README

#
# (C) Copyright 2000 - 2008
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
#
# See file CREDITS for list of people who contributed to this
# project.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 2 of
# the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
# MA 02111-1307 USA
#

Summary:
========

This directory contains the source code for U-Boot, a boot loader for
Embedded boards based on PowerPC, ARM, MIPS and several other
processors, which can be installed in a boot ROM and used to
initialize and test the hardware or to download and run application
code.

The development of U-Boot is closely related to Linux: some parts of
the source code originate in the Linux source tree, we have some
header files in common, and special provision has been made to
support booting of Linux images.

Some attention has been paid to make this software easily
configurable and extendable. For instance, all monitor commands are
implemented with the same call interface, so that it's very easy to
add new commands. Also, instead of permanently adding rarely used
code (for instance hardware test utilities) to the monitor, you can
load and run it dynamically.


Status:
=======

In general, all boards for which a configuration option exists in the
Makefile have been tested to some extent and can be considered
"working". In fact, many of them are used in production systems.

In case of problems see the CHANGELOG and CREDITS files to find out
who contributed the specific port. The MAINTAINERS file lists board
maintainers.


Where to get help:
==================

In case you have questions about, problems with or contributions for
U-Boot you should send a message to the U-Boot mailing list at
<u-boot@lists.denx.de>. There is also an archive of previous traffic
on the mailing list - please search the archive before asking FAQ's.
Please see http://lists.denx.de/pipermail/u-boot and
http://dir.gmane.org/gmane.comp.boot-loaders.u-boot


Where to get source code:
=========================

The U-Boot source code is maintained in the git repository at
git://www.denx.de/git/u-boot.git ; you can browse it online at
http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary

The "snapshot" links on this page allow you to download tarballs of
any version you might be interested in. Official releases are also
available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
directory.

Pre-built (and tested) images are available from
ftp://ftp.denx.de/pub/u-boot/images/


Where we come from:
===================

- start from 8xxrom sources
- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
- clean up code
- make it easier to add custom boards
- make it possible to add other [PowerPC] CPUs
- extend functions, especially:
  * Provide extended interface to Linux boot loader
  * S-Record download
  * network boot
  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
- create ARMBoot project (http://sourceforge.net/projects/armboot)
- add other CPU families (starting with ARM)
- create U-Boot project (http://sourceforge.net/projects/u-boot)
- current project page: see http://www.denx.de/wiki/U-Boot


Names and Spelling:
===================

The "official" name of this project is "Das U-Boot". The spelling
"U-Boot" shall be used in all written text (documentation, comments
in source files etc.). Example:

	This is the README file for the U-Boot project.

File names etc. shall be based on the string "u-boot". Examples:

	include/asm-ppc/u-boot.h

	#include <asm/u-boot.h>

Variable names, preprocessor constants etc. shall be either based on
the string "u_boot" or on "U_BOOT". Example:

	U_BOOT_VERSION		u_boot_logo
	IH_OS_U_BOOT		u_boot_hush_start


Versioning:
===========

U-Boot uses a 3 level version number containing a version, a
sub-version, and a patchlevel: "U-Boot-2.34.5" means version "2",
sub-version "34", and patchlevel "4".

The patchlevel is used to indicate certain stages of development
between released versions, i. e. officially released versions of
U-Boot will always have a patchlevel of "0".


Directory Hierarchy:
====================

- board		Board dependent files
- common	Misc architecture independent functions
- cpu		CPU specific files
  - 74xx_7xx	Files specific to Freescale MPC74xx and 7xx CPUs
  - arm720t	Files specific to ARM 720 CPUs
  - arm920t	Files specific to ARM 920 CPUs
    - at91rm9200 Files specific to Atmel AT91RM9200 CPU
    - imx	Files specific to Freescale MC9328 i.MX CPUs
    - s3c24x0	Files specific to Samsung S3C24X0 CPUs
  - arm925t	Files specific to ARM 925 CPUs
  - arm926ejs	Files specific to ARM 926 CPUs
  - arm1136	Files specific to ARM 1136 CPUs
  - at32ap	Files specific to Atmel AVR32 AP CPUs
  - i386	Files specific to i386 CPUs
  - ixp		Files specific to Intel XScale IXP CPUs
  - leon2	Files specific to Gaisler LEON2 SPARC CPU
  - leon3	Files specific to Gaisler LEON3 SPARC CPU
  - mcf52x2	Files specific to Freescale ColdFire MCF52x2 CPUs
  - mcf5227x	Files specific to Freescale ColdFire MCF5227x CPUs
  - mcf532x	Files specific to Freescale ColdFire MCF5329 CPUs
  - mcf5445x	Files specific to Freescale ColdFire MCF5445x CPUs
  - mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
  - mips	Files specific to MIPS CPUs
  - mpc5xx	Files specific to Freescale MPC5xx  CPUs
  - mpc5xxx	Files specific to Freescale MPC5xxx CPUs
  - mpc8xx	Files specific to Freescale MPC8xx  CPUs
  - mpc8220	Files specific to Freescale MPC8220 CPUs
  - mpc824x	Files specific to Freescale MPC824x CPUs
  - mpc8260	Files specific to Freescale MPC8260 CPUs
  - mpc85xx	Files specific to Freescale MPC85xx CPUs
  - nios	Files specific to Altera NIOS CPUs
  - nios2	Files specific to Altera Nios-II CPUs
  - ppc4xx	Files specific to AMCC PowerPC 4xx CPUs
  - pxa		Files specific to Intel XScale PXA CPUs
  - s3c44b0	Files specific to Samsung S3C44B0 CPUs
  - sa1100	Files specific to Intel StrongARM SA1100 CPUs
- disk		Code for disk drive partition handling
- doc		Documentation (don't expect too much)
- drivers	Commonly used device drivers
- dtt		Digital Thermometer and Thermostat drivers
- examples	Example code for standalone applications, etc.
- include	Header Files
- lib_arm	Files generic to ARM	 architecture
- lib_avr32	Files generic to AVR32	 architecture
- lib_generic	Files generic to all	 architectures
- lib_i386	Files generic to i386	 architecture
- lib_m68k	Files generic to m68k	 architecture
- lib_mips	Files generic to MIPS	 architecture
- lib_nios	Files generic to NIOS	 architecture
- lib_ppc	Files generic to PowerPC architecture
- lib_sparc	Files generic to SPARC	 architecture
- libfdt	Library files to support flattened device trees
- net		Networking code
- post		Power On Self Test
- rtc		Real Time Clock drivers
- tools		Tools to build S-Record or U-Boot images, etc.

Software Configuration:
=======================

Configuration is usually done using C preprocessor defines; the
rationale behind that is to avoid dead code whenever possible.

There are two classes of configuration variables:

* Configuration _OPTIONS_:
  These are selectable by the user and have names beginning with
  "CONFIG_".

* Configuration _SETTINGS_:
  These depend on the hardware etc. and should not be meddled with if
  you don't know what you're doing; they have names beginning with
  "CFG_".

Later we will add a configuration tool - probably similar to or even
identical to what's used for the Linux kernel. Right now, we have to
do the configuration by hand, which means creating some symbolic
links and editing some configuration files. We use the TQM8xxL boards
as an example here.


Selection of Processor Architecture and Board Type:
---------------------------------------------------

For all supported boards there are ready-to-use default
configurations available; just type "make <board_name>_config".

Example: For a TQM823L module type:

	cd u-boot
	make TQM823L_config

For the Cogent platform, you need to specify the CPU type as well;
e.g. "make cogent_mpc8xx_config". And also configure the cogent
directory according to the instructions in cogent/README.


Configuration Options:
----------------------

Configuration depends on the combination of board and CPU type; all
such information is kept in a configuration file
"include/configs/<board_name>.h".

Example: For a TQM823L module, all configuration settings are in
"include/configs/TQM823L.h".


Many of the options are named exactly as the corresponding Linux
kernel configuration options. The intention is to make it easier to
build a config tool - later.


The following options need to be configured:

- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.

- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.

- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
		Define exactly one, e.g. CONFIG_ATSTK1002

- CPU Module Type: (if CONFIG_COGENT is defined)
		Define exactly one of
		CONFIG_CMA286_60_OLD
--- FIXME --- not tested yet:
		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
		CONFIG_CMA287_23, CONFIG_CMA287_50

- Motherboard Type: (if CONFIG_COGENT is defined)
		Define exactly one of
		CONFIG_CMA101, CONFIG_CMA102

- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
		Define one or more of
		CONFIG_CMA302

- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
		Define one or more of
		CONFIG_LCD_HEARTBEAT	- update a character position on
					  the LCD display every second with
					  a "rotator" |\-/|\-/

- Board flavour: (if CONFIG_MPC8260ADS is defined)
		CONFIG_ADSTYPE
		Possible values are:
			CFG_8260ADS	- original MPC8260ADS
			CFG_8266ADS	- MPC8266ADS
			CFG_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
			CFG_8272ADS	- MPC8272ADS

- MPC824X Family Member (if CONFIG_MPC824X is defined)
		Define exactly one of
		CONFIG_MPC8240, CONFIG_MPC8245

- 8xx CPU Options: (if using an MPC8xx CPU)
		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
					  get_gclk_freq() cannot work
					  e.g. if there is no 32KHz
					  reference PIT/RTC clock
		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
					  or XTAL/EXTAL)

- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
		CFG_8xx_CPUCLK_MIN
		CFG_8xx_CPUCLK_MAX
		CONFIG_8xx_CPUCLK_DEFAULT
			See doc/README.MPC866

		CFG_MEASURE_CPUCLK

		Define this to measure the actual CPU clock instead
		of relying on the correctness of the configured
		values. Mostly useful for board bringup to make sure
		the PLL is locked at the intended frequency. Note
		that this requires a (stable) reference clock (32 kHz
		RTC clock or CFG_8XX_XIN)

- Intel Monahans options:
		CFG_MONAHANS_RUN_MODE_OSC_RATIO

		Defines the Monahans run mode to oscillator
		ratio. Valid values are 8, 16, 24, 31. The core
		frequency is this value multiplied by 13 MHz.

		CFG_MONAHANS_TURBO_RUN_MODE_RATIO

		Defines the Monahans turbo mode to oscillator
		ratio. Valid values are 1 (default if undefined) and
		2. The core frequency as calculated above is multiplied
		by this value.

- Linux Kernel Interface:
		CONFIG_CLOCKS_IN_MHZ

		U-Boot stores all clock information in Hz
		internally. For binary compatibility with older Linux
		kernels (which expect the clocks passed in the
		bd_info data to be in MHz) the environment variable
		"clocks_in_mhz" can be defined so that U-Boot
		converts clock data to MHZ before passing it to the
		Linux kernel.
		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
		"clocks_in_mhz=1" is automatically included in the
		default environment.

		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]

		When transferring memsize parameter to linux, some versions
		expect it to be in bytes, others in MB.
		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.

		CONFIG_OF_LIBFDT

		New kernel versions are expecting firmware settings to be
		passed using flattened device trees (based on open firmware
		concepts).

		CONFIG_OF_LIBFDT
		 * New libfdt-based support
		 * Adds the "fdt" command
		 * The bootm command automatically updates the fdt

		OF_CPU - The proper name of the cpus node.
		OF_SOC - The proper name of the soc node.
		OF_TBCLK - The timebase frequency.
		OF_STDOUT_PATH - The path to the console device

		boards with QUICC Engines require OF_QE to set UCC MAC
		addresses

		CONFIG_OF_BOARD_SETUP

		Board code has addition modification that it wants to make
		to the flat device tree before handing it off to the kernel

		CONFIG_OF_BOOT_CPU

		This define fills in the correct boot CPU in the boot
		param header, the default value is zero if undefined.

- Serial Ports:
		CONFIG_PL010_SERIAL

		Define this if you want support for Amba PrimeCell PL010 UARTs.

		CONFIG_PL011_SERIAL

		Define this if you want support for Amba PrimeCell PL011 UARTs.

		CONFIG_PL011_CLOCK

		If you have Amba PrimeCell PL011 UARTs, set this variable to
		the clock speed of the UARTs.

		CONFIG_PL01x_PORTS

		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
		define this to a list of base addresses for each (supported)
		port. See e.g. include/configs/versatile.h


- Console Interface:
		Depending on board, define exactly one serial port
		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
		console by defining CONFIG_8xx_CONS_NONE

		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
		port routines must be defined elsewhere
		(i.e. serial_init(), serial_getc(), ...)

		CONFIG_CFB_CONSOLE
		Enables console device for a color framebuffer. Needs following
		defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
						(default big endian)
			VIDEO_HW_RECTFILL	graphic chip supports
						rectangle fill
						(cf. smiLynxEM)
			VIDEO_HW_BITBLT		graphic chip supports
						bit-blit (cf. smiLynxEM)
			VIDEO_VISIBLE_COLS	visible pixel columns
						(cols=pitch)
			VIDEO_VISIBLE_ROWS	visible pixel rows
			VIDEO_PIXEL_SIZE	bytes per pixel
			VIDEO_DATA_FORMAT	graphic data format
						(0-5, cf. cfb_console.c)
			VIDEO_FB_ADRS		framebuffer address
			VIDEO_KBD_INIT_FCT	keyboard int fct
						(i.e. i8042_kbd_init())
			VIDEO_TSTC_FCT		test char fct
						(i.e. i8042_tstc)
			VIDEO_GETC_FCT		get char fct
						(i.e. i8042_getc)
			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
						(requires blink timer
						cf. i8042.c)
			CFG_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
			CONFIG_CONSOLE_TIME	display time/date info in
						upper right corner
						(requires CONFIG_CMD_DATE)
			CONFIG_VIDEO_LOGO	display Linux logo in
						upper left corner
			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
						linux_logo.h for logo.
						Requires CONFIG_VIDEO_LOGO
			CONFIG_CONSOLE_EXTRA_INFO
						additional board info beside
						the logo

		When CONFIG_CFB_CONSOLE is defined, video console is
		default i/o. Serial console can be forced with
		environment 'console=serial'.

		When CONFIG_SILENT_CONSOLE is defined, all console
		messages (by U-Boot and Linux!) can be silenced with
		the "silent" environment variable. See
		doc/README.silent for more information.

- Console Baudrate:
		CONFIG_BAUDRATE - in bps
		Select one of the baudrates listed in
		CFG_BAUDRATE_TABLE, see below.
		CFG_BRGCLK_PRESCALE, baudrate prescale

- Interrupt driven serial port input:
		CONFIG_SERIAL_SOFTWARE_FIFO

		PPC405GP only.
		Use an interrupt handler for receiving data on the
		serial port. It also enables using hardware handshake
		(RTS/CTS) and UART's built-in FIFO. Set the number of
		bytes the interrupt driven input buffer should have.

		Leave undefined to disable this feature, including
		disable the buffer and hardware handshake.

- Console UART Number:
		CONFIG_UART1_CONSOLE

		AMCC PPC4xx only.
		If defined internal UART1 (and not UART0) is used
		as default U-Boot console.

- Boot Delay:	CONFIG_BOOTDELAY - in seconds
		Delay before automatically booting the default image;
		set to -1 to disable autoboot.

		See doc/README.autoboot for these options that
		work with CONFIG_BOOTDELAY. None are required.
		CONFIG_BOOT_RETRY_TIME
		CONFIG_BOOT_RETRY_MIN
		CONFIG_AUTOBOOT_KEYED
		CONFIG_AUTOBOOT_PROMPT
		CONFIG_AUTOBOOT_DELAY_STR
		CONFIG_AUTOBOOT_STOP_STR
		CONFIG_AUTOBOOT_DELAY_STR2
		CONFIG_AUTOBOOT_STOP_STR2
		CONFIG_ZERO_BOOTDELAY_CHECK
		CONFIG_RESET_TO_RETRY

- Autoboot Command:
		CONFIG_BOOTCOMMAND
		Only needed when CONFIG_BOOTDELAY is enabled;
		define a command string that is automatically executed
		when no character is read on the console interface
		within "Boot Delay" after reset.

		CONFIG_BOOTARGS
		This can be used to pass arguments to the bootm
		command. The value of CONFIG_BOOTARGS goes into the
		environment value "bootargs".

		CONFIG_RAMBOOT and CONFIG_NFSBOOT
		The value of these goes into the environment as
		"ramboot" and "nfsboot" respectively, and can be used
		as a convenience, when switching between booting from
		RAM and NFS.

- Pre-Boot Commands:
		CONFIG_PREBOOT

		When this option is #defined, the existence of the
		environment variable "preboot" will be checked
		immediately before starting the CONFIG_BOOTDELAY
		countdown and/or running the auto-boot command resp.
		entering interactive mode.

		This feature is especially useful when "preboot" is
		automatically generated or modified. For an example
		see the LWMON board specific code: here "preboot" is
		modified when the user holds down a certain
		combination of keys on the (special) keyboard when
		booting the systems

- Serial Download Echo Mode:
		CONFIG_LOADS_ECHO
		If defined to 1, all characters received during a
		serial download (using the "loads" command) are
		echoed back. This might be needed by some terminal
		emulations (like "cu"), but may as well just take
		time on others. This setting #define's the initial
		value of the "loads_echo" environment variable.

- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
		CONFIG_KGDB_BAUDRATE
		Select one of the baudrates listed in
		CFG_BAUDRATE_TABLE, see below.

- Monitor Functions:
		Monitor commands can be included or excluded
		from the build by using the #include files
		"config_cmd_all.h" and #undef'ing unwanted
		commands, or using "config_cmd_default.h"
		and augmenting with additional #define's
		for wanted commands.

		The default command configuration includes all commands
		except those marked below with a "*".

		CONFIG_CMD_ASKENV	* ask for env variable
		CONFIG_CMD_AUTOSCRIPT	  Autoscript Support
		CONFIG_CMD_BDI		  bdinfo
		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
		CONFIG_CMD_BMP		* BMP support
		CONFIG_CMD_BSP		* Board specific commands
		CONFIG_CMD_BOOTD	  bootd
		CONFIG_CMD_CACHE	* icache, dcache
		CONFIG_CMD_CONSOLE	  coninfo
		CONFIG_CMD_DATE		* support for RTC, date/time...
		CONFIG_CMD_DHCP		* DHCP support
		CONFIG_CMD_DIAG		* Diagnostics
		CONFIG_CMD_DOC		* Disk-On-Chip Support
		CONFIG_CMD_DTT		* Digital Therm and Thermostat
		CONFIG_CMD_ECHO		  echo arguments
		CONFIG_CMD_EEPROM	* EEPROM read/write support
		CONFIG_CMD_ELF		* bootelf, bootvx
		CONFIG_CMD_ENV		  saveenv
		CONFIG_CMD_FDC		* Floppy Disk Support
		CONFIG_CMD_FAT		* FAT partition support
		CONFIG_CMD_FDOS		* Dos diskette Support
		CONFIG_CMD_FLASH	  flinfo, erase, protect
		CONFIG_CMD_FPGA		  FPGA device initialization support
		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
		CONFIG_CMD_I2C		* I2C serial bus support
		CONFIG_CMD_IDE		* IDE harddisk support
		CONFIG_CMD_IMI		  iminfo
		CONFIG_CMD_IMLS		  List all found images
		CONFIG_CMD_IMMAP	* IMMR dump support
		CONFIG_CMD_IRQ		* irqinfo
		CONFIG_CMD_ITEST	  Integer/string test of 2 values
		CONFIG_CMD_JFFS2	* JFFS2 Support
		CONFIG_CMD_KGDB		* kgdb
		CONFIG_CMD_LOADB	  loadb
		CONFIG_CMD_LOADS	  loads
		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
					  loop, loopw, mtest
		CONFIG_CMD_MISC		  Misc functions like sleep etc
		CONFIG_CMD_MMC		* MMC memory mapped support
		CONFIG_CMD_MII		* MII utility commands
		CONFIG_CMD_NAND		* NAND support
		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
		CONFIG_CMD_PCI		* pciinfo
		CONFIG_CMD_PCMCIA		* PCMCIA support
		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
					  host
		CONFIG_CMD_PORTIO	* Port I/O
		CONFIG_CMD_REGINFO	* Register dump
		CONFIG_CMD_RUN		  run command in env variable
		CONFIG_CMD_SAVES	* save S record dump
		CONFIG_CMD_SCSI		* SCSI Support
		CONFIG_CMD_SDRAM	* print SDRAM configuration information
					  (requires CONFIG_CMD_I2C)
		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
					  (4xx only)
		CONFIG_CMD_SPI		* SPI serial bus support
		CONFIG_CMD_USB		* USB support
		CONFIG_CMD_VFD		* VFD support (TRAB)
		CONFIG_CMD_CDP		* Cisco Discover Protocol support
		CONFIG_CMD_FSL		* Microblaze FSL support


		EXAMPLE: If you want all functions except of network
		support you can write:

		#include "config_cmd_all.h"
		#undef CONFIG_CMD_NET

	Other Commands:
		fdt (flattened device tree) command: CONFIG_OF_LIBFDT

	Note:	Don't enable the "icache" and "dcache" commands
		(configuration option CONFIG_CMD_CACHE) unless you know
		what you (and your U-Boot users) are doing. Data
		cache cannot be enabled on systems like the 8xx or
		8260 (where accesses to the IMMR region must be
		uncached), and it cannot be disabled on all other
		systems where we (mis-) use the data cache to hold an
		initial stack and some data.


		XXX - this list needs to get updated!

- Watchdog:
		CONFIG_WATCHDOG
		If this variable is defined, it enables watchdog
		support. There must be support in the platform specific
		code for a watchdog. For the 8xx and 8260 CPUs, the
		SIU Watchdog feature is enabled in the SYPCR
		register.

- U-Boot Version:
		CONFIG_VERSION_VARIABLE
		If this variable is defined, an environment variable
		named "ver" is created by U-Boot showing the U-Boot
		version as printed by the "version" command.
		This variable is readonly.

- Real-Time Clock:

		When CONFIG_CMD_DATE is selected, the type of the RTC
		has to be selected, too. Define exactly one of the
		following options:

		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
		CONFIG_RTC_MC13783	- use MC13783 RTC
		CONFIG_RTC_MC146818	- use MC146818 RTC
		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
		CFG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337

		Note that if the RTC uses I2C, then the I2C interface
		must also be configured. See I2C Support, below.

- Timestamp Support:

		When CONFIG_TIMESTAMP is selected, the timestamp
		(date and time) of an image is printed by image
		commands like bootm or iminfo. This option is
		automatically enabled when you select CONFIG_CMD_DATE .

- Partition Support:
		CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
		and/or CONFIG_ISO_PARTITION and/or CONFIG_EFI_PARTITION

		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
		CONFIG_CMD_SCSI) you must configure support for at
		least one partition type as well.

- IDE Reset method:
		CONFIG_IDE_RESET_ROUTINE - this is defined in several
		board configurations files but used nowhere!

		CONFIG_IDE_RESET - is this is defined, IDE Reset will
		be performed by calling the function
			ide_set_reset(int reset)
		which has to be defined in a board specific file

- ATAPI Support:
		CONFIG_ATAPI

		Set this to enable ATAPI support.

- LBA48 Support
		CONFIG_LBA48

		Set this to enable support for disks larger than 137GB
		Also look at CFG_64BIT_LBA ,CFG_64BIT_VSPRINTF and CFG_64BIT_STRTOUL
		Whithout these , LBA48 support uses 32bit variables and will 'only'
		support disks up to 2.1TB.

		CFG_64BIT_LBA:
			When enabled, makes the IDE subsystem use 64bit sector addresses.
			Default is 32bit.

- SCSI Support:
		At the moment only there is only support for the
		SYM53C8XX SCSI controller; define
		CONFIG_SCSI_SYM53C8XX to enable it.

		CFG_SCSI_MAX_LUN [8], CFG_SCSI_MAX_SCSI_ID [7] and
		CFG_SCSI_MAX_DEVICE [CFG_SCSI_MAX_SCSI_ID *
		CFG_SCSI_MAX_LUN] can be adjusted to define the
		maximum numbers of LUNs, SCSI ID's and target
		devices.
		CFG_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)

- NETWORK Support (PCI):
		CONFIG_E1000
		Support for Intel 8254x gigabit chips.

		CONFIG_E1000_FALLBACK_MAC
		default MAC for empty EEPROM after production.

		CONFIG_EEPRO100
		Support for Intel 82557/82559/82559ER chips.
		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
		write routine for first time initialisation.

		CONFIG_TULIP
		Support for Digital 2114x chips.
		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
		modem chip initialisation (KS8761/QS6611).

		CONFIG_NATSEMI
		Support for National dp83815 chips.

		CONFIG_NS8382X
		Support for National dp8382[01] gigabit chips.

- NETWORK Support (other):

		CONFIG_DRIVER_LAN91C96
		Support for SMSC's LAN91C96 chips.

			CONFIG_LAN91C96_BASE
			Define this to hold the physical address
			of the LAN91C96's I/O space

			CONFIG_LAN91C96_USE_32_BIT
			Define this to enable 32 bit addressing

		CONFIG_DRIVER_SMC91111
		Support for SMSC's LAN91C111 chip

			CONFIG_SMC91111_BASE
			Define this to hold the physical address
			of the device (I/O space)

			CONFIG_SMC_USE_32_BIT
			Define this if data bus is 32 bits

			CONFIG_SMC_USE_IOFUNCS
			Define this to use i/o functions instead of macros
			(some hardware wont work with macros)

		CONFIG_DRIVER_SMC911X
		Support for SMSC's LAN911x and LAN921x chips

			CONFIG_DRIVER_SMC911X_BASE
			Define this to hold the physical address
			of the device (I/O space)

			CONFIG_DRIVER_SMC911X_32_BIT
			Define this if data bus is 32 bits

			CONFIG_DRIVER_SMC911X_16_BIT
			Define this if data bus is 16 bits. If your processor
			automatically converts one 32 bit word to two 16 bit
			words you may also try CONFIG_DRIVER_SMC911X_32_BIT.

- USB Support:
		At the moment only the UHCI host controller is
		supported (PIP405, MIP405, MPC5200); define
		CONFIG_USB_UHCI to enable it.
		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
		and define CONFIG_USB_STORAGE to enable the USB
		storage devices.
		Note:
		Supported are USB Keyboards and USB Floppy drives
		(TEAC FD-05PUB).
		MPC5200 USB requires additional defines:
			CONFIG_USB_CLOCK
				for 528 MHz Clock: 0x0001bbbb
			CONFIG_USB_CONFIG
				for differential drivers: 0x00001000
				for single ended drivers: 0x00005000
			CFG_USB_EVENT_POLL
				May be defined to allow interrupt polling
				instead of using asynchronous interrupts

- USB Device:
		Define the below if you wish to use the USB console.
		Once firmware is rebuilt from a serial console issue the
		command "setenv stdin usbtty; setenv stdout usbtty" and
		attach your USB cable. The Unix command "dmesg" should print
		it has found a new device. The environment variable usbtty
		can be set to gserial or cdc_acm to enable your device to
		appear to a USB host as a Linux gserial device or a
		Common Device Class Abstract Control Model serial device.
		If you select usbtty = gserial you should be able to enumerate
		a Linux host by
		# modprobe usbserial vendor=0xVendorID product=0xProductID
		else if using cdc_acm, simply setting the environment
		variable usbtty to be cdc_acm should suffice. The following
		might be defined in YourBoardName.h

			CONFIG_USB_DEVICE
			Define this to build a UDC device

			CONFIG_USB_TTY
			Define this to have a tty type of device available to
			talk to the UDC device

			CFG_CONSOLE_IS_IN_ENV
			Define this if you want stdin, stdout &/or stderr to
			be set to usbtty.

			mpc8xx:
				CFG_USB_EXTC_CLK 0xBLAH
				Derive USB clock from external clock "blah"
				- CFG_USB_EXTC_CLK 0x02

				CFG_USB_BRG_CLK 0xBLAH
				Derive USB clock from brgclk
				- CFG_USB_BRG_CLK 0x04

		If you have a USB-IF assigned VendorID then you may wish to
		define your own vendor specific values either in BoardName.h
		or directly in usbd_vendor_info.h. If you don't define
		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
		should pretend to be a Linux device to it's target host.

			CONFIG_USBD_MANUFACTURER
			Define this string as the name of your company for
			- CONFIG_USBD_MANUFACTURER "my company"

			CONFIG_USBD_PRODUCT_NAME
			Define this string as the name of your product
			- CONFIG_USBD_PRODUCT_NAME "acme usb device"

			CONFIG_USBD_VENDORID
			Define this as your assigned Vendor ID from the USB
			Implementors Forum. This *must* be a genuine Vendor ID
			to avoid polluting the USB namespace.
			- CONFIG_USBD_VENDORID 0xFFFF

			CONFIG_USBD_PRODUCTID
			Define this as the unique Product ID
			for your device
			- CONFIG_USBD_PRODUCTID 0xFFFF


- MMC Support:
		The MMC controller on the Intel PXA is supported. To
		enable this define CONFIG_MMC. The MMC can be
		accessed from the boot prompt by mapping the device
		to physical memory similar to flash. Command line is
		enabled with CONFIG_CMD_MMC. The MMC driver also works with
		the FAT fs. This is enabled with CONFIG_CMD_FAT.

- Journaling Flash filesystem support:
		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
		CONFIG_JFFS2_NAND_DEV
		Define these for a default partition on a NAND device

		CFG_JFFS2_FIRST_SECTOR,
		CFG_JFFS2_FIRST_BANK, CFG_JFFS2_NUM_BANKS
		Define these for a default partition on a NOR device

		CFG_JFFS_CUSTOM_PART
		Define this to create an own partition. You have to provide a
		function struct part_info* jffs2_part_info(int part_num)

		If you define only one JFFS2 partition you may also want to
		#define CFG_JFFS_SINGLE_PART	1
		to disable the command chpart. This is the default when you
		have not defined a custom partition

- Keyboard Support:
		CONFIG_ISA_KEYBOARD

		Define this to enable standard (PC-Style) keyboard
		support

		CONFIG_I8042_KBD
		Standard PC keyboard driver with US (is default) and
		GERMAN key layout (switch via environment 'keymap=de') support.
		Export function i8042_kbd_init, i8042_tstc and i8042_getc
		for cfb_console. Supports cursor blinking.

- Video support:
		CONFIG_VIDEO

		Define this to enable video support (for output to
		video).

		CONFIG_VIDEO_CT69000

		Enable Chips & Technologies 69000 Video chip

		CONFIG_VIDEO_SMI_LYNXEM
		Enable Silicon Motion SMI 712/710/810 Video chip. The
		video output is selected via environment 'videoout'
		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
		assumed.

		For the CT69000 and SMI_LYNXEM drivers, videomode is
		selected via environment 'videomode'. Two different ways
		are possible:
		- "videomode=num"   'num' is a standard LiLo mode numbers.
		Following standard modes are supported	(* is default):

		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
		-------------+---------------------------------------------
		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
		-------------+---------------------------------------------
		(i.e. setenv videomode 317; saveenv; reset;)

		- "videomode=bootargs" all the video parameters are parsed
		from the bootargs. (See drivers/video/videomodes.c)


		CONFIG_VIDEO_SED13806
		Enable Epson SED13806 driver. This driver supports 8bpp
		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
		or CONFIG_VIDEO_SED13806_16BPP

- Keyboard Support:
		CONFIG_KEYBOARD

		Define this to enable a custom keyboard support.
		This simply calls drv_keyboard_init() which must be
		defined in your board-specific files.
		The only board using this so far is RBC823.

- LCD Support:	CONFIG_LCD

		Define this to enable LCD support (for output to LCD
		display); also select one of the supported displays
		by defining one of these:

		CONFIG_ATMEL_LCD:

			HITACHI TX09D70VM1CCA, 3.5", 240x320.

		CONFIG_NEC_NL6448AC33:

			NEC NL6448AC33-18. Active, color, single scan.

		CONFIG_NEC_NL6448BC20

			NEC NL6448BC20-08. 6.5", 640x480.
			Active, color, single scan.

		CONFIG_NEC_NL6448BC33_54

			NEC NL6448BC33-54. 10.4", 640x480.
			Active, color, single scan.

		CONFIG_SHARP_16x9

			Sharp 320x240. Active, color, single scan.
			It isn't 16x9, and I am not sure what it is.

		CONFIG_SHARP_LQ64D341

			Sharp LQ64D341 display, 640x480.
			Active, color, single scan.

		CONFIG_HLD1045

			HLD1045 display, 640x480.
			Active, color, single scan.

		CONFIG_OPTREX_BW

			Optrex	 CBL50840-2 NF-FW 99 22 M5
			or
			Hitachi	 LMG6912RPFC-00T
			or
			Hitachi	 SP14Q002

			320x240. Black & white.

		Normally display is black on white background; define
		CFG_WHITE_ON_BLACK to get it inverted.

- Splash Screen Support: CONFIG_SPLASH_SCREEN

		If this option is set, the environment is checked for
		a variable "splashimage". If found, the usual display
		of logo, copyright and system information on the LCD
		is suppressed and the BMP image at the address
		specified in "splashimage" is loaded instead. The
		console is redirected to the "nulldev", too. This
		allows for a "silent" boot where a splash screen is
		loaded very quickly after power-on.

- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP

		If this option is set, additionally to standard BMP
		images, gzipped BMP images can be displayed via the
		splashscreen support or the bmp command.

- Compression support:
		CONFIG_BZIP2

		If this option is set, support for bzip2 compressed
		images is included. If not, only uncompressed and gzip
		compressed images are supported.

		NOTE: the bzip2 algorithm requires a lot of RAM, so
		the malloc area (as defined by CFG_MALLOC_LEN) should
		be at least 4MB.

		CONFIG_LZMA

		If this option is set, support for lzma compressed
		images is included.

		Note: The LZMA algorithm adds between 2 and 4KB of code and it
		requires an amount of dynamic memory that is given by the
		formula:

			(1846 + 768 << (lc + lp)) * sizeof(uint16)

		Where lc and lp stand for, respectively, Literal context bits
		and Literal pos bits.

		This value is upper-bounded by 14MB in the worst case. Anyway,
		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
		a very small buffer.

		Use the lzmainfo tool to determinate the lc and lp values and
		then calculate the amount of needed dynamic memory (ensuring
		the appropriate CFG_MALLOC_LEN value).

- MII/PHY support:
		CONFIG_PHY_ADDR

		The address of PHY on MII bus.

		CONFIG_PHY_CLOCK_FREQ (ppc4xx)

		The clock frequency of the MII bus

		CONFIG_PHY_GIGE

		If this option is set, support for speed/duplex
		detection of gigabit PHY is included.

		CONFIG_PHY_RESET_DELAY

		Some PHY like Intel LXT971A need extra delay after
		reset before any MII register access is possible.
		For such PHY, set this option to the usec delay
		required. (minimum 300usec for LXT971A)

		CONFIG_PHY_CMD_DELAY (ppc4xx)

		Some PHY like Intel LXT971A need extra delay after
		command issued before MII status register can be read

- Ethernet address:
		CONFIG_ETHADDR
		CONFIG_ETH1ADDR
		CONFIG_ETH2ADDR
		CONFIG_ETH3ADDR
		CONFIG_ETH4ADDR
		CONFIG_ETH5ADDR

		Define a default value for Ethernet address to use
		for the respective Ethernet interface, in case this
		is not determined automatically.

- IP address:
		CONFIG_IPADDR

		Define a default value for the IP address to use for
		the default Ethernet interface, in case this is not
		determined through e.g. bootp.

- Server IP address:
		CONFIG_SERVERIP

		Defines a default value for the IP address of a TFTP
		server to contact when using the "tftboot" command.

- Multicast TFTP Mode:
		CONFIG_MCAST_TFTP

		Defines whether you want to support multicast TFTP as per
		rfc-2090; for example to work with atftp.  Lets lots of targets
		tftp down the same boot image concurrently.  Note: the Ethernet
		driver in use must provide a function: mcast() to join/leave a
		multicast group.

		CONFIG_BOOTP_RANDOM_DELAY
- BOOTP Recovery Mode:
		CONFIG_BOOTP_RANDOM_DELAY

		If you have many targets in a network that try to
		boot using BOOTP, you may want to avoid that all
		systems send out BOOTP requests at precisely the same
		moment (which would happen for instance at recovery
		from a power failure, when all systems will try to
		boot, thus flooding the BOOTP server. Defining
		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
		inserted before sending out BOOTP requests. The
		following delays are inserted then:

		1st BOOTP request:	delay 0 ... 1 sec
		2nd BOOTP request:	delay 0 ... 2 sec
		3rd BOOTP request:	delay 0 ... 4 sec
		4th and following
		BOOTP requests:		delay 0 ... 8 sec

- DHCP Advanced Options:
		You can fine tune the DHCP functionality by defining
		CONFIG_BOOTP_* symbols:

		CONFIG_BOOTP_SUBNETMASK
		CONFIG_BOOTP_GATEWAY
		CONFIG_BOOTP_HOSTNAME
		CONFIG_BOOTP_NISDOMAIN
		CONFIG_BOOTP_BOOTPATH
		CONFIG_BOOTP_BOOTFILESIZE
		CONFIG_BOOTP_DNS
		CONFIG_BOOTP_DNS2
		CONFIG_BOOTP_SEND_HOSTNAME
		CONFIG_BOOTP_NTPSERVER
		CONFIG_BOOTP_TIMEOFFSET
		CONFIG_BOOTP_VENDOREX

		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
		environment variable, not the BOOTP server.

		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
		serverip from a DHCP server, it is possible that more
		than one DNS serverip is offered to the client.
		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
		serverip will be stored in the additional environment
		variable "dnsip2". The first DNS serverip is always
		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
		is defined.

		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
		to do a dynamic update of a DNS server. To do this, they
		need the hostname of the DHCP requester.
		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
		of the "hostname" environment variable is passed as
		option 12 to the DHCP server.

		CONFIG_BOOTP_DHCP_REQUEST_DELAY

		A 32bit value in microseconds for a delay between
		receiving a "DHCP Offer" and sending the "DHCP Request".
		This fixes a problem with certain DHCP servers that don't
		respond 100% of the time to a "DHCP request". E.g. On an
		AT91RM9200 processor running at 180MHz, this delay needed
		to be *at least* 15,000 usec before a Windows Server 2003
		DHCP server would reply 100% of the time. I recommend at
		least 50,000 usec to be safe. The alternative is to hope
		that one of the retries will be successful but note that
		the DHCP timeout and retry process takes a longer than
		this delay.

 - CDP Options:
		CONFIG_CDP_DEVICE_ID

		The device id used in CDP trigger frames.

		CONFIG_CDP_DEVICE_ID_PREFIX

		A two character string which is prefixed to the MAC address
		of the device.

		CONFIG_CDP_PORT_ID

		A printf format string which contains the ascii name of
		the port. Normally is set to "eth%d" which sets
		eth0 for the first Ethernet, eth1 for the second etc.

		CONFIG_CDP_CAPABILITIES

		A 32bit integer which indicates the device capabilities;
		0x00000010 for a normal host which does not forwards.

		CONFIG_CDP_VERSION

		An ascii string containing the version of the software.

		CONFIG_CDP_PLATFORM

		An ascii string containing the name of the platform.

		CONFIG_CDP_TRIGGER

		A 32bit integer sent on the trigger.

		CONFIG_CDP_POWER_CONSUMPTION

		A 16bit integer containing the power consumption of the
		device in .1 of milliwatts.

		CONFIG_CDP_APPLIANCE_VLAN_TYPE

		A byte containing the id of the VLAN.

- Status LED:	CONFIG_STATUS_LED

		Several configurations allow to display the current
		status using a LED. For instance, the LED will blink
		fast while running U-Boot code, stop blinking as
		soon as a reply to a BOOTP request was received, and
		start blinking slow once the Linux kernel is running
		(supported by a status LED driver in the Linux
		kernel). Defining CONFIG_STATUS_LED enables this
		feature in U-Boot.

- CAN Support:	CONFIG_CAN_DRIVER

		Defining CONFIG_CAN_DRIVER enables CAN driver support
		on those systems that support this (optional)
		feature, like the TQM8xxL modules.

- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C

		These enable I2C serial bus commands. Defining either of
		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
		include the appropriate I2C driver for the selected CPU.

		This will allow you to use i2c commands at the u-boot
		command line (as long as you set CONFIG_CMD_I2C in
		CONFIG_COMMANDS) and communicate with i2c based realtime
		clock chips. See common/cmd_i2c.c for a description of the
		command line interface.

		CONFIG_I2C_CMD_TREE is a recommended option that places
		all I2C commands under a single 'i2c' root command.  The
		older 'imm', 'imd', 'iprobe' etc. commands are considered
		deprecated and may disappear in the future.

		CONFIG_HARD_I2C selects a hardware I2C controller.

		CONFIG_SOFT_I2C configures u-boot to use a software (aka
		bit-banging) driver instead of CPM or similar hardware
		support for I2C.

		There are several other quantities that must also be
		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.

		In both cases you will need to define CFG_I2C_SPEED
		to be the frequency (in Hz) at which you wish your i2c bus
		to run and CFG_I2C_SLAVE to be the address of this node (ie
		the CPU's i2c node address).

		Now, the u-boot i2c code for the mpc8xx (cpu/mpc8xx/i2c.c)
		sets the CPU up as a master node and so its address should
		therefore be cleared to 0 (See, eg, MPC823e User's Manual
		p.16-473). So, set CFG_I2C_SLAVE to 0.

		That's all that's required for CONFIG_HARD_I2C.

		If you use the software i2c interface (CONFIG_SOFT_I2C)
		then the following macros need to be defined (examples are
		from include/configs/lwmon.h):

		I2C_INIT

		(Optional). Any commands necessary to enable the I2C
		controller or configure ports.

		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)

		I2C_PORT

		(Only for MPC8260 CPU). The I/O port to use (the code
		assumes both bits are on the same port). Valid values
		are 0..3 for ports A..D.

		I2C_ACTIVE

		The code necessary to make the I2C data line active
		(driven).  If the data line is open collector, this
		define can be null.

		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)

		I2C_TRISTATE

		The code necessary to make the I2C data line tri-stated
		(inactive).  If the data line is open collector, this
		define can be null.

		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)

		I2C_READ

		Code that returns TRUE if the I2C data line is high,
		FALSE if it is low.

		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)

		I2C_SDA(bit)

		If <bit> is TRUE, sets the I2C data line high. If it
		is FALSE, it clears it (low).

		eg: #define I2C_SDA(bit) \
			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
			else	immr->im_cpm.cp_pbdat &= ~PB_SDA

		I2C_SCL(bit)

		If <bit> is TRUE, sets the I2C clock line high. If it
		is FALSE, it clears it (low).

		eg: #define I2C_SCL(bit) \
			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
			else	immr->im_cpm.cp_pbdat &= ~PB_SCL

		I2C_DELAY

		This delay is invoked four times per clock cycle so this
		controls the rate of data transfer.  The data rate thus
		is 1 / (I2C_DELAY * 4). Often defined to be something
		like:

		#define I2C_DELAY  udelay(2)

		CFG_I2C_INIT_BOARD

		When a board is reset during an i2c bus transfer
		chips might think that the current transfer is still
		in progress. On some boards it is possible to access
		the i2c SCLK line directly, either by using the
		processor pin as a GPIO or by having a second pin
		connected to the bus. If this option is defined a
		custom i2c_init_board() routine in boards/xxx/board.c
		is run early in the boot sequence.

		CONFIG_I2CFAST (PPC405GP|PPC405EP only)

		This option enables configuration of bi_iic_fast[] flags
		in u-boot bd_info structure based on u-boot environment
		variable "i2cfast". (see also i2cfast)

		CONFIG_I2C_MULTI_BUS

		This option allows the use of multiple I2C buses, each of which
		must have a controller.  At any point in time, only one bus is
		active.  To switch to a different bus, use the 'i2c dev' command.
		Note that bus numbering is zero-based.

		CFG_I2C_NOPROBES

		This option specifies a list of I2C devices that will be skipped
		when the 'i2c probe' command is issued (or 'iprobe' using the legacy
		command).  If CONFIG_I2C_MULTI_BUS is set, specify a list of bus-device
		pairs.	Otherwise, specify a 1D array of device addresses

		e.g.
			#undef	CONFIG_I2C_MULTI_BUS
			#define CFG_I2C_NOPROBES	{0x50,0x68}

		will skip addresses 0x50 and 0x68 on a board with one I2C bus

			#define	CONFIG_I2C_MULTI_BUS
			#define CFG_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}

		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1

		CFG_SPD_BUS_NUM

		If defined, then this indicates the I2C bus number for DDR SPD.
		If not defined, then U-Boot assumes that SPD is on I2C bus 0.

		CFG_RTC_BUS_NUM

		If defined, then this indicates the I2C bus number for the RTC.
		If not defined, then U-Boot assumes that RTC is on I2C bus 0.

		CFG_DTT_BUS_NUM

		If defined, then this indicates the I2C bus number for the DTT.
		If not defined, then U-Boot assumes that DTT is on I2C bus 0.

		CFG_I2C_DTT_ADDR:

		If defined, specifies the I2C address of the DTT device.
		If not defined, then U-Boot uses predefined value for
		specified DTT device.

		CONFIG_FSL_I2C

		Define this option if you want to use Freescale's I2C driver in
		drivers/i2c/fsl_i2c.c.

		CONFIG_I2C_MUX

		Define this option if you have I2C devices reached over 1 .. n
		I2C Muxes like the pca9544a. This option addes a new I2C
		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
		new I2C Bus to the existing I2C Busses. If you select the
		new Bus with "i2c dev", u-bbot sends first the commandos for
		the muxes to activate this new "bus".

		CONFIG_I2C_MULTI_BUS must be also defined, to use this
		feature!

		Example:
		Adding a new I2C Bus reached over 2 pca9544a muxes
			The First mux with address 70 and channel 6
			The Second mux with address 71 and channel 4

		=> i2c bus pca9544a:70:6:pca9544a:71:4

		Use the "i2c bus" command without parameter, to get a list
		of I2C Busses with muxes:

		=> i2c bus
		Busses reached over muxes:
		Bus ID: 2
		  reached over Mux(es):
		    pca9544a@70 ch: 4
		Bus ID: 3
		  reached over Mux(es):
		    pca9544a@70 ch: 6
		    pca9544a@71 ch: 4
		=>

		If you now switch to the new I2C Bus 3 with "i2c dev 3"
		u-boot sends First the Commando to the mux@70 to enable
		channel 6, and then the Commando to the mux@71 to enable
		the channel 4.

		After that, you can use the "normal" i2c commands as
		usual, to communicate with your I2C devices behind
		the 2 muxes.

		This option is actually implemented for the bitbanging
		algorithm in common/soft_i2c.c and for the Hardware I2C
		Bus on the MPC8260. But it should be not so difficult
		to add this option to other architectures.


- SPI Support:	CONFIG_SPI

		Enables SPI driver (so far only tested with
		SPI EEPROM, also an instance works with Crystal A/D and
		D/As on the SACSng board)

		CONFIG_SPI_X

		Enables extended (16-bit) SPI EEPROM addressing.
		(symmetrical to CONFIG_I2C_X)

		CONFIG_SOFT_SPI

		Enables a software (bit-bang) SPI driver rather than
		using hardware support. This is a general purpose
		driver that only requires three general I/O port pins
		(two outputs, one input) to function. If this is
		defined, the board configuration must define several
		SPI configuration items (port pins to use, etc). For
		an example, see include/configs/sacsng.h.

		CONFIG_HARD_SPI

		Enables a hardware SPI driver for general-purpose reads
		and writes.  As with CONFIG_SOFT_SPI, the board configuration
		must define a list of chip-select function pointers.
		Currently supported on some MPC8xxx processors.  For an
		example, see include/configs/mpc8349emds.h.

		CONFIG_MXC_SPI

		Enables the driver for the SPI controllers on i.MX and MXC
		SoCs. Currently only i.MX31 is supported.

- FPGA Support: CONFIG_FPGA

		Enables FPGA subsystem.

		CONFIG_FPGA_<vendor>

		Enables support for specific chip vendors.
		(ALTERA, XILINX)

		CONFIG_FPGA_<family>

		Enables support for FPGA family.
		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)

		CONFIG_FPGA_COUNT

		Specify the number of FPGA devices to support.

		CFG_FPGA_PROG_FEEDBACK

		Enable printing of hash marks during FPGA configuration.

		CFG_FPGA_CHECK_BUSY

		Enable checks on FPGA configuration interface busy
		status by the configuration function. This option
		will require a board or device specific function to
		be written.

		CONFIG_FPGA_DELAY

		If defined, a function that provides delays in the FPGA
		configuration driver.

		CFG_FPGA_CHECK_CTRLC
		Allow Control-C to interrupt FPGA configuration

		CFG_FPGA_CHECK_ERROR

		Check for configuration errors during FPGA bitfile
		loading. For example, abort during Virtex II
		configuration if the INIT_B line goes low (which
		indicated a CRC error).

		CFG_FPGA_WAIT_INIT

		Maximum time to wait for the INIT_B line to deassert
		after PROB_B has been deasserted during a Virtex II
		FPGA configuration sequence. The default time is 500
		ms.

		CFG_FPGA_WAIT_BUSY

		Maximum time to wait for BUSY to deassert during
		Virtex II FPGA configuration. The default is 5 ms.

		CFG_FPGA_WAIT_CONFIG

		Time to wait after FPGA configuration. The default is
		200 ms.

- Configuration Management:
		CONFIG_IDENT_STRING

		If defined, this string will be added to the U-Boot
		version information (U_BOOT_VERSION)

- Vendor Parameter Protection:

		U-Boot considers the values of the environment
		variables "serial#" (Board Serial Number) and
		"ethaddr" (Ethernet Address) to be parameters that
		are set once by the board vendor / manufacturer, and
		protects these variables from casual modification by
		the user. Once set, these variables are read-only,
		and write or delete attempts are rejected. You can
		change this behaviour:

		If CONFIG_ENV_OVERWRITE is #defined in your config
		file, the write protection for vendor parameters is
		completely disabled. Anybody can change or delete
		these parameters.

		Alternatively, if you #define _both_ CONFIG_ETHADDR
		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
		Ethernet address is installed in the environment,
		which can be changed exactly ONCE by the user. [The
		serial# is unaffected by this, i. e. it remains
		read-only.]

- Protected RAM:
		CONFIG_PRAM

		Define this variable to enable the reservation of
		"protected RAM", i. e. RAM which is not overwritten
		by U-Boot. Define CONFIG_PRAM to hold the number of
		kB you want to reserve for pRAM. You can overwrite
		this default value by defining an environment
		variable "pram" to the number of kB you want to
		reserve. Note that the board info structure will
		still show the full amount of RAM. If pRAM is
		reserved, a new environment variable "mem" will
		automatically be defined to hold the amount of
		remaining RAM in a form that can be passed as boot
		argument to Linux, for instance like that:

			setenv bootargs ... mem=\${mem}
			saveenv

		This way you can tell Linux not to use this memory,
		either, which results in a memory region that will
		not be affected by reboots.

		*WARNING* If your board configuration uses automatic
		detection of the RAM size, you must make sure that
		this memory test is non-destructive. So far, the
		following board configurations are known to be
		"pRAM-clean":

			ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
			HERMES, IP860, RPXlite, LWMON, LANTEC,
			PCU_E, FLAGADM, TQM8260

- Error Recovery:
		CONFIG_PANIC_HANG

		Define this variable to stop the system in case of a
		fatal error, so that you have to reset it manually.
		This is probably NOT a good idea for an embedded
		system where you want the system to reboot
		automatically as fast as possible, but it may be
		useful during development since you can try to debug
		the conditions that lead to the situation.

		CONFIG_NET_RETRY_COUNT

		This variable defines the number of retries for
		network operations like ARP, RARP, TFTP, or BOOTP
		before giving up the operation. If not defined, a
		default value of 5 is used.

		CONFIG_ARP_TIMEOUT

		Timeout waiting for an ARP reply in milliseconds.

- Command Interpreter:
		CONFIG_AUTO_COMPLETE

		Enable auto completion of commands using TAB.

		Note that this feature has NOT been implemented yet
		for the "hush" shell.


		CFG_HUSH_PARSER

		Define this variable to enable the "hush" shell (from
		Busybox) as command line interpreter, thus enabling
		powerful command line syntax like
		if...then...else...fi conditionals or `&&' and '||'
		constructs ("shell scripts").

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


		CFG_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 autoscript function 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
		CFG_SYSTEMACE_BASE macro. For example:

		#define CONFIG_SYSTEMACE
		#define CFG_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:

- 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.

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

  -30	lib_ppc/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 autoscript
  -83	common/cmd_net.c	some error in automatic boot or autoscript
   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


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

[so far only for SMDK2400 and TRAB 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:
-----------------------

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

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

- CFG_CBSIZE:	Buffer size for input from the Console

- CFG_PBSIZE:	Buffer size for Console output

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

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

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

- CFG_CONSOLE_INFO_QUIET
		Suppress display of console information at boot.

- CFG_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.

- CFG_CONSOLE_OVERWRITE_ROUTINE
		Enable the call to overwrite_console().

- CFG_CONSOLE_ENV_OVERWRITE
		Enable overwrite of previous console environment settings.

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

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

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

- CFG_MEM_TOP_HIDE (PPC only):
		If CFG_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.

- CFG_TFTP_LOADADDR:
		Default load address for network file downloads

- CFG_LOADS_BAUD_CHANGE:
		Enable temporary baudrate change while serial download

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

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

- CFG_FLASH_BASE:
		Physical start address of Flash memory.

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

- CFG_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.

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

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

- CFG_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" + CFG_BOOTMAPSZ.

- CFG_MAX_FLASH_BANKS:
		Max number of Flash memory banks

- CFG_MAX_FLASH_SECT:
		Max number of sectors on a Flash chip

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

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

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

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

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

- CFG_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.

- CFG_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

- CFG_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.

- CFG_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.

- CFG_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.

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

- 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