xref: /openbmc/u-boot/README (revision 6f94fa21cc7552dae9bf452e12eaa85c8897fcbb)
1 #
2 # (C) Copyright 2000 - 2013
3 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4 #
5 # SPDX-License-Identifier:	GPL-2.0+
6 #
7 
8 Summary:
9 ========
10 
11 This directory contains the source code for U-Boot, a boot loader for
12 Embedded boards based on PowerPC, ARM, MIPS and several other
13 processors, which can be installed in a boot ROM and used to
14 initialize and test the hardware or to download and run application
15 code.
16 
17 The development of U-Boot is closely related to Linux: some parts of
18 the source code originate in the Linux source tree, we have some
19 header files in common, and special provision has been made to
20 support booting of Linux images.
21 
22 Some attention has been paid to make this software easily
23 configurable and extendable. For instance, all monitor commands are
24 implemented with the same call interface, so that it's very easy to
25 add new commands. Also, instead of permanently adding rarely used
26 code (for instance hardware test utilities) to the monitor, you can
27 load and run it dynamically.
28 
29 
30 Status:
31 =======
32 
33 In general, all boards for which a configuration option exists in the
34 Makefile have been tested to some extent and can be considered
35 "working". In fact, many of them are used in production systems.
36 
37 In case of problems see the CHANGELOG file to find out who contributed
38 the specific port. In addition, there are various MAINTAINERS files
39 scattered throughout the U-Boot source identifying the people or
40 companies responsible for various boards and subsystems.
41 
42 Note: As of August, 2010, there is no longer a CHANGELOG file in the
43 actual U-Boot source tree; however, it can be created dynamically
44 from the Git log using:
45 
46 	make CHANGELOG
47 
48 
49 Where to get help:
50 ==================
51 
52 In case you have questions about, problems with or contributions for
53 U-Boot, you should send a message to the U-Boot mailing list at
54 <u-boot@lists.denx.de>. There is also an archive of previous traffic
55 on the mailing list - please search the archive before asking FAQ's.
56 Please see http://lists.denx.de/pipermail/u-boot and
57 http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58 
59 
60 Where to get source code:
61 =========================
62 
63 The U-Boot source code is maintained in the Git repository at
64 git://www.denx.de/git/u-boot.git ; you can browse it online at
65 http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66 
67 The "snapshot" links on this page allow you to download tarballs of
68 any version you might be interested in. Official releases are also
69 available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70 directory.
71 
72 Pre-built (and tested) images are available from
73 ftp://ftp.denx.de/pub/u-boot/images/
74 
75 
76 Where we come from:
77 ===================
78 
79 - start from 8xxrom sources
80 - create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81 - clean up code
82 - make it easier to add custom boards
83 - make it possible to add other [PowerPC] CPUs
84 - extend functions, especially:
85   * Provide extended interface to Linux boot loader
86   * S-Record download
87   * network boot
88   * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89 - create ARMBoot project (http://sourceforge.net/projects/armboot)
90 - add other CPU families (starting with ARM)
91 - create U-Boot project (http://sourceforge.net/projects/u-boot)
92 - current project page: see http://www.denx.de/wiki/U-Boot
93 
94 
95 Names and Spelling:
96 ===================
97 
98 The "official" name of this project is "Das U-Boot". The spelling
99 "U-Boot" shall be used in all written text (documentation, comments
100 in source files etc.). Example:
101 
102 	This is the README file for the U-Boot project.
103 
104 File names etc. shall be based on the string "u-boot". Examples:
105 
106 	include/asm-ppc/u-boot.h
107 
108 	#include <asm/u-boot.h>
109 
110 Variable names, preprocessor constants etc. shall be either based on
111 the string "u_boot" or on "U_BOOT". Example:
112 
113 	U_BOOT_VERSION		u_boot_logo
114 	IH_OS_U_BOOT		u_boot_hush_start
115 
116 
117 Versioning:
118 ===========
119 
120 Starting with the release in October 2008, the names of the releases
121 were changed from numerical release numbers without deeper meaning
122 into a time stamp based numbering. Regular releases are identified by
123 names consisting of the calendar year and month of the release date.
124 Additional fields (if present) indicate release candidates or bug fix
125 releases in "stable" maintenance trees.
126 
127 Examples:
128 	U-Boot v2009.11	    - Release November 2009
129 	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130 	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
131 
132 
133 Directory Hierarchy:
134 ====================
135 
136 /arch			Architecture specific files
137   /arc			Files generic to ARC architecture
138   /arm			Files generic to ARM architecture
139   /avr32		Files generic to AVR32 architecture
140   /blackfin		Files generic to Analog Devices Blackfin architecture
141   /m68k			Files generic to m68k architecture
142   /microblaze		Files generic to microblaze architecture
143   /mips			Files generic to MIPS architecture
144   /nds32		Files generic to NDS32 architecture
145   /nios2		Files generic to Altera NIOS2 architecture
146   /openrisc		Files generic to OpenRISC architecture
147   /powerpc		Files generic to PowerPC architecture
148   /sandbox		Files generic to HW-independent "sandbox"
149   /sh			Files generic to SH architecture
150   /sparc		Files generic to SPARC architecture
151   /x86			Files generic to x86 architecture
152 /api			Machine/arch independent API for external apps
153 /board			Board dependent files
154 /cmd			U-Boot commands functions
155 /common			Misc architecture independent functions
156 /configs		Board default configuration files
157 /disk			Code for disk drive partition handling
158 /doc			Documentation (don't expect too much)
159 /drivers		Commonly used device drivers
160 /dts			Contains Makefile for building internal U-Boot fdt.
161 /examples		Example code for standalone applications, etc.
162 /fs			Filesystem code (cramfs, ext2, jffs2, etc.)
163 /include		Header Files
164 /lib			Library routines generic to all architectures
165 /Licenses		Various license files
166 /net			Networking code
167 /post			Power On Self Test
168 /scripts		Various build scripts and Makefiles
169 /test			Various unit test files
170 /tools			Tools to build S-Record or U-Boot images, etc.
171 
172 Software Configuration:
173 =======================
174 
175 Configuration is usually done using C preprocessor defines; the
176 rationale behind that is to avoid dead code whenever possible.
177 
178 There are two classes of configuration variables:
179 
180 * Configuration _OPTIONS_:
181   These are selectable by the user and have names beginning with
182   "CONFIG_".
183 
184 * Configuration _SETTINGS_:
185   These depend on the hardware etc. and should not be meddled with if
186   you don't know what you're doing; they have names beginning with
187   "CONFIG_SYS_".
188 
189 Previously, all configuration was done by hand, which involved creating
190 symbolic links and editing configuration files manually. More recently,
191 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
192 allowing you to use the "make menuconfig" command to configure your
193 build.
194 
195 
196 Selection of Processor Architecture and Board Type:
197 ---------------------------------------------------
198 
199 For all supported boards there are ready-to-use default
200 configurations available; just type "make <board_name>_defconfig".
201 
202 Example: For a TQM823L module type:
203 
204 	cd u-boot
205 	make TQM823L_defconfig
206 
207 Note: If you're looking for the default configuration file for a board
208 you're sure used to be there but is now missing, check the file
209 doc/README.scrapyard for a list of no longer supported boards.
210 
211 Sandbox Environment:
212 --------------------
213 
214 U-Boot can be built natively to run on a Linux host using the 'sandbox'
215 board. This allows feature development which is not board- or architecture-
216 specific to be undertaken on a native platform. The sandbox is also used to
217 run some of U-Boot's tests.
218 
219 See board/sandbox/README.sandbox for more details.
220 
221 
222 Board Initialisation Flow:
223 --------------------------
224 
225 This is the intended start-up flow for boards. This should apply for both
226 SPL and U-Boot proper (i.e. they both follow the same rules).
227 
228 Note: "SPL" stands for "Secondary Program Loader," which is explained in
229 more detail later in this file.
230 
231 At present, SPL mostly uses a separate code path, but the function names
232 and roles of each function are the same. Some boards or architectures
233 may not conform to this.  At least most ARM boards which use
234 CONFIG_SPL_FRAMEWORK conform to this.
235 
236 Execution typically starts with an architecture-specific (and possibly
237 CPU-specific) start.S file, such as:
238 
239 	- arch/arm/cpu/armv7/start.S
240 	- arch/powerpc/cpu/mpc83xx/start.S
241 	- arch/mips/cpu/start.S
242 
243 and so on. From there, three functions are called; the purpose and
244 limitations of each of these functions are described below.
245 
246 lowlevel_init():
247 	- purpose: essential init to permit execution to reach board_init_f()
248 	- no global_data or BSS
249 	- there is no stack (ARMv7 may have one but it will soon be removed)
250 	- must not set up SDRAM or use console
251 	- must only do the bare minimum to allow execution to continue to
252 		board_init_f()
253 	- this is almost never needed
254 	- return normally from this function
255 
256 board_init_f():
257 	- purpose: set up the machine ready for running board_init_r():
258 		i.e. SDRAM and serial UART
259 	- global_data is available
260 	- stack is in SRAM
261 	- BSS is not available, so you cannot use global/static variables,
262 		only stack variables and global_data
263 
264 	Non-SPL-specific notes:
265 	- dram_init() is called to set up DRAM. If already done in SPL this
266 		can do nothing
267 
268 	SPL-specific notes:
269 	- you can override the entire board_init_f() function with your own
270 		version as needed.
271 	- preloader_console_init() can be called here in extremis
272 	- should set up SDRAM, and anything needed to make the UART work
273 	- these is no need to clear BSS, it will be done by crt0.S
274 	- must return normally from this function (don't call board_init_r()
275 		directly)
276 
277 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
278 this point the stack and global_data are relocated to below
279 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
280 memory.
281 
282 board_init_r():
283 	- purpose: main execution, common code
284 	- global_data is available
285 	- SDRAM is available
286 	- BSS is available, all static/global variables can be used
287 	- execution eventually continues to main_loop()
288 
289 	Non-SPL-specific notes:
290 	- U-Boot is relocated to the top of memory and is now running from
291 		there.
292 
293 	SPL-specific notes:
294 	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
295 		CONFIG_SPL_STACK_R_ADDR points into SDRAM
296 	- preloader_console_init() can be called here - typically this is
297 		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
298 		spl_board_init() function containing this call
299 	- loads U-Boot or (in falcon mode) Linux
300 
301 
302 
303 Configuration Options:
304 ----------------------
305 
306 Configuration depends on the combination of board and CPU type; all
307 such information is kept in a configuration file
308 "include/configs/<board_name>.h".
309 
310 Example: For a TQM823L module, all configuration settings are in
311 "include/configs/TQM823L.h".
312 
313 
314 Many of the options are named exactly as the corresponding Linux
315 kernel configuration options. The intention is to make it easier to
316 build a config tool - later.
317 
318 
319 The following options need to be configured:
320 
321 - CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
322 
323 - Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
324 
325 - CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
326 		Define exactly one, e.g. CONFIG_ATSTK1002
327 
328 - Marvell Family Member
329 		CONFIG_SYS_MVFS		- define it if you want to enable
330 					  multiple fs option at one time
331 					  for marvell soc family
332 
333 - 8xx CPU Options: (if using an MPC8xx CPU)
334 		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
335 					  get_gclk_freq() cannot work
336 					  e.g. if there is no 32KHz
337 					  reference PIT/RTC clock
338 		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
339 					  or XTAL/EXTAL)
340 
341 - 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
342 		CONFIG_SYS_8xx_CPUCLK_MIN
343 		CONFIG_SYS_8xx_CPUCLK_MAX
344 		CONFIG_8xx_CPUCLK_DEFAULT
345 			See doc/README.MPC866
346 
347 		CONFIG_SYS_MEASURE_CPUCLK
348 
349 		Define this to measure the actual CPU clock instead
350 		of relying on the correctness of the configured
351 		values. Mostly useful for board bringup to make sure
352 		the PLL is locked at the intended frequency. Note
353 		that this requires a (stable) reference clock (32 kHz
354 		RTC clock or CONFIG_SYS_8XX_XIN)
355 
356 		CONFIG_SYS_DELAYED_ICACHE
357 
358 		Define this option if you want to enable the
359 		ICache only when Code runs from RAM.
360 
361 - 85xx CPU Options:
362 		CONFIG_SYS_PPC64
363 
364 		Specifies that the core is a 64-bit PowerPC implementation (implements
365 		the "64" category of the Power ISA). This is necessary for ePAPR
366 		compliance, among other possible reasons.
367 
368 		CONFIG_SYS_FSL_TBCLK_DIV
369 
370 		Defines the core time base clock divider ratio compared to the
371 		system clock.  On most PQ3 devices this is 8, on newer QorIQ
372 		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
373 
374 		CONFIG_SYS_FSL_PCIE_COMPAT
375 
376 		Defines the string to utilize when trying to match PCIe device
377 		tree nodes for the given platform.
378 
379 		CONFIG_SYS_PPC_E500_DEBUG_TLB
380 
381 		Enables a temporary TLB entry to be used during boot to work
382 		around limitations in e500v1 and e500v2 external debugger
383 		support. This reduces the portions of the boot code where
384 		breakpoints and single stepping do not work.  The value of this
385 		symbol should be set to the TLB1 entry to be used for this
386 		purpose.
387 
388 		CONFIG_SYS_FSL_ERRATUM_A004510
389 
390 		Enables a workaround for erratum A004510.  If set,
391 		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
392 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
393 
394 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
395 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
396 
397 		Defines one or two SoC revisions (low 8 bits of SVR)
398 		for which the A004510 workaround should be applied.
399 
400 		The rest of SVR is either not relevant to the decision
401 		of whether the erratum is present (e.g. p2040 versus
402 		p2041) or is implied by the build target, which controls
403 		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
404 
405 		See Freescale App Note 4493 for more information about
406 		this erratum.
407 
408 		CONFIG_A003399_NOR_WORKAROUND
409 		Enables a workaround for IFC erratum A003399. It is only
410 		required during NOR boot.
411 
412 		CONFIG_A008044_WORKAROUND
413 		Enables a workaround for T1040/T1042 erratum A008044. It is only
414 		required during NAND boot and valid for Rev 1.0 SoC revision
415 
416 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
417 
418 		This is the value to write into CCSR offset 0x18600
419 		according to the A004510 workaround.
420 
421 		CONFIG_SYS_FSL_DSP_DDR_ADDR
422 		This value denotes start offset of DDR memory which is
423 		connected exclusively to the DSP cores.
424 
425 		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
426 		This value denotes start offset of M2 memory
427 		which is directly connected to the DSP core.
428 
429 		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
430 		This value denotes start offset of M3 memory which is directly
431 		connected to the DSP core.
432 
433 		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
434 		This value denotes start offset of DSP CCSR space.
435 
436 		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
437 		Single Source Clock is clocking mode present in some of FSL SoC's.
438 		In this mode, a single differential clock is used to supply
439 		clocks to the sysclock, ddrclock and usbclock.
440 
441 		CONFIG_SYS_CPC_REINIT_F
442 		This CONFIG is defined when the CPC is configured as SRAM at the
443 		time of U-Boot entry and is required to be re-initialized.
444 
445 		CONFIG_DEEP_SLEEP
446 		Indicates this SoC supports deep sleep feature. If deep sleep is
447 		supported, core will start to execute uboot when wakes up.
448 
449 - Generic CPU options:
450 		CONFIG_SYS_GENERIC_GLOBAL_DATA
451 		Defines global data is initialized in generic board board_init_f().
452 		If this macro is defined, global data is created and cleared in
453 		generic board board_init_f(). Without this macro, architecture/board
454 		should initialize global data before calling board_init_f().
455 
456 		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
457 
458 		Defines the endianess of the CPU. Implementation of those
459 		values is arch specific.
460 
461 		CONFIG_SYS_FSL_DDR
462 		Freescale DDR driver in use. This type of DDR controller is
463 		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
464 		SoCs.
465 
466 		CONFIG_SYS_FSL_DDR_ADDR
467 		Freescale DDR memory-mapped register base.
468 
469 		CONFIG_SYS_FSL_DDR_EMU
470 		Specify emulator support for DDR. Some DDR features such as
471 		deskew training are not available.
472 
473 		CONFIG_SYS_FSL_DDRC_GEN1
474 		Freescale DDR1 controller.
475 
476 		CONFIG_SYS_FSL_DDRC_GEN2
477 		Freescale DDR2 controller.
478 
479 		CONFIG_SYS_FSL_DDRC_GEN3
480 		Freescale DDR3 controller.
481 
482 		CONFIG_SYS_FSL_DDRC_GEN4
483 		Freescale DDR4 controller.
484 
485 		CONFIG_SYS_FSL_DDRC_ARM_GEN3
486 		Freescale DDR3 controller for ARM-based SoCs.
487 
488 		CONFIG_SYS_FSL_DDR1
489 		Board config to use DDR1. It can be enabled for SoCs with
490 		Freescale DDR1 or DDR2 controllers, depending on the board
491 		implemetation.
492 
493 		CONFIG_SYS_FSL_DDR2
494 		Board config to use DDR2. It can be enabled for SoCs with
495 		Freescale DDR2 or DDR3 controllers, depending on the board
496 		implementation.
497 
498 		CONFIG_SYS_FSL_DDR3
499 		Board config to use DDR3. It can be enabled for SoCs with
500 		Freescale DDR3 or DDR3L controllers.
501 
502 		CONFIG_SYS_FSL_DDR3L
503 		Board config to use DDR3L. It can be enabled for SoCs with
504 		DDR3L controllers.
505 
506 		CONFIG_SYS_FSL_DDR4
507 		Board config to use DDR4. It can be enabled for SoCs with
508 		DDR4 controllers.
509 
510 		CONFIG_SYS_FSL_IFC_BE
511 		Defines the IFC controller register space as Big Endian
512 
513 		CONFIG_SYS_FSL_IFC_LE
514 		Defines the IFC controller register space as Little Endian
515 
516 		CONFIG_SYS_FSL_PBL_PBI
517 		It enables addition of RCW (Power on reset configuration) in built image.
518 		Please refer doc/README.pblimage for more details
519 
520 		CONFIG_SYS_FSL_PBL_RCW
521 		It adds PBI(pre-boot instructions) commands in u-boot build image.
522 		PBI commands can be used to configure SoC before it starts the execution.
523 		Please refer doc/README.pblimage for more details
524 
525 		CONFIG_SPL_FSL_PBL
526 		It adds a target to create boot binary having SPL binary in PBI format
527 		concatenated with u-boot binary.
528 
529 		CONFIG_SYS_FSL_DDR_BE
530 		Defines the DDR controller register space as Big Endian
531 
532 		CONFIG_SYS_FSL_DDR_LE
533 		Defines the DDR controller register space as Little Endian
534 
535 		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
536 		Physical address from the view of DDR controllers. It is the
537 		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
538 		it could be different for ARM SoCs.
539 
540 		CONFIG_SYS_FSL_DDR_INTLV_256B
541 		DDR controller interleaving on 256-byte. This is a special
542 		interleaving mode, handled by Dickens for Freescale layerscape
543 		SoCs with ARM core.
544 
545 		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
546 		Number of controllers used as main memory.
547 
548 		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
549 		Number of controllers used for other than main memory.
550 
551 		CONFIG_SYS_FSL_HAS_DP_DDR
552 		Defines the SoC has DP-DDR used for DPAA.
553 
554 		CONFIG_SYS_FSL_SEC_BE
555 		Defines the SEC controller register space as Big Endian
556 
557 		CONFIG_SYS_FSL_SEC_LE
558 		Defines the SEC controller register space as Little Endian
559 
560 - MIPS CPU options:
561 		CONFIG_SYS_INIT_SP_OFFSET
562 
563 		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
564 		pointer. This is needed for the temporary stack before
565 		relocation.
566 
567 		CONFIG_SYS_MIPS_CACHE_MODE
568 
569 		Cache operation mode for the MIPS CPU.
570 		See also arch/mips/include/asm/mipsregs.h.
571 		Possible values are:
572 			CONF_CM_CACHABLE_NO_WA
573 			CONF_CM_CACHABLE_WA
574 			CONF_CM_UNCACHED
575 			CONF_CM_CACHABLE_NONCOHERENT
576 			CONF_CM_CACHABLE_CE
577 			CONF_CM_CACHABLE_COW
578 			CONF_CM_CACHABLE_CUW
579 			CONF_CM_CACHABLE_ACCELERATED
580 
581 		CONFIG_SYS_XWAY_EBU_BOOTCFG
582 
583 		Special option for Lantiq XWAY SoCs for booting from NOR flash.
584 		See also arch/mips/cpu/mips32/start.S.
585 
586 		CONFIG_XWAY_SWAP_BYTES
587 
588 		Enable compilation of tools/xway-swap-bytes needed for Lantiq
589 		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
590 		be swapped if a flash programmer is used.
591 
592 - ARM options:
593 		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
594 
595 		Select high exception vectors of the ARM core, e.g., do not
596 		clear the V bit of the c1 register of CP15.
597 
598 		CONFIG_SYS_THUMB_BUILD
599 
600 		Use this flag to build U-Boot using the Thumb instruction
601 		set for ARM architectures. Thumb instruction set provides
602 		better code density. For ARM architectures that support
603 		Thumb2 this flag will result in Thumb2 code generated by
604 		GCC.
605 
606 		CONFIG_ARM_ERRATA_716044
607 		CONFIG_ARM_ERRATA_742230
608 		CONFIG_ARM_ERRATA_743622
609 		CONFIG_ARM_ERRATA_751472
610 		CONFIG_ARM_ERRATA_761320
611 		CONFIG_ARM_ERRATA_773022
612 		CONFIG_ARM_ERRATA_774769
613 		CONFIG_ARM_ERRATA_794072
614 
615 		If set, the workarounds for these ARM errata are applied early
616 		during U-Boot startup. Note that these options force the
617 		workarounds to be applied; no CPU-type/version detection
618 		exists, unlike the similar options in the Linux kernel. Do not
619 		set these options unless they apply!
620 
621 		COUNTER_FREQUENCY
622 		Generic timer clock source frequency.
623 
624 		COUNTER_FREQUENCY_REAL
625 		Generic timer clock source frequency if the real clock is
626 		different from COUNTER_FREQUENCY, and can only be determined
627 		at run time.
628 
629 		NOTE: The following can be machine specific errata. These
630 		do have ability to provide rudimentary version and machine
631 		specific checks, but expect no product checks.
632 		CONFIG_ARM_ERRATA_430973
633 		CONFIG_ARM_ERRATA_454179
634 		CONFIG_ARM_ERRATA_621766
635 		CONFIG_ARM_ERRATA_798870
636 		CONFIG_ARM_ERRATA_801819
637 
638 - Tegra SoC options:
639 		CONFIG_TEGRA_SUPPORT_NON_SECURE
640 
641 		Support executing U-Boot in non-secure (NS) mode. Certain
642 		impossible actions will be skipped if the CPU is in NS mode,
643 		such as ARM architectural timer initialization.
644 
645 - Linux Kernel Interface:
646 		CONFIG_CLOCKS_IN_MHZ
647 
648 		U-Boot stores all clock information in Hz
649 		internally. For binary compatibility with older Linux
650 		kernels (which expect the clocks passed in the
651 		bd_info data to be in MHz) the environment variable
652 		"clocks_in_mhz" can be defined so that U-Boot
653 		converts clock data to MHZ before passing it to the
654 		Linux kernel.
655 		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
656 		"clocks_in_mhz=1" is automatically included in the
657 		default environment.
658 
659 		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
660 
661 		When transferring memsize parameter to Linux, some versions
662 		expect it to be in bytes, others in MB.
663 		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
664 
665 		CONFIG_OF_LIBFDT
666 
667 		New kernel versions are expecting firmware settings to be
668 		passed using flattened device trees (based on open firmware
669 		concepts).
670 
671 		CONFIG_OF_LIBFDT
672 		 * New libfdt-based support
673 		 * Adds the "fdt" command
674 		 * The bootm command automatically updates the fdt
675 
676 		OF_CPU - The proper name of the cpus node (only required for
677 			MPC512X and MPC5xxx based boards).
678 		OF_SOC - The proper name of the soc node (only required for
679 			MPC512X and MPC5xxx based boards).
680 		OF_TBCLK - The timebase frequency.
681 		OF_STDOUT_PATH - The path to the console device
682 
683 		boards with QUICC Engines require OF_QE to set UCC MAC
684 		addresses
685 
686 		CONFIG_OF_BOARD_SETUP
687 
688 		Board code has addition modification that it wants to make
689 		to the flat device tree before handing it off to the kernel
690 
691 		CONFIG_OF_SYSTEM_SETUP
692 
693 		Other code has addition modification that it wants to make
694 		to the flat device tree before handing it off to the kernel.
695 		This causes ft_system_setup() to be called before booting
696 		the kernel.
697 
698 		CONFIG_OF_IDE_FIXUP
699 
700 		U-Boot can detect if an IDE device is present or not.
701 		If not, and this new config option is activated, U-Boot
702 		removes the ATA node from the DTS before booting Linux,
703 		so the Linux IDE driver does not probe the device and
704 		crash. This is needed for buggy hardware (uc101) where
705 		no pull down resistor is connected to the signal IDE5V_DD7.
706 
707 		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
708 
709 		This setting is mandatory for all boards that have only one
710 		machine type and must be used to specify the machine type
711 		number as it appears in the ARM machine registry
712 		(see http://www.arm.linux.org.uk/developer/machines/).
713 		Only boards that have multiple machine types supported
714 		in a single configuration file and the machine type is
715 		runtime discoverable, do not have to use this setting.
716 
717 - vxWorks boot parameters:
718 
719 		bootvx constructs a valid bootline using the following
720 		environments variables: bootdev, bootfile, ipaddr, netmask,
721 		serverip, gatewayip, hostname, othbootargs.
722 		It loads the vxWorks image pointed bootfile.
723 
724 		Note: If a "bootargs" environment is defined, it will overwride
725 		the defaults discussed just above.
726 
727 - Cache Configuration:
728 		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
729 		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
730 		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
731 
732 - Cache Configuration for ARM:
733 		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
734 				      controller
735 		CONFIG_SYS_PL310_BASE - Physical base address of PL310
736 					controller register space
737 
738 - Serial Ports:
739 		CONFIG_PL010_SERIAL
740 
741 		Define this if you want support for Amba PrimeCell PL010 UARTs.
742 
743 		CONFIG_PL011_SERIAL
744 
745 		Define this if you want support for Amba PrimeCell PL011 UARTs.
746 
747 		CONFIG_PL011_CLOCK
748 
749 		If you have Amba PrimeCell PL011 UARTs, set this variable to
750 		the clock speed of the UARTs.
751 
752 		CONFIG_PL01x_PORTS
753 
754 		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
755 		define this to a list of base addresses for each (supported)
756 		port. See e.g. include/configs/versatile.h
757 
758 		CONFIG_SERIAL_HW_FLOW_CONTROL
759 
760 		Define this variable to enable hw flow control in serial driver.
761 		Current user of this option is drivers/serial/nsl16550.c driver
762 
763 - Console Interface:
764 		Depending on board, define exactly one serial port
765 		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
766 		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
767 		console by defining CONFIG_8xx_CONS_NONE
768 
769 		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
770 		port routines must be defined elsewhere
771 		(i.e. serial_init(), serial_getc(), ...)
772 
773 - Console Baudrate:
774 		CONFIG_BAUDRATE - in bps
775 		Select one of the baudrates listed in
776 		CONFIG_SYS_BAUDRATE_TABLE, see below.
777 		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
778 
779 - Console Rx buffer length
780 		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
781 		the maximum receive buffer length for the SMC.
782 		This option is actual only for 82xx and 8xx possible.
783 		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
784 		must be defined, to setup the maximum idle timeout for
785 		the SMC.
786 
787 - Autoboot Command:
788 		CONFIG_BOOTCOMMAND
789 		Only needed when CONFIG_BOOTDELAY is enabled;
790 		define a command string that is automatically executed
791 		when no character is read on the console interface
792 		within "Boot Delay" after reset.
793 
794 		CONFIG_BOOTARGS
795 		This can be used to pass arguments to the bootm
796 		command. The value of CONFIG_BOOTARGS goes into the
797 		environment value "bootargs".
798 
799 		CONFIG_RAMBOOT and CONFIG_NFSBOOT
800 		The value of these goes into the environment as
801 		"ramboot" and "nfsboot" respectively, and can be used
802 		as a convenience, when switching between booting from
803 		RAM and NFS.
804 
805 - Bootcount:
806 		CONFIG_BOOTCOUNT_LIMIT
807 		Implements a mechanism for detecting a repeating reboot
808 		cycle, see:
809 		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
810 
811 		CONFIG_BOOTCOUNT_ENV
812 		If no softreset save registers are found on the hardware
813 		"bootcount" is stored in the environment. To prevent a
814 		saveenv on all reboots, the environment variable
815 		"upgrade_available" is used. If "upgrade_available" is
816 		0, "bootcount" is always 0, if "upgrade_available" is
817 		1 "bootcount" is incremented in the environment.
818 		So the Userspace Applikation must set the "upgrade_available"
819 		and "bootcount" variable to 0, if a boot was successfully.
820 
821 - Pre-Boot Commands:
822 		CONFIG_PREBOOT
823 
824 		When this option is #defined, the existence of the
825 		environment variable "preboot" will be checked
826 		immediately before starting the CONFIG_BOOTDELAY
827 		countdown and/or running the auto-boot command resp.
828 		entering interactive mode.
829 
830 		This feature is especially useful when "preboot" is
831 		automatically generated or modified. For an example
832 		see the LWMON board specific code: here "preboot" is
833 		modified when the user holds down a certain
834 		combination of keys on the (special) keyboard when
835 		booting the systems
836 
837 - Serial Download Echo Mode:
838 		CONFIG_LOADS_ECHO
839 		If defined to 1, all characters received during a
840 		serial download (using the "loads" command) are
841 		echoed back. This might be needed by some terminal
842 		emulations (like "cu"), but may as well just take
843 		time on others. This setting #define's the initial
844 		value of the "loads_echo" environment variable.
845 
846 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
847 		CONFIG_KGDB_BAUDRATE
848 		Select one of the baudrates listed in
849 		CONFIG_SYS_BAUDRATE_TABLE, see below.
850 
851 - Monitor Functions:
852 		Monitor commands can be included or excluded
853 		from the build by using the #include files
854 		<config_cmd_all.h> and #undef'ing unwanted
855 		commands, or adding #define's for wanted commands.
856 
857 		The default command configuration includes all commands
858 		except those marked below with a "*".
859 
860 		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
861 		CONFIG_CMD_ASKENV	* ask for env variable
862 		CONFIG_CMD_BDI		  bdinfo
863 		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
864 		CONFIG_CMD_BMP		* BMP support
865 		CONFIG_CMD_BSP		* Board specific commands
866 		CONFIG_CMD_BOOTD	  bootd
867 		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
868 		CONFIG_CMD_CACHE	* icache, dcache
869 		CONFIG_CMD_CLK   	* clock command support
870 		CONFIG_CMD_CONSOLE	  coninfo
871 		CONFIG_CMD_CRC32	* crc32
872 		CONFIG_CMD_DATE		* support for RTC, date/time...
873 		CONFIG_CMD_DHCP		* DHCP support
874 		CONFIG_CMD_DIAG		* Diagnostics
875 		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
876 		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
877 		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
878 		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
879 		CONFIG_CMD_DTT		* Digital Therm and Thermostat
880 		CONFIG_CMD_ECHO		  echo arguments
881 		CONFIG_CMD_EDITENV	  edit env variable
882 		CONFIG_CMD_EEPROM	* EEPROM read/write support
883 		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
884 		CONFIG_CMD_ELF		* bootelf, bootvx
885 		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
886 		CONFIG_CMD_ENV_FLAGS	* display details about env flags
887 		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
888 		CONFIG_CMD_EXPORTENV	* export the environment
889 		CONFIG_CMD_EXT2		* ext2 command support
890 		CONFIG_CMD_EXT4		* ext4 command support
891 		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
892 					  that work for multiple fs types
893 		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
894 		CONFIG_CMD_SAVEENV	  saveenv
895 		CONFIG_CMD_FDC		* Floppy Disk Support
896 		CONFIG_CMD_FAT		* FAT command support
897 		CONFIG_CMD_FLASH	  flinfo, erase, protect
898 		CONFIG_CMD_FPGA		  FPGA device initialization support
899 		CONFIG_CMD_FUSE		* Device fuse support
900 		CONFIG_CMD_GETTIME	* Get time since boot
901 		CONFIG_CMD_GO		* the 'go' command (exec code)
902 		CONFIG_CMD_GREPENV	* search environment
903 		CONFIG_CMD_HASH		* calculate hash / digest
904 		CONFIG_CMD_I2C		* I2C serial bus support
905 		CONFIG_CMD_IDE		* IDE harddisk support
906 		CONFIG_CMD_IMI		  iminfo
907 		CONFIG_CMD_IMLS		  List all images found in NOR flash
908 		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
909 		CONFIG_CMD_IMMAP	* IMMR dump support
910 		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
911 		CONFIG_CMD_IMPORTENV	* import an environment
912 		CONFIG_CMD_INI		* import data from an ini file into the env
913 		CONFIG_CMD_IRQ		* irqinfo
914 		CONFIG_CMD_ITEST	  Integer/string test of 2 values
915 		CONFIG_CMD_JFFS2	* JFFS2 Support
916 		CONFIG_CMD_KGDB		* kgdb
917 		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
918 		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
919 					  (169.254.*.*)
920 		CONFIG_CMD_LOADB	  loadb
921 		CONFIG_CMD_LOADS	  loads
922 		CONFIG_CMD_MD5SUM	* print md5 message digest
923 					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
924 		CONFIG_CMD_MEMINFO	* Display detailed memory information
925 		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
926 					  loop, loopw
927 		CONFIG_CMD_MEMTEST	* mtest
928 		CONFIG_CMD_MISC		  Misc functions like sleep etc
929 		CONFIG_CMD_MMC		* MMC memory mapped support
930 		CONFIG_CMD_MII		* MII utility commands
931 		CONFIG_CMD_MTDPARTS	* MTD partition support
932 		CONFIG_CMD_NAND		* NAND support
933 		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
934 		CONFIG_CMD_NFS		  NFS support
935 		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
936 		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
937 		CONFIG_CMD_PCI		* pciinfo
938 		CONFIG_CMD_PCMCIA		* PCMCIA support
939 		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
940 					  host
941 		CONFIG_CMD_PORTIO	* Port I/O
942 		CONFIG_CMD_READ		* Read raw data from partition
943 		CONFIG_CMD_REGINFO	* Register dump
944 		CONFIG_CMD_RUN		  run command in env variable
945 		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
946 		CONFIG_CMD_SAVES	* save S record dump
947 		CONFIG_SCSI		* SCSI Support
948 		CONFIG_CMD_SDRAM	* print SDRAM configuration information
949 					  (requires CONFIG_CMD_I2C)
950 		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
951 					  (4xx only)
952 		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
953 		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
954 					  (requires CONFIG_CMD_MEMORY)
955 		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
956 		CONFIG_CMD_SOURCE	  "source" command Support
957 		CONFIG_CMD_SPI		* SPI serial bus support
958 		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
959 		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
960 		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
961 		CONFIG_CMD_TIMER	* access to the system tick timer
962 		CONFIG_CMD_USB		* USB support
963 		CONFIG_CMD_CDP		* Cisco Discover Protocol support
964 		CONFIG_CMD_MFSL		* Microblaze FSL support
965 		CONFIG_CMD_XIMG		  Load part of Multi Image
966 		CONFIG_CMD_UUID		* Generate random UUID or GUID string
967 
968 		EXAMPLE: If you want all functions except of network
969 		support you can write:
970 
971 		#include "config_cmd_all.h"
972 		#undef CONFIG_CMD_NET
973 
974 	Other Commands:
975 		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
976 
977 	Note:	Don't enable the "icache" and "dcache" commands
978 		(configuration option CONFIG_CMD_CACHE) unless you know
979 		what you (and your U-Boot users) are doing. Data
980 		cache cannot be enabled on systems like the 8xx or
981 		8260 (where accesses to the IMMR region must be
982 		uncached), and it cannot be disabled on all other
983 		systems where we (mis-) use the data cache to hold an
984 		initial stack and some data.
985 
986 
987 		XXX - this list needs to get updated!
988 
989 - Removal of commands
990 		If no commands are needed to boot, you can disable
991 		CONFIG_CMDLINE to remove them. In this case, the command line
992 		will not be available, and when U-Boot wants to execute the
993 		boot command (on start-up) it will call board_run_command()
994 		instead. This can reduce image size significantly for very
995 		simple boot procedures.
996 
997 - Regular expression support:
998 		CONFIG_REGEX
999 		If this variable is defined, U-Boot is linked against
1000 		the SLRE (Super Light Regular Expression) library,
1001 		which adds regex support to some commands, as for
1002 		example "env grep" and "setexpr".
1003 
1004 - Device tree:
1005 		CONFIG_OF_CONTROL
1006 		If this variable is defined, U-Boot will use a device tree
1007 		to configure its devices, instead of relying on statically
1008 		compiled #defines in the board file. This option is
1009 		experimental and only available on a few boards. The device
1010 		tree is available in the global data as gd->fdt_blob.
1011 
1012 		U-Boot needs to get its device tree from somewhere. This can
1013 		be done using one of the two options below:
1014 
1015 		CONFIG_OF_EMBED
1016 		If this variable is defined, U-Boot will embed a device tree
1017 		binary in its image. This device tree file should be in the
1018 		board directory and called <soc>-<board>.dts. The binary file
1019 		is then picked up in board_init_f() and made available through
1020 		the global data structure as gd->blob.
1021 
1022 		CONFIG_OF_SEPARATE
1023 		If this variable is defined, U-Boot will build a device tree
1024 		binary. It will be called u-boot.dtb. Architecture-specific
1025 		code will locate it at run-time. Generally this works by:
1026 
1027 			cat u-boot.bin u-boot.dtb >image.bin
1028 
1029 		and in fact, U-Boot does this for you, creating a file called
1030 		u-boot-dtb.bin which is useful in the common case. You can
1031 		still use the individual files if you need something more
1032 		exotic.
1033 
1034 - Watchdog:
1035 		CONFIG_WATCHDOG
1036 		If this variable is defined, it enables watchdog
1037 		support for the SoC. There must be support in the SoC
1038 		specific code for a watchdog. For the 8xx and 8260
1039 		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1040 		register.  When supported for a specific SoC is
1041 		available, then no further board specific code should
1042 		be needed to use it.
1043 
1044 		CONFIG_HW_WATCHDOG
1045 		When using a watchdog circuitry external to the used
1046 		SoC, then define this variable and provide board
1047 		specific code for the "hw_watchdog_reset" function.
1048 
1049 		CONFIG_AT91_HW_WDT_TIMEOUT
1050 		specify the timeout in seconds. default 2 seconds.
1051 
1052 - U-Boot Version:
1053 		CONFIG_VERSION_VARIABLE
1054 		If this variable is defined, an environment variable
1055 		named "ver" is created by U-Boot showing the U-Boot
1056 		version as printed by the "version" command.
1057 		Any change to this variable will be reverted at the
1058 		next reset.
1059 
1060 - Real-Time Clock:
1061 
1062 		When CONFIG_CMD_DATE is selected, the type of the RTC
1063 		has to be selected, too. Define exactly one of the
1064 		following options:
1065 
1066 		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1067 		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1068 		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1069 		CONFIG_RTC_MC146818	- use MC146818 RTC
1070 		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1071 		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1072 		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1073 		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1074 		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1075 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1076 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1077 		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1078 		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1079 					  RV3029 RTC.
1080 
1081 		Note that if the RTC uses I2C, then the I2C interface
1082 		must also be configured. See I2C Support, below.
1083 
1084 - GPIO Support:
1085 		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1086 
1087 		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1088 		chip-ngpio pairs that tell the PCA953X driver the number of
1089 		pins supported by a particular chip.
1090 
1091 		Note that if the GPIO device uses I2C, then the I2C interface
1092 		must also be configured. See I2C Support, below.
1093 
1094 - I/O tracing:
1095 		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1096 		accesses and can checksum them or write a list of them out
1097 		to memory. See the 'iotrace' command for details. This is
1098 		useful for testing device drivers since it can confirm that
1099 		the driver behaves the same way before and after a code
1100 		change. Currently this is supported on sandbox and arm. To
1101 		add support for your architecture, add '#include <iotrace.h>'
1102 		to the bottom of arch/<arch>/include/asm/io.h and test.
1103 
1104 		Example output from the 'iotrace stats' command is below.
1105 		Note that if the trace buffer is exhausted, the checksum will
1106 		still continue to operate.
1107 
1108 			iotrace is enabled
1109 			Start:  10000000	(buffer start address)
1110 			Size:   00010000	(buffer size)
1111 			Offset: 00000120	(current buffer offset)
1112 			Output: 10000120	(start + offset)
1113 			Count:  00000018	(number of trace records)
1114 			CRC32:  9526fb66	(CRC32 of all trace records)
1115 
1116 - Timestamp Support:
1117 
1118 		When CONFIG_TIMESTAMP is selected, the timestamp
1119 		(date and time) of an image is printed by image
1120 		commands like bootm or iminfo. This option is
1121 		automatically enabled when you select CONFIG_CMD_DATE .
1122 
1123 - Partition Labels (disklabels) Supported:
1124 		Zero or more of the following:
1125 		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1126 		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1127 				       Intel architecture, USB sticks, etc.
1128 		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1129 		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1130 				       bootloader.  Note 2TB partition limit; see
1131 				       disk/part_efi.c
1132 		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1133 
1134 		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1135 		CONFIG_SCSI) you must configure support for at
1136 		least one non-MTD partition type as well.
1137 
1138 - IDE Reset method:
1139 		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1140 		board configurations files but used nowhere!
1141 
1142 		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1143 		be performed by calling the function
1144 			ide_set_reset(int reset)
1145 		which has to be defined in a board specific file
1146 
1147 - ATAPI Support:
1148 		CONFIG_ATAPI
1149 
1150 		Set this to enable ATAPI support.
1151 
1152 - LBA48 Support
1153 		CONFIG_LBA48
1154 
1155 		Set this to enable support for disks larger than 137GB
1156 		Also look at CONFIG_SYS_64BIT_LBA.
1157 		Whithout these , LBA48 support uses 32bit variables and will 'only'
1158 		support disks up to 2.1TB.
1159 
1160 		CONFIG_SYS_64BIT_LBA:
1161 			When enabled, makes the IDE subsystem use 64bit sector addresses.
1162 			Default is 32bit.
1163 
1164 - SCSI Support:
1165 		At the moment only there is only support for the
1166 		SYM53C8XX SCSI controller; define
1167 		CONFIG_SCSI_SYM53C8XX to enable it.
1168 
1169 		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1170 		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1171 		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1172 		maximum numbers of LUNs, SCSI ID's and target
1173 		devices.
1174 		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1175 
1176 		The environment variable 'scsidevs' is set to the number of
1177 		SCSI devices found during the last scan.
1178 
1179 - NETWORK Support (PCI):
1180 		CONFIG_E1000
1181 		Support for Intel 8254x/8257x gigabit chips.
1182 
1183 		CONFIG_E1000_SPI
1184 		Utility code for direct access to the SPI bus on Intel 8257x.
1185 		This does not do anything useful unless you set at least one
1186 		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1187 
1188 		CONFIG_E1000_SPI_GENERIC
1189 		Allow generic access to the SPI bus on the Intel 8257x, for
1190 		example with the "sspi" command.
1191 
1192 		CONFIG_CMD_E1000
1193 		Management command for E1000 devices.  When used on devices
1194 		with SPI support you can reprogram the EEPROM from U-Boot.
1195 
1196 		CONFIG_EEPRO100
1197 		Support for Intel 82557/82559/82559ER chips.
1198 		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1199 		write routine for first time initialisation.
1200 
1201 		CONFIG_TULIP
1202 		Support for Digital 2114x chips.
1203 		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1204 		modem chip initialisation (KS8761/QS6611).
1205 
1206 		CONFIG_NATSEMI
1207 		Support for National dp83815 chips.
1208 
1209 		CONFIG_NS8382X
1210 		Support for National dp8382[01] gigabit chips.
1211 
1212 - NETWORK Support (other):
1213 
1214 		CONFIG_DRIVER_AT91EMAC
1215 		Support for AT91RM9200 EMAC.
1216 
1217 			CONFIG_RMII
1218 			Define this to use reduced MII inteface
1219 
1220 			CONFIG_DRIVER_AT91EMAC_QUIET
1221 			If this defined, the driver is quiet.
1222 			The driver doen't show link status messages.
1223 
1224 		CONFIG_CALXEDA_XGMAC
1225 		Support for the Calxeda XGMAC device
1226 
1227 		CONFIG_LAN91C96
1228 		Support for SMSC's LAN91C96 chips.
1229 
1230 			CONFIG_LAN91C96_USE_32_BIT
1231 			Define this to enable 32 bit addressing
1232 
1233 		CONFIG_SMC91111
1234 		Support for SMSC's LAN91C111 chip
1235 
1236 			CONFIG_SMC91111_BASE
1237 			Define this to hold the physical address
1238 			of the device (I/O space)
1239 
1240 			CONFIG_SMC_USE_32_BIT
1241 			Define this if data bus is 32 bits
1242 
1243 			CONFIG_SMC_USE_IOFUNCS
1244 			Define this to use i/o functions instead of macros
1245 			(some hardware wont work with macros)
1246 
1247 		CONFIG_DRIVER_TI_EMAC
1248 		Support for davinci emac
1249 
1250 			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1251 			Define this if you have more then 3 PHYs.
1252 
1253 		CONFIG_FTGMAC100
1254 		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1255 
1256 			CONFIG_FTGMAC100_EGIGA
1257 			Define this to use GE link update with gigabit PHY.
1258 			Define this if FTGMAC100 is connected to gigabit PHY.
1259 			If your system has 10/100 PHY only, it might not occur
1260 			wrong behavior. Because PHY usually return timeout or
1261 			useless data when polling gigabit status and gigabit
1262 			control registers. This behavior won't affect the
1263 			correctnessof 10/100 link speed update.
1264 
1265 		CONFIG_SMC911X
1266 		Support for SMSC's LAN911x and LAN921x chips
1267 
1268 			CONFIG_SMC911X_BASE
1269 			Define this to hold the physical address
1270 			of the device (I/O space)
1271 
1272 			CONFIG_SMC911X_32_BIT
1273 			Define this if data bus is 32 bits
1274 
1275 			CONFIG_SMC911X_16_BIT
1276 			Define this if data bus is 16 bits. If your processor
1277 			automatically converts one 32 bit word to two 16 bit
1278 			words you may also try CONFIG_SMC911X_32_BIT.
1279 
1280 		CONFIG_SH_ETHER
1281 		Support for Renesas on-chip Ethernet controller
1282 
1283 			CONFIG_SH_ETHER_USE_PORT
1284 			Define the number of ports to be used
1285 
1286 			CONFIG_SH_ETHER_PHY_ADDR
1287 			Define the ETH PHY's address
1288 
1289 			CONFIG_SH_ETHER_CACHE_WRITEBACK
1290 			If this option is set, the driver enables cache flush.
1291 
1292 - PWM Support:
1293 		CONFIG_PWM_IMX
1294 		Support for PWM module on the imx6.
1295 
1296 - TPM Support:
1297 		CONFIG_TPM
1298 		Support TPM devices.
1299 
1300 		CONFIG_TPM_TIS_INFINEON
1301 		Support for Infineon i2c bus TPM devices. Only one device
1302 		per system is supported at this time.
1303 
1304 			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1305 			Define the burst count bytes upper limit
1306 
1307 		CONFIG_TPM_ST33ZP24
1308 		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1309 
1310 			CONFIG_TPM_ST33ZP24_I2C
1311 			Support for STMicroelectronics ST33ZP24 I2C devices.
1312 			Requires TPM_ST33ZP24 and I2C.
1313 
1314 			CONFIG_TPM_ST33ZP24_SPI
1315 			Support for STMicroelectronics ST33ZP24 SPI devices.
1316 			Requires TPM_ST33ZP24 and SPI.
1317 
1318 		CONFIG_TPM_ATMEL_TWI
1319 		Support for Atmel TWI TPM device. Requires I2C support.
1320 
1321 		CONFIG_TPM_TIS_LPC
1322 		Support for generic parallel port TPM devices. Only one device
1323 		per system is supported at this time.
1324 
1325 			CONFIG_TPM_TIS_BASE_ADDRESS
1326 			Base address where the generic TPM device is mapped
1327 			to. Contemporary x86 systems usually map it at
1328 			0xfed40000.
1329 
1330 		CONFIG_CMD_TPM
1331 		Add tpm monitor functions.
1332 		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1333 		provides monitor access to authorized functions.
1334 
1335 		CONFIG_TPM
1336 		Define this to enable the TPM support library which provides
1337 		functional interfaces to some TPM commands.
1338 		Requires support for a TPM device.
1339 
1340 		CONFIG_TPM_AUTH_SESSIONS
1341 		Define this to enable authorized functions in the TPM library.
1342 		Requires CONFIG_TPM and CONFIG_SHA1.
1343 
1344 - USB Support:
1345 		At the moment only the UHCI host controller is
1346 		supported (PIP405, MIP405, MPC5200); define
1347 		CONFIG_USB_UHCI to enable it.
1348 		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1349 		and define CONFIG_USB_STORAGE to enable the USB
1350 		storage devices.
1351 		Note:
1352 		Supported are USB Keyboards and USB Floppy drives
1353 		(TEAC FD-05PUB).
1354 		MPC5200 USB requires additional defines:
1355 			CONFIG_USB_CLOCK
1356 				for 528 MHz Clock: 0x0001bbbb
1357 			CONFIG_PSC3_USB
1358 				for USB on PSC3
1359 			CONFIG_USB_CONFIG
1360 				for differential drivers: 0x00001000
1361 				for single ended drivers: 0x00005000
1362 				for differential drivers on PSC3: 0x00000100
1363 				for single ended drivers on PSC3: 0x00004100
1364 			CONFIG_SYS_USB_EVENT_POLL
1365 				May be defined to allow interrupt polling
1366 				instead of using asynchronous interrupts
1367 
1368 		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1369 		txfilltuning field in the EHCI controller on reset.
1370 
1371 		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1372 		HW module registers.
1373 
1374 - USB Device:
1375 		Define the below if you wish to use the USB console.
1376 		Once firmware is rebuilt from a serial console issue the
1377 		command "setenv stdin usbtty; setenv stdout usbtty" and
1378 		attach your USB cable. The Unix command "dmesg" should print
1379 		it has found a new device. The environment variable usbtty
1380 		can be set to gserial or cdc_acm to enable your device to
1381 		appear to a USB host as a Linux gserial device or a
1382 		Common Device Class Abstract Control Model serial device.
1383 		If you select usbtty = gserial you should be able to enumerate
1384 		a Linux host by
1385 		# modprobe usbserial vendor=0xVendorID product=0xProductID
1386 		else if using cdc_acm, simply setting the environment
1387 		variable usbtty to be cdc_acm should suffice. The following
1388 		might be defined in YourBoardName.h
1389 
1390 			CONFIG_USB_DEVICE
1391 			Define this to build a UDC device
1392 
1393 			CONFIG_USB_TTY
1394 			Define this to have a tty type of device available to
1395 			talk to the UDC device
1396 
1397 			CONFIG_USBD_HS
1398 			Define this to enable the high speed support for usb
1399 			device and usbtty. If this feature is enabled, a routine
1400 			int is_usbd_high_speed(void)
1401 			also needs to be defined by the driver to dynamically poll
1402 			whether the enumeration has succeded at high speed or full
1403 			speed.
1404 
1405 			CONFIG_SYS_CONSOLE_IS_IN_ENV
1406 			Define this if you want stdin, stdout &/or stderr to
1407 			be set to usbtty.
1408 
1409 			mpc8xx:
1410 				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1411 				Derive USB clock from external clock "blah"
1412 				- CONFIG_SYS_USB_EXTC_CLK 0x02
1413 
1414 		If you have a USB-IF assigned VendorID then you may wish to
1415 		define your own vendor specific values either in BoardName.h
1416 		or directly in usbd_vendor_info.h. If you don't define
1417 		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1418 		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1419 		should pretend to be a Linux device to it's target host.
1420 
1421 			CONFIG_USBD_MANUFACTURER
1422 			Define this string as the name of your company for
1423 			- CONFIG_USBD_MANUFACTURER "my company"
1424 
1425 			CONFIG_USBD_PRODUCT_NAME
1426 			Define this string as the name of your product
1427 			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1428 
1429 			CONFIG_USBD_VENDORID
1430 			Define this as your assigned Vendor ID from the USB
1431 			Implementors Forum. This *must* be a genuine Vendor ID
1432 			to avoid polluting the USB namespace.
1433 			- CONFIG_USBD_VENDORID 0xFFFF
1434 
1435 			CONFIG_USBD_PRODUCTID
1436 			Define this as the unique Product ID
1437 			for your device
1438 			- CONFIG_USBD_PRODUCTID 0xFFFF
1439 
1440 - ULPI Layer Support:
1441 		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1442 		the generic ULPI layer. The generic layer accesses the ULPI PHY
1443 		via the platform viewport, so you need both the genric layer and
1444 		the viewport enabled. Currently only Chipidea/ARC based
1445 		viewport is supported.
1446 		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1447 		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1448 		If your ULPI phy needs a different reference clock than the
1449 		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1450 		the appropriate value in Hz.
1451 
1452 - MMC Support:
1453 		The MMC controller on the Intel PXA is supported. To
1454 		enable this define CONFIG_MMC. The MMC can be
1455 		accessed from the boot prompt by mapping the device
1456 		to physical memory similar to flash. Command line is
1457 		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1458 		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1459 
1460 		CONFIG_SH_MMCIF
1461 		Support for Renesas on-chip MMCIF controller
1462 
1463 			CONFIG_SH_MMCIF_ADDR
1464 			Define the base address of MMCIF registers
1465 
1466 			CONFIG_SH_MMCIF_CLK
1467 			Define the clock frequency for MMCIF
1468 
1469 		CONFIG_GENERIC_MMC
1470 		Enable the generic MMC driver
1471 
1472 		CONFIG_SUPPORT_EMMC_BOOT
1473 		Enable some additional features of the eMMC boot partitions.
1474 
1475 		CONFIG_SUPPORT_EMMC_RPMB
1476 		Enable the commands for reading, writing and programming the
1477 		key for the Replay Protection Memory Block partition in eMMC.
1478 
1479 - USB Device Firmware Update (DFU) class support:
1480 		CONFIG_USB_FUNCTION_DFU
1481 		This enables the USB portion of the DFU USB class
1482 
1483 		CONFIG_CMD_DFU
1484 		This enables the command "dfu" which is used to have
1485 		U-Boot create a DFU class device via USB.  This command
1486 		requires that the "dfu_alt_info" environment variable be
1487 		set and define the alt settings to expose to the host.
1488 
1489 		CONFIG_DFU_MMC
1490 		This enables support for exposing (e)MMC devices via DFU.
1491 
1492 		CONFIG_DFU_NAND
1493 		This enables support for exposing NAND devices via DFU.
1494 
1495 		CONFIG_DFU_RAM
1496 		This enables support for exposing RAM via DFU.
1497 		Note: DFU spec refer to non-volatile memory usage, but
1498 		allow usages beyond the scope of spec - here RAM usage,
1499 		one that would help mostly the developer.
1500 
1501 		CONFIG_SYS_DFU_DATA_BUF_SIZE
1502 		Dfu transfer uses a buffer before writing data to the
1503 		raw storage device. Make the size (in bytes) of this buffer
1504 		configurable. The size of this buffer is also configurable
1505 		through the "dfu_bufsiz" environment variable.
1506 
1507 		CONFIG_SYS_DFU_MAX_FILE_SIZE
1508 		When updating files rather than the raw storage device,
1509 		we use a static buffer to copy the file into and then write
1510 		the buffer once we've been given the whole file.  Define
1511 		this to the maximum filesize (in bytes) for the buffer.
1512 		Default is 4 MiB if undefined.
1513 
1514 		DFU_DEFAULT_POLL_TIMEOUT
1515 		Poll timeout [ms], is the timeout a device can send to the
1516 		host. The host must wait for this timeout before sending
1517 		a subsequent DFU_GET_STATUS request to the device.
1518 
1519 		DFU_MANIFEST_POLL_TIMEOUT
1520 		Poll timeout [ms], which the device sends to the host when
1521 		entering dfuMANIFEST state. Host waits this timeout, before
1522 		sending again an USB request to the device.
1523 
1524 - USB Device Android Fastboot support:
1525 		CONFIG_USB_FUNCTION_FASTBOOT
1526 		This enables the USB part of the fastboot gadget
1527 
1528 		CONFIG_CMD_FASTBOOT
1529 		This enables the command "fastboot" which enables the Android
1530 		fastboot mode for the platform's USB device. Fastboot is a USB
1531 		protocol for downloading images, flashing and device control
1532 		used on Android devices.
1533 		See doc/README.android-fastboot for more information.
1534 
1535 		CONFIG_ANDROID_BOOT_IMAGE
1536 		This enables support for booting images which use the Android
1537 		image format header.
1538 
1539 		CONFIG_FASTBOOT_BUF_ADDR
1540 		The fastboot protocol requires a large memory buffer for
1541 		downloads. Define this to the starting RAM address to use for
1542 		downloaded images.
1543 
1544 		CONFIG_FASTBOOT_BUF_SIZE
1545 		The fastboot protocol requires a large memory buffer for
1546 		downloads. This buffer should be as large as possible for a
1547 		platform. Define this to the size available RAM for fastboot.
1548 
1549 		CONFIG_FASTBOOT_FLASH
1550 		The fastboot protocol includes a "flash" command for writing
1551 		the downloaded image to a non-volatile storage device. Define
1552 		this to enable the "fastboot flash" command.
1553 
1554 		CONFIG_FASTBOOT_FLASH_MMC_DEV
1555 		The fastboot "flash" command requires additional information
1556 		regarding the non-volatile storage device. Define this to
1557 		the eMMC device that fastboot should use to store the image.
1558 
1559 		CONFIG_FASTBOOT_GPT_NAME
1560 		The fastboot "flash" command supports writing the downloaded
1561 		image to the Protective MBR and the Primary GUID Partition
1562 		Table. (Additionally, this downloaded image is post-processed
1563 		to generate and write the Backup GUID Partition Table.)
1564 		This occurs when the specified "partition name" on the
1565 		"fastboot flash" command line matches this value.
1566 		The default is "gpt" if undefined.
1567 
1568 		CONFIG_FASTBOOT_MBR_NAME
1569 		The fastboot "flash" command supports writing the downloaded
1570 		image to DOS MBR.
1571 		This occurs when the "partition name" specified on the
1572 		"fastboot flash" command line matches this value.
1573 		If not defined the default value "mbr" is used.
1574 
1575 - Journaling Flash filesystem support:
1576 		CONFIG_JFFS2_NAND
1577 		Define these for a default partition on a NAND device
1578 
1579 		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1580 		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1581 		Define these for a default partition on a NOR device
1582 
1583 - FAT(File Allocation Table) filesystem write function support:
1584 		CONFIG_FAT_WRITE
1585 
1586 		Define this to enable support for saving memory data as a
1587 		file in FAT formatted partition.
1588 
1589 		This will also enable the command "fatwrite" enabling the
1590 		user to write files to FAT.
1591 
1592 CBFS (Coreboot Filesystem) support
1593 		CONFIG_CMD_CBFS
1594 
1595 		Define this to enable support for reading from a Coreboot
1596 		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1597 		and cbfsload.
1598 
1599 - FAT(File Allocation Table) filesystem cluster size:
1600 		CONFIG_FS_FAT_MAX_CLUSTSIZE
1601 
1602 		Define the max cluster size for fat operations else
1603 		a default value of 65536 will be defined.
1604 
1605 - Keyboard Support:
1606 		See Kconfig help for available keyboard drivers.
1607 
1608 		CONFIG_KEYBOARD
1609 
1610 		Define this to enable a custom keyboard support.
1611 		This simply calls drv_keyboard_init() which must be
1612 		defined in your board-specific files. This option is deprecated
1613 		and is only used by novena. For new boards, use driver model
1614 		instead.
1615 
1616 - Video support:
1617 		CONFIG_FSL_DIU_FB
1618 		Enable the Freescale DIU video driver.	Reference boards for
1619 		SOCs that have a DIU should define this macro to enable DIU
1620 		support, and should also define these other macros:
1621 
1622 			CONFIG_SYS_DIU_ADDR
1623 			CONFIG_VIDEO
1624 			CONFIG_CMD_BMP
1625 			CONFIG_CFB_CONSOLE
1626 			CONFIG_VIDEO_SW_CURSOR
1627 			CONFIG_VGA_AS_SINGLE_DEVICE
1628 			CONFIG_VIDEO_LOGO
1629 			CONFIG_VIDEO_BMP_LOGO
1630 
1631 		The DIU driver will look for the 'video-mode' environment
1632 		variable, and if defined, enable the DIU as a console during
1633 		boot.  See the documentation file doc/README.video for a
1634 		description of this variable.
1635 
1636 - LCD Support:	CONFIG_LCD
1637 
1638 		Define this to enable LCD support (for output to LCD
1639 		display); also select one of the supported displays
1640 		by defining one of these:
1641 
1642 		CONFIG_ATMEL_LCD:
1643 
1644 			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1645 
1646 		CONFIG_NEC_NL6448AC33:
1647 
1648 			NEC NL6448AC33-18. Active, color, single scan.
1649 
1650 		CONFIG_NEC_NL6448BC20
1651 
1652 			NEC NL6448BC20-08. 6.5", 640x480.
1653 			Active, color, single scan.
1654 
1655 		CONFIG_NEC_NL6448BC33_54
1656 
1657 			NEC NL6448BC33-54. 10.4", 640x480.
1658 			Active, color, single scan.
1659 
1660 		CONFIG_SHARP_16x9
1661 
1662 			Sharp 320x240. Active, color, single scan.
1663 			It isn't 16x9, and I am not sure what it is.
1664 
1665 		CONFIG_SHARP_LQ64D341
1666 
1667 			Sharp LQ64D341 display, 640x480.
1668 			Active, color, single scan.
1669 
1670 		CONFIG_HLD1045
1671 
1672 			HLD1045 display, 640x480.
1673 			Active, color, single scan.
1674 
1675 		CONFIG_OPTREX_BW
1676 
1677 			Optrex	 CBL50840-2 NF-FW 99 22 M5
1678 			or
1679 			Hitachi	 LMG6912RPFC-00T
1680 			or
1681 			Hitachi	 SP14Q002
1682 
1683 			320x240. Black & white.
1684 
1685 		Normally display is black on white background; define
1686 		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1687 
1688 		CONFIG_LCD_ALIGNMENT
1689 
1690 		Normally the LCD is page-aligned (typically 4KB). If this is
1691 		defined then the LCD will be aligned to this value instead.
1692 		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1693 		here, since it is cheaper to change data cache settings on
1694 		a per-section basis.
1695 
1696 
1697 		CONFIG_LCD_ROTATION
1698 
1699 		Sometimes, for example if the display is mounted in portrait
1700 		mode or even if it's mounted landscape but rotated by 180degree,
1701 		we need to rotate our content of the display relative to the
1702 		framebuffer, so that user can read the messages which are
1703 		printed out.
1704 		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1705 		initialized with a given rotation from "vl_rot" out of
1706 		"vidinfo_t" which is provided by the board specific code.
1707 		The value for vl_rot is coded as following (matching to
1708 		fbcon=rotate:<n> linux-kernel commandline):
1709 		0 = no rotation respectively 0 degree
1710 		1 = 90 degree rotation
1711 		2 = 180 degree rotation
1712 		3 = 270 degree rotation
1713 
1714 		If CONFIG_LCD_ROTATION is not defined, the console will be
1715 		initialized with 0degree rotation.
1716 
1717 		CONFIG_LCD_BMP_RLE8
1718 
1719 		Support drawing of RLE8-compressed bitmaps on the LCD.
1720 
1721 		CONFIG_I2C_EDID
1722 
1723 		Enables an 'i2c edid' command which can read EDID
1724 		information over I2C from an attached LCD display.
1725 
1726 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1727 
1728 		If this option is set, the environment is checked for
1729 		a variable "splashimage". If found, the usual display
1730 		of logo, copyright and system information on the LCD
1731 		is suppressed and the BMP image at the address
1732 		specified in "splashimage" is loaded instead. The
1733 		console is redirected to the "nulldev", too. This
1734 		allows for a "silent" boot where a splash screen is
1735 		loaded very quickly after power-on.
1736 
1737 		CONFIG_SPLASHIMAGE_GUARD
1738 
1739 		If this option is set, then U-Boot will prevent the environment
1740 		variable "splashimage" from being set to a problematic address
1741 		(see doc/README.displaying-bmps).
1742 		This option is useful for targets where, due to alignment
1743 		restrictions, an improperly aligned BMP image will cause a data
1744 		abort. If you think you will not have problems with unaligned
1745 		accesses (for example because your toolchain prevents them)
1746 		there is no need to set this option.
1747 
1748 		CONFIG_SPLASH_SCREEN_ALIGN
1749 
1750 		If this option is set the splash image can be freely positioned
1751 		on the screen. Environment variable "splashpos" specifies the
1752 		position as "x,y". If a positive number is given it is used as
1753 		number of pixel from left/top. If a negative number is given it
1754 		is used as number of pixel from right/bottom. You can also
1755 		specify 'm' for centering the image.
1756 
1757 		Example:
1758 		setenv splashpos m,m
1759 			=> image at center of screen
1760 
1761 		setenv splashpos 30,20
1762 			=> image at x = 30 and y = 20
1763 
1764 		setenv splashpos -10,m
1765 			=> vertically centered image
1766 			   at x = dspWidth - bmpWidth - 9
1767 
1768 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1769 
1770 		If this option is set, additionally to standard BMP
1771 		images, gzipped BMP images can be displayed via the
1772 		splashscreen support or the bmp command.
1773 
1774 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1775 
1776 		If this option is set, 8-bit RLE compressed BMP images
1777 		can be displayed via the splashscreen support or the
1778 		bmp command.
1779 
1780 - Do compressing for memory range:
1781 		CONFIG_CMD_ZIP
1782 
1783 		If this option is set, it would use zlib deflate method
1784 		to compress the specified memory at its best effort.
1785 
1786 - Compression support:
1787 		CONFIG_GZIP
1788 
1789 		Enabled by default to support gzip compressed images.
1790 
1791 		CONFIG_BZIP2
1792 
1793 		If this option is set, support for bzip2 compressed
1794 		images is included. If not, only uncompressed and gzip
1795 		compressed images are supported.
1796 
1797 		NOTE: the bzip2 algorithm requires a lot of RAM, so
1798 		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1799 		be at least 4MB.
1800 
1801 		CONFIG_LZMA
1802 
1803 		If this option is set, support for lzma compressed
1804 		images is included.
1805 
1806 		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1807 		requires an amount of dynamic memory that is given by the
1808 		formula:
1809 
1810 			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1811 
1812 		Where lc and lp stand for, respectively, Literal context bits
1813 		and Literal pos bits.
1814 
1815 		This value is upper-bounded by 14MB in the worst case. Anyway,
1816 		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1817 		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1818 		a very small buffer.
1819 
1820 		Use the lzmainfo tool to determinate the lc and lp values and
1821 		then calculate the amount of needed dynamic memory (ensuring
1822 		the appropriate CONFIG_SYS_MALLOC_LEN value).
1823 
1824 		CONFIG_LZO
1825 
1826 		If this option is set, support for LZO compressed images
1827 		is included.
1828 
1829 - MII/PHY support:
1830 		CONFIG_PHY_ADDR
1831 
1832 		The address of PHY on MII bus.
1833 
1834 		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1835 
1836 		The clock frequency of the MII bus
1837 
1838 		CONFIG_PHY_GIGE
1839 
1840 		If this option is set, support for speed/duplex
1841 		detection of gigabit PHY is included.
1842 
1843 		CONFIG_PHY_RESET_DELAY
1844 
1845 		Some PHY like Intel LXT971A need extra delay after
1846 		reset before any MII register access is possible.
1847 		For such PHY, set this option to the usec delay
1848 		required. (minimum 300usec for LXT971A)
1849 
1850 		CONFIG_PHY_CMD_DELAY (ppc4xx)
1851 
1852 		Some PHY like Intel LXT971A need extra delay after
1853 		command issued before MII status register can be read
1854 
1855 - IP address:
1856 		CONFIG_IPADDR
1857 
1858 		Define a default value for the IP address to use for
1859 		the default Ethernet interface, in case this is not
1860 		determined through e.g. bootp.
1861 		(Environment variable "ipaddr")
1862 
1863 - Server IP address:
1864 		CONFIG_SERVERIP
1865 
1866 		Defines a default value for the IP address of a TFTP
1867 		server to contact when using the "tftboot" command.
1868 		(Environment variable "serverip")
1869 
1870 		CONFIG_KEEP_SERVERADDR
1871 
1872 		Keeps the server's MAC address, in the env 'serveraddr'
1873 		for passing to bootargs (like Linux's netconsole option)
1874 
1875 - Gateway IP address:
1876 		CONFIG_GATEWAYIP
1877 
1878 		Defines a default value for the IP address of the
1879 		default router where packets to other networks are
1880 		sent to.
1881 		(Environment variable "gatewayip")
1882 
1883 - Subnet mask:
1884 		CONFIG_NETMASK
1885 
1886 		Defines a default value for the subnet mask (or
1887 		routing prefix) which is used to determine if an IP
1888 		address belongs to the local subnet or needs to be
1889 		forwarded through a router.
1890 		(Environment variable "netmask")
1891 
1892 - Multicast TFTP Mode:
1893 		CONFIG_MCAST_TFTP
1894 
1895 		Defines whether you want to support multicast TFTP as per
1896 		rfc-2090; for example to work with atftp.  Lets lots of targets
1897 		tftp down the same boot image concurrently.  Note: the Ethernet
1898 		driver in use must provide a function: mcast() to join/leave a
1899 		multicast group.
1900 
1901 - BOOTP Recovery Mode:
1902 		CONFIG_BOOTP_RANDOM_DELAY
1903 
1904 		If you have many targets in a network that try to
1905 		boot using BOOTP, you may want to avoid that all
1906 		systems send out BOOTP requests at precisely the same
1907 		moment (which would happen for instance at recovery
1908 		from a power failure, when all systems will try to
1909 		boot, thus flooding the BOOTP server. Defining
1910 		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1911 		inserted before sending out BOOTP requests. The
1912 		following delays are inserted then:
1913 
1914 		1st BOOTP request:	delay 0 ... 1 sec
1915 		2nd BOOTP request:	delay 0 ... 2 sec
1916 		3rd BOOTP request:	delay 0 ... 4 sec
1917 		4th and following
1918 		BOOTP requests:		delay 0 ... 8 sec
1919 
1920 		CONFIG_BOOTP_ID_CACHE_SIZE
1921 
1922 		BOOTP packets are uniquely identified using a 32-bit ID. The
1923 		server will copy the ID from client requests to responses and
1924 		U-Boot will use this to determine if it is the destination of
1925 		an incoming response. Some servers will check that addresses
1926 		aren't in use before handing them out (usually using an ARP
1927 		ping) and therefore take up to a few hundred milliseconds to
1928 		respond. Network congestion may also influence the time it
1929 		takes for a response to make it back to the client. If that
1930 		time is too long, U-Boot will retransmit requests. In order
1931 		to allow earlier responses to still be accepted after these
1932 		retransmissions, U-Boot's BOOTP client keeps a small cache of
1933 		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1934 		cache. The default is to keep IDs for up to four outstanding
1935 		requests. Increasing this will allow U-Boot to accept offers
1936 		from a BOOTP client in networks with unusually high latency.
1937 
1938 - DHCP Advanced Options:
1939 		You can fine tune the DHCP functionality by defining
1940 		CONFIG_BOOTP_* symbols:
1941 
1942 		CONFIG_BOOTP_SUBNETMASK
1943 		CONFIG_BOOTP_GATEWAY
1944 		CONFIG_BOOTP_HOSTNAME
1945 		CONFIG_BOOTP_NISDOMAIN
1946 		CONFIG_BOOTP_BOOTPATH
1947 		CONFIG_BOOTP_BOOTFILESIZE
1948 		CONFIG_BOOTP_DNS
1949 		CONFIG_BOOTP_DNS2
1950 		CONFIG_BOOTP_SEND_HOSTNAME
1951 		CONFIG_BOOTP_NTPSERVER
1952 		CONFIG_BOOTP_TIMEOFFSET
1953 		CONFIG_BOOTP_VENDOREX
1954 		CONFIG_BOOTP_MAY_FAIL
1955 
1956 		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1957 		environment variable, not the BOOTP server.
1958 
1959 		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1960 		after the configured retry count, the call will fail
1961 		instead of starting over.  This can be used to fail over
1962 		to Link-local IP address configuration if the DHCP server
1963 		is not available.
1964 
1965 		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1966 		serverip from a DHCP server, it is possible that more
1967 		than one DNS serverip is offered to the client.
1968 		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1969 		serverip will be stored in the additional environment
1970 		variable "dnsip2". The first DNS serverip is always
1971 		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1972 		is defined.
1973 
1974 		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1975 		to do a dynamic update of a DNS server. To do this, they
1976 		need the hostname of the DHCP requester.
1977 		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1978 		of the "hostname" environment variable is passed as
1979 		option 12 to the DHCP server.
1980 
1981 		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1982 
1983 		A 32bit value in microseconds for a delay between
1984 		receiving a "DHCP Offer" and sending the "DHCP Request".
1985 		This fixes a problem with certain DHCP servers that don't
1986 		respond 100% of the time to a "DHCP request". E.g. On an
1987 		AT91RM9200 processor running at 180MHz, this delay needed
1988 		to be *at least* 15,000 usec before a Windows Server 2003
1989 		DHCP server would reply 100% of the time. I recommend at
1990 		least 50,000 usec to be safe. The alternative is to hope
1991 		that one of the retries will be successful but note that
1992 		the DHCP timeout and retry process takes a longer than
1993 		this delay.
1994 
1995  - Link-local IP address negotiation:
1996 		Negotiate with other link-local clients on the local network
1997 		for an address that doesn't require explicit configuration.
1998 		This is especially useful if a DHCP server cannot be guaranteed
1999 		to exist in all environments that the device must operate.
2000 
2001 		See doc/README.link-local for more information.
2002 
2003  - CDP Options:
2004 		CONFIG_CDP_DEVICE_ID
2005 
2006 		The device id used in CDP trigger frames.
2007 
2008 		CONFIG_CDP_DEVICE_ID_PREFIX
2009 
2010 		A two character string which is prefixed to the MAC address
2011 		of the device.
2012 
2013 		CONFIG_CDP_PORT_ID
2014 
2015 		A printf format string which contains the ascii name of
2016 		the port. Normally is set to "eth%d" which sets
2017 		eth0 for the first Ethernet, eth1 for the second etc.
2018 
2019 		CONFIG_CDP_CAPABILITIES
2020 
2021 		A 32bit integer which indicates the device capabilities;
2022 		0x00000010 for a normal host which does not forwards.
2023 
2024 		CONFIG_CDP_VERSION
2025 
2026 		An ascii string containing the version of the software.
2027 
2028 		CONFIG_CDP_PLATFORM
2029 
2030 		An ascii string containing the name of the platform.
2031 
2032 		CONFIG_CDP_TRIGGER
2033 
2034 		A 32bit integer sent on the trigger.
2035 
2036 		CONFIG_CDP_POWER_CONSUMPTION
2037 
2038 		A 16bit integer containing the power consumption of the
2039 		device in .1 of milliwatts.
2040 
2041 		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2042 
2043 		A byte containing the id of the VLAN.
2044 
2045 - Status LED:	CONFIG_STATUS_LED
2046 
2047 		Several configurations allow to display the current
2048 		status using a LED. For instance, the LED will blink
2049 		fast while running U-Boot code, stop blinking as
2050 		soon as a reply to a BOOTP request was received, and
2051 		start blinking slow once the Linux kernel is running
2052 		(supported by a status LED driver in the Linux
2053 		kernel). Defining CONFIG_STATUS_LED enables this
2054 		feature in U-Boot.
2055 
2056 		Additional options:
2057 
2058 		CONFIG_GPIO_LED
2059 		The status LED can be connected to a GPIO pin.
2060 		In such cases, the gpio_led driver can be used as a
2061 		status LED backend implementation. Define CONFIG_GPIO_LED
2062 		to include the gpio_led driver in the U-Boot binary.
2063 
2064 		CONFIG_GPIO_LED_INVERTED_TABLE
2065 		Some GPIO connected LEDs may have inverted polarity in which
2066 		case the GPIO high value corresponds to LED off state and
2067 		GPIO low value corresponds to LED on state.
2068 		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2069 		with a list of GPIO LEDs that have inverted polarity.
2070 
2071 - CAN Support:	CONFIG_CAN_DRIVER
2072 
2073 		Defining CONFIG_CAN_DRIVER enables CAN driver support
2074 		on those systems that support this (optional)
2075 		feature, like the TQM8xxL modules.
2076 
2077 - I2C Support:	CONFIG_SYS_I2C
2078 
2079 		This enable the NEW i2c subsystem, and will allow you to use
2080 		i2c commands at the u-boot command line (as long as you set
2081 		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2082 		based realtime clock chips or other i2c devices. See
2083 		common/cmd_i2c.c for a description of the command line
2084 		interface.
2085 
2086 		ported i2c driver to the new framework:
2087 		- drivers/i2c/soft_i2c.c:
2088 		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2089 		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2090 		    for defining speed and slave address
2091 		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2092 		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2093 		    for defining speed and slave address
2094 		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2095 		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2096 		    for defining speed and slave address
2097 		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2098 		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2099 		    for defining speed and slave address
2100 
2101 		- drivers/i2c/fsl_i2c.c:
2102 		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2103 		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2104 		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2105 		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2106 		    bus.
2107 		  - If your board supports a second fsl i2c bus, define
2108 		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2109 		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2110 		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2111 		    second bus.
2112 
2113 		- drivers/i2c/tegra_i2c.c:
2114 		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2115 		  - This driver adds 4 i2c buses with a fix speed from
2116 		    100000 and the slave addr 0!
2117 
2118 		- drivers/i2c/ppc4xx_i2c.c
2119 		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2120 		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2121 		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2122 
2123 		- drivers/i2c/i2c_mxc.c
2124 		  - activate this driver with CONFIG_SYS_I2C_MXC
2125 		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2126 		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2127 		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2128 		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2129 		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2130 		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2131 		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2132 		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2133 		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2134 		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2135 		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2136 		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2137 		If those defines are not set, default value is 100000
2138 		for speed, and 0 for slave.
2139 
2140 		- drivers/i2c/rcar_i2c.c:
2141 		  - activate this driver with CONFIG_SYS_I2C_RCAR
2142 		  - This driver adds 4 i2c buses
2143 
2144 		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2145 		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2146 		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2147 		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2148 		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2149 		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2150 		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2151 		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2152 		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2153 
2154 		- drivers/i2c/sh_i2c.c:
2155 		  - activate this driver with CONFIG_SYS_I2C_SH
2156 		  - This driver adds from 2 to 5 i2c buses
2157 
2158 		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2159 		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2160 		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2161 		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2162 		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2163 		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2164 		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2165 		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2166 		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2167 		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2168 		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2169 
2170 		- drivers/i2c/omap24xx_i2c.c
2171 		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2172 		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2173 		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2174 		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2175 		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2176 		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2177 		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2178 		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2179 		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2180 		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2181 		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2182 
2183 		- drivers/i2c/zynq_i2c.c
2184 		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2185 		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2186 		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2187 
2188 		- drivers/i2c/s3c24x0_i2c.c:
2189 		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2190 		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2191 		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2192 		    with a fix speed from 100000 and the slave addr 0!
2193 
2194 		- drivers/i2c/ihs_i2c.c
2195 		  - activate this driver with CONFIG_SYS_I2C_IHS
2196 		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2197 		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2198 		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2199 		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2200 		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2201 		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2202 		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2203 		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2204 		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2205 		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2206 		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2207 		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2208 		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2209 		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2210 		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2211 		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2212 		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2213 		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2214 		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2215 		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2216 		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2217 
2218 		additional defines:
2219 
2220 		CONFIG_SYS_NUM_I2C_BUSES
2221 		Hold the number of i2c buses you want to use.
2222 
2223 		CONFIG_SYS_I2C_DIRECT_BUS
2224 		define this, if you don't use i2c muxes on your hardware.
2225 		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2226 		omit this define.
2227 
2228 		CONFIG_SYS_I2C_MAX_HOPS
2229 		define how many muxes are maximal consecutively connected
2230 		on one i2c bus. If you not use i2c muxes, omit this
2231 		define.
2232 
2233 		CONFIG_SYS_I2C_BUSES
2234 		hold a list of buses you want to use, only used if
2235 		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2236 		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2237 		CONFIG_SYS_NUM_I2C_BUSES = 9:
2238 
2239 		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2240 					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2241 					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2242 					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2243 					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2244 					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2245 					{1, {I2C_NULL_HOP}}, \
2246 					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2247 					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2248 					}
2249 
2250 		which defines
2251 			bus 0 on adapter 0 without a mux
2252 			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2253 			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2254 			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2255 			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2256 			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2257 			bus 6 on adapter 1 without a mux
2258 			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2259 			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2260 
2261 		If you do not have i2c muxes on your board, omit this define.
2262 
2263 - Legacy I2C Support:	CONFIG_HARD_I2C
2264 
2265 		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2266 		provides the following compelling advantages:
2267 
2268 		- more than one i2c adapter is usable
2269 		- approved multibus support
2270 		- better i2c mux support
2271 
2272 		** Please consider updating your I2C driver now. **
2273 
2274 		These enable legacy I2C serial bus commands. Defining
2275 		CONFIG_HARD_I2C will include the appropriate I2C driver
2276 		for the selected CPU.
2277 
2278 		This will allow you to use i2c commands at the u-boot
2279 		command line (as long as you set CONFIG_CMD_I2C in
2280 		CONFIG_COMMANDS) and communicate with i2c based realtime
2281 		clock chips. See common/cmd_i2c.c for a description of the
2282 		command line interface.
2283 
2284 		CONFIG_HARD_I2C selects a hardware I2C controller.
2285 
2286 		There are several other quantities that must also be
2287 		defined when you define CONFIG_HARD_I2C.
2288 
2289 		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2290 		to be the frequency (in Hz) at which you wish your i2c bus
2291 		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2292 		the CPU's i2c node address).
2293 
2294 		Now, the u-boot i2c code for the mpc8xx
2295 		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2296 		and so its address should therefore be cleared to 0 (See,
2297 		eg, MPC823e User's Manual p.16-473). So, set
2298 		CONFIG_SYS_I2C_SLAVE to 0.
2299 
2300 		CONFIG_SYS_I2C_INIT_MPC5XXX
2301 
2302 		When a board is reset during an i2c bus transfer
2303 		chips might think that the current transfer is still
2304 		in progress.  Reset the slave devices by sending start
2305 		commands until the slave device responds.
2306 
2307 		That's all that's required for CONFIG_HARD_I2C.
2308 
2309 		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2310 		then the following macros need to be defined (examples are
2311 		from include/configs/lwmon.h):
2312 
2313 		I2C_INIT
2314 
2315 		(Optional). Any commands necessary to enable the I2C
2316 		controller or configure ports.
2317 
2318 		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2319 
2320 		I2C_PORT
2321 
2322 		(Only for MPC8260 CPU). The I/O port to use (the code
2323 		assumes both bits are on the same port). Valid values
2324 		are 0..3 for ports A..D.
2325 
2326 		I2C_ACTIVE
2327 
2328 		The code necessary to make the I2C data line active
2329 		(driven).  If the data line is open collector, this
2330 		define can be null.
2331 
2332 		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2333 
2334 		I2C_TRISTATE
2335 
2336 		The code necessary to make the I2C data line tri-stated
2337 		(inactive).  If the data line is open collector, this
2338 		define can be null.
2339 
2340 		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2341 
2342 		I2C_READ
2343 
2344 		Code that returns true if the I2C data line is high,
2345 		false if it is low.
2346 
2347 		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2348 
2349 		I2C_SDA(bit)
2350 
2351 		If <bit> is true, sets the I2C data line high. If it
2352 		is false, it clears it (low).
2353 
2354 		eg: #define I2C_SDA(bit) \
2355 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2356 			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2357 
2358 		I2C_SCL(bit)
2359 
2360 		If <bit> is true, sets the I2C clock line high. If it
2361 		is false, it clears it (low).
2362 
2363 		eg: #define I2C_SCL(bit) \
2364 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2365 			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2366 
2367 		I2C_DELAY
2368 
2369 		This delay is invoked four times per clock cycle so this
2370 		controls the rate of data transfer.  The data rate thus
2371 		is 1 / (I2C_DELAY * 4). Often defined to be something
2372 		like:
2373 
2374 		#define I2C_DELAY  udelay(2)
2375 
2376 		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2377 
2378 		If your arch supports the generic GPIO framework (asm/gpio.h),
2379 		then you may alternatively define the two GPIOs that are to be
2380 		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2381 		have GPIO-based defaults assigned to them as appropriate.
2382 
2383 		You should define these to the GPIO value as given directly to
2384 		the generic GPIO functions.
2385 
2386 		CONFIG_SYS_I2C_INIT_BOARD
2387 
2388 		When a board is reset during an i2c bus transfer
2389 		chips might think that the current transfer is still
2390 		in progress. On some boards it is possible to access
2391 		the i2c SCLK line directly, either by using the
2392 		processor pin as a GPIO or by having a second pin
2393 		connected to the bus. If this option is defined a
2394 		custom i2c_init_board() routine in boards/xxx/board.c
2395 		is run early in the boot sequence.
2396 
2397 		CONFIG_SYS_I2C_BOARD_LATE_INIT
2398 
2399 		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2400 		defined a custom i2c_board_late_init() routine in
2401 		boards/xxx/board.c is run AFTER the operations in i2c_init()
2402 		is completed. This callpoint can be used to unreset i2c bus
2403 		using CPU i2c controller register accesses for CPUs whose i2c
2404 		controller provide such a method. It is called at the end of
2405 		i2c_init() to allow i2c_init operations to setup the i2c bus
2406 		controller on the CPU (e.g. setting bus speed & slave address).
2407 
2408 		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2409 
2410 		This option enables configuration of bi_iic_fast[] flags
2411 		in u-boot bd_info structure based on u-boot environment
2412 		variable "i2cfast". (see also i2cfast)
2413 
2414 		CONFIG_I2C_MULTI_BUS
2415 
2416 		This option allows the use of multiple I2C buses, each of which
2417 		must have a controller.	 At any point in time, only one bus is
2418 		active.	 To switch to a different bus, use the 'i2c dev' command.
2419 		Note that bus numbering is zero-based.
2420 
2421 		CONFIG_SYS_I2C_NOPROBES
2422 
2423 		This option specifies a list of I2C devices that will be skipped
2424 		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2425 		is set, specify a list of bus-device pairs.  Otherwise, specify
2426 		a 1D array of device addresses
2427 
2428 		e.g.
2429 			#undef	CONFIG_I2C_MULTI_BUS
2430 			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2431 
2432 		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2433 
2434 			#define CONFIG_I2C_MULTI_BUS
2435 			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2436 
2437 		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2438 
2439 		CONFIG_SYS_SPD_BUS_NUM
2440 
2441 		If defined, then this indicates the I2C bus number for DDR SPD.
2442 		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2443 
2444 		CONFIG_SYS_RTC_BUS_NUM
2445 
2446 		If defined, then this indicates the I2C bus number for the RTC.
2447 		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2448 
2449 		CONFIG_SYS_DTT_BUS_NUM
2450 
2451 		If defined, then this indicates the I2C bus number for the DTT.
2452 		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2453 
2454 		CONFIG_SYS_I2C_DTT_ADDR:
2455 
2456 		If defined, specifies the I2C address of the DTT device.
2457 		If not defined, then U-Boot uses predefined value for
2458 		specified DTT device.
2459 
2460 		CONFIG_SOFT_I2C_READ_REPEATED_START
2461 
2462 		defining this will force the i2c_read() function in
2463 		the soft_i2c driver to perform an I2C repeated start
2464 		between writing the address pointer and reading the
2465 		data.  If this define is omitted the default behaviour
2466 		of doing a stop-start sequence will be used.  Most I2C
2467 		devices can use either method, but some require one or
2468 		the other.
2469 
2470 - SPI Support:	CONFIG_SPI
2471 
2472 		Enables SPI driver (so far only tested with
2473 		SPI EEPROM, also an instance works with Crystal A/D and
2474 		D/As on the SACSng board)
2475 
2476 		CONFIG_SH_SPI
2477 
2478 		Enables the driver for SPI controller on SuperH. Currently
2479 		only SH7757 is supported.
2480 
2481 		CONFIG_SOFT_SPI
2482 
2483 		Enables a software (bit-bang) SPI driver rather than
2484 		using hardware support. This is a general purpose
2485 		driver that only requires three general I/O port pins
2486 		(two outputs, one input) to function. If this is
2487 		defined, the board configuration must define several
2488 		SPI configuration items (port pins to use, etc). For
2489 		an example, see include/configs/sacsng.h.
2490 
2491 		CONFIG_HARD_SPI
2492 
2493 		Enables a hardware SPI driver for general-purpose reads
2494 		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2495 		must define a list of chip-select function pointers.
2496 		Currently supported on some MPC8xxx processors.	 For an
2497 		example, see include/configs/mpc8349emds.h.
2498 
2499 		CONFIG_MXC_SPI
2500 
2501 		Enables the driver for the SPI controllers on i.MX and MXC
2502 		SoCs. Currently i.MX31/35/51 are supported.
2503 
2504 		CONFIG_SYS_SPI_MXC_WAIT
2505 		Timeout for waiting until spi transfer completed.
2506 		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2507 
2508 - FPGA Support: CONFIG_FPGA
2509 
2510 		Enables FPGA subsystem.
2511 
2512 		CONFIG_FPGA_<vendor>
2513 
2514 		Enables support for specific chip vendors.
2515 		(ALTERA, XILINX)
2516 
2517 		CONFIG_FPGA_<family>
2518 
2519 		Enables support for FPGA family.
2520 		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2521 
2522 		CONFIG_FPGA_COUNT
2523 
2524 		Specify the number of FPGA devices to support.
2525 
2526 		CONFIG_CMD_FPGA_LOADMK
2527 
2528 		Enable support for fpga loadmk command
2529 
2530 		CONFIG_CMD_FPGA_LOADP
2531 
2532 		Enable support for fpga loadp command - load partial bitstream
2533 
2534 		CONFIG_CMD_FPGA_LOADBP
2535 
2536 		Enable support for fpga loadbp command - load partial bitstream
2537 		(Xilinx only)
2538 
2539 		CONFIG_SYS_FPGA_PROG_FEEDBACK
2540 
2541 		Enable printing of hash marks during FPGA configuration.
2542 
2543 		CONFIG_SYS_FPGA_CHECK_BUSY
2544 
2545 		Enable checks on FPGA configuration interface busy
2546 		status by the configuration function. This option
2547 		will require a board or device specific function to
2548 		be written.
2549 
2550 		CONFIG_FPGA_DELAY
2551 
2552 		If defined, a function that provides delays in the FPGA
2553 		configuration driver.
2554 
2555 		CONFIG_SYS_FPGA_CHECK_CTRLC
2556 		Allow Control-C to interrupt FPGA configuration
2557 
2558 		CONFIG_SYS_FPGA_CHECK_ERROR
2559 
2560 		Check for configuration errors during FPGA bitfile
2561 		loading. For example, abort during Virtex II
2562 		configuration if the INIT_B line goes low (which
2563 		indicated a CRC error).
2564 
2565 		CONFIG_SYS_FPGA_WAIT_INIT
2566 
2567 		Maximum time to wait for the INIT_B line to de-assert
2568 		after PROB_B has been de-asserted during a Virtex II
2569 		FPGA configuration sequence. The default time is 500
2570 		ms.
2571 
2572 		CONFIG_SYS_FPGA_WAIT_BUSY
2573 
2574 		Maximum time to wait for BUSY to de-assert during
2575 		Virtex II FPGA configuration. The default is 5 ms.
2576 
2577 		CONFIG_SYS_FPGA_WAIT_CONFIG
2578 
2579 		Time to wait after FPGA configuration. The default is
2580 		200 ms.
2581 
2582 - Configuration Management:
2583 		CONFIG_BUILD_TARGET
2584 
2585 		Some SoCs need special image types (e.g. U-Boot binary
2586 		with a special header) as build targets. By defining
2587 		CONFIG_BUILD_TARGET in the SoC / board header, this
2588 		special image will be automatically built upon calling
2589 		make / buildman.
2590 
2591 		CONFIG_IDENT_STRING
2592 
2593 		If defined, this string will be added to the U-Boot
2594 		version information (U_BOOT_VERSION)
2595 
2596 - Vendor Parameter Protection:
2597 
2598 		U-Boot considers the values of the environment
2599 		variables "serial#" (Board Serial Number) and
2600 		"ethaddr" (Ethernet Address) to be parameters that
2601 		are set once by the board vendor / manufacturer, and
2602 		protects these variables from casual modification by
2603 		the user. Once set, these variables are read-only,
2604 		and write or delete attempts are rejected. You can
2605 		change this behaviour:
2606 
2607 		If CONFIG_ENV_OVERWRITE is #defined in your config
2608 		file, the write protection for vendor parameters is
2609 		completely disabled. Anybody can change or delete
2610 		these parameters.
2611 
2612 		Alternatively, if you define _both_ an ethaddr in the
2613 		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2614 		Ethernet address is installed in the environment,
2615 		which can be changed exactly ONCE by the user. [The
2616 		serial# is unaffected by this, i. e. it remains
2617 		read-only.]
2618 
2619 		The same can be accomplished in a more flexible way
2620 		for any variable by configuring the type of access
2621 		to allow for those variables in the ".flags" variable
2622 		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2623 
2624 - Protected RAM:
2625 		CONFIG_PRAM
2626 
2627 		Define this variable to enable the reservation of
2628 		"protected RAM", i. e. RAM which is not overwritten
2629 		by U-Boot. Define CONFIG_PRAM to hold the number of
2630 		kB you want to reserve for pRAM. You can overwrite
2631 		this default value by defining an environment
2632 		variable "pram" to the number of kB you want to
2633 		reserve. Note that the board info structure will
2634 		still show the full amount of RAM. If pRAM is
2635 		reserved, a new environment variable "mem" will
2636 		automatically be defined to hold the amount of
2637 		remaining RAM in a form that can be passed as boot
2638 		argument to Linux, for instance like that:
2639 
2640 			setenv bootargs ... mem=\${mem}
2641 			saveenv
2642 
2643 		This way you can tell Linux not to use this memory,
2644 		either, which results in a memory region that will
2645 		not be affected by reboots.
2646 
2647 		*WARNING* If your board configuration uses automatic
2648 		detection of the RAM size, you must make sure that
2649 		this memory test is non-destructive. So far, the
2650 		following board configurations are known to be
2651 		"pRAM-clean":
2652 
2653 			IVMS8, IVML24, SPD8xx, TQM8xxL,
2654 			HERMES, IP860, RPXlite, LWMON,
2655 			FLAGADM, TQM8260
2656 
2657 - Access to physical memory region (> 4GB)
2658 		Some basic support is provided for operations on memory not
2659 		normally accessible to U-Boot - e.g. some architectures
2660 		support access to more than 4GB of memory on 32-bit
2661 		machines using physical address extension or similar.
2662 		Define CONFIG_PHYSMEM to access this basic support, which
2663 		currently only supports clearing the memory.
2664 
2665 - Error Recovery:
2666 		CONFIG_PANIC_HANG
2667 
2668 		Define this variable to stop the system in case of a
2669 		fatal error, so that you have to reset it manually.
2670 		This is probably NOT a good idea for an embedded
2671 		system where you want the system to reboot
2672 		automatically as fast as possible, but it may be
2673 		useful during development since you can try to debug
2674 		the conditions that lead to the situation.
2675 
2676 		CONFIG_NET_RETRY_COUNT
2677 
2678 		This variable defines the number of retries for
2679 		network operations like ARP, RARP, TFTP, or BOOTP
2680 		before giving up the operation. If not defined, a
2681 		default value of 5 is used.
2682 
2683 		CONFIG_ARP_TIMEOUT
2684 
2685 		Timeout waiting for an ARP reply in milliseconds.
2686 
2687 		CONFIG_NFS_TIMEOUT
2688 
2689 		Timeout in milliseconds used in NFS protocol.
2690 		If you encounter "ERROR: Cannot umount" in nfs command,
2691 		try longer timeout such as
2692 		#define CONFIG_NFS_TIMEOUT 10000UL
2693 
2694 - Command Interpreter:
2695 		CONFIG_AUTO_COMPLETE
2696 
2697 		Enable auto completion of commands using TAB.
2698 
2699 		CONFIG_SYS_PROMPT_HUSH_PS2
2700 
2701 		This defines the secondary prompt string, which is
2702 		printed when the command interpreter needs more input
2703 		to complete a command. Usually "> ".
2704 
2705 	Note:
2706 
2707 		In the current implementation, the local variables
2708 		space and global environment variables space are
2709 		separated. Local variables are those you define by
2710 		simply typing `name=value'. To access a local
2711 		variable later on, you have write `$name' or
2712 		`${name}'; to execute the contents of a variable
2713 		directly type `$name' at the command prompt.
2714 
2715 		Global environment variables are those you use
2716 		setenv/printenv to work with. To run a command stored
2717 		in such a variable, you need to use the run command,
2718 		and you must not use the '$' sign to access them.
2719 
2720 		To store commands and special characters in a
2721 		variable, please use double quotation marks
2722 		surrounding the whole text of the variable, instead
2723 		of the backslashes before semicolons and special
2724 		symbols.
2725 
2726 - Command Line Editing and History:
2727 		CONFIG_CMDLINE_EDITING
2728 
2729 		Enable editing and History functions for interactive
2730 		command line input operations
2731 
2732 - Command Line PS1/PS2 support:
2733 		CONFIG_CMDLINE_PS_SUPPORT
2734 
2735 		Enable support for changing the command prompt string
2736 		at run-time. Only static string is supported so far.
2737 		The string is obtained from environment variables PS1
2738 		and PS2.
2739 
2740 - Default Environment:
2741 		CONFIG_EXTRA_ENV_SETTINGS
2742 
2743 		Define this to contain any number of null terminated
2744 		strings (variable = value pairs) that will be part of
2745 		the default environment compiled into the boot image.
2746 
2747 		For example, place something like this in your
2748 		board's config file:
2749 
2750 		#define CONFIG_EXTRA_ENV_SETTINGS \
2751 			"myvar1=value1\0" \
2752 			"myvar2=value2\0"
2753 
2754 		Warning: This method is based on knowledge about the
2755 		internal format how the environment is stored by the
2756 		U-Boot code. This is NOT an official, exported
2757 		interface! Although it is unlikely that this format
2758 		will change soon, there is no guarantee either.
2759 		You better know what you are doing here.
2760 
2761 		Note: overly (ab)use of the default environment is
2762 		discouraged. Make sure to check other ways to preset
2763 		the environment like the "source" command or the
2764 		boot command first.
2765 
2766 		CONFIG_ENV_VARS_UBOOT_CONFIG
2767 
2768 		Define this in order to add variables describing the
2769 		U-Boot build configuration to the default environment.
2770 		These will be named arch, cpu, board, vendor, and soc.
2771 
2772 		Enabling this option will cause the following to be defined:
2773 
2774 		- CONFIG_SYS_ARCH
2775 		- CONFIG_SYS_CPU
2776 		- CONFIG_SYS_BOARD
2777 		- CONFIG_SYS_VENDOR
2778 		- CONFIG_SYS_SOC
2779 
2780 		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2781 
2782 		Define this in order to add variables describing certain
2783 		run-time determined information about the hardware to the
2784 		environment.  These will be named board_name, board_rev.
2785 
2786 		CONFIG_DELAY_ENVIRONMENT
2787 
2788 		Normally the environment is loaded when the board is
2789 		initialised so that it is available to U-Boot. This inhibits
2790 		that so that the environment is not available until
2791 		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2792 		this is instead controlled by the value of
2793 		/config/load-environment.
2794 
2795 - Parallel Flash support:
2796 		CONFIG_SYS_NO_FLASH
2797 
2798 		Traditionally U-Boot was run on systems with parallel NOR
2799 		flash. This option is used to disable support for parallel NOR
2800 		flash. This option should be defined if the board does not have
2801 		parallel flash.
2802 
2803 		If this option is not defined one of the generic flash drivers
2804 		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2805 		selected or the board must provide an implementation of the
2806 		flash API (see include/flash.h).
2807 
2808 - DataFlash Support:
2809 		CONFIG_HAS_DATAFLASH
2810 
2811 		Defining this option enables DataFlash features and
2812 		allows to read/write in Dataflash via the standard
2813 		commands cp, md...
2814 
2815 - Serial Flash support
2816 		CONFIG_CMD_SF
2817 
2818 		Defining this option enables SPI flash commands
2819 		'sf probe/read/write/erase/update'.
2820 
2821 		Usage requires an initial 'probe' to define the serial
2822 		flash parameters, followed by read/write/erase/update
2823 		commands.
2824 
2825 		The following defaults may be provided by the platform
2826 		to handle the common case when only a single serial
2827 		flash is present on the system.
2828 
2829 		CONFIG_SF_DEFAULT_BUS		Bus identifier
2830 		CONFIG_SF_DEFAULT_CS		Chip-select
2831 		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2832 		CONFIG_SF_DEFAULT_SPEED		in Hz
2833 
2834 		CONFIG_CMD_SF_TEST
2835 
2836 		Define this option to include a destructive SPI flash
2837 		test ('sf test').
2838 
2839 		CONFIG_SF_DUAL_FLASH		Dual flash memories
2840 
2841 		Define this option to use dual flash support where two flash
2842 		memories can be connected with a given cs line.
2843 		Currently Xilinx Zynq qspi supports these type of connections.
2844 
2845 - SystemACE Support:
2846 		CONFIG_SYSTEMACE
2847 
2848 		Adding this option adds support for Xilinx SystemACE
2849 		chips attached via some sort of local bus. The address
2850 		of the chip must also be defined in the
2851 		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2852 
2853 		#define CONFIG_SYSTEMACE
2854 		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2855 
2856 		When SystemACE support is added, the "ace" device type
2857 		becomes available to the fat commands, i.e. fatls.
2858 
2859 - TFTP Fixed UDP Port:
2860 		CONFIG_TFTP_PORT
2861 
2862 		If this is defined, the environment variable tftpsrcp
2863 		is used to supply the TFTP UDP source port value.
2864 		If tftpsrcp isn't defined, the normal pseudo-random port
2865 		number generator is used.
2866 
2867 		Also, the environment variable tftpdstp is used to supply
2868 		the TFTP UDP destination port value.  If tftpdstp isn't
2869 		defined, the normal port 69 is used.
2870 
2871 		The purpose for tftpsrcp is to allow a TFTP server to
2872 		blindly start the TFTP transfer using the pre-configured
2873 		target IP address and UDP port. This has the effect of
2874 		"punching through" the (Windows XP) firewall, allowing
2875 		the remainder of the TFTP transfer to proceed normally.
2876 		A better solution is to properly configure the firewall,
2877 		but sometimes that is not allowed.
2878 
2879 - Hashing support:
2880 		CONFIG_CMD_HASH
2881 
2882 		This enables a generic 'hash' command which can produce
2883 		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2884 
2885 		CONFIG_HASH_VERIFY
2886 
2887 		Enable the hash verify command (hash -v). This adds to code
2888 		size a little.
2889 
2890 		CONFIG_SHA1 - This option enables support of hashing using SHA1
2891 		algorithm. The hash is calculated in software.
2892 		CONFIG_SHA256 - This option enables support of hashing using
2893 		SHA256 algorithm. The hash is calculated in software.
2894 		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
2895 		for SHA1/SHA256 hashing.
2896 		This affects the 'hash' command and also the
2897 		hash_lookup_algo() function.
2898 		CONFIG_SHA_PROG_HW_ACCEL - This option enables
2899 		hardware-acceleration for SHA1/SHA256 progressive hashing.
2900 		Data can be streamed in a block at a time and the hashing
2901 		is performed in hardware.
2902 
2903 		Note: There is also a sha1sum command, which should perhaps
2904 		be deprecated in favour of 'hash sha1'.
2905 
2906 - Freescale i.MX specific commands:
2907 		CONFIG_CMD_HDMIDETECT
2908 		This enables 'hdmidet' command which returns true if an
2909 		HDMI monitor is detected.  This command is i.MX 6 specific.
2910 
2911 		CONFIG_CMD_BMODE
2912 		This enables the 'bmode' (bootmode) command for forcing
2913 		a boot from specific media.
2914 
2915 		This is useful for forcing the ROM's usb downloader to
2916 		activate upon a watchdog reset which is nice when iterating
2917 		on U-Boot.  Using the reset button or running bmode normal
2918 		will set it back to normal.  This command currently
2919 		supports i.MX53 and i.MX6.
2920 
2921 - bootcount support:
2922 		CONFIG_BOOTCOUNT_LIMIT
2923 
2924 		This enables the bootcounter support, see:
2925 		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2926 
2927 		CONFIG_AT91SAM9XE
2928 		enable special bootcounter support on at91sam9xe based boards.
2929 		CONFIG_BLACKFIN
2930 		enable special bootcounter support on blackfin based boards.
2931 		CONFIG_SOC_DA8XX
2932 		enable special bootcounter support on da850 based boards.
2933 		CONFIG_BOOTCOUNT_RAM
2934 		enable support for the bootcounter in RAM
2935 		CONFIG_BOOTCOUNT_I2C
2936 		enable support for the bootcounter on an i2c (like RTC) device.
2937 			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2938 			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2939 						    the bootcounter.
2940 			CONFIG_BOOTCOUNT_ALEN = address len
2941 
2942 - Show boot progress:
2943 		CONFIG_SHOW_BOOT_PROGRESS
2944 
2945 		Defining this option allows to add some board-
2946 		specific code (calling a user-provided function
2947 		"show_boot_progress(int)") that enables you to show
2948 		the system's boot progress on some display (for
2949 		example, some LED's) on your board. At the moment,
2950 		the following checkpoints are implemented:
2951 
2952 
2953 Legacy uImage format:
2954 
2955   Arg	Where			When
2956     1	common/cmd_bootm.c	before attempting to boot an image
2957    -1	common/cmd_bootm.c	Image header has bad	 magic number
2958     2	common/cmd_bootm.c	Image header has correct magic number
2959    -2	common/cmd_bootm.c	Image header has bad	 checksum
2960     3	common/cmd_bootm.c	Image header has correct checksum
2961    -3	common/cmd_bootm.c	Image data   has bad	 checksum
2962     4	common/cmd_bootm.c	Image data   has correct checksum
2963    -4	common/cmd_bootm.c	Image is for unsupported architecture
2964     5	common/cmd_bootm.c	Architecture check OK
2965    -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2966     6	common/cmd_bootm.c	Image Type check OK
2967    -6	common/cmd_bootm.c	gunzip uncompression error
2968    -7	common/cmd_bootm.c	Unimplemented compression type
2969     7	common/cmd_bootm.c	Uncompression OK
2970     8	common/cmd_bootm.c	No uncompress/copy overwrite error
2971    -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2972 
2973     9	common/image.c		Start initial ramdisk verification
2974   -10	common/image.c		Ramdisk header has bad	   magic number
2975   -11	common/image.c		Ramdisk header has bad	   checksum
2976    10	common/image.c		Ramdisk header is OK
2977   -12	common/image.c		Ramdisk data   has bad	   checksum
2978    11	common/image.c		Ramdisk data   has correct checksum
2979    12	common/image.c		Ramdisk verification complete, start loading
2980   -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2981    13	common/image.c		Start multifile image verification
2982    14	common/image.c		No initial ramdisk, no multifile, continue.
2983 
2984    15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2985 
2986   -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2987   -31	post/post.c		POST test failed, detected by post_output_backlog()
2988   -32	post/post.c		POST test failed, detected by post_run_single()
2989 
2990    34	common/cmd_doc.c	before loading a Image from a DOC device
2991   -35	common/cmd_doc.c	Bad usage of "doc" command
2992    35	common/cmd_doc.c	correct usage of "doc" command
2993   -36	common/cmd_doc.c	No boot device
2994    36	common/cmd_doc.c	correct boot device
2995   -37	common/cmd_doc.c	Unknown Chip ID on boot device
2996    37	common/cmd_doc.c	correct chip ID found, device available
2997   -38	common/cmd_doc.c	Read Error on boot device
2998    38	common/cmd_doc.c	reading Image header from DOC device OK
2999   -39	common/cmd_doc.c	Image header has bad magic number
3000    39	common/cmd_doc.c	Image header has correct magic number
3001   -40	common/cmd_doc.c	Error reading Image from DOC device
3002    40	common/cmd_doc.c	Image header has correct magic number
3003    41	common/cmd_ide.c	before loading a Image from a IDE device
3004   -42	common/cmd_ide.c	Bad usage of "ide" command
3005    42	common/cmd_ide.c	correct usage of "ide" command
3006   -43	common/cmd_ide.c	No boot device
3007    43	common/cmd_ide.c	boot device found
3008   -44	common/cmd_ide.c	Device not available
3009    44	common/cmd_ide.c	Device available
3010   -45	common/cmd_ide.c	wrong partition selected
3011    45	common/cmd_ide.c	partition selected
3012   -46	common/cmd_ide.c	Unknown partition table
3013    46	common/cmd_ide.c	valid partition table found
3014   -47	common/cmd_ide.c	Invalid partition type
3015    47	common/cmd_ide.c	correct partition type
3016   -48	common/cmd_ide.c	Error reading Image Header on boot device
3017    48	common/cmd_ide.c	reading Image Header from IDE device OK
3018   -49	common/cmd_ide.c	Image header has bad magic number
3019    49	common/cmd_ide.c	Image header has correct magic number
3020   -50	common/cmd_ide.c	Image header has bad	 checksum
3021    50	common/cmd_ide.c	Image header has correct checksum
3022   -51	common/cmd_ide.c	Error reading Image from IDE device
3023    51	common/cmd_ide.c	reading Image from IDE device OK
3024    52	common/cmd_nand.c	before loading a Image from a NAND device
3025   -53	common/cmd_nand.c	Bad usage of "nand" command
3026    53	common/cmd_nand.c	correct usage of "nand" command
3027   -54	common/cmd_nand.c	No boot device
3028    54	common/cmd_nand.c	boot device found
3029   -55	common/cmd_nand.c	Unknown Chip ID on boot device
3030    55	common/cmd_nand.c	correct chip ID found, device available
3031   -56	common/cmd_nand.c	Error reading Image Header on boot device
3032    56	common/cmd_nand.c	reading Image Header from NAND device OK
3033   -57	common/cmd_nand.c	Image header has bad magic number
3034    57	common/cmd_nand.c	Image header has correct magic number
3035   -58	common/cmd_nand.c	Error reading Image from NAND device
3036    58	common/cmd_nand.c	reading Image from NAND device OK
3037 
3038   -60	common/env_common.c	Environment has a bad CRC, using default
3039 
3040    64	net/eth.c		starting with Ethernet configuration.
3041   -64	net/eth.c		no Ethernet found.
3042    65	net/eth.c		Ethernet found.
3043 
3044   -80	common/cmd_net.c	usage wrong
3045    80	common/cmd_net.c	before calling net_loop()
3046   -81	common/cmd_net.c	some error in net_loop() occurred
3047    81	common/cmd_net.c	net_loop() back without error
3048   -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3049    82	common/cmd_net.c	trying automatic boot
3050    83	common/cmd_net.c	running "source" command
3051   -83	common/cmd_net.c	some error in automatic boot or "source" command
3052    84	common/cmd_net.c	end without errors
3053 
3054 FIT uImage format:
3055 
3056   Arg	Where			When
3057   100	common/cmd_bootm.c	Kernel FIT Image has correct format
3058  -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3059   101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3060  -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3061   102	common/cmd_bootm.c	Kernel unit name specified
3062  -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3063   103	common/cmd_bootm.c	Found configuration node
3064   104	common/cmd_bootm.c	Got kernel subimage node offset
3065  -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3066   105	common/cmd_bootm.c	Kernel subimage hash verification OK
3067  -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3068   106	common/cmd_bootm.c	Architecture check OK
3069  -106	common/cmd_bootm.c	Kernel subimage has wrong type
3070   107	common/cmd_bootm.c	Kernel subimage type OK
3071  -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3072   108	common/cmd_bootm.c	Got kernel subimage data/size
3073  -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3074  -109	common/cmd_bootm.c	Can't get kernel subimage type
3075  -110	common/cmd_bootm.c	Can't get kernel subimage comp
3076  -111	common/cmd_bootm.c	Can't get kernel subimage os
3077  -112	common/cmd_bootm.c	Can't get kernel subimage load address
3078  -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3079 
3080   120	common/image.c		Start initial ramdisk verification
3081  -120	common/image.c		Ramdisk FIT image has incorrect format
3082   121	common/image.c		Ramdisk FIT image has correct format
3083   122	common/image.c		No ramdisk subimage unit name, using configuration
3084  -122	common/image.c		Can't get configuration for ramdisk subimage
3085   123	common/image.c		Ramdisk unit name specified
3086  -124	common/image.c		Can't get ramdisk subimage node offset
3087   125	common/image.c		Got ramdisk subimage node offset
3088  -125	common/image.c		Ramdisk subimage hash verification failed
3089   126	common/image.c		Ramdisk subimage hash verification OK
3090  -126	common/image.c		Ramdisk subimage for unsupported architecture
3091   127	common/image.c		Architecture check OK
3092  -127	common/image.c		Can't get ramdisk subimage data/size
3093   128	common/image.c		Got ramdisk subimage data/size
3094   129	common/image.c		Can't get ramdisk load address
3095  -129	common/image.c		Got ramdisk load address
3096 
3097  -130	common/cmd_doc.c	Incorrect FIT image format
3098   131	common/cmd_doc.c	FIT image format OK
3099 
3100  -140	common/cmd_ide.c	Incorrect FIT image format
3101   141	common/cmd_ide.c	FIT image format OK
3102 
3103  -150	common/cmd_nand.c	Incorrect FIT image format
3104   151	common/cmd_nand.c	FIT image format OK
3105 
3106 - legacy image format:
3107 		CONFIG_IMAGE_FORMAT_LEGACY
3108 		enables the legacy image format support in U-Boot.
3109 
3110 		Default:
3111 		enabled if CONFIG_FIT_SIGNATURE is not defined.
3112 
3113 		CONFIG_DISABLE_IMAGE_LEGACY
3114 		disable the legacy image format
3115 
3116 		This define is introduced, as the legacy image format is
3117 		enabled per default for backward compatibility.
3118 
3119 - FIT image support:
3120 		CONFIG_FIT_DISABLE_SHA256
3121 		Supporting SHA256 hashes has quite an impact on binary size.
3122 		For constrained systems sha256 hash support can be disabled
3123 		with this option.
3124 
3125 		TODO(sjg@chromium.org): Adjust this option to be positive,
3126 		and move it to Kconfig
3127 
3128 - Standalone program support:
3129 		CONFIG_STANDALONE_LOAD_ADDR
3130 
3131 		This option defines a board specific value for the
3132 		address where standalone program gets loaded, thus
3133 		overwriting the architecture dependent default
3134 		settings.
3135 
3136 - Frame Buffer Address:
3137 		CONFIG_FB_ADDR
3138 
3139 		Define CONFIG_FB_ADDR if you want to use specific
3140 		address for frame buffer.  This is typically the case
3141 		when using a graphics controller has separate video
3142 		memory.  U-Boot will then place the frame buffer at
3143 		the given address instead of dynamically reserving it
3144 		in system RAM by calling lcd_setmem(), which grabs
3145 		the memory for the frame buffer depending on the
3146 		configured panel size.
3147 
3148 		Please see board_init_f function.
3149 
3150 - Automatic software updates via TFTP server
3151 		CONFIG_UPDATE_TFTP
3152 		CONFIG_UPDATE_TFTP_CNT_MAX
3153 		CONFIG_UPDATE_TFTP_MSEC_MAX
3154 
3155 		These options enable and control the auto-update feature;
3156 		for a more detailed description refer to doc/README.update.
3157 
3158 - MTD Support (mtdparts command, UBI support)
3159 		CONFIG_MTD_DEVICE
3160 
3161 		Adds the MTD device infrastructure from the Linux kernel.
3162 		Needed for mtdparts command support.
3163 
3164 		CONFIG_MTD_PARTITIONS
3165 
3166 		Adds the MTD partitioning infrastructure from the Linux
3167 		kernel. Needed for UBI support.
3168 
3169 - UBI support
3170 		CONFIG_CMD_UBI
3171 
3172 		Adds commands for interacting with MTD partitions formatted
3173 		with the UBI flash translation layer
3174 
3175 		Requires also defining CONFIG_RBTREE
3176 
3177 		CONFIG_UBI_SILENCE_MSG
3178 
3179 		Make the verbose messages from UBI stop printing.  This leaves
3180 		warnings and errors enabled.
3181 
3182 
3183 		CONFIG_MTD_UBI_WL_THRESHOLD
3184 		This parameter defines the maximum difference between the highest
3185 		erase counter value and the lowest erase counter value of eraseblocks
3186 		of UBI devices. When this threshold is exceeded, UBI starts performing
3187 		wear leveling by means of moving data from eraseblock with low erase
3188 		counter to eraseblocks with high erase counter.
3189 
3190 		The default value should be OK for SLC NAND flashes, NOR flashes and
3191 		other flashes which have eraseblock life-cycle 100000 or more.
3192 		However, in case of MLC NAND flashes which typically have eraseblock
3193 		life-cycle less than 10000, the threshold should be lessened (e.g.,
3194 		to 128 or 256, although it does not have to be power of 2).
3195 
3196 		default: 4096
3197 
3198 		CONFIG_MTD_UBI_BEB_LIMIT
3199 		This option specifies the maximum bad physical eraseblocks UBI
3200 		expects on the MTD device (per 1024 eraseblocks). If the
3201 		underlying flash does not admit of bad eraseblocks (e.g. NOR
3202 		flash), this value is ignored.
3203 
3204 		NAND datasheets often specify the minimum and maximum NVM
3205 		(Number of Valid Blocks) for the flashes' endurance lifetime.
3206 		The maximum expected bad eraseblocks per 1024 eraseblocks
3207 		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3208 		which gives 20 for most NANDs (MaxNVB is basically the total
3209 		count of eraseblocks on the chip).
3210 
3211 		To put it differently, if this value is 20, UBI will try to
3212 		reserve about 1.9% of physical eraseblocks for bad blocks
3213 		handling. And that will be 1.9% of eraseblocks on the entire
3214 		NAND chip, not just the MTD partition UBI attaches. This means
3215 		that if you have, say, a NAND flash chip admits maximum 40 bad
3216 		eraseblocks, and it is split on two MTD partitions of the same
3217 		size, UBI will reserve 40 eraseblocks when attaching a
3218 		partition.
3219 
3220 		default: 20
3221 
3222 		CONFIG_MTD_UBI_FASTMAP
3223 		Fastmap is a mechanism which allows attaching an UBI device
3224 		in nearly constant time. Instead of scanning the whole MTD device it
3225 		only has to locate a checkpoint (called fastmap) on the device.
3226 		The on-flash fastmap contains all information needed to attach
3227 		the device. Using fastmap makes only sense on large devices where
3228 		attaching by scanning takes long. UBI will not automatically install
3229 		a fastmap on old images, but you can set the UBI parameter
3230 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3231 		that fastmap-enabled images are still usable with UBI implementations
3232 		without	fastmap support. On typical flash devices the whole fastmap
3233 		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3234 
3235 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3236 		Set this parameter to enable fastmap automatically on images
3237 		without a fastmap.
3238 		default: 0
3239 
3240 		CONFIG_MTD_UBI_FM_DEBUG
3241 		Enable UBI fastmap debug
3242 		default: 0
3243 
3244 - UBIFS support
3245 		CONFIG_CMD_UBIFS
3246 
3247 		Adds commands for interacting with UBI volumes formatted as
3248 		UBIFS.  UBIFS is read-only in u-boot.
3249 
3250 		Requires UBI support as well as CONFIG_LZO
3251 
3252 		CONFIG_UBIFS_SILENCE_MSG
3253 
3254 		Make the verbose messages from UBIFS stop printing.  This leaves
3255 		warnings and errors enabled.
3256 
3257 - SPL framework
3258 		CONFIG_SPL
3259 		Enable building of SPL globally.
3260 
3261 		CONFIG_SPL_LDSCRIPT
3262 		LDSCRIPT for linking the SPL binary.
3263 
3264 		CONFIG_SPL_MAX_FOOTPRINT
3265 		Maximum size in memory allocated to the SPL, BSS included.
3266 		When defined, the linker checks that the actual memory
3267 		used by SPL from _start to __bss_end does not exceed it.
3268 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3269 		must not be both defined at the same time.
3270 
3271 		CONFIG_SPL_MAX_SIZE
3272 		Maximum size of the SPL image (text, data, rodata, and
3273 		linker lists sections), BSS excluded.
3274 		When defined, the linker checks that the actual size does
3275 		not exceed it.
3276 
3277 		CONFIG_SPL_TEXT_BASE
3278 		TEXT_BASE for linking the SPL binary.
3279 
3280 		CONFIG_SPL_RELOC_TEXT_BASE
3281 		Address to relocate to.  If unspecified, this is equal to
3282 		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3283 
3284 		CONFIG_SPL_BSS_START_ADDR
3285 		Link address for the BSS within the SPL binary.
3286 
3287 		CONFIG_SPL_BSS_MAX_SIZE
3288 		Maximum size in memory allocated to the SPL BSS.
3289 		When defined, the linker checks that the actual memory used
3290 		by SPL from __bss_start to __bss_end does not exceed it.
3291 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3292 		must not be both defined at the same time.
3293 
3294 		CONFIG_SPL_STACK
3295 		Adress of the start of the stack SPL will use
3296 
3297 		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3298 		When defined, SPL will panic() if the image it has
3299 		loaded does not have a signature.
3300 		Defining this is useful when code which loads images
3301 		in SPL cannot guarantee that absolutely all read errors
3302 		will be caught.
3303 		An example is the LPC32XX MLC NAND driver, which will
3304 		consider that a completely unreadable NAND block is bad,
3305 		and thus should be skipped silently.
3306 
3307 		CONFIG_SPL_ABORT_ON_RAW_IMAGE
3308 		When defined, SPL will proceed to another boot method
3309 		if the image it has loaded does not have a signature.
3310 
3311 		CONFIG_SPL_RELOC_STACK
3312 		Adress of the start of the stack SPL will use after
3313 		relocation.  If unspecified, this is equal to
3314 		CONFIG_SPL_STACK.
3315 
3316 		CONFIG_SYS_SPL_MALLOC_START
3317 		Starting address of the malloc pool used in SPL.
3318 		When this option is set the full malloc is used in SPL and
3319 		it is set up by spl_init() and before that, the simple malloc()
3320 		can be used if CONFIG_SYS_MALLOC_F is defined.
3321 
3322 		CONFIG_SYS_SPL_MALLOC_SIZE
3323 		The size of the malloc pool used in SPL.
3324 
3325 		CONFIG_SPL_FRAMEWORK
3326 		Enable the SPL framework under common/.  This framework
3327 		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3328 		NAND loading of the Linux Kernel.
3329 
3330 		CONFIG_SPL_OS_BOOT
3331 		Enable booting directly to an OS from SPL.
3332 		See also: doc/README.falcon
3333 
3334 		CONFIG_SPL_DISPLAY_PRINT
3335 		For ARM, enable an optional function to print more information
3336 		about the running system.
3337 
3338 		CONFIG_SPL_INIT_MINIMAL
3339 		Arch init code should be built for a very small image
3340 
3341 		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3342 		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3343 		Address and partition on the MMC to load U-Boot from
3344 		when the MMC is being used in raw mode.
3345 
3346 		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3347 		Partition on the MMC to load U-Boot from when the MMC is being
3348 		used in raw mode
3349 
3350 		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3351 		Sector to load kernel uImage from when MMC is being
3352 		used in raw mode (for Falcon mode)
3353 
3354 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3355 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3356 		Sector and number of sectors to load kernel argument
3357 		parameters from when MMC is being used in raw mode
3358 		(for falcon mode)
3359 
3360 		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3361 		Partition on the MMC to load U-Boot from when the MMC is being
3362 		used in fs mode
3363 
3364 		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3365 		Filename to read to load U-Boot when reading from filesystem
3366 
3367 		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3368 		Filename to read to load kernel uImage when reading
3369 		from filesystem (for Falcon mode)
3370 
3371 		CONFIG_SPL_FS_LOAD_ARGS_NAME
3372 		Filename to read to load kernel argument parameters
3373 		when reading from filesystem (for Falcon mode)
3374 
3375 		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3376 		Set this for NAND SPL on PPC mpc83xx targets, so that
3377 		start.S waits for the rest of the SPL to load before
3378 		continuing (the hardware starts execution after just
3379 		loading the first page rather than the full 4K).
3380 
3381 		CONFIG_SPL_SKIP_RELOCATE
3382 		Avoid SPL relocation
3383 
3384 		CONFIG_SPL_NAND_BASE
3385 		Include nand_base.c in the SPL.  Requires
3386 		CONFIG_SPL_NAND_DRIVERS.
3387 
3388 		CONFIG_SPL_NAND_DRIVERS
3389 		SPL uses normal NAND drivers, not minimal drivers.
3390 
3391 		CONFIG_SPL_NAND_ECC
3392 		Include standard software ECC in the SPL
3393 
3394 		CONFIG_SPL_NAND_SIMPLE
3395 		Support for NAND boot using simple NAND drivers that
3396 		expose the cmd_ctrl() interface.
3397 
3398 		CONFIG_SPL_UBI
3399 		Support for a lightweight UBI (fastmap) scanner and
3400 		loader
3401 
3402 		CONFIG_SPL_NAND_RAW_ONLY
3403 		Support to boot only raw u-boot.bin images. Use this only
3404 		if you need to save space.
3405 
3406 		CONFIG_SPL_COMMON_INIT_DDR
3407 		Set for common ddr init with serial presence detect in
3408 		SPL binary.
3409 
3410 		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3411 		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3412 		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3413 		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3414 		CONFIG_SYS_NAND_ECCBYTES
3415 		Defines the size and behavior of the NAND that SPL uses
3416 		to read U-Boot
3417 
3418 		CONFIG_SPL_NAND_BOOT
3419 		Add support NAND boot
3420 
3421 		CONFIG_SYS_NAND_U_BOOT_OFFS
3422 		Location in NAND to read U-Boot from
3423 
3424 		CONFIG_SYS_NAND_U_BOOT_DST
3425 		Location in memory to load U-Boot to
3426 
3427 		CONFIG_SYS_NAND_U_BOOT_SIZE
3428 		Size of image to load
3429 
3430 		CONFIG_SYS_NAND_U_BOOT_START
3431 		Entry point in loaded image to jump to
3432 
3433 		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3434 		Define this if you need to first read the OOB and then the
3435 		data. This is used, for example, on davinci platforms.
3436 
3437 		CONFIG_SPL_OMAP3_ID_NAND
3438 		Support for an OMAP3-specific set of functions to return the
3439 		ID and MFR of the first attached NAND chip, if present.
3440 
3441 		CONFIG_SPL_RAM_DEVICE
3442 		Support for running image already present in ram, in SPL binary
3443 
3444 		CONFIG_SPL_PAD_TO
3445 		Image offset to which the SPL should be padded before appending
3446 		the SPL payload. By default, this is defined as
3447 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3448 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3449 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3450 
3451 		CONFIG_SPL_TARGET
3452 		Final target image containing SPL and payload.  Some SPLs
3453 		use an arch-specific makefile fragment instead, for
3454 		example if more than one image needs to be produced.
3455 
3456 		CONFIG_FIT_SPL_PRINT
3457 		Printing information about a FIT image adds quite a bit of
3458 		code to SPL. So this is normally disabled in SPL. Use this
3459 		option to re-enable it. This will affect the output of the
3460 		bootm command when booting a FIT image.
3461 
3462 - TPL framework
3463 		CONFIG_TPL
3464 		Enable building of TPL globally.
3465 
3466 		CONFIG_TPL_PAD_TO
3467 		Image offset to which the TPL should be padded before appending
3468 		the TPL payload. By default, this is defined as
3469 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3470 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3471 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3472 
3473 - Interrupt support (PPC):
3474 
3475 		There are common interrupt_init() and timer_interrupt()
3476 		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3477 		for CPU specific initialization. interrupt_init_cpu()
3478 		should set decrementer_count to appropriate value. If
3479 		CPU resets decrementer automatically after interrupt
3480 		(ppc4xx) it should set decrementer_count to zero.
3481 		timer_interrupt() calls timer_interrupt_cpu() for CPU
3482 		specific handling. If board has watchdog / status_led
3483 		/ other_activity_monitor it works automatically from
3484 		general timer_interrupt().
3485 
3486 
3487 Board initialization settings:
3488 ------------------------------
3489 
3490 During Initialization u-boot calls a number of board specific functions
3491 to allow the preparation of board specific prerequisites, e.g. pin setup
3492 before drivers are initialized. To enable these callbacks the
3493 following configuration macros have to be defined. Currently this is
3494 architecture specific, so please check arch/your_architecture/lib/board.c
3495 typically in board_init_f() and board_init_r().
3496 
3497 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3498 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3499 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
3500 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3501 
3502 Configuration Settings:
3503 -----------------------
3504 
3505 - CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3506 		Optionally it can be defined to support 64-bit memory commands.
3507 
3508 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3509 		undefine this when you're short of memory.
3510 
3511 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3512 		width of the commands listed in the 'help' command output.
3513 
3514 - CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3515 		prompt for user input.
3516 
3517 - CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3518 
3519 - CONFIG_SYS_PBSIZE:	Buffer size for Console output
3520 
3521 - CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3522 
3523 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3524 		the application (usually a Linux kernel) when it is
3525 		booted
3526 
3527 - CONFIG_SYS_BAUDRATE_TABLE:
3528 		List of legal baudrate settings for this board.
3529 
3530 - CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3531 		Begin and End addresses of the area used by the
3532 		simple memory test.
3533 
3534 - CONFIG_SYS_ALT_MEMTEST:
3535 		Enable an alternate, more extensive memory test.
3536 
3537 - CONFIG_SYS_MEMTEST_SCRATCH:
3538 		Scratch address used by the alternate memory test
3539 		You only need to set this if address zero isn't writeable
3540 
3541 - CONFIG_SYS_MEM_RESERVE_SECURE
3542 		Only implemented for ARMv8 for now.
3543 		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3544 		is substracted from total RAM and won't be reported to OS.
3545 		This memory can be used as secure memory. A variable
3546 		gd->arch.secure_ram is used to track the location. In systems
3547 		the RAM base is not zero, or RAM is divided into banks,
3548 		this variable needs to be recalcuated to get the address.
3549 
3550 - CONFIG_SYS_MEM_TOP_HIDE:
3551 		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3552 		this specified memory area will get subtracted from the top
3553 		(end) of RAM and won't get "touched" at all by U-Boot. By
3554 		fixing up gd->ram_size the Linux kernel should gets passed
3555 		the now "corrected" memory size and won't touch it either.
3556 		This should work for arch/ppc and arch/powerpc. Only Linux
3557 		board ports in arch/powerpc with bootwrapper support that
3558 		recalculate the memory size from the SDRAM controller setup
3559 		will have to get fixed in Linux additionally.
3560 
3561 		This option can be used as a workaround for the 440EPx/GRx
3562 		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3563 		be touched.
3564 
3565 		WARNING: Please make sure that this value is a multiple of
3566 		the Linux page size (normally 4k). If this is not the case,
3567 		then the end address of the Linux memory will be located at a
3568 		non page size aligned address and this could cause major
3569 		problems.
3570 
3571 - CONFIG_SYS_LOADS_BAUD_CHANGE:
3572 		Enable temporary baudrate change while serial download
3573 
3574 - CONFIG_SYS_SDRAM_BASE:
3575 		Physical start address of SDRAM. _Must_ be 0 here.
3576 
3577 - CONFIG_SYS_FLASH_BASE:
3578 		Physical start address of Flash memory.
3579 
3580 - CONFIG_SYS_MONITOR_BASE:
3581 		Physical start address of boot monitor code (set by
3582 		make config files to be same as the text base address
3583 		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3584 		CONFIG_SYS_FLASH_BASE when booting from flash.
3585 
3586 - CONFIG_SYS_MONITOR_LEN:
3587 		Size of memory reserved for monitor code, used to
3588 		determine _at_compile_time_ (!) if the environment is
3589 		embedded within the U-Boot image, or in a separate
3590 		flash sector.
3591 
3592 - CONFIG_SYS_MALLOC_LEN:
3593 		Size of DRAM reserved for malloc() use.
3594 
3595 - CONFIG_SYS_MALLOC_F_LEN
3596 		Size of the malloc() pool for use before relocation. If
3597 		this is defined, then a very simple malloc() implementation
3598 		will become available before relocation. The address is just
3599 		below the global data, and the stack is moved down to make
3600 		space.
3601 
3602 		This feature allocates regions with increasing addresses
3603 		within the region. calloc() is supported, but realloc()
3604 		is not available. free() is supported but does nothing.
3605 		The memory will be freed (or in fact just forgotten) when
3606 		U-Boot relocates itself.
3607 
3608 - CONFIG_SYS_MALLOC_SIMPLE
3609 		Provides a simple and small malloc() and calloc() for those
3610 		boards which do not use the full malloc in SPL (which is
3611 		enabled with CONFIG_SYS_SPL_MALLOC_START).
3612 
3613 - CONFIG_SYS_NONCACHED_MEMORY:
3614 		Size of non-cached memory area. This area of memory will be
3615 		typically located right below the malloc() area and mapped
3616 		uncached in the MMU. This is useful for drivers that would
3617 		otherwise require a lot of explicit cache maintenance. For
3618 		some drivers it's also impossible to properly maintain the
3619 		cache. For example if the regions that need to be flushed
3620 		are not a multiple of the cache-line size, *and* padding
3621 		cannot be allocated between the regions to align them (i.e.
3622 		if the HW requires a contiguous array of regions, and the
3623 		size of each region is not cache-aligned), then a flush of
3624 		one region may result in overwriting data that hardware has
3625 		written to another region in the same cache-line. This can
3626 		happen for example in network drivers where descriptors for
3627 		buffers are typically smaller than the CPU cache-line (e.g.
3628 		16 bytes vs. 32 or 64 bytes).
3629 
3630 		Non-cached memory is only supported on 32-bit ARM at present.
3631 
3632 - CONFIG_SYS_BOOTM_LEN:
3633 		Normally compressed uImages are limited to an
3634 		uncompressed size of 8 MBytes. If this is not enough,
3635 		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3636 		to adjust this setting to your needs.
3637 
3638 - CONFIG_SYS_BOOTMAPSZ:
3639 		Maximum size of memory mapped by the startup code of
3640 		the Linux kernel; all data that must be processed by
3641 		the Linux kernel (bd_info, boot arguments, FDT blob if
3642 		used) must be put below this limit, unless "bootm_low"
3643 		environment variable is defined and non-zero. In such case
3644 		all data for the Linux kernel must be between "bootm_low"
3645 		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3646 		variable "bootm_mapsize" will override the value of
3647 		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3648 		then the value in "bootm_size" will be used instead.
3649 
3650 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
3651 		Enable initrd_high functionality.  If defined then the
3652 		initrd_high feature is enabled and the bootm ramdisk subcommand
3653 		is enabled.
3654 
3655 - CONFIG_SYS_BOOT_GET_CMDLINE:
3656 		Enables allocating and saving kernel cmdline in space between
3657 		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3658 
3659 - CONFIG_SYS_BOOT_GET_KBD:
3660 		Enables allocating and saving a kernel copy of the bd_info in
3661 		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3662 
3663 - CONFIG_SYS_MAX_FLASH_BANKS:
3664 		Max number of Flash memory banks
3665 
3666 - CONFIG_SYS_MAX_FLASH_SECT:
3667 		Max number of sectors on a Flash chip
3668 
3669 - CONFIG_SYS_FLASH_ERASE_TOUT:
3670 		Timeout for Flash erase operations (in ms)
3671 
3672 - CONFIG_SYS_FLASH_WRITE_TOUT:
3673 		Timeout for Flash write operations (in ms)
3674 
3675 - CONFIG_SYS_FLASH_LOCK_TOUT
3676 		Timeout for Flash set sector lock bit operation (in ms)
3677 
3678 - CONFIG_SYS_FLASH_UNLOCK_TOUT
3679 		Timeout for Flash clear lock bits operation (in ms)
3680 
3681 - CONFIG_SYS_FLASH_PROTECTION
3682 		If defined, hardware flash sectors protection is used
3683 		instead of U-Boot software protection.
3684 
3685 - CONFIG_SYS_DIRECT_FLASH_TFTP:
3686 
3687 		Enable TFTP transfers directly to flash memory;
3688 		without this option such a download has to be
3689 		performed in two steps: (1) download to RAM, and (2)
3690 		copy from RAM to flash.
3691 
3692 		The two-step approach is usually more reliable, since
3693 		you can check if the download worked before you erase
3694 		the flash, but in some situations (when system RAM is
3695 		too limited to allow for a temporary copy of the
3696 		downloaded image) this option may be very useful.
3697 
3698 - CONFIG_SYS_FLASH_CFI:
3699 		Define if the flash driver uses extra elements in the
3700 		common flash structure for storing flash geometry.
3701 
3702 - CONFIG_FLASH_CFI_DRIVER
3703 		This option also enables the building of the cfi_flash driver
3704 		in the drivers directory
3705 
3706 - CONFIG_FLASH_CFI_MTD
3707 		This option enables the building of the cfi_mtd driver
3708 		in the drivers directory. The driver exports CFI flash
3709 		to the MTD layer.
3710 
3711 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3712 		Use buffered writes to flash.
3713 
3714 - CONFIG_FLASH_SPANSION_S29WS_N
3715 		s29ws-n MirrorBit flash has non-standard addresses for buffered
3716 		write commands.
3717 
3718 - CONFIG_SYS_FLASH_QUIET_TEST
3719 		If this option is defined, the common CFI flash doesn't
3720 		print it's warning upon not recognized FLASH banks. This
3721 		is useful, if some of the configured banks are only
3722 		optionally available.
3723 
3724 - CONFIG_FLASH_SHOW_PROGRESS
3725 		If defined (must be an integer), print out countdown
3726 		digits and dots.  Recommended value: 45 (9..1) for 80
3727 		column displays, 15 (3..1) for 40 column displays.
3728 
3729 - CONFIG_FLASH_VERIFY
3730 		If defined, the content of the flash (destination) is compared
3731 		against the source after the write operation. An error message
3732 		will be printed when the contents are not identical.
3733 		Please note that this option is useless in nearly all cases,
3734 		since such flash programming errors usually are detected earlier
3735 		while unprotecting/erasing/programming. Please only enable
3736 		this option if you really know what you are doing.
3737 
3738 - CONFIG_SYS_RX_ETH_BUFFER:
3739 		Defines the number of Ethernet receive buffers. On some
3740 		Ethernet controllers it is recommended to set this value
3741 		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3742 		buffers can be full shortly after enabling the interface
3743 		on high Ethernet traffic.
3744 		Defaults to 4 if not defined.
3745 
3746 - CONFIG_ENV_MAX_ENTRIES
3747 
3748 	Maximum number of entries in the hash table that is used
3749 	internally to store the environment settings. The default
3750 	setting is supposed to be generous and should work in most
3751 	cases. This setting can be used to tune behaviour; see
3752 	lib/hashtable.c for details.
3753 
3754 - CONFIG_ENV_FLAGS_LIST_DEFAULT
3755 - CONFIG_ENV_FLAGS_LIST_STATIC
3756 	Enable validation of the values given to environment variables when
3757 	calling env set.  Variables can be restricted to only decimal,
3758 	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3759 	the variables can also be restricted to IP address or MAC address.
3760 
3761 	The format of the list is:
3762 		type_attribute = [s|d|x|b|i|m]
3763 		access_attribute = [a|r|o|c]
3764 		attributes = type_attribute[access_attribute]
3765 		entry = variable_name[:attributes]
3766 		list = entry[,list]
3767 
3768 	The type attributes are:
3769 		s - String (default)
3770 		d - Decimal
3771 		x - Hexadecimal
3772 		b - Boolean ([1yYtT|0nNfF])
3773 		i - IP address
3774 		m - MAC address
3775 
3776 	The access attributes are:
3777 		a - Any (default)
3778 		r - Read-only
3779 		o - Write-once
3780 		c - Change-default
3781 
3782 	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3783 		Define this to a list (string) to define the ".flags"
3784 		environment variable in the default or embedded environment.
3785 
3786 	- CONFIG_ENV_FLAGS_LIST_STATIC
3787 		Define this to a list (string) to define validation that
3788 		should be done if an entry is not found in the ".flags"
3789 		environment variable.  To override a setting in the static
3790 		list, simply add an entry for the same variable name to the
3791 		".flags" variable.
3792 
3793 	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3794 	regular expression. This allows multiple variables to define the same
3795 	flags without explicitly listing them for each variable.
3796 
3797 - CONFIG_ENV_ACCESS_IGNORE_FORCE
3798 	If defined, don't allow the -f switch to env set override variable
3799 	access flags.
3800 
3801 - CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3802 	This is set by OMAP boards for the max time that reset should
3803 	be asserted. See doc/README.omap-reset-time for details on how
3804 	the value can be calculated on a given board.
3805 
3806 - CONFIG_USE_STDINT
3807 	If stdint.h is available with your toolchain you can define this
3808 	option to enable it. You can provide option 'USE_STDINT=1' when
3809 	building U-Boot to enable this.
3810 
3811 The following definitions that deal with the placement and management
3812 of environment data (variable area); in general, we support the
3813 following configurations:
3814 
3815 - CONFIG_BUILD_ENVCRC:
3816 
3817 	Builds up envcrc with the target environment so that external utils
3818 	may easily extract it and embed it in final U-Boot images.
3819 
3820 - CONFIG_ENV_IS_IN_FLASH:
3821 
3822 	Define this if the environment is in flash memory.
3823 
3824 	a) The environment occupies one whole flash sector, which is
3825 	   "embedded" in the text segment with the U-Boot code. This
3826 	   happens usually with "bottom boot sector" or "top boot
3827 	   sector" type flash chips, which have several smaller
3828 	   sectors at the start or the end. For instance, such a
3829 	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3830 	   such a case you would place the environment in one of the
3831 	   4 kB sectors - with U-Boot code before and after it. With
3832 	   "top boot sector" type flash chips, you would put the
3833 	   environment in one of the last sectors, leaving a gap
3834 	   between U-Boot and the environment.
3835 
3836 	- CONFIG_ENV_OFFSET:
3837 
3838 	   Offset of environment data (variable area) to the
3839 	   beginning of flash memory; for instance, with bottom boot
3840 	   type flash chips the second sector can be used: the offset
3841 	   for this sector is given here.
3842 
3843 	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3844 
3845 	- CONFIG_ENV_ADDR:
3846 
3847 	   This is just another way to specify the start address of
3848 	   the flash sector containing the environment (instead of
3849 	   CONFIG_ENV_OFFSET).
3850 
3851 	- CONFIG_ENV_SECT_SIZE:
3852 
3853 	   Size of the sector containing the environment.
3854 
3855 
3856 	b) Sometimes flash chips have few, equal sized, BIG sectors.
3857 	   In such a case you don't want to spend a whole sector for
3858 	   the environment.
3859 
3860 	- CONFIG_ENV_SIZE:
3861 
3862 	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3863 	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3864 	   of this flash sector for the environment. This saves
3865 	   memory for the RAM copy of the environment.
3866 
3867 	   It may also save flash memory if you decide to use this
3868 	   when your environment is "embedded" within U-Boot code,
3869 	   since then the remainder of the flash sector could be used
3870 	   for U-Boot code. It should be pointed out that this is
3871 	   STRONGLY DISCOURAGED from a robustness point of view:
3872 	   updating the environment in flash makes it always
3873 	   necessary to erase the WHOLE sector. If something goes
3874 	   wrong before the contents has been restored from a copy in
3875 	   RAM, your target system will be dead.
3876 
3877 	- CONFIG_ENV_ADDR_REDUND
3878 	  CONFIG_ENV_SIZE_REDUND
3879 
3880 	   These settings describe a second storage area used to hold
3881 	   a redundant copy of the environment data, so that there is
3882 	   a valid backup copy in case there is a power failure during
3883 	   a "saveenv" operation.
3884 
3885 BE CAREFUL! Any changes to the flash layout, and some changes to the
3886 source code will make it necessary to adapt <board>/u-boot.lds*
3887 accordingly!
3888 
3889 
3890 - CONFIG_ENV_IS_IN_NVRAM:
3891 
3892 	Define this if you have some non-volatile memory device
3893 	(NVRAM, battery buffered SRAM) which you want to use for the
3894 	environment.
3895 
3896 	- CONFIG_ENV_ADDR:
3897 	- CONFIG_ENV_SIZE:
3898 
3899 	  These two #defines are used to determine the memory area you
3900 	  want to use for environment. It is assumed that this memory
3901 	  can just be read and written to, without any special
3902 	  provision.
3903 
3904 BE CAREFUL! The first access to the environment happens quite early
3905 in U-Boot initialization (when we try to get the setting of for the
3906 console baudrate). You *MUST* have mapped your NVRAM area then, or
3907 U-Boot will hang.
3908 
3909 Please note that even with NVRAM we still use a copy of the
3910 environment in RAM: we could work on NVRAM directly, but we want to
3911 keep settings there always unmodified except somebody uses "saveenv"
3912 to save the current settings.
3913 
3914 
3915 - CONFIG_ENV_IS_IN_EEPROM:
3916 
3917 	Use this if you have an EEPROM or similar serial access
3918 	device and a driver for it.
3919 
3920 	- CONFIG_ENV_OFFSET:
3921 	- CONFIG_ENV_SIZE:
3922 
3923 	  These two #defines specify the offset and size of the
3924 	  environment area within the total memory of your EEPROM.
3925 
3926 	- CONFIG_SYS_I2C_EEPROM_ADDR:
3927 	  If defined, specified the chip address of the EEPROM device.
3928 	  The default address is zero.
3929 
3930 	- CONFIG_SYS_I2C_EEPROM_BUS:
3931 	  If defined, specified the i2c bus of the EEPROM device.
3932 
3933 	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3934 	  If defined, the number of bits used to address bytes in a
3935 	  single page in the EEPROM device.  A 64 byte page, for example
3936 	  would require six bits.
3937 
3938 	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3939 	  If defined, the number of milliseconds to delay between
3940 	  page writes.	The default is zero milliseconds.
3941 
3942 	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3943 	  The length in bytes of the EEPROM memory array address.  Note
3944 	  that this is NOT the chip address length!
3945 
3946 	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3947 	  EEPROM chips that implement "address overflow" are ones
3948 	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3949 	  address and the extra bits end up in the "chip address" bit
3950 	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3951 	  byte chips.
3952 
3953 	  Note that we consider the length of the address field to
3954 	  still be one byte because the extra address bits are hidden
3955 	  in the chip address.
3956 
3957 	- CONFIG_SYS_EEPROM_SIZE:
3958 	  The size in bytes of the EEPROM device.
3959 
3960 	- CONFIG_ENV_EEPROM_IS_ON_I2C
3961 	  define this, if you have I2C and SPI activated, and your
3962 	  EEPROM, which holds the environment, is on the I2C bus.
3963 
3964 	- CONFIG_I2C_ENV_EEPROM_BUS
3965 	  if you have an Environment on an EEPROM reached over
3966 	  I2C muxes, you can define here, how to reach this
3967 	  EEPROM. For example:
3968 
3969 	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3970 
3971 	  EEPROM which holds the environment, is reached over
3972 	  a pca9547 i2c mux with address 0x70, channel 3.
3973 
3974 - CONFIG_ENV_IS_IN_DATAFLASH:
3975 
3976 	Define this if you have a DataFlash memory device which you
3977 	want to use for the environment.
3978 
3979 	- CONFIG_ENV_OFFSET:
3980 	- CONFIG_ENV_ADDR:
3981 	- CONFIG_ENV_SIZE:
3982 
3983 	  These three #defines specify the offset and size of the
3984 	  environment area within the total memory of your DataFlash placed
3985 	  at the specified address.
3986 
3987 - CONFIG_ENV_IS_IN_SPI_FLASH:
3988 
3989 	Define this if you have a SPI Flash memory device which you
3990 	want to use for the environment.
3991 
3992 	- CONFIG_ENV_OFFSET:
3993 	- CONFIG_ENV_SIZE:
3994 
3995 	  These two #defines specify the offset and size of the
3996 	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3997 	  aligned to an erase sector boundary.
3998 
3999 	- CONFIG_ENV_SECT_SIZE:
4000 
4001 	  Define the SPI flash's sector size.
4002 
4003 	- CONFIG_ENV_OFFSET_REDUND (optional):
4004 
4005 	  This setting describes a second storage area of CONFIG_ENV_SIZE
4006 	  size used to hold a redundant copy of the environment data, so
4007 	  that there is a valid backup copy in case there is a power failure
4008 	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
4009 	  aligned to an erase sector boundary.
4010 
4011 	- CONFIG_ENV_SPI_BUS (optional):
4012 	- CONFIG_ENV_SPI_CS (optional):
4013 
4014 	  Define the SPI bus and chip select. If not defined they will be 0.
4015 
4016 	- CONFIG_ENV_SPI_MAX_HZ (optional):
4017 
4018 	  Define the SPI max work clock. If not defined then use 1MHz.
4019 
4020 	- CONFIG_ENV_SPI_MODE (optional):
4021 
4022 	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4023 
4024 - CONFIG_ENV_IS_IN_REMOTE:
4025 
4026 	Define this if you have a remote memory space which you
4027 	want to use for the local device's environment.
4028 
4029 	- CONFIG_ENV_ADDR:
4030 	- CONFIG_ENV_SIZE:
4031 
4032 	  These two #defines specify the address and size of the
4033 	  environment area within the remote memory space. The
4034 	  local device can get the environment from remote memory
4035 	  space by SRIO or PCIE links.
4036 
4037 BE CAREFUL! For some special cases, the local device can not use
4038 "saveenv" command. For example, the local device will get the
4039 environment stored in a remote NOR flash by SRIO or PCIE link,
4040 but it can not erase, write this NOR flash by SRIO or PCIE interface.
4041 
4042 - CONFIG_ENV_IS_IN_NAND:
4043 
4044 	Define this if you have a NAND device which you want to use
4045 	for the environment.
4046 
4047 	- CONFIG_ENV_OFFSET:
4048 	- CONFIG_ENV_SIZE:
4049 
4050 	  These two #defines specify the offset and size of the environment
4051 	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4052 	  aligned to an erase block boundary.
4053 
4054 	- CONFIG_ENV_OFFSET_REDUND (optional):
4055 
4056 	  This setting describes a second storage area of CONFIG_ENV_SIZE
4057 	  size used to hold a redundant copy of the environment data, so
4058 	  that there is a valid backup copy in case there is a power failure
4059 	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
4060 	  aligned to an erase block boundary.
4061 
4062 	- CONFIG_ENV_RANGE (optional):
4063 
4064 	  Specifies the length of the region in which the environment
4065 	  can be written.  This should be a multiple of the NAND device's
4066 	  block size.  Specifying a range with more erase blocks than
4067 	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4068 	  the range to be avoided.
4069 
4070 	- CONFIG_ENV_OFFSET_OOB (optional):
4071 
4072 	  Enables support for dynamically retrieving the offset of the
4073 	  environment from block zero's out-of-band data.  The
4074 	  "nand env.oob" command can be used to record this offset.
4075 	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4076 	  using CONFIG_ENV_OFFSET_OOB.
4077 
4078 - CONFIG_NAND_ENV_DST
4079 
4080 	Defines address in RAM to which the nand_spl code should copy the
4081 	environment. If redundant environment is used, it will be copied to
4082 	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4083 
4084 - CONFIG_ENV_IS_IN_UBI:
4085 
4086 	Define this if you have an UBI volume that you want to use for the
4087 	environment.  This has the benefit of wear-leveling the environment
4088 	accesses, which is important on NAND.
4089 
4090 	- CONFIG_ENV_UBI_PART:
4091 
4092 	  Define this to a string that is the mtd partition containing the UBI.
4093 
4094 	- CONFIG_ENV_UBI_VOLUME:
4095 
4096 	  Define this to the name of the volume that you want to store the
4097 	  environment in.
4098 
4099 	- CONFIG_ENV_UBI_VOLUME_REDUND:
4100 
4101 	  Define this to the name of another volume to store a second copy of
4102 	  the environment in.  This will enable redundant environments in UBI.
4103 	  It is assumed that both volumes are in the same MTD partition.
4104 
4105 	- CONFIG_UBI_SILENCE_MSG
4106 	- CONFIG_UBIFS_SILENCE_MSG
4107 
4108 	  You will probably want to define these to avoid a really noisy system
4109 	  when storing the env in UBI.
4110 
4111 - CONFIG_ENV_IS_IN_FAT:
4112        Define this if you want to use the FAT file system for the environment.
4113 
4114        - FAT_ENV_INTERFACE:
4115 
4116          Define this to a string that is the name of the block device.
4117 
4118        - FAT_ENV_DEV_AND_PART:
4119 
4120          Define this to a string to specify the partition of the device. It can
4121          be as following:
4122 
4123            "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4124                - "D:P": device D partition P. Error occurs if device D has no
4125                         partition table.
4126                - "D:0": device D.
4127                - "D" or "D:": device D partition 1 if device D has partition
4128                               table, or the whole device D if has no partition
4129                               table.
4130                - "D:auto": first partition in device D with bootable flag set.
4131                            If none, first valid partition in device D. If no
4132                            partition table then means device D.
4133 
4134        - FAT_ENV_FILE:
4135 
4136          It's a string of the FAT file name. This file use to store the
4137          environment.
4138 
4139        - CONFIG_FAT_WRITE:
4140          This should be defined. Otherwise it cannot save the environment file.
4141 
4142 - CONFIG_ENV_IS_IN_MMC:
4143 
4144 	Define this if you have an MMC device which you want to use for the
4145 	environment.
4146 
4147 	- CONFIG_SYS_MMC_ENV_DEV:
4148 
4149 	  Specifies which MMC device the environment is stored in.
4150 
4151 	- CONFIG_SYS_MMC_ENV_PART (optional):
4152 
4153 	  Specifies which MMC partition the environment is stored in. If not
4154 	  set, defaults to partition 0, the user area. Common values might be
4155 	  1 (first MMC boot partition), 2 (second MMC boot partition).
4156 
4157 	- CONFIG_ENV_OFFSET:
4158 	- CONFIG_ENV_SIZE:
4159 
4160 	  These two #defines specify the offset and size of the environment
4161 	  area within the specified MMC device.
4162 
4163 	  If offset is positive (the usual case), it is treated as relative to
4164 	  the start of the MMC partition. If offset is negative, it is treated
4165 	  as relative to the end of the MMC partition. This can be useful if
4166 	  your board may be fitted with different MMC devices, which have
4167 	  different sizes for the MMC partitions, and you always want the
4168 	  environment placed at the very end of the partition, to leave the
4169 	  maximum possible space before it, to store other data.
4170 
4171 	  These two values are in units of bytes, but must be aligned to an
4172 	  MMC sector boundary.
4173 
4174 	- CONFIG_ENV_OFFSET_REDUND (optional):
4175 
4176 	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4177 	  hold a redundant copy of the environment data. This provides a
4178 	  valid backup copy in case the other copy is corrupted, e.g. due
4179 	  to a power failure during a "saveenv" operation.
4180 
4181 	  This value may also be positive or negative; this is handled in the
4182 	  same way as CONFIG_ENV_OFFSET.
4183 
4184 	  This value is also in units of bytes, but must also be aligned to
4185 	  an MMC sector boundary.
4186 
4187 	- CONFIG_ENV_SIZE_REDUND (optional):
4188 
4189 	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4190 	  set. If this value is set, it must be set to the same value as
4191 	  CONFIG_ENV_SIZE.
4192 
4193 - CONFIG_SYS_SPI_INIT_OFFSET
4194 
4195 	Defines offset to the initial SPI buffer area in DPRAM. The
4196 	area is used at an early stage (ROM part) if the environment
4197 	is configured to reside in the SPI EEPROM: We need a 520 byte
4198 	scratch DPRAM area. It is used between the two initialization
4199 	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4200 	to be a good choice since it makes it far enough from the
4201 	start of the data area as well as from the stack pointer.
4202 
4203 Please note that the environment is read-only until the monitor
4204 has been relocated to RAM and a RAM copy of the environment has been
4205 created; also, when using EEPROM you will have to use getenv_f()
4206 until then to read environment variables.
4207 
4208 The environment is protected by a CRC32 checksum. Before the monitor
4209 is relocated into RAM, as a result of a bad CRC you will be working
4210 with the compiled-in default environment - *silently*!!! [This is
4211 necessary, because the first environment variable we need is the
4212 "baudrate" setting for the console - if we have a bad CRC, we don't
4213 have any device yet where we could complain.]
4214 
4215 Note: once the monitor has been relocated, then it will complain if
4216 the default environment is used; a new CRC is computed as soon as you
4217 use the "saveenv" command to store a valid environment.
4218 
4219 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4220 		Echo the inverted Ethernet link state to the fault LED.
4221 
4222 		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4223 		      also needs to be defined.
4224 
4225 - CONFIG_SYS_FAULT_MII_ADDR:
4226 		MII address of the PHY to check for the Ethernet link state.
4227 
4228 - CONFIG_NS16550_MIN_FUNCTIONS:
4229 		Define this if you desire to only have use of the NS16550_init
4230 		and NS16550_putc functions for the serial driver located at
4231 		drivers/serial/ns16550.c.  This option is useful for saving
4232 		space for already greatly restricted images, including but not
4233 		limited to NAND_SPL configurations.
4234 
4235 - CONFIG_DISPLAY_BOARDINFO
4236 		Display information about the board that U-Boot is running on
4237 		when U-Boot starts up. The board function checkboard() is called
4238 		to do this.
4239 
4240 - CONFIG_DISPLAY_BOARDINFO_LATE
4241 		Similar to the previous option, but display this information
4242 		later, once stdio is running and output goes to the LCD, if
4243 		present.
4244 
4245 - CONFIG_BOARD_SIZE_LIMIT:
4246 		Maximum size of the U-Boot image. When defined, the
4247 		build system checks that the actual size does not
4248 		exceed it.
4249 
4250 Low Level (hardware related) configuration options:
4251 ---------------------------------------------------
4252 
4253 - CONFIG_SYS_CACHELINE_SIZE:
4254 		Cache Line Size of the CPU.
4255 
4256 - CONFIG_SYS_DEFAULT_IMMR:
4257 		Default address of the IMMR after system reset.
4258 
4259 		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4260 		and RPXsuper) to be able to adjust the position of
4261 		the IMMR register after a reset.
4262 
4263 - CONFIG_SYS_CCSRBAR_DEFAULT:
4264 		Default (power-on reset) physical address of CCSR on Freescale
4265 		PowerPC SOCs.
4266 
4267 - CONFIG_SYS_CCSRBAR:
4268 		Virtual address of CCSR.  On a 32-bit build, this is typically
4269 		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4270 
4271 		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4272 		for cross-platform code that uses that macro instead.
4273 
4274 - CONFIG_SYS_CCSRBAR_PHYS:
4275 		Physical address of CCSR.  CCSR can be relocated to a new
4276 		physical address, if desired.  In this case, this macro should
4277 		be set to that address.	 Otherwise, it should be set to the
4278 		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4279 		is typically relocated on 36-bit builds.  It is recommended
4280 		that this macro be defined via the _HIGH and _LOW macros:
4281 
4282 		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4283 			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4284 
4285 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4286 		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4287 		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4288 		used in assembly code, so it must not contain typecasts or
4289 		integer size suffixes (e.g. "ULL").
4290 
4291 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
4292 		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4293 		used in assembly code, so it must not contain typecasts or
4294 		integer size suffixes (e.g. "ULL").
4295 
4296 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4297 		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4298 		forced to a value that ensures that CCSR is not relocated.
4299 
4300 - Floppy Disk Support:
4301 		CONFIG_SYS_FDC_DRIVE_NUMBER
4302 
4303 		the default drive number (default value 0)
4304 
4305 		CONFIG_SYS_ISA_IO_STRIDE
4306 
4307 		defines the spacing between FDC chipset registers
4308 		(default value 1)
4309 
4310 		CONFIG_SYS_ISA_IO_OFFSET
4311 
4312 		defines the offset of register from address. It
4313 		depends on which part of the data bus is connected to
4314 		the FDC chipset. (default value 0)
4315 
4316 		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4317 		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4318 		default value.
4319 
4320 		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4321 		fdc_hw_init() is called at the beginning of the FDC
4322 		setup. fdc_hw_init() must be provided by the board
4323 		source code. It is used to make hardware-dependent
4324 		initializations.
4325 
4326 - CONFIG_IDE_AHB:
4327 		Most IDE controllers were designed to be connected with PCI
4328 		interface. Only few of them were designed for AHB interface.
4329 		When software is doing ATA command and data transfer to
4330 		IDE devices through IDE-AHB controller, some additional
4331 		registers accessing to these kind of IDE-AHB controller
4332 		is required.
4333 
4334 - CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4335 		DO NOT CHANGE unless you know exactly what you're
4336 		doing! (11-4) [MPC8xx/82xx systems only]
4337 
4338 - CONFIG_SYS_INIT_RAM_ADDR:
4339 
4340 		Start address of memory area that can be used for
4341 		initial data and stack; please note that this must be
4342 		writable memory that is working WITHOUT special
4343 		initialization, i. e. you CANNOT use normal RAM which
4344 		will become available only after programming the
4345 		memory controller and running certain initialization
4346 		sequences.
4347 
4348 		U-Boot uses the following memory types:
4349 		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4350 		- MPC824X: data cache
4351 		- PPC4xx:  data cache
4352 
4353 - CONFIG_SYS_GBL_DATA_OFFSET:
4354 
4355 		Offset of the initial data structure in the memory
4356 		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4357 		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4358 		data is located at the end of the available space
4359 		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4360 		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4361 		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4362 		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4363 
4364 	Note:
4365 		On the MPC824X (or other systems that use the data
4366 		cache for initial memory) the address chosen for
4367 		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4368 		point to an otherwise UNUSED address space between
4369 		the top of RAM and the start of the PCI space.
4370 
4371 - CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4372 
4373 - CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4374 
4375 - CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4376 
4377 - CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4378 
4379 - CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4380 
4381 - CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4382 
4383 - CONFIG_SYS_OR_TIMING_SDRAM:
4384 		SDRAM timing
4385 
4386 - CONFIG_SYS_MAMR_PTA:
4387 		periodic timer for refresh
4388 
4389 - CONFIG_SYS_DER:	Debug Event Register (37-47)
4390 
4391 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4392   CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4393   CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4394   CONFIG_SYS_BR1_PRELIM:
4395 		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4396 
4397 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4398   CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4399   CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4400 		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4401 
4402 - CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4403   CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4404 		Machine Mode Register and Memory Periodic Timer
4405 		Prescaler definitions (SDRAM timing)
4406 
4407 - CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4408 		enable I2C microcode relocation patch (MPC8xx);
4409 		define relocation offset in DPRAM [DSP2]
4410 
4411 - CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4412 		enable SMC microcode relocation patch (MPC8xx);
4413 		define relocation offset in DPRAM [SMC1]
4414 
4415 - CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4416 		enable SPI microcode relocation patch (MPC8xx);
4417 		define relocation offset in DPRAM [SCC4]
4418 
4419 - CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4420 		Offset of the bootmode word in DPRAM used by post
4421 		(Power On Self Tests). This definition overrides
4422 		#define'd default value in commproc.h resp.
4423 		cpm_8260.h.
4424 
4425 - CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4426   CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4427   CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4428   CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4429   CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4430   CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4431   CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4432   CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4433 		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4434 
4435 - CONFIG_PCI_DISABLE_PCIE:
4436 		Disable PCI-Express on systems where it is supported but not
4437 		required.
4438 
4439 - CONFIG_PCI_ENUM_ONLY
4440 		Only scan through and get the devices on the buses.
4441 		Don't do any setup work, presumably because someone or
4442 		something has already done it, and we don't need to do it
4443 		a second time.	Useful for platforms that are pre-booted
4444 		by coreboot or similar.
4445 
4446 - CONFIG_PCI_INDIRECT_BRIDGE:
4447 		Enable support for indirect PCI bridges.
4448 
4449 - CONFIG_SYS_SRIO:
4450 		Chip has SRIO or not
4451 
4452 - CONFIG_SRIO1:
4453 		Board has SRIO 1 port available
4454 
4455 - CONFIG_SRIO2:
4456 		Board has SRIO 2 port available
4457 
4458 - CONFIG_SRIO_PCIE_BOOT_MASTER
4459 		Board can support master function for Boot from SRIO and PCIE
4460 
4461 - CONFIG_SYS_SRIOn_MEM_VIRT:
4462 		Virtual Address of SRIO port 'n' memory region
4463 
4464 - CONFIG_SYS_SRIOn_MEM_PHYS:
4465 		Physical Address of SRIO port 'n' memory region
4466 
4467 - CONFIG_SYS_SRIOn_MEM_SIZE:
4468 		Size of SRIO port 'n' memory region
4469 
4470 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
4471 		Defined to tell the NAND controller that the NAND chip is using
4472 		a 16 bit bus.
4473 		Not all NAND drivers use this symbol.
4474 		Example of drivers that use it:
4475 		- drivers/mtd/nand/ndfc.c
4476 		- drivers/mtd/nand/mxc_nand.c
4477 
4478 - CONFIG_SYS_NDFC_EBC0_CFG
4479 		Sets the EBC0_CFG register for the NDFC. If not defined
4480 		a default value will be used.
4481 
4482 - CONFIG_SPD_EEPROM
4483 		Get DDR timing information from an I2C EEPROM. Common
4484 		with pluggable memory modules such as SODIMMs
4485 
4486   SPD_EEPROM_ADDRESS
4487 		I2C address of the SPD EEPROM
4488 
4489 - CONFIG_SYS_SPD_BUS_NUM
4490 		If SPD EEPROM is on an I2C bus other than the first
4491 		one, specify here. Note that the value must resolve
4492 		to something your driver can deal with.
4493 
4494 - CONFIG_SYS_DDR_RAW_TIMING
4495 		Get DDR timing information from other than SPD. Common with
4496 		soldered DDR chips onboard without SPD. DDR raw timing
4497 		parameters are extracted from datasheet and hard-coded into
4498 		header files or board specific files.
4499 
4500 - CONFIG_FSL_DDR_INTERACTIVE
4501 		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4502 
4503 - CONFIG_FSL_DDR_SYNC_REFRESH
4504 		Enable sync of refresh for multiple controllers.
4505 
4506 - CONFIG_FSL_DDR_BIST
4507 		Enable built-in memory test for Freescale DDR controllers.
4508 
4509 - CONFIG_SYS_83XX_DDR_USES_CS0
4510 		Only for 83xx systems. If specified, then DDR should
4511 		be configured using CS0 and CS1 instead of CS2 and CS3.
4512 
4513 - CONFIG_ETHER_ON_FEC[12]
4514 		Define to enable FEC[12] on a 8xx series processor.
4515 
4516 - CONFIG_FEC[12]_PHY
4517 		Define to the hardcoded PHY address which corresponds
4518 		to the given FEC; i. e.
4519 			#define CONFIG_FEC1_PHY 4
4520 		means that the PHY with address 4 is connected to FEC1
4521 
4522 		When set to -1, means to probe for first available.
4523 
4524 - CONFIG_FEC[12]_PHY_NORXERR
4525 		The PHY does not have a RXERR line (RMII only).
4526 		(so program the FEC to ignore it).
4527 
4528 - CONFIG_RMII
4529 		Enable RMII mode for all FECs.
4530 		Note that this is a global option, we can't
4531 		have one FEC in standard MII mode and another in RMII mode.
4532 
4533 - CONFIG_CRC32_VERIFY
4534 		Add a verify option to the crc32 command.
4535 		The syntax is:
4536 
4537 		=> crc32 -v <address> <count> <crc32>
4538 
4539 		Where address/count indicate a memory area
4540 		and crc32 is the correct crc32 which the
4541 		area should have.
4542 
4543 - CONFIG_LOOPW
4544 		Add the "loopw" memory command. This only takes effect if
4545 		the memory commands are activated globally (CONFIG_CMD_MEM).
4546 
4547 - CONFIG_MX_CYCLIC
4548 		Add the "mdc" and "mwc" memory commands. These are cyclic
4549 		"md/mw" commands.
4550 		Examples:
4551 
4552 		=> mdc.b 10 4 500
4553 		This command will print 4 bytes (10,11,12,13) each 500 ms.
4554 
4555 		=> mwc.l 100 12345678 10
4556 		This command will write 12345678 to address 100 all 10 ms.
4557 
4558 		This only takes effect if the memory commands are activated
4559 		globally (CONFIG_CMD_MEM).
4560 
4561 - CONFIG_SKIP_LOWLEVEL_INIT
4562 		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4563 		low level initializations (like setting up the memory
4564 		controller) are omitted and/or U-Boot does not
4565 		relocate itself into RAM.
4566 
4567 		Normally this variable MUST NOT be defined. The only
4568 		exception is when U-Boot is loaded (to RAM) by some
4569 		other boot loader or by a debugger which performs
4570 		these initializations itself.
4571 
4572 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4573 		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4574 		to be skipped. The normal CP15 init (such as enabling the
4575 		instruction cache) is still performed.
4576 
4577 - CONFIG_SPL_BUILD
4578 		Modifies the behaviour of start.S when compiling a loader
4579 		that is executed before the actual U-Boot. E.g. when
4580 		compiling a NAND SPL.
4581 
4582 - CONFIG_TPL_BUILD
4583 		Modifies the behaviour of start.S  when compiling a loader
4584 		that is executed after the SPL and before the actual U-Boot.
4585 		It is loaded by the SPL.
4586 
4587 - CONFIG_SYS_MPC85XX_NO_RESETVEC
4588 		Only for 85xx systems. If this variable is specified, the section
4589 		.resetvec is not kept and the section .bootpg is placed in the
4590 		previous 4k of the .text section.
4591 
4592 - CONFIG_ARCH_MAP_SYSMEM
4593 		Generally U-Boot (and in particular the md command) uses
4594 		effective address. It is therefore not necessary to regard
4595 		U-Boot address as virtual addresses that need to be translated
4596 		to physical addresses. However, sandbox requires this, since
4597 		it maintains its own little RAM buffer which contains all
4598 		addressable memory. This option causes some memory accesses
4599 		to be mapped through map_sysmem() / unmap_sysmem().
4600 
4601 - CONFIG_USE_ARCH_MEMCPY
4602   CONFIG_USE_ARCH_MEMSET
4603 		If these options are used a optimized version of memcpy/memset will
4604 		be used if available. These functions may be faster under some
4605 		conditions but may increase the binary size.
4606 
4607 - CONFIG_X86_RESET_VECTOR
4608 		If defined, the x86 reset vector code is included. This is not
4609 		needed when U-Boot is running from Coreboot.
4610 
4611 - CONFIG_SYS_MPUCLK
4612 		Defines the MPU clock speed (in MHz).
4613 
4614 		NOTE : currently only supported on AM335x platforms.
4615 
4616 - CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4617 		Enables the RTC32K OSC on AM33xx based plattforms
4618 
4619 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4620 		Option to disable subpage write in NAND driver
4621 		driver that uses this:
4622 		drivers/mtd/nand/davinci_nand.c
4623 
4624 Freescale QE/FMAN Firmware Support:
4625 -----------------------------------
4626 
4627 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4628 loading of "firmware", which is encoded in the QE firmware binary format.
4629 This firmware often needs to be loaded during U-Boot booting, so macros
4630 are used to identify the storage device (NOR flash, SPI, etc) and the address
4631 within that device.
4632 
4633 - CONFIG_SYS_FMAN_FW_ADDR
4634 	The address in the storage device where the FMAN microcode is located.  The
4635 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4636 	is also specified.
4637 
4638 - CONFIG_SYS_QE_FW_ADDR
4639 	The address in the storage device where the QE microcode is located.  The
4640 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4641 	is also specified.
4642 
4643 - CONFIG_SYS_QE_FMAN_FW_LENGTH
4644 	The maximum possible size of the firmware.  The firmware binary format
4645 	has a field that specifies the actual size of the firmware, but it
4646 	might not be possible to read any part of the firmware unless some
4647 	local storage is allocated to hold the entire firmware first.
4648 
4649 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
4650 	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4651 	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4652 	virtual address in NOR flash.
4653 
4654 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
4655 	Specifies that QE/FMAN firmware is located in NAND flash.
4656 	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4657 
4658 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
4659 	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4660 	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4661 
4662 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4663 	Specifies that QE/FMAN firmware is located in the remote (master)
4664 	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4665 	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4666 	window->master inbound window->master LAW->the ucode address in
4667 	master's memory space.
4668 
4669 Freescale Layerscape Management Complex Firmware Support:
4670 ---------------------------------------------------------
4671 The Freescale Layerscape Management Complex (MC) supports the loading of
4672 "firmware".
4673 This firmware often needs to be loaded during U-Boot booting, so macros
4674 are used to identify the storage device (NOR flash, SPI, etc) and the address
4675 within that device.
4676 
4677 - CONFIG_FSL_MC_ENET
4678 	Enable the MC driver for Layerscape SoCs.
4679 
4680 Freescale Layerscape Debug Server Support:
4681 -------------------------------------------
4682 The Freescale Layerscape Debug Server Support supports the loading of
4683 "Debug Server firmware" and triggering SP boot-rom.
4684 This firmware often needs to be loaded during U-Boot booting.
4685 
4686 - CONFIG_SYS_MC_RSV_MEM_ALIGN
4687 	Define alignment of reserved memory MC requires
4688 
4689 Reproducible builds
4690 -------------------
4691 
4692 In order to achieve reproducible builds, timestamps used in the U-Boot build
4693 process have to be set to a fixed value.
4694 
4695 This is done using the SOURCE_DATE_EPOCH environment variable.
4696 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4697 option for U-Boot or an environment variable in U-Boot.
4698 
4699 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4700 
4701 Building the Software:
4702 ======================
4703 
4704 Building U-Boot has been tested in several native build environments
4705 and in many different cross environments. Of course we cannot support
4706 all possibly existing versions of cross development tools in all
4707 (potentially obsolete) versions. In case of tool chain problems we
4708 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4709 which is extensively used to build and test U-Boot.
4710 
4711 If you are not using a native environment, it is assumed that you
4712 have GNU cross compiling tools available in your path. In this case,
4713 you must set the environment variable CROSS_COMPILE in your shell.
4714 Note that no changes to the Makefile or any other source files are
4715 necessary. For example using the ELDK on a 4xx CPU, please enter:
4716 
4717 	$ CROSS_COMPILE=ppc_4xx-
4718 	$ export CROSS_COMPILE
4719 
4720 Note: If you wish to generate Windows versions of the utilities in
4721       the tools directory you can use the MinGW toolchain
4722       (http://www.mingw.org).  Set your HOST tools to the MinGW
4723       toolchain and execute 'make tools'.  For example:
4724 
4725        $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4726 
4727       Binaries such as tools/mkimage.exe will be created which can
4728       be executed on computers running Windows.
4729 
4730 U-Boot is intended to be simple to build. After installing the
4731 sources you must configure U-Boot for one specific board type. This
4732 is done by typing:
4733 
4734 	make NAME_defconfig
4735 
4736 where "NAME_defconfig" is the name of one of the existing configu-
4737 rations; see boards.cfg for supported names.
4738 
4739 Note: for some board special configuration names may exist; check if
4740       additional information is available from the board vendor; for
4741       instance, the TQM823L systems are available without (standard)
4742       or with LCD support. You can select such additional "features"
4743       when choosing the configuration, i. e.
4744 
4745       make TQM823L_defconfig
4746 	- will configure for a plain TQM823L, i. e. no LCD support
4747 
4748       make TQM823L_LCD_defconfig
4749 	- will configure for a TQM823L with U-Boot console on LCD
4750 
4751       etc.
4752 
4753 
4754 Finally, type "make all", and you should get some working U-Boot
4755 images ready for download to / installation on your system:
4756 
4757 - "u-boot.bin" is a raw binary image
4758 - "u-boot" is an image in ELF binary format
4759 - "u-boot.srec" is in Motorola S-Record format
4760 
4761 By default the build is performed locally and the objects are saved
4762 in the source directory. One of the two methods can be used to change
4763 this behavior and build U-Boot to some external directory:
4764 
4765 1. Add O= to the make command line invocations:
4766 
4767 	make O=/tmp/build distclean
4768 	make O=/tmp/build NAME_defconfig
4769 	make O=/tmp/build all
4770 
4771 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
4772 
4773 	export KBUILD_OUTPUT=/tmp/build
4774 	make distclean
4775 	make NAME_defconfig
4776 	make all
4777 
4778 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4779 variable.
4780 
4781 
4782 Please be aware that the Makefiles assume you are using GNU make, so
4783 for instance on NetBSD you might need to use "gmake" instead of
4784 native "make".
4785 
4786 
4787 If the system board that you have is not listed, then you will need
4788 to port U-Boot to your hardware platform. To do this, follow these
4789 steps:
4790 
4791 1.  Create a new directory to hold your board specific code. Add any
4792     files you need. In your board directory, you will need at least
4793     the "Makefile" and a "<board>.c".
4794 2.  Create a new configuration file "include/configs/<board>.h" for
4795     your board.
4796 3.  If you're porting U-Boot to a new CPU, then also create a new
4797     directory to hold your CPU specific code. Add any files you need.
4798 4.  Run "make <board>_defconfig" with your new name.
4799 5.  Type "make", and you should get a working "u-boot.srec" file
4800     to be installed on your target system.
4801 6.  Debug and solve any problems that might arise.
4802     [Of course, this last step is much harder than it sounds.]
4803 
4804 
4805 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4806 ==============================================================
4807 
4808 If you have modified U-Boot sources (for instance added a new board
4809 or support for new devices, a new CPU, etc.) you are expected to
4810 provide feedback to the other developers. The feedback normally takes
4811 the form of a "patch", i. e. a context diff against a certain (latest
4812 official or latest in the git repository) version of U-Boot sources.
4813 
4814 But before you submit such a patch, please verify that your modifi-
4815 cation did not break existing code. At least make sure that *ALL* of
4816 the supported boards compile WITHOUT ANY compiler warnings. To do so,
4817 just run the buildman script (tools/buildman/buildman), which will
4818 configure and build U-Boot for ALL supported system. Be warned, this
4819 will take a while. Please see the buildman README, or run 'buildman -H'
4820 for documentation.
4821 
4822 
4823 See also "U-Boot Porting Guide" below.
4824 
4825 
4826 Monitor Commands - Overview:
4827 ============================
4828 
4829 go	- start application at address 'addr'
4830 run	- run commands in an environment variable
4831 bootm	- boot application image from memory
4832 bootp	- boot image via network using BootP/TFTP protocol
4833 bootz   - boot zImage from memory
4834 tftpboot- boot image via network using TFTP protocol
4835 	       and env variables "ipaddr" and "serverip"
4836 	       (and eventually "gatewayip")
4837 tftpput - upload a file via network using TFTP protocol
4838 rarpboot- boot image via network using RARP/TFTP protocol
4839 diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4840 loads	- load S-Record file over serial line
4841 loadb	- load binary file over serial line (kermit mode)
4842 md	- memory display
4843 mm	- memory modify (auto-incrementing)
4844 nm	- memory modify (constant address)
4845 mw	- memory write (fill)
4846 cp	- memory copy
4847 cmp	- memory compare
4848 crc32	- checksum calculation
4849 i2c	- I2C sub-system
4850 sspi	- SPI utility commands
4851 base	- print or set address offset
4852 printenv- print environment variables
4853 setenv	- set environment variables
4854 saveenv - save environment variables to persistent storage
4855 protect - enable or disable FLASH write protection
4856 erase	- erase FLASH memory
4857 flinfo	- print FLASH memory information
4858 nand	- NAND memory operations (see doc/README.nand)
4859 bdinfo	- print Board Info structure
4860 iminfo	- print header information for application image
4861 coninfo - print console devices and informations
4862 ide	- IDE sub-system
4863 loop	- infinite loop on address range
4864 loopw	- infinite write loop on address range
4865 mtest	- simple RAM test
4866 icache	- enable or disable instruction cache
4867 dcache	- enable or disable data cache
4868 reset	- Perform RESET of the CPU
4869 echo	- echo args to console
4870 version - print monitor version
4871 help	- print online help
4872 ?	- alias for 'help'
4873 
4874 
4875 Monitor Commands - Detailed Description:
4876 ========================================
4877 
4878 TODO.
4879 
4880 For now: just type "help <command>".
4881 
4882 
4883 Environment Variables:
4884 ======================
4885 
4886 U-Boot supports user configuration using Environment Variables which
4887 can be made persistent by saving to Flash memory.
4888 
4889 Environment Variables are set using "setenv", printed using
4890 "printenv", and saved to Flash using "saveenv". Using "setenv"
4891 without a value can be used to delete a variable from the
4892 environment. As long as you don't save the environment you are
4893 working with an in-memory copy. In case the Flash area containing the
4894 environment is erased by accident, a default environment is provided.
4895 
4896 Some configuration options can be set using Environment Variables.
4897 
4898 List of environment variables (most likely not complete):
4899 
4900   baudrate	- see CONFIG_BAUDRATE
4901 
4902   bootdelay	- see CONFIG_BOOTDELAY
4903 
4904   bootcmd	- see CONFIG_BOOTCOMMAND
4905 
4906   bootargs	- Boot arguments when booting an RTOS image
4907 
4908   bootfile	- Name of the image to load with TFTP
4909 
4910   bootm_low	- Memory range available for image processing in the bootm
4911 		  command can be restricted. This variable is given as
4912 		  a hexadecimal number and defines lowest address allowed
4913 		  for use by the bootm command. See also "bootm_size"
4914 		  environment variable. Address defined by "bootm_low" is
4915 		  also the base of the initial memory mapping for the Linux
4916 		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4917 		  bootm_mapsize.
4918 
4919   bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4920 		  This variable is given as a hexadecimal number and it
4921 		  defines the size of the memory region starting at base
4922 		  address bootm_low that is accessible by the Linux kernel
4923 		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4924 		  as the default value if it is defined, and bootm_size is
4925 		  used otherwise.
4926 
4927   bootm_size	- Memory range available for image processing in the bootm
4928 		  command can be restricted. This variable is given as
4929 		  a hexadecimal number and defines the size of the region
4930 		  allowed for use by the bootm command. See also "bootm_low"
4931 		  environment variable.
4932 
4933   updatefile	- Location of the software update file on a TFTP server, used
4934 		  by the automatic software update feature. Please refer to
4935 		  documentation in doc/README.update for more details.
4936 
4937   autoload	- if set to "no" (any string beginning with 'n'),
4938 		  "bootp" will just load perform a lookup of the
4939 		  configuration from the BOOTP server, but not try to
4940 		  load any image using TFTP
4941 
4942   autostart	- if set to "yes", an image loaded using the "bootp",
4943 		  "rarpboot", "tftpboot" or "diskboot" commands will
4944 		  be automatically started (by internally calling
4945 		  "bootm")
4946 
4947 		  If set to "no", a standalone image passed to the
4948 		  "bootm" command will be copied to the load address
4949 		  (and eventually uncompressed), but NOT be started.
4950 		  This can be used to load and uncompress arbitrary
4951 		  data.
4952 
4953   fdt_high	- if set this restricts the maximum address that the
4954 		  flattened device tree will be copied into upon boot.
4955 		  For example, if you have a system with 1 GB memory
4956 		  at physical address 0x10000000, while Linux kernel
4957 		  only recognizes the first 704 MB as low memory, you
4958 		  may need to set fdt_high as 0x3C000000 to have the
4959 		  device tree blob be copied to the maximum address
4960 		  of the 704 MB low memory, so that Linux kernel can
4961 		  access it during the boot procedure.
4962 
4963 		  If this is set to the special value 0xFFFFFFFF then
4964 		  the fdt will not be copied at all on boot.  For this
4965 		  to work it must reside in writable memory, have
4966 		  sufficient padding on the end of it for u-boot to
4967 		  add the information it needs into it, and the memory
4968 		  must be accessible by the kernel.
4969 
4970   fdtcontroladdr- if set this is the address of the control flattened
4971 		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4972 		  defined.
4973 
4974   i2cfast	- (PPC405GP|PPC405EP only)
4975 		  if set to 'y' configures Linux I2C driver for fast
4976 		  mode (400kHZ). This environment variable is used in
4977 		  initialization code. So, for changes to be effective
4978 		  it must be saved and board must be reset.
4979 
4980   initrd_high	- restrict positioning of initrd images:
4981 		  If this variable is not set, initrd images will be
4982 		  copied to the highest possible address in RAM; this
4983 		  is usually what you want since it allows for
4984 		  maximum initrd size. If for some reason you want to
4985 		  make sure that the initrd image is loaded below the
4986 		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4987 		  variable to a value of "no" or "off" or "0".
4988 		  Alternatively, you can set it to a maximum upper
4989 		  address to use (U-Boot will still check that it
4990 		  does not overwrite the U-Boot stack and data).
4991 
4992 		  For instance, when you have a system with 16 MB
4993 		  RAM, and want to reserve 4 MB from use by Linux,
4994 		  you can do this by adding "mem=12M" to the value of
4995 		  the "bootargs" variable. However, now you must make
4996 		  sure that the initrd image is placed in the first
4997 		  12 MB as well - this can be done with
4998 
4999 		  setenv initrd_high 00c00000
5000 
5001 		  If you set initrd_high to 0xFFFFFFFF, this is an
5002 		  indication to U-Boot that all addresses are legal
5003 		  for the Linux kernel, including addresses in flash
5004 		  memory. In this case U-Boot will NOT COPY the
5005 		  ramdisk at all. This may be useful to reduce the
5006 		  boot time on your system, but requires that this
5007 		  feature is supported by your Linux kernel.
5008 
5009   ipaddr	- IP address; needed for tftpboot command
5010 
5011   loadaddr	- Default load address for commands like "bootp",
5012 		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5013 
5014   loads_echo	- see CONFIG_LOADS_ECHO
5015 
5016   serverip	- TFTP server IP address; needed for tftpboot command
5017 
5018   bootretry	- see CONFIG_BOOT_RETRY_TIME
5019 
5020   bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5021 
5022   bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5023 
5024   ethprime	- controls which interface is used first.
5025 
5026   ethact	- controls which interface is currently active.
5027 		  For example you can do the following
5028 
5029 		  => setenv ethact FEC
5030 		  => ping 192.168.0.1 # traffic sent on FEC
5031 		  => setenv ethact SCC
5032 		  => ping 10.0.0.1 # traffic sent on SCC
5033 
5034   ethrotate	- When set to "no" U-Boot does not go through all
5035 		  available network interfaces.
5036 		  It just stays at the currently selected interface.
5037 
5038   netretry	- When set to "no" each network operation will
5039 		  either succeed or fail without retrying.
5040 		  When set to "once" the network operation will
5041 		  fail when all the available network interfaces
5042 		  are tried once without success.
5043 		  Useful on scripts which control the retry operation
5044 		  themselves.
5045 
5046   npe_ucode	- set load address for the NPE microcode
5047 
5048   silent_linux  - If set then Linux will be told to boot silently, by
5049 		  changing the console to be empty. If "yes" it will be
5050 		  made silent. If "no" it will not be made silent. If
5051 		  unset, then it will be made silent if the U-Boot console
5052 		  is silent.
5053 
5054   tftpsrcp	- If this is set, the value is used for TFTP's
5055 		  UDP source port.
5056 
5057   tftpdstp	- If this is set, the value is used for TFTP's UDP
5058 		  destination port instead of the Well Know Port 69.
5059 
5060   tftpblocksize - Block size to use for TFTP transfers; if not set,
5061 		  we use the TFTP server's default block size
5062 
5063   tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5064 		  seconds, minimum value is 1000 = 1 second). Defines
5065 		  when a packet is considered to be lost so it has to
5066 		  be retransmitted. The default is 5000 = 5 seconds.
5067 		  Lowering this value may make downloads succeed
5068 		  faster in networks with high packet loss rates or
5069 		  with unreliable TFTP servers.
5070 
5071   tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5072 		  unit, minimum value = 0). Defines how many timeouts
5073 		  can happen during a single file transfer before that
5074 		  transfer is aborted. The default is 10, and 0 means
5075 		  'no timeouts allowed'. Increasing this value may help
5076 		  downloads succeed with high packet loss rates, or with
5077 		  unreliable TFTP servers or client hardware.
5078 
5079   vlan		- When set to a value < 4095 the traffic over
5080 		  Ethernet is encapsulated/received over 802.1q
5081 		  VLAN tagged frames.
5082 
5083   bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5084 		  Unsigned value, in milliseconds. If not set, the period will
5085 		  be either the default (28000), or a value based on
5086 		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5087 		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5088 
5089 The following image location variables contain the location of images
5090 used in booting. The "Image" column gives the role of the image and is
5091 not an environment variable name. The other columns are environment
5092 variable names. "File Name" gives the name of the file on a TFTP
5093 server, "RAM Address" gives the location in RAM the image will be
5094 loaded to, and "Flash Location" gives the image's address in NOR
5095 flash or offset in NAND flash.
5096 
5097 *Note* - these variables don't have to be defined for all boards, some
5098 boards currently use other variables for these purposes, and some
5099 boards use these variables for other purposes.
5100 
5101 Image		    File Name	     RAM Address       Flash Location
5102 -----		    ---------	     -----------       --------------
5103 u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5104 Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5105 device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5106 ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5107 
5108 The following environment variables may be used and automatically
5109 updated by the network boot commands ("bootp" and "rarpboot"),
5110 depending the information provided by your boot server:
5111 
5112   bootfile	- see above
5113   dnsip		- IP address of your Domain Name Server
5114   dnsip2	- IP address of your secondary Domain Name Server
5115   gatewayip	- IP address of the Gateway (Router) to use
5116   hostname	- Target hostname
5117   ipaddr	- see above
5118   netmask	- Subnet Mask
5119   rootpath	- Pathname of the root filesystem on the NFS server
5120   serverip	- see above
5121 
5122 
5123 There are two special Environment Variables:
5124 
5125   serial#	- contains hardware identification information such
5126 		  as type string and/or serial number
5127   ethaddr	- Ethernet address
5128 
5129 These variables can be set only once (usually during manufacturing of
5130 the board). U-Boot refuses to delete or overwrite these variables
5131 once they have been set once.
5132 
5133 
5134 Further special Environment Variables:
5135 
5136   ver		- Contains the U-Boot version string as printed
5137 		  with the "version" command. This variable is
5138 		  readonly (see CONFIG_VERSION_VARIABLE).
5139 
5140 
5141 Please note that changes to some configuration parameters may take
5142 only effect after the next boot (yes, that's just like Windoze :-).
5143 
5144 
5145 Callback functions for environment variables:
5146 ---------------------------------------------
5147 
5148 For some environment variables, the behavior of u-boot needs to change
5149 when their values are changed.  This functionality allows functions to
5150 be associated with arbitrary variables.  On creation, overwrite, or
5151 deletion, the callback will provide the opportunity for some side
5152 effect to happen or for the change to be rejected.
5153 
5154 The callbacks are named and associated with a function using the
5155 U_BOOT_ENV_CALLBACK macro in your board or driver code.
5156 
5157 These callbacks are associated with variables in one of two ways.  The
5158 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5159 in the board configuration to a string that defines a list of
5160 associations.  The list must be in the following format:
5161 
5162 	entry = variable_name[:callback_name]
5163 	list = entry[,list]
5164 
5165 If the callback name is not specified, then the callback is deleted.
5166 Spaces are also allowed anywhere in the list.
5167 
5168 Callbacks can also be associated by defining the ".callbacks" variable
5169 with the same list format above.  Any association in ".callbacks" will
5170 override any association in the static list. You can define
5171 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5172 ".callbacks" environment variable in the default or embedded environment.
5173 
5174 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5175 regular expression. This allows multiple variables to be connected to
5176 the same callback without explicitly listing them all out.
5177 
5178 
5179 Command Line Parsing:
5180 =====================
5181 
5182 There are two different command line parsers available with U-Boot:
5183 the old "simple" one, and the much more powerful "hush" shell:
5184 
5185 Old, simple command line parser:
5186 --------------------------------
5187 
5188 - supports environment variables (through setenv / saveenv commands)
5189 - several commands on one line, separated by ';'
5190 - variable substitution using "... ${name} ..." syntax
5191 - special characters ('$', ';') can be escaped by prefixing with '\',
5192   for example:
5193 	setenv bootcmd bootm \${address}
5194 - You can also escape text by enclosing in single apostrophes, for example:
5195 	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5196 
5197 Hush shell:
5198 -----------
5199 
5200 - similar to Bourne shell, with control structures like
5201   if...then...else...fi, for...do...done; while...do...done,
5202   until...do...done, ...
5203 - supports environment ("global") variables (through setenv / saveenv
5204   commands) and local shell variables (through standard shell syntax
5205   "name=value"); only environment variables can be used with "run"
5206   command
5207 
5208 General rules:
5209 --------------
5210 
5211 (1) If a command line (or an environment variable executed by a "run"
5212     command) contains several commands separated by semicolon, and
5213     one of these commands fails, then the remaining commands will be
5214     executed anyway.
5215 
5216 (2) If you execute several variables with one call to run (i. e.
5217     calling run with a list of variables as arguments), any failing
5218     command will cause "run" to terminate, i. e. the remaining
5219     variables are not executed.
5220 
5221 Note for Redundant Ethernet Interfaces:
5222 =======================================
5223 
5224 Some boards come with redundant Ethernet interfaces; U-Boot supports
5225 such configurations and is capable of automatic selection of a
5226 "working" interface when needed. MAC assignment works as follows:
5227 
5228 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5229 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5230 "eth1addr" (=>eth1), "eth2addr", ...
5231 
5232 If the network interface stores some valid MAC address (for instance
5233 in SROM), this is used as default address if there is NO correspon-
5234 ding setting in the environment; if the corresponding environment
5235 variable is set, this overrides the settings in the card; that means:
5236 
5237 o If the SROM has a valid MAC address, and there is no address in the
5238   environment, the SROM's address is used.
5239 
5240 o If there is no valid address in the SROM, and a definition in the
5241   environment exists, then the value from the environment variable is
5242   used.
5243 
5244 o If both the SROM and the environment contain a MAC address, and
5245   both addresses are the same, this MAC address is used.
5246 
5247 o If both the SROM and the environment contain a MAC address, and the
5248   addresses differ, the value from the environment is used and a
5249   warning is printed.
5250 
5251 o If neither SROM nor the environment contain a MAC address, an error
5252   is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5253   a random, locally-assigned MAC is used.
5254 
5255 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5256 will be programmed into hardware as part of the initialization process.	 This
5257 may be skipped by setting the appropriate 'ethmacskip' environment variable.
5258 The naming convention is as follows:
5259 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5260 
5261 Image Formats:
5262 ==============
5263 
5264 U-Boot is capable of booting (and performing other auxiliary operations on)
5265 images in two formats:
5266 
5267 New uImage format (FIT)
5268 -----------------------
5269 
5270 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5271 to Flattened Device Tree). It allows the use of images with multiple
5272 components (several kernels, ramdisks, etc.), with contents protected by
5273 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5274 
5275 
5276 Old uImage format
5277 -----------------
5278 
5279 Old image format is based on binary files which can be basically anything,
5280 preceded by a special header; see the definitions in include/image.h for
5281 details; basically, the header defines the following image properties:
5282 
5283 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5284   4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5285   LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5286   Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5287   INTEGRITY).
5288 * Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5289   IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5290   Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5291 * Compression Type (uncompressed, gzip, bzip2)
5292 * Load Address
5293 * Entry Point
5294 * Image Name
5295 * Image Timestamp
5296 
5297 The header is marked by a special Magic Number, and both the header
5298 and the data portions of the image are secured against corruption by
5299 CRC32 checksums.
5300 
5301 
5302 Linux Support:
5303 ==============
5304 
5305 Although U-Boot should support any OS or standalone application
5306 easily, the main focus has always been on Linux during the design of
5307 U-Boot.
5308 
5309 U-Boot includes many features that so far have been part of some
5310 special "boot loader" code within the Linux kernel. Also, any
5311 "initrd" images to be used are no longer part of one big Linux image;
5312 instead, kernel and "initrd" are separate images. This implementation
5313 serves several purposes:
5314 
5315 - the same features can be used for other OS or standalone
5316   applications (for instance: using compressed images to reduce the
5317   Flash memory footprint)
5318 
5319 - it becomes much easier to port new Linux kernel versions because
5320   lots of low-level, hardware dependent stuff are done by U-Boot
5321 
5322 - the same Linux kernel image can now be used with different "initrd"
5323   images; of course this also means that different kernel images can
5324   be run with the same "initrd". This makes testing easier (you don't
5325   have to build a new "zImage.initrd" Linux image when you just
5326   change a file in your "initrd"). Also, a field-upgrade of the
5327   software is easier now.
5328 
5329 
5330 Linux HOWTO:
5331 ============
5332 
5333 Porting Linux to U-Boot based systems:
5334 ---------------------------------------
5335 
5336 U-Boot cannot save you from doing all the necessary modifications to
5337 configure the Linux device drivers for use with your target hardware
5338 (no, we don't intend to provide a full virtual machine interface to
5339 Linux :-).
5340 
5341 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5342 
5343 Just make sure your machine specific header file (for instance
5344 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5345 Information structure as we define in include/asm-<arch>/u-boot.h,
5346 and make sure that your definition of IMAP_ADDR uses the same value
5347 as your U-Boot configuration in CONFIG_SYS_IMMR.
5348 
5349 Note that U-Boot now has a driver model, a unified model for drivers.
5350 If you are adding a new driver, plumb it into driver model. If there
5351 is no uclass available, you are encouraged to create one. See
5352 doc/driver-model.
5353 
5354 
5355 Configuring the Linux kernel:
5356 -----------------------------
5357 
5358 No specific requirements for U-Boot. Make sure you have some root
5359 device (initial ramdisk, NFS) for your target system.
5360 
5361 
5362 Building a Linux Image:
5363 -----------------------
5364 
5365 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5366 not used. If you use recent kernel source, a new build target
5367 "uImage" will exist which automatically builds an image usable by
5368 U-Boot. Most older kernels also have support for a "pImage" target,
5369 which was introduced for our predecessor project PPCBoot and uses a
5370 100% compatible format.
5371 
5372 Example:
5373 
5374 	make TQM850L_defconfig
5375 	make oldconfig
5376 	make dep
5377 	make uImage
5378 
5379 The "uImage" build target uses a special tool (in 'tools/mkimage') to
5380 encapsulate a compressed Linux kernel image with header	 information,
5381 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5382 
5383 * build a standard "vmlinux" kernel image (in ELF binary format):
5384 
5385 * convert the kernel into a raw binary image:
5386 
5387 	${CROSS_COMPILE}-objcopy -O binary \
5388 				 -R .note -R .comment \
5389 				 -S vmlinux linux.bin
5390 
5391 * compress the binary image:
5392 
5393 	gzip -9 linux.bin
5394 
5395 * package compressed binary image for U-Boot:
5396 
5397 	mkimage -A ppc -O linux -T kernel -C gzip \
5398 		-a 0 -e 0 -n "Linux Kernel Image" \
5399 		-d linux.bin.gz uImage
5400 
5401 
5402 The "mkimage" tool can also be used to create ramdisk images for use
5403 with U-Boot, either separated from the Linux kernel image, or
5404 combined into one file. "mkimage" encapsulates the images with a 64
5405 byte header containing information about target architecture,
5406 operating system, image type, compression method, entry points, time
5407 stamp, CRC32 checksums, etc.
5408 
5409 "mkimage" can be called in two ways: to verify existing images and
5410 print the header information, or to build new images.
5411 
5412 In the first form (with "-l" option) mkimage lists the information
5413 contained in the header of an existing U-Boot image; this includes
5414 checksum verification:
5415 
5416 	tools/mkimage -l image
5417 	  -l ==> list image header information
5418 
5419 The second form (with "-d" option) is used to build a U-Boot image
5420 from a "data file" which is used as image payload:
5421 
5422 	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5423 		      -n name -d data_file image
5424 	  -A ==> set architecture to 'arch'
5425 	  -O ==> set operating system to 'os'
5426 	  -T ==> set image type to 'type'
5427 	  -C ==> set compression type 'comp'
5428 	  -a ==> set load address to 'addr' (hex)
5429 	  -e ==> set entry point to 'ep' (hex)
5430 	  -n ==> set image name to 'name'
5431 	  -d ==> use image data from 'datafile'
5432 
5433 Right now, all Linux kernels for PowerPC systems use the same load
5434 address (0x00000000), but the entry point address depends on the
5435 kernel version:
5436 
5437 - 2.2.x kernels have the entry point at 0x0000000C,
5438 - 2.3.x and later kernels have the entry point at 0x00000000.
5439 
5440 So a typical call to build a U-Boot image would read:
5441 
5442 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5443 	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5444 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5445 	> examples/uImage.TQM850L
5446 	Image Name:   2.4.4 kernel for TQM850L
5447 	Created:      Wed Jul 19 02:34:59 2000
5448 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5449 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5450 	Load Address: 0x00000000
5451 	Entry Point:  0x00000000
5452 
5453 To verify the contents of the image (or check for corruption):
5454 
5455 	-> tools/mkimage -l examples/uImage.TQM850L
5456 	Image Name:   2.4.4 kernel for TQM850L
5457 	Created:      Wed Jul 19 02:34:59 2000
5458 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5459 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5460 	Load Address: 0x00000000
5461 	Entry Point:  0x00000000
5462 
5463 NOTE: for embedded systems where boot time is critical you can trade
5464 speed for memory and install an UNCOMPRESSED image instead: this
5465 needs more space in Flash, but boots much faster since it does not
5466 need to be uncompressed:
5467 
5468 	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5469 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5470 	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5471 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5472 	> examples/uImage.TQM850L-uncompressed
5473 	Image Name:   2.4.4 kernel for TQM850L
5474 	Created:      Wed Jul 19 02:34:59 2000
5475 	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5476 	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5477 	Load Address: 0x00000000
5478 	Entry Point:  0x00000000
5479 
5480 
5481 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5482 when your kernel is intended to use an initial ramdisk:
5483 
5484 	-> tools/mkimage -n 'Simple Ramdisk Image' \
5485 	> -A ppc -O linux -T ramdisk -C gzip \
5486 	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5487 	Image Name:   Simple Ramdisk Image
5488 	Created:      Wed Jan 12 14:01:50 2000
5489 	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5490 	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5491 	Load Address: 0x00000000
5492 	Entry Point:  0x00000000
5493 
5494 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5495 option performs the converse operation of the mkimage's second form (the "-d"
5496 option). Given an image built by mkimage, the dumpimage extracts a "data file"
5497 from the image:
5498 
5499 	tools/dumpimage -i image -T type -p position data_file
5500 	  -i ==> extract from the 'image' a specific 'data_file'
5501 	  -T ==> set image type to 'type'
5502 	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5503 
5504 
5505 Installing a Linux Image:
5506 -------------------------
5507 
5508 To downloading a U-Boot image over the serial (console) interface,
5509 you must convert the image to S-Record format:
5510 
5511 	objcopy -I binary -O srec examples/image examples/image.srec
5512 
5513 The 'objcopy' does not understand the information in the U-Boot
5514 image header, so the resulting S-Record file will be relative to
5515 address 0x00000000. To load it to a given address, you need to
5516 specify the target address as 'offset' parameter with the 'loads'
5517 command.
5518 
5519 Example: install the image to address 0x40100000 (which on the
5520 TQM8xxL is in the first Flash bank):
5521 
5522 	=> erase 40100000 401FFFFF
5523 
5524 	.......... done
5525 	Erased 8 sectors
5526 
5527 	=> loads 40100000
5528 	## Ready for S-Record download ...
5529 	~>examples/image.srec
5530 	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5531 	...
5532 	15989 15990 15991 15992
5533 	[file transfer complete]
5534 	[connected]
5535 	## Start Addr = 0x00000000
5536 
5537 
5538 You can check the success of the download using the 'iminfo' command;
5539 this includes a checksum verification so you can be sure no data
5540 corruption happened:
5541 
5542 	=> imi 40100000
5543 
5544 	## Checking Image at 40100000 ...
5545 	   Image Name:	 2.2.13 for initrd on TQM850L
5546 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5547 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5548 	   Load Address: 00000000
5549 	   Entry Point:	 0000000c
5550 	   Verifying Checksum ... OK
5551 
5552 
5553 Boot Linux:
5554 -----------
5555 
5556 The "bootm" command is used to boot an application that is stored in
5557 memory (RAM or Flash). In case of a Linux kernel image, the contents
5558 of the "bootargs" environment variable is passed to the kernel as
5559 parameters. You can check and modify this variable using the
5560 "printenv" and "setenv" commands:
5561 
5562 
5563 	=> printenv bootargs
5564 	bootargs=root=/dev/ram
5565 
5566 	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5567 
5568 	=> printenv bootargs
5569 	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5570 
5571 	=> bootm 40020000
5572 	## Booting Linux kernel at 40020000 ...
5573 	   Image Name:	 2.2.13 for NFS on TQM850L
5574 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5575 	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5576 	   Load Address: 00000000
5577 	   Entry Point:	 0000000c
5578 	   Verifying Checksum ... OK
5579 	   Uncompressing Kernel Image ... OK
5580 	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
5581 	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5582 	time_init: decrementer frequency = 187500000/60
5583 	Calibrating delay loop... 49.77 BogoMIPS
5584 	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5585 	...
5586 
5587 If you want to boot a Linux kernel with initial RAM disk, you pass
5588 the memory addresses of both the kernel and the initrd image (PPBCOOT
5589 format!) to the "bootm" command:
5590 
5591 	=> imi 40100000 40200000
5592 
5593 	## Checking Image at 40100000 ...
5594 	   Image Name:	 2.2.13 for initrd on TQM850L
5595 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5596 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5597 	   Load Address: 00000000
5598 	   Entry Point:	 0000000c
5599 	   Verifying Checksum ... OK
5600 
5601 	## Checking Image at 40200000 ...
5602 	   Image Name:	 Simple Ramdisk Image
5603 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5604 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5605 	   Load Address: 00000000
5606 	   Entry Point:	 00000000
5607 	   Verifying Checksum ... OK
5608 
5609 	=> bootm 40100000 40200000
5610 	## Booting Linux kernel at 40100000 ...
5611 	   Image Name:	 2.2.13 for initrd on TQM850L
5612 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5613 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5614 	   Load Address: 00000000
5615 	   Entry Point:	 0000000c
5616 	   Verifying Checksum ... OK
5617 	   Uncompressing Kernel Image ... OK
5618 	## Loading RAMDisk Image at 40200000 ...
5619 	   Image Name:	 Simple Ramdisk Image
5620 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5621 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5622 	   Load Address: 00000000
5623 	   Entry Point:	 00000000
5624 	   Verifying Checksum ... OK
5625 	   Loading Ramdisk ... OK
5626 	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
5627 	Boot arguments: root=/dev/ram
5628 	time_init: decrementer frequency = 187500000/60
5629 	Calibrating delay loop... 49.77 BogoMIPS
5630 	...
5631 	RAMDISK: Compressed image found at block 0
5632 	VFS: Mounted root (ext2 filesystem).
5633 
5634 	bash#
5635 
5636 Boot Linux and pass a flat device tree:
5637 -----------
5638 
5639 First, U-Boot must be compiled with the appropriate defines. See the section
5640 titled "Linux Kernel Interface" above for a more in depth explanation. The
5641 following is an example of how to start a kernel and pass an updated
5642 flat device tree:
5643 
5644 => print oftaddr
5645 oftaddr=0x300000
5646 => print oft
5647 oft=oftrees/mpc8540ads.dtb
5648 => tftp $oftaddr $oft
5649 Speed: 1000, full duplex
5650 Using TSEC0 device
5651 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5652 Filename 'oftrees/mpc8540ads.dtb'.
5653 Load address: 0x300000
5654 Loading: #
5655 done
5656 Bytes transferred = 4106 (100a hex)
5657 => tftp $loadaddr $bootfile
5658 Speed: 1000, full duplex
5659 Using TSEC0 device
5660 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5661 Filename 'uImage'.
5662 Load address: 0x200000
5663 Loading:############
5664 done
5665 Bytes transferred = 1029407 (fb51f hex)
5666 => print loadaddr
5667 loadaddr=200000
5668 => print oftaddr
5669 oftaddr=0x300000
5670 => bootm $loadaddr - $oftaddr
5671 ## Booting image at 00200000 ...
5672    Image Name:	 Linux-2.6.17-dirty
5673    Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5674    Data Size:	 1029343 Bytes = 1005.2 kB
5675    Load Address: 00000000
5676    Entry Point:	 00000000
5677    Verifying Checksum ... OK
5678    Uncompressing Kernel Image ... OK
5679 Booting using flat device tree at 0x300000
5680 Using MPC85xx ADS machine description
5681 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5682 [snip]
5683 
5684 
5685 More About U-Boot Image Types:
5686 ------------------------------
5687 
5688 U-Boot supports the following image types:
5689 
5690    "Standalone Programs" are directly runnable in the environment
5691 	provided by U-Boot; it is expected that (if they behave
5692 	well) you can continue to work in U-Boot after return from
5693 	the Standalone Program.
5694    "OS Kernel Images" are usually images of some Embedded OS which
5695 	will take over control completely. Usually these programs
5696 	will install their own set of exception handlers, device
5697 	drivers, set up the MMU, etc. - this means, that you cannot
5698 	expect to re-enter U-Boot except by resetting the CPU.
5699    "RAMDisk Images" are more or less just data blocks, and their
5700 	parameters (address, size) are passed to an OS kernel that is
5701 	being started.
5702    "Multi-File Images" contain several images, typically an OS
5703 	(Linux) kernel image and one or more data images like
5704 	RAMDisks. This construct is useful for instance when you want
5705 	to boot over the network using BOOTP etc., where the boot
5706 	server provides just a single image file, but you want to get
5707 	for instance an OS kernel and a RAMDisk image.
5708 
5709 	"Multi-File Images" start with a list of image sizes, each
5710 	image size (in bytes) specified by an "uint32_t" in network
5711 	byte order. This list is terminated by an "(uint32_t)0".
5712 	Immediately after the terminating 0 follow the images, one by
5713 	one, all aligned on "uint32_t" boundaries (size rounded up to
5714 	a multiple of 4 bytes).
5715 
5716    "Firmware Images" are binary images containing firmware (like
5717 	U-Boot or FPGA images) which usually will be programmed to
5718 	flash memory.
5719 
5720    "Script files" are command sequences that will be executed by
5721 	U-Boot's command interpreter; this feature is especially
5722 	useful when you configure U-Boot to use a real shell (hush)
5723 	as command interpreter.
5724 
5725 Booting the Linux zImage:
5726 -------------------------
5727 
5728 On some platforms, it's possible to boot Linux zImage. This is done
5729 using the "bootz" command. The syntax of "bootz" command is the same
5730 as the syntax of "bootm" command.
5731 
5732 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5733 kernel with raw initrd images. The syntax is slightly different, the
5734 address of the initrd must be augmented by it's size, in the following
5735 format: "<initrd addres>:<initrd size>".
5736 
5737 
5738 Standalone HOWTO:
5739 =================
5740 
5741 One of the features of U-Boot is that you can dynamically load and
5742 run "standalone" applications, which can use some resources of
5743 U-Boot like console I/O functions or interrupt services.
5744 
5745 Two simple examples are included with the sources:
5746 
5747 "Hello World" Demo:
5748 -------------------
5749 
5750 'examples/hello_world.c' contains a small "Hello World" Demo
5751 application; it is automatically compiled when you build U-Boot.
5752 It's configured to run at address 0x00040004, so you can play with it
5753 like that:
5754 
5755 	=> loads
5756 	## Ready for S-Record download ...
5757 	~>examples/hello_world.srec
5758 	1 2 3 4 5 6 7 8 9 10 11 ...
5759 	[file transfer complete]
5760 	[connected]
5761 	## Start Addr = 0x00040004
5762 
5763 	=> go 40004 Hello World! This is a test.
5764 	## Starting application at 0x00040004 ...
5765 	Hello World
5766 	argc = 7
5767 	argv[0] = "40004"
5768 	argv[1] = "Hello"
5769 	argv[2] = "World!"
5770 	argv[3] = "This"
5771 	argv[4] = "is"
5772 	argv[5] = "a"
5773 	argv[6] = "test."
5774 	argv[7] = "<NULL>"
5775 	Hit any key to exit ...
5776 
5777 	## Application terminated, rc = 0x0
5778 
5779 Another example, which demonstrates how to register a CPM interrupt
5780 handler with the U-Boot code, can be found in 'examples/timer.c'.
5781 Here, a CPM timer is set up to generate an interrupt every second.
5782 The interrupt service routine is trivial, just printing a '.'
5783 character, but this is just a demo program. The application can be
5784 controlled by the following keys:
5785 
5786 	? - print current values og the CPM Timer registers
5787 	b - enable interrupts and start timer
5788 	e - stop timer and disable interrupts
5789 	q - quit application
5790 
5791 	=> loads
5792 	## Ready for S-Record download ...
5793 	~>examples/timer.srec
5794 	1 2 3 4 5 6 7 8 9 10 11 ...
5795 	[file transfer complete]
5796 	[connected]
5797 	## Start Addr = 0x00040004
5798 
5799 	=> go 40004
5800 	## Starting application at 0x00040004 ...
5801 	TIMERS=0xfff00980
5802 	Using timer 1
5803 	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5804 
5805 Hit 'b':
5806 	[q, b, e, ?] Set interval 1000000 us
5807 	Enabling timer
5808 Hit '?':
5809 	[q, b, e, ?] ........
5810 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5811 Hit '?':
5812 	[q, b, e, ?] .
5813 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5814 Hit '?':
5815 	[q, b, e, ?] .
5816 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5817 Hit '?':
5818 	[q, b, e, ?] .
5819 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5820 Hit 'e':
5821 	[q, b, e, ?] ...Stopping timer
5822 Hit 'q':
5823 	[q, b, e, ?] ## Application terminated, rc = 0x0
5824 
5825 
5826 Minicom warning:
5827 ================
5828 
5829 Over time, many people have reported problems when trying to use the
5830 "minicom" terminal emulation program for serial download. I (wd)
5831 consider minicom to be broken, and recommend not to use it. Under
5832 Unix, I recommend to use C-Kermit for general purpose use (and
5833 especially for kermit binary protocol download ("loadb" command), and
5834 use "cu" for S-Record download ("loads" command).  See
5835 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5836 for help with kermit.
5837 
5838 
5839 Nevertheless, if you absolutely want to use it try adding this
5840 configuration to your "File transfer protocols" section:
5841 
5842 	   Name	   Program			Name U/D FullScr IO-Red. Multi
5843 	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5844 	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5845 
5846 
5847 NetBSD Notes:
5848 =============
5849 
5850 Starting at version 0.9.2, U-Boot supports NetBSD both as host
5851 (build U-Boot) and target system (boots NetBSD/mpc8xx).
5852 
5853 Building requires a cross environment; it is known to work on
5854 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5855 need gmake since the Makefiles are not compatible with BSD make).
5856 Note that the cross-powerpc package does not install include files;
5857 attempting to build U-Boot will fail because <machine/ansi.h> is
5858 missing.  This file has to be installed and patched manually:
5859 
5860 	# cd /usr/pkg/cross/powerpc-netbsd/include
5861 	# mkdir powerpc
5862 	# ln -s powerpc machine
5863 	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5864 	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5865 
5866 Native builds *don't* work due to incompatibilities between native
5867 and U-Boot include files.
5868 
5869 Booting assumes that (the first part of) the image booted is a
5870 stage-2 loader which in turn loads and then invokes the kernel
5871 proper. Loader sources will eventually appear in the NetBSD source
5872 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5873 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5874 
5875 
5876 Implementation Internals:
5877 =========================
5878 
5879 The following is not intended to be a complete description of every
5880 implementation detail. However, it should help to understand the
5881 inner workings of U-Boot and make it easier to port it to custom
5882 hardware.
5883 
5884 
5885 Initial Stack, Global Data:
5886 ---------------------------
5887 
5888 The implementation of U-Boot is complicated by the fact that U-Boot
5889 starts running out of ROM (flash memory), usually without access to
5890 system RAM (because the memory controller is not initialized yet).
5891 This means that we don't have writable Data or BSS segments, and BSS
5892 is not initialized as zero. To be able to get a C environment working
5893 at all, we have to allocate at least a minimal stack. Implementation
5894 options for this are defined and restricted by the CPU used: Some CPU
5895 models provide on-chip memory (like the IMMR area on MPC8xx and
5896 MPC826x processors), on others (parts of) the data cache can be
5897 locked as (mis-) used as memory, etc.
5898 
5899 	Chris Hallinan posted a good summary of these issues to the
5900 	U-Boot mailing list:
5901 
5902 	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5903 	From: "Chris Hallinan" <clh@net1plus.com>
5904 	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5905 	...
5906 
5907 	Correct me if I'm wrong, folks, but the way I understand it
5908 	is this: Using DCACHE as initial RAM for Stack, etc, does not
5909 	require any physical RAM backing up the cache. The cleverness
5910 	is that the cache is being used as a temporary supply of
5911 	necessary storage before the SDRAM controller is setup. It's
5912 	beyond the scope of this list to explain the details, but you
5913 	can see how this works by studying the cache architecture and
5914 	operation in the architecture and processor-specific manuals.
5915 
5916 	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5917 	is another option for the system designer to use as an
5918 	initial stack/RAM area prior to SDRAM being available. Either
5919 	option should work for you. Using CS 4 should be fine if your
5920 	board designers haven't used it for something that would
5921 	cause you grief during the initial boot! It is frequently not
5922 	used.
5923 
5924 	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5925 	with your processor/board/system design. The default value
5926 	you will find in any recent u-boot distribution in
5927 	walnut.h should work for you. I'd set it to a value larger
5928 	than your SDRAM module. If you have a 64MB SDRAM module, set
5929 	it above 400_0000. Just make sure your board has no resources
5930 	that are supposed to respond to that address! That code in
5931 	start.S has been around a while and should work as is when
5932 	you get the config right.
5933 
5934 	-Chris Hallinan
5935 	DS4.COM, Inc.
5936 
5937 It is essential to remember this, since it has some impact on the C
5938 code for the initialization procedures:
5939 
5940 * Initialized global data (data segment) is read-only. Do not attempt
5941   to write it.
5942 
5943 * Do not use any uninitialized global data (or implicitly initialized
5944   as zero data - BSS segment) at all - this is undefined, initiali-
5945   zation is performed later (when relocating to RAM).
5946 
5947 * Stack space is very limited. Avoid big data buffers or things like
5948   that.
5949 
5950 Having only the stack as writable memory limits means we cannot use
5951 normal global data to share information between the code. But it
5952 turned out that the implementation of U-Boot can be greatly
5953 simplified by making a global data structure (gd_t) available to all
5954 functions. We could pass a pointer to this data as argument to _all_
5955 functions, but this would bloat the code. Instead we use a feature of
5956 the GCC compiler (Global Register Variables) to share the data: we
5957 place a pointer (gd) to the global data into a register which we
5958 reserve for this purpose.
5959 
5960 When choosing a register for such a purpose we are restricted by the
5961 relevant  (E)ABI  specifications for the current architecture, and by
5962 GCC's implementation.
5963 
5964 For PowerPC, the following registers have specific use:
5965 	R1:	stack pointer
5966 	R2:	reserved for system use
5967 	R3-R4:	parameter passing and return values
5968 	R5-R10: parameter passing
5969 	R13:	small data area pointer
5970 	R30:	GOT pointer
5971 	R31:	frame pointer
5972 
5973 	(U-Boot also uses R12 as internal GOT pointer. r12
5974 	is a volatile register so r12 needs to be reset when
5975 	going back and forth between asm and C)
5976 
5977     ==> U-Boot will use R2 to hold a pointer to the global data
5978 
5979     Note: on PPC, we could use a static initializer (since the
5980     address of the global data structure is known at compile time),
5981     but it turned out that reserving a register results in somewhat
5982     smaller code - although the code savings are not that big (on
5983     average for all boards 752 bytes for the whole U-Boot image,
5984     624 text + 127 data).
5985 
5986 On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5987 	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5988 
5989     ==> U-Boot will use P3 to hold a pointer to the global data
5990 
5991 On ARM, the following registers are used:
5992 
5993 	R0:	function argument word/integer result
5994 	R1-R3:	function argument word
5995 	R9:	platform specific
5996 	R10:	stack limit (used only if stack checking is enabled)
5997 	R11:	argument (frame) pointer
5998 	R12:	temporary workspace
5999 	R13:	stack pointer
6000 	R14:	link register
6001 	R15:	program counter
6002 
6003     ==> U-Boot will use R9 to hold a pointer to the global data
6004 
6005     Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6006 
6007 On Nios II, the ABI is documented here:
6008 	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6009 
6010     ==> U-Boot will use gp to hold a pointer to the global data
6011 
6012     Note: on Nios II, we give "-G0" option to gcc and don't use gp
6013     to access small data sections, so gp is free.
6014 
6015 On NDS32, the following registers are used:
6016 
6017 	R0-R1:	argument/return
6018 	R2-R5:	argument
6019 	R15:	temporary register for assembler
6020 	R16:	trampoline register
6021 	R28:	frame pointer (FP)
6022 	R29:	global pointer (GP)
6023 	R30:	link register (LP)
6024 	R31:	stack pointer (SP)
6025 	PC:	program counter (PC)
6026 
6027     ==> U-Boot will use R10 to hold a pointer to the global data
6028 
6029 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6030 or current versions of GCC may "optimize" the code too much.
6031 
6032 Memory Management:
6033 ------------------
6034 
6035 U-Boot runs in system state and uses physical addresses, i.e. the
6036 MMU is not used either for address mapping nor for memory protection.
6037 
6038 The available memory is mapped to fixed addresses using the memory
6039 controller. In this process, a contiguous block is formed for each
6040 memory type (Flash, SDRAM, SRAM), even when it consists of several
6041 physical memory banks.
6042 
6043 U-Boot is installed in the first 128 kB of the first Flash bank (on
6044 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6045 booting and sizing and initializing DRAM, the code relocates itself
6046 to the upper end of DRAM. Immediately below the U-Boot code some
6047 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6048 configuration setting]. Below that, a structure with global Board
6049 Info data is placed, followed by the stack (growing downward).
6050 
6051 Additionally, some exception handler code is copied to the low 8 kB
6052 of DRAM (0x00000000 ... 0x00001FFF).
6053 
6054 So a typical memory configuration with 16 MB of DRAM could look like
6055 this:
6056 
6057 	0x0000 0000	Exception Vector code
6058 	      :
6059 	0x0000 1FFF
6060 	0x0000 2000	Free for Application Use
6061 	      :
6062 	      :
6063 
6064 	      :
6065 	      :
6066 	0x00FB FF20	Monitor Stack (Growing downward)
6067 	0x00FB FFAC	Board Info Data and permanent copy of global data
6068 	0x00FC 0000	Malloc Arena
6069 	      :
6070 	0x00FD FFFF
6071 	0x00FE 0000	RAM Copy of Monitor Code
6072 	...		eventually: LCD or video framebuffer
6073 	...		eventually: pRAM (Protected RAM - unchanged by reset)
6074 	0x00FF FFFF	[End of RAM]
6075 
6076 
6077 System Initialization:
6078 ----------------------
6079 
6080 In the reset configuration, U-Boot starts at the reset entry point
6081 (on most PowerPC systems at address 0x00000100). Because of the reset
6082 configuration for CS0# this is a mirror of the on board Flash memory.
6083 To be able to re-map memory U-Boot then jumps to its link address.
6084 To be able to implement the initialization code in C, a (small!)
6085 initial stack is set up in the internal Dual Ported RAM (in case CPUs
6086 which provide such a feature like MPC8xx or MPC8260), or in a locked
6087 part of the data cache. After that, U-Boot initializes the CPU core,
6088 the caches and the SIU.
6089 
6090 Next, all (potentially) available memory banks are mapped using a
6091 preliminary mapping. For example, we put them on 512 MB boundaries
6092 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6093 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6094 programmed for SDRAM access. Using the temporary configuration, a
6095 simple memory test is run that determines the size of the SDRAM
6096 banks.
6097 
6098 When there is more than one SDRAM bank, and the banks are of
6099 different size, the largest is mapped first. For equal size, the first
6100 bank (CS2#) is mapped first. The first mapping is always for address
6101 0x00000000, with any additional banks following immediately to create
6102 contiguous memory starting from 0.
6103 
6104 Then, the monitor installs itself at the upper end of the SDRAM area
6105 and allocates memory for use by malloc() and for the global Board
6106 Info data; also, the exception vector code is copied to the low RAM
6107 pages, and the final stack is set up.
6108 
6109 Only after this relocation will you have a "normal" C environment;
6110 until that you are restricted in several ways, mostly because you are
6111 running from ROM, and because the code will have to be relocated to a
6112 new address in RAM.
6113 
6114 
6115 U-Boot Porting Guide:
6116 ----------------------
6117 
6118 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6119 list, October 2002]
6120 
6121 
6122 int main(int argc, char *argv[])
6123 {
6124 	sighandler_t no_more_time;
6125 
6126 	signal(SIGALRM, no_more_time);
6127 	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6128 
6129 	if (available_money > available_manpower) {
6130 		Pay consultant to port U-Boot;
6131 		return 0;
6132 	}
6133 
6134 	Download latest U-Boot source;
6135 
6136 	Subscribe to u-boot mailing list;
6137 
6138 	if (clueless)
6139 		email("Hi, I am new to U-Boot, how do I get started?");
6140 
6141 	while (learning) {
6142 		Read the README file in the top level directory;
6143 		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6144 		Read applicable doc/*.README;
6145 		Read the source, Luke;
6146 		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6147 	}
6148 
6149 	if (available_money > toLocalCurrency ($2500))
6150 		Buy a BDI3000;
6151 	else
6152 		Add a lot of aggravation and time;
6153 
6154 	if (a similar board exists) {	/* hopefully... */
6155 		cp -a board/<similar> board/<myboard>
6156 		cp include/configs/<similar>.h include/configs/<myboard>.h
6157 	} else {
6158 		Create your own board support subdirectory;
6159 		Create your own board include/configs/<myboard>.h file;
6160 	}
6161 	Edit new board/<myboard> files
6162 	Edit new include/configs/<myboard>.h
6163 
6164 	while (!accepted) {
6165 		while (!running) {
6166 			do {
6167 				Add / modify source code;
6168 			} until (compiles);
6169 			Debug;
6170 			if (clueless)
6171 				email("Hi, I am having problems...");
6172 		}
6173 		Send patch file to the U-Boot email list;
6174 		if (reasonable critiques)
6175 			Incorporate improvements from email list code review;
6176 		else
6177 			Defend code as written;
6178 	}
6179 
6180 	return 0;
6181 }
6182 
6183 void no_more_time (int sig)
6184 {
6185       hire_a_guru();
6186 }
6187 
6188 
6189 Coding Standards:
6190 -----------------
6191 
6192 All contributions to U-Boot should conform to the Linux kernel
6193 coding style; see the file "Documentation/CodingStyle" and the script
6194 "scripts/Lindent" in your Linux kernel source directory.
6195 
6196 Source files originating from a different project (for example the
6197 MTD subsystem) are generally exempt from these guidelines and are not
6198 reformatted to ease subsequent migration to newer versions of those
6199 sources.
6200 
6201 Please note that U-Boot is implemented in C (and to some small parts in
6202 Assembler); no C++ is used, so please do not use C++ style comments (//)
6203 in your code.
6204 
6205 Please also stick to the following formatting rules:
6206 - remove any trailing white space
6207 - use TAB characters for indentation and vertical alignment, not spaces
6208 - make sure NOT to use DOS '\r\n' line feeds
6209 - do not add more than 2 consecutive empty lines to source files
6210 - do not add trailing empty lines to source files
6211 
6212 Submissions which do not conform to the standards may be returned
6213 with a request to reformat the changes.
6214 
6215 
6216 Submitting Patches:
6217 -------------------
6218 
6219 Since the number of patches for U-Boot is growing, we need to
6220 establish some rules. Submissions which do not conform to these rules
6221 may be rejected, even when they contain important and valuable stuff.
6222 
6223 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6224 
6225 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6226 see http://lists.denx.de/mailman/listinfo/u-boot
6227 
6228 When you send a patch, please include the following information with
6229 it:
6230 
6231 * For bug fixes: a description of the bug and how your patch fixes
6232   this bug. Please try to include a way of demonstrating that the
6233   patch actually fixes something.
6234 
6235 * For new features: a description of the feature and your
6236   implementation.
6237 
6238 * A CHANGELOG entry as plaintext (separate from the patch)
6239 
6240 * For major contributions, add a MAINTAINERS file with your
6241   information and associated file and directory references.
6242 
6243 * When you add support for a new board, don't forget to add a
6244   maintainer e-mail address to the boards.cfg file, too.
6245 
6246 * If your patch adds new configuration options, don't forget to
6247   document these in the README file.
6248 
6249 * The patch itself. If you are using git (which is *strongly*
6250   recommended) you can easily generate the patch using the
6251   "git format-patch". If you then use "git send-email" to send it to
6252   the U-Boot mailing list, you will avoid most of the common problems
6253   with some other mail clients.
6254 
6255   If you cannot use git, use "diff -purN OLD NEW". If your version of
6256   diff does not support these options, then get the latest version of
6257   GNU diff.
6258 
6259   The current directory when running this command shall be the parent
6260   directory of the U-Boot source tree (i. e. please make sure that
6261   your patch includes sufficient directory information for the
6262   affected files).
6263 
6264   We prefer patches as plain text. MIME attachments are discouraged,
6265   and compressed attachments must not be used.
6266 
6267 * If one logical set of modifications affects or creates several
6268   files, all these changes shall be submitted in a SINGLE patch file.
6269 
6270 * Changesets that contain different, unrelated modifications shall be
6271   submitted as SEPARATE patches, one patch per changeset.
6272 
6273 
6274 Notes:
6275 
6276 * Before sending the patch, run the buildman script on your patched
6277   source tree and make sure that no errors or warnings are reported
6278   for any of the boards.
6279 
6280 * Keep your modifications to the necessary minimum: A patch
6281   containing several unrelated changes or arbitrary reformats will be
6282   returned with a request to re-formatting / split it.
6283 
6284 * If you modify existing code, make sure that your new code does not
6285   add to the memory footprint of the code ;-) Small is beautiful!
6286   When adding new features, these should compile conditionally only
6287   (using #ifdef), and the resulting code with the new feature
6288   disabled must not need more memory than the old code without your
6289   modification.
6290 
6291 * Remember that there is a size limit of 100 kB per message on the
6292   u-boot mailing list. Bigger patches will be moderated. If they are
6293   reasonable and not too big, they will be acknowledged. But patches
6294   bigger than the size limit should be avoided.
6295