xref: /rk3399_rockchip-uboot/README (revision 9558b48af006a34d3ab7f0bd13a76b97acd45e47)
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_USB		* USB support
787		CONFIG_CMD_CDP		* Cisco Discover Protocol support
788		CONFIG_CMD_FSL		* Microblaze FSL support
789
790
791		EXAMPLE: If you want all functions except of network
792		support you can write:
793
794		#include "config_cmd_all.h"
795		#undef CONFIG_CMD_NET
796
797	Other Commands:
798		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
799
800	Note:	Don't enable the "icache" and "dcache" commands
801		(configuration option CONFIG_CMD_CACHE) unless you know
802		what you (and your U-Boot users) are doing. Data
803		cache cannot be enabled on systems like the 8xx or
804		8260 (where accesses to the IMMR region must be
805		uncached), and it cannot be disabled on all other
806		systems where we (mis-) use the data cache to hold an
807		initial stack and some data.
808
809
810		XXX - this list needs to get updated!
811
812- Watchdog:
813		CONFIG_WATCHDOG
814		If this variable is defined, it enables watchdog
815		support for the SoC. There must be support in the SoC
816		specific code for a watchdog. For the 8xx and 8260
817		CPUs, the SIU Watchdog feature is enabled in the SYPCR
818		register.  When supported for a specific SoC is
819		available, then no further board specific code should
820		be needed to use it.
821
822		CONFIG_HW_WATCHDOG
823		When using a watchdog circuitry external to the used
824		SoC, then define this variable and provide board
825		specific code for the "hw_watchdog_reset" function.
826
827- U-Boot Version:
828		CONFIG_VERSION_VARIABLE
829		If this variable is defined, an environment variable
830		named "ver" is created by U-Boot showing the U-Boot
831		version as printed by the "version" command.
832		This variable is readonly.
833
834- Real-Time Clock:
835
836		When CONFIG_CMD_DATE is selected, the type of the RTC
837		has to be selected, too. Define exactly one of the
838		following options:
839
840		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
841		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
842		CONFIG_RTC_MC13783	- use MC13783 RTC
843		CONFIG_RTC_MC146818	- use MC146818 RTC
844		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
845		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
846		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
847		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
848		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
849		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
850		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
851		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
852					  RV3029 RTC.
853
854		Note that if the RTC uses I2C, then the I2C interface
855		must also be configured. See I2C Support, below.
856
857- GPIO Support:
858		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
859		CONFIG_PCA953X_INFO	- enable pca953x info command
860
861		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
862		chip-ngpio pairs that tell the PCA953X driver the number of
863		pins supported by a particular chip.
864
865		Note that if the GPIO device uses I2C, then the I2C interface
866		must also be configured. See I2C Support, below.
867
868- Timestamp Support:
869
870		When CONFIG_TIMESTAMP is selected, the timestamp
871		(date and time) of an image is printed by image
872		commands like bootm or iminfo. This option is
873		automatically enabled when you select CONFIG_CMD_DATE .
874
875- Partition Support:
876		CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
877		and/or CONFIG_ISO_PARTITION and/or CONFIG_EFI_PARTITION
878
879		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
880		CONFIG_CMD_SCSI) you must configure support for at
881		least one partition type as well.
882
883- IDE Reset method:
884		CONFIG_IDE_RESET_ROUTINE - this is defined in several
885		board configurations files but used nowhere!
886
887		CONFIG_IDE_RESET - is this is defined, IDE Reset will
888		be performed by calling the function
889			ide_set_reset(int reset)
890		which has to be defined in a board specific file
891
892- ATAPI Support:
893		CONFIG_ATAPI
894
895		Set this to enable ATAPI support.
896
897- LBA48 Support
898		CONFIG_LBA48
899
900		Set this to enable support for disks larger than 137GB
901		Also look at CONFIG_SYS_64BIT_LBA.
902		Whithout these , LBA48 support uses 32bit variables and will 'only'
903		support disks up to 2.1TB.
904
905		CONFIG_SYS_64BIT_LBA:
906			When enabled, makes the IDE subsystem use 64bit sector addresses.
907			Default is 32bit.
908
909- SCSI Support:
910		At the moment only there is only support for the
911		SYM53C8XX SCSI controller; define
912		CONFIG_SCSI_SYM53C8XX to enable it.
913
914		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
915		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
916		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
917		maximum numbers of LUNs, SCSI ID's and target
918		devices.
919		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
920
921- NETWORK Support (PCI):
922		CONFIG_E1000
923		Support for Intel 8254x gigabit chips.
924
925		CONFIG_E1000_FALLBACK_MAC
926		default MAC for empty EEPROM after production.
927
928		CONFIG_EEPRO100
929		Support for Intel 82557/82559/82559ER chips.
930		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
931		write routine for first time initialisation.
932
933		CONFIG_TULIP
934		Support for Digital 2114x chips.
935		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
936		modem chip initialisation (KS8761/QS6611).
937
938		CONFIG_NATSEMI
939		Support for National dp83815 chips.
940
941		CONFIG_NS8382X
942		Support for National dp8382[01] gigabit chips.
943
944- NETWORK Support (other):
945
946		CONFIG_DRIVER_AT91EMAC
947		Support for AT91RM9200 EMAC.
948
949			CONFIG_RMII
950			Define this to use reduced MII inteface
951
952			CONFIG_DRIVER_AT91EMAC_QUIET
953			If this defined, the driver is quiet.
954			The driver doen't show link status messages.
955
956		CONFIG_DRIVER_LAN91C96
957		Support for SMSC's LAN91C96 chips.
958
959			CONFIG_LAN91C96_BASE
960			Define this to hold the physical address
961			of the LAN91C96's I/O space
962
963			CONFIG_LAN91C96_USE_32_BIT
964			Define this to enable 32 bit addressing
965
966		CONFIG_DRIVER_SMC91111
967		Support for SMSC's LAN91C111 chip
968
969			CONFIG_SMC91111_BASE
970			Define this to hold the physical address
971			of the device (I/O space)
972
973			CONFIG_SMC_USE_32_BIT
974			Define this if data bus is 32 bits
975
976			CONFIG_SMC_USE_IOFUNCS
977			Define this to use i/o functions instead of macros
978			(some hardware wont work with macros)
979
980		CONFIG_FTGMAC100
981		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
982
983			CONFIG_FTGMAC100_EGIGA
984			Define this to use GE link update with gigabit PHY.
985			Define this if FTGMAC100 is connected to gigabit PHY.
986			If your system has 10/100 PHY only, it might not occur
987			wrong behavior. Because PHY usually return timeout or
988			useless data when polling gigabit status and gigabit
989			control registers. This behavior won't affect the
990			correctnessof 10/100 link speed update.
991
992		CONFIG_SMC911X
993		Support for SMSC's LAN911x and LAN921x chips
994
995			CONFIG_SMC911X_BASE
996			Define this to hold the physical address
997			of the device (I/O space)
998
999			CONFIG_SMC911X_32_BIT
1000			Define this if data bus is 32 bits
1001
1002			CONFIG_SMC911X_16_BIT
1003			Define this if data bus is 16 bits. If your processor
1004			automatically converts one 32 bit word to two 16 bit
1005			words you may also try CONFIG_SMC911X_32_BIT.
1006
1007		CONFIG_SH_ETHER
1008		Support for Renesas on-chip Ethernet controller
1009
1010			CONFIG_SH_ETHER_USE_PORT
1011			Define the number of ports to be used
1012
1013			CONFIG_SH_ETHER_PHY_ADDR
1014			Define the ETH PHY's address
1015
1016			CONFIG_SH_ETHER_CACHE_WRITEBACK
1017			If this option is set, the driver enables cache flush.
1018
1019- USB Support:
1020		At the moment only the UHCI host controller is
1021		supported (PIP405, MIP405, MPC5200); define
1022		CONFIG_USB_UHCI to enable it.
1023		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1024		and define CONFIG_USB_STORAGE to enable the USB
1025		storage devices.
1026		Note:
1027		Supported are USB Keyboards and USB Floppy drives
1028		(TEAC FD-05PUB).
1029		MPC5200 USB requires additional defines:
1030			CONFIG_USB_CLOCK
1031				for 528 MHz Clock: 0x0001bbbb
1032			CONFIG_PSC3_USB
1033				for USB on PSC3
1034			CONFIG_USB_CONFIG
1035				for differential drivers: 0x00001000
1036				for single ended drivers: 0x00005000
1037				for differential drivers on PSC3: 0x00000100
1038				for single ended drivers on PSC3: 0x00004100
1039			CONFIG_SYS_USB_EVENT_POLL
1040				May be defined to allow interrupt polling
1041				instead of using asynchronous interrupts
1042
1043- USB Device:
1044		Define the below if you wish to use the USB console.
1045		Once firmware is rebuilt from a serial console issue the
1046		command "setenv stdin usbtty; setenv stdout usbtty" and
1047		attach your USB cable. The Unix command "dmesg" should print
1048		it has found a new device. The environment variable usbtty
1049		can be set to gserial or cdc_acm to enable your device to
1050		appear to a USB host as a Linux gserial device or a
1051		Common Device Class Abstract Control Model serial device.
1052		If you select usbtty = gserial you should be able to enumerate
1053		a Linux host by
1054		# modprobe usbserial vendor=0xVendorID product=0xProductID
1055		else if using cdc_acm, simply setting the environment
1056		variable usbtty to be cdc_acm should suffice. The following
1057		might be defined in YourBoardName.h
1058
1059			CONFIG_USB_DEVICE
1060			Define this to build a UDC device
1061
1062			CONFIG_USB_TTY
1063			Define this to have a tty type of device available to
1064			talk to the UDC device
1065
1066			CONFIG_SYS_CONSOLE_IS_IN_ENV
1067			Define this if you want stdin, stdout &/or stderr to
1068			be set to usbtty.
1069
1070			mpc8xx:
1071				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1072				Derive USB clock from external clock "blah"
1073				- CONFIG_SYS_USB_EXTC_CLK 0x02
1074
1075				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1076				Derive USB clock from brgclk
1077				- CONFIG_SYS_USB_BRG_CLK 0x04
1078
1079		If you have a USB-IF assigned VendorID then you may wish to
1080		define your own vendor specific values either in BoardName.h
1081		or directly in usbd_vendor_info.h. If you don't define
1082		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1083		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1084		should pretend to be a Linux device to it's target host.
1085
1086			CONFIG_USBD_MANUFACTURER
1087			Define this string as the name of your company for
1088			- CONFIG_USBD_MANUFACTURER "my company"
1089
1090			CONFIG_USBD_PRODUCT_NAME
1091			Define this string as the name of your product
1092			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1093
1094			CONFIG_USBD_VENDORID
1095			Define this as your assigned Vendor ID from the USB
1096			Implementors Forum. This *must* be a genuine Vendor ID
1097			to avoid polluting the USB namespace.
1098			- CONFIG_USBD_VENDORID 0xFFFF
1099
1100			CONFIG_USBD_PRODUCTID
1101			Define this as the unique Product ID
1102			for your device
1103			- CONFIG_USBD_PRODUCTID 0xFFFF
1104
1105
1106- MMC Support:
1107		The MMC controller on the Intel PXA is supported. To
1108		enable this define CONFIG_MMC. The MMC can be
1109		accessed from the boot prompt by mapping the device
1110		to physical memory similar to flash. Command line is
1111		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1112		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1113
1114		CONFIG_SH_MMCIF
1115		Support for Renesas on-chip MMCIF controller
1116
1117			CONFIG_SH_MMCIF_ADDR
1118			Define the base address of MMCIF registers
1119
1120			CONFIG_SH_MMCIF_CLK
1121			Define the clock frequency for MMCIF
1122
1123- Journaling Flash filesystem support:
1124		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1125		CONFIG_JFFS2_NAND_DEV
1126		Define these for a default partition on a NAND device
1127
1128		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1129		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1130		Define these for a default partition on a NOR device
1131
1132		CONFIG_SYS_JFFS_CUSTOM_PART
1133		Define this to create an own partition. You have to provide a
1134		function struct part_info* jffs2_part_info(int part_num)
1135
1136		If you define only one JFFS2 partition you may also want to
1137		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1138		to disable the command chpart. This is the default when you
1139		have not defined a custom partition
1140
1141- Keyboard Support:
1142		CONFIG_ISA_KEYBOARD
1143
1144		Define this to enable standard (PC-Style) keyboard
1145		support
1146
1147		CONFIG_I8042_KBD
1148		Standard PC keyboard driver with US (is default) and
1149		GERMAN key layout (switch via environment 'keymap=de') support.
1150		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1151		for cfb_console. Supports cursor blinking.
1152
1153- Video support:
1154		CONFIG_VIDEO
1155
1156		Define this to enable video support (for output to
1157		video).
1158
1159		CONFIG_VIDEO_CT69000
1160
1161		Enable Chips & Technologies 69000 Video chip
1162
1163		CONFIG_VIDEO_SMI_LYNXEM
1164		Enable Silicon Motion SMI 712/710/810 Video chip. The
1165		video output is selected via environment 'videoout'
1166		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1167		assumed.
1168
1169		For the CT69000 and SMI_LYNXEM drivers, videomode is
1170		selected via environment 'videomode'. Two different ways
1171		are possible:
1172		- "videomode=num"   'num' is a standard LiLo mode numbers.
1173		Following standard modes are supported	(* is default):
1174
1175		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1176		-------------+---------------------------------------------
1177		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1178		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1179		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1180		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1181		-------------+---------------------------------------------
1182		(i.e. setenv videomode 317; saveenv; reset;)
1183
1184		- "videomode=bootargs" all the video parameters are parsed
1185		from the bootargs. (See drivers/video/videomodes.c)
1186
1187
1188		CONFIG_VIDEO_SED13806
1189		Enable Epson SED13806 driver. This driver supports 8bpp
1190		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1191		or CONFIG_VIDEO_SED13806_16BPP
1192
1193		CONFIG_FSL_DIU_FB
1194		Enable the Freescale DIU video driver.	Reference boards for
1195		SOCs that have a DIU should define this macro to enable DIU
1196		support, and should also define these other macros:
1197
1198			CONFIG_SYS_DIU_ADDR
1199			CONFIG_VIDEO
1200			CONFIG_CMD_BMP
1201			CONFIG_CFB_CONSOLE
1202			CONFIG_VIDEO_SW_CURSOR
1203			CONFIG_VGA_AS_SINGLE_DEVICE
1204			CONFIG_VIDEO_LOGO
1205			CONFIG_VIDEO_BMP_LOGO
1206
1207		The DIU driver will look for the 'video-mode' environment
1208		variable, and if defined, enable the DIU as a console during
1209		boot.  See the documentation file README.video for a
1210		description of this variable.
1211
1212- Keyboard Support:
1213		CONFIG_KEYBOARD
1214
1215		Define this to enable a custom keyboard support.
1216		This simply calls drv_keyboard_init() which must be
1217		defined in your board-specific files.
1218		The only board using this so far is RBC823.
1219
1220- LCD Support:	CONFIG_LCD
1221
1222		Define this to enable LCD support (for output to LCD
1223		display); also select one of the supported displays
1224		by defining one of these:
1225
1226		CONFIG_ATMEL_LCD:
1227
1228			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1229
1230		CONFIG_NEC_NL6448AC33:
1231
1232			NEC NL6448AC33-18. Active, color, single scan.
1233
1234		CONFIG_NEC_NL6448BC20
1235
1236			NEC NL6448BC20-08. 6.5", 640x480.
1237			Active, color, single scan.
1238
1239		CONFIG_NEC_NL6448BC33_54
1240
1241			NEC NL6448BC33-54. 10.4", 640x480.
1242			Active, color, single scan.
1243
1244		CONFIG_SHARP_16x9
1245
1246			Sharp 320x240. Active, color, single scan.
1247			It isn't 16x9, and I am not sure what it is.
1248
1249		CONFIG_SHARP_LQ64D341
1250
1251			Sharp LQ64D341 display, 640x480.
1252			Active, color, single scan.
1253
1254		CONFIG_HLD1045
1255
1256			HLD1045 display, 640x480.
1257			Active, color, single scan.
1258
1259		CONFIG_OPTREX_BW
1260
1261			Optrex	 CBL50840-2 NF-FW 99 22 M5
1262			or
1263			Hitachi	 LMG6912RPFC-00T
1264			or
1265			Hitachi	 SP14Q002
1266
1267			320x240. Black & white.
1268
1269		Normally display is black on white background; define
1270		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1271
1272- Splash Screen Support: CONFIG_SPLASH_SCREEN
1273
1274		If this option is set, the environment is checked for
1275		a variable "splashimage". If found, the usual display
1276		of logo, copyright and system information on the LCD
1277		is suppressed and the BMP image at the address
1278		specified in "splashimage" is loaded instead. The
1279		console is redirected to the "nulldev", too. This
1280		allows for a "silent" boot where a splash screen is
1281		loaded very quickly after power-on.
1282
1283		CONFIG_SPLASH_SCREEN_ALIGN
1284
1285		If this option is set the splash image can be freely positioned
1286		on the screen. Environment variable "splashpos" specifies the
1287		position as "x,y". If a positive number is given it is used as
1288		number of pixel from left/top. If a negative number is given it
1289		is used as number of pixel from right/bottom. You can also
1290		specify 'm' for centering the image.
1291
1292		Example:
1293		setenv splashpos m,m
1294			=> image at center of screen
1295
1296		setenv splashpos 30,20
1297			=> image at x = 30 and y = 20
1298
1299		setenv splashpos -10,m
1300			=> vertically centered image
1301			   at x = dspWidth - bmpWidth - 9
1302
1303- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1304
1305		If this option is set, additionally to standard BMP
1306		images, gzipped BMP images can be displayed via the
1307		splashscreen support or the bmp command.
1308
1309- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1310
1311		If this option is set, 8-bit RLE compressed BMP images
1312		can be displayed via the splashscreen support or the
1313		bmp command.
1314
1315- Compression support:
1316		CONFIG_BZIP2
1317
1318		If this option is set, support for bzip2 compressed
1319		images is included. If not, only uncompressed and gzip
1320		compressed images are supported.
1321
1322		NOTE: the bzip2 algorithm requires a lot of RAM, so
1323		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1324		be at least 4MB.
1325
1326		CONFIG_LZMA
1327
1328		If this option is set, support for lzma compressed
1329		images is included.
1330
1331		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1332		requires an amount of dynamic memory that is given by the
1333		formula:
1334
1335			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1336
1337		Where lc and lp stand for, respectively, Literal context bits
1338		and Literal pos bits.
1339
1340		This value is upper-bounded by 14MB in the worst case. Anyway,
1341		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1342		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1343		a very small buffer.
1344
1345		Use the lzmainfo tool to determinate the lc and lp values and
1346		then calculate the amount of needed dynamic memory (ensuring
1347		the appropriate CONFIG_SYS_MALLOC_LEN value).
1348
1349- MII/PHY support:
1350		CONFIG_PHY_ADDR
1351
1352		The address of PHY on MII bus.
1353
1354		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1355
1356		The clock frequency of the MII bus
1357
1358		CONFIG_PHY_GIGE
1359
1360		If this option is set, support for speed/duplex
1361		detection of gigabit PHY is included.
1362
1363		CONFIG_PHY_RESET_DELAY
1364
1365		Some PHY like Intel LXT971A need extra delay after
1366		reset before any MII register access is possible.
1367		For such PHY, set this option to the usec delay
1368		required. (minimum 300usec for LXT971A)
1369
1370		CONFIG_PHY_CMD_DELAY (ppc4xx)
1371
1372		Some PHY like Intel LXT971A need extra delay after
1373		command issued before MII status register can be read
1374
1375- Ethernet address:
1376		CONFIG_ETHADDR
1377		CONFIG_ETH1ADDR
1378		CONFIG_ETH2ADDR
1379		CONFIG_ETH3ADDR
1380		CONFIG_ETH4ADDR
1381		CONFIG_ETH5ADDR
1382
1383		Define a default value for Ethernet address to use
1384		for the respective Ethernet interface, in case this
1385		is not determined automatically.
1386
1387- IP address:
1388		CONFIG_IPADDR
1389
1390		Define a default value for the IP address to use for
1391		the default Ethernet interface, in case this is not
1392		determined through e.g. bootp.
1393
1394- Server IP address:
1395		CONFIG_SERVERIP
1396
1397		Defines a default value for the IP address of a TFTP
1398		server to contact when using the "tftboot" command.
1399
1400		CONFIG_KEEP_SERVERADDR
1401
1402		Keeps the server's MAC address, in the env 'serveraddr'
1403		for passing to bootargs (like Linux's netconsole option)
1404
1405- Multicast TFTP Mode:
1406		CONFIG_MCAST_TFTP
1407
1408		Defines whether you want to support multicast TFTP as per
1409		rfc-2090; for example to work with atftp.  Lets lots of targets
1410		tftp down the same boot image concurrently.  Note: the Ethernet
1411		driver in use must provide a function: mcast() to join/leave a
1412		multicast group.
1413
1414- BOOTP Recovery Mode:
1415		CONFIG_BOOTP_RANDOM_DELAY
1416
1417		If you have many targets in a network that try to
1418		boot using BOOTP, you may want to avoid that all
1419		systems send out BOOTP requests at precisely the same
1420		moment (which would happen for instance at recovery
1421		from a power failure, when all systems will try to
1422		boot, thus flooding the BOOTP server. Defining
1423		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1424		inserted before sending out BOOTP requests. The
1425		following delays are inserted then:
1426
1427		1st BOOTP request:	delay 0 ... 1 sec
1428		2nd BOOTP request:	delay 0 ... 2 sec
1429		3rd BOOTP request:	delay 0 ... 4 sec
1430		4th and following
1431		BOOTP requests:		delay 0 ... 8 sec
1432
1433- DHCP Advanced Options:
1434		You can fine tune the DHCP functionality by defining
1435		CONFIG_BOOTP_* symbols:
1436
1437		CONFIG_BOOTP_SUBNETMASK
1438		CONFIG_BOOTP_GATEWAY
1439		CONFIG_BOOTP_HOSTNAME
1440		CONFIG_BOOTP_NISDOMAIN
1441		CONFIG_BOOTP_BOOTPATH
1442		CONFIG_BOOTP_BOOTFILESIZE
1443		CONFIG_BOOTP_DNS
1444		CONFIG_BOOTP_DNS2
1445		CONFIG_BOOTP_SEND_HOSTNAME
1446		CONFIG_BOOTP_NTPSERVER
1447		CONFIG_BOOTP_TIMEOFFSET
1448		CONFIG_BOOTP_VENDOREX
1449
1450		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1451		environment variable, not the BOOTP server.
1452
1453		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1454		serverip from a DHCP server, it is possible that more
1455		than one DNS serverip is offered to the client.
1456		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1457		serverip will be stored in the additional environment
1458		variable "dnsip2". The first DNS serverip is always
1459		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1460		is defined.
1461
1462		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1463		to do a dynamic update of a DNS server. To do this, they
1464		need the hostname of the DHCP requester.
1465		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1466		of the "hostname" environment variable is passed as
1467		option 12 to the DHCP server.
1468
1469		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1470
1471		A 32bit value in microseconds for a delay between
1472		receiving a "DHCP Offer" and sending the "DHCP Request".
1473		This fixes a problem with certain DHCP servers that don't
1474		respond 100% of the time to a "DHCP request". E.g. On an
1475		AT91RM9200 processor running at 180MHz, this delay needed
1476		to be *at least* 15,000 usec before a Windows Server 2003
1477		DHCP server would reply 100% of the time. I recommend at
1478		least 50,000 usec to be safe. The alternative is to hope
1479		that one of the retries will be successful but note that
1480		the DHCP timeout and retry process takes a longer than
1481		this delay.
1482
1483 - CDP Options:
1484		CONFIG_CDP_DEVICE_ID
1485
1486		The device id used in CDP trigger frames.
1487
1488		CONFIG_CDP_DEVICE_ID_PREFIX
1489
1490		A two character string which is prefixed to the MAC address
1491		of the device.
1492
1493		CONFIG_CDP_PORT_ID
1494
1495		A printf format string which contains the ascii name of
1496		the port. Normally is set to "eth%d" which sets
1497		eth0 for the first Ethernet, eth1 for the second etc.
1498
1499		CONFIG_CDP_CAPABILITIES
1500
1501		A 32bit integer which indicates the device capabilities;
1502		0x00000010 for a normal host which does not forwards.
1503
1504		CONFIG_CDP_VERSION
1505
1506		An ascii string containing the version of the software.
1507
1508		CONFIG_CDP_PLATFORM
1509
1510		An ascii string containing the name of the platform.
1511
1512		CONFIG_CDP_TRIGGER
1513
1514		A 32bit integer sent on the trigger.
1515
1516		CONFIG_CDP_POWER_CONSUMPTION
1517
1518		A 16bit integer containing the power consumption of the
1519		device in .1 of milliwatts.
1520
1521		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1522
1523		A byte containing the id of the VLAN.
1524
1525- Status LED:	CONFIG_STATUS_LED
1526
1527		Several configurations allow to display the current
1528		status using a LED. For instance, the LED will blink
1529		fast while running U-Boot code, stop blinking as
1530		soon as a reply to a BOOTP request was received, and
1531		start blinking slow once the Linux kernel is running
1532		(supported by a status LED driver in the Linux
1533		kernel). Defining CONFIG_STATUS_LED enables this
1534		feature in U-Boot.
1535
1536- CAN Support:	CONFIG_CAN_DRIVER
1537
1538		Defining CONFIG_CAN_DRIVER enables CAN driver support
1539		on those systems that support this (optional)
1540		feature, like the TQM8xxL modules.
1541
1542- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1543
1544		These enable I2C serial bus commands. Defining either of
1545		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1546		include the appropriate I2C driver for the selected CPU.
1547
1548		This will allow you to use i2c commands at the u-boot
1549		command line (as long as you set CONFIG_CMD_I2C in
1550		CONFIG_COMMANDS) and communicate with i2c based realtime
1551		clock chips. See common/cmd_i2c.c for a description of the
1552		command line interface.
1553
1554		CONFIG_HARD_I2C selects a hardware I2C controller.
1555
1556		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1557		bit-banging) driver instead of CPM or similar hardware
1558		support for I2C.
1559
1560		There are several other quantities that must also be
1561		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1562
1563		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1564		to be the frequency (in Hz) at which you wish your i2c bus
1565		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1566		the CPU's i2c node address).
1567
1568		Now, the u-boot i2c code for the mpc8xx
1569		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1570		and so its address should therefore be cleared to 0 (See,
1571		eg, MPC823e User's Manual p.16-473). So, set
1572		CONFIG_SYS_I2C_SLAVE to 0.
1573
1574		CONFIG_SYS_I2C_INIT_MPC5XXX
1575
1576		When a board is reset during an i2c bus transfer
1577		chips might think that the current transfer is still
1578		in progress.  Reset the slave devices by sending start
1579		commands until the slave device responds.
1580
1581		That's all that's required for CONFIG_HARD_I2C.
1582
1583		If you use the software i2c interface (CONFIG_SOFT_I2C)
1584		then the following macros need to be defined (examples are
1585		from include/configs/lwmon.h):
1586
1587		I2C_INIT
1588
1589		(Optional). Any commands necessary to enable the I2C
1590		controller or configure ports.
1591
1592		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1593
1594		I2C_PORT
1595
1596		(Only for MPC8260 CPU). The I/O port to use (the code
1597		assumes both bits are on the same port). Valid values
1598		are 0..3 for ports A..D.
1599
1600		I2C_ACTIVE
1601
1602		The code necessary to make the I2C data line active
1603		(driven).  If the data line is open collector, this
1604		define can be null.
1605
1606		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1607
1608		I2C_TRISTATE
1609
1610		The code necessary to make the I2C data line tri-stated
1611		(inactive).  If the data line is open collector, this
1612		define can be null.
1613
1614		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1615
1616		I2C_READ
1617
1618		Code that returns TRUE if the I2C data line is high,
1619		FALSE if it is low.
1620
1621		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1622
1623		I2C_SDA(bit)
1624
1625		If <bit> is TRUE, sets the I2C data line high. If it
1626		is FALSE, it clears it (low).
1627
1628		eg: #define I2C_SDA(bit) \
1629			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1630			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1631
1632		I2C_SCL(bit)
1633
1634		If <bit> is TRUE, sets the I2C clock line high. If it
1635		is FALSE, it clears it (low).
1636
1637		eg: #define I2C_SCL(bit) \
1638			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1639			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1640
1641		I2C_DELAY
1642
1643		This delay is invoked four times per clock cycle so this
1644		controls the rate of data transfer.  The data rate thus
1645		is 1 / (I2C_DELAY * 4). Often defined to be something
1646		like:
1647
1648		#define I2C_DELAY  udelay(2)
1649
1650		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1651
1652		If your arch supports the generic GPIO framework (asm/gpio.h),
1653		then you may alternatively define the two GPIOs that are to be
1654		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1655		have GPIO-based defaults assigned to them as appropriate.
1656
1657		You should define these to the GPIO value as given directly to
1658		the generic GPIO functions.
1659
1660		CONFIG_SYS_I2C_INIT_BOARD
1661
1662		When a board is reset during an i2c bus transfer
1663		chips might think that the current transfer is still
1664		in progress. On some boards it is possible to access
1665		the i2c SCLK line directly, either by using the
1666		processor pin as a GPIO or by having a second pin
1667		connected to the bus. If this option is defined a
1668		custom i2c_init_board() routine in boards/xxx/board.c
1669		is run early in the boot sequence.
1670
1671		CONFIG_SYS_I2C_BOARD_LATE_INIT
1672
1673		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
1674		defined a custom i2c_board_late_init() routine in
1675		boards/xxx/board.c is run AFTER the operations in i2c_init()
1676		is completed. This callpoint can be used to unreset i2c bus
1677		using CPU i2c controller register accesses for CPUs whose i2c
1678		controller provide such a method. It is called at the end of
1679		i2c_init() to allow i2c_init operations to setup the i2c bus
1680		controller on the CPU (e.g. setting bus speed & slave address).
1681
1682		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1683
1684		This option enables configuration of bi_iic_fast[] flags
1685		in u-boot bd_info structure based on u-boot environment
1686		variable "i2cfast". (see also i2cfast)
1687
1688		CONFIG_I2C_MULTI_BUS
1689
1690		This option allows the use of multiple I2C buses, each of which
1691		must have a controller.  At any point in time, only one bus is
1692		active.  To switch to a different bus, use the 'i2c dev' command.
1693		Note that bus numbering is zero-based.
1694
1695		CONFIG_SYS_I2C_NOPROBES
1696
1697		This option specifies a list of I2C devices that will be skipped
1698		when the 'i2c probe' command is issued.  If CONFIG_I2C_MULTI_BUS
1699		is set, specify a list of bus-device pairs.  Otherwise, specify
1700		a 1D array of device addresses
1701
1702		e.g.
1703			#undef	CONFIG_I2C_MULTI_BUS
1704			#define CONFIG_SYS_I2C_NOPROBES	{0x50,0x68}
1705
1706		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1707
1708			#define	CONFIG_I2C_MULTI_BUS
1709			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1710
1711		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1712
1713		CONFIG_SYS_SPD_BUS_NUM
1714
1715		If defined, then this indicates the I2C bus number for DDR SPD.
1716		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1717
1718		CONFIG_SYS_RTC_BUS_NUM
1719
1720		If defined, then this indicates the I2C bus number for the RTC.
1721		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1722
1723		CONFIG_SYS_DTT_BUS_NUM
1724
1725		If defined, then this indicates the I2C bus number for the DTT.
1726		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1727
1728		CONFIG_SYS_I2C_DTT_ADDR:
1729
1730		If defined, specifies the I2C address of the DTT device.
1731		If not defined, then U-Boot uses predefined value for
1732		specified DTT device.
1733
1734		CONFIG_FSL_I2C
1735
1736		Define this option if you want to use Freescale's I2C driver in
1737		drivers/i2c/fsl_i2c.c.
1738
1739		CONFIG_I2C_MUX
1740
1741		Define this option if you have I2C devices reached over 1 .. n
1742		I2C Muxes like the pca9544a. This option addes a new I2C
1743		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
1744		new I2C Bus to the existing I2C Busses. If you select the
1745		new Bus with "i2c dev", u-bbot sends first the commandos for
1746		the muxes to activate this new "bus".
1747
1748		CONFIG_I2C_MULTI_BUS must be also defined, to use this
1749		feature!
1750
1751		Example:
1752		Adding a new I2C Bus reached over 2 pca9544a muxes
1753			The First mux with address 70 and channel 6
1754			The Second mux with address 71 and channel 4
1755
1756		=> i2c bus pca9544a:70:6:pca9544a:71:4
1757
1758		Use the "i2c bus" command without parameter, to get a list
1759		of I2C Busses with muxes:
1760
1761		=> i2c bus
1762		Busses reached over muxes:
1763		Bus ID: 2
1764		  reached over Mux(es):
1765		    pca9544a@70 ch: 4
1766		Bus ID: 3
1767		  reached over Mux(es):
1768		    pca9544a@70 ch: 6
1769		    pca9544a@71 ch: 4
1770		=>
1771
1772		If you now switch to the new I2C Bus 3 with "i2c dev 3"
1773		u-boot first sends the command to the mux@70 to enable
1774		channel 6, and then the command to the mux@71 to enable
1775		the channel 4.
1776
1777		After that, you can use the "normal" i2c commands as
1778		usual to communicate with your I2C devices behind
1779		the 2 muxes.
1780
1781		This option is actually implemented for the bitbanging
1782		algorithm in common/soft_i2c.c and for the Hardware I2C
1783		Bus on the MPC8260. But it should be not so difficult
1784		to add this option to other architectures.
1785
1786		CONFIG_SOFT_I2C_READ_REPEATED_START
1787
1788		defining this will force the i2c_read() function in
1789		the soft_i2c driver to perform an I2C repeated start
1790		between writing the address pointer and reading the
1791		data.  If this define is omitted the default behaviour
1792		of doing a stop-start sequence will be used.  Most I2C
1793		devices can use either method, but some require one or
1794		the other.
1795
1796- SPI Support:	CONFIG_SPI
1797
1798		Enables SPI driver (so far only tested with
1799		SPI EEPROM, also an instance works with Crystal A/D and
1800		D/As on the SACSng board)
1801
1802		CONFIG_SH_SPI
1803
1804		Enables the driver for SPI controller on SuperH. Currently
1805		only SH7757 is supported.
1806
1807		CONFIG_SPI_X
1808
1809		Enables extended (16-bit) SPI EEPROM addressing.
1810		(symmetrical to CONFIG_I2C_X)
1811
1812		CONFIG_SOFT_SPI
1813
1814		Enables a software (bit-bang) SPI driver rather than
1815		using hardware support. This is a general purpose
1816		driver that only requires three general I/O port pins
1817		(two outputs, one input) to function. If this is
1818		defined, the board configuration must define several
1819		SPI configuration items (port pins to use, etc). For
1820		an example, see include/configs/sacsng.h.
1821
1822		CONFIG_HARD_SPI
1823
1824		Enables a hardware SPI driver for general-purpose reads
1825		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1826		must define a list of chip-select function pointers.
1827		Currently supported on some MPC8xxx processors.  For an
1828		example, see include/configs/mpc8349emds.h.
1829
1830		CONFIG_MXC_SPI
1831
1832		Enables the driver for the SPI controllers on i.MX and MXC
1833		SoCs. Currently only i.MX31 is supported.
1834
1835- FPGA Support: CONFIG_FPGA
1836
1837		Enables FPGA subsystem.
1838
1839		CONFIG_FPGA_<vendor>
1840
1841		Enables support for specific chip vendors.
1842		(ALTERA, XILINX)
1843
1844		CONFIG_FPGA_<family>
1845
1846		Enables support for FPGA family.
1847		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1848
1849		CONFIG_FPGA_COUNT
1850
1851		Specify the number of FPGA devices to support.
1852
1853		CONFIG_SYS_FPGA_PROG_FEEDBACK
1854
1855		Enable printing of hash marks during FPGA configuration.
1856
1857		CONFIG_SYS_FPGA_CHECK_BUSY
1858
1859		Enable checks on FPGA configuration interface busy
1860		status by the configuration function. This option
1861		will require a board or device specific function to
1862		be written.
1863
1864		CONFIG_FPGA_DELAY
1865
1866		If defined, a function that provides delays in the FPGA
1867		configuration driver.
1868
1869		CONFIG_SYS_FPGA_CHECK_CTRLC
1870		Allow Control-C to interrupt FPGA configuration
1871
1872		CONFIG_SYS_FPGA_CHECK_ERROR
1873
1874		Check for configuration errors during FPGA bitfile
1875		loading. For example, abort during Virtex II
1876		configuration if the INIT_B line goes low (which
1877		indicated a CRC error).
1878
1879		CONFIG_SYS_FPGA_WAIT_INIT
1880
1881		Maximum time to wait for the INIT_B line to deassert
1882		after PROB_B has been deasserted during a Virtex II
1883		FPGA configuration sequence. The default time is 500
1884		ms.
1885
1886		CONFIG_SYS_FPGA_WAIT_BUSY
1887
1888		Maximum time to wait for BUSY to deassert during
1889		Virtex II FPGA configuration. The default is 5 ms.
1890
1891		CONFIG_SYS_FPGA_WAIT_CONFIG
1892
1893		Time to wait after FPGA configuration. The default is
1894		200 ms.
1895
1896- Configuration Management:
1897		CONFIG_IDENT_STRING
1898
1899		If defined, this string will be added to the U-Boot
1900		version information (U_BOOT_VERSION)
1901
1902- Vendor Parameter Protection:
1903
1904		U-Boot considers the values of the environment
1905		variables "serial#" (Board Serial Number) and
1906		"ethaddr" (Ethernet Address) to be parameters that
1907		are set once by the board vendor / manufacturer, and
1908		protects these variables from casual modification by
1909		the user. Once set, these variables are read-only,
1910		and write or delete attempts are rejected. You can
1911		change this behaviour:
1912
1913		If CONFIG_ENV_OVERWRITE is #defined in your config
1914		file, the write protection for vendor parameters is
1915		completely disabled. Anybody can change or delete
1916		these parameters.
1917
1918		Alternatively, if you #define _both_ CONFIG_ETHADDR
1919		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1920		Ethernet address is installed in the environment,
1921		which can be changed exactly ONCE by the user. [The
1922		serial# is unaffected by this, i. e. it remains
1923		read-only.]
1924
1925- Protected RAM:
1926		CONFIG_PRAM
1927
1928		Define this variable to enable the reservation of
1929		"protected RAM", i. e. RAM which is not overwritten
1930		by U-Boot. Define CONFIG_PRAM to hold the number of
1931		kB you want to reserve for pRAM. You can overwrite
1932		this default value by defining an environment
1933		variable "pram" to the number of kB you want to
1934		reserve. Note that the board info structure will
1935		still show the full amount of RAM. If pRAM is
1936		reserved, a new environment variable "mem" will
1937		automatically be defined to hold the amount of
1938		remaining RAM in a form that can be passed as boot
1939		argument to Linux, for instance like that:
1940
1941			setenv bootargs ... mem=\${mem}
1942			saveenv
1943
1944		This way you can tell Linux not to use this memory,
1945		either, which results in a memory region that will
1946		not be affected by reboots.
1947
1948		*WARNING* If your board configuration uses automatic
1949		detection of the RAM size, you must make sure that
1950		this memory test is non-destructive. So far, the
1951		following board configurations are known to be
1952		"pRAM-clean":
1953
1954			ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
1955			HERMES, IP860, RPXlite, LWMON, LANTEC,
1956			FLAGADM, TQM8260
1957
1958- Error Recovery:
1959		CONFIG_PANIC_HANG
1960
1961		Define this variable to stop the system in case of a
1962		fatal error, so that you have to reset it manually.
1963		This is probably NOT a good idea for an embedded
1964		system where you want the system to reboot
1965		automatically as fast as possible, but it may be
1966		useful during development since you can try to debug
1967		the conditions that lead to the situation.
1968
1969		CONFIG_NET_RETRY_COUNT
1970
1971		This variable defines the number of retries for
1972		network operations like ARP, RARP, TFTP, or BOOTP
1973		before giving up the operation. If not defined, a
1974		default value of 5 is used.
1975
1976		CONFIG_ARP_TIMEOUT
1977
1978		Timeout waiting for an ARP reply in milliseconds.
1979
1980- Command Interpreter:
1981		CONFIG_AUTO_COMPLETE
1982
1983		Enable auto completion of commands using TAB.
1984
1985		Note that this feature has NOT been implemented yet
1986		for the "hush" shell.
1987
1988
1989		CONFIG_SYS_HUSH_PARSER
1990
1991		Define this variable to enable the "hush" shell (from
1992		Busybox) as command line interpreter, thus enabling
1993		powerful command line syntax like
1994		if...then...else...fi conditionals or `&&' and '||'
1995		constructs ("shell scripts").
1996
1997		If undefined, you get the old, much simpler behaviour
1998		with a somewhat smaller memory footprint.
1999
2000
2001		CONFIG_SYS_PROMPT_HUSH_PS2
2002
2003		This defines the secondary prompt string, which is
2004		printed when the command interpreter needs more input
2005		to complete a command. Usually "> ".
2006
2007	Note:
2008
2009		In the current implementation, the local variables
2010		space and global environment variables space are
2011		separated. Local variables are those you define by
2012		simply typing `name=value'. To access a local
2013		variable later on, you have write `$name' or
2014		`${name}'; to execute the contents of a variable
2015		directly type `$name' at the command prompt.
2016
2017		Global environment variables are those you use
2018		setenv/printenv to work with. To run a command stored
2019		in such a variable, you need to use the run command,
2020		and you must not use the '$' sign to access them.
2021
2022		To store commands and special characters in a
2023		variable, please use double quotation marks
2024		surrounding the whole text of the variable, instead
2025		of the backslashes before semicolons and special
2026		symbols.
2027
2028- Commandline Editing and History:
2029		CONFIG_CMDLINE_EDITING
2030
2031		Enable editing and History functions for interactive
2032		commandline input operations
2033
2034- Default Environment:
2035		CONFIG_EXTRA_ENV_SETTINGS
2036
2037		Define this to contain any number of null terminated
2038		strings (variable = value pairs) that will be part of
2039		the default environment compiled into the boot image.
2040
2041		For example, place something like this in your
2042		board's config file:
2043
2044		#define CONFIG_EXTRA_ENV_SETTINGS \
2045			"myvar1=value1\0" \
2046			"myvar2=value2\0"
2047
2048		Warning: This method is based on knowledge about the
2049		internal format how the environment is stored by the
2050		U-Boot code. This is NOT an official, exported
2051		interface! Although it is unlikely that this format
2052		will change soon, there is no guarantee either.
2053		You better know what you are doing here.
2054
2055		Note: overly (ab)use of the default environment is
2056		discouraged. Make sure to check other ways to preset
2057		the environment like the "source" command or the
2058		boot command first.
2059
2060- DataFlash Support:
2061		CONFIG_HAS_DATAFLASH
2062
2063		Defining this option enables DataFlash features and
2064		allows to read/write in Dataflash via the standard
2065		commands cp, md...
2066
2067- SystemACE Support:
2068		CONFIG_SYSTEMACE
2069
2070		Adding this option adds support for Xilinx SystemACE
2071		chips attached via some sort of local bus. The address
2072		of the chip must also be defined in the
2073		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2074
2075		#define CONFIG_SYSTEMACE
2076		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2077
2078		When SystemACE support is added, the "ace" device type
2079		becomes available to the fat commands, i.e. fatls.
2080
2081- TFTP Fixed UDP Port:
2082		CONFIG_TFTP_PORT
2083
2084		If this is defined, the environment variable tftpsrcp
2085		is used to supply the TFTP UDP source port value.
2086		If tftpsrcp isn't defined, the normal pseudo-random port
2087		number generator is used.
2088
2089		Also, the environment variable tftpdstp is used to supply
2090		the TFTP UDP destination port value.  If tftpdstp isn't
2091		defined, the normal port 69 is used.
2092
2093		The purpose for tftpsrcp is to allow a TFTP server to
2094		blindly start the TFTP transfer using the pre-configured
2095		target IP address and UDP port. This has the effect of
2096		"punching through" the (Windows XP) firewall, allowing
2097		the remainder of the TFTP transfer to proceed normally.
2098		A better solution is to properly configure the firewall,
2099		but sometimes that is not allowed.
2100
2101- Show boot progress:
2102		CONFIG_SHOW_BOOT_PROGRESS
2103
2104		Defining this option allows to add some board-
2105		specific code (calling a user-provided function
2106		"show_boot_progress(int)") that enables you to show
2107		the system's boot progress on some display (for
2108		example, some LED's) on your board. At the moment,
2109		the following checkpoints are implemented:
2110
2111- Standalone program support:
2112		CONFIG_STANDALONE_LOAD_ADDR
2113
2114		This option allows to define board specific values
2115		for the address where standalone program gets loaded,
2116		thus overwriting the architecutre dependent default
2117		settings.
2118
2119- Frame Buffer Address:
2120	CONFIG_FB_ADDR
2121
2122	Define CONFIG_FB_ADDR if you want to use specific address for
2123	frame buffer.
2124	Then system will reserve the frame buffer address to defined address
2125	instead of lcd_setmem (this function grab the memory for frame buffer
2126	by panel's size).
2127
2128	Please see board_init_f function.
2129
2130	If you want this config option then,
2131	please define it at your board config file
2132
2133Legacy uImage format:
2134
2135  Arg	Where			When
2136    1	common/cmd_bootm.c	before attempting to boot an image
2137   -1	common/cmd_bootm.c	Image header has bad	 magic number
2138    2	common/cmd_bootm.c	Image header has correct magic number
2139   -2	common/cmd_bootm.c	Image header has bad	 checksum
2140    3	common/cmd_bootm.c	Image header has correct checksum
2141   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2142    4	common/cmd_bootm.c	Image data   has correct checksum
2143   -4	common/cmd_bootm.c	Image is for unsupported architecture
2144    5	common/cmd_bootm.c	Architecture check OK
2145   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2146    6	common/cmd_bootm.c	Image Type check OK
2147   -6	common/cmd_bootm.c	gunzip uncompression error
2148   -7	common/cmd_bootm.c	Unimplemented compression type
2149    7	common/cmd_bootm.c	Uncompression OK
2150    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2151   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2152
2153    9	common/image.c		Start initial ramdisk verification
2154  -10	common/image.c		Ramdisk header has bad	   magic number
2155  -11	common/image.c		Ramdisk header has bad	   checksum
2156   10	common/image.c		Ramdisk header is OK
2157  -12	common/image.c		Ramdisk data   has bad	   checksum
2158   11	common/image.c		Ramdisk data   has correct checksum
2159   12	common/image.c		Ramdisk verification complete, start loading
2160  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2161   13	common/image.c		Start multifile image verification
2162   14	common/image.c		No initial ramdisk, no multifile, continue.
2163
2164   15	arch/<arch>/lib/bootm.c	All preparation done, transferring control to OS
2165
2166  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2167  -31	post/post.c		POST test failed, detected by post_output_backlog()
2168  -32	post/post.c		POST test failed, detected by post_run_single()
2169
2170   34	common/cmd_doc.c	before loading a Image from a DOC device
2171  -35	common/cmd_doc.c	Bad usage of "doc" command
2172   35	common/cmd_doc.c	correct usage of "doc" command
2173  -36	common/cmd_doc.c	No boot device
2174   36	common/cmd_doc.c	correct boot device
2175  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2176   37	common/cmd_doc.c	correct chip ID found, device available
2177  -38	common/cmd_doc.c	Read Error on boot device
2178   38	common/cmd_doc.c	reading Image header from DOC device OK
2179  -39	common/cmd_doc.c	Image header has bad magic number
2180   39	common/cmd_doc.c	Image header has correct magic number
2181  -40	common/cmd_doc.c	Error reading Image from DOC device
2182   40	common/cmd_doc.c	Image header has correct magic number
2183   41	common/cmd_ide.c	before loading a Image from a IDE device
2184  -42	common/cmd_ide.c	Bad usage of "ide" command
2185   42	common/cmd_ide.c	correct usage of "ide" command
2186  -43	common/cmd_ide.c	No boot device
2187   43	common/cmd_ide.c	boot device found
2188  -44	common/cmd_ide.c	Device not available
2189   44	common/cmd_ide.c	Device available
2190  -45	common/cmd_ide.c	wrong partition selected
2191   45	common/cmd_ide.c	partition selected
2192  -46	common/cmd_ide.c	Unknown partition table
2193   46	common/cmd_ide.c	valid partition table found
2194  -47	common/cmd_ide.c	Invalid partition type
2195   47	common/cmd_ide.c	correct partition type
2196  -48	common/cmd_ide.c	Error reading Image Header on boot device
2197   48	common/cmd_ide.c	reading Image Header from IDE device OK
2198  -49	common/cmd_ide.c	Image header has bad magic number
2199   49	common/cmd_ide.c	Image header has correct magic number
2200  -50	common/cmd_ide.c	Image header has bad	 checksum
2201   50	common/cmd_ide.c	Image header has correct checksum
2202  -51	common/cmd_ide.c	Error reading Image from IDE device
2203   51	common/cmd_ide.c	reading Image from IDE device OK
2204   52	common/cmd_nand.c	before loading a Image from a NAND device
2205  -53	common/cmd_nand.c	Bad usage of "nand" command
2206   53	common/cmd_nand.c	correct usage of "nand" command
2207  -54	common/cmd_nand.c	No boot device
2208   54	common/cmd_nand.c	boot device found
2209  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2210   55	common/cmd_nand.c	correct chip ID found, device available
2211  -56	common/cmd_nand.c	Error reading Image Header on boot device
2212   56	common/cmd_nand.c	reading Image Header from NAND device OK
2213  -57	common/cmd_nand.c	Image header has bad magic number
2214   57	common/cmd_nand.c	Image header has correct magic number
2215  -58	common/cmd_nand.c	Error reading Image from NAND device
2216   58	common/cmd_nand.c	reading Image from NAND device OK
2217
2218  -60	common/env_common.c	Environment has a bad CRC, using default
2219
2220   64	net/eth.c		starting with Ethernet configuration.
2221  -64	net/eth.c		no Ethernet found.
2222   65	net/eth.c		Ethernet found.
2223
2224  -80	common/cmd_net.c	usage wrong
2225   80	common/cmd_net.c	before calling NetLoop()
2226  -81	common/cmd_net.c	some error in NetLoop() occurred
2227   81	common/cmd_net.c	NetLoop() back without error
2228  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2229   82	common/cmd_net.c	trying automatic boot
2230   83	common/cmd_net.c	running "source" command
2231  -83	common/cmd_net.c	some error in automatic boot or "source" command
2232   84	common/cmd_net.c	end without errors
2233
2234FIT uImage format:
2235
2236  Arg	Where			When
2237  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2238 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2239  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2240 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2241  102	common/cmd_bootm.c	Kernel unit name specified
2242 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2243  103	common/cmd_bootm.c	Found configuration node
2244  104	common/cmd_bootm.c	Got kernel subimage node offset
2245 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2246  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2247 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2248  106	common/cmd_bootm.c	Architecture check OK
2249 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2250  107	common/cmd_bootm.c	Kernel subimage type OK
2251 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2252  108	common/cmd_bootm.c	Got kernel subimage data/size
2253 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2254 -109	common/cmd_bootm.c	Can't get kernel subimage type
2255 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2256 -111	common/cmd_bootm.c	Can't get kernel subimage os
2257 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2258 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2259
2260  120	common/image.c		Start initial ramdisk verification
2261 -120	common/image.c		Ramdisk FIT image has incorrect format
2262  121	common/image.c		Ramdisk FIT image has correct format
2263  122	common/image.c		No ramdisk subimage unit name, using configuration
2264 -122	common/image.c		Can't get configuration for ramdisk subimage
2265  123	common/image.c		Ramdisk unit name specified
2266 -124	common/image.c		Can't get ramdisk subimage node offset
2267  125	common/image.c		Got ramdisk subimage node offset
2268 -125	common/image.c		Ramdisk subimage hash verification failed
2269  126	common/image.c		Ramdisk subimage hash verification OK
2270 -126	common/image.c		Ramdisk subimage for unsupported architecture
2271  127	common/image.c		Architecture check OK
2272 -127	common/image.c		Can't get ramdisk subimage data/size
2273  128	common/image.c		Got ramdisk subimage data/size
2274  129	common/image.c		Can't get ramdisk load address
2275 -129	common/image.c		Got ramdisk load address
2276
2277 -130	common/cmd_doc.c	Incorrect FIT image format
2278  131	common/cmd_doc.c	FIT image format OK
2279
2280 -140	common/cmd_ide.c	Incorrect FIT image format
2281  141	common/cmd_ide.c	FIT image format OK
2282
2283 -150	common/cmd_nand.c	Incorrect FIT image format
2284  151	common/cmd_nand.c	FIT image format OK
2285
2286- Automatic software updates via TFTP server
2287		CONFIG_UPDATE_TFTP
2288		CONFIG_UPDATE_TFTP_CNT_MAX
2289		CONFIG_UPDATE_TFTP_MSEC_MAX
2290
2291		These options enable and control the auto-update feature;
2292		for a more detailed description refer to doc/README.update.
2293
2294- MTD Support (mtdparts command, UBI support)
2295		CONFIG_MTD_DEVICE
2296
2297		Adds the MTD device infrastructure from the Linux kernel.
2298		Needed for mtdparts command support.
2299
2300		CONFIG_MTD_PARTITIONS
2301
2302		Adds the MTD partitioning infrastructure from the Linux
2303		kernel. Needed for UBI support.
2304
2305- SPL framework
2306		CONFIG_SPL
2307		Enable building of SPL globally.
2308
2309		CONFIG_SPL_TEXT_BASE
2310		TEXT_BASE for linking the SPL binary.
2311
2312		CONFIG_SPL_LDSCRIPT
2313		LDSCRIPT for linking the SPL binary.
2314
2315		CONFIG_SPL_LIBCOMMON_SUPPORT
2316		Support for common/libcommon.o in SPL binary
2317
2318		CONFIG_SPL_LIBDISK_SUPPORT
2319		Support for disk/libdisk.o in SPL binary
2320
2321		CONFIG_SPL_I2C_SUPPORT
2322		Support for drivers/i2c/libi2c.o in SPL binary
2323
2324		CONFIG_SPL_GPIO_SUPPORT
2325		Support for drivers/gpio/libgpio.o in SPL binary
2326
2327		CONFIG_SPL_MMC_SUPPORT
2328		Support for drivers/mmc/libmmc.o in SPL binary
2329
2330		CONFIG_SPL_SERIAL_SUPPORT
2331		Support for drivers/serial/libserial.o in SPL binary
2332
2333		CONFIG_SPL_SPI_FLASH_SUPPORT
2334		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2335
2336		CONFIG_SPL_SPI_SUPPORT
2337		Support for drivers/spi/libspi.o in SPL binary
2338
2339		CONFIG_SPL_FAT_SUPPORT
2340		Support for fs/fat/libfat.o in SPL binary
2341
2342		CONFIG_SPL_LIBGENERIC_SUPPORT
2343		Support for lib/libgeneric.o in SPL binary
2344
2345Modem Support:
2346--------------
2347
2348[so far only for SMDK2400 boards]
2349
2350- Modem support enable:
2351		CONFIG_MODEM_SUPPORT
2352
2353- RTS/CTS Flow control enable:
2354		CONFIG_HWFLOW
2355
2356- Modem debug support:
2357		CONFIG_MODEM_SUPPORT_DEBUG
2358
2359		Enables debugging stuff (char screen[1024], dbg())
2360		for modem support. Useful only with BDI2000.
2361
2362- Interrupt support (PPC):
2363
2364		There are common interrupt_init() and timer_interrupt()
2365		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2366		for CPU specific initialization. interrupt_init_cpu()
2367		should set decrementer_count to appropriate value. If
2368		CPU resets decrementer automatically after interrupt
2369		(ppc4xx) it should set decrementer_count to zero.
2370		timer_interrupt() calls timer_interrupt_cpu() for CPU
2371		specific handling. If board has watchdog / status_led
2372		/ other_activity_monitor it works automatically from
2373		general timer_interrupt().
2374
2375- General:
2376
2377		In the target system modem support is enabled when a
2378		specific key (key combination) is pressed during
2379		power-on. Otherwise U-Boot will boot normally
2380		(autoboot). The key_pressed() function is called from
2381		board_init(). Currently key_pressed() is a dummy
2382		function, returning 1 and thus enabling modem
2383		initialization.
2384
2385		If there are no modem init strings in the
2386		environment, U-Boot proceed to autoboot; the
2387		previous output (banner, info printfs) will be
2388		suppressed, though.
2389
2390		See also: doc/README.Modem
2391
2392
2393Configuration Settings:
2394-----------------------
2395
2396- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2397		undefine this when you're short of memory.
2398
2399- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2400		width of the commands listed in the 'help' command output.
2401
2402- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2403		prompt for user input.
2404
2405- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2406
2407- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2408
2409- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2410
2411- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2412		the application (usually a Linux kernel) when it is
2413		booted
2414
2415- CONFIG_SYS_BAUDRATE_TABLE:
2416		List of legal baudrate settings for this board.
2417
2418- CONFIG_SYS_CONSOLE_INFO_QUIET
2419		Suppress display of console information at boot.
2420
2421- CONFIG_SYS_CONSOLE_IS_IN_ENV
2422		If the board specific function
2423			extern int overwrite_console (void);
2424		returns 1, the stdin, stderr and stdout are switched to the
2425		serial port, else the settings in the environment are used.
2426
2427- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
2428		Enable the call to overwrite_console().
2429
2430- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
2431		Enable overwrite of previous console environment settings.
2432
2433- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2434		Begin and End addresses of the area used by the
2435		simple memory test.
2436
2437- CONFIG_SYS_ALT_MEMTEST:
2438		Enable an alternate, more extensive memory test.
2439
2440- CONFIG_SYS_MEMTEST_SCRATCH:
2441		Scratch address used by the alternate memory test
2442		You only need to set this if address zero isn't writeable
2443
2444- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
2445		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2446		this specified memory area will get subtracted from the top
2447		(end) of RAM and won't get "touched" at all by U-Boot. By
2448		fixing up gd->ram_size the Linux kernel should gets passed
2449		the now "corrected" memory size and won't touch it either.
2450		This should work for arch/ppc and arch/powerpc. Only Linux
2451		board ports in arch/powerpc with bootwrapper support that
2452		recalculate the memory size from the SDRAM controller setup
2453		will have to get fixed in Linux additionally.
2454
2455		This option can be used as a workaround for the 440EPx/GRx
2456		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2457		be touched.
2458
2459		WARNING: Please make sure that this value is a multiple of
2460		the Linux page size (normally 4k). If this is not the case,
2461		then the end address of the Linux memory will be located at a
2462		non page size aligned address and this could cause major
2463		problems.
2464
2465- CONFIG_SYS_TFTP_LOADADDR:
2466		Default load address for network file downloads
2467
2468- CONFIG_SYS_LOADS_BAUD_CHANGE:
2469		Enable temporary baudrate change while serial download
2470
2471- CONFIG_SYS_SDRAM_BASE:
2472		Physical start address of SDRAM. _Must_ be 0 here.
2473
2474- CONFIG_SYS_MBIO_BASE:
2475		Physical start address of Motherboard I/O (if using a
2476		Cogent motherboard)
2477
2478- CONFIG_SYS_FLASH_BASE:
2479		Physical start address of Flash memory.
2480
2481- CONFIG_SYS_MONITOR_BASE:
2482		Physical start address of boot monitor code (set by
2483		make config files to be same as the text base address
2484		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2485		CONFIG_SYS_FLASH_BASE when booting from flash.
2486
2487- CONFIG_SYS_MONITOR_LEN:
2488		Size of memory reserved for monitor code, used to
2489		determine _at_compile_time_ (!) if the environment is
2490		embedded within the U-Boot image, or in a separate
2491		flash sector.
2492
2493- CONFIG_SYS_MALLOC_LEN:
2494		Size of DRAM reserved for malloc() use.
2495
2496- CONFIG_SYS_BOOTM_LEN:
2497		Normally compressed uImages are limited to an
2498		uncompressed size of 8 MBytes. If this is not enough,
2499		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2500		to adjust this setting to your needs.
2501
2502- CONFIG_SYS_BOOTMAPSZ:
2503		Maximum size of memory mapped by the startup code of
2504		the Linux kernel; all data that must be processed by
2505		the Linux kernel (bd_info, boot arguments, FDT blob if
2506		used) must be put below this limit, unless "bootm_low"
2507		enviroment variable is defined and non-zero. In such case
2508		all data for the Linux kernel must be between "bootm_low"
2509		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.  The environment
2510		variable "bootm_mapsize" will override the value of
2511		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2512		then the value in "bootm_size" will be used instead.
2513
2514- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2515		Enable initrd_high functionality.  If defined then the
2516		initrd_high feature is enabled and the bootm ramdisk subcommand
2517		is enabled.
2518
2519- CONFIG_SYS_BOOT_GET_CMDLINE:
2520		Enables allocating and saving kernel cmdline in space between
2521		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2522
2523- CONFIG_SYS_BOOT_GET_KBD:
2524		Enables allocating and saving a kernel copy of the bd_info in
2525		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2526
2527- CONFIG_SYS_MAX_FLASH_BANKS:
2528		Max number of Flash memory banks
2529
2530- CONFIG_SYS_MAX_FLASH_SECT:
2531		Max number of sectors on a Flash chip
2532
2533- CONFIG_SYS_FLASH_ERASE_TOUT:
2534		Timeout for Flash erase operations (in ms)
2535
2536- CONFIG_SYS_FLASH_WRITE_TOUT:
2537		Timeout for Flash write operations (in ms)
2538
2539- CONFIG_SYS_FLASH_LOCK_TOUT
2540		Timeout for Flash set sector lock bit operation (in ms)
2541
2542- CONFIG_SYS_FLASH_UNLOCK_TOUT
2543		Timeout for Flash clear lock bits operation (in ms)
2544
2545- CONFIG_SYS_FLASH_PROTECTION
2546		If defined, hardware flash sectors protection is used
2547		instead of U-Boot software protection.
2548
2549- CONFIG_SYS_DIRECT_FLASH_TFTP:
2550
2551		Enable TFTP transfers directly to flash memory;
2552		without this option such a download has to be
2553		performed in two steps: (1) download to RAM, and (2)
2554		copy from RAM to flash.
2555
2556		The two-step approach is usually more reliable, since
2557		you can check if the download worked before you erase
2558		the flash, but in some situations (when system RAM is
2559		too limited to allow for a temporary copy of the
2560		downloaded image) this option may be very useful.
2561
2562- CONFIG_SYS_FLASH_CFI:
2563		Define if the flash driver uses extra elements in the
2564		common flash structure for storing flash geometry.
2565
2566- CONFIG_FLASH_CFI_DRIVER
2567		This option also enables the building of the cfi_flash driver
2568		in the drivers directory
2569
2570- CONFIG_FLASH_CFI_MTD
2571		This option enables the building of the cfi_mtd driver
2572		in the drivers directory. The driver exports CFI flash
2573		to the MTD layer.
2574
2575- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2576		Use buffered writes to flash.
2577
2578- CONFIG_FLASH_SPANSION_S29WS_N
2579		s29ws-n MirrorBit flash has non-standard addresses for buffered
2580		write commands.
2581
2582- CONFIG_SYS_FLASH_QUIET_TEST
2583		If this option is defined, the common CFI flash doesn't
2584		print it's warning upon not recognized FLASH banks. This
2585		is useful, if some of the configured banks are only
2586		optionally available.
2587
2588- CONFIG_FLASH_SHOW_PROGRESS
2589		If defined (must be an integer), print out countdown
2590		digits and dots.  Recommended value: 45 (9..1) for 80
2591		column displays, 15 (3..1) for 40 column displays.
2592
2593- CONFIG_SYS_RX_ETH_BUFFER:
2594		Defines the number of Ethernet receive buffers. On some
2595		Ethernet controllers it is recommended to set this value
2596		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2597		buffers can be full shortly after enabling the interface
2598		on high Ethernet traffic.
2599		Defaults to 4 if not defined.
2600
2601- CONFIG_ENV_MAX_ENTRIES
2602
2603	Maximum number of entries in the hash table that is used
2604	internally to store the environment settings. The default
2605	setting is supposed to be generous and should work in most
2606	cases. This setting can be used to tune behaviour; see
2607	lib/hashtable.c for details.
2608
2609The following definitions that deal with the placement and management
2610of environment data (variable area); in general, we support the
2611following configurations:
2612
2613- CONFIG_BUILD_ENVCRC:
2614
2615	Builds up envcrc with the target environment so that external utils
2616	may easily extract it and embed it in final U-Boot images.
2617
2618- CONFIG_ENV_IS_IN_FLASH:
2619
2620	Define this if the environment is in flash memory.
2621
2622	a) The environment occupies one whole flash sector, which is
2623	   "embedded" in the text segment with the U-Boot code. This
2624	   happens usually with "bottom boot sector" or "top boot
2625	   sector" type flash chips, which have several smaller
2626	   sectors at the start or the end. For instance, such a
2627	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
2628	   such a case you would place the environment in one of the
2629	   4 kB sectors - with U-Boot code before and after it. With
2630	   "top boot sector" type flash chips, you would put the
2631	   environment in one of the last sectors, leaving a gap
2632	   between U-Boot and the environment.
2633
2634	- CONFIG_ENV_OFFSET:
2635
2636	   Offset of environment data (variable area) to the
2637	   beginning of flash memory; for instance, with bottom boot
2638	   type flash chips the second sector can be used: the offset
2639	   for this sector is given here.
2640
2641	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
2642
2643	- CONFIG_ENV_ADDR:
2644
2645	   This is just another way to specify the start address of
2646	   the flash sector containing the environment (instead of
2647	   CONFIG_ENV_OFFSET).
2648
2649	- CONFIG_ENV_SECT_SIZE:
2650
2651	   Size of the sector containing the environment.
2652
2653
2654	b) Sometimes flash chips have few, equal sized, BIG sectors.
2655	   In such a case you don't want to spend a whole sector for
2656	   the environment.
2657
2658	- CONFIG_ENV_SIZE:
2659
2660	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
2661	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
2662	   of this flash sector for the environment. This saves
2663	   memory for the RAM copy of the environment.
2664
2665	   It may also save flash memory if you decide to use this
2666	   when your environment is "embedded" within U-Boot code,
2667	   since then the remainder of the flash sector could be used
2668	   for U-Boot code. It should be pointed out that this is
2669	   STRONGLY DISCOURAGED from a robustness point of view:
2670	   updating the environment in flash makes it always
2671	   necessary to erase the WHOLE sector. If something goes
2672	   wrong before the contents has been restored from a copy in
2673	   RAM, your target system will be dead.
2674
2675	- CONFIG_ENV_ADDR_REDUND
2676	  CONFIG_ENV_SIZE_REDUND
2677
2678	   These settings describe a second storage area used to hold
2679	   a redundant copy of the environment data, so that there is
2680	   a valid backup copy in case there is a power failure during
2681	   a "saveenv" operation.
2682
2683BE CAREFUL! Any changes to the flash layout, and some changes to the
2684source code will make it necessary to adapt <board>/u-boot.lds*
2685accordingly!
2686
2687
2688- CONFIG_ENV_IS_IN_NVRAM:
2689
2690	Define this if you have some non-volatile memory device
2691	(NVRAM, battery buffered SRAM) which you want to use for the
2692	environment.
2693
2694	- CONFIG_ENV_ADDR:
2695	- CONFIG_ENV_SIZE:
2696
2697	  These two #defines are used to determine the memory area you
2698	  want to use for environment. It is assumed that this memory
2699	  can just be read and written to, without any special
2700	  provision.
2701
2702BE CAREFUL! The first access to the environment happens quite early
2703in U-Boot initalization (when we try to get the setting of for the
2704console baudrate). You *MUST* have mapped your NVRAM area then, or
2705U-Boot will hang.
2706
2707Please note that even with NVRAM we still use a copy of the
2708environment in RAM: we could work on NVRAM directly, but we want to
2709keep settings there always unmodified except somebody uses "saveenv"
2710to save the current settings.
2711
2712
2713- CONFIG_ENV_IS_IN_EEPROM:
2714
2715	Use this if you have an EEPROM or similar serial access
2716	device and a driver for it.
2717
2718	- CONFIG_ENV_OFFSET:
2719	- CONFIG_ENV_SIZE:
2720
2721	  These two #defines specify the offset and size of the
2722	  environment area within the total memory of your EEPROM.
2723
2724	- CONFIG_SYS_I2C_EEPROM_ADDR:
2725	  If defined, specified the chip address of the EEPROM device.
2726	  The default address is zero.
2727
2728	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
2729	  If defined, the number of bits used to address bytes in a
2730	  single page in the EEPROM device.  A 64 byte page, for example
2731	  would require six bits.
2732
2733	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
2734	  If defined, the number of milliseconds to delay between
2735	  page writes.	The default is zero milliseconds.
2736
2737	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
2738	  The length in bytes of the EEPROM memory array address.  Note
2739	  that this is NOT the chip address length!
2740
2741	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
2742	  EEPROM chips that implement "address overflow" are ones
2743	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
2744	  address and the extra bits end up in the "chip address" bit
2745	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
2746	  byte chips.
2747
2748	  Note that we consider the length of the address field to
2749	  still be one byte because the extra address bits are hidden
2750	  in the chip address.
2751
2752	- CONFIG_SYS_EEPROM_SIZE:
2753	  The size in bytes of the EEPROM device.
2754
2755	- CONFIG_ENV_EEPROM_IS_ON_I2C
2756	  define this, if you have I2C and SPI activated, and your
2757	  EEPROM, which holds the environment, is on the I2C bus.
2758
2759	- CONFIG_I2C_ENV_EEPROM_BUS
2760	  if you have an Environment on an EEPROM reached over
2761	  I2C muxes, you can define here, how to reach this
2762	  EEPROM. For example:
2763
2764	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
2765
2766	  EEPROM which holds the environment, is reached over
2767	  a pca9547 i2c mux with address 0x70, channel 3.
2768
2769- CONFIG_ENV_IS_IN_DATAFLASH:
2770
2771	Define this if you have a DataFlash memory device which you
2772	want to use for the environment.
2773
2774	- CONFIG_ENV_OFFSET:
2775	- CONFIG_ENV_ADDR:
2776	- CONFIG_ENV_SIZE:
2777
2778	  These three #defines specify the offset and size of the
2779	  environment area within the total memory of your DataFlash placed
2780	  at the specified address.
2781
2782- CONFIG_ENV_IS_IN_NAND:
2783
2784	Define this if you have a NAND device which you want to use
2785	for the environment.
2786
2787	- CONFIG_ENV_OFFSET:
2788	- CONFIG_ENV_SIZE:
2789
2790	  These two #defines specify the offset and size of the environment
2791	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
2792	  aligned to an erase block boundary.
2793
2794	- CONFIG_ENV_OFFSET_REDUND (optional):
2795
2796	  This setting describes a second storage area of CONFIG_ENV_SIZE
2797	  size used to hold a redundant copy of the environment data, so
2798	  that there is a valid backup copy in case there is a power failure
2799	  during a "saveenv" operation.  CONFIG_ENV_OFFSET_RENDUND must be
2800	  aligned to an erase block boundary.
2801
2802	- CONFIG_ENV_RANGE (optional):
2803
2804	  Specifies the length of the region in which the environment
2805	  can be written.  This should be a multiple of the NAND device's
2806	  block size.  Specifying a range with more erase blocks than
2807	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
2808	  the range to be avoided.
2809
2810	- CONFIG_ENV_OFFSET_OOB (optional):
2811
2812	  Enables support for dynamically retrieving the offset of the
2813	  environment from block zero's out-of-band data.  The
2814	  "nand env.oob" command can be used to record this offset.
2815	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
2816	  using CONFIG_ENV_OFFSET_OOB.
2817
2818- CONFIG_NAND_ENV_DST
2819
2820	Defines address in RAM to which the nand_spl code should copy the
2821	environment. If redundant environment is used, it will be copied to
2822	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2823
2824- CONFIG_SYS_SPI_INIT_OFFSET
2825
2826	Defines offset to the initial SPI buffer area in DPRAM. The
2827	area is used at an early stage (ROM part) if the environment
2828	is configured to reside in the SPI EEPROM: We need a 520 byte
2829	scratch DPRAM area. It is used between the two initialization
2830	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
2831	to be a good choice since it makes it far enough from the
2832	start of the data area as well as from the stack pointer.
2833
2834Please note that the environment is read-only until the monitor
2835has been relocated to RAM and a RAM copy of the environment has been
2836created; also, when using EEPROM you will have to use getenv_f()
2837until then to read environment variables.
2838
2839The environment is protected by a CRC32 checksum. Before the monitor
2840is relocated into RAM, as a result of a bad CRC you will be working
2841with the compiled-in default environment - *silently*!!! [This is
2842necessary, because the first environment variable we need is the
2843"baudrate" setting for the console - if we have a bad CRC, we don't
2844have any device yet where we could complain.]
2845
2846Note: once the monitor has been relocated, then it will complain if
2847the default environment is used; a new CRC is computed as soon as you
2848use the "saveenv" command to store a valid environment.
2849
2850- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2851		Echo the inverted Ethernet link state to the fault LED.
2852
2853		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2854		      also needs to be defined.
2855
2856- CONFIG_SYS_FAULT_MII_ADDR:
2857		MII address of the PHY to check for the Ethernet link state.
2858
2859- CONFIG_NS16550_MIN_FUNCTIONS:
2860		Define this if you desire to only have use of the NS16550_init
2861		and NS16550_putc functions for the serial driver located at
2862		drivers/serial/ns16550.c.  This option is useful for saving
2863		space for already greatly restricted images, including but not
2864		limited to NAND_SPL configurations.
2865
2866Low Level (hardware related) configuration options:
2867---------------------------------------------------
2868
2869- CONFIG_SYS_CACHELINE_SIZE:
2870		Cache Line Size of the CPU.
2871
2872- CONFIG_SYS_DEFAULT_IMMR:
2873		Default address of the IMMR after system reset.
2874
2875		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
2876		and RPXsuper) to be able to adjust the position of
2877		the IMMR register after a reset.
2878
2879- CONFIG_SYS_CCSRBAR_DEFAULT:
2880		Default (power-on reset) physical address of CCSR on Freescale
2881		PowerPC SOCs.
2882
2883- CONFIG_SYS_CCSRBAR:
2884		Virtual address of CCSR.  On a 32-bit build, this is typically
2885		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2886
2887		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
2888		for cross-platform code that uses that macro instead.
2889
2890- CONFIG_SYS_CCSRBAR_PHYS:
2891		Physical address of CCSR.  CCSR can be relocated to a new
2892		physical address, if desired.  In this case, this macro should
2893		be set to that address.  Otherwise, it should be set to the
2894		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2895		is typically relocated on 36-bit builds.  It is recommended
2896		that this macro be defined via the _HIGH and _LOW macros:
2897
2898		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2899			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2900
2901- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2902		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.  This value is typically
2903		either 0 (32-bit build) or 0xF (36-bit build).  This macro is
2904		used in assembly code, so it must not contain typecasts or
2905		integer size suffixes (e.g. "ULL").
2906
2907- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2908		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2909		used in assembly code, so it must not contain typecasts or
2910		integer size suffixes (e.g. "ULL").
2911
2912- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2913		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2914		forced to a value that ensures that CCSR is not relocated.
2915
2916- Floppy Disk Support:
2917		CONFIG_SYS_FDC_DRIVE_NUMBER
2918
2919		the default drive number (default value 0)
2920
2921		CONFIG_SYS_ISA_IO_STRIDE
2922
2923		defines the spacing between FDC chipset registers
2924		(default value 1)
2925
2926		CONFIG_SYS_ISA_IO_OFFSET
2927
2928		defines the offset of register from address. It
2929		depends on which part of the data bus is connected to
2930		the FDC chipset. (default value 0)
2931
2932		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
2933		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
2934		default value.
2935
2936		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
2937		fdc_hw_init() is called at the beginning of the FDC
2938		setup. fdc_hw_init() must be provided by the board
2939		source code. It is used to make hardware dependant
2940		initializations.
2941
2942- CONFIG_IDE_AHB:
2943		Most IDE controllers were designed to be connected with PCI
2944		interface. Only few of them were designed for AHB interface.
2945		When software is doing ATA command and data transfer to
2946		IDE devices through IDE-AHB controller, some additional
2947		registers accessing to these kind of IDE-AHB controller
2948		is requierd.
2949
2950- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
2951		DO NOT CHANGE unless you know exactly what you're
2952		doing! (11-4) [MPC8xx/82xx systems only]
2953
2954- CONFIG_SYS_INIT_RAM_ADDR:
2955
2956		Start address of memory area that can be used for
2957		initial data and stack; please note that this must be
2958		writable memory that is working WITHOUT special
2959		initialization, i. e. you CANNOT use normal RAM which
2960		will become available only after programming the
2961		memory controller and running certain initialization
2962		sequences.
2963
2964		U-Boot uses the following memory types:
2965		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
2966		- MPC824X: data cache
2967		- PPC4xx:  data cache
2968
2969- CONFIG_SYS_GBL_DATA_OFFSET:
2970
2971		Offset of the initial data structure in the memory
2972		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2973		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2974		data is located at the end of the available space
2975		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2976		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
2977		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2978		CONFIG_SYS_GBL_DATA_OFFSET) downward.
2979
2980	Note:
2981		On the MPC824X (or other systems that use the data
2982		cache for initial memory) the address chosen for
2983		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2984		point to an otherwise UNUSED address space between
2985		the top of RAM and the start of the PCI space.
2986
2987- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
2988
2989- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
2990
2991- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
2992
2993- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
2994
2995- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
2996
2997- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
2998
2999- CONFIG_SYS_OR_TIMING_SDRAM:
3000		SDRAM timing
3001
3002- CONFIG_SYS_MAMR_PTA:
3003		periodic timer for refresh
3004
3005- CONFIG_SYS_DER:	Debug Event Register (37-47)
3006
3007- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3008  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3009  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3010  CONFIG_SYS_BR1_PRELIM:
3011		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3012
3013- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3014  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3015  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3016		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3017
3018- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3019  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3020		Machine Mode Register and Memory Periodic Timer
3021		Prescaler definitions (SDRAM timing)
3022
3023- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3024		enable I2C microcode relocation patch (MPC8xx);
3025		define relocation offset in DPRAM [DSP2]
3026
3027- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3028		enable SMC microcode relocation patch (MPC8xx);
3029		define relocation offset in DPRAM [SMC1]
3030
3031- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3032		enable SPI microcode relocation patch (MPC8xx);
3033		define relocation offset in DPRAM [SCC4]
3034
3035- CONFIG_SYS_USE_OSCCLK:
3036		Use OSCM clock mode on MBX8xx board. Be careful,
3037		wrong setting might damage your board. Read
3038		doc/README.MBX before setting this variable!
3039
3040- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3041		Offset of the bootmode word in DPRAM used by post
3042		(Power On Self Tests). This definition overrides
3043		#define'd default value in commproc.h resp.
3044		cpm_8260.h.
3045
3046- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3047  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3048  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3049  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3050  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3051  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3052  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3053  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3054		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3055
3056- CONFIG_PCI_DISABLE_PCIE:
3057		Disable PCI-Express on systems where it is supported but not
3058		required.
3059
3060- CONFIG_SYS_SRIO:
3061		Chip has SRIO or not
3062
3063- CONFIG_SRIO1:
3064		Board has SRIO 1 port available
3065
3066- CONFIG_SRIO2:
3067		Board has SRIO 2 port available
3068
3069- CONFIG_SYS_SRIOn_MEM_VIRT:
3070		Virtual Address of SRIO port 'n' memory region
3071
3072- CONFIG_SYS_SRIOn_MEM_PHYS:
3073		Physical Address of SRIO port 'n' memory region
3074
3075- CONFIG_SYS_SRIOn_MEM_SIZE:
3076		Size of SRIO port 'n' memory region
3077
3078- CONFIG_SYS_NDFC_16
3079		Defined to tell the NDFC that the NAND chip is using a
3080		16 bit bus.
3081
3082- CONFIG_SYS_NDFC_EBC0_CFG
3083		Sets the EBC0_CFG register for the NDFC. If not defined
3084		a default value will be used.
3085
3086- CONFIG_SPD_EEPROM
3087		Get DDR timing information from an I2C EEPROM. Common
3088		with pluggable memory modules such as SODIMMs
3089
3090  SPD_EEPROM_ADDRESS
3091		I2C address of the SPD EEPROM
3092
3093- CONFIG_SYS_SPD_BUS_NUM
3094		If SPD EEPROM is on an I2C bus other than the first
3095		one, specify here. Note that the value must resolve
3096		to something your driver can deal with.
3097
3098- CONFIG_SYS_DDR_RAW_TIMING
3099		Get DDR timing information from other than SPD. Common with
3100		soldered DDR chips onboard without SPD. DDR raw timing
3101		parameters are extracted from datasheet and hard-coded into
3102		header files or board specific files.
3103
3104- CONFIG_SYS_83XX_DDR_USES_CS0
3105		Only for 83xx systems. If specified, then DDR should
3106		be configured using CS0 and CS1 instead of CS2 and CS3.
3107
3108- CONFIG_ETHER_ON_FEC[12]
3109		Define to enable FEC[12] on a 8xx series processor.
3110
3111- CONFIG_FEC[12]_PHY
3112		Define to the hardcoded PHY address which corresponds
3113		to the given FEC; i. e.
3114			#define CONFIG_FEC1_PHY 4
3115		means that the PHY with address 4 is connected to FEC1
3116
3117		When set to -1, means to probe for first available.
3118
3119- CONFIG_FEC[12]_PHY_NORXERR
3120		The PHY does not have a RXERR line (RMII only).
3121		(so program the FEC to ignore it).
3122
3123- CONFIG_RMII
3124		Enable RMII mode for all FECs.
3125		Note that this is a global option, we can't
3126		have one FEC in standard MII mode and another in RMII mode.
3127
3128- CONFIG_CRC32_VERIFY
3129		Add a verify option to the crc32 command.
3130		The syntax is:
3131
3132		=> crc32 -v <address> <count> <crc32>
3133
3134		Where address/count indicate a memory area
3135		and crc32 is the correct crc32 which the
3136		area should have.
3137
3138- CONFIG_LOOPW
3139		Add the "loopw" memory command. This only takes effect if
3140		the memory commands are activated globally (CONFIG_CMD_MEM).
3141
3142- CONFIG_MX_CYCLIC
3143		Add the "mdc" and "mwc" memory commands. These are cyclic
3144		"md/mw" commands.
3145		Examples:
3146
3147		=> mdc.b 10 4 500
3148		This command will print 4 bytes (10,11,12,13) each 500 ms.
3149
3150		=> mwc.l 100 12345678 10
3151		This command will write 12345678 to address 100 all 10 ms.
3152
3153		This only takes effect if the memory commands are activated
3154		globally (CONFIG_CMD_MEM).
3155
3156- CONFIG_SKIP_LOWLEVEL_INIT
3157		[ARM, MIPS only] If this variable is defined, then certain
3158		low level initializations (like setting up the memory
3159		controller) are omitted and/or U-Boot does not
3160		relocate itself into RAM.
3161
3162		Normally this variable MUST NOT be defined. The only
3163		exception is when U-Boot is loaded (to RAM) by some
3164		other boot loader or by a debugger which performs
3165		these initializations itself.
3166
3167- CONFIG_SPL_BUILD
3168		Modifies the behaviour of start.S when compiling a loader
3169		that is executed before the actual U-Boot. E.g. when
3170		compiling a NAND SPL.
3171
3172- CONFIG_USE_ARCH_MEMCPY
3173  CONFIG_USE_ARCH_MEMSET
3174		If these options are used a optimized version of memcpy/memset will
3175		be used if available. These functions may be faster under some
3176		conditions but may increase the binary size.
3177
3178Building the Software:
3179======================
3180
3181Building U-Boot has been tested in several native build environments
3182and in many different cross environments. Of course we cannot support
3183all possibly existing versions of cross development tools in all
3184(potentially obsolete) versions. In case of tool chain problems we
3185recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3186which is extensively used to build and test U-Boot.
3187
3188If you are not using a native environment, it is assumed that you
3189have GNU cross compiling tools available in your path. In this case,
3190you must set the environment variable CROSS_COMPILE in your shell.
3191Note that no changes to the Makefile or any other source files are
3192necessary. For example using the ELDK on a 4xx CPU, please enter:
3193
3194	$ CROSS_COMPILE=ppc_4xx-
3195	$ export CROSS_COMPILE
3196
3197Note: If you wish to generate Windows versions of the utilities in
3198      the tools directory you can use the MinGW toolchain
3199      (http://www.mingw.org).  Set your HOST tools to the MinGW
3200      toolchain and execute 'make tools'.  For example:
3201
3202       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3203
3204      Binaries such as tools/mkimage.exe will be created which can
3205      be executed on computers running Windows.
3206
3207U-Boot is intended to be simple to build. After installing the
3208sources you must configure U-Boot for one specific board type. This
3209is done by typing:
3210
3211	make NAME_config
3212
3213where "NAME_config" is the name of one of the existing configu-
3214rations; see the main Makefile for supported names.
3215
3216Note: for some board special configuration names may exist; check if
3217      additional information is available from the board vendor; for
3218      instance, the TQM823L systems are available without (standard)
3219      or with LCD support. You can select such additional "features"
3220      when choosing the configuration, i. e.
3221
3222      make TQM823L_config
3223	- will configure for a plain TQM823L, i. e. no LCD support
3224
3225      make TQM823L_LCD_config
3226	- will configure for a TQM823L with U-Boot console on LCD
3227
3228      etc.
3229
3230
3231Finally, type "make all", and you should get some working U-Boot
3232images ready for download to / installation on your system:
3233
3234- "u-boot.bin" is a raw binary image
3235- "u-boot" is an image in ELF binary format
3236- "u-boot.srec" is in Motorola S-Record format
3237
3238By default the build is performed locally and the objects are saved
3239in the source directory. One of the two methods can be used to change
3240this behavior and build U-Boot to some external directory:
3241
32421. Add O= to the make command line invocations:
3243
3244	make O=/tmp/build distclean
3245	make O=/tmp/build NAME_config
3246	make O=/tmp/build all
3247
32482. Set environment variable BUILD_DIR to point to the desired location:
3249
3250	export BUILD_DIR=/tmp/build
3251	make distclean
3252	make NAME_config
3253	make all
3254
3255Note that the command line "O=" setting overrides the BUILD_DIR environment
3256variable.
3257
3258
3259Please be aware that the Makefiles assume you are using GNU make, so
3260for instance on NetBSD you might need to use "gmake" instead of
3261native "make".
3262
3263
3264If the system board that you have is not listed, then you will need
3265to port U-Boot to your hardware platform. To do this, follow these
3266steps:
3267
32681.  Add a new configuration option for your board to the toplevel
3269    "Makefile" and to the "MAKEALL" script, using the existing
3270    entries as examples. Note that here and at many other places
3271    boards and other names are listed in alphabetical sort order. Please
3272    keep this order.
32732.  Create a new directory to hold your board specific code. Add any
3274    files you need. In your board directory, you will need at least
3275    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
32763.  Create a new configuration file "include/configs/<board>.h" for
3277    your board
32783.  If you're porting U-Boot to a new CPU, then also create a new
3279    directory to hold your CPU specific code. Add any files you need.
32804.  Run "make <board>_config" with your new name.
32815.  Type "make", and you should get a working "u-boot.srec" file
3282    to be installed on your target system.
32836.  Debug and solve any problems that might arise.
3284    [Of course, this last step is much harder than it sounds.]
3285
3286
3287Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3288==============================================================
3289
3290If you have modified U-Boot sources (for instance added a new board
3291or support for new devices, a new CPU, etc.) you are expected to
3292provide feedback to the other developers. The feedback normally takes
3293the form of a "patch", i. e. a context diff against a certain (latest
3294official or latest in the git repository) version of U-Boot sources.
3295
3296But before you submit such a patch, please verify that your modifi-
3297cation did not break existing code. At least make sure that *ALL* of
3298the supported boards compile WITHOUT ANY compiler warnings. To do so,
3299just run the "MAKEALL" script, which will configure and build U-Boot
3300for ALL supported system. Be warned, this will take a while. You can
3301select which (cross) compiler to use by passing a `CROSS_COMPILE'
3302environment variable to the script, i. e. to use the ELDK cross tools
3303you can type
3304
3305	CROSS_COMPILE=ppc_8xx- MAKEALL
3306
3307or to build on a native PowerPC system you can type
3308
3309	CROSS_COMPILE=' ' MAKEALL
3310
3311When using the MAKEALL script, the default behaviour is to build
3312U-Boot in the source directory. This location can be changed by
3313setting the BUILD_DIR environment variable. Also, for each target
3314built, the MAKEALL script saves two log files (<target>.ERR and
3315<target>.MAKEALL) in the <source dir>/LOG directory. This default
3316location can be changed by setting the MAKEALL_LOGDIR environment
3317variable. For example:
3318
3319	export BUILD_DIR=/tmp/build
3320	export MAKEALL_LOGDIR=/tmp/log
3321	CROSS_COMPILE=ppc_8xx- MAKEALL
3322
3323With the above settings build objects are saved in the /tmp/build,
3324log files are saved in the /tmp/log and the source tree remains clean
3325during the whole build process.
3326
3327
3328See also "U-Boot Porting Guide" below.
3329
3330
3331Monitor Commands - Overview:
3332============================
3333
3334go	- start application at address 'addr'
3335run	- run commands in an environment variable
3336bootm	- boot application image from memory
3337bootp	- boot image via network using BootP/TFTP protocol
3338tftpboot- boot image via network using TFTP protocol
3339	       and env variables "ipaddr" and "serverip"
3340	       (and eventually "gatewayip")
3341rarpboot- boot image via network using RARP/TFTP protocol
3342diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3343loads	- load S-Record file over serial line
3344loadb	- load binary file over serial line (kermit mode)
3345md	- memory display
3346mm	- memory modify (auto-incrementing)
3347nm	- memory modify (constant address)
3348mw	- memory write (fill)
3349cp	- memory copy
3350cmp	- memory compare
3351crc32	- checksum calculation
3352i2c	- I2C sub-system
3353sspi	- SPI utility commands
3354base	- print or set address offset
3355printenv- print environment variables
3356setenv	- set environment variables
3357saveenv - save environment variables to persistent storage
3358protect - enable or disable FLASH write protection
3359erase	- erase FLASH memory
3360flinfo	- print FLASH memory information
3361bdinfo	- print Board Info structure
3362iminfo	- print header information for application image
3363coninfo - print console devices and informations
3364ide	- IDE sub-system
3365loop	- infinite loop on address range
3366loopw	- infinite write loop on address range
3367mtest	- simple RAM test
3368icache	- enable or disable instruction cache
3369dcache	- enable or disable data cache
3370reset	- Perform RESET of the CPU
3371echo	- echo args to console
3372version - print monitor version
3373help	- print online help
3374?	- alias for 'help'
3375
3376
3377Monitor Commands - Detailed Description:
3378========================================
3379
3380TODO.
3381
3382For now: just type "help <command>".
3383
3384
3385Environment Variables:
3386======================
3387
3388U-Boot supports user configuration using Environment Variables which
3389can be made persistent by saving to Flash memory.
3390
3391Environment Variables are set using "setenv", printed using
3392"printenv", and saved to Flash using "saveenv". Using "setenv"
3393without a value can be used to delete a variable from the
3394environment. As long as you don't save the environment you are
3395working with an in-memory copy. In case the Flash area containing the
3396environment is erased by accident, a default environment is provided.
3397
3398Some configuration options can be set using Environment Variables.
3399
3400List of environment variables (most likely not complete):
3401
3402  baudrate	- see CONFIG_BAUDRATE
3403
3404  bootdelay	- see CONFIG_BOOTDELAY
3405
3406  bootcmd	- see CONFIG_BOOTCOMMAND
3407
3408  bootargs	- Boot arguments when booting an RTOS image
3409
3410  bootfile	- Name of the image to load with TFTP
3411
3412  bootm_low	- Memory range available for image processing in the bootm
3413		  command can be restricted. This variable is given as
3414		  a hexadecimal number and defines lowest address allowed
3415		  for use by the bootm command. See also "bootm_size"
3416		  environment variable. Address defined by "bootm_low" is
3417		  also the base of the initial memory mapping for the Linux
3418		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3419		  bootm_mapsize.
3420
3421  bootm_mapsize	- Size of the initial memory mapping for the Linux kernel.
3422		  This variable is given as a hexadecimal number and it
3423		  defines the size of the memory region starting at base
3424		  address bootm_low that is accessible by the Linux kernel
3425		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3426		  as the default value if it is defined, and bootm_size is
3427		  used otherwise.
3428
3429  bootm_size	- Memory range available for image processing in the bootm
3430		  command can be restricted. This variable is given as
3431		  a hexadecimal number and defines the size of the region
3432		  allowed for use by the bootm command. See also "bootm_low"
3433		  environment variable.
3434
3435  updatefile	- Location of the software update file on a TFTP server, used
3436		  by the automatic software update feature. Please refer to
3437		  documentation in doc/README.update for more details.
3438
3439  autoload	- if set to "no" (any string beginning with 'n'),
3440		  "bootp" will just load perform a lookup of the
3441		  configuration from the BOOTP server, but not try to
3442		  load any image using TFTP
3443
3444  autostart	- if set to "yes", an image loaded using the "bootp",
3445		  "rarpboot", "tftpboot" or "diskboot" commands will
3446		  be automatically started (by internally calling
3447		  "bootm")
3448
3449		  If set to "no", a standalone image passed to the
3450		  "bootm" command will be copied to the load address
3451		  (and eventually uncompressed), but NOT be started.
3452		  This can be used to load and uncompress arbitrary
3453		  data.
3454
3455  fdt_high	- if set this restricts the maximum address that the
3456		  flattened device tree will be copied into upon boot.
3457		  If this is set to the special value 0xFFFFFFFF then
3458		  the fdt will not be copied at all on boot.  For this
3459		  to work it must reside in writable memory, have
3460		  sufficient padding on the end of it for u-boot to
3461		  add the information it needs into it, and the memory
3462		  must be accessible by the kernel.
3463
3464  i2cfast	- (PPC405GP|PPC405EP only)
3465		  if set to 'y' configures Linux I2C driver for fast
3466		  mode (400kHZ). This environment variable is used in
3467		  initialization code. So, for changes to be effective
3468		  it must be saved and board must be reset.
3469
3470  initrd_high	- restrict positioning of initrd images:
3471		  If this variable is not set, initrd images will be
3472		  copied to the highest possible address in RAM; this
3473		  is usually what you want since it allows for
3474		  maximum initrd size. If for some reason you want to
3475		  make sure that the initrd image is loaded below the
3476		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3477		  variable to a value of "no" or "off" or "0".
3478		  Alternatively, you can set it to a maximum upper
3479		  address to use (U-Boot will still check that it
3480		  does not overwrite the U-Boot stack and data).
3481
3482		  For instance, when you have a system with 16 MB
3483		  RAM, and want to reserve 4 MB from use by Linux,
3484		  you can do this by adding "mem=12M" to the value of
3485		  the "bootargs" variable. However, now you must make
3486		  sure that the initrd image is placed in the first
3487		  12 MB as well - this can be done with
3488
3489		  setenv initrd_high 00c00000
3490
3491		  If you set initrd_high to 0xFFFFFFFF, this is an
3492		  indication to U-Boot that all addresses are legal
3493		  for the Linux kernel, including addresses in flash
3494		  memory. In this case U-Boot will NOT COPY the
3495		  ramdisk at all. This may be useful to reduce the
3496		  boot time on your system, but requires that this
3497		  feature is supported by your Linux kernel.
3498
3499  ipaddr	- IP address; needed for tftpboot command
3500
3501  loadaddr	- Default load address for commands like "bootp",
3502		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3503
3504  loads_echo	- see CONFIG_LOADS_ECHO
3505
3506  serverip	- TFTP server IP address; needed for tftpboot command
3507
3508  bootretry	- see CONFIG_BOOT_RETRY_TIME
3509
3510  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3511
3512  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3513
3514  ethprime	- When CONFIG_NET_MULTI is enabled controls which
3515		  interface is used first.
3516
3517  ethact	- When CONFIG_NET_MULTI is enabled controls which
3518		  interface is currently active. For example you
3519		  can do the following
3520
3521		  => setenv ethact FEC
3522		  => ping 192.168.0.1 # traffic sent on FEC
3523		  => setenv ethact SCC
3524		  => ping 10.0.0.1 # traffic sent on SCC
3525
3526  ethrotate	- When set to "no" U-Boot does not go through all
3527		  available network interfaces.
3528		  It just stays at the currently selected interface.
3529
3530  netretry	- When set to "no" each network operation will
3531		  either succeed or fail without retrying.
3532		  When set to "once" the network operation will
3533		  fail when all the available network interfaces
3534		  are tried once without success.
3535		  Useful on scripts which control the retry operation
3536		  themselves.
3537
3538  npe_ucode	- set load address for the NPE microcode
3539
3540  tftpsrcport	- If this is set, the value is used for TFTP's
3541		  UDP source port.
3542
3543  tftpdstport	- If this is set, the value is used for TFTP's UDP
3544		  destination port instead of the Well Know Port 69.
3545
3546  tftpblocksize - Block size to use for TFTP transfers; if not set,
3547		  we use the TFTP server's default block size
3548
3549  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3550		  seconds, minimum value is 1000 = 1 second). Defines
3551		  when a packet is considered to be lost so it has to
3552		  be retransmitted. The default is 5000 = 5 seconds.
3553		  Lowering this value may make downloads succeed
3554		  faster in networks with high packet loss rates or
3555		  with unreliable TFTP servers.
3556
3557  vlan		- When set to a value < 4095 the traffic over
3558		  Ethernet is encapsulated/received over 802.1q
3559		  VLAN tagged frames.
3560
3561The following environment variables may be used and automatically
3562updated by the network boot commands ("bootp" and "rarpboot"),
3563depending the information provided by your boot server:
3564
3565  bootfile	- see above
3566  dnsip		- IP address of your Domain Name Server
3567  dnsip2	- IP address of your secondary Domain Name Server
3568  gatewayip	- IP address of the Gateway (Router) to use
3569  hostname	- Target hostname
3570  ipaddr	- see above
3571  netmask	- Subnet Mask
3572  rootpath	- Pathname of the root filesystem on the NFS server
3573  serverip	- see above
3574
3575
3576There are two special Environment Variables:
3577
3578  serial#	- contains hardware identification information such
3579		  as type string and/or serial number
3580  ethaddr	- Ethernet address
3581
3582These variables can be set only once (usually during manufacturing of
3583the board). U-Boot refuses to delete or overwrite these variables
3584once they have been set once.
3585
3586
3587Further special Environment Variables:
3588
3589  ver		- Contains the U-Boot version string as printed
3590		  with the "version" command. This variable is
3591		  readonly (see CONFIG_VERSION_VARIABLE).
3592
3593
3594Please note that changes to some configuration parameters may take
3595only effect after the next boot (yes, that's just like Windoze :-).
3596
3597
3598Command Line Parsing:
3599=====================
3600
3601There are two different command line parsers available with U-Boot:
3602the old "simple" one, and the much more powerful "hush" shell:
3603
3604Old, simple command line parser:
3605--------------------------------
3606
3607- supports environment variables (through setenv / saveenv commands)
3608- several commands on one line, separated by ';'
3609- variable substitution using "... ${name} ..." syntax
3610- special characters ('$', ';') can be escaped by prefixing with '\',
3611  for example:
3612	setenv bootcmd bootm \${address}
3613- You can also escape text by enclosing in single apostrophes, for example:
3614	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3615
3616Hush shell:
3617-----------
3618
3619- similar to Bourne shell, with control structures like
3620  if...then...else...fi, for...do...done; while...do...done,
3621  until...do...done, ...
3622- supports environment ("global") variables (through setenv / saveenv
3623  commands) and local shell variables (through standard shell syntax
3624  "name=value"); only environment variables can be used with "run"
3625  command
3626
3627General rules:
3628--------------
3629
3630(1) If a command line (or an environment variable executed by a "run"
3631    command) contains several commands separated by semicolon, and
3632    one of these commands fails, then the remaining commands will be
3633    executed anyway.
3634
3635(2) If you execute several variables with one call to run (i. e.
3636    calling run with a list of variables as arguments), any failing
3637    command will cause "run" to terminate, i. e. the remaining
3638    variables are not executed.
3639
3640Note for Redundant Ethernet Interfaces:
3641=======================================
3642
3643Some boards come with redundant Ethernet interfaces; U-Boot supports
3644such configurations and is capable of automatic selection of a
3645"working" interface when needed. MAC assignment works as follows:
3646
3647Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3648MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3649"eth1addr" (=>eth1), "eth2addr", ...
3650
3651If the network interface stores some valid MAC address (for instance
3652in SROM), this is used as default address if there is NO correspon-
3653ding setting in the environment; if the corresponding environment
3654variable is set, this overrides the settings in the card; that means:
3655
3656o If the SROM has a valid MAC address, and there is no address in the
3657  environment, the SROM's address is used.
3658
3659o If there is no valid address in the SROM, and a definition in the
3660  environment exists, then the value from the environment variable is
3661  used.
3662
3663o If both the SROM and the environment contain a MAC address, and
3664  both addresses are the same, this MAC address is used.
3665
3666o If both the SROM and the environment contain a MAC address, and the
3667  addresses differ, the value from the environment is used and a
3668  warning is printed.
3669
3670o If neither SROM nor the environment contain a MAC address, an error
3671  is raised.
3672
3673If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3674will be programmed into hardware as part of the initialization process.  This
3675may be skipped by setting the appropriate 'ethmacskip' environment variable.
3676The naming convention is as follows:
3677"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3678
3679Image Formats:
3680==============
3681
3682U-Boot is capable of booting (and performing other auxiliary operations on)
3683images in two formats:
3684
3685New uImage format (FIT)
3686-----------------------
3687
3688Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3689to Flattened Device Tree). It allows the use of images with multiple
3690components (several kernels, ramdisks, etc.), with contents protected by
3691SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3692
3693
3694Old uImage format
3695-----------------
3696
3697Old image format is based on binary files which can be basically anything,
3698preceded by a special header; see the definitions in include/image.h for
3699details; basically, the header defines the following image properties:
3700
3701* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3702  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3703  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3704  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3705  INTEGRITY).
3706* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
3707  IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3708  Currently supported: ARM, AVR32, Intel x86, MIPS, Nios II, PowerPC).
3709* Compression Type (uncompressed, gzip, bzip2)
3710* Load Address
3711* Entry Point
3712* Image Name
3713* Image Timestamp
3714
3715The header is marked by a special Magic Number, and both the header
3716and the data portions of the image are secured against corruption by
3717CRC32 checksums.
3718
3719
3720Linux Support:
3721==============
3722
3723Although U-Boot should support any OS or standalone application
3724easily, the main focus has always been on Linux during the design of
3725U-Boot.
3726
3727U-Boot includes many features that so far have been part of some
3728special "boot loader" code within the Linux kernel. Also, any
3729"initrd" images to be used are no longer part of one big Linux image;
3730instead, kernel and "initrd" are separate images. This implementation
3731serves several purposes:
3732
3733- the same features can be used for other OS or standalone
3734  applications (for instance: using compressed images to reduce the
3735  Flash memory footprint)
3736
3737- it becomes much easier to port new Linux kernel versions because
3738  lots of low-level, hardware dependent stuff are done by U-Boot
3739
3740- the same Linux kernel image can now be used with different "initrd"
3741  images; of course this also means that different kernel images can
3742  be run with the same "initrd". This makes testing easier (you don't
3743  have to build a new "zImage.initrd" Linux image when you just
3744  change a file in your "initrd"). Also, a field-upgrade of the
3745  software is easier now.
3746
3747
3748Linux HOWTO:
3749============
3750
3751Porting Linux to U-Boot based systems:
3752---------------------------------------
3753
3754U-Boot cannot save you from doing all the necessary modifications to
3755configure the Linux device drivers for use with your target hardware
3756(no, we don't intend to provide a full virtual machine interface to
3757Linux :-).
3758
3759But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3760
3761Just make sure your machine specific header file (for instance
3762include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3763Information structure as we define in include/asm-<arch>/u-boot.h,
3764and make sure that your definition of IMAP_ADDR uses the same value
3765as your U-Boot configuration in CONFIG_SYS_IMMR.
3766
3767
3768Configuring the Linux kernel:
3769-----------------------------
3770
3771No specific requirements for U-Boot. Make sure you have some root
3772device (initial ramdisk, NFS) for your target system.
3773
3774
3775Building a Linux Image:
3776-----------------------
3777
3778With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3779not used. If you use recent kernel source, a new build target
3780"uImage" will exist which automatically builds an image usable by
3781U-Boot. Most older kernels also have support for a "pImage" target,
3782which was introduced for our predecessor project PPCBoot and uses a
3783100% compatible format.
3784
3785Example:
3786
3787	make TQM850L_config
3788	make oldconfig
3789	make dep
3790	make uImage
3791
3792The "uImage" build target uses a special tool (in 'tools/mkimage') to
3793encapsulate a compressed Linux kernel image with header	 information,
3794CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3795
3796* build a standard "vmlinux" kernel image (in ELF binary format):
3797
3798* convert the kernel into a raw binary image:
3799
3800	${CROSS_COMPILE}-objcopy -O binary \
3801				 -R .note -R .comment \
3802				 -S vmlinux linux.bin
3803
3804* compress the binary image:
3805
3806	gzip -9 linux.bin
3807
3808* package compressed binary image for U-Boot:
3809
3810	mkimage -A ppc -O linux -T kernel -C gzip \
3811		-a 0 -e 0 -n "Linux Kernel Image" \
3812		-d linux.bin.gz uImage
3813
3814
3815The "mkimage" tool can also be used to create ramdisk images for use
3816with U-Boot, either separated from the Linux kernel image, or
3817combined into one file. "mkimage" encapsulates the images with a 64
3818byte header containing information about target architecture,
3819operating system, image type, compression method, entry points, time
3820stamp, CRC32 checksums, etc.
3821
3822"mkimage" can be called in two ways: to verify existing images and
3823print the header information, or to build new images.
3824
3825In the first form (with "-l" option) mkimage lists the information
3826contained in the header of an existing U-Boot image; this includes
3827checksum verification:
3828
3829	tools/mkimage -l image
3830	  -l ==> list image header information
3831
3832The second form (with "-d" option) is used to build a U-Boot image
3833from a "data file" which is used as image payload:
3834
3835	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3836		      -n name -d data_file image
3837	  -A ==> set architecture to 'arch'
3838	  -O ==> set operating system to 'os'
3839	  -T ==> set image type to 'type'
3840	  -C ==> set compression type 'comp'
3841	  -a ==> set load address to 'addr' (hex)
3842	  -e ==> set entry point to 'ep' (hex)
3843	  -n ==> set image name to 'name'
3844	  -d ==> use image data from 'datafile'
3845
3846Right now, all Linux kernels for PowerPC systems use the same load
3847address (0x00000000), but the entry point address depends on the
3848kernel version:
3849
3850- 2.2.x kernels have the entry point at 0x0000000C,
3851- 2.3.x and later kernels have the entry point at 0x00000000.
3852
3853So a typical call to build a U-Boot image would read:
3854
3855	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3856	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3857	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3858	> examples/uImage.TQM850L
3859	Image Name:   2.4.4 kernel for TQM850L
3860	Created:      Wed Jul 19 02:34:59 2000
3861	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3862	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3863	Load Address: 0x00000000
3864	Entry Point:  0x00000000
3865
3866To verify the contents of the image (or check for corruption):
3867
3868	-> tools/mkimage -l examples/uImage.TQM850L
3869	Image Name:   2.4.4 kernel for TQM850L
3870	Created:      Wed Jul 19 02:34:59 2000
3871	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3872	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3873	Load Address: 0x00000000
3874	Entry Point:  0x00000000
3875
3876NOTE: for embedded systems where boot time is critical you can trade
3877speed for memory and install an UNCOMPRESSED image instead: this
3878needs more space in Flash, but boots much faster since it does not
3879need to be uncompressed:
3880
3881	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3882	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3883	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3884	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3885	> examples/uImage.TQM850L-uncompressed
3886	Image Name:   2.4.4 kernel for TQM850L
3887	Created:      Wed Jul 19 02:34:59 2000
3888	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3889	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3890	Load Address: 0x00000000
3891	Entry Point:  0x00000000
3892
3893
3894Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3895when your kernel is intended to use an initial ramdisk:
3896
3897	-> tools/mkimage -n 'Simple Ramdisk Image' \
3898	> -A ppc -O linux -T ramdisk -C gzip \
3899	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3900	Image Name:   Simple Ramdisk Image
3901	Created:      Wed Jan 12 14:01:50 2000
3902	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
3903	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
3904	Load Address: 0x00000000
3905	Entry Point:  0x00000000
3906
3907
3908Installing a Linux Image:
3909-------------------------
3910
3911To downloading a U-Boot image over the serial (console) interface,
3912you must convert the image to S-Record format:
3913
3914	objcopy -I binary -O srec examples/image examples/image.srec
3915
3916The 'objcopy' does not understand the information in the U-Boot
3917image header, so the resulting S-Record file will be relative to
3918address 0x00000000. To load it to a given address, you need to
3919specify the target address as 'offset' parameter with the 'loads'
3920command.
3921
3922Example: install the image to address 0x40100000 (which on the
3923TQM8xxL is in the first Flash bank):
3924
3925	=> erase 40100000 401FFFFF
3926
3927	.......... done
3928	Erased 8 sectors
3929
3930	=> loads 40100000
3931	## Ready for S-Record download ...
3932	~>examples/image.srec
3933	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3934	...
3935	15989 15990 15991 15992
3936	[file transfer complete]
3937	[connected]
3938	## Start Addr = 0x00000000
3939
3940
3941You can check the success of the download using the 'iminfo' command;
3942this includes a checksum verification so you can be sure no data
3943corruption happened:
3944
3945	=> imi 40100000
3946
3947	## Checking Image at 40100000 ...
3948	   Image Name:	 2.2.13 for initrd on TQM850L
3949	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3950	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3951	   Load Address: 00000000
3952	   Entry Point:	 0000000c
3953	   Verifying Checksum ... OK
3954
3955
3956Boot Linux:
3957-----------
3958
3959The "bootm" command is used to boot an application that is stored in
3960memory (RAM or Flash). In case of a Linux kernel image, the contents
3961of the "bootargs" environment variable is passed to the kernel as
3962parameters. You can check and modify this variable using the
3963"printenv" and "setenv" commands:
3964
3965
3966	=> printenv bootargs
3967	bootargs=root=/dev/ram
3968
3969	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3970
3971	=> printenv bootargs
3972	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3973
3974	=> bootm 40020000
3975	## Booting Linux kernel at 40020000 ...
3976	   Image Name:	 2.2.13 for NFS on TQM850L
3977	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3978	   Data Size:	 381681 Bytes = 372 kB = 0 MB
3979	   Load Address: 00000000
3980	   Entry Point:	 0000000c
3981	   Verifying Checksum ... OK
3982	   Uncompressing Kernel Image ... OK
3983	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
3984	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3985	time_init: decrementer frequency = 187500000/60
3986	Calibrating delay loop... 49.77 BogoMIPS
3987	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3988	...
3989
3990If you want to boot a Linux kernel with initial RAM disk, you pass
3991the memory addresses of both the kernel and the initrd image (PPBCOOT
3992format!) to the "bootm" command:
3993
3994	=> imi 40100000 40200000
3995
3996	## Checking Image at 40100000 ...
3997	   Image Name:	 2.2.13 for initrd on TQM850L
3998	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3999	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4000	   Load Address: 00000000
4001	   Entry Point:	 0000000c
4002	   Verifying Checksum ... OK
4003
4004	## Checking Image at 40200000 ...
4005	   Image Name:	 Simple Ramdisk Image
4006	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4007	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4008	   Load Address: 00000000
4009	   Entry Point:	 00000000
4010	   Verifying Checksum ... OK
4011
4012	=> bootm 40100000 40200000
4013	## Booting Linux kernel at 40100000 ...
4014	   Image Name:	 2.2.13 for initrd on TQM850L
4015	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4016	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4017	   Load Address: 00000000
4018	   Entry Point:	 0000000c
4019	   Verifying Checksum ... OK
4020	   Uncompressing Kernel Image ... OK
4021	## Loading RAMDisk Image at 40200000 ...
4022	   Image Name:	 Simple Ramdisk Image
4023	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4024	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4025	   Load Address: 00000000
4026	   Entry Point:	 00000000
4027	   Verifying Checksum ... OK
4028	   Loading Ramdisk ... OK
4029	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
4030	Boot arguments: root=/dev/ram
4031	time_init: decrementer frequency = 187500000/60
4032	Calibrating delay loop... 49.77 BogoMIPS
4033	...
4034	RAMDISK: Compressed image found at block 0
4035	VFS: Mounted root (ext2 filesystem).
4036
4037	bash#
4038
4039Boot Linux and pass a flat device tree:
4040-----------
4041
4042First, U-Boot must be compiled with the appropriate defines. See the section
4043titled "Linux Kernel Interface" above for a more in depth explanation. The
4044following is an example of how to start a kernel and pass an updated
4045flat device tree:
4046
4047=> print oftaddr
4048oftaddr=0x300000
4049=> print oft
4050oft=oftrees/mpc8540ads.dtb
4051=> tftp $oftaddr $oft
4052Speed: 1000, full duplex
4053Using TSEC0 device
4054TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4055Filename 'oftrees/mpc8540ads.dtb'.
4056Load address: 0x300000
4057Loading: #
4058done
4059Bytes transferred = 4106 (100a hex)
4060=> tftp $loadaddr $bootfile
4061Speed: 1000, full duplex
4062Using TSEC0 device
4063TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4064Filename 'uImage'.
4065Load address: 0x200000
4066Loading:############
4067done
4068Bytes transferred = 1029407 (fb51f hex)
4069=> print loadaddr
4070loadaddr=200000
4071=> print oftaddr
4072oftaddr=0x300000
4073=> bootm $loadaddr - $oftaddr
4074## Booting image at 00200000 ...
4075   Image Name:	 Linux-2.6.17-dirty
4076   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4077   Data Size:	 1029343 Bytes = 1005.2 kB
4078   Load Address: 00000000
4079   Entry Point:	 00000000
4080   Verifying Checksum ... OK
4081   Uncompressing Kernel Image ... OK
4082Booting using flat device tree at 0x300000
4083Using MPC85xx ADS machine description
4084Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4085[snip]
4086
4087
4088More About U-Boot Image Types:
4089------------------------------
4090
4091U-Boot supports the following image types:
4092
4093   "Standalone Programs" are directly runnable in the environment
4094	provided by U-Boot; it is expected that (if they behave
4095	well) you can continue to work in U-Boot after return from
4096	the Standalone Program.
4097   "OS Kernel Images" are usually images of some Embedded OS which
4098	will take over control completely. Usually these programs
4099	will install their own set of exception handlers, device
4100	drivers, set up the MMU, etc. - this means, that you cannot
4101	expect to re-enter U-Boot except by resetting the CPU.
4102   "RAMDisk Images" are more or less just data blocks, and their
4103	parameters (address, size) are passed to an OS kernel that is
4104	being started.
4105   "Multi-File Images" contain several images, typically an OS
4106	(Linux) kernel image and one or more data images like
4107	RAMDisks. This construct is useful for instance when you want
4108	to boot over the network using BOOTP etc., where the boot
4109	server provides just a single image file, but you want to get
4110	for instance an OS kernel and a RAMDisk image.
4111
4112	"Multi-File Images" start with a list of image sizes, each
4113	image size (in bytes) specified by an "uint32_t" in network
4114	byte order. This list is terminated by an "(uint32_t)0".
4115	Immediately after the terminating 0 follow the images, one by
4116	one, all aligned on "uint32_t" boundaries (size rounded up to
4117	a multiple of 4 bytes).
4118
4119   "Firmware Images" are binary images containing firmware (like
4120	U-Boot or FPGA images) which usually will be programmed to
4121	flash memory.
4122
4123   "Script files" are command sequences that will be executed by
4124	U-Boot's command interpreter; this feature is especially
4125	useful when you configure U-Boot to use a real shell (hush)
4126	as command interpreter.
4127
4128
4129Standalone HOWTO:
4130=================
4131
4132One of the features of U-Boot is that you can dynamically load and
4133run "standalone" applications, which can use some resources of
4134U-Boot like console I/O functions or interrupt services.
4135
4136Two simple examples are included with the sources:
4137
4138"Hello World" Demo:
4139-------------------
4140
4141'examples/hello_world.c' contains a small "Hello World" Demo
4142application; it is automatically compiled when you build U-Boot.
4143It's configured to run at address 0x00040004, so you can play with it
4144like that:
4145
4146	=> loads
4147	## Ready for S-Record download ...
4148	~>examples/hello_world.srec
4149	1 2 3 4 5 6 7 8 9 10 11 ...
4150	[file transfer complete]
4151	[connected]
4152	## Start Addr = 0x00040004
4153
4154	=> go 40004 Hello World! This is a test.
4155	## Starting application at 0x00040004 ...
4156	Hello World
4157	argc = 7
4158	argv[0] = "40004"
4159	argv[1] = "Hello"
4160	argv[2] = "World!"
4161	argv[3] = "This"
4162	argv[4] = "is"
4163	argv[5] = "a"
4164	argv[6] = "test."
4165	argv[7] = "<NULL>"
4166	Hit any key to exit ...
4167
4168	## Application terminated, rc = 0x0
4169
4170Another example, which demonstrates how to register a CPM interrupt
4171handler with the U-Boot code, can be found in 'examples/timer.c'.
4172Here, a CPM timer is set up to generate an interrupt every second.
4173The interrupt service routine is trivial, just printing a '.'
4174character, but this is just a demo program. The application can be
4175controlled by the following keys:
4176
4177	? - print current values og the CPM Timer registers
4178	b - enable interrupts and start timer
4179	e - stop timer and disable interrupts
4180	q - quit application
4181
4182	=> loads
4183	## Ready for S-Record download ...
4184	~>examples/timer.srec
4185	1 2 3 4 5 6 7 8 9 10 11 ...
4186	[file transfer complete]
4187	[connected]
4188	## Start Addr = 0x00040004
4189
4190	=> go 40004
4191	## Starting application at 0x00040004 ...
4192	TIMERS=0xfff00980
4193	Using timer 1
4194	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4195
4196Hit 'b':
4197	[q, b, e, ?] Set interval 1000000 us
4198	Enabling timer
4199Hit '?':
4200	[q, b, e, ?] ........
4201	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4202Hit '?':
4203	[q, b, e, ?] .
4204	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4205Hit '?':
4206	[q, b, e, ?] .
4207	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4208Hit '?':
4209	[q, b, e, ?] .
4210	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4211Hit 'e':
4212	[q, b, e, ?] ...Stopping timer
4213Hit 'q':
4214	[q, b, e, ?] ## Application terminated, rc = 0x0
4215
4216
4217Minicom warning:
4218================
4219
4220Over time, many people have reported problems when trying to use the
4221"minicom" terminal emulation program for serial download. I (wd)
4222consider minicom to be broken, and recommend not to use it. Under
4223Unix, I recommend to use C-Kermit for general purpose use (and
4224especially for kermit binary protocol download ("loadb" command), and
4225use "cu" for S-Record download ("loads" command).
4226
4227Nevertheless, if you absolutely want to use it try adding this
4228configuration to your "File transfer protocols" section:
4229
4230	   Name	   Program			Name U/D FullScr IO-Red. Multi
4231	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4232	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4233
4234
4235NetBSD Notes:
4236=============
4237
4238Starting at version 0.9.2, U-Boot supports NetBSD both as host
4239(build U-Boot) and target system (boots NetBSD/mpc8xx).
4240
4241Building requires a cross environment; it is known to work on
4242NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4243need gmake since the Makefiles are not compatible with BSD make).
4244Note that the cross-powerpc package does not install include files;
4245attempting to build U-Boot will fail because <machine/ansi.h> is
4246missing.  This file has to be installed and patched manually:
4247
4248	# cd /usr/pkg/cross/powerpc-netbsd/include
4249	# mkdir powerpc
4250	# ln -s powerpc machine
4251	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4252	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4253
4254Native builds *don't* work due to incompatibilities between native
4255and U-Boot include files.
4256
4257Booting assumes that (the first part of) the image booted is a
4258stage-2 loader which in turn loads and then invokes the kernel
4259proper. Loader sources will eventually appear in the NetBSD source
4260tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4261meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4262
4263
4264Implementation Internals:
4265=========================
4266
4267The following is not intended to be a complete description of every
4268implementation detail. However, it should help to understand the
4269inner workings of U-Boot and make it easier to port it to custom
4270hardware.
4271
4272
4273Initial Stack, Global Data:
4274---------------------------
4275
4276The implementation of U-Boot is complicated by the fact that U-Boot
4277starts running out of ROM (flash memory), usually without access to
4278system RAM (because the memory controller is not initialized yet).
4279This means that we don't have writable Data or BSS segments, and BSS
4280is not initialized as zero. To be able to get a C environment working
4281at all, we have to allocate at least a minimal stack. Implementation
4282options for this are defined and restricted by the CPU used: Some CPU
4283models provide on-chip memory (like the IMMR area on MPC8xx and
4284MPC826x processors), on others (parts of) the data cache can be
4285locked as (mis-) used as memory, etc.
4286
4287	Chris Hallinan posted a good summary of these issues to the
4288	U-Boot mailing list:
4289
4290	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4291	From: "Chris Hallinan" <clh@net1plus.com>
4292	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4293	...
4294
4295	Correct me if I'm wrong, folks, but the way I understand it
4296	is this: Using DCACHE as initial RAM for Stack, etc, does not
4297	require any physical RAM backing up the cache. The cleverness
4298	is that the cache is being used as a temporary supply of
4299	necessary storage before the SDRAM controller is setup. It's
4300	beyond the scope of this list to explain the details, but you
4301	can see how this works by studying the cache architecture and
4302	operation in the architecture and processor-specific manuals.
4303
4304	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4305	is another option for the system designer to use as an
4306	initial stack/RAM area prior to SDRAM being available. Either
4307	option should work for you. Using CS 4 should be fine if your
4308	board designers haven't used it for something that would
4309	cause you grief during the initial boot! It is frequently not
4310	used.
4311
4312	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4313	with your processor/board/system design. The default value
4314	you will find in any recent u-boot distribution in
4315	walnut.h should work for you. I'd set it to a value larger
4316	than your SDRAM module. If you have a 64MB SDRAM module, set
4317	it above 400_0000. Just make sure your board has no resources
4318	that are supposed to respond to that address! That code in
4319	start.S has been around a while and should work as is when
4320	you get the config right.
4321
4322	-Chris Hallinan
4323	DS4.COM, Inc.
4324
4325It is essential to remember this, since it has some impact on the C
4326code for the initialization procedures:
4327
4328* Initialized global data (data segment) is read-only. Do not attempt
4329  to write it.
4330
4331* Do not use any uninitialized global data (or implicitely initialized
4332  as zero data - BSS segment) at all - this is undefined, initiali-
4333  zation is performed later (when relocating to RAM).
4334
4335* Stack space is very limited. Avoid big data buffers or things like
4336  that.
4337
4338Having only the stack as writable memory limits means we cannot use
4339normal global data to share information beween the code. But it
4340turned out that the implementation of U-Boot can be greatly
4341simplified by making a global data structure (gd_t) available to all
4342functions. We could pass a pointer to this data as argument to _all_
4343functions, but this would bloat the code. Instead we use a feature of
4344the GCC compiler (Global Register Variables) to share the data: we
4345place a pointer (gd) to the global data into a register which we
4346reserve for this purpose.
4347
4348When choosing a register for such a purpose we are restricted by the
4349relevant  (E)ABI  specifications for the current architecture, and by
4350GCC's implementation.
4351
4352For PowerPC, the following registers have specific use:
4353	R1:	stack pointer
4354	R2:	reserved for system use
4355	R3-R4:	parameter passing and return values
4356	R5-R10: parameter passing
4357	R13:	small data area pointer
4358	R30:	GOT pointer
4359	R31:	frame pointer
4360
4361	(U-Boot also uses R12 as internal GOT pointer. r12
4362	is a volatile register so r12 needs to be reset when
4363	going back and forth between asm and C)
4364
4365    ==> U-Boot will use R2 to hold a pointer to the global data
4366
4367    Note: on PPC, we could use a static initializer (since the
4368    address of the global data structure is known at compile time),
4369    but it turned out that reserving a register results in somewhat
4370    smaller code - although the code savings are not that big (on
4371    average for all boards 752 bytes for the whole U-Boot image,
4372    624 text + 127 data).
4373
4374On Blackfin, the normal C ABI (except for P3) is followed as documented here:
4375	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
4376
4377    ==> U-Boot will use P3 to hold a pointer to the global data
4378
4379On ARM, the following registers are used:
4380
4381	R0:	function argument word/integer result
4382	R1-R3:	function argument word
4383	R9:	GOT pointer
4384	R10:	stack limit (used only if stack checking if enabled)
4385	R11:	argument (frame) pointer
4386	R12:	temporary workspace
4387	R13:	stack pointer
4388	R14:	link register
4389	R15:	program counter
4390
4391    ==> U-Boot will use R8 to hold a pointer to the global data
4392
4393On Nios II, the ABI is documented here:
4394	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4395
4396    ==> U-Boot will use gp to hold a pointer to the global data
4397
4398    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4399    to access small data sections, so gp is free.
4400
4401NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4402or current versions of GCC may "optimize" the code too much.
4403
4404Memory Management:
4405------------------
4406
4407U-Boot runs in system state and uses physical addresses, i.e. the
4408MMU is not used either for address mapping nor for memory protection.
4409
4410The available memory is mapped to fixed addresses using the memory
4411controller. In this process, a contiguous block is formed for each
4412memory type (Flash, SDRAM, SRAM), even when it consists of several
4413physical memory banks.
4414
4415U-Boot is installed in the first 128 kB of the first Flash bank (on
4416TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4417booting and sizing and initializing DRAM, the code relocates itself
4418to the upper end of DRAM. Immediately below the U-Boot code some
4419memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4420configuration setting]. Below that, a structure with global Board
4421Info data is placed, followed by the stack (growing downward).
4422
4423Additionally, some exception handler code is copied to the low 8 kB
4424of DRAM (0x00000000 ... 0x00001FFF).
4425
4426So a typical memory configuration with 16 MB of DRAM could look like
4427this:
4428
4429	0x0000 0000	Exception Vector code
4430	      :
4431	0x0000 1FFF
4432	0x0000 2000	Free for Application Use
4433	      :
4434	      :
4435
4436	      :
4437	      :
4438	0x00FB FF20	Monitor Stack (Growing downward)
4439	0x00FB FFAC	Board Info Data and permanent copy of global data
4440	0x00FC 0000	Malloc Arena
4441	      :
4442	0x00FD FFFF
4443	0x00FE 0000	RAM Copy of Monitor Code
4444	...		eventually: LCD or video framebuffer
4445	...		eventually: pRAM (Protected RAM - unchanged by reset)
4446	0x00FF FFFF	[End of RAM]
4447
4448
4449System Initialization:
4450----------------------
4451
4452In the reset configuration, U-Boot starts at the reset entry point
4453(on most PowerPC systems at address 0x00000100). Because of the reset
4454configuration for CS0# this is a mirror of the onboard Flash memory.
4455To be able to re-map memory U-Boot then jumps to its link address.
4456To be able to implement the initialization code in C, a (small!)
4457initial stack is set up in the internal Dual Ported RAM (in case CPUs
4458which provide such a feature like MPC8xx or MPC8260), or in a locked
4459part of the data cache. After that, U-Boot initializes the CPU core,
4460the caches and the SIU.
4461
4462Next, all (potentially) available memory banks are mapped using a
4463preliminary mapping. For example, we put them on 512 MB boundaries
4464(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4465on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4466programmed for SDRAM access. Using the temporary configuration, a
4467simple memory test is run that determines the size of the SDRAM
4468banks.
4469
4470When there is more than one SDRAM bank, and the banks are of
4471different size, the largest is mapped first. For equal size, the first
4472bank (CS2#) is mapped first. The first mapping is always for address
44730x00000000, with any additional banks following immediately to create
4474contiguous memory starting from 0.
4475
4476Then, the monitor installs itself at the upper end of the SDRAM area
4477and allocates memory for use by malloc() and for the global Board
4478Info data; also, the exception vector code is copied to the low RAM
4479pages, and the final stack is set up.
4480
4481Only after this relocation will you have a "normal" C environment;
4482until that you are restricted in several ways, mostly because you are
4483running from ROM, and because the code will have to be relocated to a
4484new address in RAM.
4485
4486
4487U-Boot Porting Guide:
4488----------------------
4489
4490[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4491list, October 2002]
4492
4493
4494int main(int argc, char *argv[])
4495{
4496	sighandler_t no_more_time;
4497
4498	signal(SIGALRM, no_more_time);
4499	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4500
4501	if (available_money > available_manpower) {
4502		Pay consultant to port U-Boot;
4503		return 0;
4504	}
4505
4506	Download latest U-Boot source;
4507
4508	Subscribe to u-boot mailing list;
4509
4510	if (clueless)
4511		email("Hi, I am new to U-Boot, how do I get started?");
4512
4513	while (learning) {
4514		Read the README file in the top level directory;
4515		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4516		Read applicable doc/*.README;
4517		Read the source, Luke;
4518		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4519	}
4520
4521	if (available_money > toLocalCurrency ($2500))
4522		Buy a BDI3000;
4523	else
4524		Add a lot of aggravation and time;
4525
4526	if (a similar board exists) {	/* hopefully... */
4527		cp -a board/<similar> board/<myboard>
4528		cp include/configs/<similar>.h include/configs/<myboard>.h
4529	} else {
4530		Create your own board support subdirectory;
4531		Create your own board include/configs/<myboard>.h file;
4532	}
4533	Edit new board/<myboard> files
4534	Edit new include/configs/<myboard>.h
4535
4536	while (!accepted) {
4537		while (!running) {
4538			do {
4539				Add / modify source code;
4540			} until (compiles);
4541			Debug;
4542			if (clueless)
4543				email("Hi, I am having problems...");
4544		}
4545		Send patch file to the U-Boot email list;
4546		if (reasonable critiques)
4547			Incorporate improvements from email list code review;
4548		else
4549			Defend code as written;
4550	}
4551
4552	return 0;
4553}
4554
4555void no_more_time (int sig)
4556{
4557      hire_a_guru();
4558}
4559
4560
4561Coding Standards:
4562-----------------
4563
4564All contributions to U-Boot should conform to the Linux kernel
4565coding style; see the file "Documentation/CodingStyle" and the script
4566"scripts/Lindent" in your Linux kernel source directory.
4567
4568Source files originating from a different project (for example the
4569MTD subsystem) are generally exempt from these guidelines and are not
4570reformated to ease subsequent migration to newer versions of those
4571sources.
4572
4573Please note that U-Boot is implemented in C (and to some small parts in
4574Assembler); no C++ is used, so please do not use C++ style comments (//)
4575in your code.
4576
4577Please also stick to the following formatting rules:
4578- remove any trailing white space
4579- use TAB characters for indentation and vertical alignment, not spaces
4580- make sure NOT to use DOS '\r\n' line feeds
4581- do not add more than 2 consecutive empty lines to source files
4582- do not add trailing empty lines to source files
4583
4584Submissions which do not conform to the standards may be returned
4585with a request to reformat the changes.
4586
4587
4588Submitting Patches:
4589-------------------
4590
4591Since the number of patches for U-Boot is growing, we need to
4592establish some rules. Submissions which do not conform to these rules
4593may be rejected, even when they contain important and valuable stuff.
4594
4595Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4596
4597Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4598see http://lists.denx.de/mailman/listinfo/u-boot
4599
4600When you send a patch, please include the following information with
4601it:
4602
4603* For bug fixes: a description of the bug and how your patch fixes
4604  this bug. Please try to include a way of demonstrating that the
4605  patch actually fixes something.
4606
4607* For new features: a description of the feature and your
4608  implementation.
4609
4610* A CHANGELOG entry as plaintext (separate from the patch)
4611
4612* For major contributions, your entry to the CREDITS file
4613
4614* When you add support for a new board, don't forget to add this
4615  board to the MAINTAINERS file, too.
4616
4617* If your patch adds new configuration options, don't forget to
4618  document these in the README file.
4619
4620* The patch itself. If you are using git (which is *strongly*
4621  recommended) you can easily generate the patch using the
4622  "git format-patch". If you then use "git send-email" to send it to
4623  the U-Boot mailing list, you will avoid most of the common problems
4624  with some other mail clients.
4625
4626  If you cannot use git, use "diff -purN OLD NEW". If your version of
4627  diff does not support these options, then get the latest version of
4628  GNU diff.
4629
4630  The current directory when running this command shall be the parent
4631  directory of the U-Boot source tree (i. e. please make sure that
4632  your patch includes sufficient directory information for the
4633  affected files).
4634
4635  We prefer patches as plain text. MIME attachments are discouraged,
4636  and compressed attachments must not be used.
4637
4638* If one logical set of modifications affects or creates several
4639  files, all these changes shall be submitted in a SINGLE patch file.
4640
4641* Changesets that contain different, unrelated modifications shall be
4642  submitted as SEPARATE patches, one patch per changeset.
4643
4644
4645Notes:
4646
4647* Before sending the patch, run the MAKEALL script on your patched
4648  source tree and make sure that no errors or warnings are reported
4649  for any of the boards.
4650
4651* Keep your modifications to the necessary minimum: A patch
4652  containing several unrelated changes or arbitrary reformats will be
4653  returned with a request to re-formatting / split it.
4654
4655* If you modify existing code, make sure that your new code does not
4656  add to the memory footprint of the code ;-) Small is beautiful!
4657  When adding new features, these should compile conditionally only
4658  (using #ifdef), and the resulting code with the new feature
4659  disabled must not need more memory than the old code without your
4660  modification.
4661
4662* Remember that there is a size limit of 100 kB per message on the
4663  u-boot mailing list. Bigger patches will be moderated. If they are
4664  reasonable and not too big, they will be acknowledged. But patches
4665  bigger than the size limit should be avoided.
4666