xref: /openbmc/u-boot/README (revision 712cf7ab0b58e51a69e339397457d3591b6b650e)
1#
2# (C) Copyright 2000 - 2011
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# See file CREDITS for list of people who contributed to this
6# project.
7#
8# This program is free software; you can redistribute it and/or
9# modify it under the terms of the GNU General Public License as
10# published by the Free Software Foundation; either version 2 of
11# the License, or (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program; if not, write to the Free Software
20# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21# MA 02111-1307 USA
22#
23
24Summary:
25========
26
27This directory contains the source code for U-Boot, a boot loader for
28Embedded boards based on PowerPC, ARM, MIPS and several other
29processors, which can be installed in a boot ROM and used to
30initialize and test the hardware or to download and run application
31code.
32
33The development of U-Boot is closely related to Linux: some parts of
34the source code originate in the Linux source tree, we have some
35header files in common, and special provision has been made to
36support booting of Linux images.
37
38Some attention has been paid to make this software easily
39configurable and extendable. For instance, all monitor commands are
40implemented with the same call interface, so that it's very easy to
41add new commands. Also, instead of permanently adding rarely used
42code (for instance hardware test utilities) to the monitor, you can
43load and run it dynamically.
44
45
46Status:
47=======
48
49In general, all boards for which a configuration option exists in the
50Makefile have been tested to some extent and can be considered
51"working". In fact, many of them are used in production systems.
52
53In case of problems see the CHANGELOG and CREDITS files to find out
54who contributed the specific port. The MAINTAINERS file lists board
55maintainers.
56
57
58Where to get help:
59==================
60
61In case you have questions about, problems with or contributions for
62U-Boot you should send a message to the U-Boot mailing list at
63<u-boot@lists.denx.de>. There is also an archive of previous traffic
64on the mailing list - please search the archive before asking FAQ's.
65Please see http://lists.denx.de/pipermail/u-boot and
66http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
67
68
69Where to get source code:
70=========================
71
72The U-Boot source code is maintained in the git repository at
73git://www.denx.de/git/u-boot.git ; you can browse it online at
74http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
75
76The "snapshot" links on this page allow you to download tarballs of
77any version you might be interested in. Official releases are also
78available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
79directory.
80
81Pre-built (and tested) images are available from
82ftp://ftp.denx.de/pub/u-boot/images/
83
84
85Where we come from:
86===================
87
88- start from 8xxrom sources
89- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
90- clean up code
91- make it easier to add custom boards
92- make it possible to add other [PowerPC] CPUs
93- extend functions, especially:
94  * Provide extended interface to Linux boot loader
95  * S-Record download
96  * network boot
97  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
98- create ARMBoot project (http://sourceforge.net/projects/armboot)
99- add other CPU families (starting with ARM)
100- create U-Boot project (http://sourceforge.net/projects/u-boot)
101- current project page: see http://www.denx.de/wiki/U-Boot
102
103
104Names and Spelling:
105===================
106
107The "official" name of this project is "Das U-Boot". The spelling
108"U-Boot" shall be used in all written text (documentation, comments
109in source files etc.). Example:
110
111	This is the README file for the U-Boot project.
112
113File names etc. shall be based on the string "u-boot". Examples:
114
115	include/asm-ppc/u-boot.h
116
117	#include <asm/u-boot.h>
118
119Variable names, preprocessor constants etc. shall be either based on
120the string "u_boot" or on "U_BOOT". Example:
121
122	U_BOOT_VERSION		u_boot_logo
123	IH_OS_U_BOOT		u_boot_hush_start
124
125
126Versioning:
127===========
128
129Starting with the release in October 2008, the names of the releases
130were changed from numerical release numbers without deeper meaning
131into a time stamp based numbering. Regular releases are identified by
132names consisting of the calendar year and month of the release date.
133Additional fields (if present) indicate release candidates or bug fix
134releases in "stable" maintenance trees.
135
136Examples:
137	U-Boot v2009.11     - Release November 2009
138	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
139	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
140
141
142Directory Hierarchy:
143====================
144
145/arch			Architecture specific files
146  /arm			Files generic to ARM architecture
147    /cpu		CPU specific files
148      /arm720t		Files specific to ARM 720 CPUs
149      /arm920t		Files specific to ARM 920 CPUs
150	/at91		Files specific to Atmel AT91RM9200 CPU
151	/imx		Files specific to Freescale MC9328 i.MX CPUs
152	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
153      /arm925t		Files specific to ARM 925 CPUs
154      /arm926ejs	Files specific to ARM 926 CPUs
155      /arm1136		Files specific to ARM 1136 CPUs
156      /ixp		Files specific to Intel XScale IXP CPUs
157      /pxa		Files specific to Intel XScale PXA CPUs
158      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
159      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
160    /lib		Architecture specific library files
161  /avr32		Files generic to AVR32 architecture
162    /cpu		CPU specific files
163    /lib		Architecture specific library files
164  /blackfin		Files generic to Analog Devices Blackfin architecture
165    /cpu		CPU specific files
166    /lib		Architecture specific library files
167  /x86			Files generic to x86 architecture
168    /cpu		CPU specific files
169    /lib		Architecture specific library files
170  /m68k			Files generic to m68k architecture
171    /cpu		CPU specific files
172      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
173      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
174      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
175      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
176      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
177    /lib		Architecture specific library files
178  /microblaze		Files generic to microblaze architecture
179    /cpu		CPU specific files
180    /lib		Architecture specific library files
181  /mips			Files generic to MIPS architecture
182    /cpu		CPU specific files
183      /mips32		Files specific to MIPS32 CPUs
184    /lib		Architecture specific library files
185  /nios2		Files generic to Altera NIOS2 architecture
186    /cpu		CPU specific files
187    /lib		Architecture specific library files
188  /powerpc		Files generic to PowerPC architecture
189    /cpu		CPU specific files
190      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
191      /mpc5xx		Files specific to Freescale MPC5xx CPUs
192      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
193      /mpc8xx		Files specific to Freescale MPC8xx CPUs
194      /mpc8220		Files specific to Freescale MPC8220 CPUs
195      /mpc824x		Files specific to Freescale MPC824x CPUs
196      /mpc8260		Files specific to Freescale MPC8260 CPUs
197      /mpc85xx		Files specific to Freescale MPC85xx CPUs
198      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
199    /lib		Architecture specific library files
200  /sh			Files generic to SH architecture
201    /cpu		CPU specific files
202      /sh2		Files specific to sh2 CPUs
203      /sh3		Files specific to sh3 CPUs
204      /sh4		Files specific to sh4 CPUs
205    /lib		Architecture specific library files
206  /sparc		Files generic to SPARC architecture
207    /cpu		CPU specific files
208      /leon2		Files specific to Gaisler LEON2 SPARC CPU
209      /leon3		Files specific to Gaisler LEON3 SPARC CPU
210    /lib		Architecture specific library files
211/api			Machine/arch independent API for external apps
212/board			Board dependent files
213/common			Misc architecture independent functions
214/disk			Code for disk drive partition handling
215/doc			Documentation (don't expect too much)
216/drivers		Commonly used device drivers
217/examples		Example code for standalone applications, etc.
218/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
219/include		Header Files
220/lib			Files generic to all architectures
221  /libfdt		Library files to support flattened device trees
222  /lzma			Library files to support LZMA decompression
223  /lzo			Library files to support LZO decompression
224/net			Networking code
225/post			Power On Self Test
226/rtc			Real Time Clock drivers
227/tools			Tools to build S-Record or U-Boot images, etc.
228
229Software Configuration:
230=======================
231
232Configuration is usually done using C preprocessor defines; the
233rationale behind that is to avoid dead code whenever possible.
234
235There are two classes of configuration variables:
236
237* Configuration _OPTIONS_:
238  These are selectable by the user and have names beginning with
239  "CONFIG_".
240
241* Configuration _SETTINGS_:
242  These depend on the hardware etc. and should not be meddled with if
243  you don't know what you're doing; they have names beginning with
244  "CONFIG_SYS_".
245
246Later we will add a configuration tool - probably similar to or even
247identical to what's used for the Linux kernel. Right now, we have to
248do the configuration by hand, which means creating some symbolic
249links and editing some configuration files. We use the TQM8xxL boards
250as an example here.
251
252
253Selection of Processor Architecture and Board Type:
254---------------------------------------------------
255
256For all supported boards there are ready-to-use default
257configurations available; just type "make <board_name>_config".
258
259Example: For a TQM823L module type:
260
261	cd u-boot
262	make TQM823L_config
263
264For the Cogent platform, you need to specify the CPU type as well;
265e.g. "make cogent_mpc8xx_config". And also configure the cogent
266directory according to the instructions in cogent/README.
267
268
269Configuration Options:
270----------------------
271
272Configuration depends on the combination of board and CPU type; all
273such information is kept in a configuration file
274"include/configs/<board_name>.h".
275
276Example: For a TQM823L module, all configuration settings are in
277"include/configs/TQM823L.h".
278
279
280Many of the options are named exactly as the corresponding Linux
281kernel configuration options. The intention is to make it easier to
282build a config tool - later.
283
284
285The following options need to be configured:
286
287- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
288
289- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
290
291- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
292		Define exactly one, e.g. CONFIG_ATSTK1002
293
294- CPU Module Type: (if CONFIG_COGENT is defined)
295		Define exactly one of
296		CONFIG_CMA286_60_OLD
297--- FIXME --- not tested yet:
298		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
299		CONFIG_CMA287_23, CONFIG_CMA287_50
300
301- Motherboard Type: (if CONFIG_COGENT is defined)
302		Define exactly one of
303		CONFIG_CMA101, CONFIG_CMA102
304
305- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
306		Define one or more of
307		CONFIG_CMA302
308
309- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
310		Define one or more of
311		CONFIG_LCD_HEARTBEAT	- update a character position on
312					  the LCD display every second with
313					  a "rotator" |\-/|\-/
314
315- Board flavour: (if CONFIG_MPC8260ADS is defined)
316		CONFIG_ADSTYPE
317		Possible values are:
318			CONFIG_SYS_8260ADS	- original MPC8260ADS
319			CONFIG_SYS_8266ADS	- MPC8266ADS
320			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
321			CONFIG_SYS_8272ADS	- MPC8272ADS
322
323- Marvell Family Member
324		CONFIG_SYS_MVFS		- define it if you want to enable
325					  multiple fs option at one time
326					  for marvell soc family
327
328- MPC824X Family Member (if CONFIG_MPC824X is defined)
329		Define exactly one of
330		CONFIG_MPC8240, CONFIG_MPC8245
331
332- 8xx CPU Options: (if using an MPC8xx CPU)
333		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
334					  get_gclk_freq() cannot work
335					  e.g. if there is no 32KHz
336					  reference PIT/RTC clock
337		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
338					  or XTAL/EXTAL)
339
340- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
341		CONFIG_SYS_8xx_CPUCLK_MIN
342		CONFIG_SYS_8xx_CPUCLK_MAX
343		CONFIG_8xx_CPUCLK_DEFAULT
344			See doc/README.MPC866
345
346		CONFIG_SYS_MEASURE_CPUCLK
347
348		Define this to measure the actual CPU clock instead
349		of relying on the correctness of the configured
350		values. Mostly useful for board bringup to make sure
351		the PLL is locked at the intended frequency. Note
352		that this requires a (stable) reference clock (32 kHz
353		RTC clock or CONFIG_SYS_8XX_XIN)
354
355		CONFIG_SYS_DELAYED_ICACHE
356
357		Define this option if you want to enable the
358		ICache only when Code runs from RAM.
359
360- 85xx CPU Options:
361		CONFIG_SYS_FSL_TBCLK_DIV
362
363		Defines the core time base clock divider ratio compared to the
364		system clock.  On most PQ3 devices this is 8, on newer QorIQ
365		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
366
367		CONFIG_SYS_FSL_PCIE_COMPAT
368
369		Defines the string to utilize when trying to match PCIe device
370		tree nodes for the given platform.
371
372- Intel Monahans options:
373		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
374
375		Defines the Monahans run mode to oscillator
376		ratio. Valid values are 8, 16, 24, 31. The core
377		frequency is this value multiplied by 13 MHz.
378
379		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
380
381		Defines the Monahans turbo mode to oscillator
382		ratio. Valid values are 1 (default if undefined) and
383		2. The core frequency as calculated above is multiplied
384		by this value.
385
386- MIPS CPU options:
387		CONFIG_SYS_INIT_SP_OFFSET
388
389		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
390		pointer. This is needed for the temporary stack before
391		relocation.
392
393		CONFIG_SYS_MIPS_CACHE_MODE
394
395		Cache operation mode for the MIPS CPU.
396		See also arch/mips/include/asm/mipsregs.h.
397		Possible values are:
398			CONF_CM_CACHABLE_NO_WA
399			CONF_CM_CACHABLE_WA
400			CONF_CM_UNCACHED
401			CONF_CM_CACHABLE_NONCOHERENT
402			CONF_CM_CACHABLE_CE
403			CONF_CM_CACHABLE_COW
404			CONF_CM_CACHABLE_CUW
405			CONF_CM_CACHABLE_ACCELERATED
406
407		CONFIG_SYS_XWAY_EBU_BOOTCFG
408
409		Special option for Lantiq XWAY SoCs for booting from NOR flash.
410		See also arch/mips/cpu/mips32/start.S.
411
412		CONFIG_XWAY_SWAP_BYTES
413
414		Enable compilation of tools/xway-swap-bytes needed for Lantiq
415		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
416		be swapped if a flash programmer is used.
417
418- Linux Kernel Interface:
419		CONFIG_CLOCKS_IN_MHZ
420
421		U-Boot stores all clock information in Hz
422		internally. For binary compatibility with older Linux
423		kernels (which expect the clocks passed in the
424		bd_info data to be in MHz) the environment variable
425		"clocks_in_mhz" can be defined so that U-Boot
426		converts clock data to MHZ before passing it to the
427		Linux kernel.
428		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
429		"clocks_in_mhz=1" is automatically included in the
430		default environment.
431
432		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
433
434		When transferring memsize parameter to linux, some versions
435		expect it to be in bytes, others in MB.
436		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
437
438		CONFIG_OF_LIBFDT
439
440		New kernel versions are expecting firmware settings to be
441		passed using flattened device trees (based on open firmware
442		concepts).
443
444		CONFIG_OF_LIBFDT
445		 * New libfdt-based support
446		 * Adds the "fdt" command
447		 * The bootm command automatically updates the fdt
448
449		OF_CPU - The proper name of the cpus node (only required for
450			MPC512X and MPC5xxx based boards).
451		OF_SOC - The proper name of the soc node (only required for
452			MPC512X and MPC5xxx based boards).
453		OF_TBCLK - The timebase frequency.
454		OF_STDOUT_PATH - The path to the console device
455
456		boards with QUICC Engines require OF_QE to set UCC MAC
457		addresses
458
459		CONFIG_OF_BOARD_SETUP
460
461		Board code has addition modification that it wants to make
462		to the flat device tree before handing it off to the kernel
463
464		CONFIG_OF_BOOT_CPU
465
466		This define fills in the correct boot CPU in the boot
467		param header, the default value is zero if undefined.
468
469		CONFIG_OF_IDE_FIXUP
470
471		U-Boot can detect if an IDE device is present or not.
472		If not, and this new config option is activated, U-Boot
473		removes the ATA node from the DTS before booting Linux,
474		so the Linux IDE driver does not probe the device and
475		crash. This is needed for buggy hardware (uc101) where
476		no pull down resistor is connected to the signal IDE5V_DD7.
477
478		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
479
480		This setting is mandatory for all boards that have only one
481		machine type and must be used to specify the machine type
482		number as it appears in the ARM machine registry
483		(see http://www.arm.linux.org.uk/developer/machines/).
484		Only boards that have multiple machine types supported
485		in a single configuration file and the machine type is
486		runtime discoverable, do not have to use this setting.
487
488- vxWorks boot parameters:
489
490		bootvx constructs a valid bootline using the following
491		environments variables: bootfile, ipaddr, serverip, hostname.
492		It loads the vxWorks image pointed bootfile.
493
494		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
495		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
496		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
497		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
498
499		CONFIG_SYS_VXWORKS_ADD_PARAMS
500
501		Add it at the end of the bootline. E.g "u=username pw=secret"
502
503		Note: If a "bootargs" environment is defined, it will overwride
504		the defaults discussed just above.
505
506- Cache Configuration:
507		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
508		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
509		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
510
511- Cache Configuration for ARM:
512		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
513				      controller
514		CONFIG_SYS_PL310_BASE - Physical base address of PL310
515					controller register space
516
517- Serial Ports:
518		CONFIG_PL010_SERIAL
519
520		Define this if you want support for Amba PrimeCell PL010 UARTs.
521
522		CONFIG_PL011_SERIAL
523
524		Define this if you want support for Amba PrimeCell PL011 UARTs.
525
526		CONFIG_PL011_CLOCK
527
528		If you have Amba PrimeCell PL011 UARTs, set this variable to
529		the clock speed of the UARTs.
530
531		CONFIG_PL01x_PORTS
532
533		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
534		define this to a list of base addresses for each (supported)
535		port. See e.g. include/configs/versatile.h
536
537		CONFIG_PL011_SERIAL_RLCR
538
539		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
540		have separate receive and transmit line control registers.  Set
541		this variable to initialize the extra register.
542
543		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
544
545		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
546		boot loader that has already initialized the UART.  Define this
547		variable to flush the UART at init time.
548
549
550- Console Interface:
551		Depending on board, define exactly one serial port
552		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
553		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
554		console by defining CONFIG_8xx_CONS_NONE
555
556		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
557		port routines must be defined elsewhere
558		(i.e. serial_init(), serial_getc(), ...)
559
560		CONFIG_CFB_CONSOLE
561		Enables console device for a color framebuffer. Needs following
562		defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
563			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
564						(default big endian)
565			VIDEO_HW_RECTFILL	graphic chip supports
566						rectangle fill
567						(cf. smiLynxEM)
568			VIDEO_HW_BITBLT		graphic chip supports
569						bit-blit (cf. smiLynxEM)
570			VIDEO_VISIBLE_COLS	visible pixel columns
571						(cols=pitch)
572			VIDEO_VISIBLE_ROWS	visible pixel rows
573			VIDEO_PIXEL_SIZE	bytes per pixel
574			VIDEO_DATA_FORMAT	graphic data format
575						(0-5, cf. cfb_console.c)
576			VIDEO_FB_ADRS		framebuffer address
577			VIDEO_KBD_INIT_FCT	keyboard int fct
578						(i.e. i8042_kbd_init())
579			VIDEO_TSTC_FCT		test char fct
580						(i.e. i8042_tstc)
581			VIDEO_GETC_FCT		get char fct
582						(i.e. i8042_getc)
583			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
584						(requires blink timer
585						cf. i8042.c)
586			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
587			CONFIG_CONSOLE_TIME	display time/date info in
588						upper right corner
589						(requires CONFIG_CMD_DATE)
590			CONFIG_VIDEO_LOGO	display Linux logo in
591						upper left corner
592			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
593						linux_logo.h for logo.
594						Requires CONFIG_VIDEO_LOGO
595			CONFIG_CONSOLE_EXTRA_INFO
596						additional board info beside
597						the logo
598
599		When CONFIG_CFB_CONSOLE is defined, video console is
600		default i/o. Serial console can be forced with
601		environment 'console=serial'.
602
603		When CONFIG_SILENT_CONSOLE is defined, all console
604		messages (by U-Boot and Linux!) can be silenced with
605		the "silent" environment variable. See
606		doc/README.silent for more information.
607
608- Console Baudrate:
609		CONFIG_BAUDRATE - in bps
610		Select one of the baudrates listed in
611		CONFIG_SYS_BAUDRATE_TABLE, see below.
612		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
613
614- Console Rx buffer length
615		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
616		the maximum receive buffer length for the SMC.
617		This option is actual only for 82xx and 8xx possible.
618		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
619		must be defined, to setup the maximum idle timeout for
620		the SMC.
621
622- Pre-Console Buffer:
623		Prior to the console being initialised (i.e. serial UART
624		initialised etc) all console output is silently discarded.
625		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
626		buffer any console messages prior to the console being
627		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
628		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
629		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
630		bytes are output before the console is initialised, the
631		earlier bytes are discarded.
632
633		'Sane' compilers will generate smaller code if
634		CONFIG_PRE_CON_BUF_SZ is a power of 2
635
636- Boot Delay:	CONFIG_BOOTDELAY - in seconds
637		Delay before automatically booting the default image;
638		set to -1 to disable autoboot.
639
640		See doc/README.autoboot for these options that
641		work with CONFIG_BOOTDELAY. None are required.
642		CONFIG_BOOT_RETRY_TIME
643		CONFIG_BOOT_RETRY_MIN
644		CONFIG_AUTOBOOT_KEYED
645		CONFIG_AUTOBOOT_PROMPT
646		CONFIG_AUTOBOOT_DELAY_STR
647		CONFIG_AUTOBOOT_STOP_STR
648		CONFIG_AUTOBOOT_DELAY_STR2
649		CONFIG_AUTOBOOT_STOP_STR2
650		CONFIG_ZERO_BOOTDELAY_CHECK
651		CONFIG_RESET_TO_RETRY
652
653- Autoboot Command:
654		CONFIG_BOOTCOMMAND
655		Only needed when CONFIG_BOOTDELAY is enabled;
656		define a command string that is automatically executed
657		when no character is read on the console interface
658		within "Boot Delay" after reset.
659
660		CONFIG_BOOTARGS
661		This can be used to pass arguments to the bootm
662		command. The value of CONFIG_BOOTARGS goes into the
663		environment value "bootargs".
664
665		CONFIG_RAMBOOT and CONFIG_NFSBOOT
666		The value of these goes into the environment as
667		"ramboot" and "nfsboot" respectively, and can be used
668		as a convenience, when switching between booting from
669		RAM and NFS.
670
671- Pre-Boot Commands:
672		CONFIG_PREBOOT
673
674		When this option is #defined, the existence of the
675		environment variable "preboot" will be checked
676		immediately before starting the CONFIG_BOOTDELAY
677		countdown and/or running the auto-boot command resp.
678		entering interactive mode.
679
680		This feature is especially useful when "preboot" is
681		automatically generated or modified. For an example
682		see the LWMON board specific code: here "preboot" is
683		modified when the user holds down a certain
684		combination of keys on the (special) keyboard when
685		booting the systems
686
687- Serial Download Echo Mode:
688		CONFIG_LOADS_ECHO
689		If defined to 1, all characters received during a
690		serial download (using the "loads" command) are
691		echoed back. This might be needed by some terminal
692		emulations (like "cu"), but may as well just take
693		time on others. This setting #define's the initial
694		value of the "loads_echo" environment variable.
695
696- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
697		CONFIG_KGDB_BAUDRATE
698		Select one of the baudrates listed in
699		CONFIG_SYS_BAUDRATE_TABLE, see below.
700
701- Monitor Functions:
702		Monitor commands can be included or excluded
703		from the build by using the #include files
704		"config_cmd_all.h" and #undef'ing unwanted
705		commands, or using "config_cmd_default.h"
706		and augmenting with additional #define's
707		for wanted commands.
708
709		The default command configuration includes all commands
710		except those marked below with a "*".
711
712		CONFIG_CMD_ASKENV	* ask for env variable
713		CONFIG_CMD_BDI		  bdinfo
714		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
715		CONFIG_CMD_BMP		* BMP support
716		CONFIG_CMD_BSP		* Board specific commands
717		CONFIG_CMD_BOOTD	  bootd
718		CONFIG_CMD_CACHE	* icache, dcache
719		CONFIG_CMD_CONSOLE	  coninfo
720		CONFIG_CMD_CRC32	* crc32
721		CONFIG_CMD_DATE		* support for RTC, date/time...
722		CONFIG_CMD_DHCP		* DHCP support
723		CONFIG_CMD_DIAG		* Diagnostics
724		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
725		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
726		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
727		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
728		CONFIG_CMD_DTT		* Digital Therm and Thermostat
729		CONFIG_CMD_ECHO		  echo arguments
730		CONFIG_CMD_EDITENV	  edit env variable
731		CONFIG_CMD_EEPROM	* EEPROM read/write support
732		CONFIG_CMD_ELF		* bootelf, bootvx
733		CONFIG_CMD_EXPORTENV	* export the environment
734		CONFIG_CMD_SAVEENV	  saveenv
735		CONFIG_CMD_FDC		* Floppy Disk Support
736		CONFIG_CMD_FAT		* FAT partition support
737		CONFIG_CMD_FDOS		* Dos diskette Support
738		CONFIG_CMD_FLASH	  flinfo, erase, protect
739		CONFIG_CMD_FPGA		  FPGA device initialization support
740		CONFIG_CMD_GO		* the 'go' command (exec code)
741		CONFIG_CMD_GREPENV	* search environment
742		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
743		CONFIG_CMD_I2C		* I2C serial bus support
744		CONFIG_CMD_IDE		* IDE harddisk support
745		CONFIG_CMD_IMI		  iminfo
746		CONFIG_CMD_IMLS		  List all found images
747		CONFIG_CMD_IMMAP	* IMMR dump support
748		CONFIG_CMD_IMPORTENV	* import an environment
749		CONFIG_CMD_IRQ		* irqinfo
750		CONFIG_CMD_ITEST	  Integer/string test of 2 values
751		CONFIG_CMD_JFFS2	* JFFS2 Support
752		CONFIG_CMD_KGDB		* kgdb
753		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
754		CONFIG_CMD_LOADB	  loadb
755		CONFIG_CMD_LOADS	  loads
756		CONFIG_CMD_MD5SUM	  print md5 message digest
757					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
758		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
759					  loop, loopw, mtest
760		CONFIG_CMD_MISC		  Misc functions like sleep etc
761		CONFIG_CMD_MMC		* MMC memory mapped support
762		CONFIG_CMD_MII		* MII utility commands
763		CONFIG_CMD_MTDPARTS	* MTD partition support
764		CONFIG_CMD_NAND		* NAND support
765		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
766		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
767		CONFIG_CMD_PCA953X_INFO	* PCA953x I2C gpio info command
768		CONFIG_CMD_PCI		* pciinfo
769		CONFIG_CMD_PCMCIA		* PCMCIA support
770		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
771					  host
772		CONFIG_CMD_PORTIO	* Port I/O
773		CONFIG_CMD_REGINFO	* Register dump
774		CONFIG_CMD_RUN		  run command in env variable
775		CONFIG_CMD_SAVES	* save S record dump
776		CONFIG_CMD_SCSI		* SCSI Support
777		CONFIG_CMD_SDRAM	* print SDRAM configuration information
778					  (requires CONFIG_CMD_I2C)
779		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
780					  (4xx only)
781		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
782					  (requires CONFIG_CMD_MEMORY)
783		CONFIG_CMD_SOURCE	  "source" command Support
784		CONFIG_CMD_SPI		* SPI serial bus support
785		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
786		CONFIG_CMD_TIME		* run command and report execution time
787		CONFIG_CMD_USB		* USB support
788		CONFIG_CMD_CDP		* Cisco Discover Protocol support
789		CONFIG_CMD_FSL		* Microblaze FSL support
790
791
792		EXAMPLE: If you want all functions except of network
793		support you can write:
794
795		#include "config_cmd_all.h"
796		#undef CONFIG_CMD_NET
797
798	Other Commands:
799		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
800
801	Note:	Don't enable the "icache" and "dcache" commands
802		(configuration option CONFIG_CMD_CACHE) unless you know
803		what you (and your U-Boot users) are doing. Data
804		cache cannot be enabled on systems like the 8xx or
805		8260 (where accesses to the IMMR region must be
806		uncached), and it cannot be disabled on all other
807		systems where we (mis-) use the data cache to hold an
808		initial stack and some data.
809
810
811		XXX - this list needs to get updated!
812
813- Watchdog:
814		CONFIG_WATCHDOG
815		If this variable is defined, it enables watchdog
816		support for the SoC. There must be support in the SoC
817		specific code for a watchdog. For the 8xx and 8260
818		CPUs, the SIU Watchdog feature is enabled in the SYPCR
819		register.  When supported for a specific SoC is
820		available, then no further board specific code should
821		be needed to use it.
822
823		CONFIG_HW_WATCHDOG
824		When using a watchdog circuitry external to the used
825		SoC, then define this variable and provide board
826		specific code for the "hw_watchdog_reset" function.
827
828- U-Boot Version:
829		CONFIG_VERSION_VARIABLE
830		If this variable is defined, an environment variable
831		named "ver" is created by U-Boot showing the U-Boot
832		version as printed by the "version" command.
833		This variable is readonly.
834
835- Real-Time Clock:
836
837		When CONFIG_CMD_DATE is selected, the type of the RTC
838		has to be selected, too. Define exactly one of the
839		following options:
840
841		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
842		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
843		CONFIG_RTC_MC13783	- use MC13783 RTC
844		CONFIG_RTC_MC146818	- use MC146818 RTC
845		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
846		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
847		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
848		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
849		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
850		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
851		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
852		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
853					  RV3029 RTC.
854
855		Note that if the RTC uses I2C, then the I2C interface
856		must also be configured. See I2C Support, below.
857
858- GPIO Support:
859		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
860		CONFIG_PCA953X_INFO	- enable pca953x info command
861
862		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
863		chip-ngpio pairs that tell the PCA953X driver the number of
864		pins supported by a particular chip.
865
866		Note that if the GPIO device uses I2C, then the I2C interface
867		must also be configured. See I2C Support, below.
868
869- Timestamp Support:
870
871		When CONFIG_TIMESTAMP is selected, the timestamp
872		(date and time) of an image is printed by image
873		commands like bootm or iminfo. This option is
874		automatically enabled when you select CONFIG_CMD_DATE .
875
876- Partition Support:
877		CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
878		and/or CONFIG_ISO_PARTITION and/or CONFIG_EFI_PARTITION
879
880		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
881		CONFIG_CMD_SCSI) you must configure support for at
882		least one partition type as well.
883
884- IDE Reset method:
885		CONFIG_IDE_RESET_ROUTINE - this is defined in several
886		board configurations files but used nowhere!
887
888		CONFIG_IDE_RESET - is this is defined, IDE Reset will
889		be performed by calling the function
890			ide_set_reset(int reset)
891		which has to be defined in a board specific file
892
893- ATAPI Support:
894		CONFIG_ATAPI
895
896		Set this to enable ATAPI support.
897
898- LBA48 Support
899		CONFIG_LBA48
900
901		Set this to enable support for disks larger than 137GB
902		Also look at CONFIG_SYS_64BIT_LBA.
903		Whithout these , LBA48 support uses 32bit variables and will 'only'
904		support disks up to 2.1TB.
905
906		CONFIG_SYS_64BIT_LBA:
907			When enabled, makes the IDE subsystem use 64bit sector addresses.
908			Default is 32bit.
909
910- SCSI Support:
911		At the moment only there is only support for the
912		SYM53C8XX SCSI controller; define
913		CONFIG_SCSI_SYM53C8XX to enable it.
914
915		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
916		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
917		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
918		maximum numbers of LUNs, SCSI ID's and target
919		devices.
920		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
921
922- NETWORK Support (PCI):
923		CONFIG_E1000
924		Support for Intel 8254x gigabit chips.
925
926		CONFIG_E1000_FALLBACK_MAC
927		default MAC for empty EEPROM after production.
928
929		CONFIG_EEPRO100
930		Support for Intel 82557/82559/82559ER chips.
931		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
932		write routine for first time initialisation.
933
934		CONFIG_TULIP
935		Support for Digital 2114x chips.
936		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
937		modem chip initialisation (KS8761/QS6611).
938
939		CONFIG_NATSEMI
940		Support for National dp83815 chips.
941
942		CONFIG_NS8382X
943		Support for National dp8382[01] gigabit chips.
944
945- NETWORK Support (other):
946
947		CONFIG_DRIVER_AT91EMAC
948		Support for AT91RM9200 EMAC.
949
950			CONFIG_RMII
951			Define this to use reduced MII inteface
952
953			CONFIG_DRIVER_AT91EMAC_QUIET
954			If this defined, the driver is quiet.
955			The driver doen't show link status messages.
956
957		CONFIG_DRIVER_LAN91C96
958		Support for SMSC's LAN91C96 chips.
959
960			CONFIG_LAN91C96_BASE
961			Define this to hold the physical address
962			of the LAN91C96's I/O space
963
964			CONFIG_LAN91C96_USE_32_BIT
965			Define this to enable 32 bit addressing
966
967		CONFIG_DRIVER_SMC91111
968		Support for SMSC's LAN91C111 chip
969
970			CONFIG_SMC91111_BASE
971			Define this to hold the physical address
972			of the device (I/O space)
973
974			CONFIG_SMC_USE_32_BIT
975			Define this if data bus is 32 bits
976
977			CONFIG_SMC_USE_IOFUNCS
978			Define this to use i/o functions instead of macros
979			(some hardware wont work with macros)
980
981		CONFIG_FTGMAC100
982		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
983
984			CONFIG_FTGMAC100_EGIGA
985			Define this to use GE link update with gigabit PHY.
986			Define this if FTGMAC100 is connected to gigabit PHY.
987			If your system has 10/100 PHY only, it might not occur
988			wrong behavior. Because PHY usually return timeout or
989			useless data when polling gigabit status and gigabit
990			control registers. This behavior won't affect the
991			correctnessof 10/100 link speed update.
992
993		CONFIG_SMC911X
994		Support for SMSC's LAN911x and LAN921x chips
995
996			CONFIG_SMC911X_BASE
997			Define this to hold the physical address
998			of the device (I/O space)
999
1000			CONFIG_SMC911X_32_BIT
1001			Define this if data bus is 32 bits
1002
1003			CONFIG_SMC911X_16_BIT
1004			Define this if data bus is 16 bits. If your processor
1005			automatically converts one 32 bit word to two 16 bit
1006			words you may also try CONFIG_SMC911X_32_BIT.
1007
1008		CONFIG_SH_ETHER
1009		Support for Renesas on-chip Ethernet controller
1010
1011			CONFIG_SH_ETHER_USE_PORT
1012			Define the number of ports to be used
1013
1014			CONFIG_SH_ETHER_PHY_ADDR
1015			Define the ETH PHY's address
1016
1017			CONFIG_SH_ETHER_CACHE_WRITEBACK
1018			If this option is set, the driver enables cache flush.
1019
1020- USB Support:
1021		At the moment only the UHCI host controller is
1022		supported (PIP405, MIP405, MPC5200); define
1023		CONFIG_USB_UHCI to enable it.
1024		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1025		and define CONFIG_USB_STORAGE to enable the USB
1026		storage devices.
1027		Note:
1028		Supported are USB Keyboards and USB Floppy drives
1029		(TEAC FD-05PUB).
1030		MPC5200 USB requires additional defines:
1031			CONFIG_USB_CLOCK
1032				for 528 MHz Clock: 0x0001bbbb
1033			CONFIG_PSC3_USB
1034				for USB on PSC3
1035			CONFIG_USB_CONFIG
1036				for differential drivers: 0x00001000
1037				for single ended drivers: 0x00005000
1038				for differential drivers on PSC3: 0x00000100
1039				for single ended drivers on PSC3: 0x00004100
1040			CONFIG_SYS_USB_EVENT_POLL
1041				May be defined to allow interrupt polling
1042				instead of using asynchronous interrupts
1043
1044- USB Device:
1045		Define the below if you wish to use the USB console.
1046		Once firmware is rebuilt from a serial console issue the
1047		command "setenv stdin usbtty; setenv stdout usbtty" and
1048		attach your USB cable. The Unix command "dmesg" should print
1049		it has found a new device. The environment variable usbtty
1050		can be set to gserial or cdc_acm to enable your device to
1051		appear to a USB host as a Linux gserial device or a
1052		Common Device Class Abstract Control Model serial device.
1053		If you select usbtty = gserial you should be able to enumerate
1054		a Linux host by
1055		# modprobe usbserial vendor=0xVendorID product=0xProductID
1056		else if using cdc_acm, simply setting the environment
1057		variable usbtty to be cdc_acm should suffice. The following
1058		might be defined in YourBoardName.h
1059
1060			CONFIG_USB_DEVICE
1061			Define this to build a UDC device
1062
1063			CONFIG_USB_TTY
1064			Define this to have a tty type of device available to
1065			talk to the UDC device
1066
1067			CONFIG_SYS_CONSOLE_IS_IN_ENV
1068			Define this if you want stdin, stdout &/or stderr to
1069			be set to usbtty.
1070
1071			mpc8xx:
1072				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1073				Derive USB clock from external clock "blah"
1074				- CONFIG_SYS_USB_EXTC_CLK 0x02
1075
1076				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1077				Derive USB clock from brgclk
1078				- CONFIG_SYS_USB_BRG_CLK 0x04
1079
1080		If you have a USB-IF assigned VendorID then you may wish to
1081		define your own vendor specific values either in BoardName.h
1082		or directly in usbd_vendor_info.h. If you don't define
1083		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1084		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1085		should pretend to be a Linux device to it's target host.
1086
1087			CONFIG_USBD_MANUFACTURER
1088			Define this string as the name of your company for
1089			- CONFIG_USBD_MANUFACTURER "my company"
1090
1091			CONFIG_USBD_PRODUCT_NAME
1092			Define this string as the name of your product
1093			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1094
1095			CONFIG_USBD_VENDORID
1096			Define this as your assigned Vendor ID from the USB
1097			Implementors Forum. This *must* be a genuine Vendor ID
1098			to avoid polluting the USB namespace.
1099			- CONFIG_USBD_VENDORID 0xFFFF
1100
1101			CONFIG_USBD_PRODUCTID
1102			Define this as the unique Product ID
1103			for your device
1104			- CONFIG_USBD_PRODUCTID 0xFFFF
1105
1106
1107- MMC Support:
1108		The MMC controller on the Intel PXA is supported. To
1109		enable this define CONFIG_MMC. The MMC can be
1110		accessed from the boot prompt by mapping the device
1111		to physical memory similar to flash. Command line is
1112		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1113		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1114
1115		CONFIG_SH_MMCIF
1116		Support for Renesas on-chip MMCIF controller
1117
1118			CONFIG_SH_MMCIF_ADDR
1119			Define the base address of MMCIF registers
1120
1121			CONFIG_SH_MMCIF_CLK
1122			Define the clock frequency for MMCIF
1123
1124- Journaling Flash filesystem support:
1125		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1126		CONFIG_JFFS2_NAND_DEV
1127		Define these for a default partition on a NAND device
1128
1129		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1130		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1131		Define these for a default partition on a NOR device
1132
1133		CONFIG_SYS_JFFS_CUSTOM_PART
1134		Define this to create an own partition. You have to provide a
1135		function struct part_info* jffs2_part_info(int part_num)
1136
1137		If you define only one JFFS2 partition you may also want to
1138		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1139		to disable the command chpart. This is the default when you
1140		have not defined a custom partition
1141
1142- Keyboard Support:
1143		CONFIG_ISA_KEYBOARD
1144
1145		Define this to enable standard (PC-Style) keyboard
1146		support
1147
1148		CONFIG_I8042_KBD
1149		Standard PC keyboard driver with US (is default) and
1150		GERMAN key layout (switch via environment 'keymap=de') support.
1151		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1152		for cfb_console. Supports cursor blinking.
1153
1154- Video support:
1155		CONFIG_VIDEO
1156
1157		Define this to enable video support (for output to
1158		video).
1159
1160		CONFIG_VIDEO_CT69000
1161
1162		Enable Chips & Technologies 69000 Video chip
1163
1164		CONFIG_VIDEO_SMI_LYNXEM
1165		Enable Silicon Motion SMI 712/710/810 Video chip. The
1166		video output is selected via environment 'videoout'
1167		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1168		assumed.
1169
1170		For the CT69000 and SMI_LYNXEM drivers, videomode is
1171		selected via environment 'videomode'. Two different ways
1172		are possible:
1173		- "videomode=num"   'num' is a standard LiLo mode numbers.
1174		Following standard modes are supported	(* is default):
1175
1176		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1177		-------------+---------------------------------------------
1178		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1179		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1180		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1181		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1182		-------------+---------------------------------------------
1183		(i.e. setenv videomode 317; saveenv; reset;)
1184
1185		- "videomode=bootargs" all the video parameters are parsed
1186		from the bootargs. (See drivers/video/videomodes.c)
1187
1188
1189		CONFIG_VIDEO_SED13806
1190		Enable Epson SED13806 driver. This driver supports 8bpp
1191		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1192		or CONFIG_VIDEO_SED13806_16BPP
1193
1194		CONFIG_FSL_DIU_FB
1195		Enable the Freescale DIU video driver.	Reference boards for
1196		SOCs that have a DIU should define this macro to enable DIU
1197		support, and should also define these other macros:
1198
1199			CONFIG_SYS_DIU_ADDR
1200			CONFIG_VIDEO
1201			CONFIG_CMD_BMP
1202			CONFIG_CFB_CONSOLE
1203			CONFIG_VIDEO_SW_CURSOR
1204			CONFIG_VGA_AS_SINGLE_DEVICE
1205			CONFIG_VIDEO_LOGO
1206			CONFIG_VIDEO_BMP_LOGO
1207
1208		The DIU driver will look for the 'video-mode' environment
1209		variable, and if defined, enable the DIU as a console during
1210		boot.  See the documentation file README.video for a
1211		description of this variable.
1212
1213- Keyboard Support:
1214		CONFIG_KEYBOARD
1215
1216		Define this to enable a custom keyboard support.
1217		This simply calls drv_keyboard_init() which must be
1218		defined in your board-specific files.
1219		The only board using this so far is RBC823.
1220
1221- LCD Support:	CONFIG_LCD
1222
1223		Define this to enable LCD support (for output to LCD
1224		display); also select one of the supported displays
1225		by defining one of these:
1226
1227		CONFIG_ATMEL_LCD:
1228
1229			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1230
1231		CONFIG_NEC_NL6448AC33:
1232
1233			NEC NL6448AC33-18. Active, color, single scan.
1234
1235		CONFIG_NEC_NL6448BC20
1236
1237			NEC NL6448BC20-08. 6.5", 640x480.
1238			Active, color, single scan.
1239
1240		CONFIG_NEC_NL6448BC33_54
1241
1242			NEC NL6448BC33-54. 10.4", 640x480.
1243			Active, color, single scan.
1244
1245		CONFIG_SHARP_16x9
1246
1247			Sharp 320x240. Active, color, single scan.
1248			It isn't 16x9, and I am not sure what it is.
1249
1250		CONFIG_SHARP_LQ64D341
1251
1252			Sharp LQ64D341 display, 640x480.
1253			Active, color, single scan.
1254
1255		CONFIG_HLD1045
1256
1257			HLD1045 display, 640x480.
1258			Active, color, single scan.
1259
1260		CONFIG_OPTREX_BW
1261
1262			Optrex	 CBL50840-2 NF-FW 99 22 M5
1263			or
1264			Hitachi	 LMG6912RPFC-00T
1265			or
1266			Hitachi	 SP14Q002
1267
1268			320x240. Black & white.
1269
1270		Normally display is black on white background; define
1271		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1272
1273- Splash Screen Support: CONFIG_SPLASH_SCREEN
1274
1275		If this option is set, the environment is checked for
1276		a variable "splashimage". If found, the usual display
1277		of logo, copyright and system information on the LCD
1278		is suppressed and the BMP image at the address
1279		specified in "splashimage" is loaded instead. The
1280		console is redirected to the "nulldev", too. This
1281		allows for a "silent" boot where a splash screen is
1282		loaded very quickly after power-on.
1283
1284		CONFIG_SPLASH_SCREEN_ALIGN
1285
1286		If this option is set the splash image can be freely positioned
1287		on the screen. Environment variable "splashpos" specifies the
1288		position as "x,y". If a positive number is given it is used as
1289		number of pixel from left/top. If a negative number is given it
1290		is used as number of pixel from right/bottom. You can also
1291		specify 'm' for centering the image.
1292
1293		Example:
1294		setenv splashpos m,m
1295			=> image at center of screen
1296
1297		setenv splashpos 30,20
1298			=> image at x = 30 and y = 20
1299
1300		setenv splashpos -10,m
1301			=> vertically centered image
1302			   at x = dspWidth - bmpWidth - 9
1303
1304- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1305
1306		If this option is set, additionally to standard BMP
1307		images, gzipped BMP images can be displayed via the
1308		splashscreen support or the bmp command.
1309
1310- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1311
1312		If this option is set, 8-bit RLE compressed BMP images
1313		can be displayed via the splashscreen support or the
1314		bmp command.
1315
1316- Compression support:
1317		CONFIG_BZIP2
1318
1319		If this option is set, support for bzip2 compressed
1320		images is included. If not, only uncompressed and gzip
1321		compressed images are supported.
1322
1323		NOTE: the bzip2 algorithm requires a lot of RAM, so
1324		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1325		be at least 4MB.
1326
1327		CONFIG_LZMA
1328
1329		If this option is set, support for lzma compressed
1330		images is included.
1331
1332		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1333		requires an amount of dynamic memory that is given by the
1334		formula:
1335
1336			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1337
1338		Where lc and lp stand for, respectively, Literal context bits
1339		and Literal pos bits.
1340
1341		This value is upper-bounded by 14MB in the worst case. Anyway,
1342		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1343		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1344		a very small buffer.
1345
1346		Use the lzmainfo tool to determinate the lc and lp values and
1347		then calculate the amount of needed dynamic memory (ensuring
1348		the appropriate CONFIG_SYS_MALLOC_LEN value).
1349
1350- MII/PHY support:
1351		CONFIG_PHY_ADDR
1352
1353		The address of PHY on MII bus.
1354
1355		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1356
1357		The clock frequency of the MII bus
1358
1359		CONFIG_PHY_GIGE
1360
1361		If this option is set, support for speed/duplex
1362		detection of gigabit PHY is included.
1363
1364		CONFIG_PHY_RESET_DELAY
1365
1366		Some PHY like Intel LXT971A need extra delay after
1367		reset before any MII register access is possible.
1368		For such PHY, set this option to the usec delay
1369		required. (minimum 300usec for LXT971A)
1370
1371		CONFIG_PHY_CMD_DELAY (ppc4xx)
1372
1373		Some PHY like Intel LXT971A need extra delay after
1374		command issued before MII status register can be read
1375
1376- Ethernet address:
1377		CONFIG_ETHADDR
1378		CONFIG_ETH1ADDR
1379		CONFIG_ETH2ADDR
1380		CONFIG_ETH3ADDR
1381		CONFIG_ETH4ADDR
1382		CONFIG_ETH5ADDR
1383
1384		Define a default value for Ethernet address to use
1385		for the respective Ethernet interface, in case this
1386		is not determined automatically.
1387
1388- IP address:
1389		CONFIG_IPADDR
1390
1391		Define a default value for the IP address to use for
1392		the default Ethernet interface, in case this is not
1393		determined through e.g. bootp.
1394
1395- Server IP address:
1396		CONFIG_SERVERIP
1397
1398		Defines a default value for the IP address of a TFTP
1399		server to contact when using the "tftboot" command.
1400
1401		CONFIG_KEEP_SERVERADDR
1402
1403		Keeps the server's MAC address, in the env 'serveraddr'
1404		for passing to bootargs (like Linux's netconsole option)
1405
1406- Multicast TFTP Mode:
1407		CONFIG_MCAST_TFTP
1408
1409		Defines whether you want to support multicast TFTP as per
1410		rfc-2090; for example to work with atftp.  Lets lots of targets
1411		tftp down the same boot image concurrently.  Note: the Ethernet
1412		driver in use must provide a function: mcast() to join/leave a
1413		multicast group.
1414
1415- BOOTP Recovery Mode:
1416		CONFIG_BOOTP_RANDOM_DELAY
1417
1418		If you have many targets in a network that try to
1419		boot using BOOTP, you may want to avoid that all
1420		systems send out BOOTP requests at precisely the same
1421		moment (which would happen for instance at recovery
1422		from a power failure, when all systems will try to
1423		boot, thus flooding the BOOTP server. Defining
1424		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1425		inserted before sending out BOOTP requests. The
1426		following delays are inserted then:
1427
1428		1st BOOTP request:	delay 0 ... 1 sec
1429		2nd BOOTP request:	delay 0 ... 2 sec
1430		3rd BOOTP request:	delay 0 ... 4 sec
1431		4th and following
1432		BOOTP requests:		delay 0 ... 8 sec
1433
1434- DHCP Advanced Options:
1435		You can fine tune the DHCP functionality by defining
1436		CONFIG_BOOTP_* symbols:
1437
1438		CONFIG_BOOTP_SUBNETMASK
1439		CONFIG_BOOTP_GATEWAY
1440		CONFIG_BOOTP_HOSTNAME
1441		CONFIG_BOOTP_NISDOMAIN
1442		CONFIG_BOOTP_BOOTPATH
1443		CONFIG_BOOTP_BOOTFILESIZE
1444		CONFIG_BOOTP_DNS
1445		CONFIG_BOOTP_DNS2
1446		CONFIG_BOOTP_SEND_HOSTNAME
1447		CONFIG_BOOTP_NTPSERVER
1448		CONFIG_BOOTP_TIMEOFFSET
1449		CONFIG_BOOTP_VENDOREX
1450
1451		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1452		environment variable, not the BOOTP server.
1453
1454		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1455		serverip from a DHCP server, it is possible that more
1456		than one DNS serverip is offered to the client.
1457		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1458		serverip will be stored in the additional environment
1459		variable "dnsip2". The first DNS serverip is always
1460		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1461		is defined.
1462
1463		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1464		to do a dynamic update of a DNS server. To do this, they
1465		need the hostname of the DHCP requester.
1466		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1467		of the "hostname" environment variable is passed as
1468		option 12 to the DHCP server.
1469
1470		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1471
1472		A 32bit value in microseconds for a delay between
1473		receiving a "DHCP Offer" and sending the "DHCP Request".
1474		This fixes a problem with certain DHCP servers that don't
1475		respond 100% of the time to a "DHCP request". E.g. On an
1476		AT91RM9200 processor running at 180MHz, this delay needed
1477		to be *at least* 15,000 usec before a Windows Server 2003
1478		DHCP server would reply 100% of the time. I recommend at
1479		least 50,000 usec to be safe. The alternative is to hope
1480		that one of the retries will be successful but note that
1481		the DHCP timeout and retry process takes a longer than
1482		this delay.
1483
1484 - CDP Options:
1485		CONFIG_CDP_DEVICE_ID
1486
1487		The device id used in CDP trigger frames.
1488
1489		CONFIG_CDP_DEVICE_ID_PREFIX
1490
1491		A two character string which is prefixed to the MAC address
1492		of the device.
1493
1494		CONFIG_CDP_PORT_ID
1495
1496		A printf format string which contains the ascii name of
1497		the port. Normally is set to "eth%d" which sets
1498		eth0 for the first Ethernet, eth1 for the second etc.
1499
1500		CONFIG_CDP_CAPABILITIES
1501
1502		A 32bit integer which indicates the device capabilities;
1503		0x00000010 for a normal host which does not forwards.
1504
1505		CONFIG_CDP_VERSION
1506
1507		An ascii string containing the version of the software.
1508
1509		CONFIG_CDP_PLATFORM
1510
1511		An ascii string containing the name of the platform.
1512
1513		CONFIG_CDP_TRIGGER
1514
1515		A 32bit integer sent on the trigger.
1516
1517		CONFIG_CDP_POWER_CONSUMPTION
1518
1519		A 16bit integer containing the power consumption of the
1520		device in .1 of milliwatts.
1521
1522		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1523
1524		A byte containing the id of the VLAN.
1525
1526- Status LED:	CONFIG_STATUS_LED
1527
1528		Several configurations allow to display the current
1529		status using a LED. For instance, the LED will blink
1530		fast while running U-Boot code, stop blinking as
1531		soon as a reply to a BOOTP request was received, and
1532		start blinking slow once the Linux kernel is running
1533		(supported by a status LED driver in the Linux
1534		kernel). Defining CONFIG_STATUS_LED enables this
1535		feature in U-Boot.
1536
1537- CAN Support:	CONFIG_CAN_DRIVER
1538
1539		Defining CONFIG_CAN_DRIVER enables CAN driver support
1540		on those systems that support this (optional)
1541		feature, like the TQM8xxL modules.
1542
1543- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1544
1545		These enable I2C serial bus commands. Defining either of
1546		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1547		include the appropriate I2C driver for the selected CPU.
1548
1549		This will allow you to use i2c commands at the u-boot
1550		command line (as long as you set CONFIG_CMD_I2C in
1551		CONFIG_COMMANDS) and communicate with i2c based realtime
1552		clock chips. See common/cmd_i2c.c for a description of the
1553		command line interface.
1554
1555		CONFIG_HARD_I2C selects a hardware I2C controller.
1556
1557		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1558		bit-banging) driver instead of CPM or similar hardware
1559		support for I2C.
1560
1561		There are several other quantities that must also be
1562		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1563
1564		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1565		to be the frequency (in Hz) at which you wish your i2c bus
1566		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1567		the CPU's i2c node address).
1568
1569		Now, the u-boot i2c code for the mpc8xx
1570		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1571		and so its address should therefore be cleared to 0 (See,
1572		eg, MPC823e User's Manual p.16-473). So, set
1573		CONFIG_SYS_I2C_SLAVE to 0.
1574
1575		CONFIG_SYS_I2C_INIT_MPC5XXX
1576
1577		When a board is reset during an i2c bus transfer
1578		chips might think that the current transfer is still
1579		in progress.  Reset the slave devices by sending start
1580		commands until the slave device responds.
1581
1582		That's all that's required for CONFIG_HARD_I2C.
1583
1584		If you use the software i2c interface (CONFIG_SOFT_I2C)
1585		then the following macros need to be defined (examples are
1586		from include/configs/lwmon.h):
1587
1588		I2C_INIT
1589
1590		(Optional). Any commands necessary to enable the I2C
1591		controller or configure ports.
1592
1593		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1594
1595		I2C_PORT
1596
1597		(Only for MPC8260 CPU). The I/O port to use (the code
1598		assumes both bits are on the same port). Valid values
1599		are 0..3 for ports A..D.
1600
1601		I2C_ACTIVE
1602
1603		The code necessary to make the I2C data line active
1604		(driven).  If the data line is open collector, this
1605		define can be null.
1606
1607		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1608
1609		I2C_TRISTATE
1610
1611		The code necessary to make the I2C data line tri-stated
1612		(inactive).  If the data line is open collector, this
1613		define can be null.
1614
1615		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1616
1617		I2C_READ
1618
1619		Code that returns TRUE if the I2C data line is high,
1620		FALSE if it is low.
1621
1622		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1623
1624		I2C_SDA(bit)
1625
1626		If <bit> is TRUE, sets the I2C data line high. If it
1627		is FALSE, it clears it (low).
1628
1629		eg: #define I2C_SDA(bit) \
1630			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1631			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1632
1633		I2C_SCL(bit)
1634
1635		If <bit> is TRUE, sets the I2C clock line high. If it
1636		is FALSE, it clears it (low).
1637
1638		eg: #define I2C_SCL(bit) \
1639			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1640			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1641
1642		I2C_DELAY
1643
1644		This delay is invoked four times per clock cycle so this
1645		controls the rate of data transfer.  The data rate thus
1646		is 1 / (I2C_DELAY * 4). Often defined to be something
1647		like:
1648
1649		#define I2C_DELAY  udelay(2)
1650
1651		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1652
1653		If your arch supports the generic GPIO framework (asm/gpio.h),
1654		then you may alternatively define the two GPIOs that are to be
1655		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1656		have GPIO-based defaults assigned to them as appropriate.
1657
1658		You should define these to the GPIO value as given directly to
1659		the generic GPIO functions.
1660
1661		CONFIG_SYS_I2C_INIT_BOARD
1662
1663		When a board is reset during an i2c bus transfer
1664		chips might think that the current transfer is still
1665		in progress. On some boards it is possible to access
1666		the i2c SCLK line directly, either by using the
1667		processor pin as a GPIO or by having a second pin
1668		connected to the bus. If this option is defined a
1669		custom i2c_init_board() routine in boards/xxx/board.c
1670		is run early in the boot sequence.
1671
1672		CONFIG_SYS_I2C_BOARD_LATE_INIT
1673
1674		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
1675		defined a custom i2c_board_late_init() routine in
1676		boards/xxx/board.c is run AFTER the operations in i2c_init()
1677		is completed. This callpoint can be used to unreset i2c bus
1678		using CPU i2c controller register accesses for CPUs whose i2c
1679		controller provide such a method. It is called at the end of
1680		i2c_init() to allow i2c_init operations to setup the i2c bus
1681		controller on the CPU (e.g. setting bus speed & slave address).
1682
1683		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1684
1685		This option enables configuration of bi_iic_fast[] flags
1686		in u-boot bd_info structure based on u-boot environment
1687		variable "i2cfast". (see also i2cfast)
1688
1689		CONFIG_I2C_MULTI_BUS
1690
1691		This option allows the use of multiple I2C buses, each of which
1692		must have a controller.  At any point in time, only one bus is
1693		active.  To switch to a different bus, use the 'i2c dev' command.
1694		Note that bus numbering is zero-based.
1695
1696		CONFIG_SYS_I2C_NOPROBES
1697
1698		This option specifies a list of I2C devices that will be skipped
1699		when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1700		is set, specify a list of bus-device pairs.  Otherwise, specify
1701		a 1D array of device addresses
1702
1703		e.g.
1704			#undef	CONFIG_I2C_MULTI_BUS
1705			#define CONFIG_SYS_I2C_NOPROBES	{0x50,0x68}
1706
1707		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1708
1709			#define	CONFIG_I2C_MULTI_BUS
1710			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1711
1712		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1713
1714		CONFIG_SYS_SPD_BUS_NUM
1715
1716		If defined, then this indicates the I2C bus number for DDR SPD.
1717		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1718
1719		CONFIG_SYS_RTC_BUS_NUM
1720
1721		If defined, then this indicates the I2C bus number for the RTC.
1722		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1723
1724		CONFIG_SYS_DTT_BUS_NUM
1725
1726		If defined, then this indicates the I2C bus number for the DTT.
1727		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1728
1729		CONFIG_SYS_I2C_DTT_ADDR:
1730
1731		If defined, specifies the I2C address of the DTT device.
1732		If not defined, then U-Boot uses predefined value for
1733		specified DTT device.
1734
1735		CONFIG_FSL_I2C
1736
1737		Define this option if you want to use Freescale's I2C driver in
1738		drivers/i2c/fsl_i2c.c.
1739
1740		CONFIG_I2C_MUX
1741
1742		Define this option if you have I2C devices reached over 1 .. n
1743		I2C Muxes like the pca9544a. This option addes a new I2C
1744		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
1745		new I2C Bus to the existing I2C Busses. If you select the
1746		new Bus with "i2c dev", u-bbot sends first the commandos for
1747		the muxes to activate this new "bus".
1748
1749		CONFIG_I2C_MULTI_BUS must be also defined, to use this
1750		feature!
1751
1752		Example:
1753		Adding a new I2C Bus reached over 2 pca9544a muxes
1754			The First mux with address 70 and channel 6
1755			The Second mux with address 71 and channel 4
1756
1757		=> i2c bus pca9544a:70:6:pca9544a:71:4
1758
1759		Use the "i2c bus" command without parameter, to get a list
1760		of I2C Busses with muxes:
1761
1762		=> i2c bus
1763		Busses reached over muxes:
1764		Bus ID: 2
1765		  reached over Mux(es):
1766		    pca9544a@70 ch: 4
1767		Bus ID: 3
1768		  reached over Mux(es):
1769		    pca9544a@70 ch: 6
1770		    pca9544a@71 ch: 4
1771		=>
1772
1773		If you now switch to the new I2C Bus 3 with "i2c dev 3"
1774		u-boot first sends the command to the mux@70 to enable
1775		channel 6, and then the command to the mux@71 to enable
1776		the channel 4.
1777
1778		After that, you can use the "normal" i2c commands as
1779		usual to communicate with your I2C devices behind
1780		the 2 muxes.
1781
1782		This option is actually implemented for the bitbanging
1783		algorithm in common/soft_i2c.c and for the Hardware I2C
1784		Bus on the MPC8260. But it should be not so difficult
1785		to add this option to other architectures.
1786
1787		CONFIG_SOFT_I2C_READ_REPEATED_START
1788
1789		defining this will force the i2c_read() function in
1790		the soft_i2c driver to perform an I2C repeated start
1791		between writing the address pointer and reading the
1792		data.  If this define is omitted the default behaviour
1793		of doing a stop-start sequence will be used.  Most I2C
1794		devices can use either method, but some require one or
1795		the other.
1796
1797- SPI Support:	CONFIG_SPI
1798
1799		Enables SPI driver (so far only tested with
1800		SPI EEPROM, also an instance works with Crystal A/D and
1801		D/As on the SACSng board)
1802
1803		CONFIG_SH_SPI
1804
1805		Enables the driver for SPI controller on SuperH. Currently
1806		only SH7757 is supported.
1807
1808		CONFIG_SPI_X
1809
1810		Enables extended (16-bit) SPI EEPROM addressing.
1811		(symmetrical to CONFIG_I2C_X)
1812
1813		CONFIG_SOFT_SPI
1814
1815		Enables a software (bit-bang) SPI driver rather than
1816		using hardware support. This is a general purpose
1817		driver that only requires three general I/O port pins
1818		(two outputs, one input) to function. If this is
1819		defined, the board configuration must define several
1820		SPI configuration items (port pins to use, etc). For
1821		an example, see include/configs/sacsng.h.
1822
1823		CONFIG_HARD_SPI
1824
1825		Enables a hardware SPI driver for general-purpose reads
1826		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1827		must define a list of chip-select function pointers.
1828		Currently supported on some MPC8xxx processors.  For an
1829		example, see include/configs/mpc8349emds.h.
1830
1831		CONFIG_MXC_SPI
1832
1833		Enables the driver for the SPI controllers on i.MX and MXC
1834		SoCs. Currently only i.MX31 is supported.
1835
1836- FPGA Support: CONFIG_FPGA
1837
1838		Enables FPGA subsystem.
1839
1840		CONFIG_FPGA_<vendor>
1841
1842		Enables support for specific chip vendors.
1843		(ALTERA, XILINX)
1844
1845		CONFIG_FPGA_<family>
1846
1847		Enables support for FPGA family.
1848		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1849
1850		CONFIG_FPGA_COUNT
1851
1852		Specify the number of FPGA devices to support.
1853
1854		CONFIG_SYS_FPGA_PROG_FEEDBACK
1855
1856		Enable printing of hash marks during FPGA configuration.
1857
1858		CONFIG_SYS_FPGA_CHECK_BUSY
1859
1860		Enable checks on FPGA configuration interface busy
1861		status by the configuration function. This option
1862		will require a board or device specific function to
1863		be written.
1864
1865		CONFIG_FPGA_DELAY
1866
1867		If defined, a function that provides delays in the FPGA
1868		configuration driver.
1869
1870		CONFIG_SYS_FPGA_CHECK_CTRLC
1871		Allow Control-C to interrupt FPGA configuration
1872
1873		CONFIG_SYS_FPGA_CHECK_ERROR
1874
1875		Check for configuration errors during FPGA bitfile
1876		loading. For example, abort during Virtex II
1877		configuration if the INIT_B line goes low (which
1878		indicated a CRC error).
1879
1880		CONFIG_SYS_FPGA_WAIT_INIT
1881
1882		Maximum time to wait for the INIT_B line to deassert
1883		after PROB_B has been deasserted during a Virtex II
1884		FPGA configuration sequence. The default time is 500
1885		ms.
1886
1887		CONFIG_SYS_FPGA_WAIT_BUSY
1888
1889		Maximum time to wait for BUSY to deassert during
1890		Virtex II FPGA configuration. The default is 5 ms.
1891
1892		CONFIG_SYS_FPGA_WAIT_CONFIG
1893
1894		Time to wait after FPGA configuration. The default is
1895		200 ms.
1896
1897- Configuration Management:
1898		CONFIG_IDENT_STRING
1899
1900		If defined, this string will be added to the U-Boot
1901		version information (U_BOOT_VERSION)
1902
1903- Vendor Parameter Protection:
1904
1905		U-Boot considers the values of the environment
1906		variables "serial#" (Board Serial Number) and
1907		"ethaddr" (Ethernet Address) to be parameters that
1908		are set once by the board vendor / manufacturer, and
1909		protects these variables from casual modification by
1910		the user. Once set, these variables are read-only,
1911		and write or delete attempts are rejected. You can
1912		change this behaviour:
1913
1914		If CONFIG_ENV_OVERWRITE is #defined in your config
1915		file, the write protection for vendor parameters is
1916		completely disabled. Anybody can change or delete
1917		these parameters.
1918
1919		Alternatively, if you #define _both_ CONFIG_ETHADDR
1920		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1921		Ethernet address is installed in the environment,
1922		which can be changed exactly ONCE by the user. [The
1923		serial# is unaffected by this, i. e. it remains
1924		read-only.]
1925
1926- Protected RAM:
1927		CONFIG_PRAM
1928
1929		Define this variable to enable the reservation of
1930		"protected RAM", i. e. RAM which is not overwritten
1931		by U-Boot. Define CONFIG_PRAM to hold the number of
1932		kB you want to reserve for pRAM. You can overwrite
1933		this default value by defining an environment
1934		variable "pram" to the number of kB you want to
1935		reserve. Note that the board info structure will
1936		still show the full amount of RAM. If pRAM is
1937		reserved, a new environment variable "mem" will
1938		automatically be defined to hold the amount of
1939		remaining RAM in a form that can be passed as boot
1940		argument to Linux, for instance like that:
1941
1942			setenv bootargs ... mem=\${mem}
1943			saveenv
1944
1945		This way you can tell Linux not to use this memory,
1946		either, which results in a memory region that will
1947		not be affected by reboots.
1948
1949		*WARNING* If your board configuration uses automatic
1950		detection of the RAM size, you must make sure that
1951		this memory test is non-destructive. So far, the
1952		following board configurations are known to be
1953		"pRAM-clean":
1954
1955			ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
1956			HERMES, IP860, RPXlite, LWMON, LANTEC,
1957			FLAGADM, TQM8260
1958
1959- Error Recovery:
1960		CONFIG_PANIC_HANG
1961
1962		Define this variable to stop the system in case of a
1963		fatal error, so that you have to reset it manually.
1964		This is probably NOT a good idea for an embedded
1965		system where you want the system to reboot
1966		automatically as fast as possible, but it may be
1967		useful during development since you can try to debug
1968		the conditions that lead to the situation.
1969
1970		CONFIG_NET_RETRY_COUNT
1971
1972		This variable defines the number of retries for
1973		network operations like ARP, RARP, TFTP, or BOOTP
1974		before giving up the operation. If not defined, a
1975		default value of 5 is used.
1976
1977		CONFIG_ARP_TIMEOUT
1978
1979		Timeout waiting for an ARP reply in milliseconds.
1980
1981- Command Interpreter:
1982		CONFIG_AUTO_COMPLETE
1983
1984		Enable auto completion of commands using TAB.
1985
1986		Note that this feature has NOT been implemented yet
1987		for the "hush" shell.
1988
1989
1990		CONFIG_SYS_HUSH_PARSER
1991
1992		Define this variable to enable the "hush" shell (from
1993		Busybox) as command line interpreter, thus enabling
1994		powerful command line syntax like
1995		if...then...else...fi conditionals or `&&' and '||'
1996		constructs ("shell scripts").
1997
1998		If undefined, you get the old, much simpler behaviour
1999		with a somewhat smaller memory footprint.
2000
2001
2002		CONFIG_SYS_PROMPT_HUSH_PS2
2003
2004		This defines the secondary prompt string, which is
2005		printed when the command interpreter needs more input
2006		to complete a command. Usually "> ".
2007
2008	Note:
2009
2010		In the current implementation, the local variables
2011		space and global environment variables space are
2012		separated. Local variables are those you define by
2013		simply typing `name=value'. To access a local
2014		variable later on, you have write `$name' or
2015		`${name}'; to execute the contents of a variable
2016		directly type `$name' at the command prompt.
2017
2018		Global environment variables are those you use
2019		setenv/printenv to work with. To run a command stored
2020		in such a variable, you need to use the run command,
2021		and you must not use the '$' sign to access them.
2022
2023		To store commands and special characters in a
2024		variable, please use double quotation marks
2025		surrounding the whole text of the variable, instead
2026		of the backslashes before semicolons and special
2027		symbols.
2028
2029- Commandline Editing and History:
2030		CONFIG_CMDLINE_EDITING
2031
2032		Enable editing and History functions for interactive
2033		commandline input operations
2034
2035- Default Environment:
2036		CONFIG_EXTRA_ENV_SETTINGS
2037
2038		Define this to contain any number of null terminated
2039		strings (variable = value pairs) that will be part of
2040		the default environment compiled into the boot image.
2041
2042		For example, place something like this in your
2043		board's config file:
2044
2045		#define CONFIG_EXTRA_ENV_SETTINGS \
2046			"myvar1=value1\0" \
2047			"myvar2=value2\0"
2048
2049		Warning: This method is based on knowledge about the
2050		internal format how the environment is stored by the
2051		U-Boot code. This is NOT an official, exported
2052		interface! Although it is unlikely that this format
2053		will change soon, there is no guarantee either.
2054		You better know what you are doing here.
2055
2056		Note: overly (ab)use of the default environment is
2057		discouraged. Make sure to check other ways to preset
2058		the environment like the "source" command or the
2059		boot command first.
2060
2061- DataFlash Support:
2062		CONFIG_HAS_DATAFLASH
2063
2064		Defining this option enables DataFlash features and
2065		allows to read/write in Dataflash via the standard
2066		commands cp, md...
2067
2068- SystemACE Support:
2069		CONFIG_SYSTEMACE
2070
2071		Adding this option adds support for Xilinx SystemACE
2072		chips attached via some sort of local bus. The address
2073		of the chip must also be defined in the
2074		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2075
2076		#define CONFIG_SYSTEMACE
2077		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2078
2079		When SystemACE support is added, the "ace" device type
2080		becomes available to the fat commands, i.e. fatls.
2081
2082- TFTP Fixed UDP Port:
2083		CONFIG_TFTP_PORT
2084
2085		If this is defined, the environment variable tftpsrcp
2086		is used to supply the TFTP UDP source port value.
2087		If tftpsrcp isn't defined, the normal pseudo-random port
2088		number generator is used.
2089
2090		Also, the environment variable tftpdstp is used to supply
2091		the TFTP UDP destination port value.  If tftpdstp isn't
2092		defined, the normal port 69 is used.
2093
2094		The purpose for tftpsrcp is to allow a TFTP server to
2095		blindly start the TFTP transfer using the pre-configured
2096		target IP address and UDP port. This has the effect of
2097		"punching through" the (Windows XP) firewall, allowing
2098		the remainder of the TFTP transfer to proceed normally.
2099		A better solution is to properly configure the firewall,
2100		but sometimes that is not allowed.
2101
2102- Show boot progress:
2103		CONFIG_SHOW_BOOT_PROGRESS
2104
2105		Defining this option allows to add some board-
2106		specific code (calling a user-provided function
2107		"show_boot_progress(int)") that enables you to show
2108		the system's boot progress on some display (for
2109		example, some LED's) on your board. At the moment,
2110		the following checkpoints are implemented:
2111
2112Legacy uImage format:
2113
2114  Arg	Where			When
2115    1	common/cmd_bootm.c	before attempting to boot an image
2116   -1	common/cmd_bootm.c	Image header has bad	 magic number
2117    2	common/cmd_bootm.c	Image header has correct magic number
2118   -2	common/cmd_bootm.c	Image header has bad	 checksum
2119    3	common/cmd_bootm.c	Image header has correct checksum
2120   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2121    4	common/cmd_bootm.c	Image data   has correct checksum
2122   -4	common/cmd_bootm.c	Image is for unsupported architecture
2123    5	common/cmd_bootm.c	Architecture check OK
2124   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2125    6	common/cmd_bootm.c	Image Type check OK
2126   -6	common/cmd_bootm.c	gunzip uncompression error
2127   -7	common/cmd_bootm.c	Unimplemented compression type
2128    7	common/cmd_bootm.c	Uncompression OK
2129    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2130   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2131
2132    9	common/image.c		Start initial ramdisk verification
2133  -10	common/image.c		Ramdisk header has bad	   magic number
2134  -11	common/image.c		Ramdisk header has bad	   checksum
2135   10	common/image.c		Ramdisk header is OK
2136  -12	common/image.c		Ramdisk data   has bad	   checksum
2137   11	common/image.c		Ramdisk data   has correct checksum
2138   12	common/image.c		Ramdisk verification complete, start loading
2139  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2140   13	common/image.c		Start multifile image verification
2141   14	common/image.c		No initial ramdisk, no multifile, continue.
2142
2143   15	arch/<arch>/lib/bootm.c	All preparation done, transferring control to OS
2144
2145  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2146  -31	post/post.c		POST test failed, detected by post_output_backlog()
2147  -32	post/post.c		POST test failed, detected by post_run_single()
2148
2149   34	common/cmd_doc.c	before loading a Image from a DOC device
2150  -35	common/cmd_doc.c	Bad usage of "doc" command
2151   35	common/cmd_doc.c	correct usage of "doc" command
2152  -36	common/cmd_doc.c	No boot device
2153   36	common/cmd_doc.c	correct boot device
2154  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2155   37	common/cmd_doc.c	correct chip ID found, device available
2156  -38	common/cmd_doc.c	Read Error on boot device
2157   38	common/cmd_doc.c	reading Image header from DOC device OK
2158  -39	common/cmd_doc.c	Image header has bad magic number
2159   39	common/cmd_doc.c	Image header has correct magic number
2160  -40	common/cmd_doc.c	Error reading Image from DOC device
2161   40	common/cmd_doc.c	Image header has correct magic number
2162   41	common/cmd_ide.c	before loading a Image from a IDE device
2163  -42	common/cmd_ide.c	Bad usage of "ide" command
2164   42	common/cmd_ide.c	correct usage of "ide" command
2165  -43	common/cmd_ide.c	No boot device
2166   43	common/cmd_ide.c	boot device found
2167  -44	common/cmd_ide.c	Device not available
2168   44	common/cmd_ide.c	Device available
2169  -45	common/cmd_ide.c	wrong partition selected
2170   45	common/cmd_ide.c	partition selected
2171  -46	common/cmd_ide.c	Unknown partition table
2172   46	common/cmd_ide.c	valid partition table found
2173  -47	common/cmd_ide.c	Invalid partition type
2174   47	common/cmd_ide.c	correct partition type
2175  -48	common/cmd_ide.c	Error reading Image Header on boot device
2176   48	common/cmd_ide.c	reading Image Header from IDE device OK
2177  -49	common/cmd_ide.c	Image header has bad magic number
2178   49	common/cmd_ide.c	Image header has correct magic number
2179  -50	common/cmd_ide.c	Image header has bad	 checksum
2180   50	common/cmd_ide.c	Image header has correct checksum
2181  -51	common/cmd_ide.c	Error reading Image from IDE device
2182   51	common/cmd_ide.c	reading Image from IDE device OK
2183   52	common/cmd_nand.c	before loading a Image from a NAND device
2184  -53	common/cmd_nand.c	Bad usage of "nand" command
2185   53	common/cmd_nand.c	correct usage of "nand" command
2186  -54	common/cmd_nand.c	No boot device
2187   54	common/cmd_nand.c	boot device found
2188  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2189   55	common/cmd_nand.c	correct chip ID found, device available
2190  -56	common/cmd_nand.c	Error reading Image Header on boot device
2191   56	common/cmd_nand.c	reading Image Header from NAND device OK
2192  -57	common/cmd_nand.c	Image header has bad magic number
2193   57	common/cmd_nand.c	Image header has correct magic number
2194  -58	common/cmd_nand.c	Error reading Image from NAND device
2195   58	common/cmd_nand.c	reading Image from NAND device OK
2196
2197  -60	common/env_common.c	Environment has a bad CRC, using default
2198
2199   64	net/eth.c		starting with Ethernet configuration.
2200  -64	net/eth.c		no Ethernet found.
2201   65	net/eth.c		Ethernet found.
2202
2203  -80	common/cmd_net.c	usage wrong
2204   80	common/cmd_net.c	before calling NetLoop()
2205  -81	common/cmd_net.c	some error in NetLoop() occurred
2206   81	common/cmd_net.c	NetLoop() back without error
2207  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2208   82	common/cmd_net.c	trying automatic boot
2209   83	common/cmd_net.c	running "source" command
2210  -83	common/cmd_net.c	some error in automatic boot or "source" command
2211   84	common/cmd_net.c	end without errors
2212
2213FIT uImage format:
2214
2215  Arg	Where			When
2216  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2217 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2218  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2219 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2220  102	common/cmd_bootm.c	Kernel unit name specified
2221 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2222  103	common/cmd_bootm.c	Found configuration node
2223  104	common/cmd_bootm.c	Got kernel subimage node offset
2224 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2225  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2226 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2227  106	common/cmd_bootm.c	Architecture check OK
2228 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2229  107	common/cmd_bootm.c	Kernel subimage type OK
2230 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2231  108	common/cmd_bootm.c	Got kernel subimage data/size
2232 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2233 -109	common/cmd_bootm.c	Can't get kernel subimage type
2234 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2235 -111	common/cmd_bootm.c	Can't get kernel subimage os
2236 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2237 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2238
2239  120	common/image.c		Start initial ramdisk verification
2240 -120	common/image.c		Ramdisk FIT image has incorrect format
2241  121	common/image.c		Ramdisk FIT image has correct format
2242  122	common/image.c		No ramdisk subimage unit name, using configuration
2243 -122	common/image.c		Can't get configuration for ramdisk subimage
2244  123	common/image.c		Ramdisk unit name specified
2245 -124	common/image.c		Can't get ramdisk subimage node offset
2246  125	common/image.c		Got ramdisk subimage node offset
2247 -125	common/image.c		Ramdisk subimage hash verification failed
2248  126	common/image.c		Ramdisk subimage hash verification OK
2249 -126	common/image.c		Ramdisk subimage for unsupported architecture
2250  127	common/image.c		Architecture check OK
2251 -127	common/image.c		Can't get ramdisk subimage data/size
2252  128	common/image.c		Got ramdisk subimage data/size
2253  129	common/image.c		Can't get ramdisk load address
2254 -129	common/image.c		Got ramdisk load address
2255
2256 -130	common/cmd_doc.c	Incorrect FIT image format
2257  131	common/cmd_doc.c	FIT image format OK
2258
2259 -140	common/cmd_ide.c	Incorrect FIT image format
2260  141	common/cmd_ide.c	FIT image format OK
2261
2262 -150	common/cmd_nand.c	Incorrect FIT image format
2263  151	common/cmd_nand.c	FIT image format OK
2264
2265- Standalone program support:
2266		CONFIG_STANDALONE_LOAD_ADDR
2267
2268		This option defines a board specific value for the
2269		address where standalone program gets loaded, thus
2270		overwriting the architecture dependent default
2271		settings.
2272
2273- Frame Buffer Address:
2274		CONFIG_FB_ADDR
2275
2276		Define CONFIG_FB_ADDR if you want to use specific
2277		address for frame buffer.
2278		Then system will reserve the frame buffer address to
2279		defined address instead of lcd_setmem (this function
2280		grabs the memory for frame buffer by panel's size).
2281
2282		Please see board_init_f function.
2283
2284- Automatic software updates via TFTP server
2285		CONFIG_UPDATE_TFTP
2286		CONFIG_UPDATE_TFTP_CNT_MAX
2287		CONFIG_UPDATE_TFTP_MSEC_MAX
2288
2289		These options enable and control the auto-update feature;
2290		for a more detailed description refer to doc/README.update.
2291
2292- MTD Support (mtdparts command, UBI support)
2293		CONFIG_MTD_DEVICE
2294
2295		Adds the MTD device infrastructure from the Linux kernel.
2296		Needed for mtdparts command support.
2297
2298		CONFIG_MTD_PARTITIONS
2299
2300		Adds the MTD partitioning infrastructure from the Linux
2301		kernel. Needed for UBI support.
2302
2303- SPL framework
2304		CONFIG_SPL
2305		Enable building of SPL globally.
2306
2307		CONFIG_SPL_TEXT_BASE
2308		TEXT_BASE for linking the SPL binary.
2309
2310		CONFIG_SPL_LDSCRIPT
2311		LDSCRIPT for linking the SPL binary.
2312
2313		CONFIG_SPL_LIBCOMMON_SUPPORT
2314		Support for common/libcommon.o in SPL binary
2315
2316		CONFIG_SPL_LIBDISK_SUPPORT
2317		Support for disk/libdisk.o in SPL binary
2318
2319		CONFIG_SPL_I2C_SUPPORT
2320		Support for drivers/i2c/libi2c.o in SPL binary
2321
2322		CONFIG_SPL_GPIO_SUPPORT
2323		Support for drivers/gpio/libgpio.o in SPL binary
2324
2325		CONFIG_SPL_MMC_SUPPORT
2326		Support for drivers/mmc/libmmc.o in SPL binary
2327
2328		CONFIG_SPL_SERIAL_SUPPORT
2329		Support for drivers/serial/libserial.o in SPL binary
2330
2331		CONFIG_SPL_SPI_FLASH_SUPPORT
2332		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2333
2334		CONFIG_SPL_SPI_SUPPORT
2335		Support for drivers/spi/libspi.o in SPL binary
2336
2337		CONFIG_SPL_FAT_SUPPORT
2338		Support for fs/fat/libfat.o in SPL binary
2339
2340		CONFIG_SPL_LIBGENERIC_SUPPORT
2341		Support for lib/libgeneric.o in SPL binary
2342
2343Modem Support:
2344--------------
2345
2346[so far only for SMDK2400 boards]
2347
2348- Modem support enable:
2349		CONFIG_MODEM_SUPPORT
2350
2351- RTS/CTS Flow control enable:
2352		CONFIG_HWFLOW
2353
2354- Modem debug support:
2355		CONFIG_MODEM_SUPPORT_DEBUG
2356
2357		Enables debugging stuff (char screen[1024], dbg())
2358		for modem support. Useful only with BDI2000.
2359
2360- Interrupt support (PPC):
2361
2362		There are common interrupt_init() and timer_interrupt()
2363		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2364		for CPU specific initialization. interrupt_init_cpu()
2365		should set decrementer_count to appropriate value. If
2366		CPU resets decrementer automatically after interrupt
2367		(ppc4xx) it should set decrementer_count to zero.
2368		timer_interrupt() calls timer_interrupt_cpu() for CPU
2369		specific handling. If board has watchdog / status_led
2370		/ other_activity_monitor it works automatically from
2371		general timer_interrupt().
2372
2373- General:
2374
2375		In the target system modem support is enabled when a
2376		specific key (key combination) is pressed during
2377		power-on. Otherwise U-Boot will boot normally
2378		(autoboot). The key_pressed() function is called from
2379		board_init(). Currently key_pressed() is a dummy
2380		function, returning 1 and thus enabling modem
2381		initialization.
2382
2383		If there are no modem init strings in the
2384		environment, U-Boot proceed to autoboot; the
2385		previous output (banner, info printfs) will be
2386		suppressed, though.
2387
2388		See also: doc/README.Modem
2389
2390
2391Configuration Settings:
2392-----------------------
2393
2394- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2395		undefine this when you're short of memory.
2396
2397- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2398		width of the commands listed in the 'help' command output.
2399
2400- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2401		prompt for user input.
2402
2403- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2404
2405- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2406
2407- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2408
2409- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2410		the application (usually a Linux kernel) when it is
2411		booted
2412
2413- CONFIG_SYS_BAUDRATE_TABLE:
2414		List of legal baudrate settings for this board.
2415
2416- CONFIG_SYS_CONSOLE_INFO_QUIET
2417		Suppress display of console information at boot.
2418
2419- CONFIG_SYS_CONSOLE_IS_IN_ENV
2420		If the board specific function
2421			extern int overwrite_console (void);
2422		returns 1, the stdin, stderr and stdout are switched to the
2423		serial port, else the settings in the environment are used.
2424
2425- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
2426		Enable the call to overwrite_console().
2427
2428- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
2429		Enable overwrite of previous console environment settings.
2430
2431- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2432		Begin and End addresses of the area used by the
2433		simple memory test.
2434
2435- CONFIG_SYS_ALT_MEMTEST:
2436		Enable an alternate, more extensive memory test.
2437
2438- CONFIG_SYS_MEMTEST_SCRATCH:
2439		Scratch address used by the alternate memory test
2440		You only need to set this if address zero isn't writeable
2441
2442- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
2443		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2444		this specified memory area will get subtracted from the top
2445		(end) of RAM and won't get "touched" at all by U-Boot. By
2446		fixing up gd->ram_size the Linux kernel should gets passed
2447		the now "corrected" memory size and won't touch it either.
2448		This should work for arch/ppc and arch/powerpc. Only Linux
2449		board ports in arch/powerpc with bootwrapper support that
2450		recalculate the memory size from the SDRAM controller setup
2451		will have to get fixed in Linux additionally.
2452
2453		This option can be used as a workaround for the 440EPx/GRx
2454		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2455		be touched.
2456
2457		WARNING: Please make sure that this value is a multiple of
2458		the Linux page size (normally 4k). If this is not the case,
2459		then the end address of the Linux memory will be located at a
2460		non page size aligned address and this could cause major
2461		problems.
2462
2463- CONFIG_SYS_TFTP_LOADADDR:
2464		Default load address for network file downloads
2465
2466- CONFIG_SYS_LOADS_BAUD_CHANGE:
2467		Enable temporary baudrate change while serial download
2468
2469- CONFIG_SYS_SDRAM_BASE:
2470		Physical start address of SDRAM. _Must_ be 0 here.
2471
2472- CONFIG_SYS_MBIO_BASE:
2473		Physical start address of Motherboard I/O (if using a
2474		Cogent motherboard)
2475
2476- CONFIG_SYS_FLASH_BASE:
2477		Physical start address of Flash memory.
2478
2479- CONFIG_SYS_MONITOR_BASE:
2480		Physical start address of boot monitor code (set by
2481		make config files to be same as the text base address
2482		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2483		CONFIG_SYS_FLASH_BASE when booting from flash.
2484
2485- CONFIG_SYS_MONITOR_LEN:
2486		Size of memory reserved for monitor code, used to
2487		determine _at_compile_time_ (!) if the environment is
2488		embedded within the U-Boot image, or in a separate
2489		flash sector.
2490
2491- CONFIG_SYS_MALLOC_LEN:
2492		Size of DRAM reserved for malloc() use.
2493
2494- CONFIG_SYS_BOOTM_LEN:
2495		Normally compressed uImages are limited to an
2496		uncompressed size of 8 MBytes. If this is not enough,
2497		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2498		to adjust this setting to your needs.
2499
2500- CONFIG_SYS_BOOTMAPSZ:
2501		Maximum size of memory mapped by the startup code of
2502		the Linux kernel; all data that must be processed by
2503		the Linux kernel (bd_info, boot arguments, FDT blob if
2504		used) must be put below this limit, unless "bootm_low"
2505		enviroment variable is defined and non-zero. In such case
2506		all data for the Linux kernel must be between "bootm_low"
2507		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2508		variable "bootm_mapsize" will override the value of
2509		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2510		then the value in "bootm_size" will be used instead.
2511
2512- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2513		Enable initrd_high functionality.  If defined then the
2514		initrd_high feature is enabled and the bootm ramdisk subcommand
2515		is enabled.
2516
2517- CONFIG_SYS_BOOT_GET_CMDLINE:
2518		Enables allocating and saving kernel cmdline in space between
2519		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2520
2521- CONFIG_SYS_BOOT_GET_KBD:
2522		Enables allocating and saving a kernel copy of the bd_info in
2523		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2524
2525- CONFIG_SYS_MAX_FLASH_BANKS:
2526		Max number of Flash memory banks
2527
2528- CONFIG_SYS_MAX_FLASH_SECT:
2529		Max number of sectors on a Flash chip
2530
2531- CONFIG_SYS_FLASH_ERASE_TOUT:
2532		Timeout for Flash erase operations (in ms)
2533
2534- CONFIG_SYS_FLASH_WRITE_TOUT:
2535		Timeout for Flash write operations (in ms)
2536
2537- CONFIG_SYS_FLASH_LOCK_TOUT
2538		Timeout for Flash set sector lock bit operation (in ms)
2539
2540- CONFIG_SYS_FLASH_UNLOCK_TOUT
2541		Timeout for Flash clear lock bits operation (in ms)
2542
2543- CONFIG_SYS_FLASH_PROTECTION
2544		If defined, hardware flash sectors protection is used
2545		instead of U-Boot software protection.
2546
2547- CONFIG_SYS_DIRECT_FLASH_TFTP:
2548
2549		Enable TFTP transfers directly to flash memory;
2550		without this option such a download has to be
2551		performed in two steps: (1) download to RAM, and (2)
2552		copy from RAM to flash.
2553
2554		The two-step approach is usually more reliable, since
2555		you can check if the download worked before you erase
2556		the flash, but in some situations (when system RAM is
2557		too limited to allow for a temporary copy of the
2558		downloaded image) this option may be very useful.
2559
2560- CONFIG_SYS_FLASH_CFI:
2561		Define if the flash driver uses extra elements in the
2562		common flash structure for storing flash geometry.
2563
2564- CONFIG_FLASH_CFI_DRIVER
2565		This option also enables the building of the cfi_flash driver
2566		in the drivers directory
2567
2568- CONFIG_FLASH_CFI_MTD
2569		This option enables the building of the cfi_mtd driver
2570		in the drivers directory. The driver exports CFI flash
2571		to the MTD layer.
2572
2573- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2574		Use buffered writes to flash.
2575
2576- CONFIG_FLASH_SPANSION_S29WS_N
2577		s29ws-n MirrorBit flash has non-standard addresses for buffered
2578		write commands.
2579
2580- CONFIG_SYS_FLASH_QUIET_TEST
2581		If this option is defined, the common CFI flash doesn't
2582		print it's warning upon not recognized FLASH banks. This
2583		is useful, if some of the configured banks are only
2584		optionally available.
2585
2586- CONFIG_FLASH_SHOW_PROGRESS
2587		If defined (must be an integer), print out countdown
2588		digits and dots.  Recommended value: 45 (9..1) for 80
2589		column displays, 15 (3..1) for 40 column displays.
2590
2591- CONFIG_SYS_RX_ETH_BUFFER:
2592		Defines the number of Ethernet receive buffers. On some
2593		Ethernet controllers it is recommended to set this value
2594		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2595		buffers can be full shortly after enabling the interface
2596		on high Ethernet traffic.
2597		Defaults to 4 if not defined.
2598
2599- CONFIG_ENV_MAX_ENTRIES
2600
2601	Maximum number of entries in the hash table that is used
2602	internally to store the environment settings. The default
2603	setting is supposed to be generous and should work in most
2604	cases. This setting can be used to tune behaviour; see
2605	lib/hashtable.c for details.
2606
2607The following definitions that deal with the placement and management
2608of environment data (variable area); in general, we support the
2609following configurations:
2610
2611- CONFIG_BUILD_ENVCRC:
2612
2613	Builds up envcrc with the target environment so that external utils
2614	may easily extract it and embed it in final U-Boot images.
2615
2616- CONFIG_ENV_IS_IN_FLASH:
2617
2618	Define this if the environment is in flash memory.
2619
2620	a) The environment occupies one whole flash sector, which is
2621	   "embedded" in the text segment with the U-Boot code. This
2622	   happens usually with "bottom boot sector" or "top boot
2623	   sector" type flash chips, which have several smaller
2624	   sectors at the start or the end. For instance, such a
2625	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
2626	   such a case you would place the environment in one of the
2627	   4 kB sectors - with U-Boot code before and after it. With
2628	   "top boot sector" type flash chips, you would put the
2629	   environment in one of the last sectors, leaving a gap
2630	   between U-Boot and the environment.
2631
2632	- CONFIG_ENV_OFFSET:
2633
2634	   Offset of environment data (variable area) to the
2635	   beginning of flash memory; for instance, with bottom boot
2636	   type flash chips the second sector can be used: the offset
2637	   for this sector is given here.
2638
2639	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
2640
2641	- CONFIG_ENV_ADDR:
2642
2643	   This is just another way to specify the start address of
2644	   the flash sector containing the environment (instead of
2645	   CONFIG_ENV_OFFSET).
2646
2647	- CONFIG_ENV_SECT_SIZE:
2648
2649	   Size of the sector containing the environment.
2650
2651
2652	b) Sometimes flash chips have few, equal sized, BIG sectors.
2653	   In such a case you don't want to spend a whole sector for
2654	   the environment.
2655
2656	- CONFIG_ENV_SIZE:
2657
2658	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
2659	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
2660	   of this flash sector for the environment. This saves
2661	   memory for the RAM copy of the environment.
2662
2663	   It may also save flash memory if you decide to use this
2664	   when your environment is "embedded" within U-Boot code,
2665	   since then the remainder of the flash sector could be used
2666	   for U-Boot code. It should be pointed out that this is
2667	   STRONGLY DISCOURAGED from a robustness point of view:
2668	   updating the environment in flash makes it always
2669	   necessary to erase the WHOLE sector. If something goes
2670	   wrong before the contents has been restored from a copy in
2671	   RAM, your target system will be dead.
2672
2673	- CONFIG_ENV_ADDR_REDUND
2674	  CONFIG_ENV_SIZE_REDUND
2675
2676	   These settings describe a second storage area used to hold
2677	   a redundant copy of the environment data, so that there is
2678	   a valid backup copy in case there is a power failure during
2679	   a "saveenv" operation.
2680
2681BE CAREFUL! Any changes to the flash layout, and some changes to the
2682source code will make it necessary to adapt <board>/u-boot.lds*
2683accordingly!
2684
2685
2686- CONFIG_ENV_IS_IN_NVRAM:
2687
2688	Define this if you have some non-volatile memory device
2689	(NVRAM, battery buffered SRAM) which you want to use for the
2690	environment.
2691
2692	- CONFIG_ENV_ADDR:
2693	- CONFIG_ENV_SIZE:
2694
2695	  These two #defines are used to determine the memory area you
2696	  want to use for environment. It is assumed that this memory
2697	  can just be read and written to, without any special
2698	  provision.
2699
2700BE CAREFUL! The first access to the environment happens quite early
2701in U-Boot initalization (when we try to get the setting of for the
2702console baudrate). You *MUST* have mapped your NVRAM area then, or
2703U-Boot will hang.
2704
2705Please note that even with NVRAM we still use a copy of the
2706environment in RAM: we could work on NVRAM directly, but we want to
2707keep settings there always unmodified except somebody uses "saveenv"
2708to save the current settings.
2709
2710
2711- CONFIG_ENV_IS_IN_EEPROM:
2712
2713	Use this if you have an EEPROM or similar serial access
2714	device and a driver for it.
2715
2716	- CONFIG_ENV_OFFSET:
2717	- CONFIG_ENV_SIZE:
2718
2719	  These two #defines specify the offset and size of the
2720	  environment area within the total memory of your EEPROM.
2721
2722	- CONFIG_SYS_I2C_EEPROM_ADDR:
2723	  If defined, specified the chip address of the EEPROM device.
2724	  The default address is zero.
2725
2726	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
2727	  If defined, the number of bits used to address bytes in a
2728	  single page in the EEPROM device.  A 64 byte page, for example
2729	  would require six bits.
2730
2731	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
2732	  If defined, the number of milliseconds to delay between
2733	  page writes.	The default is zero milliseconds.
2734
2735	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
2736	  The length in bytes of the EEPROM memory array address.  Note
2737	  that this is NOT the chip address length!
2738
2739	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
2740	  EEPROM chips that implement "address overflow" are ones
2741	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
2742	  address and the extra bits end up in the "chip address" bit
2743	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
2744	  byte chips.
2745
2746	  Note that we consider the length of the address field to
2747	  still be one byte because the extra address bits are hidden
2748	  in the chip address.
2749
2750	- CONFIG_SYS_EEPROM_SIZE:
2751	  The size in bytes of the EEPROM device.
2752
2753	- CONFIG_ENV_EEPROM_IS_ON_I2C
2754	  define this, if you have I2C and SPI activated, and your
2755	  EEPROM, which holds the environment, is on the I2C bus.
2756
2757	- CONFIG_I2C_ENV_EEPROM_BUS
2758	  if you have an Environment on an EEPROM reached over
2759	  I2C muxes, you can define here, how to reach this
2760	  EEPROM. For example:
2761
2762	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
2763
2764	  EEPROM which holds the environment, is reached over
2765	  a pca9547 i2c mux with address 0x70, channel 3.
2766
2767- CONFIG_ENV_IS_IN_DATAFLASH:
2768
2769	Define this if you have a DataFlash memory device which you
2770	want to use for the environment.
2771
2772	- CONFIG_ENV_OFFSET:
2773	- CONFIG_ENV_ADDR:
2774	- CONFIG_ENV_SIZE:
2775
2776	  These three #defines specify the offset and size of the
2777	  environment area within the total memory of your DataFlash placed
2778	  at the specified address.
2779
2780- CONFIG_ENV_IS_IN_NAND:
2781
2782	Define this if you have a NAND device which you want to use
2783	for the environment.
2784
2785	- CONFIG_ENV_OFFSET:
2786	- CONFIG_ENV_SIZE:
2787
2788	  These two #defines specify the offset and size of the environment
2789	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
2790	  aligned to an erase block boundary.
2791
2792	- CONFIG_ENV_OFFSET_REDUND (optional):
2793
2794	  This setting describes a second storage area of CONFIG_ENV_SIZE
2795	  size used to hold a redundant copy of the environment data, so
2796	  that there is a valid backup copy in case there is a power failure
2797	  during a "saveenv" operation.  CONFIG_ENV_OFFSET_RENDUND must be
2798	  aligned to an erase block boundary.
2799
2800	- CONFIG_ENV_RANGE (optional):
2801
2802	  Specifies the length of the region in which the environment
2803	  can be written.  This should be a multiple of the NAND device's
2804	  block size.  Specifying a range with more erase blocks than
2805	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
2806	  the range to be avoided.
2807
2808	- CONFIG_ENV_OFFSET_OOB (optional):
2809
2810	  Enables support for dynamically retrieving the offset of the
2811	  environment from block zero's out-of-band data.  The
2812	  "nand env.oob" command can be used to record this offset.
2813	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
2814	  using CONFIG_ENV_OFFSET_OOB.
2815
2816- CONFIG_NAND_ENV_DST
2817
2818	Defines address in RAM to which the nand_spl code should copy the
2819	environment. If redundant environment is used, it will be copied to
2820	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2821
2822- CONFIG_SYS_SPI_INIT_OFFSET
2823
2824	Defines offset to the initial SPI buffer area in DPRAM. The
2825	area is used at an early stage (ROM part) if the environment
2826	is configured to reside in the SPI EEPROM: We need a 520 byte
2827	scratch DPRAM area. It is used between the two initialization
2828	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
2829	to be a good choice since it makes it far enough from the
2830	start of the data area as well as from the stack pointer.
2831
2832Please note that the environment is read-only until the monitor
2833has been relocated to RAM and a RAM copy of the environment has been
2834created; also, when using EEPROM you will have to use getenv_f()
2835until then to read environment variables.
2836
2837The environment is protected by a CRC32 checksum. Before the monitor
2838is relocated into RAM, as a result of a bad CRC you will be working
2839with the compiled-in default environment - *silently*!!! [This is
2840necessary, because the first environment variable we need is the
2841"baudrate" setting for the console - if we have a bad CRC, we don't
2842have any device yet where we could complain.]
2843
2844Note: once the monitor has been relocated, then it will complain if
2845the default environment is used; a new CRC is computed as soon as you
2846use the "saveenv" command to store a valid environment.
2847
2848- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2849		Echo the inverted Ethernet link state to the fault LED.
2850
2851		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2852		      also needs to be defined.
2853
2854- CONFIG_SYS_FAULT_MII_ADDR:
2855		MII address of the PHY to check for the Ethernet link state.
2856
2857- CONFIG_NS16550_MIN_FUNCTIONS:
2858		Define this if you desire to only have use of the NS16550_init
2859		and NS16550_putc functions for the serial driver located at
2860		drivers/serial/ns16550.c.  This option is useful for saving
2861		space for already greatly restricted images, including but not
2862		limited to NAND_SPL configurations.
2863
2864Low Level (hardware related) configuration options:
2865---------------------------------------------------
2866
2867- CONFIG_SYS_CACHELINE_SIZE:
2868		Cache Line Size of the CPU.
2869
2870- CONFIG_SYS_DEFAULT_IMMR:
2871		Default address of the IMMR after system reset.
2872
2873		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
2874		and RPXsuper) to be able to adjust the position of
2875		the IMMR register after a reset.
2876
2877- CONFIG_SYS_CCSRBAR_DEFAULT:
2878		Default (power-on reset) physical address of CCSR on Freescale
2879		PowerPC SOCs.
2880
2881- CONFIG_SYS_CCSRBAR:
2882		Virtual address of CCSR.  On a 32-bit build, this is typically
2883		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2884
2885		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
2886		for cross-platform code that uses that macro instead.
2887
2888- CONFIG_SYS_CCSRBAR_PHYS:
2889		Physical address of CCSR.  CCSR can be relocated to a new
2890		physical address, if desired.  In this case, this macro should
2891		be set to that address.  Otherwise, it should be set to the
2892		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2893		is typically relocated on 36-bit builds.  It is recommended
2894		that this macro be defined via the _HIGH and _LOW macros:
2895
2896		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2897			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2898
2899- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2900		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
2901		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
2902		used in assembly code, so it must not contain typecasts or
2903		integer size suffixes (e.g. "ULL").
2904
2905- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2906		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2907		used in assembly code, so it must not contain typecasts or
2908		integer size suffixes (e.g. "ULL").
2909
2910- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2911		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2912		forced to a value that ensures that CCSR is not relocated.
2913
2914- Floppy Disk Support:
2915		CONFIG_SYS_FDC_DRIVE_NUMBER
2916
2917		the default drive number (default value 0)
2918
2919		CONFIG_SYS_ISA_IO_STRIDE
2920
2921		defines the spacing between FDC chipset registers
2922		(default value 1)
2923
2924		CONFIG_SYS_ISA_IO_OFFSET
2925
2926		defines the offset of register from address. It
2927		depends on which part of the data bus is connected to
2928		the FDC chipset. (default value 0)
2929
2930		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
2931		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
2932		default value.
2933
2934		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
2935		fdc_hw_init() is called at the beginning of the FDC
2936		setup. fdc_hw_init() must be provided by the board
2937		source code. It is used to make hardware dependant
2938		initializations.
2939
2940- CONFIG_IDE_AHB:
2941		Most IDE controllers were designed to be connected with PCI
2942		interface. Only few of them were designed for AHB interface.
2943		When software is doing ATA command and data transfer to
2944		IDE devices through IDE-AHB controller, some additional
2945		registers accessing to these kind of IDE-AHB controller
2946		is requierd.
2947
2948- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
2949		DO NOT CHANGE unless you know exactly what you're
2950		doing! (11-4) [MPC8xx/82xx systems only]
2951
2952- CONFIG_SYS_INIT_RAM_ADDR:
2953
2954		Start address of memory area that can be used for
2955		initial data and stack; please note that this must be
2956		writable memory that is working WITHOUT special
2957		initialization, i. e. you CANNOT use normal RAM which
2958		will become available only after programming the
2959		memory controller and running certain initialization
2960		sequences.
2961
2962		U-Boot uses the following memory types:
2963		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
2964		- MPC824X: data cache
2965		- PPC4xx:  data cache
2966
2967- CONFIG_SYS_GBL_DATA_OFFSET:
2968
2969		Offset of the initial data structure in the memory
2970		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2971		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2972		data is located at the end of the available space
2973		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2974		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
2975		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2976		CONFIG_SYS_GBL_DATA_OFFSET) downward.
2977
2978	Note:
2979		On the MPC824X (or other systems that use the data
2980		cache for initial memory) the address chosen for
2981		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2982		point to an otherwise UNUSED address space between
2983		the top of RAM and the start of the PCI space.
2984
2985- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
2986
2987- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
2988
2989- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
2990
2991- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
2992
2993- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
2994
2995- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
2996
2997- CONFIG_SYS_OR_TIMING_SDRAM:
2998		SDRAM timing
2999
3000- CONFIG_SYS_MAMR_PTA:
3001		periodic timer for refresh
3002
3003- CONFIG_SYS_DER:	Debug Event Register (37-47)
3004
3005- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3006  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3007  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3008  CONFIG_SYS_BR1_PRELIM:
3009		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3010
3011- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3012  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3013  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3014		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3015
3016- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3017  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3018		Machine Mode Register and Memory Periodic Timer
3019		Prescaler definitions (SDRAM timing)
3020
3021- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3022		enable I2C microcode relocation patch (MPC8xx);
3023		define relocation offset in DPRAM [DSP2]
3024
3025- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3026		enable SMC microcode relocation patch (MPC8xx);
3027		define relocation offset in DPRAM [SMC1]
3028
3029- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3030		enable SPI microcode relocation patch (MPC8xx);
3031		define relocation offset in DPRAM [SCC4]
3032
3033- CONFIG_SYS_USE_OSCCLK:
3034		Use OSCM clock mode on MBX8xx board. Be careful,
3035		wrong setting might damage your board. Read
3036		doc/README.MBX before setting this variable!
3037
3038- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3039		Offset of the bootmode word in DPRAM used by post
3040		(Power On Self Tests). This definition overrides
3041		#define'd default value in commproc.h resp.
3042		cpm_8260.h.
3043
3044- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3045  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3046  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3047  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3048  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3049  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3050  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3051  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3052		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3053
3054- CONFIG_PCI_DISABLE_PCIE:
3055		Disable PCI-Express on systems where it is supported but not
3056		required.
3057
3058- CONFIG_SYS_SRIO:
3059		Chip has SRIO or not
3060
3061- CONFIG_SRIO1:
3062		Board has SRIO 1 port available
3063
3064- CONFIG_SRIO2:
3065		Board has SRIO 2 port available
3066
3067- CONFIG_SYS_SRIOn_MEM_VIRT:
3068		Virtual Address of SRIO port 'n' memory region
3069
3070- CONFIG_SYS_SRIOn_MEM_PHYS:
3071		Physical Address of SRIO port 'n' memory region
3072
3073- CONFIG_SYS_SRIOn_MEM_SIZE:
3074		Size of SRIO port 'n' memory region
3075
3076- CONFIG_SYS_NDFC_16
3077		Defined to tell the NDFC that the NAND chip is using a
3078		16 bit bus.
3079
3080- CONFIG_SYS_NDFC_EBC0_CFG
3081		Sets the EBC0_CFG register for the NDFC. If not defined
3082		a default value will be used.
3083
3084- CONFIG_SPD_EEPROM
3085		Get DDR timing information from an I2C EEPROM. Common
3086		with pluggable memory modules such as SODIMMs
3087
3088  SPD_EEPROM_ADDRESS
3089		I2C address of the SPD EEPROM
3090
3091- CONFIG_SYS_SPD_BUS_NUM
3092		If SPD EEPROM is on an I2C bus other than the first
3093		one, specify here. Note that the value must resolve
3094		to something your driver can deal with.
3095
3096- CONFIG_SYS_DDR_RAW_TIMING
3097		Get DDR timing information from other than SPD. Common with
3098		soldered DDR chips onboard without SPD. DDR raw timing
3099		parameters are extracted from datasheet and hard-coded into
3100		header files or board specific files.
3101
3102- CONFIG_FSL_DDR_INTERACTIVE
3103		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3104
3105- CONFIG_SYS_83XX_DDR_USES_CS0
3106		Only for 83xx systems. If specified, then DDR should
3107		be configured using CS0 and CS1 instead of CS2 and CS3.
3108
3109- CONFIG_ETHER_ON_FEC[12]
3110		Define to enable FEC[12] on a 8xx series processor.
3111
3112- CONFIG_FEC[12]_PHY
3113		Define to the hardcoded PHY address which corresponds
3114		to the given FEC; i. e.
3115			#define CONFIG_FEC1_PHY 4
3116		means that the PHY with address 4 is connected to FEC1
3117
3118		When set to -1, means to probe for first available.
3119
3120- CONFIG_FEC[12]_PHY_NORXERR
3121		The PHY does not have a RXERR line (RMII only).
3122		(so program the FEC to ignore it).
3123
3124- CONFIG_RMII
3125		Enable RMII mode for all FECs.
3126		Note that this is a global option, we can't
3127		have one FEC in standard MII mode and another in RMII mode.
3128
3129- CONFIG_CRC32_VERIFY
3130		Add a verify option to the crc32 command.
3131		The syntax is:
3132
3133		=> crc32 -v <address> <count> <crc32>
3134
3135		Where address/count indicate a memory area
3136		and crc32 is the correct crc32 which the
3137		area should have.
3138
3139- CONFIG_LOOPW
3140		Add the "loopw" memory command. This only takes effect if
3141		the memory commands are activated globally (CONFIG_CMD_MEM).
3142
3143- CONFIG_MX_CYCLIC
3144		Add the "mdc" and "mwc" memory commands. These are cyclic
3145		"md/mw" commands.
3146		Examples:
3147
3148		=> mdc.b 10 4 500
3149		This command will print 4 bytes (10,11,12,13) each 500 ms.
3150
3151		=> mwc.l 100 12345678 10
3152		This command will write 12345678 to address 100 all 10 ms.
3153
3154		This only takes effect if the memory commands are activated
3155		globally (CONFIG_CMD_MEM).
3156
3157- CONFIG_SKIP_LOWLEVEL_INIT
3158		[ARM, MIPS only] If this variable is defined, then certain
3159		low level initializations (like setting up the memory
3160		controller) are omitted and/or U-Boot does not
3161		relocate itself into RAM.
3162
3163		Normally this variable MUST NOT be defined. The only
3164		exception is when U-Boot is loaded (to RAM) by some
3165		other boot loader or by a debugger which performs
3166		these initializations itself.
3167
3168- CONFIG_SPL_BUILD
3169		Modifies the behaviour of start.S when compiling a loader
3170		that is executed before the actual U-Boot. E.g. when
3171		compiling a NAND SPL.
3172
3173- CONFIG_USE_ARCH_MEMCPY
3174  CONFIG_USE_ARCH_MEMSET
3175		If these options are used a optimized version of memcpy/memset will
3176		be used if available. These functions may be faster under some
3177		conditions but may increase the binary size.
3178
3179Building the Software:
3180======================
3181
3182Building U-Boot has been tested in several native build environments
3183and in many different cross environments. Of course we cannot support
3184all possibly existing versions of cross development tools in all
3185(potentially obsolete) versions. In case of tool chain problems we
3186recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3187which is extensively used to build and test U-Boot.
3188
3189If you are not using a native environment, it is assumed that you
3190have GNU cross compiling tools available in your path. In this case,
3191you must set the environment variable CROSS_COMPILE in your shell.
3192Note that no changes to the Makefile or any other source files are
3193necessary. For example using the ELDK on a 4xx CPU, please enter:
3194
3195	$ CROSS_COMPILE=ppc_4xx-
3196	$ export CROSS_COMPILE
3197
3198Note: If you wish to generate Windows versions of the utilities in
3199      the tools directory you can use the MinGW toolchain
3200      (http://www.mingw.org).  Set your HOST tools to the MinGW
3201      toolchain and execute 'make tools'.  For example:
3202
3203       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3204
3205      Binaries such as tools/mkimage.exe will be created which can
3206      be executed on computers running Windows.
3207
3208U-Boot is intended to be simple to build. After installing the
3209sources you must configure U-Boot for one specific board type. This
3210is done by typing:
3211
3212	make NAME_config
3213
3214where "NAME_config" is the name of one of the existing configu-
3215rations; see the main Makefile for supported names.
3216
3217Note: for some board special configuration names may exist; check if
3218      additional information is available from the board vendor; for
3219      instance, the TQM823L systems are available without (standard)
3220      or with LCD support. You can select such additional "features"
3221      when choosing the configuration, i. e.
3222
3223      make TQM823L_config
3224	- will configure for a plain TQM823L, i. e. no LCD support
3225
3226      make TQM823L_LCD_config
3227	- will configure for a TQM823L with U-Boot console on LCD
3228
3229      etc.
3230
3231
3232Finally, type "make all", and you should get some working U-Boot
3233images ready for download to / installation on your system:
3234
3235- "u-boot.bin" is a raw binary image
3236- "u-boot" is an image in ELF binary format
3237- "u-boot.srec" is in Motorola S-Record format
3238
3239By default the build is performed locally and the objects are saved
3240in the source directory. One of the two methods can be used to change
3241this behavior and build U-Boot to some external directory:
3242
32431. Add O= to the make command line invocations:
3244
3245	make O=/tmp/build distclean
3246	make O=/tmp/build NAME_config
3247	make O=/tmp/build all
3248
32492. Set environment variable BUILD_DIR to point to the desired location:
3250
3251	export BUILD_DIR=/tmp/build
3252	make distclean
3253	make NAME_config
3254	make all
3255
3256Note that the command line "O=" setting overrides the BUILD_DIR environment
3257variable.
3258
3259
3260Please be aware that the Makefiles assume you are using GNU make, so
3261for instance on NetBSD you might need to use "gmake" instead of
3262native "make".
3263
3264
3265If the system board that you have is not listed, then you will need
3266to port U-Boot to your hardware platform. To do this, follow these
3267steps:
3268
32691.  Add a new configuration option for your board to the toplevel
3270    "Makefile" and to the "MAKEALL" script, using the existing
3271    entries as examples. Note that here and at many other places
3272    boards and other names are listed in alphabetical sort order. Please
3273    keep this order.
32742.  Create a new directory to hold your board specific code. Add any
3275    files you need. In your board directory, you will need at least
3276    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
32773.  Create a new configuration file "include/configs/<board>.h" for
3278    your board
32793.  If you're porting U-Boot to a new CPU, then also create a new
3280    directory to hold your CPU specific code. Add any files you need.
32814.  Run "make <board>_config" with your new name.
32825.  Type "make", and you should get a working "u-boot.srec" file
3283    to be installed on your target system.
32846.  Debug and solve any problems that might arise.
3285    [Of course, this last step is much harder than it sounds.]
3286
3287
3288Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3289==============================================================
3290
3291If you have modified U-Boot sources (for instance added a new board
3292or support for new devices, a new CPU, etc.) you are expected to
3293provide feedback to the other developers. The feedback normally takes
3294the form of a "patch", i. e. a context diff against a certain (latest
3295official or latest in the git repository) version of U-Boot sources.
3296
3297But before you submit such a patch, please verify that your modifi-
3298cation did not break existing code. At least make sure that *ALL* of
3299the supported boards compile WITHOUT ANY compiler warnings. To do so,
3300just run the "MAKEALL" script, which will configure and build U-Boot
3301for ALL supported system. Be warned, this will take a while. You can
3302select which (cross) compiler to use by passing a `CROSS_COMPILE'
3303environment variable to the script, i. e. to use the ELDK cross tools
3304you can type
3305
3306	CROSS_COMPILE=ppc_8xx- MAKEALL
3307
3308or to build on a native PowerPC system you can type
3309
3310	CROSS_COMPILE=' ' MAKEALL
3311
3312When using the MAKEALL script, the default behaviour is to build
3313U-Boot in the source directory. This location can be changed by
3314setting the BUILD_DIR environment variable. Also, for each target
3315built, the MAKEALL script saves two log files (<target>.ERR and
3316<target>.MAKEALL) in the <source dir>/LOG directory. This default
3317location can be changed by setting the MAKEALL_LOGDIR environment
3318variable. For example:
3319
3320	export BUILD_DIR=/tmp/build
3321	export MAKEALL_LOGDIR=/tmp/log
3322	CROSS_COMPILE=ppc_8xx- MAKEALL
3323
3324With the above settings build objects are saved in the /tmp/build,
3325log files are saved in the /tmp/log and the source tree remains clean
3326during the whole build process.
3327
3328
3329See also "U-Boot Porting Guide" below.
3330
3331
3332Monitor Commands - Overview:
3333============================
3334
3335go	- start application at address 'addr'
3336run	- run commands in an environment variable
3337bootm	- boot application image from memory
3338bootp	- boot image via network using BootP/TFTP protocol
3339tftpboot- boot image via network using TFTP protocol
3340	       and env variables "ipaddr" and "serverip"
3341	       (and eventually "gatewayip")
3342rarpboot- boot image via network using RARP/TFTP protocol
3343diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3344loads	- load S-Record file over serial line
3345loadb	- load binary file over serial line (kermit mode)
3346md	- memory display
3347mm	- memory modify (auto-incrementing)
3348nm	- memory modify (constant address)
3349mw	- memory write (fill)
3350cp	- memory copy
3351cmp	- memory compare
3352crc32	- checksum calculation
3353i2c	- I2C sub-system
3354sspi	- SPI utility commands
3355base	- print or set address offset
3356printenv- print environment variables
3357setenv	- set environment variables
3358saveenv - save environment variables to persistent storage
3359protect - enable or disable FLASH write protection
3360erase	- erase FLASH memory
3361flinfo	- print FLASH memory information
3362bdinfo	- print Board Info structure
3363iminfo	- print header information for application image
3364coninfo - print console devices and informations
3365ide	- IDE sub-system
3366loop	- infinite loop on address range
3367loopw	- infinite write loop on address range
3368mtest	- simple RAM test
3369icache	- enable or disable instruction cache
3370dcache	- enable or disable data cache
3371reset	- Perform RESET of the CPU
3372echo	- echo args to console
3373version - print monitor version
3374help	- print online help
3375?	- alias for 'help'
3376
3377
3378Monitor Commands - Detailed Description:
3379========================================
3380
3381TODO.
3382
3383For now: just type "help <command>".
3384
3385
3386Environment Variables:
3387======================
3388
3389U-Boot supports user configuration using Environment Variables which
3390can be made persistent by saving to Flash memory.
3391
3392Environment Variables are set using "setenv", printed using
3393"printenv", and saved to Flash using "saveenv". Using "setenv"
3394without a value can be used to delete a variable from the
3395environment. As long as you don't save the environment you are
3396working with an in-memory copy. In case the Flash area containing the
3397environment is erased by accident, a default environment is provided.
3398
3399Some configuration options can be set using Environment Variables.
3400
3401List of environment variables (most likely not complete):
3402
3403  baudrate	- see CONFIG_BAUDRATE
3404
3405  bootdelay	- see CONFIG_BOOTDELAY
3406
3407  bootcmd	- see CONFIG_BOOTCOMMAND
3408
3409  bootargs	- Boot arguments when booting an RTOS image
3410
3411  bootfile	- Name of the image to load with TFTP
3412
3413  bootm_low	- Memory range available for image processing in the bootm
3414		  command can be restricted. This variable is given as
3415		  a hexadecimal number and defines lowest address allowed
3416		  for use by the bootm command. See also "bootm_size"
3417		  environment variable. Address defined by "bootm_low" is
3418		  also the base of the initial memory mapping for the Linux
3419		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3420		  bootm_mapsize.
3421
3422  bootm_mapsize	- Size of the initial memory mapping for the Linux kernel.
3423		  This variable is given as a hexadecimal number and it
3424		  defines the size of the memory region starting at base
3425		  address bootm_low that is accessible by the Linux kernel
3426		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3427		  as the default value if it is defined, and bootm_size is
3428		  used otherwise.
3429
3430  bootm_size	- Memory range available for image processing in the bootm
3431		  command can be restricted. This variable is given as
3432		  a hexadecimal number and defines the size of the region
3433		  allowed for use by the bootm command. See also "bootm_low"
3434		  environment variable.
3435
3436  updatefile	- Location of the software update file on a TFTP server, used
3437		  by the automatic software update feature. Please refer to
3438		  documentation in doc/README.update for more details.
3439
3440  autoload	- if set to "no" (any string beginning with 'n'),
3441		  "bootp" will just load perform a lookup of the
3442		  configuration from the BOOTP server, but not try to
3443		  load any image using TFTP
3444
3445  autostart	- if set to "yes", an image loaded using the "bootp",
3446		  "rarpboot", "tftpboot" or "diskboot" commands will
3447		  be automatically started (by internally calling
3448		  "bootm")
3449
3450		  If set to "no", a standalone image passed to the
3451		  "bootm" command will be copied to the load address
3452		  (and eventually uncompressed), but NOT be started.
3453		  This can be used to load and uncompress arbitrary
3454		  data.
3455
3456  fdt_high	- if set this restricts the maximum address that the
3457		  flattened device tree will be copied into upon boot.
3458		  If this is set to the special value 0xFFFFFFFF then
3459		  the fdt will not be copied at all on boot.  For this
3460		  to work it must reside in writable memory, have
3461		  sufficient padding on the end of it for u-boot to
3462		  add the information it needs into it, and the memory
3463		  must be accessible by the kernel.
3464
3465  i2cfast	- (PPC405GP|PPC405EP only)
3466		  if set to 'y' configures Linux I2C driver for fast
3467		  mode (400kHZ). This environment variable is used in
3468		  initialization code. So, for changes to be effective
3469		  it must be saved and board must be reset.
3470
3471  initrd_high	- restrict positioning of initrd images:
3472		  If this variable is not set, initrd images will be
3473		  copied to the highest possible address in RAM; this
3474		  is usually what you want since it allows for
3475		  maximum initrd size. If for some reason you want to
3476		  make sure that the initrd image is loaded below the
3477		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3478		  variable to a value of "no" or "off" or "0".
3479		  Alternatively, you can set it to a maximum upper
3480		  address to use (U-Boot will still check that it
3481		  does not overwrite the U-Boot stack and data).
3482
3483		  For instance, when you have a system with 16 MB
3484		  RAM, and want to reserve 4 MB from use by Linux,
3485		  you can do this by adding "mem=12M" to the value of
3486		  the "bootargs" variable. However, now you must make
3487		  sure that the initrd image is placed in the first
3488		  12 MB as well - this can be done with
3489
3490		  setenv initrd_high 00c00000
3491
3492		  If you set initrd_high to 0xFFFFFFFF, this is an
3493		  indication to U-Boot that all addresses are legal
3494		  for the Linux kernel, including addresses in flash
3495		  memory. In this case U-Boot will NOT COPY the
3496		  ramdisk at all. This may be useful to reduce the
3497		  boot time on your system, but requires that this
3498		  feature is supported by your Linux kernel.
3499
3500  ipaddr	- IP address; needed for tftpboot command
3501
3502  loadaddr	- Default load address for commands like "bootp",
3503		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3504
3505  loads_echo	- see CONFIG_LOADS_ECHO
3506
3507  serverip	- TFTP server IP address; needed for tftpboot command
3508
3509  bootretry	- see CONFIG_BOOT_RETRY_TIME
3510
3511  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3512
3513  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3514
3515  ethprime	- controls which interface is used first.
3516
3517  ethact	- controls which interface is currently active.
3518		  For example you can do the following
3519
3520		  => setenv ethact FEC
3521		  => ping 192.168.0.1 # traffic sent on FEC
3522		  => setenv ethact SCC
3523		  => ping 10.0.0.1 # traffic sent on SCC
3524
3525  ethrotate	- When set to "no" U-Boot does not go through all
3526		  available network interfaces.
3527		  It just stays at the currently selected interface.
3528
3529  netretry	- When set to "no" each network operation will
3530		  either succeed or fail without retrying.
3531		  When set to "once" the network operation will
3532		  fail when all the available network interfaces
3533		  are tried once without success.
3534		  Useful on scripts which control the retry operation
3535		  themselves.
3536
3537  npe_ucode	- set load address for the NPE microcode
3538
3539  tftpsrcport	- If this is set, the value is used for TFTP's
3540		  UDP source port.
3541
3542  tftpdstport	- If this is set, the value is used for TFTP's UDP
3543		  destination port instead of the Well Know Port 69.
3544
3545  tftpblocksize - Block size to use for TFTP transfers; if not set,
3546		  we use the TFTP server's default block size
3547
3548  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3549		  seconds, minimum value is 1000 = 1 second). Defines
3550		  when a packet is considered to be lost so it has to
3551		  be retransmitted. The default is 5000 = 5 seconds.
3552		  Lowering this value may make downloads succeed
3553		  faster in networks with high packet loss rates or
3554		  with unreliable TFTP servers.
3555
3556  vlan		- When set to a value < 4095 the traffic over
3557		  Ethernet is encapsulated/received over 802.1q
3558		  VLAN tagged frames.
3559
3560The following environment variables may be used and automatically
3561updated by the network boot commands ("bootp" and "rarpboot"),
3562depending the information provided by your boot server:
3563
3564  bootfile	- see above
3565  dnsip		- IP address of your Domain Name Server
3566  dnsip2	- IP address of your secondary Domain Name Server
3567  gatewayip	- IP address of the Gateway (Router) to use
3568  hostname	- Target hostname
3569  ipaddr	- see above
3570  netmask	- Subnet Mask
3571  rootpath	- Pathname of the root filesystem on the NFS server
3572  serverip	- see above
3573
3574
3575There are two special Environment Variables:
3576
3577  serial#	- contains hardware identification information such
3578		  as type string and/or serial number
3579  ethaddr	- Ethernet address
3580
3581These variables can be set only once (usually during manufacturing of
3582the board). U-Boot refuses to delete or overwrite these variables
3583once they have been set once.
3584
3585
3586Further special Environment Variables:
3587
3588  ver		- Contains the U-Boot version string as printed
3589		  with the "version" command. This variable is
3590		  readonly (see CONFIG_VERSION_VARIABLE).
3591
3592
3593Please note that changes to some configuration parameters may take
3594only effect after the next boot (yes, that's just like Windoze :-).
3595
3596
3597Command Line Parsing:
3598=====================
3599
3600There are two different command line parsers available with U-Boot:
3601the old "simple" one, and the much more powerful "hush" shell:
3602
3603Old, simple command line parser:
3604--------------------------------
3605
3606- supports environment variables (through setenv / saveenv commands)
3607- several commands on one line, separated by ';'
3608- variable substitution using "... ${name} ..." syntax
3609- special characters ('$', ';') can be escaped by prefixing with '\',
3610  for example:
3611	setenv bootcmd bootm \${address}
3612- You can also escape text by enclosing in single apostrophes, for example:
3613	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3614
3615Hush shell:
3616-----------
3617
3618- similar to Bourne shell, with control structures like
3619  if...then...else...fi, for...do...done; while...do...done,
3620  until...do...done, ...
3621- supports environment ("global") variables (through setenv / saveenv
3622  commands) and local shell variables (through standard shell syntax
3623  "name=value"); only environment variables can be used with "run"
3624  command
3625
3626General rules:
3627--------------
3628
3629(1) If a command line (or an environment variable executed by a "run"
3630    command) contains several commands separated by semicolon, and
3631    one of these commands fails, then the remaining commands will be
3632    executed anyway.
3633
3634(2) If you execute several variables with one call to run (i. e.
3635    calling run with a list of variables as arguments), any failing
3636    command will cause "run" to terminate, i. e. the remaining
3637    variables are not executed.
3638
3639Note for Redundant Ethernet Interfaces:
3640=======================================
3641
3642Some boards come with redundant Ethernet interfaces; U-Boot supports
3643such configurations and is capable of automatic selection of a
3644"working" interface when needed. MAC assignment works as follows:
3645
3646Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3647MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3648"eth1addr" (=>eth1), "eth2addr", ...
3649
3650If the network interface stores some valid MAC address (for instance
3651in SROM), this is used as default address if there is NO correspon-
3652ding setting in the environment; if the corresponding environment
3653variable is set, this overrides the settings in the card; that means:
3654
3655o If the SROM has a valid MAC address, and there is no address in the
3656  environment, the SROM's address is used.
3657
3658o If there is no valid address in the SROM, and a definition in the
3659  environment exists, then the value from the environment variable is
3660  used.
3661
3662o If both the SROM and the environment contain a MAC address, and
3663  both addresses are the same, this MAC address is used.
3664
3665o If both the SROM and the environment contain a MAC address, and the
3666  addresses differ, the value from the environment is used and a
3667  warning is printed.
3668
3669o If neither SROM nor the environment contain a MAC address, an error
3670  is raised.
3671
3672If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3673will be programmed into hardware as part of the initialization process.  This
3674may be skipped by setting the appropriate 'ethmacskip' environment variable.
3675The naming convention is as follows:
3676"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3677
3678Image Formats:
3679==============
3680
3681U-Boot is capable of booting (and performing other auxiliary operations on)
3682images in two formats:
3683
3684New uImage format (FIT)
3685-----------------------
3686
3687Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3688to Flattened Device Tree). It allows the use of images with multiple
3689components (several kernels, ramdisks, etc.), with contents protected by
3690SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3691
3692
3693Old uImage format
3694-----------------
3695
3696Old image format is based on binary files which can be basically anything,
3697preceded by a special header; see the definitions in include/image.h for
3698details; basically, the header defines the following image properties:
3699
3700* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3701  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3702  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3703  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3704  INTEGRITY).
3705* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
3706  IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3707  Currently supported: ARM, AVR32, Intel x86, MIPS, Nios II, PowerPC).
3708* Compression Type (uncompressed, gzip, bzip2)
3709* Load Address
3710* Entry Point
3711* Image Name
3712* Image Timestamp
3713
3714The header is marked by a special Magic Number, and both the header
3715and the data portions of the image are secured against corruption by
3716CRC32 checksums.
3717
3718
3719Linux Support:
3720==============
3721
3722Although U-Boot should support any OS or standalone application
3723easily, the main focus has always been on Linux during the design of
3724U-Boot.
3725
3726U-Boot includes many features that so far have been part of some
3727special "boot loader" code within the Linux kernel. Also, any
3728"initrd" images to be used are no longer part of one big Linux image;
3729instead, kernel and "initrd" are separate images. This implementation
3730serves several purposes:
3731
3732- the same features can be used for other OS or standalone
3733  applications (for instance: using compressed images to reduce the
3734  Flash memory footprint)
3735
3736- it becomes much easier to port new Linux kernel versions because
3737  lots of low-level, hardware dependent stuff are done by U-Boot
3738
3739- the same Linux kernel image can now be used with different "initrd"
3740  images; of course this also means that different kernel images can
3741  be run with the same "initrd". This makes testing easier (you don't
3742  have to build a new "zImage.initrd" Linux image when you just
3743  change a file in your "initrd"). Also, a field-upgrade of the
3744  software is easier now.
3745
3746
3747Linux HOWTO:
3748============
3749
3750Porting Linux to U-Boot based systems:
3751---------------------------------------
3752
3753U-Boot cannot save you from doing all the necessary modifications to
3754configure the Linux device drivers for use with your target hardware
3755(no, we don't intend to provide a full virtual machine interface to
3756Linux :-).
3757
3758But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3759
3760Just make sure your machine specific header file (for instance
3761include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3762Information structure as we define in include/asm-<arch>/u-boot.h,
3763and make sure that your definition of IMAP_ADDR uses the same value
3764as your U-Boot configuration in CONFIG_SYS_IMMR.
3765
3766
3767Configuring the Linux kernel:
3768-----------------------------
3769
3770No specific requirements for U-Boot. Make sure you have some root
3771device (initial ramdisk, NFS) for your target system.
3772
3773
3774Building a Linux Image:
3775-----------------------
3776
3777With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3778not used. If you use recent kernel source, a new build target
3779"uImage" will exist which automatically builds an image usable by
3780U-Boot. Most older kernels also have support for a "pImage" target,
3781which was introduced for our predecessor project PPCBoot and uses a
3782100% compatible format.
3783
3784Example:
3785
3786	make TQM850L_config
3787	make oldconfig
3788	make dep
3789	make uImage
3790
3791The "uImage" build target uses a special tool (in 'tools/mkimage') to
3792encapsulate a compressed Linux kernel image with header	 information,
3793CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3794
3795* build a standard "vmlinux" kernel image (in ELF binary format):
3796
3797* convert the kernel into a raw binary image:
3798
3799	${CROSS_COMPILE}-objcopy -O binary \
3800				 -R .note -R .comment \
3801				 -S vmlinux linux.bin
3802
3803* compress the binary image:
3804
3805	gzip -9 linux.bin
3806
3807* package compressed binary image for U-Boot:
3808
3809	mkimage -A ppc -O linux -T kernel -C gzip \
3810		-a 0 -e 0 -n "Linux Kernel Image" \
3811		-d linux.bin.gz uImage
3812
3813
3814The "mkimage" tool can also be used to create ramdisk images for use
3815with U-Boot, either separated from the Linux kernel image, or
3816combined into one file. "mkimage" encapsulates the images with a 64
3817byte header containing information about target architecture,
3818operating system, image type, compression method, entry points, time
3819stamp, CRC32 checksums, etc.
3820
3821"mkimage" can be called in two ways: to verify existing images and
3822print the header information, or to build new images.
3823
3824In the first form (with "-l" option) mkimage lists the information
3825contained in the header of an existing U-Boot image; this includes
3826checksum verification:
3827
3828	tools/mkimage -l image
3829	  -l ==> list image header information
3830
3831The second form (with "-d" option) is used to build a U-Boot image
3832from a "data file" which is used as image payload:
3833
3834	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3835		      -n name -d data_file image
3836	  -A ==> set architecture to 'arch'
3837	  -O ==> set operating system to 'os'
3838	  -T ==> set image type to 'type'
3839	  -C ==> set compression type 'comp'
3840	  -a ==> set load address to 'addr' (hex)
3841	  -e ==> set entry point to 'ep' (hex)
3842	  -n ==> set image name to 'name'
3843	  -d ==> use image data from 'datafile'
3844
3845Right now, all Linux kernels for PowerPC systems use the same load
3846address (0x00000000), but the entry point address depends on the
3847kernel version:
3848
3849- 2.2.x kernels have the entry point at 0x0000000C,
3850- 2.3.x and later kernels have the entry point at 0x00000000.
3851
3852So a typical call to build a U-Boot image would read:
3853
3854	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3855	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3856	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3857	> examples/uImage.TQM850L
3858	Image Name:   2.4.4 kernel for TQM850L
3859	Created:      Wed Jul 19 02:34:59 2000
3860	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3861	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3862	Load Address: 0x00000000
3863	Entry Point:  0x00000000
3864
3865To verify the contents of the image (or check for corruption):
3866
3867	-> tools/mkimage -l examples/uImage.TQM850L
3868	Image Name:   2.4.4 kernel for TQM850L
3869	Created:      Wed Jul 19 02:34:59 2000
3870	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3871	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3872	Load Address: 0x00000000
3873	Entry Point:  0x00000000
3874
3875NOTE: for embedded systems where boot time is critical you can trade
3876speed for memory and install an UNCOMPRESSED image instead: this
3877needs more space in Flash, but boots much faster since it does not
3878need to be uncompressed:
3879
3880	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3881	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3882	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3883	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3884	> examples/uImage.TQM850L-uncompressed
3885	Image Name:   2.4.4 kernel for TQM850L
3886	Created:      Wed Jul 19 02:34:59 2000
3887	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3888	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3889	Load Address: 0x00000000
3890	Entry Point:  0x00000000
3891
3892
3893Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3894when your kernel is intended to use an initial ramdisk:
3895
3896	-> tools/mkimage -n 'Simple Ramdisk Image' \
3897	> -A ppc -O linux -T ramdisk -C gzip \
3898	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3899	Image Name:   Simple Ramdisk Image
3900	Created:      Wed Jan 12 14:01:50 2000
3901	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
3902	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
3903	Load Address: 0x00000000
3904	Entry Point:  0x00000000
3905
3906
3907Installing a Linux Image:
3908-------------------------
3909
3910To downloading a U-Boot image over the serial (console) interface,
3911you must convert the image to S-Record format:
3912
3913	objcopy -I binary -O srec examples/image examples/image.srec
3914
3915The 'objcopy' does not understand the information in the U-Boot
3916image header, so the resulting S-Record file will be relative to
3917address 0x00000000. To load it to a given address, you need to
3918specify the target address as 'offset' parameter with the 'loads'
3919command.
3920
3921Example: install the image to address 0x40100000 (which on the
3922TQM8xxL is in the first Flash bank):
3923
3924	=> erase 40100000 401FFFFF
3925
3926	.......... done
3927	Erased 8 sectors
3928
3929	=> loads 40100000
3930	## Ready for S-Record download ...
3931	~>examples/image.srec
3932	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3933	...
3934	15989 15990 15991 15992
3935	[file transfer complete]
3936	[connected]
3937	## Start Addr = 0x00000000
3938
3939
3940You can check the success of the download using the 'iminfo' command;
3941this includes a checksum verification so you can be sure no data
3942corruption happened:
3943
3944	=> imi 40100000
3945
3946	## Checking Image at 40100000 ...
3947	   Image Name:	 2.2.13 for initrd on TQM850L
3948	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3949	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3950	   Load Address: 00000000
3951	   Entry Point:	 0000000c
3952	   Verifying Checksum ... OK
3953
3954
3955Boot Linux:
3956-----------
3957
3958The "bootm" command is used to boot an application that is stored in
3959memory (RAM or Flash). In case of a Linux kernel image, the contents
3960of the "bootargs" environment variable is passed to the kernel as
3961parameters. You can check and modify this variable using the
3962"printenv" and "setenv" commands:
3963
3964
3965	=> printenv bootargs
3966	bootargs=root=/dev/ram
3967
3968	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3969
3970	=> printenv bootargs
3971	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3972
3973	=> bootm 40020000
3974	## Booting Linux kernel at 40020000 ...
3975	   Image Name:	 2.2.13 for NFS on TQM850L
3976	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3977	   Data Size:	 381681 Bytes = 372 kB = 0 MB
3978	   Load Address: 00000000
3979	   Entry Point:	 0000000c
3980	   Verifying Checksum ... OK
3981	   Uncompressing Kernel Image ... OK
3982	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
3983	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3984	time_init: decrementer frequency = 187500000/60
3985	Calibrating delay loop... 49.77 BogoMIPS
3986	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3987	...
3988
3989If you want to boot a Linux kernel with initial RAM disk, you pass
3990the memory addresses of both the kernel and the initrd image (PPBCOOT
3991format!) to the "bootm" command:
3992
3993	=> imi 40100000 40200000
3994
3995	## Checking Image at 40100000 ...
3996	   Image Name:	 2.2.13 for initrd on TQM850L
3997	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3998	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3999	   Load Address: 00000000
4000	   Entry Point:	 0000000c
4001	   Verifying Checksum ... OK
4002
4003	## Checking Image at 40200000 ...
4004	   Image Name:	 Simple Ramdisk Image
4005	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4006	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4007	   Load Address: 00000000
4008	   Entry Point:	 00000000
4009	   Verifying Checksum ... OK
4010
4011	=> bootm 40100000 40200000
4012	## Booting Linux kernel at 40100000 ...
4013	   Image Name:	 2.2.13 for initrd on TQM850L
4014	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4015	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4016	   Load Address: 00000000
4017	   Entry Point:	 0000000c
4018	   Verifying Checksum ... OK
4019	   Uncompressing Kernel Image ... OK
4020	## Loading RAMDisk Image at 40200000 ...
4021	   Image Name:	 Simple Ramdisk Image
4022	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4023	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4024	   Load Address: 00000000
4025	   Entry Point:	 00000000
4026	   Verifying Checksum ... OK
4027	   Loading Ramdisk ... OK
4028	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
4029	Boot arguments: root=/dev/ram
4030	time_init: decrementer frequency = 187500000/60
4031	Calibrating delay loop... 49.77 BogoMIPS
4032	...
4033	RAMDISK: Compressed image found at block 0
4034	VFS: Mounted root (ext2 filesystem).
4035
4036	bash#
4037
4038Boot Linux and pass a flat device tree:
4039-----------
4040
4041First, U-Boot must be compiled with the appropriate defines. See the section
4042titled "Linux Kernel Interface" above for a more in depth explanation. The
4043following is an example of how to start a kernel and pass an updated
4044flat device tree:
4045
4046=> print oftaddr
4047oftaddr=0x300000
4048=> print oft
4049oft=oftrees/mpc8540ads.dtb
4050=> tftp $oftaddr $oft
4051Speed: 1000, full duplex
4052Using TSEC0 device
4053TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4054Filename 'oftrees/mpc8540ads.dtb'.
4055Load address: 0x300000
4056Loading: #
4057done
4058Bytes transferred = 4106 (100a hex)
4059=> tftp $loadaddr $bootfile
4060Speed: 1000, full duplex
4061Using TSEC0 device
4062TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4063Filename 'uImage'.
4064Load address: 0x200000
4065Loading:############
4066done
4067Bytes transferred = 1029407 (fb51f hex)
4068=> print loadaddr
4069loadaddr=200000
4070=> print oftaddr
4071oftaddr=0x300000
4072=> bootm $loadaddr - $oftaddr
4073## Booting image at 00200000 ...
4074   Image Name:	 Linux-2.6.17-dirty
4075   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4076   Data Size:	 1029343 Bytes = 1005.2 kB
4077   Load Address: 00000000
4078   Entry Point:	 00000000
4079   Verifying Checksum ... OK
4080   Uncompressing Kernel Image ... OK
4081Booting using flat device tree at 0x300000
4082Using MPC85xx ADS machine description
4083Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4084[snip]
4085
4086
4087More About U-Boot Image Types:
4088------------------------------
4089
4090U-Boot supports the following image types:
4091
4092   "Standalone Programs" are directly runnable in the environment
4093	provided by U-Boot; it is expected that (if they behave
4094	well) you can continue to work in U-Boot after return from
4095	the Standalone Program.
4096   "OS Kernel Images" are usually images of some Embedded OS which
4097	will take over control completely. Usually these programs
4098	will install their own set of exception handlers, device
4099	drivers, set up the MMU, etc. - this means, that you cannot
4100	expect to re-enter U-Boot except by resetting the CPU.
4101   "RAMDisk Images" are more or less just data blocks, and their
4102	parameters (address, size) are passed to an OS kernel that is
4103	being started.
4104   "Multi-File Images" contain several images, typically an OS
4105	(Linux) kernel image and one or more data images like
4106	RAMDisks. This construct is useful for instance when you want
4107	to boot over the network using BOOTP etc., where the boot
4108	server provides just a single image file, but you want to get
4109	for instance an OS kernel and a RAMDisk image.
4110
4111	"Multi-File Images" start with a list of image sizes, each
4112	image size (in bytes) specified by an "uint32_t" in network
4113	byte order. This list is terminated by an "(uint32_t)0".
4114	Immediately after the terminating 0 follow the images, one by
4115	one, all aligned on "uint32_t" boundaries (size rounded up to
4116	a multiple of 4 bytes).
4117
4118   "Firmware Images" are binary images containing firmware (like
4119	U-Boot or FPGA images) which usually will be programmed to
4120	flash memory.
4121
4122   "Script files" are command sequences that will be executed by
4123	U-Boot's command interpreter; this feature is especially
4124	useful when you configure U-Boot to use a real shell (hush)
4125	as command interpreter.
4126
4127
4128Standalone HOWTO:
4129=================
4130
4131One of the features of U-Boot is that you can dynamically load and
4132run "standalone" applications, which can use some resources of
4133U-Boot like console I/O functions or interrupt services.
4134
4135Two simple examples are included with the sources:
4136
4137"Hello World" Demo:
4138-------------------
4139
4140'examples/hello_world.c' contains a small "Hello World" Demo
4141application; it is automatically compiled when you build U-Boot.
4142It's configured to run at address 0x00040004, so you can play with it
4143like that:
4144
4145	=> loads
4146	## Ready for S-Record download ...
4147	~>examples/hello_world.srec
4148	1 2 3 4 5 6 7 8 9 10 11 ...
4149	[file transfer complete]
4150	[connected]
4151	## Start Addr = 0x00040004
4152
4153	=> go 40004 Hello World! This is a test.
4154	## Starting application at 0x00040004 ...
4155	Hello World
4156	argc = 7
4157	argv[0] = "40004"
4158	argv[1] = "Hello"
4159	argv[2] = "World!"
4160	argv[3] = "This"
4161	argv[4] = "is"
4162	argv[5] = "a"
4163	argv[6] = "test."
4164	argv[7] = "<NULL>"
4165	Hit any key to exit ...
4166
4167	## Application terminated, rc = 0x0
4168
4169Another example, which demonstrates how to register a CPM interrupt
4170handler with the U-Boot code, can be found in 'examples/timer.c'.
4171Here, a CPM timer is set up to generate an interrupt every second.
4172The interrupt service routine is trivial, just printing a '.'
4173character, but this is just a demo program. The application can be
4174controlled by the following keys:
4175
4176	? - print current values og the CPM Timer registers
4177	b - enable interrupts and start timer
4178	e - stop timer and disable interrupts
4179	q - quit application
4180
4181	=> loads
4182	## Ready for S-Record download ...
4183	~>examples/timer.srec
4184	1 2 3 4 5 6 7 8 9 10 11 ...
4185	[file transfer complete]
4186	[connected]
4187	## Start Addr = 0x00040004
4188
4189	=> go 40004
4190	## Starting application at 0x00040004 ...
4191	TIMERS=0xfff00980
4192	Using timer 1
4193	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4194
4195Hit 'b':
4196	[q, b, e, ?] Set interval 1000000 us
4197	Enabling timer
4198Hit '?':
4199	[q, b, e, ?] ........
4200	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4201Hit '?':
4202	[q, b, e, ?] .
4203	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4204Hit '?':
4205	[q, b, e, ?] .
4206	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4207Hit '?':
4208	[q, b, e, ?] .
4209	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4210Hit 'e':
4211	[q, b, e, ?] ...Stopping timer
4212Hit 'q':
4213	[q, b, e, ?] ## Application terminated, rc = 0x0
4214
4215
4216Minicom warning:
4217================
4218
4219Over time, many people have reported problems when trying to use the
4220"minicom" terminal emulation program for serial download. I (wd)
4221consider minicom to be broken, and recommend not to use it. Under
4222Unix, I recommend to use C-Kermit for general purpose use (and
4223especially for kermit binary protocol download ("loadb" command), and
4224use "cu" for S-Record download ("loads" command).
4225
4226Nevertheless, if you absolutely want to use it try adding this
4227configuration to your "File transfer protocols" section:
4228
4229	   Name	   Program			Name U/D FullScr IO-Red. Multi
4230	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4231	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4232
4233
4234NetBSD Notes:
4235=============
4236
4237Starting at version 0.9.2, U-Boot supports NetBSD both as host
4238(build U-Boot) and target system (boots NetBSD/mpc8xx).
4239
4240Building requires a cross environment; it is known to work on
4241NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4242need gmake since the Makefiles are not compatible with BSD make).
4243Note that the cross-powerpc package does not install include files;
4244attempting to build U-Boot will fail because <machine/ansi.h> is
4245missing.  This file has to be installed and patched manually:
4246
4247	# cd /usr/pkg/cross/powerpc-netbsd/include
4248	# mkdir powerpc
4249	# ln -s powerpc machine
4250	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4251	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4252
4253Native builds *don't* work due to incompatibilities between native
4254and U-Boot include files.
4255
4256Booting assumes that (the first part of) the image booted is a
4257stage-2 loader which in turn loads and then invokes the kernel
4258proper. Loader sources will eventually appear in the NetBSD source
4259tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4260meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4261
4262
4263Implementation Internals:
4264=========================
4265
4266The following is not intended to be a complete description of every
4267implementation detail. However, it should help to understand the
4268inner workings of U-Boot and make it easier to port it to custom
4269hardware.
4270
4271
4272Initial Stack, Global Data:
4273---------------------------
4274
4275The implementation of U-Boot is complicated by the fact that U-Boot
4276starts running out of ROM (flash memory), usually without access to
4277system RAM (because the memory controller is not initialized yet).
4278This means that we don't have writable Data or BSS segments, and BSS
4279is not initialized as zero. To be able to get a C environment working
4280at all, we have to allocate at least a minimal stack. Implementation
4281options for this are defined and restricted by the CPU used: Some CPU
4282models provide on-chip memory (like the IMMR area on MPC8xx and
4283MPC826x processors), on others (parts of) the data cache can be
4284locked as (mis-) used as memory, etc.
4285
4286	Chris Hallinan posted a good summary of these issues to the
4287	U-Boot mailing list:
4288
4289	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4290	From: "Chris Hallinan" <clh@net1plus.com>
4291	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4292	...
4293
4294	Correct me if I'm wrong, folks, but the way I understand it
4295	is this: Using DCACHE as initial RAM for Stack, etc, does not
4296	require any physical RAM backing up the cache. The cleverness
4297	is that the cache is being used as a temporary supply of
4298	necessary storage before the SDRAM controller is setup. It's
4299	beyond the scope of this list to explain the details, but you
4300	can see how this works by studying the cache architecture and
4301	operation in the architecture and processor-specific manuals.
4302
4303	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4304	is another option for the system designer to use as an
4305	initial stack/RAM area prior to SDRAM being available. Either
4306	option should work for you. Using CS 4 should be fine if your
4307	board designers haven't used it for something that would
4308	cause you grief during the initial boot! It is frequently not
4309	used.
4310
4311	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4312	with your processor/board/system design. The default value
4313	you will find in any recent u-boot distribution in
4314	walnut.h should work for you. I'd set it to a value larger
4315	than your SDRAM module. If you have a 64MB SDRAM module, set
4316	it above 400_0000. Just make sure your board has no resources
4317	that are supposed to respond to that address! That code in
4318	start.S has been around a while and should work as is when
4319	you get the config right.
4320
4321	-Chris Hallinan
4322	DS4.COM, Inc.
4323
4324It is essential to remember this, since it has some impact on the C
4325code for the initialization procedures:
4326
4327* Initialized global data (data segment) is read-only. Do not attempt
4328  to write it.
4329
4330* Do not use any uninitialized global data (or implicitely initialized
4331  as zero data - BSS segment) at all - this is undefined, initiali-
4332  zation is performed later (when relocating to RAM).
4333
4334* Stack space is very limited. Avoid big data buffers or things like
4335  that.
4336
4337Having only the stack as writable memory limits means we cannot use
4338normal global data to share information beween the code. But it
4339turned out that the implementation of U-Boot can be greatly
4340simplified by making a global data structure (gd_t) available to all
4341functions. We could pass a pointer to this data as argument to _all_
4342functions, but this would bloat the code. Instead we use a feature of
4343the GCC compiler (Global Register Variables) to share the data: we
4344place a pointer (gd) to the global data into a register which we
4345reserve for this purpose.
4346
4347When choosing a register for such a purpose we are restricted by the
4348relevant  (E)ABI  specifications for the current architecture, and by
4349GCC's implementation.
4350
4351For PowerPC, the following registers have specific use:
4352	R1:	stack pointer
4353	R2:	reserved for system use
4354	R3-R4:	parameter passing and return values
4355	R5-R10: parameter passing
4356	R13:	small data area pointer
4357	R30:	GOT pointer
4358	R31:	frame pointer
4359
4360	(U-Boot also uses R12 as internal GOT pointer. r12
4361	is a volatile register so r12 needs to be reset when
4362	going back and forth between asm and C)
4363
4364    ==> U-Boot will use R2 to hold a pointer to the global data
4365
4366    Note: on PPC, we could use a static initializer (since the
4367    address of the global data structure is known at compile time),
4368    but it turned out that reserving a register results in somewhat
4369    smaller code - although the code savings are not that big (on
4370    average for all boards 752 bytes for the whole U-Boot image,
4371    624 text + 127 data).
4372
4373On Blackfin, the normal C ABI (except for P3) is followed as documented here:
4374	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
4375
4376    ==> U-Boot will use P3 to hold a pointer to the global data
4377
4378On ARM, the following registers are used:
4379
4380	R0:	function argument word/integer result
4381	R1-R3:	function argument word
4382	R9:	GOT pointer
4383	R10:	stack limit (used only if stack checking if enabled)
4384	R11:	argument (frame) pointer
4385	R12:	temporary workspace
4386	R13:	stack pointer
4387	R14:	link register
4388	R15:	program counter
4389
4390    ==> U-Boot will use R8 to hold a pointer to the global data
4391
4392On Nios II, the ABI is documented here:
4393	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4394
4395    ==> U-Boot will use gp to hold a pointer to the global data
4396
4397    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4398    to access small data sections, so gp is free.
4399
4400NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4401or current versions of GCC may "optimize" the code too much.
4402
4403Memory Management:
4404------------------
4405
4406U-Boot runs in system state and uses physical addresses, i.e. the
4407MMU is not used either for address mapping nor for memory protection.
4408
4409The available memory is mapped to fixed addresses using the memory
4410controller. In this process, a contiguous block is formed for each
4411memory type (Flash, SDRAM, SRAM), even when it consists of several
4412physical memory banks.
4413
4414U-Boot is installed in the first 128 kB of the first Flash bank (on
4415TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4416booting and sizing and initializing DRAM, the code relocates itself
4417to the upper end of DRAM. Immediately below the U-Boot code some
4418memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4419configuration setting]. Below that, a structure with global Board
4420Info data is placed, followed by the stack (growing downward).
4421
4422Additionally, some exception handler code is copied to the low 8 kB
4423of DRAM (0x00000000 ... 0x00001FFF).
4424
4425So a typical memory configuration with 16 MB of DRAM could look like
4426this:
4427
4428	0x0000 0000	Exception Vector code
4429	      :
4430	0x0000 1FFF
4431	0x0000 2000	Free for Application Use
4432	      :
4433	      :
4434
4435	      :
4436	      :
4437	0x00FB FF20	Monitor Stack (Growing downward)
4438	0x00FB FFAC	Board Info Data and permanent copy of global data
4439	0x00FC 0000	Malloc Arena
4440	      :
4441	0x00FD FFFF
4442	0x00FE 0000	RAM Copy of Monitor Code
4443	...		eventually: LCD or video framebuffer
4444	...		eventually: pRAM (Protected RAM - unchanged by reset)
4445	0x00FF FFFF	[End of RAM]
4446
4447
4448System Initialization:
4449----------------------
4450
4451In the reset configuration, U-Boot starts at the reset entry point
4452(on most PowerPC systems at address 0x00000100). Because of the reset
4453configuration for CS0# this is a mirror of the onboard Flash memory.
4454To be able to re-map memory U-Boot then jumps to its link address.
4455To be able to implement the initialization code in C, a (small!)
4456initial stack is set up in the internal Dual Ported RAM (in case CPUs
4457which provide such a feature like MPC8xx or MPC8260), or in a locked
4458part of the data cache. After that, U-Boot initializes the CPU core,
4459the caches and the SIU.
4460
4461Next, all (potentially) available memory banks are mapped using a
4462preliminary mapping. For example, we put them on 512 MB boundaries
4463(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4464on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4465programmed for SDRAM access. Using the temporary configuration, a
4466simple memory test is run that determines the size of the SDRAM
4467banks.
4468
4469When there is more than one SDRAM bank, and the banks are of
4470different size, the largest is mapped first. For equal size, the first
4471bank (CS2#) is mapped first. The first mapping is always for address
44720x00000000, with any additional banks following immediately to create
4473contiguous memory starting from 0.
4474
4475Then, the monitor installs itself at the upper end of the SDRAM area
4476and allocates memory for use by malloc() and for the global Board
4477Info data; also, the exception vector code is copied to the low RAM
4478pages, and the final stack is set up.
4479
4480Only after this relocation will you have a "normal" C environment;
4481until that you are restricted in several ways, mostly because you are
4482running from ROM, and because the code will have to be relocated to a
4483new address in RAM.
4484
4485
4486U-Boot Porting Guide:
4487----------------------
4488
4489[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4490list, October 2002]
4491
4492
4493int main(int argc, char *argv[])
4494{
4495	sighandler_t no_more_time;
4496
4497	signal(SIGALRM, no_more_time);
4498	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4499
4500	if (available_money > available_manpower) {
4501		Pay consultant to port U-Boot;
4502		return 0;
4503	}
4504
4505	Download latest U-Boot source;
4506
4507	Subscribe to u-boot mailing list;
4508
4509	if (clueless)
4510		email("Hi, I am new to U-Boot, how do I get started?");
4511
4512	while (learning) {
4513		Read the README file in the top level directory;
4514		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4515		Read applicable doc/*.README;
4516		Read the source, Luke;
4517		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4518	}
4519
4520	if (available_money > toLocalCurrency ($2500))
4521		Buy a BDI3000;
4522	else
4523		Add a lot of aggravation and time;
4524
4525	if (a similar board exists) {	/* hopefully... */
4526		cp -a board/<similar> board/<myboard>
4527		cp include/configs/<similar>.h include/configs/<myboard>.h
4528	} else {
4529		Create your own board support subdirectory;
4530		Create your own board include/configs/<myboard>.h file;
4531	}
4532	Edit new board/<myboard> files
4533	Edit new include/configs/<myboard>.h
4534
4535	while (!accepted) {
4536		while (!running) {
4537			do {
4538				Add / modify source code;
4539			} until (compiles);
4540			Debug;
4541			if (clueless)
4542				email("Hi, I am having problems...");
4543		}
4544		Send patch file to the U-Boot email list;
4545		if (reasonable critiques)
4546			Incorporate improvements from email list code review;
4547		else
4548			Defend code as written;
4549	}
4550
4551	return 0;
4552}
4553
4554void no_more_time (int sig)
4555{
4556      hire_a_guru();
4557}
4558
4559
4560Coding Standards:
4561-----------------
4562
4563All contributions to U-Boot should conform to the Linux kernel
4564coding style; see the file "Documentation/CodingStyle" and the script
4565"scripts/Lindent" in your Linux kernel source directory.
4566
4567Source files originating from a different project (for example the
4568MTD subsystem) are generally exempt from these guidelines and are not
4569reformated to ease subsequent migration to newer versions of those
4570sources.
4571
4572Please note that U-Boot is implemented in C (and to some small parts in
4573Assembler); no C++ is used, so please do not use C++ style comments (//)
4574in your code.
4575
4576Please also stick to the following formatting rules:
4577- remove any trailing white space
4578- use TAB characters for indentation and vertical alignment, not spaces
4579- make sure NOT to use DOS '\r\n' line feeds
4580- do not add more than 2 consecutive empty lines to source files
4581- do not add trailing empty lines to source files
4582
4583Submissions which do not conform to the standards may be returned
4584with a request to reformat the changes.
4585
4586
4587Submitting Patches:
4588-------------------
4589
4590Since the number of patches for U-Boot is growing, we need to
4591establish some rules. Submissions which do not conform to these rules
4592may be rejected, even when they contain important and valuable stuff.
4593
4594Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4595
4596Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4597see http://lists.denx.de/mailman/listinfo/u-boot
4598
4599When you send a patch, please include the following information with
4600it:
4601
4602* For bug fixes: a description of the bug and how your patch fixes
4603  this bug. Please try to include a way of demonstrating that the
4604  patch actually fixes something.
4605
4606* For new features: a description of the feature and your
4607  implementation.
4608
4609* A CHANGELOG entry as plaintext (separate from the patch)
4610
4611* For major contributions, your entry to the CREDITS file
4612
4613* When you add support for a new board, don't forget to add this
4614  board to the MAINTAINERS file, too.
4615
4616* If your patch adds new configuration options, don't forget to
4617  document these in the README file.
4618
4619* The patch itself. If you are using git (which is *strongly*
4620  recommended) you can easily generate the patch using the
4621  "git format-patch". If you then use "git send-email" to send it to
4622  the U-Boot mailing list, you will avoid most of the common problems
4623  with some other mail clients.
4624
4625  If you cannot use git, use "diff -purN OLD NEW". If your version of
4626  diff does not support these options, then get the latest version of
4627  GNU diff.
4628
4629  The current directory when running this command shall be the parent
4630  directory of the U-Boot source tree (i. e. please make sure that
4631  your patch includes sufficient directory information for the
4632  affected files).
4633
4634  We prefer patches as plain text. MIME attachments are discouraged,
4635  and compressed attachments must not be used.
4636
4637* If one logical set of modifications affects or creates several
4638  files, all these changes shall be submitted in a SINGLE patch file.
4639
4640* Changesets that contain different, unrelated modifications shall be
4641  submitted as SEPARATE patches, one patch per changeset.
4642
4643
4644Notes:
4645
4646* Before sending the patch, run the MAKEALL script on your patched
4647  source tree and make sure that no errors or warnings are reported
4648  for any of the boards.
4649
4650* Keep your modifications to the necessary minimum: A patch
4651  containing several unrelated changes or arbitrary reformats will be
4652  returned with a request to re-formatting / split it.
4653
4654* If you modify existing code, make sure that your new code does not
4655  add to the memory footprint of the code ;-) Small is beautiful!
4656  When adding new features, these should compile conditionally only
4657  (using #ifdef), and the resulting code with the new feature
4658  disabled must not need more memory than the old code without your
4659  modification.
4660
4661* Remember that there is a size limit of 100 kB per message on the
4662  u-boot mailing list. Bigger patches will be moderated. If they are
4663  reasonable and not too big, they will be acknowledged. But patches
4664  bigger than the size limit should be avoided.
4665