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-users@lists.sourceforge.net>. There is also an archive of
previous traffic on the mailing list - please search the archive
before asking FAQ's. Please see
http://lists.sourceforge.net/lists/listinfo/u-boot-users/


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/UBoot


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:
		CFG_PL010_SERIAL

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

		CFG_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

		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.