uboot/README
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   1# SPDX-License-Identifier: GPL-2.0+
   2#
   3# (C) Copyright 2000 - 2013
   4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   5
   6Summary:
   7========
   8
   9This directory contains the source code for U-Boot, a boot loader for
  10Embedded boards based on PowerPC, ARM, MIPS and several other
  11processors, which can be installed in a boot ROM and used to
  12initialize and test the hardware or to download and run application
  13code.
  14
  15The development of U-Boot is closely related to Linux: some parts of
  16the source code originate in the Linux source tree, we have some
  17header files in common, and special provision has been made to
  18support booting of Linux images.
  19
  20Some attention has been paid to make this software easily
  21configurable and extendable. For instance, all monitor commands are
  22implemented with the same call interface, so that it's very easy to
  23add new commands. Also, instead of permanently adding rarely used
  24code (for instance hardware test utilities) to the monitor, you can
  25load and run it dynamically.
  26
  27
  28Status:
  29=======
  30
  31In general, all boards for which a configuration option exists in the
  32Makefile have been tested to some extent and can be considered
  33"working". In fact, many of them are used in production systems.
  34
  35In case of problems see the CHANGELOG file to find out who contributed
  36the specific port. In addition, there are various MAINTAINERS files
  37scattered throughout the U-Boot source identifying the people or
  38companies responsible for various boards and subsystems.
  39
  40Note: As of August, 2010, there is no longer a CHANGELOG file in the
  41actual U-Boot source tree; however, it can be created dynamically
  42from the Git log using:
  43
  44        make CHANGELOG
  45
  46
  47Where to get help:
  48==================
  49
  50In case you have questions about, problems with or contributions for
  51U-Boot, you should send a message to the U-Boot mailing list at
  52<u-boot@lists.denx.de>. There is also an archive of previous traffic
  53on the mailing list - please search the archive before asking FAQ's.
  54Please see http://lists.denx.de/pipermail/u-boot and
  55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
  56
  57
  58Where to get source code:
  59=========================
  60
  61The U-Boot source code is maintained in the Git repository at
  62git://www.denx.de/git/u-boot.git ; you can browse it online at
  63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
  64
  65The "snapshot" links on this page allow you to download tarballs of
  66any version you might be interested in. Official releases are also
  67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
  68directory.
  69
  70Pre-built (and tested) images are available from
  71ftp://ftp.denx.de/pub/u-boot/images/
  72
  73
  74Where we come from:
  75===================
  76
  77- start from 8xxrom sources
  78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
  79- clean up code
  80- make it easier to add custom boards
  81- make it possible to add other [PowerPC] CPUs
  82- extend functions, especially:
  83  * Provide extended interface to Linux boot loader
  84  * S-Record download
  85  * network boot
  86  * 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 doc/arch/index.rst 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        - for specific scenarios on certain architectures an early BSS *can*
 271          be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
 272          of BSS prior to entering board_init_f()) but doing so is discouraged.
 273          Instead it is strongly recommended to architect any code changes
 274          or additions such to not depend on the availability of BSS during
 275          board_init_f() as indicated in other sections of this README to
 276          maintain compatibility and consistency across the entire code base.
 277        - must return normally from this function (don't call board_init_r()
 278                directly)
 279
 280Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
 281this point the stack and global_data are relocated to below
 282CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
 283memory.
 284
 285board_init_r():
 286        - purpose: main execution, common code
 287        - global_data is available
 288        - SDRAM is available
 289        - BSS is available, all static/global variables can be used
 290        - execution eventually continues to main_loop()
 291
 292        Non-SPL-specific notes:
 293        - U-Boot is relocated to the top of memory and is now running from
 294                there.
 295
 296        SPL-specific notes:
 297        - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
 298                CONFIG_SPL_STACK_R_ADDR points into SDRAM
 299        - preloader_console_init() can be called here - typically this is
 300                done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
 301                spl_board_init() function containing this call
 302        - loads U-Boot or (in falcon mode) Linux
 303
 304
 305
 306Configuration Options:
 307----------------------
 308
 309Configuration depends on the combination of board and CPU type; all
 310such information is kept in a configuration file
 311"include/configs/<board_name>.h".
 312
 313Example: For a TQM823L module, all configuration settings are in
 314"include/configs/TQM823L.h".
 315
 316
 317Many of the options are named exactly as the corresponding Linux
 318kernel configuration options. The intention is to make it easier to
 319build a config tool - later.
 320
 321- ARM Platform Bus Type(CCI):
 322                CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
 323                provides full cache coherency between two clusters of multi-core
 324                CPUs and I/O coherency for devices and I/O masters
 325
 326                CONFIG_SYS_FSL_HAS_CCI400
 327
 328                Defined For SoC that has cache coherent interconnect
 329                CCN-400
 330
 331                CONFIG_SYS_FSL_HAS_CCN504
 332
 333                Defined for SoC that has cache coherent interconnect CCN-504
 334
 335The following options need to be configured:
 336
 337- CPU Type:     Define exactly one, e.g. CONFIG_MPC85XX.
 338
 339- Board Type:   Define exactly one, e.g. CONFIG_MPC8540ADS.
 340
 341- 85xx CPU Options:
 342                CONFIG_SYS_PPC64
 343
 344                Specifies that the core is a 64-bit PowerPC implementation (implements
 345                the "64" category of the Power ISA). This is necessary for ePAPR
 346                compliance, among other possible reasons.
 347
 348                CONFIG_SYS_FSL_TBCLK_DIV
 349
 350                Defines the core time base clock divider ratio compared to the
 351                system clock.  On most PQ3 devices this is 8, on newer QorIQ
 352                devices it can be 16 or 32.  The ratio varies from SoC to Soc.
 353
 354                CONFIG_SYS_FSL_PCIE_COMPAT
 355
 356                Defines the string to utilize when trying to match PCIe device
 357                tree nodes for the given platform.
 358
 359                CONFIG_SYS_FSL_ERRATUM_A004510
 360
 361                Enables a workaround for erratum A004510.  If set,
 362                then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
 363                CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
 364
 365                CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
 366                CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
 367
 368                Defines one or two SoC revisions (low 8 bits of SVR)
 369                for which the A004510 workaround should be applied.
 370
 371                The rest of SVR is either not relevant to the decision
 372                of whether the erratum is present (e.g. p2040 versus
 373                p2041) or is implied by the build target, which controls
 374                whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
 375
 376                See Freescale App Note 4493 for more information about
 377                this erratum.
 378
 379                CONFIG_A003399_NOR_WORKAROUND
 380                Enables a workaround for IFC erratum A003399. It is only
 381                required during NOR boot.
 382
 383                CONFIG_A008044_WORKAROUND
 384                Enables a workaround for T1040/T1042 erratum A008044. It is only
 385                required during NAND boot and valid for Rev 1.0 SoC revision
 386
 387                CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
 388
 389                This is the value to write into CCSR offset 0x18600
 390                according to the A004510 workaround.
 391
 392                CONFIG_SYS_FSL_DSP_DDR_ADDR
 393                This value denotes start offset of DDR memory which is
 394                connected exclusively to the DSP cores.
 395
 396                CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
 397                This value denotes start offset of M2 memory
 398                which is directly connected to the DSP core.
 399
 400                CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
 401                This value denotes start offset of M3 memory which is directly
 402                connected to the DSP core.
 403
 404                CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
 405                This value denotes start offset of DSP CCSR space.
 406
 407                CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
 408                Single Source Clock is clocking mode present in some of FSL SoC's.
 409                In this mode, a single differential clock is used to supply
 410                clocks to the sysclock, ddrclock and usbclock.
 411
 412                CONFIG_SYS_CPC_REINIT_F
 413                This CONFIG is defined when the CPC is configured as SRAM at the
 414                time of U-Boot entry and is required to be re-initialized.
 415
 416                CONFIG_DEEP_SLEEP
 417                Indicates this SoC supports deep sleep feature. If deep sleep is
 418                supported, core will start to execute uboot when wakes up.
 419
 420- Generic CPU options:
 421                CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
 422
 423                Defines the endianess of the CPU. Implementation of those
 424                values is arch specific.
 425
 426                CONFIG_SYS_FSL_DDR
 427                Freescale DDR driver in use. This type of DDR controller is
 428                found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
 429                SoCs.
 430
 431                CONFIG_SYS_FSL_DDR_ADDR
 432                Freescale DDR memory-mapped register base.
 433
 434                CONFIG_SYS_FSL_DDR_EMU
 435                Specify emulator support for DDR. Some DDR features such as
 436                deskew training are not available.
 437
 438                CONFIG_SYS_FSL_DDRC_GEN1
 439                Freescale DDR1 controller.
 440
 441                CONFIG_SYS_FSL_DDRC_GEN2
 442                Freescale DDR2 controller.
 443
 444                CONFIG_SYS_FSL_DDRC_GEN3
 445                Freescale DDR3 controller.
 446
 447                CONFIG_SYS_FSL_DDRC_GEN4
 448                Freescale DDR4 controller.
 449
 450                CONFIG_SYS_FSL_DDRC_ARM_GEN3
 451                Freescale DDR3 controller for ARM-based SoCs.
 452
 453                CONFIG_SYS_FSL_DDR1
 454                Board config to use DDR1. It can be enabled for SoCs with
 455                Freescale DDR1 or DDR2 controllers, depending on the board
 456                implemetation.
 457
 458                CONFIG_SYS_FSL_DDR2
 459                Board config to use DDR2. It can be enabled for SoCs with
 460                Freescale DDR2 or DDR3 controllers, depending on the board
 461                implementation.
 462
 463                CONFIG_SYS_FSL_DDR3
 464                Board config to use DDR3. It can be enabled for SoCs with
 465                Freescale DDR3 or DDR3L controllers.
 466
 467                CONFIG_SYS_FSL_DDR3L
 468                Board config to use DDR3L. It can be enabled for SoCs with
 469                DDR3L controllers.
 470
 471                CONFIG_SYS_FSL_DDR4
 472                Board config to use DDR4. It can be enabled for SoCs with
 473                DDR4 controllers.
 474
 475                CONFIG_SYS_FSL_IFC_BE
 476                Defines the IFC controller register space as Big Endian
 477
 478                CONFIG_SYS_FSL_IFC_LE
 479                Defines the IFC controller register space as Little Endian
 480
 481                CONFIG_SYS_FSL_IFC_CLK_DIV
 482                Defines divider of platform clock(clock input to IFC controller).
 483
 484                CONFIG_SYS_FSL_LBC_CLK_DIV
 485                Defines divider of platform clock(clock input to eLBC controller).
 486
 487                CONFIG_SYS_FSL_PBL_PBI
 488                It enables addition of RCW (Power on reset configuration) in built image.
 489                Please refer doc/README.pblimage for more details
 490
 491                CONFIG_SYS_FSL_PBL_RCW
 492                It adds PBI(pre-boot instructions) commands in u-boot build image.
 493                PBI commands can be used to configure SoC before it starts the execution.
 494                Please refer doc/README.pblimage for more details
 495
 496                CONFIG_SYS_FSL_DDR_BE
 497                Defines the DDR controller register space as Big Endian
 498
 499                CONFIG_SYS_FSL_DDR_LE
 500                Defines the DDR controller register space as Little Endian
 501
 502                CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
 503                Physical address from the view of DDR controllers. It is the
 504                same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
 505                it could be different for ARM SoCs.
 506
 507                CONFIG_SYS_FSL_DDR_INTLV_256B
 508                DDR controller interleaving on 256-byte. This is a special
 509                interleaving mode, handled by Dickens for Freescale layerscape
 510                SoCs with ARM core.
 511
 512                CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
 513                Number of controllers used as main memory.
 514
 515                CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
 516                Number of controllers used for other than main memory.
 517
 518                CONFIG_SYS_FSL_HAS_DP_DDR
 519                Defines the SoC has DP-DDR used for DPAA.
 520
 521                CONFIG_SYS_FSL_SEC_BE
 522                Defines the SEC controller register space as Big Endian
 523
 524                CONFIG_SYS_FSL_SEC_LE
 525                Defines the SEC controller register space as Little Endian
 526
 527- MIPS CPU options:
 528                CONFIG_SYS_INIT_SP_OFFSET
 529
 530                Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
 531                pointer. This is needed for the temporary stack before
 532                relocation.
 533
 534                CONFIG_XWAY_SWAP_BYTES
 535
 536                Enable compilation of tools/xway-swap-bytes needed for Lantiq
 537                XWAY SoCs for booting from NOR flash. The U-Boot image needs to
 538                be swapped if a flash programmer is used.
 539
 540- ARM options:
 541                CONFIG_SYS_EXCEPTION_VECTORS_HIGH
 542
 543                Select high exception vectors of the ARM core, e.g., do not
 544                clear the V bit of the c1 register of CP15.
 545
 546                COUNTER_FREQUENCY
 547                Generic timer clock source frequency.
 548
 549                COUNTER_FREQUENCY_REAL
 550                Generic timer clock source frequency if the real clock is
 551                different from COUNTER_FREQUENCY, and can only be determined
 552                at run time.
 553
 554- Tegra SoC options:
 555                CONFIG_TEGRA_SUPPORT_NON_SECURE
 556
 557                Support executing U-Boot in non-secure (NS) mode. Certain
 558                impossible actions will be skipped if the CPU is in NS mode,
 559                such as ARM architectural timer initialization.
 560
 561- Linux Kernel Interface:
 562                CONFIG_CLOCKS_IN_MHZ
 563
 564                U-Boot stores all clock information in Hz
 565                internally. For binary compatibility with older Linux
 566                kernels (which expect the clocks passed in the
 567                bd_info data to be in MHz) the environment variable
 568                "clocks_in_mhz" can be defined so that U-Boot
 569                converts clock data to MHZ before passing it to the
 570                Linux kernel.
 571                When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
 572                "clocks_in_mhz=1" is automatically included in the
 573                default environment.
 574
 575                CONFIG_MEMSIZE_IN_BYTES         [relevant for MIPS only]
 576
 577                When transferring memsize parameter to Linux, some versions
 578                expect it to be in bytes, others in MB.
 579                Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
 580
 581                CONFIG_OF_LIBFDT
 582
 583                New kernel versions are expecting firmware settings to be
 584                passed using flattened device trees (based on open firmware
 585                concepts).
 586
 587                CONFIG_OF_LIBFDT
 588                 * New libfdt-based support
 589                 * Adds the "fdt" command
 590                 * The bootm command automatically updates the fdt
 591
 592                OF_TBCLK - The timebase frequency.
 593                OF_STDOUT_PATH - The path to the console device
 594
 595                boards with QUICC Engines require OF_QE to set UCC MAC
 596                addresses
 597
 598                CONFIG_OF_BOARD_SETUP
 599
 600                Board code has addition modification that it wants to make
 601                to the flat device tree before handing it off to the kernel
 602
 603                CONFIG_OF_SYSTEM_SETUP
 604
 605                Other code has addition modification that it wants to make
 606                to the flat device tree before handing it off to the kernel.
 607                This causes ft_system_setup() to be called before booting
 608                the kernel.
 609
 610                CONFIG_OF_IDE_FIXUP
 611
 612                U-Boot can detect if an IDE device is present or not.
 613                If not, and this new config option is activated, U-Boot
 614                removes the ATA node from the DTS before booting Linux,
 615                so the Linux IDE driver does not probe the device and
 616                crash. This is needed for buggy hardware (uc101) where
 617                no pull down resistor is connected to the signal IDE5V_DD7.
 618
 619                CONFIG_MACH_TYPE        [relevant for ARM only][mandatory]
 620
 621                This setting is mandatory for all boards that have only one
 622                machine type and must be used to specify the machine type
 623                number as it appears in the ARM machine registry
 624                (see http://www.arm.linux.org.uk/developer/machines/).
 625                Only boards that have multiple machine types supported
 626                in a single configuration file and the machine type is
 627                runtime discoverable, do not have to use this setting.
 628
 629- vxWorks boot parameters:
 630
 631                bootvx constructs a valid bootline using the following
 632                environments variables: bootdev, bootfile, ipaddr, netmask,
 633                serverip, gatewayip, hostname, othbootargs.
 634                It loads the vxWorks image pointed bootfile.
 635
 636                Note: If a "bootargs" environment is defined, it will overwride
 637                the defaults discussed just above.
 638
 639- Cache Configuration:
 640                CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
 641
 642- Cache Configuration for ARM:
 643                CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
 644                                      controller
 645                CONFIG_SYS_PL310_BASE - Physical base address of PL310
 646                                        controller register space
 647
 648- Serial Ports:
 649                CONFIG_PL010_SERIAL
 650
 651                Define this if you want support for Amba PrimeCell PL010 UARTs.
 652
 653                CONFIG_PL011_SERIAL
 654
 655                Define this if you want support for Amba PrimeCell PL011 UARTs.
 656
 657                CONFIG_PL011_CLOCK
 658
 659                If you have Amba PrimeCell PL011 UARTs, set this variable to
 660                the clock speed of the UARTs.
 661
 662                CONFIG_PL01x_PORTS
 663
 664                If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
 665                define this to a list of base addresses for each (supported)
 666                port. See e.g. include/configs/versatile.h
 667
 668                CONFIG_SERIAL_HW_FLOW_CONTROL
 669
 670                Define this variable to enable hw flow control in serial driver.
 671                Current user of this option is drivers/serial/nsl16550.c driver
 672
 673- Console Baudrate:
 674                CONFIG_BAUDRATE - in bps
 675                Select one of the baudrates listed in
 676                CONFIG_SYS_BAUDRATE_TABLE, see below.
 677
 678- Autoboot Command:
 679                CONFIG_BOOTCOMMAND
 680                Only needed when CONFIG_BOOTDELAY is enabled;
 681                define a command string that is automatically executed
 682                when no character is read on the console interface
 683                within "Boot Delay" after reset.
 684
 685                CONFIG_RAMBOOT and CONFIG_NFSBOOT
 686                The value of these goes into the environment as
 687                "ramboot" and "nfsboot" respectively, and can be used
 688                as a convenience, when switching between booting from
 689                RAM and NFS.
 690
 691- Serial Download Echo Mode:
 692                CONFIG_LOADS_ECHO
 693                If defined to 1, all characters received during a
 694                serial download (using the "loads" command) are
 695                echoed back. This might be needed by some terminal
 696                emulations (like "cu"), but may as well just take
 697                time on others. This setting #define's the initial
 698                value of the "loads_echo" environment variable.
 699
 700- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
 701                CONFIG_KGDB_BAUDRATE
 702                Select one of the baudrates listed in
 703                CONFIG_SYS_BAUDRATE_TABLE, see below.
 704
 705- Removal of commands
 706                If no commands are needed to boot, you can disable
 707                CONFIG_CMDLINE to remove them. In this case, the command line
 708                will not be available, and when U-Boot wants to execute the
 709                boot command (on start-up) it will call board_run_command()
 710                instead. This can reduce image size significantly for very
 711                simple boot procedures.
 712
 713- Regular expression support:
 714                CONFIG_REGEX
 715                If this variable is defined, U-Boot is linked against
 716                the SLRE (Super Light Regular Expression) library,
 717                which adds regex support to some commands, as for
 718                example "env grep" and "setexpr".
 719
 720- Device tree:
 721                CONFIG_OF_CONTROL
 722                If this variable is defined, U-Boot will use a device tree
 723                to configure its devices, instead of relying on statically
 724                compiled #defines in the board file. This option is
 725                experimental and only available on a few boards. The device
 726                tree is available in the global data as gd->fdt_blob.
 727
 728                U-Boot needs to get its device tree from somewhere. This can
 729                be done using one of the three options below:
 730
 731                CONFIG_OF_EMBED
 732                If this variable is defined, U-Boot will embed a device tree
 733                binary in its image. This device tree file should be in the
 734                board directory and called <soc>-<board>.dts. The binary file
 735                is then picked up in board_init_f() and made available through
 736                the global data structure as gd->fdt_blob.
 737
 738                CONFIG_OF_SEPARATE
 739                If this variable is defined, U-Boot will build a device tree
 740                binary. It will be called u-boot.dtb. Architecture-specific
 741                code will locate it at run-time. Generally this works by:
 742
 743                        cat u-boot.bin u-boot.dtb >image.bin
 744
 745                and in fact, U-Boot does this for you, creating a file called
 746                u-boot-dtb.bin which is useful in the common case. You can
 747                still use the individual files if you need something more
 748                exotic.
 749
 750                CONFIG_OF_BOARD
 751                If this variable is defined, U-Boot will use the device tree
 752                provided by the board at runtime instead of embedding one with
 753                the image. Only boards defining board_fdt_blob_setup() support
 754                this option (see include/fdtdec.h file).
 755
 756- Watchdog:
 757                CONFIG_WATCHDOG
 758                If this variable is defined, it enables watchdog
 759                support for the SoC. There must be support in the SoC
 760                specific code for a watchdog. For the 8xx
 761                CPUs, the SIU Watchdog feature is enabled in the SYPCR
 762                register.  When supported for a specific SoC is
 763                available, then no further board specific code should
 764                be needed to use it.
 765
 766                CONFIG_HW_WATCHDOG
 767                When using a watchdog circuitry external to the used
 768                SoC, then define this variable and provide board
 769                specific code for the "hw_watchdog_reset" function.
 770
 771- Real-Time Clock:
 772
 773                When CONFIG_CMD_DATE is selected, the type of the RTC
 774                has to be selected, too. Define exactly one of the
 775                following options:
 776
 777                CONFIG_RTC_PCF8563      - use Philips PCF8563 RTC
 778                CONFIG_RTC_MC13XXX      - use MC13783 or MC13892 RTC
 779                CONFIG_RTC_MC146818     - use MC146818 RTC
 780                CONFIG_RTC_DS1307       - use Maxim, Inc. DS1307 RTC
 781                CONFIG_RTC_DS1337       - use Maxim, Inc. DS1337 RTC
 782                CONFIG_RTC_DS1338       - use Maxim, Inc. DS1338 RTC
 783                CONFIG_RTC_DS1339       - use Maxim, Inc. DS1339 RTC
 784                CONFIG_RTC_DS164x       - use Dallas DS164x RTC
 785                CONFIG_RTC_ISL1208      - use Intersil ISL1208 RTC
 786                CONFIG_RTC_MAX6900      - use Maxim, Inc. MAX6900 RTC
 787                CONFIG_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
 788                CONFIG_SYS_RV3029_TCR   - enable trickle charger on
 789                                          RV3029 RTC.
 790
 791                Note that if the RTC uses I2C, then the I2C interface
 792                must also be configured. See I2C Support, below.
 793
 794- GPIO Support:
 795                CONFIG_PCA953X          - use NXP's PCA953X series I2C GPIO
 796
 797                The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
 798                chip-ngpio pairs that tell the PCA953X driver the number of
 799                pins supported by a particular chip.
 800
 801                Note that if the GPIO device uses I2C, then the I2C interface
 802                must also be configured. See I2C Support, below.
 803
 804- I/O tracing:
 805                When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
 806                accesses and can checksum them or write a list of them out
 807                to memory. See the 'iotrace' command for details. This is
 808                useful for testing device drivers since it can confirm that
 809                the driver behaves the same way before and after a code
 810                change. Currently this is supported on sandbox and arm. To
 811                add support for your architecture, add '#include <iotrace.h>'
 812                to the bottom of arch/<arch>/include/asm/io.h and test.
 813
 814                Example output from the 'iotrace stats' command is below.
 815                Note that if the trace buffer is exhausted, the checksum will
 816                still continue to operate.
 817
 818                        iotrace is enabled
 819                        Start:  10000000        (buffer start address)
 820                        Size:   00010000        (buffer size)
 821                        Offset: 00000120        (current buffer offset)
 822                        Output: 10000120        (start + offset)
 823                        Count:  00000018        (number of trace records)
 824                        CRC32:  9526fb66        (CRC32 of all trace records)
 825
 826- Timestamp Support:
 827
 828                When CONFIG_TIMESTAMP is selected, the timestamp
 829                (date and time) of an image is printed by image
 830                commands like bootm or iminfo. This option is
 831                automatically enabled when you select CONFIG_CMD_DATE .
 832
 833- Partition Labels (disklabels) Supported:
 834                Zero or more of the following:
 835                CONFIG_MAC_PARTITION   Apple's MacOS partition table.
 836                CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
 837                CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
 838                                       bootloader.  Note 2TB partition limit; see
 839                                       disk/part_efi.c
 840                CONFIG_SCSI) you must configure support for at
 841                least one non-MTD partition type as well.
 842
 843- IDE Reset method:
 844                CONFIG_IDE_RESET_ROUTINE - this is defined in several
 845                board configurations files but used nowhere!
 846
 847                CONFIG_IDE_RESET - is this is defined, IDE Reset will
 848                be performed by calling the function
 849                        ide_set_reset(int reset)
 850                which has to be defined in a board specific file
 851
 852- ATAPI Support:
 853                CONFIG_ATAPI
 854
 855                Set this to enable ATAPI support.
 856
 857- LBA48 Support
 858                CONFIG_LBA48
 859
 860                Set this to enable support for disks larger than 137GB
 861                Also look at CONFIG_SYS_64BIT_LBA.
 862                Whithout these , LBA48 support uses 32bit variables and will 'only'
 863                support disks up to 2.1TB.
 864
 865                CONFIG_SYS_64BIT_LBA:
 866                        When enabled, makes the IDE subsystem use 64bit sector addresses.
 867                        Default is 32bit.
 868
 869- SCSI Support:
 870                CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
 871                CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
 872                CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
 873                maximum numbers of LUNs, SCSI ID's and target
 874                devices.
 875
 876                The environment variable 'scsidevs' is set to the number of
 877                SCSI devices found during the last scan.
 878
 879- NETWORK Support (PCI):
 880                CONFIG_E1000
 881                Support for Intel 8254x/8257x gigabit chips.
 882
 883                CONFIG_E1000_SPI
 884                Utility code for direct access to the SPI bus on Intel 8257x.
 885                This does not do anything useful unless you set at least one
 886                of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
 887
 888                CONFIG_E1000_SPI_GENERIC
 889                Allow generic access to the SPI bus on the Intel 8257x, for
 890                example with the "sspi" command.
 891
 892                CONFIG_EEPRO100
 893                Support for Intel 82557/82559/82559ER chips.
 894                Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
 895                write routine for first time initialisation.
 896
 897                CONFIG_TULIP
 898                Support for Digital 2114x chips.
 899                Optional CONFIG_TULIP_SELECT_MEDIA for board specific
 900                modem chip initialisation (KS8761/QS6611).
 901
 902                CONFIG_NATSEMI
 903                Support for National dp83815 chips.
 904
 905                CONFIG_NS8382X
 906                Support for National dp8382[01] gigabit chips.
 907
 908- NETWORK Support (other):
 909
 910                CONFIG_DRIVER_AT91EMAC
 911                Support for AT91RM9200 EMAC.
 912
 913                        CONFIG_RMII
 914                        Define this to use reduced MII inteface
 915
 916                        CONFIG_DRIVER_AT91EMAC_QUIET
 917                        If this defined, the driver is quiet.
 918                        The driver doen't show link status messages.
 919
 920                CONFIG_CALXEDA_XGMAC
 921                Support for the Calxeda XGMAC device
 922
 923                CONFIG_LAN91C96
 924                Support for SMSC's LAN91C96 chips.
 925
 926                        CONFIG_LAN91C96_USE_32_BIT
 927                        Define this to enable 32 bit addressing
 928
 929                CONFIG_SMC91111
 930                Support for SMSC's LAN91C111 chip
 931
 932                        CONFIG_SMC91111_BASE
 933                        Define this to hold the physical address
 934                        of the device (I/O space)
 935
 936                        CONFIG_SMC_USE_32_BIT
 937                        Define this if data bus is 32 bits
 938
 939                        CONFIG_SMC_USE_IOFUNCS
 940                        Define this to use i/o functions instead of macros
 941                        (some hardware wont work with macros)
 942
 943                        CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
 944                        Define this if you have more then 3 PHYs.
 945
 946                CONFIG_FTGMAC100
 947                Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
 948
 949                        CONFIG_FTGMAC100_EGIGA
 950                        Define this to use GE link update with gigabit PHY.
 951                        Define this if FTGMAC100 is connected to gigabit PHY.
 952                        If your system has 10/100 PHY only, it might not occur
 953                        wrong behavior. Because PHY usually return timeout or
 954                        useless data when polling gigabit status and gigabit
 955                        control registers. This behavior won't affect the
 956                        correctnessof 10/100 link speed update.
 957
 958                CONFIG_SH_ETHER
 959                Support for Renesas on-chip Ethernet controller
 960
 961                        CONFIG_SH_ETHER_USE_PORT
 962                        Define the number of ports to be used
 963
 964                        CONFIG_SH_ETHER_PHY_ADDR
 965                        Define the ETH PHY's address
 966
 967                        CONFIG_SH_ETHER_CACHE_WRITEBACK
 968                        If this option is set, the driver enables cache flush.
 969
 970- TPM Support:
 971                CONFIG_TPM
 972                Support TPM devices.
 973
 974                CONFIG_TPM_TIS_INFINEON
 975                Support for Infineon i2c bus TPM devices. Only one device
 976                per system is supported at this time.
 977
 978                        CONFIG_TPM_TIS_I2C_BURST_LIMITATION
 979                        Define the burst count bytes upper limit
 980
 981                CONFIG_TPM_ST33ZP24
 982                Support for STMicroelectronics TPM devices. Requires DM_TPM support.
 983
 984                        CONFIG_TPM_ST33ZP24_I2C
 985                        Support for STMicroelectronics ST33ZP24 I2C devices.
 986                        Requires TPM_ST33ZP24 and I2C.
 987
 988                        CONFIG_TPM_ST33ZP24_SPI
 989                        Support for STMicroelectronics ST33ZP24 SPI devices.
 990                        Requires TPM_ST33ZP24 and SPI.
 991
 992                CONFIG_TPM_ATMEL_TWI
 993                Support for Atmel TWI TPM device. Requires I2C support.
 994
 995                CONFIG_TPM_TIS_LPC
 996                Support for generic parallel port TPM devices. Only one device
 997                per system is supported at this time.
 998
 999                        CONFIG_TPM_TIS_BASE_ADDRESS
1000                        Base address where the generic TPM device is mapped
1001                        to. Contemporary x86 systems usually map it at
1002                        0xfed40000.
1003
1004                CONFIG_TPM
1005                Define this to enable the TPM support library which provides
1006                functional interfaces to some TPM commands.
1007                Requires support for a TPM device.
1008
1009                CONFIG_TPM_AUTH_SESSIONS
1010                Define this to enable authorized functions in the TPM library.
1011                Requires CONFIG_TPM and CONFIG_SHA1.
1012
1013- USB Support:
1014                At the moment only the UHCI host controller is
1015                supported (PIP405, MIP405); define
1016                CONFIG_USB_UHCI to enable it.
1017                define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1018                and define CONFIG_USB_STORAGE to enable the USB
1019                storage devices.
1020                Note:
1021                Supported are USB Keyboards and USB Floppy drives
1022                (TEAC FD-05PUB).
1023
1024                CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1025                txfilltuning field in the EHCI controller on reset.
1026
1027                CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1028                HW module registers.
1029
1030- USB Device:
1031                Define the below if you wish to use the USB console.
1032                Once firmware is rebuilt from a serial console issue the
1033                command "setenv stdin usbtty; setenv stdout usbtty" and
1034                attach your USB cable. The Unix command "dmesg" should print
1035                it has found a new device. The environment variable usbtty
1036                can be set to gserial or cdc_acm to enable your device to
1037                appear to a USB host as a Linux gserial device or a
1038                Common Device Class Abstract Control Model serial device.
1039                If you select usbtty = gserial you should be able to enumerate
1040                a Linux host by
1041                # modprobe usbserial vendor=0xVendorID product=0xProductID
1042                else if using cdc_acm, simply setting the environment
1043                variable usbtty to be cdc_acm should suffice. The following
1044                might be defined in YourBoardName.h
1045
1046                        CONFIG_USB_DEVICE
1047                        Define this to build a UDC device
1048
1049                        CONFIG_USB_TTY
1050                        Define this to have a tty type of device available to
1051                        talk to the UDC device
1052
1053                        CONFIG_USBD_HS
1054                        Define this to enable the high speed support for usb
1055                        device and usbtty. If this feature is enabled, a routine
1056                        int is_usbd_high_speed(void)
1057                        also needs to be defined by the driver to dynamically poll
1058                        whether the enumeration has succeded at high speed or full
1059                        speed.
1060
1061                        CONFIG_SYS_CONSOLE_IS_IN_ENV
1062                        Define this if you want stdin, stdout &/or stderr to
1063                        be set to usbtty.
1064
1065                If you have a USB-IF assigned VendorID then you may wish to
1066                define your own vendor specific values either in BoardName.h
1067                or directly in usbd_vendor_info.h. If you don't define
1068                CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1069                CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1070                should pretend to be a Linux device to it's target host.
1071
1072                        CONFIG_USBD_MANUFACTURER
1073                        Define this string as the name of your company for
1074                        - CONFIG_USBD_MANUFACTURER "my company"
1075
1076                        CONFIG_USBD_PRODUCT_NAME
1077                        Define this string as the name of your product
1078                        - CONFIG_USBD_PRODUCT_NAME "acme usb device"
1079
1080                        CONFIG_USBD_VENDORID
1081                        Define this as your assigned Vendor ID from the USB
1082                        Implementors Forum. This *must* be a genuine Vendor ID
1083                        to avoid polluting the USB namespace.
1084                        - CONFIG_USBD_VENDORID 0xFFFF
1085
1086                        CONFIG_USBD_PRODUCTID
1087                        Define this as the unique Product ID
1088                        for your device
1089                        - CONFIG_USBD_PRODUCTID 0xFFFF
1090
1091- ULPI Layer Support:
1092                The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1093                the generic ULPI layer. The generic layer accesses the ULPI PHY
1094                via the platform viewport, so you need both the genric layer and
1095                the viewport enabled. Currently only Chipidea/ARC based
1096                viewport is supported.
1097                To enable the ULPI layer support, define CONFIG_USB_ULPI and
1098                CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1099                If your ULPI phy needs a different reference clock than the
1100                standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1101                the appropriate value in Hz.
1102
1103- MMC Support:
1104                The MMC controller on the Intel PXA is supported. To
1105                enable this define CONFIG_MMC. The MMC can be
1106                accessed from the boot prompt by mapping the device
1107                to physical memory similar to flash. Command line is
1108                enabled with CONFIG_CMD_MMC. The MMC driver also works with
1109                the FAT fs. This is enabled with CONFIG_CMD_FAT.
1110
1111                CONFIG_SH_MMCIF
1112                Support for Renesas on-chip MMCIF controller
1113
1114                        CONFIG_SH_MMCIF_ADDR
1115                        Define the base address of MMCIF registers
1116
1117                        CONFIG_SH_MMCIF_CLK
1118                        Define the clock frequency for MMCIF
1119
1120- USB Device Firmware Update (DFU) class support:
1121                CONFIG_DFU_OVER_USB
1122                This enables the USB portion of the DFU USB class
1123
1124                CONFIG_DFU_NAND
1125                This enables support for exposing NAND devices via DFU.
1126
1127                CONFIG_DFU_RAM
1128                This enables support for exposing RAM via DFU.
1129                Note: DFU spec refer to non-volatile memory usage, but
1130                allow usages beyond the scope of spec - here RAM usage,
1131                one that would help mostly the developer.
1132
1133                CONFIG_SYS_DFU_DATA_BUF_SIZE
1134                Dfu transfer uses a buffer before writing data to the
1135                raw storage device. Make the size (in bytes) of this buffer
1136                configurable. The size of this buffer is also configurable
1137                through the "dfu_bufsiz" environment variable.
1138
1139                CONFIG_SYS_DFU_MAX_FILE_SIZE
1140                When updating files rather than the raw storage device,
1141                we use a static buffer to copy the file into and then write
1142                the buffer once we've been given the whole file.  Define
1143                this to the maximum filesize (in bytes) for the buffer.
1144                Default is 4 MiB if undefined.
1145
1146                DFU_DEFAULT_POLL_TIMEOUT
1147                Poll timeout [ms], is the timeout a device can send to the
1148                host. The host must wait for this timeout before sending
1149                a subsequent DFU_GET_STATUS request to the device.
1150
1151                DFU_MANIFEST_POLL_TIMEOUT
1152                Poll timeout [ms], which the device sends to the host when
1153                entering dfuMANIFEST state. Host waits this timeout, before
1154                sending again an USB request to the device.
1155
1156- Journaling Flash filesystem support:
1157                CONFIG_JFFS2_NAND
1158                Define these for a default partition on a NAND device
1159
1160                CONFIG_SYS_JFFS2_FIRST_SECTOR,
1161                CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1162                Define these for a default partition on a NOR device
1163
1164- Keyboard Support:
1165                See Kconfig help for available keyboard drivers.
1166
1167                CONFIG_KEYBOARD
1168
1169                Define this to enable a custom keyboard support.
1170                This simply calls drv_keyboard_init() which must be
1171                defined in your board-specific files. This option is deprecated
1172                and is only used by novena. For new boards, use driver model
1173                instead.
1174
1175- Video support:
1176                CONFIG_FSL_DIU_FB
1177                Enable the Freescale DIU video driver.  Reference boards for
1178                SOCs that have a DIU should define this macro to enable DIU
1179                support, and should also define these other macros:
1180
1181                        CONFIG_SYS_DIU_ADDR
1182                        CONFIG_VIDEO
1183                        CONFIG_CFB_CONSOLE
1184                        CONFIG_VIDEO_SW_CURSOR
1185                        CONFIG_VGA_AS_SINGLE_DEVICE
1186                        CONFIG_VIDEO_LOGO
1187                        CONFIG_VIDEO_BMP_LOGO
1188
1189                The DIU driver will look for the 'video-mode' environment
1190                variable, and if defined, enable the DIU as a console during
1191                boot.  See the documentation file doc/README.video for a
1192                description of this variable.
1193
1194- LCD Support:  CONFIG_LCD
1195
1196                Define this to enable LCD support (for output to LCD
1197                display); also select one of the supported displays
1198                by defining one of these:
1199
1200                CONFIG_ATMEL_LCD:
1201
1202                        HITACHI TX09D70VM1CCA, 3.5", 240x320.
1203
1204                CONFIG_NEC_NL6448AC33:
1205
1206                        NEC NL6448AC33-18. Active, color, single scan.
1207
1208                CONFIG_NEC_NL6448BC20
1209
1210                        NEC NL6448BC20-08. 6.5", 640x480.
1211                        Active, color, single scan.
1212
1213                CONFIG_NEC_NL6448BC33_54
1214
1215                        NEC NL6448BC33-54. 10.4", 640x480.
1216                        Active, color, single scan.
1217
1218                CONFIG_SHARP_16x9
1219
1220                        Sharp 320x240. Active, color, single scan.
1221                        It isn't 16x9, and I am not sure what it is.
1222
1223                CONFIG_SHARP_LQ64D341
1224
1225                        Sharp LQ64D341 display, 640x480.
1226                        Active, color, single scan.
1227
1228                CONFIG_HLD1045
1229
1230                        HLD1045 display, 640x480.
1231                        Active, color, single scan.
1232
1233                CONFIG_OPTREX_BW
1234
1235                        Optrex   CBL50840-2 NF-FW 99 22 M5
1236                        or
1237                        Hitachi  LMG6912RPFC-00T
1238                        or
1239                        Hitachi  SP14Q002
1240
1241                        320x240. Black & white.
1242
1243                CONFIG_LCD_ALIGNMENT
1244
1245                Normally the LCD is page-aligned (typically 4KB). If this is
1246                defined then the LCD will be aligned to this value instead.
1247                For ARM it is sometimes useful to use MMU_SECTION_SIZE
1248                here, since it is cheaper to change data cache settings on
1249                a per-section basis.
1250
1251
1252                CONFIG_LCD_ROTATION
1253
1254                Sometimes, for example if the display is mounted in portrait
1255                mode or even if it's mounted landscape but rotated by 180degree,
1256                we need to rotate our content of the display relative to the
1257                framebuffer, so that user can read the messages which are
1258                printed out.
1259                Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1260                initialized with a given rotation from "vl_rot" out of
1261                "vidinfo_t" which is provided by the board specific code.
1262                The value for vl_rot is coded as following (matching to
1263                fbcon=rotate:<n> linux-kernel commandline):
1264                0 = no rotation respectively 0 degree
1265                1 = 90 degree rotation
1266                2 = 180 degree rotation
1267                3 = 270 degree rotation
1268
1269                If CONFIG_LCD_ROTATION is not defined, the console will be
1270                initialized with 0degree rotation.
1271
1272                CONFIG_LCD_BMP_RLE8
1273
1274                Support drawing of RLE8-compressed bitmaps on the LCD.
1275
1276                CONFIG_I2C_EDID
1277
1278                Enables an 'i2c edid' command which can read EDID
1279                information over I2C from an attached LCD display.
1280
1281- Splash Screen Support: CONFIG_SPLASH_SCREEN
1282
1283                If this option is set, the environment is checked for
1284                a variable "splashimage". If found, the usual display
1285                of logo, copyright and system information on the LCD
1286                is suppressed and the BMP image at the address
1287                specified in "splashimage" is loaded instead. The
1288                console is redirected to the "nulldev", too. This
1289                allows for a "silent" boot where a splash screen is
1290                loaded very quickly after power-on.
1291
1292                CONFIG_SPLASHIMAGE_GUARD
1293
1294                If this option is set, then U-Boot will prevent the environment
1295                variable "splashimage" from being set to a problematic address
1296                (see doc/README.displaying-bmps).
1297                This option is useful for targets where, due to alignment
1298                restrictions, an improperly aligned BMP image will cause a data
1299                abort. If you think you will not have problems with unaligned
1300                accesses (for example because your toolchain prevents them)
1301                there is no need to set this option.
1302
1303                CONFIG_SPLASH_SCREEN_ALIGN
1304
1305                If this option is set the splash image can be freely positioned
1306                on the screen. Environment variable "splashpos" specifies the
1307                position as "x,y". If a positive number is given it is used as
1308                number of pixel from left/top. If a negative number is given it
1309                is used as number of pixel from right/bottom. You can also
1310                specify 'm' for centering the image.
1311
1312                Example:
1313                setenv splashpos m,m
1314                        => image at center of screen
1315
1316                setenv splashpos 30,20
1317                        => image at x = 30 and y = 20
1318
1319                setenv splashpos -10,m
1320                        => vertically centered image
1321                           at x = dspWidth - bmpWidth - 9
1322
1323- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1324
1325                If this option is set, additionally to standard BMP
1326                images, gzipped BMP images can be displayed via the
1327                splashscreen support or the bmp command.
1328
1329- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1330
1331                If this option is set, 8-bit RLE compressed BMP images
1332                can be displayed via the splashscreen support or the
1333                bmp command.
1334
1335- Compression support:
1336                CONFIG_GZIP
1337
1338                Enabled by default to support gzip compressed images.
1339
1340                CONFIG_BZIP2
1341
1342                If this option is set, support for bzip2 compressed
1343                images is included. If not, only uncompressed and gzip
1344                compressed images are supported.
1345
1346                NOTE: the bzip2 algorithm requires a lot of RAM, so
1347                the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1348                be at least 4MB.
1349
1350- MII/PHY support:
1351                CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1352
1353                The clock frequency of the MII bus
1354
1355                CONFIG_PHY_RESET_DELAY
1356
1357                Some PHY like Intel LXT971A need extra delay after
1358                reset before any MII register access is possible.
1359                For such PHY, set this option to the usec delay
1360                required. (minimum 300usec for LXT971A)
1361
1362                CONFIG_PHY_CMD_DELAY (ppc4xx)
1363
1364                Some PHY like Intel LXT971A need extra delay after
1365                command issued before MII status register can be read
1366
1367- IP address:
1368                CONFIG_IPADDR
1369
1370                Define a default value for the IP address to use for
1371                the default Ethernet interface, in case this is not
1372                determined through e.g. bootp.
1373                (Environment variable "ipaddr")
1374
1375- Server IP address:
1376                CONFIG_SERVERIP
1377
1378                Defines a default value for the IP address of a TFTP
1379                server to contact when using the "tftboot" command.
1380                (Environment variable "serverip")
1381
1382                CONFIG_KEEP_SERVERADDR
1383
1384                Keeps the server's MAC address, in the env 'serveraddr'
1385                for passing to bootargs (like Linux's netconsole option)
1386
1387- Gateway IP address:
1388                CONFIG_GATEWAYIP
1389
1390                Defines a default value for the IP address of the
1391                default router where packets to other networks are
1392                sent to.
1393                (Environment variable "gatewayip")
1394
1395- Subnet mask:
1396                CONFIG_NETMASK
1397
1398                Defines a default value for the subnet mask (or
1399                routing prefix) which is used to determine if an IP
1400                address belongs to the local subnet or needs to be
1401                forwarded through a router.
1402                (Environment variable "netmask")
1403
1404- BOOTP Recovery Mode:
1405                CONFIG_BOOTP_RANDOM_DELAY
1406
1407                If you have many targets in a network that try to
1408                boot using BOOTP, you may want to avoid that all
1409                systems send out BOOTP requests at precisely the same
1410                moment (which would happen for instance at recovery
1411                from a power failure, when all systems will try to
1412                boot, thus flooding the BOOTP server. Defining
1413                CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1414                inserted before sending out BOOTP requests. The
1415                following delays are inserted then:
1416
1417                1st BOOTP request:      delay 0 ... 1 sec
1418                2nd BOOTP request:      delay 0 ... 2 sec
1419                3rd BOOTP request:      delay 0 ... 4 sec
1420                4th and following
1421                BOOTP requests:         delay 0 ... 8 sec
1422
1423                CONFIG_BOOTP_ID_CACHE_SIZE
1424
1425                BOOTP packets are uniquely identified using a 32-bit ID. The
1426                server will copy the ID from client requests to responses and
1427                U-Boot will use this to determine if it is the destination of
1428                an incoming response. Some servers will check that addresses
1429                aren't in use before handing them out (usually using an ARP
1430                ping) and therefore take up to a few hundred milliseconds to
1431                respond. Network congestion may also influence the time it
1432                takes for a response to make it back to the client. If that
1433                time is too long, U-Boot will retransmit requests. In order
1434                to allow earlier responses to still be accepted after these
1435                retransmissions, U-Boot's BOOTP client keeps a small cache of
1436                IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1437                cache. The default is to keep IDs for up to four outstanding
1438                requests. Increasing this will allow U-Boot to accept offers
1439                from a BOOTP client in networks with unusually high latency.
1440
1441- DHCP Advanced Options:
1442                You can fine tune the DHCP functionality by defining
1443                CONFIG_BOOTP_* symbols:
1444
1445                CONFIG_BOOTP_NISDOMAIN
1446                CONFIG_BOOTP_BOOTFILESIZE
1447                CONFIG_BOOTP_SEND_HOSTNAME
1448                CONFIG_BOOTP_NTPSERVER
1449                CONFIG_BOOTP_TIMEOFFSET
1450                CONFIG_BOOTP_VENDOREX
1451                CONFIG_BOOTP_MAY_FAIL
1452
1453                CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1454                environment variable, not the BOOTP server.
1455
1456                CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1457                after the configured retry count, the call will fail
1458                instead of starting over.  This can be used to fail over
1459                to Link-local IP address configuration if the DHCP server
1460                is not available.
1461
1462                CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1463                to do a dynamic update of a DNS server. To do this, they
1464                need the hostname of the DHCP requester.
1465                If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1466                of the "hostname" environment variable is passed as
1467                option 12 to the DHCP server.
1468
1469                CONFIG_BOOTP_DHCP_REQUEST_DELAY
1470
1471                A 32bit value in microseconds for a delay between
1472                receiving a "DHCP Offer" and sending the "DHCP Request".
1473                This fixes a problem with certain DHCP servers that don't
1474                respond 100% of the time to a "DHCP request". E.g. On an
1475                AT91RM9200 processor running at 180MHz, this delay needed
1476                to be *at least* 15,000 usec before a Windows Server 2003
1477                DHCP server would reply 100% of the time. I recommend at
1478                least 50,000 usec to be safe. The alternative is to hope
1479                that one of the retries will be successful but note that
1480                the DHCP timeout and retry process takes a longer than
1481                this delay.
1482
1483 - Link-local IP address negotiation:
1484                Negotiate with other link-local clients on the local network
1485                for an address that doesn't require explicit configuration.
1486                This is especially useful if a DHCP server cannot be guaranteed
1487                to exist in all environments that the device must operate.
1488
1489                See doc/README.link-local for more information.
1490
1491 - MAC address from environment variables
1492
1493                FDT_SEQ_MACADDR_FROM_ENV
1494
1495                Fix-up device tree with MAC addresses fetched sequentially from
1496                environment variables. This config work on assumption that
1497                non-usable ethernet node of device-tree are either not present
1498                or their status has been marked as "disabled".
1499
1500 - CDP Options:
1501                CONFIG_CDP_DEVICE_ID
1502
1503                The device id used in CDP trigger frames.
1504
1505                CONFIG_CDP_DEVICE_ID_PREFIX
1506
1507                A two character string which is prefixed to the MAC address
1508                of the device.
1509
1510                CONFIG_CDP_PORT_ID
1511
1512                A printf format string which contains the ascii name of
1513                the port. Normally is set to "eth%d" which sets
1514                eth0 for the first Ethernet, eth1 for the second etc.
1515
1516                CONFIG_CDP_CAPABILITIES
1517
1518                A 32bit integer which indicates the device capabilities;
1519                0x00000010 for a normal host which does not forwards.
1520
1521                CONFIG_CDP_VERSION
1522
1523                An ascii string containing the version of the software.
1524
1525                CONFIG_CDP_PLATFORM
1526
1527                An ascii string containing the name of the platform.
1528
1529                CONFIG_CDP_TRIGGER
1530
1531                A 32bit integer sent on the trigger.
1532
1533                CONFIG_CDP_POWER_CONSUMPTION
1534
1535                A 16bit integer containing the power consumption of the
1536                device in .1 of milliwatts.
1537
1538                CONFIG_CDP_APPLIANCE_VLAN_TYPE
1539
1540                A byte containing the id of the VLAN.
1541
1542- Status LED:   CONFIG_LED_STATUS
1543
1544                Several configurations allow to display the current
1545                status using a LED. For instance, the LED will blink
1546                fast while running U-Boot code, stop blinking as
1547                soon as a reply to a BOOTP request was received, and
1548                start blinking slow once the Linux kernel is running
1549                (supported by a status LED driver in the Linux
1550                kernel). Defining CONFIG_LED_STATUS enables this
1551                feature in U-Boot.
1552
1553                Additional options:
1554
1555                CONFIG_LED_STATUS_GPIO
1556                The status LED can be connected to a GPIO pin.
1557                In such cases, the gpio_led driver can be used as a
1558                status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1559                to include the gpio_led driver in the U-Boot binary.
1560
1561                CONFIG_GPIO_LED_INVERTED_TABLE
1562                Some GPIO connected LEDs may have inverted polarity in which
1563                case the GPIO high value corresponds to LED off state and
1564                GPIO low value corresponds to LED on state.
1565                In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1566                with a list of GPIO LEDs that have inverted polarity.
1567
1568- I2C Support:  CONFIG_SYS_I2C
1569
1570                This enable the NEW i2c subsystem, and will allow you to use
1571                i2c commands at the u-boot command line (as long as you set
1572                CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1573                based realtime clock chips or other i2c devices. See
1574                common/cmd_i2c.c for a description of the command line
1575                interface.
1576
1577                ported i2c driver to the new framework:
1578                - drivers/i2c/soft_i2c.c:
1579                  - activate first bus with CONFIG_SYS_I2C_SOFT define
1580                    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1581                    for defining speed and slave address
1582                  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1583                    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1584                    for defining speed and slave address
1585                  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1586                    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1587                    for defining speed and slave address
1588                  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1589                    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1590                    for defining speed and slave address
1591
1592                - drivers/i2c/fsl_i2c.c:
1593                  - activate i2c driver with CONFIG_SYS_I2C_FSL
1594                    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1595                    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1596                    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1597                    bus.
1598                  - If your board supports a second fsl i2c bus, define
1599                    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1600                    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1601                    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1602                    second bus.
1603
1604                - drivers/i2c/tegra_i2c.c:
1605                  - activate this driver with CONFIG_SYS_I2C_TEGRA
1606                  - This driver adds 4 i2c buses with a fix speed from
1607                    100000 and the slave addr 0!
1608
1609                - drivers/i2c/ppc4xx_i2c.c
1610                  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1611                  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1612                  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1613
1614                - drivers/i2c/i2c_mxc.c
1615                  - activate this driver with CONFIG_SYS_I2C_MXC
1616                  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1617                  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1618                  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1619                  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1620                  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1621                  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1622                  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1623                  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1624                  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1625                  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1626                  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1627                  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1628                If those defines are not set, default value is 100000
1629                for speed, and 0 for slave.
1630
1631                - drivers/i2c/rcar_i2c.c:
1632                  - activate this driver with CONFIG_SYS_I2C_RCAR
1633                  - This driver adds 4 i2c buses
1634
1635                  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1636                  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1637                  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1638                  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1639                  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1640                  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1641                  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1642                  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1643                  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1644
1645                - drivers/i2c/sh_i2c.c:
1646                  - activate this driver with CONFIG_SYS_I2C_SH
1647                  - This driver adds from 2 to 5 i2c buses
1648
1649                  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1650                  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1651                  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1652                  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1653                  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1654                  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1655                  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1656                  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1657                  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1658                  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1659                  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1660
1661                - drivers/i2c/omap24xx_i2c.c
1662                  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1663                  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1664                  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1665                  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1666                  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1667                  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1668                  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1669                  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1670                  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1671                  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1672                  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1673
1674                - drivers/i2c/s3c24x0_i2c.c:
1675                  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1676                  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1677                    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1678                    with a fix speed from 100000 and the slave addr 0!
1679
1680                - drivers/i2c/ihs_i2c.c
1681                  - activate this driver with CONFIG_SYS_I2C_IHS
1682                  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1683                  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1684                  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1685                  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1686                  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1687                  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1688                  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1689                  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1690                  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1691                  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1692                  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1693                  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1694                  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1695                  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1696                  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1697                  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1698                  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1699                  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1700                  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1701                  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1702                  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1703
1704                additional defines:
1705
1706                CONFIG_SYS_NUM_I2C_BUSES
1707                Hold the number of i2c buses you want to use.
1708
1709                CONFIG_SYS_I2C_DIRECT_BUS
1710                define this, if you don't use i2c muxes on your hardware.
1711                if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1712                omit this define.
1713
1714                CONFIG_SYS_I2C_MAX_HOPS
1715                define how many muxes are maximal consecutively connected
1716                on one i2c bus. If you not use i2c muxes, omit this
1717                define.
1718
1719                CONFIG_SYS_I2C_BUSES
1720                hold a list of buses you want to use, only used if
1721                CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1722                a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1723                CONFIG_SYS_NUM_I2C_BUSES = 9:
1724
1725                 CONFIG_SYS_I2C_BUSES   {{0, {I2C_NULL_HOP}}, \
1726                                        {0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1727                                        {0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1728                                        {0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1729                                        {0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1730                                        {0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1731                                        {1, {I2C_NULL_HOP}}, \
1732                                        {1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1733                                        {1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1734                                        }
1735
1736                which defines
1737                        bus 0 on adapter 0 without a mux
1738                        bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1739                        bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1740                        bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1741                        bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1742                        bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1743                        bus 6 on adapter 1 without a mux
1744                        bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1745                        bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1746
1747                If you do not have i2c muxes on your board, omit this define.
1748
1749- Legacy I2C Support:
1750                If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1751                then the following macros need to be defined (examples are
1752                from include/configs/lwmon.h):
1753
1754                I2C_INIT
1755
1756                (Optional). Any commands necessary to enable the I2C
1757                controller or configure ports.
1758
1759                eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=  PB_SCL)
1760
1761                I2C_ACTIVE
1762
1763                The code necessary to make the I2C data line active
1764                (driven).  If the data line is open collector, this
1765                define can be null.
1766
1767                eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1768
1769                I2C_TRISTATE
1770
1771                The code necessary to make the I2C data line tri-stated
1772                (inactive).  If the data line is open collector, this
1773                define can be null.
1774
1775                eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1776
1777                I2C_READ
1778
1779                Code that returns true if the I2C data line is high,
1780                false if it is low.
1781
1782                eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1783
1784                I2C_SDA(bit)
1785
1786                If <bit> is true, sets the I2C data line high. If it
1787                is false, it clears it (low).
1788
1789                eg: #define I2C_SDA(bit) \
1790                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1791                        else    immr->im_cpm.cp_pbdat &= ~PB_SDA
1792
1793                I2C_SCL(bit)
1794
1795                If <bit> is true, sets the I2C clock line high. If it
1796                is false, it clears it (low).
1797
1798                eg: #define I2C_SCL(bit) \
1799                        if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1800                        else    immr->im_cpm.cp_pbdat &= ~PB_SCL
1801
1802                I2C_DELAY
1803
1804                This delay is invoked four times per clock cycle so this
1805                controls the rate of data transfer.  The data rate thus
1806                is 1 / (I2C_DELAY * 4). Often defined to be something
1807                like:
1808
1809                #define I2C_DELAY  udelay(2)
1810
1811                CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1812
1813                If your arch supports the generic GPIO framework (asm/gpio.h),
1814                then you may alternatively define the two GPIOs that are to be
1815                used as SCL / SDA.  Any of the previous I2C_xxx macros will
1816                have GPIO-based defaults assigned to them as appropriate.
1817
1818                You should define these to the GPIO value as given directly to
1819                the generic GPIO functions.
1820
1821                CONFIG_SYS_I2C_INIT_BOARD
1822
1823                When a board is reset during an i2c bus transfer
1824                chips might think that the current transfer is still
1825                in progress. On some boards it is possible to access
1826                the i2c SCLK line directly, either by using the
1827                processor pin as a GPIO or by having a second pin
1828                connected to the bus. If this option is defined a
1829                custom i2c_init_board() routine in boards/xxx/board.c
1830                is run early in the boot sequence.
1831
1832                CONFIG_I2C_MULTI_BUS
1833
1834                This option allows the use of multiple I2C buses, each of which
1835                must have a controller.  At any point in time, only one bus is
1836                active.  To switch to a different bus, use the 'i2c dev' command.
1837                Note that bus numbering is zero-based.
1838
1839                CONFIG_SYS_I2C_NOPROBES
1840
1841                This option specifies a list of I2C devices that will be skipped
1842                when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1843                is set, specify a list of bus-device pairs.  Otherwise, specify
1844                a 1D array of device addresses
1845
1846                e.g.
1847                        #undef  CONFIG_I2C_MULTI_BUS
1848                        #define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1849
1850                will skip addresses 0x50 and 0x68 on a board with one I2C bus
1851
1852                        #define CONFIG_I2C_MULTI_BUS
1853                        #define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
1854
1855                will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1856
1857                CONFIG_SYS_SPD_BUS_NUM
1858
1859                If defined, then this indicates the I2C bus number for DDR SPD.
1860                If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1861
1862                CONFIG_SYS_RTC_BUS_NUM
1863
1864                If defined, then this indicates the I2C bus number for the RTC.
1865                If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1866
1867                CONFIG_SOFT_I2C_READ_REPEATED_START
1868
1869                defining this will force the i2c_read() function in
1870                the soft_i2c driver to perform an I2C repeated start
1871                between writing the address pointer and reading the
1872                data.  If this define is omitted the default behaviour
1873                of doing a stop-start sequence will be used.  Most I2C
1874                devices can use either method, but some require one or
1875                the other.
1876
1877- SPI Support:  CONFIG_SPI
1878
1879                Enables SPI driver (so far only tested with
1880                SPI EEPROM, also an instance works with Crystal A/D and
1881                D/As on the SACSng board)
1882
1883                CONFIG_SOFT_SPI
1884
1885                Enables a software (bit-bang) SPI driver rather than
1886                using hardware support. This is a general purpose
1887                driver that only requires three general I/O port pins
1888                (two outputs, one input) to function. If this is
1889                defined, the board configuration must define several
1890                SPI configuration items (port pins to use, etc). For
1891                an example, see include/configs/sacsng.h.
1892
1893                CONFIG_SYS_SPI_MXC_WAIT
1894                Timeout for waiting until spi transfer completed.
1895                default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1896
1897- FPGA Support: CONFIG_FPGA
1898
1899                Enables FPGA subsystem.
1900
1901                CONFIG_FPGA_<vendor>
1902
1903                Enables support for specific chip vendors.
1904                (ALTERA, XILINX)
1905
1906                CONFIG_FPGA_<family>
1907
1908                Enables support for FPGA family.
1909                (SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1910
1911                CONFIG_FPGA_COUNT
1912
1913                Specify the number of FPGA devices to support.
1914
1915                CONFIG_SYS_FPGA_PROG_FEEDBACK
1916
1917                Enable printing of hash marks during FPGA configuration.
1918
1919                CONFIG_SYS_FPGA_CHECK_BUSY
1920
1921                Enable checks on FPGA configuration interface busy
1922                status by the configuration function. This option
1923                will require a board or device specific function to
1924                be written.
1925
1926                CONFIG_FPGA_DELAY
1927
1928                If defined, a function that provides delays in the FPGA
1929                configuration driver.
1930
1931                CONFIG_SYS_FPGA_CHECK_CTRLC
1932                Allow Control-C to interrupt FPGA configuration
1933
1934                CONFIG_SYS_FPGA_CHECK_ERROR
1935
1936                Check for configuration errors during FPGA bitfile
1937                loading. For example, abort during Virtex II
1938                configuration if the INIT_B line goes low (which
1939                indicated a CRC error).
1940
1941                CONFIG_SYS_FPGA_WAIT_INIT
1942
1943                Maximum time to wait for the INIT_B line to de-assert
1944                after PROB_B has been de-asserted during a Virtex II
1945                FPGA configuration sequence. The default time is 500
1946                ms.
1947
1948                CONFIG_SYS_FPGA_WAIT_BUSY
1949
1950                Maximum time to wait for BUSY to de-assert during
1951                Virtex II FPGA configuration. The default is 5 ms.
1952
1953                CONFIG_SYS_FPGA_WAIT_CONFIG
1954
1955                Time to wait after FPGA configuration. The default is
1956                200 ms.
1957
1958- Configuration Management:
1959
1960                CONFIG_IDENT_STRING
1961
1962                If defined, this string will be added to the U-Boot
1963                version information (U_BOOT_VERSION)
1964
1965- Vendor Parameter Protection:
1966
1967                U-Boot considers the values of the environment
1968                variables "serial#" (Board Serial Number) and
1969                "ethaddr" (Ethernet Address) to be parameters that
1970                are set once by the board vendor / manufacturer, and
1971                protects these variables from casual modification by
1972                the user. Once set, these variables are read-only,
1973                and write or delete attempts are rejected. You can
1974                change this behaviour:
1975
1976                If CONFIG_ENV_OVERWRITE is #defined in your config
1977                file, the write protection for vendor parameters is
1978                completely disabled. Anybody can change or delete
1979                these parameters.
1980
1981                Alternatively, if you define _both_ an ethaddr in the
1982                default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1983                Ethernet address is installed in the environment,
1984                which can be changed exactly ONCE by the user. [The
1985                serial# is unaffected by this, i. e. it remains
1986                read-only.]
1987
1988                The same can be accomplished in a more flexible way
1989                for any variable by configuring the type of access
1990                to allow for those variables in the ".flags" variable
1991                or define CONFIG_ENV_FLAGS_LIST_STATIC.
1992
1993- Protected RAM:
1994                CONFIG_PRAM
1995
1996                Define this variable to enable the reservation of
1997                "protected RAM", i. e. RAM which is not overwritten
1998                by U-Boot. Define CONFIG_PRAM to hold the number of
1999                kB you want to reserve for pRAM. You can overwrite
2000                this default value by defining an environment
2001                variable "pram" to the number of kB you want to
2002                reserve. Note that the board info structure will
2003                still show the full amount of RAM. If pRAM is
2004                reserved, a new environment variable "mem" will
2005                automatically be defined to hold the amount of
2006                remaining RAM in a form that can be passed as boot
2007                argument to Linux, for instance like that:
2008
2009                        setenv bootargs ... mem=\${mem}
2010                        saveenv
2011
2012                This way you can tell Linux not to use this memory,
2013                either, which results in a memory region that will
2014                not be affected by reboots.
2015
2016                *WARNING* If your board configuration uses automatic
2017                detection of the RAM size, you must make sure that
2018                this memory test is non-destructive. So far, the
2019                following board configurations are known to be
2020                "pRAM-clean":
2021
2022                        IVMS8, IVML24, SPD8xx,
2023                        HERMES, IP860, RPXlite, LWMON,
2024                        FLAGADM
2025
2026- Access to physical memory region (> 4GB)
2027                Some basic support is provided for operations on memory not
2028                normally accessible to U-Boot - e.g. some architectures
2029                support access to more than 4GB of memory on 32-bit
2030                machines using physical address extension or similar.
2031                Define CONFIG_PHYSMEM to access this basic support, which
2032                currently only supports clearing the memory.
2033
2034- Error Recovery:
2035                CONFIG_NET_RETRY_COUNT
2036
2037                This variable defines the number of retries for
2038                network operations like ARP, RARP, TFTP, or BOOTP
2039                before giving up the operation. If not defined, a
2040                default value of 5 is used.
2041
2042                CONFIG_ARP_TIMEOUT
2043
2044                Timeout waiting for an ARP reply in milliseconds.
2045
2046                CONFIG_NFS_TIMEOUT
2047
2048                Timeout in milliseconds used in NFS protocol.
2049                If you encounter "ERROR: Cannot umount" in nfs command,
2050                try longer timeout such as
2051                #define CONFIG_NFS_TIMEOUT 10000UL
2052
2053- Command Interpreter:
2054                CONFIG_SYS_PROMPT_HUSH_PS2
2055
2056                This defines the secondary prompt string, which is
2057                printed when the command interpreter needs more input
2058                to complete a command. Usually "> ".
2059
2060        Note:
2061
2062                In the current implementation, the local variables
2063                space and global environment variables space are
2064                separated. Local variables are those you define by
2065                simply typing `name=value'. To access a local
2066                variable later on, you have write `$name' or
2067                `${name}'; to execute the contents of a variable
2068                directly type `$name' at the command prompt.
2069
2070                Global environment variables are those you use
2071                setenv/printenv to work with. To run a command stored
2072                in such a variable, you need to use the run command,
2073                and you must not use the '$' sign to access them.
2074
2075                To store commands and special characters in a
2076                variable, please use double quotation marks
2077                surrounding the whole text of the variable, instead
2078                of the backslashes before semicolons and special
2079                symbols.
2080
2081- Command Line Editing and History:
2082                CONFIG_CMDLINE_PS_SUPPORT
2083
2084                Enable support for changing the command prompt string
2085                at run-time. Only static string is supported so far.
2086                The string is obtained from environment variables PS1
2087                and PS2.
2088
2089- Default Environment:
2090                CONFIG_EXTRA_ENV_SETTINGS
2091
2092                Define this to contain any number of null terminated
2093                strings (variable = value pairs) that will be part of
2094                the default environment compiled into the boot image.
2095
2096                For example, place something like this in your
2097                board's config file:
2098
2099                #define CONFIG_EXTRA_ENV_SETTINGS \
2100                        "myvar1=value1\0" \
2101                        "myvar2=value2\0"
2102
2103                Warning: This method is based on knowledge about the
2104                internal format how the environment is stored by the
2105                U-Boot code. This is NOT an official, exported
2106                interface! Although it is unlikely that this format
2107                will change soon, there is no guarantee either.
2108                You better know what you are doing here.
2109
2110                Note: overly (ab)use of the default environment is
2111                discouraged. Make sure to check other ways to preset
2112                the environment like the "source" command or the
2113                boot command first.
2114
2115                CONFIG_DELAY_ENVIRONMENT
2116
2117                Normally the environment is loaded when the board is
2118                initialised so that it is available to U-Boot. This inhibits
2119                that so that the environment is not available until
2120                explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2121                this is instead controlled by the value of
2122                /config/load-environment.
2123
2124- TFTP Fixed UDP Port:
2125                CONFIG_TFTP_PORT
2126
2127                If this is defined, the environment variable tftpsrcp
2128                is used to supply the TFTP UDP source port value.
2129                If tftpsrcp isn't defined, the normal pseudo-random port
2130                number generator is used.
2131
2132                Also, the environment variable tftpdstp is used to supply
2133                the TFTP UDP destination port value.  If tftpdstp isn't
2134                defined, the normal port 69 is used.
2135
2136                The purpose for tftpsrcp is to allow a TFTP server to
2137                blindly start the TFTP transfer using the pre-configured
2138                target IP address and UDP port. This has the effect of
2139                "punching through" the (Windows XP) firewall, allowing
2140                the remainder of the TFTP transfer to proceed normally.
2141                A better solution is to properly configure the firewall,
2142                but sometimes that is not allowed.
2143
2144                CONFIG_STANDALONE_LOAD_ADDR
2145
2146                This option defines a board specific value for the
2147                address where standalone program gets loaded, thus
2148                overwriting the architecture dependent default
2149                settings.
2150
2151- Frame Buffer Address:
2152                CONFIG_FB_ADDR
2153
2154                Define CONFIG_FB_ADDR if you want to use specific
2155                address for frame buffer.  This is typically the case
2156                when using a graphics controller has separate video
2157                memory.  U-Boot will then place the frame buffer at
2158                the given address instead of dynamically reserving it
2159                in system RAM by calling lcd_setmem(), which grabs
2160                the memory for the frame buffer depending on the
2161                configured panel size.
2162
2163                Please see board_init_f function.
2164
2165- Automatic software updates via TFTP server
2166                CONFIG_UPDATE_TFTP
2167                CONFIG_UPDATE_TFTP_CNT_MAX
2168                CONFIG_UPDATE_TFTP_MSEC_MAX
2169
2170                These options enable and control the auto-update feature;
2171                for a more detailed description refer to doc/README.update.
2172
2173- MTD Support (mtdparts command, UBI support)
2174                CONFIG_MTD_UBI_WL_THRESHOLD
2175                This parameter defines the maximum difference between the highest
2176                erase counter value and the lowest erase counter value of eraseblocks
2177                of UBI devices. When this threshold is exceeded, UBI starts performing
2178                wear leveling by means of moving data from eraseblock with low erase
2179                counter to eraseblocks with high erase counter.
2180
2181                The default value should be OK for SLC NAND flashes, NOR flashes and
2182                other flashes which have eraseblock life-cycle 100000 or more.
2183                However, in case of MLC NAND flashes which typically have eraseblock
2184                life-cycle less than 10000, the threshold should be lessened (e.g.,
2185                to 128 or 256, although it does not have to be power of 2).
2186
2187                default: 4096
2188
2189                CONFIG_MTD_UBI_BEB_LIMIT
2190                This option specifies the maximum bad physical eraseblocks UBI
2191                expects on the MTD device (per 1024 eraseblocks). If the
2192                underlying flash does not admit of bad eraseblocks (e.g. NOR
2193                flash), this value is ignored.
2194
2195                NAND datasheets often specify the minimum and maximum NVM
2196                (Number of Valid Blocks) for the flashes' endurance lifetime.
2197                The maximum expected bad eraseblocks per 1024 eraseblocks
2198                then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2199                which gives 20 for most NANDs (MaxNVB is basically the total
2200                count of eraseblocks on the chip).
2201
2202                To put it differently, if this value is 20, UBI will try to
2203                reserve about 1.9% of physical eraseblocks for bad blocks
2204                handling. And that will be 1.9% of eraseblocks on the entire
2205                NAND chip, not just the MTD partition UBI attaches. This means
2206                that if you have, say, a NAND flash chip admits maximum 40 bad
2207                eraseblocks, and it is split on two MTD partitions of the same
2208                size, UBI will reserve 40 eraseblocks when attaching a
2209                partition.
2210
2211                default: 20
2212
2213                CONFIG_MTD_UBI_FASTMAP
2214                Fastmap is a mechanism which allows attaching an UBI device
2215                in nearly constant time. Instead of scanning the whole MTD device it
2216                only has to locate a checkpoint (called fastmap) on the device.
2217                The on-flash fastmap contains all information needed to attach
2218                the device. Using fastmap makes only sense on large devices where
2219                attaching by scanning takes long. UBI will not automatically install
2220                a fastmap on old images, but you can set the UBI parameter
2221                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2222                that fastmap-enabled images are still usable with UBI implementations
2223                without fastmap support. On typical flash devices the whole fastmap
2224                fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2225
2226                CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2227                Set this parameter to enable fastmap automatically on images
2228                without a fastmap.
2229                default: 0
2230
2231                CONFIG_MTD_UBI_FM_DEBUG
2232                Enable UBI fastmap debug
2233                default: 0
2234
2235- SPL framework
2236                CONFIG_SPL
2237                Enable building of SPL globally.
2238
2239                CONFIG_SPL_LDSCRIPT
2240                LDSCRIPT for linking the SPL binary.
2241
2242                CONFIG_SPL_MAX_FOOTPRINT
2243                Maximum size in memory allocated to the SPL, BSS included.
2244                When defined, the linker checks that the actual memory
2245                used by SPL from _start to __bss_end does not exceed it.
2246                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2247                must not be both defined at the same time.
2248
2249                CONFIG_SPL_MAX_SIZE
2250                Maximum size of the SPL image (text, data, rodata, and
2251                linker lists sections), BSS excluded.
2252                When defined, the linker checks that the actual size does
2253                not exceed it.
2254
2255                CONFIG_SPL_RELOC_TEXT_BASE
2256                Address to relocate to.  If unspecified, this is equal to
2257                CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2258
2259                CONFIG_SPL_BSS_START_ADDR
2260                Link address for the BSS within the SPL binary.
2261
2262                CONFIG_SPL_BSS_MAX_SIZE
2263                Maximum size in memory allocated to the SPL BSS.
2264                When defined, the linker checks that the actual memory used
2265                by SPL from __bss_start to __bss_end does not exceed it.
2266                CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2267                must not be both defined at the same time.
2268
2269                CONFIG_SPL_STACK
2270                Adress of the start of the stack SPL will use
2271
2272                CONFIG_SPL_PANIC_ON_RAW_IMAGE
2273                When defined, SPL will panic() if the image it has
2274                loaded does not have a signature.
2275                Defining this is useful when code which loads images
2276                in SPL cannot guarantee that absolutely all read errors
2277                will be caught.
2278                An example is the LPC32XX MLC NAND driver, which will
2279                consider that a completely unreadable NAND block is bad,
2280                and thus should be skipped silently.
2281
2282                CONFIG_SPL_RELOC_STACK
2283                Adress of the start of the stack SPL will use after
2284                relocation.  If unspecified, this is equal to
2285                CONFIG_SPL_STACK.
2286
2287                CONFIG_SYS_SPL_MALLOC_START
2288                Starting address of the malloc pool used in SPL.
2289                When this option is set the full malloc is used in SPL and
2290                it is set up by spl_init() and before that, the simple malloc()
2291                can be used if CONFIG_SYS_MALLOC_F is defined.
2292
2293                CONFIG_SYS_SPL_MALLOC_SIZE
2294                The size of the malloc pool used in SPL.
2295
2296                CONFIG_SPL_OS_BOOT
2297                Enable booting directly to an OS from SPL.
2298                See also: doc/README.falcon
2299
2300                CONFIG_SPL_DISPLAY_PRINT
2301                For ARM, enable an optional function to print more information
2302                about the running system.
2303
2304                CONFIG_SPL_INIT_MINIMAL
2305                Arch init code should be built for a very small image
2306
2307                CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2308                Partition on the MMC to load U-Boot from when the MMC is being
2309                used in raw mode
2310
2311                CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2312                Sector to load kernel uImage from when MMC is being
2313                used in raw mode (for Falcon mode)
2314
2315                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2316                CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2317                Sector and number of sectors to load kernel argument
2318                parameters from when MMC is being used in raw mode
2319                (for falcon mode)
2320
2321                CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2322                Partition on the MMC to load U-Boot from when the MMC is being
2323                used in fs mode
2324
2325                CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2326                Filename to read to load U-Boot when reading from filesystem
2327
2328                CONFIG_SPL_FS_LOAD_KERNEL_NAME
2329                Filename to read to load kernel uImage when reading
2330                from filesystem (for Falcon mode)
2331
2332                CONFIG_SPL_FS_LOAD_ARGS_NAME
2333                Filename to read to load kernel argument parameters
2334                when reading from filesystem (for Falcon mode)
2335
2336                CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2337                Set this for NAND SPL on PPC mpc83xx targets, so that
2338                start.S waits for the rest of the SPL to load before
2339                continuing (the hardware starts execution after just
2340                loading the first page rather than the full 4K).
2341
2342                CONFIG_SPL_SKIP_RELOCATE
2343                Avoid SPL relocation
2344
2345                CONFIG_SPL_NAND_BASE
2346                Include nand_base.c in the SPL.  Requires
2347                CONFIG_SPL_NAND_DRIVERS.
2348
2349                CONFIG_SPL_NAND_DRIVERS
2350                SPL uses normal NAND drivers, not minimal drivers.
2351
2352                CONFIG_SPL_NAND_IDENT
2353                SPL uses the chip ID list to identify the NAND flash.
2354                Requires CONFIG_SPL_NAND_BASE.
2355
2356                CONFIG_SPL_NAND_ECC
2357                Include standard software ECC in the SPL
2358
2359                CONFIG_SPL_NAND_SIMPLE
2360                Support for NAND boot using simple NAND drivers that
2361                expose the cmd_ctrl() interface.
2362
2363                CONFIG_SPL_UBI
2364                Support for a lightweight UBI (fastmap) scanner and
2365                loader
2366
2367                CONFIG_SPL_NAND_RAW_ONLY
2368                Support to boot only raw u-boot.bin images. Use this only
2369                if you need to save space.
2370
2371                CONFIG_SPL_COMMON_INIT_DDR
2372                Set for common ddr init with serial presence detect in
2373                SPL binary.
2374
2375                CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2376                CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2377                CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2378                CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2379                CONFIG_SYS_NAND_ECCBYTES
2380                Defines the size and behavior of the NAND that SPL uses
2381                to read U-Boot
2382
2383                CONFIG_SYS_NAND_U_BOOT_OFFS
2384                Location in NAND to read U-Boot from
2385
2386                CONFIG_SYS_NAND_U_BOOT_DST
2387                Location in memory to load U-Boot to
2388
2389                CONFIG_SYS_NAND_U_BOOT_SIZE
2390                Size of image to load
2391
2392                CONFIG_SYS_NAND_U_BOOT_START
2393                Entry point in loaded image to jump to
2394
2395                CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2396                Define this if you need to first read the OOB and then the
2397                data. This is used, for example, on davinci platforms.
2398
2399                CONFIG_SPL_RAM_DEVICE
2400                Support for running image already present in ram, in SPL binary
2401
2402                CONFIG_SPL_PAD_TO
2403                Image offset to which the SPL should be padded before appending
2404                the SPL payload. By default, this is defined as
2405                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2406                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2407                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2408
2409                CONFIG_SPL_TARGET
2410                Final target image containing SPL and payload.  Some SPLs
2411                use an arch-specific makefile fragment instead, for
2412                example if more than one image needs to be produced.
2413
2414                CONFIG_SPL_FIT_PRINT
2415                Printing information about a FIT image adds quite a bit of
2416                code to SPL. So this is normally disabled in SPL. Use this
2417                option to re-enable it. This will affect the output of the
2418                bootm command when booting a FIT image.
2419
2420- TPL framework
2421                CONFIG_TPL
2422                Enable building of TPL globally.
2423
2424                CONFIG_TPL_PAD_TO
2425                Image offset to which the TPL should be padded before appending
2426                the TPL payload. By default, this is defined as
2427                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2428                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2429                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2430
2431- Interrupt support (PPC):
2432
2433                There are common interrupt_init() and timer_interrupt()
2434                for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2435                for CPU specific initialization. interrupt_init_cpu()
2436                should set decrementer_count to appropriate value. If
2437                CPU resets decrementer automatically after interrupt
2438                (ppc4xx) it should set decrementer_count to zero.
2439                timer_interrupt() calls timer_interrupt_cpu() for CPU
2440                specific handling. If board has watchdog / status_led
2441                / other_activity_monitor it works automatically from
2442                general timer_interrupt().
2443
2444
2445Board initialization settings:
2446------------------------------
2447
2448During Initialization u-boot calls a number of board specific functions
2449to allow the preparation of board specific prerequisites, e.g. pin setup
2450before drivers are initialized. To enable these callbacks the
2451following configuration macros have to be defined. Currently this is
2452architecture specific, so please check arch/your_architecture/lib/board.c
2453typically in board_init_f() and board_init_r().
2454
2455- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2456- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2457- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2458- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2459
2460Configuration Settings:
2461-----------------------
2462
2463- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2464                Optionally it can be defined to support 64-bit memory commands.
2465
2466- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2467                undefine this when you're short of memory.
2468
2469- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2470                width of the commands listed in the 'help' command output.
2471
2472- CONFIG_SYS_PROMPT:    This is what U-Boot prints on the console to
2473                prompt for user input.
2474
2475- CONFIG_SYS_CBSIZE:    Buffer size for input from the Console
2476
2477- CONFIG_SYS_PBSIZE:    Buffer size for Console output
2478
2479- CONFIG_SYS_MAXARGS:   max. Number of arguments accepted for monitor commands
2480
2481- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2482                the application (usually a Linux kernel) when it is
2483                booted
2484
2485- CONFIG_SYS_BAUDRATE_TABLE:
2486                List of legal baudrate settings for this board.
2487
2488- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2489                Begin and End addresses of the area used by the
2490                simple memory test.
2491
2492- CONFIG_SYS_MEMTEST_SCRATCH:
2493                Scratch address used by the alternate memory test
2494                You only need to set this if address zero isn't writeable
2495
2496- CONFIG_SYS_MEM_RESERVE_SECURE
2497                Only implemented for ARMv8 for now.
2498                If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2499                is substracted from total RAM and won't be reported to OS.
2500                This memory can be used as secure memory. A variable
2501                gd->arch.secure_ram is used to track the location. In systems
2502                the RAM base is not zero, or RAM is divided into banks,
2503                this variable needs to be recalcuated to get the address.
2504
2505- CONFIG_SYS_MEM_TOP_HIDE:
2506                If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2507                this specified memory area will get subtracted from the top
2508                (end) of RAM and won't get "touched" at all by U-Boot. By
2509                fixing up gd->ram_size the Linux kernel should gets passed
2510                the now "corrected" memory size and won't touch it either.
2511                This should work for arch/ppc and arch/powerpc. Only Linux
2512                board ports in arch/powerpc with bootwrapper support that
2513                recalculate the memory size from the SDRAM controller setup
2514                will have to get fixed in Linux additionally.
2515
2516                This option can be used as a workaround for the 440EPx/GRx
2517                CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2518                be touched.
2519
2520                WARNING: Please make sure that this value is a multiple of
2521                the Linux page size (normally 4k). If this is not the case,
2522                then the end address of the Linux memory will be located at a
2523                non page size aligned address and this could cause major
2524                problems.
2525
2526- CONFIG_SYS_LOADS_BAUD_CHANGE:
2527                Enable temporary baudrate change while serial download
2528
2529- CONFIG_SYS_SDRAM_BASE:
2530                Physical start address of SDRAM. _Must_ be 0 here.
2531
2532- CONFIG_SYS_FLASH_BASE:
2533                Physical start address of Flash memory.
2534
2535- CONFIG_SYS_MONITOR_BASE:
2536                Physical start address of boot monitor code (set by
2537                make config files to be same as the text base address
2538                (CONFIG_SYS_TEXT_BASE) used when linking) - same as
2539                CONFIG_SYS_FLASH_BASE when booting from flash.
2540
2541- CONFIG_SYS_MONITOR_LEN:
2542                Size of memory reserved for monitor code, used to
2543                determine _at_compile_time_ (!) if the environment is
2544                embedded within the U-Boot image, or in a separate
2545                flash sector.
2546
2547- CONFIG_SYS_MALLOC_LEN:
2548                Size of DRAM reserved for malloc() use.
2549
2550- CONFIG_SYS_MALLOC_F_LEN
2551                Size of the malloc() pool for use before relocation. If
2552                this is defined, then a very simple malloc() implementation
2553                will become available before relocation. The address is just
2554                below the global data, and the stack is moved down to make
2555                space.
2556
2557                This feature allocates regions with increasing addresses
2558                within the region. calloc() is supported, but realloc()
2559                is not available. free() is supported but does nothing.
2560                The memory will be freed (or in fact just forgotten) when
2561                U-Boot relocates itself.
2562
2563- CONFIG_SYS_MALLOC_SIMPLE
2564                Provides a simple and small malloc() and calloc() for those
2565                boards which do not use the full malloc in SPL (which is
2566                enabled with CONFIG_SYS_SPL_MALLOC_START).
2567
2568- CONFIG_SYS_NONCACHED_MEMORY:
2569                Size of non-cached memory area. This area of memory will be
2570                typically located right below the malloc() area and mapped
2571                uncached in the MMU. This is useful for drivers that would
2572                otherwise require a lot of explicit cache maintenance. For
2573                some drivers it's also impossible to properly maintain the
2574                cache. For example if the regions that need to be flushed
2575                are not a multiple of the cache-line size, *and* padding
2576                cannot be allocated between the regions to align them (i.e.
2577                if the HW requires a contiguous array of regions, and the
2578                size of each region is not cache-aligned), then a flush of
2579                one region may result in overwriting data that hardware has
2580                written to another region in the same cache-line. This can
2581                happen for example in network drivers where descriptors for
2582                buffers are typically smaller than the CPU cache-line (e.g.
2583                16 bytes vs. 32 or 64 bytes).
2584
2585                Non-cached memory is only supported on 32-bit ARM at present.
2586
2587- CONFIG_SYS_BOOTM_LEN:
2588                Normally compressed uImages are limited to an
2589                uncompressed size of 8 MBytes. If this is not enough,
2590                you can define CONFIG_SYS_BOOTM_LEN in your board config file
2591                to adjust this setting to your needs.
2592
2593- CONFIG_SYS_BOOTMAPSZ:
2594                Maximum size of memory mapped by the startup code of
2595                the Linux kernel; all data that must be processed by
2596                the Linux kernel (bd_info, boot arguments, FDT blob if
2597                used) must be put below this limit, unless "bootm_low"
2598                environment variable is defined and non-zero. In such case
2599                all data for the Linux kernel must be between "bootm_low"
2600                and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2601                variable "bootm_mapsize" will override the value of
2602                CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2603                then the value in "bootm_size" will be used instead.
2604
2605- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2606                Enable initrd_high functionality.  If defined then the
2607                initrd_high feature is enabled and the bootm ramdisk subcommand
2608                is enabled.
2609
2610- CONFIG_SYS_BOOT_GET_CMDLINE:
2611                Enables allocating and saving kernel cmdline in space between
2612                "bootm_low" and "bootm_low" + BOOTMAPSZ.
2613
2614- CONFIG_SYS_BOOT_GET_KBD:
2615                Enables allocating and saving a kernel copy of the bd_info in
2616                space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2617
2618- CONFIG_SYS_MAX_FLASH_BANKS:
2619                Max number of Flash memory banks
2620
2621- CONFIG_SYS_MAX_FLASH_SECT:
2622                Max number of sectors on a Flash chip
2623
2624- CONFIG_SYS_FLASH_ERASE_TOUT:
2625                Timeout for Flash erase operations (in ms)
2626
2627- CONFIG_SYS_FLASH_WRITE_TOUT:
2628                Timeout for Flash write operations (in ms)
2629
2630- CONFIG_SYS_FLASH_LOCK_TOUT
2631                Timeout for Flash set sector lock bit operation (in ms)
2632
2633- CONFIG_SYS_FLASH_UNLOCK_TOUT
2634                Timeout for Flash clear lock bits operation (in ms)
2635
2636- CONFIG_SYS_FLASH_PROTECTION
2637                If defined, hardware flash sectors protection is used
2638                instead of U-Boot software protection.
2639
2640- CONFIG_SYS_DIRECT_FLASH_TFTP:
2641
2642                Enable TFTP transfers directly to flash memory;
2643                without this option such a download has to be
2644                performed in two steps: (1) download to RAM, and (2)
2645                copy from RAM to flash.
2646
2647                The two-step approach is usually more reliable, since
2648                you can check if the download worked before you erase
2649                the flash, but in some situations (when system RAM is
2650                too limited to allow for a temporary copy of the
2651                downloaded image) this option may be very useful.
2652
2653- CONFIG_SYS_FLASH_CFI:
2654                Define if the flash driver uses extra elements in the
2655                common flash structure for storing flash geometry.
2656
2657- CONFIG_FLASH_CFI_DRIVER
2658                This option also enables the building of the cfi_flash driver
2659                in the drivers directory
2660
2661- CONFIG_FLASH_CFI_MTD
2662                This option enables the building of the cfi_mtd driver
2663                in the drivers directory. The driver exports CFI flash
2664                to the MTD layer.
2665
2666- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2667                Use buffered writes to flash.
2668
2669- CONFIG_FLASH_SPANSION_S29WS_N
2670                s29ws-n MirrorBit flash has non-standard addresses for buffered
2671                write commands.
2672
2673- CONFIG_SYS_FLASH_QUIET_TEST
2674                If this option is defined, the common CFI flash doesn't
2675                print it's warning upon not recognized FLASH banks. This
2676                is useful, if some of the configured banks are only
2677                optionally available.
2678
2679- CONFIG_FLASH_SHOW_PROGRESS
2680                If defined (must be an integer), print out countdown
2681                digits and dots.  Recommended value: 45 (9..1) for 80
2682                column displays, 15 (3..1) for 40 column displays.
2683
2684- CONFIG_FLASH_VERIFY
2685                If defined, the content of the flash (destination) is compared
2686                against the source after the write operation. An error message
2687                will be printed when the contents are not identical.
2688                Please note that this option is useless in nearly all cases,
2689                since such flash programming errors usually are detected earlier
2690                while unprotecting/erasing/programming. Please only enable
2691                this option if you really know what you are doing.
2692
2693- CONFIG_SYS_RX_ETH_BUFFER:
2694                Defines the number of Ethernet receive buffers. On some
2695                Ethernet controllers it is recommended to set this value
2696                to 8 or even higher (EEPRO100 or 405 EMAC), since all
2697                buffers can be full shortly after enabling the interface
2698                on high Ethernet traffic.
2699                Defaults to 4 if not defined.
2700
2701- CONFIG_ENV_MAX_ENTRIES
2702
2703        Maximum number of entries in the hash table that is used
2704        internally to store the environment settings. The default
2705        setting is supposed to be generous and should work in most
2706        cases. This setting can be used to tune behaviour; see
2707        lib/hashtable.c for details.
2708
2709- CONFIG_ENV_FLAGS_LIST_DEFAULT
2710- CONFIG_ENV_FLAGS_LIST_STATIC
2711        Enable validation of the values given to environment variables when
2712        calling env set.  Variables can be restricted to only decimal,
2713        hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2714        the variables can also be restricted to IP address or MAC address.
2715
2716        The format of the list is:
2717                type_attribute = [s|d|x|b|i|m]
2718                access_attribute = [a|r|o|c]
2719                attributes = type_attribute[access_attribute]
2720                entry = variable_name[:attributes]
2721                list = entry[,list]
2722
2723        The type attributes are:
2724                s - String (default)
2725                d - Decimal
2726                x - Hexadecimal
2727                b - Boolean ([1yYtT|0nNfF])
2728                i - IP address
2729                m - MAC address
2730
2731        The access attributes are:
2732                a - Any (default)
2733                r - Read-only
2734                o - Write-once
2735                c - Change-default
2736
2737        - CONFIG_ENV_FLAGS_LIST_DEFAULT
2738                Define this to a list (string) to define the ".flags"
2739                environment variable in the default or embedded environment.
2740
2741        - CONFIG_ENV_FLAGS_LIST_STATIC
2742                Define this to a list (string) to define validation that
2743                should be done if an entry is not found in the ".flags"
2744                environment variable.  To override a setting in the static
2745                list, simply add an entry for the same variable name to the
2746                ".flags" variable.
2747
2748        If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2749        regular expression. This allows multiple variables to define the same
2750        flags without explicitly listing them for each variable.
2751
2752- CONFIG_ENV_ACCESS_IGNORE_FORCE
2753        If defined, don't allow the -f switch to env set override variable
2754        access flags.
2755
2756The following definitions that deal with the placement and management
2757of environment data (variable area); in general, we support the
2758following configurations:
2759
2760- CONFIG_BUILD_ENVCRC:
2761
2762        Builds up envcrc with the target environment so that external utils
2763        may easily extract it and embed it in final U-Boot images.
2764
2765BE CAREFUL! The first access to the environment happens quite early
2766in U-Boot initialization (when we try to get the setting of for the
2767console baudrate). You *MUST* have mapped your NVRAM area then, or
2768U-Boot will hang.
2769
2770Please note that even with NVRAM we still use a copy of the
2771environment in RAM: we could work on NVRAM directly, but we want to
2772keep settings there always unmodified except somebody uses "saveenv"
2773to save the current settings.
2774
2775BE CAREFUL! For some special cases, the local device can not use
2776"saveenv" command. For example, the local device will get the
2777environment stored in a remote NOR flash by SRIO or PCIE link,
2778but it can not erase, write this NOR flash by SRIO or PCIE interface.
2779
2780- CONFIG_NAND_ENV_DST
2781
2782        Defines address in RAM to which the nand_spl code should copy the
2783        environment. If redundant environment is used, it will be copied to
2784        CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2785
2786Please note that the environment is read-only until the monitor
2787has been relocated to RAM and a RAM copy of the environment has been
2788created; also, when using EEPROM you will have to use env_get_f()
2789until then to read environment variables.
2790
2791The environment is protected by a CRC32 checksum. Before the monitor
2792is relocated into RAM, as a result of a bad CRC you will be working
2793with the compiled-in default environment - *silently*!!! [This is
2794necessary, because the first environment variable we need is the
2795"baudrate" setting for the console - if we have a bad CRC, we don't
2796have any device yet where we could complain.]
2797
2798Note: once the monitor has been relocated, then it will complain if
2799the default environment is used; a new CRC is computed as soon as you
2800use the "saveenv" command to store a valid environment.
2801
2802- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2803                Echo the inverted Ethernet link state to the fault LED.
2804
2805                Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2806                      also needs to be defined.
2807
2808- CONFIG_SYS_FAULT_MII_ADDR:
2809                MII address of the PHY to check for the Ethernet link state.
2810
2811- CONFIG_NS16550_MIN_FUNCTIONS:
2812                Define this if you desire to only have use of the NS16550_init
2813                and NS16550_putc functions for the serial driver located at
2814                drivers/serial/ns16550.c.  This option is useful for saving
2815                space for already greatly restricted images, including but not
2816                limited to NAND_SPL configurations.
2817
2818- CONFIG_DISPLAY_BOARDINFO
2819                Display information about the board that U-Boot is running on
2820                when U-Boot starts up. The board function checkboard() is called
2821                to do this.
2822
2823- CONFIG_DISPLAY_BOARDINFO_LATE
2824                Similar to the previous option, but display this information
2825                later, once stdio is running and output goes to the LCD, if
2826                present.
2827
2828- CONFIG_BOARD_SIZE_LIMIT:
2829                Maximum size of the U-Boot image. When defined, the
2830                build system checks that the actual size does not
2831                exceed it.
2832
2833Low Level (hardware related) configuration options:
2834---------------------------------------------------
2835
2836- CONFIG_SYS_CACHELINE_SIZE:
2837                Cache Line Size of the CPU.
2838
2839- CONFIG_SYS_CCSRBAR_DEFAULT:
2840                Default (power-on reset) physical address of CCSR on Freescale
2841                PowerPC SOCs.
2842
2843- CONFIG_SYS_CCSRBAR:
2844                Virtual address of CCSR.  On a 32-bit build, this is typically
2845                the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2846
2847- CONFIG_SYS_CCSRBAR_PHYS:
2848                Physical address of CCSR.  CCSR can be relocated to a new
2849                physical address, if desired.  In this case, this macro should
2850                be set to that address.  Otherwise, it should be set to the
2851                same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2852                is typically relocated on 36-bit builds.  It is recommended
2853                that this macro be defined via the _HIGH and _LOW macros:
2854
2855                #define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2856                        * 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2857
2858- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2859                Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.  This value is typically
2860                either 0 (32-bit build) or 0xF (36-bit build).  This macro is
2861                used in assembly code, so it must not contain typecasts or
2862                integer size suffixes (e.g. "ULL").
2863
2864- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2865                Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2866                used in assembly code, so it must not contain typecasts or
2867                integer size suffixes (e.g. "ULL").
2868
2869- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2870                If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2871                forced to a value that ensures that CCSR is not relocated.
2872
2873- Floppy Disk Support:
2874                CONFIG_SYS_FDC_DRIVE_NUMBER
2875
2876                the default drive number (default value 0)
2877
2878                CONFIG_SYS_ISA_IO_STRIDE
2879
2880                defines the spacing between FDC chipset registers
2881                (default value 1)
2882
2883                CONFIG_SYS_ISA_IO_OFFSET
2884
2885                defines the offset of register from address. It
2886                depends on which part of the data bus is connected to
2887                the FDC chipset. (default value 0)
2888
2889                If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
2890                CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
2891                default value.
2892
2893                if CONFIG_SYS_FDC_HW_INIT is defined, then the function
2894                fdc_hw_init() is called at the beginning of the FDC
2895                setup. fdc_hw_init() must be provided by the board
2896                source code. It is used to make hardware-dependent
2897                initializations.
2898
2899- CONFIG_IDE_AHB:
2900                Most IDE controllers were designed to be connected with PCI
2901                interface. Only few of them were designed for AHB interface.
2902                When software is doing ATA command and data transfer to
2903                IDE devices through IDE-AHB controller, some additional
2904                registers accessing to these kind of IDE-AHB controller
2905                is required.
2906
2907- CONFIG_SYS_IMMR:      Physical address of the Internal Memory.
2908                DO NOT CHANGE unless you know exactly what you're
2909                doing! (11-4) [MPC8xx systems only]
2910
2911- CONFIG_SYS_INIT_RAM_ADDR:
2912
2913                Start address of memory area that can be used for
2914                initial data and stack; please note that this must be
2915                writable memory that is working WITHOUT special
2916                initialization, i. e. you CANNOT use normal RAM which
2917                will become available only after programming the
2918                memory controller and running certain initialization
2919                sequences.
2920
2921                U-Boot uses the following memory types:
2922                - MPC8xx: IMMR (internal memory of the CPU)
2923
2924- CONFIG_SYS_GBL_DATA_OFFSET:
2925
2926                Offset of the initial data structure in the memory
2927                area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2928                CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2929                data is located at the end of the available space
2930                (sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2931                GENERATED_GBL_DATA_SIZE), and the initial stack is just
2932                below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2933                CONFIG_SYS_GBL_DATA_OFFSET) downward.
2934
2935        Note:
2936                On the MPC824X (or other systems that use the data
2937                cache for initial memory) the address chosen for
2938                CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2939                point to an otherwise UNUSED address space between
2940                the top of RAM and the start of the PCI space.
2941
2942- CONFIG_SYS_SCCR:      System Clock and reset Control Register (15-27)
2943
2944- CONFIG_SYS_OR_TIMING_SDRAM:
2945                SDRAM timing
2946
2947- CONFIG_SYS_MAMR_PTA:
2948                periodic timer for refresh
2949
2950- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2951  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2952  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2953  CONFIG_SYS_BR1_PRELIM:
2954                Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2955
2956- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2957  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2958  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2959                Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2960
2961- CONFIG_PCI_ENUM_ONLY
2962                Only scan through and get the devices on the buses.
2963                Don't do any setup work, presumably because someone or
2964                something has already done it, and we don't need to do it
2965                a second time.  Useful for platforms that are pre-booted
2966                by coreboot or similar.
2967
2968- CONFIG_PCI_INDIRECT_BRIDGE:
2969                Enable support for indirect PCI bridges.
2970
2971- CONFIG_SYS_SRIO:
2972                Chip has SRIO or not
2973
2974- CONFIG_SRIO1:
2975                Board has SRIO 1 port available
2976
2977- CONFIG_SRIO2:
2978                Board has SRIO 2 port available
2979
2980- CONFIG_SRIO_PCIE_BOOT_MASTER
2981                Board can support master function for Boot from SRIO and PCIE
2982
2983- CONFIG_SYS_SRIOn_MEM_VIRT:
2984                Virtual Address of SRIO port 'n' memory region
2985
2986- CONFIG_SYS_SRIOn_MEM_PHYxS:
2987                Physical Address of SRIO port 'n' memory region
2988
2989- CONFIG_SYS_SRIOn_MEM_SIZE:
2990                Size of SRIO port 'n' memory region
2991
2992- CONFIG_SYS_NAND_BUSWIDTH_16BIT
2993                Defined to tell the NAND controller that the NAND chip is using
2994                a 16 bit bus.
2995                Not all NAND drivers use this symbol.
2996                Example of drivers that use it:
2997                - drivers/mtd/nand/raw/ndfc.c
2998                - drivers/mtd/nand/raw/mxc_nand.c
2999
3000- CONFIG_SYS_NDFC_EBC0_CFG
3001                Sets the EBC0_CFG register for the NDFC. If not defined
3002                a default value will be used.
3003
3004- CONFIG_SPD_EEPROM
3005                Get DDR timing information from an I2C EEPROM. Common
3006                with pluggable memory modules such as SODIMMs
3007
3008  SPD_EEPROM_ADDRESS
3009                I2C address of the SPD EEPROM
3010
3011- CONFIG_SYS_SPD_BUS_NUM
3012                If SPD EEPROM is on an I2C bus other than the first
3013                one, specify here. Note that the value must resolve
3014                to something your driver can deal with.
3015
3016- CONFIG_SYS_DDR_RAW_TIMING
3017                Get DDR timing information from other than SPD. Common with
3018                soldered DDR chips onboard without SPD. DDR raw timing
3019                parameters are extracted from datasheet and hard-coded into
3020                header files or board specific files.
3021
3022- CONFIG_FSL_DDR_INTERACTIVE
3023                Enable interactive DDR debugging. See doc/README.fsl-ddr.
3024
3025- CONFIG_FSL_DDR_SYNC_REFRESH
3026                Enable sync of refresh for multiple controllers.
3027
3028- CONFIG_FSL_DDR_BIST
3029                Enable built-in memory test for Freescale DDR controllers.
3030
3031- CONFIG_SYS_83XX_DDR_USES_CS0
3032                Only for 83xx systems. If specified, then DDR should
3033                be configured using CS0 and CS1 instead of CS2 and CS3.
3034
3035- CONFIG_RMII
3036                Enable RMII mode for all FECs.
3037                Note that this is a global option, we can't
3038                have one FEC in standard MII mode and another in RMII mode.
3039
3040- CONFIG_CRC32_VERIFY
3041                Add a verify option to the crc32 command.
3042                The syntax is:
3043
3044                => crc32 -v <address> <count> <crc32>
3045
3046                Where address/count indicate a memory area
3047                and crc32 is the correct crc32 which the
3048                area should have.
3049
3050- CONFIG_LOOPW
3051                Add the "loopw" memory command. This only takes effect if
3052                the memory commands are activated globally (CONFIG_CMD_MEMORY).
3053
3054- CONFIG_MX_CYCLIC
3055                Add the "mdc" and "mwc" memory commands. These are cyclic
3056                "md/mw" commands.
3057                Examples:
3058
3059                => mdc.b 10 4 500
3060                This command will print 4 bytes (10,11,12,13) each 500 ms.
3061
3062                => mwc.l 100 12345678 10
3063                This command will write 12345678 to address 100 all 10 ms.
3064
3065                This only takes effect if the memory commands are activated
3066                globally (CONFIG_CMD_MEMORY).
3067
3068- CONFIG_SKIP_LOWLEVEL_INIT
3069                [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3070                low level initializations (like setting up the memory
3071                controller) are omitted and/or U-Boot does not
3072                relocate itself into RAM.
3073
3074                Normally this variable MUST NOT be defined. The only
3075                exception is when U-Boot is loaded (to RAM) by some
3076                other boot loader or by a debugger which performs
3077                these initializations itself.
3078
3079- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3080                [ARM926EJ-S only] This allows just the call to lowlevel_init()
3081                to be skipped. The normal CP15 init (such as enabling the
3082                instruction cache) is still performed.
3083
3084- CONFIG_SPL_BUILD
3085                Set when the currently-running compilation is for an artifact
3086                that will end up in the SPL (as opposed to the TPL or U-Boot
3087                proper). Code that needs stage-specific behavior should check
3088                this.
3089
3090- CONFIG_TPL_BUILD
3091                Set when the currently-running compilation is for an artifact
3092                that will end up in the TPL (as opposed to the SPL or U-Boot
3093                proper). Code that needs stage-specific behavior should check
3094                this.
3095
3096- CONFIG_SYS_MPC85XX_NO_RESETVEC
3097                Only for 85xx systems. If this variable is specified, the section
3098                .resetvec is not kept and the section .bootpg is placed in the
3099                previous 4k of the .text section.
3100
3101- CONFIG_ARCH_MAP_SYSMEM
3102                Generally U-Boot (and in particular the md command) uses
3103                effective address. It is therefore not necessary to regard
3104                U-Boot address as virtual addresses that need to be translated
3105                to physical addresses. However, sandbox requires this, since
3106                it maintains its own little RAM buffer which contains all
3107                addressable memory. This option causes some memory accesses
3108                to be mapped through map_sysmem() / unmap_sysmem().
3109
3110- CONFIG_X86_RESET_VECTOR
3111                If defined, the x86 reset vector code is included. This is not
3112                needed when U-Boot is running from Coreboot.
3113
3114- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3115                Option to disable subpage write in NAND driver
3116                driver that uses this:
3117                drivers/mtd/nand/raw/davinci_nand.c
3118
3119Freescale QE/FMAN Firmware Support:
3120-----------------------------------
3121
3122The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3123loading of "firmware", which is encoded in the QE firmware binary format.
3124This firmware often needs to be loaded during U-Boot booting, so macros
3125are used to identify the storage device (NOR flash, SPI, etc) and the address
3126within that device.
3127
3128- CONFIG_SYS_FMAN_FW_ADDR
3129        The address in the storage device where the FMAN microcode is located.  The
3130        meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3131        is also specified.
3132
3133- CONFIG_SYS_QE_FW_ADDR
3134        The address in the storage device where the QE microcode is located.  The
3135        meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3136        is also specified.
3137
3138- CONFIG_SYS_QE_FMAN_FW_LENGTH
3139        The maximum possible size of the firmware.  The firmware binary format
3140        has a field that specifies the actual size of the firmware, but it
3141        might not be possible to read any part of the firmware unless some
3142        local storage is allocated to hold the entire firmware first.
3143
3144- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3145        Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3146        normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3147        virtual address in NOR flash.
3148
3149- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3150        Specifies that QE/FMAN firmware is located in NAND flash.
3151        CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3152
3153- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3154        Specifies that QE/FMAN firmware is located on the primary SD/MMC
3155        device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3156
3157- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3158        Specifies that QE/FMAN firmware is located in the remote (master)
3159        memory space.   CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3160        can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3161        window->master inbound window->master LAW->the ucode address in
3162        master's memory space.
3163
3164Freescale Layerscape Management Complex Firmware Support:
3165---------------------------------------------------------
3166The Freescale Layerscape Management Complex (MC) supports the loading of
3167"firmware".
3168This firmware often needs to be loaded during U-Boot booting, so macros
3169are used to identify the storage device (NOR flash, SPI, etc) and the address
3170within that device.
3171
3172- CONFIG_FSL_MC_ENET
3173        Enable the MC driver for Layerscape SoCs.
3174
3175Freescale Layerscape Debug Server Support:
3176-------------------------------------------
3177The Freescale Layerscape Debug Server Support supports the loading of
3178"Debug Server firmware" and triggering SP boot-rom.
3179This firmware often needs to be loaded during U-Boot booting.
3180
3181- CONFIG_SYS_MC_RSV_MEM_ALIGN
3182        Define alignment of reserved memory MC requires
3183
3184Reproducible builds
3185-------------------
3186
3187In order to achieve reproducible builds, timestamps used in the U-Boot build
3188process have to be set to a fixed value.
3189
3190This is done using the SOURCE_DATE_EPOCH environment variable.
3191SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3192option for U-Boot or an environment variable in U-Boot.
3193
3194SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3195
3196Building the Software:
3197======================
3198
3199Building U-Boot has been tested in several native build environments
3200and in many different cross environments. Of course we cannot support
3201all possibly existing versions of cross development tools in all
3202(potentially obsolete) versions. In case of tool chain problems we
3203recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3204which is extensively used to build and test U-Boot.
3205
3206If you are not using a native environment, it is assumed that you
3207have GNU cross compiling tools available in your path. In this case,
3208you must set the environment variable CROSS_COMPILE in your shell.
3209Note that no changes to the Makefile or any other source files are
3210necessary. For example using the ELDK on a 4xx CPU, please enter:
3211
3212        $ CROSS_COMPILE=ppc_4xx-
3213        $ export CROSS_COMPILE
3214
3215Note: If you wish to generate Windows versions of the utilities in
3216      the tools directory you can use the MinGW toolchain
3217      (http://www.mingw.org).  Set your HOST tools to the MinGW
3218      toolchain and execute 'make tools'.  For example:
3219
3220       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3221
3222      Binaries such as tools/mkimage.exe will be created which can
3223      be executed on computers running Windows.
3224
3225U-Boot is intended to be simple to build. After installing the
3226sources you must configure U-Boot for one specific board type. This
3227is done by typing:
3228
3229        make NAME_defconfig
3230
3231where "NAME_defconfig" is the name of one of the existing configu-
3232rations; see boards.cfg for supported names.
3233
3234Note: for some board special configuration names may exist; check if
3235      additional information is available from the board vendor; for
3236      instance, the TQM823L systems are available without (standard)
3237      or with LCD support. You can select such additional "features"
3238      when choosing the configuration, i. e.
3239
3240      make TQM823L_defconfig
3241        - will configure for a plain TQM823L, i. e. no LCD support
3242
3243      make TQM823L_LCD_defconfig
3244        - will configure for a TQM823L with U-Boot console on LCD
3245
3246      etc.
3247
3248
3249Finally, type "make all", and you should get some working U-Boot
3250images ready for download to / installation on your system:
3251
3252- "u-boot.bin" is a raw binary image
3253- "u-boot" is an image in ELF binary format
3254- "u-boot.srec" is in Motorola S-Record format
3255
3256By default the build is performed locally and the objects are saved
3257in the source directory. One of the two methods can be used to change
3258this behavior and build U-Boot to some external directory:
3259
32601. Add O= to the make command line invocations:
3261
3262        make O=/tmp/build distclean
3263        make O=/tmp/build NAME_defconfig
3264        make O=/tmp/build all
3265
32662. Set environment variable KBUILD_OUTPUT to point to the desired location:
3267
3268        export KBUILD_OUTPUT=/tmp/build
3269        make distclean
3270        make NAME_defconfig
3271        make all
3272
3273Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3274variable.
3275
3276User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3277setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3278For example to treat all compiler warnings as errors:
3279
3280        make KCFLAGS=-Werror
3281
3282Please be aware that the Makefiles assume you are using GNU make, so
3283for instance on NetBSD you might need to use "gmake" instead of
3284native "make".
3285
3286
3287If the system board that you have is not listed, then you will need
3288to port U-Boot to your hardware platform. To do this, follow these
3289steps:
3290
32911.  Create a new directory to hold your board specific code. Add any
3292    files you need. In your board directory, you will need at least
3293    the "Makefile" and a "<board>.c".
32942.  Create a new configuration file "include/configs/<board>.h" for
3295    your board.
32963.  If you're porting U-Boot to a new CPU, then also create a new
3297    directory to hold your CPU specific code. Add any files you need.
32984.  Run "make <board>_defconfig" with your new name.
32995.  Type "make", and you should get a working "u-boot.srec" file
3300    to be installed on your target system.
33016.  Debug and solve any problems that might arise.
3302    [Of course, this last step is much harder than it sounds.]
3303
3304
3305Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3306==============================================================
3307
3308If you have modified U-Boot sources (for instance added a new board
3309or support for new devices, a new CPU, etc.) you are expected to
3310provide feedback to the other developers. The feedback normally takes
3311the form of a "patch", i.e. a context diff against a certain (latest
3312official or latest in the git repository) version of U-Boot sources.
3313
3314But before you submit such a patch, please verify that your modifi-
3315cation did not break existing code. At least make sure that *ALL* of
3316the supported boards compile WITHOUT ANY compiler warnings. To do so,
3317just run the buildman script (tools/buildman/buildman), which will
3318configure and build U-Boot for ALL supported system. Be warned, this
3319will take a while. Please see the buildman README, or run 'buildman -H'
3320for documentation.
3321
3322
3323See also "U-Boot Porting Guide" below.
3324
3325
3326Monitor Commands - Overview:
3327============================
3328
3329go      - start application at address 'addr'
3330run     - run commands in an environment variable
3331bootm   - boot application image from memory
3332bootp   - boot image via network using BootP/TFTP protocol
3333bootz   - boot zImage from memory
3334tftpboot- boot image via network using TFTP protocol
3335               and env variables "ipaddr" and "serverip"
3336               (and eventually "gatewayip")
3337tftpput - upload a file via network using TFTP protocol
3338rarpboot- boot image via network using RARP/TFTP protocol
3339diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3340loads   - load S-Record file over serial line
3341loadb   - load binary file over serial line (kermit mode)
3342md      - memory display
3343mm      - memory modify (auto-incrementing)
3344nm      - memory modify (constant address)
3345mw      - memory write (fill)
3346cp      - memory copy
3347cmp     - memory compare
3348crc32   - checksum calculation
3349i2c     - I2C sub-system
3350sspi    - SPI utility commands
3351base    - print or set address offset
3352printenv- print environment variables
3353setenv  - set environment variables
3354saveenv - save environment variables to persistent storage
3355protect - enable or disable FLASH write protection
3356erase   - erase FLASH memory
3357flinfo  - print FLASH memory information
3358nand    - NAND memory operations (see doc/README.nand)
3359bdinfo  - print Board Info structure
3360iminfo  - print header information for application image
3361coninfo - print console devices and informations
3362ide     - IDE sub-system
3363loop    - infinite loop on address range
3364loopw   - infinite write loop on address range
3365mtest   - simple RAM test
3366icache  - enable or disable instruction cache
3367dcache  - enable or disable data cache
3368reset   - Perform RESET of the CPU
3369echo    - echo args to console
3370version - print monitor version
3371help    - print online help
3372?       - alias for 'help'
3373
3374
3375Monitor Commands - Detailed Description:
3376========================================
3377
3378TODO.
3379
3380For now: just type "help <command>".
3381
3382
3383Environment Variables:
3384======================
3385
3386U-Boot supports user configuration using Environment Variables which
3387can be made persistent by saving to Flash memory.
3388
3389Environment Variables are set using "setenv", printed using
3390"printenv", and saved to Flash using "saveenv". Using "setenv"
3391without a value can be used to delete a variable from the
3392environment. As long as you don't save the environment you are
3393working with an in-memory copy. In case the Flash area containing the
3394environment is erased by accident, a default environment is provided.
3395
3396Some configuration options can be set using Environment Variables.
3397
3398List of environment variables (most likely not complete):
3399
3400  baudrate      - see CONFIG_BAUDRATE
3401
3402  bootdelay     - see CONFIG_BOOTDELAY
3403
3404  bootcmd       - see CONFIG_BOOTCOMMAND
3405
3406  bootargs      - Boot arguments when booting an RTOS image
3407
3408  bootfile      - Name of the image to load with TFTP
3409
3410  bootm_low     - Memory range available for image processing in the bootm
3411                  command can be restricted. This variable is given as
3412                  a hexadecimal number and defines lowest address allowed
3413                  for use by the bootm command. See also "bootm_size"
3414                  environment variable. Address defined by "bootm_low" is
3415                  also the base of the initial memory mapping for the Linux
3416                  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3417                  bootm_mapsize.
3418
3419  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3420                  This variable is given as a hexadecimal number and it
3421                  defines the size of the memory region starting at base
3422                  address bootm_low that is accessible by the Linux kernel
3423                  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3424                  as the default value if it is defined, and bootm_size is
3425                  used otherwise.
3426
3427  bootm_size    - Memory range available for image processing in the bootm
3428                  command can be restricted. This variable is given as
3429                  a hexadecimal number and defines the size of the region
3430                  allowed for use by the bootm command. See also "bootm_low"
3431                  environment variable.
3432
3433  bootstopkeysha256, bootdelaykey, bootstopkey  - See README.autoboot
3434
3435  updatefile    - Location of the software update file on a TFTP server, used
3436                  by the automatic software update feature. Please refer to
3437                  documentation in doc/README.update for more details.
3438
3439  autoload      - if set to "no" (any string beginning with 'n'),
3440                  "bootp" will just load perform a lookup of the
3441                  configuration from the BOOTP server, but not try to
3442                  load any image using TFTP
3443
3444  autostart     - if set to "yes", an image loaded using the "bootp",
3445                  "rarpboot", "tftpboot" or "diskboot" commands will
3446                  be automatically started (by internally calling
3447                  "bootm")
3448
3449                  If set to "no", a standalone image passed to the
3450                  "bootm" command will be copied to the load address
3451                  (and eventually uncompressed), but NOT be started.
3452                  This can be used to load and uncompress arbitrary
3453                  data.
3454
3455  fdt_high      - if set this restricts the maximum address that the
3456                  flattened device tree will be copied into upon boot.
3457                  For example, if you have a system with 1 GB memory
3458                  at physical address 0x10000000, while Linux kernel
3459                  only recognizes the first 704 MB as low memory, you
3460                  may need to set fdt_high as 0x3C000000 to have the
3461                  device tree blob be copied to the maximum address
3462                  of the 704 MB low memory, so that Linux kernel can
3463                  access it during the boot procedure.
3464
3465                  If this is set to the special value 0xFFFFFFFF then
3466                  the fdt will not be copied at all on boot.  For this
3467                  to work it must reside in writable memory, have
3468                  sufficient padding on the end of it for u-boot to
3469                  add the information it needs into it, and the memory
3470                  must be accessible by the kernel.
3471
3472  fdtcontroladdr- if set this is the address of the control flattened
3473                  device tree used by U-Boot when CONFIG_OF_CONTROL is
3474                  defined.
3475
3476  i2cfast       - (PPC405GP|PPC405EP only)
3477                  if set to 'y' configures Linux I2C driver for fast
3478                  mode (400kHZ). This environment variable is used in
3479                  initialization code. So, for changes to be effective
3480                  it must be saved and board must be reset.
3481
3482  initrd_high   - restrict positioning of initrd images:
3483                  If this variable is not set, initrd images will be
3484                  copied to the highest possible address in RAM; this
3485                  is usually what you want since it allows for
3486                  maximum initrd size. If for some reason you want to
3487                  make sure that the initrd image is loaded below the
3488                  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3489                  variable to a value of "no" or "off" or "0".
3490                  Alternatively, you can set it to a maximum upper
3491                  address to use (U-Boot will still check that it
3492                  does not overwrite the U-Boot stack and data).
3493
3494                  For instance, when you have a system with 16 MB
3495                  RAM, and want to reserve 4 MB from use by Linux,
3496                  you can do this by adding "mem=12M" to the value of
3497                  the "bootargs" variable. However, now you must make
3498                  sure that the initrd image is placed in the first
3499                  12 MB as well - this can be done with
3500
3501                  setenv initrd_high 00c00000
3502
3503                  If you set initrd_high to 0xFFFFFFFF, this is an
3504                  indication to U-Boot that all addresses are legal
3505                  for the Linux kernel, including addresses in flash
3506                  memory. In this case U-Boot will NOT COPY the
3507                  ramdisk at all. This may be useful to reduce the
3508                  boot time on your system, but requires that this
3509                  feature is supported by your Linux kernel.
3510
3511  ipaddr        - IP address; needed for tftpboot command
3512
3513  loadaddr      - Default load address for commands like "bootp",
3514                  "rarpboot", "tftpboot", "loadb" or "diskboot"
3515
3516  loads_echo    - see CONFIG_LOADS_ECHO
3517
3518  serverip      - TFTP server IP address; needed for tftpboot command
3519
3520  bootretry     - see CONFIG_BOOT_RETRY_TIME
3521
3522  bootdelaykey  - see CONFIG_AUTOBOOT_DELAY_STR
3523
3524  bootstopkey   - see CONFIG_AUTOBOOT_STOP_STR
3525
3526  ethprime      - controls which interface is used first.
3527
3528  ethact        - controls which interface is currently active.
3529                  For example you can do the following
3530
3531                  => setenv ethact FEC
3532                  => ping 192.168.0.1 # traffic sent on FEC
3533                  => setenv ethact SCC
3534                  => ping 10.0.0.1 # traffic sent on SCC
3535
3536  ethrotate     - When set to "no" U-Boot does not go through all
3537                  available network interfaces.
3538                  It just stays at the currently selected interface.
3539
3540  netretry      - When set to "no" each network operation will
3541                  either succeed or fail without retrying.
3542                  When set to "once" the network operation will
3543                  fail when all the available network interfaces
3544                  are tried once without success.
3545                  Useful on scripts which control the retry operation
3546                  themselves.
3547
3548  npe_ucode     - set load address for the NPE microcode
3549
3550  silent_linux  - If set then Linux will be told to boot silently, by
3551                  changing the console to be empty. If "yes" it will be
3552                  made silent. If "no" it will not be made silent. If
3553                  unset, then it will be made silent if the U-Boot console
3554                  is silent.
3555
3556  tftpsrcp      - If this is set, the value is used for TFTP's
3557                  UDP source port.
3558
3559  tftpdstp      - If this is set, the value is used for TFTP's UDP
3560                  destination port instead of the Well Know Port 69.
3561
3562  tftpblocksize - Block size to use for TFTP transfers; if not set,
3563                  we use the TFTP server's default block size
3564
3565  tftptimeout   - Retransmission timeout for TFTP packets (in milli-
3566                  seconds, minimum value is 1000 = 1 second). Defines
3567                  when a packet is considered to be lost so it has to
3568                  be retransmitted. The default is 5000 = 5 seconds.
3569                  Lowering this value may make downloads succeed
3570                  faster in networks with high packet loss rates or
3571                  with unreliable TFTP servers.
3572
3573  tftptimeoutcountmax   - maximum count of TFTP timeouts (no
3574                  unit, minimum value = 0). Defines how many timeouts
3575                  can happen during a single file transfer before that
3576                  transfer is aborted. The default is 10, and 0 means
3577                  'no timeouts allowed'. Increasing this value may help
3578                  downloads succeed with high packet loss rates, or with
3579                  unreliable TFTP servers or client hardware.
3580
3581  vlan          - When set to a value < 4095 the traffic over
3582                  Ethernet is encapsulated/received over 802.1q
3583                  VLAN tagged frames.
3584
3585  bootpretryperiod      - Period during which BOOTP/DHCP sends retries.
3586                  Unsigned value, in milliseconds. If not set, the period will
3587                  be either the default (28000), or a value based on
3588                  CONFIG_NET_RETRY_COUNT, if defined. This value has
3589                  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3590
3591The following image location variables contain the location of images
3592used in booting. The "Image" column gives the role of the image and is
3593not an environment variable name. The other columns are environment
3594variable names. "File Name" gives the name of the file on a TFTP
3595server, "RAM Address" gives the location in RAM the image will be
3596loaded to, and "Flash Location" gives the image's address in NOR
3597flash or offset in NAND flash.
3598
3599*Note* - these variables don't have to be defined for all boards, some
3600boards currently use other variables for these purposes, and some
3601boards use these variables for other purposes.
3602
3603Image               File Name        RAM Address       Flash Location
3604-----               ---------        -----------       --------------
3605u-boot              u-boot           u-boot_addr_r     u-boot_addr
3606Linux kernel        bootfile         kernel_addr_r     kernel_addr
3607device tree blob    fdtfile          fdt_addr_r        fdt_addr
3608ramdisk             ramdiskfile      ramdisk_addr_r    ramdisk_addr
3609
3610The following environment variables may be used and automatically
3611updated by the network boot commands ("bootp" and "rarpboot"),
3612depending the information provided by your boot server:
3613
3614  bootfile      - see above
3615  dnsip         - IP address of your Domain Name Server
3616  dnsip2        - IP address of your secondary Domain Name Server
3617  gatewayip     - IP address of the Gateway (Router) to use
3618  hostname      - Target hostname
3619  ipaddr        - see above
3620  netmask       - Subnet Mask
3621  rootpath      - Pathname of the root filesystem on the NFS server
3622  serverip      - see above
3623
3624
3625There are two special Environment Variables:
3626
3627  serial#       - contains hardware identification information such
3628                  as type string and/or serial number
3629  ethaddr       - Ethernet address
3630
3631These variables can be set only once (usually during manufacturing of
3632the board). U-Boot refuses to delete or overwrite these variables
3633once they have been set once.
3634
3635
3636Further special Environment Variables:
3637
3638  ver           - Contains the U-Boot version string as printed
3639                  with the "version" command. This variable is
3640                  readonly (see CONFIG_VERSION_VARIABLE).
3641
3642
3643Please note that changes to some configuration parameters may take
3644only effect after the next boot (yes, that's just like Windoze :-).
3645
3646
3647Callback functions for environment variables:
3648---------------------------------------------
3649
3650For some environment variables, the behavior of u-boot needs to change
3651when their values are changed.  This functionality allows functions to
3652be associated with arbitrary variables.  On creation, overwrite, or
3653deletion, the callback will provide the opportunity for some side
3654effect to happen or for the change to be rejected.
3655
3656The callbacks are named and associated with a function using the
3657U_BOOT_ENV_CALLBACK macro in your board or driver code.
3658
3659These callbacks are associated with variables in one of two ways.  The
3660static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3661in the board configuration to a string that defines a list of
3662associations.  The list must be in the following format:
3663
3664        entry = variable_name[:callback_name]
3665        list = entry[,list]
3666
3667If the callback name is not specified, then the callback is deleted.
3668Spaces are also allowed anywhere in the list.
3669
3670Callbacks can also be associated by defining the ".callbacks" variable
3671with the same list format above.  Any association in ".callbacks" will
3672override any association in the static list. You can define
3673CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3674".callbacks" environment variable in the default or embedded environment.
3675
3676If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3677regular expression. This allows multiple variables to be connected to
3678the same callback without explicitly listing them all out.
3679
3680The signature of the callback functions is:
3681
3682    int callback(const char *name, const char *value, enum env_op op, int flags)
3683
3684* name - changed environment variable
3685* value - new value of the environment variable
3686* op - operation (create, overwrite, or delete)
3687* flags - attributes of the environment variable change, see flags H_* in
3688  include/search.h
3689
3690The return value is 0 if the variable change is accepted and 1 otherwise.
3691
3692Command Line Parsing:
3693=====================
3694
3695There are two different command line parsers available with U-Boot:
3696the old "simple" one, and the much more powerful "hush" shell:
3697
3698Old, simple command line parser:
3699--------------------------------
3700
3701- supports environment variables (through setenv / saveenv commands)
3702- several commands on one line, separated by ';'
3703- variable substitution using "... ${name} ..." syntax
3704- special characters ('$', ';') can be escaped by prefixing with '\',
3705  for example:
3706        setenv bootcmd bootm \${address}
3707- You can also escape text by enclosing in single apostrophes, for example:
3708        setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3709
3710Hush shell:
3711-----------
3712
3713- similar to Bourne shell, with control structures like
3714  if...then...else...fi, for...do...done; while...do...done,
3715  until...do...done, ...
3716- supports environment ("global") variables (through setenv / saveenv
3717  commands) and local shell variables (through standard shell syntax
3718  "name=value"); only environment variables can be used with "run"
3719  command
3720
3721General rules:
3722--------------
3723
3724(1) If a command line (or an environment variable executed by a "run"
3725    command) contains several commands separated by semicolon, and
3726    one of these commands fails, then the remaining commands will be
3727    executed anyway.
3728
3729(2) If you execute several variables with one call to run (i. e.
3730    calling run with a list of variables as arguments), any failing
3731    command will cause "run" to terminate, i. e. the remaining
3732    variables are not executed.
3733
3734Note for Redundant Ethernet Interfaces:
3735=======================================
3736
3737Some boards come with redundant Ethernet interfaces; U-Boot supports
3738such configurations and is capable of automatic selection of a
3739"working" interface when needed. MAC assignment works as follows:
3740
3741Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3742MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3743"eth1addr" (=>eth1), "eth2addr", ...
3744
3745If the network interface stores some valid MAC address (for instance
3746in SROM), this is used as default address if there is NO correspon-
3747ding setting in the environment; if the corresponding environment
3748variable is set, this overrides the settings in the card; that means:
3749
3750o If the SROM has a valid MAC address, and there is no address in the
3751  environment, the SROM's address is used.
3752
3753o If there is no valid address in the SROM, and a definition in the
3754  environment exists, then the value from the environment variable is
3755  used.
3756
3757o If both the SROM and the environment contain a MAC address, and
3758  both addresses are the same, this MAC address is used.
3759
3760o If both the SROM and the environment contain a MAC address, and the
3761  addresses differ, the value from the environment is used and a
3762  warning is printed.
3763
3764o If neither SROM nor the environment contain a MAC address, an error
3765  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3766  a random, locally-assigned MAC is used.
3767
3768If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3769will be programmed into hardware as part of the initialization process.  This
3770may be skipped by setting the appropriate 'ethmacskip' environment variable.
3771The naming convention is as follows:
3772"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3773
3774Image Formats:
3775==============
3776
3777U-Boot is capable of booting (and performing other auxiliary operations on)
3778images in two formats:
3779
3780New uImage format (FIT)
3781-----------------------
3782
3783Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3784to Flattened Device Tree). It allows the use of images with multiple
3785components (several kernels, ramdisks, etc.), with contents protected by
3786SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3787
3788
3789Old uImage format
3790-----------------
3791
3792Old image format is based on binary files which can be basically anything,
3793preceded by a special header; see the definitions in include/image.h for
3794details; basically, the header defines the following image properties:
3795
3796* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3797  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3798  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3799  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3800  INTEGRITY).
3801* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3802  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3803  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3804* Compression Type (uncompressed, gzip, bzip2)
3805* Load Address
3806* Entry Point
3807* Image Name
3808* Image Timestamp
3809
3810The header is marked by a special Magic Number, and both the header
3811and the data portions of the image are secured against corruption by
3812CRC32 checksums.
3813
3814
3815Linux Support:
3816==============
3817
3818Although U-Boot should support any OS or standalone application
3819easily, the main focus has always been on Linux during the design of
3820U-Boot.
3821
3822U-Boot includes many features that so far have been part of some
3823special "boot loader" code within the Linux kernel. Also, any
3824"initrd" images to be used are no longer part of one big Linux image;
3825instead, kernel and "initrd" are separate images. This implementation
3826serves several purposes:
3827
3828- the same features can be used for other OS or standalone
3829  applications (for instance: using compressed images to reduce the
3830  Flash memory footprint)
3831
3832- it becomes much easier to port new Linux kernel versions because
3833  lots of low-level, hardware dependent stuff are done by U-Boot
3834
3835- the same Linux kernel image can now be used with different "initrd"
3836  images; of course this also means that different kernel images can
3837  be run with the same "initrd". This makes testing easier (you don't
3838  have to build a new "zImage.initrd" Linux image when you just
3839  change a file in your "initrd"). Also, a field-upgrade of the
3840  software is easier now.
3841
3842
3843Linux HOWTO:
3844============
3845
3846Porting Linux to U-Boot based systems:
3847---------------------------------------
3848
3849U-Boot cannot save you from doing all the necessary modifications to
3850configure the Linux device drivers for use with your target hardware
3851(no, we don't intend to provide a full virtual machine interface to
3852Linux :-).
3853
3854But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3855
3856Just make sure your machine specific header file (for instance
3857include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3858Information structure as we define in include/asm-<arch>/u-boot.h,
3859and make sure that your definition of IMAP_ADDR uses the same value
3860as your U-Boot configuration in CONFIG_SYS_IMMR.
3861
3862Note that U-Boot now has a driver model, a unified model for drivers.
3863If you are adding a new driver, plumb it into driver model. If there
3864is no uclass available, you are encouraged to create one. See
3865doc/driver-model.
3866
3867
3868Configuring the Linux kernel:
3869-----------------------------
3870
3871No specific requirements for U-Boot. Make sure you have some root
3872device (initial ramdisk, NFS) for your target system.
3873
3874
3875Building a Linux Image:
3876-----------------------
3877
3878With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3879not used. If you use recent kernel source, a new build target
3880"uImage" will exist which automatically builds an image usable by
3881U-Boot. Most older kernels also have support for a "pImage" target,
3882which was introduced for our predecessor project PPCBoot and uses a
3883100% compatible format.
3884
3885Example:
3886
3887        make TQM850L_defconfig
3888        make oldconfig
3889        make dep
3890        make uImage
3891
3892The "uImage" build target uses a special tool (in 'tools/mkimage') to
3893encapsulate a compressed Linux kernel image with header  information,
3894CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3895
3896* build a standard "vmlinux" kernel image (in ELF binary format):
3897
3898* convert the kernel into a raw binary image:
3899
3900        ${CROSS_COMPILE}-objcopy -O binary \
3901                                 -R .note -R .comment \
3902                                 -S vmlinux linux.bin
3903
3904* compress the binary image:
3905
3906        gzip -9 linux.bin
3907
3908* package compressed binary image for U-Boot:
3909
3910        mkimage -A ppc -O linux -T kernel -C gzip \
3911                -a 0 -e 0 -n "Linux Kernel Image" \
3912                -d linux.bin.gz uImage
3913
3914
3915The "mkimage" tool can also be used to create ramdisk images for use
3916with U-Boot, either separated from the Linux kernel image, or
3917combined into one file. "mkimage" encapsulates the images with a 64
3918byte header containing information about target architecture,
3919operating system, image type, compression method, entry points, time
3920stamp, CRC32 checksums, etc.
3921
3922"mkimage" can be called in two ways: to verify existing images and
3923print the header information, or to build new images.
3924
3925In the first form (with "-l" option) mkimage lists the information
3926contained in the header of an existing U-Boot image; this includes
3927checksum verification:
3928
3929        tools/mkimage -l image
3930          -l ==> list image header information
3931
3932The second form (with "-d" option) is used to build a U-Boot image
3933from a "data file" which is used as image payload:
3934
3935        tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3936                      -n name -d data_file image
3937          -A ==> set architecture to 'arch'
3938          -O ==> set operating system to 'os'
3939          -T ==> set image type to 'type'
3940          -C ==> set compression type 'comp'
3941          -a ==> set load address to 'addr' (hex)
3942          -e ==> set entry point to 'ep' (hex)
3943          -n ==> set image name to 'name'
3944          -d ==> use image data from 'datafile'
3945
3946Right now, all Linux kernels for PowerPC systems use the same load
3947address (0x00000000), but the entry point address depends on the
3948kernel version:
3949
3950- 2.2.x kernels have the entry point at 0x0000000C,
3951- 2.3.x and later kernels have the entry point at 0x00000000.
3952
3953So a typical call to build a U-Boot image would read:
3954
3955        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3956        > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3957        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3958        > examples/uImage.TQM850L
3959        Image Name:   2.4.4 kernel for TQM850L
3960        Created:      Wed Jul 19 02:34:59 2000
3961        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3962        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3963        Load Address: 0x00000000
3964        Entry Point:  0x00000000
3965
3966To verify the contents of the image (or check for corruption):
3967
3968        -> tools/mkimage -l examples/uImage.TQM850L
3969        Image Name:   2.4.4 kernel for TQM850L
3970        Created:      Wed Jul 19 02:34:59 2000
3971        Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3972        Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3973        Load Address: 0x00000000
3974        Entry Point:  0x00000000
3975
3976NOTE: for embedded systems where boot time is critical you can trade
3977speed for memory and install an UNCOMPRESSED image instead: this
3978needs more space in Flash, but boots much faster since it does not
3979need to be uncompressed:
3980
3981        -> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3982        -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3983        > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3984        > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3985        > examples/uImage.TQM850L-uncompressed
3986        Image Name:   2.4.4 kernel for TQM850L
3987        Created:      Wed Jul 19 02:34:59 2000
3988        Image Type:   PowerPC Linux Kernel Image (uncompressed)
3989        Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3990        Load Address: 0x00000000
3991        Entry Point:  0x00000000
3992
3993
3994Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3995when your kernel is intended to use an initial ramdisk:
3996
3997        -> tools/mkimage -n 'Simple Ramdisk Image' \
3998        > -A ppc -O linux -T ramdisk -C gzip \
3999        > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4000        Image Name:   Simple Ramdisk Image
4001        Created:      Wed Jan 12 14:01:50 2000
4002        Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4003        Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4004        Load Address: 0x00000000
4005        Entry Point:  0x00000000
4006
4007The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4008option performs the converse operation of the mkimage's second form (the "-d"
4009option). Given an image built by mkimage, the dumpimage extracts a "data file"
4010from the image:
4011
4012        tools/dumpimage -i image -T type -p position data_file
4013          -i ==> extract from the 'image' a specific 'data_file'
4014          -T ==> set image type to 'type'
4015          -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4016
4017
4018Installing a Linux Image:
4019-------------------------
4020
4021To downloading a U-Boot image over the serial (console) interface,
4022you must convert the image to S-Record format:
4023
4024        objcopy -I binary -O srec examples/image examples/image.srec
4025
4026The 'objcopy' does not understand the information in the U-Boot
4027image header, so the resulting S-Record file will be relative to
4028address 0x00000000. To load it to a given address, you need to
4029specify the target address as 'offset' parameter with the 'loads'
4030command.
4031
4032Example: install the image to address 0x40100000 (which on the
4033TQM8xxL is in the first Flash bank):
4034
4035        => erase 40100000 401FFFFF
4036
4037        .......... done
4038        Erased 8 sectors
4039
4040        => loads 40100000
4041        ## Ready for S-Record download ...
4042        ~>examples/image.srec
4043        1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4044        ...
4045        15989 15990 15991 15992
4046        [file transfer complete]
4047        [connected]
4048        ## Start Addr = 0x00000000
4049
4050
4051You can check the success of the download using the 'iminfo' command;
4052this includes a checksum verification so you can be sure no data
4053corruption happened:
4054
4055        => imi 40100000
4056
4057        ## Checking Image at 40100000 ...
4058           Image Name:   2.2.13 for initrd on TQM850L
4059           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4060           Data Size:    335725 Bytes = 327 kB = 0 MB
4061           Load Address: 00000000
4062           Entry Point:  0000000c
4063           Verifying Checksum ... OK
4064
4065
4066Boot Linux:
4067-----------
4068
4069The "bootm" command is used to boot an application that is stored in
4070memory (RAM or Flash). In case of a Linux kernel image, the contents
4071of the "bootargs" environment variable is passed to the kernel as
4072parameters. You can check and modify this variable using the
4073"printenv" and "setenv" commands:
4074
4075
4076        => printenv bootargs
4077        bootargs=root=/dev/ram
4078
4079        => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4080
4081        => printenv bootargs
4082        bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4083
4084        => bootm 40020000
4085        ## Booting Linux kernel at 40020000 ...
4086           Image Name:   2.2.13 for NFS on TQM850L
4087           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4088           Data Size:    381681 Bytes = 372 kB = 0 MB
4089           Load Address: 00000000
4090           Entry Point:  0000000c
4091           Verifying Checksum ... OK
4092           Uncompressing Kernel Image ... OK
4093        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
4094        Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4095        time_init: decrementer frequency = 187500000/60
4096        Calibrating delay loop... 49.77 BogoMIPS
4097        Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4098        ...
4099
4100If you want to boot a Linux kernel with initial RAM disk, you pass
4101the memory addresses of both the kernel and the initrd image (PPBCOOT
4102format!) to the "bootm" command:
4103
4104        => imi 40100000 40200000
4105
4106        ## Checking Image at 40100000 ...
4107           Image Name:   2.2.13 for initrd on TQM850L
4108           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4109           Data Size:    335725 Bytes = 327 kB = 0 MB
4110           Load Address: 00000000
4111           Entry Point:  0000000c
4112           Verifying Checksum ... OK
4113
4114        ## Checking Image at 40200000 ...
4115           Image Name:   Simple Ramdisk Image
4116           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4117           Data Size:    566530 Bytes = 553 kB = 0 MB
4118           Load Address: 00000000
4119           Entry Point:  00000000
4120           Verifying Checksum ... OK
4121
4122        => bootm 40100000 40200000
4123        ## Booting Linux kernel at 40100000 ...
4124           Image Name:   2.2.13 for initrd on TQM850L
4125           Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4126           Data Size:    335725 Bytes = 327 kB = 0 MB
4127           Load Address: 00000000
4128           Entry Point:  0000000c
4129           Verifying Checksum ... OK
4130           Uncompressing Kernel Image ... OK
4131        ## Loading RAMDisk Image at 40200000 ...
4132           Image Name:   Simple Ramdisk Image
4133           Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4134           Data Size:    566530 Bytes = 553 kB = 0 MB
4135           Load Address: 00000000
4136           Entry Point:  00000000
4137           Verifying Checksum ... OK
4138           Loading Ramdisk ... OK
4139        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
4140        Boot arguments: root=/dev/ram
4141        time_init: decrementer frequency = 187500000/60
4142        Calibrating delay loop... 49.77 BogoMIPS
4143        ...
4144        RAMDISK: Compressed image found at block 0
4145        VFS: Mounted root (ext2 filesystem).
4146
4147        bash#
4148
4149Boot Linux and pass a flat device tree:
4150-----------
4151
4152First, U-Boot must be compiled with the appropriate defines. See the section
4153titled "Linux Kernel Interface" above for a more in depth explanation. The
4154following is an example of how to start a kernel and pass an updated
4155flat device tree:
4156
4157=> print oftaddr
4158oftaddr=0x300000
4159=> print oft
4160oft=oftrees/mpc8540ads.dtb
4161=> tftp $oftaddr $oft
4162Speed: 1000, full duplex
4163Using TSEC0 device
4164TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4165Filename 'oftrees/mpc8540ads.dtb'.
4166Load address: 0x300000
4167Loading: #
4168done
4169Bytes transferred = 4106 (100a hex)
4170=> tftp $loadaddr $bootfile
4171Speed: 1000, full duplex
4172Using TSEC0 device
4173TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4174Filename 'uImage'.
4175Load address: 0x200000
4176Loading:############
4177done
4178Bytes transferred = 1029407 (fb51f hex)
4179=> print loadaddr
4180loadaddr=200000
4181=> print oftaddr
4182oftaddr=0x300000
4183=> bootm $loadaddr - $oftaddr
4184## Booting image at 00200000 ...
4185   Image Name:   Linux-2.6.17-dirty
4186   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4187   Data Size:    1029343 Bytes = 1005.2 kB
4188   Load Address: 00000000
4189   Entry Point:  00000000
4190   Verifying Checksum ... OK
4191   Uncompressing Kernel Image ... OK
4192Booting using flat device tree at 0x300000
4193Using MPC85xx ADS machine description
4194Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4195[snip]
4196
4197
4198More About U-Boot Image Types:
4199------------------------------
4200
4201U-Boot supports the following image types:
4202
4203   "Standalone Programs" are directly runnable in the environment
4204        provided by U-Boot; it is expected that (if they behave
4205        well) you can continue to work in U-Boot after return from
4206        the Standalone Program.
4207   "OS Kernel Images" are usually images of some Embedded OS which
4208        will take over control completely. Usually these programs
4209        will install their own set of exception handlers, device
4210        drivers, set up the MMU, etc. - this means, that you cannot
4211        expect to re-enter U-Boot except by resetting the CPU.
4212   "RAMDisk Images" are more or less just data blocks, and their
4213        parameters (address, size) are passed to an OS kernel that is
4214        being started.
4215   "Multi-File Images" contain several images, typically an OS
4216        (Linux) kernel image and one or more data images like
4217        RAMDisks. This construct is useful for instance when you want
4218        to boot over the network using BOOTP etc., where the boot
4219        server provides just a single image file, but you want to get
4220        for instance an OS kernel and a RAMDisk image.
4221
4222        "Multi-File Images" start with a list of image sizes, each
4223        image size (in bytes) specified by an "uint32_t" in network
4224        byte order. This list is terminated by an "(uint32_t)0".
4225        Immediately after the terminating 0 follow the images, one by
4226        one, all aligned on "uint32_t" boundaries (size rounded up to
4227        a multiple of 4 bytes).
4228
4229   "Firmware Images" are binary images containing firmware (like
4230        U-Boot or FPGA images) which usually will be programmed to
4231        flash memory.
4232
4233   "Script files" are command sequences that will be executed by
4234        U-Boot's command interpreter; this feature is especially
4235        useful when you configure U-Boot to use a real shell (hush)
4236        as command interpreter.
4237
4238Booting the Linux zImage:
4239-------------------------
4240
4241On some platforms, it's possible to boot Linux zImage. This is done
4242using the "bootz" command. The syntax of "bootz" command is the same
4243as the syntax of "bootm" command.
4244
4245Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4246kernel with raw initrd images. The syntax is slightly different, the
4247address of the initrd must be augmented by it's size, in the following
4248format: "<initrd addres>:<initrd size>".
4249
4250
4251Standalone HOWTO:
4252=================
4253
4254One of the features of U-Boot is that you can dynamically load and
4255run "standalone" applications, which can use some resources of
4256U-Boot like console I/O functions or interrupt services.
4257
4258Two simple examples are included with the sources:
4259
4260"Hello World" Demo:
4261-------------------
4262
4263'examples/hello_world.c' contains a small "Hello World" Demo
4264application; it is automatically compiled when you build U-Boot.
4265It's configured to run at address 0x00040004, so you can play with it
4266like that:
4267
4268        => loads
4269        ## Ready for S-Record download ...
4270        ~>examples/hello_world.srec
4271        1 2 3 4 5 6 7 8 9 10 11 ...
4272        [file transfer complete]
4273        [connected]
4274        ## Start Addr = 0x00040004
4275
4276        => go 40004 Hello World! This is a test.
4277        ## Starting application at 0x00040004 ...
4278        Hello World
4279        argc = 7
4280        argv[0] = "40004"
4281        argv[1] = "Hello"
4282        argv[2] = "World!"
4283        argv[3] = "This"
4284        argv[4] = "is"
4285        argv[5] = "a"
4286        argv[6] = "test."
4287        argv[7] = "<NULL>"
4288        Hit any key to exit ...
4289
4290        ## Application terminated, rc = 0x0
4291
4292Another example, which demonstrates how to register a CPM interrupt
4293handler with the U-Boot code, can be found in 'examples/timer.c'.
4294Here, a CPM timer is set up to generate an interrupt every second.
4295The interrupt service routine is trivial, just printing a '.'
4296character, but this is just a demo program. The application can be
4297controlled by the following keys:
4298
4299        ? - print current values og the CPM Timer registers
4300        b - enable interrupts and start timer
4301        e - stop timer and disable interrupts
4302        q - quit application
4303
4304        => loads
4305        ## Ready for S-Record download ...
4306        ~>examples/timer.srec
4307        1 2 3 4 5 6 7 8 9 10 11 ...
4308        [file transfer complete]
4309        [connected]
4310        ## Start Addr = 0x00040004
4311
4312        => go 40004
4313        ## Starting application at 0x00040004 ...
4314        TIMERS=0xfff00980
4315        Using timer 1
4316          tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4317
4318Hit 'b':
4319        [q, b, e, ?] Set interval 1000000 us
4320        Enabling timer
4321Hit '?':
4322        [q, b, e, ?] ........
4323        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4324Hit '?':
4325        [q, b, e, ?] .
4326        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4327Hit '?':
4328        [q, b, e, ?] .
4329        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4330Hit '?':
4331        [q, b, e, ?] .
4332        tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4333Hit 'e':
4334        [q, b, e, ?] ...Stopping timer
4335Hit 'q':
4336        [q, b, e, ?] ## Application terminated, rc = 0x0
4337
4338
4339Minicom warning:
4340================
4341
4342Over time, many people have reported problems when trying to use the
4343"minicom" terminal emulation program for serial download. I (wd)
4344consider minicom to be broken, and recommend not to use it. Under
4345Unix, I recommend to use C-Kermit for general purpose use (and
4346especially for kermit binary protocol download ("loadb" command), and
4347use "cu" for S-Record download ("loads" command).  See
4348http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4349for help with kermit.
4350
4351
4352Nevertheless, if you absolutely want to use it try adding this
4353configuration to your "File transfer protocols" section:
4354
4355           Name    Program                      Name U/D FullScr IO-Red. Multi
4356        X  kermit  /usr/bin/kermit -i -l %l -s   Y    U    Y       N      N
4357        Y  kermit  /usr/bin/kermit -i -l %l -r   N    D    Y       N      N
4358
4359
4360NetBSD Notes:
4361=============
4362
4363Starting at version 0.9.2, U-Boot supports NetBSD both as host
4364(build U-Boot) and target system (boots NetBSD/mpc8xx).
4365
4366Building requires a cross environment; it is known to work on
4367NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4368need gmake since the Makefiles are not compatible with BSD make).
4369Note that the cross-powerpc package does not install include files;
4370attempting to build U-Boot will fail because <machine/ansi.h> is
4371missing.  This file has to be installed and patched manually:
4372
4373        # cd /usr/pkg/cross/powerpc-netbsd/include
4374        # mkdir powerpc
4375        # ln -s powerpc machine
4376        # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4377        # ${EDIT} powerpc/ansi.h        ## must remove __va_list, _BSD_VA_LIST
4378
4379Native builds *don't* work due to incompatibilities between native
4380and U-Boot include files.
4381
4382Booting assumes that (the first part of) the image booted is a
4383stage-2 loader which in turn loads and then invokes the kernel
4384proper. Loader sources will eventually appear in the NetBSD source
4385tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4386meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4387
4388
4389Implementation Internals:
4390=========================
4391
4392The following is not intended to be a complete description of every
4393implementation detail. However, it should help to understand the
4394inner workings of U-Boot and make it easier to port it to custom
4395hardware.
4396
4397
4398Initial Stack, Global Data:
4399---------------------------
4400
4401The implementation of U-Boot is complicated by the fact that U-Boot
4402starts running out of ROM (flash memory), usually without access to
4403system RAM (because the memory controller is not initialized yet).
4404This means that we don't have writable Data or BSS segments, and BSS
4405is not initialized as zero. To be able to get a C environment working
4406at all, we have to allocate at least a minimal stack. Implementation
4407options for this are defined and restricted by the CPU used: Some CPU
4408models provide on-chip memory (like the IMMR area on MPC8xx and
4409MPC826x processors), on others (parts of) the data cache can be
4410locked as (mis-) used as memory, etc.
4411
4412        Chris Hallinan posted a good summary of these issues to the
4413        U-Boot mailing list:
4414
4415        Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4416        From: "Chris Hallinan" <clh@net1plus.com>
4417        Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4418        ...
4419
4420        Correct me if I'm wrong, folks, but the way I understand it
4421        is this: Using DCACHE as initial RAM for Stack, etc, does not
4422        require any physical RAM backing up the cache. The cleverness
4423        is that the cache is being used as a temporary supply of
4424        necessary storage before the SDRAM controller is setup. It's
4425        beyond the scope of this list to explain the details, but you
4426        can see how this works by studying the cache architecture and
4427        operation in the architecture and processor-specific manuals.
4428
4429        OCM is On Chip Memory, which I believe the 405GP has 4K. It
4430        is another option for the system designer to use as an
4431        initial stack/RAM area prior to SDRAM being available. Either
4432        option should work for you. Using CS 4 should be fine if your
4433        board designers haven't used it for something that would
4434        cause you grief during the initial boot! It is frequently not
4435        used.
4436
4437        CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4438        with your processor/board/system design. The default value
4439        you will find in any recent u-boot distribution in
4440        walnut.h should work for you. I'd set it to a value larger
4441        than your SDRAM module. If you have a 64MB SDRAM module, set
4442        it above 400_0000. Just make sure your board has no resources
4443        that are supposed to respond to that address! That code in
4444        start.S has been around a while and should work as is when
4445        you get the config right.
4446
4447        -Chris Hallinan
4448        DS4.COM, Inc.
4449
4450It is essential to remember this, since it has some impact on the C
4451code for the initialization procedures:
4452
4453* Initialized global data (data segment) is read-only. Do not attempt
4454  to write it.
4455
4456* Do not use any uninitialized global data (or implicitly initialized
4457  as zero data - BSS segment) at all - this is undefined, initiali-
4458  zation is performed later (when relocating to RAM).
4459
4460* Stack space is very limited. Avoid big data buffers or things like
4461  that.
4462
4463Having only the stack as writable memory limits means we cannot use
4464normal global data to share information between the code. But it
4465turned out that the implementation of U-Boot can be greatly
4466simplified by making a global data structure (gd_t) available to all
4467functions. We could pass a pointer to this data as argument to _all_
4468functions, but this would bloat the code. Instead we use a feature of
4469the GCC compiler (Global Register Variables) to share the data: we
4470place a pointer (gd) to the global data into a register which we
4471reserve for this purpose.
4472
4473When choosing a register for such a purpose we are restricted by the
4474relevant  (E)ABI  specifications for the current architecture, and by
4475GCC's implementation.
4476
4477For PowerPC, the following registers have specific use:
4478        R1:     stack pointer
4479        R2:     reserved for system use
4480        R3-R4:  parameter passing and return values
4481        R5-R10: parameter passing
4482        R13:    small data area pointer
4483        R30:    GOT pointer
4484        R31:    frame pointer
4485
4486        (U-Boot also uses R12 as internal GOT pointer. r12
4487        is a volatile register so r12 needs to be reset when
4488        going back and forth between asm and C)
4489
4490    ==> U-Boot will use R2 to hold a pointer to the global data
4491
4492    Note: on PPC, we could use a static initializer (since the
4493    address of the global data structure is known at compile time),
4494    but it turned out that reserving a register results in somewhat
4495    smaller code - although the code savings are not that big (on
4496    average for all boards 752 bytes for the whole U-Boot image,
4497    624 text + 127 data).
4498
4499On ARM, the following registers are used:
4500
4501        R0:     function argument word/integer result
4502        R1-R3:  function argument word
4503        R9:     platform specific
4504        R10:    stack limit (used only if stack checking is enabled)
4505        R11:    argument (frame) pointer
4506        R12:    temporary workspace
4507        R13:    stack pointer
4508        R14:    link register
4509        R15:    program counter
4510
4511    ==> U-Boot will use R9 to hold a pointer to the global data
4512
4513    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4514
4515On Nios II, the ABI is documented here:
4516        http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4517
4518    ==> U-Boot will use gp to hold a pointer to the global data
4519
4520    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4521    to access small data sections, so gp is free.
4522
4523On NDS32, the following registers are used:
4524
4525        R0-R1:  argument/return
4526        R2-R5:  argument
4527        R15:    temporary register for assembler
4528        R16:    trampoline register
4529        R28:    frame pointer (FP)
4530        R29:    global pointer (GP)
4531        R30:    link register (LP)
4532        R31:    stack pointer (SP)
4533        PC:     program counter (PC)
4534
4535    ==> U-Boot will use R10 to hold a pointer to the global data
4536
4537NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4538or current versions of GCC may "optimize" the code too much.
4539
4540On RISC-V, the following registers are used:
4541
4542        x0: hard-wired zero (zero)
4543        x1: return address (ra)
4544        x2:     stack pointer (sp)
4545        x3:     global pointer (gp)
4546        x4:     thread pointer (tp)
4547        x5:     link register (t0)
4548        x8:     frame pointer (fp)
4549        x10-x11:        arguments/return values (a0-1)
4550        x12-x17:        arguments (a2-7)
4551        x28-31:  temporaries (t3-6)
4552        pc:     program counter (pc)
4553
4554    ==> U-Boot will use gp to hold a pointer to the global data
4555
4556Memory Management:
4557------------------
4558
4559U-Boot runs in system state and uses physical addresses, i.e. the
4560MMU is not used either for address mapping nor for memory protection.
4561
4562The available memory is mapped to fixed addresses using the memory
4563controller. In this process, a contiguous block is formed for each
4564memory type (Flash, SDRAM, SRAM), even when it consists of several
4565physical memory banks.
4566
4567U-Boot is installed in the first 128 kB of the first Flash bank (on
4568TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4569booting and sizing and initializing DRAM, the code relocates itself
4570to the upper end of DRAM. Immediately below the U-Boot code some
4571memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4572configuration setting]. Below that, a structure with global Board
4573Info data is placed, followed by the stack (growing downward).
4574
4575Additionally, some exception handler code is copied to the low 8 kB
4576of DRAM (0x00000000 ... 0x00001FFF).
4577
4578So a typical memory configuration with 16 MB of DRAM could look like
4579this:
4580
4581        0x0000 0000     Exception Vector code
4582              :
4583        0x0000 1FFF
4584        0x0000 2000     Free for Application Use
4585              :
4586              :
4587
4588              :
4589              :
4590        0x00FB FF20     Monitor Stack (Growing downward)
4591        0x00FB FFAC     Board Info Data and permanent copy of global data
4592        0x00FC 0000     Malloc Arena
4593              :
4594        0x00FD FFFF
4595        0x00FE 0000     RAM Copy of Monitor Code
4596        ...             eventually: LCD or video framebuffer
4597        ...             eventually: pRAM (Protected RAM - unchanged by reset)
4598        0x00FF FFFF     [End of RAM]
4599
4600
4601System Initialization:
4602----------------------
4603
4604In the reset configuration, U-Boot starts at the reset entry point
4605(on most PowerPC systems at address 0x00000100). Because of the reset
4606configuration for CS0# this is a mirror of the on board Flash memory.
4607To be able to re-map memory U-Boot then jumps to its link address.
4608To be able to implement the initialization code in C, a (small!)
4609initial stack is set up in the internal Dual Ported RAM (in case CPUs
4610which provide such a feature like), or in a locked part of the data
4611cache. After that, U-Boot initializes the CPU core, the caches and
4612the SIU.
4613
4614Next, all (potentially) available memory banks are mapped using a
4615preliminary mapping. For example, we put them on 512 MB boundaries
4616(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4617on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4618programmed for SDRAM access. Using the temporary configuration, a
4619simple memory test is run that determines the size of the SDRAM
4620banks.
4621
4622When there is more than one SDRAM bank, and the banks are of
4623different size, the largest is mapped first. For equal size, the first
4624bank (CS2#) is mapped first. The first mapping is always for address
46250x00000000, with any additional banks following immediately to create
4626contiguous memory starting from 0.
4627
4628Then, the monitor installs itself at the upper end of the SDRAM area
4629and allocates memory for use by malloc() and for the global Board
4630Info data; also, the exception vector code is copied to the low RAM
4631pages, and the final stack is set up.
4632
4633Only after this relocation will you have a "normal" C environment;
4634until that you are restricted in several ways, mostly because you are
4635running from ROM, and because the code will have to be relocated to a
4636new address in RAM.
4637
4638
4639U-Boot Porting Guide:
4640----------------------
4641
4642[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4643list, October 2002]
4644
4645
4646int main(int argc, char *argv[])
4647{
4648        sighandler_t no_more_time;
4649
4650        signal(SIGALRM, no_more_time);
4651        alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4652
4653        if (available_money > available_manpower) {
4654                Pay consultant to port U-Boot;
4655                return 0;
4656        }
4657
4658        Download latest U-Boot source;
4659
4660        Subscribe to u-boot mailing list;
4661
4662        if (clueless)
4663                email("Hi, I am new to U-Boot, how do I get started?");
4664
4665        while (learning) {
4666                Read the README file in the top level directory;
4667                Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4668                Read applicable doc/*.README;
4669                Read the source, Luke;
4670                /* find . -name "*.[chS]" | xargs grep -i <keyword> */
4671        }
4672
4673        if (available_money > toLocalCurrency ($2500))
4674                Buy a BDI3000;
4675        else
4676                Add a lot of aggravation and time;
4677
4678        if (a similar board exists) {   /* hopefully... */
4679                cp -a board/<similar> board/<myboard>
4680                cp include/configs/<similar>.h include/configs/<myboard>.h
4681        } else {
4682                Create your own board support subdirectory;
4683                Create your own board include/configs/<myboard>.h file;
4684        }
4685        Edit new board/<myboard> files
4686        Edit new include/configs/<myboard>.h
4687
4688        while (!accepted) {
4689                while (!running) {
4690                        do {
4691                                Add / modify source code;
4692                        } until (compiles);
4693                        Debug;
4694                        if (clueless)
4695                                email("Hi, I am having problems...");
4696                }
4697                Send patch file to the U-Boot email list;
4698                if (reasonable critiques)
4699                        Incorporate improvements from email list code review;
4700                else
4701                        Defend code as written;
4702        }
4703
4704        return 0;
4705}
4706
4707void no_more_time (int sig)
4708{
4709      hire_a_guru();
4710}
4711
4712
4713Coding Standards:
4714-----------------
4715
4716All contributions to U-Boot should conform to the Linux kernel
4717coding style; see the kernel coding style guide at
4718https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4719script "scripts/Lindent" in your Linux kernel source directory.
4720
4721Source files originating from a different project (for example the
4722MTD subsystem) are generally exempt from these guidelines and are not
4723reformatted to ease subsequent migration to newer versions of those
4724sources.
4725
4726Please note that U-Boot is implemented in C (and to some small parts in
4727Assembler); no C++ is used, so please do not use C++ style comments (//)
4728in your code.
4729
4730Please also stick to the following formatting rules:
4731- remove any trailing white space
4732- use TAB characters for indentation and vertical alignment, not spaces
4733- make sure NOT to use DOS '\r\n' line feeds
4734- do not add more than 2 consecutive empty lines to source files
4735- do not add trailing empty lines to source files
4736
4737Submissions which do not conform to the standards may be returned
4738with a request to reformat the changes.
4739
4740
4741Submitting Patches:
4742-------------------
4743
4744Since the number of patches for U-Boot is growing, we need to
4745establish some rules. Submissions which do not conform to these rules
4746may be rejected, even when they contain important and valuable stuff.
4747
4748Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4749
4750Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4751see https://lists.denx.de/listinfo/u-boot
4752
4753When you send a patch, please include the following information with
4754it:
4755
4756* For bug fixes: a description of the bug and how your patch fixes
4757  this bug. Please try to include a way of demonstrating that the
4758  patch actually fixes something.
4759
4760* For new features: a description of the feature and your
4761  implementation.
4762
4763* A CHANGELOG entry as plaintext (separate from the patch)
4764
4765* For major contributions, add a MAINTAINERS file with your
4766  information and associated file and directory references.
4767
4768* When you add support for a new board, don't forget to add a
4769  maintainer e-mail address to the boards.cfg file, too.
4770
4771* If your patch adds new configuration options, don't forget to
4772  document these in the README file.
4773
4774* The patch itself. If you are using git (which is *strongly*
4775  recommended) you can easily generate the patch using the
4776  "git format-patch". If you then use "git send-email" to send it to
4777  the U-Boot mailing list, you will avoid most of the common problems
4778  with some other mail clients.
4779
4780  If you cannot use git, use "diff -purN OLD NEW". If your version of
4781  diff does not support these options, then get the latest version of
4782  GNU diff.
4783
4784  The current directory when running this command shall be the parent
4785  directory of the U-Boot source tree (i. e. please make sure that
4786  your patch includes sufficient directory information for the
4787  affected files).
4788
4789  We prefer patches as plain text. MIME attachments are discouraged,
4790  and compressed attachments must not be used.
4791
4792* If one logical set of modifications affects or creates several
4793  files, all these changes shall be submitted in a SINGLE patch file.
4794
4795* Changesets that contain different, unrelated modifications shall be
4796  submitted as SEPARATE patches, one patch per changeset.
4797
4798
4799Notes:
4800
4801* Before sending the patch, run the buildman script on your patched
4802  source tree and make sure that no errors or warnings are reported
4803  for any of the boards.
4804
4805* Keep your modifications to the necessary minimum: A patch
4806  containing several unrelated changes or arbitrary reformats will be
4807  returned with a request to re-formatting / split it.
4808
4809* If you modify existing code, make sure that your new code does not
4810  add to the memory footprint of the code ;-) Small is beautiful!
4811  When adding new features, these should compile conditionally only
4812  (using #ifdef), and the resulting code with the new feature
4813  disabled must not need more memory than the old code without your
4814  modification.
4815
4816* Remember that there is a size limit of 100 kB per message on the
4817  u-boot mailing list. Bigger patches will be moderated. If they are
4818  reasonable and not too big, they will be acknowledged. But patches
4819  bigger than the size limit should be avoided.
4820