xref: /rk3399_rockchip-uboot/README (revision ce981dc857adfc8036ca2f6d5d5a06c2a8aa77d6)
1#
2# (C) Copyright 2000 - 2005
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# See file CREDITS for list of people who contributed to this
6# project.
7#
8# This program is free software; you can redistribute it and/or
9# modify it under the terms of the GNU General Public License as
10# published by the Free Software Foundation; either version 2 of
11# the License, or (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program; if not, write to the Free Software
20# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21# MA 02111-1307 USA
22#
23
24Summary:
25========
26
27This directory contains the source code for U-Boot, a boot loader for
28Embedded boards based on PowerPC, ARM, MIPS and several other
29processors, which can be installed in a boot ROM and used to
30initialize and test the hardware or to download and run application
31code.
32
33The development of U-Boot is closely related to Linux: some parts of
34the source code originate in the Linux source tree, we have some
35header files in common, and special provision has been made to
36support booting of Linux images.
37
38Some attention has been paid to make this software easily
39configurable and extendable. For instance, all monitor commands are
40implemented with the same call interface, so that it's very easy to
41add new commands. Also, instead of permanently adding rarely used
42code (for instance hardware test utilities) to the monitor, you can
43load and run it dynamically.
44
45
46Status:
47=======
48
49In general, all boards for which a configuration option exists in the
50Makefile have been tested to some extent and can be considered
51"working". In fact, many of them are used in production systems.
52
53In case of problems see the CHANGELOG and CREDITS files to find out
54who contributed the specific port.
55
56
57Where to get help:
58==================
59
60In case you have questions about, problems with or contributions for
61U-Boot you should send a message to the U-Boot mailing list at
62<u-boot-users@lists.sourceforge.net>. There is also an archive of
63previous traffic on the mailing list - please search the archive
64before asking FAQ's. Please see
65http://lists.sourceforge.net/lists/listinfo/u-boot-users/
66
67
68Where we come from:
69===================
70
71- start from 8xxrom sources
72- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
73- clean up code
74- make it easier to add custom boards
75- make it possible to add other [PowerPC] CPUs
76- extend functions, especially:
77  * Provide extended interface to Linux boot loader
78  * S-Record download
79  * network boot
80  * PCMCIA / CompactFLash / ATA disk / SCSI ... boot
81- create ARMBoot project (http://sourceforge.net/projects/armboot)
82- add other CPU families (starting with ARM)
83- create U-Boot project (http://sourceforge.net/projects/u-boot)
84
85
86Names and Spelling:
87===================
88
89The "official" name of this project is "Das U-Boot". The spelling
90"U-Boot" shall be used in all written text (documentation, comments
91in source files etc.). Example:
92
93	This is the README file for the U-Boot project.
94
95File names etc. shall be based on the string "u-boot". Examples:
96
97	include/asm-ppc/u-boot.h
98
99	#include <asm/u-boot.h>
100
101Variable names, preprocessor constants etc. shall be either based on
102the string "u_boot" or on "U_BOOT". Example:
103
104	U_BOOT_VERSION		u_boot_logo
105	IH_OS_U_BOOT		u_boot_hush_start
106
107
108Versioning:
109===========
110
111U-Boot uses a 3 level version number containing a version, a
112sub-version, and a patchlevel: "U-Boot-2.34.5" means version "2",
113sub-version "34", and patchlevel "4".
114
115The patchlevel is used to indicate certain stages of development
116between released versions, i. e. officially released versions of
117U-Boot will always have a patchlevel of "0".
118
119
120Directory Hierarchy:
121====================
122
123- board		Board dependent files
124- common	Misc architecture independent functions
125- cpu		CPU specific files
126  - 74xx_7xx	Files specific to Freescale MPC74xx and 7xx CPUs
127  - arm720t	Files specific to ARM 720 CPUs
128  - arm920t	Files specific to ARM 920 CPUs
129    - at91rm9200 Files specific to Atmel AT91RM9200 CPU
130    - imx	Files specific to Freescale MC9328 i.MX CPUs
131    - s3c24x0	Files specific to Samsung S3C24X0 CPUs
132  - arm925t	Files specific to ARM 925 CPUs
133  - arm926ejs	Files specific to ARM 926 CPUs
134  - arm1136	Files specific to ARM 1136 CPUs
135  - at32ap	Files specific to Atmel AVR32 AP CPUs
136  - i386	Files specific to i386 CPUs
137  - ixp		Files specific to Intel XScale IXP CPUs
138  - mcf52x2	Files specific to Freescale ColdFire MCF52x2 CPUs
139  - mips	Files specific to MIPS CPUs
140  - mpc5xx	Files specific to Freescale MPC5xx  CPUs
141  - mpc5xxx	Files specific to Freescale MPC5xxx CPUs
142  - mpc8xx	Files specific to Freescale MPC8xx  CPUs
143  - mpc8220	Files specific to Freescale MPC8220 CPUs
144  - mpc824x	Files specific to Freescale MPC824x CPUs
145  - mpc8260	Files specific to Freescale MPC8260 CPUs
146  - mpc85xx	Files specific to Freescale MPC85xx CPUs
147  - nios	Files specific to Altera NIOS CPUs
148  - nios2	Files specific to Altera Nios-II CPUs
149  - ppc4xx	Files specific to AMCC PowerPC 4xx CPUs
150  - pxa		Files specific to Intel XScale PXA CPUs
151  - s3c44b0	Files specific to Samsung S3C44B0 CPUs
152  - sa1100	Files specific to Intel StrongARM SA1100 CPUs
153- disk		Code for disk drive partition handling
154- doc		Documentation (don't expect too much)
155- drivers	Commonly used device drivers
156- dtt		Digital Thermometer and Thermostat drivers
157- examples	Example code for standalone applications, etc.
158- include	Header Files
159- lib_arm	Files generic to ARM	 architecture
160- lib_avr32	Files generic to AVR32	 architecture
161- lib_generic	Files generic to all	 architectures
162- lib_i386	Files generic to i386	 architecture
163- lib_m68k	Files generic to m68k	 architecture
164- lib_mips	Files generic to MIPS	 architecture
165- lib_nios	Files generic to NIOS	 architecture
166- lib_ppc	Files generic to PowerPC architecture
167- libfdt 	Library files to support flattened device trees
168- net		Networking code
169- post		Power On Self Test
170- rtc		Real Time Clock drivers
171- tools		Tools to build S-Record or U-Boot images, etc.
172
173Software Configuration:
174=======================
175
176Configuration is usually done using C preprocessor defines; the
177rationale behind that is to avoid dead code whenever possible.
178
179There are two classes of configuration variables:
180
181* Configuration _OPTIONS_:
182  These are selectable by the user and have names beginning with
183  "CONFIG_".
184
185* Configuration _SETTINGS_:
186  These depend on the hardware etc. and should not be meddled with if
187  you don't know what you're doing; they have names beginning with
188  "CFG_".
189
190Later we will add a configuration tool - probably similar to or even
191identical to what's used for the Linux kernel. Right now, we have to
192do the configuration by hand, which means creating some symbolic
193links and editing some configuration files. We use the TQM8xxL boards
194as an example here.
195
196
197Selection of Processor Architecture and Board Type:
198---------------------------------------------------
199
200For all supported boards there are ready-to-use default
201configurations available; just type "make <board_name>_config".
202
203Example: For a TQM823L module type:
204
205	cd u-boot
206	make TQM823L_config
207
208For the Cogent platform, you need to specify the cpu type as well;
209e.g. "make cogent_mpc8xx_config". And also configure the cogent
210directory according to the instructions in cogent/README.
211
212
213Configuration Options:
214----------------------
215
216Configuration depends on the combination of board and CPU type; all
217such information is kept in a configuration file
218"include/configs/<board_name>.h".
219
220Example: For a TQM823L module, all configuration settings are in
221"include/configs/TQM823L.h".
222
223
224Many of the options are named exactly as the corresponding Linux
225kernel configuration options. The intention is to make it easier to
226build a config tool - later.
227
228
229The following options need to be configured:
230
231- CPU Type:	Define exactly one of
232
233		PowerPC based CPUs:
234		-------------------
235		CONFIG_MPC823,	CONFIG_MPC850,	CONFIG_MPC855,	CONFIG_MPC860
236	or	CONFIG_MPC5xx
237	or	CONFIG_MPC8220
238	or	CONFIG_MPC824X, CONFIG_MPC8260
239	or	CONFIG_MPC85xx
240	or	CONFIG_IOP480
241	or	CONFIG_405GP
242	or	CONFIG_405EP
243	or	CONFIG_440
244	or	CONFIG_MPC74xx
245	or	CONFIG_750FX
246
247		ARM based CPUs:
248		---------------
249		CONFIG_SA1110
250		CONFIG_ARM7
251		CONFIG_PXA250
252		CONFIG_CPU_MONAHANS
253
254		MicroBlaze based CPUs:
255		----------------------
256		CONFIG_MICROBLAZE
257
258		Nios-2 based CPUs:
259		----------------------
260		CONFIG_NIOS2
261
262		AVR32 based CPUs:
263		----------------------
264		CONFIG_AT32AP
265
266- Board Type:	Define exactly one of
267
268		PowerPC based boards:
269		---------------------
270
271		CONFIG_ADCIOP		CONFIG_FPS860L		CONFIG_OXC
272		CONFIG_ADS860		CONFIG_GEN860T		CONFIG_PCI405
273		CONFIG_AMX860		CONFIG_GENIETV		CONFIG_PCIPPC2
274		CONFIG_AP1000		CONFIG_GTH		CONFIG_PCIPPC6
275		CONFIG_AR405		CONFIG_gw8260		CONFIG_pcu_e
276		CONFIG_BAB7xx		CONFIG_hermes		CONFIG_PIP405
277		CONFIG_BC3450		CONFIG_hymod		CONFIG_PM826
278		CONFIG_c2mon		CONFIG_IAD210		CONFIG_ppmc8260
279		CONFIG_CANBT		CONFIG_ICU862		CONFIG_QS823
280		CONFIG_CCM		CONFIG_IP860		CONFIG_QS850
281		CONFIG_CMI		CONFIG_IPHASE4539	CONFIG_QS860T
282		CONFIG_cogent_mpc8260	CONFIG_IVML24		CONFIG_RBC823
283		CONFIG_cogent_mpc8xx	CONFIG_IVML24_128	CONFIG_RPXClassic
284		CONFIG_CPCI405		CONFIG_IVML24_256	CONFIG_RPXlite
285		CONFIG_CPCI4052		CONFIG_IVMS8		CONFIG_RPXsuper
286		CONFIG_CPCIISER4	CONFIG_IVMS8_128	CONFIG_rsdproto
287		CONFIG_CPU86		CONFIG_IVMS8_256	CONFIG_sacsng
288		CONFIG_CRAYL1		CONFIG_JSE		CONFIG_Sandpoint8240
289		CONFIG_CSB272		CONFIG_LANTEC		CONFIG_Sandpoint8245
290		CONFIG_CU824		CONFIG_LITE5200B	CONFIG_sbc8260
291		CONFIG_DASA_SIM		CONFIG_lwmon		CONFIG_sbc8560
292		CONFIG_DB64360		CONFIG_MBX		CONFIG_SM850
293		CONFIG_DB64460		CONFIG_MBX860T		CONFIG_SPD823TS
294		CONFIG_DU405		CONFIG_MHPC		CONFIG_STXGP3
295		CONFIG_DUET_ADS		CONFIG_MIP405		CONFIG_SXNI855T
296		CONFIG_EBONY		CONFIG_MOUSSE		CONFIG_TQM823L
297		CONFIG_ELPPC		CONFIG_MPC8260ADS	CONFIG_TQM8260
298		CONFIG_ELPT860		CONFIG_MPC8540ADS	CONFIG_TQM850L
299		CONFIG_ep8260		CONFIG_MPC8540EVAL	CONFIG_TQM855L
300		CONFIG_ERIC		CONFIG_MPC8560ADS	CONFIG_TQM860L
301		CONFIG_ESTEEM192E	CONFIG_MUSENKI		CONFIG_TTTech
302		CONFIG_ETX094		CONFIG_MVS1		CONFIG_UTX8245
303		CONFIG_EVB64260		CONFIG_NETPHONE		CONFIG_V37
304		CONFIG_FADS823		CONFIG_NETTA		CONFIG_W7OLMC
305		CONFIG_FADS850SAR	CONFIG_NETVIA		CONFIG_W7OLMG
306		CONFIG_FADS860T		CONFIG_NX823		CONFIG_WALNUT
307		CONFIG_FLAGADM		CONFIG_OCRTC		CONFIG_ZPC1900
308		CONFIG_FPS850L		CONFIG_ORSG		CONFIG_ZUMA
309
310		ARM based boards:
311		-----------------
312
313		CONFIG_ARMADILLO,	CONFIG_AT91RM9200DK,	CONFIG_CERF250,
314		CONFIG_CSB637,		CONFIG_DELTA,		CONFIG_DNP1110,
315		CONFIG_EP7312,		CONFIG_H2_OMAP1610,	CONFIG_HHP_CRADLE,
316		CONFIG_IMPA7,	    CONFIG_INNOVATOROMAP1510,	CONFIG_INNOVATOROMAP1610,
317		CONFIG_KB9202,		CONFIG_LART,		CONFIG_LPD7A400,
318		CONFIG_LUBBOCK,		CONFIG_OSK_OMAP5912,	CONFIG_OMAP2420H4,
319		CONFIG_PLEB2,		CONFIG_SHANNON,		CONFIG_P2_OMAP730,
320		CONFIG_SMDK2400,	CONFIG_SMDK2410,	CONFIG_TRAB,
321		CONFIG_VCMA9
322
323		MicroBlaze based boards:
324		------------------------
325
326		CONFIG_SUZAKU
327
328		Nios-2 based boards:
329		------------------------
330
331		CONFIG_PCI5441 CONFIG_PK1C20
332		CONFIG_EP1C20 CONFIG_EP1S10 CONFIG_EP1S40
333
334		AVR32 based boards:
335		-------------------
336
337		CONFIG_ATSTK1000
338
339- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
340		Define exactly one of
341		CONFIG_ATSTK1002
342
343
344- CPU Module Type: (if CONFIG_COGENT is defined)
345		Define exactly one of
346		CONFIG_CMA286_60_OLD
347--- FIXME --- not tested yet:
348		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
349		CONFIG_CMA287_23, CONFIG_CMA287_50
350
351- Motherboard Type: (if CONFIG_COGENT is defined)
352		Define exactly one of
353		CONFIG_CMA101, CONFIG_CMA102
354
355- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
356		Define one or more of
357		CONFIG_CMA302
358
359- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
360		Define one or more of
361		CONFIG_LCD_HEARTBEAT	- update a character position on
362					  the lcd display every second with
363					  a "rotator" |\-/|\-/
364
365- Board flavour: (if CONFIG_MPC8260ADS is defined)
366		CONFIG_ADSTYPE
367		Possible values are:
368			CFG_8260ADS	- original MPC8260ADS
369			CFG_8266ADS	- MPC8266ADS
370			CFG_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
371			CFG_8272ADS	- MPC8272ADS
372
373- MPC824X Family Member (if CONFIG_MPC824X is defined)
374		Define exactly one of
375		CONFIG_MPC8240, CONFIG_MPC8245
376
377- 8xx CPU Options: (if using an MPC8xx cpu)
378		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
379					  get_gclk_freq() cannot work
380					  e.g. if there is no 32KHz
381					  reference PIT/RTC clock
382		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
383					  or XTAL/EXTAL)
384
385- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
386		CFG_8xx_CPUCLK_MIN
387		CFG_8xx_CPUCLK_MAX
388		CONFIG_8xx_CPUCLK_DEFAULT
389			See doc/README.MPC866
390
391		CFG_MEASURE_CPUCLK
392
393		Define this to measure the actual CPU clock instead
394		of relying on the correctness of the configured
395		values. Mostly useful for board bringup to make sure
396		the PLL is locked at the intended frequency. Note
397		that this requires a (stable) reference clock (32 kHz
398		RTC clock or CFG_8XX_XIN)
399
400- Intel Monahans options:
401		CFG_MONAHANS_RUN_MODE_OSC_RATIO
402
403		Defines the Monahans run mode to oscillator
404		ratio. Valid values are 8, 16, 24, 31. The core
405		frequency is this value multiplied by 13 MHz.
406
407		CFG_MONAHANS_TURBO_RUN_MODE_RATIO
408
409		Defines the Monahans turbo mode to oscillator
410		ratio. Valid values are 1 (default if undefined) and
411		2. The core frequency as calculated above is multiplied
412		by this value.
413
414- Linux Kernel Interface:
415		CONFIG_CLOCKS_IN_MHZ
416
417		U-Boot stores all clock information in Hz
418		internally. For binary compatibility with older Linux
419		kernels (which expect the clocks passed in the
420		bd_info data to be in MHz) the environment variable
421		"clocks_in_mhz" can be defined so that U-Boot
422		converts clock data to MHZ before passing it to the
423		Linux kernel.
424		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
425		"clocks_in_mhz=1" is  automatically  included  in  the
426		default environment.
427
428		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
429
430		When transfering memsize parameter to linux, some versions
431		expect it to be in bytes, others in MB.
432		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
433
434		CONFIG_OF_LIBFDT / CONFIG_OF_FLAT_TREE
435
436		New kernel versions are expecting firmware settings to be
437		passed using flattened device trees (based on open firmware
438		concepts).
439
440		CONFIG_OF_LIBFDT
441		 * New libfdt-based support
442		 * Adds the "fdt" command
443		 * The bootm command does _not_ modify the fdt
444
445		CONFIG_OF_FLAT_TREE
446		 * Deprecated, see CONFIG_OF_LIBFDT
447		 * Original ft_build.c-based support
448		 * Automatically modifies the dft as part of the bootm command
449		 * The environment variable "disable_of", when set,
450		     disables this functionality.
451
452		CONFIG_OF_FLAT_TREE_MAX_SIZE
453
454		The maximum size of the constructed OF tree.
455
456		OF_CPU - The proper name of the cpus node.
457		OF_SOC - The proper name of the soc node.
458		OF_TBCLK - The timebase frequency.
459		OF_STDOUT_PATH - The path to the console device
460
461		CONFIG_OF_HAS_BD_T
462
463		 * CONFIG_OF_LIBFDT - enables the "fdt bd_t" command
464		 * CONFIG_OF_FLAT_TREE - The resulting flat device tree
465		     will have a copy of the bd_t.  Space should be
466		     pre-allocated in the dts for the bd_t.
467
468		CONFIG_OF_HAS_UBOOT_ENV
469
470		 * CONFIG_OF_LIBFDT - enables the "fdt bd_t" command
471		 * CONFIG_OF_FLAT_TREE - The resulting flat device tree
472		     will have a copy of u-boot's environment variables
473
474		CONFIG_OF_BOARD_SETUP
475
476		Board code has addition modification that it wants to make
477		to the flat device tree before handing it off to the kernel
478
479		CONFIG_OF_BOOT_CPU
480
481		This define fills in the correct boot cpu in the boot
482		param header, the default value is zero if undefined.
483
484- Serial Ports:
485		CFG_PL010_SERIAL
486
487		Define this if you want support for Amba PrimeCell PL010 UARTs.
488
489		CFG_PL011_SERIAL
490
491		Define this if you want support for Amba PrimeCell PL011 UARTs.
492
493		CONFIG_PL011_CLOCK
494
495		If you have Amba PrimeCell PL011 UARTs, set this variable to
496		the clock speed of the UARTs.
497
498		CONFIG_PL01x_PORTS
499
500		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
501		define this to a list of base addresses for each (supported)
502		port. See e.g. include/configs/versatile.h
503
504
505- Console Interface:
506		Depending on board, define exactly one serial port
507		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
508		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
509		console by defining CONFIG_8xx_CONS_NONE
510
511		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
512		port routines must be defined elsewhere
513		(i.e. serial_init(), serial_getc(), ...)
514
515		CONFIG_CFB_CONSOLE
516		Enables console device for a color framebuffer. Needs following
517		defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
518			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
519						(default big endian)
520			VIDEO_HW_RECTFILL	graphic chip supports
521						rectangle fill
522						(cf. smiLynxEM)
523			VIDEO_HW_BITBLT		graphic chip supports
524						bit-blit (cf. smiLynxEM)
525			VIDEO_VISIBLE_COLS	visible pixel columns
526						(cols=pitch)
527			VIDEO_VISIBLE_ROWS	visible pixel rows
528			VIDEO_PIXEL_SIZE	bytes per pixel
529			VIDEO_DATA_FORMAT	graphic data format
530						(0-5, cf. cfb_console.c)
531			VIDEO_FB_ADRS		framebuffer address
532			VIDEO_KBD_INIT_FCT	keyboard int fct
533						(i.e. i8042_kbd_init())
534			VIDEO_TSTC_FCT		test char fct
535						(i.e. i8042_tstc)
536			VIDEO_GETC_FCT		get char fct
537						(i.e. i8042_getc)
538			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
539						(requires blink timer
540						cf. i8042.c)
541			CFG_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
542			CONFIG_CONSOLE_TIME	display time/date info in
543						upper right corner
544						(requires CONFIG_CMD_DATE)
545			CONFIG_VIDEO_LOGO	display Linux logo in
546						upper left corner
547			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
548						linux_logo.h for logo.
549						Requires CONFIG_VIDEO_LOGO
550			CONFIG_CONSOLE_EXTRA_INFO
551						addional board info beside
552						the logo
553
554		When CONFIG_CFB_CONSOLE is defined, video console is
555		default i/o. Serial console can be forced with
556		environment 'console=serial'.
557
558		When CONFIG_SILENT_CONSOLE is defined, all console
559		messages (by U-Boot and Linux!) can be silenced with
560		the "silent" environment variable. See
561		doc/README.silent for more information.
562
563- Console Baudrate:
564		CONFIG_BAUDRATE - in bps
565		Select one of the baudrates listed in
566		CFG_BAUDRATE_TABLE, see below.
567		CFG_BRGCLK_PRESCALE, baudrate prescale
568
569- Interrupt driven serial port input:
570		CONFIG_SERIAL_SOFTWARE_FIFO
571
572		PPC405GP only.
573		Use an interrupt handler for receiving data on the
574		serial port. It also enables using hardware handshake
575		(RTS/CTS) and UART's built-in FIFO. Set the number of
576		bytes the interrupt driven input buffer should have.
577
578		Leave undefined to disable this feature, including
579		disable the buffer and hardware handshake.
580
581- Console UART Number:
582		CONFIG_UART1_CONSOLE
583
584		AMCC PPC4xx only.
585		If defined internal UART1 (and not UART0) is used
586		as default U-Boot console.
587
588- Boot Delay:	CONFIG_BOOTDELAY - in seconds
589		Delay before automatically booting the default image;
590		set to -1 to disable autoboot.
591
592		See doc/README.autoboot for these options that
593		work with CONFIG_BOOTDELAY. None are required.
594		CONFIG_BOOT_RETRY_TIME
595		CONFIG_BOOT_RETRY_MIN
596		CONFIG_AUTOBOOT_KEYED
597		CONFIG_AUTOBOOT_PROMPT
598		CONFIG_AUTOBOOT_DELAY_STR
599		CONFIG_AUTOBOOT_STOP_STR
600		CONFIG_AUTOBOOT_DELAY_STR2
601		CONFIG_AUTOBOOT_STOP_STR2
602		CONFIG_ZERO_BOOTDELAY_CHECK
603		CONFIG_RESET_TO_RETRY
604
605- Autoboot Command:
606		CONFIG_BOOTCOMMAND
607		Only needed when CONFIG_BOOTDELAY is enabled;
608		define a command string that is automatically executed
609		when no character is read on the console interface
610		within "Boot Delay" after reset.
611
612		CONFIG_BOOTARGS
613		This can be used to pass arguments to the bootm
614		command. The value of CONFIG_BOOTARGS goes into the
615		environment value "bootargs".
616
617		CONFIG_RAMBOOT and CONFIG_NFSBOOT
618		The value of these goes into the environment as
619		"ramboot" and "nfsboot" respectively, and can be used
620		as a convenience, when switching between booting from
621		ram and nfs.
622
623- Pre-Boot Commands:
624		CONFIG_PREBOOT
625
626		When this option is #defined, the existence of the
627		environment variable "preboot" will be checked
628		immediately before starting the CONFIG_BOOTDELAY
629		countdown and/or running the auto-boot command resp.
630		entering interactive mode.
631
632		This feature is especially useful when "preboot" is
633		automatically generated or modified. For an example
634		see the LWMON board specific code: here "preboot" is
635		modified when the user holds down a certain
636		combination of keys on the (special) keyboard when
637		booting the systems
638
639- Serial Download Echo Mode:
640		CONFIG_LOADS_ECHO
641		If defined to 1, all characters received during a
642		serial download (using the "loads" command) are
643		echoed back. This might be needed by some terminal
644		emulations (like "cu"), but may as well just take
645		time on others. This setting #define's the initial
646		value of the "loads_echo" environment variable.
647
648- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
649		CONFIG_KGDB_BAUDRATE
650		Select one of the baudrates listed in
651		CFG_BAUDRATE_TABLE, see below.
652
653- Monitor Functions:
654		Monitor commands can be included or excluded
655		from the build by using the #include files
656		"config_cmd_all.h" and #undef'ing unwanted
657		commands, or using "config_cmd_default.h"
658		and augmenting with additional #define's
659		for wanted commands.
660
661		The default command configuration includes all commands
662		except those marked below with a "*".
663
664		CONFIG_CMD_ASKENV	* ask for env variable
665		CONFIG_CMD_AUTOSCRIPT	  Autoscript Support
666		CONFIG_CMD_BDI		  bdinfo
667		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
668		CONFIG_CMD_BMP		* BMP support
669		CONFIG_CMD_BSP		* Board specific commands
670		CONFIG_CMD_BOOTD	  bootd
671		CONFIG_CMD_CACHE	* icache, dcache
672		CONFIG_CMD_CONSOLE	  coninfo
673		CONFIG_CMD_DATE		* support for RTC, date/time...
674		CONFIG_CMD_DHCP		* DHCP support
675		CONFIG_CMD_DIAG		* Diagnostics
676		CONFIG_CMD_DOC		* Disk-On-Chip Support
677		CONFIG_CMD_DTT		* Digital Therm and Thermostat
678		CONFIG_CMD_ECHO		  echo arguments
679		CONFIG_CMD_EEPROM	* EEPROM read/write support
680		CONFIG_CMD_ELF		* bootelf, bootvx
681		CONFIG_CMD_ENV		  saveenv
682		CONFIG_CMD_FDC		* Floppy Disk Support
683		CONFIG_CMD_FAT		* FAT partition support
684		CONFIG_CMD_FDOS		* Dos diskette Support
685		CONFIG_CMD_FLASH	  flinfo, erase, protect
686		CONFIG_CMD_FPGA		  FPGA device initialization support
687		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
688		CONFIG_CMD_I2C		* I2C serial bus support
689		CONFIG_CMD_IDE		* IDE harddisk support
690		CONFIG_CMD_IMI		  iminfo
691		CONFIG_CMD_IMLS		  List all found images
692		CONFIG_CMD_IMMAP	* IMMR dump support
693		CONFIG_CMD_IRQ		* irqinfo
694		CONFIG_CMD_ITEST	  Integer/string test of 2 values
695		CONFIG_CMD_JFFS2	* JFFS2 Support
696		CONFIG_CMD_KGDB		* kgdb
697		CONFIG_CMD_LOADB	  loadb
698		CONFIG_CMD_LOADS	  loads
699		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
700					  loop, loopw, mtest
701		CONFIG_CMD_MISC		  Misc functions like sleep etc
702		CONFIG_CMD_MMC		* MMC memory mapped support
703		CONFIG_CMD_MII		* MII utility commands
704		CONFIG_CMD_NAND		* NAND support
705		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
706		CONFIG_CMD_PCI		* pciinfo
707		CONFIG_CMD_PCMCIA		* PCMCIA support
708		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
709					  host
710		CONFIG_CMD_PORTIO	* Port I/O
711		CONFIG_CMD_REGINFO	* Register dump
712		CONFIG_CMD_RUN		  run command in env variable
713		CONFIG_CMD_SAVES	* save S record dump
714		CONFIG_CMD_SCSI		* SCSI Support
715		CONFIG_CMD_SDRAM	* print SDRAM configuration information
716					  (requires CONFIG_CMD_I2C)
717		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
718					  (4xx only)
719		CONFIG_CMD_SPI		* SPI serial bus support
720		CONFIG_CMD_USB		* USB support
721		CONFIG_CMD_VFD		* VFD support (TRAB)
722		CONFIG_CMD_BSP		* Board SPecific functions
723		CONFIG_CMD_CDP		* Cisco Discover Protocol support
724		CONFIG_CMD_FSL		* Microblaze FSL support
725
726
727		EXAMPLE: If you want all functions except of network
728		support you can write:
729
730		#include "config_cmd_all.h"
731		#undef CONFIG_CMD_NET
732
733	Other Commands:
734		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
735
736	Note:	Don't enable the "icache" and "dcache" commands
737		(configuration option CONFIG_CMD_CACHE) unless you know
738		what you (and your U-Boot users) are doing. Data
739		cache cannot be enabled on systems like the 8xx or
740		8260 (where accesses to the IMMR region must be
741		uncached), and it cannot be disabled on all other
742		systems where we (mis-) use the data cache to hold an
743		initial stack and some data.
744
745
746		XXX - this list needs to get updated!
747
748- Watchdog:
749		CONFIG_WATCHDOG
750		If this variable is defined, it enables watchdog
751		support. There must be support in the platform specific
752		code for a watchdog. For the 8xx and 8260 CPUs, the
753		SIU Watchdog feature is enabled in the SYPCR
754		register.
755
756- U-Boot Version:
757		CONFIG_VERSION_VARIABLE
758		If this variable is defined, an environment variable
759		named "ver" is created by U-Boot showing the U-Boot
760		version as printed by the "version" command.
761		This variable is readonly.
762
763- Real-Time Clock:
764
765		When CONFIG_CMD_DATE is selected, the type of the RTC
766		has to be selected, too. Define exactly one of the
767		following options:
768
769		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
770		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
771		CONFIG_RTC_MC146818	- use MC146818 RTC
772		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
773		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
774		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
775		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
776		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
777
778		Note that if the RTC uses I2C, then the I2C interface
779		must also be configured. See I2C Support, below.
780
781- Timestamp Support:
782
783		When CONFIG_TIMESTAMP is selected, the timestamp
784		(date and time) of an image is printed by image
785		commands like bootm or iminfo. This option is
786		automatically enabled when you select CONFIG_CMD_DATE .
787
788- Partition Support:
789		CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
790		and/or CONFIG_ISO_PARTITION
791
792		If IDE or SCSI support	is  enabled  (CONFIG_CMD_IDE or
793		CONFIG_CMD_SCSI) you must configure support for at least
794		one partition type as well.
795
796- IDE Reset method:
797		CONFIG_IDE_RESET_ROUTINE - this is defined in several
798		board configurations files but used nowhere!
799
800		CONFIG_IDE_RESET - is this is defined, IDE Reset will
801		be performed by calling the function
802			ide_set_reset(int reset)
803		which has to be defined in a board specific file
804
805- ATAPI Support:
806		CONFIG_ATAPI
807
808		Set this to enable ATAPI support.
809
810- LBA48 Support
811		CONFIG_LBA48
812
813		Set this to enable support for disks larger than 137GB
814		Also look at CFG_64BIT_LBA ,CFG_64BIT_VSPRINTF and CFG_64BIT_STRTOUL
815		Whithout these , LBA48 support uses 32bit variables and will 'only'
816		support disks up to 2.1TB.
817
818		CFG_64BIT_LBA:
819			When enabled, makes the IDE subsystem use 64bit sector addresses.
820			Default is 32bit.
821
822- SCSI Support:
823		At the moment only there is only support for the
824		SYM53C8XX SCSI controller; define
825		CONFIG_SCSI_SYM53C8XX to enable it.
826
827		CFG_SCSI_MAX_LUN [8], CFG_SCSI_MAX_SCSI_ID [7] and
828		CFG_SCSI_MAX_DEVICE [CFG_SCSI_MAX_SCSI_ID *
829		CFG_SCSI_MAX_LUN] can be adjusted to define the
830		maximum numbers of LUNs, SCSI ID's and target
831		devices.
832		CFG_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
833
834- NETWORK Support (PCI):
835		CONFIG_E1000
836		Support for Intel 8254x gigabit chips.
837
838		CONFIG_EEPRO100
839		Support for Intel 82557/82559/82559ER chips.
840		Optional CONFIG_EEPRO100_SROM_WRITE enables eeprom
841		write routine for first time initialisation.
842
843		CONFIG_TULIP
844		Support for Digital 2114x chips.
845		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
846		modem chip initialisation (KS8761/QS6611).
847
848		CONFIG_NATSEMI
849		Support for National dp83815 chips.
850
851		CONFIG_NS8382X
852		Support for National dp8382[01] gigabit chips.
853
854- NETWORK Support (other):
855
856		CONFIG_DRIVER_LAN91C96
857		Support for SMSC's LAN91C96 chips.
858
859			CONFIG_LAN91C96_BASE
860			Define this to hold the physical address
861			of the LAN91C96's I/O space
862
863			CONFIG_LAN91C96_USE_32_BIT
864			Define this to enable 32 bit addressing
865
866		CONFIG_DRIVER_SMC91111
867		Support for SMSC's LAN91C111 chip
868
869			CONFIG_SMC91111_BASE
870			Define this to hold the physical address
871			of the device (I/O space)
872
873			CONFIG_SMC_USE_32_BIT
874			Define this if data bus is 32 bits
875
876			CONFIG_SMC_USE_IOFUNCS
877			Define this to use i/o functions instead of macros
878			(some hardware wont work with macros)
879
880- USB Support:
881		At the moment only the UHCI host controller is
882		supported (PIP405, MIP405, MPC5200); define
883		CONFIG_USB_UHCI to enable it.
884		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
885		and define CONFIG_USB_STORAGE to enable the USB
886		storage devices.
887		Note:
888		Supported are USB Keyboards and USB Floppy drives
889		(TEAC FD-05PUB).
890		MPC5200 USB requires additional defines:
891			CONFIG_USB_CLOCK
892				for 528 MHz Clock: 0x0001bbbb
893			CONFIG_USB_CONFIG
894				for differential drivers: 0x00001000
895				for single ended drivers: 0x00005000
896
897
898- MMC Support:
899		The MMC controller on the Intel PXA is supported. To
900		enable this define CONFIG_MMC. The MMC can be
901		accessed from the boot prompt by mapping the device
902		to physical memory similar to flash. Command line is
903		enabled with CONFIG_CMD_MMC. The MMC driver also works with
904		the FAT fs. This is enabled with CONFIG_CMD_FAT.
905
906- Journaling Flash filesystem support:
907		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
908		CONFIG_JFFS2_NAND_DEV
909		Define these for a default partition on a NAND device
910
911		CFG_JFFS2_FIRST_SECTOR,
912		CFG_JFFS2_FIRST_BANK, CFG_JFFS2_NUM_BANKS
913		Define these for a default partition on a NOR device
914
915		CFG_JFFS_CUSTOM_PART
916		Define this to create an own partition. You have to provide a
917		function struct part_info* jffs2_part_info(int part_num)
918
919		If you define only one JFFS2 partition you may also want to
920		#define CFG_JFFS_SINGLE_PART	1
921		to disable the command chpart. This is the default when you
922		have not defined a custom partition
923
924- Keyboard Support:
925		CONFIG_ISA_KEYBOARD
926
927		Define this to enable standard (PC-Style) keyboard
928		support
929
930		CONFIG_I8042_KBD
931		Standard PC keyboard driver with US (is default) and
932		GERMAN key layout (switch via environment 'keymap=de') support.
933		Export function i8042_kbd_init, i8042_tstc and i8042_getc
934		for cfb_console. Supports cursor blinking.
935
936- Video support:
937		CONFIG_VIDEO
938
939		Define this to enable video support (for output to
940		video).
941
942		CONFIG_VIDEO_CT69000
943
944		Enable Chips & Technologies 69000 Video chip
945
946		CONFIG_VIDEO_SMI_LYNXEM
947		Enable Silicon Motion SMI 712/710/810 Video chip. The
948		video output is selected via environment 'videoout'
949		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
950		assumed.
951
952		For the CT69000 and SMI_LYNXEM drivers, videomode is
953		selected via environment 'videomode'. Two diferent ways
954		are possible:
955		- "videomode=num"   'num' is a standard LiLo mode numbers.
956		Following standard modes are supported	(* is default):
957
958		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
959		-------------+---------------------------------------------
960		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
961		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
962		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
963		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
964		-------------+---------------------------------------------
965		(i.e. setenv videomode 317; saveenv; reset;)
966
967		- "videomode=bootargs" all the video parameters are parsed
968		from the bootargs. (See drivers/videomodes.c)
969
970
971		CONFIG_VIDEO_SED13806
972		Enable Epson SED13806 driver. This driver supports 8bpp
973		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
974		or CONFIG_VIDEO_SED13806_16BPP
975
976- Keyboard Support:
977		CONFIG_KEYBOARD
978
979		Define this to enable a custom keyboard support.
980		This simply calls drv_keyboard_init() which must be
981		defined in your board-specific files.
982		The only board using this so far is RBC823.
983
984- LCD Support:	CONFIG_LCD
985
986		Define this to enable LCD support (for output to LCD
987		display); also select one of the supported displays
988		by defining one of these:
989
990		CONFIG_NEC_NL6448AC33:
991
992			NEC NL6448AC33-18. Active, color, single scan.
993
994		CONFIG_NEC_NL6448BC20
995
996			NEC NL6448BC20-08. 6.5", 640x480.
997			Active, color, single scan.
998
999		CONFIG_NEC_NL6448BC33_54
1000
1001			NEC NL6448BC33-54. 10.4", 640x480.
1002			Active, color, single scan.
1003
1004		CONFIG_SHARP_16x9
1005
1006			Sharp 320x240. Active, color, single scan.
1007			It isn't 16x9, and I am not sure what it is.
1008
1009		CONFIG_SHARP_LQ64D341
1010
1011			Sharp LQ64D341 display, 640x480.
1012			Active, color, single scan.
1013
1014		CONFIG_HLD1045
1015
1016			HLD1045 display, 640x480.
1017			Active, color, single scan.
1018
1019		CONFIG_OPTREX_BW
1020
1021			Optrex	 CBL50840-2 NF-FW 99 22 M5
1022			or
1023			Hitachi	 LMG6912RPFC-00T
1024			or
1025			Hitachi	 SP14Q002
1026
1027			320x240. Black & white.
1028
1029		Normally display is black on white background; define
1030		CFG_WHITE_ON_BLACK to get it inverted.
1031
1032- Splash Screen Support: CONFIG_SPLASH_SCREEN
1033
1034		If this option is set, the environment is checked for
1035		a variable "splashimage". If found, the usual display
1036		of logo, copyright and system information on the LCD
1037		is suppressed and the BMP image at the address
1038		specified in "splashimage" is loaded instead. The
1039		console is redirected to the "nulldev", too. This
1040		allows for a "silent" boot where a splash screen is
1041		loaded very quickly after power-on.
1042
1043- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1044
1045		If this option is set, additionally to standard BMP
1046		images, gzipped BMP images can be displayed via the
1047		splashscreen support or the bmp command.
1048
1049- Compression support:
1050		CONFIG_BZIP2
1051
1052		If this option is set, support for bzip2 compressed
1053		images is included. If not, only uncompressed and gzip
1054		compressed images are supported.
1055
1056		NOTE: the bzip2 algorithm requires a lot of RAM, so
1057		the malloc area (as defined by CFG_MALLOC_LEN) should
1058		be at least 4MB.
1059
1060- MII/PHY support:
1061		CONFIG_PHY_ADDR
1062
1063		The address of PHY on MII bus.
1064
1065		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1066
1067		The clock frequency of the MII bus
1068
1069		CONFIG_PHY_GIGE
1070
1071		If this option is set, support for speed/duplex
1072		detection of Gigabit PHY is included.
1073
1074		CONFIG_PHY_RESET_DELAY
1075
1076		Some PHY like Intel LXT971A need extra delay after
1077		reset before any MII register access is possible.
1078		For such PHY, set this option to the usec delay
1079		required. (minimum 300usec for LXT971A)
1080
1081		CONFIG_PHY_CMD_DELAY (ppc4xx)
1082
1083		Some PHY like Intel LXT971A need extra delay after
1084		command issued before MII status register can be read
1085
1086- Ethernet address:
1087		CONFIG_ETHADDR
1088		CONFIG_ETH2ADDR
1089		CONFIG_ETH3ADDR
1090
1091		Define a default value for ethernet address to use
1092		for the respective ethernet interface, in case this
1093		is not determined automatically.
1094
1095- IP address:
1096		CONFIG_IPADDR
1097
1098		Define a default value for the IP address to use for
1099		the default ethernet interface, in case this is not
1100		determined through e.g. bootp.
1101
1102- Server IP address:
1103		CONFIG_SERVERIP
1104
1105		Defines a default value for theIP address of a TFTP
1106		server to contact when using the "tftboot" command.
1107
1108- BOOTP Recovery Mode:
1109		CONFIG_BOOTP_RANDOM_DELAY
1110
1111		If you have many targets in a network that try to
1112		boot using BOOTP, you may want to avoid that all
1113		systems send out BOOTP requests at precisely the same
1114		moment (which would happen for instance at recovery
1115		from a power failure, when all systems will try to
1116		boot, thus flooding the BOOTP server. Defining
1117		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1118		inserted before sending out BOOTP requests. The
1119		following delays are inserted then:
1120
1121		1st BOOTP request:	delay 0 ... 1 sec
1122		2nd BOOTP request:	delay 0 ... 2 sec
1123		3rd BOOTP request:	delay 0 ... 4 sec
1124		4th and following
1125		BOOTP requests:		delay 0 ... 8 sec
1126
1127- DHCP Advanced Options:
1128		You can fine tune the DHCP functionality by defining
1129		CONFIG_BOOTP_* symbols:
1130
1131		CONFIG_BOOTP_SUBNETMASK
1132		CONFIG_BOOTP_GATEWAY
1133		CONFIG_BOOTP_HOSTNAME
1134		CONFIG_BOOTP_NISDOMAIN
1135		CONFIG_BOOTP_BOOTPATH
1136		CONFIG_BOOTP_BOOTFILESIZE
1137		CONFIG_BOOTP_DNS
1138		CONFIG_BOOTP_DNS2
1139		CONFIG_BOOTP_SEND_HOSTNAME
1140		CONFIG_BOOTP_NTPSERVER
1141		CONFIG_BOOTP_TIMEOFFSET
1142		CONFIG_BOOTP_VENDOREX
1143
1144		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1145		serverip from a DHCP server, it is possible that more
1146		than one DNS serverip is offered to the client.
1147		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1148		serverip will be stored in the additional environment
1149		variable "dnsip2". The first DNS serverip is always
1150		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1151		is defined.
1152
1153		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1154		to do a dynamic update of a DNS server. To do this, they
1155		need the hostname of the DHCP requester.
1156		If CONFIG_BOOP_SEND_HOSTNAME is defined, the content
1157		of the "hostname" environment variable is passed as
1158		option 12 to the DHCP server.
1159
1160 - CDP Options:
1161		CONFIG_CDP_DEVICE_ID
1162
1163		The device id used in CDP trigger frames.
1164
1165		CONFIG_CDP_DEVICE_ID_PREFIX
1166
1167		A two character string which is prefixed to the MAC address
1168		of the device.
1169
1170		CONFIG_CDP_PORT_ID
1171
1172		A printf format string which contains the ascii name of
1173		the port. Normally is set to "eth%d" which sets
1174		eth0 for the first ethernet, eth1 for the second etc.
1175
1176		CONFIG_CDP_CAPABILITIES
1177
1178		A 32bit integer which indicates the device capabilities;
1179		0x00000010 for a normal host which does not forwards.
1180
1181		CONFIG_CDP_VERSION
1182
1183		An ascii string containing the version of the software.
1184
1185		CONFIG_CDP_PLATFORM
1186
1187		An ascii string containing the name of the platform.
1188
1189		CONFIG_CDP_TRIGGER
1190
1191		A 32bit integer sent on the trigger.
1192
1193		CONFIG_CDP_POWER_CONSUMPTION
1194
1195		A 16bit integer containing the power consumption of the
1196		device in .1 of milliwatts.
1197
1198		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1199
1200		A byte containing the id of the VLAN.
1201
1202- Status LED:	CONFIG_STATUS_LED
1203
1204		Several configurations allow to display the current
1205		status using a LED. For instance, the LED will blink
1206		fast while running U-Boot code, stop blinking as
1207		soon as a reply to a BOOTP request was received, and
1208		start blinking slow once the Linux kernel is running
1209		(supported by a status LED driver in the Linux
1210		kernel). Defining CONFIG_STATUS_LED enables this
1211		feature in U-Boot.
1212
1213- CAN Support:	CONFIG_CAN_DRIVER
1214
1215		Defining CONFIG_CAN_DRIVER enables CAN driver support
1216		on those systems that support this (optional)
1217		feature, like the TQM8xxL modules.
1218
1219- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1220
1221		These enable I2C serial bus commands. Defining either of
1222		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1223		include the appropriate I2C driver for the selected cpu.
1224
1225		This will allow you to use i2c commands at the u-boot
1226		command line (as long as you set CONFIG_CMD_I2C in
1227		CONFIG_COMMANDS) and communicate with i2c based realtime
1228		clock chips. See common/cmd_i2c.c for a description of the
1229		command line interface.
1230
1231		CONFIG_I2C_CMD_TREE is a recommended option that places
1232		all I2C commands under a single 'i2c' root command.  The
1233		older 'imm', 'imd', 'iprobe' etc. commands are considered
1234		deprecated and may disappear in the future.
1235
1236		CONFIG_HARD_I2C selects a hardware I2C controller.
1237
1238		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1239		bit-banging) driver instead of CPM or similar hardware
1240		support for I2C.
1241
1242		There are several other quantities that must also be
1243		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1244
1245		In both cases you will need to define CFG_I2C_SPEED
1246		to be the frequency (in Hz) at which you wish your i2c bus
1247		to run and CFG_I2C_SLAVE to be the address of this node (ie
1248		the cpu's i2c node address).
1249
1250		Now, the u-boot i2c code for the mpc8xx (cpu/mpc8xx/i2c.c)
1251		sets the cpu up as a master node and so its address should
1252		therefore be cleared to 0 (See, eg, MPC823e User's Manual
1253		p.16-473). So, set CFG_I2C_SLAVE to 0.
1254
1255		That's all that's required for CONFIG_HARD_I2C.
1256
1257		If you use the software i2c interface (CONFIG_SOFT_I2C)
1258		then the following macros need to be defined (examples are
1259		from include/configs/lwmon.h):
1260
1261		I2C_INIT
1262
1263		(Optional). Any commands necessary to enable the I2C
1264		controller or configure ports.
1265
1266		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1267
1268		I2C_PORT
1269
1270		(Only for MPC8260 CPU). The I/O port to use (the code
1271		assumes both bits are on the same port). Valid values
1272		are 0..3 for ports A..D.
1273
1274		I2C_ACTIVE
1275
1276		The code necessary to make the I2C data line active
1277		(driven).  If the data line is open collector, this
1278		define can be null.
1279
1280		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1281
1282		I2C_TRISTATE
1283
1284		The code necessary to make the I2C data line tri-stated
1285		(inactive).  If the data line is open collector, this
1286		define can be null.
1287
1288		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1289
1290		I2C_READ
1291
1292		Code that returns TRUE if the I2C data line is high,
1293		FALSE if it is low.
1294
1295		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1296
1297		I2C_SDA(bit)
1298
1299		If <bit> is TRUE, sets the I2C data line high. If it
1300		is FALSE, it clears it (low).
1301
1302		eg: #define I2C_SDA(bit) \
1303			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1304			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1305
1306		I2C_SCL(bit)
1307
1308		If <bit> is TRUE, sets the I2C clock line high. If it
1309		is FALSE, it clears it (low).
1310
1311		eg: #define I2C_SCL(bit) \
1312			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1313			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1314
1315		I2C_DELAY
1316
1317		This delay is invoked four times per clock cycle so this
1318		controls the rate of data transfer.  The data rate thus
1319		is 1 / (I2C_DELAY * 4). Often defined to be something
1320		like:
1321
1322		#define I2C_DELAY  udelay(2)
1323
1324		CFG_I2C_INIT_BOARD
1325
1326		When a board is reset during an i2c bus transfer
1327		chips might think that the current transfer is still
1328		in progress. On some boards it is possible to access
1329		the i2c SCLK line directly, either by using the
1330		processor pin as a GPIO or by having a second pin
1331		connected to the bus. If this option is defined a
1332		custom i2c_init_board() routine in boards/xxx/board.c
1333		is run early in the boot sequence.
1334
1335		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1336
1337		This option enables configuration of bi_iic_fast[] flags
1338		in u-boot bd_info structure based on u-boot environment
1339		variable "i2cfast". (see also i2cfast)
1340
1341		CONFIG_I2C_MULTI_BUS
1342
1343		This option allows the use of multiple I2C buses, each of which
1344		must have a controller.  At any point in time, only one bus is
1345		active.  To switch to a different bus, use the 'i2c dev' command.
1346		Note that bus numbering is zero-based.
1347
1348		CFG_I2C_NOPROBES
1349
1350		This option specifies a list of I2C devices that will be skipped
1351		when the 'i2c probe' command is issued (or 'iprobe' using the legacy
1352		command).  If CONFIG_I2C_MULTI_BUS is set, specify a list of bus-device
1353		pairs.  Otherwise, specify a 1D array of device addresses
1354
1355		e.g.
1356			#undef	CONFIG_I2C_MULTI_BUS
1357			#define CFG_I2C_NOPROBES	{0x50,0x68}
1358
1359		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1360
1361			#define	CONFIG_I2C_MULTI_BUS
1362			#define CFG_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1363
1364		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1365
1366		CFG_SPD_BUS_NUM
1367
1368		If defined, then this indicates the I2C bus number for DDR SPD.
1369		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1370
1371		CFG_RTC_BUS_NUM
1372
1373		If defined, then this indicates the I2C bus number for the RTC.
1374		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1375
1376		CFG_DTT_BUS_NUM
1377
1378		If defined, then this indicates the I2C bus number for the DTT.
1379		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1380
1381		CONFIG_FSL_I2C
1382
1383		Define this option if you want to use Freescale's I2C driver in
1384		drivers/fsl_i2c.c.
1385
1386
1387- SPI Support:	CONFIG_SPI
1388
1389		Enables SPI driver (so far only tested with
1390		SPI EEPROM, also an instance works with Crystal A/D and
1391		D/As on the SACSng board)
1392
1393		CONFIG_SPI_X
1394
1395		Enables extended (16-bit) SPI EEPROM addressing.
1396		(symmetrical to CONFIG_I2C_X)
1397
1398		CONFIG_SOFT_SPI
1399
1400		Enables a software (bit-bang) SPI driver rather than
1401		using hardware support. This is a general purpose
1402		driver that only requires three general I/O port pins
1403		(two outputs, one input) to function. If this is
1404		defined, the board configuration must define several
1405		SPI configuration items (port pins to use, etc). For
1406		an example, see include/configs/sacsng.h.
1407
1408- FPGA Support: CONFIG_FPGA_COUNT
1409
1410		Specify the number of FPGA devices to support.
1411
1412		CONFIG_FPGA
1413
1414		Used to specify the types of FPGA devices.  For example,
1415		#define CONFIG_FPGA  CFG_XILINX_VIRTEX2
1416
1417		CFG_FPGA_PROG_FEEDBACK
1418
1419		Enable printing of hash marks during FPGA configuration.
1420
1421		CFG_FPGA_CHECK_BUSY
1422
1423		Enable checks on FPGA configuration interface busy
1424		status by the configuration function. This option
1425		will require a board or device specific function to
1426		be written.
1427
1428		CONFIG_FPGA_DELAY
1429
1430		If defined, a function that provides delays in the FPGA
1431		configuration driver.
1432
1433		CFG_FPGA_CHECK_CTRLC
1434		Allow Control-C to interrupt FPGA configuration
1435
1436		CFG_FPGA_CHECK_ERROR
1437
1438		Check for configuration errors during FPGA bitfile
1439		loading. For example, abort during Virtex II
1440		configuration if the INIT_B line goes low (which
1441		indicated a CRC error).
1442
1443		CFG_FPGA_WAIT_INIT
1444
1445		Maximum time to wait for the INIT_B line to deassert
1446		after PROB_B has been deasserted during a Virtex II
1447		FPGA configuration sequence. The default time is 500
1448		mS.
1449
1450		CFG_FPGA_WAIT_BUSY
1451
1452		Maximum time to wait for BUSY to deassert during
1453		Virtex II FPGA configuration. The default is 5 mS.
1454
1455		CFG_FPGA_WAIT_CONFIG
1456
1457		Time to wait after FPGA configuration. The default is
1458		200 mS.
1459
1460- Configuration Management:
1461		CONFIG_IDENT_STRING
1462
1463		If defined, this string will be added to the U-Boot
1464		version information (U_BOOT_VERSION)
1465
1466- Vendor Parameter Protection:
1467
1468		U-Boot considers the values of the environment
1469		variables "serial#" (Board Serial Number) and
1470		"ethaddr" (Ethernet Address) to be parameters that
1471		are set once by the board vendor / manufacturer, and
1472		protects these variables from casual modification by
1473		the user. Once set, these variables are read-only,
1474		and write or delete attempts are rejected. You can
1475		change this behviour:
1476
1477		If CONFIG_ENV_OVERWRITE is #defined in your config
1478		file, the write protection for vendor parameters is
1479		completely disabled. Anybody can change or delete
1480		these parameters.
1481
1482		Alternatively, if you #define _both_ CONFIG_ETHADDR
1483		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1484		ethernet address is installed in the environment,
1485		which can be changed exactly ONCE by the user. [The
1486		serial# is unaffected by this, i. e. it remains
1487		read-only.]
1488
1489- Protected RAM:
1490		CONFIG_PRAM
1491
1492		Define this variable to enable the reservation of
1493		"protected RAM", i. e. RAM which is not overwritten
1494		by U-Boot. Define CONFIG_PRAM to hold the number of
1495		kB you want to reserve for pRAM. You can overwrite
1496		this default value by defining an environment
1497		variable "pram" to the number of kB you want to
1498		reserve. Note that the board info structure will
1499		still show the full amount of RAM. If pRAM is
1500		reserved, a new environment variable "mem" will
1501		automatically be defined to hold the amount of
1502		remaining RAM in a form that can be passed as boot
1503		argument to Linux, for instance like that:
1504
1505			setenv bootargs ... mem=\${mem}
1506			saveenv
1507
1508		This way you can tell Linux not to use this memory,
1509		either, which results in a memory region that will
1510		not be affected by reboots.
1511
1512		*WARNING* If your board configuration uses automatic
1513		detection of the RAM size, you must make sure that
1514		this memory test is non-destructive. So far, the
1515		following board configurations are known to be
1516		"pRAM-clean":
1517
1518			ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
1519			HERMES, IP860, RPXlite, LWMON, LANTEC,
1520			PCU_E, FLAGADM, TQM8260
1521
1522- Error Recovery:
1523		CONFIG_PANIC_HANG
1524
1525		Define this variable to stop the system in case of a
1526		fatal error, so that you have to reset it manually.
1527		This is probably NOT a good idea for an embedded
1528		system where you want to system to reboot
1529		automatically as fast as possible, but it may be
1530		useful during development since you can try to debug
1531		the conditions that lead to the situation.
1532
1533		CONFIG_NET_RETRY_COUNT
1534
1535		This variable defines the number of retries for
1536		network operations like ARP, RARP, TFTP, or BOOTP
1537		before giving up the operation. If not defined, a
1538		default value of 5 is used.
1539
1540- Command Interpreter:
1541		CONFIG_AUTO_COMPLETE
1542
1543		Enable auto completion of commands using TAB.
1544
1545		Note that this feature has NOT been implemented yet
1546		for the "hush" shell.
1547
1548
1549		CFG_HUSH_PARSER
1550
1551		Define this variable to enable the "hush" shell (from
1552		Busybox) as command line interpreter, thus enabling
1553		powerful command line syntax like
1554		if...then...else...fi conditionals or `&&' and '||'
1555		constructs ("shell scripts").
1556
1557		If undefined, you get the old, much simpler behaviour
1558		with a somewhat smaller memory footprint.
1559
1560
1561		CFG_PROMPT_HUSH_PS2
1562
1563		This defines the secondary prompt string, which is
1564		printed when the command interpreter needs more input
1565		to complete a command. Usually "> ".
1566
1567	Note:
1568
1569		In the current implementation, the local variables
1570		space and global environment variables space are
1571		separated. Local variables are those you define by
1572		simply typing `name=value'. To access a local
1573		variable later on, you have write `$name' or
1574		`${name}'; to execute the contents of a variable
1575		directly type `$name' at the command prompt.
1576
1577		Global environment variables are those you use
1578		setenv/printenv to work with. To run a command stored
1579		in such a variable, you need to use the run command,
1580		and you must not use the '$' sign to access them.
1581
1582		To store commands and special characters in a
1583		variable, please use double quotation marks
1584		surrounding the whole text of the variable, instead
1585		of the backslashes before semicolons and special
1586		symbols.
1587
1588- Commandline Editing and History:
1589		CONFIG_CMDLINE_EDITING
1590
1591		Enable editiong and History functions for interactive
1592		commandline input operations
1593
1594- Default Environment:
1595		CONFIG_EXTRA_ENV_SETTINGS
1596
1597		Define this to contain any number of null terminated
1598		strings (variable = value pairs) that will be part of
1599		the default environment compiled into the boot image.
1600
1601		For example, place something like this in your
1602		board's config file:
1603
1604		#define CONFIG_EXTRA_ENV_SETTINGS \
1605			"myvar1=value1\0" \
1606			"myvar2=value2\0"
1607
1608		Warning: This method is based on knowledge about the
1609		internal format how the environment is stored by the
1610		U-Boot code. This is NOT an official, exported
1611		interface! Although it is unlikely that this format
1612		will change soon, there is no guarantee either.
1613		You better know what you are doing here.
1614
1615		Note: overly (ab)use of the default environment is
1616		discouraged. Make sure to check other ways to preset
1617		the environment like the autoscript function or the
1618		boot command first.
1619
1620- DataFlash Support:
1621		CONFIG_HAS_DATAFLASH
1622
1623		Defining this option enables DataFlash features and
1624		allows to read/write in Dataflash via the standard
1625		commands cp, md...
1626
1627- SystemACE Support:
1628		CONFIG_SYSTEMACE
1629
1630		Adding this option adds support for Xilinx SystemACE
1631		chips attached via some sort of local bus. The address
1632		of the chip must alsh be defined in the
1633		CFG_SYSTEMACE_BASE macro. For example:
1634
1635		#define CONFIG_SYSTEMACE
1636		#define CFG_SYSTEMACE_BASE 0xf0000000
1637
1638		When SystemACE support is added, the "ace" device type
1639		becomes available to the fat commands, i.e. fatls.
1640
1641- TFTP Fixed UDP Port:
1642		CONFIG_TFTP_PORT
1643
1644		If this is defined, the environment variable tftpsrcp
1645		is used to supply the TFTP UDP source port value.
1646		If tftpsrcp isn't defined, the normal pseudo-random port
1647		number generator is used.
1648
1649		Also, the environment variable tftpdstp is used to supply
1650		the TFTP UDP destination port value.  If tftpdstp isn't
1651		defined, the normal port 69 is used.
1652
1653		The purpose for tftpsrcp is to allow a TFTP server to
1654		blindly start the TFTP transfer using the pre-configured
1655		target IP address and UDP port. This has the effect of
1656		"punching through" the (Windows XP) firewall, allowing
1657		the remainder of the TFTP transfer to proceed normally.
1658		A better solution is to properly configure the firewall,
1659		but sometimes that is not allowed.
1660
1661- Show boot progress:
1662		CONFIG_SHOW_BOOT_PROGRESS
1663
1664		Defining this option allows to add some board-
1665		specific code (calling a user-provided function
1666		"show_boot_progress(int)") that enables you to show
1667		the system's boot progress on some display (for
1668		example, some LED's) on your board. At the moment,
1669		the following checkpoints are implemented:
1670
1671  Arg	Where			When
1672    1	common/cmd_bootm.c	before attempting to boot an image
1673   -1	common/cmd_bootm.c	Image header has bad	 magic number
1674    2	common/cmd_bootm.c	Image header has correct magic number
1675   -2	common/cmd_bootm.c	Image header has bad	 checksum
1676    3	common/cmd_bootm.c	Image header has correct checksum
1677   -3	common/cmd_bootm.c	Image data   has bad	 checksum
1678    4	common/cmd_bootm.c	Image data   has correct checksum
1679   -4	common/cmd_bootm.c	Image is for unsupported architecture
1680    5	common/cmd_bootm.c	Architecture check OK
1681   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi, standalone)
1682    6	common/cmd_bootm.c	Image Type check OK
1683   -6	common/cmd_bootm.c	gunzip uncompression error
1684   -7	common/cmd_bootm.c	Unimplemented compression type
1685    7	common/cmd_bootm.c	Uncompression OK
1686   -8	common/cmd_bootm.c	Wrong Image Type (not kernel, multi, standalone)
1687    8	common/cmd_bootm.c	Image Type check OK
1688   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
1689    9	common/cmd_bootm.c	Start initial ramdisk verification
1690  -10	common/cmd_bootm.c	Ramdisk header has bad	   magic number
1691  -11	common/cmd_bootm.c	Ramdisk header has bad	   checksum
1692   10	common/cmd_bootm.c	Ramdisk header is OK
1693  -12	common/cmd_bootm.c	Ramdisk data   has bad	   checksum
1694   11	common/cmd_bootm.c	Ramdisk data   has correct checksum
1695   12	common/cmd_bootm.c	Ramdisk verification complete, start loading
1696  -13	common/cmd_bootm.c	Wrong Image Type (not PPC Linux Ramdisk)
1697   13	common/cmd_bootm.c	Start multifile image verification
1698   14	common/cmd_bootm.c	No initial ramdisk, no multifile, continue.
1699   15	common/cmd_bootm.c	All preparation done, transferring control to OS
1700
1701  -30	lib_ppc/board.c		Fatal error, hang the system
1702  -31	post/post.c		POST test failed, detected by post_output_backlog()
1703  -32	post/post.c		POST test failed, detected by post_run_single()
1704
1705   34	common/cmd_doc.c	before loading a Image from a DOC device
1706  -35	common/cmd_doc.c	Bad usage of "doc" command
1707   35	common/cmd_doc.c	correct usage of "doc" command
1708  -36	common/cmd_doc.c	No boot device
1709   36	common/cmd_doc.c	correct boot device
1710  -37	common/cmd_doc.c	Unknown Chip ID on boot device
1711   37	common/cmd_doc.c	correct chip ID found, device available
1712  -38	common/cmd_doc.c	Read Error on boot device
1713   38	common/cmd_doc.c	reading Image header from DOC device OK
1714  -39	common/cmd_doc.c	Image header has bad magic number
1715   39	common/cmd_doc.c	Image header has correct magic number
1716  -40	common/cmd_doc.c	Error reading Image from DOC device
1717   40	common/cmd_doc.c	Image header has correct magic number
1718   41	common/cmd_ide.c	before loading a Image from a IDE device
1719  -42	common/cmd_ide.c	Bad usage of "ide" command
1720   42	common/cmd_ide.c	correct usage of "ide" command
1721  -43	common/cmd_ide.c	No boot device
1722   43	common/cmd_ide.c	boot device found
1723  -44	common/cmd_ide.c	Device not available
1724   44	common/cmd_ide.c	Device available
1725  -45	common/cmd_ide.c	wrong partition selected
1726   45	common/cmd_ide.c	partition selected
1727  -46	common/cmd_ide.c	Unknown partition table
1728   46	common/cmd_ide.c	valid partition table found
1729  -47	common/cmd_ide.c	Invalid partition type
1730   47	common/cmd_ide.c	correct partition type
1731  -48	common/cmd_ide.c	Error reading Image Header on boot device
1732   48	common/cmd_ide.c	reading Image Header from IDE device OK
1733  -49	common/cmd_ide.c	Image header has bad magic number
1734   49	common/cmd_ide.c	Image header has correct magic number
1735  -50	common/cmd_ide.c	Image header has bad	 checksum
1736   50	common/cmd_ide.c	Image header has correct checksum
1737  -51	common/cmd_ide.c	Error reading Image from IDE device
1738   51	common/cmd_ide.c	reading Image from IDE device OK
1739   52	common/cmd_nand.c	before loading a Image from a NAND device
1740  -53	common/cmd_nand.c	Bad usage of "nand" command
1741   53	common/cmd_nand.c	correct usage of "nand" command
1742  -54	common/cmd_nand.c	No boot device
1743   54	common/cmd_nand.c	boot device found
1744  -55	common/cmd_nand.c	Unknown Chip ID on boot device
1745   55	common/cmd_nand.c	correct chip ID found, device available
1746  -56	common/cmd_nand.c	Error reading Image Header on boot device
1747   56	common/cmd_nand.c	reading Image Header from NAND device OK
1748  -57	common/cmd_nand.c	Image header has bad magic number
1749   57	common/cmd_nand.c	Image header has correct magic number
1750  -58	common/cmd_nand.c	Error reading Image from NAND device
1751   58	common/cmd_nand.c	reading Image from NAND device OK
1752
1753  -60	common/env_common.c	Environment has a bad CRC, using default
1754
1755   64	net/eth.c		starting with Ethernetconfiguration.
1756  -64	net/eth.c		no Ethernet found.
1757   65	net/eth.c		Ethernet found.
1758
1759  -80	common/cmd_net.c	usage wrong
1760   80	common/cmd_net.c	before calling NetLoop()
1761  -81	common/cmd_net.c	some error in NetLoop() occured
1762   81	common/cmd_net.c	NetLoop() back without error
1763  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
1764   82	common/cmd_net.c	trying automatic boot
1765   83	common/cmd_net.c	running autoscript
1766  -83	common/cmd_net.c	some error in automatic boot or autoscript
1767   84	common/cmd_net.c	end without errors
1768
1769Modem Support:
1770--------------
1771
1772[so far only for SMDK2400 and TRAB boards]
1773
1774- Modem support endable:
1775		CONFIG_MODEM_SUPPORT
1776
1777- RTS/CTS Flow control enable:
1778		CONFIG_HWFLOW
1779
1780- Modem debug support:
1781		CONFIG_MODEM_SUPPORT_DEBUG
1782
1783		Enables debugging stuff (char screen[1024], dbg())
1784		for modem support. Useful only with BDI2000.
1785
1786- Interrupt support (PPC):
1787
1788		There are common interrupt_init() and timer_interrupt()
1789		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
1790		for cpu specific initialization. interrupt_init_cpu()
1791		should set decrementer_count to appropriate value. If
1792		cpu resets decrementer automatically after interrupt
1793		(ppc4xx) it should set decrementer_count to zero.
1794		timer_interrupt() calls timer_interrupt_cpu() for cpu
1795		specific handling. If board has watchdog / status_led
1796		/ other_activity_monitor it works automatically from
1797		general timer_interrupt().
1798
1799- General:
1800
1801		In the target system modem support is enabled when a
1802		specific key (key combination) is pressed during
1803		power-on. Otherwise U-Boot will boot normally
1804		(autoboot). The key_pressed() fuction is called from
1805		board_init(). Currently key_pressed() is a dummy
1806		function, returning 1 and thus enabling modem
1807		initialization.
1808
1809		If there are no modem init strings in the
1810		environment, U-Boot proceed to autoboot; the
1811		previous output (banner, info printfs) will be
1812		supressed, though.
1813
1814		See also: doc/README.Modem
1815
1816
1817Configuration Settings:
1818-----------------------
1819
1820- CFG_LONGHELP: Defined when you want long help messages included;
1821		undefine this when you're short of memory.
1822
1823- CFG_PROMPT:	This is what U-Boot prints on the console to
1824		prompt for user input.
1825
1826- CFG_CBSIZE:	Buffer size for input from the Console
1827
1828- CFG_PBSIZE:	Buffer size for Console output
1829
1830- CFG_MAXARGS:	max. Number of arguments accepted for monitor commands
1831
1832- CFG_BARGSIZE: Buffer size for Boot Arguments which are passed to
1833		the application (usually a Linux kernel) when it is
1834		booted
1835
1836- CFG_BAUDRATE_TABLE:
1837		List of legal baudrate settings for this board.
1838
1839- CFG_CONSOLE_INFO_QUIET
1840		Suppress display of console information at boot.
1841
1842- CFG_CONSOLE_IS_IN_ENV
1843		If the board specific function
1844			extern int overwrite_console (void);
1845		returns 1, the stdin, stderr and stdout are switched to the
1846		serial port, else the settings in the environment are used.
1847
1848- CFG_CONSOLE_OVERWRITE_ROUTINE
1849		Enable the call to overwrite_console().
1850
1851- CFG_CONSOLE_ENV_OVERWRITE
1852		Enable overwrite of previous console environment settings.
1853
1854- CFG_MEMTEST_START, CFG_MEMTEST_END:
1855		Begin and End addresses of the area used by the
1856		simple memory test.
1857
1858- CFG_ALT_MEMTEST:
1859		Enable an alternate, more extensive memory test.
1860
1861- CFG_MEMTEST_SCRATCH:
1862		Scratch address used by the alternate memory test
1863		You only need to set this if address zero isn't writeable
1864
1865- CFG_TFTP_LOADADDR:
1866		Default load address for network file downloads
1867
1868- CFG_LOADS_BAUD_CHANGE:
1869		Enable temporary baudrate change while serial download
1870
1871- CFG_SDRAM_BASE:
1872		Physical start address of SDRAM. _Must_ be 0 here.
1873
1874- CFG_MBIO_BASE:
1875		Physical start address of Motherboard I/O (if using a
1876		Cogent motherboard)
1877
1878- CFG_FLASH_BASE:
1879		Physical start address of Flash memory.
1880
1881- CFG_MONITOR_BASE:
1882		Physical start address of boot monitor code (set by
1883		make config files to be same as the text base address
1884		(TEXT_BASE) used when linking) - same as
1885		CFG_FLASH_BASE when booting from flash.
1886
1887- CFG_MONITOR_LEN:
1888		Size of memory reserved for monitor code, used to
1889		determine _at_compile_time_ (!) if the environment is
1890		embedded within the U-Boot image, or in a separate
1891		flash sector.
1892
1893- CFG_MALLOC_LEN:
1894		Size of DRAM reserved for malloc() use.
1895
1896- CFG_BOOTM_LEN:
1897		Normally compressed uImages are limited to an
1898		uncompressed size of 8 MBytes. If this is not enough,
1899		you can define CFG_BOOTM_LEN in your board config file
1900		to adjust this setting to your needs.
1901
1902- CFG_BOOTMAPSZ:
1903		Maximum size of memory mapped by the startup code of
1904		the Linux kernel; all data that must be processed by
1905		the Linux kernel (bd_info, boot arguments, eventually
1906		initrd image) must be put below this limit.
1907
1908- CFG_MAX_FLASH_BANKS:
1909		Max number of Flash memory banks
1910
1911- CFG_MAX_FLASH_SECT:
1912		Max number of sectors on a Flash chip
1913
1914- CFG_FLASH_ERASE_TOUT:
1915		Timeout for Flash erase operations (in ms)
1916
1917- CFG_FLASH_WRITE_TOUT:
1918		Timeout for Flash write operations (in ms)
1919
1920- CFG_FLASH_LOCK_TOUT
1921		Timeout for Flash set sector lock bit operation (in ms)
1922
1923- CFG_FLASH_UNLOCK_TOUT
1924		Timeout for Flash clear lock bits operation (in ms)
1925
1926- CFG_FLASH_PROTECTION
1927		If defined, hardware flash sectors protection is used
1928		instead of U-Boot software protection.
1929
1930- CFG_DIRECT_FLASH_TFTP:
1931
1932		Enable TFTP transfers directly to flash memory;
1933		without this option such a download has to be
1934		performed in two steps: (1) download to RAM, and (2)
1935		copy from RAM to flash.
1936
1937		The two-step approach is usually more reliable, since
1938		you can check if the download worked before you erase
1939		the flash, but in some situations (when sytem RAM is
1940		too limited to allow for a tempory copy of the
1941		downloaded image) this option may be very useful.
1942
1943- CFG_FLASH_CFI:
1944		Define if the flash driver uses extra elements in the
1945		common flash structure for storing flash geometry.
1946
1947- CFG_FLASH_CFI_DRIVER
1948		This option also enables the building of the cfi_flash driver
1949		in the drivers directory
1950
1951- CFG_FLASH_QUIET_TEST
1952		If this option is defined, the common CFI flash doesn't
1953		print it's warning upon not recognized FLASH banks. This
1954		is useful, if some of the configured banks are only
1955		optionally available.
1956
1957- CFG_RX_ETH_BUFFER:
1958		Defines the number of ethernet receive buffers. On some
1959		ethernet controllers it is recommended to set this value
1960		to 8 or even higher (EEPRO100 or 405 EMAC), since all
1961		buffers can be full shortly after enabling the interface
1962		on high ethernet traffic.
1963		Defaults to 4 if not defined.
1964
1965The following definitions that deal with the placement and management
1966of environment data (variable area); in general, we support the
1967following configurations:
1968
1969- CFG_ENV_IS_IN_FLASH:
1970
1971	Define this if the environment is in flash memory.
1972
1973	a) The environment occupies one whole flash sector, which is
1974	   "embedded" in the text segment with the U-Boot code. This
1975	   happens usually with "bottom boot sector" or "top boot
1976	   sector" type flash chips, which have several smaller
1977	   sectors at the start or the end. For instance, such a
1978	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
1979	   such a case you would place the environment in one of the
1980	   4 kB sectors - with U-Boot code before and after it. With
1981	   "top boot sector" type flash chips, you would put the
1982	   environment in one of the last sectors, leaving a gap
1983	   between U-Boot and the environment.
1984
1985	- CFG_ENV_OFFSET:
1986
1987	   Offset of environment data (variable area) to the
1988	   beginning of flash memory; for instance, with bottom boot
1989	   type flash chips the second sector can be used: the offset
1990	   for this sector is given here.
1991
1992	   CFG_ENV_OFFSET is used relative to CFG_FLASH_BASE.
1993
1994	- CFG_ENV_ADDR:
1995
1996	   This is just another way to specify the start address of
1997	   the flash sector containing the environment (instead of
1998	   CFG_ENV_OFFSET).
1999
2000	- CFG_ENV_SECT_SIZE:
2001
2002	   Size of the sector containing the environment.
2003
2004
2005	b) Sometimes flash chips have few, equal sized, BIG sectors.
2006	   In such a case you don't want to spend a whole sector for
2007	   the environment.
2008
2009	- CFG_ENV_SIZE:
2010
2011	   If you use this in combination with CFG_ENV_IS_IN_FLASH
2012	   and CFG_ENV_SECT_SIZE, you can specify to use only a part
2013	   of this flash sector for the environment. This saves
2014	   memory for the RAM copy of the environment.
2015
2016	   It may also save flash memory if you decide to use this
2017	   when your environment is "embedded" within U-Boot code,
2018	   since then the remainder of the flash sector could be used
2019	   for U-Boot code. It should be pointed out that this is
2020	   STRONGLY DISCOURAGED from a robustness point of view:
2021	   updating the environment in flash makes it always
2022	   necessary to erase the WHOLE sector. If something goes
2023	   wrong before the contents has been restored from a copy in
2024	   RAM, your target system will be dead.
2025
2026	- CFG_ENV_ADDR_REDUND
2027	  CFG_ENV_SIZE_REDUND
2028
2029	   These settings describe a second storage area used to hold
2030	   a redundand copy of the environment data, so that there is
2031	   a valid backup copy in case there is a power failure during
2032	   a "saveenv" operation.
2033
2034BE CAREFUL! Any changes to the flash layout, and some changes to the
2035source code will make it necessary to adapt <board>/u-boot.lds*
2036accordingly!
2037
2038
2039- CFG_ENV_IS_IN_NVRAM:
2040
2041	Define this if you have some non-volatile memory device
2042	(NVRAM, battery buffered SRAM) which you want to use for the
2043	environment.
2044
2045	- CFG_ENV_ADDR:
2046	- CFG_ENV_SIZE:
2047
2048	  These two #defines are used to determin the memory area you
2049	  want to use for environment. It is assumed that this memory
2050	  can just be read and written to, without any special
2051	  provision.
2052
2053BE CAREFUL! The first access to the environment happens quite early
2054in U-Boot initalization (when we try to get the setting of for the
2055console baudrate). You *MUST* have mappend your NVRAM area then, or
2056U-Boot will hang.
2057
2058Please note that even with NVRAM we still use a copy of the
2059environment in RAM: we could work on NVRAM directly, but we want to
2060keep settings there always unmodified except somebody uses "saveenv"
2061to save the current settings.
2062
2063
2064- CFG_ENV_IS_IN_EEPROM:
2065
2066	Use this if you have an EEPROM or similar serial access
2067	device and a driver for it.
2068
2069	- CFG_ENV_OFFSET:
2070	- CFG_ENV_SIZE:
2071
2072	  These two #defines specify the offset and size of the
2073	  environment area within the total memory of your EEPROM.
2074
2075	- CFG_I2C_EEPROM_ADDR:
2076	  If defined, specified the chip address of the EEPROM device.
2077	  The default address is zero.
2078
2079	- CFG_EEPROM_PAGE_WRITE_BITS:
2080	  If defined, the number of bits used to address bytes in a
2081	  single page in the EEPROM device.  A 64 byte page, for example
2082	  would require six bits.
2083
2084	- CFG_EEPROM_PAGE_WRITE_DELAY_MS:
2085	  If defined, the number of milliseconds to delay between
2086	  page writes.	The default is zero milliseconds.
2087
2088	- CFG_I2C_EEPROM_ADDR_LEN:
2089	  The length in bytes of the EEPROM memory array address.  Note
2090	  that this is NOT the chip address length!
2091
2092	- CFG_I2C_EEPROM_ADDR_OVERFLOW:
2093	  EEPROM chips that implement "address overflow" are ones
2094	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
2095	  address and the extra bits end up in the "chip address" bit
2096	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
2097	  byte chips.
2098
2099	  Note that we consider the length of the address field to
2100	  still be one byte because the extra address bits are hidden
2101	  in the chip address.
2102
2103	- CFG_EEPROM_SIZE:
2104	  The size in bytes of the EEPROM device.
2105
2106
2107- CFG_ENV_IS_IN_DATAFLASH:
2108
2109	Define this if you have a DataFlash memory device which you
2110	want to use for the environment.
2111
2112	- CFG_ENV_OFFSET:
2113	- CFG_ENV_ADDR:
2114	- CFG_ENV_SIZE:
2115
2116	  These three #defines specify the offset and size of the
2117	  environment area within the total memory of your DataFlash placed
2118	  at the specified address.
2119
2120- CFG_ENV_IS_IN_NAND:
2121
2122	Define this if you have a NAND device which you want to use
2123	for the environment.
2124
2125	- CFG_ENV_OFFSET:
2126	- CFG_ENV_SIZE:
2127
2128	  These two #defines specify the offset and size of the environment
2129	  area within the first NAND device.
2130
2131	- CFG_ENV_OFFSET_REDUND
2132
2133	  This setting describes a second storage area of CFG_ENV_SIZE
2134	  size used to hold a redundant copy of the environment data,
2135	  so that there is a valid backup copy in case there is a
2136	  power failure during a "saveenv" operation.
2137
2138	Note: CFG_ENV_OFFSET and CFG_ENV_OFFSET_REDUND must be aligned
2139	to a block boundary, and CFG_ENV_SIZE must be a multiple of
2140	the NAND devices block size.
2141
2142- CFG_SPI_INIT_OFFSET
2143
2144	Defines offset to the initial SPI buffer area in DPRAM. The
2145	area is used at an early stage (ROM part) if the environment
2146	is configured to reside in the SPI EEPROM: We need a 520 byte
2147	scratch DPRAM area. It is used between the two initialization
2148	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
2149	to be a good choice since it makes it far enough from the
2150	start of the data area as well as from the stack pointer.
2151
2152Please note that the environment is read-only as long as the monitor
2153has been relocated to RAM and a RAM copy of the environment has been
2154created; also, when using EEPROM you will have to use getenv_r()
2155until then to read environment variables.
2156
2157The environment is protected by a CRC32 checksum. Before the monitor
2158is relocated into RAM, as a result of a bad CRC you will be working
2159with the compiled-in default environment - *silently*!!! [This is
2160necessary, because the first environment variable we need is the
2161"baudrate" setting for the console - if we have a bad CRC, we don't
2162have any device yet where we could complain.]
2163
2164Note: once the monitor has been relocated, then it will complain if
2165the default environment is used; a new CRC is computed as soon as you
2166use the "saveenv" command to store a valid environment.
2167
2168- CFG_FAULT_ECHO_LINK_DOWN:
2169		Echo the inverted Ethernet link state to the fault LED.
2170
2171		Note: If this option is active, then CFG_FAULT_MII_ADDR
2172		      also needs to be defined.
2173
2174- CFG_FAULT_MII_ADDR:
2175		MII address of the PHY to check for the Ethernet link state.
2176
2177- CFG_64BIT_VSPRINTF:
2178		Makes vsprintf (and all *printf functions) support printing
2179		of 64bit values by using the L quantifier
2180
2181- CFG_64BIT_STRTOUL:
2182		Adds simple_strtoull that returns a 64bit value
2183
2184Low Level (hardware related) configuration options:
2185---------------------------------------------------
2186
2187- CFG_CACHELINE_SIZE:
2188		Cache Line Size of the CPU.
2189
2190- CFG_DEFAULT_IMMR:
2191		Default address of the IMMR after system reset.
2192
2193		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
2194		and RPXsuper) to be able to adjust the position of
2195		the IMMR register after a reset.
2196
2197- Floppy Disk Support:
2198		CFG_FDC_DRIVE_NUMBER
2199
2200		the default drive number (default value 0)
2201
2202		CFG_ISA_IO_STRIDE
2203
2204		defines the spacing between fdc chipset registers
2205		(default value 1)
2206
2207		CFG_ISA_IO_OFFSET
2208
2209		defines the offset of register from address. It
2210		depends on which part of the data bus is connected to
2211		the fdc chipset. (default value 0)
2212
2213		If CFG_ISA_IO_STRIDE CFG_ISA_IO_OFFSET and
2214		CFG_FDC_DRIVE_NUMBER are undefined, they take their
2215		default value.
2216
2217		if CFG_FDC_HW_INIT is defined, then the function
2218		fdc_hw_init() is called at the beginning of the FDC
2219		setup. fdc_hw_init() must be provided by the board
2220		source code. It is used to make hardware dependant
2221		initializations.
2222
2223- CFG_IMMR:	Physical address of the Internal Memory.
2224		DO NOT CHANGE unless you know exactly what you're
2225		doing! (11-4) [MPC8xx/82xx systems only]
2226
2227- CFG_INIT_RAM_ADDR:
2228
2229		Start address of memory area that can be used for
2230		initial data and stack; please note that this must be
2231		writable memory that is working WITHOUT special
2232		initialization, i. e. you CANNOT use normal RAM which
2233		will become available only after programming the
2234		memory controller and running certain initialization
2235		sequences.
2236
2237		U-Boot uses the following memory types:
2238		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
2239		- MPC824X: data cache
2240		- PPC4xx:  data cache
2241
2242- CFG_GBL_DATA_OFFSET:
2243
2244		Offset of the initial data structure in the memory
2245		area defined by CFG_INIT_RAM_ADDR. Usually
2246		CFG_GBL_DATA_OFFSET is chosen such that the initial
2247		data is located at the end of the available space
2248		(sometimes written as (CFG_INIT_RAM_END -
2249		CFG_INIT_DATA_SIZE), and the initial stack is just
2250		below that area (growing from (CFG_INIT_RAM_ADDR +
2251		CFG_GBL_DATA_OFFSET) downward.
2252
2253	Note:
2254		On the MPC824X (or other systems that use the data
2255		cache for initial memory) the address chosen for
2256		CFG_INIT_RAM_ADDR is basically arbitrary - it must
2257		point to an otherwise UNUSED address space between
2258		the top of RAM and the start of the PCI space.
2259
2260- CFG_SIUMCR:	SIU Module Configuration (11-6)
2261
2262- CFG_SYPCR:	System Protection Control (11-9)
2263
2264- CFG_TBSCR:	Time Base Status and Control (11-26)
2265
2266- CFG_PISCR:	Periodic Interrupt Status and Control (11-31)
2267
2268- CFG_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
2269
2270- CFG_SCCR:	System Clock and reset Control Register (15-27)
2271
2272- CFG_OR_TIMING_SDRAM:
2273		SDRAM timing
2274
2275- CFG_MAMR_PTA:
2276		periodic timer for refresh
2277
2278- CFG_DER:	Debug Event Register (37-47)
2279
2280- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CFG_REMAP_OR_AM,
2281  CFG_PRELIM_OR_AM, CFG_OR_TIMING_FLASH, CFG_OR0_REMAP,
2282  CFG_OR0_PRELIM, CFG_BR0_PRELIM, CFG_OR1_REMAP, CFG_OR1_PRELIM,
2283  CFG_BR1_PRELIM:
2284		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2285
2286- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2287  CFG_OR_TIMING_SDRAM, CFG_OR2_PRELIM, CFG_BR2_PRELIM,
2288  CFG_OR3_PRELIM, CFG_BR3_PRELIM:
2289		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2290
2291- CFG_MAMR_PTA, CFG_MPTPR_2BK_4K, CFG_MPTPR_1BK_4K, CFG_MPTPR_2BK_8K,
2292  CFG_MPTPR_1BK_8K, CFG_MAMR_8COL, CFG_MAMR_9COL:
2293		Machine Mode Register and Memory Periodic Timer
2294		Prescaler definitions (SDRAM timing)
2295
2296- CFG_I2C_UCODE_PATCH, CFG_I2C_DPMEM_OFFSET [0x1FC0]:
2297		enable I2C microcode relocation patch (MPC8xx);
2298		define relocation offset in DPRAM [DSP2]
2299
2300- CFG_SPI_UCODE_PATCH, CFG_SPI_DPMEM_OFFSET [0x1FC0]:
2301		enable SPI microcode relocation patch (MPC8xx);
2302		define relocation offset in DPRAM [SCC4]
2303
2304- CFG_USE_OSCCLK:
2305		Use OSCM clock mode on MBX8xx board. Be careful,
2306		wrong setting might damage your board. Read
2307		doc/README.MBX before setting this variable!
2308
2309- CFG_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
2310		Offset of the bootmode word in DPRAM used by post
2311		(Power On Self Tests). This definition overrides
2312		#define'd default value in commproc.h resp.
2313		cpm_8260.h.
2314
2315- CFG_PCI_SLV_MEM_LOCAL, CFG_PCI_SLV_MEM_BUS, CFG_PICMR0_MASK_ATTRIB,
2316  CFG_PCI_MSTR0_LOCAL, CFG_PCIMSK0_MASK, CFG_PCI_MSTR1_LOCAL,
2317  CFG_PCIMSK1_MASK, CFG_PCI_MSTR_MEM_LOCAL, CFG_PCI_MSTR_MEM_BUS,
2318  CFG_CPU_PCI_MEM_START, CFG_PCI_MSTR_MEM_SIZE, CFG_POCMR0_MASK_ATTRIB,
2319  CFG_PCI_MSTR_MEMIO_LOCAL, CFG_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
2320  CFG_PCI_MSTR_MEMIO_SIZE, CFG_POCMR1_MASK_ATTRIB, CFG_PCI_MSTR_IO_LOCAL,
2321  CFG_PCI_MSTR_IO_BUS, CFG_CPU_PCI_IO_START, CFG_PCI_MSTR_IO_SIZE,
2322  CFG_POCMR2_MASK_ATTRIB: (MPC826x only)
2323		Overrides the default PCI memory map in cpu/mpc8260/pci.c if set.
2324
2325- CONFIG_SPD_EEPROM
2326		Get DDR timing information from an I2C EEPROM.  Common with pluggable
2327		memory modules such as SODIMMs
2328  SPD_EEPROM_ADDRESS
2329		I2C address of the SPD EEPROM
2330
2331- CFG_SPD_BUS_NUM
2332		If SPD EEPROM is on an I2C bus other than the first one, specify here.
2333		Note that the value must resolve to something your driver can deal with.
2334
2335- CFG_83XX_DDR_USES_CS0
2336		Only for 83xx systems. If specified, then DDR should be configured
2337		using CS0 and CS1 instead of CS2 and CS3.
2338
2339- CFG_83XX_DDR_USES_CS0
2340		Only for 83xx systems. If specified, then DDR should be configured
2341		using CS0 and CS1 instead of CS2 and CS3.
2342
2343- CONFIG_ETHER_ON_FEC[12]
2344		Define to enable FEC[12] on a 8xx series processor.
2345
2346- CONFIG_FEC[12]_PHY
2347		Define to the hardcoded PHY address which corresponds
2348		to the given FEC; i. e.
2349			#define CONFIG_FEC1_PHY 4
2350		means that the PHY with address 4 is connected to FEC1
2351
2352		When set to -1, means to probe for first available.
2353
2354- CONFIG_FEC[12]_PHY_NORXERR
2355		The PHY does not have a RXERR line (RMII only).
2356		(so program the FEC to ignore it).
2357
2358- CONFIG_RMII
2359		Enable RMII mode for all FECs.
2360		Note that this is a global option, we can't
2361		have one FEC in standard MII mode and another in RMII mode.
2362
2363- CONFIG_CRC32_VERIFY
2364		Add a verify option to the crc32 command.
2365		The syntax is:
2366
2367		=> crc32 -v <address> <count> <crc32>
2368
2369		Where address/count indicate a memory area
2370		and crc32 is the correct crc32 which the
2371		area should have.
2372
2373- CONFIG_LOOPW
2374		Add the "loopw" memory command. This only takes effect if
2375		the memory commands are activated globally (CONFIG_CMD_MEM).
2376
2377- CONFIG_MX_CYCLIC
2378		Add the "mdc" and "mwc" memory commands. These are cyclic
2379		"md/mw" commands.
2380		Examples:
2381
2382		=> mdc.b 10 4 500
2383		This command will print 4 bytes (10,11,12,13) each 500 ms.
2384
2385		=> mwc.l 100 12345678 10
2386		This command will write 12345678 to address 100 all 10 ms.
2387
2388		This only takes effect if the memory commands are activated
2389		globally (CONFIG_CMD_MEM).
2390
2391- CONFIG_SKIP_LOWLEVEL_INIT
2392- CONFIG_SKIP_RELOCATE_UBOOT
2393
2394		[ARM only] If these variables are defined, then
2395		certain low level initializations (like setting up
2396		the memory controller) are omitted and/or U-Boot does
2397		not relocate itself into RAM.
2398		Normally these variables MUST NOT be defined. The
2399		only exception is when U-Boot is loaded (to RAM) by
2400		some other boot loader or by a debugger which
2401		performs these intializations itself.
2402
2403
2404Building the Software:
2405======================
2406
2407Building U-Boot has been tested in native PPC environments (on a
2408PowerBook G3 running LinuxPPC 2000) and in cross environments
2409(running RedHat 6.x and 7.x Linux on x86, Solaris 2.6 on a SPARC, and
2410NetBSD 1.5 on x86).
2411
2412If you are not using a native PPC environment, it is assumed that you
2413have the GNU cross compiling tools available in your path and named
2414with a prefix of "powerpc-linux-". If this is not the case, (e.g. if
2415you are using Monta Vista's Hard Hat Linux CDK 1.2) you must change
2416the definition of CROSS_COMPILE in Makefile. For HHL on a 4xx CPU,
2417change it to:
2418
2419	CROSS_COMPILE = ppc_4xx-
2420
2421
2422U-Boot is intended to be  simple  to  build.  After  installing	 the
2423sources	 you must configure U-Boot for one specific board type. This
2424is done by typing:
2425
2426	make NAME_config
2427
2428where "NAME_config" is the name of one of the existing
2429configurations; the following names are supported:
2430
2431	ADCIOP_config		FPS860L_config		omap730p2_config
2432	ADS860_config		GEN860T_config		pcu_e_config
2433	Alaska8220_config
2434	AR405_config		GENIETV_config		PIP405_config
2435	at91rm9200dk_config	GTH_config		QS823_config
2436	CANBT_config		hermes_config		QS850_config
2437	cmi_mpc5xx_config	hymod_config		QS860T_config
2438	cogent_common_config	IP860_config		RPXlite_config
2439	cogent_mpc8260_config	IVML24_config		RPXlite_DW_config
2440	cogent_mpc8xx_config	IVMS8_config		RPXsuper_config
2441	CPCI405_config		JSE_config		rsdproto_config
2442	CPCIISER4_config	LANTEC_config		Sandpoint8240_config
2443	csb272_config		lwmon_config		sbc8260_config
2444	CU824_config		MBX860T_config		sbc8560_33_config
2445	DUET_ADS_config		MBX_config		sbc8560_66_config
2446	EBONY_config		mpc7448hpc2_config	SM850_config
2447	ELPT860_config		MPC8260ADS_config	SPD823TS_config
2448	ESTEEM192E_config	MPC8540ADS_config	stxgp3_config
2449	ETX094_config		MPC8540EVAL_config	SXNI855T_config
2450	FADS823_config		NMPC8560ADS_config	TQM823L_config
2451	FADS850SAR_config	NETVIA_config		TQM850L_config
2452	FADS860T_config		omap1510inn_config	TQM855L_config
2453	FPS850L_config		omap1610h2_config	TQM860L_config
2454				omap1610inn_config	walnut_config
2455				omap5912osk_config	Yukon8220_config
2456				omap2420h4_config	ZPC1900_config
2457
2458Note: for some board special configuration names may exist; check if
2459      additional information is available from the board vendor; for
2460      instance, the TQM823L systems are available without (standard)
2461      or with LCD support. You can select such additional "features"
2462      when chosing the configuration, i. e.
2463
2464      make TQM823L_config
2465	- will configure for a plain TQM823L, i. e. no LCD support
2466
2467      make TQM823L_LCD_config
2468	- will configure for a TQM823L with U-Boot console on LCD
2469
2470      etc.
2471
2472
2473Finally, type "make all", and you should get some working U-Boot
2474images ready for download to / installation on your system:
2475
2476- "u-boot.bin" is a raw binary image
2477- "u-boot" is an image in ELF binary format
2478- "u-boot.srec" is in Motorola S-Record format
2479
2480By default the build is performed locally and the objects are saved
2481in the source directory. One of the two methods can be used to change
2482this behavior and build U-Boot to some external directory:
2483
24841. Add O= to the make command line invocations:
2485
2486	make O=/tmp/build distclean
2487	make O=/tmp/build NAME_config
2488	make O=/tmp/build all
2489
24902. Set environment variable BUILD_DIR to point to the desired location:
2491
2492	export BUILD_DIR=/tmp/build
2493	make distclean
2494	make NAME_config
2495	make all
2496
2497Note that the command line "O=" setting overrides the BUILD_DIR environment
2498variable.
2499
2500
2501Please be aware that the Makefiles assume you are using GNU make, so
2502for instance on NetBSD you might need to use "gmake" instead of
2503native "make".
2504
2505
2506If the system board that you have is not listed, then you will need
2507to port U-Boot to your hardware platform. To do this, follow these
2508steps:
2509
25101.  Add a new configuration option for your board to the toplevel
2511    "Makefile" and to the "MAKEALL" script, using the existing
2512    entries as examples. Note that here and at many other places
2513    boards and other names are listed in alphabetical sort order. Please
2514    keep this order.
25152.  Create a new directory to hold your board specific code. Add any
2516    files you need. In your board directory, you will need at least
2517    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
25183.  Create a new configuration file "include/configs/<board>.h" for
2519    your board
25203.  If you're porting U-Boot to a new CPU, then also create a new
2521    directory to hold your CPU specific code. Add any files you need.
25224.  Run "make <board>_config" with your new name.
25235.  Type "make", and you should get a working "u-boot.srec" file
2524    to be installed on your target system.
25256.  Debug and solve any problems that might arise.
2526    [Of course, this last step is much harder than it sounds.]
2527
2528
2529Testing of U-Boot Modifications, Ports to New Hardware, etc.:
2530==============================================================
2531
2532If you have modified U-Boot sources (for instance added a new	board
2533or  support  for  new  devices,	 a new CPU, etc.) you are expected to
2534provide feedback to the other developers. The feedback normally takes
2535the form of a "patch", i. e. a context diff against a certain (latest
2536official or latest in CVS) version of U-Boot sources.
2537
2538But before you submit such a patch, please verify that	your  modifi-
2539cation	did not break existing code. At least make sure that *ALL* of
2540the supported boards compile WITHOUT ANY compiler warnings. To do so,
2541just run the "MAKEALL" script, which will configure and build U-Boot
2542for ALL supported system. Be warned, this will take a while. You  can
2543select	which  (cross)	compiler  to use by passing a `CROSS_COMPILE'
2544environment variable to the script, i. e. to use the cross tools from
2545MontaVista's Hard Hat Linux you can type
2546
2547	CROSS_COMPILE=ppc_8xx- MAKEALL
2548
2549or to build on a native PowerPC system you can type
2550
2551	CROSS_COMPILE=' ' MAKEALL
2552
2553When using the MAKEALL script, the default behaviour is to build U-Boot
2554in the source directory. This location can be changed by setting the
2555BUILD_DIR environment variable. Also, for each target built, the MAKEALL
2556script saves two log files (<target>.ERR and <target>.MAKEALL) in the
2557<source dir>/LOG directory. This default location can be changed by
2558setting the MAKEALL_LOGDIR environment variable. For example:
2559
2560	export BUILD_DIR=/tmp/build
2561	export MAKEALL_LOGDIR=/tmp/log
2562	CROSS_COMPILE=ppc_8xx- MAKEALL
2563
2564With the above settings build objects are saved in the /tmp/build, log
2565files are saved in the /tmp/log and the source tree remains clean during
2566the whole build process.
2567
2568
2569See also "U-Boot Porting Guide" below.
2570
2571
2572Monitor Commands - Overview:
2573============================
2574
2575go	- start application at address 'addr'
2576run	- run commands in an environment variable
2577bootm	- boot application image from memory
2578bootp	- boot image via network using BootP/TFTP protocol
2579tftpboot- boot image via network using TFTP protocol
2580	       and env variables "ipaddr" and "serverip"
2581	       (and eventually "gatewayip")
2582rarpboot- boot image via network using RARP/TFTP protocol
2583diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
2584loads	- load S-Record file over serial line
2585loadb	- load binary file over serial line (kermit mode)
2586md	- memory display
2587mm	- memory modify (auto-incrementing)
2588nm	- memory modify (constant address)
2589mw	- memory write (fill)
2590cp	- memory copy
2591cmp	- memory compare
2592crc32	- checksum calculation
2593imd	- i2c memory display
2594imm	- i2c memory modify (auto-incrementing)
2595inm	- i2c memory modify (constant address)
2596imw	- i2c memory write (fill)
2597icrc32	- i2c checksum calculation
2598iprobe	- probe to discover valid I2C chip addresses
2599iloop	- infinite loop on address range
2600isdram	- print SDRAM configuration information
2601sspi	- SPI utility commands
2602base	- print or set address offset
2603printenv- print environment variables
2604setenv	- set environment variables
2605saveenv - save environment variables to persistent storage
2606protect - enable or disable FLASH write protection
2607erase	- erase FLASH memory
2608flinfo	- print FLASH memory information
2609bdinfo	- print Board Info structure
2610iminfo	- print header information for application image
2611coninfo - print console devices and informations
2612ide	- IDE sub-system
2613loop	- infinite loop on address range
2614loopw	- infinite write loop on address range
2615mtest	- simple RAM test
2616icache	- enable or disable instruction cache
2617dcache	- enable or disable data cache
2618reset	- Perform RESET of the CPU
2619echo	- echo args to console
2620version - print monitor version
2621help	- print online help
2622?	- alias for 'help'
2623
2624
2625Monitor Commands - Detailed Description:
2626========================================
2627
2628TODO.
2629
2630For now: just type "help <command>".
2631
2632
2633Environment Variables:
2634======================
2635
2636U-Boot supports user configuration using Environment Variables which
2637can be made persistent by saving to Flash memory.
2638
2639Environment Variables are set using "setenv", printed using
2640"printenv", and saved to Flash using "saveenv". Using "setenv"
2641without a value can be used to delete a variable from the
2642environment. As long as you don't save the environment you are
2643working with an in-memory copy. In case the Flash area containing the
2644environment is erased by accident, a default environment is provided.
2645
2646Some configuration options can be set using Environment Variables:
2647
2648  baudrate	- see CONFIG_BAUDRATE
2649
2650  bootdelay	- see CONFIG_BOOTDELAY
2651
2652  bootcmd	- see CONFIG_BOOTCOMMAND
2653
2654  bootargs	- Boot arguments when booting an RTOS image
2655
2656  bootfile	- Name of the image to load with TFTP
2657
2658  autoload	- if set to "no" (any string beginning with 'n'),
2659		  "bootp" will just load perform a lookup of the
2660		  configuration from the BOOTP server, but not try to
2661		  load any image using TFTP
2662
2663  autostart	- if set to "yes", an image loaded using the "bootp",
2664		  "rarpboot", "tftpboot" or "diskboot" commands will
2665		  be automatically started (by internally calling
2666		  "bootm")
2667
2668		  If set to "no", a standalone image passed to the
2669		  "bootm" command will be copied to the load address
2670		  (and eventually uncompressed), but NOT be started.
2671		  This can be used to load and uncompress arbitrary
2672		  data.
2673
2674  i2cfast	- (PPC405GP|PPC405EP only)
2675		  if set to 'y' configures Linux I2C driver for fast
2676		  mode (400kHZ). This environment variable is used in
2677		  initialization code. So, for changes to be effective
2678		  it must be saved and board must be reset.
2679
2680  initrd_high	- restrict positioning of initrd images:
2681		  If this variable is not set, initrd images will be
2682		  copied to the highest possible address in RAM; this
2683		  is usually what you want since it allows for
2684		  maximum initrd size. If for some reason you want to
2685		  make sure that the initrd image is loaded below the
2686		  CFG_BOOTMAPSZ limit, you can set this environment
2687		  variable to a value of "no" or "off" or "0".
2688		  Alternatively, you can set it to a maximum upper
2689		  address to use (U-Boot will still check that it
2690		  does not overwrite the U-Boot stack and data).
2691
2692		  For instance, when you have a system with 16 MB
2693		  RAM, and want to reserve 4 MB from use by Linux,
2694		  you can do this by adding "mem=12M" to the value of
2695		  the "bootargs" variable. However, now you must make
2696		  sure that the initrd image is placed in the first
2697		  12 MB as well - this can be done with
2698
2699		  setenv initrd_high 00c00000
2700
2701		  If you set initrd_high to 0xFFFFFFFF, this is an
2702		  indication to U-Boot that all addresses are legal
2703		  for the Linux kernel, including addresses in flash
2704		  memory. In this case U-Boot will NOT COPY the
2705		  ramdisk at all. This may be useful to reduce the
2706		  boot time on your system, but requires that this
2707		  feature is supported by your Linux kernel.
2708
2709  ipaddr	- IP address; needed for tftpboot command
2710
2711  loadaddr	- Default load address for commands like "bootp",
2712		  "rarpboot", "tftpboot", "loadb" or "diskboot"
2713
2714  loads_echo	- see CONFIG_LOADS_ECHO
2715
2716  serverip	- TFTP server IP address; needed for tftpboot command
2717
2718  bootretry	- see CONFIG_BOOT_RETRY_TIME
2719
2720  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
2721
2722  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
2723
2724  ethprime	- When CONFIG_NET_MULTI is enabled controls which
2725		  interface is used first.
2726
2727  ethact	- When CONFIG_NET_MULTI is enabled controls which
2728		  interface is currently active. For example you
2729		  can do the following
2730
2731		  => setenv ethact FEC ETHERNET
2732		  => ping 192.168.0.1 # traffic sent on FEC ETHERNET
2733		  => setenv ethact SCC ETHERNET
2734		  => ping 10.0.0.1 # traffic sent on SCC ETHERNET
2735
2736   netretry	- When set to "no" each network operation will
2737		  either succeed or fail without retrying.
2738		  When set to "once" the network operation will
2739		  fail when all the available network interfaces
2740		  are tried once without success.
2741		  Useful on scripts which control the retry operation
2742		  themselves.
2743
2744  tftpsrcport	- If this is set, the value is used for TFTP's
2745		  UDP source port.
2746
2747  tftpdstport	- If this is set, the value is used for TFTP's UDP
2748		  destination port instead of the Well Know Port 69.
2749
2750   vlan		- When set to a value < 4095 the traffic over
2751		  ethernet is encapsulated/received over 802.1q
2752		  VLAN tagged frames.
2753
2754The following environment variables may be used and automatically
2755updated by the network boot commands ("bootp" and "rarpboot"),
2756depending the information provided by your boot server:
2757
2758  bootfile	- see above
2759  dnsip		- IP address of your Domain Name Server
2760  dnsip2	- IP address of your secondary Domain Name Server
2761  gatewayip	- IP address of the Gateway (Router) to use
2762  hostname	- Target hostname
2763  ipaddr	- see above
2764  netmask	- Subnet Mask
2765  rootpath	- Pathname of the root filesystem on the NFS server
2766  serverip	- see above
2767
2768
2769There are two special Environment Variables:
2770
2771  serial#	- contains hardware identification information such
2772		  as type string and/or serial number
2773  ethaddr	- Ethernet address
2774
2775These variables can be set only once (usually during manufacturing of
2776the board). U-Boot refuses to delete or overwrite these variables
2777once they have been set once.
2778
2779
2780Further special Environment Variables:
2781
2782  ver		- Contains the U-Boot version string as printed
2783		  with the "version" command. This variable is
2784		  readonly (see CONFIG_VERSION_VARIABLE).
2785
2786
2787Please note that changes to some configuration parameters may take
2788only effect after the next boot (yes, that's just like Windoze :-).
2789
2790
2791Command Line Parsing:
2792=====================
2793
2794There are two different command line parsers available with U-Boot:
2795the old "simple" one, and the much more powerful "hush" shell:
2796
2797Old, simple command line parser:
2798--------------------------------
2799
2800- supports environment variables (through setenv / saveenv commands)
2801- several commands on one line, separated by ';'
2802- variable substitution using "... ${name} ..." syntax
2803- special characters ('$', ';') can be escaped by prefixing with '\',
2804  for example:
2805	setenv bootcmd bootm \${address}
2806- You can also escape text by enclosing in single apostrophes, for example:
2807	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
2808
2809Hush shell:
2810-----------
2811
2812- similar to Bourne shell, with control structures like
2813  if...then...else...fi, for...do...done; while...do...done,
2814  until...do...done, ...
2815- supports environment ("global") variables (through setenv / saveenv
2816  commands) and local shell variables (through standard shell syntax
2817  "name=value"); only environment variables can be used with "run"
2818  command
2819
2820General rules:
2821--------------
2822
2823(1) If a command line (or an environment variable executed by a "run"
2824    command) contains several commands separated by semicolon, and
2825    one of these commands fails, then the remaining commands will be
2826    executed anyway.
2827
2828(2) If you execute several variables with one call to run (i. e.
2829    calling run with a list af variables as arguments), any failing
2830    command will cause "run" to terminate, i. e. the remaining
2831    variables are not executed.
2832
2833Note for Redundant Ethernet Interfaces:
2834=======================================
2835
2836Some boards come with redundant ethernet interfaces; U-Boot supports
2837such configurations and is capable of automatic selection of a
2838"working" interface when needed. MAC assignment works as follows:
2839
2840Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
2841MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
2842"eth1addr" (=>eth1), "eth2addr", ...
2843
2844If the network interface stores some valid MAC address (for instance
2845in SROM), this is used as default address if there is NO correspon-
2846ding setting in the environment; if the corresponding environment
2847variable is set, this overrides the settings in the card; that means:
2848
2849o If the SROM has a valid MAC address, and there is no address in the
2850  environment, the SROM's address is used.
2851
2852o If there is no valid address in the SROM, and a definition in the
2853  environment exists, then the value from the environment variable is
2854  used.
2855
2856o If both the SROM and the environment contain a MAC address, and
2857  both addresses are the same, this MAC address is used.
2858
2859o If both the SROM and the environment contain a MAC address, and the
2860  addresses differ, the value from the environment is used and a
2861  warning is printed.
2862
2863o If neither SROM nor the environment contain a MAC address, an error
2864  is raised.
2865
2866
2867Image Formats:
2868==============
2869
2870The "boot" commands of this monitor operate on "image" files which
2871can be basicly anything, preceeded by a special header; see the
2872definitions in include/image.h for details; basicly, the header
2873defines the following image properties:
2874
2875* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
2876  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
2877  LynxOS, pSOS, QNX, RTEMS, ARTOS;
2878  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, LynxOS).
2879* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
2880  IA64, MIPS, NIOS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
2881  Currently supported: ARM, AVR32, Intel x86, MIPS, NIOS, PowerPC).
2882* Compression Type (uncompressed, gzip, bzip2)
2883* Load Address
2884* Entry Point
2885* Image Name
2886* Image Timestamp
2887
2888The header is marked by a special Magic Number, and both the header
2889and the data portions of the image are secured against corruption by
2890CRC32 checksums.
2891
2892
2893Linux Support:
2894==============
2895
2896Although U-Boot should support any OS or standalone application
2897easily, the main focus has always been on Linux during the design of
2898U-Boot.
2899
2900U-Boot includes many features that so far have been part of some
2901special "boot loader" code within the Linux kernel. Also, any
2902"initrd" images to be used are no longer part of one big Linux image;
2903instead, kernel and "initrd" are separate images. This implementation
2904serves several purposes:
2905
2906- the same features can be used for other OS or standalone
2907  applications (for instance: using compressed images to reduce the
2908  Flash memory footprint)
2909
2910- it becomes much easier to port new Linux kernel versions because
2911  lots of low-level, hardware dependent stuff are done by U-Boot
2912
2913- the same Linux kernel image can now be used with different "initrd"
2914  images; of course this also means that different kernel images can
2915  be run with the same "initrd". This makes testing easier (you don't
2916  have to build a new "zImage.initrd" Linux image when you just
2917  change a file in your "initrd"). Also, a field-upgrade of the
2918  software is easier now.
2919
2920
2921Linux HOWTO:
2922============
2923
2924Porting Linux to U-Boot based systems:
2925---------------------------------------
2926
2927U-Boot cannot save you from doing all the necessary modifications to
2928configure the Linux device drivers for use with your target hardware
2929(no, we don't intend to provide a full virtual machine interface to
2930Linux :-).
2931
2932But now you can ignore ALL boot loader code (in arch/ppc/mbxboot).
2933
2934Just make sure your machine specific header file (for instance
2935include/asm-ppc/tqm8xx.h) includes the same definition of the Board
2936Information structure as we define in include/u-boot.h, and make
2937sure that your definition of IMAP_ADDR uses the same value as your
2938U-Boot configuration in CFG_IMMR.
2939
2940
2941Configuring the Linux kernel:
2942-----------------------------
2943
2944No specific requirements for U-Boot. Make sure you have some root
2945device (initial ramdisk, NFS) for your target system.
2946
2947
2948Building a Linux Image:
2949-----------------------
2950
2951With U-Boot, "normal" build targets like "zImage" or "bzImage" are
2952not used. If you use recent kernel source, a new build target
2953"uImage" will exist which automatically builds an image usable by
2954U-Boot. Most older kernels also have support for a "pImage" target,
2955which was introduced for our predecessor project PPCBoot and uses a
2956100% compatible format.
2957
2958Example:
2959
2960	make TQM850L_config
2961	make oldconfig
2962	make dep
2963	make uImage
2964
2965The "uImage" build target uses a special tool (in 'tools/mkimage') to
2966encapsulate a compressed Linux kernel image with header	 information,
2967CRC32 checksum etc. for use with U-Boot. This is what we are doing:
2968
2969* build a standard "vmlinux" kernel image (in ELF binary format):
2970
2971* convert the kernel into a raw binary image:
2972
2973	${CROSS_COMPILE}-objcopy -O binary \
2974				 -R .note -R .comment \
2975				 -S vmlinux linux.bin
2976
2977* compress the binary image:
2978
2979	gzip -9 linux.bin
2980
2981* package compressed binary image for U-Boot:
2982
2983	mkimage -A ppc -O linux -T kernel -C gzip \
2984		-a 0 -e 0 -n "Linux Kernel Image" \
2985		-d linux.bin.gz uImage
2986
2987
2988The "mkimage" tool can also be used to create ramdisk images for use
2989with U-Boot, either separated from the Linux kernel image, or
2990combined into one file. "mkimage" encapsulates the images with a 64
2991byte header containing information about target architecture,
2992operating system, image type, compression method, entry points, time
2993stamp, CRC32 checksums, etc.
2994
2995"mkimage" can be called in two ways: to verify existing images and
2996print the header information, or to build new images.
2997
2998In the first form (with "-l" option) mkimage lists the information
2999contained in the header of an existing U-Boot image; this includes
3000checksum verification:
3001
3002	tools/mkimage -l image
3003	  -l ==> list image header information
3004
3005The second form (with "-d" option) is used to build a U-Boot image
3006from a "data file" which is used as image payload:
3007
3008	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3009		      -n name -d data_file image
3010	  -A ==> set architecture to 'arch'
3011	  -O ==> set operating system to 'os'
3012	  -T ==> set image type to 'type'
3013	  -C ==> set compression type 'comp'
3014	  -a ==> set load address to 'addr' (hex)
3015	  -e ==> set entry point to 'ep' (hex)
3016	  -n ==> set image name to 'name'
3017	  -d ==> use image data from 'datafile'
3018
3019Right now, all Linux kernels for PowerPC systems use the same load
3020address (0x00000000), but the entry point address depends on the
3021kernel version:
3022
3023- 2.2.x kernels have the entry point at 0x0000000C,
3024- 2.3.x and later kernels have the entry point at 0x00000000.
3025
3026So a typical call to build a U-Boot image would read:
3027
3028	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3029	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3030	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz \
3031	> examples/uImage.TQM850L
3032	Image Name:   2.4.4 kernel for TQM850L
3033	Created:      Wed Jul 19 02:34:59 2000
3034	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3035	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3036	Load Address: 0x00000000
3037	Entry Point:  0x00000000
3038
3039To verify the contents of the image (or check for corruption):
3040
3041	-> tools/mkimage -l examples/uImage.TQM850L
3042	Image Name:   2.4.4 kernel for TQM850L
3043	Created:      Wed Jul 19 02:34:59 2000
3044	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3045	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3046	Load Address: 0x00000000
3047	Entry Point:  0x00000000
3048
3049NOTE: for embedded systems where boot time is critical you can trade
3050speed for memory and install an UNCOMPRESSED image instead: this
3051needs more space in Flash, but boots much faster since it does not
3052need to be uncompressed:
3053
3054	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
3055	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3056	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3057	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
3058	> examples/uImage.TQM850L-uncompressed
3059	Image Name:   2.4.4 kernel for TQM850L
3060	Created:      Wed Jul 19 02:34:59 2000
3061	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3062	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3063	Load Address: 0x00000000
3064	Entry Point:  0x00000000
3065
3066
3067Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3068when your kernel is intended to use an initial ramdisk:
3069
3070	-> tools/mkimage -n 'Simple Ramdisk Image' \
3071	> -A ppc -O linux -T ramdisk -C gzip \
3072	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3073	Image Name:   Simple Ramdisk Image
3074	Created:      Wed Jan 12 14:01:50 2000
3075	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
3076	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
3077	Load Address: 0x00000000
3078	Entry Point:  0x00000000
3079
3080
3081Installing a Linux Image:
3082-------------------------
3083
3084To downloading a U-Boot image over the serial (console) interface,
3085you must convert the image to S-Record format:
3086
3087	objcopy -I binary -O srec examples/image examples/image.srec
3088
3089The 'objcopy' does not understand the information in the U-Boot
3090image header, so the resulting S-Record file will be relative to
3091address 0x00000000. To load it to a given address, you need to
3092specify the target address as 'offset' parameter with the 'loads'
3093command.
3094
3095Example: install the image to address 0x40100000 (which on the
3096TQM8xxL is in the first Flash bank):
3097
3098	=> erase 40100000 401FFFFF
3099
3100	.......... done
3101	Erased 8 sectors
3102
3103	=> loads 40100000
3104	## Ready for S-Record download ...
3105	~>examples/image.srec
3106	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3107	...
3108	15989 15990 15991 15992
3109	[file transfer complete]
3110	[connected]
3111	## Start Addr = 0x00000000
3112
3113
3114You can check the success of the download using the 'iminfo' command;
3115this includes a checksum verification so you  can  be  sure  no	 data
3116corruption happened:
3117
3118	=> imi 40100000
3119
3120	## Checking Image at 40100000 ...
3121	   Image Name:	 2.2.13 for initrd on TQM850L
3122	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3123	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3124	   Load Address: 00000000
3125	   Entry Point:	 0000000c
3126	   Verifying Checksum ... OK
3127
3128
3129Boot Linux:
3130-----------
3131
3132The "bootm" command is used to boot an application that is stored in
3133memory (RAM or Flash). In case of a Linux kernel image, the contents
3134of the "bootargs" environment variable is passed to the kernel as
3135parameters. You can check and modify this variable using the
3136"printenv" and "setenv" commands:
3137
3138
3139	=> printenv bootargs
3140	bootargs=root=/dev/ram
3141
3142	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3143
3144	=> printenv bootargs
3145	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3146
3147	=> bootm 40020000
3148	## Booting Linux kernel at 40020000 ...
3149	   Image Name:	 2.2.13 for NFS on TQM850L
3150	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3151	   Data Size:	 381681 Bytes = 372 kB = 0 MB
3152	   Load Address: 00000000
3153	   Entry Point:	 0000000c
3154	   Verifying Checksum ... OK
3155	   Uncompressing Kernel Image ... OK
3156	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
3157	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3158	time_init: decrementer frequency = 187500000/60
3159	Calibrating delay loop... 49.77 BogoMIPS
3160	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3161	...
3162
3163If you want to boot a Linux kernel with initial ram disk, you pass
3164the memory addresses of both the kernel and the initrd image (PPBCOOT
3165format!) to the "bootm" command:
3166
3167	=> imi 40100000 40200000
3168
3169	## Checking Image at 40100000 ...
3170	   Image Name:	 2.2.13 for initrd on TQM850L
3171	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3172	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3173	   Load Address: 00000000
3174	   Entry Point:	 0000000c
3175	   Verifying Checksum ... OK
3176
3177	## Checking Image at 40200000 ...
3178	   Image Name:	 Simple Ramdisk Image
3179	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3180	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3181	   Load Address: 00000000
3182	   Entry Point:	 00000000
3183	   Verifying Checksum ... OK
3184
3185	=> bootm 40100000 40200000
3186	## Booting Linux kernel at 40100000 ...
3187	   Image Name:	 2.2.13 for initrd on TQM850L
3188	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3189	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3190	   Load Address: 00000000
3191	   Entry Point:	 0000000c
3192	   Verifying Checksum ... OK
3193	   Uncompressing Kernel Image ... OK
3194	## Loading RAMDisk Image at 40200000 ...
3195	   Image Name:	 Simple Ramdisk Image
3196	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3197	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3198	   Load Address: 00000000
3199	   Entry Point:	 00000000
3200	   Verifying Checksum ... OK
3201	   Loading Ramdisk ... OK
3202	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
3203	Boot arguments: root=/dev/ram
3204	time_init: decrementer frequency = 187500000/60
3205	Calibrating delay loop... 49.77 BogoMIPS
3206	...
3207	RAMDISK: Compressed image found at block 0
3208	VFS: Mounted root (ext2 filesystem).
3209
3210	bash#
3211
3212Boot Linux and pass a flat device tree:
3213-----------
3214
3215First, U-Boot must be compiled with the appropriate defines. See the section
3216titled "Linux Kernel Interface" above for a more in depth explanation. The
3217following is an example of how to start a kernel and pass an updated
3218flat device tree:
3219
3220=> print oftaddr
3221oftaddr=0x300000
3222=> print oft
3223oft=oftrees/mpc8540ads.dtb
3224=> tftp $oftaddr $oft
3225Speed: 1000, full duplex
3226Using TSEC0 device
3227TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3228Filename 'oftrees/mpc8540ads.dtb'.
3229Load address: 0x300000
3230Loading: #
3231done
3232Bytes transferred = 4106 (100a hex)
3233=> tftp $loadaddr $bootfile
3234Speed: 1000, full duplex
3235Using TSEC0 device
3236TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3237Filename 'uImage'.
3238Load address: 0x200000
3239Loading:############
3240done
3241Bytes transferred = 1029407 (fb51f hex)
3242=> print loadaddr
3243loadaddr=200000
3244=> print oftaddr
3245oftaddr=0x300000
3246=> bootm $loadaddr - $oftaddr
3247## Booting image at 00200000 ...
3248   Image Name:	 Linux-2.6.17-dirty
3249   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3250   Data Size:	 1029343 Bytes = 1005.2 kB
3251   Load Address: 00000000
3252   Entry Point:	 00000000
3253   Verifying Checksum ... OK
3254   Uncompressing Kernel Image ... OK
3255Booting using flat device tree at 0x300000
3256Using MPC85xx ADS machine description
3257Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
3258[snip]
3259
3260
3261More About U-Boot Image Types:
3262------------------------------
3263
3264U-Boot supports the following image types:
3265
3266   "Standalone Programs" are directly runnable in the environment
3267	provided by U-Boot; it is expected that (if they behave
3268	well) you can continue to work in U-Boot after return from
3269	the Standalone Program.
3270   "OS Kernel Images" are usually images of some Embedded OS which
3271	will take over control completely. Usually these programs
3272	will install their own set of exception handlers, device
3273	drivers, set up the MMU, etc. - this means, that you cannot
3274	expect to re-enter U-Boot except by resetting the CPU.
3275   "RAMDisk Images" are more or less just data blocks, and their
3276	parameters (address, size) are passed to an OS kernel that is
3277	being started.
3278   "Multi-File Images" contain several images, typically an OS
3279	(Linux) kernel image and one or more data images like
3280	RAMDisks. This construct is useful for instance when you want
3281	to boot over the network using BOOTP etc., where the boot
3282	server provides just a single image file, but you want to get
3283	for instance an OS kernel and a RAMDisk image.
3284
3285	"Multi-File Images" start with a list of image sizes, each
3286	image size (in bytes) specified by an "uint32_t" in network
3287	byte order. This list is terminated by an "(uint32_t)0".
3288	Immediately after the terminating 0 follow the images, one by
3289	one, all aligned on "uint32_t" boundaries (size rounded up to
3290	a multiple of 4 bytes).
3291
3292   "Firmware Images" are binary images containing firmware (like
3293	U-Boot or FPGA images) which usually will be programmed to
3294	flash memory.
3295
3296   "Script files" are command sequences that will be executed by
3297	U-Boot's command interpreter; this feature is especially
3298	useful when you configure U-Boot to use a real shell (hush)
3299	as command interpreter.
3300
3301
3302Standalone HOWTO:
3303=================
3304
3305One of the features of U-Boot is that you can dynamically load and
3306run "standalone" applications, which can use some resources of
3307U-Boot like console I/O functions or interrupt services.
3308
3309Two simple examples are included with the sources:
3310
3311"Hello World" Demo:
3312-------------------
3313
3314'examples/hello_world.c' contains a small "Hello World" Demo
3315application; it is automatically compiled when you build U-Boot.
3316It's configured to run at address 0x00040004, so you can play with it
3317like that:
3318
3319	=> loads
3320	## Ready for S-Record download ...
3321	~>examples/hello_world.srec
3322	1 2 3 4 5 6 7 8 9 10 11 ...
3323	[file transfer complete]
3324	[connected]
3325	## Start Addr = 0x00040004
3326
3327	=> go 40004 Hello World! This is a test.
3328	## Starting application at 0x00040004 ...
3329	Hello World
3330	argc = 7
3331	argv[0] = "40004"
3332	argv[1] = "Hello"
3333	argv[2] = "World!"
3334	argv[3] = "This"
3335	argv[4] = "is"
3336	argv[5] = "a"
3337	argv[6] = "test."
3338	argv[7] = "<NULL>"
3339	Hit any key to exit ...
3340
3341	## Application terminated, rc = 0x0
3342
3343Another example, which demonstrates how to register a CPM interrupt
3344handler with the U-Boot code, can be found in 'examples/timer.c'.
3345Here, a CPM timer is set up to generate an interrupt every second.
3346The interrupt service routine is trivial, just printing a '.'
3347character, but this is just a demo program. The application can be
3348controlled by the following keys:
3349
3350	? - print current values og the CPM Timer registers
3351	b - enable interrupts and start timer
3352	e - stop timer and disable interrupts
3353	q - quit application
3354
3355	=> loads
3356	## Ready for S-Record download ...
3357	~>examples/timer.srec
3358	1 2 3 4 5 6 7 8 9 10 11 ...
3359	[file transfer complete]
3360	[connected]
3361	## Start Addr = 0x00040004
3362
3363	=> go 40004
3364	## Starting application at 0x00040004 ...
3365	TIMERS=0xfff00980
3366	Using timer 1
3367	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
3368
3369Hit 'b':
3370	[q, b, e, ?] Set interval 1000000 us
3371	Enabling timer
3372Hit '?':
3373	[q, b, e, ?] ........
3374	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
3375Hit '?':
3376	[q, b, e, ?] .
3377	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
3378Hit '?':
3379	[q, b, e, ?] .
3380	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
3381Hit '?':
3382	[q, b, e, ?] .
3383	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
3384Hit 'e':
3385	[q, b, e, ?] ...Stopping timer
3386Hit 'q':
3387	[q, b, e, ?] ## Application terminated, rc = 0x0
3388
3389
3390Minicom warning:
3391================
3392
3393Over time, many people have reported problems when trying to use the
3394"minicom" terminal emulation program for serial download. I (wd)
3395consider minicom to be broken, and recommend not to use it. Under
3396Unix, I recommend to use C-Kermit for general purpose use (and
3397especially for kermit binary protocol download ("loadb" command), and
3398use "cu" for S-Record download ("loads" command).
3399
3400Nevertheless, if you absolutely want to use it try adding this
3401configuration to your "File transfer protocols" section:
3402
3403	   Name	   Program			Name U/D FullScr IO-Red. Multi
3404	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
3405	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
3406
3407
3408NetBSD Notes:
3409=============
3410
3411Starting at version 0.9.2, U-Boot supports NetBSD both as host
3412(build U-Boot) and target system (boots NetBSD/mpc8xx).
3413
3414Building requires a cross environment; it is known to work on
3415NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
3416need gmake since the Makefiles are not compatible with BSD make).
3417Note that the cross-powerpc package does not install include files;
3418attempting to build U-Boot will fail because <machine/ansi.h> is
3419missing.  This file has to be installed and patched manually:
3420
3421	# cd /usr/pkg/cross/powerpc-netbsd/include
3422	# mkdir powerpc
3423	# ln -s powerpc machine
3424	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
3425	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
3426
3427Native builds *don't* work due to incompatibilities between native
3428and U-Boot include files.
3429
3430Booting assumes that (the first part of) the image booted is a
3431stage-2 loader which in turn loads and then invokes the kernel
3432proper. Loader sources will eventually appear in the NetBSD source
3433tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
3434meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
3435
3436
3437Implementation Internals:
3438=========================
3439
3440The following is not intended to be a complete description of every
3441implementation detail. However, it should help to understand the
3442inner workings of U-Boot and make it easier to port it to custom
3443hardware.
3444
3445
3446Initial Stack, Global Data:
3447---------------------------
3448
3449The implementation of U-Boot is complicated by the fact that U-Boot
3450starts running out of ROM (flash memory), usually without access to
3451system RAM (because the memory controller is not initialized yet).
3452This means that we don't have writable Data or BSS segments, and BSS
3453is not initialized as zero. To be able to get a C environment working
3454at all, we have to allocate at least a minimal stack. Implementation
3455options for this are defined and restricted by the CPU used: Some CPU
3456models provide on-chip memory (like the IMMR area on MPC8xx and
3457MPC826x processors), on others (parts of) the data cache can be
3458locked as (mis-) used as memory, etc.
3459
3460	Chris Hallinan posted a good summary of	 these	issues	to  the
3461	u-boot-users mailing list:
3462
3463	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
3464	From: "Chris Hallinan" <clh@net1plus.com>
3465	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
3466	...
3467
3468	Correct me if I'm wrong, folks, but the way I understand it
3469	is this: Using DCACHE as initial RAM for Stack, etc, does not
3470	require any physical RAM backing up the cache. The cleverness
3471	is that the cache is being used as a temporary supply of
3472	necessary storage before the SDRAM controller is setup. It's
3473	beyond the scope of this list to expain the details, but you
3474	can see how this works by studying the cache architecture and
3475	operation in the architecture and processor-specific manuals.
3476
3477	OCM is On Chip Memory, which I believe the 405GP has 4K. It
3478	is another option for the system designer to use as an
3479	initial stack/ram area prior to SDRAM being available. Either
3480	option should work for you. Using CS 4 should be fine if your
3481	board designers haven't used it for something that would
3482	cause you grief during the initial boot! It is frequently not
3483	used.
3484
3485	CFG_INIT_RAM_ADDR should be somewhere that won't interfere
3486	with your processor/board/system design. The default value
3487	you will find in any recent u-boot distribution in
3488	walnut.h should work for you. I'd set it to a value larger
3489	than your SDRAM module. If you have a 64MB SDRAM module, set
3490	it above 400_0000. Just make sure your board has no resources
3491	that are supposed to respond to that address! That code in
3492	start.S has been around a while and should work as is when
3493	you get the config right.
3494
3495	-Chris Hallinan
3496	DS4.COM, Inc.
3497
3498It is essential to remember this, since it has some impact on the C
3499code for the initialization procedures:
3500
3501* Initialized global data (data segment) is read-only. Do not attempt
3502  to write it.
3503
3504* Do not use any unitialized global data (or implicitely initialized
3505  as zero data - BSS segment) at all - this is undefined, initiali-
3506  zation is performed later (when relocating to RAM).
3507
3508* Stack space is very limited. Avoid big data buffers or things like
3509  that.
3510
3511Having only the stack as writable memory limits means we cannot use
3512normal global data to share information beween the code. But it
3513turned out that the implementation of U-Boot can be greatly
3514simplified by making a global data structure (gd_t) available to all
3515functions. We could pass a pointer to this data as argument to _all_
3516functions, but this would bloat the code. Instead we use a feature of
3517the GCC compiler (Global Register Variables) to share the data: we
3518place a pointer (gd) to the global data into a register which we
3519reserve for this purpose.
3520
3521When choosing a register for such a purpose we are restricted by the
3522relevant  (E)ABI  specifications for the current architecture, and by
3523GCC's implementation.
3524
3525For PowerPC, the following registers have specific use:
3526	R1:	stack pointer
3527	R2:	TOC pointer
3528	R3-R4:	parameter passing and return values
3529	R5-R10: parameter passing
3530	R13:	small data area pointer
3531	R30:	GOT pointer
3532	R31:	frame pointer
3533
3534	(U-Boot also uses R14 as internal GOT pointer.)
3535
3536    ==> U-Boot will use R29 to hold a pointer to the global data
3537
3538    Note: on PPC, we could use a static initializer (since the
3539    address of the global data structure is known at compile time),
3540    but it turned out that reserving a register results in somewhat
3541    smaller code - although the code savings are not that big (on
3542    average for all boards 752 bytes for the whole U-Boot image,
3543    624 text + 127 data).
3544
3545On ARM, the following registers are used:
3546
3547	R0:	function argument word/integer result
3548	R1-R3:	function argument word
3549	R9:	GOT pointer
3550	R10:	stack limit (used only if stack checking if enabled)
3551	R11:	argument (frame) pointer
3552	R12:	temporary workspace
3553	R13:	stack pointer
3554	R14:	link register
3555	R15:	program counter
3556
3557    ==> U-Boot will use R8 to hold a pointer to the global data
3558
3559NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
3560or current versions of GCC may "optimize" the code too much.
3561
3562Memory Management:
3563------------------
3564
3565U-Boot runs in system state and uses physical addresses, i.e. the
3566MMU is not used either for address mapping nor for memory protection.
3567
3568The available memory is mapped to fixed addresses using the memory
3569controller. In this process, a contiguous block is formed for each
3570memory type (Flash, SDRAM, SRAM), even when it consists of several
3571physical memory banks.
3572
3573U-Boot is installed in the first 128 kB of the first Flash bank (on
3574TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
3575booting and sizing and initializing DRAM, the code relocates itself
3576to the upper end of DRAM. Immediately below the U-Boot code some
3577memory is reserved for use by malloc() [see CFG_MALLOC_LEN
3578configuration setting]. Below that, a structure with global Board
3579Info data is placed, followed by the stack (growing downward).
3580
3581Additionally, some exception handler code is copied to the low 8 kB
3582of DRAM (0x00000000 ... 0x00001FFF).
3583
3584So a typical memory configuration with 16 MB of DRAM could look like
3585this:
3586
3587	0x0000 0000	Exception Vector code
3588	      :
3589	0x0000 1FFF
3590	0x0000 2000	Free for Application Use
3591	      :
3592	      :
3593
3594	      :
3595	      :
3596	0x00FB FF20	Monitor Stack (Growing downward)
3597	0x00FB FFAC	Board Info Data and permanent copy of global data
3598	0x00FC 0000	Malloc Arena
3599	      :
3600	0x00FD FFFF
3601	0x00FE 0000	RAM Copy of Monitor Code
3602	...		eventually: LCD or video framebuffer
3603	...		eventually: pRAM (Protected RAM - unchanged by reset)
3604	0x00FF FFFF	[End of RAM]
3605
3606
3607System Initialization:
3608----------------------
3609
3610In the reset configuration, U-Boot starts at the reset entry point
3611(on most PowerPC systens at address 0x00000100). Because of the reset
3612configuration for CS0# this is a mirror of the onboard Flash memory.
3613To be able to re-map memory U-Boot then jumps to its link address.
3614To be able to implement the initialization code in C, a (small!)
3615initial stack is set up in the internal Dual Ported RAM (in case CPUs
3616which provide such a feature like MPC8xx or MPC8260), or in a locked
3617part of the data cache. After that, U-Boot initializes the CPU core,
3618the caches and the SIU.
3619
3620Next, all (potentially) available memory banks are mapped using a
3621preliminary mapping. For example, we put them on 512 MB boundaries
3622(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
3623on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
3624programmed for SDRAM access. Using the temporary configuration, a
3625simple memory test is run that determines the size of the SDRAM
3626banks.
3627
3628When there is more than one SDRAM bank, and the banks are of
3629different size, the largest is mapped first. For equal size, the first
3630bank (CS2#) is mapped first. The first mapping is always for address
36310x00000000, with any additional banks following immediately to create
3632contiguous memory starting from 0.
3633
3634Then, the monitor installs itself at the upper end of the SDRAM area
3635and allocates memory for use by malloc() and for the global Board
3636Info data; also, the exception vector code is copied to the low RAM
3637pages, and the final stack is set up.
3638
3639Only after this relocation will you have a "normal" C environment;
3640until that you are restricted in several ways, mostly because you are
3641running from ROM, and because the code will have to be relocated to a
3642new address in RAM.
3643
3644
3645U-Boot Porting Guide:
3646----------------------
3647
3648[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
3649list, October 2002]
3650
3651
3652int main (int argc, char *argv[])
3653{
3654	sighandler_t no_more_time;
3655
3656	signal (SIGALRM, no_more_time);
3657	alarm (PROJECT_DEADLINE - toSec (3 * WEEK));
3658
3659	if (available_money > available_manpower) {
3660		pay consultant to port U-Boot;
3661		return 0;
3662	}
3663
3664	Download latest U-Boot source;
3665
3666	Subscribe to u-boot-users mailing list;
3667
3668	if (clueless) {
3669		email ("Hi, I am new to U-Boot, how do I get started?");
3670	}
3671
3672	while (learning) {
3673		Read the README file in the top level directory;
3674		Read http://www.denx.de/twiki/bin/view/DULG/Manual ;
3675		Read the source, Luke;
3676	}
3677
3678	if (available_money > toLocalCurrency ($2500)) {
3679		Buy a BDI2000;
3680	} else {
3681		Add a lot of aggravation and time;
3682	}
3683
3684	Create your own board support subdirectory;
3685
3686	Create your own board config file;
3687
3688	while (!running) {
3689		do {
3690			Add / modify source code;
3691		} until (compiles);
3692		Debug;
3693		if (clueless)
3694			email ("Hi, I am having problems...");
3695	}
3696	Send patch file to Wolfgang;
3697
3698	return 0;
3699}
3700
3701void no_more_time (int sig)
3702{
3703      hire_a_guru();
3704}
3705
3706
3707Coding Standards:
3708-----------------
3709
3710All contributions to U-Boot should conform to the Linux kernel
3711coding style; see the file "Documentation/CodingStyle" and the script
3712"scripts/Lindent" in your Linux kernel source directory.  In sources
3713originating from U-Boot a style corresponding to "Lindent -pcs" (adding
3714spaces before parameters to function calls) is actually used.
3715
3716Source files originating from a different project (for example the
3717MTD subsystem) are generally exempt from these guidelines and are not
3718reformated to ease subsequent migration to newer versions of those
3719sources.
3720
3721Please note that U-Boot is implemented in C (and to some small parts in
3722Assembler); no C++ is used, so please do not use C++ style comments (//)
3723in your code.
3724
3725Please also stick to the following formatting rules:
3726- remove any trailing white space
3727- use TAB characters for indentation, not spaces
3728- make sure NOT to use DOS '\r\n' line feeds
3729- do not add more than 2 empty lines to source files
3730- do not add trailing empty lines to source files
3731
3732Submissions which do not conform to the standards may be returned
3733with a request to reformat the changes.
3734
3735
3736Submitting Patches:
3737-------------------
3738
3739Since the number of patches for U-Boot is growing, we need to
3740establish some rules. Submissions which do not conform to these rules
3741may be rejected, even when they contain important and valuable stuff.
3742
3743Patches shall be sent to the u-boot-users mailing list.
3744
3745When you send a patch, please include the following information with
3746it:
3747
3748* For bug fixes: a description of the bug and how your patch fixes
3749  this bug. Please try to include a way of demonstrating that the
3750  patch actually fixes something.
3751
3752* For new features: a description of the feature and your
3753  implementation.
3754
3755* A CHANGELOG entry as plaintext (separate from the patch)
3756
3757* For major contributions, your entry to the CREDITS file
3758
3759* When you add support for a new board, don't forget to add this
3760  board to the MAKEALL script, too.
3761
3762* If your patch adds new configuration options, don't forget to
3763  document these in the README file.
3764
3765* The patch itself. If you are accessing the CVS repository use "cvs
3766  update; cvs diff -puRN"; else, use "diff -purN OLD NEW". If your
3767  version of diff does not support these options, then get the latest
3768  version of GNU diff.
3769
3770  The current directory when running this command shall be the top
3771  level directory of the U-Boot source tree, or it's parent directory
3772  (i. e. please make sure that your patch includes sufficient
3773  directory information for the affected files).
3774
3775  We accept patches as plain text, MIME attachments or as uuencoded
3776  gzipped text.
3777
3778* If one logical set of modifications affects or creates several
3779  files, all these changes shall be submitted in a SINGLE patch file.
3780
3781* Changesets that contain different, unrelated modifications shall be
3782  submitted as SEPARATE patches, one patch per changeset.
3783
3784
3785Notes:
3786
3787* Before sending the patch, run the MAKEALL script on your patched
3788  source tree and make sure that no errors or warnings are reported
3789  for any of the boards.
3790
3791* Keep your modifications to the necessary minimum: A patch
3792  containing several unrelated changes or arbitrary reformats will be
3793  returned with a request to re-formatting / split it.
3794
3795* If you modify existing code, make sure that your new code does not
3796  add to the memory footprint of the code ;-) Small is beautiful!
3797  When adding new features, these should compile conditionally only
3798  (using #ifdef), and the resulting code with the new feature
3799  disabled must not need more memory than the old code without your
3800  modification.
3801
3802* Remember that there is a size limit of 40 kB per message on the
3803  u-boot-users mailing list. Compression may help.
3804