xref: /openbmc/u-boot/README (revision a25f862b)
1#
2# (C) Copyright 2000 - 2002
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 and ARM processors, which can be
29installed in a boot ROM and used to initialize and test the hardware
30or to download and run application code.
31
32The development of U-Boot is closely related to Linux: some parts of
33the source code originate in the Linux source tree, we have some
34header files in common, and special provision has been made to
35support booting of Linux images.
36
37Some attention has been paid to make this software easily
38configurable and extendable. For instance, all monitor commands are
39implemented with the same call interface, so that it's very easy to
40add new commands. Also, instead of permanently adding rarely used
41code (for instance hardware test utilities) to the monitor, you can
42load and run it dynamically.
43
44
45Status:
46=======
47
48In general, all boards for which a configuration option exists in the
49Makefile have been tested to some extent and can be considered
50"working". In fact, many of them are used in production systems.
51
52In case of problems see the CHANGELOG and CREDITS files to find out
53who contributed the specific port.
54
55
56Where to get help:
57==================
58
59In case you have questions about, problems with or contributions for
60U-Boot you should send a message to the U-Boot mailing list at
61<u-boot-users@lists.sourceforge.net>. There is also an archive of
62previous traffic on the mailing list - please search the archive
63before asking FAQ's. Please see
64http://lists.sourceforge.net/lists/listinfo/u-boot-users/
65
66
67Where we come from:
68===================
69
70- start from 8xxrom sources
71- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
72- clean up code
73- make it easier to add custom boards
74- make it possible to add other [PowerPC] CPUs
75- extend functions, especially:
76  * Provide extended interface to Linux boot loader
77  * S-Record download
78  * network boot
79  * PCMCIA / CompactFLash / ATA disk / SCSI ... boot
80- create ARMBoot project (http://sourceforge.net/projects/armboot)
81- add other CPU families (starting with ARM)
82- create U-Boot project (http://sourceforge.net/projects/u-boot)
83
84
85Names and Spelling:
86===================
87
88The "official" name of this project is "Das U-Boot". The spelling
89"U-Boot" shall be used in all written text (documentation, comments
90in source files etc.). Example:
91
92	This is the README file for the U-Boot project.
93
94File names etc. shall be based on the string "u-boot". Examples:
95
96	include/asm-ppc/u-boot.h
97
98	#include <asm/u-boot.h>
99
100Variable names, preprocessor constants etc. shall be either based on
101the string "u_boot" or on "U_BOOT". Example:
102
103	U_BOOT_VERSION		u_boot_logo
104	IH_OS_U_BOOT		u_boot_hush_start
105
106
107Versioning:
108===========
109
110U-Boot uses a 3 level version number containing a version, a
111sub-version, and a patchlevel: "U-Boot-2.34.5" means version "2",
112sub-version "34", and patchlevel "4".
113
114The patchlevel is used to indicate certain stages of development
115between released versions, i. e. officially released versions of
116U-Boot will always have a patchlevel of "0".
117
118
119Directory Hierarchy:
120====================
121
122- board		Board dependend files
123- common	Misc architecture independend functions
124- cpu		CPU specific files
125- disk		Code for disk drive partition handling
126- doc		Documentation (don't expect too much)
127- drivers	Common used device drivers
128- dtt		Digital Thermometer and Thermostat drivers
129- examples	Example code for standalone applications, etc.
130- include	Header Files
131- disk		Harddisk interface code
132- net		Networking code
133- ppc		Files generic to PowerPC architecture
134- post		Power On Self Test
135- post/arch		Symlink to architecture specific Power On Self Test
136- post/arch-ppc		PowerPC architecture specific Power On Self Test
137- post/cpu/mpc8260	MPC8260 CPU specific Power On Self Test
138- post/cpu/mpc8xx	MPC8xx CPU specific Power On Self Test
139- rtc		Real Time Clock drivers
140- tools		Tools to build S-Record or U-Boot images, etc.
141
142- cpu/74xx_7xx	Files specific to Motorola MPC74xx and 7xx CPUs
143- cpu/mpc8xx	Files specific to Motorola MPC8xx  CPUs
144- cpu/mpc824x	Files specific to Motorola MPC824x CPUs
145- cpu/mpc8260	Files specific to Motorola MPC8260 CPU
146- cpu/ppc4xx	Files specific to IBM	   4xx	   CPUs
147
148- board/RPXClassic
149		Files specific to RPXClassic boards
150- board/RPXlite	Files specific to RPXlite    boards
151- board/c2mon	Files specific to c2mon	     boards
152- board/cogent	Files specific to Cogent     boards
153		(need further configuration)
154		Files specific to CPCIISER4  boards
155- board/cpu86	Files specific to CPU86      boards
156- board/cray/	Files specific to boards manufactured by Cray
157- board/cray/L1		Files specific to L1         boards
158- board/cu824	Files specific to CU824	     boards
159- board/ebony   Files specific to IBM Ebony board
160- board/eric	Files specific to ERIC	     boards
161- board/esd/	Files specific to boards manufactured by ESD
162- board/esd/adciop	Files specific to ADCIOP     boards
163- board/esd/ar405	Files specific to AR405	     boards
164- board/esd/canbt	Files specific to CANBT	     boards
165- board/esd/cpci405	Files specific to CPCI405    boards
166- board/esd/cpciiser4	Files specific to CPCIISER4  boards
167- board/esd/common	Common files for ESD boards
168- board/esd/dasa_sim	Files specific to DASA_SIM   boards
169- board/esd/du405	Files specific to DU405      boards
170- board/esd/ocrtc	Files specific to OCRTC      boards
171- board/esd/pci405	Files specific to PCI405     boards
172- board/esteem192e
173		Files specific to ESTEEM192E boards
174- board/etx094	Files specific to ETX_094    boards
175- board/evb64260
176		Files specific to EVB64260   boards
177- board/fads	Files specific to FADS	     boards
178- board/flagadm Files specific to FLAGADM    boards
179- board/gen860t Files specific to GEN860T    boards
180- board/genietv Files specific to GENIETV    boards
181- board/gth	Files specific to GTH	     boards
182- board/hermes	Files specific to HERMES     boards
183- board/hymod	Files specific to HYMOD	     boards
184- board/icu862	Files specific to ICU862     boards
185- board/ip860	Files specific to IP860	     boards
186- board/iphase4539
187		Files specific to Interphase4539 boards
188- board/ivm	Files specific to IVMS8/IVML24 boards
189- board/lantec	Files specific to LANTEC     boards
190- board/lwmon	Files specific to LWMON	     boards
191- board/mbx8xx	Files specific to MBX	     boards
192- board/mpc8260ads
193		Files specific to MMPC8260ADS boards
194- board/mpl/	Files specific to boards manufactured by MPL
195- board/mpl/common	Common files for MPL boards
196- board/mpl/pip405	Files specific to PIP405     boards
197- board/mpl/mip405	Files specific to MIP405     boards
198- board/musenki	Files specific to MUSEKNI    boards
199- board/mvs1	Files specific to MVS1       boards
200- board/nx823   Files specific to NX823      boards
201- board/oxc	Files specific to OXC        boards
202- board/pcippc2	Files specific to PCIPPC2/PCIPPC6 boards
203- board/pm826	Files specific to PM826      boards
204- board/ppmc8260
205		Files specific to PPMC8260   boards
206- board/rpxsuper
207		Files specific to RPXsuper   boards
208- board/rsdproto
209		Files specific to RSDproto   boards
210- board/sandpoint
211		Files specific to Sandpoint  boards
212- board/sbc8260	Files specific to SBC8260    boards
213- board/sacsng	Files specific to SACSng     boards
214- board/siemens Files specific to boards manufactured by Siemens AG
215- board/siemens/CCM	Files specific to CCM	     boards
216- board/siemens/IAD210	Files specific to IAD210     boards
217- board/siemens/SCM	Files specific to SCM        boards
218- board/siemens/pcu_e	Files specific to PCU_E	     boards
219- board/sixnet	Files specific to SIXNET     boards
220- board/spd8xx	Files specific to SPD8xxTS   boards
221- board/tqm8260 Files specific to TQM8260    boards
222- board/tqm8xx	Files specific to TQM8xxL    boards
223- board/w7o	Files specific to W7O        boards
224- board/walnut405
225		Files specific to Walnut405  boards
226- board/westel/	Files specific to boards manufactured by Westel Wireless
227- board/westel/amx860	Files specific to AMX860     boards
228- board/utx8245	Files specific to UTX8245   boards
229
230Software Configuration:
231=======================
232
233Configuration is usually done using C preprocessor defines; the
234rationale behind that is to avoid dead code whenever possible.
235
236There are two classes of configuration variables:
237
238* Configuration _OPTIONS_:
239  These are selectable by the user and have names beginning with
240  "CONFIG_".
241
242* Configuration _SETTINGS_:
243  These depend on the hardware etc. and should not be meddled with if
244  you don't know what you're doing; they have names beginning with
245  "CFG_".
246
247Later we will add a configuration tool - probably similar to or even
248identical to what's used for the Linux kernel. Right now, we have to
249do the configuration by hand, which means creating some symbolic
250links and editing some configuration files. We use the TQM8xxL boards
251as an example here.
252
253
254Selection of Processor Architecture and Board Type:
255---------------------------------------------------
256
257For all supported boards there are ready-to-use default
258configurations available; just type "make <board_name>_config".
259
260Example: For a TQM823L module type:
261
262	cd u-boot
263	make TQM823L_config
264
265For the Cogent platform, you need to specify the cpu type as well;
266e.g. "make cogent_mpc8xx_config". And also configure the cogent
267directory according to the instructions in cogent/README.
268
269
270Configuration Options:
271----------------------
272
273Configuration depends on the combination of board and CPU type; all
274such information is kept in a configuration file
275"include/configs/<board_name>.h".
276
277Example: For a TQM823L module, all configuration settings are in
278"include/configs/TQM823L.h".
279
280
281Many of the options are named exactly as the corresponding Linux
282kernel configuration options. The intention is to make it easier to
283build a config tool - later.
284
285
286The following options need to be configured:
287
288- CPU Type:	Define exactly one of
289
290		PowerPC based CPUs:
291		-------------------
292		CONFIG_MPC823,	CONFIG_MPC850,	CONFIG_MPC855,	CONFIG_MPC860
293	or	CONFIG_MPC824X, CONFIG_MPC8260
294	or	CONFIG_IOP480
295	or	CONFIG_405GP
296	or	CONFIG_440
297	or	CONFIG_MPC74xx
298
299		ARM based CPUs:
300		---------------
301		CONFIG_SA1110
302		CONFIG_ARM7
303		CONFIG_PXA250
304
305
306- Board Type:	Define exactly one of
307
308		PowerPC based boards:
309		---------------------
310
311		CONFIG_ADCIOP,     CONFIG_ICU862      CONFIG_RPXsuper,
312		CONFIG_ADS860,     CONFIG_IP860,      CONFIG_SM850,
313		CONFIG_AMX860,     CONFIG_IPHASE4539, CONFIG_SPD823TS,
314		CONFIG_AR405,      CONFIG_IVML24,     CONFIG_SXNI855T,
315		CONFIG_BAB7xx,     CONFIG_IVML24_128, CONFIG_Sandpoint8240,
316		CONFIG_CANBT,      CONFIG_IVML24_256, CONFIG_Sandpoint8245,
317		CONFIG_CCM,        CONFIG_IVMS8,      CONFIG_TQM823L,
318		CONFIG_CPCI405,    CONFIG_IVMS8_128,  CONFIG_TQM850L,
319		CONFIG_CPCI4052,   CONFIG_IVMS8_256,  CONFIG_TQM855L,
320		CONFIG_CPCIISER4,  CONFIG_LANTEC,     CONFIG_TQM860L,
321		CONFIG_CPU86,      CONFIG_MBX,        CONFIG_TQM8260,
322		CONFIG_CRAYL1,     CONFIG_MBX860T,    CONFIG_TTTech,
323		CONFIG_CU824,      CONFIG_MHPC,       CONFIG_UTX8245,
324		CONFIG_DASA_SIM,   CONFIG_MIP405,     CONFIG_W7OLMC,
325		CONFIG_DU405,      CONFIG_MOUSSE,     CONFIG_W7OLMG,
326		CONFIG_ELPPC,      CONFIG_MPC8260ADS, CONFIG_WALNUT405,
327		CONFIG_ERIC,       CONFIG_MUSENKI,    CONFIG_ZUMA,
328		CONFIG_ESTEEM192E, CONFIG_MVS1,       CONFIG_c2mon,
329		CONFIG_ETX094,     CONFIG_NX823,      CONFIG_cogent_mpc8260,
330		CONFIG_EVB64260,   CONFIG_OCRTC,      CONFIG_cogent_mpc8xx,
331		CONFIG_FADS823,    CONFIG_ORSG,       CONFIG_ep8260,
332		CONFIG_FADS850SAR, CONFIG_OXC,        CONFIG_gw8260,
333		CONFIG_FADS860T,   CONFIG_PCI405,     CONFIG_hermes,
334		CONFIG_FLAGADM,    CONFIG_PCIPPC2,    CONFIG_hymod,
335		CONFIG_FPS850L,    CONFIG_PCIPPC6,    CONFIG_lwmon,
336		CONFIG_GEN860T,    CONFIG_PIP405,     CONFIG_pcu_e,
337		CONFIG_GENIETV,    CONFIG_PM826,      CONFIG_ppmc8260,
338		CONFIG_GTH,        CONFIG_RPXClassic, CONFIG_rsdproto,
339		CONFIG_IAD210,     CONFIG_RPXlite,    CONFIG_sbc8260,
340		CONFIG_EBONY,      CONFIG_sacsng,     CONFIG_FPS860L
341
342		ARM based boards:
343		-----------------
344
345		CONFIG_HHP_CRADLE,  CONFIG_DNP1110,    CONFIG_EP7312,
346		CONFIG_IMPA7,       CONFIG_LART,       CONFIG_LUBBOCK,
347		CONFIG_SHANNON,     CONFIG_SMDK2400,   CONFIG_SMDK2410,
348		CONFIG_TRAB
349
350
351- CPU Module Type: (if CONFIG_COGENT is defined)
352		Define exactly one of
353		CONFIG_CMA286_60_OLD
354--- FIXME --- not tested yet:
355		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
356		CONFIG_CMA287_23, CONFIG_CMA287_50
357
358- Motherboard Type: (if CONFIG_COGENT is defined)
359		Define exactly one of
360		CONFIG_CMA101, CONFIG_CMA102
361
362- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
363		Define one or more of
364		CONFIG_CMA302
365
366- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
367		Define one or more of
368		CONFIG_LCD_HEARTBEAT	- update a character position on
369					  the lcd display every second with
370					  a "rotator" |\-/|\-/
371
372- MPC824X Family Member (if CONFIG_MPC824X is defined)
373	Define exactly one of
374	CONFIG_MPC8240, CONFIG_MPC8245
375
376- 8xx CPU Options: (if using an 8xx cpu)
377		Define one or more of
378		CONFIG_8xx_GCLK_FREQ	- if get_gclk_freq() can not work e.g.
379					  no 32KHz reference PIT/RTC clock
380
381- Clock Interface:
382		CONFIG_CLOCKS_IN_MHZ
383
384		U-Boot stores all clock information in Hz
385		internally. For binary compatibility with older Linux
386		kernels (which expect the clocks passed in the
387		bd_info data to be in MHz) the environment variable
388		"clocks_in_mhz" can be defined so that U-Boot
389		converts clock data to MHZ before passing it to the
390		Linux kernel.
391
392		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
393		"clocks_in_mhz=1" is  automatically  included  in  the
394		default environment.
395
396- Console Interface:
397                Depending on board, define exactly one serial port
398                (like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
399                CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
400                console by defining CONFIG_8xx_CONS_NONE
401
402		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
403		port routines must be defined elsewhere
404		(i.e. serial_init(), serial_getc(), ...)
405
406		CONFIG_CFB_CONSOLE
407		Enables console device for a color framebuffer. Needs following
408		defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
409			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
410						(default big endian)
411			VIDEO_HW_RECTFILL	graphic chip supports
412						rectangle fill
413						(cf. smiLynxEM)
414			VIDEO_HW_BITBLT		graphic chip supports
415						bit-blit (cf. smiLynxEM)
416			VIDEO_VISIBLE_COLS	visible pixel columns
417						(cols=pitch)
418			VIDEO_VISIBLE_ROWS      visible pixel rows
419			VIDEO_PIXEL_SIZE        bytes per pixel
420			VIDEO_DATA_FORMAT	graphic data format
421						(0-5, cf. cfb_console.c)
422			VIDEO_FB_ADRS           framebuffer address
423			VIDEO_KBD_INIT_FCT	keyboard int fct
424						(i.e. i8042_kbd_init())
425			VIDEO_TSTC_FCT		test char fct
426						(i.e. i8042_tstc)
427			VIDEO_GETC_FCT		get char fct
428						(i.e. i8042_getc)
429			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
430						(requires blink timer
431						cf. i8042.c)
432			CFG_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
433			CONFIG_CONSOLE_TIME	display time/date info in
434						upper right corner
435						(requires CFG_CMD_DATE)
436			CONFIG_VIDEO_LOGO	display Linux logo in
437						upper left corner
438			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
439						linux_logo.h for logo.
440						Requires CONFIG_VIDEO_LOGO
441			CONFIG_CONSOLE_EXTRA_INFO
442						addional board info beside
443						the logo
444
445                When CONFIG_CFB_CONSOLE is defined, video console is
446                default i/o. Serial console can be forced with
447                environment 'console=serial'.
448
449- Console Baudrate:
450		CONFIG_BAUDRATE - in bps
451		Select one of the baudrates listed in
452		CFG_BAUDRATE_TABLE, see below.
453
454- Interrupt driven serial port input:
455		CONFIG_SERIAL_SOFTWARE_FIFO
456
457		PPC405GP only.
458		Use an interrupt handler for receiving data on the
459		serial port. It also enables using hardware handshake
460		(RTS/CTS) and UART's built-in FIFO. Set the number of
461		bytes the interrupt driven input buffer should have.
462
463		Set to 0 to disable this feature (this is the default).
464		This will also disable hardware handshake.
465
466- Boot Delay:	CONFIG_BOOTDELAY - in seconds
467		Delay before automatically booting the default image;
468		set to -1 to disable autoboot.
469
470		See doc/README.autoboot for these options that
471		work with CONFIG_BOOTDELAY. None are required.
472		CONFIG_BOOT_RETRY_TIME
473		CONFIG_BOOT_RETRY_MIN
474		CONFIG_AUTOBOOT_KEYED
475		CONFIG_AUTOBOOT_PROMPT
476		CONFIG_AUTOBOOT_DELAY_STR
477		CONFIG_AUTOBOOT_STOP_STR
478		CONFIG_AUTOBOOT_DELAY_STR2
479		CONFIG_AUTOBOOT_STOP_STR2
480		CONFIG_ZERO_BOOTDELAY_CHECK
481		CONFIG_RESET_TO_RETRY
482
483- Autoboot Command:
484		CONFIG_BOOTCOMMAND
485		Only needed when CONFIG_BOOTDELAY is enabled;
486		define a command string that is automatically executed
487		when no character is read on the console interface
488		within "Boot Delay" after reset.
489
490		CONFIG_BOOTARGS
491                This can be used to pass arguments to the bootm
492                command. The value of CONFIG_BOOTARGS goes into the
493                environment value "bootargs".
494
495		CONFIG_RAMBOOT and CONFIG_NFSBOOT
496                The value of these goes into the environment as
497                "ramboot" and "nfsboot" respectively, and can be used
498                as a convenience, when switching between booting from
499                ram and nfs.
500
501- Pre-Boot Commands:
502		CONFIG_PREBOOT
503
504		When this option is #defined, the existence of the
505		environment variable "preboot" will be checked
506		immediately before starting the CONFIG_BOOTDELAY
507		countdown and/or running the auto-boot command resp.
508		entering interactive mode.
509
510		This feature is especially useful when "preboot" is
511		automatically generated or modified. For an example
512		see the LWMON board specific code: here "preboot" is
513		modified when the user holds down a certain
514		combination of keys on the (special) keyboard when
515		booting the systems
516
517- Serial Download Echo Mode:
518		CONFIG_LOADS_ECHO
519		If defined to 1, all characters received during a
520		serial download (using the "loads" command) are
521		echoed back. This might be needed by some terminal
522		emulations (like "cu"), but may as well just take
523		time on others. This setting #define's the initial
524		value of the "loads_echo" environment variable.
525
526- Kgdb Serial Baudrate: (if CFG_CMD_KGDB is defined)
527		CONFIG_KGDB_BAUDRATE
528		Select one of the baudrates listed in
529		CFG_BAUDRATE_TABLE, see below.
530
531- Monitor Functions:
532		CONFIG_COMMANDS
533		Most monitor functions can be selected (or
534		de-selected) by adjusting the definition of
535		CONFIG_COMMANDS; to select individual functions,
536		#define CONFIG_COMMANDS by "OR"ing any of the
537		following values:
538
539		#define enables commands:
540		-------------------------
541		CFG_CMD_ASKENV	* ask for env variable
542		CFG_CMD_BDI	  bdinfo
543		CFG_CMD_BEDBUG	  Include BedBug Debugger
544		CFG_CMD_BOOTD	  bootd
545		CFG_CMD_CACHE	  icache, dcache
546		CFG_CMD_CONSOLE	  coninfo
547		CFG_CMD_DATE	* support for RTC, date/time...
548		CFG_CMD_DHCP	  DHCP support
549		CFG_CMD_ECHO	* echo arguments
550		CFG_CMD_EEPROM	* EEPROM read/write support
551		CFG_CMD_ELF	  bootelf, bootvx
552		CFG_CMD_ENV	  saveenv
553		CFG_CMD_FDC	* Floppy Disk Support
554		CFG_CMD_FDOS	* Dos diskette Support
555		CFG_CMD_FLASH	  flinfo, erase, protect
556		CFG_CMD_FPGA	  FPGA device initialization support
557		CFG_CMD_I2C	* I2C serial bus support
558		CFG_CMD_IDE	* IDE harddisk support
559		CFG_CMD_IMI	  iminfo
560		CFG_CMD_IMMAP	* IMMR dump support
561		CFG_CMD_IRQ	* irqinfo
562		CFG_CMD_KGDB	* kgdb
563		CFG_CMD_LOADB	  loadb
564		CFG_CMD_LOADS	  loads
565		CFG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
566				  loop, mtest
567		CFG_CMD_MII	  MII utility commands
568		CFG_CMD_NET	  bootp, tftpboot, rarpboot
569		CFG_CMD_PCI	* pciinfo
570		CFG_CMD_PCMCIA	* PCMCIA support
571		CFG_CMD_REGINFO * Register dump
572		CFG_CMD_RUN	  run command in env variable
573		CFG_CMD_SCSI	* SCSI Support
574		CFG_CMD_SETGETDCR Support for DCR Register access (4xx only)
575		CFG_CMD_SPI	* SPI serial bus support
576		CFG_CMD_USB	* USB support
577		CFG_CMD_BSP	* Board SPecific functions
578		-----------------------------------------------
579		CFG_CMD_ALL	all
580
581		CFG_CMD_DFL	Default configuration; at the moment
582				this is includes all commands, except
583				the ones marked with "*" in the list
584				above.
585
586		If you don't define CONFIG_COMMANDS it defaults to
587		CFG_CMD_DFL in include/cmd_confdefs.h. A board can
588		override the default settings in the respective
589		include file.
590
591		EXAMPLE: If you want all functions except of network
592		support you can write:
593
594		#define CONFIG_COMMANDS (CFG_CMD_ALL & ~CFG_CMD_NET)
595
596
597	Note:	Don't enable the "icache" and "dcache" commands
598                (configuration option CFG_CMD_CACHE) unless you know
599                what you (and your U-Boot users) are doing. Data
600                cache cannot be enabled on systems like the 8xx or
601                8260 (where accesses to the IMMR region must be
602                uncached), and it cannot be disabled on all other
603                systems where we (mis-) use the data cache to hold an
604                initial stack and some data.
605
606
607		XXX - this list needs to get updated!
608
609- Watchdog:
610		CONFIG_WATCHDOG
611		If this variable is defined, it enables watchdog
612		support. There must support in the platform specific
613		code for a watchdog. For the 8xx and 8260 CPUs, the
614		SIU Watchdog feature is enabled in the SYPCR
615		register.
616
617- Real-Time Clock:
618
619		When CFG_CMD_DATE is selected, the type of the RTC
620		has to be selected, too. Define exactly one of the
621		following options:
622
623		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
624		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
625		CONFIG_RTC_MC146818	- use MC146818 RTC
626		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
627
628- Timestamp Support:
629
630                When CONFIG_TIMESTAMP is selected, the timestamp
631                (date and time) of an image is printed by image
632                commands like bootm or iminfo. This option is
633                automatically enabled when you select CFG_CMD_DATE .
634
635- Partition Support:
636		CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
637		and/or CONFIG_ISO_PARTITION
638
639		If IDE or SCSI support	is  enabled  (CFG_CMD_IDE  or
640		CFG_CMD_SCSI) you must configure support for at least
641		one partition type as well.
642
643- IDE Reset method:
644		CONFIG_IDE_RESET_ROUTINE
645
646		Set this to define that instead of a reset Pin, the
647		routine ide_set_reset(int idereset) will be used.
648
649- ATAPI Support:
650		CONFIG_ATAPI
651
652		Set this to enable ATAPI support.
653
654- SCSI Support:
655		At the moment only there is only support for the
656		SYM53C8XX SCSI controller; define
657		CONFIG_SCSI_SYM53C8XX to enable it.
658
659		CFG_SCSI_MAX_LUN [8], CFG_SCSI_MAX_SCSI_ID [7] and
660		CFG_SCSI_MAX_DEVICE [CFG_SCSI_MAX_SCSI_ID *
661		CFG_SCSI_MAX_LUN] can be adjusted to define the
662		maximum numbers of LUNs, SCSI ID's and target
663		devices.
664		CFG_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
665
666- NETWORK Support (PCI):
667		CONFIG_EEPRO100
668		Support for Intel 82557/82559/82559ER chips.
669		Optional CONFIG_EEPRO100_SROM_WRITE enables eeprom
670		write routine for first time initialisation.
671
672		CONFIG_TULIP
673		Support for Digital 2114x chips.
674		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
675		modem chip initialisation (KS8761/QS6611).
676
677		CONFIG_NATSEMI
678		Support for National dp83815 chips.
679
680		CONFIG_NS8382X
681		Support for National dp8382[01] gigabit chips.
682
683- USB Support:
684		At the moment only the UHCI host controller is
685		supported (PIP405, MIP405); define
686		CONFIG_USB_UHCI to enable it.
687		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
688		end define CONFIG_USB_STORAGE to enable the USB
689		storage devices.
690		Note:
691		Supported are USB Keyboards and USB Floppy drives
692		(TEAC FD-05PUB).
693
694- Keyboard Support:
695		CONFIG_ISA_KEYBOARD
696
697		Define this to enable standard (PC-Style) keyboard
698		support
699
700		CONFIG_I8042_KBD
701		Standard PC keyboard driver with US (is default) and
702		GERMAN key layout (switch via environment 'keymap=de') support.
703		Export function i8042_kbd_init, i8042_tstc and i8042_getc
704		for cfb_console. Supports cursor blinking.
705
706- Video support:
707		CONFIG_VIDEO
708
709		Define this to enable video support (for output to
710		video).
711
712		CONFIG_VIDEO_CT69000
713
714		Enable Chips & Technologies 69000 Video chip
715
716		CONFIG_VIDEO_SMI_LYNXEM
717		Enable Silicon Motion SMI 712/710/810 Video chip
718		Videomode are selected via environment 'videomode' with
719		standard LiLo mode numbers.
720		Following modes are supported  (* is default):
721
722                            800x600  1024x768  1280x1024
723              256  (8bit)     303*      305       307
724            65536 (16bit)     314       317       31a
725        16,7 Mill (24bit)     315       318       31b
726		(i.e. setenv videomode 317; saveenv; reset;)
727
728		CONFIG_VIDEO_SED13806
729                Enable Epson SED13806 driver. This driver supports 8bpp
730		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
731		or CONFIG_VIDEO_SED13806_16BPP
732
733
734- LCD Support:	CONFIG_LCD
735
736		Define this to enable LCD support (for output to LCD
737		display); also select one of the supported displays
738		by defining one of these:
739
740		CONFIG_NEC_NL6648AC33:
741
742			NEC NL6648AC33-18. Active, color, single scan.
743
744		CONFIG_NEC_NL6648BC20
745
746			NEC NL6648BC20-08. 6.5", 640x480.
747			Active, color, single scan.
748
749		CONFIG_SHARP_16x9
750
751			Sharp 320x240. Active, color, single scan.
752			It isn't 16x9, and I am not sure what it is.
753
754		CONFIG_SHARP_LQ64D341
755
756			Sharp LQ64D341 display, 640x480.
757			Active, color, single scan.
758
759		CONFIG_HLD1045
760
761			HLD1045 display, 640x480.
762			Active, color, single scan.
763
764		CONFIG_OPTREX_BW
765
766			Optrex	 CBL50840-2 NF-FW 99 22 M5
767			or
768			Hitachi	 LMG6912RPFC-00T
769			or
770			Hitachi	 SP14Q002
771
772			320x240. Black & white.
773
774		Normally display is black on white background; define
775		CFG_WHITE_ON_BLACK to get it inverted.
776
777- Ethernet address:
778		CONFIG_ETHADDR
779		CONFIG_ETH2ADDR
780		CONFIG_ETH3ADDR
781
782		Define a default value for ethernet address to use
783		for the respective ethernet interface, in case this
784		is not determined automatically.
785
786- IP address:
787		CONFIG_IPADDR
788
789		Define a default value for the IP address to use for
790		the default ethernet interface, in case this is not
791		determined through e.g. bootp.
792
793- Server IP address:
794		CONFIG_SERVERIP
795
796		Defines a default value for theIP address of a TFTP
797		server to contact when using the "tftboot" command.
798
799- BOOTP Recovery Mode:
800		CONFIG_BOOTP_RANDOM_DELAY
801
802		If you have many targets in a network that try to
803		boot using BOOTP, you may want to avoid that all
804		systems send out BOOTP requests at precisely the same
805		moment (which would happen for instance at recovery
806		from a power failure, when all systems will try to
807		boot, thus flooding the BOOTP server. Defining
808		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
809		inserted before sending out BOOTP requests. The
810		following delays are insterted then:
811
812		1st BOOTP request:	delay 0 ... 1 sec
813		2nd BOOTP request:	delay 0 ... 2 sec
814		3rd BOOTP request:	delay 0 ... 4 sec
815		4th and following
816		BOOTP requests:		delay 0 ... 8 sec
817
818- Status LED:	CONFIG_STATUS_LED
819
820		Several configurations allow to display the current
821		status using a LED. For instance, the LED will blink
822		fast while running U-Boot code, stop blinking as
823		soon as a reply to a BOOTP request was received, and
824		start blinking slow once the Linux kernel is running
825		(supported by a status LED driver in the Linux
826		kernel). Defining CONFIG_STATUS_LED enables this
827		feature in U-Boot.
828
829- CAN Support:	CONFIG_CAN_DRIVER
830
831		Defining CONFIG_CAN_DRIVER enables CAN driver support
832		on those systems that support this (optional)
833		feature, like the TQM8xxL modules.
834
835- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
836
837		Enables I2C serial bus commands.  If this is selected,
838		either CONFIG_HARD_I2C or CONFIG_SOFT_I2C must be defined
839		to include the appropriate I2C driver.
840
841                See also: common/cmd_i2c.c for a description of the
842                command line interface.
843
844
845		CONFIG_HARD_I2C
846
847		Selects the CPM hardware driver for I2C.
848
849		CONFIG_SOFT_I2C
850
851		Use software (aka bit-banging) driver instead of CPM
852		or similar hardware support for I2C.  This is configured
853		via the following defines.
854
855		I2C_INIT
856
857                (Optional). Any commands necessary to enable I2C
858                controller or configure ports.
859
860		I2C_PORT
861
862                (Only for MPC8260 CPU). The I/O port to use (the code
863                assumes both bits are on the same port). Valid values
864                are 0..3 for ports A..D.
865
866		I2C_ACTIVE
867
868		The code necessary to make the I2C data line active
869		(driven).  If the data line is open collector, this
870		define can be null.
871
872		I2C_TRISTATE
873
874		The code necessary to make the I2C data line tri-stated
875		(inactive).  If the data line is open collector, this
876		define can be null.
877
878		I2C_READ
879
880		Code that returns TRUE if the I2C data line is high,
881		FALSE if it is low.
882
883		I2C_SDA(bit)
884
885		If <bit> is TRUE, sets the I2C data line high. If it
886		is FALSE, it clears it (low).
887
888		I2C_SCL(bit)
889
890		If <bit> is TRUE, sets the I2C clock line high. If it
891		is FALSE, it clears it (low).
892
893		I2C_DELAY
894
895		This delay is invoked four times per clock cycle so this
896		controls the rate of data transfer.  The data rate thus
897		is 1 / (I2C_DELAY * 4).
898
899- SPI Support:	CONFIG_SPI
900
901		Enables SPI driver (so far only tested with
902		SPI EEPROM, also an instance works with Crystal A/D and
903		D/As on the SACSng board)
904
905		CONFIG_SPI_X
906
907		Enables extended (16-bit) SPI EEPROM addressing.
908		(symmetrical to CONFIG_I2C_X)
909
910		CONFIG_SOFT_SPI
911
912                Enables a software (bit-bang) SPI driver rather than
913                using hardware support. This is a general purpose
914                driver that only requires three general I/O port pins
915                (two outputs, one input) to function. If this is
916                defined, the board configuration must define several
917                SPI configuration items (port pins to use, etc). For
918                an example, see include/configs/sacsng.h.
919
920- FPGA Support: CONFIG_FPGA_COUNT
921
922                Specify the number of FPGA devices to support.
923
924                CONFIG_FPGA
925
926                Used to specify the types of FPGA devices. For
927		example,
928 		#define CONFIG_FPGA  CFG_XILINX_VIRTEX2
929
930 		CFG_FPGA_PROG_FEEDBACK
931
932                Enable printing of hash marks during FPGA
933		configuration.
934
935		CFG_FPGA_CHECK_BUSY
936
937                Enable checks on FPGA configuration interface busy
938                status by the configuration function. This option
939                will require a board or device specific function to
940                be written.
941
942		CONFIG_FPGA_DELAY
943
944                If defined, a function that provides delays in the
945                FPGA configuration driver.
946
947		CFG_FPGA_CHECK_CTRLC
948
949		Allow Control-C to interrupt FPGA configuration
950
951		CFG_FPGA_CHECK_ERROR
952
953                Check for configuration errors during FPGA bitfile
954                loading. For example, abort during Virtex II
955                configuration if the INIT_B line goes low (which
956                indicated a CRC error).
957
958		CFG_FPGA_WAIT_INIT
959
960                Maximum time to wait for the INIT_B line to deassert
961                after PROB_B has been deasserted during a Virtex II
962                FPGA configuration sequence. The default time is 500 mS.
963
964		CFG_FPGA_WAIT_BUSY
965
966                Maximum time to wait for BUSY to deassert during
967                Virtex II FPGA configuration. The default is 5 mS.
968
969		CFG_FPGA_WAIT_CONFIG
970
971                Time to wait after FPGA configuration. The default is
972		200 mS.
973
974- FPGA Support:	CONFIG_FPGA_COUNT
975
976 		Specify the number of FPGA devices to support.
977
978 		CONFIG_FPGA
979
980 		Used to specify the types of FPGA devices.  For example,
981 		#define CONFIG_FPGA  CFG_XILINX_VIRTEX2
982
983 		CFG_FPGA_PROG_FEEDBACK
984
985 		Enable printing of hash marks during FPGA configuration.
986
987		CFG_FPGA_CHECK_BUSY
988
989                Enable checks on FPGA configuration interface busy
990                status by the configuration function. This option
991                will require a board or device specific function to
992                be written.
993
994		CONFIG_FPGA_DELAY
995
996		If defined, a function that provides delays in the FPGA
997		configuration driver.
998
999		CFG_FPGA_CHECK_CTRLC
1000		Allow Control-C to interrupt FPGA configuration
1001
1002		CFG_FPGA_CHECK_ERROR
1003
1004                Check for configuration errors during FPGA bitfile
1005                loading. For example, abort during Virtex II
1006                configuration if the INIT_B line goes low (which
1007                indicated a CRC error).
1008
1009		CFG_FPGA_WAIT_INIT
1010
1011                Maximum time to wait for the INIT_B line to deassert
1012                after PROB_B has been deasserted during a Virtex II
1013                FPGA configuration sequence. The default time is 500
1014                mS.
1015
1016		CFG_FPGA_WAIT_BUSY
1017
1018                Maximum time to wait for BUSY to deassert during
1019                Virtex II FPGA configuration. The default is 5 mS.
1020
1021		CFG_FPGA_WAIT_CONFIG
1022
1023                Time to wait after FPGA configuration. The default is
1024                200 mS.
1025
1026- Configuration Management:
1027		CONFIG_IDENT_STRING
1028
1029                If defined, this string will be added to the U-Boot
1030                version information (U_BOOT_VERSION)
1031
1032- Vendor Parameter Protection:
1033
1034                U-Boot considers the values of the environment
1035                variables "serial#" (Board Serial Number) and
1036                "ethaddr" (Ethernet Address) to bb parameters that
1037                are set once by the board vendor / manufacturer, and
1038                protects these variables from casual modification by
1039                the user. Once set, these variables are read-only,
1040                and write or delete attempts are rejected. You can
1041                change this behviour:
1042
1043		If CONFIG_ENV_OVERWRITE is #defined in your config
1044		file, the write protection for vendor parameters is
1045		completely disabled. Anybody can change or delte
1046		these parameters.
1047
1048		Alternatively, if you #define _both_ CONFIG_ETHADDR
1049		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1050		ethernet address is installed in the environment,
1051		which can be changed exactly ONCE by the user. [The
1052		serial# is unaffected by this, i. e. it remains
1053		read-only.]
1054
1055- Protected RAM:
1056		CONFIG_PRAM
1057
1058		Define this variable to enable the reservation of
1059		"protected RAM", i. e. RAM which is not overwritten
1060		by U-Boot. Define CONFIG_PRAM to hold the number of
1061		kB you want to reserve for pRAM. You can overwrite
1062		this default value by defining an environment
1063		variable "pram" to the number of kB you want to
1064		reserve. Note that the board info structure will
1065		still show the full amount of RAM. If pRAM is
1066		reserved, a new environment variable "mem" will
1067		automatically be defined to hold the amount of
1068		remaining RAM in a form that can be passed as boot
1069		argument to Linux, for instance like that:
1070
1071			setenv bootargs ... mem=\$(mem)
1072			saveenv
1073
1074		This way you can tell Linux not to use this memory,
1075		either, which results in a memory region that will
1076		not be affected by reboots.
1077
1078		*WARNING* If your board configuration uses automatic
1079		detection of the RAM size, you must make sure that
1080		this memory test is non-destructive. So far, the
1081		following board configurations are known to be
1082		"pRAM-clean":
1083
1084			ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
1085			HERMES, IP860, RPXlite, LWMON, LANTEC,
1086			PCU_E, FLAGADM, TQM8260
1087
1088- Error Recovery:
1089		CONFIG_PANIC_HANG
1090
1091		Define this variable to stop the system in case of a
1092		fatal error, so that you have to reset it manually.
1093		This is probably NOT a good idea for an embedded
1094		system where you want to system to reboot
1095		automatically as fast as possible, but it may be
1096		useful during development since you can try to debug
1097		the conditions that lead to the situation.
1098
1099		CONFIG_NET_RETRY_COUNT
1100
1101                This variable defines the number of retries for
1102                network operations like ARP, RARP, TFTP, or BOOTP
1103                before giving up the operation. If not defined, a
1104                default value of 5 is used.
1105
1106- Command Interpreter:
1107		CFG_HUSH_PARSER
1108
1109		Define this variable to enable the "hush" shell (from
1110		Busybox) as command line interpreter, thus enabling
1111		powerful command line syntax like
1112		if...then...else...fi conditionals or `&&' and '||'
1113		constructs ("shell scripts").
1114
1115		If undefined, you get the old, much simpler behaviour
1116		with a somewhat smaller memory footprint.
1117
1118
1119		CFG_PROMPT_HUSH_PS2
1120
1121		This defines the secondary prompt string, which is
1122		printed when the command interpreter needs more input
1123		to complete a command. Usually "> ".
1124
1125	Note:
1126
1127                In the current implementation, the local variables
1128                space and global environment variables space are
1129                separated. Local variables are those you define by
1130                simply typing like `name=value'. To access a local
1131                variable later on, you have write `$name' or
1132                `${name}'; variable directly by typing say `$name' at
1133                the command prompt.
1134
1135                Global environment variables are those you use
1136                setenv/printenv to work with. To run a command stored
1137                in such a variable, you need to use the run command,
1138                and you must not use the '$' sign to access them.
1139
1140		To store commands and special characters in a
1141		variable, please use double quotation marks
1142		surrounding the whole text of the variable, instead
1143		of the backslashes before semicolons and special
1144		symbols.
1145
1146- Default Environment
1147		CONFIG_EXTRA_ENV_SETTINGS
1148
1149                Define this to contain any number of null terminated
1150                strings (variable = value pairs) that will be part of
1151                the default enviroment compiled into the boot image.
1152
1153                For example, place something like this in your
1154                board's config file:
1155
1156		#define CONFIG_EXTRA_ENV_SETTINGS \
1157			"myvar1=value1\0" \
1158			"myvar2=value2\0"
1159
1160                Warning: This method is based on knowledge about the
1161                internal format how the environment is stored by the
1162                U-Boot code. This is NOT an official, exported
1163                interface! Although it is unlikely that this format
1164                will change soon, but there is no guarantee either.
1165		You better know what you are doing here.
1166
1167                Note: overly (ab)use of the default environment is
1168                discouraged. Make sure to check other ways to preset
1169                the environment like the autoscript function or the
1170                boot command first.
1171
1172- Show boot progress
1173		CONFIG_SHOW_BOOT_PROGRESS
1174
1175                Defining this option allows to add some board-
1176                specific code (calling a user-provided function
1177                "show_boot_progress(int)") that enables you to show
1178                the system's boot progress on some display (for
1179                example, some LED's) on your board. At the moment,
1180                the following checkpoints are implemented:
1181
1182  Arg	Where			When
1183    1	common/cmd_bootm.c	before attempting to boot an image
1184   -1	common/cmd_bootm.c	Image header has bad     magic number
1185    2	common/cmd_bootm.c	Image header has correct magic number
1186   -2	common/cmd_bootm.c	Image header has bad     checksum
1187    3	common/cmd_bootm.c	Image header has correct checksum
1188   -3	common/cmd_bootm.c	Image data   has bad     checksum
1189    4	common/cmd_bootm.c	Image data   has correct checksum
1190   -4	common/cmd_bootm.c	Image is for unsupported architecture
1191    5	common/cmd_bootm.c	Architecture check OK
1192   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi, standalone)
1193    6	common/cmd_bootm.c	Image Type check OK
1194   -6	common/cmd_bootm.c	gunzip uncompression error
1195   -7	common/cmd_bootm.c	Unimplemented compression type
1196    7	common/cmd_bootm.c	Uncompression OK
1197   -8	common/cmd_bootm.c	Wrong Image Type (not kernel, multi, standalone)
1198    8	common/cmd_bootm.c	Image Type check OK
1199   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
1200    9	common/cmd_bootm.c	Start initial ramdisk verification
1201  -10	common/cmd_bootm.c	Ramdisk header has bad     magic number
1202  -11	common/cmd_bootm.c	Ramdisk header has bad     checksum
1203   10	common/cmd_bootm.c	Ramdisk header is OK
1204  -12	common/cmd_bootm.c	Ramdisk data   has bad     checksum
1205   11	common/cmd_bootm.c	Ramdisk data   has correct checksum
1206   12	common/cmd_bootm.c	Ramdisk verification complete, start loading
1207  -13	common/cmd_bootm.c	Wrong Image Type (not PPC Linux Ramdisk)
1208   13	common/cmd_bootm.c	Start multifile image verification
1209   14	common/cmd_bootm.c	No initial ramdisk, no multifile, continue.
1210   15	common/cmd_bootm.c	All preparation done, transferring control to OS
1211
1212   -1	common/cmd_doc.c	Bad usage of "doc" command
1213   -1	common/cmd_doc.c	No boot device
1214   -1	common/cmd_doc.c	Unknown Chip ID on boot device
1215   -1	common/cmd_doc.c	Read Error on boot device
1216   -1	common/cmd_doc.c	Image header has bad magic number
1217
1218   -1	common/cmd_ide.c	Bad usage of "ide" command
1219   -1	common/cmd_ide.c	No boot device
1220   -1	common/cmd_ide.c	Unknown boot device
1221   -1	common/cmd_ide.c	Unknown partition table
1222   -1	common/cmd_ide.c	Invalid partition type
1223   -1	common/cmd_ide.c	Read Error on boot device
1224   -1	common/cmd_ide.c	Image header has bad magic number
1225
1226   -1	common/cmd_nvedit.c	Environment not changable, but has bad CRC
1227
1228
1229Modem Support:
1230--------------
1231
1232[so far only for SMDK2400 board]
1233
1234- Modem support endable:
1235		CONFIG_MODEM_SUPPORT
1236
1237- RTS/CTS Flow control enable:
1238		CONFIG_HWFLOW
1239
1240- Modem debug support:
1241		CONFIG_MODEM_SUPPORT_DEBUG
1242
1243                Enables debugging stuff (char screen[1024], dbg())
1244                for modem support. Useful only with BDI2000.
1245
1246- General:
1247
1248                In the target system modem support is enabled when a
1249                specific key (key combination) is pressed during
1250                power-on. Otherwise U-Boot will boot normally
1251                (autoboot). The key_pressed() fuction is called from
1252                board_init(). Currently key_pressed() is a dummy
1253                function, returning 1 and thus enabling modem
1254                initialization.
1255
1256                If there are no modem init strings in the
1257                environment, U-Boot proceed to autoboot; the
1258                previous output (banner, info printfs) will be
1259                supressed, though.
1260
1261		See also: doc/README.Modem
1262
1263
1264
1265
1266Configuration Settings:
1267-----------------------
1268
1269- CFG_LONGHELP: Defined when you want long help messages included;
1270		undefine this when you're short of memory.
1271
1272- CFG_PROMPT:	This is what U-Boot prints on the console to
1273		prompt for user input.
1274
1275- CFG_CBSIZE:	Buffer size for input from the Console
1276
1277- CFG_PBSIZE:	Buffer size for Console output
1278
1279- CFG_MAXARGS:	max. Number of arguments accepted for monitor commands
1280
1281- CFG_BARGSIZE: Buffer size for Boot Arguments which are passed to
1282		the application (usually a Linux kernel) when it is
1283		booted
1284
1285- CFG_BAUDRATE_TABLE:
1286		List of legal baudrate settings for this board.
1287
1288- CFG_CONSOLE_INFO_QUIET
1289 		Suppress display of console information at boot.
1290
1291- CFG_CONSOLE_IS_IN_ENV
1292 		If the board specific function
1293 			extern int overwrite_console (void);
1294 		returns 1, the stdin, stderr and stdout are switched to the
1295		serial port, else the settings in the environment are used.
1296
1297- CFG_CONSOLE_OVERWRITE_ROUTINE
1298 		Enable the call to overwrite_console().
1299
1300- CFG_CONSOLE_ENV_OVERWRITE
1301		Enable overwrite of previous console environment settings.
1302
1303- CFG_MEMTEST_START, CFG_MEMTEST_END:
1304		Begin and End addresses of the area used by the
1305		simple memory test.
1306
1307- CFG_ALT_MEMTEST:
1308 		Enable an alternate, more extensive memory test.
1309
1310- CFG_TFTP_LOADADDR:
1311		Default load address for network file downloads
1312
1313- CFG_LOADS_BAUD_CHANGE:
1314		Enable temporary baudrate change while serial download
1315
1316- CFG_SDRAM_BASE:
1317		Physical start address of SDRAM. _Must_ be 0 here.
1318
1319- CFG_MBIO_BASE:
1320		Physical start address of Motherboard I/O (if using a
1321		Cogent motherboard)
1322
1323- CFG_FLASH_BASE:
1324		Physical start address of Flash memory.
1325
1326- CFG_MONITOR_BASE:
1327		Physical start address of boot monitor code (set by
1328		make config files to be same as the text base address
1329		(TEXT_BASE) used when linking) - same as
1330		CFG_FLASH_BASE when booting from flash.
1331
1332- CFG_MONITOR_LEN:
1333		Size of memory reserved for monitor code
1334
1335- CFG_MALLOC_LEN:
1336		Size of DRAM reserved for malloc() use.
1337
1338- CFG_BOOTMAPSZ:
1339		Maximum size of memory mapped by the startup code of
1340		the Linux kernel; all data that must be processed by
1341		the Linux kernel (bd_info, boot arguments, eventually
1342		initrd image) must be put below this limit.
1343
1344- CFG_MAX_FLASH_BANKS:
1345		Max number of Flash memory banks
1346
1347- CFG_MAX_FLASH_SECT:
1348		Max number of sectors on a Flash chip
1349
1350- CFG_FLASH_ERASE_TOUT:
1351		Timeout for Flash erase operations (in ms)
1352
1353- CFG_FLASH_WRITE_TOUT:
1354		Timeout for Flash write operations (in ms)
1355
1356- CFG_DIRECT_FLASH_TFTP:
1357
1358		Enable TFTP transfers directly to flash memory;
1359		without this option such a download has to be
1360		performed in two steps: (1) download to RAM, and (2)
1361		copy from RAM to flash.
1362
1363		The two-step approach is usually more reliable, since
1364		you can check if the download worked before you erase
1365		the flash, but in some situations (when sytem RAM is
1366		too limited to allow for a tempory copy of the
1367		downloaded image) this option may be very useful.
1368
1369- CFG_FLASH_CFI:
1370                Define if the flash driver uses extra elements in the
1371                common flash structure for storing flash geometry
1372
1373The following definitions that deal with the placement and management
1374of environment data (variable area); in general, we support the
1375following configurations:
1376
1377- CFG_ENV_IS_IN_FLASH:
1378
1379	Define this if the environment is in flash memory.
1380
1381	a) The environment occupies one whole flash sector, which is
1382	   "embedded" in the text segment with the U-Boot code. This
1383	   happens usually with "bottom boot sector" or "top boot
1384	   sector" type flash chips, which have several smaller
1385	   sectors at the start or the end. For instance, such a
1386	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
1387	   such a case you would place the environment in one of the
1388	   4 kB sectors - with U-Boot code before and after it. With
1389	   "top boot sector" type flash chips, you would put the
1390	   environment in one of the last sectors, leaving a gap
1391	   between U-Boot and the environment.
1392
1393	- CFG_ENV_OFFSET:
1394
1395	   Offset of environment data (variable area) to the
1396	   beginning of flash memory; for instance, with bottom boot
1397	   type flash chips the second sector can be used: the offset
1398	   for this sector is given here.
1399
1400	   CFG_ENV_OFFSET is used relative to CFG_FLASH_BASE.
1401
1402	- CFG_ENV_ADDR:
1403
1404	   This is just another way to specify the start address of
1405	   the flash sector containing the environment (instead of
1406	   CFG_ENV_OFFSET).
1407
1408	- CFG_ENV_SECT_SIZE:
1409
1410	   Size of the sector containing the environment.
1411
1412
1413	b) Sometimes flash chips have few, equal sized, BIG sectors.
1414	   In such a case you don't want to spend a whole sector for
1415	   the environment.
1416
1417	- CFG_ENV_SIZE:
1418
1419	   If you use this in combination with CFG_ENV_IS_IN_FLASH
1420	   and CFG_ENV_SECT_SIZE, you can specify to use only a part
1421	   of this flash sector for the environment. This saves
1422	   memory for the RAM copy of the environment.
1423
1424	   It may also save flash memory if you decide to use this
1425	   when your environment is "embedded" within U-Boot code,
1426	   since then the remainder of the flash sector could be used
1427	   for U-Boot code. It should be pointed out that this is
1428	   STRONGLY DISCOURAGED from a robustness point of view:
1429	   updating the environment in flash makes it always
1430	   necessary to erase the WHOLE sector. If something goes
1431	   wrong before the contents has been restored from a copy in
1432	   RAM, your target system will be dead.
1433
1434	- CFG_ENV_ADDR_REDUND
1435	  CFG_ENV_SIZE_REDUND
1436
1437           These settings describe a second storage area used to hold
1438           a redundand copy of the environment data, so that there is
1439           a valid backup copy in case there is a power failur during
1440           a "saveenv" operation.
1441
1442BE CAREFUL! Any changes to the flash layout, and some changes to the
1443source code will make it necessary to adapt <board>/u-boot.lds*
1444accordingly!
1445
1446
1447- CFG_ENV_IS_IN_NVRAM:
1448
1449	Define this if you have some non-volatile memory device
1450	(NVRAM, battery buffered SRAM) which you want to use for the
1451	environment.
1452
1453	- CFG_ENV_ADDR:
1454	- CFG_ENV_SIZE:
1455
1456	  These two #defines are used to determin the memory area you
1457	  want to use for environment. It is assumed that this memory
1458	  can just be read and written to, without any special
1459	  provision.
1460
1461BE CAREFUL! The first access to the environment happens quite early
1462in U-Boot initalization (when we try to get the setting of for the
1463console baudrate). You *MUST* have mappend your NVRAM area then, or
1464U-Boot will hang.
1465
1466Please note that even with NVRAM we still use a copy of the
1467environment in RAM: we could work on NVRAM directly, but we want to
1468keep settings there always unmodified except somebody uses "saveenv"
1469to save the current settings.
1470
1471
1472- CFG_ENV_IS_IN_EEPROM:
1473
1474	Use this if you have an EEPROM or similar serial access
1475	device and a driver for it.
1476
1477	- CFG_ENV_OFFSET:
1478	- CFG_ENV_SIZE:
1479
1480	  These two #defines specify the offset and size of the
1481	  environment area within the total memory of your EEPROM.
1482
1483	- CFG_I2C_EEPROM_ADDR:
1484	  If defined, specified the chip address of the EEPROM device.
1485	  The default address is zero.
1486
1487	- CFG_EEPROM_PAGE_WRITE_BITS:
1488	  If defined, the number of bits used to address bytes in a
1489	  single page in the EEPROM device.  A 64 byte page, for example
1490	  would require six bits.
1491
1492	- CFG_EEPROM_PAGE_WRITE_DELAY_MS:
1493	  If defined, the number of milliseconds to delay between
1494	  page writes.  The default is zero milliseconds.
1495
1496	- CFG_I2C_EEPROM_ADDR_LEN:
1497	  The length in bytes of the EEPROM memory array address.  Note
1498	  that this is NOT the chip address length!
1499
1500	- CFG_EEPROM_SIZE:
1501	  The size in bytes of the EEPROM device.
1502
1503	- CFG_I2C_EEPROM_ADDR:
1504	  If defined, specified the chip address of the EEPROM device.
1505	  The default address is zero.
1506
1507	- CFG_EEPROM_PAGE_WRITE_BITS:
1508	  If defined, the number of bits used to address bytes in a
1509	  single page in the EEPROM device.  A 64 byte page, for example
1510	  would require six bits.
1511
1512	- CFG_EEPROM_PAGE_WRITE_DELAY_MS:
1513	  If defined, the number of milliseconds to delay between
1514	  page writes.  The default is zero milliseconds.
1515
1516	- CFG_I2C_EEPROM_ADDR_LEN:
1517	  The length in bytes of the EEPROM memory array address.  Note
1518	  that this is NOT the chip address length!
1519
1520	- CFG_EEPROM_SIZE:
1521	  The size in bytes of the EEPROM device.
1522
1523- CFG_SPI_INIT_OFFSET
1524
1525	Defines offset to the initial SPI buffer area in DPRAM. The
1526	area is used at an early stage (ROM part) if the environment
1527	is configured to reside in the SPI EEPROM: We need a 520 byte
1528	scratch DPRAM area. It is used between the two initialization
1529	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
1530	to be a good choice since it makes it far enough from the
1531	start of the data area as well as from the stack pointer.
1532
1533Please note that the environment is read-only as long as the monitor
1534has been relocated to RAM and a RAM copy of the environment has been
1535created; also, when using EEPROM you will have to use getenv_r()
1536until then to read environment variables.
1537
1538The environment is now protected by a CRC32 checksum. Before the
1539monitor is relocated into RAM, as a result of a bad CRC you will be
1540working with the compiled-in default environment - *silently*!!!
1541[This is necessary, because the first environment variable we need is
1542the "baudrate" setting for the console - if we have a bad CRC, we
1543don't have any device yet where we could complain.]
1544
1545Note: once the monitor has been relocated, then it will complain if
1546the default environment is used; a new CRC is computed as soon as you
1547use the "setenv" command to modify / delete / add any environment
1548variable [even when you try to delete a non-existing variable!].
1549
1550Note2: you must edit your u-boot.lds file to reflect this
1551configuration.
1552
1553
1554Low Level (hardware related) configuration options:
1555
1556- CFG_CACHELINE_SIZE:
1557		Cache Line Size of the CPU.
1558
1559- CFG_DEFAULT_IMMR:
1560		Default address of the IMMR after system reset.
1561		Needed on some 8260 systems (MPC8260ADS and RPXsuper)
1562		to be able to adjust the position of the IMMR
1563		register after a reset.
1564
1565- Floppy Disk Support:
1566		CFG_FDC_DRIVE_NUMBER
1567
1568		the default drive number (default value 0)
1569
1570		CFG_ISA_IO_STRIDE
1571
1572		defines the spacing between fdc chipset registers
1573		(default value 1)
1574
1575		CFG_ISA_IO_OFFSET
1576
1577                defines the offset of register from address. It
1578                depends on which part of the data bus is connected to
1579                the fdc chipset. (default value 0)
1580
1581                If CFG_ISA_IO_STRIDE CFG_ISA_IO_OFFSET and
1582                CFG_FDC_DRIVE_NUMBER are undefined, they take their
1583                default value.
1584
1585                if CFG_FDC_HW_INIT is defined, then the function
1586                fdc_hw_init() is called at the beginning of the FDC
1587                setup. fdc_hw_init() must be provided by the board
1588                source code. It is used to make hardware dependant
1589                initializations.
1590
1591- CFG_IMMR:	Physical address of the Internal Memory Mapped
1592		Register; DO NOT CHANGE! (11-4)
1593		[MPC8xx systems only]
1594
1595- CFG_INIT_RAM_ADDR:
1596
1597		Start address of memory area tha can be used for
1598		initial data and stack; please note that this must be
1599		writable memory that is working WITHOUT special
1600		initialization, i. e. you CANNOT use normal RAM which
1601		will become available only after programming the
1602		memory controller and running certain initialization
1603		sequences.
1604
1605		U-Boot uses the following memory types:
1606		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
1607		- MPC824X: data cache
1608		- PPC4xx:  data cache
1609
1610- CFG_INIT_DATA_OFFSET:
1611
1612		Offset of the initial data structure in the memory
1613		area defined by CFG_INIT_RAM_ADDR. Usually
1614		CFG_INIT_DATA_OFFSET is chosen such that the initial
1615		data is located at the end of the available space
1616		(sometimes written as (CFG_INIT_RAM_END -
1617		CFG_INIT_DATA_SIZE), and the initial stack is just
1618		below that area (growing from (CFG_INIT_RAM_ADDR +
1619		CFG_INIT_DATA_OFFSET) downward.
1620
1621	Note:
1622		On the MPC824X (or other systems that use the data
1623		cache for initial memory) the address chosen for
1624		CFG_INIT_RAM_ADDR is basically arbitrary - it must
1625		point to an otherwise UNUSED address space between
1626		the top of RAM and the start of the PCI space.
1627
1628- CFG_SIUMCR:	SIU Module Configuration (11-6)
1629
1630- CFG_SYPCR:	System Protection Control (11-9)
1631
1632- CFG_TBSCR:	Time Base Status and Control (11-26)
1633
1634- CFG_PISCR:	Periodic Interrupt Status and Control (11-31)
1635
1636- CFG_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
1637
1638- CFG_SCCR:	System Clock and reset Control Register (15-27)
1639
1640- CFG_OR_TIMING_SDRAM:
1641		SDRAM timing
1642
1643- CFG_MAMR_PTA:
1644		periodic timer for refresh
1645
1646- CFG_DER:	Debug Event Register (37-47)
1647
1648- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CFG_REMAP_OR_AM,
1649  CFG_PRELIM_OR_AM, CFG_OR_TIMING_FLASH, CFG_OR0_REMAP,
1650  CFG_OR0_PRELIM, CFG_BR0_PRELIM, CFG_OR1_REMAP, CFG_OR1_PRELIM,
1651  CFG_BR1_PRELIM:
1652		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
1653
1654- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
1655  CFG_OR_TIMING_SDRAM, CFG_OR2_PRELIM, CFG_BR2_PRELIM,
1656  CFG_OR3_PRELIM, CFG_BR3_PRELIM:
1657		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
1658
1659- CFG_MAMR_PTA, CFG_MPTPR_2BK_4K, CFG_MPTPR_1BK_4K, CFG_MPTPR_2BK_8K,
1660  CFG_MPTPR_1BK_8K, CFG_MAMR_8COL, CFG_MAMR_9COL:
1661		Machine Mode Register and Memory Periodic Timer
1662		Prescaler definitions (SDRAM timing)
1663
1664- CFG_I2C_UCODE_PATCH, CFG_I2C_DPMEM_OFFSET [0x1FC0]:
1665		enable I2C microcode relocation patch (MPC8xx);
1666		define relocation offset in DPRAM [DSP2]
1667
1668- CFG_SPI_UCODE_PATCH, CFG_SPI_DPMEM_OFFSET [0x1FC0]:
1669		enable SPI microcode relocation patch (MPC8xx);
1670		define relocation offset in DPRAM [SCC4]
1671
1672- CFG_USE_OSCCLK:
1673		Use OSCM clock mode on MBX8xx board. Be careful,
1674		wrong setting might damage your board. Read
1675		doc/README.MBX before setting this variable!
1676
1677- CFG_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
1678                Offset of the bootmode word in DPRAM used by post
1679                (Power On Self Tests). This definition overrides
1680                #define'd default value in commproc.h resp.
1681                cpm_8260.h.
1682
1683Building the Software:
1684======================
1685
1686Building U-Boot has been tested in native PPC environments (on a
1687PowerBook G3 running LinuxPPC 2000) and in cross environments
1688(running RedHat 6.x and 7.x Linux on x86, Solaris 2.6 on a SPARC, and
1689NetBSD 1.5 on x86).
1690
1691If you are not using a native PPC environment, it is assumed that you
1692have the GNU cross compiling tools available in your path and named
1693with a prefix of "powerpc-linux-". If this is not the case, (e.g. if
1694you are using Monta Vista's Hard Hat Linux CDK 1.2) you must change
1695the definition of CROSS_COMPILE in Makefile. For HHL on a 4xx CPU,
1696change it to:
1697
1698	CROSS_COMPILE = ppc_4xx-
1699
1700
1701U-Boot is intended to be  simple  to  build.  After  installing  the
1702sources	 you must configure U-Boot for one specific board type. This
1703is done by typing:
1704
1705	make NAME_config
1706
1707where "NAME_config" is the name of one of the existing
1708configurations; the following names are supported:
1709
1710    ADCIOP_config	  GTH_config		TQM850L_config
1711    ADS860_config	  IP860_config		TQM855L_config
1712    AR405_config	  IVML24_config		TQM860L_config
1713    CANBT_config	  IVMS8_config		WALNUT405_config
1714    CPCI405_config	  LANTEC_config		cogent_common_config
1715    CPCIISER4_config	  MBX_config		cogent_mpc8260_config
1716    CU824_config	  MBX860T_config	cogent_mpc8xx_config
1717    ESTEEM192E_config	  RPXlite_config	hermes_config
1718    ETX094_config	  RPXsuper_config	hymod_config
1719    FADS823_config	  SM850_config		lwmon_config
1720    FADS850SAR_config	  SPD823TS_config	pcu_e_config
1721    FADS860T_config	  SXNI855T_config	rsdproto_config
1722    FPS850L_config	  Sandpoint8240_config	sbc8260_config
1723    GENIETV_config	  TQM823L_config	PIP405_config
1724    GEN860T_config	  EBONY_config		FPS860L_config
1725
1726Note: for some board special configuration names may exist; check  if
1727      additional  information is available from the board vendor; for
1728      instance, the TQM8xxL systems run normally at 50 MHz and use  a
1729      SCC  for	10baseT	 ethernet; there are also systems with 80 MHz
1730      CPU clock, and an optional Fast Ethernet	module	is  available
1731      for  CPU's  with FEC. You can select such additional "features"
1732      when chosing the configuration, i. e.
1733
1734      make TQM860L_config
1735	- will configure for a plain TQM860L, i. e. 50MHz, no FEC
1736
1737      make TQM860L_FEC_config
1738	- will configure for a TQM860L at 50MHz with FEC for ethernet
1739
1740      make TQM860L_80MHz_config
1741	- will configure for a TQM860L at 80 MHz, with normal 10baseT
1742	  interface
1743
1744      make TQM860L_FEC_80MHz_config
1745	- will configure for a TQM860L at 80 MHz with FEC for ethernet
1746
1747      make TQM823L_LCD_config
1748	- will configure for a TQM823L with U-Boot console on LCD
1749
1750      make TQM823L_LCD_80MHz_config
1751	- will configure for a TQM823L at 80 MHz with U-Boot console on LCD
1752
1753      etc.
1754
1755
1756
1757Finally, type "make all", and you should get some working U-Boot
1758images ready for downlod to / installation on your system:
1759
1760- "u-boot.bin" is a raw binary image
1761- "u-boot" is an image in ELF binary format
1762- "u-boot.srec" is in Motorola S-Record format
1763
1764
1765Please be aware that the Makefiles assume you are using GNU make, so
1766for instance on NetBSD you might need to use "gmake" instead of
1767native "make".
1768
1769
1770If the system board that you have is not listed, then you will need
1771to port U-Boot to your hardware platform. To do this, follow these
1772steps:
1773
17741.  Add a new configuration option for your board to the toplevel
1775    "Makefile", using the existing entries as examples.
17762.  Create a new directory to hold your board specific code. Add any
1777    files you need.
17783.  If you're porting U-Boot to a new CPU, then also create a new
1779    directory to hold your CPU specific code. Add any files you need.
17804.  Run "make config_name" with your new name.
17815.  Type "make", and you should get a working "u-boot.srec" file
1782    to be installed on your target system.
1783    [Of course, this last step is much harder than it sounds.]
1784
1785
1786Testing of U-Boot Modifications, Ports to New Hardware, etc.:
1787==============================================================
1788
1789If you have modified U-Boot sources (for instance added a new	board
1790or  support  for  new  devices,	 a new CPU, etc.) you are expected to
1791provide feedback to the other developers. The feedback normally takes
1792the form of a "patch", i. e. a context diff against a certain (latest
1793official or latest in CVS) version of U-Boot sources.
1794
1795But before you submit such a patch, please verify that	your  modifi-
1796cation	did not break existing code. At least make sure that *ALL* of
1797the supported boards compile WITHOUT ANY compiler warnings. To do so,
1798just run the "MAKEALL" script, which will configure and build U-Boot
1799for ALL supported system. Be warned, this will take a while. You  can
1800select	which  (cross)	compiler  to use py passing a `CROSS_COMPILE'
1801environment variable to the script, i. e. to use the cross tools from
1802MontaVista's Hard Hat Linux you can type
1803
1804	CROSS_COMPILE=ppc_8xx- MAKEALL
1805
1806or to build on a native PowerPC system you can type
1807
1808	CROSS_COMPILE=' ' MAKEALL
1809
1810See also "U-Boot Porting Guide" below.
1811
1812
1813
1814Monitor Commands - Overview:
1815============================
1816
1817go	- start application at address 'addr'
1818run	- run commands in an environment variable
1819bootm	- boot application image from memory
1820bootp	- boot image via network using BootP/TFTP protocol
1821tftpboot- boot image via network using TFTP protocol
1822	       and env variables "ipaddr" and "serverip"
1823	       (and eventually "gatewayip")
1824rarpboot- boot image via network using RARP/TFTP protocol
1825diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
1826loads	- load S-Record file over serial line
1827loadb	- load binary file over serial line (kermit mode)
1828md	- memory display
1829mm	- memory modify (auto-incrementing)
1830nm	- memory modify (constant address)
1831mw	- memory write (fill)
1832cp	- memory copy
1833cmp	- memory compare
1834crc32	- checksum calculation
1835imd     - i2c memory display
1836imm     - i2c memory modify (auto-incrementing)
1837inm     - i2c memory modify (constant address)
1838imw     - i2c memory write (fill)
1839icrc32  - i2c checksum calculation
1840iprobe  - probe to discover valid I2C chip addresses
1841iloop   - infinite loop on address range
1842isdram  - print SDRAM configuration information
1843sspi    - SPI utility commands
1844base	- print or set address offset
1845printenv- print environment variables
1846setenv	- set environment variables
1847saveenv - save environment variables to persistent storage
1848protect - enable or disable FLASH write protection
1849erase	- erase FLASH memory
1850flinfo	- print FLASH memory information
1851bdinfo	- print Board Info structure
1852iminfo	- print header information for application image
1853coninfo - print console devices and informations
1854ide	- IDE sub-system
1855loop	- infinite loop on address range
1856mtest	- simple RAM test
1857icache	- enable or disable instruction cache
1858dcache	- enable or disable data cache
1859reset	- Perform RESET of the CPU
1860echo	- echo args to console
1861version - print monitor version
1862help	- print online help
1863?	- alias for 'help'
1864
1865
1866Monitor Commands - Detailed Description:
1867========================================
1868
1869TODO.
1870
1871For now: just type "help <command>".
1872
1873
1874Environment Variables:
1875======================
1876
1877U-Boot supports user configuration using Environment Variables which
1878can be made persistent by saving to Flash memory.
1879
1880Environment Variables are set using "setenv", printed using
1881"printenv", and saved to Flash using "saveenv". Using "setenv"
1882without a value can be used to delete a variable from the
1883environment. As long as you don't save the environment you are
1884working with an in-memory copy. In case the Flash area containing the
1885environment is erased by accident, a default environment is provided.
1886
1887Some configuration options can be set using Environment Variables:
1888
1889  baudrate	- see CONFIG_BAUDRATE
1890
1891  bootdelay	- see CONFIG_BOOTDELAY
1892
1893  bootcmd	- see CONFIG_BOOTCOMMAND
1894
1895  bootargs	- Boot arguments when booting an RTOS image
1896
1897  bootfile	- Name of the image to load with TFTP
1898
1899  autoload	- if set to "no" (any string beginning with 'n'),
1900		  "bootp" will just load perform a lookup of the
1901		  configuration from the BOOTP server, but not try to
1902		  load any image using TFTP
1903
1904  autostart	- if set to "yes", an image loaded using the "bootp",
1905		  "rarpboot", "tftpboot" or "diskboot" commands will
1906		  be automatically started (by internally calling
1907		  "bootm")
1908
1909  initrd_high	- restrict positioning of initrd images:
1910		  If this variable is not set, initrd images will be
1911		  copied to the highest possible address in RAM; this
1912		  is usually what you want since it allows for
1913		  maximum initrd size. If for some reason you want to
1914		  make sure that the initrd image is loaded below the
1915		  CFG_BOOTMAPSZ limit, you can set this environment
1916		  variable to a value of "no" or "off" or "0".
1917		  Alternatively, you can set it to a maximum upper
1918		  address to use (U-Boot will still check that it
1919		  does not overwrite the U-Boot stack and data).
1920
1921		  For instance, when you have a system with 16 MB
1922		  RAM, and want to reseve 4 MB from use by Linux,
1923		  you can do this by adding "mem=12M" to the value of
1924		  the "bootargs" variable. However, now you must make
1925		  sure, that the initrd image is placed in the first
1926		  12 MB as well - this can be done with
1927
1928		  setenv initrd_high 00c00000
1929
1930  ipaddr	- IP address; needed for tftpboot command
1931
1932  loadaddr	- Default load address for commands like "bootp",
1933		  "rarpboot", "tftpboot" or "diskboot"
1934
1935  loads_echo	- see CONFIG_LOADS_ECHO
1936
1937  serverip	- TFTP server IP address; needed for tftpboot command
1938
1939  bootretry	- see CONFIG_BOOT_RETRY_TIME
1940
1941  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
1942
1943  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
1944
1945
1946The following environment variables may be used and automatically
1947updated by the network boot commands ("bootp" and "rarpboot"),
1948depending the information provided by your boot server:
1949
1950  bootfile	- see above
1951  dnsip		- IP address of your Domain Name Server
1952  gatewayip	- IP address of the Gateway (Router) to use
1953  hostname	- Target hostname
1954  ipaddr	- see above
1955  netmask	- Subnet Mask
1956  rootpath	- Pathname of the root filesystem on the NFS server
1957  serverip	- see above
1958
1959
1960There are two special Environment Variables:
1961
1962  serial#	- contains hardware identification information such
1963		  as type string and/or serial number
1964  ethaddr	- Ethernet address
1965
1966These variables can be set only once (usually during manufacturing of
1967the board). U-Boot refuses to delete or overwrite these variables
1968once they have been set once.
1969
1970
1971Please note that changes to some configuration parameters may take
1972only effect after the next boot (yes, that's just like Windoze :-).
1973
1974
1975Note for Redundant Ethernet Interfaces:
1976=======================================
1977
1978Some boards come with redundand ethernet interfaces; U-Boot supports
1979such configurations and is capable of automatic selection of a
1980"working" interface when needed. MAC assignemnt works as follows:
1981
1982Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
1983MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
1984"eth1addr" (=>eth1), "eth2addr", ...
1985
1986If the network interface stores some valid MAC address (for instance
1987in SROM), this is used as default address if there is NO correspon-
1988ding setting in the environment; if the corresponding environment
1989variable is set, this overrides the settings in the card; that means:
1990
1991o If the SROM has a valid MAC address, and there is no address in the
1992  environment, the SROM's address is used.
1993
1994o If there is no valid address in the SROM, and a definition in the
1995  environment exists, then the value from the environment variable is
1996  used.
1997
1998o If both the SROM and the environment contain a MAC address, and
1999  both addresses are the same, this MAC address is used.
2000
2001o If both the SROM and the environment contain a MAC address, and the
2002  addresses differ, the value from the environment is used and a
2003  warning is printed.
2004
2005o If neither SROM nor the environment contain a MAC address, an error
2006  is raised.
2007
2008
2009
2010Image Formats:
2011==============
2012
2013The "boot" commands of this monitor operate on "image" files which
2014can be basicly anything, preceeded by a special header; see the
2015definitions in include/image.h for details; basicly, the header
2016defines the following image properties:
2017
2018* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2019  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2020  LynxOS, pSOS, QNX;
2021  Currently supported: Linux, NetBSD, VxWorks, QNX).
2022* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
2023  IA64, MIPS, MIPS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2024  Currently supported: PowerPC).
2025* Compression Type (Provisions for uncompressed, gzip, bzip2;
2026  Currently supported: uncompressed, gzip).
2027* Load Address
2028* Entry Point
2029* Image Name
2030* Image Timestamp
2031
2032The header is marked by a special Magic Number, and both the header
2033and the data portions of the image are secured against corruption by
2034CRC32 checksums.
2035
2036
2037Linux Support:
2038==============
2039
2040Although U-Boot should support any OS or standalone application
2041easily, Linux has always been in the focus during the design of
2042U-Boot.
2043
2044U-Boot includes many features that so far have been part of some
2045special "boot loader" code within the Linux kernel. Also, any
2046"initrd" images to be used are no longer part of one big Linux image;
2047instead, kernel and "initrd" are separate images. This implementation
2048serves serveral purposes:
2049
2050- the same features can be used for other OS or standalone
2051  applications (for instance: using compressed images to reduce the
2052  Flash memory footprint)
2053
2054- it becomes much easier to port new Linux kernel versions because
2055  lots of low-level, hardware dependend stuff are done by U-Boot
2056
2057- the same Linux kernel image can now be used with different "initrd"
2058  images; of course this also means that different kernel images can
2059  be run with the same "initrd". This makes testing easier (you don't
2060  have to build a new "zImage.initrd" Linux image when you just
2061  change a file in your "initrd"). Also, a field-upgrade of the
2062  software is easier now.
2063
2064
2065Linux HOWTO:
2066============
2067
2068Porting Linux to U-Boot based systems:
2069---------------------------------------
2070
2071U-Boot cannot save you from doing all the necessary modifications to
2072configure the Linux device drivers for use with your target hardware
2073(no, we don't intend to provide a full virtual machine interface to
2074Linux :-).
2075
2076But now you can ignore ALL boot loader code (in arch/ppc/mbxboot).
2077
2078Just make sure your machine specific header file (for instance
2079include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2080Information structure as we define in include/u-boot.h, and make
2081sure that your definition of IMAP_ADDR uses the same value as your
2082U-Boot configuration in CFG_IMMR.
2083
2084
2085Configuring the Linux kernel:
2086-----------------------------
2087
2088No specific requirements for U-Boot. Make sure you have some root
2089device (initial ramdisk, NFS) for your target system.
2090
2091
2092Building a Linux Image:
2093-----------------------
2094
2095With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2096not used. If you use recent kernel source, a new build target
2097"uImage" will exist which automatically builds an image usable by
2098U-Boot. Most older kernels also have support for a "pImage" target,
2099which was introduced for our predecessor project PPCBoot and uses a
2100100% compatible format.
2101
2102Example:
2103
2104	make TQM850L_config
2105	make oldconfig
2106	make dep
2107	make uImage
2108
2109The "uImage" build target uses a special tool (in 'tools/mkimage') to
2110encapsulate a compressed Linux kernel image with header  information,
2111CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2112
2113* build a standard "vmlinux" kernel image (in ELF binary format):
2114
2115* convert the kernel into a raw binary image:
2116
2117	${CROSS_COMPILE}-objcopy -O binary \
2118				 -R .note -R .comment \
2119				 -S vmlinux linux.bin
2120
2121* compress the binary image:
2122
2123	gzip -9 linux.bin
2124
2125* package compressed binary image for U-Boot:
2126
2127	mkimage -A ppc -O linux -T kernel -C gzip \
2128		-a 0 -e 0 -n "Linux Kernel Image" \
2129		-d linux.bin.gz uImage
2130
2131
2132The "mkimage" tool can also be used to create ramdisk images for use
2133with U-Boot, either separated from the Linux kernel image, or
2134combined into one file. "mkimage" encapsulates the images with a 64
2135byte header containing information about target architecture,
2136operating system, image type, compression method, entry points, time
2137stamp, CRC32 checksums, etc.
2138
2139"mkimage" can be called in two ways: to verify existing images and
2140print the header information, or to build new images.
2141
2142In the first form (with "-l" option) mkimage lists the information
2143contained in the header of an existing U-Boot image; this includes
2144checksum verification:
2145
2146	tools/mkimage -l image
2147	  -l ==> list image header information
2148
2149The second form (with "-d" option) is used to build a U-Boot image
2150from a "data file" which is used as image payload:
2151
2152	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
2153		      -n name -d data_file image
2154	  -A ==> set architecture to 'arch'
2155	  -O ==> set operating system to 'os'
2156	  -T ==> set image type to 'type'
2157	  -C ==> set compression type 'comp'
2158	  -a ==> set load address to 'addr' (hex)
2159	  -e ==> set entry point to 'ep' (hex)
2160	  -n ==> set image name to 'name'
2161	  -d ==> use image data from 'datafile'
2162
2163Right now, all Linux kernels use the same load address	(0x00000000),
2164but the entry point address depends on the kernel version:
2165
2166- 2.2.x kernels have the entry point at 0x0000000C,
2167- 2.3.x and later kernels have the entry point at 0x00000000.
2168
2169So a typical call to build a U-Boot image would read:
2170
2171	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2172	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
2173	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz \
2174	> examples/uImage.TQM850L
2175	Image Name:   2.4.4 kernel for TQM850L
2176	Created:      Wed Jul 19 02:34:59 2000
2177	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
2178	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
2179	Load Address: 0x00000000
2180	Entry Point:  0x00000000
2181
2182To verify the contents of the image (or check for corruption):
2183
2184	-> tools/mkimage -l examples/uImage.TQM850L
2185	Image Name:   2.4.4 kernel for TQM850L
2186	Created:      Wed Jul 19 02:34:59 2000
2187	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
2188	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
2189	Load Address: 0x00000000
2190	Entry Point:  0x00000000
2191
2192NOTE: for embedded systems where boot time is critical you can trade
2193speed for memory and install an UNCOMPRESSED image instead: this
2194needs more space in Flash, but boots much faster since it does not
2195need to be uncompressed:
2196
2197	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
2198	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
2199	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
2200	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
2201	> examples/uImage.TQM850L-uncompressed
2202	Image Name:   2.4.4 kernel for TQM850L
2203	Created:      Wed Jul 19 02:34:59 2000
2204	Image Type:   PowerPC Linux Kernel Image (uncompressed)
2205	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
2206	Load Address: 0x00000000
2207	Entry Point:  0x00000000
2208
2209
2210Similar you can build U-Boot images from a 'ramdisk.image.gz' file
2211when your kernel is intended to use an initial ramdisk:
2212
2213	-> tools/mkimage -n 'Simple Ramdisk Image' \
2214	> -A ppc -O linux -T ramdisk -C gzip \
2215	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
2216	Image Name:   Simple Ramdisk Image
2217	Created:      Wed Jan 12 14:01:50 2000
2218	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
2219	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
2220	Load Address: 0x00000000
2221	Entry Point:  0x00000000
2222
2223
2224Installing a Linux Image:
2225-------------------------
2226
2227To downloading a U-Boot image over the serial (console) interface,
2228you must convert the image to S-Record format:
2229
2230	objcopy -I binary -O srec examples/image examples/image.srec
2231
2232The 'objcopy' does not understand the information in the U-Boot
2233image header, so the resulting S-Record file will be relative to
2234address 0x00000000. To load it to a given address, you need to
2235specify the target address as 'offset' parameter with the 'loads'
2236command.
2237
2238Example: install the image to address 0x40100000 (which on the
2239TQM8xxL is in the first Flash bank):
2240
2241	=> erase 40100000 401FFFFF
2242
2243	.......... done
2244	Erased 8 sectors
2245
2246	=> loads 40100000
2247	## Ready for S-Record download ...
2248	~>examples/image.srec
2249	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
2250	...
2251	15989 15990 15991 15992
2252	[file transfer complete]
2253	[connected]
2254	## Start Addr = 0x00000000
2255
2256
2257You can check the success of the download using the 'iminfo' command;
2258this includes a checksum verification so you  can  be  sure  no	 data
2259corruption happened:
2260
2261	=> imi 40100000
2262
2263	## Checking Image at 40100000 ...
2264	   Image Name:	 2.2.13 for initrd on TQM850L
2265	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
2266	   Data Size:	 335725 Bytes = 327 kB = 0 MB
2267	   Load Address: 00000000
2268	   Entry Point:	 0000000c
2269	   Verifying Checksum ... OK
2270
2271
2272
2273Boot Linux:
2274-----------
2275
2276The "bootm" command is used to boot an application that is stored in
2277memory (RAM or Flash). In case of a Linux kernel image, the contents
2278of the "bootargs" environment variable is passed to the kernel as
2279parameters. You can check and modify this variable using the
2280"printenv" and "setenv" commands:
2281
2282
2283	=> printenv bootargs
2284	bootargs=root=/dev/ram
2285
2286	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2287
2288	=> printenv bootargs
2289	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2290
2291	=> bootm 40020000
2292	## Booting Linux kernel at 40020000 ...
2293	   Image Name:	 2.2.13 for NFS on TQM850L
2294	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
2295	   Data Size:	 381681 Bytes = 372 kB = 0 MB
2296	   Load Address: 00000000
2297	   Entry Point:	 0000000c
2298	   Verifying Checksum ... OK
2299	   Uncompressing Kernel Image ... OK
2300	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
2301	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
2302	time_init: decrementer frequency = 187500000/60
2303	Calibrating delay loop... 49.77 BogoMIPS
2304	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
2305	...
2306
2307If you want to boot a Linux kernel with initial ram disk, you pass
2308the memory addreses of both the kernel and the initrd image (PPBCOOT
2309format!) to the "bootm" command:
2310
2311	=> imi 40100000 40200000
2312
2313	## Checking Image at 40100000 ...
2314	   Image Name:	 2.2.13 for initrd on TQM850L
2315	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
2316	   Data Size:	 335725 Bytes = 327 kB = 0 MB
2317	   Load Address: 00000000
2318	   Entry Point:	 0000000c
2319	   Verifying Checksum ... OK
2320
2321	## Checking Image at 40200000 ...
2322	   Image Name:	 Simple Ramdisk Image
2323	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
2324	   Data Size:	 566530 Bytes = 553 kB = 0 MB
2325	   Load Address: 00000000
2326	   Entry Point:	 00000000
2327	   Verifying Checksum ... OK
2328
2329	=> bootm 40100000 40200000
2330	## Booting Linux kernel at 40100000 ...
2331	   Image Name:	 2.2.13 for initrd on TQM850L
2332	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
2333	   Data Size:	 335725 Bytes = 327 kB = 0 MB
2334	   Load Address: 00000000
2335	   Entry Point:	 0000000c
2336	   Verifying Checksum ... OK
2337	   Uncompressing Kernel Image ... OK
2338	## Loading RAMDisk Image at 40200000 ...
2339	   Image Name:	 Simple Ramdisk Image
2340	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
2341	   Data Size:	 566530 Bytes = 553 kB = 0 MB
2342	   Load Address: 00000000
2343	   Entry Point:	 00000000
2344	   Verifying Checksum ... OK
2345	   Loading Ramdisk ... OK
2346	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
2347	Boot arguments: root=/dev/ram
2348	time_init: decrementer frequency = 187500000/60
2349	Calibrating delay loop... 49.77 BogoMIPS
2350	...
2351	RAMDISK: Compressed image found at block 0
2352	VFS: Mounted root (ext2 filesystem).
2353
2354	bash#
2355
2356
2357Standalone HOWTO:
2358=================
2359
2360One of the features of U-Boot is that you can dynamically load and
2361run "standalone" applications, which can use some resources of
2362U-Boot like console I/O functions or interrupt services.
2363
2364Two simple examples are included with the sources:
2365
2366"Hello World" Demo:
2367-------------------
2368
2369'examples/hello_world.c' contains a small "Hello World" Demo
2370application; it is automatically compiled when you build U-Boot.
2371It's configured to run at address 0x00040004, so you can play with it
2372like that:
2373
2374	=> loads
2375	## Ready for S-Record download ...
2376	~>examples/hello_world.srec
2377	1 2 3 4 5 6 7 8 9 10 11 ...
2378	[file transfer complete]
2379	[connected]
2380	## Start Addr = 0x00040004
2381
2382	=> go 40004 Hello World! This is a test.
2383	## Starting application at 0x00040004 ...
2384	Hello World
2385	argc = 7
2386	argv[0] = "40004"
2387	argv[1] = "Hello"
2388	argv[2] = "World!"
2389	argv[3] = "This"
2390	argv[4] = "is"
2391	argv[5] = "a"
2392	argv[6] = "test."
2393	argv[7] = "<NULL>"
2394	Hit any key to exit ...
2395
2396	## Application terminated, rc = 0x0
2397
2398Another example, which demonstrates how to register a CPM interrupt
2399handler with the U-Boot code, can be found in 'examples/timer.c'.
2400Here, a CPM timer is set up to generate an interrupt every second.
2401The interrupt service routine is trivial, just printing a '.'
2402character, but this is just a demo program. The application can be
2403controlled by the following keys:
2404
2405	? - print current values og the CPM Timer registers
2406	b - enable interrupts and start timer
2407	e - stop timer and disable interrupts
2408	q - quit application
2409
2410	=> loads
2411	## Ready for S-Record download ...
2412	~>examples/timer.srec
2413	1 2 3 4 5 6 7 8 9 10 11 ...
2414	[file transfer complete]
2415	[connected]
2416	## Start Addr = 0x00040004
2417
2418	=> go 40004
2419	## Starting application at 0x00040004 ...
2420	TIMERS=0xfff00980
2421	Using timer 1
2422	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
2423
2424Hit 'b':
2425	[q, b, e, ?] Set interval 1000000 us
2426	Enabling timer
2427Hit '?':
2428	[q, b, e, ?] ........
2429	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
2430Hit '?':
2431	[q, b, e, ?] .
2432	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
2433Hit '?':
2434	[q, b, e, ?] .
2435	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
2436Hit '?':
2437	[q, b, e, ?] .
2438	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
2439Hit 'e':
2440	[q, b, e, ?] ...Stopping timer
2441Hit 'q':
2442	[q, b, e, ?] ## Application terminated, rc = 0x0
2443
2444
2445NetBSD Notes:
2446=============
2447
2448Starting at version 0.9.2, U-Boot supports NetBSD both as host
2449(build U-Boot) and target system (boots NetBSD/mpc8xx).
2450
2451Building requires a cross environment; it is known to work on
2452NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
2453need gmake since the Makefiles are not compatible with BSD make).
2454Note that the cross-powerpc package does not install include files;
2455attempting to build U-Boot will fail because <machine/ansi.h> is
2456missing.  This file has to be installed and patched manually:
2457
2458	# cd /usr/pkg/cross/powerpc-netbsd/include
2459	# mkdir powerpc
2460	# ln -s powerpc machine
2461	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
2462	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
2463
2464Native builds *don't* work due to incompatibilities between native
2465and U-Boot include files.
2466
2467Booting assumes that (the first part of) the image booted is a
2468stage-2 loader which in turn loads and then invokes the kernel
2469proper. Loader sources will eventually appear in the NetBSD source
2470tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
2471meantime, send mail to bruno@exet-ag.de and/or wd@denx.de for
2472details.
2473
2474
2475Implementation Internals:
2476=========================
2477
2478The following is not intended to be a complete description of every
2479implementation detail. However, it should help to understand the
2480inner workings of U-Boot and make it easier to port it to custom
2481hardware.
2482
2483
2484Initial Stack, Global Data:
2485---------------------------
2486
2487The implementation of U-Boot is complicated by the fact that U-Boot
2488starts running out of ROM (flash memory), usually without access to
2489system RAM (because the memory controller is not initialized yet).
2490This means that we don't have writable Data or BSS segments, and BSS
2491is not initialized as zero. To be able to get a C environment working
2492at all, we have to allocate at least a minimal stack. Implementation
2493options for this are defined and restricted by the CPU used: Some CPU
2494models provide on-chip memory (like the IMMR area on MPC8xx and
2495MPC826x processors), on others (parts of) the data cache can be
2496locked as (mis-) used as memory, etc.
2497
2498It is essential to remember this, since it has some impact on the C
2499code for the initialization procedures:
2500
2501* Initialized global data (data segment) is read-only. Do not attempt
2502  to write it.
2503
2504* Do not use any unitialized global data (or implicitely initialized
2505  as zero data - BSS segment) at all - this is undefined, initiali-
2506  zation is performed later (when relocationg to RAM).
2507
2508* Stack space is very limited. Avoid big data buffers or things  like
2509  that.
2510
2511Having only the stack as writable memory limits means we cannot use
2512normal global data to share information beween the code. But it
2513turned out that the implementation of U-Boot can be greatly
2514simplified by making a global data structure (gd_t) available to all
2515functions. We could pass a pointer to this data as argument to _all_
2516functions, but this would bloat the code. Instead we use a feature of
2517the GCC compiler (Global Register Variables) to share the data: we
2518place a pointer (gd) to the global data into a register which we
2519reserve for this purpose.
2520
2521When chosing a register for such a purpose we are restricted  by  the
2522relevant  (E)ABI  specifications for the current architecture, and by
2523GCC's implementation.
2524
2525For PowerPC, the following registers have specific use:
2526	R1:	stack pointer
2527	R2:	TOC pointer
2528	R3-R4:	parameter passing and return values
2529	R5-R10:	parameter passing
2530	R13:	small data area pointer
2531	R30:	GOT pointer
2532	R31:	frame pointer
2533
2534	(U-Boot also uses R14 as internal GOT pointer.)
2535
2536    ==> U-Boot will use R29 to hold a pointer to the global data
2537
2538    Note: on PPC, we could use a static initializer (since the
2539    address of the global data structure is known at compile time),
2540    but it turned out that reserving a register results in somewhat
2541    smaller code - although the code savings are not that big (on
2542    average for all boards 752 bytes for the whole U-Boot image,
2543    624 text + 127 data).
2544
2545On ARM, the following registers are used:
2546
2547	R0:	function argument word/integer result
2548	R1-R3:	function argument word
2549	R9:	GOT pointer
2550	R10:	stack limit (used only if stack checking if enabled)
2551	R11:	argument (frame) pointer
2552	R12:	temporary workspace
2553	R13:	stack pointer
2554	R14:	link register
2555	R15:	program counter
2556
2557    ==> U-Boot will use R8 to hold a pointer to the global data
2558
2559
2560
2561Memory Management:
2562------------------
2563
2564U-Boot runs in system state and uses physical addresses, i.e. the
2565MMU is not used either for address mapping nor for memory protection.
2566
2567The available memory is mapped to fixed addresses using the memory
2568controller. In this process, a contiguous block is formed for each
2569memory type (Flash, SDRAM, SRAM), even when it consists of several
2570physical memory banks.
2571
2572U-Boot is installed in the first 128 kB of the first Flash bank (on
2573TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
2574booting and sizing and initializing DRAM, the code relocates itself
2575to the upper end of DRAM. Immediately below the U-Boot code some
2576memory is reserved for use by malloc() [see CFG_MALLOC_LEN
2577configuration setting]. Below that, a structure with global Board
2578Info data is placed, followed by the stack (growing downward).
2579
2580Additionally, some exception handler code is copied to the low 8 kB
2581of DRAM (0x00000000 ... 0x00001FFF).
2582
2583So a typical memory configuration with 16 MB of DRAM could look like
2584this:
2585
2586	0x0000 0000	Exception Vector code
2587	      :
2588	0x0000 1FFF
2589	0x0000 2000	Free for Application Use
2590	      :
2591	      :
2592
2593	      :
2594	      :
2595	0x00FB FF20	Monitor Stack (Growing downward)
2596	0x00FB FFAC	Board Info Data and permanent copy of global data
2597	0x00FC 0000	Malloc Arena
2598	      :
2599	0x00FD FFFF
2600	0x00FE 0000	RAM Copy of Monitor Code
2601	...		eventually: LCD or video framebuffer
2602	...		eventually: pRAM (Protected RAM - unchanged by reset)
2603	0x00FF FFFF	[End of RAM]
2604
2605
2606System Initialization:
2607----------------------
2608
2609In the reset configuration, U-Boot starts at the reset entry point
2610(on most PowerPC systens at address 0x00000100). Because of the reset
2611configuration for CS0# this is a mirror of the onboard Flash memory.
2612To be able to re-map memory U-Boot then jumps to it's link address.
2613To be able to implement the initialization code in C, a (small!)
2614initial stack is set up in the internal Dual Ported RAM (in case CPUs
2615which provide such a feature like MPC8xx or MPC8260), or in a locked
2616part of the data cache. After that, U-Boot initializes the CPU core,
2617the caches and the SIU.
2618
2619Next, all (potentially) available memory banks are mapped using a
2620preliminary mapping. For example, we put them on 512 MB boundaries
2621(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
2622on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
2623programmed for SDRAM access. Using the temporary configuration, a
2624simple memory test is run that determines the size of the SDRAM
2625banks.
2626
2627When there is more than one SDRAM bank, and the banks are of
2628different size, the larger is mapped first. For equal size, the first
2629bank (CS2#) is mapped first. The first mapping is always for address
26300x00000000, with any additional banks following immediately to create
2631contiguous memory starting from 0.
2632
2633Then, the monitor installs itself at the upper end of the SDRAM area
2634and allocates memory for use by malloc() and for the global Board
2635Info data; also, the exception vector code is copied to the low RAM
2636pages, and the final stack is set up.
2637
2638Only after this relocation will you have a "normal" C environment;
2639until that you are restricted in several ways, mostly because you are
2640running from ROM, and because the code will have to be relocated to a
2641new address in RAM.
2642
2643
2644U-Boot Porting Guide:
2645----------------------
2646
2647[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
2648list, October 2002]
2649
2650
2651int main (int argc, char *argv[])
2652{
2653	sighandler_t no_more_time;
2654
2655	signal (SIGALRM, no_more_time);
2656	alarm (PROJECT_DEADLINE - toSec (3 * WEEK));
2657
2658	if (available_money > available_manpower) {
2659		pay consultant to port U-Boot;
2660		return 0;
2661	}
2662
2663	Download latest U-Boot source;
2664
2665	Subscribe to u-boot-users mailing list;
2666
2667	if (clueless) {
2668		email ("Hi, I am new to U-Boot, how do I get started?");
2669	}
2670
2671	while (learning) {
2672		Read the README file in the top level directory;
2673		Read http://www.denx.de/re/DPLG.html
2674		Read the source, Luke;
2675	}
2676
2677	if (available_money > toLocalCurrency ($2500)) {
2678		Buy a BDI2000;
2679	} else {
2680		Add a lot of aggravation and time;
2681	}
2682
2683	Create your own board support subdirectory;
2684
2685	Create your own board config file;
2686
2687	while (!running) {
2688		do {
2689			Add / modify source code;
2690		} until (compiles);
2691		Debug;
2692		if (clueless)
2693			email ("Hi, I am having problems...");
2694	}
2695	Send patch file to Wolfgang;
2696
2697	return 0;
2698}
2699
2700void no_more_time (int sig)
2701{
2702      hire_a_guru();
2703}
2704
2705
2706
2707Coding Standards:
2708-----------------
2709
2710All contributions to U-Boot should conform to the Linux kernel
2711coding style; see the file "Documentation/CodingStyle" in your Linux
2712kernel source directory.
2713
2714Please note that U-Boot is implemented in C (and to some small parts
2715in Assembler); no C++ is used, so please do not use C++ style
2716comments (//) in your code.
2717
2718Submissions which do not conform to the standards may be returned
2719with a request to reformat the changes.
2720
2721
2722Submitting Patches:
2723-------------------
2724
2725Since the number of patches for U-Boot is growing, we need to
2726establish some rules. Submissions which do not conform to these rules
2727may be rejected, even when they contain important and valuable stuff.
2728
2729
2730When you send a patch, please include the following information with
2731it:
2732
2733* For bug fixes: a description of the bug and how your patch fixes
2734  this bug. Please try to include a way of demonstrating that the
2735  patch actually fixes something.
2736
2737* For new features: a description of the feature and your
2738  implementation.
2739
2740* A CHANGELOG entry as plaintext (separate from the patch)
2741
2742* For major contributions, your entry to the CREDITS file
2743
2744* When you add support for a new board, don't forget to add this
2745  board to the MAKEALL script, too.
2746
2747* If your patch adds new configuration options, don't forget to
2748  document these in the README file.
2749
2750* The patch itself. If you are accessing the CVS repository use "cvs
2751  update; cvs diff -puRN"; else, use "diff -purN OLD NEW". If your
2752  version of diff does not support these options, then get the latest
2753  version of GNU diff.
2754
2755  We accept patches as plain text, MIME attachments or as uuencoded
2756  gzipped text.
2757
2758Notes:
2759
2760* Before sending the patch, run the MAKEALL script on your patched
2761  source tree and make sure that no errors or warnings are reported
2762  for any of the boards.
2763
2764* Keep your modifications to the necessary minimum: A patch
2765  containing several unrelated changes or arbitrary reformats will be
2766  returned with a request to re-formatting / split it.
2767
2768* If you modify existing code, make sure that your new code does not
2769  add to the memory footprint of the code ;-) Small is beautiful!
2770  When adding new features, these should compile conditionally only
2771  (using #ifdef), and the resulting code with the new feature
2772  disabled must not need more memory than the old code without your
2773  modification.
2774