(C) Copyright 2000 - 2005

Wolfgang Denk, DENX Software Engineering, [email protected].

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.

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 [email protected]. 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 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)

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
  - 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
- at91rm9200 Files specific to Atmel AT91RM9200 CPUs
- i386 Files specific to i386 CPUs
- ixp Files specific to Intel XScale IXP CPUs
- mcf52x2 Files specific to Freescale ColdFire MCF52x2 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 IBM 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_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
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 of

  PowerPC based CPUs:
  -------------------
  CONFIG_MPC823,	CONFIG_MPC850,	CONFIG_MPC855,	CONFIG_MPC860

or CONFIG_MPC5xx or CONFIG_MPC8220 or CONFIG_MPC824X, CONFIG_MPC8260 or CONFIG_MPC85xx or CONFIG_IOP480 or CONFIG_405GP or CONFIG_405EP or CONFIG_440 or CONFIG_MPC74xx or CONFIG_750FX

  ARM based CPUs:
  ---------------
  CONFIG_SA1110
  CONFIG_ARM7
  CONFIG_PXA250

  MicroBlaze based CPUs:
  ----------------------
  CONFIG_MICROBLAZE

  Nios-2 based CPUs:
  ----------------------
  CONFIG_NIOS2

Board Type: Define exactly one of

  PowerPC based boards:
  ---------------------

  CONFIG_ADCIOP		CONFIG_GEN860T		CONFIG_PCI405
  CONFIG_ADS860		CONFIG_GENIETV		CONFIG_PCIPPC2
  CONFIG_AMX860		CONFIG_GTH		CONFIG_PCIPPC6
  CONFIG_AR405		CONFIG_gw8260		CONFIG_pcu_e
  CONFIG_BAB7xx		CONFIG_hermes		CONFIG_PIP405
  CONFIG_c2mon		CONFIG_hymod		CONFIG_PM826
  CONFIG_CANBT		CONFIG_IAD210		CONFIG_ppmc8260
  CONFIG_CCM		CONFIG_ICU862		CONFIG_QS823
  CONFIG_CMI		CONFIG_IP860		CONFIG_QS850
  CONFIG_cogent_mpc8260	CONFIG_IPHASE4539	CONFIG_QS860T
  CONFIG_cogent_mpc8xx	CONFIG_IVML24		CONFIG_RBC823
  CONFIG_CPCI405		CONFIG_IVML24_128	CONFIG_RPXClassic
  CONFIG_CPCI4052		CONFIG_IVML24_256	CONFIG_RPXlite
  CONFIG_CPCIISER4	CONFIG_IVMS8		CONFIG_RPXsuper
  CONFIG_CPU86		CONFIG_IVMS8_128	CONFIG_rsdproto
  CONFIG_CRAYL1		CONFIG_IVMS8_256	CONFIG_sacsng
  CONFIG_CSB272		CONFIG_JSE		CONFIG_Sandpoint8240
  CONFIG_CU824		CONFIG_LANTEC		CONFIG_Sandpoint8245
  CONFIG_DASA_SIM		CONFIG_lwmon		CONFIG_sbc8260
  CONFIG_DB64360		CONFIG_MBX		CONFIG_sbc8560
  CONFIG_DB64460		CONFIG_MBX860T		CONFIG_SM850
  CONFIG_DU405		CONFIG_MHPC		CONFIG_SPD823TS
  CONFIG_DUET_ADS		CONFIG_MIP405		CONFIG_STXGP3
  CONFIG_EBONY		CONFIG_MOUSSE		CONFIG_SXNI855T
  CONFIG_ELPPC		CONFIG_MPC8260ADS	CONFIG_TQM823L
  CONFIG_ELPT860		CONFIG_MPC8540ADS	CONFIG_TQM8260
  CONFIG_ep8260		CONFIG_MPC8560ADS	CONFIG_TQM850L
  CONFIG_ERIC		CONFIG_MUSENKI		CONFIG_TQM855L
  CONFIG_ESTEEM192E	CONFIG_MVS1		CONFIG_TQM860L
  CONFIG_ETX094		CONFIG_NETPHONE		CONFIG_TTTech
  CONFIG_EVB64260		CONFIG_NETTA		CONFIG_UTX8245
  CONFIG_FADS823		CONFIG_NETVIA		CONFIG_V37
  CONFIG_FADS850SAR	CONFIG_NX823		CONFIG_W7OLMC
  CONFIG_FADS860T		CONFIG_OCRTC		CONFIG_W7OLMG
  CONFIG_FLAGADM		CONFIG_ORSG		CONFIG_WALNUT405
  CONFIG_FPS850L		CONFIG_OXC		CONFIG_ZPC1900
  CONFIG_FPS860L					CONFIG_ZUMA

  ARM based boards:
  -----------------

  CONFIG_AT91RM9200DK,	CONFIG_CERF250,		CONFIG_DNP1110,
  CONFIG_EP7312,		CONFIG_H2_OMAP1610,	CONFIG_HHP_CRADLE,
  CONFIG_IMPA7,		CONFIG_INNOVATOROMAP1510, CONFIG_INNOVATOROMAP1610,
  CONFIG_LART,		CONFIG_LPD7A400		CONFIG_LUBBOCK,
  CONFIG_OSK_OMAP5912,	CONFIG_OMAP2420H4,	CONFIG_SHANNON,
  CONFIG_P2_OMAP730,	CONFIG_SMDK2400,	CONFIG_SMDK2410,
  CONFIG_TRAB,		CONFIG_VCMA9

  MicroBlaze based boards:
  ------------------------

  CONFIG_SUZAKU

  Nios-2 based boards:
  ------------------------

  CONFIG_PCI5441 CONFIG_PK1C20

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)

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 transfering 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.

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 CFG_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
  				addional 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

  IBM 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 CFG_CMD_KGDB is defined) CONFIG_KGDB_BAUDRATE Select one of the baudrates listed in CFG_BAUDRATE_TABLE, see below.

Monitor Functions: CONFIG_COMMANDS Most monitor functions can be selected (or de-selected) by adjusting the definition of CONFIG_COMMANDS; to select individual functions, #define CONFIG_COMMANDS by "OR"ing any of the following values:

  #define enables commands:
  -------------------------
  CFG_CMD_ASKENV	* ask for env variable
  CFG_CMD_AUTOSCRIPT Autoscript Support
  CFG_CMD_BDI	  bdinfo
  CFG_CMD_BEDBUG	* Include BedBug Debugger
  CFG_CMD_BMP	* BMP support
  CFG_CMD_BSP	* Board specific commands
  CFG_CMD_BOOTD	  bootd
  CFG_CMD_CACHE	* icache, dcache
  CFG_CMD_CONSOLE	  coninfo
  CFG_CMD_DATE	* support for RTC, date/time...
  CFG_CMD_DHCP	* DHCP support
  CFG_CMD_DIAG	* Diagnostics
  CFG_CMD_DOC	* Disk-On-Chip Support
  CFG_CMD_DTT	* Digital Therm and Thermostat
  CFG_CMD_ECHO	* echo arguments
  CFG_CMD_EEPROM	* EEPROM read/write support
  CFG_CMD_ELF	* bootelf, bootvx
  CFG_CMD_ENV	  saveenv
  CFG_CMD_FDC	* Floppy Disk Support
  CFG_CMD_FAT	* FAT partition support
  CFG_CMD_FDOS	* Dos diskette Support
  CFG_CMD_FLASH	  flinfo, erase, protect
  CFG_CMD_FPGA	  FPGA device initialization support
  CFG_CMD_HWFLOW	* RTS/CTS hw flow control
  CFG_CMD_I2C	* I2C serial bus support
  CFG_CMD_IDE	* IDE harddisk support
  CFG_CMD_IMI	  iminfo
  CFG_CMD_IMLS	  List all found images
  CFG_CMD_IMMAP	* IMMR dump support
  CFG_CMD_IRQ	* irqinfo
  CFG_CMD_ITEST	  Integer/string test of 2 values
  CFG_CMD_JFFS2	* JFFS2 Support
  CFG_CMD_KGDB	* kgdb
  CFG_CMD_LOADB	  loadb
  CFG_CMD_LOADS	  loads
  CFG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
  		  loop, loopw, mtest
  CFG_CMD_MISC	  Misc functions like sleep etc
  CFG_CMD_MMC	* MMC memory mapped support
  CFG_CMD_MII	* MII utility commands
  CFG_CMD_NAND	* NAND support
  CFG_CMD_NET	  bootp, tftpboot, rarpboot
  CFG_CMD_PCI	* pciinfo
  CFG_CMD_PCMCIA	* PCMCIA support
  CFG_CMD_PING	* send ICMP ECHO_REQUEST to network host
  CFG_CMD_PORTIO	* Port I/O
  CFG_CMD_REGINFO * Register dump
  CFG_CMD_RUN	  run command in env variable
  CFG_CMD_SAVES	* save S record dump
  CFG_CMD_SCSI	* SCSI Support
  CFG_CMD_SDRAM	* print SDRAM configuration information
  CFG_CMD_SETGETDCR Support for DCR Register access (4xx only)
  CFG_CMD_SPI	* SPI serial bus support
  CFG_CMD_USB	* USB support
  CFG_CMD_VFD	* VFD support (TRAB)
  CFG_CMD_BSP	* Board SPecific functions
  CFG_CMD_CDP	* Cisco Discover Protocol support
  -----------------------------------------------
  CFG_CMD_ALL	all

  CONFIG_CMD_DFL	Default configuration; at the moment
  		this is includes all commands, except
  		the ones marked with "*" in the list
  		above.

  If you don't define CONFIG_COMMANDS it defaults to
  CONFIG_CMD_DFL in include/cmd_confdefs.h. A board can
  override the default settings in the respective
  include file.

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

  #define CONFIG_COMMANDS (CFG_CMD_ALL & ~CFG_CMD_NET)

Note: Don't enable the "icache" and "dcache" commands (configuration option CFG_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 CFG_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_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_MAX6900	- use Maxim, Inc. MAX6900 RTC

  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 CFG_CMD_DATE .

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

  If IDE or SCSI support	is  enabled  (CFG_CMD_IDE  or
  CFG_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_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)

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
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 CFG_CMD_MMC. The MMC driver also works with the FAT fs. This is enabled with CFG_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 diferent 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/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_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.

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.

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_ETH2ADDR CONFIG_ETH3ADDR

  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 theIP address of a TFTP
  server to contact when using the "tftboot" command.

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 insterted 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: CONFIG_BOOTP_MASK

  You can fine tune the DHCP functionality by adding
  these flags to the CONFIG_BOOTP_MASK define:

  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 added to the CONFIG_BOOTP_MASK.

  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_BOOP_SEND_HOSTNAME is added to the
  CONFIG_BOOTP_MASK, the content of the "hostname"
  environment variable is passed as option 12 to
  the DHCP server.

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 CFG_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_HARD_I2C selects the CPM hardware driver for I2C.

  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)

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.

FPGA Support: CONFIG_FPGA_COUNT

  Specify the number of FPGA devices to support.

  CONFIG_FPGA

  Used to specify the types of FPGA devices.  For example,
  #define CONFIG_FPGA  CFG_XILINX_VIRTEX2

  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 behviour:

  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 to 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.

Command Interpreter: CFG_AUTO_COMPLETE

  Enable auto completion of commands using TAB.

  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.

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 alsh 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.

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:
```
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, standalone) 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 Wrong Image Type (not kernel, multi, standalone) 8 common/cmd_bootm.c Image Type check OK -9 common/cmd_bootm.c Unsupported OS (not Linux, BSD, VxWorks, QNX) 9 common/cmd_bootm.c Start initial ramdisk verification -10 common/cmd_bootm.c Ramdisk header has bad magic number -11 common/cmd_bootm.c Ramdisk header has bad checksum 10 common/cmd_bootm.c Ramdisk header is OK -12 common/cmd_bootm.c Ramdisk data has bad checksum 11 common/cmd_bootm.c Ramdisk data has correct checksum 12 common/cmd_bootm.c Ramdisk verification complete, start loading -13 common/cmd_bootm.c Wrong Image Type (not PPC Linux Ramdisk) 13 common/cmd_bootm.c Start multifile image verification 14 common/cmd_bootm.c No initial ramdisk, no multifile, continue. 15 common/cmd_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()

-1 common/cmd_doc.c Bad usage of "doc" command -1 common/cmd_doc.c No boot device -1 common/cmd_doc.c Unknown Chip ID on boot device -1 common/cmd_doc.c Read Error on boot device -1 common/cmd_doc.c Image header has bad magic number

-1 common/cmd_ide.c Bad usage of "ide" command -1 common/cmd_ide.c No boot device -1 common/cmd_ide.c Unknown boot device -1 common/cmd_ide.c Unknown partition table -1 common/cmd_ide.c Invalid partition type -1 common/cmd_ide.c Read Error on boot device -1 common/cmd_ide.c Image header has bad magic number

-1 common/cmd_nand.c Bad usage of "nand" command -1 common/cmd_nand.c No boot device -1 common/cmd_nand.c Unknown Chip ID on boot device -1 common/cmd_nand.c Read Error on boot device -1 common/cmd_nand.c Image header has bad magic number

-1 common/env_common.c Environment has a bad CRC, using default

Modem Support:

[so far only for SMDK2400 and TRAB boards]

Modem support endable: 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() fuction 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
  supressed, 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_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_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, eventually initrd image) must be put below this limit.
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 sytem RAM is
  too limited to allow for a tempory 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.
CFG_FLASH_CFI_DRIVER This option also enables the building of the cfi_flash driver in the drivers directory
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:

CFG_ENV_IS_IN_FLASH:

Define this if the environment is in flash memory.

a) The environment occupies one whole flash sector, which is "embedded" in the text segment with the U-Boot code. This happens usually with "bottom boot sector" or "top boot sector" type flash chips, which have several smaller sectors at the start or the end. For instance, such a layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In such a case you would place the environment in one of the 4 kB sectors - with U-Boot code before and after it. With "top boot sector" type flash chips, you would put the environment in one of the last sectors, leaving a gap between U-Boot and the environment.
- CFG_ENV_OFFSET:
  
  Offset of environment data (variable area) to the beginning of flash memory; for instance, with bottom boot type flash chips the second sector can be used: the offset for this sector is given here.
  
  CFG_ENV_OFFSET is used relative to CFG_FLASH_BASE.
- CFG_ENV_ADDR:
  
  This is just another way to specify the start address of the flash sector containing the environment (instead of CFG_ENV_OFFSET).
- CFG_ENV_SECT_SIZE:
  
  Size of the sector containing the environment.
b) Sometimes flash chips have few, equal sized, BIG sectors. In such a case you don't want to spend a whole sector for the environment.
- CFG_ENV_SIZE:
  
  If you use this in combination with CFG_ENV_IS_IN_FLASH and CFG_ENV_SECT_SIZE, you can specify to use only a part of this flash sector for the environment. This saves memory for the RAM copy of the environment.
  
  It may also save flash memory if you decide to use this when your environment is "embedded" within U-Boot code, since then the remainder of the flash sector could be used for U-Boot code. It should be pointed out that this is STRONGLY DISCOURAGED from a robustness point of view: updating the environment in flash makes it always necessary to erase the WHOLE sector. If something goes wrong before the contents has been restored from a copy in RAM, your target system will be dead.
- CFG_ENV_ADDR_REDUND CFG_ENV_SIZE_REDUND
  
  These settings describe a second storage area used to hold a redundand copy of the environment data, so that there is a valid backup copy in case there is a power failure during a "saveenv" operation.

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

CFG_ENV_IS_IN_NVRAM:

Define this if you have some non-volatile memory device (NVRAM, battery buffered SRAM) which you want to use for the environment.
- CFG_ENV_ADDR:
- CFG_ENV_SIZE:
  
  These two #defines are used to determin the memory area you want to use for environment. It is assumed that this memory can just be read and written to, without any special provision.

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

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

CFG_ENV_IS_IN_EEPROM:

Use this if you have an EEPROM or similar serial access device and a driver for it.
- CFG_ENV_OFFSET:
- CFG_ENV_SIZE:
  
  These two #defines specify the offset and size of the environment area within the total memory of your EEPROM.
- CFG_I2C_EEPROM_ADDR: If defined, specified the chip address of the EEPROM device. The default address is zero.
- CFG_EEPROM_PAGE_WRITE_BITS: If defined, the number of bits used to address bytes in a single page in the EEPROM device. A 64 byte page, for example would require six bits.
- CFG_EEPROM_PAGE_WRITE_DELAY_MS: If defined, the number of milliseconds to delay between page writes. The default is zero milliseconds.
- CFG_I2C_EEPROM_ADDR_LEN: The length in bytes of the EEPROM memory array address. Note that this is NOT the chip address length!
- CFG_I2C_EEPROM_ADDR_OVERFLOW: EEPROM chips that implement "address overflow" are ones like Catalyst 24WC04/08/16 which has 9/10/11 bits of address and the extra bits end up in the "chip address" bit slots. This makes a 24WC08 (1Kbyte) chip look like four 256 byte chips.
  
  Note that we consider the length of the address field to still be one byte because the extra address bits are hidden in the chip address.
- CFG_EEPROM_SIZE: The size in bytes of the EEPROM device.
CFG_ENV_IS_IN_DATAFLASH:

Define this if you have a DataFlash memory device which you want to use for the environment.
- CFG_ENV_OFFSET:
- CFG_ENV_ADDR:
- CFG_ENV_SIZE:
  
  These three #defines specify the offset and size of the environment area within the total memory of your DataFlash placed at the specified address.
CFG_ENV_IS_IN_NAND:

Define this if you have a NAND device which you want to use for the environment.
- CFG_ENV_OFFSET:
- CFG_ENV_SIZE:
  
  These two #defines specify the offset and size of the environment area within the first NAND device.
CFG_SPI_INIT_OFFSET

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

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

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

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

CFG_FAULT_ECHO_LINK_DOWN: Echo the inverted Ethernet link state to the fault LED.

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

CFG_FAULT_MII_ADDR: MII address of the PHY to check for the Ethernet link state.
CFG_64BIT_VSPRINTF: Makes vsprintf (and all *printf functions) support printing of 64bit values by using the L quantifier
CFG_64BIT_STRTOUL: Adds simple_strtoull that returns a 64bit value

Low Level (hardware related) configuration options:

CFG_CACHELINE_SIZE: Cache Line Size of the CPU.

CFG_DEFAULT_IMMR: Default address of the IMMR after system reset.

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

Floppy Disk Support: CFG_FDC_DRIVE_NUMBER

  the default drive number (default value 0)

  CFG_ISA_IO_STRIDE

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

  CFG_ISA_IO_OFFSET

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

  If CFG_ISA_IO_STRIDE CFG_ISA_IO_OFFSET and
  CFG_FDC_DRIVE_NUMBER are undefined, they take their
  default value.

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

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

CFG_INIT_RAM_ADDR:

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

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

CFG_GBL_DATA_OFFSET:

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

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

CFG_SIUMCR: SIU Module Configuration (11-6)
CFG_SYPCR: System Protection Control (11-9)
CFG_TBSCR: Time Base Status and Control (11-26)
CFG_PISCR: Periodic Interrupt Status and Control (11-31)
CFG_PLPRCR: PLL, Low-Power, and Reset Control Register (15-30)
CFG_SCCR: System Clock and reset Control Register (15-27)
CFG_OR_TIMING_SDRAM: SDRAM timing
CFG_MAMR_PTA: periodic timer for refresh
CFG_DER: Debug Event Register (37-47)
FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CFG_REMAP_OR_AM, CFG_PRELIM_OR_AM, CFG_OR_TIMING_FLASH, CFG_OR0_REMAP, CFG_OR0_PRELIM, CFG_BR0_PRELIM, CFG_OR1_REMAP, CFG_OR1_PRELIM, CFG_BR1_PRELIM: Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE, CFG_OR_TIMING_SDRAM, CFG_OR2_PRELIM, CFG_BR2_PRELIM, CFG_OR3_PRELIM, CFG_BR3_PRELIM: Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
CFG_MAMR_PTA, CFG_MPTPR_2BK_4K, CFG_MPTPR_1BK_4K, CFG_MPTPR_2BK_8K, CFG_MPTPR_1BK_8K, CFG_MAMR_8COL, CFG_MAMR_9COL: Machine Mode Register and Memory Periodic Timer Prescaler definitions (SDRAM timing)
CFG_I2C_UCODE_PATCH, CFG_I2C_DPMEM_OFFSET [0x1FC0]: enable I2C microcode relocation patch (MPC8xx); define relocation offset in DPRAM [DSP2]
CFG_SPI_UCODE_PATCH, CFG_SPI_DPMEM_OFFSET [0x1FC0]: enable SPI microcode relocation patch (MPC8xx); define relocation offset in DPRAM [SCC4]
CFG_USE_OSCCLK: Use OSCM clock mode on MBX8xx board. Be careful, wrong setting might damage your board. Read doc/README.MBX before setting this variable!
CFG_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only) Offset of the bootmode word in DPRAM used by post (Power On Self Tests). This definition overrides #define'd default value in commproc.h resp. cpm_8260.h.
CFG_PCI_SLV_MEM_LOCAL, CFG_PCI_SLV_MEM_BUS, CFG_PICMR0_MASK_ATTRIB, CFG_PCI_MSTR0_LOCAL, CFG_PCIMSK0_MASK, CFG_PCI_MSTR1_LOCAL, CFG_PCIMSK1_MASK, CFG_PCI_MSTR_MEM_LOCAL, CFG_PCI_MSTR_MEM_BUS, CFG_CPU_PCI_MEM_START, CFG_PCI_MSTR_MEM_SIZE, CFG_POCMR0_MASK_ATTRIB, CFG_PCI_MSTR_MEMIO_LOCAL, CFG_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START, CFG_PCI_MSTR_MEMIO_SIZE, CFG_POCMR1_MASK_ATTRIB, CFG_PCI_MSTR_IO_LOCAL, CFG_PCI_MSTR_IO_BUS, CFG_CPU_PCI_IO_START, CFG_PCI_MSTR_IO_SIZE, CFG_POCMR2_MASK_ATTRIB: (MPC826x only) Overrides the default PCI memory map in cpu/mpc8260/pci.c if set.
CONFIG_ETHER_ON_FEC[12] Define to enable FEC[12] on a 8xx series processor.
CONFIG_FEC[12]_PHY Define to the hardcoded PHY address which corresponds to the given FEC; i. e. #define CONFIG_FEC1_PHY 4 means that the PHY with address 4 is connected to FEC1
```
  When set to -1, means to probe for first available.
```
CONFIG_FEC[12]_PHY_NORXERR The PHY does not have a RXERR line (RMII only). (so program the FEC to ignore it).
CONFIG_RMII Enable RMII mode for all FECs. Note that this is a global option, we can't have one FEC in standard MII mode and another in RMII mode.

CONFIG_CRC32_VERIFY Add a verify option to the crc32 command. The syntax is:

  => crc32 -v <address> <count> <crc32>

  Where address/count indicate a memory area
  and crc32 is the correct crc32 which the
  area should have.

CONFIG_LOOPW Add the "loopw" memory command. This only takes effect if the memory commands are activated globally (CFG_CMD_MEM).

CONFIG_MX_CYCLIC Add the "mdc" and "mwc" memory commands. These are cyclic "md/mw" commands. Examples:

  => mdc.b 10 4 500
  This command will print 4 bytes (10,11,12,13) each 500 ms.

  => mwc.l 100 12345678 10
  This command will write 12345678 to address 100 all 10 ms.

  This only takes effect if the memory commands are activated
  globally (CFG_CMD_MEM).

Building the Software:

Building U-Boot has been tested in native PPC environments (on a PowerBook G3 running LinuxPPC 2000) and in cross environments (running RedHat 6.x and 7.x Linux on x86, Solaris 2.6 on a SPARC, and NetBSD 1.5 on x86).

If you are not using a native PPC environment, it is assumed that you have the GNU cross compiling tools available in your path and named with a prefix of "powerpc-linux-". If this is not the case, (e.g. if you are using Monta Vista's Hard Hat Linux CDK 1.2) you must change the definition of CROSS_COMPILE in Makefile. For HHL on a 4xx CPU, change it to:

CROSS_COMPILE = ppc_4xx-

U-Boot is intended to be simple to build. After installing the sources you must configure U-Boot for one specific board type. This is done by typing:

make NAME_config

where "NAME_config" is the name of one of the existing configurations; the following names are supported:

ADCIOP_config		FPS860L_config		omap730p2_config
ADS860_config		GEN860T_config		pcu_e_config
Alaska8220_config
AR405_config		GENIETV_config		PIP405_config
at91rm9200dk_config	GTH_config		QS823_config
CANBT_config		hermes_config		QS850_config
cmi_mpc5xx_config	hymod_config		QS860T_config
cogent_common_config	IP860_config		RPXlite_config
cogent_mpc8260_config	IVML24_config		RPXlite_DW_config
cogent_mpc8xx_config	IVMS8_config		RPXsuper_config
CPCI405_config		JSE_config		rsdproto_config
CPCIISER4_config	LANTEC_config		Sandpoint8240_config
csb272_config		lwmon_config		sbc8260_config
CU824_config		MBX860T_config		sbc8560_33_config
DUET_ADS_config		MBX_config		sbc8560_66_config
EBONY_config		MPC8260ADS_config	SM850_config
ELPT860_config		MPC8540ADS_config	SPD823TS_config
ESTEEM192E_config	MPC8560ADS_config	stxgp3_config
ETX094_config		NETVIA_config		SXNI855T_config
FADS823_config		omap1510inn_config	TQM823L_config
FADS850SAR_config	omap1610h2_config	TQM850L_config
FADS860T_config		omap1610inn_config	TQM855L_config
FPS850L_config		omap5912osk_config	TQM860L_config
			omap2420h4_config	WALNUT405_config
						Yukon8220_config
						ZPC1900_config

Note: for some board special configuration names may exist; check if additional information is available from the board vendor; for instance, the TQM823L systems are available without (standard) or with LCD support. You can select such additional "features" when chosing the configuration, i. e.

  make TQM823L_config
- will configure for a plain TQM823L, i. e. no LCD support

  make TQM823L_LCD_config
- will configure for a TQM823L with U-Boot console on LCD

  etc.

Finally, type "make all", and you should get some working U-Boot images ready for download to / installation on your system:

"u-boot.bin" is a raw binary image
"u-boot" is an image in ELF binary format
"u-boot.srec" is in Motorola S-Record format

Please be aware that the Makefiles assume you are using GNU make, so for instance on NetBSD you might need to use "gmake" instead of native "make".

If the system board that you have is not listed, then you will need to port U-Boot to your hardware platform. To do this, follow these steps:

Add a new configuration option for your board to the toplevel "Makefile" and to the "MAKEALL" script, using the existing entries as examples. Note that here and at many other places boards and other names are listed in alphabetical sort order. Please keep this order.
Create a new directory to hold your board specific code. Add any files you need. In your board directory, you will need at least the "Makefile", a ".c", "flash.c" and "u-boot.lds".
Create a new configuration file "include/configs/.h" for your board
If you're porting U-Boot to a new CPU, then also create a new directory to hold your CPU specific code. Add any files you need.
Run "make _config" with your new name.
Type "make", and you should get a working "u-boot.srec" file to be installed on your target system.
Debug and solve any problems that might arise. [Of course, this last step is much harder than it sounds.]

Testing of U-Boot Modifications, Ports to New Hardware, etc.:

If you have modified U-Boot sources (for instance added a new board or support for new devices, a new CPU, etc.) you are expected to provide feedback to the other developers. The feedback normally takes the form of a "patch", i. e. a context diff against a certain (latest official or latest in CVS) version of U-Boot sources.

But before you submit such a patch, please verify that your modifi- cation did not break existing code. At least make sure that ALL of the supported boards compile WITHOUT ANY compiler warnings. To do so, just run the "MAKEALL" script, which will configure and build U-Boot for ALL supported system. Be warned, this will take a while. You can select which (cross) compiler to use by passing a `CROSS_COMPILE' environment variable to the script, i. e. to use the cross tools from MontaVista's Hard Hat Linux you can type

CROSS_COMPILE=ppc_8xx- MAKEALL

or to build on a native PowerPC system you can type

CROSS_COMPILE=' ' MAKEALL

Monitor Commands - Overview:

go - start application at address 'addr' run - run commands in an environment variable bootm - boot application image from memory bootp - boot image via network using BootP/TFTP protocol tftpboot- boot image via network using TFTP protocol and env variables "ipaddr" and "serverip" (and eventually "gatewayip") rarpboot- boot image via network using RARP/TFTP protocol diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd' loads - load S-Record file over serial line loadb - load binary file over serial line (kermit mode) md - memory display mm - memory modify (auto-incrementing) nm - memory modify (constant address) mw - memory write (fill) cp - memory copy cmp - memory compare crc32 - checksum calculation imd - i2c memory display imm - i2c memory modify (auto-incrementing) inm - i2c memory modify (constant address) imw - i2c memory write (fill) icrc32 - i2c checksum calculation iprobe - probe to discover valid I2C chip addresses iloop - infinite loop on address range isdram - print SDRAM configuration information sspi - SPI utility commands base - print or set address offset printenv- print environment variables setenv - set environment variables saveenv - save environment variables to persistent storage protect - enable or disable FLASH write protection erase - erase FLASH memory flinfo - print FLASH memory information bdinfo - print Board Info structure iminfo - print header information for application image coninfo - print console devices and informations ide - IDE sub-system loop - infinite loop on address range loopw - infinite write loop on address range mtest - simple RAM test icache - enable or disable instruction cache dcache - enable or disable data cache reset - Perform RESET of the CPU echo - echo args to console version - print monitor version help - print online help ? - alias for 'help'

Monitor Commands - Detailed Description:

TODO.

For now: just type "help ".

Environment Variables:

U-Boot supports user configuration using Environment Variables which can be made persistent by saving to Flash memory.

Environment Variables are set using "setenv", printed using "printenv", and saved to Flash using "saveenv". Using "setenv" without a value can be used to delete a variable from the environment. As long as you don't save the environment you are working with an in-memory copy. In case the Flash area containing the environment is erased by accident, a default environment is provided.

Some configuration options can be set using Environment Variables:

baudrate - see CONFIG_BAUDRATE

bootdelay - see CONFIG_BOOTDELAY

bootcmd - see CONFIG_BOOTCOMMAND

bootargs - Boot arguments when booting an RTOS image

bootfile - Name of the image to load with TFTP

autoload - if set to "no" (any string beginning with 'n'), "bootp" will just load perform a lookup of the configuration from the BOOTP server, but not try to load any image using TFTP

autostart - if set to "yes", an image loaded using the "bootp", "rarpboot", "tftpboot" or "diskboot" commands will be automatically started (by internally calling "bootm")

	  If set to "no", a standalone image passed to the
	  "bootm" command will be copied to the load address
	  (and eventually uncompressed), but NOT be started.
	  This can be used to load and uncompress arbitrary
	  data.

i2cfast - (PPC405GP|PPC405EP only) if set to 'y' configures Linux I2C driver for fast mode (400kHZ). This environment variable is used in initialization code. So, for changes to be effective it must be saved and board must be reset.

initrd_high - restrict positioning of initrd images: If this variable is not set, initrd images will be copied to the highest possible address in RAM; this is usually what you want since it allows for maximum initrd size. If for some reason you want to make sure that the initrd image is loaded below the CFG_BOOTMAPSZ limit, you can set this environment variable to a value of "no" or "off" or "0". Alternatively, you can set it to a maximum upper address to use (U-Boot will still check that it does not overwrite the U-Boot stack and data).

	  For instance, when you have a system with 16 MB
	  RAM, and want to reserve 4 MB from use by Linux,
	  you can do this by adding "mem=12M" to the value of
	  the "bootargs" variable. However, now you must make
	  sure that the initrd image is placed in the first
	  12 MB as well - this can be done with

	  setenv initrd_high 00c00000

	  If you set initrd_high to 0xFFFFFFFF, this is an
	  indication to U-Boot that all addresses are legal
	  for the Linux kernel, including addresses in flash
	  memory. In this case U-Boot will NOT COPY the
	  ramdisk at all. This may be useful to reduce the
	  boot time on your system, but requires that this
	  feature is supported by your Linux kernel.

ipaddr - IP address; needed for tftpboot command

loadaddr - Default load address for commands like "bootp", "rarpboot", "tftpboot", "loadb" or "diskboot"

loads_echo - see CONFIG_LOADS_ECHO

serverip - TFTP server IP address; needed for tftpboot command

bootretry - see CONFIG_BOOT_RETRY_TIME

bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR

bootstopkey - see CONFIG_AUTOBOOT_STOP_STR

ethprime - When CONFIG_NET_MULTI is enabled controls which interface is used first.

ethact - When CONFIG_NET_MULTI is enabled controls which interface is currently active. For example you can do the following

	  => setenv ethact FEC ETHERNET
	  => ping 192.168.0.1 # traffic sent on FEC ETHERNET
	  => setenv ethact SCC ETHERNET
	  => ping 10.0.0.1 # traffic sent on SCC ETHERNET

netretry - When set to "no" each network operation will either succeed or fail without retrying. When set to "once" the network operation will fail when all the available network interfaces are tried once without success. Useful on scripts which control the retry operation themselves.

vlan - When set to a value < 4095 the traffic over ethernet is encapsulated/received over 802.1q VLAN tagged frames.

The following environment variables may be used and automatically updated by the network boot commands ("bootp" and "rarpboot"), depending the information provided by your boot server:

bootfile - see above dnsip - IP address of your Domain Name Server dnsip2 - IP address of your secondary Domain Name Server gatewayip - IP address of the Gateway (Router) to use hostname - Target hostname ipaddr - see above netmask - Subnet Mask rootpath - Pathname of the root filesystem on the NFS server serverip - see above

There are two special Environment Variables:

serial# - contains hardware identification information such as type string and/or serial number ethaddr - Ethernet address

These variables can be set only once (usually during manufacturing of the board). U-Boot refuses to delete or overwrite these variables once they have been set once.

Further special Environment Variables:

ver - Contains the U-Boot version string as printed with the "version" command. This variable is readonly (see CONFIG_VERSION_VARIABLE).

Please note that changes to some configuration parameters may take only effect after the next boot (yes, that's just like Windoze :-).

Command Line Parsing:

There are two different command line parsers available with U-Boot: the old "simple" one, and the much more powerful "hush" shell:

Old, simple command line parser:

supports environment variables (through setenv / saveenv commands)
several commands on one line, separated by ';'
variable substitution using "... $(name) ..." syntax
special characters ('$', ';') can be escaped by prefixing with '', for example: setenv bootcmd bootm $(address)
You can also escape text by enclosing in single apostrophes, for example: setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'

Hush shell:

similar to Bourne shell, with control structures like if...then...else...fi, for...do...done; while...do...done, until...do...done, ...
supports environment ("global") variables (through setenv / saveenv commands) and local shell variables (through standard shell syntax "name=value"); only environment variables can be used with "run" command

General rules:

(1) If a command line (or an environment variable executed by a "run" command) contains several commands separated by semicolon, and one of these commands fails, then the remaining commands will be executed anyway.

(2) If you execute several variables with one call to run (i. e. calling run with a list af variables as arguments), any failing command will cause "run" to terminate, i. e. the remaining variables are not executed.

Note for Redundant Ethernet Interfaces:

Some boards come with redundant ethernet interfaces; U-Boot supports such configurations and is capable of automatic selection of a "working" interface when needed. MAC assignment works as follows:

Network interfaces are numbered eth0, eth1, eth2, ... Corresponding MAC addresses can be stored in the environment as "ethaddr" (=>eth0), "eth1addr" (=>eth1), "eth2addr", ...

If the network interface stores some valid MAC address (for instance in SROM), this is used as default address if there is NO correspon- ding setting in the environment; if the corresponding environment variable is set, this overrides the settings in the card; that means:

o If the SROM has a valid MAC address, and there is no address in the environment, the SROM's address is used.

o If there is no valid address in the SROM, and a definition in the environment exists, then the value from the environment variable is used.

o If both the SROM and the environment contain a MAC address, and both addresses are the same, this MAC address is used.

o If both the SROM and the environment contain a MAC address, and the addresses differ, the value from the environment is used and a warning is printed.

o If neither SROM nor the environment contain a MAC address, an error is raised.

Image Formats:

The "boot" commands of this monitor operate on "image" files which can be basicly anything, preceeded by a special header; see the definitions in include/image.h for details; basicly, the header defines the following image properties:

Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD, 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks, LynxOS, pSOS, QNX, RTEMS, ARTOS; Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, LynxOS).
Target CPU Architecture (Provisions for Alpha, ARM, Intel x86, IA64, MIPS, NIOS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit; Currently supported: ARM, Intel x86, MIPS, NIOS, PowerPC).
Compression Type (uncompressed, gzip, bzip2)
Load Address
Entry Point
Image Name
Image Timestamp

The header is marked by a special Magic Number, and both the header and the data portions of the image are secured against corruption by CRC32 checksums.

Linux Support:

Although U-Boot should support any OS or standalone application easily, the main focus has always been on Linux during the design of U-Boot.

U-Boot includes many features that so far have been part of some special "boot loader" code within the Linux kernel. Also, any "initrd" images to be used are no longer part of one big Linux image; instead, kernel and "initrd" are separate images. This implementation serves several purposes:

the same features can be used for other OS or standalone applications (for instance: using compressed images to reduce the Flash memory footprint)
it becomes much easier to port new Linux kernel versions because lots of low-level, hardware dependent stuff are done by U-Boot
the same Linux kernel image can now be used with different "initrd" images; of course this also means that different kernel images can be run with the same "initrd". This makes testing easier (you don't have to build a new "zImage.initrd" Linux image when you just change a file in your "initrd"). Also, a field-upgrade of the software is easier now.

Linux HOWTO:

Porting Linux to U-Boot based systems:

U-Boot cannot save you from doing all the necessary modifications to configure the Linux device drivers for use with your target hardware (no, we don't intend to provide a full virtual machine interface to Linux :-).

But now you can ignore ALL boot loader code (in arch/ppc/mbxboot).

Just make sure your machine specific header file (for instance include/asm-ppc/tqm8xx.h) includes the same definition of the Board Information structure as we define in include/u-boot.h, and make sure that your definition of IMAP_ADDR uses the same value as your U-Boot configuration in CFG_IMMR.

Configuring the Linux kernel:

No specific requirements for U-Boot. Make sure you have some root device (initial ramdisk, NFS) for your target system.

Building a Linux Image:

With U-Boot, "normal" build targets like "zImage" or "bzImage" are not used. If you use recent kernel source, a new build target "uImage" will exist which automatically builds an image usable by U-Boot. Most older kernels also have support for a "pImage" target, which was introduced for our predecessor project PPCBoot and uses a 100% compatible format.

Example:

make TQM850L_config
make oldconfig
make dep
make uImage

The "uImage" build target uses a special tool (in 'tools/mkimage') to encapsulate a compressed Linux kernel image with header information, CRC32 checksum etc. for use with U-Boot. This is what we are doing:

build a standard "vmlinux" kernel image (in ELF binary format):
convert the kernel into a raw binary image:

${CROSS_COMPILE}-objcopy -O binary
-R .note -R .comment
-S vmlinux linux.bin
compress the binary image:

gzip -9 linux.bin
package compressed binary image for U-Boot:

mkimage -A ppc -O linux -T kernel -C gzip
-a 0 -e 0 -n "Linux Kernel Image"
-d linux.bin.gz uImage

The "mkimage" tool can also be used to create ramdisk images for use with U-Boot, either separated from the Linux kernel image, or combined into one file. "mkimage" encapsulates the images with a 64 byte header containing information about target architecture, operating system, image type, compression method, entry points, time stamp, CRC32 checksums, etc.

"mkimage" can be called in two ways: to verify existing images and print the header information, or to build new images.

In the first form (with "-l" option) mkimage lists the information contained in the header of an existing U-Boot image; this includes checksum verification:

tools/mkimage -l image
  -l ==> list image header information

The second form (with "-d" option) is used to build a U-Boot image from a "data file" which is used as image payload:

tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
	      -n name -d data_file image
  -A ==> set architecture to 'arch'
  -O ==> set operating system to 'os'
  -T ==> set image type to 'type'
  -C ==> set compression type 'comp'
  -a ==> set load address to 'addr' (hex)
  -e ==> set entry point to 'ep' (hex)
  -n ==> set image name to 'name'
  -d ==> use image data from 'datafile'

Right now, all Linux kernels for PowerPC systems use the same load address (0x00000000), but the entry point address depends on the kernel version:

2.2.x kernels have the entry point at 0x0000000C,
2.3.x and later kernels have the entry point at 0x00000000.

So a typical call to build a U-Boot image would read:

-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz \
> examples/uImage.TQM850L
Image Name:   2.4.4 kernel for TQM850L
Created:      Wed Jul 19 02:34:59 2000
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point:  0x00000000

To verify the contents of the image (or check for corruption):

-> tools/mkimage -l examples/uImage.TQM850L
Image Name:   2.4.4 kernel for TQM850L
Created:      Wed Jul 19 02:34:59 2000
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point:  0x00000000

NOTE: for embedded systems where boot time is critical you can trade speed for memory and install an UNCOMPRESSED image instead: this needs more space in Flash, but boots much faster since it does not need to be uncompressed:

-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
> examples/uImage.TQM850L-uncompressed
Image Name:   2.4.4 kernel for TQM850L
Created:      Wed Jul 19 02:34:59 2000
Image Type:   PowerPC Linux Kernel Image (uncompressed)
Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
Load Address: 0x00000000
Entry Point:  0x00000000

Similar you can build U-Boot images from a 'ramdisk.image.gz' file when your kernel is intended to use an initial ramdisk:

-> tools/mkimage -n 'Simple Ramdisk Image' \
> -A ppc -O linux -T ramdisk -C gzip \
> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
Image Name:   Simple Ramdisk Image
Created:      Wed Jan 12 14:01:50 2000
Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
Load Address: 0x00000000
Entry Point:  0x00000000

Installing a Linux Image:

To downloading a U-Boot image over the serial (console) interface, you must convert the image to S-Record format:

objcopy -I binary -O srec examples/image examples/image.srec

The 'objcopy' does not understand the information in the U-Boot image header, so the resulting S-Record file will be relative to address 0x00000000. To load it to a given address, you need to specify the target address as 'offset' parameter with the 'loads' command.

Example: install the image to address 0x40100000 (which on the TQM8xxL is in the first Flash bank):

=> erase 40100000 401FFFFF

.......... done
Erased 8 sectors

=> loads 40100000
## Ready for S-Record download ...
~>examples/image.srec
1 2 3 4 5 6 7 8 9 10 11 12 13 ...
...
15989 15990 15991 15992
[file transfer complete]
[connected]
## Start Addr = 0x00000000

You can check the success of the download using the 'iminfo' command; this includes a checksum verification so you can be sure no data corruption happened:

=> imi 40100000

## Checking Image at 40100000 ...
   Image Name:	 2.2.13 for initrd on TQM850L
   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
   Data Size:	 335725 Bytes = 327 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 0000000c
   Verifying Checksum ... OK

Boot Linux:

The "bootm" command is used to boot an application that is stored in memory (RAM or Flash). In case of a Linux kernel image, the contents of the "bootargs" environment variable is passed to the kernel as parameters. You can check and modify this variable using the "printenv" and "setenv" commands:

=> printenv bootargs
bootargs=root=/dev/ram

=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> printenv bootargs
bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> bootm 40020000
## Booting Linux kernel at 40020000 ...
   Image Name:	 2.2.13 for NFS on TQM850L
   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
   Data Size:	 381681 Bytes = 372 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 0000000c
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK
Linux version 2.2.13 ([email protected]) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
...

If you want to boot a Linux kernel with initial ram disk, you pass the memory addresses of both the kernel and the initrd image (PPBCOOT format!) to the "bootm" command:

=> imi 40100000 40200000

## Checking Image at 40100000 ...
   Image Name:	 2.2.13 for initrd on TQM850L
   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
   Data Size:	 335725 Bytes = 327 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 0000000c
   Verifying Checksum ... OK

## Checking Image at 40200000 ...
   Image Name:	 Simple Ramdisk Image
   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
   Data Size:	 566530 Bytes = 553 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 00000000
   Verifying Checksum ... OK

=> bootm 40100000 40200000
## Booting Linux kernel at 40100000 ...
   Image Name:	 2.2.13 for initrd on TQM850L
   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
   Data Size:	 335725 Bytes = 327 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 0000000c
   Verifying Checksum ... OK
   Uncompressing Kernel Image ... OK
## Loading RAMDisk Image at 40200000 ...
   Image Name:	 Simple Ramdisk Image
   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
   Data Size:	 566530 Bytes = 553 kB = 0 MB
   Load Address: 00000000
   Entry Point:	 00000000
   Verifying Checksum ... OK
   Loading Ramdisk ... OK
Linux version 2.2.13 ([email protected]) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
Boot arguments: root=/dev/ram
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
...
RAMDISK: Compressed image found at block 0
VFS: Mounted root (ext2 filesystem).

bash#

More About U-Boot Image Types:

U-Boot supports the following image types:

"Standalone Programs" are directly runnable in the environment provided by U-Boot; it is expected that (if they behave well) you can continue to work in U-Boot after return from the Standalone Program. "OS Kernel Images" are usually images of some Embedded OS which will take over control completely. Usually these programs will install their own set of exception handlers, device drivers, set up the MMU, etc. - this means, that you cannot expect to re-enter U-Boot except by resetting the CPU. "RAMDisk Images" are more or less just data blocks, and their parameters (address, size) are passed to an OS kernel that is being started. "Multi-File Images" contain several images, typically an OS (Linux) kernel image and one or more data images like RAMDisks. This construct is useful for instance when you want to boot over the network using BOOTP etc., where the boot server provides just a single image file, but you want to get for instance an OS kernel and a RAMDisk image.

"Multi-File Images" start with a list of image sizes, each
image size (in bytes) specified by an "uint32_t" in network
byte order. This list is terminated by an "(uint32_t)0".
Immediately after the terminating 0 follow the images, one by
one, all aligned on "uint32_t" boundaries (size rounded up to
a multiple of 4 bytes).

"Firmware Images" are binary images containing firmware (like U-Boot or FPGA images) which usually will be programmed to flash memory.

"Script files" are command sequences that will be executed by U-Boot's command interpreter; this feature is especially useful when you configure U-Boot to use a real shell (hush) as command interpreter.

Standalone HOWTO:

One of the features of U-Boot is that you can dynamically load and run "standalone" applications, which can use some resources of U-Boot like console I/O functions or interrupt services.

Two simple examples are included with the sources:

"Hello World" Demo:

'examples/hello_world.c' contains a small "Hello World" Demo application; it is automatically compiled when you build U-Boot. It's configured to run at address 0x00040004, so you can play with it like that:

=> loads
## Ready for S-Record download ...
~>examples/hello_world.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004

=> go 40004 Hello World! This is a test.
## Starting application at 0x00040004 ...
Hello World
argc = 7
argv[0] = "40004"
argv[1] = "Hello"
argv[2] = "World!"
argv[3] = "This"
argv[4] = "is"
argv[5] = "a"
argv[6] = "test."
argv[7] = "<NULL>"
Hit any key to exit ...

## Application terminated, rc = 0x0

Another example, which demonstrates how to register a CPM interrupt handler with the U-Boot code, can be found in 'examples/timer.c'. Here, a CPM timer is set up to generate an interrupt every second. The interrupt service routine is trivial, just printing a '.' character, but this is just a demo program. The application can be controlled by the following keys:

? - print current values og the CPM Timer registers
b - enable interrupts and start timer
e - stop timer and disable interrupts
q - quit application

=> loads
## Ready for S-Record download ...
~>examples/timer.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004

=> go 40004
## Starting application at 0x00040004 ...
TIMERS=0xfff00980
Using timer 1
  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0

Hit 'b': [q, b, e, ?] Set interval 1000000 us Enabling timer Hit '?': [q, b, e, ?] ........ tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0 Hit '?': [q, b, e, ?] . tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0 Hit '?': [q, b, e, ?] . tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0 Hit '?': [q, b, e, ?] . tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0 Hit 'e': [q, b, e, ?] ...Stopping timer Hit 'q': [q, b, e, ?] ## Application terminated, rc = 0x0

Minicom warning:

Over time, many people have reported problems when trying to use the "minicom" terminal emulation program for serial download. I (wd) consider minicom to be broken, and recommend not to use it. Under Unix, I recommend to use C-Kermit for general purpose use (and especially for kermit binary protocol download ("loadb" command), and use "cu" for S-Record download ("loads" command).

Nevertheless, if you absolutely want to use it try adding this configuration to your "File transfer protocols" section:

   Name	   Program			Name U/D FullScr IO-Red. Multi
X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N

NetBSD Notes:

Starting at version 0.9.2, U-Boot supports NetBSD both as host (build U-Boot) and target system (boots NetBSD/mpc8xx).

Building requires a cross environment; it is known to work on NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also need gmake since the Makefiles are not compatible with BSD make). Note that the cross-powerpc package does not install include files; attempting to build U-Boot will fail because <machine/ansi.h> is missing. This file has to be installed and patched manually:

# cd /usr/pkg/cross/powerpc-netbsd/include
# mkdir powerpc
# ln -s powerpc machine
# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST

Native builds don't work due to incompatibilities between native and U-Boot include files.

Booting assumes that (the first part of) the image booted is a stage-2 loader which in turn loads and then invokes the kernel proper. Loader sources will eventually appear in the NetBSD source tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the meantime, send mail to [email protected] and/or [email protected] for details.

Implementation Internals:

The following is not intended to be a complete description of every implementation detail. However, it should help to understand the inner workings of U-Boot and make it easier to port it to custom hardware.

Initial Stack, Global Data:

The implementation of U-Boot is complicated by the fact that U-Boot starts running out of ROM (flash memory), usually without access to system RAM (because the memory controller is not initialized yet). This means that we don't have writable Data or BSS segments, and BSS is not initialized as zero. To be able to get a C environment working at all, we have to allocate at least a minimal stack. Implementation options for this are defined and restricted by the CPU used: Some CPU models provide on-chip memory (like the IMMR area on MPC8xx and MPC826x processors), on others (parts of) the data cache can be locked as (mis-) used as memory, etc.

Chris Hallinan posted a good summary of	 these	issues	to  the
u-boot-users mailing list:

Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
From: "Chris Hallinan" <[email protected]>
Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
...

Correct me if I'm wrong, folks, but the way I understand it
is this: Using DCACHE as initial RAM for Stack, etc, does not
require any physical RAM backing up the cache. The cleverness
is that the cache is being used as a temporary supply of
necessary storage before the SDRAM controller is setup. It's
beyond the scope of this list to expain the details, but you
can see how this works by studying the cache architecture and
operation in the architecture and processor-specific manuals.

OCM is On Chip Memory, which I believe the 405GP has 4K. It
is another option for the system designer to use as an
initial stack/ram area prior to SDRAM being available. Either
option should work for you. Using CS 4 should be fine if your
board designers haven't used it for something that would
cause you grief during the initial boot! It is frequently not
used.

CFG_INIT_RAM_ADDR should be somewhere that won't interfere
with your processor/board/system design. The default value
you will find in any recent u-boot distribution in
Walnut405.h should work for you. I'd set it to a value larger
than your SDRAM module. If you have a 64MB SDRAM module, set
it above 400_0000. Just make sure your board has no resources
that are supposed to respond to that address! That code in
start.S has been around a while and should work as is when
you get the config right.

-Chris Hallinan
DS4.COM, Inc.

It is essential to remember this, since it has some impact on the C code for the initialization procedures:

Initialized global data (data segment) is read-only. Do not attempt to write it.
Do not use any unitialized global data (or implicitely initialized as zero data - BSS segment) at all - this is undefined, initiali- zation is performed later (when relocating to RAM).
Stack space is very limited. Avoid big data buffers or things like that.

Having only the stack as writable memory limits means we cannot use normal global data to share information beween the code. But it turned out that the implementation of U-Boot can be greatly simplified by making a global data structure (gd_t) available to all functions. We could pass a pointer to this data as argument to all functions, but this would bloat the code. Instead we use a feature of the GCC compiler (Global Register Variables) to share the data: we place a pointer (gd) to the global data into a register which we reserve for this purpose.

When choosing a register for such a purpose we are restricted by the relevant (E)ABI specifications for the current architecture, and by GCC's implementation.

For PowerPC, the following registers have specific use: R1: stack pointer R2: TOC pointer R3-R4: parameter passing and return values R5-R10: parameter passing R13: small data area pointer R30: GOT pointer R31: frame pointer

(U-Boot also uses R14 as internal GOT pointer.)

==> U-Boot will use R29 to hold a pointer to the global data

Note: on PPC, we could use a static initializer (since the
address of the global data structure is known at compile time),
but it turned out that reserving a register results in somewhat
smaller code - although the code savings are not that big (on
average for all boards 752 bytes for the whole U-Boot image,
624 text + 127 data).

On ARM, the following registers are used:

R0:	function argument word/integer result
R1-R3:	function argument word
R9:	GOT pointer
R10:	stack limit (used only if stack checking if enabled)
R11:	argument (frame) pointer
R12:	temporary workspace
R13:	stack pointer
R14:	link register
R15:	program counter

==> U-Boot will use R8 to hold a pointer to the global data

Memory Management:

U-Boot runs in system state and uses physical addresses, i.e. the MMU is not used either for address mapping nor for memory protection.

The available memory is mapped to fixed addresses using the memory controller. In this process, a contiguous block is formed for each memory type (Flash, SDRAM, SRAM), even when it consists of several physical memory banks.

U-Boot is installed in the first 128 kB of the first Flash bank (on TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After booting and sizing and initializing DRAM, the code relocates itself to the upper end of DRAM. Immediately below the U-Boot code some memory is reserved for use by malloc() [see CFG_MALLOC_LEN configuration setting]. Below that, a structure with global Board Info data is placed, followed by the stack (growing downward).

Additionally, some exception handler code is copied to the low 8 kB of DRAM (0x00000000 ... 0x00001FFF).

So a typical memory configuration with 16 MB of DRAM could look like this:

0x0000 0000	Exception Vector code
      :
0x0000 1FFF
0x0000 2000	Free for Application Use
      :
      :

      :
      :
0x00FB FF20	Monitor Stack (Growing downward)
0x00FB FFAC	Board Info Data and permanent copy of global data
0x00FC 0000	Malloc Arena
      :
0x00FD FFFF
0x00FE 0000	RAM Copy of Monitor Code
...		eventually: LCD or video framebuffer
...		eventually: pRAM (Protected RAM - unchanged by reset)
0x00FF FFFF	[End of RAM]

System Initialization:

In the reset configuration, U-Boot starts at the reset entry point (on most PowerPC systens at address 0x00000100). Because of the reset configuration for CS0# this is a mirror of the onboard Flash memory. To be able to re-map memory U-Boot then jumps to its link address. To be able to implement the initialization code in C, a (small!) initial stack is set up in the internal Dual Ported RAM (in case CPUs which provide such a feature like MPC8xx or MPC8260), or in a locked part of the data cache. After that, U-Boot initializes the CPU core, the caches and the SIU.

Next, all (potentially) available memory banks are mapped using a preliminary mapping. For example, we put them on 512 MB boundaries (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is programmed for SDRAM access. Using the temporary configuration, a simple memory test is run that determines the size of the SDRAM banks.

When there is more than one SDRAM bank, and the banks are of different size, the largest is mapped first. For equal size, the first bank (CS2#) is mapped first. The first mapping is always for address 0x00000000, with any additional banks following immediately to create contiguous memory starting from 0.

Then, the monitor installs itself at the upper end of the SDRAM area and allocates memory for use by malloc() and for the global Board Info data; also, the exception vector code is copied to the low RAM pages, and the final stack is set up.

Only after this relocation will you have a "normal" C environment; until that you are restricted in several ways, mostly because you are running from ROM, and because the code will have to be relocated to a new address in RAM.

U-Boot Porting Guide:

[Based on messages by Jerry Van Baren in the U-Boot-Users mailing list, October 2002]

int main (int argc, char *argv[]) { sighandler_t no_more_time;

signal (SIGALRM, no_more_time);
alarm (PROJECT_DEADLINE - toSec (3 * WEEK));

if (available_money > available_manpower) {
	pay consultant to port U-Boot;
	return 0;
}

Download latest U-Boot source;

Subscribe to u-boot-users mailing list;

if (clueless) {
	email ("Hi, I am new to U-Boot, how do I get started?");
}

while (learning) {
	Read the README file in the top level directory;
	Read http://www.denx.de/twiki/bin/view/DULG/Manual ;
	Read the source, Luke;
}

if (available_money > toLocalCurrency ($2500)) {
	Buy a BDI2000;
} else {
	Add a lot of aggravation and time;
}

Create your own board support subdirectory;

Create your own board config file;

while (!running) {
	do {
		Add / modify source code;
	} until (compiles);
	Debug;
	if (clueless)
		email ("Hi, I am having problems...");
}
Send patch file to Wolfgang;

return 0;

}

void no_more_time (int sig) { hire_a_guru(); }

Coding Standards:

All contributions to U-Boot should conform to the Linux kernel coding style; see the file "Documentation/CodingStyle" in your Linux kernel source directory.

Please note that U-Boot is implemented in C (and to some small parts in Assembler); no C++ is used, so please do not use C++ style comments (//) in your code.

Please also stick to the following formatting rules:

remove any trailing white space
use TAB characters for indentation, not spaces
make sure NOT to use DOS '\r\n' line feeds
do not add more than 2 empty lines to source files
do not add trailing empty lines to source files

Submissions which do not conform to the standards may be returned with a request to reformat the changes.

Submitting Patches:

Since the number of patches for U-Boot is growing, we need to establish some rules. Submissions which do not conform to these rules may be rejected, even when they contain important and valuable stuff.

When you send a patch, please include the following information with it:

For bug fixes: a description of the bug and how your patch fixes this bug. Please try to include a way of demonstrating that the patch actually fixes something.
For new features: a description of the feature and your implementation.
A CHANGELOG entry as plaintext (separate from the patch)
For major contributions, your entry to the CREDITS file
When you add support for a new board, don't forget to add this board to the MAKEALL script, too.
If your patch adds new configuration options, don't forget to document these in the README file.
The patch itself. If you are accessing the CVS repository use "cvs update; cvs diff -puRN"; else, use "diff -purN OLD NEW". If your version of diff does not support these options, then get the latest version of GNU diff.

The current directory when running this command shall be the top level directory of the U-Boot source tree, or it's parent directory (i. e. please make sure that your patch includes sufficient directory information for the affected files).

We accept patches as plain text, MIME attachments or as uuencoded gzipped text.
If one logical set of modifications affects or creates several files, all these changes shall be submitted in a SINGLE patch file.
Changesets that contain different, unrelated modifications shall be submitted as SEPARATE patches, one patch per changeset.

Notes:

Before sending the patch, run the MAKEALL script on your patched source tree and make sure that no errors or warnings are reported for any of the boards.
Keep your modifications to the necessary minimum: A patch containing several unrelated changes or arbitrary reformats will be returned with a request to re-formatting / split it.
If you modify existing code, make sure that your new code does not add to the memory footprint of the code ;-) Small is beautiful! When adding new features, these should compile conditionally only (using #ifdef), and the resulting code with the new feature disabled must not need more memory than the old code without your modification.

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Metadata

(C) Copyright 2000 - 2005

Wolfgang Denk, DENX Software Engineering, [email protected].

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:

Status:

Where to get help:

Where we come from:

Names and Spelling:

Versioning:

Directory Hierarchy:

Software Configuration:

Selection of Processor Architecture and Board Type:

Configuration Options:

Modem Support:

Configuration Settings:

Low Level (hardware related) configuration options:

Building the Software:

Testing of U-Boot Modifications, Ports to New Hardware, etc.:

Monitor Commands - Overview:

Monitor Commands - Detailed Description:

Environment Variables:

Command Line Parsing:

Old, simple command line parser:

Hush shell:

General rules:

Note for Redundant Ethernet Interfaces:

Image Formats:

Linux Support:

Linux HOWTO:

Porting Linux to U-Boot based systems:

Configuring the Linux kernel:

Building a Linux Image:

Installing a Linux Image:

Boot Linux:

More About U-Boot Image Types:

Standalone HOWTO:

"Hello World" Demo:

Minicom warning:

NetBSD Notes:

Implementation Internals:

Initial Stack, Global Data:

Memory Management:

System Initialization:

U-Boot Porting Guide:

Coding Standards:

Submitting Patches:

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