
1747
1748                CONFIG_SYS_NUM_I2C_BUSES
1749                Hold the number of i2c buses you want to use.
1750
1751                CONFIG_SYS_I2C_DIRECT_BUS
1752                define this, if you don't use i2c muxes on your hardware.
1753                if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1754                omit this define.
1755
1756                CONFIG_SYS_I2C_MAX_HOPS
1757                define how many muxes are maximal consecutively connected
1758                on one i2c bus. If you not use i2c muxes, omit this
1759                define.
1760
1761                CONFIG_SYS_I2C_BUSES
1762                hold a list of buses you want to use, only used if
1763                CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1764                a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1765                CONFIG_SYS_NUM_I2C_BUSES = 9:
1766
1767                 CONFIG_SYS_I2C_BUSES   {{0, {I2C_NULL_HOP}}, \
1768                                        {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1769                                        {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1770                                        {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1771                                        {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1772                                        {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1773                                        {1, {I2C_NULL_HOP}}, \
1774                                        {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1775                                        {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1776                                        }
1777
1778                which defines
1779                        bus 0 on adapter 0 without a mux
1780                        bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1781                        bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1782                        bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1783                        bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1784                        bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1785                        bus 6 on adapter 1 without a mux
1786                        bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1787                        bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1788
1789                If you do not have i2c muxes on your board, omit this define.
1790
1791- Legacy I2C Support:
1792                If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1793                then the following macros need to be defined (examples are
1794                from include/configs/lwmon.h):
1795
1796                I2C_INIT
1797
1798                (Optional). Any commands necessary to enable the I2C
1799                controller or configure ports.
1800
1801                eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=  PB_SCL)
1802
1803                I2C_ACTIVE
1804
1805                The code necessary to make the I2C data line active
1806                (driven).  If the data line is open collector, this
1807                define can be null.
1808
1809                eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1810
1811                I2C_TRISTATE
1812
1813                The code necessary to make the I2C data line tri-stated
1814                (inactive).  If the data line is open collector, this
1815                define can be null.
1816
1817                eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1818
1819                I2C_READ
1820
1821                Code that returns true if the I2C data line is high,
1822                false if it is low.
1823
1824                eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1825
1826                I2C_SDA(bit)
1827
1828                If <bit> is true, sets the I2C data line high. If it
1829                is false, it clears it (low).
1830
1831                eg: #define I2C_SDA(bit) \
1832                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1833                        else    immr->im_cpm.cp_pbdat &= ~PB_SDA
1834
1835                I2C_SCL(bit)
1836
1837                If <bit> is true, sets the I2C clock line high. If it
1838                is false, it clears it (low).
1839
1840                eg: #define I2C_SCL(bit) \
1841                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1842                        else    immr->im_cpm.cp_pbdat &= ~PB_SCL
1843
1844                I2C_DELAY
1845
1846                This delay is invoked four times per clock cycle so this
1847                controls the rate of data transfer.  The data rate thus
1848                is 1 / (I2C_DELAY * 4). Often defined to be something
1849                like:
1850
1851                #define I2C_DELAY  udelay(2)
1852
1853                CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1854
1855                If your arch supports the generic GPIO framework (asm/gpio.h),
1856                then you may alternatively define the two GPIOs that are to be
1857                used as SCL / SDA.  Any of the previous I2C_xxx macros will
1858                have GPIO-based defaults assigned to them as appropriate.
1859
1860                You should define these to the GPIO value as given directly to
1861                the generic GPIO functions.
1862
1863                CONFIG_SYS_I2C_INIT_BOARD
1864
1865                When a board is reset during an i2c bus transfer
1866                chips might think that the current transfer is still
1867                in progress. On some boards it is possible to access
1868                the i2c SCLK line directly, either by using the
1869                processor pin as a GPIO or by having a second pin
1870                connected to the bus. If this option is defined a
1871                custom i2c_init_board() routine in boards/xxx/board.c
1872                is run early in the boot sequence.
1873
1874                CONFIG_I2C_MULTI_BUS
1875
1876                This option allows the use of multiple I2C buses, each of which
1877                must have a controller.  At any point in time, only one bus is
1878                active.  To switch to a different bus, use the 'i2c dev' command.
1879                Note that bus numbering is zero-based.
1880
1881                CONFIG_SYS_I2C_NOPROBES
1882
1883                This option specifies a list of I2C devices that will be skipped
1884                when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1885                is set, specify a list of bus-device pairs.  Otherwise, specify
1886                a 1D array of device addresses
1887
1888                e.g.
1889                        #undef  CONFIG_I2C_MULTI_BUS
1890                        #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1891
1892                will skip addresses 0x50 and 0x68 on a board with one I2C bus
1893
1894                        #define CONFIG_I2C_MULTI_BUS
1895                        #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1896
1897                will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1898
1899                CONFIG_SYS_SPD_BUS_NUM
1900
1901                If defined, then this indicates the I2C bus number for DDR SPD.
1902                If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1903
1904                CONFIG_SYS_RTC_BUS_NUM
1905
1906                If defined, then this indicates the I2C bus number for the RTC.
1907                If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1908
1909                CONFIG_SOFT_I2C_READ_REPEATED_START
1910
1911                defining this will force the i2c_read() function in
1912                the soft_i2c driver to perform an I2C repeated start
1913                between writing the address pointer and reading the
1914                data.  If this define is omitted the default behaviour
1915                of doing a stop-start sequence will be used.  Most I2C
1916                devices can use either method, but some require one or
1917                the other.
1918
1919- SPI Support:  CONFIG_SPI
1920
1921                Enables SPI driver (so far only tested with
1922                SPI EEPROM, also an instance works with Crystal A/D and
1923                D/As on the SACSng board)
1924
1925                CONFIG_SOFT_SPI
1926
1927                Enables a software (bit-bang) SPI driver rather than
1928                using hardware support. This is a general purpose
1929                driver that only requires three general I/O port pins
1930                (two outputs, one input) to function. If this is
1931                defined, the board configuration must define several
1932                SPI configuration items (port pins to use, etc). For
1933                an example, see include/configs/sacsng.h.
1934
1935                CONFIG_SYS_SPI_MXC_WAIT
1936                Timeout for waiting until spi transfer completed.
1937                default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1938
1939- FPGA Support: CONFIG_FPGA
1940
1941                Enables FPGA subsystem.
1942
1943                CONFIG_FPGA_<vendor>
1944
1945                Enables support for specific chip vendors.
1946                (ALTERA, XILINX)
1947
1948                CONFIG_FPGA_<family>
1949
1950                Enables support for FPGA family.
1951                (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1952
1953                CONFIG_FPGA_COUNT
1954
1955                Specify the number of FPGA devices to support.
1956
1957                CONFIG_SYS_FPGA_PROG_FEEDBACK
1958
1959                Enable printing of hash marks during FPGA configuration.
1960
1961                CONFIG_SYS_FPGA_CHECK_BUSY
1962
1963                Enable checks on FPGA configuration interface busy
1964                status by the configuration function. This option
1965                will require a board or device specific function to
1966                be written.
1967
1968                CONFIG_FPGA_DELAY
1969
1970                If defined, a function that provides delays in the FPGA
1971                configuration driver.
1972
1973                CONFIG_SYS_FPGA_CHECK_CTRLC
1974                Allow Control-C to interrupt FPGA configuration
1975
1976                CONFIG_SYS_FPGA_CHECK_ERROR
1977
1978                Check for configuration errors during FPGA bitfile
1979                loading. For example, abort during Virtex II
1980                configuration if the INIT_B line goes low (which
1981                indicated a CRC error).
1982
1983                CONFIG_SYS_FPGA_WAIT_INIT
1984
1985                Maximum time to wait for the INIT_B line to de-assert
1986                after PROB_B has been de-asserted during a Virtex II
1987                FPGA configuration sequence. The default time is 500
1988                ms.
1989
1990                CONFIG_SYS_FPGA_WAIT_BUSY
1991
1992                Maximum time to wait for BUSY to de-assert during
1993                Virtex II FPGA configuration. The default is 5 ms.
1994
1995                CONFIG_SYS_FPGA_WAIT_CONFIG
1996
1997                Time to wait after FPGA configuration. The default is
1998                200 ms.
1999
2000- Configuration Management:
2001                CONFIG_BUILD_TARGET
2002
2003                Some SoCs need special image types (e.g. U-Boot binary
2004                with a special header) as build targets. By defining
2005                CONFIG_BUILD_TARGET in the SoC / board header, this
2006                special image will be automatically built upon calling
2007                make / buildman.
2008
2009                CONFIG_IDENT_STRING
2010
2011                If defined, this string will be added to the U-Boot
2012                version information (U_BOOT_VERSION)
2013
2014- Vendor Parameter Protection:
2015
2016                U-Boot considers the values of the environment
2017                variables "serial#" (Board Serial Number) and
2018                "ethaddr" (Ethernet Address) to be parameters that
2019                are set once by the board vendor / manufacturer, and
2020                protects these variables from casual modification by
2021                the user. Once set, these variables are read-only,
2022                and write or delete attempts are rejected. You can
2023                change this behaviour:
2024
2025                If CONFIG_ENV_OVERWRITE is #defined in your config
2026                file, the write protection for vendor parameters is
2027                completely disabled. Anybody can change or delete
2028                these parameters.
2029
2030                Alternatively, if you define _both_ an ethaddr in the
2031                default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2032                Ethernet address is installed in the environment,
2033                which can be changed exactly ONCE by the user. [The
2034                serial# is unaffected by this, i. e. it remains
2035                read-only.]
2036
2037                The same can be accomplished in a more flexible way
2038                for any variable by configuring the type of access
2039                to allow for those variables in the ".flags" variable
2040                or define CONFIG_ENV_FLAGS_LIST_STATIC.
2041
2042- Protected RAM:
2043                CONFIG_PRAM
2044
2045                Define this variable to enable the reservation of
2046                "protected RAM", i. e. RAM which is not overwritten
2047                by U-Boot. Define CONFIG_PRAM to hold the number of
2048                kB you want to reserve for pRAM. You can overwrite
2049                this default value by defining an environment
2050                variable "pram" to the number of kB you want to
2051                reserve. Note that the board info structure will
2052                still show the full amount of RAM. If pRAM is
2053                reserved, a new environment variable "mem" will
2054                automatically be defined to hold the amount of
2055                remaining RAM in a form that can be passed as boot
2056                argument to Linux, for instance like that:
2057
2058                        setenv bootargs ... mem=\${mem}
2059                        saveenv
2060
2061                This way you can tell Linux not to use this memory,
2062                either, which results in a memory region that will
2063                not be affected by reboots.
2064
2065                *WARNING* If your board configuration uses automatic
2066                detection of the RAM size, you must make sure that
2067                this memory test is non-destructive. So far, the
2068                following board configurations are known to be
2069                "pRAM-clean":
2070
2071                        IVMS8, IVML24, SPD8xx,
2072                        HERMES, IP860, RPXlite, LWMON,
2073                        FLAGADM
2074
2075- Access to physical memory region (> 4GB)
2076                Some basic support is provided for operations on memory not
2077                normally accessible to U-Boot - e.g. some architectures
2078                support access to more than 4GB of memory on 32-bit
2079                machines using physical address extension or similar.
2080                Define CONFIG_PHYSMEM to access this basic support, which
2081                currently only supports clearing the memory.
2082
2083- Error Recovery:
2084                CONFIG_NET_RETRY_COUNT
2085
2086                This variable defines the number of retries for
2087                network operations like ARP, RARP, TFTP, or BOOTP
2088                before giving up the operation. If not defined, a
2089                default value of 5 is used.
2090
2091                CONFIG_ARP_TIMEOUT
2092
2093                Timeout waiting for an ARP reply in milliseconds.
2094
2095                CONFIG_NFS_TIMEOUT
2096
2097                Timeout in milliseconds used in NFS protocol.
2098                If you encounter "ERROR: Cannot umount" in nfs command,
2099                try longer timeout such as
2100                #define CONFIG_NFS_TIMEOUT 10000UL
2101
2102- Command Interpreter:
2103                CONFIG_SYS_PROMPT_HUSH_PS2
2104
2105                This defines the secondary prompt string, which is
2106                printed when the command interpreter needs more input
2107                to complete a command. Usually "> ".
2108
2109        Note:
2110
2111                In the current implementation, the local variables
2112                space and global environment variables space are
2113                separated. Local variables are those you define by
2114                simply typing `name=value'. To access a local
2115                variable later on, you have write `$name' or
2116                `${name}'; to execute the contents of a variable
2117                directly type `$name' at the command prompt.
2118
2119                Global environment variables are those you use
2120                setenv/printenv to work with. To run a command stored
2121                in such a variable, you need to use the run command,
2122                and you must not use the '$' sign to access them.
2123
2124                To store commands and special characters in a
2125                variable, please use double quotation marks
2126                surrounding the whole text of the variable, instead
2127                of the backslashes before semicolons and special
2128                symbols.
2129
2130- Command Line Editing and History:
2131                CONFIG_CMDLINE_PS_SUPPORT
2132
2133                Enable support for changing the command prompt string
2134                at run-time. Only static string is supported so far.
2135                The string is obtained from environment variables PS1
2136                and PS2.
2137
2138- Default Environment:
2139                CONFIG_EXTRA_ENV_SETTINGS
2140
2141                Define this to contain any number of null terminated
2142                strings (variable = value pairs) that will be part of
2143                the default environment compiled into the boot image.
2144
2145                For example, place something like this in your
2146                board's config file:
2147
2148                #define CONFIG_EXTRA_ENV_SETTINGS \
2149                        "myvar1=value1\0" \
2150                        "myvar2=value2\0"
2151
2152                Warning: This method is based on knowledge about the
2153                internal format how the environment is stored by the
2154                U-Boot code. This is NOT an official, exported
2155                interface! Although it is unlikely that this format
2156                will change soon, there is no guarantee either.
2157                You better know what you are doing here.
2158
2159                Note: overly (ab)use of the default environment is
2160                discouraged. Make sure to check other ways to preset
2161                the environment like the "source" command or the
2162                boot command first.
2163
2164                CONFIG_DELAY_ENVIRONMENT
2165
2166                Normally the environment is loaded when the board is
2167                initialised so that it is available to U-Boot. This inhibits
2168                that so that the environment is not available until
2169                explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2170                this is instead controlled by the value of
2171                /config/load-environment.
2172
2173- Serial Flash support
2174                Usage requires an initial 'sf probe' to define the serial
2175                flash parameters, followed by read/write/erase/update
2176                commands.
2177
2178                The following defaults may be provided by the platform
2179                to handle the common case when only a single serial
2180                flash is present on the system.
2181
2182                CONFIG_SF_DEFAULT_BUS           Bus identifier
2183                CONFIG_SF_DEFAULT_CS            Chip-select
2184                CONFIG_SF_DEFAULT_MODE          (see include/spi.h)
2185                CONFIG_SF_DEFAULT_SPEED         in Hz
2186
2187
2188- TFTP Fixed UDP Port:
2189                CONFIG_TFTP_PORT
2190
2191                If this is defined, the environment variable tftpsrcp
2192                is used to supply the TFTP UDP source port value.
2193                If tftpsrcp isn't defined, the normal pseudo-random port
2194                number generator is used.
2195
2196                Also, the environment variable tftpdstp is used to supply
2197                the TFTP UDP destination port value.  If tftpdstp isn't
2198                defined, the normal port 69 is used.
2199
2200                The purpose for tftpsrcp is to allow a TFTP server to
2201                blindly start the TFTP transfer using the pre-configured
2202                target IP address and UDP port. This has the effect of
2203                "punching through" the (Windows XP) firewall, allowing
2204                the remainder of the TFTP transfer to proceed normally.
2205                A better solution is to properly configure the firewall,
2206                but sometimes that is not allowed.
2207
2208- Show boot progress:
2209                CONFIG_SHOW_BOOT_PROGRESS
2210
2211                Defining this option allows to add some board-
2212                specific code (calling a user-provided function
2213                "show_boot_progress(int)") that enables you to show
2214                the system's boot progress on some display (for
2215                example, some LED's) on your board. At the moment,
2216                the following checkpoints are implemented:
2217
2218
2219Legacy uImage format:
2220
2221  Arg   Where                   When
2222    1   common/cmd_bootm.c      before attempting to boot an image
2223   -1   common/cmd_bootm.c      Image header has bad     magic number
2224    2   common/cmd_bootm.c      Image header has correct magic number
2225   -2   common/cmd_bootm.c      Image header has bad     checksum
2226    3   common/cmd_bootm.c      Image header has correct checksum
2227   -3   common/cmd_bootm.c      Image data   has bad     checksum
2228    4   common/cmd_bootm.c      Image data   has correct checksum
2229   -4   common/cmd_bootm.c      Image is for unsupported architecture
2230    5   common/cmd_bootm.c      Architecture check OK
2231   -5   common/cmd_bootm.c      Wrong Image Type (not kernel, multi)
2232    6   common/cmd_bootm.c      Image Type check OK
2233   -6   common/cmd_bootm.c      gunzip uncompression error
2234   -7   common/cmd_bootm.c      Unimplemented compression type
2235    7   common/cmd_bootm.c      Uncompression OK
2236    8   common/cmd_bootm.c      No uncompress/copy overwrite error
2237   -9   common/cmd_bootm.c      Unsupported OS (not Linux, BSD, VxWorks, QNX)
2238
2239    9   common/image.c          Start initial ramdisk verification
2240  -10   common/image.c          Ramdisk header has bad     magic number
2241  -11   common/image.c          Ramdisk header has bad     checksum
2242   10   common/image.c          Ramdisk header is OK
2243  -12   common/image.c          Ramdisk data   has bad     checksum
2244   11   common/image.c          Ramdisk data   has correct checksum
2245   12   common/image.c          Ramdisk verification complete, start loading
2246  -13   common/image.c          Wrong Image Type (not PPC Linux ramdisk)
2247   13   common/image.c          Start multifile image verification
2248   14   common/image.c          No initial ramdisk, no multifile, continue.
2249
2250   15   arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2251
2252  -30   arch/powerpc/lib/board.c        Fatal error, hang the system
2253  -31   post/post.c             POST test failed, detected by post_output_backlog()
2254  -32   post/post.c             POST test failed, detected by post_run_single()
2255
2256   34   common/cmd_doc.c        before loading a Image from a DOC device
2257  -35   common/cmd_doc.c        Bad usage of "doc" command
2258   35   common/cmd_doc.c        correct usage of "doc" command
2259  -36   common/cmd_doc.c        No boot device
2260   36   common/cmd_doc.c        correct boot device
2261  -37   common/cmd_doc.c        Unknown Chip ID on boot device
2262   37   common/cmd_doc.c        correct chip ID found, device available
2263  -38   common/cmd_doc.c        Read Error on boot device
2264   38   common/cmd_doc.c        reading Image header from DOC device OK
2265  -39   common/cmd_doc.c        Image header has bad magic number
2266   39   common/cmd_doc.c        Image header has correct magic number
2267  -40   common/cmd_doc.c        Error reading Image from DOC device
2268   40   common/cmd_doc.c        Image header has correct magic number
2269   41   common/cmd_ide.c        before loading a Image from a IDE device
2270  -42   common/cmd_ide.c        Bad usage of "ide" command
2271   42   common/cmd_ide.c        correct usage of "ide" command
2272  -43   common/cmd_ide.c        No boot device
2273   43   common/cmd_ide.c        boot device found
2274  -44   common/cmd_ide.c        Device not available
2275   44   common/cmd_ide.c        Device available
2276  -45   common/cmd_ide.c        wrong partition selected
2277   45   common/cmd_ide.c        partition selected
2278  -46   common/cmd_ide.c        Unknown partition table
2279   46   common/cmd_ide.c        valid partition table found
2280  -47   common/cmd_ide.c        Invalid partition type
2281   47   common/cmd_ide.c        correct partition type
2282  -48   common/cmd_ide.c        Error reading Image Header on boot device
2283   48   common/cmd_ide.c        reading Image Header from IDE device OK
2284  -49   common/cmd_ide.c        Image header has bad magic number
2285   49   common/cmd_ide.c        Image header has correct magic number
2286  -50   common/cmd_ide.c        Image header has bad     checksum
2287   50   common/cmd_ide.c        Image header has correct checksum
2288  -51   common/cmd_ide.c        Error reading Image from IDE device
2289   51   common/cmd_ide.c        reading Image from IDE device OK
2290   52   common/cmd_nand.c       before loading a Image from a NAND device
2291  -53   common/cmd_nand.c       Bad usage of "nand" command
2292   53   common/cmd_nand.c       correct usage of "nand" command
2293  -54   common/cmd_nand.c       No boot device
2294   54   common/cmd_nand.c       boot device found
2295  -55   common/cmd_nand.c       Unknown Chip ID on boot device
2296   55   common/cmd_nand.c       correct chip ID found, device available
2297  -56   common/cmd_nand.c       Error reading Image Header on boot device
2298   56   common/cmd_nand.c       reading Image Header from NAND device OK
2299  -57   common/cmd_nand.c       Image header has bad magic number
2300   57   common/cmd_nand.c       Image header has correct magic number
2301  -58   common/cmd_nand.c       Error reading Image from NAND device
2302   58   common/cmd_nand.c       reading Image from NAND device OK
2303
2304  -60   common/env_common.c     Environment has a bad CRC, using default
2305
2306   64   net/eth.c               starting with Ethernet configuration.
2307  -64   net/eth.c               no Ethernet found.
2308   65   net/eth.c               Ethernet found.
2309
2310  -80   common/cmd_net.c        usage wrong
2311   80   common/cmd_net.c        before calling net_loop()
2312  -81   common/cmd_net.c        some error in net_loop() occurred
2313   81   common/cmd_net.c        net_loop() back without error
2314  -82   common/cmd_net.c        size == 0 (File with size 0 loaded)
2315   82   common/cmd_net.c        trying automatic boot
2316   83   common/cmd_net.c        running "source" command
2317  -83   common/cmd_net.c        some error in automatic boot or "source" command
2318   84   common/cmd_net.c        end without errors
2319
2320FIT uImage format:
2321
2322  Arg   Where                   When
2323  100   common/cmd_bootm.c      Kernel FIT Image has correct format
2324 -100   common/cmd_bootm.c      Kernel FIT Image has incorrect format
2325  101   common/cmd_bootm.c      No Kernel subimage unit name, using configuration
2326 -101   common/cmd_bootm.c      Can't get configuration for kernel subimage
2327  102   common/cmd_bootm.c      Kernel unit name specified
2328 -103   common/cmd_bootm.c      Can't get kernel subimage node offset
2329  103   common/cmd_bootm.c      Found configuration node
2330  104   common/cmd_bootm.c      Got kernel subimage node offset
2331 -104   common/cmd_bootm.c      Kernel subimage hash verification failed
2332  105   common/cmd_bootm.c      Kernel subimage hash verification OK
2333 -105   common/cmd_bootm.c      Kernel subimage is for unsupported architecture
2334  106   common/cmd_bootm.c      Architecture check OK
2335 -106   common/cmd_bootm.c      Kernel subimage has wrong type
2336  107   common/cmd_bootm.c      Kernel subimage type OK
2337 -107   common/cmd_bootm.c      Can't get kernel subimage data/size
2338  108   common/cmd_bootm.c      Got kernel subimage data/size
2339 -108   common/cmd_bootm.c      Wrong image type (not legacy, FIT)
2340 -109   common/cmd_bootm.c      Can't get kernel subimage type
2341 -110   common/cmd_bootm.c      Can't get kernel subimage comp
2342 -111   common/cmd_bootm.c      Can't get kernel subimage os
2343 -112   common/cmd_bootm.c      Can't get kernel subimage load address
2344 -113   common/cmd_bootm.c      Image uncompress/copy overwrite error
2345
2346  120   common/image.c          Start initial ramdisk verification
2347 -120   common/image.c          Ramdisk FIT image has incorrect format
2348  121   common/image.c          Ramdisk FIT image has correct format
2349  122   common/image.c          No ramdisk subimage unit name, using configuration
2350 -122   common/image.c          Can't get configuration for ramdisk subimage
2351  123   common/image.c          Ramdisk unit name specified
2352 -124   common/image.c          Can't get ramdisk subimage node offset
2353  125   common/image.c          Got ramdisk subimage node offset
2354 -125   common/image.c          Ramdisk subimage hash verification failed
2355  126   common/image.c          Ramdisk subimage hash verification OK
2356 -126   common/image.c          Ramdisk subimage for unsupported architecture
2357  127   common/image.c          Architecture check OK
2358 -127   common/image.c          Can't get ramdisk subimage data/size
2359  128   common/image.c          Got ramdisk subimage data/size
2360  129   common/image.c          Can't get ramdisk load address
2361 -129   common/image.c          Got ramdisk load address
2362
2363 -130   common/cmd_doc.c        Incorrect FIT image format
2364  131   common/cmd_doc.c        FIT image format OK
2365
2366 -140   common/cmd_ide.c        Incorrect FIT image format
2367  141   common/cmd_ide.c        FIT image format OK
2368
2369 -150   common/cmd_nand.c       Incorrect FIT image format
2370  151   common/cmd_nand.c       FIT image format OK
2371
2372- Standalone program support:
2373                CONFIG_STANDALONE_LOAD_ADDR
2374
2375                This option defines a board specific value for the
2376                address where standalone program gets loaded, thus
2377                overwriting the architecture dependent default
2378                settings.
2379
2380- Frame Buffer Address:
2381                CONFIG_FB_ADDR
2382
2383                Define CONFIG_FB_ADDR if you want to use specific
2384                address for frame buffer.  This is typically the case
2385                when using a graphics controller has separate video
2386                memory.  U-Boot will then place the frame buffer at
2387                the given address instead of dynamically reserving it
2388                in system RAM by calling lcd_setmem(), which grabs
2389                the memory for the frame buffer depending on the
2390                configured panel size.
2391
2392                Please see board_init_f function.
2393
2394- Automatic software updates via TFTP server
2395                CONFIG_UPDATE_TFTP
2396                CONFIG_UPDATE_TFTP_CNT_MAX
2397                CONFIG_UPDATE_TFTP_MSEC_MAX
2398
2399                These options enable and control the auto-update feature;
2400                for a more detailed description refer to doc/README.update.
2401
2402- MTD Support (mtdparts command, UBI support)
2403                CONFIG_MTD_UBI_WL_THRESHOLD
2404                This parameter defines the maximum difference between the highest
2405                erase counter value and the lowest erase counter value of eraseblocks
2406                of UBI devices. When this threshold is exceeded, UBI starts performing
2407                wear leveling by means of moving data from eraseblock with low erase
2408                counter to eraseblocks with high erase counter.
2409
2410                The default value should be OK for SLC NAND flashes, NOR flashes and
2411                other flashes which have eraseblock life-cycle 100000 or more.
2412                However, in case of MLC NAND flashes which typically have eraseblock
2413                life-cycle less than 10000, the threshold should be lessened (e.g.,
2414                to 128 or 256, although it does not have to be power of 2).
2415
2416                default: 4096
2417
2418                CONFIG_MTD_UBI_BEB_LIMIT
2419                This option specifies the maximum bad physical eraseblocks UBI
2420                expects on the MTD device (per 1024 eraseblocks). If the
2421                underlying flash does not admit of bad eraseblocks (e.g. NOR
2422                flash), this value is ignored.
2423
2424                NAND datasheets often specify the minimum and maximum NVM
2425                (Number of Valid Blocks) for the flashes' endurance lifetime.
2426                The maximum expected bad eraseblocks per 1024 eraseblocks
2427                then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2428                which gives 20 for most NANDs (MaxNVB is basically the total
2429                count of eraseblocks on the chip).
2430
2431                To put it differently, if this value is 20, UBI will try to
2432                reserve about 1.9% of physical eraseblocks for bad blocks
2433                handling. And that will be 1.9% of eraseblocks on the entire
2434                NAND chip, not just the MTD partition UBI attaches. This means
2435                that if you have, say, a NAND flash chip admits maximum 40 bad
2436                eraseblocks, and it is split on two MTD partitions of the same
2437                size, UBI will reserve 40 eraseblocks when attaching a
2438                partition.
2439
2440                default: 20
2441
2442                CONFIG_MTD_UBI_FASTMAP
2443                Fastmap is a mechanism which allows attaching an UBI device
2444                in nearly constant time. Instead of scanning the whole MTD device it
2445                only has to locate a checkpoint (called fastmap) on the device.
2446                The on-flash fastmap contains all information needed to attach
2447                the device. Using fastmap makes only sense on large devices where
2448                attaching by scanning takes long. UBI will not automatically install
2449                a fastmap on old images, but you can set the UBI parameter
2450                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2451                that fastmap-enabled images are still usable with UBI implementations
2452                without fastmap support. On typical flash devices the whole fastmap
2453                fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2454
2455                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2456                Set this parameter to enable fastmap automatically on images
2457                without a fastmap.
2458                default: 0
2459
2460                CONFIG_MTD_UBI_FM_DEBUG
2461                Enable UBI fastmap debug
2462                default: 0
2463
2464- SPL framework
2465                CONFIG_SPL
2466                Enable building of SPL globally.
2467
2468                CONFIG_SPL_LDSCRIPT
2469                LDSCRIPT for linking the SPL binary.
2470
2471                CONFIG_SPL_MAX_FOOTPRINT
2472                Maximum size in memory allocated to the SPL, BSS included.
2473                When defined, the linker checks that the actual memory
2474                used by SPL from _start to __bss_end does not exceed it.
2475                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2476                must not be both defined at the same time.
2477
2478                CONFIG_SPL_MAX_SIZE
2479                Maximum size of the SPL image (text, data, rodata, and
2480                linker lists sections), BSS excluded.
2481                When defined, the linker checks that the actual size does
2482                not exceed it.
2483
2484                CONFIG_SPL_TEXT_BASE
2485                TEXT_BASE for linking the SPL binary.
2486
2487                CONFIG_SPL_RELOC_TEXT_BASE
2488                Address to relocate to.  If unspecified, this is equal to
2489                CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2490
2491                CONFIG_SPL_BSS_START_ADDR
2492                Link address for the BSS within the SPL binary.
2493
2494                CONFIG_SPL_BSS_MAX_SIZE
2495                Maximum size in memory allocated to the SPL BSS.
2496                When defined, the linker checks that the actual memory used
2497                by SPL from __bss_start to __bss_end does not exceed it.
2498                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2499                must not be both defined at the same time.
2500
2501                CONFIG_SPL_STACK
2502                Adress of the start of the stack SPL will use
2503
2504                CONFIG_SPL_PANIC_ON_RAW_IMAGE
2505                When defined, SPL will panic() if the image it has
2506                loaded does not have a signature.
2507                Defining this is useful when code which loads images
2508                in SPL cannot guarantee that absolutely all read errors
2509                will be caught.
2510                An example is the LPC32XX MLC NAND driver, which will
2511                consider that a completely unreadable NAND block is bad,
2512                and thus should be skipped silently.
2513
2514                CONFIG_SPL_RELOC_STACK
2515                Adress of the start of the stack SPL will use after
2516                relocation.  If unspecified, this is equal to
2517                CONFIG_SPL_STACK.
2518
2519                CONFIG_SYS_SPL_MALLOC_START
2520                Starting address of the malloc pool used in SPL.
2521                When this option is set the full malloc is used in SPL and
2522                it is set up by spl_init() and before that, the simple malloc()
2523                can be used if CONFIG_SYS_MALLOC_F is defined.
2524
2525                CONFIG_SYS_SPL_MALLOC_SIZE
2526                The size of the malloc pool used in SPL.
2527
2528                CONFIG_SPL_OS_BOOT
2529                Enable booting directly to an OS from SPL.
2530                See also: doc/README.falcon
2531
2532                CONFIG_SPL_DISPLAY_PRINT
2533                For ARM, enable an optional function to print more information
2534                about the running system.
2535
2536                CONFIG_SPL_INIT_MINIMAL
2537                Arch init code should be built for a very small image
2538
2539                CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2540                Partition on the MMC to load U-Boot from when the MMC is being
2541                used in raw mode
2542
2543                CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2544                Sector to load kernel uImage from when MMC is being
2545                used in raw mode (for Falcon mode)
2546
2547                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2548                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2549                Sector and number of sectors to load kernel argument
2550                parameters from when MMC is being used in raw mode
2551                (for falcon mode)
2552
2553                CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2554                Partition on the MMC to load U-Boot from when the MMC is being
2555                used in fs mode
2556
2557                CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2558                Filename to read to load U-Boot when reading from filesystem
2559
2560                CONFIG_SPL_FS_LOAD_KERNEL_NAME
2561                Filename to read to load kernel uImage when reading
2562                from filesystem (for Falcon mode)
2563
2564                CONFIG_SPL_FS_LOAD_ARGS_NAME
2565                Filename to read to load kernel argument parameters
2566                when reading from filesystem (for Falcon mode)
2567
2568                CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2569                Set this for NAND SPL on PPC mpc83xx targets, so that
2570                start.S waits for the rest of the SPL to load before
2571                continuing (the hardware starts execution after just
2572                loading the first page rather than the full 4K).
2573
2574                CONFIG_SPL_SKIP_RELOCATE
2575                Avoid SPL relocation
2576
2577                CONFIG_SPL_NAND_BASE
2578                Include nand_base.c in the SPL.  Requires
2579                CONFIG_SPL_NAND_DRIVERS.
2580
2581                CONFIG_SPL_NAND_DRIVERS
2582                SPL uses normal NAND drivers, not minimal drivers.
2583
2584                CONFIG_SPL_NAND_IDENT
2585                SPL uses the chip ID list to identify the NAND flash.
2586                Requires CONFIG_SPL_NAND_BASE.
2587
2588                CONFIG_SPL_NAND_ECC
2589                Include standard software ECC in the SPL
2590
2591                CONFIG_SPL_NAND_SIMPLE
2592                Support for NAND boot using simple NAND drivers that
2593                expose the cmd_ctrl() interface.
2594
2595                CONFIG_SPL_UBI
2596                Support for a lightweight UBI (fastmap) scanner and
2597                loader
2598
2599                CONFIG_SPL_NAND_RAW_ONLY
2600                Support to boot only raw u-boot.bin images. Use this only
2601                if you need to save space.
2602
2603                CONFIG_SPL_COMMON_INIT_DDR
2604                Set for common ddr init with serial presence detect in
2605                SPL binary.
2606
2607                CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2608                CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2609                CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2610                CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2611                CONFIG_SYS_NAND_ECCBYTES
2612                Defines the size and behavior of the NAND that SPL uses
2613                to read U-Boot
2614
2615                CONFIG_SPL_NAND_BOOT
2616                Add support NAND boot
2617
2618                CONFIG_SYS_NAND_U_BOOT_OFFS
2619                Location in NAND to read U-Boot from
2620
2621                CONFIG_SYS_NAND_U_BOOT_DST
2622                Location in memory to load U-Boot to
2623
2624                CONFIG_SYS_NAND_U_BOOT_SIZE
2625                Size of image to load
2626
2627                CONFIG_SYS_NAND_U_BOOT_START
2628                Entry point in loaded image to jump to
2629
2630                CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2631                Define this if you need to first read the OOB and then the
2632                data. This is used, for example, on davinci platforms.
2633
2634                CONFIG_SPL_RAM_DEVICE
2635                Support for running image already present in ram, in SPL binary
2636
2637                CONFIG_SPL_PAD_TO
2638                Image offset to which the SPL should be padded before appending
2639                the SPL payload. By default, this is defined as
2640                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2641                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2642                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2643
2644                CONFIG_SPL_TARGET
2645                Final target image containing SPL and payload.  Some SPLs
2646                use an arch-specific makefile fragment instead, for
2647                example if more than one image needs to be produced.
2648
2649                CONFIG_SPL_FIT_PRINT
2650                Printing information about a FIT image adds quite a bit of
2651                code to SPL. So this is normally disabled in SPL. Use this
2652                option to re-enable it. This will affect the output of the
2653                bootm command when booting a FIT image.
2654
2655- TPL framework
2656                CONFIG_TPL
2657                Enable building of TPL globally.
2658
2659                CONFIG_TPL_PAD_TO
2660                Image offset to which the TPL should be padded before appending
2661                the TPL payload. By default, this is defined as
2662                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2663                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2664                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2665
2666- Interrupt support (PPC):
2667
2668                There are common interrupt_init() and timer_interrupt()
2669                for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2670                for CPU specific initialization. interrupt_init_cpu()
2671                should set decrementer_count to appropriate value. If
2672                CPU resets decrementer automatically after interrupt
2673                (ppc4xx) it should set decrementer_count to zero.
2674                timer_interrupt() calls timer_interrupt_cpu() for CPU
2675                specific handling. If board has watchdog / status_led
2676                / other_activity_monitor it works automatically from
2677                general timer_interrupt().
2678
2679
2680Board initialization settings:
2681------------------------------
2682
2683During Initialization u-boot calls a number of board specific functions
2684to allow the preparation of board specific prerequisites, e.g. pin setup
2685before drivers are initialized. To enable these callbacks the
2686following configuration macros have to be defined. Currently this is
2687architecture specific, so please check arch/your_architecture/lib/board.c
2688typically in board_init_f() and board_init_r().
2689
2690- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2691- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2692- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2693- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2694
2695Configuration Settings:
2696-----------------------
2697
2698- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2699                Optionally it can be defined to support 64-bit memory commands.
2700
2701- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2702                undefine this when you're short of memory.
2703
2704- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2705                width of the commands listed in the 'help' command output.
2706
2707- CONFIG_SYS_PROMPT:    This is what U-Boot prints on the console to
2708                prompt for user input.
2709
2710- CONFIG_SYS_CBSIZE:    Buffer size for input from the Console
2711
2712- CONFIG_SYS_PBSIZE:    Buffer size for Console output
2713
2714- CONFIG_SYS_MAXARGS:   max. Number of arguments accepted for monitor commands
2715
2716- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2717                the application (usually a Linux kernel) when it is
2718                booted
2719
2720- CONFIG_SYS_BAUDRATE_TABLE:
2721                List of legal baudrate settings for this board.
2722
2723- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2724                Begin and End addresses of the area used by the
2725                simple memory test.
2726
2727- CONFIG_SYS_MEMTEST_SCRATCH:
2728                Scratch address used by the alternate memory test
2729                You only need to set this if address zero isn't writeable
2730
2731- CONFIG_SYS_MEM_RESERVE_SECURE
2732                Only implemented for ARMv8 for now.
2733                If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2734                is substracted from total RAM and won't be reported to OS.
2735                This memory can be used as secure memory. A variable
2736                gd->arch.secure_ram is used to track the location. In systems
2737                the RAM base is not zero, or RAM is divided into banks,
2738                this variable needs to be recalcuated to get the address.
2739
2740- CONFIG_SYS_MEM_TOP_HIDE:
2741                If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2742                this specified memory area will get subtracted from the top
2743                (end) of RAM and won't get "touched" at all by U-Boot. By
2744                fixing up gd->ram_size the Linux kernel should gets passed
2745                the now "corrected" memory size and won't touch it either.
2746                This should work for arch/ppc and arch/powerpc. Only Linux
2747                board ports in arch/powerpc with bootwrapper support that
2748                recalculate the memory size from the SDRAM controller setup
2749                will have to get fixed in Linux additionally.
2750
2751                This option can be used as a workaround for the 440EPx/GRx
2752                CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2753                be touched.
2754
2755                WARNING: Please make sure that this value is a multiple of
2756                the Linux page size (normally 4k). If this is not the case,
2757                then the end address of the Linux memory will be located at a
2758                non page size aligned address and this could cause major
2759                problems.
2760
2761- CONFIG_SYS_LOADS_BAUD_CHANGE:
2762                Enable temporary baudrate change while serial download
2763
2764- CONFIG_SYS_SDRAM_BASE:
2765                Physical start address of SDRAM. _Must_ be 0 here.
2766
2767- CONFIG_SYS_FLASH_BASE:
2768                Physical start address of Flash memory.
2769
2770- CONFIG_SYS_MONITOR_BASE:
2771                Physical start address of boot monitor code (set by
2772                make config files to be same as the text base address
2773                (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2774                CONFIG_SYS_FLASH_BASE when booting from flash.
2775
2776- CONFIG_SYS_MONITOR_LEN:
2777                Size of memory reserved for monitor code, used to
2778                determine _at_compile_time_ (!) if the environment is
2779                embedded within the U-Boot image, or in a separate
2780                flash sector.
2781
2782- CONFIG_SYS_MALLOC_LEN:
2783                Size of DRAM reserved for malloc() use.
2784
2785- CONFIG_SYS_MALLOC_F_LEN
2786                Size of the malloc() pool for use before relocation. If
2787                this is defined, then a very simple malloc() implementation
2788                will become available before relocation. The address is just
2789                below the global data, and the stack is moved down to make
2790                space.
2791
2792                This feature allocates regions with increasing addresses
2793                within the region. calloc() is supported, but realloc()
2794                is not available. free() is supported but does nothing.
2795                The memory will be freed (or in fact just forgotten) when
2796                U-Boot relocates itself.
2797
2798- CONFIG_SYS_MALLOC_SIMPLE
2799                Provides a simple and small malloc() and calloc() for those
2800                boards which do not use the full malloc in SPL (which is
2801                enabled with CONFIG_SYS_SPL_MALLOC_START).
2802
2803- CONFIG_SYS_NONCACHED_MEMORY:
2804                Size of non-cached memory area. This area of memory will be
2805                typically located right below the malloc() area and mapped
2806                uncached in the MMU. This is useful for drivers that would
2807                otherwise require a lot of explicit cache maintenance. For
2808                some drivers it's also impossible to properly maintain the
2809                cache. For example if the regions that need to be flushed
2810                are not a multiple of the cache-line size, *and* padding
2811                cannot be allocated between the regions to align them (i.e.
2812                if the HW requires a contiguous array of regions, and the
2813                size of each region is not cache-aligned), then a flush of
2814                one region may result in overwriting data that hardware has
2815                written to another region in the same cache-line. This can
2816                happen for example in network drivers where descriptors for
2817                buffers are typically smaller than the CPU cache-line (e.g.
2818                16 bytes vs. 32 or 64 bytes).
2819
2820                Non-cached memory is only supported on 32-bit ARM at present.
2821
2822- CONFIG_SYS_BOOTM_LEN:
2823                Normally compressed uImages are limited to an
2824                uncompressed size of 8 MBytes. If this is not enough,
2825                you can define CONFIG_SYS_BOOTM_LEN in your board config file
2826                to adjust this setting to your needs.
2827
2828- CONFIG_SYS_BOOTMAPSZ:
2829                Maximum size of memory mapped by the startup code of
2830                the Linux kernel; all data that must be processed by
2831                the Linux kernel (bd_info, boot arguments, FDT blob if
2832                used) must be put below this limit, unless "bootm_low"
2833                environment variable is defined and non-zero. In such case
2834                all data for the Linux kernel must be between "bootm_low"
2835                and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2836                variable "bootm_mapsize" will override the value of
2837                CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2838                then the value in "bootm_size" will be used instead.
2839
2840- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2841                Enable initrd_high functionality.  If defined then the
2842                initrd_high feature is enabled and the bootm ramdisk subcommand
2843                is enabled.
2844
2845- CONFIG_SYS_BOOT_GET_CMDLINE:
2846                Enables allocating and saving kernel cmdline in space between
2847                "bootm_low" and "bootm_low" + BOOTMAPSZ.
2848
2849- CONFIG_SYS_BOOT_GET_KBD:
2850                Enables allocating and saving a kernel copy of the bd_info in
2851                space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2852
2853- CONFIG_SYS_MAX_FLASH_BANKS:
2854                Max number of Flash memory banks
2855
2856- CONFIG_SYS_MAX_FLASH_SECT:
2857                Max number of sectors on a Flash chip
2858
2859- CONFIG_SYS_FLASH_ERASE_TOUT:
2860                Timeout for Flash erase operations (in ms)
2861
2862- CONFIG_SYS_FLASH_WRITE_TOUT:
2863                Timeout for Flash write operations (in ms)
2864
2865- CONFIG_SYS_FLASH_LOCK_TOUT
2866                Timeout for Flash set sector lock bit operation (in ms)
2867
2868- CONFIG_SYS_FLASH_UNLOCK_TOUT
2869                Timeout for Flash clear lock bits operation (in ms)
2870
2871- CONFIG_SYS_FLASH_PROTECTION
2872                If defined, hardware flash sectors protection is used
2873                instead of U-Boot software protection.
2874
2875- CONFIG_SYS_DIRECT_FLASH_TFTP:
2876
2877                Enable TFTP transfers directly to flash memory;
2878                without this option such a download has to be
2879                performed in two steps: (1) download to RAM, and (2)
2880                copy from RAM to flash.
2881
2882                The two-step approach is usually more reliable, since
2883                you can check if the download worked before you erase
2884                the flash, but in some situations (when system RAM is
2885                too limited to allow for a temporary copy of the
2886                downloaded image) this option may be very useful.
2887
2888- CONFIG_SYS_FLASH_CFI:
2889                Define if the flash driver uses extra elements in the
2890                common flash structure for storing flash geometry.
2891
2892- CONFIG_FLASH_CFI_DRIVER
2893                This option also enables the building of the cfi_flash driver
2894                in the drivers directory
2895
2896- CONFIG_FLASH_CFI_MTD
2897                This option enables the building of the cfi_mtd driver
2898                in the drivers directory. The driver exports CFI flash
2899                to the MTD layer.
2900
2901- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2902                Use buffered writes to flash.
2903
2904- CONFIG_FLASH_SPANSION_S29WS_N
2905                s29ws-n MirrorBit flash has non-standard addresses for buffered
2906                write commands.
2907
2908- CONFIG_SYS_FLASH_QUIET_TEST
2909                If this option is defined, the common CFI flash doesn't
2910                print it's warning upon not recognized FLASH banks. This
2911                is useful, if some of the configured banks are only
2912                optionally available.
2913
2914- CONFIG_FLASH_SHOW_PROGRESS
2915                If defined (must be an integer), print out countdown
2916                digits and dots.  Recommended value: 45 (9..1) for 80
2917                column displays, 15 (3..1) for 40 column displays.
2918
2919- CONFIG_FLASH_VERIFY
2920                If defined, the content of the flash (destination) is compared
2921                against the source after the write operation. An error message
2922                will be printed when the contents are not identical.
2923                Please note that this option is useless in nearly all cases,
2924                since such flash programming errors usually are detected earlier
2925                while unprotecting/erasing/programming. Please only enable
2926                this option if you really know what you are doing.
2927
2928- CONFIG_SYS_RX_ETH_BUFFER:
2929                Defines the number of Ethernet receive buffers. On some
2930                Ethernet controllers it is recommended to set this value
2931                to 8 or even higher (EEPRO100 or 405 EMAC), since all
2932                buffers can be full shortly after enabling the interface
2933                on high Ethernet traffic.
2934                Defaults to 4 if not defined.
2935
2936- CONFIG_ENV_MAX_ENTRIES
2937
2938        Maximum number of entries in the hash table that is used
2939        internally to store the environment settings. The default
2940        setting is supposed to be generous and should work in most
2941        cases. This setting can be used to tune behaviour; see
2942        lib/hashtable.c for details.
2943
2944- CONFIG_ENV_FLAGS_LIST_DEFAULT
2945- CONFIG_ENV_FLAGS_LIST_STATIC
2946        Enable validation of the values given to environment variables when
2947        calling env set.  Variables can be restricted to only decimal,
2948        hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2949        the variables can also be restricted to IP address or MAC address.
2950
2951        The format of the list is:
2952                type_attribute = [s|d|x|b|i|m]
2953                access_attribute = [a|r|o|c]
2954                attributes = type_attribute[access_attribute]
2955                entry = variable_name[:attributes]
2956                list = entry[,list]
2957
2958        The type attributes are:
2959                s - String (default)
2960                d - Decimal
2961                x - Hexadecimal
2962                b - Boolean ([1yYtT|0nNfF])
2963                i - IP address
2964                m - MAC address
2965
2966        The access attributes are:
2967                a - Any (default)
2968                r - Read-only
2969                o - Write-once
2970                c - Change-default
2971
2972        - CONFIG_ENV_FLAGS_LIST_DEFAULT
2973                Define this to a list (string) to define the ".flags"
2974                environment variable in the default or embedded environment.
2975
2976        - CONFIG_ENV_FLAGS_LIST_STATIC
2977                Define this to a list (string) to define validation that
2978                should be done if an entry is not found in the ".flags"
2979                environment variable.  To override a setting in the static
2980                list, simply add an entry for the same variable name to the
2981                ".flags" variable.
2982
2983        If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2984        regular expression. This allows multiple variables to define the same
2985        flags without explicitly listing them for each variable.
2986
2987- CONFIG_ENV_ACCESS_IGNORE_FORCE
2988        If defined, don't allow the -f switch to env set override variable
2989        access flags.
2990
2991The following definitions that deal with the placement and management
2992of environment data (variable area); in general, we support the
2993following configurations:
2994
2995- CONFIG_BUILD_ENVCRC:
2996
2997        Builds up envcrc with the target environment so that external utils
2998        may easily extract it and embed it in final U-Boot images.
2999
3000BE CAREFUL! The first access to the environment happens quite early
3001in U-Boot initialization (when we try to get the setting of for the
3002console baudrate). You *MUST* have mapped your NVRAM area then, or
3003U-Boot will hang.
3004
3005Please note that even with NVRAM we still use a copy of the
3006environment in RAM: we could work on NVRAM directly, but we want to
3007keep settings there always unmodified except somebody uses "saveenv"
3008to save the current settings.
3009
3010BE CAREFUL! For some special cases, the local device can not use
3011"saveenv" command. For example, the local device will get the
3012environment stored in a remote NOR flash by SRIO or PCIE link,
3013but it can not erase, write this NOR flash by SRIO or PCIE interface.
3014
3015- CONFIG_NAND_ENV_DST
3016
3017        Defines address in RAM to which the nand_spl code should copy the
3018        environment. If redundant environment is used, it will be copied to
3019        CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3020
3021Please note that the environment is read-only until the monitor
3022has been relocated to RAM and a RAM copy of the environment has been
3023created; also, when using EEPROM you will have to use env_get_f()
3024until then to read environment variables.
3025
3026The environment is protected by a CRC32 checksum. Before the monitor
3027is relocated into RAM, as a result of a bad CRC you will be working
3028with the compiled-in default environment - *silently*!!! [This is
3029necessary, because the first environment variable we need is the
3030"baudrate" setting for the console - if we have a bad CRC, we don't
3031have any device yet where we could complain.]
3032
3033Note: once the monitor has been relocated, then it will complain if
3034the default environment is used; a new CRC is computed as soon as you
3035use the "saveenv" command to store a valid environment.
3036
3037- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3038                Echo the inverted Ethernet link state to the fault LED.
3039
3040                Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3041                      also needs to be defined.
3042
3043- CONFIG_SYS_FAULT_MII_ADDR:
3044                MII address of the PHY to check for the Ethernet link state.
3045
3046- CONFIG_NS16550_MIN_FUNCTIONS:
3047                Define this if you desire to only have use of the NS16550_init
3048                and NS16550_putc functions for the serial driver located at
3049                drivers/serial/ns16550.c.  This option is useful for saving
3050                space for already greatly restricted images, including but not
3051                limited to NAND_SPL configurations.
3052
3053- CONFIG_DISPLAY_BOARDINFO
3054                Display information about the board that U-Boot is running on
3055                when U-Boot starts up. The board function checkboard() is called
3056                to do this.
3057
3058- CONFIG_DISPLAY_BOARDINFO_LATE
3059                Similar to the previous option, but display this information
3060                later, once stdio is running and output goes to the LCD, if
3061                present.
3062
3063- CONFIG_BOARD_SIZE_LIMIT:
3064                Maximum size of the U-Boot image. When defined, the
3065                build system checks that the actual size does not
3066                exceed it.
3067
3068Low Level (hardware related) configuration options:
3069---------------------------------------------------
3070
3071- CONFIG_SYS_CACHELINE_SIZE:
3072                Cache Line Size of the CPU.
3073
3074- CONFIG_SYS_CCSRBAR_DEFAULT:
3075                Default (power-on reset) physical address of CCSR on Freescale
3076                PowerPC SOCs.
3077
3078- CONFIG_SYS_CCSRBAR:
3079                Virtual address of CCSR.  On a 32-bit build, this is typically
3080                the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3081
3082- CONFIG_SYS_CCSRBAR_PHYS:
3083                Physical address of CCSR.  CCSR can be relocated to a new
3084                physical address, if desired.  In this case, this macro should
3085                be set to that address.  Otherwise, it should be set to the
3086                same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3087                is typically relocated on 36-bit builds.  It is recommended
3088                that this macro be defined via the _HIGH and _LOW macros:
3089
3090                #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3091                        * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3092
3093- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3094                Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.  This value is typically
3095                either 0 (32-bit build) or 0xF (36-bit build).  This macro is
3096                used in assembly code, so it must not contain typecasts or
3097                integer size suffixes (e.g. "ULL").
3098
3099- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3100                Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3101                used in assembly code, so it must not contain typecasts or
3102                integer size suffixes (e.g. "ULL").
3103
3104- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3105                If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3106                forced to a value that ensures that CCSR is not relocated.
3107
3108- Floppy Disk Support:
3109                CONFIG_SYS_FDC_DRIVE_NUMBER
3110
3111                the default drive number (default value 0)
3112
3113                CONFIG_SYS_ISA_IO_STRIDE
3114
3115                defines the spacing between FDC chipset registers
3116                (default value 1)
3117
3118                CONFIG_SYS_ISA_IO_OFFSET
3119
3120                defines the offset of register from address. It
3121                depends on which part of the data bus is connected to
3122                the FDC chipset. (default value 0)
3123
3124                If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3125                CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3126                default value.
3127
3128                if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3129                fdc_hw_init() is called at the beginning of the FDC
3130                setup. fdc_hw_init() must be provided by the board
3131                source code. It is used to make hardware-dependent
3132                initializations.
3133
3134- CONFIG_IDE_AHB:
3135                Most IDE controllers were designed to be connected with PCI
3136                interface. Only few of them were designed for AHB interface.
3137                When software is doing ATA command and data transfer to
3138                IDE devices through IDE-AHB controller, some additional
3139                registers accessing to these kind of IDE-AHB controller
3140                is required.
3141
3142- CONFIG_SYS_IMMR:      Physical address of the Internal Memory.
3143                DO NOT CHANGE unless you know exactly what you're
3144                doing! (11-4) [MPC8xx systems only]
3145
3146- CONFIG_SYS_INIT_RAM_ADDR:
3147
3148                Start address of memory area that can be used for
3149                initial data and stack; please note that this must be
3150                writable memory that is working WITHOUT special
3151                initialization, i. e. you CANNOT use normal RAM which
3152                will become available only after programming the
3153                memory controller and running certain initialization
3154                sequences.
3155
3156                U-Boot uses the following memory types:
3157                - MPC8xx: IMMR (internal memory of the CPU)
3158
3159- CONFIG_SYS_GBL_DATA_OFFSET:
3160
3161                Offset of the initial data structure in the memory
3162                area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3163                CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3164                data is located at the end of the available space
3165                (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3166                GENERATED_GBL_DATA_SIZE), and the initial stack is just
3167                below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3168                CONFIG_SYS_GBL_DATA_OFFSET) downward.
3169
3170        Note:
3171                On the MPC824X (or other systems that use the data
3172                cache for initial memory) the address chosen for
3173                CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3174                point to an otherwise UNUSED address space between
3175                the top of RAM and the start of the PCI space.
3176
3177- CONFIG_SYS_SCCR:      System Clock and reset Control Register (15-27)
3178
3179- CONFIG_SYS_OR_TIMING_SDRAM:
3180                SDRAM timing
3181
3182- CONFIG_SYS_MAMR_PTA:
3183                periodic timer for refresh
3184
3185- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3186  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3187  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3188  CONFIG_SYS_BR1_PRELIM:
3189                Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3190
3191- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3192  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3193  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3194                Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3195
3196- CONFIG_PCI_ENUM_ONLY
3197                Only scan through and get the devices on the buses.
3198                Don't do any setup work, presumably because someone or
3199                something has already done it, and we don't need to do it
3200                a second time.  Useful for platforms that are pre-booted
3201                by coreboot or similar.
3202
3203- CONFIG_PCI_INDIRECT_BRIDGE:
3204                Enable support for indirect PCI bridges.
3205
3206- CONFIG_SYS_SRIO:
3207                Chip has SRIO or not
3208
3209- CONFIG_SRIO1:
3210                Board has SRIO 1 port available
3211
3212- CONFIG_SRIO2:
3213                Board has SRIO 2 port available
3214
3215- CONFIG_SRIO_PCIE_BOOT_MASTER
3216                Board can support master function for Boot from SRIO and PCIE
3217
3218- CONFIG_SYS_SRIOn_MEM_VIRT:
3219                Virtual Address of SRIO port 'n' memory region
3220
3221- CONFIG_SYS_SRIOn_MEM_PHYS:
3222                Physical Address of SRIO port 'n' memory region
3223
3224- CONFIG_SYS_SRIOn_MEM_SIZE:
3225                Size of SRIO port 'n' memory region
3226
3227- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3228                Defined to tell the NAND controller that the NAND chip is using
3229                a 16 bit bus.
3230                Not all NAND drivers use this symbol.
3231                Example of drivers that use it:
3232                - drivers/mtd/nand/raw/ndfc.c
3233                - drivers/mtd/nand/raw/mxc_nand.c
3234
3235- CONFIG_SYS_NDFC_EBC0_CFG
3236                Sets the EBC0_CFG register for the NDFC. If not defined
3237                a default value will be used.
3238
3239- CONFIG_SPD_EEPROM
3240                Get DDR timing information from an I2C EEPROM. Common
3241                with pluggable memory modules such as SODIMMs
3242
3243  SPD_EEPROM_ADDRESS
3244                I2C address of the SPD EEPROM
3245
3246- CONFIG_SYS_SPD_BUS_NUM
3247                If SPD EEPROM is on an I2C bus other than the first
3248                one, specify here. Note that the value must resolve
3249                to something your driver can deal with.
3250
3251- CONFIG_SYS_DDR_RAW_TIMING
3252                Get DDR timing information from other than SPD. Common with
3253                soldered DDR chips onboard without SPD. DDR raw timing
3254                parameters are extracted from datasheet and hard-coded into
3255                header files or board specific files.
3256
3257- CONFIG_FSL_DDR_INTERACTIVE
3258                Enable interactive DDR debugging. See doc/README.fsl-ddr.
3259
3260- CONFIG_FSL_DDR_SYNC_REFRESH
3261                Enable sync of refresh for multiple controllers.
3262
3263- CONFIG_FSL_DDR_BIST
3264                Enable built-in memory test for Freescale DDR controllers.
3265
3266- CONFIG_SYS_83XX_DDR_USES_CS0
3267                Only for 83xx systems. If specified, then DDR should
3268                be configured using CS0 and CS1 instead of CS2 and CS3.
3269
3270- CONFIG_RMII
3271                Enable RMII mode for all FECs.
3272                Note that this is a global option, we can't
3273                have one FEC in standard MII mode and another in RMII mode.
3274
3275- CONFIG_CRC32_VERIFY
3276                Add a verify option to the crc32 command.
3277                The syntax is:
3278
3279                => crc32 -v <address> <count> <crc32>
3280
3281                Where address/count indicate a memory area
3282                and crc32 is the correct crc32 which the
3283                area should have.
3284
3285- CONFIG_LOOPW
3286                Add the "loopw" memory command. This only takes effect if
3287                the memory commands are activated globally (CONFIG_CMD_MEMORY).
3288
3289- CONFIG_MX_CYCLIC
3290                Add the "mdc" and "mwc" memory commands. These are cyclic
3291                "md/mw" commands.
3292                Examples:
3293
3294                => mdc.b 10 4 500
3295                This command will print 4 bytes (10,11,12,13) each 500 ms.
3296
3297                => mwc.l 100 12345678 10
3298                This command will write 12345678 to address 100 all 10 ms.
3299
3300                This only takes effect if the memory commands are activated
3301                globally (CONFIG_CMD_MEMORY).
3302
3303- CONFIG_SKIP_LOWLEVEL_INIT
3304                [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3305                low level initializations (like setting up the memory
3306                controller) are omitted and/or U-Boot does not
3307                relocate itself into RAM.
3308
3309                Normally this variable MUST NOT be defined. The only
3310                exception is when U-Boot is loaded (to RAM) by some
3311                other boot loader or by a debugger which performs
3312                these initializations itself.
3313
3314- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3315                [ARM926EJ-S only] This allows just the call to lowlevel_init()
3316                to be skipped. The normal CP15 init (such as enabling the
3317                instruction cache) is still performed.
3318
3319- CONFIG_SPL_BUILD
3320                Modifies the behaviour of start.S when compiling a loader
3321                that is executed before the actual U-Boot. E.g. when
3322                compiling a NAND SPL.
3323
3324- CONFIG_TPL_BUILD
3325                Modifies the behaviour of start.S  when compiling a loader
3326                that is executed after the SPL and before the actual U-Boot.
3327                It is loaded by the SPL.
3328
3329- CONFIG_SYS_MPC85XX_NO_RESETVEC
3330                Only for 85xx systems. If this variable is specified, the section
3331                .resetvec is not kept and the section .bootpg is placed in the
3332                previous 4k of the .text section.
3333
3334- CONFIG_ARCH_MAP_SYSMEM
3335                Generally U-Boot (and in particular the md command) uses
3336                effective address. It is therefore not necessary to regard
3337                U-Boot address as virtual addresses that need to be translated
3338                to physical addresses. However, sandbox requires this, since
3339                it maintains its own little RAM buffer which contains all
3340                addressable memory. This option causes some memory accesses
3341                to be mapped through map_sysmem() / unmap_sysmem().
3342
3343- CONFIG_X86_RESET_VECTOR
3344                If defined, the x86 reset vector code is included. This is not
3345                needed when U-Boot is running from Coreboot.
3346
3347- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3348                Option to disable subpage write in NAND driver
3349                driver that uses this:
3350                drivers/mtd/nand/raw/davinci_nand.c
3351
3352Freescale QE/FMAN Firmware Support:
3353-----------------------------------
3354
3355The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3356loading of "firmware", which is encoded in the QE firmware binary format.
3357This firmware often needs to be loaded during U-Boot booting, so macros
3358are used to identify the storage device (NOR flash, SPI, etc) and the address
3359within that device.
3360
3361- CONFIG_SYS_FMAN_FW_ADDR
3362        The address in the storage device where the FMAN microcode is located.  The
3363        meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3364        is also specified.
3365
3366- CONFIG_SYS_QE_FW_ADDR
3367        The address in the storage device where the QE microcode is located.  The
3368        meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3369        is also specified.
3370
3371- CONFIG_SYS_QE_FMAN_FW_LENGTH
3372        The maximum possible size of the firmware.  The firmware binary format
3373        has a field that specifies the actual size of the firmware, but it
3374        might not be possible to read any part of the firmware unless some
3375        local storage is allocated to hold the entire firmware first.
3376
3377- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3378        Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3379        normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3380        virtual address in NOR flash.
3381
3382- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3383        Specifies that QE/FMAN firmware is located in NAND flash.
3384        CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3385
3386- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3387        Specifies that QE/FMAN firmware is located on the primary SD/MMC
3388        device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3389
3390- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3391        Specifies that QE/FMAN firmware is located in the remote (master)
3392        memory space.   CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3393        can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3394        window->master inbound window->master LAW->the ucode address in
3395        master's memory space.
3396
3397Freescale Layerscape Management Complex Firmware Support:
3398---------------------------------------------------------
3399The Freescale Layerscape Management Complex (MC) supports the loading of
3400"firmware".
3401This firmware often needs to be loaded during U-Boot booting, so macros
3402are used to identify the storage device (NOR flash, SPI, etc) and the address
3403within that device.
3404
3405- CONFIG_FSL_MC_ENET
3406        Enable the MC driver for Layerscape SoCs.
3407
3408Freescale Layerscape Debug Server Support:
3409-------------------------------------------
3410The Freescale Layerscape Debug Server Support supports the loading of
3411"Debug Server firmware" and triggering SP boot-rom.
3412This firmware often needs to be loaded during U-Boot booting.
3413
3414- CONFIG_SYS_MC_RSV_MEM_ALIGN
3415        Define alignment of reserved memory MC requires
3416
3417Reproducible builds
3418-------------------
3419
3420In order to achieve reproducible builds, timestamps used in the U-Boot build
3421process have to be set to a fixed value.
3422
3423This is done using the SOURCE_DATE_EPOCH environment variable.
3424SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3425option for U-Boot or an environment variable in U-Boot.
3426
3427SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3428
3429Building the Software:
3430======================
3431
3432Building U-Boot has been tested in several native build environments
3433and in many different cross environments. Of course we cannot support
3434all possibly existing versions of cross development tools in all
3435(potentially obsolete) versions. In case of tool chain problems we
3436recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3437which is extensively used to build and test U-Boot.
3438
3439If you are not using a native environment, it is assumed that you
3440have GNU cross compiling tools available in your path. In this case,
3441you must set the environment variable CROSS_COMPILE in your shell.
3442Note that no changes to the Makefile or any other source files are
3443necessary. For example using the ELDK on a 4xx CPU, please enter:
3444
3445        $ CROSS_COMPILE=ppc_4xx-
3446        $ export CROSS_COMPILE
3447
3448Note: If you wish to generate Windows versions of the utilities in
3449      the tools directory you can use the MinGW toolchain
3450      (http://www.mingw.org).  Set your HOST tools to the MinGW
3451      toolchain and execute 'make tools'.  For example:
3452
3453       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3454
3455      Binaries such as tools/mkimage.exe will be created which can
3456      be executed on computers running Windows.
3457
3458U-Boot is intended to be simple to build. After installing the
3459sources you must configure U-Boot for one specific board type. This
3460is done by typing:
3461
3462        make NAME_defconfig
3463
3464where "NAME_defconfig" is the name of one of the existing configu-
3465rations; see boards.cfg for supported names.
3466
3467Note: for some board special configuration names may exist; check if
3468      additional information is available from the board vendor; for
3469      instance, the TQM823L systems are available without (standard)
3470      or with LCD support. You can select such additional "features"
3471      when choosing the configuration, i. e.
3472
3473      make TQM823L_defconfig
3474        - will configure for a plain TQM823L, i. e. no LCD support
3475
3476      make TQM823L_LCD_defconfig
3477        - will configure for a TQM823L with U-Boot console on LCD
3478
3479      etc.
3480
3481
3482Finally, type "make all", and you should get some working U-Boot
3483images ready for download to / installation on your system:
3484
3485- "u-boot.bin" is a raw binary image
3486- "u-boot" is an image in ELF binary format
3487- "u-boot.srec" is in Motorola S-Record format
3488
3489By default the build is performed locally and the objects are saved
3490in the source directory. One of the two methods can be used to change
3491this behavior and build U-Boot to some external directory:
3492
34931. Add O= to the make command line invocations:
3494
3495        make O=/tmp/build distclean
3496        make O=/tmp/build NAME_defconfig
3497        make O=/tmp/build all
3498
34992. Set environment variable KBUILD_OUTPUT to point to the desired location:
3500
3501        export KBUILD_OUTPUT=/tmp/build
3502        make distclean
3503        make NAME_defconfig
3504        make all
3505
3506Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3507variable.
3508
3509User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3510setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3511For example to treat all compiler warnings as errors:
3512
3513        make KCFLAGS=-Werror
3514
3515Please be aware that the Makefiles assume you are using GNU make, so
3516for instance on NetBSD you might need to use "gmake" instead of
3517native "make".
3518
3519
3520If the system board that you have is not listed, then you will need
3521to port U-Boot to your hardware platform. To do this, follow these
3522steps:
3523
35241.  Create a new directory to hold your board specific code. Add any
3525    files you need. In your board directory, you will need at least
3526    the "Makefile" and a "<board>.c".
35272.  Create a new configuration file "include/configs/<board>.h" for
3528    your board.
35293.  If you're porting U-Boot to a new CPU, then also create a new
3530    directory to hold your CPU specific code. Add any files you need.
35314.  Run "make <board>_defconfig" with your new name.
35325.  Type "make", and you should get a working "u-boot.srec" file
3533    to be installed on your target system.
35346.  Debug and solve any problems that might arise.
3535    [Of course, this last step is much harder than it sounds.]
3536
3537
3538Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3539==============================================================
3540
3541If you have modified U-Boot sources (for instance added a new board
3542or support for new devices, a new CPU, etc.) you are expected to
3543provide feedback to the other developers. The feedback normally takes
3544the form of a "patch", i. e. a context diff against a certain (latest
3545official or latest in the git repository) version of U-Boot sources.
3546
3547But before you submit such a patch, please verify that your modifi-
3548cation did not break existing code. At least make sure that *ALL* of
3549the supported boards compile WITHOUT ANY compiler warnings. To do so,
3550just run the buildman script (tools/buildman/buildman), which will
3551configure and build U-Boot for ALL supported system. Be warned, this
3552will take a while. Please see the buildman README, or run 'buildman -H'
3553for documentation.
3554
3555
3556See also "U-Boot Porting Guide" below.
3557
3558
3559Monitor Commands - Overview:
3560============================
3561
3562go      - start application at address 'addr'
3563run     - run commands in an environment variable
3564bootm   - boot application image from memory
3565bootp   - boot image via network using BootP/TFTP protocol
3566bootz   - boot zImage from memory
3567tftpboot- boot image via network using TFTP protocol
3568               and env variables "ipaddr" and "serverip"
3569               (and eventually "gatewayip")
3570tftpput - upload a file via network using TFTP protocol
3571rarpboot- boot image via network using RARP/TFTP protocol
3572diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3573loads   - load S-Record file over serial line
3574loadb   - load binary file over serial line (kermit mode)
3575md      - memory display
3576mm      - memory modify (auto-incrementing)
3577nm      - memory modify (constant address)
3578mw      - memory write (fill)
3579cp      - memory copy
3580cmp     - memory compare
3581crc32   - checksum calculation
3582i2c     - I2C sub-system
3583sspi    - SPI utility commands
3584base    - print or set address offset
3585printenv- print environment variables
3586setenv  - set environment variables
3587saveenv - save environment variables to persistent storage
3588protect - enable or disable FLASH write protection
3589erase   - erase FLASH memory
3590flinfo  - print FLASH memory information
3591nand    - NAND memory operations (see doc/README.nand)
3592bdinfo  - print Board Info structure
3593iminfo  - print header information for application image
3594coninfo - print console devices and informations
3595ide     - IDE sub-system
3596loop    - infinite loop on address range
3597loopw   - infinite write loop on address range
3598mtest   - simple RAM test
3599icache  - enable or disable instruction cache
3600dcache  - enable or disable data cache
3601reset   - Perform RESET of the CPU
3602echo    - echo args to console
3603version - print monitor version
3604help    - print online help
3605?       - alias for 'help'
3606
3607
3608Monitor Commands - Detailed Description:
3609========================================
3610
3611TODO.
3612
3613For now: just type "help <command>".
3614
3615
3616Environment Variables:
3617======================
3618
3619U-Boot supports user configuration using Environment Variables which
3620can be made persistent by saving to Flash memory.
3621
3622Environment Variables are set using "setenv", printed using
3623"printenv", and saved to Flash using "saveenv". Using "setenv"
3624without a value can be used to delete a variable from the
3625environment. As long as you don't save the environment you are
3626working with an in-memory copy. In case the Flash area containing the
3627environment is erased by accident, a default environment is provided.
3628
3629Some configuration options can be set using Environment Variables.
3630
3631List of environment variables (most likely not complete):
3632
3633  baudrate      - see CONFIG_BAUDRATE
3634
3635  bootdelay     - see CONFIG_BOOTDELAY
3636
3637  bootcmd       - see CONFIG_BOOTCOMMAND
3638
3639  bootargs      - Boot arguments when booting an RTOS image
3640
3641  bootfile      - Name of the image to load with TFTP
3642
3643  bootm_low     - Memory range available for image processing in the bootm
3644                  command can be restricted. This variable is given as
3645                  a hexadecimal number and defines lowest address allowed
3646                  for use by the bootm command. See also "bootm_size"
3647                  environment variable. Address defined by "bootm_low" is
3648                  also the base of the initial memory mapping for the Linux
3649                  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3650                  bootm_mapsize.
3651
3652  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3653                  This variable is given as a hexadecimal number and it
3654                  defines the size of the memory region starting at base
3655                  address bootm_low that is accessible by the Linux kernel
3656                  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3657                  as the default value if it is defined, and bootm_size is
3658                  used otherwise.
3659
3660  bootm_size    - Memory range available for image processing in the bootm
3661                  command can be restricted. This variable is given as
3662                  a hexadecimal number and defines the size of the region
3663                  allowed for use by the bootm command. See also "bootm_low"
3664                  environment variable.
3665
3666  updatefile    - Location of the software update file on a TFTP server, used
3667                  by the automatic software update feature. Please refer to
3668                  documentation in doc/README.update for more details.
3669
3670  autoload      - if set to "no" (any string beginning with 'n'),
3671                  "bootp" will just load perform a lookup of the
3672                  configuration from the BOOTP server, but not try to
3673                  load any image using TFTP
3674
3675  autostart     - if set to "yes", an image loaded using the "bootp",
3676                  "rarpboot", "tftpboot" or "diskboot" commands will
3677                  be automatically started (by internally calling
3678                  "bootm")
3679
3680                  If set to "no", a standalone image passed to the
3681                  "bootm" command will be copied to the load address
3682                  (and eventually uncompressed), but NOT be started.
3683                  This can be used to load and uncompress arbitrary
3684                  data.
3685
3686  fdt_high      - if set this restricts the maximum address that the
3687                  flattened device tree will be copied into upon boot.
3688                  For example, if you have a system with 1 GB memory
3689                  at physical address 0x10000000, while Linux kernel
3690                  only recognizes the first 704 MB as low memory, you
3691                  may need to set fdt_high as 0x3C000000 to have the
3692                  device tree blob be copied to the maximum address
3693                  of the 704 MB low memory, so that Linux kernel can
3694                  access it during the boot procedure.
3695
3696                  If this is set to the special value 0xFFFFFFFF then
3697                  the fdt will not be copied at all on boot.  For this
3698                  to work it must reside in writable memory, have
3699                  sufficient padding on the end of it for u-boot to
3700                  add the information it needs into it, and the memory
3701                  must be accessible by the kernel.
3702
3703  fdtcontroladdr- if set this is the address of the control flattened
3704                  device tree used by U-Boot when CONFIG_OF_CONTROL is
3705                  defined.
3706
3707  i2cfast       - (PPC405GP|PPC405EP only)
3708                  if set to 'y' configures Linux I2C driver for fast
3709                  mode (400kHZ). This environment variable is used in
3710                  initialization code. So, for changes to be effective
3711                  it must be saved and board must be reset.
3712
3713  initrd_high   - restrict positioning of initrd images:
3714                  If this variable is not set, initrd images will be
3715                  copied to the highest possible address in RAM; this
3716                  is usually what you want since it allows for
3717                  maximum initrd size. If for some reason you want to
3718                  make sure that the initrd image is loaded below the
3719                  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3720                  variable to a value of "no" or "off" or "0".
3721                  Alternatively, you can set it to a maximum upper
3722                  address to use (U-Boot will still check that it
3723                  does not overwrite the U-Boot stack and data).
3724
3725                  For instance, when you have a system with 16 MB
3726                  RAM, and want to reserve 4 MB from use by Linux,
3727                  you can do this by adding "mem=12M" to the value of
3728                  the "bootargs" variable. However, now you must make
3729                  sure that the initrd image is placed in the first
3730                  12 MB as well - this can be done with
3731
3732                  setenv initrd_high 00c00000
3733
3734                  If you set initrd_high to 0xFFFFFFFF, this is an
3735                  indication to U-Boot that all addresses are legal
3736                  for the Linux kernel, including addresses in flash
3737                  memory. In this case U-Boot will NOT COPY the
3738                  ramdisk at all. This may be useful to reduce the
3739                  boot time on your system, but requires that this
3740                  feature is supported by your Linux kernel.
3741
3742  ipaddr        - IP address; needed for tftpboot command
3743
3744  loadaddr      - Default load address for commands like "bootp",
3745                  "rarpboot", "tftpboot", "loadb" or "diskboot"
3746
3747  loads_echo    - see CONFIG_LOADS_ECHO
3748
3749  serverip      - TFTP server IP address; needed for tftpboot command
3750
3751  bootretry     - see CONFIG_BOOT_RETRY_TIME
3752
3753  bootdelaykey  - see CONFIG_AUTOBOOT_DELAY_STR
3754
3755  bootstopkey   - see CONFIG_AUTOBOOT_STOP_STR
3756
3757  ethprime      - controls which interface is used first.
3758
3759  ethact        - controls which interface is currently active.
3760                  For example you can do the following
3761
3762                  => setenv ethact FEC
3763                  => ping 192.168.0.1 # traffic sent on FEC
3764                  => setenv ethact SCC
3765                  => ping 10.0.0.1 # traffic sent on SCC
3766
3767  ethrotate     - When set to "no" U-Boot does not go through all
3768                  available network interfaces.
3769                  It just stays at the currently selected interface.
3770
3771  netretry      - When set to "no" each network operation will
3772                  either succeed or fail without retrying.
3773                  When set to "once" the network operation will
3774                  fail when all the available network interfaces
3775                  are tried once without success.
3776                  Useful on scripts which control the retry operation
3777                  themselves.
3778
3779  npe_ucode     - set load address for the NPE microcode
3780
3781  silent_linux  - If set then Linux will be told to boot silently, by
3782                  changing the console to be empty. If "yes" it will be
3783                  made silent. If "no" it will not be made silent. If
3784                  unset, then it will be made silent if the U-Boot console
3785                  is silent.
3786
3787  tftpsrcp      - If this is set, the value is used for TFTP's
3788                  UDP source port.
3789
3790  tftpdstp      - If this is set, the value is used for TFTP's UDP
3791                  destination port instead of the Well Know Port 69.
3792
3793  tftpblocksize - Block size to use for TFTP transfers; if not set,
3794                  we use the TFTP server's default block size
3795
3796  tftptimeout   - Retransmission timeout for TFTP packets (in milli-
3797                  seconds, minimum value is 1000 = 1 second). Defines
3798                  when a packet is considered to be lost so it has to
3799                  be retransmitted. The default is 5000 = 5 seconds.
3800                  Lowering this value may make downloads succeed
3801                  faster in networks with high packet loss rates or
3802                  with unreliable TFTP servers.
3803
3804  tftptimeoutcountmax   - maximum count of TFTP timeouts (no
3805                  unit, minimum value = 0). Defines how many timeouts
3806                  can happen during a single file transfer before that
3807                  transfer is aborted. The default is 10, and 0 means
3808                  'no timeouts allowed'. Increasing this value may help
3809                  downloads succeed with high packet loss rates, or with
3810                  unreliable TFTP servers or client hardware.
3811
3812  vlan          - When set to a value < 4095 the traffic over
3813                  Ethernet is encapsulated/received over 802.1q
3814                  VLAN tagged frames.
3815
3816  bootpretryperiod      - Period during which BOOTP/DHCP sends retries.
3817                  Unsigned value, in milliseconds. If not set, the period will
3818                  be either the default (28000), or a value based on
3819                  CONFIG_NET_RETRY_COUNT, if defined. This value has
3820                  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3821
3822The following image location variables contain the location of images
3823used in booting. The "Image" column gives the role of the image and is
3824not an environment variable name. The other columns are environment
3825variable names. "File Name" gives the name of the file on a TFTP
3826server, "RAM Address" gives the location in RAM the image will be
3827loaded to, and "Flash Location" gives the image's address in NOR
3828flash or offset in NAND flash.
3829
3830*Note* - these variables don't have to be defined for all boards, some
3831boards currently use other variables for these purposes, and some
3832boards use these variables for other purposes.
3833
3834Image               File Name        RAM Address       Flash Location
3835-----               ---------        -----------       --------------
3836u-boot              u-boot           u-boot_addr_r     u-boot_addr
3837Linux kernel        bootfile         kernel_addr_r     kernel_addr
3838device tree blob    fdtfile          fdt_addr_r        fdt_addr
3839ramdisk             ramdiskfile      ramdisk_addr_r    ramdisk_addr
3840
3841The following environment variables may be used and automatically
3842updated by the network boot commands ("bootp" and "rarpboot"),
3843depending the information provided by your boot server:
3844
3845  bootfile      - see above
3846  dnsip         - IP address of your Domain Name Server
3847  dnsip2        - IP address of your secondary Domain Name Server
3848  gatewayip     - IP address of the Gateway (Router) to use
3849  hostname      - Target hostname
3850  ipaddr        - see above
3851  netmask       - Subnet Mask
3852  rootpath      - Pathname of the root filesystem on the NFS server
3853  serverip      - see above
3854
3855
3856There are two special Environment Variables:
3857
3858  serial#       - contains hardware identification information such
3859                  as type string and/or serial number
3860  ethaddr       - Ethernet address
3861
3862These variables can be set only once (usually during manufacturing of
3863the board). U-Boot refuses to delete or overwrite these variables
3864once they have been set once.
3865
3866
3867Further special Environment Variables:
3868
3869  ver           - Contains the U-Boot version string as printed
3870                  with the "version" command. This variable is
3871                  readonly (see CONFIG_VERSION_VARIABLE).
3872
3873
3874Please note that changes to some configuration parameters may take
3875only effect after the next boot (yes, that's just like Windoze :-).
3876
3877
3878Callback functions for environment variables:
3879---------------------------------------------
3880
3881For some environment variables, the behavior of u-boot needs to change
3882when their values are changed.  This functionality allows functions to
3883be associated with arbitrary variables.  On creation, overwrite, or
3884deletion, the callback will provide the opportunity for some side
3885effect to happen or for the change to be rejected.
3886
3887The callbacks are named and associated with a function using the
3888U_BOOT_ENV_CALLBACK macro in your board or driver code.
3889
3890These callbacks are associated with variables in one of two ways.  The
3891static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3892in the board configuration to a string that defines a list of
3893associations.  The list must be in the following format:
3894
3895        entry = variable_name[:callback_name]
3896        list = entry[,list]
3897
3898If the callback name is not specified, then the callback is deleted.
3899Spaces are also allowed anywhere in the list.
3900
3901Callbacks can also be associated by defining the ".callbacks" variable
3902with the same list format above.  Any association in ".callbacks" will
3903override any association in the static list. You can define
3904CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3905".callbacks" environment variable in the default or embedded environment.
3906
3907If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3908regular expression. This allows multiple variables to be connected to
3909the same callback without explicitly listing them all out.
3910
3911The signature of the callback functions is:
3912
3913    int callback(const char *name, const char *value, enum env_op op, int flags)
3914
3915* name - changed environment variable
3916* value - new value of the environment variable
3917* op - operation (create, overwrite, or delete)
3918* flags - attributes of the environment variable change, see flags H_* in
3919  include/search.h
3920
3921The return value is 0 if the variable change is accepted and 1 otherwise.
3922
3923Command Line Parsing:
3924=====================
3925
3926There are two different command line parsers available with U-Boot:
3927the old "simple" one, and the much more powerful "hush" shell:
3928
3929Old, simple command line parser:
3930--------------------------------
3931
3932- supports environment variables (through setenv / saveenv commands)
3933- several commands on one line, separated by ';'
3934- variable substitution using "... ${name} ..." syntax
3935- special characters ('$', ';') can be escaped by prefixing with '\',
3936  for example:
3937        setenv bootcmd bootm \${address}
3938- You can also escape text by enclosing in single apostrophes, for example:
3939        setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3940
3941Hush shell:
3942-----------
3943
3944- similar to Bourne shell, with control structures like
3945  if...then...else...fi, for...do...done; while...do...done,
3946  until...do...done, ...
3947- supports environment ("global") variables (through setenv / saveenv
3948  commands) and local shell variables (through standard shell syntax
3949  "name=value"); only environment variables can be used with "run"
3950  command
3951
3952General rules:
3953--------------
3954
3955(1) If a command line (or an environment variable executed by a "run"
3956    command) contains several commands separated by semicolon, and
3957    one of these commands fails, then the remaining commands will be
3958    executed anyway.
3959
3960(2) If you execute several variables with one call to run (i. e.
3961    calling run with a list of variables as arguments), any failing
3962    command will cause "run" to terminate, i. e. the remaining
3963    variables are not executed.
3964
3965Note for Redundant Ethernet Interfaces:
3966=======================================
3967
3968Some boards come with redundant Ethernet interfaces; U-Boot supports
3969such configurations and is capable of automatic selection of a
3970"working" interface when needed. MAC assignment works as follows:
3971
3972Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3973MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3974"eth1addr" (=>eth1), "eth2addr", ...
3975
3976If the network interface stores some valid MAC address (for instance
3977in SROM), this is used as default address if there is NO correspon-
3978ding setting in the environment; if the corresponding environment
3979variable is set, this overrides the settings in the card; that means:
3980
3981o If the SROM has a valid MAC address, and there is no address in the
3982  environment, the SROM's address is used.
3983
3984o If there is no valid address in the SROM, and a definition in the
3985  environment exists, then the value from the environment variable is
3986  used.
3987
3988o If both the SROM and the environment contain a MAC address, and
3989  both addresses are the same, this MAC address is used.
3990
3991o If both the SROM and the environment contain a MAC address, and the
3992  addresses differ, the value from the environment is used and a
3993  warning is printed.
3994
3995o If neither SROM nor the environment contain a MAC address, an error
3996  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3997  a random, locally-assigned MAC is used.
3998
3999If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4000will be programmed into hardware as part of the initialization process.  This
4001may be skipped by setting the appropriate 'ethmacskip' environment variable.
4002The naming convention is as follows:
4003"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4004
4005Image Formats:
4006==============
4007
4008U-Boot is capable of booting (and performing other auxiliary operations on)
4009images in two formats:
4010
4011New uImage format (FIT)
4012-----------------------
4013
4014Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4015to Flattened Device Tree). It allows the use of images with multiple
4016components (several kernels, ramdisks, etc.), with contents protected by
4017SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4018
4019
4020Old uImage format
4021-----------------
4022
4023Old image format is based on binary files which can be basically anything,
4024preceded by a special header; see the definitions in include/image.h for
4025details; basically, the header defines the following image properties:
4026
4027* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4028  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4029  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4030  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4031  INTEGRITY).
4032* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4033  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4034  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4035* Compression Type (uncompressed, gzip, bzip2)
4036* Load Address
4037* Entry Point
4038* Image Name
4039* Image Timestamp
4040
4041The header is marked by a special Magic Number, and both the header
4042and the data portions of the image are secured against corruption by
4043CRC32 checksums.
4044
4045
4046Linux Support:
4047==============
4048
4049Although U-Boot should support any OS or standalone application
4050easily, the main focus has always been on Linux during the design of
4051U-Boot.
4052
4053U-Boot includes many features that so far have been part of some
4054special "boot loader" code within the Linux kernel. Also, any
4055"initrd" images to be used are no longer part of one big Linux image;
4056instead, kernel and "initrd" are separate images. This implementation
4057serves several purposes:
4058
4059- the same features can be used for other OS or standalone
4060  applications (for instance: using compressed images to reduce the
4061  Flash memory footprint)
4062
4063- it becomes much easier to port new Linux kernel versions because
4064  lots of low-level, hardware dependent stuff are done by U-Boot
4065
4066- the same Linux kernel image can now be used with different "initrd"
4067  images; of course this also means that different kernel images can
4068  be run with the same "initrd". This makes testing easier (you don't
4069  have to build a new "zImage.initrd" Linux image when you just
4070  change a file in your "initrd"). Also, a field-upgrade of the
4071  software is easier now.
4072
4073
4074Linux HOWTO:
4075============
4076
4077Porting Linux to U-Boot based systems:
4078---------------------------------------
4079
4080U-Boot cannot save you from doing all the necessary modifications to
4081configure the Linux device drivers for use with your target hardware
4082(no, we don't intend to provide a full virtual machine interface to
4083Linux :-).
4084
4085But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4086
4087Just make sure your machine specific header file (for instance
4088include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4089Information structure as we define in include/asm-<arch>/u-boot.h,
4090and make sure that your definition of IMAP_ADDR uses the same value
4091as your U-Boot configuration in CONFIG_SYS_IMMR.
4092
4093Note that U-Boot now has a driver model, a unified model for drivers.
4094If you are adding a new driver, plumb it into driver model. If there
4095is no uclass available, you are encouraged to create one. See
4096doc/driver-model.
4097
4098
4099Configuring the Linux kernel:
4100-----------------------------
4101
4102No specific requirements for U-Boot. Make sure you have some root
4103device (initial ramdisk, NFS) for your target system.
4104
4105
4106Building a Linux Image:
4107-----------------------
4108
4109With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4110not used. If you use recent kernel source, a new build target
4111"uImage" will exist which automatically builds an image usable by
4112U-Boot. Most older kernels also have support for a "pImage" target,
4113which was introduced for our predecessor project PPCBoot and uses a
4114100% compatible format.
4115
4116Example:
4117
4118        make TQM850L_defconfig
4119        make oldconfig
4120        make dep
4121        make uImage
4122
4123The "uImage" build target uses a special tool (in 'tools/mkimage') to
4124encapsulate a compressed Linux kernel image with header  information,
4125CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4126
4127* build a standard "vmlinux" kernel image (in ELF binary format):
4128
4129* convert the kernel into a raw binary image:
4130
4131        ${CROSS_COMPILE}-objcopy -O binary \
4132                                 -R .note -R .comment \
4133                                 -S vmlinux linux.bin
4134
4135* compress the binary image:
4136
4137        gzip -9 linux.bin
4138
4139* package compressed binary image for U-Boot:
4140
4141        mkimage -A ppc -O linux -T kernel -C gzip \
4142                -a 0 -e 0 -n "Linux Kernel Image" \
4143                -d linux.bin.gz uImage
4144
4145
4146The "mkimage" tool can also be used to create ramdisk images for use
4147with U-Boot, either separated from the Linux kernel image, or
4148combined into one file. "mkimage" encapsulates the images with a 64
4149byte header containing information about target architecture,
4150operating system, image type, compression method, entry points, time
4151stamp, CRC32 checksums, etc.
4152
4153"mkimage" can be called in two ways: to verify existing images and
4154print the header information, or to build new images.
4155
4156In the first form (with "-l" option) mkimage lists the information
4157contained in the header of an existing U-Boot image; this includes
4158checksum verification:
4159
4160        tools/mkimage -l image
4161          -l ==> list image header information
4162
4163The second form (with "-d" option) is used to build a U-Boot image
4164from a "data file" which is used as image payload:
4165
4166        tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4167                      -n name -d data_file image
4168          -A ==> set architecture to 'arch'
4169          -O ==> set operating system to 'os'
4170          -T ==> set image type to 'type'
4171          -C ==> set compression type 'comp'
4172          -a ==> set load address to 'addr' (hex)
4173          -e ==> set entry point to 'ep' (hex)
4174          -n ==> set image name to 'name'
4175          -d ==> use image data from 'datafile'
4176
4177Right now, all Linux kernels for PowerPC systems use the same load
4178address (0x00000000), but the entry point address depends on the
4179kernel version:
4180
4181- 2.2.x kernels have the entry point at 0x0000000C,
4182- 2.3.x and later kernels have the entry point at 0x00000000.
4183
4184So a typical call to build a U-Boot image would read:
4185
4186        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4187        > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4188        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4189        > examples/uImage.TQM850L
4190        Image Name:   2.4.4 kernel for TQM850L
4191        Created:      Wed Jul 19 02:34:59 2000
4192        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4193        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4194        Load Address: 0x00000000
4195        Entry Point:  0x00000000
4196
4197To verify the contents of the image (or check for corruption):
4198
4199        -> tools/mkimage -l examples/uImage.TQM850L
4200        Image Name:   2.4.4 kernel for TQM850L
4201        Created:      Wed Jul 19 02:34:59 2000
4202        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4203        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4204        Load Address: 0x00000000
4205        Entry Point:  0x00000000
4206
4207NOTE: for embedded systems where boot time is critical you can trade
4208speed for memory and install an UNCOMPRESSED image instead: this
4209needs more space in Flash, but boots much faster since it does not
4210need to be uncompressed:
4211
4212        -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4213        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4214        > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4215        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4216        > examples/uImage.TQM850L-uncompressed
4217        Image Name:   2.4.4 kernel for TQM850L
4218        Created:      Wed Jul 19 02:34:59 2000
4219        Image Type:   PowerPC Linux Kernel Image (uncompressed)
4220        Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4221        Load Address: 0x00000000
4222        Entry Point:  0x00000000
4223
4224
4225Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4226when your kernel is intended to use an initial ramdisk:
4227
4228        -> tools/mkimage -n 'Simple Ramdisk Image' \
4229        > -A ppc -O linux -T ramdisk -C gzip \
4230        > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4231        Image Name:   Simple Ramdisk Image
4232        Created:      Wed Jan 12 14:01:50 2000
4233        Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4234        Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4235        Load Address: 0x00000000
4236        Entry Point:  0x00000000
4237
4238The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4239option performs the converse operation of the mkimage's second form (the "-d"
4240option). Given an image built by mkimage, the dumpimage extracts a "data file"
4241from the image:
4242
4243        tools/dumpimage -i image -T type -p position data_file
4244          -i ==> extract from the 'image' a specific 'data_file'
4245          -T ==> set image type to 'type'
4246          -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4247
4248
4249Installing a Linux Image:
4250-------------------------
4251
4252To downloading a U-Boot image over the serial (console) interface,
4253you must convert the image to S-Record format:
4254
4255        objcopy -I binary -O srec examples/image examples/image.srec
4256
4257The 'objcopy' does not understand the information in the U-Boot
4258image header, so the resulting S-Record file will be relative to
4259address 0x00000000. To load it to a given address, you need to
4260specify the target address as 'offset' parameter with the 'loads'
4261command.
4262
4263Example: install the image to address 0x40100000 (which on the
4264TQM8xxL is in the first Flash bank):
4265
4266        => erase 40100000 401FFFFF
4267
4268        .......... done
4269        Erased 8 sectors
4270
4271        => loads 40100000
4272        ## Ready for S-Record download ...
4273        ~>examples/image.srec
4274        1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4275        ...
4276        15989 15990 15991 15992
4277        [file transfer complete]
4278        [connected]
4279        ## Start Addr = 0x00000000
4280
4281
4282You can check the success of the download using the 'iminfo' command;
4283this includes a checksum verification so you can be sure no data
4284corruption happened:
4285
4286        => imi 40100000
4287
4288        ## Checking Image at 40100000 ...
4289           Image Name:   2.2.13 for initrd on TQM850L
4290           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4291           Data Size:    335725 Bytes = 327 kB = 0 MB
4292           Load Address: 00000000
4293           Entry Point:  0000000c
4294           Verifying Checksum ... OK
4295
4296
4297Boot Linux:
4298-----------
4299
4300The "bootm" command is used to boot an application that is stored in
4301memory (RAM or Flash). In case of a Linux kernel image, the contents
4302of the "bootargs" environment variable is passed to the kernel as
4303parameters. You can check and modify this variable using the
4304"printenv" and "setenv" commands:
4305
4306
4307        => printenv bootargs
4308        bootargs=root=/dev/ram
4309
4310        => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4311
4312        => printenv bootargs
4313        bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4314
4315        => bootm 40020000
4316        ## Booting Linux kernel at 40020000 ...
4317           Image Name:   2.2.13 for NFS on TQM850L
4318           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4319           Data Size:    381681 Bytes = 372 kB = 0 MB
4320           Load Address: 00000000
4321           Entry Point:  0000000c
4322           Verifying Checksum ... OK
4323           Uncompressing Kernel Image ... OK
4324        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
4325        Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4326        time_init: decrementer frequency = 187500000/60
4327        Calibrating delay loop... 49.77 BogoMIPS
4328        Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4329        ...
4330
4331If you want to boot a Linux kernel with initial RAM disk, you pass
4332the memory addresses of both the kernel and the initrd image (PPBCOOT
4333format!) to the "bootm" command:
4334
4335        => imi 40100000 40200000
4336
4337        ## Checking Image at 40100000 ...
4338           Image Name:   2.2.13 for initrd on TQM850L
4339           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4340           Data Size:    335725 Bytes = 327 kB = 0 MB
4341           Load Address: 00000000
4342           Entry Point:  0000000c
4343           Verifying Checksum ... OK
4344
4345        ## Checking Image at 40200000 ...
4346           Image Name:   Simple Ramdisk Image
4347           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4348           Data Size:    566530 Bytes = 553 kB = 0 MB
4349           Load Address: 00000000
4350           Entry Point:  00000000
4351           Verifying Checksum ... OK
4352
4353        => bootm 40100000 40200000
4354        ## Booting Linux kernel at 40100000 ...
4355           Image Name:   2.2.13 for initrd on TQM850L
4356           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4357           Data Size:    335725 Bytes = 327 kB = 0 MB
4358           Load Address: 00000000
4359           Entry Point:  0000000c
4360           Verifying Checksum ... OK
4361           Uncompressing Kernel Image ... OK
4362        ## Loading RAMDisk Image at 40200000 ...
4363           Image Name:   Simple Ramdisk Image
4364           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4365           Data Size:    566530 Bytes = 553 kB = 0 MB
4366           Load Address: 00000000
4367           Entry Point:  00000000
4368           Verifying Checksum ... OK
4369           Loading Ramdisk ... OK
4370        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
4371        Boot arguments: root=/dev/ram
4372        time_init: decrementer frequency = 187500000/60
4373        Calibrating delay loop... 49.77 BogoMIPS
4374        ...
4375        RAMDISK: Compressed image found at block 0
4376        VFS: Mounted root (ext2 filesystem).
4377
4378        bash#
4379
4380Boot Linux and pass a flat device tree:
4381-----------
4382
4383First, U-Boot must be compiled with the appropriate defines. See the section
4384titled "Linux Kernel Interface" above for a more in depth explanation. The
4385following is an example of how to start a kernel and pass an updated
4386flat device tree:
4387
4388=> print oftaddr
4389oftaddr=0x300000
4390=> print oft
4391oft=oftrees/mpc8540ads.dtb
4392=> tftp $oftaddr $oft
4393Speed: 1000, full duplex
4394Using TSEC0 device
4395TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4396Filename 'oftrees/mpc8540ads.dtb'.
4397Load address: 0x300000
4398Loading: #
4399done
4400Bytes transferred = 4106 (100a hex)
4401=> tftp $loadaddr $bootfile
4402Speed: 1000, full duplex
4403Using TSEC0 device
4404TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4405Filename 'uImage'.
4406Load address: 0x200000
4407Loading:############
4408done
4409Bytes transferred = 1029407 (fb51f hex)
4410=> print loadaddr
4411loadaddr=200000
4412=> print oftaddr
4413oftaddr=0x300000
4414=> bootm $loadaddr - $oftaddr
4415## Booting image at 00200000 ...
4416   Image Name:   Linux-2.6.17-dirty
4417   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4418   Data Size:    1029343 Bytes = 1005.2 kB
4419   Load Address: 00000000
4420   Entry Point:  00000000
4421   Verifying Checksum ... OK
4422   Uncompressing Kernel Image ... OK
4423Booting using flat device tree at 0x300000
4424Using MPC85xx ADS machine description
4425Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4426[snip]
4427
4428
4429More About U-Boot Image Types:
4430------------------------------
4431
4432U-Boot supports the following image types:
4433
4434   "Standalone Programs" are directly runnable in the environment
4435        provided by U-Boot; it is expected that (if they behave
4436        well) you can continue to work in U-Boot after return from
4437        the Standalone Program.
4438   "OS Kernel Images" are usually images of some Embedded OS which
4439        will take over control completely. Usually these programs
4440        will install their own set of exception handlers, device
4441        drivers, set up the MMU, etc. - this means, that you cannot
4442        expect to re-enter U-Boot except by resetting the CPU.
4443   "RAMDisk Images" are more or less just data blocks, and their
4444        parameters (address, size) are passed to an OS kernel that is
4445        being started.
4446   "Multi-File Images" contain several images, typically an OS
4447        (Linux) kernel image and one or more data images like
4448        RAMDisks. This construct is useful for instance when you want
4449        to boot over the network using BOOTP etc., where the boot
4450        server provides just a single image file, but you want to get
4451        for instance an OS kernel and a RAMDisk image.
4452
4453        "Multi-File Images" start with a list of image sizes, each
4454        image size (in bytes) specified by an "uint32_t" in network
4455        byte order. This list is terminated by an "(uint32_t)0".
4456        Immediately after the terminating 0 follow the images, one by
4457        one, all aligned on "uint32_t" boundaries (size rounded up to
4458        a multiple of 4 bytes).
4459
4460   "Firmware Images" are binary images containing firmware (like
4461        U-Boot or FPGA images) which usually will be programmed to
4462        flash memory.
4463
4464   "Script files" are command sequences that will be executed by
4465        U-Boot's command interpreter; this feature is especially
4466        useful when you configure U-Boot to use a real shell (hush)
4467        as command interpreter.
4468
4469Booting the Linux zImage:
4470-------------------------
4471
4472On some platforms, it's possible to boot Linux zImage. This is done
4473using the "bootz" command. The syntax of "bootz" command is the same
4474as the syntax of "bootm" command.
4475
4476Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4477kernel with raw initrd images. The syntax is slightly different, the
4478address of the initrd must be augmented by it's size, in the following
4479format: "<initrd addres>:<initrd size>".
4480
4481
4482Standalone HOWTO:
4483=================
4484
4485One of the features of U-Boot is that you can dynamically load and
4486run "standalone" applications, which can use some resources of
4487U-Boot like console I/O functions or interrupt services.
4488
4489Two simple examples are included with the sources:
4490
4491"Hello World" Demo:
4492-------------------
4493
4494'examples/hello_world.c' contains a small "Hello World" Demo
4495application; it is automatically compiled when you build U-Boot.
4496It's configured to run at address 0x00040004, so you can play with it
4497like that:
4498
4499        => loads
4500        ## Ready for S-Record download ...
4501        ~>examples/hello_world.srec
4502        1 2 3 4 5 6 7 8 9 10 11 ...
4503        [file transfer complete]
4504        [connected]
4505        ## Start Addr = 0x00040004
4506
4507        => go 40004 Hello World! This is a test.
4508        ## Starting application at 0x00040004 ...
4509        Hello World
4510        argc = 7
4511        argv[0] = "40004"
4512        argv[1] = "Hello"
4513        argv[2] = "World!"
4514        argv[3] = "This"
4515        argv[4] = "is"
4516        argv[5] = "a"
4517        argv[6] = "test."
4518        argv[7] = "<NULL>"
4519        Hit any key to exit ...
4520
4521        ## Application terminated, rc = 0x0
4522
4523Another example, which demonstrates how to register a CPM interrupt
4524handler with the U-Boot code, can be found in 'examples/timer.c'.
4525Here, a CPM timer is set up to generate an interrupt every second.
4526The interrupt service routine is trivial, just printing a '.'
4527character, but this is just a demo program. The application can be
4528controlled by the following keys:
4529
4530        ? - print current values og the CPM Timer registers
4531        b - enable interrupts and start timer
4532        e - stop timer and disable interrupts
4533        q - quit application
4534
4535        => loads
4536        ## Ready for S-Record download ...
4537        ~>examples/timer.srec
4538        1 2 3 4 5 6 7 8 9 10 11 ...
4539        [file transfer complete]
4540        [connected]
4541        ## Start Addr = 0x00040004
4542
4543        => go 40004
4544        ## Starting application at 0x00040004 ...
4545        TIMERS=0xfff00980
4546        Using timer 1
4547          tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4548
4549Hit 'b':
4550        [q, b, e, ?] Set interval 1000000 us
4551        Enabling timer
4552Hit '?':
4553        [q, b, e, ?] ........
4554        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4555Hit '?':
4556        [q, b, e, ?] .
4557        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4558Hit '?':
4559        [q, b, e, ?] .
4560        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4561Hit '?':
4562        [q, b, e, ?] .
4563        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4564Hit 'e':
4565        [q, b, e, ?] ...Stopping timer
4566Hit 'q':
4567        [q, b, e, ?] ## Application terminated, rc = 0x0
4568
4569
4570Minicom warning:
4571================
4572
4573Over time, many people have reported problems when trying to use the
4574"minicom" terminal emulation program for serial download. I (wd)
4575consider minicom to be broken, and recommend not to use it. Under
4576Unix, I recommend to use C-Kermit for general purpose use (and
4577especially for kermit binary protocol download ("loadb" command), and
4578use "cu" for S-Record download ("loads" command).  See
4579http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4580for help with kermit.
4581
4582
4583Nevertheless, if you absolutely want to use it try adding this
4584configuration to your "File transfer protocols" section:
4585
4586           Name    Program                      Name U/D FullScr IO-Red. Multi
4587        X  kermit  /usr/bin/kermit -i -l %l -s   Y    U    Y       N      N
4588        Y  kermit  /usr/bin/kermit -i -l %l -r   N    D    Y       N      N
4589
4590
4591NetBSD Notes:
4592=============
4593
4594Starting at version 0.9.2, U-Boot supports NetBSD both as host
4595(build U-Boot) and target system (boots NetBSD/mpc8xx).
4596
4597Building requires a cross environment; it is known to work on
4598NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4599need gmake since the Makefiles are not compatible with BSD make).
4600Note that the cross-powerpc package does not install include files;
4601attempting to build U-Boot will fail because <machine/ansi.h> is
4602missing.  This file has to be installed and patched manually:
4603
4604        # cd /usr/pkg/cross/powerpc-netbsd/include
4605        # mkdir powerpc
4606        # ln -s powerpc machine
4607        # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4608        # ${EDIT} powerpc/ansi.h        ## must remove __va_list, _BSD_VA_LIST
4609
4610Native builds *don't* work due to incompatibilities between native
4611and U-Boot include files.
4612
4613Booting assumes that (the first part of) the image booted is a
4614stage-2 loader which in turn loads and then invokes the kernel
4615proper. Loader sources will eventually appear in the NetBSD source
4616tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4617meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4618
4619
4620Implementation Internals:
4621=========================
4622
4623The following is not intended to be a complete description of every
4624implementation detail. However, it should help to understand the
4625inner workings of U-Boot and make it easier to port it to custom
4626hardware.
4627
4628
4629Initial Stack, Global Data:
4630---------------------------
4631
4632The implementation of U-Boot is complicated by the fact that U-Boot
4633starts running out of ROM (flash memory), usually without access to
4634system RAM (because the memory controller is not initialized yet).
4635This means that we don't have writable Data or BSS segments, and BSS
4636is not initialized as zero. To be able to get a C environment working
4637at all, we have to allocate at least a minimal stack. Implementation
4638options for this are defined and restricted by the CPU used: Some CPU
4639models provide on-chip memory (like the IMMR area on MPC8xx and
4640MPC826x processors), on others (parts of) the data cache can be
4641locked as (mis-) used as memory, etc.
4642
4643        Chris Hallinan posted a good summary of these issues to the
4644        U-Boot mailing list:
4645
4646        Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4647        From: "Chris Hallinan" <clh@net1plus.com>
4648        Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4649        ...
4650
4651        Correct me if I'm wrong, folks, but the way I understand it
4652        is this: Using DCACHE as initial RAM for Stack, etc, does not
4653        require any physical RAM backing up the cache. The cleverness
4654        is that the cache is being used as a temporary supply of
4655        necessary storage before the SDRAM controller is setup. It's
4656        beyond the scope of this list to explain the details, but you
4657        can see how this works by studying the cache architecture and
4658        operation in the architecture and processor-specific manuals.
4659
4660        OCM is On Chip Memory, which I believe the 405GP has 4K. It
4661        is another option for the system designer to use as an
4662        initial stack/RAM area prior to SDRAM being available. Either
4663        option should work for you. Using CS 4 should be fine if your
4664        board designers haven't used it for something that would
4665        cause you grief during the initial boot! It is frequently not
4666        used.
4667
4668        CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4669        with your processor/board/system design. The default value
4670        you will find in any recent u-boot distribution in
4671        walnut.h should work for you. I'd set it to a value larger
4672        than your SDRAM module. If you have a 64MB SDRAM module, set
4673        it above 400_0000. Just make sure your board has no resources
4674        that are supposed to respond to that address! That code in
4675        start.S has been around a while and should work as is when
4676        you get the config right.
4677
4678        -Chris Hallinan
4679        DS4.COM, Inc.
4680
4681It is essential to remember this, since it has some impact on the C
4682code for the initialization procedures:
4683
4684* Initialized global data (data segment) is read-only. Do not attempt
4685  to write it.
4686
4687* Do not use any uninitialized global data (or implicitly initialized
4688  as zero data - BSS segment) at all - this is undefined, initiali-
4689  zation is performed later (when relocating to RAM).
4690
4691* Stack space is very limited. Avoid big data buffers or things like
4692  that.
4693
4694Having only the stack as writable memory limits means we cannot use
4695normal global data to share information between the code. But it
4696turned out that the implementation of U-Boot can be greatly
4697simplified by making a global data structure (gd_t) available to all
4698functions. We could pass a pointer to this data as argument to _all_
4699functions, but this would bloat the code. Instead we use a feature of
4700the GCC compiler (Global Register Variables) to share the data: we
4701place a pointer (gd) to the global data into a register which we
4702reserve for this purpose.
4703
4704When choosing a register for such a purpose we are restricted by the
4705relevant  (E)ABI  specifications for the current architecture, and by
4706GCC's implementation.
4707
4708For PowerPC, the following registers have specific use:
4709        R1:     stack pointer
4710        R2:     reserved for system use
4711        R3-R4:  parameter passing and return values
4712        R5-R10: parameter passing
4713        R13:    small data area pointer
4714        R30:    GOT pointer
4715        R31:    frame pointer
4716
4717        (U-Boot also uses R12 as internal GOT pointer. r12
4718        is a volatile register so r12 needs to be reset when
4719        going back and forth between asm and C)
4720
4721    ==> U-Boot will use R2 to hold a pointer to the global data
4722
4723    Note: on PPC, we could use a static initializer (since the
4724    address of the global data structure is known at compile time),
4725    but it turned out that reserving a register results in somewhat
4726    smaller code - although the code savings are not that big (on
4727    average for all boards 752 bytes for the whole U-Boot image,
4728    624 text + 127 data).
4729
4730On ARM, the following registers are used:
4731
4732        R0:     function argument word/integer result
4733        R1-R3:  function argument word
4734        R9:     platform specific
4735        R10:    stack limit (used only if stack checking is enabled)
4736        R11:    argument (frame) pointer
4737        R12:    temporary workspace
4738        R13:    stack pointer
4739        R14:    link register
4740        R15:    program counter
4741
4742    ==> U-Boot will use R9 to hold a pointer to the global data
4743
4744    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4745
4746On Nios II, the ABI is documented here:
4747        http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4748
4749    ==> U-Boot will use gp to hold a pointer to the global data
4750
4751    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4752    to access small data sections, so gp is free.
4753
4754On NDS32, the following registers are used:
4755
4756        R0-R1:  argument/return
4757        R2-R5:  argument
4758        R15:    temporary register for assembler
4759        R16:    trampoline register
4760        R28:    frame pointer (FP)
4761        R29:    global pointer (GP)
4762        R30:    link register (LP)
4763        R31:    stack pointer (SP)
4764        PC:     program counter (PC)
4765
4766    ==> U-Boot will use R10 to hold a pointer to the global data
4767
4768NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4769or current versions of GCC may "optimize" the code too much.
4770
4771On RISC-V, the following registers are used:
4772
4773        x0: hard-wired zero (zero)
4774        x1: return address (ra)
4775        x2:     stack pointer (sp)
4776        x3:     global pointer (gp)
4777        x4:     thread pointer (tp)
4778        x5:     link register (t0)
4779        x8:     frame pointer (fp)
4780        x10-x11:        arguments/return values (a0-1)
4781        x12-x17:        arguments (a2-7)
4782        x28-31:  temporaries (t3-6)
4783        pc:     program counter (pc)
4784
4785    ==> U-Boot will use gp to hold a pointer to the global data
4786
4787Memory Management:
4788------------------
4789
4790U-Boot runs in system state and uses physical addresses, i.e. the
4791MMU is not used either for address mapping nor for memory protection.
4792
4793The available memory is mapped to fixed addresses using the memory
4794controller. In this process, a contiguous block is formed for each
4795memory type (Flash, SDRAM, SRAM), even when it consists of several
4796physical memory banks.
4797
4798U-Boot is installed in the first 128 kB of the first Flash bank (on
4799TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4800booting and sizing and initializing DRAM, the code relocates itself
4801to the upper end of DRAM. Immediately below the U-Boot code some
4802memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4803configuration setting]. Below that, a structure with global Board
4804Info data is placed, followed by the stack (growing downward).
4805
4806Additionally, some exception handler code is copied to the low 8 kB
4807of DRAM (0x00000000 ... 0x00001FFF).
4808
4809So a typical memory configuration with 16 MB of DRAM could look like
4810this:
4811
4812        0x0000 0000     Exception Vector code
4813              :
4814        0x0000 1FFF
4815        0x0000 2000     Free for Application Use
4816              :
4817              :
4818
4819              :
4820              :
4821        0x00FB FF20     Monitor Stack (Growing downward)
4822        0x00FB FFAC     Board Info Data and permanent copy of global data
4823        0x00FC 0000     Malloc Arena
4824              :
4825        0x00FD FFFF
4826        0x00FE 0000     RAM Copy of Monitor Code
4827        ...             eventually: LCD or video framebuffer
4828        ...             eventually: pRAM (Protected RAM - unchanged by reset)
4829        0x00FF FFFF     [End of RAM]
4830
4831
4832System Initialization:
4833----------------------
4834
4835In the reset configuration, U-Boot starts at the reset entry point
4836(on most PowerPC systems at address 0x00000100). Because of the reset
4837configuration for CS0# this is a mirror of the on board Flash memory.
4838To be able to re-map memory U-Boot then jumps to its link address.
4839To be able to implement the initialization code in C, a (small!)
4840initial stack is set up in the internal Dual Ported RAM (in case CPUs
4841which provide such a feature like), or in a locked part of the data
4842cache. After that, U-Boot initializes the CPU core, the caches and
4843the SIU.
4844
4845Next, all (potentially) available memory banks are mapped using a
4846preliminary mapping. For example, we put them on 512 MB boundaries
4847(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4848on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4849programmed for SDRAM access. Using the temporary configuration, a
4850simple memory test is run that determines the size of the SDRAM
4851banks.
4852
4853When there is more than one SDRAM bank, and the banks are of
4854different size, the largest is mapped first. For equal size, the first
4855bank (CS2#) is mapped first. The first mapping is always for address
48560x00000000, with any additional banks following immediately to create
4857contiguous memory starting from 0.
4858
4859Then, the monitor installs itself at the upper end of the SDRAM area
4860and allocates memory for use by malloc() and for the global Board
4861Info data; also, the exception vector code is copied to the low RAM
4862pages, and the final stack is set up.
4863
4864Only after this relocation will you have a "normal" C environment;
4865until that you are restricted in several ways, mostly because you are
4866running from ROM, and because the code will have to be relocated to a
4867new address in RAM.
4868
4869
4870U-Boot Porting Guide:
4871----------------------
4872
4873[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4874list, October 2002]
4875
4876
4877int main(int argc, char *argv[])
4878{
4879        sighandler_t no_more_time;
4880
4881        signal(SIGALRM, no_more_time);
4882        alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4883
4884        if (available_money > available_manpower) {
4885                Pay consultant to port U-Boot;
4886                return 0;
4887        }
4888
4889        Download latest U-Boot source;
4890
4891        Subscribe to u-boot mailing list;
4892
4893        if (clueless)
4894                email("Hi, I am new to U-Boot, how do I get started?");
4895
4896        while (learning) {
4897                Read the README file in the top level directory;
4898                Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4899                Read applicable doc/*.README;
4900                Read the source, Luke;
4901                /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4902        }
4903
4904        if (available_money > toLocalCurrency ($2500))
4905                Buy a BDI3000;
4906        else
4907                Add a lot of aggravation and time;
4908
4909        if (a similar board exists) {   /* hopefully... */
4910                cp -a board/<similar> board/<myboard>
4911                cp include/configs/<similar>.h include/configs/<myboard>.h
4912        } else {
4913                Create your own board support subdirectory;
4914                Create your own board include/configs/<myboard>.h file;
4915        }
4916        Edit new board/<myboard> files
4917        Edit new include/configs/<myboard>.h
4918
4919        while (!accepted) {
4920                while (!running) {
4921                        do {
4922                                Add / modify source code;
4923                        } until (compiles);
4924                        Debug;
4925                        if (clueless)
4926                                email("Hi, I am having problems...");
4927                }
4928                Send patch file to the U-Boot email list;
4929                if (reasonable critiques)
4930                        Incorporate improvements from email list code review;
4931                else
4932                        Defend code as written;
4933        }
4934
4935        return 0;
4936}
4937
4938void no_more_time (int sig)
4939{
4940      hire_a_guru();
4941}
4942
4943
4944Coding Standards:
4945-----------------
4946
4947All contributions to U-Boot should conform to the Linux kernel
4948coding style; see the kernel coding style guide at
4949https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4950script "scripts/Lindent" in your Linux kernel source directory.
4951
4952Source files originating from a different project (for example the
4953MTD subsystem) are generally exempt from these guidelines and are not
4954reformatted to ease subsequent migration to newer versions of those
4955sources.
4956
4957Please note that U-Boot is implemented in C (and to some small parts in
4958Assembler); no C++ is used, so please do not use C++ style comments (//)
4959in your code.
4960
4961Please also stick to the following formatting rules:
4962- remove any trailing white space
4963- use TAB characters for indentation and vertical alignment, not spaces
4964- make sure NOT to use DOS '\r\n' line feeds
4965- do not add more than 2 consecutive empty lines to source files
4966- do not add trailing empty lines to source files
4967
4968Submissions which do not conform to the standards may be returned
4969with a request to reformat the changes.
4970
4971
4972Submitting Patches:
4973-------------------
4974
4975Since the number of patches for U-Boot is growing, we need to
4976establish some rules. Submissions which do not conform to these rules
4977may be rejected, even when they contain important and valuable stuff.
4978
4979Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4980
4981Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4982see https://lists.denx.de/listinfo/u-boot
4983
4984When you send a patch, please include the following information with
4985it:
4986
4987* For bug fixes: a description of the bug and how your patch fixes
4988  this bug. Please try to include a way of demonstrating that the
4989  patch actually fixes something.
4990
4991* For new features: a description of the feature and your
4992  implementation.
4993
4994* A CHANGELOG entry as plaintext (separate from the patch)
4995
4996* For major contributions, add a MAINTAINERS file with your
4997  information and associated file and directory references.
4998
4999* When you add support for a new board, don't forget to add a
5000  maintainer e-mail address to the boards.cfg file, too.
5001
5002* If your patch adds new configuration options, don't forget to
5003  document these in the README file.
5004
5005* The patch itself. If you are using git (which is *strongly*
5006  recommended) you can easily generate the patch using the
5007  "git format-patch". If you then use "git send-email" to send it to
5008  the U-Boot mailing list, you will avoid most of the common problems
5009  with some other mail clients.
5010
5011  If you cannot use git, use "diff -purN OLD NEW". If your version of
5012  diff does not support these options, then get the latest version of
5013  GNU diff.
5014
5015  The current directory when running this command shall be the parent
5016  directory of the U-Boot source tree (i. e. please make sure that
5017  your patch includes sufficient directory information for the
5018  affected files).
5019
5020  We prefer patches as plain text. MIME attachments are discouraged,
5021  and compressed attachments must not be used.
5022
5023* If one logical set of modifications affects or creates several
5024  files, all these changes shall be submitted in a SINGLE patch file.
5025
5026* Changesets that contain different, unrelated modifications shall be
5027  submitted as SEPARATE patches, one patch per changeset.
5028
5029
5030Notes:
5031
5032* Before sending the patch, run the buildman script on your patched
5033  source tree and make sure that no errors or warnings are reported
5034  for any of the boards.
5035
5036* Keep your modifications to the necessary minimum: A patch
5037  containing several unrelated changes or arbitrary reformats will be
5038  returned with a request to re-formatting / split it.
5039
5040* If you modify existing code, make sure that your new code does not
5041  add to the memory footprint of the code ;-) Small is beautiful!
5042  When adding new features, these should compile conditionally only
5043  (using #ifdef), and the resulting code with the new feature
5044  disabled must not need more memory than the old code without your
5045  modification.
5046
5047* Remember that there is a size limit of 100 kB per message on the
5048  u-boot mailing list. Bigger patches will be moderated. If they are
5049  reasonable and not too big, they will be acknowledged. But patches
5050  bigger than the size limit should be avoided.
5051