uboot/README
<<
>>
Prefs
   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_SYS_FSL_DDR_BE
 490                Defines the DDR controller register space as Big Endian
 491
 492                CONFIG_SYS_FSL_DDR_LE
 493                Defines the DDR controller register space as Little Endian
 494
 495                CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
 496                Physical address from the view of DDR controllers. It is the
 497                same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
 498                it could be different for ARM SoCs.
 499
 500                CONFIG_SYS_FSL_DDR_INTLV_256B
 501                DDR controller interleaving on 256-byte. This is a special
 502                interleaving mode, handled by Dickens for Freescale layerscape
 503                SoCs with ARM core.
 504
 505                CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
 506                Number of controllers used as main memory.
 507
 508                CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
 509                Number of controllers used for other than main memory.
 510
 511                CONFIG_SYS_FSL_HAS_DP_DDR
 512                Defines the SoC has DP-DDR used for DPAA.
 513
 514                CONFIG_SYS_FSL_SEC_BE
 515                Defines the SEC controller register space as Big Endian
 516
 517                CONFIG_SYS_FSL_SEC_LE
 518                Defines the SEC controller register space as Little Endian
 519
 520- MIPS CPU options:
 521                CONFIG_SYS_INIT_SP_OFFSET
 522
 523                Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
 524                pointer. This is needed for the temporary stack before
 525                relocation.
 526
 527                CONFIG_XWAY_SWAP_BYTES
 528
 529                Enable compilation of tools/xway-swap-bytes needed for Lantiq
 530                XWAY SoCs for booting from NOR flash. The U-Boot image needs to
 531                be swapped if a flash programmer is used.
 532
 533- ARM options:
 534                CONFIG_SYS_EXCEPTION_VECTORS_HIGH
 535
 536                Select high exception vectors of the ARM core, e.g., do not
 537                clear the V bit of the c1 register of CP15.
 538
 539                COUNTER_FREQUENCY
 540                Generic timer clock source frequency.
 541
 542                COUNTER_FREQUENCY_REAL
 543                Generic timer clock source frequency if the real clock is
 544                different from COUNTER_FREQUENCY, and can only be determined
 545                at run time.
 546
 547- Tegra SoC options:
 548                CONFIG_TEGRA_SUPPORT_NON_SECURE
 549
 550                Support executing U-Boot in non-secure (NS) mode. Certain
 551                impossible actions will be skipped if the CPU is in NS mode,
 552                such as ARM architectural timer initialization.
 553
 554- Linux Kernel Interface:
 555                CONFIG_CLOCKS_IN_MHZ
 556
 557                U-Boot stores all clock information in Hz
 558                internally. For binary compatibility with older Linux
 559                kernels (which expect the clocks passed in the
 560                bd_info data to be in MHz) the environment variable
 561                "clocks_in_mhz" can be defined so that U-Boot
 562                converts clock data to MHZ before passing it to the
 563                Linux kernel.
 564                When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
 565                "clocks_in_mhz=1" is automatically included in the
 566                default environment.
 567
 568                CONFIG_MEMSIZE_IN_BYTES         [relevant for MIPS only]
 569
 570                When transferring memsize parameter to Linux, some versions
 571                expect it to be in bytes, others in MB.
 572                Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
 573
 574                CONFIG_OF_LIBFDT
 575
 576                New kernel versions are expecting firmware settings to be
 577                passed using flattened device trees (based on open firmware
 578                concepts).
 579
 580                CONFIG_OF_LIBFDT
 581                 * New libfdt-based support
 582                 * Adds the "fdt" command
 583                 * The bootm command automatically updates the fdt
 584
 585                OF_TBCLK - The timebase frequency.
 586                OF_STDOUT_PATH - The path to the console device
 587
 588                boards with QUICC Engines require OF_QE to set UCC MAC
 589                addresses
 590
 591                CONFIG_OF_BOARD_SETUP
 592
 593                Board code has addition modification that it wants to make
 594                to the flat device tree before handing it off to the kernel
 595
 596                CONFIG_OF_SYSTEM_SETUP
 597
 598                Other code has addition modification that it wants to make
 599                to the flat device tree before handing it off to the kernel.
 600                This causes ft_system_setup() to be called before booting
 601                the kernel.
 602
 603                CONFIG_OF_IDE_FIXUP
 604
 605                U-Boot can detect if an IDE device is present or not.
 606                If not, and this new config option is activated, U-Boot
 607                removes the ATA node from the DTS before booting Linux,
 608                so the Linux IDE driver does not probe the device and
 609                crash. This is needed for buggy hardware (uc101) where
 610                no pull down resistor is connected to the signal IDE5V_DD7.
 611
 612                CONFIG_MACH_TYPE        [relevant for ARM only][mandatory]
 613
 614                This setting is mandatory for all boards that have only one
 615                machine type and must be used to specify the machine type
 616                number as it appears in the ARM machine registry
 617                (see http://www.arm.linux.org.uk/developer/machines/).
 618                Only boards that have multiple machine types supported
 619                in a single configuration file and the machine type is
 620                runtime discoverable, do not have to use this setting.
 621
 622- vxWorks boot parameters:
 623
 624                bootvx constructs a valid bootline using the following
 625                environments variables: bootdev, bootfile, ipaddr, netmask,
 626                serverip, gatewayip, hostname, othbootargs.
 627                It loads the vxWorks image pointed bootfile.
 628
 629                Note: If a "bootargs" environment is defined, it will overwride
 630                the defaults discussed just above.
 631
 632- Cache Configuration:
 633                CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
 634
 635- Cache Configuration for ARM:
 636                CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
 637                                      controller
 638                CONFIG_SYS_PL310_BASE - Physical base address of PL310
 639                                        controller register space
 640
 641- Serial Ports:
 642                CONFIG_PL010_SERIAL
 643
 644                Define this if you want support for Amba PrimeCell PL010 UARTs.
 645
 646                CONFIG_PL011_SERIAL
 647
 648                Define this if you want support for Amba PrimeCell PL011 UARTs.
 649
 650                CONFIG_PL011_CLOCK
 651
 652                If you have Amba PrimeCell PL011 UARTs, set this variable to
 653                the clock speed of the UARTs.
 654
 655                CONFIG_PL01x_PORTS
 656
 657                If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
 658                define this to a list of base addresses for each (supported)
 659                port. See e.g. include/configs/versatile.h
 660
 661                CONFIG_SERIAL_HW_FLOW_CONTROL
 662
 663                Define this variable to enable hw flow control in serial driver.
 664                Current user of this option is drivers/serial/nsl16550.c driver
 665
 666- Console Baudrate:
 667                CONFIG_BAUDRATE - in bps
 668                Select one of the baudrates listed in
 669                CONFIG_SYS_BAUDRATE_TABLE, see below.
 670
 671- Autoboot Command:
 672                CONFIG_BOOTCOMMAND
 673                Only needed when CONFIG_BOOTDELAY is enabled;
 674                define a command string that is automatically executed
 675                when no character is read on the console interface
 676                within "Boot Delay" after reset.
 677
 678                CONFIG_RAMBOOT and CONFIG_NFSBOOT
 679                The value of these goes into the environment as
 680                "ramboot" and "nfsboot" respectively, and can be used
 681                as a convenience, when switching between booting from
 682                RAM and NFS.
 683
 684- Serial Download Echo Mode:
 685                CONFIG_LOADS_ECHO
 686                If defined to 1, all characters received during a
 687                serial download (using the "loads" command) are
 688                echoed back. This might be needed by some terminal
 689                emulations (like "cu"), but may as well just take
 690                time on others. This setting #define's the initial
 691                value of the "loads_echo" environment variable.
 692
 693- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
 694                CONFIG_KGDB_BAUDRATE
 695                Select one of the baudrates listed in
 696                CONFIG_SYS_BAUDRATE_TABLE, see below.
 697
 698- Removal of commands
 699                If no commands are needed to boot, you can disable
 700                CONFIG_CMDLINE to remove them. In this case, the command line
 701                will not be available, and when U-Boot wants to execute the
 702                boot command (on start-up) it will call board_run_command()
 703                instead. This can reduce image size significantly for very
 704                simple boot procedures.
 705
 706- Regular expression support:
 707                CONFIG_REGEX
 708                If this variable is defined, U-Boot is linked against
 709                the SLRE (Super Light Regular Expression) library,
 710                which adds regex support to some commands, as for
 711                example "env grep" and "setexpr".
 712
 713- Device tree:
 714                CONFIG_OF_CONTROL
 715                If this variable is defined, U-Boot will use a device tree
 716                to configure its devices, instead of relying on statically
 717                compiled #defines in the board file. This option is
 718                experimental and only available on a few boards. The device
 719                tree is available in the global data as gd->fdt_blob.
 720
 721                U-Boot needs to get its device tree from somewhere. This can
 722                be done using one of the three options below:
 723
 724                CONFIG_OF_EMBED
 725                If this variable is defined, U-Boot will embed a device tree
 726                binary in its image. This device tree file should be in the
 727                board directory and called <soc>-<board>.dts. The binary file
 728                is then picked up in board_init_f() and made available through
 729                the global data structure as gd->fdt_blob.
 730
 731                CONFIG_OF_SEPARATE
 732                If this variable is defined, U-Boot will build a device tree
 733                binary. It will be called u-boot.dtb. Architecture-specific
 734                code will locate it at run-time. Generally this works by:
 735
 736                        cat u-boot.bin u-boot.dtb >image.bin
 737
 738                and in fact, U-Boot does this for you, creating a file called
 739                u-boot-dtb.bin which is useful in the common case. You can
 740                still use the individual files if you need something more
 741                exotic.
 742
 743                CONFIG_OF_BOARD
 744                If this variable is defined, U-Boot will use the device tree
 745                provided by the board at runtime instead of embedding one with
 746                the image. Only boards defining board_fdt_blob_setup() support
 747                this option (see include/fdtdec.h file).
 748
 749- Watchdog:
 750                CONFIG_WATCHDOG
 751                If this variable is defined, it enables watchdog
 752                support for the SoC. There must be support in the SoC
 753                specific code for a watchdog. For the 8xx
 754                CPUs, the SIU Watchdog feature is enabled in the SYPCR
 755                register.  When supported for a specific SoC is
 756                available, then no further board specific code should
 757                be needed to use it.
 758
 759                CONFIG_HW_WATCHDOG
 760                When using a watchdog circuitry external to the used
 761                SoC, then define this variable and provide board
 762                specific code for the "hw_watchdog_reset" function.
 763
 764- Real-Time Clock:
 765
 766                When CONFIG_CMD_DATE is selected, the type of the RTC
 767                has to be selected, too. Define exactly one of the
 768                following options:
 769
 770                CONFIG_RTC_PCF8563      - use Philips PCF8563 RTC
 771                CONFIG_RTC_MC13XXX      - use MC13783 or MC13892 RTC
 772                CONFIG_RTC_MC146818     - use MC146818 RTC
 773                CONFIG_RTC_DS1307       - use Maxim, Inc. DS1307 RTC
 774                CONFIG_RTC_DS1337       - use Maxim, Inc. DS1337 RTC
 775                CONFIG_RTC_DS1338       - use Maxim, Inc. DS1338 RTC
 776                CONFIG_RTC_DS1339       - use Maxim, Inc. DS1339 RTC
 777                CONFIG_RTC_DS164x       - use Dallas DS164x RTC
 778                CONFIG_RTC_ISL1208      - use Intersil ISL1208 RTC
 779                CONFIG_RTC_MAX6900      - use Maxim, Inc. MAX6900 RTC
 780                CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
 781                CONFIG_SYS_RV3029_TCR   - enable trickle charger on
 782                                          RV3029 RTC.
 783
 784                Note that if the RTC uses I2C, then the I2C interface
 785                must also be configured. See I2C Support, below.
 786
 787- GPIO Support:
 788                CONFIG_PCA953X          - use NXP's PCA953X series I2C GPIO
 789
 790                The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
 791                chip-ngpio pairs that tell the PCA953X driver the number of
 792                pins supported by a particular chip.
 793
 794                Note that if the GPIO device uses I2C, then the I2C interface
 795                must also be configured. See I2C Support, below.
 796
 797- I/O tracing:
 798                When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
 799                accesses and can checksum them or write a list of them out
 800                to memory. See the 'iotrace' command for details. This is
 801                useful for testing device drivers since it can confirm that
 802                the driver behaves the same way before and after a code
 803                change. Currently this is supported on sandbox and arm. To
 804                add support for your architecture, add '#include <iotrace.h>'
 805                to the bottom of arch/<arch>/include/asm/io.h and test.
 806
 807                Example output from the 'iotrace stats' command is below.
 808                Note that if the trace buffer is exhausted, the checksum will
 809                still continue to operate.
 810
 811                        iotrace is enabled
 812                        Start:  10000000        (buffer start address)
 813                        Size:   00010000        (buffer size)
 814                        Offset: 00000120        (current buffer offset)
 815                        Output: 10000120        (start + offset)
 816                        Count:  00000018        (number of trace records)
 817                        CRC32:  9526fb66        (CRC32 of all trace records)
 818
 819- Timestamp Support:
 820
 821                When CONFIG_TIMESTAMP is selected, the timestamp
 822                (date and time) of an image is printed by image
 823                commands like bootm or iminfo. This option is
 824                automatically enabled when you select CONFIG_CMD_DATE .
 825
 826- Partition Labels (disklabels) Supported:
 827                Zero or more of the following:
 828                CONFIG_MAC_PARTITION   Apple's MacOS partition table.
 829                CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
 830                CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
 831                                       bootloader.  Note 2TB partition limit; see
 832                                       disk/part_efi.c
 833                CONFIG_SCSI) you must configure support for at
 834                least one non-MTD partition type as well.
 835
 836- IDE Reset method:
 837                CONFIG_IDE_RESET_ROUTINE - this is defined in several
 838                board configurations files but used nowhere!
 839
 840                CONFIG_IDE_RESET - is this is defined, IDE Reset will
 841                be performed by calling the function
 842                        ide_set_reset(int reset)
 843                which has to be defined in a board specific file
 844
 845- ATAPI Support:
 846                CONFIG_ATAPI
 847
 848                Set this to enable ATAPI support.
 849
 850- LBA48 Support
 851                CONFIG_LBA48
 852
 853                Set this to enable support for disks larger than 137GB
 854                Also look at CONFIG_SYS_64BIT_LBA.
 855                Whithout these , LBA48 support uses 32bit variables and will 'only'
 856                support disks up to 2.1TB.
 857
 858                CONFIG_SYS_64BIT_LBA:
 859                        When enabled, makes the IDE subsystem use 64bit sector addresses.
 860                        Default is 32bit.
 861
 862- SCSI Support:
 863                CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
 864                CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
 865                CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
 866                maximum numbers of LUNs, SCSI ID's and target
 867                devices.
 868
 869                The environment variable 'scsidevs' is set to the number of
 870                SCSI devices found during the last scan.
 871
 872- NETWORK Support (PCI):
 873                CONFIG_E1000
 874                Support for Intel 8254x/8257x gigabit chips.
 875
 876                CONFIG_E1000_SPI
 877                Utility code for direct access to the SPI bus on Intel 8257x.
 878                This does not do anything useful unless you set at least one
 879                of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
 880
 881                CONFIG_E1000_SPI_GENERIC
 882                Allow generic access to the SPI bus on the Intel 8257x, for
 883                example with the "sspi" command.
 884
 885                CONFIG_EEPRO100
 886                Support for Intel 82557/82559/82559ER chips.
 887                Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
 888                write routine for first time initialisation.
 889
 890                CONFIG_TULIP
 891                Support for Digital 2114x chips.
 892                Optional CONFIG_TULIP_SELECT_MEDIA for board specific
 893                modem chip initialisation (KS8761/QS6611).
 894
 895                CONFIG_NATSEMI
 896                Support for National dp83815 chips.
 897
 898                CONFIG_NS8382X
 899                Support for National dp8382[01] gigabit chips.
 900
 901- NETWORK Support (other):
 902
 903                CONFIG_DRIVER_AT91EMAC
 904                Support for AT91RM9200 EMAC.
 905
 906                        CONFIG_RMII
 907                        Define this to use reduced MII inteface
 908
 909                        CONFIG_DRIVER_AT91EMAC_QUIET
 910                        If this defined, the driver is quiet.
 911                        The driver doen't show link status messages.
 912
 913                CONFIG_CALXEDA_XGMAC
 914                Support for the Calxeda XGMAC device
 915
 916                CONFIG_LAN91C96
 917                Support for SMSC's LAN91C96 chips.
 918
 919                        CONFIG_LAN91C96_USE_32_BIT
 920                        Define this to enable 32 bit addressing
 921
 922                CONFIG_SMC91111
 923                Support for SMSC's LAN91C111 chip
 924
 925                        CONFIG_SMC91111_BASE
 926                        Define this to hold the physical address
 927                        of the device (I/O space)
 928
 929                        CONFIG_SMC_USE_32_BIT
 930                        Define this if data bus is 32 bits
 931
 932                        CONFIG_SMC_USE_IOFUNCS
 933                        Define this to use i/o functions instead of macros
 934                        (some hardware wont work with macros)
 935
 936                        CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
 937                        Define this if you have more then 3 PHYs.
 938
 939                CONFIG_FTGMAC100
 940                Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
 941
 942                        CONFIG_FTGMAC100_EGIGA
 943                        Define this to use GE link update with gigabit PHY.
 944                        Define this if FTGMAC100 is connected to gigabit PHY.
 945                        If your system has 10/100 PHY only, it might not occur
 946                        wrong behavior. Because PHY usually return timeout or
 947                        useless data when polling gigabit status and gigabit
 948                        control registers. This behavior won't affect the
 949                        correctnessof 10/100 link speed update.
 950
 951                CONFIG_SH_ETHER
 952                Support for Renesas on-chip Ethernet controller
 953
 954                        CONFIG_SH_ETHER_USE_PORT
 955                        Define the number of ports to be used
 956
 957                        CONFIG_SH_ETHER_PHY_ADDR
 958                        Define the ETH PHY's address
 959
 960                        CONFIG_SH_ETHER_CACHE_WRITEBACK
 961                        If this option is set, the driver enables cache flush.
 962
 963- PWM Support:
 964                CONFIG_PWM_IMX
 965                Support for PWM module on the imx6.
 966
 967- TPM Support:
 968                CONFIG_TPM
 969                Support TPM devices.
 970
 971                CONFIG_TPM_TIS_INFINEON
 972                Support for Infineon i2c bus TPM devices. Only one device
 973                per system is supported at this time.
 974
 975                        CONFIG_TPM_TIS_I2C_BURST_LIMITATION
 976                        Define the burst count bytes upper limit
 977
 978                CONFIG_TPM_ST33ZP24
 979                Support for STMicroelectronics TPM devices. Requires DM_TPM support.
 980
 981                        CONFIG_TPM_ST33ZP24_I2C
 982                        Support for STMicroelectronics ST33ZP24 I2C devices.
 983                        Requires TPM_ST33ZP24 and I2C.
 984
 985                        CONFIG_TPM_ST33ZP24_SPI
 986                        Support for STMicroelectronics ST33ZP24 SPI devices.
 987                        Requires TPM_ST33ZP24 and SPI.
 988
 989                CONFIG_TPM_ATMEL_TWI
 990                Support for Atmel TWI TPM device. Requires I2C support.
 991
 992                CONFIG_TPM_TIS_LPC
 993                Support for generic parallel port TPM devices. Only one device
 994                per system is supported at this time.
 995
 996                        CONFIG_TPM_TIS_BASE_ADDRESS
 997                        Base address where the generic TPM device is mapped
 998                        to. Contemporary x86 systems usually map it at
 999                        0xfed40000.
1000
1001                CONFIG_TPM
1002                Define this to enable the TPM support library which provides
1003                functional interfaces to some TPM commands.
1004                Requires support for a TPM device.
1005
1006                CONFIG_TPM_AUTH_SESSIONS
1007                Define this to enable authorized functions in the TPM library.
1008                Requires CONFIG_TPM and CONFIG_SHA1.
1009
1010- USB Support:
1011                At the moment only the UHCI host controller is
1012                supported (PIP405, MIP405); define
1013                CONFIG_USB_UHCI to enable it.
1014                define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1015                and define CONFIG_USB_STORAGE to enable the USB
1016                storage devices.
1017                Note:
1018                Supported are USB Keyboards and USB Floppy drives
1019                (TEAC FD-05PUB).
1020
1021                CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1022                txfilltuning field in the EHCI controller on reset.
1023
1024                CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1025                HW module registers.
1026
1027- USB Device:
1028                Define the below if you wish to use the USB console.
1029                Once firmware is rebuilt from a serial console issue the
1030                command "setenv stdin usbtty; setenv stdout usbtty" and
1031                attach your USB cable. The Unix command "dmesg" should print
1032                it has found a new device. The environment variable usbtty
1033                can be set to gserial or cdc_acm to enable your device to
1034                appear to a USB host as a Linux gserial device or a
1035                Common Device Class Abstract Control Model serial device.
1036                If you select usbtty = gserial you should be able to enumerate
1037                a Linux host by
1038                # modprobe usbserial vendor=0xVendorID product=0xProductID
1039                else if using cdc_acm, simply setting the environment
1040                variable usbtty to be cdc_acm should suffice. The following
1041                might be defined in YourBoardName.h
1042
1043                        CONFIG_USB_DEVICE
1044                        Define this to build a UDC device
1045
1046                        CONFIG_USB_TTY
1047                        Define this to have a tty type of device available to
1048                        talk to the UDC device
1049
1050                        CONFIG_USBD_HS
1051                        Define this to enable the high speed support for usb
1052                        device and usbtty. If this feature is enabled, a routine
1053                        int is_usbd_high_speed(void)
1054                        also needs to be defined by the driver to dynamically poll
1055                        whether the enumeration has succeded at high speed or full
1056                        speed.
1057
1058                        CONFIG_SYS_CONSOLE_IS_IN_ENV
1059                        Define this if you want stdin, stdout &/or stderr to
1060                        be set to usbtty.
1061
1062                If you have a USB-IF assigned VendorID then you may wish to
1063                define your own vendor specific values either in BoardName.h
1064                or directly in usbd_vendor_info.h. If you don't define
1065                CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1066                CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1067                should pretend to be a Linux device to it's target host.
1068
1069                        CONFIG_USBD_MANUFACTURER
1070                        Define this string as the name of your company for
1071                        - CONFIG_USBD_MANUFACTURER "my company"
1072
1073                        CONFIG_USBD_PRODUCT_NAME
1074                        Define this string as the name of your product
1075                        - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1076
1077                        CONFIG_USBD_VENDORID
1078                        Define this as your assigned Vendor ID from the USB
1079                        Implementors Forum. This *must* be a genuine Vendor ID
1080                        to avoid polluting the USB namespace.
1081                        - CONFIG_USBD_VENDORID 0xFFFF
1082
1083                        CONFIG_USBD_PRODUCTID
1084                        Define this as the unique Product ID
1085                        for your device
1086                        - CONFIG_USBD_PRODUCTID 0xFFFF
1087
1088- ULPI Layer Support:
1089                The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1090                the generic ULPI layer. The generic layer accesses the ULPI PHY
1091                via the platform viewport, so you need both the genric layer and
1092                the viewport enabled. Currently only Chipidea/ARC based
1093                viewport is supported.
1094                To enable the ULPI layer support, define CONFIG_USB_ULPI and
1095                CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1096                If your ULPI phy needs a different reference clock than the
1097                standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1098                the appropriate value in Hz.
1099
1100- MMC Support:
1101                The MMC controller on the Intel PXA is supported. To
1102                enable this define CONFIG_MMC. The MMC can be
1103                accessed from the boot prompt by mapping the device
1104                to physical memory similar to flash. Command line is
1105                enabled with CONFIG_CMD_MMC. The MMC driver also works with
1106                the FAT fs. This is enabled with CONFIG_CMD_FAT.
1107
1108                CONFIG_SH_MMCIF
1109                Support for Renesas on-chip MMCIF controller
1110
1111                        CONFIG_SH_MMCIF_ADDR
1112                        Define the base address of MMCIF registers
1113
1114                        CONFIG_SH_MMCIF_CLK
1115                        Define the clock frequency for MMCIF
1116
1117- USB Device Firmware Update (DFU) class support:
1118                CONFIG_DFU_OVER_USB
1119                This enables the USB portion of the DFU USB class
1120
1121                CONFIG_DFU_NAND
1122                This enables support for exposing NAND devices via DFU.
1123
1124                CONFIG_DFU_RAM
1125                This enables support for exposing RAM via DFU.
1126                Note: DFU spec refer to non-volatile memory usage, but
1127                allow usages beyond the scope of spec - here RAM usage,
1128                one that would help mostly the developer.
1129
1130                CONFIG_SYS_DFU_DATA_BUF_SIZE
1131                Dfu transfer uses a buffer before writing data to the
1132                raw storage device. Make the size (in bytes) of this buffer
1133                configurable. The size of this buffer is also configurable
1134                through the "dfu_bufsiz" environment variable.
1135
1136                CONFIG_SYS_DFU_MAX_FILE_SIZE
1137                When updating files rather than the raw storage device,
1138                we use a static buffer to copy the file into and then write
1139                the buffer once we've been given the whole file.  Define
1140                this to the maximum filesize (in bytes) for the buffer.
1141                Default is 4 MiB if undefined.
1142
1143                DFU_DEFAULT_POLL_TIMEOUT
1144                Poll timeout [ms], is the timeout a device can send to the
1145                host. The host must wait for this timeout before sending
1146                a subsequent DFU_GET_STATUS request to the device.
1147
1148                DFU_MANIFEST_POLL_TIMEOUT
1149                Poll timeout [ms], which the device sends to the host when
1150                entering dfuMANIFEST state. Host waits this timeout, before
1151                sending again an USB request to the device.
1152
1153- Journaling Flash filesystem support:
1154                CONFIG_JFFS2_NAND
1155                Define these for a default partition on a NAND device
1156
1157                CONFIG_SYS_JFFS2_FIRST_SECTOR,
1158                CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1159                Define these for a default partition on a NOR device
1160
1161- Keyboard Support:
1162                See Kconfig help for available keyboard drivers.
1163
1164                CONFIG_KEYBOARD
1165
1166                Define this to enable a custom keyboard support.
1167                This simply calls drv_keyboard_init() which must be
1168                defined in your board-specific files. This option is deprecated
1169                and is only used by novena. For new boards, use driver model
1170                instead.
1171
1172- Video support:
1173                CONFIG_FSL_DIU_FB
1174                Enable the Freescale DIU video driver.  Reference boards for
1175                SOCs that have a DIU should define this macro to enable DIU
1176                support, and should also define these other macros:
1177
1178                        CONFIG_SYS_DIU_ADDR
1179                        CONFIG_VIDEO
1180                        CONFIG_CFB_CONSOLE
1181                        CONFIG_VIDEO_SW_CURSOR
1182                        CONFIG_VGA_AS_SINGLE_DEVICE
1183                        CONFIG_VIDEO_LOGO
1184                        CONFIG_VIDEO_BMP_LOGO
1185
1186                The DIU driver will look for the 'video-mode' environment
1187                variable, and if defined, enable the DIU as a console during
1188                boot.  See the documentation file doc/README.video for a
1189                description of this variable.
1190
1191- LCD Support:  CONFIG_LCD
1192
1193                Define this to enable LCD support (for output to LCD
1194                display); also select one of the supported displays
1195                by defining one of these:
1196
1197                CONFIG_ATMEL_LCD:
1198
1199                        HITACHI TX09D70VM1CCA, 3.5", 240x320.
1200
1201                CONFIG_NEC_NL6448AC33:
1202
1203                        NEC NL6448AC33-18. Active, color, single scan.
1204
1205                CONFIG_NEC_NL6448BC20
1206
1207                        NEC NL6448BC20-08. 6.5", 640x480.
1208                        Active, color, single scan.
1209
1210                CONFIG_NEC_NL6448BC33_54
1211
1212                        NEC NL6448BC33-54. 10.4", 640x480.
1213                        Active, color, single scan.
1214
1215                CONFIG_SHARP_16x9
1216
1217                        Sharp 320x240. Active, color, single scan.
1218                        It isn't 16x9, and I am not sure what it is.
1219
1220                CONFIG_SHARP_LQ64D341
1221
1222                        Sharp LQ64D341 display, 640x480.
1223                        Active, color, single scan.
1224
1225                CONFIG_HLD1045
1226
1227                        HLD1045 display, 640x480.
1228                        Active, color, single scan.
1229
1230                CONFIG_OPTREX_BW
1231
1232                        Optrex   CBL50840-2 NF-FW 99 22 M5
1233                        or
1234                        Hitachi  LMG6912RPFC-00T
1235                        or
1236                        Hitachi  SP14Q002
1237
1238                        320x240. Black & white.
1239
1240                CONFIG_LCD_ALIGNMENT
1241
1242                Normally the LCD is page-aligned (typically 4KB). If this is
1243                defined then the LCD will be aligned to this value instead.
1244                For ARM it is sometimes useful to use MMU_SECTION_SIZE
1245                here, since it is cheaper to change data cache settings on
1246                a per-section basis.
1247
1248
1249                CONFIG_LCD_ROTATION
1250
1251                Sometimes, for example if the display is mounted in portrait
1252                mode or even if it's mounted landscape but rotated by 180degree,
1253                we need to rotate our content of the display relative to the
1254                framebuffer, so that user can read the messages which are
1255                printed out.
1256                Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1257                initialized with a given rotation from "vl_rot" out of
1258                "vidinfo_t" which is provided by the board specific code.
1259                The value for vl_rot is coded as following (matching to
1260                fbcon=rotate:<n> linux-kernel commandline):
1261                0 = no rotation respectively 0 degree
1262                1 = 90 degree rotation
1263                2 = 180 degree rotation
1264                3 = 270 degree rotation
1265
1266                If CONFIG_LCD_ROTATION is not defined, the console will be
1267                initialized with 0degree rotation.
1268
1269                CONFIG_LCD_BMP_RLE8
1270
1271                Support drawing of RLE8-compressed bitmaps on the LCD.
1272
1273                CONFIG_I2C_EDID
1274
1275                Enables an 'i2c edid' command which can read EDID
1276                information over I2C from an attached LCD display.
1277
1278- Splash Screen Support: CONFIG_SPLASH_SCREEN
1279
1280                If this option is set, the environment is checked for
1281                a variable "splashimage". If found, the usual display
1282                of logo, copyright and system information on the LCD
1283                is suppressed and the BMP image at the address
1284                specified in "splashimage" is loaded instead. The
1285                console is redirected to the "nulldev", too. This
1286                allows for a "silent" boot where a splash screen is
1287                loaded very quickly after power-on.
1288
1289                CONFIG_SPLASHIMAGE_GUARD
1290
1291                If this option is set, then U-Boot will prevent the environment
1292                variable "splashimage" from being set to a problematic address
1293                (see doc/README.displaying-bmps).
1294                This option is useful for targets where, due to alignment
1295                restrictions, an improperly aligned BMP image will cause a data
1296                abort. If you think you will not have problems with unaligned
1297                accesses (for example because your toolchain prevents them)
1298                there is no need to set this option.
1299
1300                CONFIG_SPLASH_SCREEN_ALIGN
1301
1302                If this option is set the splash image can be freely positioned
1303                on the screen. Environment variable "splashpos" specifies the
1304                position as "x,y". If a positive number is given it is used as
1305                number of pixel from left/top. If a negative number is given it
1306                is used as number of pixel from right/bottom. You can also
1307                specify 'm' for centering the image.
1308
1309                Example:
1310                setenv splashpos m,m
1311                        => image at center of screen
1312
1313                setenv splashpos 30,20
1314                        => image at x = 30 and y = 20
1315
1316                setenv splashpos -10,m
1317                        => vertically centered image
1318                           at x = dspWidth - bmpWidth - 9
1319
1320- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1321
1322                If this option is set, additionally to standard BMP
1323                images, gzipped BMP images can be displayed via the
1324                splashscreen support or the bmp command.
1325
1326- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1327
1328                If this option is set, 8-bit RLE compressed BMP images
1329                can be displayed via the splashscreen support or the
1330                bmp command.
1331
1332- Compression support:
1333                CONFIG_GZIP
1334
1335                Enabled by default to support gzip compressed images.
1336
1337                CONFIG_BZIP2
1338
1339                If this option is set, support for bzip2 compressed
1340                images is included. If not, only uncompressed and gzip
1341                compressed images are supported.
1342
1343                NOTE: the bzip2 algorithm requires a lot of RAM, so
1344                the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1345                be at least 4MB.
1346
1347- MII/PHY support:
1348                CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1349
1350                The clock frequency of the MII bus
1351
1352                CONFIG_PHY_RESET_DELAY
1353
1354                Some PHY like Intel LXT971A need extra delay after
1355                reset before any MII register access is possible.
1356                For such PHY, set this option to the usec delay
1357                required. (minimum 300usec for LXT971A)
1358
1359                CONFIG_PHY_CMD_DELAY (ppc4xx)
1360
1361                Some PHY like Intel LXT971A need extra delay after
1362                command issued before MII status register can be read
1363
1364- IP address:
1365                CONFIG_IPADDR
1366
1367                Define a default value for the IP address to use for
1368                the default Ethernet interface, in case this is not
1369                determined through e.g. bootp.
1370                (Environment variable "ipaddr")
1371
1372- Server IP address:
1373                CONFIG_SERVERIP
1374
1375                Defines a default value for the IP address of a TFTP
1376                server to contact when using the "tftboot" command.
1377                (Environment variable "serverip")
1378
1379                CONFIG_KEEP_SERVERADDR
1380
1381                Keeps the server's MAC address, in the env 'serveraddr'
1382                for passing to bootargs (like Linux's netconsole option)
1383
1384- Gateway IP address:
1385                CONFIG_GATEWAYIP
1386
1387                Defines a default value for the IP address of the
1388                default router where packets to other networks are
1389                sent to.
1390                (Environment variable "gatewayip")
1391
1392- Subnet mask:
1393                CONFIG_NETMASK
1394
1395                Defines a default value for the subnet mask (or
1396                routing prefix) which is used to determine if an IP
1397                address belongs to the local subnet or needs to be
1398                forwarded through a router.
1399                (Environment variable "netmask")
1400
1401- BOOTP Recovery Mode:
1402                CONFIG_BOOTP_RANDOM_DELAY
1403
1404                If you have many targets in a network that try to
1405                boot using BOOTP, you may want to avoid that all
1406                systems send out BOOTP requests at precisely the same
1407                moment (which would happen for instance at recovery
1408                from a power failure, when all systems will try to
1409                boot, thus flooding the BOOTP server. Defining
1410                CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1411                inserted before sending out BOOTP requests. The
1412                following delays are inserted then:
1413
1414                1st BOOTP request:      delay 0 ... 1 sec
1415                2nd BOOTP request:      delay 0 ... 2 sec
1416                3rd BOOTP request:      delay 0 ... 4 sec
1417                4th and following
1418                BOOTP requests:         delay 0 ... 8 sec
1419
1420                CONFIG_BOOTP_ID_CACHE_SIZE
1421
1422                BOOTP packets are uniquely identified using a 32-bit ID. The
1423                server will copy the ID from client requests to responses and
1424                U-Boot will use this to determine if it is the destination of
1425                an incoming response. Some servers will check that addresses
1426                aren't in use before handing them out (usually using an ARP
1427                ping) and therefore take up to a few hundred milliseconds to
1428                respond. Network congestion may also influence the time it
1429                takes for a response to make it back to the client. If that
1430                time is too long, U-Boot will retransmit requests. In order
1431                to allow earlier responses to still be accepted after these
1432                retransmissions, U-Boot's BOOTP client keeps a small cache of
1433                IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1434                cache. The default is to keep IDs for up to four outstanding
1435                requests. Increasing this will allow U-Boot to accept offers
1436                from a BOOTP client in networks with unusually high latency.
1437
1438- DHCP Advanced Options:
1439                You can fine tune the DHCP functionality by defining
1440                CONFIG_BOOTP_* symbols:
1441
1442                CONFIG_BOOTP_NISDOMAIN
1443                CONFIG_BOOTP_BOOTFILESIZE
1444                CONFIG_BOOTP_SEND_HOSTNAME
1445                CONFIG_BOOTP_NTPSERVER
1446                CONFIG_BOOTP_TIMEOFFSET
1447                CONFIG_BOOTP_VENDOREX
1448                CONFIG_BOOTP_MAY_FAIL
1449
1450                CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1451                environment variable, not the BOOTP server.
1452
1453                CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1454                after the configured retry count, the call will fail
1455                instead of starting over.  This can be used to fail over
1456                to Link-local IP address configuration if the DHCP server
1457                is not available.
1458
1459                CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1460                to do a dynamic update of a DNS server. To do this, they
1461                need the hostname of the DHCP requester.
1462                If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1463                of the "hostname" environment variable is passed as
1464                option 12 to the DHCP server.
1465
1466                CONFIG_BOOTP_DHCP_REQUEST_DELAY
1467
1468                A 32bit value in microseconds for a delay between
1469                receiving a "DHCP Offer" and sending the "DHCP Request".
1470                This fixes a problem with certain DHCP servers that don't
1471                respond 100% of the time to a "DHCP request". E.g. On an
1472                AT91RM9200 processor running at 180MHz, this delay needed
1473                to be *at least* 15,000 usec before a Windows Server 2003
1474                DHCP server would reply 100% of the time. I recommend at
1475                least 50,000 usec to be safe. The alternative is to hope
1476                that one of the retries will be successful but note that
1477                the DHCP timeout and retry process takes a longer than
1478                this delay.
1479
1480 - Link-local IP address negotiation:
1481                Negotiate with other link-local clients on the local network
1482                for an address that doesn't require explicit configuration.
1483                This is especially useful if a DHCP server cannot be guaranteed
1484                to exist in all environments that the device must operate.
1485
1486                See doc/README.link-local for more information.
1487
1488 - MAC address from environment variables
1489
1490                FDT_SEQ_MACADDR_FROM_ENV
1491
1492                Fix-up device tree with MAC addresses fetched sequentially from
1493                environment variables. This config work on assumption that
1494                non-usable ethernet node of device-tree are either not present
1495                or their status has been marked as "disabled".
1496
1497 - CDP Options:
1498                CONFIG_CDP_DEVICE_ID
1499
1500                The device id used in CDP trigger frames.
1501
1502                CONFIG_CDP_DEVICE_ID_PREFIX
1503
1504                A two character string which is prefixed to the MAC address
1505                of the device.
1506
1507                CONFIG_CDP_PORT_ID
1508
1509                A printf format string which contains the ascii name of
1510                the port. Normally is set to "eth%d" which sets
1511                eth0 for the first Ethernet, eth1 for the second etc.
1512
1513                CONFIG_CDP_CAPABILITIES
1514
1515                A 32bit integer which indicates the device capabilities;
1516                0x00000010 for a normal host which does not forwards.
1517
1518                CONFIG_CDP_VERSION
1519
1520                An ascii string containing the version of the software.
1521
1522                CONFIG_CDP_PLATFORM
1523
1524                An ascii string containing the name of the platform.
1525
1526                CONFIG_CDP_TRIGGER
1527
1528                A 32bit integer sent on the trigger.
1529
1530                CONFIG_CDP_POWER_CONSUMPTION
1531
1532                A 16bit integer containing the power consumption of the
1533                device in .1 of milliwatts.
1534
1535                CONFIG_CDP_APPLIANCE_VLAN_TYPE
1536
1537                A byte containing the id of the VLAN.
1538
1539- Status LED:   CONFIG_LED_STATUS
1540
1541                Several configurations allow to display the current
1542                status using a LED. For instance, the LED will blink
1543                fast while running U-Boot code, stop blinking as
1544                soon as a reply to a BOOTP request was received, and
1545                start blinking slow once the Linux kernel is running
1546                (supported by a status LED driver in the Linux
1547                kernel). Defining CONFIG_LED_STATUS enables this
1548                feature in U-Boot.
1549
1550                Additional options:
1551
1552                CONFIG_LED_STATUS_GPIO
1553                The status LED can be connected to a GPIO pin.
1554                In such cases, the gpio_led driver can be used as a
1555                status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1556                to include the gpio_led driver in the U-Boot binary.
1557
1558                CONFIG_GPIO_LED_INVERTED_TABLE
1559                Some GPIO connected LEDs may have inverted polarity in which
1560                case the GPIO high value corresponds to LED off state and
1561                GPIO low value corresponds to LED on state.
1562                In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1563                with a list of GPIO LEDs that have inverted polarity.
1564
1565- I2C Support:  CONFIG_SYS_I2C
1566
1567                This enable the NEW i2c subsystem, and will allow you to use
1568                i2c commands at the u-boot command line (as long as you set
1569                CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1570                based realtime clock chips or other i2c devices. See
1571                common/cmd_i2c.c for a description of the command line
1572                interface.
1573
1574                ported i2c driver to the new framework:
1575                - drivers/i2c/soft_i2c.c:
1576                  - activate first bus with CONFIG_SYS_I2C_SOFT define
1577                    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1578                    for defining speed and slave address
1579                  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1580                    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1581                    for defining speed and slave address
1582                  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1583                    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1584                    for defining speed and slave address
1585                  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1586                    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1587                    for defining speed and slave address
1588
1589                - drivers/i2c/fsl_i2c.c:
1590                  - activate i2c driver with CONFIG_SYS_I2C_FSL
1591                    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1592                    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1593                    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1594                    bus.
1595                  - If your board supports a second fsl i2c bus, define
1596                    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1597                    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1598                    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1599                    second bus.
1600
1601                - drivers/i2c/tegra_i2c.c:
1602                  - activate this driver with CONFIG_SYS_I2C_TEGRA
1603                  - This driver adds 4 i2c buses with a fix speed from
1604                    100000 and the slave addr 0!
1605
1606                - drivers/i2c/ppc4xx_i2c.c
1607                  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1608                  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1609                  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1610
1611                - drivers/i2c/i2c_mxc.c
1612                  - activate this driver with CONFIG_SYS_I2C_MXC
1613                  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1614                  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1615                  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1616                  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1617                  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1618                  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1619                  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1620                  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1621                  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1622                  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1623                  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1624                  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1625                If those defines are not set, default value is 100000
1626                for speed, and 0 for slave.
1627
1628                - drivers/i2c/rcar_i2c.c:
1629                  - activate this driver with CONFIG_SYS_I2C_RCAR
1630                  - This driver adds 4 i2c buses
1631
1632                  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1633                  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1634                  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1635                  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1636                  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1637                  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1638                  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1639                  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1640                  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1641
1642                - drivers/i2c/sh_i2c.c:
1643                  - activate this driver with CONFIG_SYS_I2C_SH
1644                  - This driver adds from 2 to 5 i2c buses
1645
1646                  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1647                  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1648                  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1649                  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1650                  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1651                  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1652                  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1653                  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1654                  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1655                  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1656                  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1657
1658                - drivers/i2c/omap24xx_i2c.c
1659                  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1660                  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1661                  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1662                  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1663                  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1664                  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1665                  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1666                  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1667                  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1668                  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1669                  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1670
1671                - drivers/i2c/s3c24x0_i2c.c:
1672                  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1673                  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1674                    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1675                    with a fix speed from 100000 and the slave addr 0!
1676
1677                - drivers/i2c/ihs_i2c.c
1678                  - activate this driver with CONFIG_SYS_I2C_IHS
1679                  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1680                  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1681                  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1682                  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1683                  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1684                  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1685                  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1686                  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1687                  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1688                  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1689                  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1690                  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1691                  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1692                  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1693                  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1694                  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1695                  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1696                  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1697                  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1698                  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1699                  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1700
1701                additional defines:
1702
1703                CONFIG_SYS_NUM_I2C_BUSES
1704                Hold the number of i2c buses you want to use.
1705
1706                CONFIG_SYS_I2C_DIRECT_BUS
1707                define this, if you don't use i2c muxes on your hardware.
1708                if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1709                omit this define.
1710
1711                CONFIG_SYS_I2C_MAX_HOPS
1712                define how many muxes are maximal consecutively connected
1713                on one i2c bus. If you not use i2c muxes, omit this
1714                define.
1715
1716                CONFIG_SYS_I2C_BUSES
1717                hold a list of buses you want to use, only used if
1718                CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1719                a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1720                CONFIG_SYS_NUM_I2C_BUSES = 9:
1721
1722                 CONFIG_SYS_I2C_BUSES   {{0, {I2C_NULL_HOP}}, \
1723                                        {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1724                                        {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1725                                        {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1726                                        {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1727                                        {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1728                                        {1, {I2C_NULL_HOP}}, \
1729                                        {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1730                                        {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1731                                        }
1732
1733                which defines
1734                        bus 0 on adapter 0 without a mux
1735                        bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1736                        bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1737                        bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1738                        bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1739                        bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1740                        bus 6 on adapter 1 without a mux
1741                        bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1742                        bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1743
1744                If you do not have i2c muxes on your board, omit this define.
1745
1746- Legacy I2C Support:
1747                If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1748                then the following macros need to be defined (examples are
1749                from include/configs/lwmon.h):
1750
1751                I2C_INIT
1752
1753                (Optional). Any commands necessary to enable the I2C
1754                controller or configure ports.
1755
1756                eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=  PB_SCL)
1757
1758                I2C_ACTIVE
1759
1760                The code necessary to make the I2C data line active
1761                (driven).  If the data line is open collector, this
1762                define can be null.
1763
1764                eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1765
1766                I2C_TRISTATE
1767
1768                The code necessary to make the I2C data line tri-stated
1769                (inactive).  If the data line is open collector, this
1770                define can be null.
1771
1772                eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1773
1774                I2C_READ
1775
1776                Code that returns true if the I2C data line is high,
1777                false if it is low.
1778
1779                eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1780
1781                I2C_SDA(bit)
1782
1783                If <bit> is true, sets the I2C data line high. If it
1784                is false, it clears it (low).
1785
1786                eg: #define I2C_SDA(bit) \
1787                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1788                        else    immr->im_cpm.cp_pbdat &= ~PB_SDA
1789
1790                I2C_SCL(bit)
1791
1792                If <bit> is true, sets the I2C clock line high. If it
1793                is false, it clears it (low).
1794
1795                eg: #define I2C_SCL(bit) \
1796                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1797                        else    immr->im_cpm.cp_pbdat &= ~PB_SCL
1798
1799                I2C_DELAY
1800
1801                This delay is invoked four times per clock cycle so this
1802                controls the rate of data transfer.  The data rate thus
1803                is 1 / (I2C_DELAY * 4). Often defined to be something
1804                like:
1805
1806                #define I2C_DELAY  udelay(2)
1807
1808                CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1809
1810                If your arch supports the generic GPIO framework (asm/gpio.h),
1811                then you may alternatively define the two GPIOs that are to be
1812                used as SCL / SDA.  Any of the previous I2C_xxx macros will
1813                have GPIO-based defaults assigned to them as appropriate.
1814
1815                You should define these to the GPIO value as given directly to
1816                the generic GPIO functions.
1817
1818                CONFIG_SYS_I2C_INIT_BOARD
1819
1820                When a board is reset during an i2c bus transfer
1821                chips might think that the current transfer is still
1822                in progress. On some boards it is possible to access
1823                the i2c SCLK line directly, either by using the
1824                processor pin as a GPIO or by having a second pin
1825                connected to the bus. If this option is defined a
1826                custom i2c_init_board() routine in boards/xxx/board.c
1827                is run early in the boot sequence.
1828
1829                CONFIG_I2C_MULTI_BUS
1830
1831                This option allows the use of multiple I2C buses, each of which
1832                must have a controller.  At any point in time, only one bus is
1833                active.  To switch to a different bus, use the 'i2c dev' command.
1834                Note that bus numbering is zero-based.
1835
1836                CONFIG_SYS_I2C_NOPROBES
1837
1838                This option specifies a list of I2C devices that will be skipped
1839                when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1840                is set, specify a list of bus-device pairs.  Otherwise, specify
1841                a 1D array of device addresses
1842
1843                e.g.
1844                        #undef  CONFIG_I2C_MULTI_BUS
1845                        #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1846
1847                will skip addresses 0x50 and 0x68 on a board with one I2C bus
1848
1849                        #define CONFIG_I2C_MULTI_BUS
1850                        #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1851
1852                will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1853
1854                CONFIG_SYS_SPD_BUS_NUM
1855
1856                If defined, then this indicates the I2C bus number for DDR SPD.
1857                If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1858
1859                CONFIG_SYS_RTC_BUS_NUM
1860
1861                If defined, then this indicates the I2C bus number for the RTC.
1862                If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1863
1864                CONFIG_SOFT_I2C_READ_REPEATED_START
1865
1866                defining this will force the i2c_read() function in
1867                the soft_i2c driver to perform an I2C repeated start
1868                between writing the address pointer and reading the
1869                data.  If this define is omitted the default behaviour
1870                of doing a stop-start sequence will be used.  Most I2C
1871                devices can use either method, but some require one or
1872                the other.
1873
1874- SPI Support:  CONFIG_SPI
1875
1876                Enables SPI driver (so far only tested with
1877                SPI EEPROM, also an instance works with Crystal A/D and
1878                D/As on the SACSng board)
1879
1880                CONFIG_SOFT_SPI
1881
1882                Enables a software (bit-bang) SPI driver rather than
1883                using hardware support. This is a general purpose
1884                driver that only requires three general I/O port pins
1885                (two outputs, one input) to function. If this is
1886                defined, the board configuration must define several
1887                SPI configuration items (port pins to use, etc). For
1888                an example, see include/configs/sacsng.h.
1889
1890                CONFIG_SYS_SPI_MXC_WAIT
1891                Timeout for waiting until spi transfer completed.
1892                default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1893
1894- FPGA Support: CONFIG_FPGA
1895
1896                Enables FPGA subsystem.
1897
1898                CONFIG_FPGA_<vendor>
1899
1900                Enables support for specific chip vendors.
1901                (ALTERA, XILINX)
1902
1903                CONFIG_FPGA_<family>
1904
1905                Enables support for FPGA family.
1906                (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1907
1908                CONFIG_FPGA_COUNT
1909
1910                Specify the number of FPGA devices to support.
1911
1912                CONFIG_SYS_FPGA_PROG_FEEDBACK
1913
1914                Enable printing of hash marks during FPGA configuration.
1915
1916                CONFIG_SYS_FPGA_CHECK_BUSY
1917
1918                Enable checks on FPGA configuration interface busy
1919                status by the configuration function. This option
1920                will require a board or device specific function to
1921                be written.
1922
1923                CONFIG_FPGA_DELAY
1924
1925                If defined, a function that provides delays in the FPGA
1926                configuration driver.
1927
1928                CONFIG_SYS_FPGA_CHECK_CTRLC
1929                Allow Control-C to interrupt FPGA configuration
1930
1931                CONFIG_SYS_FPGA_CHECK_ERROR
1932
1933                Check for configuration errors during FPGA bitfile
1934                loading. For example, abort during Virtex II
1935                configuration if the INIT_B line goes low (which
1936                indicated a CRC error).
1937
1938                CONFIG_SYS_FPGA_WAIT_INIT
1939
1940                Maximum time to wait for the INIT_B line to de-assert
1941                after PROB_B has been de-asserted during a Virtex II
1942                FPGA configuration sequence. The default time is 500
1943                ms.
1944
1945                CONFIG_SYS_FPGA_WAIT_BUSY
1946
1947                Maximum time to wait for BUSY to de-assert during
1948                Virtex II FPGA configuration. The default is 5 ms.
1949
1950                CONFIG_SYS_FPGA_WAIT_CONFIG
1951
1952                Time to wait after FPGA configuration. The default is
1953                200 ms.
1954
1955- Configuration Management:
1956
1957                CONFIG_IDENT_STRING
1958
1959                If defined, this string will be added to the U-Boot
1960                version information (U_BOOT_VERSION)
1961
1962- Vendor Parameter Protection:
1963
1964                U-Boot considers the values of the environment
1965                variables "serial#" (Board Serial Number) and
1966                "ethaddr" (Ethernet Address) to be parameters that
1967                are set once by the board vendor / manufacturer, and
1968                protects these variables from casual modification by
1969                the user. Once set, these variables are read-only,
1970                and write or delete attempts are rejected. You can
1971                change this behaviour:
1972
1973                If CONFIG_ENV_OVERWRITE is #defined in your config
1974                file, the write protection for vendor parameters is
1975                completely disabled. Anybody can change or delete
1976                these parameters.
1977
1978                Alternatively, if you define _both_ an ethaddr in the
1979                default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1980                Ethernet address is installed in the environment,
1981                which can be changed exactly ONCE by the user. [The
1982                serial# is unaffected by this, i. e. it remains
1983                read-only.]
1984
1985                The same can be accomplished in a more flexible way
1986                for any variable by configuring the type of access
1987                to allow for those variables in the ".flags" variable
1988                or define CONFIG_ENV_FLAGS_LIST_STATIC.
1989
1990- Protected RAM:
1991                CONFIG_PRAM
1992
1993                Define this variable to enable the reservation of
1994                "protected RAM", i. e. RAM which is not overwritten
1995                by U-Boot. Define CONFIG_PRAM to hold the number of
1996                kB you want to reserve for pRAM. You can overwrite
1997                this default value by defining an environment
1998                variable "pram" to the number of kB you want to
1999                reserve. Note that the board info structure will
2000                still show the full amount of RAM. If pRAM is
2001                reserved, a new environment variable "mem" will
2002                automatically be defined to hold the amount of
2003                remaining RAM in a form that can be passed as boot
2004                argument to Linux, for instance like that:
2005
2006                        setenv bootargs ... mem=\${mem}
2007                        saveenv
2008
2009                This way you can tell Linux not to use this memory,
2010                either, which results in a memory region that will
2011                not be affected by reboots.
2012
2013                *WARNING* If your board configuration uses automatic
2014                detection of the RAM size, you must make sure that
2015                this memory test is non-destructive. So far, the
2016                following board configurations are known to be
2017                "pRAM-clean":
2018
2019                        IVMS8, IVML24, SPD8xx,
2020                        HERMES, IP860, RPXlite, LWMON,
2021                        FLAGADM
2022
2023- Access to physical memory region (> 4GB)
2024                Some basic support is provided for operations on memory not
2025                normally accessible to U-Boot - e.g. some architectures
2026                support access to more than 4GB of memory on 32-bit
2027                machines using physical address extension or similar.
2028                Define CONFIG_PHYSMEM to access this basic support, which
2029                currently only supports clearing the memory.
2030
2031- Error Recovery:
2032                CONFIG_NET_RETRY_COUNT
2033
2034                This variable defines the number of retries for
2035                network operations like ARP, RARP, TFTP, or BOOTP
2036                before giving up the operation. If not defined, a
2037                default value of 5 is used.
2038
2039                CONFIG_ARP_TIMEOUT
2040
2041                Timeout waiting for an ARP reply in milliseconds.
2042
2043                CONFIG_NFS_TIMEOUT
2044
2045                Timeout in milliseconds used in NFS protocol.
2046                If you encounter "ERROR: Cannot umount" in nfs command,
2047                try longer timeout such as
2048                #define CONFIG_NFS_TIMEOUT 10000UL
2049
2050- Command Interpreter:
2051                CONFIG_SYS_PROMPT_HUSH_PS2
2052
2053                This defines the secondary prompt string, which is
2054                printed when the command interpreter needs more input
2055                to complete a command. Usually "> ".
2056
2057        Note:
2058
2059                In the current implementation, the local variables
2060                space and global environment variables space are
2061                separated. Local variables are those you define by
2062                simply typing `name=value'. To access a local
2063                variable later on, you have write `$name' or
2064                `${name}'; to execute the contents of a variable
2065                directly type `$name' at the command prompt.
2066
2067                Global environment variables are those you use
2068                setenv/printenv to work with. To run a command stored
2069                in such a variable, you need to use the run command,
2070                and you must not use the '$' sign to access them.
2071
2072                To store commands and special characters in a
2073                variable, please use double quotation marks
2074                surrounding the whole text of the variable, instead
2075                of the backslashes before semicolons and special
2076                symbols.
2077
2078- Command Line Editing and History:
2079                CONFIG_CMDLINE_PS_SUPPORT
2080
2081                Enable support for changing the command prompt string
2082                at run-time. Only static string is supported so far.
2083                The string is obtained from environment variables PS1
2084                and PS2.
2085
2086- Default Environment:
2087                CONFIG_EXTRA_ENV_SETTINGS
2088
2089                Define this to contain any number of null terminated
2090                strings (variable = value pairs) that will be part of
2091                the default environment compiled into the boot image.
2092
2093                For example, place something like this in your
2094                board's config file:
2095
2096                #define CONFIG_EXTRA_ENV_SETTINGS \
2097                        "myvar1=value1\0" \
2098                        "myvar2=value2\0"
2099
2100                Warning: This method is based on knowledge about the
2101                internal format how the environment is stored by the
2102                U-Boot code. This is NOT an official, exported
2103                interface! Although it is unlikely that this format
2104                will change soon, there is no guarantee either.
2105                You better know what you are doing here.
2106
2107                Note: overly (ab)use of the default environment is
2108                discouraged. Make sure to check other ways to preset
2109                the environment like the "source" command or the
2110                boot command first.
2111
2112                CONFIG_DELAY_ENVIRONMENT
2113
2114                Normally the environment is loaded when the board is
2115                initialised so that it is available to U-Boot. This inhibits
2116                that so that the environment is not available until
2117                explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2118                this is instead controlled by the value of
2119                /config/load-environment.
2120
2121- TFTP Fixed UDP Port:
2122                CONFIG_TFTP_PORT
2123
2124                If this is defined, the environment variable tftpsrcp
2125                is used to supply the TFTP UDP source port value.
2126                If tftpsrcp isn't defined, the normal pseudo-random port
2127                number generator is used.
2128
2129                Also, the environment variable tftpdstp is used to supply
2130                the TFTP UDP destination port value.  If tftpdstp isn't
2131                defined, the normal port 69 is used.
2132
2133                The purpose for tftpsrcp is to allow a TFTP server to
2134                blindly start the TFTP transfer using the pre-configured
2135                target IP address and UDP port. This has the effect of
2136                "punching through" the (Windows XP) firewall, allowing
2137                the remainder of the TFTP transfer to proceed normally.
2138                A better solution is to properly configure the firewall,
2139                but sometimes that is not allowed.
2140
2141- Show boot progress:
2142                CONFIG_SHOW_BOOT_PROGRESS
2143
2144                Defining this option allows to add some board-
2145                specific code (calling a user-provided function
2146                "show_boot_progress(int)") that enables you to show
2147                the system's boot progress on some display (for
2148                example, some LED's) on your board. At the moment,
2149                the following checkpoints are implemented:
2150
2151
2152Legacy uImage format:
2153
2154  Arg   Where                   When
2155    1   common/cmd_bootm.c      before attempting to boot an image
2156   -1   common/cmd_bootm.c      Image header has bad     magic number
2157    2   common/cmd_bootm.c      Image header has correct magic number
2158   -2   common/cmd_bootm.c      Image header has bad     checksum
2159    3   common/cmd_bootm.c      Image header has correct checksum
2160   -3   common/cmd_bootm.c      Image data   has bad     checksum
2161    4   common/cmd_bootm.c      Image data   has correct checksum
2162   -4   common/cmd_bootm.c      Image is for unsupported architecture
2163    5   common/cmd_bootm.c      Architecture check OK
2164   -5   common/cmd_bootm.c      Wrong Image Type (not kernel, multi)
2165    6   common/cmd_bootm.c      Image Type check OK
2166   -6   common/cmd_bootm.c      gunzip uncompression error
2167   -7   common/cmd_bootm.c      Unimplemented compression type
2168    7   common/cmd_bootm.c      Uncompression OK
2169    8   common/cmd_bootm.c      No uncompress/copy overwrite error
2170   -9   common/cmd_bootm.c      Unsupported OS (not Linux, BSD, VxWorks, QNX)
2171
2172    9   common/image.c          Start initial ramdisk verification
2173  -10   common/image.c          Ramdisk header has bad     magic number
2174  -11   common/image.c          Ramdisk header has bad     checksum
2175   10   common/image.c          Ramdisk header is OK
2176  -12   common/image.c          Ramdisk data   has bad     checksum
2177   11   common/image.c          Ramdisk data   has correct checksum
2178   12   common/image.c          Ramdisk verification complete, start loading
2179  -13   common/image.c          Wrong Image Type (not PPC Linux ramdisk)
2180   13   common/image.c          Start multifile image verification
2181   14   common/image.c          No initial ramdisk, no multifile, continue.
2182
2183   15   arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2184
2185  -30   arch/powerpc/lib/board.c        Fatal error, hang the system
2186  -31   post/post.c             POST test failed, detected by post_output_backlog()
2187  -32   post/post.c             POST test failed, detected by post_run_single()
2188
2189   34   common/cmd_doc.c        before loading a Image from a DOC device
2190  -35   common/cmd_doc.c        Bad usage of "doc" command
2191   35   common/cmd_doc.c        correct usage of "doc" command
2192  -36   common/cmd_doc.c        No boot device
2193   36   common/cmd_doc.c        correct boot device
2194  -37   common/cmd_doc.c        Unknown Chip ID on boot device
2195   37   common/cmd_doc.c        correct chip ID found, device available
2196  -38   common/cmd_doc.c        Read Error on boot device
2197   38   common/cmd_doc.c        reading Image header from DOC device OK
2198  -39   common/cmd_doc.c        Image header has bad magic number
2199   39   common/cmd_doc.c        Image header has correct magic number
2200  -40   common/cmd_doc.c        Error reading Image from DOC device
2201   40   common/cmd_doc.c        Image header has correct magic number
2202   41   common/cmd_ide.c        before loading a Image from a IDE device
2203  -42   common/cmd_ide.c        Bad usage of "ide" command
2204   42   common/cmd_ide.c        correct usage of "ide" command
2205  -43   common/cmd_ide.c        No boot device
2206   43   common/cmd_ide.c        boot device found
2207  -44   common/cmd_ide.c        Device not available
2208   44   common/cmd_ide.c        Device available
2209  -45   common/cmd_ide.c        wrong partition selected
2210   45   common/cmd_ide.c        partition selected
2211  -46   common/cmd_ide.c        Unknown partition table
2212   46   common/cmd_ide.c        valid partition table found
2213  -47   common/cmd_ide.c        Invalid partition type
2214   47   common/cmd_ide.c        correct partition type
2215  -48   common/cmd_ide.c        Error reading Image Header on boot device
2216   48   common/cmd_ide.c        reading Image Header from IDE device OK
2217  -49   common/cmd_ide.c        Image header has bad magic number
2218   49   common/cmd_ide.c        Image header has correct magic number
2219  -50   common/cmd_ide.c        Image header has bad     checksum
2220   50   common/cmd_ide.c        Image header has correct checksum
2221  -51   common/cmd_ide.c        Error reading Image from IDE device
2222   51   common/cmd_ide.c        reading Image from IDE device OK
2223   52   common/cmd_nand.c       before loading a Image from a NAND device
2224  -53   common/cmd_nand.c       Bad usage of "nand" command
2225   53   common/cmd_nand.c       correct usage of "nand" command
2226  -54   common/cmd_nand.c       No boot device
2227   54   common/cmd_nand.c       boot device found
2228  -55   common/cmd_nand.c       Unknown Chip ID on boot device
2229   55   common/cmd_nand.c       correct chip ID found, device available
2230  -56   common/cmd_nand.c       Error reading Image Header on boot device
2231   56   common/cmd_nand.c       reading Image Header from NAND device OK
2232  -57   common/cmd_nand.c       Image header has bad magic number
2233   57   common/cmd_nand.c       Image header has correct magic number
2234  -58   common/cmd_nand.c       Error reading Image from NAND device
2235   58   common/cmd_nand.c       reading Image from NAND device OK
2236
2237  -60   common/env_common.c     Environment has a bad CRC, using default
2238
2239   64   net/eth.c               starting with Ethernet configuration.
2240  -64   net/eth.c               no Ethernet found.
2241   65   net/eth.c               Ethernet found.
2242
2243  -80   common/cmd_net.c        usage wrong
2244   80   common/cmd_net.c        before calling net_loop()
2245  -81   common/cmd_net.c        some error in net_loop() occurred
2246   81   common/cmd_net.c        net_loop() back without error
2247  -82   common/cmd_net.c        size == 0 (File with size 0 loaded)
2248   82   common/cmd_net.c        trying automatic boot
2249   83   common/cmd_net.c        running "source" command
2250  -83   common/cmd_net.c        some error in automatic boot or "source" command
2251   84   common/cmd_net.c        end without errors
2252
2253FIT uImage format:
2254
2255  Arg   Where                   When
2256  100   common/cmd_bootm.c      Kernel FIT Image has correct format
2257 -100   common/cmd_bootm.c      Kernel FIT Image has incorrect format
2258  101   common/cmd_bootm.c      No Kernel subimage unit name, using configuration
2259 -101   common/cmd_bootm.c      Can't get configuration for kernel subimage
2260  102   common/cmd_bootm.c      Kernel unit name specified
2261 -103   common/cmd_bootm.c      Can't get kernel subimage node offset
2262  103   common/cmd_bootm.c      Found configuration node
2263  104   common/cmd_bootm.c      Got kernel subimage node offset
2264 -104   common/cmd_bootm.c      Kernel subimage hash verification failed
2265  105   common/cmd_bootm.c      Kernel subimage hash verification OK
2266 -105   common/cmd_bootm.c      Kernel subimage is for unsupported architecture
2267  106   common/cmd_bootm.c      Architecture check OK
2268 -106   common/cmd_bootm.c      Kernel subimage has wrong type
2269  107   common/cmd_bootm.c      Kernel subimage type OK
2270 -107   common/cmd_bootm.c      Can't get kernel subimage data/size
2271  108   common/cmd_bootm.c      Got kernel subimage data/size
2272 -108   common/cmd_bootm.c      Wrong image type (not legacy, FIT)
2273 -109   common/cmd_bootm.c      Can't get kernel subimage type
2274 -110   common/cmd_bootm.c      Can't get kernel subimage comp
2275 -111   common/cmd_bootm.c      Can't get kernel subimage os
2276 -112   common/cmd_bootm.c      Can't get kernel subimage load address
2277 -113   common/cmd_bootm.c      Image uncompress/copy overwrite error
2278
2279  120   common/image.c          Start initial ramdisk verification
2280 -120   common/image.c          Ramdisk FIT image has incorrect format
2281  121   common/image.c          Ramdisk FIT image has correct format
2282  122   common/image.c          No ramdisk subimage unit name, using configuration
2283 -122   common/image.c          Can't get configuration for ramdisk subimage
2284  123   common/image.c          Ramdisk unit name specified
2285 -124   common/image.c          Can't get ramdisk subimage node offset
2286  125   common/image.c          Got ramdisk subimage node offset
2287 -125   common/image.c          Ramdisk subimage hash verification failed
2288  126   common/image.c          Ramdisk subimage hash verification OK
2289 -126   common/image.c          Ramdisk subimage for unsupported architecture
2290  127   common/image.c          Architecture check OK
2291 -127   common/image.c          Can't get ramdisk subimage data/size
2292  128   common/image.c          Got ramdisk subimage data/size
2293  129   common/image.c          Can't get ramdisk load address
2294 -129   common/image.c          Got ramdisk load address
2295
2296 -130   common/cmd_doc.c        Incorrect FIT image format
2297  131   common/cmd_doc.c        FIT image format OK
2298
2299 -140   common/cmd_ide.c        Incorrect FIT image format
2300  141   common/cmd_ide.c        FIT image format OK
2301
2302 -150   common/cmd_nand.c       Incorrect FIT image format
2303  151   common/cmd_nand.c       FIT image format OK
2304
2305- Standalone program support:
2306                CONFIG_STANDALONE_LOAD_ADDR
2307
2308                This option defines a board specific value for the
2309                address where standalone program gets loaded, thus
2310                overwriting the architecture dependent default
2311                settings.
2312
2313- Frame Buffer Address:
2314                CONFIG_FB_ADDR
2315
2316                Define CONFIG_FB_ADDR if you want to use specific
2317                address for frame buffer.  This is typically the case
2318                when using a graphics controller has separate video
2319                memory.  U-Boot will then place the frame buffer at
2320                the given address instead of dynamically reserving it
2321                in system RAM by calling lcd_setmem(), which grabs
2322                the memory for the frame buffer depending on the
2323                configured panel size.
2324
2325                Please see board_init_f function.
2326
2327- Automatic software updates via TFTP server
2328                CONFIG_UPDATE_TFTP
2329                CONFIG_UPDATE_TFTP_CNT_MAX
2330                CONFIG_UPDATE_TFTP_MSEC_MAX
2331
2332                These options enable and control the auto-update feature;
2333                for a more detailed description refer to doc/README.update.
2334
2335- MTD Support (mtdparts command, UBI support)
2336                CONFIG_MTD_UBI_WL_THRESHOLD
2337                This parameter defines the maximum difference between the highest
2338                erase counter value and the lowest erase counter value of eraseblocks
2339                of UBI devices. When this threshold is exceeded, UBI starts performing
2340                wear leveling by means of moving data from eraseblock with low erase
2341                counter to eraseblocks with high erase counter.
2342
2343                The default value should be OK for SLC NAND flashes, NOR flashes and
2344                other flashes which have eraseblock life-cycle 100000 or more.
2345                However, in case of MLC NAND flashes which typically have eraseblock
2346                life-cycle less than 10000, the threshold should be lessened (e.g.,
2347                to 128 or 256, although it does not have to be power of 2).
2348
2349                default: 4096
2350
2351                CONFIG_MTD_UBI_BEB_LIMIT
2352                This option specifies the maximum bad physical eraseblocks UBI
2353                expects on the MTD device (per 1024 eraseblocks). If the
2354                underlying flash does not admit of bad eraseblocks (e.g. NOR
2355                flash), this value is ignored.
2356
2357                NAND datasheets often specify the minimum and maximum NVM
2358                (Number of Valid Blocks) for the flashes' endurance lifetime.
2359                The maximum expected bad eraseblocks per 1024 eraseblocks
2360                then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2361                which gives 20 for most NANDs (MaxNVB is basically the total
2362                count of eraseblocks on the chip).
2363
2364                To put it differently, if this value is 20, UBI will try to
2365                reserve about 1.9% of physical eraseblocks for bad blocks
2366                handling. And that will be 1.9% of eraseblocks on the entire
2367                NAND chip, not just the MTD partition UBI attaches. This means
2368                that if you have, say, a NAND flash chip admits maximum 40 bad
2369                eraseblocks, and it is split on two MTD partitions of the same
2370                size, UBI will reserve 40 eraseblocks when attaching a
2371                partition.
2372
2373                default: 20
2374
2375                CONFIG_MTD_UBI_FASTMAP
2376                Fastmap is a mechanism which allows attaching an UBI device
2377                in nearly constant time. Instead of scanning the whole MTD device it
2378                only has to locate a checkpoint (called fastmap) on the device.
2379                The on-flash fastmap contains all information needed to attach
2380                the device. Using fastmap makes only sense on large devices where
2381                attaching by scanning takes long. UBI will not automatically install
2382                a fastmap on old images, but you can set the UBI parameter
2383                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2384                that fastmap-enabled images are still usable with UBI implementations
2385                without fastmap support. On typical flash devices the whole fastmap
2386                fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2387
2388                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2389                Set this parameter to enable fastmap automatically on images
2390                without a fastmap.
2391                default: 0
2392
2393                CONFIG_MTD_UBI_FM_DEBUG
2394                Enable UBI fastmap debug
2395                default: 0
2396
2397- SPL framework
2398                CONFIG_SPL
2399                Enable building of SPL globally.
2400
2401                CONFIG_SPL_LDSCRIPT
2402                LDSCRIPT for linking the SPL binary.
2403
2404                CONFIG_SPL_MAX_FOOTPRINT
2405                Maximum size in memory allocated to the SPL, BSS included.
2406                When defined, the linker checks that the actual memory
2407                used by SPL from _start to __bss_end does not exceed it.
2408                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2409                must not be both defined at the same time.
2410
2411                CONFIG_SPL_MAX_SIZE
2412                Maximum size of the SPL image (text, data, rodata, and
2413                linker lists sections), BSS excluded.
2414                When defined, the linker checks that the actual size does
2415                not exceed it.
2416
2417                CONFIG_SPL_RELOC_TEXT_BASE
2418                Address to relocate to.  If unspecified, this is equal to
2419                CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2420
2421                CONFIG_SPL_BSS_START_ADDR
2422                Link address for the BSS within the SPL binary.
2423
2424                CONFIG_SPL_BSS_MAX_SIZE
2425                Maximum size in memory allocated to the SPL BSS.
2426                When defined, the linker checks that the actual memory used
2427                by SPL from __bss_start to __bss_end does not exceed it.
2428                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2429                must not be both defined at the same time.
2430
2431                CONFIG_SPL_STACK
2432                Adress of the start of the stack SPL will use
2433
2434                CONFIG_SPL_PANIC_ON_RAW_IMAGE
2435                When defined, SPL will panic() if the image it has
2436                loaded does not have a signature.
2437                Defining this is useful when code which loads images
2438                in SPL cannot guarantee that absolutely all read errors
2439                will be caught.
2440                An example is the LPC32XX MLC NAND driver, which will
2441                consider that a completely unreadable NAND block is bad,
2442                and thus should be skipped silently.
2443
2444                CONFIG_SPL_RELOC_STACK
2445                Adress of the start of the stack SPL will use after
2446                relocation.  If unspecified, this is equal to
2447                CONFIG_SPL_STACK.
2448
2449                CONFIG_SYS_SPL_MALLOC_START
2450                Starting address of the malloc pool used in SPL.
2451                When this option is set the full malloc is used in SPL and
2452                it is set up by spl_init() and before that, the simple malloc()
2453                can be used if CONFIG_SYS_MALLOC_F is defined.
2454
2455                CONFIG_SYS_SPL_MALLOC_SIZE
2456                The size of the malloc pool used in SPL.
2457
2458                CONFIG_SPL_OS_BOOT
2459                Enable booting directly to an OS from SPL.
2460                See also: doc/README.falcon
2461
2462                CONFIG_SPL_DISPLAY_PRINT
2463                For ARM, enable an optional function to print more information
2464                about the running system.
2465
2466                CONFIG_SPL_INIT_MINIMAL
2467                Arch init code should be built for a very small image
2468
2469                CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2470                Partition on the MMC to load U-Boot from when the MMC is being
2471                used in raw mode
2472
2473                CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2474                Sector to load kernel uImage from when MMC is being
2475                used in raw mode (for Falcon mode)
2476
2477                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2478                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2479                Sector and number of sectors to load kernel argument
2480                parameters from when MMC is being used in raw mode
2481                (for falcon mode)
2482
2483                CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2484                Partition on the MMC to load U-Boot from when the MMC is being
2485                used in fs mode
2486
2487                CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2488                Filename to read to load U-Boot when reading from filesystem
2489
2490                CONFIG_SPL_FS_LOAD_KERNEL_NAME
2491                Filename to read to load kernel uImage when reading
2492                from filesystem (for Falcon mode)
2493
2494                CONFIG_SPL_FS_LOAD_ARGS_NAME
2495                Filename to read to load kernel argument parameters
2496                when reading from filesystem (for Falcon mode)
2497
2498                CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2499                Set this for NAND SPL on PPC mpc83xx targets, so that
2500                start.S waits for the rest of the SPL to load before
2501                continuing (the hardware starts execution after just
2502                loading the first page rather than the full 4K).
2503
2504                CONFIG_SPL_SKIP_RELOCATE
2505                Avoid SPL relocation
2506
2507                CONFIG_SPL_NAND_BASE
2508                Include nand_base.c in the SPL.  Requires
2509                CONFIG_SPL_NAND_DRIVERS.
2510
2511                CONFIG_SPL_NAND_DRIVERS
2512                SPL uses normal NAND drivers, not minimal drivers.
2513
2514                CONFIG_SPL_NAND_IDENT
2515                SPL uses the chip ID list to identify the NAND flash.
2516                Requires CONFIG_SPL_NAND_BASE.
2517
2518                CONFIG_SPL_NAND_ECC
2519                Include standard software ECC in the SPL
2520
2521                CONFIG_SPL_NAND_SIMPLE
2522                Support for NAND boot using simple NAND drivers that
2523                expose the cmd_ctrl() interface.
2524
2525                CONFIG_SPL_UBI
2526                Support for a lightweight UBI (fastmap) scanner and
2527                loader
2528
2529                CONFIG_SPL_NAND_RAW_ONLY
2530                Support to boot only raw u-boot.bin images. Use this only
2531                if you need to save space.
2532
2533                CONFIG_SPL_COMMON_INIT_DDR
2534                Set for common ddr init with serial presence detect in
2535                SPL binary.
2536
2537                CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2538                CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2539                CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2540                CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2541                CONFIG_SYS_NAND_ECCBYTES
2542                Defines the size and behavior of the NAND that SPL uses
2543                to read U-Boot
2544
2545                CONFIG_SYS_NAND_U_BOOT_OFFS
2546                Location in NAND to read U-Boot from
2547
2548                CONFIG_SYS_NAND_U_BOOT_DST
2549                Location in memory to load U-Boot to
2550
2551                CONFIG_SYS_NAND_U_BOOT_SIZE
2552                Size of image to load
2553
2554                CONFIG_SYS_NAND_U_BOOT_START
2555                Entry point in loaded image to jump to
2556
2557                CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2558                Define this if you need to first read the OOB and then the
2559                data. This is used, for example, on davinci platforms.
2560
2561                CONFIG_SPL_RAM_DEVICE
2562                Support for running image already present in ram, in SPL binary
2563
2564                CONFIG_SPL_PAD_TO
2565                Image offset to which the SPL should be padded before appending
2566                the SPL payload. By default, this is defined as
2567                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2568                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2569                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2570
2571                CONFIG_SPL_TARGET
2572                Final target image containing SPL and payload.  Some SPLs
2573                use an arch-specific makefile fragment instead, for
2574                example if more than one image needs to be produced.
2575
2576                CONFIG_SPL_FIT_PRINT
2577                Printing information about a FIT image adds quite a bit of
2578                code to SPL. So this is normally disabled in SPL. Use this
2579                option to re-enable it. This will affect the output of the
2580                bootm command when booting a FIT image.
2581
2582- TPL framework
2583                CONFIG_TPL
2584                Enable building of TPL globally.
2585
2586                CONFIG_TPL_PAD_TO
2587                Image offset to which the TPL should be padded before appending
2588                the TPL payload. By default, this is defined as
2589                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2590                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2591                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2592
2593- Interrupt support (PPC):
2594
2595                There are common interrupt_init() and timer_interrupt()
2596                for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2597                for CPU specific initialization. interrupt_init_cpu()
2598                should set decrementer_count to appropriate value. If
2599                CPU resets decrementer automatically after interrupt
2600                (ppc4xx) it should set decrementer_count to zero.
2601                timer_interrupt() calls timer_interrupt_cpu() for CPU
2602                specific handling. If board has watchdog / status_led
2603                / other_activity_monitor it works automatically from
2604                general timer_interrupt().
2605
2606
2607Board initialization settings:
2608------------------------------
2609
2610During Initialization u-boot calls a number of board specific functions
2611to allow the preparation of board specific prerequisites, e.g. pin setup
2612before drivers are initialized. To enable these callbacks the
2613following configuration macros have to be defined. Currently this is
2614architecture specific, so please check arch/your_architecture/lib/board.c
2615typically in board_init_f() and board_init_r().
2616
2617- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2618- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2619- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2620- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2621
2622Configuration Settings:
2623-----------------------
2624
2625- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2626                Optionally it can be defined to support 64-bit memory commands.
2627
2628- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2629                undefine this when you're short of memory.
2630
2631- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2632                width of the commands listed in the 'help' command output.
2633
2634- CONFIG_SYS_PROMPT:    This is what U-Boot prints on the console to
2635                prompt for user input.
2636
2637- CONFIG_SYS_CBSIZE:    Buffer size for input from the Console
2638
2639- CONFIG_SYS_PBSIZE:    Buffer size for Console output
2640
2641- CONFIG_SYS_MAXARGS:   max. Number of arguments accepted for monitor commands
2642
2643- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2644                the application (usually a Linux kernel) when it is
2645                booted
2646
2647- CONFIG_SYS_BAUDRATE_TABLE:
2648                List of legal baudrate settings for this board.
2649
2650- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2651                Begin and End addresses of the area used by the
2652                simple memory test.
2653
2654- CONFIG_SYS_MEMTEST_SCRATCH:
2655                Scratch address used by the alternate memory test
2656                You only need to set this if address zero isn't writeable
2657
2658- CONFIG_SYS_MEM_RESERVE_SECURE
2659                Only implemented for ARMv8 for now.
2660                If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2661                is substracted from total RAM and won't be reported to OS.
2662                This memory can be used as secure memory. A variable
2663                gd->arch.secure_ram is used to track the location. In systems
2664                the RAM base is not zero, or RAM is divided into banks,
2665                this variable needs to be recalcuated to get the address.
2666
2667- CONFIG_SYS_MEM_TOP_HIDE:
2668                If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2669                this specified memory area will get subtracted from the top
2670                (end) of RAM and won't get "touched" at all by U-Boot. By
2671                fixing up gd->ram_size the Linux kernel should gets passed
2672                the now "corrected" memory size and won't touch it either.
2673                This should work for arch/ppc and arch/powerpc. Only Linux
2674                board ports in arch/powerpc with bootwrapper support that
2675                recalculate the memory size from the SDRAM controller setup
2676                will have to get fixed in Linux additionally.
2677
2678                This option can be used as a workaround for the 440EPx/GRx
2679                CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2680                be touched.
2681
2682                WARNING: Please make sure that this value is a multiple of
2683                the Linux page size (normally 4k). If this is not the case,
2684                then the end address of the Linux memory will be located at a
2685                non page size aligned address and this could cause major
2686                problems.
2687
2688- CONFIG_SYS_LOADS_BAUD_CHANGE:
2689                Enable temporary baudrate change while serial download
2690
2691- CONFIG_SYS_SDRAM_BASE:
2692                Physical start address of SDRAM. _Must_ be 0 here.
2693
2694- CONFIG_SYS_FLASH_BASE:
2695                Physical start address of Flash memory.
2696
2697- CONFIG_SYS_MONITOR_BASE:
2698                Physical start address of boot monitor code (set by
2699                make config files to be same as the text base address
2700                (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2701                CONFIG_SYS_FLASH_BASE when booting from flash.
2702
2703- CONFIG_SYS_MONITOR_LEN:
2704                Size of memory reserved for monitor code, used to
2705                determine _at_compile_time_ (!) if the environment is
2706                embedded within the U-Boot image, or in a separate
2707                flash sector.
2708
2709- CONFIG_SYS_MALLOC_LEN:
2710                Size of DRAM reserved for malloc() use.
2711
2712- CONFIG_SYS_MALLOC_F_LEN
2713                Size of the malloc() pool for use before relocation. If
2714                this is defined, then a very simple malloc() implementation
2715                will become available before relocation. The address is just
2716                below the global data, and the stack is moved down to make
2717                space.
2718
2719                This feature allocates regions with increasing addresses
2720                within the region. calloc() is supported, but realloc()
2721                is not available. free() is supported but does nothing.
2722                The memory will be freed (or in fact just forgotten) when
2723                U-Boot relocates itself.
2724
2725- CONFIG_SYS_MALLOC_SIMPLE
2726                Provides a simple and small malloc() and calloc() for those
2727                boards which do not use the full malloc in SPL (which is
2728                enabled with CONFIG_SYS_SPL_MALLOC_START).
2729
2730- CONFIG_SYS_NONCACHED_MEMORY:
2731                Size of non-cached memory area. This area of memory will be
2732                typically located right below the malloc() area and mapped
2733                uncached in the MMU. This is useful for drivers that would
2734                otherwise require a lot of explicit cache maintenance. For
2735                some drivers it's also impossible to properly maintain the
2736                cache. For example if the regions that need to be flushed
2737                are not a multiple of the cache-line size, *and* padding
2738                cannot be allocated between the regions to align them (i.e.
2739                if the HW requires a contiguous array of regions, and the
2740                size of each region is not cache-aligned), then a flush of
2741                one region may result in overwriting data that hardware has
2742                written to another region in the same cache-line. This can
2743                happen for example in network drivers where descriptors for
2744                buffers are typically smaller than the CPU cache-line (e.g.
2745                16 bytes vs. 32 or 64 bytes).
2746
2747                Non-cached memory is only supported on 32-bit ARM at present.
2748
2749- CONFIG_SYS_BOOTM_LEN:
2750                Normally compressed uImages are limited to an
2751                uncompressed size of 8 MBytes. If this is not enough,
2752                you can define CONFIG_SYS_BOOTM_LEN in your board config file
2753                to adjust this setting to your needs.
2754
2755- CONFIG_SYS_BOOTMAPSZ:
2756                Maximum size of memory mapped by the startup code of
2757                the Linux kernel; all data that must be processed by
2758                the Linux kernel (bd_info, boot arguments, FDT blob if
2759                used) must be put below this limit, unless "bootm_low"
2760                environment variable is defined and non-zero. In such case
2761                all data for the Linux kernel must be between "bootm_low"
2762                and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2763                variable "bootm_mapsize" will override the value of
2764                CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2765                then the value in "bootm_size" will be used instead.
2766
2767- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2768                Enable initrd_high functionality.  If defined then the
2769                initrd_high feature is enabled and the bootm ramdisk subcommand
2770                is enabled.
2771
2772- CONFIG_SYS_BOOT_GET_CMDLINE:
2773                Enables allocating and saving kernel cmdline in space between
2774                "bootm_low" and "bootm_low" + BOOTMAPSZ.
2775
2776- CONFIG_SYS_BOOT_GET_KBD:
2777                Enables allocating and saving a kernel copy of the bd_info in
2778                space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2779
2780- CONFIG_SYS_MAX_FLASH_BANKS:
2781                Max number of Flash memory banks
2782
2783- CONFIG_SYS_MAX_FLASH_SECT:
2784                Max number of sectors on a Flash chip
2785
2786- CONFIG_SYS_FLASH_ERASE_TOUT:
2787                Timeout for Flash erase operations (in ms)
2788
2789- CONFIG_SYS_FLASH_WRITE_TOUT:
2790                Timeout for Flash write operations (in ms)
2791
2792- CONFIG_SYS_FLASH_LOCK_TOUT
2793                Timeout for Flash set sector lock bit operation (in ms)
2794
2795- CONFIG_SYS_FLASH_UNLOCK_TOUT
2796                Timeout for Flash clear lock bits operation (in ms)
2797
2798- CONFIG_SYS_FLASH_PROTECTION
2799                If defined, hardware flash sectors protection is used
2800                instead of U-Boot software protection.
2801
2802- CONFIG_SYS_DIRECT_FLASH_TFTP:
2803
2804                Enable TFTP transfers directly to flash memory;
2805                without this option such a download has to be
2806                performed in two steps: (1) download to RAM, and (2)
2807                copy from RAM to flash.
2808
2809                The two-step approach is usually more reliable, since
2810                you can check if the download worked before you erase
2811                the flash, but in some situations (when system RAM is
2812                too limited to allow for a temporary copy of the
2813                downloaded image) this option may be very useful.
2814
2815- CONFIG_SYS_FLASH_CFI:
2816                Define if the flash driver uses extra elements in the
2817                common flash structure for storing flash geometry.
2818
2819- CONFIG_FLASH_CFI_DRIVER
2820                This option also enables the building of the cfi_flash driver
2821                in the drivers directory
2822
2823- CONFIG_FLASH_CFI_MTD
2824                This option enables the building of the cfi_mtd driver
2825                in the drivers directory. The driver exports CFI flash
2826                to the MTD layer.
2827
2828- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2829                Use buffered writes to flash.
2830
2831- CONFIG_FLASH_SPANSION_S29WS_N
2832                s29ws-n MirrorBit flash has non-standard addresses for buffered
2833                write commands.
2834
2835- CONFIG_SYS_FLASH_QUIET_TEST
2836                If this option is defined, the common CFI flash doesn't
2837                print it's warning upon not recognized FLASH banks. This
2838                is useful, if some of the configured banks are only
2839                optionally available.
2840
2841- CONFIG_FLASH_SHOW_PROGRESS
2842                If defined (must be an integer), print out countdown
2843                digits and dots.  Recommended value: 45 (9..1) for 80
2844                column displays, 15 (3..1) for 40 column displays.
2845
2846- CONFIG_FLASH_VERIFY
2847                If defined, the content of the flash (destination) is compared
2848                against the source after the write operation. An error message
2849                will be printed when the contents are not identical.
2850                Please note that this option is useless in nearly all cases,
2851                since such flash programming errors usually are detected earlier
2852                while unprotecting/erasing/programming. Please only enable
2853                this option if you really know what you are doing.
2854
2855- CONFIG_SYS_RX_ETH_BUFFER:
2856                Defines the number of Ethernet receive buffers. On some
2857                Ethernet controllers it is recommended to set this value
2858                to 8 or even higher (EEPRO100 or 405 EMAC), since all
2859                buffers can be full shortly after enabling the interface
2860                on high Ethernet traffic.
2861                Defaults to 4 if not defined.
2862
2863- CONFIG_ENV_MAX_ENTRIES
2864
2865        Maximum number of entries in the hash table that is used
2866        internally to store the environment settings. The default
2867        setting is supposed to be generous and should work in most
2868        cases. This setting can be used to tune behaviour; see
2869        lib/hashtable.c for details.
2870
2871- CONFIG_ENV_FLAGS_LIST_DEFAULT
2872- CONFIG_ENV_FLAGS_LIST_STATIC
2873        Enable validation of the values given to environment variables when
2874        calling env set.  Variables can be restricted to only decimal,
2875        hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2876        the variables can also be restricted to IP address or MAC address.
2877
2878        The format of the list is:
2879                type_attribute = [s|d|x|b|i|m]
2880                access_attribute = [a|r|o|c]
2881                attributes = type_attribute[access_attribute]
2882                entry = variable_name[:attributes]
2883                list = entry[,list]
2884
2885        The type attributes are:
2886                s - String (default)
2887                d - Decimal
2888                x - Hexadecimal
2889                b - Boolean ([1yYtT|0nNfF])
2890                i - IP address
2891                m - MAC address
2892
2893        The access attributes are:
2894                a - Any (default)
2895                r - Read-only
2896                o - Write-once
2897                c - Change-default
2898
2899        - CONFIG_ENV_FLAGS_LIST_DEFAULT
2900                Define this to a list (string) to define the ".flags"
2901                environment variable in the default or embedded environment.
2902
2903        - CONFIG_ENV_FLAGS_LIST_STATIC
2904                Define this to a list (string) to define validation that
2905                should be done if an entry is not found in the ".flags"
2906                environment variable.  To override a setting in the static
2907                list, simply add an entry for the same variable name to the
2908                ".flags" variable.
2909
2910        If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2911        regular expression. This allows multiple variables to define the same
2912        flags without explicitly listing them for each variable.
2913
2914- CONFIG_ENV_ACCESS_IGNORE_FORCE
2915        If defined, don't allow the -f switch to env set override variable
2916        access flags.
2917
2918The following definitions that deal with the placement and management
2919of environment data (variable area); in general, we support the
2920following configurations:
2921
2922- CONFIG_BUILD_ENVCRC:
2923
2924        Builds up envcrc with the target environment so that external utils
2925        may easily extract it and embed it in final U-Boot images.
2926
2927BE CAREFUL! The first access to the environment happens quite early
2928in U-Boot initialization (when we try to get the setting of for the
2929console baudrate). You *MUST* have mapped your NVRAM area then, or
2930U-Boot will hang.
2931
2932Please note that even with NVRAM we still use a copy of the
2933environment in RAM: we could work on NVRAM directly, but we want to
2934keep settings there always unmodified except somebody uses "saveenv"
2935to save the current settings.
2936
2937BE CAREFUL! For some special cases, the local device can not use
2938"saveenv" command. For example, the local device will get the
2939environment stored in a remote NOR flash by SRIO or PCIE link,
2940but it can not erase, write this NOR flash by SRIO or PCIE interface.
2941
2942- CONFIG_NAND_ENV_DST
2943
2944        Defines address in RAM to which the nand_spl code should copy the
2945        environment. If redundant environment is used, it will be copied to
2946        CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2947
2948Please note that the environment is read-only until the monitor
2949has been relocated to RAM and a RAM copy of the environment has been
2950created; also, when using EEPROM you will have to use env_get_f()
2951until then to read environment variables.
2952
2953The environment is protected by a CRC32 checksum. Before the monitor
2954is relocated into RAM, as a result of a bad CRC you will be working
2955with the compiled-in default environment - *silently*!!! [This is
2956necessary, because the first environment variable we need is the
2957"baudrate" setting for the console - if we have a bad CRC, we don't
2958have any device yet where we could complain.]
2959
2960Note: once the monitor has been relocated, then it will complain if
2961the default environment is used; a new CRC is computed as soon as you
2962use the "saveenv" command to store a valid environment.
2963
2964- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2965                Echo the inverted Ethernet link state to the fault LED.
2966
2967                Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2968                      also needs to be defined.
2969
2970- CONFIG_SYS_FAULT_MII_ADDR:
2971                MII address of the PHY to check for the Ethernet link state.
2972
2973- CONFIG_NS16550_MIN_FUNCTIONS:
2974                Define this if you desire to only have use of the NS16550_init
2975                and NS16550_putc functions for the serial driver located at
2976                drivers/serial/ns16550.c.  This option is useful for saving
2977                space for already greatly restricted images, including but not
2978                limited to NAND_SPL configurations.
2979
2980- CONFIG_DISPLAY_BOARDINFO
2981                Display information about the board that U-Boot is running on
2982                when U-Boot starts up. The board function checkboard() is called
2983                to do this.
2984
2985- CONFIG_DISPLAY_BOARDINFO_LATE
2986                Similar to the previous option, but display this information
2987                later, once stdio is running and output goes to the LCD, if
2988                present.
2989
2990- CONFIG_BOARD_SIZE_LIMIT:
2991                Maximum size of the U-Boot image. When defined, the
2992                build system checks that the actual size does not
2993                exceed it.
2994
2995Low Level (hardware related) configuration options:
2996---------------------------------------------------
2997
2998- CONFIG_SYS_CACHELINE_SIZE:
2999                Cache Line Size of the CPU.
3000
3001- CONFIG_SYS_CCSRBAR_DEFAULT:
3002                Default (power-on reset) physical address of CCSR on Freescale
3003                PowerPC SOCs.
3004
3005- CONFIG_SYS_CCSRBAR:
3006                Virtual address of CCSR.  On a 32-bit build, this is typically
3007                the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3008
3009- CONFIG_SYS_CCSRBAR_PHYS:
3010                Physical address of CCSR.  CCSR can be relocated to a new
3011                physical address, if desired.  In this case, this macro should
3012                be set to that address.  Otherwise, it should be set to the
3013                same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3014                is typically relocated on 36-bit builds.  It is recommended
3015                that this macro be defined via the _HIGH and _LOW macros:
3016
3017                #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3018                        * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3019
3020- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3021                Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.  This value is typically
3022                either 0 (32-bit build) or 0xF (36-bit build).  This macro is
3023                used in assembly code, so it must not contain typecasts or
3024                integer size suffixes (e.g. "ULL").
3025
3026- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3027                Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3028                used in assembly code, so it must not contain typecasts or
3029                integer size suffixes (e.g. "ULL").
3030
3031- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3032                If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3033                forced to a value that ensures that CCSR is not relocated.
3034
3035- Floppy Disk Support:
3036                CONFIG_SYS_FDC_DRIVE_NUMBER
3037
3038                the default drive number (default value 0)
3039
3040                CONFIG_SYS_ISA_IO_STRIDE
3041
3042                defines the spacing between FDC chipset registers
3043                (default value 1)
3044
3045                CONFIG_SYS_ISA_IO_OFFSET
3046
3047                defines the offset of register from address. It
3048                depends on which part of the data bus is connected to
3049                the FDC chipset. (default value 0)
3050
3051                If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3052                CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3053                default value.
3054
3055                if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3056                fdc_hw_init() is called at the beginning of the FDC
3057                setup. fdc_hw_init() must be provided by the board
3058                source code. It is used to make hardware-dependent
3059                initializations.
3060
3061- CONFIG_IDE_AHB:
3062                Most IDE controllers were designed to be connected with PCI
3063                interface. Only few of them were designed for AHB interface.
3064                When software is doing ATA command and data transfer to
3065                IDE devices through IDE-AHB controller, some additional
3066                registers accessing to these kind of IDE-AHB controller
3067                is required.
3068
3069- CONFIG_SYS_IMMR:      Physical address of the Internal Memory.
3070                DO NOT CHANGE unless you know exactly what you're
3071                doing! (11-4) [MPC8xx systems only]
3072
3073- CONFIG_SYS_INIT_RAM_ADDR:
3074
3075                Start address of memory area that can be used for
3076                initial data and stack; please note that this must be
3077                writable memory that is working WITHOUT special
3078                initialization, i. e. you CANNOT use normal RAM which
3079                will become available only after programming the
3080                memory controller and running certain initialization
3081                sequences.
3082
3083                U-Boot uses the following memory types:
3084                - MPC8xx: IMMR (internal memory of the CPU)
3085
3086- CONFIG_SYS_GBL_DATA_OFFSET:
3087
3088                Offset of the initial data structure in the memory
3089                area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3090                CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3091                data is located at the end of the available space
3092                (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3093                GENERATED_GBL_DATA_SIZE), and the initial stack is just
3094                below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3095                CONFIG_SYS_GBL_DATA_OFFSET) downward.
3096
3097        Note:
3098                On the MPC824X (or other systems that use the data
3099                cache for initial memory) the address chosen for
3100                CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3101                point to an otherwise UNUSED address space between
3102                the top of RAM and the start of the PCI space.
3103
3104- CONFIG_SYS_SCCR:      System Clock and reset Control Register (15-27)
3105
3106- CONFIG_SYS_OR_TIMING_SDRAM:
3107                SDRAM timing
3108
3109- CONFIG_SYS_MAMR_PTA:
3110                periodic timer for refresh
3111
3112- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3113  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3114  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3115  CONFIG_SYS_BR1_PRELIM:
3116                Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3117
3118- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3119  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3120  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3121                Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3122
3123- CONFIG_PCI_ENUM_ONLY
3124                Only scan through and get the devices on the buses.
3125                Don't do any setup work, presumably because someone or
3126                something has already done it, and we don't need to do it
3127                a second time.  Useful for platforms that are pre-booted
3128                by coreboot or similar.
3129
3130- CONFIG_PCI_INDIRECT_BRIDGE:
3131                Enable support for indirect PCI bridges.
3132
3133- CONFIG_SYS_SRIO:
3134                Chip has SRIO or not
3135
3136- CONFIG_SRIO1:
3137                Board has SRIO 1 port available
3138
3139- CONFIG_SRIO2:
3140                Board has SRIO 2 port available
3141
3142- CONFIG_SRIO_PCIE_BOOT_MASTER
3143                Board can support master function for Boot from SRIO and PCIE
3144
3145- CONFIG_SYS_SRIOn_MEM_VIRT:
3146                Virtual Address of SRIO port 'n' memory region
3147
3148- CONFIG_SYS_SRIOn_MEM_PHYS:
3149                Physical Address of SRIO port 'n' memory region
3150
3151- CONFIG_SYS_SRIOn_MEM_SIZE:
3152                Size of SRIO port 'n' memory region
3153
3154- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3155                Defined to tell the NAND controller that the NAND chip is using
3156                a 16 bit bus.
3157                Not all NAND drivers use this symbol.
3158                Example of drivers that use it:
3159                - drivers/mtd/nand/raw/ndfc.c
3160                - drivers/mtd/nand/raw/mxc_nand.c
3161
3162- CONFIG_SYS_NDFC_EBC0_CFG
3163                Sets the EBC0_CFG register for the NDFC. If not defined
3164                a default value will be used.
3165
3166- CONFIG_SPD_EEPROM
3167                Get DDR timing information from an I2C EEPROM. Common
3168                with pluggable memory modules such as SODIMMs
3169
3170  SPD_EEPROM_ADDRESS
3171                I2C address of the SPD EEPROM
3172
3173- CONFIG_SYS_SPD_BUS_NUM
3174                If SPD EEPROM is on an I2C bus other than the first
3175                one, specify here. Note that the value must resolve
3176                to something your driver can deal with.
3177
3178- CONFIG_SYS_DDR_RAW_TIMING
3179                Get DDR timing information from other than SPD. Common with
3180                soldered DDR chips onboard without SPD. DDR raw timing
3181                parameters are extracted from datasheet and hard-coded into
3182                header files or board specific files.
3183
3184- CONFIG_FSL_DDR_INTERACTIVE
3185                Enable interactive DDR debugging. See doc/README.fsl-ddr.
3186
3187- CONFIG_FSL_DDR_SYNC_REFRESH
3188                Enable sync of refresh for multiple controllers.
3189
3190- CONFIG_FSL_DDR_BIST
3191                Enable built-in memory test for Freescale DDR controllers.
3192
3193- CONFIG_SYS_83XX_DDR_USES_CS0
3194                Only for 83xx systems. If specified, then DDR should
3195                be configured using CS0 and CS1 instead of CS2 and CS3.
3196
3197- CONFIG_RMII
3198                Enable RMII mode for all FECs.
3199                Note that this is a global option, we can't
3200                have one FEC in standard MII mode and another in RMII mode.
3201
3202- CONFIG_CRC32_VERIFY
3203                Add a verify option to the crc32 command.
3204                The syntax is:
3205
3206                => crc32 -v <address> <count> <crc32>
3207
3208                Where address/count indicate a memory area
3209                and crc32 is the correct crc32 which the
3210                area should have.
3211
3212- CONFIG_LOOPW
3213                Add the "loopw" memory command. This only takes effect if
3214                the memory commands are activated globally (CONFIG_CMD_MEMORY).
3215
3216- CONFIG_MX_CYCLIC
3217                Add the "mdc" and "mwc" memory commands. These are cyclic
3218                "md/mw" commands.
3219                Examples:
3220
3221                => mdc.b 10 4 500
3222                This command will print 4 bytes (10,11,12,13) each 500 ms.
3223
3224                => mwc.l 100 12345678 10
3225                This command will write 12345678 to address 100 all 10 ms.
3226
3227                This only takes effect if the memory commands are activated
3228                globally (CONFIG_CMD_MEMORY).
3229
3230- CONFIG_SKIP_LOWLEVEL_INIT
3231                [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3232                low level initializations (like setting up the memory
3233                controller) are omitted and/or U-Boot does not
3234                relocate itself into RAM.
3235
3236                Normally this variable MUST NOT be defined. The only
3237                exception is when U-Boot is loaded (to RAM) by some
3238                other boot loader or by a debugger which performs
3239                these initializations itself.
3240
3241- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3242                [ARM926EJ-S only] This allows just the call to lowlevel_init()
3243                to be skipped. The normal CP15 init (such as enabling the
3244                instruction cache) is still performed.
3245
3246- CONFIG_SPL_BUILD
3247                Modifies the behaviour of start.S when compiling a loader
3248                that is executed before the actual U-Boot. E.g. when
3249                compiling a NAND SPL.
3250
3251- CONFIG_TPL_BUILD
3252                Modifies the behaviour of start.S  when compiling a loader
3253                that is executed after the SPL and before the actual U-Boot.
3254                It is loaded by the SPL.
3255
3256- CONFIG_SYS_MPC85XX_NO_RESETVEC
3257                Only for 85xx systems. If this variable is specified, the section
3258                .resetvec is not kept and the section .bootpg is placed in the
3259                previous 4k of the .text section.
3260
3261- CONFIG_ARCH_MAP_SYSMEM
3262                Generally U-Boot (and in particular the md command) uses
3263                effective address. It is therefore not necessary to regard
3264                U-Boot address as virtual addresses that need to be translated
3265                to physical addresses. However, sandbox requires this, since
3266                it maintains its own little RAM buffer which contains all
3267                addressable memory. This option causes some memory accesses
3268                to be mapped through map_sysmem() / unmap_sysmem().
3269
3270- CONFIG_X86_RESET_VECTOR
3271                If defined, the x86 reset vector code is included. This is not
3272                needed when U-Boot is running from Coreboot.
3273
3274- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3275                Option to disable subpage write in NAND driver
3276                driver that uses this:
3277                drivers/mtd/nand/raw/davinci_nand.c
3278
3279Freescale QE/FMAN Firmware Support:
3280-----------------------------------
3281
3282The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3283loading of "firmware", which is encoded in the QE firmware binary format.
3284This firmware often needs to be loaded during U-Boot booting, so macros
3285are used to identify the storage device (NOR flash, SPI, etc) and the address
3286within that device.
3287
3288- CONFIG_SYS_FMAN_FW_ADDR
3289        The address in the storage device where the FMAN microcode is located.  The
3290        meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3291        is also specified.
3292
3293- CONFIG_SYS_QE_FW_ADDR
3294        The address in the storage device where the QE microcode is located.  The
3295        meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3296        is also specified.
3297
3298- CONFIG_SYS_QE_FMAN_FW_LENGTH
3299        The maximum possible size of the firmware.  The firmware binary format
3300        has a field that specifies the actual size of the firmware, but it
3301        might not be possible to read any part of the firmware unless some
3302        local storage is allocated to hold the entire firmware first.
3303
3304- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3305        Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3306        normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3307        virtual address in NOR flash.
3308
3309- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3310        Specifies that QE/FMAN firmware is located in NAND flash.
3311        CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3312
3313- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3314        Specifies that QE/FMAN firmware is located on the primary SD/MMC
3315        device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3316
3317- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3318        Specifies that QE/FMAN firmware is located in the remote (master)
3319        memory space.   CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3320        can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3321        window->master inbound window->master LAW->the ucode address in
3322        master's memory space.
3323
3324Freescale Layerscape Management Complex Firmware Support:
3325---------------------------------------------------------
3326The Freescale Layerscape Management Complex (MC) supports the loading of
3327"firmware".
3328This firmware often needs to be loaded during U-Boot booting, so macros
3329are used to identify the storage device (NOR flash, SPI, etc) and the address
3330within that device.
3331
3332- CONFIG_FSL_MC_ENET
3333        Enable the MC driver for Layerscape SoCs.
3334
3335Freescale Layerscape Debug Server Support:
3336-------------------------------------------
3337The Freescale Layerscape Debug Server Support supports the loading of
3338"Debug Server firmware" and triggering SP boot-rom.
3339This firmware often needs to be loaded during U-Boot booting.
3340
3341- CONFIG_SYS_MC_RSV_MEM_ALIGN
3342        Define alignment of reserved memory MC requires
3343
3344Reproducible builds
3345-------------------
3346
3347In order to achieve reproducible builds, timestamps used in the U-Boot build
3348process have to be set to a fixed value.
3349
3350This is done using the SOURCE_DATE_EPOCH environment variable.
3351SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3352option for U-Boot or an environment variable in U-Boot.
3353
3354SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3355
3356Building the Software:
3357======================
3358
3359Building U-Boot has been tested in several native build environments
3360and in many different cross environments. Of course we cannot support
3361all possibly existing versions of cross development tools in all
3362(potentially obsolete) versions. In case of tool chain problems we
3363recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3364which is extensively used to build and test U-Boot.
3365
3366If you are not using a native environment, it is assumed that you
3367have GNU cross compiling tools available in your path. In this case,
3368you must set the environment variable CROSS_COMPILE in your shell.
3369Note that no changes to the Makefile or any other source files are
3370necessary. For example using the ELDK on a 4xx CPU, please enter:
3371
3372        $ CROSS_COMPILE=ppc_4xx-
3373        $ export CROSS_COMPILE
3374
3375Note: If you wish to generate Windows versions of the utilities in
3376      the tools directory you can use the MinGW toolchain
3377      (http://www.mingw.org).  Set your HOST tools to the MinGW
3378      toolchain and execute 'make tools'.  For example:
3379
3380       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3381
3382      Binaries such as tools/mkimage.exe will be created which can
3383      be executed on computers running Windows.
3384
3385U-Boot is intended to be simple to build. After installing the
3386sources you must configure U-Boot for one specific board type. This
3387is done by typing:
3388
3389        make NAME_defconfig
3390
3391where "NAME_defconfig" is the name of one of the existing configu-
3392rations; see boards.cfg for supported names.
3393
3394Note: for some board special configuration names may exist; check if
3395      additional information is available from the board vendor; for
3396      instance, the TQM823L systems are available without (standard)
3397      or with LCD support. You can select such additional "features"
3398      when choosing the configuration, i. e.
3399
3400      make TQM823L_defconfig
3401        - will configure for a plain TQM823L, i. e. no LCD support
3402
3403      make TQM823L_LCD_defconfig
3404        - will configure for a TQM823L with U-Boot console on LCD
3405
3406      etc.
3407
3408
3409Finally, type "make all", and you should get some working U-Boot
3410images ready for download to / installation on your system:
3411
3412- "u-boot.bin" is a raw binary image
3413- "u-boot" is an image in ELF binary format
3414- "u-boot.srec" is in Motorola S-Record format
3415
3416By default the build is performed locally and the objects are saved
3417in the source directory. One of the two methods can be used to change
3418this behavior and build U-Boot to some external directory:
3419
34201. Add O= to the make command line invocations:
3421
3422        make O=/tmp/build distclean
3423        make O=/tmp/build NAME_defconfig
3424        make O=/tmp/build all
3425
34262. Set environment variable KBUILD_OUTPUT to point to the desired location:
3427
3428        export KBUILD_OUTPUT=/tmp/build
3429        make distclean
3430        make NAME_defconfig
3431        make all
3432
3433Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3434variable.
3435
3436User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3437setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3438For example to treat all compiler warnings as errors:
3439
3440        make KCFLAGS=-Werror
3441
3442Please be aware that the Makefiles assume you are using GNU make, so
3443for instance on NetBSD you might need to use "gmake" instead of
3444native "make".
3445
3446
3447If the system board that you have is not listed, then you will need
3448to port U-Boot to your hardware platform. To do this, follow these
3449steps:
3450
34511.  Create a new directory to hold your board specific code. Add any
3452    files you need. In your board directory, you will need at least
3453    the "Makefile" and a "<board>.c".
34542.  Create a new configuration file "include/configs/<board>.h" for
3455    your board.
34563.  If you're porting U-Boot to a new CPU, then also create a new
3457    directory to hold your CPU specific code. Add any files you need.
34584.  Run "make <board>_defconfig" with your new name.
34595.  Type "make", and you should get a working "u-boot.srec" file
3460    to be installed on your target system.
34616.  Debug and solve any problems that might arise.
3462    [Of course, this last step is much harder than it sounds.]
3463
3464
3465Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3466==============================================================
3467
3468If you have modified U-Boot sources (for instance added a new board
3469or support for new devices, a new CPU, etc.) you are expected to
3470provide feedback to the other developers. The feedback normally takes
3471the form of a "patch", i. e. a context diff against a certain (latest
3472official or latest in the git repository) version of U-Boot sources.
3473
3474But before you submit such a patch, please verify that your modifi-
3475cation did not break existing code. At least make sure that *ALL* of
3476the supported boards compile WITHOUT ANY compiler warnings. To do so,
3477just run the buildman script (tools/buildman/buildman), which will
3478configure and build U-Boot for ALL supported system. Be warned, this
3479will take a while. Please see the buildman README, or run 'buildman -H'
3480for documentation.
3481
3482
3483See also "U-Boot Porting Guide" below.
3484
3485
3486Monitor Commands - Overview:
3487============================
3488
3489go      - start application at address 'addr'
3490run     - run commands in an environment variable
3491bootm   - boot application image from memory
3492bootp   - boot image via network using BootP/TFTP protocol
3493bootz   - boot zImage from memory
3494tftpboot- boot image via network using TFTP protocol
3495               and env variables "ipaddr" and "serverip"
3496               (and eventually "gatewayip")
3497tftpput - upload a file via network using TFTP protocol
3498rarpboot- boot image via network using RARP/TFTP protocol
3499diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3500loads   - load S-Record file over serial line
3501loadb   - load binary file over serial line (kermit mode)
3502md      - memory display
3503mm      - memory modify (auto-incrementing)
3504nm      - memory modify (constant address)
3505mw      - memory write (fill)
3506cp      - memory copy
3507cmp     - memory compare
3508crc32   - checksum calculation
3509i2c     - I2C sub-system
3510sspi    - SPI utility commands
3511base    - print or set address offset
3512printenv- print environment variables
3513setenv  - set environment variables
3514saveenv - save environment variables to persistent storage
3515protect - enable or disable FLASH write protection
3516erase   - erase FLASH memory
3517flinfo  - print FLASH memory information
3518nand    - NAND memory operations (see doc/README.nand)
3519bdinfo  - print Board Info structure
3520iminfo  - print header information for application image
3521coninfo - print console devices and informations
3522ide     - IDE sub-system
3523loop    - infinite loop on address range
3524loopw   - infinite write loop on address range
3525mtest   - simple RAM test
3526icache  - enable or disable instruction cache
3527dcache  - enable or disable data cache
3528reset   - Perform RESET of the CPU
3529echo    - echo args to console
3530version - print monitor version
3531help    - print online help
3532?       - alias for 'help'
3533
3534
3535Monitor Commands - Detailed Description:
3536========================================
3537
3538TODO.
3539
3540For now: just type "help <command>".
3541
3542
3543Environment Variables:
3544======================
3545
3546U-Boot supports user configuration using Environment Variables which
3547can be made persistent by saving to Flash memory.
3548
3549Environment Variables are set using "setenv", printed using
3550"printenv", and saved to Flash using "saveenv". Using "setenv"
3551without a value can be used to delete a variable from the
3552environment. As long as you don't save the environment you are
3553working with an in-memory copy. In case the Flash area containing the
3554environment is erased by accident, a default environment is provided.
3555
3556Some configuration options can be set using Environment Variables.
3557
3558List of environment variables (most likely not complete):
3559
3560  baudrate      - see CONFIG_BAUDRATE
3561
3562  bootdelay     - see CONFIG_BOOTDELAY
3563
3564  bootcmd       - see CONFIG_BOOTCOMMAND
3565
3566  bootargs      - Boot arguments when booting an RTOS image
3567
3568  bootfile      - Name of the image to load with TFTP
3569
3570  bootm_low     - Memory range available for image processing in the bootm
3571                  command can be restricted. This variable is given as
3572                  a hexadecimal number and defines lowest address allowed
3573                  for use by the bootm command. See also "bootm_size"
3574                  environment variable. Address defined by "bootm_low" is
3575                  also the base of the initial memory mapping for the Linux
3576                  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3577                  bootm_mapsize.
3578
3579  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3580                  This variable is given as a hexadecimal number and it
3581                  defines the size of the memory region starting at base
3582                  address bootm_low that is accessible by the Linux kernel
3583                  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3584                  as the default value if it is defined, and bootm_size is
3585                  used otherwise.
3586
3587  bootm_size    - Memory range available for image processing in the bootm
3588                  command can be restricted. This variable is given as
3589                  a hexadecimal number and defines the size of the region
3590                  allowed for use by the bootm command. See also "bootm_low"
3591                  environment variable.
3592
3593  updatefile    - Location of the software update file on a TFTP server, used
3594                  by the automatic software update feature. Please refer to
3595                  documentation in doc/README.update for more details.
3596
3597  autoload      - if set to "no" (any string beginning with 'n'),
3598                  "bootp" will just load perform a lookup of the
3599                  configuration from the BOOTP server, but not try to
3600                  load any image using TFTP
3601
3602  autostart     - if set to "yes", an image loaded using the "bootp",
3603                  "rarpboot", "tftpboot" or "diskboot" commands will
3604                  be automatically started (by internally calling
3605                  "bootm")
3606
3607                  If set to "no", a standalone image passed to the
3608                  "bootm" command will be copied to the load address
3609                  (and eventually uncompressed), but NOT be started.
3610                  This can be used to load and uncompress arbitrary
3611                  data.
3612
3613  fdt_high      - if set this restricts the maximum address that the
3614                  flattened device tree will be copied into upon boot.
3615                  For example, if you have a system with 1 GB memory
3616                  at physical address 0x10000000, while Linux kernel
3617                  only recognizes the first 704 MB as low memory, you
3618                  may need to set fdt_high as 0x3C000000 to have the
3619                  device tree blob be copied to the maximum address
3620                  of the 704 MB low memory, so that Linux kernel can
3621                  access it during the boot procedure.
3622
3623                  If this is set to the special value 0xFFFFFFFF then
3624                  the fdt will not be copied at all on boot.  For this
3625                  to work it must reside in writable memory, have
3626                  sufficient padding on the end of it for u-boot to
3627                  add the information it needs into it, and the memory
3628                  must be accessible by the kernel.
3629
3630  fdtcontroladdr- if set this is the address of the control flattened
3631                  device tree used by U-Boot when CONFIG_OF_CONTROL is
3632                  defined.
3633
3634  i2cfast       - (PPC405GP|PPC405EP only)
3635                  if set to 'y' configures Linux I2C driver for fast
3636                  mode (400kHZ). This environment variable is used in
3637                  initialization code. So, for changes to be effective
3638                  it must be saved and board must be reset.
3639
3640  initrd_high   - restrict positioning of initrd images:
3641                  If this variable is not set, initrd images will be
3642                  copied to the highest possible address in RAM; this
3643                  is usually what you want since it allows for
3644                  maximum initrd size. If for some reason you want to
3645                  make sure that the initrd image is loaded below the
3646                  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3647                  variable to a value of "no" or "off" or "0".
3648                  Alternatively, you can set it to a maximum upper
3649                  address to use (U-Boot will still check that it
3650                  does not overwrite the U-Boot stack and data).
3651
3652                  For instance, when you have a system with 16 MB
3653                  RAM, and want to reserve 4 MB from use by Linux,
3654                  you can do this by adding "mem=12M" to the value of
3655                  the "bootargs" variable. However, now you must make
3656                  sure that the initrd image is placed in the first
3657                  12 MB as well - this can be done with
3658
3659                  setenv initrd_high 00c00000
3660
3661                  If you set initrd_high to 0xFFFFFFFF, this is an
3662                  indication to U-Boot that all addresses are legal
3663                  for the Linux kernel, including addresses in flash
3664                  memory. In this case U-Boot will NOT COPY the
3665                  ramdisk at all. This may be useful to reduce the
3666                  boot time on your system, but requires that this
3667                  feature is supported by your Linux kernel.
3668
3669  ipaddr        - IP address; needed for tftpboot command
3670
3671  loadaddr      - Default load address for commands like "bootp",
3672                  "rarpboot", "tftpboot", "loadb" or "diskboot"
3673
3674  loads_echo    - see CONFIG_LOADS_ECHO
3675
3676  serverip      - TFTP server IP address; needed for tftpboot command
3677
3678  bootretry     - see CONFIG_BOOT_RETRY_TIME
3679
3680  bootdelaykey  - see CONFIG_AUTOBOOT_DELAY_STR
3681
3682  bootstopkey   - see CONFIG_AUTOBOOT_STOP_STR
3683
3684  ethprime      - controls which interface is used first.
3685
3686  ethact        - controls which interface is currently active.
3687                  For example you can do the following
3688
3689                  => setenv ethact FEC
3690                  => ping 192.168.0.1 # traffic sent on FEC
3691                  => setenv ethact SCC
3692                  => ping 10.0.0.1 # traffic sent on SCC
3693
3694  ethrotate     - When set to "no" U-Boot does not go through all
3695                  available network interfaces.
3696                  It just stays at the currently selected interface.
3697
3698  netretry      - When set to "no" each network operation will
3699                  either succeed or fail without retrying.
3700                  When set to "once" the network operation will
3701                  fail when all the available network interfaces
3702                  are tried once without success.
3703                  Useful on scripts which control the retry operation
3704                  themselves.
3705
3706  npe_ucode     - set load address for the NPE microcode
3707
3708  silent_linux  - If set then Linux will be told to boot silently, by
3709                  changing the console to be empty. If "yes" it will be
3710                  made silent. If "no" it will not be made silent. If
3711                  unset, then it will be made silent if the U-Boot console
3712                  is silent.
3713
3714  tftpsrcp      - If this is set, the value is used for TFTP's
3715                  UDP source port.
3716
3717  tftpdstp      - If this is set, the value is used for TFTP's UDP
3718                  destination port instead of the Well Know Port 69.
3719
3720  tftpblocksize - Block size to use for TFTP transfers; if not set,
3721                  we use the TFTP server's default block size
3722
3723  tftptimeout   - Retransmission timeout for TFTP packets (in milli-
3724                  seconds, minimum value is 1000 = 1 second). Defines
3725                  when a packet is considered to be lost so it has to
3726                  be retransmitted. The default is 5000 = 5 seconds.
3727                  Lowering this value may make downloads succeed
3728                  faster in networks with high packet loss rates or
3729                  with unreliable TFTP servers.
3730
3731  tftptimeoutcountmax   - maximum count of TFTP timeouts (no
3732                  unit, minimum value = 0). Defines how many timeouts
3733                  can happen during a single file transfer before that
3734                  transfer is aborted. The default is 10, and 0 means
3735                  'no timeouts allowed'. Increasing this value may help
3736                  downloads succeed with high packet loss rates, or with
3737                  unreliable TFTP servers or client hardware.
3738
3739  vlan          - When set to a value < 4095 the traffic over
3740                  Ethernet is encapsulated/received over 802.1q
3741                  VLAN tagged frames.
3742
3743  bootpretryperiod      - Period during which BOOTP/DHCP sends retries.
3744                  Unsigned value, in milliseconds. If not set, the period will
3745                  be either the default (28000), or a value based on
3746                  CONFIG_NET_RETRY_COUNT, if defined. This value has
3747                  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3748
3749The following image location variables contain the location of images
3750used in booting. The "Image" column gives the role of the image and is
3751not an environment variable name. The other columns are environment
3752variable names. "File Name" gives the name of the file on a TFTP
3753server, "RAM Address" gives the location in RAM the image will be
3754loaded to, and "Flash Location" gives the image's address in NOR
3755flash or offset in NAND flash.
3756
3757*Note* - these variables don't have to be defined for all boards, some
3758boards currently use other variables for these purposes, and some
3759boards use these variables for other purposes.
3760
3761Image               File Name        RAM Address       Flash Location
3762-----               ---------        -----------       --------------
3763u-boot              u-boot           u-boot_addr_r     u-boot_addr
3764Linux kernel        bootfile         kernel_addr_r     kernel_addr
3765device tree blob    fdtfile          fdt_addr_r        fdt_addr
3766ramdisk             ramdiskfile      ramdisk_addr_r    ramdisk_addr
3767
3768The following environment variables may be used and automatically
3769updated by the network boot commands ("bootp" and "rarpboot"),
3770depending the information provided by your boot server:
3771
3772  bootfile      - see above
3773  dnsip         - IP address of your Domain Name Server
3774  dnsip2        - IP address of your secondary Domain Name Server
3775  gatewayip     - IP address of the Gateway (Router) to use
3776  hostname      - Target hostname
3777  ipaddr        - see above
3778  netmask       - Subnet Mask
3779  rootpath      - Pathname of the root filesystem on the NFS server
3780  serverip      - see above
3781
3782
3783There are two special Environment Variables:
3784
3785  serial#       - contains hardware identification information such
3786                  as type string and/or serial number
3787  ethaddr       - Ethernet address
3788
3789These variables can be set only once (usually during manufacturing of
3790the board). U-Boot refuses to delete or overwrite these variables
3791once they have been set once.
3792
3793
3794Further special Environment Variables:
3795
3796  ver           - Contains the U-Boot version string as printed
3797                  with the "version" command. This variable is
3798                  readonly (see CONFIG_VERSION_VARIABLE).
3799
3800
3801Please note that changes to some configuration parameters may take
3802only effect after the next boot (yes, that's just like Windoze :-).
3803
3804
3805Callback functions for environment variables:
3806---------------------------------------------
3807
3808For some environment variables, the behavior of u-boot needs to change
3809when their values are changed.  This functionality allows functions to
3810be associated with arbitrary variables.  On creation, overwrite, or
3811deletion, the callback will provide the opportunity for some side
3812effect to happen or for the change to be rejected.
3813
3814The callbacks are named and associated with a function using the
3815U_BOOT_ENV_CALLBACK macro in your board or driver code.
3816
3817These callbacks are associated with variables in one of two ways.  The
3818static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3819in the board configuration to a string that defines a list of
3820associations.  The list must be in the following format:
3821
3822        entry = variable_name[:callback_name]
3823        list = entry[,list]
3824
3825If the callback name is not specified, then the callback is deleted.
3826Spaces are also allowed anywhere in the list.
3827
3828Callbacks can also be associated by defining the ".callbacks" variable
3829with the same list format above.  Any association in ".callbacks" will
3830override any association in the static list. You can define
3831CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3832".callbacks" environment variable in the default or embedded environment.
3833
3834If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3835regular expression. This allows multiple variables to be connected to
3836the same callback without explicitly listing them all out.
3837
3838The signature of the callback functions is:
3839
3840    int callback(const char *name, const char *value, enum env_op op, int flags)
3841
3842* name - changed environment variable
3843* value - new value of the environment variable
3844* op - operation (create, overwrite, or delete)
3845* flags - attributes of the environment variable change, see flags H_* in
3846  include/search.h
3847
3848The return value is 0 if the variable change is accepted and 1 otherwise.
3849
3850Command Line Parsing:
3851=====================
3852
3853There are two different command line parsers available with U-Boot:
3854the old "simple" one, and the much more powerful "hush" shell:
3855
3856Old, simple command line parser:
3857--------------------------------
3858
3859- supports environment variables (through setenv / saveenv commands)
3860- several commands on one line, separated by ';'
3861- variable substitution using "... ${name} ..." syntax
3862- special characters ('$', ';') can be escaped by prefixing with '\',
3863  for example:
3864        setenv bootcmd bootm \${address}
3865- You can also escape text by enclosing in single apostrophes, for example:
3866        setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3867
3868Hush shell:
3869-----------
3870
3871- similar to Bourne shell, with control structures like
3872  if...then...else...fi, for...do...done; while...do...done,
3873  until...do...done, ...
3874- supports environment ("global") variables (through setenv / saveenv
3875  commands) and local shell variables (through standard shell syntax
3876  "name=value"); only environment variables can be used with "run"
3877  command
3878
3879General rules:
3880--------------
3881
3882(1) If a command line (or an environment variable executed by a "run"
3883    command) contains several commands separated by semicolon, and
3884    one of these commands fails, then the remaining commands will be
3885    executed anyway.
3886
3887(2) If you execute several variables with one call to run (i. e.
3888    calling run with a list of variables as arguments), any failing
3889    command will cause "run" to terminate, i. e. the remaining
3890    variables are not executed.
3891
3892Note for Redundant Ethernet Interfaces:
3893=======================================
3894
3895Some boards come with redundant Ethernet interfaces; U-Boot supports
3896such configurations and is capable of automatic selection of a
3897"working" interface when needed. MAC assignment works as follows:
3898
3899Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3900MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3901"eth1addr" (=>eth1), "eth2addr", ...
3902
3903If the network interface stores some valid MAC address (for instance
3904in SROM), this is used as default address if there is NO correspon-
3905ding setting in the environment; if the corresponding environment
3906variable is set, this overrides the settings in the card; that means:
3907
3908o If the SROM has a valid MAC address, and there is no address in the
3909  environment, the SROM's address is used.
3910
3911o If there is no valid address in the SROM, and a definition in the
3912  environment exists, then the value from the environment variable is
3913  used.
3914
3915o If both the SROM and the environment contain a MAC address, and
3916  both addresses are the same, this MAC address is used.
3917
3918o If both the SROM and the environment contain a MAC address, and the
3919  addresses differ, the value from the environment is used and a
3920  warning is printed.
3921
3922o If neither SROM nor the environment contain a MAC address, an error
3923  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3924  a random, locally-assigned MAC is used.
3925
3926If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3927will be programmed into hardware as part of the initialization process.  This
3928may be skipped by setting the appropriate 'ethmacskip' environment variable.
3929The naming convention is as follows:
3930"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3931
3932Image Formats:
3933==============
3934
3935U-Boot is capable of booting (and performing other auxiliary operations on)
3936images in two formats:
3937
3938New uImage format (FIT)
3939-----------------------
3940
3941Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3942to Flattened Device Tree). It allows the use of images with multiple
3943components (several kernels, ramdisks, etc.), with contents protected by
3944SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3945
3946
3947Old uImage format
3948-----------------
3949
3950Old image format is based on binary files which can be basically anything,
3951preceded by a special header; see the definitions in include/image.h for
3952details; basically, the header defines the following image properties:
3953
3954* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3955  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3956  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3957  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3958  INTEGRITY).
3959* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3960  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3961  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3962* Compression Type (uncompressed, gzip, bzip2)
3963* Load Address
3964* Entry Point
3965* Image Name
3966* Image Timestamp
3967
3968The header is marked by a special Magic Number, and both the header
3969and the data portions of the image are secured against corruption by
3970CRC32 checksums.
3971
3972
3973Linux Support:
3974==============
3975
3976Although U-Boot should support any OS or standalone application
3977easily, the main focus has always been on Linux during the design of
3978U-Boot.
3979
3980U-Boot includes many features that so far have been part of some
3981special "boot loader" code within the Linux kernel. Also, any
3982"initrd" images to be used are no longer part of one big Linux image;
3983instead, kernel and "initrd" are separate images. This implementation
3984serves several purposes:
3985
3986- the same features can be used for other OS or standalone
3987  applications (for instance: using compressed images to reduce the
3988  Flash memory footprint)
3989
3990- it becomes much easier to port new Linux kernel versions because
3991  lots of low-level, hardware dependent stuff are done by U-Boot
3992
3993- the same Linux kernel image can now be used with different "initrd"
3994  images; of course this also means that different kernel images can
3995  be run with the same "initrd". This makes testing easier (you don't
3996  have to build a new "zImage.initrd" Linux image when you just
3997  change a file in your "initrd"). Also, a field-upgrade of the
3998  software is easier now.
3999
4000
4001Linux HOWTO:
4002============
4003
4004Porting Linux to U-Boot based systems:
4005---------------------------------------
4006
4007U-Boot cannot save you from doing all the necessary modifications to
4008configure the Linux device drivers for use with your target hardware
4009(no, we don't intend to provide a full virtual machine interface to
4010Linux :-).
4011
4012But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4013
4014Just make sure your machine specific header file (for instance
4015include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4016Information structure as we define in include/asm-<arch>/u-boot.h,
4017and make sure that your definition of IMAP_ADDR uses the same value
4018as your U-Boot configuration in CONFIG_SYS_IMMR.
4019
4020Note that U-Boot now has a driver model, a unified model for drivers.
4021If you are adding a new driver, plumb it into driver model. If there
4022is no uclass available, you are encouraged to create one. See
4023doc/driver-model.
4024
4025
4026Configuring the Linux kernel:
4027-----------------------------
4028
4029No specific requirements for U-Boot. Make sure you have some root
4030device (initial ramdisk, NFS) for your target system.
4031
4032
4033Building a Linux Image:
4034-----------------------
4035
4036With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4037not used. If you use recent kernel source, a new build target
4038"uImage" will exist which automatically builds an image usable by
4039U-Boot. Most older kernels also have support for a "pImage" target,
4040which was introduced for our predecessor project PPCBoot and uses a
4041100% compatible format.
4042
4043Example:
4044
4045        make TQM850L_defconfig
4046        make oldconfig
4047        make dep
4048        make uImage
4049
4050The "uImage" build target uses a special tool (in 'tools/mkimage') to
4051encapsulate a compressed Linux kernel image with header  information,
4052CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4053
4054* build a standard "vmlinux" kernel image (in ELF binary format):
4055
4056* convert the kernel into a raw binary image:
4057
4058        ${CROSS_COMPILE}-objcopy -O binary \
4059                                 -R .note -R .comment \
4060                                 -S vmlinux linux.bin
4061
4062* compress the binary image:
4063
4064        gzip -9 linux.bin
4065
4066* package compressed binary image for U-Boot:
4067
4068        mkimage -A ppc -O linux -T kernel -C gzip \
4069                -a 0 -e 0 -n "Linux Kernel Image" \
4070                -d linux.bin.gz uImage
4071
4072
4073The "mkimage" tool can also be used to create ramdisk images for use
4074with U-Boot, either separated from the Linux kernel image, or
4075combined into one file. "mkimage" encapsulates the images with a 64
4076byte header containing information about target architecture,
4077operating system, image type, compression method, entry points, time
4078stamp, CRC32 checksums, etc.
4079
4080"mkimage" can be called in two ways: to verify existing images and
4081print the header information, or to build new images.
4082
4083In the first form (with "-l" option) mkimage lists the information
4084contained in the header of an existing U-Boot image; this includes
4085checksum verification:
4086
4087        tools/mkimage -l image
4088          -l ==> list image header information
4089
4090The second form (with "-d" option) is used to build a U-Boot image
4091from a "data file" which is used as image payload:
4092
4093        tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4094                      -n name -d data_file image
4095          -A ==> set architecture to 'arch'
4096          -O ==> set operating system to 'os'
4097          -T ==> set image type to 'type'
4098          -C ==> set compression type 'comp'
4099          -a ==> set load address to 'addr' (hex)
4100          -e ==> set entry point to 'ep' (hex)
4101          -n ==> set image name to 'name'
4102          -d ==> use image data from 'datafile'
4103
4104Right now, all Linux kernels for PowerPC systems use the same load
4105address (0x00000000), but the entry point address depends on the
4106kernel version:
4107
4108- 2.2.x kernels have the entry point at 0x0000000C,
4109- 2.3.x and later kernels have the entry point at 0x00000000.
4110
4111So a typical call to build a U-Boot image would read:
4112
4113        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4114        > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4115        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4116        > examples/uImage.TQM850L
4117        Image Name:   2.4.4 kernel for TQM850L
4118        Created:      Wed Jul 19 02:34:59 2000
4119        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4120        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4121        Load Address: 0x00000000
4122        Entry Point:  0x00000000
4123
4124To verify the contents of the image (or check for corruption):
4125
4126        -> tools/mkimage -l examples/uImage.TQM850L
4127        Image Name:   2.4.4 kernel for TQM850L
4128        Created:      Wed Jul 19 02:34:59 2000
4129        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4130        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4131        Load Address: 0x00000000
4132        Entry Point:  0x00000000
4133
4134NOTE: for embedded systems where boot time is critical you can trade
4135speed for memory and install an UNCOMPRESSED image instead: this
4136needs more space in Flash, but boots much faster since it does not
4137need to be uncompressed:
4138
4139        -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4140        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4141        > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4142        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4143        > examples/uImage.TQM850L-uncompressed
4144        Image Name:   2.4.4 kernel for TQM850L
4145        Created:      Wed Jul 19 02:34:59 2000
4146        Image Type:   PowerPC Linux Kernel Image (uncompressed)
4147        Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4148        Load Address: 0x00000000
4149        Entry Point:  0x00000000
4150
4151
4152Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4153when your kernel is intended to use an initial ramdisk:
4154
4155        -> tools/mkimage -n 'Simple Ramdisk Image' \
4156        > -A ppc -O linux -T ramdisk -C gzip \
4157        > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4158        Image Name:   Simple Ramdisk Image
4159        Created:      Wed Jan 12 14:01:50 2000
4160        Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4161        Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4162        Load Address: 0x00000000
4163        Entry Point:  0x00000000
4164
4165The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4166option performs the converse operation of the mkimage's second form (the "-d"
4167option). Given an image built by mkimage, the dumpimage extracts a "data file"
4168from the image:
4169
4170        tools/dumpimage -i image -T type -p position data_file
4171          -i ==> extract from the 'image' a specific 'data_file'
4172          -T ==> set image type to 'type'
4173          -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4174
4175
4176Installing a Linux Image:
4177-------------------------
4178
4179To downloading a U-Boot image over the serial (console) interface,
4180you must convert the image to S-Record format:
4181
4182        objcopy -I binary -O srec examples/image examples/image.srec
4183
4184The 'objcopy' does not understand the information in the U-Boot
4185image header, so the resulting S-Record file will be relative to
4186address 0x00000000. To load it to a given address, you need to
4187specify the target address as 'offset' parameter with the 'loads'
4188command.
4189
4190Example: install the image to address 0x40100000 (which on the
4191TQM8xxL is in the first Flash bank):
4192
4193        => erase 40100000 401FFFFF
4194
4195        .......... done
4196        Erased 8 sectors
4197
4198        => loads 40100000
4199        ## Ready for S-Record download ...
4200        ~>examples/image.srec
4201        1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4202        ...
4203        15989 15990 15991 15992
4204        [file transfer complete]
4205        [connected]
4206        ## Start Addr = 0x00000000
4207
4208
4209You can check the success of the download using the 'iminfo' command;
4210this includes a checksum verification so you can be sure no data
4211corruption happened:
4212
4213        => imi 40100000
4214
4215        ## Checking Image at 40100000 ...
4216           Image Name:   2.2.13 for initrd on TQM850L
4217           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4218           Data Size:    335725 Bytes = 327 kB = 0 MB
4219           Load Address: 00000000
4220           Entry Point:  0000000c
4221           Verifying Checksum ... OK
4222
4223
4224Boot Linux:
4225-----------
4226
4227The "bootm" command is used to boot an application that is stored in
4228memory (RAM or Flash). In case of a Linux kernel image, the contents
4229of the "bootargs" environment variable is passed to the kernel as
4230parameters. You can check and modify this variable using the
4231"printenv" and "setenv" commands:
4232
4233
4234        => printenv bootargs
4235        bootargs=root=/dev/ram
4236
4237        => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4238
4239        => printenv bootargs
4240        bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4241
4242        => bootm 40020000
4243        ## Booting Linux kernel at 40020000 ...
4244           Image Name:   2.2.13 for NFS on TQM850L
4245           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4246           Data Size:    381681 Bytes = 372 kB = 0 MB
4247           Load Address: 00000000
4248           Entry Point:  0000000c
4249           Verifying Checksum ... OK
4250           Uncompressing Kernel Image ... OK
4251        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
4252        Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4253        time_init: decrementer frequency = 187500000/60
4254        Calibrating delay loop... 49.77 BogoMIPS
4255        Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4256        ...
4257
4258If you want to boot a Linux kernel with initial RAM disk, you pass
4259the memory addresses of both the kernel and the initrd image (PPBCOOT
4260format!) to the "bootm" command:
4261
4262        => imi 40100000 40200000
4263
4264        ## Checking Image at 40100000 ...
4265           Image Name:   2.2.13 for initrd on TQM850L
4266           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4267           Data Size:    335725 Bytes = 327 kB = 0 MB
4268           Load Address: 00000000
4269           Entry Point:  0000000c
4270           Verifying Checksum ... OK
4271
4272        ## Checking Image at 40200000 ...
4273           Image Name:   Simple Ramdisk Image
4274           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4275           Data Size:    566530 Bytes = 553 kB = 0 MB
4276           Load Address: 00000000
4277           Entry Point:  00000000
4278           Verifying Checksum ... OK
4279
4280        => bootm 40100000 40200000
4281        ## Booting Linux kernel at 40100000 ...
4282           Image Name:   2.2.13 for initrd on TQM850L
4283           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4284           Data Size:    335725 Bytes = 327 kB = 0 MB
4285           Load Address: 00000000
4286           Entry Point:  0000000c
4287           Verifying Checksum ... OK
4288           Uncompressing Kernel Image ... OK
4289        ## Loading RAMDisk Image at 40200000 ...
4290           Image Name:   Simple Ramdisk Image
4291           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4292           Data Size:    566530 Bytes = 553 kB = 0 MB
4293           Load Address: 00000000
4294           Entry Point:  00000000
4295           Verifying Checksum ... OK
4296           Loading Ramdisk ... OK
4297        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
4298        Boot arguments: root=/dev/ram
4299        time_init: decrementer frequency = 187500000/60
4300        Calibrating delay loop... 49.77 BogoMIPS
4301        ...
4302        RAMDISK: Compressed image found at block 0
4303        VFS: Mounted root (ext2 filesystem).
4304
4305        bash#
4306
4307Boot Linux and pass a flat device tree:
4308-----------
4309
4310First, U-Boot must be compiled with the appropriate defines. See the section
4311titled "Linux Kernel Interface" above for a more in depth explanation. The
4312following is an example of how to start a kernel and pass an updated
4313flat device tree:
4314
4315=> print oftaddr
4316oftaddr=0x300000
4317=> print oft
4318oft=oftrees/mpc8540ads.dtb
4319=> tftp $oftaddr $oft
4320Speed: 1000, full duplex
4321Using TSEC0 device
4322TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4323Filename 'oftrees/mpc8540ads.dtb'.
4324Load address: 0x300000
4325Loading: #
4326done
4327Bytes transferred = 4106 (100a hex)
4328=> tftp $loadaddr $bootfile
4329Speed: 1000, full duplex
4330Using TSEC0 device
4331TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4332Filename 'uImage'.
4333Load address: 0x200000
4334Loading:############
4335done
4336Bytes transferred = 1029407 (fb51f hex)
4337=> print loadaddr
4338loadaddr=200000
4339=> print oftaddr
4340oftaddr=0x300000
4341=> bootm $loadaddr - $oftaddr
4342## Booting image at 00200000 ...
4343   Image Name:   Linux-2.6.17-dirty
4344   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4345   Data Size:    1029343 Bytes = 1005.2 kB
4346   Load Address: 00000000
4347   Entry Point:  00000000
4348   Verifying Checksum ... OK
4349   Uncompressing Kernel Image ... OK
4350Booting using flat device tree at 0x300000
4351Using MPC85xx ADS machine description
4352Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4353[snip]
4354
4355
4356More About U-Boot Image Types:
4357------------------------------
4358
4359U-Boot supports the following image types:
4360
4361   "Standalone Programs" are directly runnable in the environment
4362        provided by U-Boot; it is expected that (if they behave
4363        well) you can continue to work in U-Boot after return from
4364        the Standalone Program.
4365   "OS Kernel Images" are usually images of some Embedded OS which
4366        will take over control completely. Usually these programs
4367        will install their own set of exception handlers, device
4368        drivers, set up the MMU, etc. - this means, that you cannot
4369        expect to re-enter U-Boot except by resetting the CPU.
4370   "RAMDisk Images" are more or less just data blocks, and their
4371        parameters (address, size) are passed to an OS kernel that is
4372        being started.
4373   "Multi-File Images" contain several images, typically an OS
4374        (Linux) kernel image and one or more data images like
4375        RAMDisks. This construct is useful for instance when you want
4376        to boot over the network using BOOTP etc., where the boot
4377        server provides just a single image file, but you want to get
4378        for instance an OS kernel and a RAMDisk image.
4379
4380        "Multi-File Images" start with a list of image sizes, each
4381        image size (in bytes) specified by an "uint32_t" in network
4382        byte order. This list is terminated by an "(uint32_t)0".
4383        Immediately after the terminating 0 follow the images, one by
4384        one, all aligned on "uint32_t" boundaries (size rounded up to
4385        a multiple of 4 bytes).
4386
4387   "Firmware Images" are binary images containing firmware (like
4388        U-Boot or FPGA images) which usually will be programmed to
4389        flash memory.
4390
4391   "Script files" are command sequences that will be executed by
4392        U-Boot's command interpreter; this feature is especially
4393        useful when you configure U-Boot to use a real shell (hush)
4394        as command interpreter.
4395
4396Booting the Linux zImage:
4397-------------------------
4398
4399On some platforms, it's possible to boot Linux zImage. This is done
4400using the "bootz" command. The syntax of "bootz" command is the same
4401as the syntax of "bootm" command.
4402
4403Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4404kernel with raw initrd images. The syntax is slightly different, the
4405address of the initrd must be augmented by it's size, in the following
4406format: "<initrd addres>:<initrd size>".
4407
4408
4409Standalone HOWTO:
4410=================
4411
4412One of the features of U-Boot is that you can dynamically load and
4413run "standalone" applications, which can use some resources of
4414U-Boot like console I/O functions or interrupt services.
4415
4416Two simple examples are included with the sources:
4417
4418"Hello World" Demo:
4419-------------------
4420
4421'examples/hello_world.c' contains a small "Hello World" Demo
4422application; it is automatically compiled when you build U-Boot.
4423It's configured to run at address 0x00040004, so you can play with it
4424like that:
4425
4426        => loads
4427        ## Ready for S-Record download ...
4428        ~>examples/hello_world.srec
4429        1 2 3 4 5 6 7 8 9 10 11 ...
4430        [file transfer complete]
4431        [connected]
4432        ## Start Addr = 0x00040004
4433
4434        => go 40004 Hello World! This is a test.
4435        ## Starting application at 0x00040004 ...
4436        Hello World
4437        argc = 7
4438        argv[0] = "40004"
4439        argv[1] = "Hello"
4440        argv[2] = "World!"
4441        argv[3] = "This"
4442        argv[4] = "is"
4443        argv[5] = "a"
4444        argv[6] = "test."
4445        argv[7] = "<NULL>"
4446        Hit any key to exit ...
4447
4448        ## Application terminated, rc = 0x0
4449
4450Another example, which demonstrates how to register a CPM interrupt
4451handler with the U-Boot code, can be found in 'examples/timer.c'.
4452Here, a CPM timer is set up to generate an interrupt every second.
4453The interrupt service routine is trivial, just printing a '.'
4454character, but this is just a demo program. The application can be
4455controlled by the following keys:
4456
4457        ? - print current values og the CPM Timer registers
4458        b - enable interrupts and start timer
4459        e - stop timer and disable interrupts
4460        q - quit application
4461
4462        => loads
4463        ## Ready for S-Record download ...
4464        ~>examples/timer.srec
4465        1 2 3 4 5 6 7 8 9 10 11 ...
4466        [file transfer complete]
4467        [connected]
4468        ## Start Addr = 0x00040004
4469
4470        => go 40004
4471        ## Starting application at 0x00040004 ...
4472        TIMERS=0xfff00980
4473        Using timer 1
4474          tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4475
4476Hit 'b':
4477        [q, b, e, ?] Set interval 1000000 us
4478        Enabling timer
4479Hit '?':
4480        [q, b, e, ?] ........
4481        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4482Hit '?':
4483        [q, b, e, ?] .
4484        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4485Hit '?':
4486        [q, b, e, ?] .
4487        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4488Hit '?':
4489        [q, b, e, ?] .
4490        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4491Hit 'e':
4492        [q, b, e, ?] ...Stopping timer
4493Hit 'q':
4494        [q, b, e, ?] ## Application terminated, rc = 0x0
4495
4496
4497Minicom warning:
4498================
4499
4500Over time, many people have reported problems when trying to use the
4501"minicom" terminal emulation program for serial download. I (wd)
4502consider minicom to be broken, and recommend not to use it. Under
4503Unix, I recommend to use C-Kermit for general purpose use (and
4504especially for kermit binary protocol download ("loadb" command), and
4505use "cu" for S-Record download ("loads" command).  See
4506http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4507for help with kermit.
4508
4509
4510Nevertheless, if you absolutely want to use it try adding this
4511configuration to your "File transfer protocols" section:
4512
4513           Name    Program                      Name U/D FullScr IO-Red. Multi
4514        X  kermit  /usr/bin/kermit -i -l %l -s   Y    U    Y       N      N
4515        Y  kermit  /usr/bin/kermit -i -l %l -r   N    D    Y       N      N
4516
4517
4518NetBSD Notes:
4519=============
4520
4521Starting at version 0.9.2, U-Boot supports NetBSD both as host
4522(build U-Boot) and target system (boots NetBSD/mpc8xx).
4523
4524Building requires a cross environment; it is known to work on
4525NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4526need gmake since the Makefiles are not compatible with BSD make).
4527Note that the cross-powerpc package does not install include files;
4528attempting to build U-Boot will fail because <machine/ansi.h> is
4529missing.  This file has to be installed and patched manually:
4530
4531        # cd /usr/pkg/cross/powerpc-netbsd/include
4532        # mkdir powerpc
4533        # ln -s powerpc machine
4534        # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4535        # ${EDIT} powerpc/ansi.h        ## must remove __va_list, _BSD_VA_LIST
4536
4537Native builds *don't* work due to incompatibilities between native
4538and U-Boot include files.
4539
4540Booting assumes that (the first part of) the image booted is a
4541stage-2 loader which in turn loads and then invokes the kernel
4542proper. Loader sources will eventually appear in the NetBSD source
4543tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4544meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4545
4546
4547Implementation Internals:
4548=========================
4549
4550The following is not intended to be a complete description of every
4551implementation detail. However, it should help to understand the
4552inner workings of U-Boot and make it easier to port it to custom
4553hardware.
4554
4555
4556Initial Stack, Global Data:
4557---------------------------
4558
4559The implementation of U-Boot is complicated by the fact that U-Boot
4560starts running out of ROM (flash memory), usually without access to
4561system RAM (because the memory controller is not initialized yet).
4562This means that we don't have writable Data or BSS segments, and BSS
4563is not initialized as zero. To be able to get a C environment working
4564at all, we have to allocate at least a minimal stack. Implementation
4565options for this are defined and restricted by the CPU used: Some CPU
4566models provide on-chip memory (like the IMMR area on MPC8xx and
4567MPC826x processors), on others (parts of) the data cache can be
4568locked as (mis-) used as memory, etc.
4569
4570        Chris Hallinan posted a good summary of these issues to the
4571        U-Boot mailing list:
4572
4573        Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4574        From: "Chris Hallinan" <clh@net1plus.com>
4575        Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4576        ...
4577
4578        Correct me if I'm wrong, folks, but the way I understand it
4579        is this: Using DCACHE as initial RAM for Stack, etc, does not
4580        require any physical RAM backing up the cache. The cleverness
4581        is that the cache is being used as a temporary supply of
4582        necessary storage before the SDRAM controller is setup. It's
4583        beyond the scope of this list to explain the details, but you
4584        can see how this works by studying the cache architecture and
4585        operation in the architecture and processor-specific manuals.
4586
4587        OCM is On Chip Memory, which I believe the 405GP has 4K. It
4588        is another option for the system designer to use as an
4589        initial stack/RAM area prior to SDRAM being available. Either
4590        option should work for you. Using CS 4 should be fine if your
4591        board designers haven't used it for something that would
4592        cause you grief during the initial boot! It is frequently not
4593        used.
4594
4595        CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4596        with your processor/board/system design. The default value
4597        you will find in any recent u-boot distribution in
4598        walnut.h should work for you. I'd set it to a value larger
4599        than your SDRAM module. If you have a 64MB SDRAM module, set
4600        it above 400_0000. Just make sure your board has no resources
4601        that are supposed to respond to that address! That code in
4602        start.S has been around a while and should work as is when
4603        you get the config right.
4604
4605        -Chris Hallinan
4606        DS4.COM, Inc.
4607
4608It is essential to remember this, since it has some impact on the C
4609code for the initialization procedures:
4610
4611* Initialized global data (data segment) is read-only. Do not attempt
4612  to write it.
4613
4614* Do not use any uninitialized global data (or implicitly initialized
4615  as zero data - BSS segment) at all - this is undefined, initiali-
4616  zation is performed later (when relocating to RAM).
4617
4618* Stack space is very limited. Avoid big data buffers or things like
4619  that.
4620
4621Having only the stack as writable memory limits means we cannot use
4622normal global data to share information between the code. But it
4623turned out that the implementation of U-Boot can be greatly
4624simplified by making a global data structure (gd_t) available to all
4625functions. We could pass a pointer to this data as argument to _all_
4626functions, but this would bloat the code. Instead we use a feature of
4627the GCC compiler (Global Register Variables) to share the data: we
4628place a pointer (gd) to the global data into a register which we
4629reserve for this purpose.
4630
4631When choosing a register for such a purpose we are restricted by the
4632relevant  (E)ABI  specifications for the current architecture, and by
4633GCC's implementation.
4634
4635For PowerPC, the following registers have specific use:
4636        R1:     stack pointer
4637        R2:     reserved for system use
4638        R3-R4:  parameter passing and return values
4639        R5-R10: parameter passing
4640        R13:    small data area pointer
4641        R30:    GOT pointer
4642        R31:    frame pointer
4643
4644        (U-Boot also uses R12 as internal GOT pointer. r12
4645        is a volatile register so r12 needs to be reset when
4646        going back and forth between asm and C)
4647
4648    ==> U-Boot will use R2 to hold a pointer to the global data
4649
4650    Note: on PPC, we could use a static initializer (since the
4651    address of the global data structure is known at compile time),
4652    but it turned out that reserving a register results in somewhat
4653    smaller code - although the code savings are not that big (on
4654    average for all boards 752 bytes for the whole U-Boot image,
4655    624 text + 127 data).
4656
4657On ARM, the following registers are used:
4658
4659        R0:     function argument word/integer result
4660        R1-R3:  function argument word
4661        R9:     platform specific
4662        R10:    stack limit (used only if stack checking is enabled)
4663        R11:    argument (frame) pointer
4664        R12:    temporary workspace
4665        R13:    stack pointer
4666        R14:    link register
4667        R15:    program counter
4668
4669    ==> U-Boot will use R9 to hold a pointer to the global data
4670
4671    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4672
4673On Nios II, the ABI is documented here:
4674        http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4675
4676    ==> U-Boot will use gp to hold a pointer to the global data
4677
4678    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4679    to access small data sections, so gp is free.
4680
4681On NDS32, the following registers are used:
4682
4683        R0-R1:  argument/return
4684        R2-R5:  argument
4685        R15:    temporary register for assembler
4686        R16:    trampoline register
4687        R28:    frame pointer (FP)
4688        R29:    global pointer (GP)
4689        R30:    link register (LP)
4690        R31:    stack pointer (SP)
4691        PC:     program counter (PC)
4692
4693    ==> U-Boot will use R10 to hold a pointer to the global data
4694
4695NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4696or current versions of GCC may "optimize" the code too much.
4697
4698On RISC-V, the following registers are used:
4699
4700        x0: hard-wired zero (zero)
4701        x1: return address (ra)
4702        x2:     stack pointer (sp)
4703        x3:     global pointer (gp)
4704        x4:     thread pointer (tp)
4705        x5:     link register (t0)
4706        x8:     frame pointer (fp)
4707        x10-x11:        arguments/return values (a0-1)
4708        x12-x17:        arguments (a2-7)
4709        x28-31:  temporaries (t3-6)
4710        pc:     program counter (pc)
4711
4712    ==> U-Boot will use gp to hold a pointer to the global data
4713
4714Memory Management:
4715------------------
4716
4717U-Boot runs in system state and uses physical addresses, i.e. the
4718MMU is not used either for address mapping nor for memory protection.
4719
4720The available memory is mapped to fixed addresses using the memory
4721controller. In this process, a contiguous block is formed for each
4722memory type (Flash, SDRAM, SRAM), even when it consists of several
4723physical memory banks.
4724
4725U-Boot is installed in the first 128 kB of the first Flash bank (on
4726TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4727booting and sizing and initializing DRAM, the code relocates itself
4728to the upper end of DRAM. Immediately below the U-Boot code some
4729memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4730configuration setting]. Below that, a structure with global Board
4731Info data is placed, followed by the stack (growing downward).
4732
4733Additionally, some exception handler code is copied to the low 8 kB
4734of DRAM (0x00000000 ... 0x00001FFF).
4735
4736So a typical memory configuration with 16 MB of DRAM could look like
4737this:
4738
4739        0x0000 0000     Exception Vector code
4740              :
4741        0x0000 1FFF
4742        0x0000 2000     Free for Application Use
4743              :
4744              :
4745
4746              :
4747              :
4748        0x00FB FF20     Monitor Stack (Growing downward)
4749        0x00FB FFAC     Board Info Data and permanent copy of global data
4750        0x00FC 0000     Malloc Arena
4751              :
4752        0x00FD FFFF
4753        0x00FE 0000     RAM Copy of Monitor Code
4754        ...             eventually: LCD or video framebuffer
4755        ...             eventually: pRAM (Protected RAM - unchanged by reset)
4756        0x00FF FFFF     [End of RAM]
4757
4758
4759System Initialization:
4760----------------------
4761
4762In the reset configuration, U-Boot starts at the reset entry point
4763(on most PowerPC systems at address 0x00000100). Because of the reset
4764configuration for CS0# this is a mirror of the on board Flash memory.
4765To be able to re-map memory U-Boot then jumps to its link address.
4766To be able to implement the initialization code in C, a (small!)
4767initial stack is set up in the internal Dual Ported RAM (in case CPUs
4768which provide such a feature like), or in a locked part of the data
4769cache. After that, U-Boot initializes the CPU core, the caches and
4770the SIU.
4771
4772Next, all (potentially) available memory banks are mapped using a
4773preliminary mapping. For example, we put them on 512 MB boundaries
4774(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4775on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4776programmed for SDRAM access. Using the temporary configuration, a
4777simple memory test is run that determines the size of the SDRAM
4778banks.
4779
4780When there is more than one SDRAM bank, and the banks are of
4781different size, the largest is mapped first. For equal size, the first
4782bank (CS2#) is mapped first. The first mapping is always for address
47830x00000000, with any additional banks following immediately to create
4784contiguous memory starting from 0.
4785
4786Then, the monitor installs itself at the upper end of the SDRAM area
4787and allocates memory for use by malloc() and for the global Board
4788Info data; also, the exception vector code is copied to the low RAM
4789pages, and the final stack is set up.
4790
4791Only after this relocation will you have a "normal" C environment;
4792until that you are restricted in several ways, mostly because you are
4793running from ROM, and because the code will have to be relocated to a
4794new address in RAM.
4795
4796
4797U-Boot Porting Guide:
4798----------------------
4799
4800[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4801list, October 2002]
4802
4803
4804int main(int argc, char *argv[])
4805{
4806        sighandler_t no_more_time;
4807
4808        signal(SIGALRM, no_more_time);
4809        alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4810
4811        if (available_money > available_manpower) {
4812                Pay consultant to port U-Boot;
4813                return 0;
4814        }
4815
4816        Download latest U-Boot source;
4817
4818        Subscribe to u-boot mailing list;
4819
4820        if (clueless)
4821                email("Hi, I am new to U-Boot, how do I get started?");
4822
4823        while (learning) {
4824                Read the README file in the top level directory;
4825                Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4826                Read applicable doc/*.README;
4827                Read the source, Luke;
4828                /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4829        }
4830
4831        if (available_money > toLocalCurrency ($2500))
4832                Buy a BDI3000;
4833        else
4834                Add a lot of aggravation and time;
4835
4836        if (a similar board exists) {   /* hopefully... */
4837                cp -a board/<similar> board/<myboard>
4838                cp include/configs/<similar>.h include/configs/<myboard>.h
4839        } else {
4840                Create your own board support subdirectory;
4841                Create your own board include/configs/<myboard>.h file;
4842        }
4843        Edit new board/<myboard> files
4844        Edit new include/configs/<myboard>.h
4845
4846        while (!accepted) {
4847                while (!running) {
4848                        do {
4849                                Add / modify source code;
4850                        } until (compiles);
4851                        Debug;
4852                        if (clueless)
4853                                email("Hi, I am having problems...");
4854                }
4855                Send patch file to the U-Boot email list;
4856                if (reasonable critiques)
4857                        Incorporate improvements from email list code review;
4858                else
4859                        Defend code as written;
4860        }
4861
4862        return 0;
4863}
4864
4865void no_more_time (int sig)
4866{
4867      hire_a_guru();
4868}
4869
4870
4871Coding Standards:
4872-----------------
4873
4874All contributions to U-Boot should conform to the Linux kernel
4875coding style; see the kernel coding style guide at
4876https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4877script "scripts/Lindent" in your Linux kernel source directory.
4878
4879Source files originating from a different project (for example the
4880MTD subsystem) are generally exempt from these guidelines and are not
4881reformatted to ease subsequent migration to newer versions of those
4882sources.
4883
4884Please note that U-Boot is implemented in C (and to some small parts in
4885Assembler); no C++ is used, so please do not use C++ style comments (//)
4886in your code.
4887
4888Please also stick to the following formatting rules:
4889- remove any trailing white space
4890- use TAB characters for indentation and vertical alignment, not spaces
4891- make sure NOT to use DOS '\r\n' line feeds
4892- do not add more than 2 consecutive empty lines to source files
4893- do not add trailing empty lines to source files
4894
4895Submissions which do not conform to the standards may be returned
4896with a request to reformat the changes.
4897
4898
4899Submitting Patches:
4900-------------------
4901
4902Since the number of patches for U-Boot is growing, we need to
4903establish some rules. Submissions which do not conform to these rules
4904may be rejected, even when they contain important and valuable stuff.
4905
4906Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4907
4908Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4909see https://lists.denx.de/listinfo/u-boot
4910
4911When you send a patch, please include the following information with
4912it:
4913
4914* For bug fixes: a description of the bug and how your patch fixes
4915  this bug. Please try to include a way of demonstrating that the
4916  patch actually fixes something.
4917
4918* For new features: a description of the feature and your
4919  implementation.
4920
4921* A CHANGELOG entry as plaintext (separate from the patch)
4922
4923* For major contributions, add a MAINTAINERS file with your
4924  information and associated file and directory references.
4925
4926* When you add support for a new board, don't forget to add a
4927  maintainer e-mail address to the boards.cfg file, too.
4928
4929* If your patch adds new configuration options, don't forget to
4930  document these in the README file.
4931
4932* The patch itself. If you are using git (which is *strongly*
4933  recommended) you can easily generate the patch using the
4934  "git format-patch". If you then use "git send-email" to send it to
4935  the U-Boot mailing list, you will avoid most of the common problems
4936  with some other mail clients.
4937
4938  If you cannot use git, use "diff -purN OLD NEW". If your version of
4939  diff does not support these options, then get the latest version of
4940  GNU diff.
4941
4942  The current directory when running this command shall be the parent
4943  directory of the U-Boot source tree (i. e. please make sure that
4944  your patch includes sufficient directory information for the
4945  affected files).
4946
4947  We prefer patches as plain text. MIME attachments are discouraged,
4948  and compressed attachments must not be used.
4949
4950* If one logical set of modifications affects or creates several
4951  files, all these changes shall be submitted in a SINGLE patch file.
4952
4953* Changesets that contain different, unrelated modifications shall be
4954  submitted as SEPARATE patches, one patch per changeset.
4955
4956
4957Notes:
4958
4959* Before sending the patch, run the buildman script on your patched
4960  source tree and make sure that no errors or warnings are reported
4961  for any of the boards.
4962
4963* Keep your modifications to the necessary minimum: A patch
4964  containing several unrelated changes or arbitrary reformats will be
4965  returned with a request to re-formatting / split it.
4966
4967* If you modify existing code, make sure that your new code does not
4968  add to the memory footprint of the code ;-) Small is beautiful!
4969  When adding new features, these should compile conditionally only
4970  (using #ifdef), and the resulting code with the new feature
4971  disabled must not need more memory than the old code without your
4972  modification.
4973
4974* Remember that there is a size limit of 100 kB per message on the
4975  u-boot mailing list. Bigger patches will be moderated. If they are
4976  reasonable and not too big, they will be acknowledged. But patches
4977  bigger than the size limit should be avoided.
4978