README

		constructs ("shell scripts").

		If undefined, you get the old, much simpler behaviour
		with a somewhat smaller memory footprint.


		CONFIG_SYS_PROMPT_HUSH_PS2

		This defines the secondary prompt string, which is
		printed when the command interpreter needs more input
		to complete a command. Usually "> ".

	Note:

		In the current implementation, the local variables
		space and global environment variables space are
		separated. Local variables are those you define by
		simply typing `name=value'. To access a local
		variable later on, you have write `$name' or
		`${name}'; to execute the contents of a variable
		directly type `$name' at the command prompt.

		Global environment variables are those you use
		setenv/printenv to work with. To run a command stored
		in such a variable, you need to use the run command,
		and you must not use the '$' sign to access them.

		To store commands and special characters in a
		variable, please use double quotation marks
		surrounding the whole text of the variable, instead
		of the backslashes before semicolons and special
		symbols.

- Commandline Editing and History:
		CONFIG_CMDLINE_EDITING

		Enable editing and History functions for interactive
		commandline input operations

- Default Environment:
		CONFIG_EXTRA_ENV_SETTINGS

		Define this to contain any number of null terminated
		strings (variable = value pairs) that will be part of
		the default environment compiled into the boot image.

		For example, place something like this in your
		board's config file:

		#define CONFIG_EXTRA_ENV_SETTINGS \
			"myvar1=value1\0" \
			"myvar2=value2\0"

		Warning: This method is based on knowledge about the
		internal format how the environment is stored by the
		U-Boot code. This is NOT an official, exported
		interface! Although it is unlikely that this format
		will change soon, there is no guarantee either.
		You better know what you are doing here.

		Note: overly (ab)use of the default environment is
		discouraged. Make sure to check other ways to preset
		the environment like the "source" command or the
		boot command first.

- DataFlash Support:
		CONFIG_HAS_DATAFLASH

		Defining this option enables DataFlash features and
		allows to read/write in Dataflash via the standard
		commands cp, md...

- SystemACE Support:
		CONFIG_SYSTEMACE

		Adding this option adds support for Xilinx SystemACE
		chips attached via some sort of local bus. The address
		of the chip must also be defined in the
		CONFIG_SYS_SYSTEMACE_BASE macro. For example:

		#define CONFIG_SYSTEMACE
		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000

		When SystemACE support is added, the "ace" device type
		becomes available to the fat commands, i.e. fatls.

- TFTP Fixed UDP Port:
		CONFIG_TFTP_PORT

		If this is defined, the environment variable tftpsrcp
		is used to supply the TFTP UDP source port value.
		If tftpsrcp isn't defined, the normal pseudo-random port
		number generator is used.

		Also, the environment variable tftpdstp is used to supply
		the TFTP UDP destination port value.  If tftpdstp isn't
		defined, the normal port 69 is used.

		The purpose for tftpsrcp is to allow a TFTP server to
		blindly start the TFTP transfer using the pre-configured
		target IP address and UDP port. This has the effect of
		"punching through" the (Windows XP) firewall, allowing
		the remainder of the TFTP transfer to proceed normally.
		A better solution is to properly configure the firewall,
		but sometimes that is not allowed.

- Show boot progress:
		CONFIG_SHOW_BOOT_PROGRESS

		Defining this option allows to add some board-
		specific code (calling a user-provided function
		"show_boot_progress(int)") that enables you to show
		the system's boot progress on some display (for
		example, some LED's) on your board. At the moment,
		the following checkpoints are implemented:

Legacy uImage format:

  Arg	Where			When
    1	common/cmd_bootm.c	before attempting to boot an image
   -1	common/cmd_bootm.c	Image header has bad	 magic number
    2	common/cmd_bootm.c	Image header has correct magic number
   -2	common/cmd_bootm.c	Image header has bad	 checksum
    3	common/cmd_bootm.c	Image header has correct checksum
   -3	common/cmd_bootm.c	Image data   has bad	 checksum
    4	common/cmd_bootm.c	Image data   has correct checksum
   -4	common/cmd_bootm.c	Image is for unsupported architecture
    5	common/cmd_bootm.c	Architecture check OK
   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
    6	common/cmd_bootm.c	Image Type check OK
   -6	common/cmd_bootm.c	gunzip uncompression error
   -7	common/cmd_bootm.c	Unimplemented compression type
    7	common/cmd_bootm.c	Uncompression OK
    8	common/cmd_bootm.c	No uncompress/copy overwrite error
   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)

    9	common/image.c		Start initial ramdisk verification
  -10	common/image.c		Ramdisk header has bad	   magic number
  -11	common/image.c		Ramdisk header has bad	   checksum
   10	common/image.c		Ramdisk header is OK
  -12	common/image.c		Ramdisk data   has bad	   checksum
   11	common/image.c		Ramdisk data   has correct checksum
   12	common/image.c		Ramdisk verification complete, start loading
  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
   13	common/image.c		Start multifile image verification
   14	common/image.c		No initial ramdisk, no multifile, continue.

   15	arch/<arch>/lib/bootm.c	All preparation done, transferring control to OS

  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
  -31	post/post.c		POST test failed, detected by post_output_backlog()
  -32	post/post.c		POST test failed, detected by post_run_single()

   34	common/cmd_doc.c	before loading a Image from a DOC device
  -35	common/cmd_doc.c	Bad usage of "doc" command
   35	common/cmd_doc.c	correct usage of "doc" command
  -36	common/cmd_doc.c	No boot device
   36	common/cmd_doc.c	correct boot device
  -37	common/cmd_doc.c	Unknown Chip ID on boot device
   37	common/cmd_doc.c	correct chip ID found, device available
  -38	common/cmd_doc.c	Read Error on boot device
   38	common/cmd_doc.c	reading Image header from DOC device OK
  -39	common/cmd_doc.c	Image header has bad magic number
   39	common/cmd_doc.c	Image header has correct magic number
  -40	common/cmd_doc.c	Error reading Image from DOC device
   40	common/cmd_doc.c	Image header has correct magic number
   41	common/cmd_ide.c	before loading a Image from a IDE device
  -42	common/cmd_ide.c	Bad usage of "ide" command
   42	common/cmd_ide.c	correct usage of "ide" command
  -43	common/cmd_ide.c	No boot device
   43	common/cmd_ide.c	boot device found
  -44	common/cmd_ide.c	Device not available
   44	common/cmd_ide.c	Device available
  -45	common/cmd_ide.c	wrong partition selected
   45	common/cmd_ide.c	partition selected
  -46	common/cmd_ide.c	Unknown partition table
   46	common/cmd_ide.c	valid partition table found
  -47	common/cmd_ide.c	Invalid partition type
   47	common/cmd_ide.c	correct partition type
  -48	common/cmd_ide.c	Error reading Image Header on boot device
   48	common/cmd_ide.c	reading Image Header from IDE device OK
  -49	common/cmd_ide.c	Image header has bad magic number
   49	common/cmd_ide.c	Image header has correct magic number
  -50	common/cmd_ide.c	Image header has bad	 checksum
   50	common/cmd_ide.c	Image header has correct checksum
  -51	common/cmd_ide.c	Error reading Image from IDE device
   51	common/cmd_ide.c	reading Image from IDE device OK
   52	common/cmd_nand.c	before loading a Image from a NAND device
  -53	common/cmd_nand.c	Bad usage of "nand" command
   53	common/cmd_nand.c	correct usage of "nand" command
  -54	common/cmd_nand.c	No boot device
   54	common/cmd_nand.c	boot device found
  -55	common/cmd_nand.c	Unknown Chip ID on boot device
   55	common/cmd_nand.c	correct chip ID found, device available
  -56	common/cmd_nand.c	Error reading Image Header on boot device
   56	common/cmd_nand.c	reading Image Header from NAND device OK
  -57	common/cmd_nand.c	Image header has bad magic number
   57	common/cmd_nand.c	Image header has correct magic number
  -58	common/cmd_nand.c	Error reading Image from NAND device
   58	common/cmd_nand.c	reading Image from NAND device OK

  -60	common/env_common.c	Environment has a bad CRC, using default

   64	net/eth.c		starting with Ethernet configuration.
  -64	net/eth.c		no Ethernet found.
   65	net/eth.c		Ethernet found.

  -80	common/cmd_net.c	usage wrong
   80	common/cmd_net.c	before calling NetLoop()
  -81	common/cmd_net.c	some error in NetLoop() occurred
   81	common/cmd_net.c	NetLoop() back without error
  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
   82	common/cmd_net.c	trying automatic boot
   83	common/cmd_net.c	running "source" command
  -83	common/cmd_net.c	some error in automatic boot or "source" command
   84	common/cmd_net.c	end without errors

FIT uImage format:

  Arg	Where			When
  100	common/cmd_bootm.c	Kernel FIT Image has correct format
 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
  102	common/cmd_bootm.c	Kernel unit name specified
 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
  103	common/cmd_bootm.c	Found configuration node
  104	common/cmd_bootm.c	Got kernel subimage node offset
 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
  105	common/cmd_bootm.c	Kernel subimage hash verification OK
 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
  106	common/cmd_bootm.c	Architecture check OK
 -106	common/cmd_bootm.c	Kernel subimage has wrong type
  107	common/cmd_bootm.c	Kernel subimage type OK
 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
  108	common/cmd_bootm.c	Got kernel subimage data/size
 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
 -109	common/cmd_bootm.c	Can't get kernel subimage type
 -110	common/cmd_bootm.c	Can't get kernel subimage comp
 -111	common/cmd_bootm.c	Can't get kernel subimage os
 -112	common/cmd_bootm.c	Can't get kernel subimage load address
 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error

  120	common/image.c		Start initial ramdisk verification
 -120	common/image.c		Ramdisk FIT image has incorrect format
  121	common/image.c		Ramdisk FIT image has correct format
  122	common/image.c		No ramdisk subimage unit name, using configuration
 -122	common/image.c		Can't get configuration for ramdisk subimage
  123	common/image.c		Ramdisk unit name specified
 -124	common/image.c		Can't get ramdisk subimage node offset
  125	common/image.c		Got ramdisk subimage node offset
 -125	common/image.c		Ramdisk subimage hash verification failed
  126	common/image.c		Ramdisk subimage hash verification OK
 -126	common/image.c		Ramdisk subimage for unsupported architecture
  127	common/image.c		Architecture check OK
 -127	common/image.c		Can't get ramdisk subimage data/size
  128	common/image.c		Got ramdisk subimage data/size
  129	common/image.c		Can't get ramdisk load address
 -129	common/image.c		Got ramdisk load address

 -130	common/cmd_doc.c	Incorrect FIT image format
  131	common/cmd_doc.c	FIT image format OK

 -140	common/cmd_ide.c	Incorrect FIT image format
  141	common/cmd_ide.c	FIT image format OK

 -150	common/cmd_nand.c	Incorrect FIT image format
  151	common/cmd_nand.c	FIT image format OK

- Standalone program support:
		CONFIG_STANDALONE_LOAD_ADDR

		This option defines a board specific value for the
		address where standalone program gets loaded, thus
		overwriting the architecture dependent default
		settings.

- Frame Buffer Address:
		CONFIG_FB_ADDR

		Define CONFIG_FB_ADDR if you want to use specific
		address for frame buffer.
		Then system will reserve the frame buffer address to
		defined address instead of lcd_setmem (this function
		grabs the memory for frame buffer by panel's size).

		Please see board_init_f function.

- Automatic software updates via TFTP server
		CONFIG_UPDATE_TFTP
		CONFIG_UPDATE_TFTP_CNT_MAX
		CONFIG_UPDATE_TFTP_MSEC_MAX

		These options enable and control the auto-update feature;
		for a more detailed description refer to doc/README.update.

- MTD Support (mtdparts command, UBI support)
		CONFIG_MTD_DEVICE

		Adds the MTD device infrastructure from the Linux kernel.
		Needed for mtdparts command support.

		CONFIG_MTD_PARTITIONS

		Adds the MTD partitioning infrastructure from the Linux
		kernel. Needed for UBI support.

- SPL framework
		CONFIG_SPL
		Enable building of SPL globally.

		CONFIG_SPL_TEXT_BASE
		TEXT_BASE for linking the SPL binary.

		CONFIG_SPL_LDSCRIPT
		LDSCRIPT for linking the SPL binary.

		CONFIG_SPL_LIBCOMMON_SUPPORT
		Support for common/libcommon.o in SPL binary

		CONFIG_SPL_LIBDISK_SUPPORT
		Support for disk/libdisk.o in SPL binary

		CONFIG_SPL_I2C_SUPPORT
		Support for drivers/i2c/libi2c.o in SPL binary

		CONFIG_SPL_GPIO_SUPPORT
		Support for drivers/gpio/libgpio.o in SPL binary

		CONFIG_SPL_MMC_SUPPORT
		Support for drivers/mmc/libmmc.o in SPL binary

		CONFIG_SPL_SERIAL_SUPPORT
		Support for drivers/serial/libserial.o in SPL binary

		CONFIG_SPL_SPI_FLASH_SUPPORT
		Support for drivers/mtd/spi/libspi_flash.o in SPL binary

		CONFIG_SPL_SPI_SUPPORT
		Support for drivers/spi/libspi.o in SPL binary

		CONFIG_SPL_FAT_SUPPORT
		Support for fs/fat/libfat.o in SPL binary

		CONFIG_SPL_LIBGENERIC_SUPPORT
		Support for lib/libgeneric.o in SPL binary

Modem Support:
--------------

[so far only for SMDK2400 boards]

- Modem support enable:
		CONFIG_MODEM_SUPPORT

- RTS/CTS Flow control enable:
		CONFIG_HWFLOW

- Modem debug support:
		CONFIG_MODEM_SUPPORT_DEBUG

		Enables debugging stuff (char screen[1024], dbg())
		for modem support. Useful only with BDI2000.

- Interrupt support (PPC):

		There are common interrupt_init() and timer_interrupt()
		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
		for CPU specific initialization. interrupt_init_cpu()
		should set decrementer_count to appropriate value. If
		CPU resets decrementer automatically after interrupt
		(ppc4xx) it should set decrementer_count to zero.
		timer_interrupt() calls timer_interrupt_cpu() for CPU
		specific handling. If board has watchdog / status_led
		/ other_activity_monitor it works automatically from
		general timer_interrupt().

- General:

		In the target system modem support is enabled when a
		specific key (key combination) is pressed during
		power-on. Otherwise U-Boot will boot normally
		(autoboot). The key_pressed() function is called from
		board_init(). Currently key_pressed() is a dummy
		function, returning 1 and thus enabling modem
		initialization.

		If there are no modem init strings in the
		environment, U-Boot proceed to autoboot; the
		previous output (banner, info printfs) will be
		suppressed, though.

		See also: doc/README.Modem


Configuration Settings:
-----------------------

- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
		undefine this when you're short of memory.

- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
		width of the commands listed in the 'help' command output.

- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
		prompt for user input.

- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console

- CONFIG_SYS_PBSIZE:	Buffer size for Console output

- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands

- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
		the application (usually a Linux kernel) when it is
		booted

- CONFIG_SYS_BAUDRATE_TABLE:
		List of legal baudrate settings for this board.

- CONFIG_SYS_CONSOLE_INFO_QUIET
		Suppress display of console information at boot.

- CONFIG_SYS_CONSOLE_IS_IN_ENV
		If the board specific function
			extern int overwrite_console (void);
		returns 1, the stdin, stderr and stdout are switched to the
		serial port, else the settings in the environment are used.

- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
		Enable the call to overwrite_console().

- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
		Enable overwrite of previous console environment settings.

- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
		Begin and End addresses of the area used by the
		simple memory test.

- CONFIG_SYS_ALT_MEMTEST:
		Enable an alternate, more extensive memory test.

- CONFIG_SYS_MEMTEST_SCRATCH:
		Scratch address used by the alternate memory test
		You only need to set this if address zero isn't writeable

- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
		this specified memory area will get subtracted from the top
		(end) of RAM and won't get "touched" at all by U-Boot. By
		fixing up gd->ram_size the Linux kernel should gets passed
		the now "corrected" memory size and won't touch it either.
		This should work for arch/ppc and arch/powerpc. Only Linux
		board ports in arch/powerpc with bootwrapper support that
		recalculate the memory size from the SDRAM controller setup
		will have to get fixed in Linux additionally.

		This option can be used as a workaround for the 440EPx/GRx
		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
		be touched.

		WARNING: Please make sure that this value is a multiple of
		the Linux page size (normally 4k). If this is not the case,
		then the end address of the Linux memory will be located at a
		non page size aligned address and this could cause major
		problems.

- CONFIG_SYS_TFTP_LOADADDR:
		Default load address for network file downloads

- CONFIG_SYS_LOADS_BAUD_CHANGE:
		Enable temporary baudrate change while serial download

- CONFIG_SYS_SDRAM_BASE:
		Physical start address of SDRAM. _Must_ be 0 here.

- CONFIG_SYS_MBIO_BASE:
		Physical start address of Motherboard I/O (if using a
		Cogent motherboard)

- CONFIG_SYS_FLASH_BASE:
		Physical start address of Flash memory.

- CONFIG_SYS_MONITOR_BASE:
		Physical start address of boot monitor code (set by
		make config files to be same as the text base address
		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
		CONFIG_SYS_FLASH_BASE when booting from flash.

- CONFIG_SYS_MONITOR_LEN:
		Size of memory reserved for monitor code, used to
		determine _at_compile_time_ (!) if the environment is
		embedded within the U-Boot image, or in a separate
		flash sector.

- CONFIG_SYS_MALLOC_LEN:
		Size of DRAM reserved for malloc() use.

- CONFIG_SYS_BOOTM_LEN:
		Normally compressed uImages are limited to an
		uncompressed size of 8 MBytes. If this is not enough,
		you can define CONFIG_SYS_BOOTM_LEN in your board config file
		to adjust this setting to your needs.

- CONFIG_SYS_BOOTMAPSZ:
		Maximum size of memory mapped by the startup code of
		the Linux kernel; all data that must be processed by
		the Linux kernel (bd_info, boot arguments, FDT blob if
		used) must be put below this limit, unless "bootm_low"
		enviroment variable is defined and non-zero. In such case
		all data for the Linux kernel must be between "bootm_low"
		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
		variable "bootm_mapsize" will override the value of
		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
		then the value in "bootm_size" will be used instead.

- CONFIG_SYS_BOOT_RAMDISK_HIGH:
		Enable initrd_high functionality.  If defined then the
		initrd_high feature is enabled and the bootm ramdisk subcommand
		is enabled.

- CONFIG_SYS_BOOT_GET_CMDLINE:
		Enables allocating and saving kernel cmdline in space between
		"bootm_low" and "bootm_low" + BOOTMAPSZ.

- CONFIG_SYS_BOOT_GET_KBD:
		Enables allocating and saving a kernel copy of the bd_info in
		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.

- CONFIG_SYS_MAX_FLASH_BANKS:
		Max number of Flash memory banks

- CONFIG_SYS_MAX_FLASH_SECT:
		Max number of sectors on a Flash chip

- CONFIG_SYS_FLASH_ERASE_TOUT:
		Timeout for Flash erase operations (in ms)

- CONFIG_SYS_FLASH_WRITE_TOUT:
		Timeout for Flash write operations (in ms)

- CONFIG_SYS_FLASH_LOCK_TOUT
		Timeout for Flash set sector lock bit operation (in ms)

- CONFIG_SYS_FLASH_UNLOCK_TOUT
		Timeout for Flash clear lock bits operation (in ms)

- CONFIG_SYS_FLASH_PROTECTION
		If defined, hardware flash sectors protection is used
		instead of U-Boot software protection.

- CONFIG_SYS_DIRECT_FLASH_TFTP:

		Enable TFTP transfers directly to flash memory;
		without this option such a download has to be
		performed in two steps: (1) download to RAM, and (2)
		copy from RAM to flash.

		The two-step approach is usually more reliable, since
		you can check if the download worked before you erase
		the flash, but in some situations (when system RAM is
		too limited to allow for a temporary copy of the
		downloaded image) this option may be very useful.

- CONFIG_SYS_FLASH_CFI:
		Define if the flash driver uses extra elements in the
		common flash structure for storing flash geometry.

- CONFIG_FLASH_CFI_DRIVER
		This option also enables the building of the cfi_flash driver
		in the drivers directory

- CONFIG_FLASH_CFI_MTD
		This option enables the building of the cfi_mtd driver
		in the drivers directory. The driver exports CFI flash
		to the MTD layer.

- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
		Use buffered writes to flash.

- CONFIG_FLASH_SPANSION_S29WS_N
		s29ws-n MirrorBit flash has non-standard addresses for buffered
		write commands.

- CONFIG_SYS_FLASH_QUIET_TEST
		If this option is defined, the common CFI flash doesn't
		print it's warning upon not recognized FLASH banks. This
		is useful, if some of the configured banks are only
		optionally available.

- CONFIG_FLASH_SHOW_PROGRESS
		If defined (must be an integer), print out countdown
		digits and dots.  Recommended value: 45 (9..1) for 80
		column displays, 15 (3..1) for 40 column displays.

- CONFIG_SYS_RX_ETH_BUFFER:
		Defines the number of Ethernet receive buffers. On some
		Ethernet controllers it is recommended to set this value
		to 8 or even higher (EEPRO100 or 405 EMAC), since all
		buffers can be full shortly after enabling the interface
		on high Ethernet traffic.
		Defaults to 4 if not defined.

- CONFIG_ENV_MAX_ENTRIES

	Maximum number of entries in the hash table that is used
	internally to store the environment settings. The default
	setting is supposed to be generous and should work in most
	cases. This setting can be used to tune behaviour; see
	lib/hashtable.c for details.

The following definitions that deal with the placement and management
of environment data (variable area); in general, we support the
following configurations:

- CONFIG_BUILD_ENVCRC:

	Builds up envcrc with the target environment so that external utils
	may easily extract it and embed it in final U-Boot images.

- CONFIG_ENV_IS_IN_FLASH:

	Define this if the environment is in flash memory.

	a) The environment occupies one whole flash sector, which is
	   "embedded" in the text segment with the U-Boot code. This
	   happens usually with "bottom boot sector" or "top boot
	   sector" type flash chips, which have several smaller
	   sectors at the start or the end. For instance, such a
	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
	   such a case you would place the environment in one of the
	   4 kB sectors - with U-Boot code before and after it. With
	   "top boot sector" type flash chips, you would put the
	   environment in one of the last sectors, leaving a gap
	   between U-Boot and the environment.

	- CONFIG_ENV_OFFSET:

	   Offset of environment data (variable area) to the
	   beginning of flash memory; for instance, with bottom boot
	   type flash chips the second sector can be used: the offset
	   for this sector is given here.

	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.

	- CONFIG_ENV_ADDR:

	   This is just another way to specify the start address of
	   the flash sector containing the environment (instead of
	   CONFIG_ENV_OFFSET).

	- CONFIG_ENV_SECT_SIZE:

	   Size of the sector containing the environment.


	b) Sometimes flash chips have few, equal sized, BIG sectors.
	   In such a case you don't want to spend a whole sector for
	   the environment.

	- CONFIG_ENV_SIZE:

	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
	   of this flash sector for the environment. This saves
	   memory for the RAM copy of the environment.

	   It may also save flash memory if you decide to use this
	   when your environment is "embedded" within U-Boot code,
	   since then the remainder of the flash sector could be used
	   for U-Boot code. It should be pointed out that this is
	   STRONGLY DISCOURAGED from a robustness point of view:
	   updating the environment in flash makes it always
	   necessary to erase the WHOLE sector. If something goes
	   wrong before the contents has been restored from a copy in
	   RAM, your target system will be dead.

	- CONFIG_ENV_ADDR_REDUND
	  CONFIG_ENV_SIZE_REDUND

	   These settings describe a second storage area used to hold
	   a redundant copy of the environment data, so that there is
	   a valid backup copy in case there is a power failure during
	   a "saveenv" operation.

BE CAREFUL! Any changes to the flash layout, and some changes to the
source code will make it necessary to adapt <board>/u-boot.lds*
accordingly!


- CONFIG_ENV_IS_IN_NVRAM:

	Define this if you have some non-volatile memory device
	(NVRAM, battery buffered SRAM) which you want to use for the
	environment.

	- CONFIG_ENV_ADDR:
	- CONFIG_ENV_SIZE:

	  These two #defines are used to determine the memory area you
	  want to use for environment. It is assumed that this memory
	  can just be read and written to, without any special
	  provision.

BE CAREFUL! The first access to the environment happens quite early
in U-Boot initalization (when we try to get the setting of for the
console baudrate). You *MUST* have mapped your NVRAM area then, or
U-Boot will hang.

Please note that even with NVRAM we still use a copy of the
environment in RAM: we could work on NVRAM directly, but we want to
keep settings there always unmodified except somebody uses "saveenv"
to save the current settings.


- CONFIG_ENV_IS_IN_EEPROM:

	Use this if you have an EEPROM or similar serial access
	device and a driver for it.

	- CONFIG_ENV_OFFSET:
	- CONFIG_ENV_SIZE:

	  These two #defines specify the offset and size of the
	  environment area within the total memory of your EEPROM.

	- CONFIG_SYS_I2C_EEPROM_ADDR:
	  If defined, specified the chip address of the EEPROM device.
	  The default address is zero.

	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
	  If defined, the number of bits used to address bytes in a
	  single page in the EEPROM device.  A 64 byte page, for example
	  would require six bits.

	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
	  If defined, the number of milliseconds to delay between
	  page writes.	The default is zero milliseconds.

	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
	  The length in bytes of the EEPROM memory array address.  Note
	  that this is NOT the chip address length!

	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
	  EEPROM chips that implement "address overflow" are ones
	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
	  address and the extra bits end up in the "chip address" bit
	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
	  byte chips.

	  Note that we consider the length of the address field to
	  still be one byte because the extra address bits are hidden
	  in the chip address.

	- CONFIG_SYS_EEPROM_SIZE:
	  The size in bytes of the EEPROM device.

	- CONFIG_ENV_EEPROM_IS_ON_I2C
	  define this, if you have I2C and SPI activated, and your
	  EEPROM, which holds the environment, is on the I2C bus.

	- CONFIG_I2C_ENV_EEPROM_BUS
	  if you have an Environment on an EEPROM reached over
	  I2C muxes, you can define here, how to reach this
	  EEPROM. For example:

	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"

	  EEPROM which holds the environment, is reached over
	  a pca9547 i2c mux with address 0x70, channel 3.

- CONFIG_ENV_IS_IN_DATAFLASH:

	Define this if you have a DataFlash memory device which you
	want to use for the environment.

	- CONFIG_ENV_OFFSET:
	- CONFIG_ENV_ADDR:
	- CONFIG_ENV_SIZE:

	  These three #defines specify the offset and size of the
	  environment area within the total memory of your DataFlash placed
	  at the specified address.

- CONFIG_ENV_IS_IN_NAND:

	Define this if you have a NAND device which you want to use
	for the environment.

	- CONFIG_ENV_OFFSET:
	- CONFIG_ENV_SIZE:

	  These two #defines specify the offset and size of the environment
	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
	  aligned to an erase block boundary.

	- CONFIG_ENV_OFFSET_REDUND (optional):

	  This setting describes a second storage area of CONFIG_ENV_SIZE
	  size used to hold a redundant copy of the environment data, so
	  that there is a valid backup copy in case there is a power failure
	  during a "saveenv" operation.  CONFIG_ENV_OFFSET_RENDUND must be
	  aligned to an erase block boundary.

	- CONFIG_ENV_RANGE (optional):

	  Specifies the length of the region in which the environment
	  can be written.  This should be a multiple of the NAND device's
	  block size.  Specifying a range with more erase blocks than
	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
	  the range to be avoided.

	- CONFIG_ENV_OFFSET_OOB (optional):

	  Enables support for dynamically retrieving the offset of the
	  environment from block zero's out-of-band data.  The
	  "nand env.oob" command can be used to record this offset.
	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
	  using CONFIG_ENV_OFFSET_OOB.

- CONFIG_NAND_ENV_DST

	Defines address in RAM to which the nand_spl code should copy the
	environment. If redundant environment is used, it will be copied to
	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.

- CONFIG_SYS_SPI_INIT_OFFSET

	Defines offset to the initial SPI buffer area in DPRAM. The
	area is used at an early stage (ROM part) if the environment
	is configured to reside in the SPI EEPROM: We need a 520 byte
	scratch DPRAM area. It is used between the two initialization
	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
	to be a good choice since it makes it far enough from the
	start of the data area as well as from the stack pointer.

Please note that the environment is read-only until the monitor
has been relocated to RAM and a RAM copy of the environment has been
created; also, when using EEPROM you will have to use getenv_f()
until then to read environment variables.

The environment is protected by a CRC32 checksum. Before the monitor
is relocated into RAM, as a result of a bad CRC you will be working
with the compiled-in default environment - *silently*!!! [This is
necessary, because the first environment variable we need is the
"baudrate" setting for the console - if we have a bad CRC, we don't
have any device yet where we could complain.]

Note: once the monitor has been relocated, then it will complain if
the default environment is used; a new CRC is computed as soon as you
use the "saveenv" command to store a valid environment.

- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
		Echo the inverted Ethernet link state to the fault LED.

		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
		      also needs to be defined.

- CONFIG_SYS_FAULT_MII_ADDR:
		MII address of the PHY to check for the Ethernet link state.

- CONFIG_NS16550_MIN_FUNCTIONS:
		Define this if you desire to only have use of the NS16550_init
		and NS16550_putc functions for the serial driver located at
		drivers/serial/ns16550.c.  This option is useful for saving
		space for already greatly restricted images, including but not
		limited to NAND_SPL configurations.

Low Level (hardware related) configuration options:
---------------------------------------------------

- CONFIG_SYS_CACHELINE_SIZE:
		Cache Line Size of the CPU.

- CONFIG_SYS_DEFAULT_IMMR:
		Default address of the IMMR after system reset.

		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
		and RPXsuper) to be able to adjust the position of
		the IMMR register after a reset.

- CONFIG_SYS_CCSRBAR_DEFAULT:
		Default (power-on reset) physical address of CCSR on Freescale
		PowerPC SOCs.

- CONFIG_SYS_CCSRBAR:
		Virtual address of CCSR.  On a 32-bit build, this is typically
		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.

		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
		for cross-platform code that uses that macro instead.

- CONFIG_SYS_CCSRBAR_PHYS:
		Physical address of CCSR.  CCSR can be relocated to a new
		physical address, if desired.  In this case, this macro should
		be set to that address.  Otherwise, it should be set to the
		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
		is typically relocated on 36-bit builds.  It is recommended
		that this macro be defined via the _HIGH and _LOW macros:

		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)

- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
		used in assembly code, so it must not contain typecasts or
		integer size suffixes (e.g. "ULL").

- CONFIG_SYS_CCSRBAR_PHYS_LOW:
		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
		used in assembly code, so it must not contain typecasts or
		integer size suffixes (e.g. "ULL").

- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
		forced to a value that ensures that CCSR is not relocated.

- Floppy Disk Support:
		CONFIG_SYS_FDC_DRIVE_NUMBER

		the default drive number (default value 0)

		CONFIG_SYS_ISA_IO_STRIDE

		defines the spacing between FDC chipset registers
		(default value 1)

		CONFIG_SYS_ISA_IO_OFFSET

		defines the offset of register from address. It
		depends on which part of the data bus is connected to
		the FDC chipset. (default value 0)

		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
		default value.

		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
		fdc_hw_init() is called at the beginning of the FDC
		setup. fdc_hw_init() must be provided by the board
		source code. It is used to make hardware dependant
		initializations.

- CONFIG_IDE_AHB:
		Most IDE controllers were designed to be connected with PCI
		interface. Only few of them were designed for AHB interface.
		When software is doing ATA command and data transfer to
		IDE devices through IDE-AHB controller, some additional
		registers accessing to these kind of IDE-AHB controller
		is requierd.

- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
		DO NOT CHANGE unless you know exactly what you're
		doing! (11-4) [MPC8xx/82xx systems only]

- CONFIG_SYS_INIT_RAM_ADDR:

		Start address of memory area that can be used for
		initial data and stack; please note that this must be
		writable memory that is working WITHOUT special
		initialization, i. e. you CANNOT use normal RAM which
		will become available only after programming the
		memory controller and running certain initialization
		sequences.

		U-Boot uses the following memory types:
		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
		- MPC824X: data cache
		- PPC4xx:  data cache

- CONFIG_SYS_GBL_DATA_OFFSET:

		Offset of the initial data structure in the memory
		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
		data is located at the end of the available space
		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
		CONFIG_SYS_GBL_DATA_OFFSET) downward.

	Note:
		On the MPC824X (or other systems that use the data
		cache for initial memory) the address chosen for
		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
		point to an otherwise UNUSED address space between
		the top of RAM and the start of the PCI space.

- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)

- CONFIG_SYS_SYPCR:	System Protection Control (11-9)

- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)

- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)

- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)

- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)