xref: /openbmc/u-boot/README (revision 0bb430c8)
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
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-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
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where 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
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File 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
110Variable names, preprocessor constants etc. shall be either based on
111the 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
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
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 candidate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /m68k			Files generic to m68k architecture
140  /microblaze		Files generic to microblaze architecture
141  /mips			Files generic to MIPS architecture
142  /nds32		Files generic to NDS32 architecture
143  /nios2		Files generic to Altera NIOS2 architecture
144  /openrisc		Files generic to OpenRISC architecture
145  /powerpc		Files generic to PowerPC architecture
146  /riscv		Files generic to RISC-V architecture
147  /sandbox		Files generic to HW-independent "sandbox"
148  /sh			Files generic to SH architecture
149  /x86			Files generic to x86 architecture
150/api			Machine/arch independent API for external apps
151/board			Board dependent files
152/cmd			U-Boot commands functions
153/common			Misc architecture independent functions
154/configs		Board default configuration files
155/disk			Code for disk drive partition handling
156/doc			Documentation (don't expect too much)
157/drivers		Commonly used device drivers
158/dts			Contains Makefile for building internal U-Boot fdt.
159/examples		Example code for standalone applications, etc.
160/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161/include		Header Files
162/lib			Library routines generic to all architectures
163/Licenses		Various license files
164/net			Networking code
165/post			Power On Self Test
166/scripts		Various build scripts and Makefiles
167/test			Various unit test files
168/tools			Tools to build S-Record or U-Boot images, etc.
169
170Software Configuration:
171=======================
172
173Configuration is usually done using C preprocessor defines; the
174rationale behind that is to avoid dead code whenever possible.
175
176There are two classes of configuration variables:
177
178* Configuration _OPTIONS_:
179  These are selectable by the user and have names beginning with
180  "CONFIG_".
181
182* Configuration _SETTINGS_:
183  These depend on the hardware etc. and should not be meddled with if
184  you don't know what you're doing; they have names beginning with
185  "CONFIG_SYS_".
186
187Previously, all configuration was done by hand, which involved creating
188symbolic links and editing configuration files manually. More recently,
189U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190allowing you to use the "make menuconfig" command to configure your
191build.
192
193
194Selection of Processor Architecture and Board Type:
195---------------------------------------------------
196
197For all supported boards there are ready-to-use default
198configurations available; just type "make <board_name>_defconfig".
199
200Example: For a TQM823L module type:
201
202	cd u-boot
203	make TQM823L_defconfig
204
205Note: If you're looking for the default configuration file for a board
206you're sure used to be there but is now missing, check the file
207doc/README.scrapyard for a list of no longer supported boards.
208
209Sandbox Environment:
210--------------------
211
212U-Boot can be built natively to run on a Linux host using the 'sandbox'
213board. This allows feature development which is not board- or architecture-
214specific to be undertaken on a native platform. The sandbox is also used to
215run some of U-Boot's tests.
216
217See board/sandbox/README.sandbox for more details.
218
219
220Board Initialisation Flow:
221--------------------------
222
223This is the intended start-up flow for boards. This should apply for both
224SPL and U-Boot proper (i.e. they both follow the same rules).
225
226Note: "SPL" stands for "Secondary Program Loader," which is explained in
227more detail later in this file.
228
229At present, SPL mostly uses a separate code path, but the function names
230and roles of each function are the same. Some boards or architectures
231may not conform to this.  At least most ARM boards which use
232CONFIG_SPL_FRAMEWORK conform to this.
233
234Execution typically starts with an architecture-specific (and possibly
235CPU-specific) start.S file, such as:
236
237	- arch/arm/cpu/armv7/start.S
238	- arch/powerpc/cpu/mpc83xx/start.S
239	- arch/mips/cpu/start.S
240
241and so on. From there, three functions are called; the purpose and
242limitations of each of these functions are described below.
243
244lowlevel_init():
245	- purpose: essential init to permit execution to reach board_init_f()
246	- no global_data or BSS
247	- there is no stack (ARMv7 may have one but it will soon be removed)
248	- must not set up SDRAM or use console
249	- must only do the bare minimum to allow execution to continue to
250		board_init_f()
251	- this is almost never needed
252	- return normally from this function
253
254board_init_f():
255	- purpose: set up the machine ready for running board_init_r():
256		i.e. SDRAM and serial UART
257	- global_data is available
258	- stack is in SRAM
259	- BSS is not available, so you cannot use global/static variables,
260		only stack variables and global_data
261
262	Non-SPL-specific notes:
263	- dram_init() is called to set up DRAM. If already done in SPL this
264		can do nothing
265
266	SPL-specific notes:
267	- you can override the entire board_init_f() function with your own
268		version as needed.
269	- preloader_console_init() can be called here in extremis
270	- should set up SDRAM, and anything needed to make the UART work
271	- these is no need to clear BSS, it will be done by crt0.S
272	- must return normally from this function (don't call board_init_r()
273		directly)
274
275Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276this point the stack and global_data are relocated to below
277CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278memory.
279
280board_init_r():
281	- purpose: main execution, common code
282	- global_data is available
283	- SDRAM is available
284	- BSS is available, all static/global variables can be used
285	- execution eventually continues to main_loop()
286
287	Non-SPL-specific notes:
288	- U-Boot is relocated to the top of memory and is now running from
289		there.
290
291	SPL-specific notes:
292	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294	- preloader_console_init() can be called here - typically this is
295		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296		spl_board_init() function containing this call
297	- loads U-Boot or (in falcon mode) Linux
298
299
300
301Configuration Options:
302----------------------
303
304Configuration depends on the combination of board and CPU type; all
305such information is kept in a configuration file
306"include/configs/<board_name>.h".
307
308Example: For a TQM823L module, all configuration settings are in
309"include/configs/TQM823L.h".
310
311
312Many of the options are named exactly as the corresponding Linux
313kernel configuration options. The intention is to make it easier to
314build a config tool - later.
315
316- ARM Platform Bus Type(CCI):
317		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
318		provides full cache coherency between two clusters of multi-core
319		CPUs and I/O coherency for devices and I/O masters
320
321		CONFIG_SYS_FSL_HAS_CCI400
322
323		Defined For SoC that has cache coherent interconnect
324		CCN-400
325
326		CONFIG_SYS_FSL_HAS_CCN504
327
328		Defined for SoC that has cache coherent interconnect CCN-504
329
330The following options need to be configured:
331
332- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
333
334- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
335
336- Marvell Family Member
337		CONFIG_SYS_MVFS		- define it if you want to enable
338					  multiple fs option at one time
339					  for marvell soc family
340
341- 85xx CPU Options:
342		CONFIG_SYS_PPC64
343
344		Specifies that the core is a 64-bit PowerPC implementation (implements
345		the "64" category of the Power ISA). This is necessary for ePAPR
346		compliance, among other possible reasons.
347
348		CONFIG_SYS_FSL_TBCLK_DIV
349
350		Defines the core time base clock divider ratio compared to the
351		system clock.  On most PQ3 devices this is 8, on newer QorIQ
352		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
353
354		CONFIG_SYS_FSL_PCIE_COMPAT
355
356		Defines the string to utilize when trying to match PCIe device
357		tree nodes for the given platform.
358
359		CONFIG_SYS_FSL_ERRATUM_A004510
360
361		Enables a workaround for erratum A004510.  If set,
362		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
363		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
364
365		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
366		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
367
368		Defines one or two SoC revisions (low 8 bits of SVR)
369		for which the A004510 workaround should be applied.
370
371		The rest of SVR is either not relevant to the decision
372		of whether the erratum is present (e.g. p2040 versus
373		p2041) or is implied by the build target, which controls
374		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
375
376		See Freescale App Note 4493 for more information about
377		this erratum.
378
379		CONFIG_A003399_NOR_WORKAROUND
380		Enables a workaround for IFC erratum A003399. It is only
381		required during NOR boot.
382
383		CONFIG_A008044_WORKAROUND
384		Enables a workaround for T1040/T1042 erratum A008044. It is only
385		required during NAND boot and valid for Rev 1.0 SoC revision
386
387		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
388
389		This is the value to write into CCSR offset 0x18600
390		according to the A004510 workaround.
391
392		CONFIG_SYS_FSL_DSP_DDR_ADDR
393		This value denotes start offset of DDR memory which is
394		connected exclusively to the DSP cores.
395
396		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
397		This value denotes start offset of M2 memory
398		which is directly connected to the DSP core.
399
400		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
401		This value denotes start offset of M3 memory which is directly
402		connected to the DSP core.
403
404		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
405		This value denotes start offset of DSP CCSR space.
406
407		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
408		Single Source Clock is clocking mode present in some of FSL SoC's.
409		In this mode, a single differential clock is used to supply
410		clocks to the sysclock, ddrclock and usbclock.
411
412		CONFIG_SYS_CPC_REINIT_F
413		This CONFIG is defined when the CPC is configured as SRAM at the
414		time of U-Boot entry and is required to be re-initialized.
415
416		CONFIG_DEEP_SLEEP
417		Indicates this SoC supports deep sleep feature. If deep sleep is
418		supported, core will start to execute uboot when wakes up.
419
420- Generic CPU options:
421		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
422
423		Defines the endianess of the CPU. Implementation of those
424		values is arch specific.
425
426		CONFIG_SYS_FSL_DDR
427		Freescale DDR driver in use. This type of DDR controller is
428		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
429		SoCs.
430
431		CONFIG_SYS_FSL_DDR_ADDR
432		Freescale DDR memory-mapped register base.
433
434		CONFIG_SYS_FSL_DDR_EMU
435		Specify emulator support for DDR. Some DDR features such as
436		deskew training are not available.
437
438		CONFIG_SYS_FSL_DDRC_GEN1
439		Freescale DDR1 controller.
440
441		CONFIG_SYS_FSL_DDRC_GEN2
442		Freescale DDR2 controller.
443
444		CONFIG_SYS_FSL_DDRC_GEN3
445		Freescale DDR3 controller.
446
447		CONFIG_SYS_FSL_DDRC_GEN4
448		Freescale DDR4 controller.
449
450		CONFIG_SYS_FSL_DDRC_ARM_GEN3
451		Freescale DDR3 controller for ARM-based SoCs.
452
453		CONFIG_SYS_FSL_DDR1
454		Board config to use DDR1. It can be enabled for SoCs with
455		Freescale DDR1 or DDR2 controllers, depending on the board
456		implemetation.
457
458		CONFIG_SYS_FSL_DDR2
459		Board config to use DDR2. It can be enabled for SoCs with
460		Freescale DDR2 or DDR3 controllers, depending on the board
461		implementation.
462
463		CONFIG_SYS_FSL_DDR3
464		Board config to use DDR3. It can be enabled for SoCs with
465		Freescale DDR3 or DDR3L controllers.
466
467		CONFIG_SYS_FSL_DDR3L
468		Board config to use DDR3L. It can be enabled for SoCs with
469		DDR3L controllers.
470
471		CONFIG_SYS_FSL_DDR4
472		Board config to use DDR4. It can be enabled for SoCs with
473		DDR4 controllers.
474
475		CONFIG_SYS_FSL_IFC_BE
476		Defines the IFC controller register space as Big Endian
477
478		CONFIG_SYS_FSL_IFC_LE
479		Defines the IFC controller register space as Little Endian
480
481		CONFIG_SYS_FSL_IFC_CLK_DIV
482		Defines divider of platform clock(clock input to IFC controller).
483
484		CONFIG_SYS_FSL_LBC_CLK_DIV
485		Defines divider of platform clock(clock input to eLBC controller).
486
487		CONFIG_SYS_FSL_PBL_PBI
488		It enables addition of RCW (Power on reset configuration) in built image.
489		Please refer doc/README.pblimage for more details
490
491		CONFIG_SYS_FSL_PBL_RCW
492		It adds PBI(pre-boot instructions) commands in u-boot build image.
493		PBI commands can be used to configure SoC before it starts the execution.
494		Please refer doc/README.pblimage for more details
495
496		CONFIG_SPL_FSL_PBL
497		It adds a target to create boot binary having SPL binary in PBI format
498		concatenated with u-boot binary.
499
500		CONFIG_SYS_FSL_DDR_BE
501		Defines the DDR controller register space as Big Endian
502
503		CONFIG_SYS_FSL_DDR_LE
504		Defines the DDR controller register space as Little Endian
505
506		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
507		Physical address from the view of DDR controllers. It is the
508		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
509		it could be different for ARM SoCs.
510
511		CONFIG_SYS_FSL_DDR_INTLV_256B
512		DDR controller interleaving on 256-byte. This is a special
513		interleaving mode, handled by Dickens for Freescale layerscape
514		SoCs with ARM core.
515
516		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
517		Number of controllers used as main memory.
518
519		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
520		Number of controllers used for other than main memory.
521
522		CONFIG_SYS_FSL_HAS_DP_DDR
523		Defines the SoC has DP-DDR used for DPAA.
524
525		CONFIG_SYS_FSL_SEC_BE
526		Defines the SEC controller register space as Big Endian
527
528		CONFIG_SYS_FSL_SEC_LE
529		Defines the SEC controller register space as Little Endian
530
531- MIPS CPU options:
532		CONFIG_SYS_INIT_SP_OFFSET
533
534		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
535		pointer. This is needed for the temporary stack before
536		relocation.
537
538		CONFIG_SYS_MIPS_CACHE_MODE
539
540		Cache operation mode for the MIPS CPU.
541		See also arch/mips/include/asm/mipsregs.h.
542		Possible values are:
543			CONF_CM_CACHABLE_NO_WA
544			CONF_CM_CACHABLE_WA
545			CONF_CM_UNCACHED
546			CONF_CM_CACHABLE_NONCOHERENT
547			CONF_CM_CACHABLE_CE
548			CONF_CM_CACHABLE_COW
549			CONF_CM_CACHABLE_CUW
550			CONF_CM_CACHABLE_ACCELERATED
551
552		CONFIG_SYS_XWAY_EBU_BOOTCFG
553
554		Special option for Lantiq XWAY SoCs for booting from NOR flash.
555		See also arch/mips/cpu/mips32/start.S.
556
557		CONFIG_XWAY_SWAP_BYTES
558
559		Enable compilation of tools/xway-swap-bytes needed for Lantiq
560		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
561		be swapped if a flash programmer is used.
562
563- ARM options:
564		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
565
566		Select high exception vectors of the ARM core, e.g., do not
567		clear the V bit of the c1 register of CP15.
568
569		COUNTER_FREQUENCY
570		Generic timer clock source frequency.
571
572		COUNTER_FREQUENCY_REAL
573		Generic timer clock source frequency if the real clock is
574		different from COUNTER_FREQUENCY, and can only be determined
575		at run time.
576
577- Tegra SoC options:
578		CONFIG_TEGRA_SUPPORT_NON_SECURE
579
580		Support executing U-Boot in non-secure (NS) mode. Certain
581		impossible actions will be skipped if the CPU is in NS mode,
582		such as ARM architectural timer initialization.
583
584- Linux Kernel Interface:
585		CONFIG_CLOCKS_IN_MHZ
586
587		U-Boot stores all clock information in Hz
588		internally. For binary compatibility with older Linux
589		kernels (which expect the clocks passed in the
590		bd_info data to be in MHz) the environment variable
591		"clocks_in_mhz" can be defined so that U-Boot
592		converts clock data to MHZ before passing it to the
593		Linux kernel.
594		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
595		"clocks_in_mhz=1" is automatically included in the
596		default environment.
597
598		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
599
600		When transferring memsize parameter to Linux, some versions
601		expect it to be in bytes, others in MB.
602		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
603
604		CONFIG_OF_LIBFDT
605
606		New kernel versions are expecting firmware settings to be
607		passed using flattened device trees (based on open firmware
608		concepts).
609
610		CONFIG_OF_LIBFDT
611		 * New libfdt-based support
612		 * Adds the "fdt" command
613		 * The bootm command automatically updates the fdt
614
615		OF_TBCLK - The timebase frequency.
616		OF_STDOUT_PATH - The path to the console device
617
618		boards with QUICC Engines require OF_QE to set UCC MAC
619		addresses
620
621		CONFIG_OF_BOARD_SETUP
622
623		Board code has addition modification that it wants to make
624		to the flat device tree before handing it off to the kernel
625
626		CONFIG_OF_SYSTEM_SETUP
627
628		Other code has addition modification that it wants to make
629		to the flat device tree before handing it off to the kernel.
630		This causes ft_system_setup() to be called before booting
631		the kernel.
632
633		CONFIG_OF_IDE_FIXUP
634
635		U-Boot can detect if an IDE device is present or not.
636		If not, and this new config option is activated, U-Boot
637		removes the ATA node from the DTS before booting Linux,
638		so the Linux IDE driver does not probe the device and
639		crash. This is needed for buggy hardware (uc101) where
640		no pull down resistor is connected to the signal IDE5V_DD7.
641
642		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
643
644		This setting is mandatory for all boards that have only one
645		machine type and must be used to specify the machine type
646		number as it appears in the ARM machine registry
647		(see http://www.arm.linux.org.uk/developer/machines/).
648		Only boards that have multiple machine types supported
649		in a single configuration file and the machine type is
650		runtime discoverable, do not have to use this setting.
651
652- vxWorks boot parameters:
653
654		bootvx constructs a valid bootline using the following
655		environments variables: bootdev, bootfile, ipaddr, netmask,
656		serverip, gatewayip, hostname, othbootargs.
657		It loads the vxWorks image pointed bootfile.
658
659		Note: If a "bootargs" environment is defined, it will overwride
660		the defaults discussed just above.
661
662- Cache Configuration:
663		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
664		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
665		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
666
667- Cache Configuration for ARM:
668		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
669				      controller
670		CONFIG_SYS_PL310_BASE - Physical base address of PL310
671					controller register space
672
673- Serial Ports:
674		CONFIG_PL010_SERIAL
675
676		Define this if you want support for Amba PrimeCell PL010 UARTs.
677
678		CONFIG_PL011_SERIAL
679
680		Define this if you want support for Amba PrimeCell PL011 UARTs.
681
682		CONFIG_PL011_CLOCK
683
684		If you have Amba PrimeCell PL011 UARTs, set this variable to
685		the clock speed of the UARTs.
686
687		CONFIG_PL01x_PORTS
688
689		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
690		define this to a list of base addresses for each (supported)
691		port. See e.g. include/configs/versatile.h
692
693		CONFIG_SERIAL_HW_FLOW_CONTROL
694
695		Define this variable to enable hw flow control in serial driver.
696		Current user of this option is drivers/serial/nsl16550.c driver
697
698- Console Baudrate:
699		CONFIG_BAUDRATE - in bps
700		Select one of the baudrates listed in
701		CONFIG_SYS_BAUDRATE_TABLE, see below.
702
703- Autoboot Command:
704		CONFIG_BOOTCOMMAND
705		Only needed when CONFIG_BOOTDELAY is enabled;
706		define a command string that is automatically executed
707		when no character is read on the console interface
708		within "Boot Delay" after reset.
709
710		CONFIG_RAMBOOT and CONFIG_NFSBOOT
711		The value of these goes into the environment as
712		"ramboot" and "nfsboot" respectively, and can be used
713		as a convenience, when switching between booting from
714		RAM and NFS.
715
716- Bootcount:
717		CONFIG_BOOTCOUNT_ENV
718		If no softreset save registers are found on the hardware
719		"bootcount" is stored in the environment. To prevent a
720		saveenv on all reboots, the environment variable
721		"upgrade_available" is used. If "upgrade_available" is
722		0, "bootcount" is always 0, if "upgrade_available" is
723		1 "bootcount" is incremented in the environment.
724		So the Userspace Applikation must set the "upgrade_available"
725		and "bootcount" variable to 0, if a boot was successfully.
726
727- Pre-Boot Commands:
728		CONFIG_PREBOOT
729
730		When this option is #defined, the existence of the
731		environment variable "preboot" will be checked
732		immediately before starting the CONFIG_BOOTDELAY
733		countdown and/or running the auto-boot command resp.
734		entering interactive mode.
735
736		This feature is especially useful when "preboot" is
737		automatically generated or modified. For an example
738		see the LWMON board specific code: here "preboot" is
739		modified when the user holds down a certain
740		combination of keys on the (special) keyboard when
741		booting the systems
742
743- Serial Download Echo Mode:
744		CONFIG_LOADS_ECHO
745		If defined to 1, all characters received during a
746		serial download (using the "loads" command) are
747		echoed back. This might be needed by some terminal
748		emulations (like "cu"), but may as well just take
749		time on others. This setting #define's the initial
750		value of the "loads_echo" environment variable.
751
752- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
753		CONFIG_KGDB_BAUDRATE
754		Select one of the baudrates listed in
755		CONFIG_SYS_BAUDRATE_TABLE, see below.
756
757- Removal of commands
758		If no commands are needed to boot, you can disable
759		CONFIG_CMDLINE to remove them. In this case, the command line
760		will not be available, and when U-Boot wants to execute the
761		boot command (on start-up) it will call board_run_command()
762		instead. This can reduce image size significantly for very
763		simple boot procedures.
764
765- Regular expression support:
766		CONFIG_REGEX
767		If this variable is defined, U-Boot is linked against
768		the SLRE (Super Light Regular Expression) library,
769		which adds regex support to some commands, as for
770		example "env grep" and "setexpr".
771
772- Device tree:
773		CONFIG_OF_CONTROL
774		If this variable is defined, U-Boot will use a device tree
775		to configure its devices, instead of relying on statically
776		compiled #defines in the board file. This option is
777		experimental and only available on a few boards. The device
778		tree is available in the global data as gd->fdt_blob.
779
780		U-Boot needs to get its device tree from somewhere. This can
781		be done using one of the three options below:
782
783		CONFIG_OF_EMBED
784		If this variable is defined, U-Boot will embed a device tree
785		binary in its image. This device tree file should be in the
786		board directory and called <soc>-<board>.dts. The binary file
787		is then picked up in board_init_f() and made available through
788		the global data structure as gd->fdt_blob.
789
790		CONFIG_OF_SEPARATE
791		If this variable is defined, U-Boot will build a device tree
792		binary. It will be called u-boot.dtb. Architecture-specific
793		code will locate it at run-time. Generally this works by:
794
795			cat u-boot.bin u-boot.dtb >image.bin
796
797		and in fact, U-Boot does this for you, creating a file called
798		u-boot-dtb.bin which is useful in the common case. You can
799		still use the individual files if you need something more
800		exotic.
801
802		CONFIG_OF_BOARD
803		If this variable is defined, U-Boot will use the device tree
804		provided by the board at runtime instead of embedding one with
805		the image. Only boards defining board_fdt_blob_setup() support
806		this option (see include/fdtdec.h file).
807
808- Watchdog:
809		CONFIG_WATCHDOG
810		If this variable is defined, it enables watchdog
811		support for the SoC. There must be support in the SoC
812		specific code for a watchdog. For the 8xx
813		CPUs, the SIU Watchdog feature is enabled in the SYPCR
814		register.  When supported for a specific SoC is
815		available, then no further board specific code should
816		be needed to use it.
817
818		CONFIG_HW_WATCHDOG
819		When using a watchdog circuitry external to the used
820		SoC, then define this variable and provide board
821		specific code for the "hw_watchdog_reset" function.
822
823		CONFIG_AT91_HW_WDT_TIMEOUT
824		specify the timeout in seconds. default 2 seconds.
825
826- U-Boot Version:
827		CONFIG_VERSION_VARIABLE
828		If this variable is defined, an environment variable
829		named "ver" is created by U-Boot showing the U-Boot
830		version as printed by the "version" command.
831		Any change to this variable will be reverted at the
832		next reset.
833
834- Real-Time Clock:
835
836		When CONFIG_CMD_DATE is selected, the type of the RTC
837		has to be selected, too. Define exactly one of the
838		following options:
839
840		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
841		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
842		CONFIG_RTC_MC146818	- use MC146818 RTC
843		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
844		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
845		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
846		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
847		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
848		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
849		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
850		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
851		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
852					  RV3029 RTC.
853
854		Note that if the RTC uses I2C, then the I2C interface
855		must also be configured. See I2C Support, below.
856
857- GPIO Support:
858		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
859
860		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
861		chip-ngpio pairs that tell the PCA953X driver the number of
862		pins supported by a particular chip.
863
864		Note that if the GPIO device uses I2C, then the I2C interface
865		must also be configured. See I2C Support, below.
866
867- I/O tracing:
868		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
869		accesses and can checksum them or write a list of them out
870		to memory. See the 'iotrace' command for details. This is
871		useful for testing device drivers since it can confirm that
872		the driver behaves the same way before and after a code
873		change. Currently this is supported on sandbox and arm. To
874		add support for your architecture, add '#include <iotrace.h>'
875		to the bottom of arch/<arch>/include/asm/io.h and test.
876
877		Example output from the 'iotrace stats' command is below.
878		Note that if the trace buffer is exhausted, the checksum will
879		still continue to operate.
880
881			iotrace is enabled
882			Start:  10000000	(buffer start address)
883			Size:   00010000	(buffer size)
884			Offset: 00000120	(current buffer offset)
885			Output: 10000120	(start + offset)
886			Count:  00000018	(number of trace records)
887			CRC32:  9526fb66	(CRC32 of all trace records)
888
889- Timestamp Support:
890
891		When CONFIG_TIMESTAMP is selected, the timestamp
892		(date and time) of an image is printed by image
893		commands like bootm or iminfo. This option is
894		automatically enabled when you select CONFIG_CMD_DATE .
895
896- Partition Labels (disklabels) Supported:
897		Zero or more of the following:
898		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
899		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
900		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
901				       bootloader.  Note 2TB partition limit; see
902				       disk/part_efi.c
903		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
904
905		If IDE or SCSI support is enabled (CONFIG_IDE or
906		CONFIG_SCSI) you must configure support for at
907		least one non-MTD partition type as well.
908
909- IDE Reset method:
910		CONFIG_IDE_RESET_ROUTINE - this is defined in several
911		board configurations files but used nowhere!
912
913		CONFIG_IDE_RESET - is this is defined, IDE Reset will
914		be performed by calling the function
915			ide_set_reset(int reset)
916		which has to be defined in a board specific file
917
918- ATAPI Support:
919		CONFIG_ATAPI
920
921		Set this to enable ATAPI support.
922
923- LBA48 Support
924		CONFIG_LBA48
925
926		Set this to enable support for disks larger than 137GB
927		Also look at CONFIG_SYS_64BIT_LBA.
928		Whithout these , LBA48 support uses 32bit variables and will 'only'
929		support disks up to 2.1TB.
930
931		CONFIG_SYS_64BIT_LBA:
932			When enabled, makes the IDE subsystem use 64bit sector addresses.
933			Default is 32bit.
934
935- SCSI Support:
936		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
937		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
938		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
939		maximum numbers of LUNs, SCSI ID's and target
940		devices.
941
942		The environment variable 'scsidevs' is set to the number of
943		SCSI devices found during the last scan.
944
945- NETWORK Support (PCI):
946		CONFIG_E1000
947		Support for Intel 8254x/8257x gigabit chips.
948
949		CONFIG_E1000_SPI
950		Utility code for direct access to the SPI bus on Intel 8257x.
951		This does not do anything useful unless you set at least one
952		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
953
954		CONFIG_E1000_SPI_GENERIC
955		Allow generic access to the SPI bus on the Intel 8257x, for
956		example with the "sspi" command.
957
958		CONFIG_EEPRO100
959		Support for Intel 82557/82559/82559ER chips.
960		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
961		write routine for first time initialisation.
962
963		CONFIG_TULIP
964		Support for Digital 2114x chips.
965		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
966		modem chip initialisation (KS8761/QS6611).
967
968		CONFIG_NATSEMI
969		Support for National dp83815 chips.
970
971		CONFIG_NS8382X
972		Support for National dp8382[01] gigabit chips.
973
974- NETWORK Support (other):
975
976		CONFIG_DRIVER_AT91EMAC
977		Support for AT91RM9200 EMAC.
978
979			CONFIG_RMII
980			Define this to use reduced MII inteface
981
982			CONFIG_DRIVER_AT91EMAC_QUIET
983			If this defined, the driver is quiet.
984			The driver doen't show link status messages.
985
986		CONFIG_CALXEDA_XGMAC
987		Support for the Calxeda XGMAC device
988
989		CONFIG_LAN91C96
990		Support for SMSC's LAN91C96 chips.
991
992			CONFIG_LAN91C96_USE_32_BIT
993			Define this to enable 32 bit addressing
994
995		CONFIG_SMC91111
996		Support for SMSC's LAN91C111 chip
997
998			CONFIG_SMC91111_BASE
999			Define this to hold the physical address
1000			of the device (I/O space)
1001
1002			CONFIG_SMC_USE_32_BIT
1003			Define this if data bus is 32 bits
1004
1005			CONFIG_SMC_USE_IOFUNCS
1006			Define this to use i/o functions instead of macros
1007			(some hardware wont work with macros)
1008
1009		CONFIG_DRIVER_TI_EMAC
1010		Support for davinci emac
1011
1012			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1013			Define this if you have more then 3 PHYs.
1014
1015		CONFIG_FTGMAC100
1016		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1017
1018			CONFIG_FTGMAC100_EGIGA
1019			Define this to use GE link update with gigabit PHY.
1020			Define this if FTGMAC100 is connected to gigabit PHY.
1021			If your system has 10/100 PHY only, it might not occur
1022			wrong behavior. Because PHY usually return timeout or
1023			useless data when polling gigabit status and gigabit
1024			control registers. This behavior won't affect the
1025			correctnessof 10/100 link speed update.
1026
1027		CONFIG_SH_ETHER
1028		Support for Renesas on-chip Ethernet controller
1029
1030			CONFIG_SH_ETHER_USE_PORT
1031			Define the number of ports to be used
1032
1033			CONFIG_SH_ETHER_PHY_ADDR
1034			Define the ETH PHY's address
1035
1036			CONFIG_SH_ETHER_CACHE_WRITEBACK
1037			If this option is set, the driver enables cache flush.
1038
1039- PWM Support:
1040		CONFIG_PWM_IMX
1041		Support for PWM module on the imx6.
1042
1043- TPM Support:
1044		CONFIG_TPM
1045		Support TPM devices.
1046
1047		CONFIG_TPM_TIS_INFINEON
1048		Support for Infineon i2c bus TPM devices. Only one device
1049		per system is supported at this time.
1050
1051			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1052			Define the burst count bytes upper limit
1053
1054		CONFIG_TPM_ST33ZP24
1055		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1056
1057			CONFIG_TPM_ST33ZP24_I2C
1058			Support for STMicroelectronics ST33ZP24 I2C devices.
1059			Requires TPM_ST33ZP24 and I2C.
1060
1061			CONFIG_TPM_ST33ZP24_SPI
1062			Support for STMicroelectronics ST33ZP24 SPI devices.
1063			Requires TPM_ST33ZP24 and SPI.
1064
1065		CONFIG_TPM_ATMEL_TWI
1066		Support for Atmel TWI TPM device. Requires I2C support.
1067
1068		CONFIG_TPM_TIS_LPC
1069		Support for generic parallel port TPM devices. Only one device
1070		per system is supported at this time.
1071
1072			CONFIG_TPM_TIS_BASE_ADDRESS
1073			Base address where the generic TPM device is mapped
1074			to. Contemporary x86 systems usually map it at
1075			0xfed40000.
1076
1077		CONFIG_TPM
1078		Define this to enable the TPM support library which provides
1079		functional interfaces to some TPM commands.
1080		Requires support for a TPM device.
1081
1082		CONFIG_TPM_AUTH_SESSIONS
1083		Define this to enable authorized functions in the TPM library.
1084		Requires CONFIG_TPM and CONFIG_SHA1.
1085
1086- USB Support:
1087		At the moment only the UHCI host controller is
1088		supported (PIP405, MIP405); define
1089		CONFIG_USB_UHCI to enable it.
1090		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1091		and define CONFIG_USB_STORAGE to enable the USB
1092		storage devices.
1093		Note:
1094		Supported are USB Keyboards and USB Floppy drives
1095		(TEAC FD-05PUB).
1096
1097		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1098		txfilltuning field in the EHCI controller on reset.
1099
1100		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1101		HW module registers.
1102
1103- USB Device:
1104		Define the below if you wish to use the USB console.
1105		Once firmware is rebuilt from a serial console issue the
1106		command "setenv stdin usbtty; setenv stdout usbtty" and
1107		attach your USB cable. The Unix command "dmesg" should print
1108		it has found a new device. The environment variable usbtty
1109		can be set to gserial or cdc_acm to enable your device to
1110		appear to a USB host as a Linux gserial device or a
1111		Common Device Class Abstract Control Model serial device.
1112		If you select usbtty = gserial you should be able to enumerate
1113		a Linux host by
1114		# modprobe usbserial vendor=0xVendorID product=0xProductID
1115		else if using cdc_acm, simply setting the environment
1116		variable usbtty to be cdc_acm should suffice. The following
1117		might be defined in YourBoardName.h
1118
1119			CONFIG_USB_DEVICE
1120			Define this to build a UDC device
1121
1122			CONFIG_USB_TTY
1123			Define this to have a tty type of device available to
1124			talk to the UDC device
1125
1126			CONFIG_USBD_HS
1127			Define this to enable the high speed support for usb
1128			device and usbtty. If this feature is enabled, a routine
1129			int is_usbd_high_speed(void)
1130			also needs to be defined by the driver to dynamically poll
1131			whether the enumeration has succeded at high speed or full
1132			speed.
1133
1134			CONFIG_SYS_CONSOLE_IS_IN_ENV
1135			Define this if you want stdin, stdout &/or stderr to
1136			be set to usbtty.
1137
1138		If you have a USB-IF assigned VendorID then you may wish to
1139		define your own vendor specific values either in BoardName.h
1140		or directly in usbd_vendor_info.h. If you don't define
1141		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1142		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1143		should pretend to be a Linux device to it's target host.
1144
1145			CONFIG_USBD_MANUFACTURER
1146			Define this string as the name of your company for
1147			- CONFIG_USBD_MANUFACTURER "my company"
1148
1149			CONFIG_USBD_PRODUCT_NAME
1150			Define this string as the name of your product
1151			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1152
1153			CONFIG_USBD_VENDORID
1154			Define this as your assigned Vendor ID from the USB
1155			Implementors Forum. This *must* be a genuine Vendor ID
1156			to avoid polluting the USB namespace.
1157			- CONFIG_USBD_VENDORID 0xFFFF
1158
1159			CONFIG_USBD_PRODUCTID
1160			Define this as the unique Product ID
1161			for your device
1162			- CONFIG_USBD_PRODUCTID 0xFFFF
1163
1164- ULPI Layer Support:
1165		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1166		the generic ULPI layer. The generic layer accesses the ULPI PHY
1167		via the platform viewport, so you need both the genric layer and
1168		the viewport enabled. Currently only Chipidea/ARC based
1169		viewport is supported.
1170		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1171		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1172		If your ULPI phy needs a different reference clock than the
1173		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1174		the appropriate value in Hz.
1175
1176- MMC Support:
1177		The MMC controller on the Intel PXA is supported. To
1178		enable this define CONFIG_MMC. The MMC can be
1179		accessed from the boot prompt by mapping the device
1180		to physical memory similar to flash. Command line is
1181		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1182		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1183
1184		CONFIG_SH_MMCIF
1185		Support for Renesas on-chip MMCIF controller
1186
1187			CONFIG_SH_MMCIF_ADDR
1188			Define the base address of MMCIF registers
1189
1190			CONFIG_SH_MMCIF_CLK
1191			Define the clock frequency for MMCIF
1192
1193		CONFIG_SUPPORT_EMMC_BOOT
1194		Enable some additional features of the eMMC boot partitions.
1195
1196		CONFIG_SUPPORT_EMMC_RPMB
1197		Enable the commands for reading, writing and programming the
1198		key for the Replay Protection Memory Block partition in eMMC.
1199
1200- USB Device Firmware Update (DFU) class support:
1201		CONFIG_DFU_OVER_USB
1202		This enables the USB portion of the DFU USB class
1203
1204		CONFIG_DFU_MMC
1205		This enables support for exposing (e)MMC devices via DFU.
1206
1207		CONFIG_DFU_NAND
1208		This enables support for exposing NAND devices via DFU.
1209
1210		CONFIG_DFU_RAM
1211		This enables support for exposing RAM via DFU.
1212		Note: DFU spec refer to non-volatile memory usage, but
1213		allow usages beyond the scope of spec - here RAM usage,
1214		one that would help mostly the developer.
1215
1216		CONFIG_SYS_DFU_DATA_BUF_SIZE
1217		Dfu transfer uses a buffer before writing data to the
1218		raw storage device. Make the size (in bytes) of this buffer
1219		configurable. The size of this buffer is also configurable
1220		through the "dfu_bufsiz" environment variable.
1221
1222		CONFIG_SYS_DFU_MAX_FILE_SIZE
1223		When updating files rather than the raw storage device,
1224		we use a static buffer to copy the file into and then write
1225		the buffer once we've been given the whole file.  Define
1226		this to the maximum filesize (in bytes) for the buffer.
1227		Default is 4 MiB if undefined.
1228
1229		DFU_DEFAULT_POLL_TIMEOUT
1230		Poll timeout [ms], is the timeout a device can send to the
1231		host. The host must wait for this timeout before sending
1232		a subsequent DFU_GET_STATUS request to the device.
1233
1234		DFU_MANIFEST_POLL_TIMEOUT
1235		Poll timeout [ms], which the device sends to the host when
1236		entering dfuMANIFEST state. Host waits this timeout, before
1237		sending again an USB request to the device.
1238
1239- Journaling Flash filesystem support:
1240		CONFIG_JFFS2_NAND
1241		Define these for a default partition on a NAND device
1242
1243		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1244		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1245		Define these for a default partition on a NOR device
1246
1247- Keyboard Support:
1248		See Kconfig help for available keyboard drivers.
1249
1250		CONFIG_KEYBOARD
1251
1252		Define this to enable a custom keyboard support.
1253		This simply calls drv_keyboard_init() which must be
1254		defined in your board-specific files. This option is deprecated
1255		and is only used by novena. For new boards, use driver model
1256		instead.
1257
1258- Video support:
1259		CONFIG_FSL_DIU_FB
1260		Enable the Freescale DIU video driver.	Reference boards for
1261		SOCs that have a DIU should define this macro to enable DIU
1262		support, and should also define these other macros:
1263
1264			CONFIG_SYS_DIU_ADDR
1265			CONFIG_VIDEO
1266			CONFIG_CFB_CONSOLE
1267			CONFIG_VIDEO_SW_CURSOR
1268			CONFIG_VGA_AS_SINGLE_DEVICE
1269			CONFIG_VIDEO_LOGO
1270			CONFIG_VIDEO_BMP_LOGO
1271
1272		The DIU driver will look for the 'video-mode' environment
1273		variable, and if defined, enable the DIU as a console during
1274		boot.  See the documentation file doc/README.video for a
1275		description of this variable.
1276
1277- LCD Support:	CONFIG_LCD
1278
1279		Define this to enable LCD support (for output to LCD
1280		display); also select one of the supported displays
1281		by defining one of these:
1282
1283		CONFIG_ATMEL_LCD:
1284
1285			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1286
1287		CONFIG_NEC_NL6448AC33:
1288
1289			NEC NL6448AC33-18. Active, color, single scan.
1290
1291		CONFIG_NEC_NL6448BC20
1292
1293			NEC NL6448BC20-08. 6.5", 640x480.
1294			Active, color, single scan.
1295
1296		CONFIG_NEC_NL6448BC33_54
1297
1298			NEC NL6448BC33-54. 10.4", 640x480.
1299			Active, color, single scan.
1300
1301		CONFIG_SHARP_16x9
1302
1303			Sharp 320x240. Active, color, single scan.
1304			It isn't 16x9, and I am not sure what it is.
1305
1306		CONFIG_SHARP_LQ64D341
1307
1308			Sharp LQ64D341 display, 640x480.
1309			Active, color, single scan.
1310
1311		CONFIG_HLD1045
1312
1313			HLD1045 display, 640x480.
1314			Active, color, single scan.
1315
1316		CONFIG_OPTREX_BW
1317
1318			Optrex	 CBL50840-2 NF-FW 99 22 M5
1319			or
1320			Hitachi	 LMG6912RPFC-00T
1321			or
1322			Hitachi	 SP14Q002
1323
1324			320x240. Black & white.
1325
1326		CONFIG_LCD_ALIGNMENT
1327
1328		Normally the LCD is page-aligned (typically 4KB). If this is
1329		defined then the LCD will be aligned to this value instead.
1330		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1331		here, since it is cheaper to change data cache settings on
1332		a per-section basis.
1333
1334
1335		CONFIG_LCD_ROTATION
1336
1337		Sometimes, for example if the display is mounted in portrait
1338		mode or even if it's mounted landscape but rotated by 180degree,
1339		we need to rotate our content of the display relative to the
1340		framebuffer, so that user can read the messages which are
1341		printed out.
1342		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1343		initialized with a given rotation from "vl_rot" out of
1344		"vidinfo_t" which is provided by the board specific code.
1345		The value for vl_rot is coded as following (matching to
1346		fbcon=rotate:<n> linux-kernel commandline):
1347		0 = no rotation respectively 0 degree
1348		1 = 90 degree rotation
1349		2 = 180 degree rotation
1350		3 = 270 degree rotation
1351
1352		If CONFIG_LCD_ROTATION is not defined, the console will be
1353		initialized with 0degree rotation.
1354
1355		CONFIG_LCD_BMP_RLE8
1356
1357		Support drawing of RLE8-compressed bitmaps on the LCD.
1358
1359		CONFIG_I2C_EDID
1360
1361		Enables an 'i2c edid' command which can read EDID
1362		information over I2C from an attached LCD display.
1363
1364- Splash Screen Support: CONFIG_SPLASH_SCREEN
1365
1366		If this option is set, the environment is checked for
1367		a variable "splashimage". If found, the usual display
1368		of logo, copyright and system information on the LCD
1369		is suppressed and the BMP image at the address
1370		specified in "splashimage" is loaded instead. The
1371		console is redirected to the "nulldev", too. This
1372		allows for a "silent" boot where a splash screen is
1373		loaded very quickly after power-on.
1374
1375		CONFIG_SPLASHIMAGE_GUARD
1376
1377		If this option is set, then U-Boot will prevent the environment
1378		variable "splashimage" from being set to a problematic address
1379		(see doc/README.displaying-bmps).
1380		This option is useful for targets where, due to alignment
1381		restrictions, an improperly aligned BMP image will cause a data
1382		abort. If you think you will not have problems with unaligned
1383		accesses (for example because your toolchain prevents them)
1384		there is no need to set this option.
1385
1386		CONFIG_SPLASH_SCREEN_ALIGN
1387
1388		If this option is set the splash image can be freely positioned
1389		on the screen. Environment variable "splashpos" specifies the
1390		position as "x,y". If a positive number is given it is used as
1391		number of pixel from left/top. If a negative number is given it
1392		is used as number of pixel from right/bottom. You can also
1393		specify 'm' for centering the image.
1394
1395		Example:
1396		setenv splashpos m,m
1397			=> image at center of screen
1398
1399		setenv splashpos 30,20
1400			=> image at x = 30 and y = 20
1401
1402		setenv splashpos -10,m
1403			=> vertically centered image
1404			   at x = dspWidth - bmpWidth - 9
1405
1406- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1407
1408		If this option is set, additionally to standard BMP
1409		images, gzipped BMP images can be displayed via the
1410		splashscreen support or the bmp command.
1411
1412- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1413
1414		If this option is set, 8-bit RLE compressed BMP images
1415		can be displayed via the splashscreen support or the
1416		bmp command.
1417
1418- Compression support:
1419		CONFIG_GZIP
1420
1421		Enabled by default to support gzip compressed images.
1422
1423		CONFIG_BZIP2
1424
1425		If this option is set, support for bzip2 compressed
1426		images is included. If not, only uncompressed and gzip
1427		compressed images are supported.
1428
1429		NOTE: the bzip2 algorithm requires a lot of RAM, so
1430		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1431		be at least 4MB.
1432
1433- MII/PHY support:
1434		CONFIG_PHY_ADDR
1435
1436		The address of PHY on MII bus.
1437
1438		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1439
1440		The clock frequency of the MII bus
1441
1442		CONFIG_PHY_RESET_DELAY
1443
1444		Some PHY like Intel LXT971A need extra delay after
1445		reset before any MII register access is possible.
1446		For such PHY, set this option to the usec delay
1447		required. (minimum 300usec for LXT971A)
1448
1449		CONFIG_PHY_CMD_DELAY (ppc4xx)
1450
1451		Some PHY like Intel LXT971A need extra delay after
1452		command issued before MII status register can be read
1453
1454- IP address:
1455		CONFIG_IPADDR
1456
1457		Define a default value for the IP address to use for
1458		the default Ethernet interface, in case this is not
1459		determined through e.g. bootp.
1460		(Environment variable "ipaddr")
1461
1462- Server IP address:
1463		CONFIG_SERVERIP
1464
1465		Defines a default value for the IP address of a TFTP
1466		server to contact when using the "tftboot" command.
1467		(Environment variable "serverip")
1468
1469		CONFIG_KEEP_SERVERADDR
1470
1471		Keeps the server's MAC address, in the env 'serveraddr'
1472		for passing to bootargs (like Linux's netconsole option)
1473
1474- Gateway IP address:
1475		CONFIG_GATEWAYIP
1476
1477		Defines a default value for the IP address of the
1478		default router where packets to other networks are
1479		sent to.
1480		(Environment variable "gatewayip")
1481
1482- Subnet mask:
1483		CONFIG_NETMASK
1484
1485		Defines a default value for the subnet mask (or
1486		routing prefix) which is used to determine if an IP
1487		address belongs to the local subnet or needs to be
1488		forwarded through a router.
1489		(Environment variable "netmask")
1490
1491- Multicast TFTP Mode:
1492		CONFIG_MCAST_TFTP
1493
1494		Defines whether you want to support multicast TFTP as per
1495		rfc-2090; for example to work with atftp.  Lets lots of targets
1496		tftp down the same boot image concurrently.  Note: the Ethernet
1497		driver in use must provide a function: mcast() to join/leave a
1498		multicast group.
1499
1500- BOOTP Recovery Mode:
1501		CONFIG_BOOTP_RANDOM_DELAY
1502
1503		If you have many targets in a network that try to
1504		boot using BOOTP, you may want to avoid that all
1505		systems send out BOOTP requests at precisely the same
1506		moment (which would happen for instance at recovery
1507		from a power failure, when all systems will try to
1508		boot, thus flooding the BOOTP server. Defining
1509		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1510		inserted before sending out BOOTP requests. The
1511		following delays are inserted then:
1512
1513		1st BOOTP request:	delay 0 ... 1 sec
1514		2nd BOOTP request:	delay 0 ... 2 sec
1515		3rd BOOTP request:	delay 0 ... 4 sec
1516		4th and following
1517		BOOTP requests:		delay 0 ... 8 sec
1518
1519		CONFIG_BOOTP_ID_CACHE_SIZE
1520
1521		BOOTP packets are uniquely identified using a 32-bit ID. The
1522		server will copy the ID from client requests to responses and
1523		U-Boot will use this to determine if it is the destination of
1524		an incoming response. Some servers will check that addresses
1525		aren't in use before handing them out (usually using an ARP
1526		ping) and therefore take up to a few hundred milliseconds to
1527		respond. Network congestion may also influence the time it
1528		takes for a response to make it back to the client. If that
1529		time is too long, U-Boot will retransmit requests. In order
1530		to allow earlier responses to still be accepted after these
1531		retransmissions, U-Boot's BOOTP client keeps a small cache of
1532		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1533		cache. The default is to keep IDs for up to four outstanding
1534		requests. Increasing this will allow U-Boot to accept offers
1535		from a BOOTP client in networks with unusually high latency.
1536
1537- DHCP Advanced Options:
1538		You can fine tune the DHCP functionality by defining
1539		CONFIG_BOOTP_* symbols:
1540
1541		CONFIG_BOOTP_NISDOMAIN
1542		CONFIG_BOOTP_BOOTFILESIZE
1543		CONFIG_BOOTP_SEND_HOSTNAME
1544		CONFIG_BOOTP_NTPSERVER
1545		CONFIG_BOOTP_TIMEOFFSET
1546		CONFIG_BOOTP_VENDOREX
1547		CONFIG_BOOTP_MAY_FAIL
1548
1549		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1550		environment variable, not the BOOTP server.
1551
1552		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1553		after the configured retry count, the call will fail
1554		instead of starting over.  This can be used to fail over
1555		to Link-local IP address configuration if the DHCP server
1556		is not available.
1557
1558		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1559		to do a dynamic update of a DNS server. To do this, they
1560		need the hostname of the DHCP requester.
1561		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1562		of the "hostname" environment variable is passed as
1563		option 12 to the DHCP server.
1564
1565		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1566
1567		A 32bit value in microseconds for a delay between
1568		receiving a "DHCP Offer" and sending the "DHCP Request".
1569		This fixes a problem with certain DHCP servers that don't
1570		respond 100% of the time to a "DHCP request". E.g. On an
1571		AT91RM9200 processor running at 180MHz, this delay needed
1572		to be *at least* 15,000 usec before a Windows Server 2003
1573		DHCP server would reply 100% of the time. I recommend at
1574		least 50,000 usec to be safe. The alternative is to hope
1575		that one of the retries will be successful but note that
1576		the DHCP timeout and retry process takes a longer than
1577		this delay.
1578
1579 - Link-local IP address negotiation:
1580		Negotiate with other link-local clients on the local network
1581		for an address that doesn't require explicit configuration.
1582		This is especially useful if a DHCP server cannot be guaranteed
1583		to exist in all environments that the device must operate.
1584
1585		See doc/README.link-local for more information.
1586
1587 - MAC address from environment variables
1588
1589		FDT_SEQ_MACADDR_FROM_ENV
1590
1591		Fix-up device tree with MAC addresses fetched sequentially from
1592		environment variables. This config work on assumption that
1593		non-usable ethernet node of device-tree are either not present
1594		or their status has been marked as "disabled".
1595
1596 - CDP Options:
1597		CONFIG_CDP_DEVICE_ID
1598
1599		The device id used in CDP trigger frames.
1600
1601		CONFIG_CDP_DEVICE_ID_PREFIX
1602
1603		A two character string which is prefixed to the MAC address
1604		of the device.
1605
1606		CONFIG_CDP_PORT_ID
1607
1608		A printf format string which contains the ascii name of
1609		the port. Normally is set to "eth%d" which sets
1610		eth0 for the first Ethernet, eth1 for the second etc.
1611
1612		CONFIG_CDP_CAPABILITIES
1613
1614		A 32bit integer which indicates the device capabilities;
1615		0x00000010 for a normal host which does not forwards.
1616
1617		CONFIG_CDP_VERSION
1618
1619		An ascii string containing the version of the software.
1620
1621		CONFIG_CDP_PLATFORM
1622
1623		An ascii string containing the name of the platform.
1624
1625		CONFIG_CDP_TRIGGER
1626
1627		A 32bit integer sent on the trigger.
1628
1629		CONFIG_CDP_POWER_CONSUMPTION
1630
1631		A 16bit integer containing the power consumption of the
1632		device in .1 of milliwatts.
1633
1634		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1635
1636		A byte containing the id of the VLAN.
1637
1638- Status LED:	CONFIG_LED_STATUS
1639
1640		Several configurations allow to display the current
1641		status using a LED. For instance, the LED will blink
1642		fast while running U-Boot code, stop blinking as
1643		soon as a reply to a BOOTP request was received, and
1644		start blinking slow once the Linux kernel is running
1645		(supported by a status LED driver in the Linux
1646		kernel). Defining CONFIG_LED_STATUS enables this
1647		feature in U-Boot.
1648
1649		Additional options:
1650
1651		CONFIG_LED_STATUS_GPIO
1652		The status LED can be connected to a GPIO pin.
1653		In such cases, the gpio_led driver can be used as a
1654		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1655		to include the gpio_led driver in the U-Boot binary.
1656
1657		CONFIG_GPIO_LED_INVERTED_TABLE
1658		Some GPIO connected LEDs may have inverted polarity in which
1659		case the GPIO high value corresponds to LED off state and
1660		GPIO low value corresponds to LED on state.
1661		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1662		with a list of GPIO LEDs that have inverted polarity.
1663
1664- I2C Support:	CONFIG_SYS_I2C
1665
1666		This enable the NEW i2c subsystem, and will allow you to use
1667		i2c commands at the u-boot command line (as long as you set
1668		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1669		based realtime clock chips or other i2c devices. See
1670		common/cmd_i2c.c for a description of the command line
1671		interface.
1672
1673		ported i2c driver to the new framework:
1674		- drivers/i2c/soft_i2c.c:
1675		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1676		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1677		    for defining speed and slave address
1678		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1679		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1680		    for defining speed and slave address
1681		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1682		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1683		    for defining speed and slave address
1684		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1685		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1686		    for defining speed and slave address
1687
1688		- drivers/i2c/fsl_i2c.c:
1689		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1690		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1691		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1692		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1693		    bus.
1694		  - If your board supports a second fsl i2c bus, define
1695		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1696		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1697		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1698		    second bus.
1699
1700		- drivers/i2c/tegra_i2c.c:
1701		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1702		  - This driver adds 4 i2c buses with a fix speed from
1703		    100000 and the slave addr 0!
1704
1705		- drivers/i2c/ppc4xx_i2c.c
1706		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1707		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1708		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1709
1710		- drivers/i2c/i2c_mxc.c
1711		  - activate this driver with CONFIG_SYS_I2C_MXC
1712		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1713		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1714		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1715		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1716		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1717		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1718		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1719		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1720		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1721		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1722		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1723		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1724		If those defines are not set, default value is 100000
1725		for speed, and 0 for slave.
1726
1727		- drivers/i2c/rcar_i2c.c:
1728		  - activate this driver with CONFIG_SYS_I2C_RCAR
1729		  - This driver adds 4 i2c buses
1730
1731		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1732		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1733		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1734		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1735		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1736		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1737		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1738		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1739		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1740
1741		- drivers/i2c/sh_i2c.c:
1742		  - activate this driver with CONFIG_SYS_I2C_SH
1743		  - This driver adds from 2 to 5 i2c buses
1744
1745		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1746		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1747		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1748		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1749		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1750		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1751		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1752		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1753		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1754		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1755		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1756
1757		- drivers/i2c/omap24xx_i2c.c
1758		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1759		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1760		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1761		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1762		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1763		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1764		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1765		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1766		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1767		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1768		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1769
1770		- drivers/i2c/zynq_i2c.c
1771		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1772		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1773		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1774
1775		- drivers/i2c/s3c24x0_i2c.c:
1776		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1777		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1778		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1779		    with a fix speed from 100000 and the slave addr 0!
1780
1781		- drivers/i2c/ihs_i2c.c
1782		  - activate this driver with CONFIG_SYS_I2C_IHS
1783		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1784		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1785		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1786		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1787		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1788		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1789		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1790		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1791		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1792		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1793		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1794		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1795		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1796		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1797		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1798		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1799		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1800		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1801		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1802		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1803		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1804
1805		additional defines:
1806
1807		CONFIG_SYS_NUM_I2C_BUSES
1808		Hold the number of i2c buses you want to use.
1809
1810		CONFIG_SYS_I2C_DIRECT_BUS
1811		define this, if you don't use i2c muxes on your hardware.
1812		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1813		omit this define.
1814
1815		CONFIG_SYS_I2C_MAX_HOPS
1816		define how many muxes are maximal consecutively connected
1817		on one i2c bus. If you not use i2c muxes, omit this
1818		define.
1819
1820		CONFIG_SYS_I2C_BUSES
1821		hold a list of buses you want to use, only used if
1822		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1823		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1824		CONFIG_SYS_NUM_I2C_BUSES = 9:
1825
1826		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1827					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1828					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1829					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1830					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1831					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1832					{1, {I2C_NULL_HOP}}, \
1833					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1834					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1835					}
1836
1837		which defines
1838			bus 0 on adapter 0 without a mux
1839			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1840			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1841			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1842			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1843			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1844			bus 6 on adapter 1 without a mux
1845			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1846			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1847
1848		If you do not have i2c muxes on your board, omit this define.
1849
1850- Legacy I2C Support:
1851		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1852		then the following macros need to be defined (examples are
1853		from include/configs/lwmon.h):
1854
1855		I2C_INIT
1856
1857		(Optional). Any commands necessary to enable the I2C
1858		controller or configure ports.
1859
1860		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1861
1862		I2C_ACTIVE
1863
1864		The code necessary to make the I2C data line active
1865		(driven).  If the data line is open collector, this
1866		define can be null.
1867
1868		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1869
1870		I2C_TRISTATE
1871
1872		The code necessary to make the I2C data line tri-stated
1873		(inactive).  If the data line is open collector, this
1874		define can be null.
1875
1876		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1877
1878		I2C_READ
1879
1880		Code that returns true if the I2C data line is high,
1881		false if it is low.
1882
1883		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1884
1885		I2C_SDA(bit)
1886
1887		If <bit> is true, sets the I2C data line high. If it
1888		is false, it clears it (low).
1889
1890		eg: #define I2C_SDA(bit) \
1891			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1892			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1893
1894		I2C_SCL(bit)
1895
1896		If <bit> is true, sets the I2C clock line high. If it
1897		is false, it clears it (low).
1898
1899		eg: #define I2C_SCL(bit) \
1900			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1901			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1902
1903		I2C_DELAY
1904
1905		This delay is invoked four times per clock cycle so this
1906		controls the rate of data transfer.  The data rate thus
1907		is 1 / (I2C_DELAY * 4). Often defined to be something
1908		like:
1909
1910		#define I2C_DELAY  udelay(2)
1911
1912		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1913
1914		If your arch supports the generic GPIO framework (asm/gpio.h),
1915		then you may alternatively define the two GPIOs that are to be
1916		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1917		have GPIO-based defaults assigned to them as appropriate.
1918
1919		You should define these to the GPIO value as given directly to
1920		the generic GPIO functions.
1921
1922		CONFIG_SYS_I2C_INIT_BOARD
1923
1924		When a board is reset during an i2c bus transfer
1925		chips might think that the current transfer is still
1926		in progress. On some boards it is possible to access
1927		the i2c SCLK line directly, either by using the
1928		processor pin as a GPIO or by having a second pin
1929		connected to the bus. If this option is defined a
1930		custom i2c_init_board() routine in boards/xxx/board.c
1931		is run early in the boot sequence.
1932
1933		CONFIG_I2C_MULTI_BUS
1934
1935		This option allows the use of multiple I2C buses, each of which
1936		must have a controller.	 At any point in time, only one bus is
1937		active.	 To switch to a different bus, use the 'i2c dev' command.
1938		Note that bus numbering is zero-based.
1939
1940		CONFIG_SYS_I2C_NOPROBES
1941
1942		This option specifies a list of I2C devices that will be skipped
1943		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1944		is set, specify a list of bus-device pairs.  Otherwise, specify
1945		a 1D array of device addresses
1946
1947		e.g.
1948			#undef	CONFIG_I2C_MULTI_BUS
1949			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1950
1951		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1952
1953			#define CONFIG_I2C_MULTI_BUS
1954			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1955
1956		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1957
1958		CONFIG_SYS_SPD_BUS_NUM
1959
1960		If defined, then this indicates the I2C bus number for DDR SPD.
1961		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1962
1963		CONFIG_SYS_RTC_BUS_NUM
1964
1965		If defined, then this indicates the I2C bus number for the RTC.
1966		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1967
1968		CONFIG_SOFT_I2C_READ_REPEATED_START
1969
1970		defining this will force the i2c_read() function in
1971		the soft_i2c driver to perform an I2C repeated start
1972		between writing the address pointer and reading the
1973		data.  If this define is omitted the default behaviour
1974		of doing a stop-start sequence will be used.  Most I2C
1975		devices can use either method, but some require one or
1976		the other.
1977
1978- SPI Support:	CONFIG_SPI
1979
1980		Enables SPI driver (so far only tested with
1981		SPI EEPROM, also an instance works with Crystal A/D and
1982		D/As on the SACSng board)
1983
1984		CONFIG_SOFT_SPI
1985
1986		Enables a software (bit-bang) SPI driver rather than
1987		using hardware support. This is a general purpose
1988		driver that only requires three general I/O port pins
1989		(two outputs, one input) to function. If this is
1990		defined, the board configuration must define several
1991		SPI configuration items (port pins to use, etc). For
1992		an example, see include/configs/sacsng.h.
1993
1994		CONFIG_HARD_SPI
1995
1996		Enables a hardware SPI driver for general-purpose reads
1997		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1998		must define a list of chip-select function pointers.
1999		Currently supported on some MPC8xxx processors.	 For an
2000		example, see include/configs/mpc8349emds.h.
2001
2002		CONFIG_SYS_SPI_MXC_WAIT
2003		Timeout for waiting until spi transfer completed.
2004		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2005
2006- FPGA Support: CONFIG_FPGA
2007
2008		Enables FPGA subsystem.
2009
2010		CONFIG_FPGA_<vendor>
2011
2012		Enables support for specific chip vendors.
2013		(ALTERA, XILINX)
2014
2015		CONFIG_FPGA_<family>
2016
2017		Enables support for FPGA family.
2018		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2019
2020		CONFIG_FPGA_COUNT
2021
2022		Specify the number of FPGA devices to support.
2023
2024		CONFIG_SYS_FPGA_PROG_FEEDBACK
2025
2026		Enable printing of hash marks during FPGA configuration.
2027
2028		CONFIG_SYS_FPGA_CHECK_BUSY
2029
2030		Enable checks on FPGA configuration interface busy
2031		status by the configuration function. This option
2032		will require a board or device specific function to
2033		be written.
2034
2035		CONFIG_FPGA_DELAY
2036
2037		If defined, a function that provides delays in the FPGA
2038		configuration driver.
2039
2040		CONFIG_SYS_FPGA_CHECK_CTRLC
2041		Allow Control-C to interrupt FPGA configuration
2042
2043		CONFIG_SYS_FPGA_CHECK_ERROR
2044
2045		Check for configuration errors during FPGA bitfile
2046		loading. For example, abort during Virtex II
2047		configuration if the INIT_B line goes low (which
2048		indicated a CRC error).
2049
2050		CONFIG_SYS_FPGA_WAIT_INIT
2051
2052		Maximum time to wait for the INIT_B line to de-assert
2053		after PROB_B has been de-asserted during a Virtex II
2054		FPGA configuration sequence. The default time is 500
2055		ms.
2056
2057		CONFIG_SYS_FPGA_WAIT_BUSY
2058
2059		Maximum time to wait for BUSY to de-assert during
2060		Virtex II FPGA configuration. The default is 5 ms.
2061
2062		CONFIG_SYS_FPGA_WAIT_CONFIG
2063
2064		Time to wait after FPGA configuration. The default is
2065		200 ms.
2066
2067- Configuration Management:
2068		CONFIG_BUILD_TARGET
2069
2070		Some SoCs need special image types (e.g. U-Boot binary
2071		with a special header) as build targets. By defining
2072		CONFIG_BUILD_TARGET in the SoC / board header, this
2073		special image will be automatically built upon calling
2074		make / buildman.
2075
2076		CONFIG_IDENT_STRING
2077
2078		If defined, this string will be added to the U-Boot
2079		version information (U_BOOT_VERSION)
2080
2081- Vendor Parameter Protection:
2082
2083		U-Boot considers the values of the environment
2084		variables "serial#" (Board Serial Number) and
2085		"ethaddr" (Ethernet Address) to be parameters that
2086		are set once by the board vendor / manufacturer, and
2087		protects these variables from casual modification by
2088		the user. Once set, these variables are read-only,
2089		and write or delete attempts are rejected. You can
2090		change this behaviour:
2091
2092		If CONFIG_ENV_OVERWRITE is #defined in your config
2093		file, the write protection for vendor parameters is
2094		completely disabled. Anybody can change or delete
2095		these parameters.
2096
2097		Alternatively, if you define _both_ an ethaddr in the
2098		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2099		Ethernet address is installed in the environment,
2100		which can be changed exactly ONCE by the user. [The
2101		serial# is unaffected by this, i. e. it remains
2102		read-only.]
2103
2104		The same can be accomplished in a more flexible way
2105		for any variable by configuring the type of access
2106		to allow for those variables in the ".flags" variable
2107		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2108
2109- Protected RAM:
2110		CONFIG_PRAM
2111
2112		Define this variable to enable the reservation of
2113		"protected RAM", i. e. RAM which is not overwritten
2114		by U-Boot. Define CONFIG_PRAM to hold the number of
2115		kB you want to reserve for pRAM. You can overwrite
2116		this default value by defining an environment
2117		variable "pram" to the number of kB you want to
2118		reserve. Note that the board info structure will
2119		still show the full amount of RAM. If pRAM is
2120		reserved, a new environment variable "mem" will
2121		automatically be defined to hold the amount of
2122		remaining RAM in a form that can be passed as boot
2123		argument to Linux, for instance like that:
2124
2125			setenv bootargs ... mem=\${mem}
2126			saveenv
2127
2128		This way you can tell Linux not to use this memory,
2129		either, which results in a memory region that will
2130		not be affected by reboots.
2131
2132		*WARNING* If your board configuration uses automatic
2133		detection of the RAM size, you must make sure that
2134		this memory test is non-destructive. So far, the
2135		following board configurations are known to be
2136		"pRAM-clean":
2137
2138			IVMS8, IVML24, SPD8xx,
2139			HERMES, IP860, RPXlite, LWMON,
2140			FLAGADM
2141
2142- Access to physical memory region (> 4GB)
2143		Some basic support is provided for operations on memory not
2144		normally accessible to U-Boot - e.g. some architectures
2145		support access to more than 4GB of memory on 32-bit
2146		machines using physical address extension or similar.
2147		Define CONFIG_PHYSMEM to access this basic support, which
2148		currently only supports clearing the memory.
2149
2150- Error Recovery:
2151		CONFIG_NET_RETRY_COUNT
2152
2153		This variable defines the number of retries for
2154		network operations like ARP, RARP, TFTP, or BOOTP
2155		before giving up the operation. If not defined, a
2156		default value of 5 is used.
2157
2158		CONFIG_ARP_TIMEOUT
2159
2160		Timeout waiting for an ARP reply in milliseconds.
2161
2162		CONFIG_NFS_TIMEOUT
2163
2164		Timeout in milliseconds used in NFS protocol.
2165		If you encounter "ERROR: Cannot umount" in nfs command,
2166		try longer timeout such as
2167		#define CONFIG_NFS_TIMEOUT 10000UL
2168
2169- Command Interpreter:
2170		CONFIG_SYS_PROMPT_HUSH_PS2
2171
2172		This defines the secondary prompt string, which is
2173		printed when the command interpreter needs more input
2174		to complete a command. Usually "> ".
2175
2176	Note:
2177
2178		In the current implementation, the local variables
2179		space and global environment variables space are
2180		separated. Local variables are those you define by
2181		simply typing `name=value'. To access a local
2182		variable later on, you have write `$name' or
2183		`${name}'; to execute the contents of a variable
2184		directly type `$name' at the command prompt.
2185
2186		Global environment variables are those you use
2187		setenv/printenv to work with. To run a command stored
2188		in such a variable, you need to use the run command,
2189		and you must not use the '$' sign to access them.
2190
2191		To store commands and special characters in a
2192		variable, please use double quotation marks
2193		surrounding the whole text of the variable, instead
2194		of the backslashes before semicolons and special
2195		symbols.
2196
2197- Command Line Editing and History:
2198		CONFIG_CMDLINE_PS_SUPPORT
2199
2200		Enable support for changing the command prompt string
2201		at run-time. Only static string is supported so far.
2202		The string is obtained from environment variables PS1
2203		and PS2.
2204
2205- Default Environment:
2206		CONFIG_EXTRA_ENV_SETTINGS
2207
2208		Define this to contain any number of null terminated
2209		strings (variable = value pairs) that will be part of
2210		the default environment compiled into the boot image.
2211
2212		For example, place something like this in your
2213		board's config file:
2214
2215		#define CONFIG_EXTRA_ENV_SETTINGS \
2216			"myvar1=value1\0" \
2217			"myvar2=value2\0"
2218
2219		Warning: This method is based on knowledge about the
2220		internal format how the environment is stored by the
2221		U-Boot code. This is NOT an official, exported
2222		interface! Although it is unlikely that this format
2223		will change soon, there is no guarantee either.
2224		You better know what you are doing here.
2225
2226		Note: overly (ab)use of the default environment is
2227		discouraged. Make sure to check other ways to preset
2228		the environment like the "source" command or the
2229		boot command first.
2230
2231		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2232
2233		Define this in order to add variables describing certain
2234		run-time determined information about the hardware to the
2235		environment.  These will be named board_name, board_rev.
2236
2237		CONFIG_DELAY_ENVIRONMENT
2238
2239		Normally the environment is loaded when the board is
2240		initialised so that it is available to U-Boot. This inhibits
2241		that so that the environment is not available until
2242		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2243		this is instead controlled by the value of
2244		/config/load-environment.
2245
2246- Serial Flash support
2247		Usage requires an initial 'sf probe' to define the serial
2248		flash parameters, followed by read/write/erase/update
2249		commands.
2250
2251		The following defaults may be provided by the platform
2252		to handle the common case when only a single serial
2253		flash is present on the system.
2254
2255		CONFIG_SF_DEFAULT_BUS		Bus identifier
2256		CONFIG_SF_DEFAULT_CS		Chip-select
2257		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2258		CONFIG_SF_DEFAULT_SPEED		in Hz
2259
2260
2261- TFTP Fixed UDP Port:
2262		CONFIG_TFTP_PORT
2263
2264		If this is defined, the environment variable tftpsrcp
2265		is used to supply the TFTP UDP source port value.
2266		If tftpsrcp isn't defined, the normal pseudo-random port
2267		number generator is used.
2268
2269		Also, the environment variable tftpdstp is used to supply
2270		the TFTP UDP destination port value.  If tftpdstp isn't
2271		defined, the normal port 69 is used.
2272
2273		The purpose for tftpsrcp is to allow a TFTP server to
2274		blindly start the TFTP transfer using the pre-configured
2275		target IP address and UDP port. This has the effect of
2276		"punching through" the (Windows XP) firewall, allowing
2277		the remainder of the TFTP transfer to proceed normally.
2278		A better solution is to properly configure the firewall,
2279		but sometimes that is not allowed.
2280
2281- bootcount support:
2282		CONFIG_AT91SAM9XE
2283		enable special bootcounter support on at91sam9xe based boards.
2284		CONFIG_SOC_DA8XX
2285		enable special bootcounter support on da850 based boards.
2286		CONFIG_BOOTCOUNT_RAM
2287		enable support for the bootcounter in RAM
2288		CONFIG_BOOTCOUNT_I2C
2289		enable support for the bootcounter on an i2c (like RTC) device.
2290			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2291			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2292						    the bootcounter.
2293			CONFIG_BOOTCOUNT_ALEN = address len
2294		CONFIG_BOOTCOUNT_EXT
2295		enable support for the bootcounter in EXT filesystem
2296			CONFIG_SYS_BOOTCOUNT_ADDR = RAM address used for read
2297                                                    and write.
2298			CONFIG_SYS_BOOTCOUNT_EXT_INTERFACE = interface
2299			CONFIG_SYS_BOOTCOUNT_EXT_DEVPART = device and part
2300			CONFIG_SYS_BOOTCOUNT_EXT_NAME = filename
2301
2302- Show boot progress:
2303		CONFIG_SHOW_BOOT_PROGRESS
2304
2305		Defining this option allows to add some board-
2306		specific code (calling a user-provided function
2307		"show_boot_progress(int)") that enables you to show
2308		the system's boot progress on some display (for
2309		example, some LED's) on your board. At the moment,
2310		the following checkpoints are implemented:
2311
2312
2313Legacy uImage format:
2314
2315  Arg	Where			When
2316    1	common/cmd_bootm.c	before attempting to boot an image
2317   -1	common/cmd_bootm.c	Image header has bad	 magic number
2318    2	common/cmd_bootm.c	Image header has correct magic number
2319   -2	common/cmd_bootm.c	Image header has bad	 checksum
2320    3	common/cmd_bootm.c	Image header has correct checksum
2321   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2322    4	common/cmd_bootm.c	Image data   has correct checksum
2323   -4	common/cmd_bootm.c	Image is for unsupported architecture
2324    5	common/cmd_bootm.c	Architecture check OK
2325   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2326    6	common/cmd_bootm.c	Image Type check OK
2327   -6	common/cmd_bootm.c	gunzip uncompression error
2328   -7	common/cmd_bootm.c	Unimplemented compression type
2329    7	common/cmd_bootm.c	Uncompression OK
2330    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2331   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2332
2333    9	common/image.c		Start initial ramdisk verification
2334  -10	common/image.c		Ramdisk header has bad	   magic number
2335  -11	common/image.c		Ramdisk header has bad	   checksum
2336   10	common/image.c		Ramdisk header is OK
2337  -12	common/image.c		Ramdisk data   has bad	   checksum
2338   11	common/image.c		Ramdisk data   has correct checksum
2339   12	common/image.c		Ramdisk verification complete, start loading
2340  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2341   13	common/image.c		Start multifile image verification
2342   14	common/image.c		No initial ramdisk, no multifile, continue.
2343
2344   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2345
2346  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2347  -31	post/post.c		POST test failed, detected by post_output_backlog()
2348  -32	post/post.c		POST test failed, detected by post_run_single()
2349
2350   34	common/cmd_doc.c	before loading a Image from a DOC device
2351  -35	common/cmd_doc.c	Bad usage of "doc" command
2352   35	common/cmd_doc.c	correct usage of "doc" command
2353  -36	common/cmd_doc.c	No boot device
2354   36	common/cmd_doc.c	correct boot device
2355  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2356   37	common/cmd_doc.c	correct chip ID found, device available
2357  -38	common/cmd_doc.c	Read Error on boot device
2358   38	common/cmd_doc.c	reading Image header from DOC device OK
2359  -39	common/cmd_doc.c	Image header has bad magic number
2360   39	common/cmd_doc.c	Image header has correct magic number
2361  -40	common/cmd_doc.c	Error reading Image from DOC device
2362   40	common/cmd_doc.c	Image header has correct magic number
2363   41	common/cmd_ide.c	before loading a Image from a IDE device
2364  -42	common/cmd_ide.c	Bad usage of "ide" command
2365   42	common/cmd_ide.c	correct usage of "ide" command
2366  -43	common/cmd_ide.c	No boot device
2367   43	common/cmd_ide.c	boot device found
2368  -44	common/cmd_ide.c	Device not available
2369   44	common/cmd_ide.c	Device available
2370  -45	common/cmd_ide.c	wrong partition selected
2371   45	common/cmd_ide.c	partition selected
2372  -46	common/cmd_ide.c	Unknown partition table
2373   46	common/cmd_ide.c	valid partition table found
2374  -47	common/cmd_ide.c	Invalid partition type
2375   47	common/cmd_ide.c	correct partition type
2376  -48	common/cmd_ide.c	Error reading Image Header on boot device
2377   48	common/cmd_ide.c	reading Image Header from IDE device OK
2378  -49	common/cmd_ide.c	Image header has bad magic number
2379   49	common/cmd_ide.c	Image header has correct magic number
2380  -50	common/cmd_ide.c	Image header has bad	 checksum
2381   50	common/cmd_ide.c	Image header has correct checksum
2382  -51	common/cmd_ide.c	Error reading Image from IDE device
2383   51	common/cmd_ide.c	reading Image from IDE device OK
2384   52	common/cmd_nand.c	before loading a Image from a NAND device
2385  -53	common/cmd_nand.c	Bad usage of "nand" command
2386   53	common/cmd_nand.c	correct usage of "nand" command
2387  -54	common/cmd_nand.c	No boot device
2388   54	common/cmd_nand.c	boot device found
2389  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2390   55	common/cmd_nand.c	correct chip ID found, device available
2391  -56	common/cmd_nand.c	Error reading Image Header on boot device
2392   56	common/cmd_nand.c	reading Image Header from NAND device OK
2393  -57	common/cmd_nand.c	Image header has bad magic number
2394   57	common/cmd_nand.c	Image header has correct magic number
2395  -58	common/cmd_nand.c	Error reading Image from NAND device
2396   58	common/cmd_nand.c	reading Image from NAND device OK
2397
2398  -60	common/env_common.c	Environment has a bad CRC, using default
2399
2400   64	net/eth.c		starting with Ethernet configuration.
2401  -64	net/eth.c		no Ethernet found.
2402   65	net/eth.c		Ethernet found.
2403
2404  -80	common/cmd_net.c	usage wrong
2405   80	common/cmd_net.c	before calling net_loop()
2406  -81	common/cmd_net.c	some error in net_loop() occurred
2407   81	common/cmd_net.c	net_loop() back without error
2408  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2409   82	common/cmd_net.c	trying automatic boot
2410   83	common/cmd_net.c	running "source" command
2411  -83	common/cmd_net.c	some error in automatic boot or "source" command
2412   84	common/cmd_net.c	end without errors
2413
2414FIT uImage format:
2415
2416  Arg	Where			When
2417  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2418 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2419  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2420 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2421  102	common/cmd_bootm.c	Kernel unit name specified
2422 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2423  103	common/cmd_bootm.c	Found configuration node
2424  104	common/cmd_bootm.c	Got kernel subimage node offset
2425 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2426  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2427 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2428  106	common/cmd_bootm.c	Architecture check OK
2429 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2430  107	common/cmd_bootm.c	Kernel subimage type OK
2431 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2432  108	common/cmd_bootm.c	Got kernel subimage data/size
2433 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2434 -109	common/cmd_bootm.c	Can't get kernel subimage type
2435 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2436 -111	common/cmd_bootm.c	Can't get kernel subimage os
2437 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2438 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2439
2440  120	common/image.c		Start initial ramdisk verification
2441 -120	common/image.c		Ramdisk FIT image has incorrect format
2442  121	common/image.c		Ramdisk FIT image has correct format
2443  122	common/image.c		No ramdisk subimage unit name, using configuration
2444 -122	common/image.c		Can't get configuration for ramdisk subimage
2445  123	common/image.c		Ramdisk unit name specified
2446 -124	common/image.c		Can't get ramdisk subimage node offset
2447  125	common/image.c		Got ramdisk subimage node offset
2448 -125	common/image.c		Ramdisk subimage hash verification failed
2449  126	common/image.c		Ramdisk subimage hash verification OK
2450 -126	common/image.c		Ramdisk subimage for unsupported architecture
2451  127	common/image.c		Architecture check OK
2452 -127	common/image.c		Can't get ramdisk subimage data/size
2453  128	common/image.c		Got ramdisk subimage data/size
2454  129	common/image.c		Can't get ramdisk load address
2455 -129	common/image.c		Got ramdisk load address
2456
2457 -130	common/cmd_doc.c	Incorrect FIT image format
2458  131	common/cmd_doc.c	FIT image format OK
2459
2460 -140	common/cmd_ide.c	Incorrect FIT image format
2461  141	common/cmd_ide.c	FIT image format OK
2462
2463 -150	common/cmd_nand.c	Incorrect FIT image format
2464  151	common/cmd_nand.c	FIT image format OK
2465
2466- legacy image format:
2467		CONFIG_IMAGE_FORMAT_LEGACY
2468		enables the legacy image format support in U-Boot.
2469
2470		Default:
2471		enabled if CONFIG_FIT_SIGNATURE is not defined.
2472
2473		CONFIG_DISABLE_IMAGE_LEGACY
2474		disable the legacy image format
2475
2476		This define is introduced, as the legacy image format is
2477		enabled per default for backward compatibility.
2478
2479- Standalone program support:
2480		CONFIG_STANDALONE_LOAD_ADDR
2481
2482		This option defines a board specific value for the
2483		address where standalone program gets loaded, thus
2484		overwriting the architecture dependent default
2485		settings.
2486
2487- Frame Buffer Address:
2488		CONFIG_FB_ADDR
2489
2490		Define CONFIG_FB_ADDR if you want to use specific
2491		address for frame buffer.  This is typically the case
2492		when using a graphics controller has separate video
2493		memory.  U-Boot will then place the frame buffer at
2494		the given address instead of dynamically reserving it
2495		in system RAM by calling lcd_setmem(), which grabs
2496		the memory for the frame buffer depending on the
2497		configured panel size.
2498
2499		Please see board_init_f function.
2500
2501- Automatic software updates via TFTP server
2502		CONFIG_UPDATE_TFTP
2503		CONFIG_UPDATE_TFTP_CNT_MAX
2504		CONFIG_UPDATE_TFTP_MSEC_MAX
2505
2506		These options enable and control the auto-update feature;
2507		for a more detailed description refer to doc/README.update.
2508
2509- MTD Support (mtdparts command, UBI support)
2510		CONFIG_MTD_DEVICE
2511
2512		Adds the MTD device infrastructure from the Linux kernel.
2513		Needed for mtdparts command support.
2514
2515		CONFIG_MTD_PARTITIONS
2516
2517		Adds the MTD partitioning infrastructure from the Linux
2518		kernel. Needed for UBI support.
2519
2520- UBI support
2521		CONFIG_UBI_SILENCE_MSG
2522
2523		Make the verbose messages from UBI stop printing.  This leaves
2524		warnings and errors enabled.
2525
2526
2527		CONFIG_MTD_UBI_WL_THRESHOLD
2528		This parameter defines the maximum difference between the highest
2529		erase counter value and the lowest erase counter value of eraseblocks
2530		of UBI devices. When this threshold is exceeded, UBI starts performing
2531		wear leveling by means of moving data from eraseblock with low erase
2532		counter to eraseblocks with high erase counter.
2533
2534		The default value should be OK for SLC NAND flashes, NOR flashes and
2535		other flashes which have eraseblock life-cycle 100000 or more.
2536		However, in case of MLC NAND flashes which typically have eraseblock
2537		life-cycle less than 10000, the threshold should be lessened (e.g.,
2538		to 128 or 256, although it does not have to be power of 2).
2539
2540		default: 4096
2541
2542		CONFIG_MTD_UBI_BEB_LIMIT
2543		This option specifies the maximum bad physical eraseblocks UBI
2544		expects on the MTD device (per 1024 eraseblocks). If the
2545		underlying flash does not admit of bad eraseblocks (e.g. NOR
2546		flash), this value is ignored.
2547
2548		NAND datasheets often specify the minimum and maximum NVM
2549		(Number of Valid Blocks) for the flashes' endurance lifetime.
2550		The maximum expected bad eraseblocks per 1024 eraseblocks
2551		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2552		which gives 20 for most NANDs (MaxNVB is basically the total
2553		count of eraseblocks on the chip).
2554
2555		To put it differently, if this value is 20, UBI will try to
2556		reserve about 1.9% of physical eraseblocks for bad blocks
2557		handling. And that will be 1.9% of eraseblocks on the entire
2558		NAND chip, not just the MTD partition UBI attaches. This means
2559		that if you have, say, a NAND flash chip admits maximum 40 bad
2560		eraseblocks, and it is split on two MTD partitions of the same
2561		size, UBI will reserve 40 eraseblocks when attaching a
2562		partition.
2563
2564		default: 20
2565
2566		CONFIG_MTD_UBI_FASTMAP
2567		Fastmap is a mechanism which allows attaching an UBI device
2568		in nearly constant time. Instead of scanning the whole MTD device it
2569		only has to locate a checkpoint (called fastmap) on the device.
2570		The on-flash fastmap contains all information needed to attach
2571		the device. Using fastmap makes only sense on large devices where
2572		attaching by scanning takes long. UBI will not automatically install
2573		a fastmap on old images, but you can set the UBI parameter
2574		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2575		that fastmap-enabled images are still usable with UBI implementations
2576		without	fastmap support. On typical flash devices the whole fastmap
2577		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2578
2579		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2580		Set this parameter to enable fastmap automatically on images
2581		without a fastmap.
2582		default: 0
2583
2584		CONFIG_MTD_UBI_FM_DEBUG
2585		Enable UBI fastmap debug
2586		default: 0
2587
2588- UBIFS support
2589		CONFIG_UBIFS_SILENCE_MSG
2590
2591		Make the verbose messages from UBIFS stop printing.  This leaves
2592		warnings and errors enabled.
2593
2594- SPL framework
2595		CONFIG_SPL
2596		Enable building of SPL globally.
2597
2598		CONFIG_SPL_LDSCRIPT
2599		LDSCRIPT for linking the SPL binary.
2600
2601		CONFIG_SPL_MAX_FOOTPRINT
2602		Maximum size in memory allocated to the SPL, BSS included.
2603		When defined, the linker checks that the actual memory
2604		used by SPL from _start to __bss_end does not exceed it.
2605		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2606		must not be both defined at the same time.
2607
2608		CONFIG_SPL_MAX_SIZE
2609		Maximum size of the SPL image (text, data, rodata, and
2610		linker lists sections), BSS excluded.
2611		When defined, the linker checks that the actual size does
2612		not exceed it.
2613
2614		CONFIG_SPL_TEXT_BASE
2615		TEXT_BASE for linking the SPL binary.
2616
2617		CONFIG_SPL_RELOC_TEXT_BASE
2618		Address to relocate to.  If unspecified, this is equal to
2619		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2620
2621		CONFIG_SPL_BSS_START_ADDR
2622		Link address for the BSS within the SPL binary.
2623
2624		CONFIG_SPL_BSS_MAX_SIZE
2625		Maximum size in memory allocated to the SPL BSS.
2626		When defined, the linker checks that the actual memory used
2627		by SPL from __bss_start to __bss_end does not exceed it.
2628		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2629		must not be both defined at the same time.
2630
2631		CONFIG_SPL_STACK
2632		Adress of the start of the stack SPL will use
2633
2634		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2635		When defined, SPL will panic() if the image it has
2636		loaded does not have a signature.
2637		Defining this is useful when code which loads images
2638		in SPL cannot guarantee that absolutely all read errors
2639		will be caught.
2640		An example is the LPC32XX MLC NAND driver, which will
2641		consider that a completely unreadable NAND block is bad,
2642		and thus should be skipped silently.
2643
2644		CONFIG_SPL_RELOC_STACK
2645		Adress of the start of the stack SPL will use after
2646		relocation.  If unspecified, this is equal to
2647		CONFIG_SPL_STACK.
2648
2649		CONFIG_SYS_SPL_MALLOC_START
2650		Starting address of the malloc pool used in SPL.
2651		When this option is set the full malloc is used in SPL and
2652		it is set up by spl_init() and before that, the simple malloc()
2653		can be used if CONFIG_SYS_MALLOC_F is defined.
2654
2655		CONFIG_SYS_SPL_MALLOC_SIZE
2656		The size of the malloc pool used in SPL.
2657
2658		CONFIG_SPL_OS_BOOT
2659		Enable booting directly to an OS from SPL.
2660		See also: doc/README.falcon
2661
2662		CONFIG_SPL_DISPLAY_PRINT
2663		For ARM, enable an optional function to print more information
2664		about the running system.
2665
2666		CONFIG_SPL_INIT_MINIMAL
2667		Arch init code should be built for a very small image
2668
2669		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2670		Partition on the MMC to load U-Boot from when the MMC is being
2671		used in raw mode
2672
2673		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2674		Sector to load kernel uImage from when MMC is being
2675		used in raw mode (for Falcon mode)
2676
2677		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2678		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2679		Sector and number of sectors to load kernel argument
2680		parameters from when MMC is being used in raw mode
2681		(for falcon mode)
2682
2683		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2684		Partition on the MMC to load U-Boot from when the MMC is being
2685		used in fs mode
2686
2687		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2688		Filename to read to load U-Boot when reading from filesystem
2689
2690		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2691		Filename to read to load kernel uImage when reading
2692		from filesystem (for Falcon mode)
2693
2694		CONFIG_SPL_FS_LOAD_ARGS_NAME
2695		Filename to read to load kernel argument parameters
2696		when reading from filesystem (for Falcon mode)
2697
2698		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2699		Set this for NAND SPL on PPC mpc83xx targets, so that
2700		start.S waits for the rest of the SPL to load before
2701		continuing (the hardware starts execution after just
2702		loading the first page rather than the full 4K).
2703
2704		CONFIG_SPL_SKIP_RELOCATE
2705		Avoid SPL relocation
2706
2707		CONFIG_SPL_NAND_BASE
2708		Include nand_base.c in the SPL.  Requires
2709		CONFIG_SPL_NAND_DRIVERS.
2710
2711		CONFIG_SPL_NAND_DRIVERS
2712		SPL uses normal NAND drivers, not minimal drivers.
2713
2714		CONFIG_SPL_NAND_ECC
2715		Include standard software ECC in the SPL
2716
2717		CONFIG_SPL_NAND_SIMPLE
2718		Support for NAND boot using simple NAND drivers that
2719		expose the cmd_ctrl() interface.
2720
2721		CONFIG_SPL_UBI
2722		Support for a lightweight UBI (fastmap) scanner and
2723		loader
2724
2725		CONFIG_SPL_NAND_RAW_ONLY
2726		Support to boot only raw u-boot.bin images. Use this only
2727		if you need to save space.
2728
2729		CONFIG_SPL_COMMON_INIT_DDR
2730		Set for common ddr init with serial presence detect in
2731		SPL binary.
2732
2733		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2734		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2735		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2736		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2737		CONFIG_SYS_NAND_ECCBYTES
2738		Defines the size and behavior of the NAND that SPL uses
2739		to read U-Boot
2740
2741		CONFIG_SPL_NAND_BOOT
2742		Add support NAND boot
2743
2744		CONFIG_SYS_NAND_U_BOOT_OFFS
2745		Location in NAND to read U-Boot from
2746
2747		CONFIG_SYS_NAND_U_BOOT_DST
2748		Location in memory to load U-Boot to
2749
2750		CONFIG_SYS_NAND_U_BOOT_SIZE
2751		Size of image to load
2752
2753		CONFIG_SYS_NAND_U_BOOT_START
2754		Entry point in loaded image to jump to
2755
2756		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2757		Define this if you need to first read the OOB and then the
2758		data. This is used, for example, on davinci platforms.
2759
2760		CONFIG_SPL_RAM_DEVICE
2761		Support for running image already present in ram, in SPL binary
2762
2763		CONFIG_SPL_PAD_TO
2764		Image offset to which the SPL should be padded before appending
2765		the SPL payload. By default, this is defined as
2766		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2767		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2768		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2769
2770		CONFIG_SPL_TARGET
2771		Final target image containing SPL and payload.  Some SPLs
2772		use an arch-specific makefile fragment instead, for
2773		example if more than one image needs to be produced.
2774
2775		CONFIG_FIT_SPL_PRINT
2776		Printing information about a FIT image adds quite a bit of
2777		code to SPL. So this is normally disabled in SPL. Use this
2778		option to re-enable it. This will affect the output of the
2779		bootm command when booting a FIT image.
2780
2781- TPL framework
2782		CONFIG_TPL
2783		Enable building of TPL globally.
2784
2785		CONFIG_TPL_PAD_TO
2786		Image offset to which the TPL should be padded before appending
2787		the TPL payload. By default, this is defined as
2788		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2789		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2790		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2791
2792- Interrupt support (PPC):
2793
2794		There are common interrupt_init() and timer_interrupt()
2795		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2796		for CPU specific initialization. interrupt_init_cpu()
2797		should set decrementer_count to appropriate value. If
2798		CPU resets decrementer automatically after interrupt
2799		(ppc4xx) it should set decrementer_count to zero.
2800		timer_interrupt() calls timer_interrupt_cpu() for CPU
2801		specific handling. If board has watchdog / status_led
2802		/ other_activity_monitor it works automatically from
2803		general timer_interrupt().
2804
2805
2806Board initialization settings:
2807------------------------------
2808
2809During Initialization u-boot calls a number of board specific functions
2810to allow the preparation of board specific prerequisites, e.g. pin setup
2811before drivers are initialized. To enable these callbacks the
2812following configuration macros have to be defined. Currently this is
2813architecture specific, so please check arch/your_architecture/lib/board.c
2814typically in board_init_f() and board_init_r().
2815
2816- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2817- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2818- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2819- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2820
2821Configuration Settings:
2822-----------------------
2823
2824- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2825		Optionally it can be defined to support 64-bit memory commands.
2826
2827- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2828		undefine this when you're short of memory.
2829
2830- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2831		width of the commands listed in the 'help' command output.
2832
2833- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2834		prompt for user input.
2835
2836- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2837
2838- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2839
2840- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2841
2842- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2843		the application (usually a Linux kernel) when it is
2844		booted
2845
2846- CONFIG_SYS_BAUDRATE_TABLE:
2847		List of legal baudrate settings for this board.
2848
2849- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2850		Begin and End addresses of the area used by the
2851		simple memory test.
2852
2853- CONFIG_SYS_ALT_MEMTEST:
2854		Enable an alternate, more extensive memory test.
2855
2856- CONFIG_SYS_MEMTEST_SCRATCH:
2857		Scratch address used by the alternate memory test
2858		You only need to set this if address zero isn't writeable
2859
2860- CONFIG_SYS_MEM_RESERVE_SECURE
2861		Only implemented for ARMv8 for now.
2862		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2863		is substracted from total RAM and won't be reported to OS.
2864		This memory can be used as secure memory. A variable
2865		gd->arch.secure_ram is used to track the location. In systems
2866		the RAM base is not zero, or RAM is divided into banks,
2867		this variable needs to be recalcuated to get the address.
2868
2869- CONFIG_SYS_MEM_TOP_HIDE:
2870		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2871		this specified memory area will get subtracted from the top
2872		(end) of RAM and won't get "touched" at all by U-Boot. By
2873		fixing up gd->ram_size the Linux kernel should gets passed
2874		the now "corrected" memory size and won't touch it either.
2875		This should work for arch/ppc and arch/powerpc. Only Linux
2876		board ports in arch/powerpc with bootwrapper support that
2877		recalculate the memory size from the SDRAM controller setup
2878		will have to get fixed in Linux additionally.
2879
2880		This option can be used as a workaround for the 440EPx/GRx
2881		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2882		be touched.
2883
2884		WARNING: Please make sure that this value is a multiple of
2885		the Linux page size (normally 4k). If this is not the case,
2886		then the end address of the Linux memory will be located at a
2887		non page size aligned address and this could cause major
2888		problems.
2889
2890- CONFIG_SYS_LOADS_BAUD_CHANGE:
2891		Enable temporary baudrate change while serial download
2892
2893- CONFIG_SYS_SDRAM_BASE:
2894		Physical start address of SDRAM. _Must_ be 0 here.
2895
2896- CONFIG_SYS_FLASH_BASE:
2897		Physical start address of Flash memory.
2898
2899- CONFIG_SYS_MONITOR_BASE:
2900		Physical start address of boot monitor code (set by
2901		make config files to be same as the text base address
2902		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2903		CONFIG_SYS_FLASH_BASE when booting from flash.
2904
2905- CONFIG_SYS_MONITOR_LEN:
2906		Size of memory reserved for monitor code, used to
2907		determine _at_compile_time_ (!) if the environment is
2908		embedded within the U-Boot image, or in a separate
2909		flash sector.
2910
2911- CONFIG_SYS_MALLOC_LEN:
2912		Size of DRAM reserved for malloc() use.
2913
2914- CONFIG_SYS_MALLOC_F_LEN
2915		Size of the malloc() pool for use before relocation. If
2916		this is defined, then a very simple malloc() implementation
2917		will become available before relocation. The address is just
2918		below the global data, and the stack is moved down to make
2919		space.
2920
2921		This feature allocates regions with increasing addresses
2922		within the region. calloc() is supported, but realloc()
2923		is not available. free() is supported but does nothing.
2924		The memory will be freed (or in fact just forgotten) when
2925		U-Boot relocates itself.
2926
2927- CONFIG_SYS_MALLOC_SIMPLE
2928		Provides a simple and small malloc() and calloc() for those
2929		boards which do not use the full malloc in SPL (which is
2930		enabled with CONFIG_SYS_SPL_MALLOC_START).
2931
2932- CONFIG_SYS_NONCACHED_MEMORY:
2933		Size of non-cached memory area. This area of memory will be
2934		typically located right below the malloc() area and mapped
2935		uncached in the MMU. This is useful for drivers that would
2936		otherwise require a lot of explicit cache maintenance. For
2937		some drivers it's also impossible to properly maintain the
2938		cache. For example if the regions that need to be flushed
2939		are not a multiple of the cache-line size, *and* padding
2940		cannot be allocated between the regions to align them (i.e.
2941		if the HW requires a contiguous array of regions, and the
2942		size of each region is not cache-aligned), then a flush of
2943		one region may result in overwriting data that hardware has
2944		written to another region in the same cache-line. This can
2945		happen for example in network drivers where descriptors for
2946		buffers are typically smaller than the CPU cache-line (e.g.
2947		16 bytes vs. 32 or 64 bytes).
2948
2949		Non-cached memory is only supported on 32-bit ARM at present.
2950
2951- CONFIG_SYS_BOOTM_LEN:
2952		Normally compressed uImages are limited to an
2953		uncompressed size of 8 MBytes. If this is not enough,
2954		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2955		to adjust this setting to your needs.
2956
2957- CONFIG_SYS_BOOTMAPSZ:
2958		Maximum size of memory mapped by the startup code of
2959		the Linux kernel; all data that must be processed by
2960		the Linux kernel (bd_info, boot arguments, FDT blob if
2961		used) must be put below this limit, unless "bootm_low"
2962		environment variable is defined and non-zero. In such case
2963		all data for the Linux kernel must be between "bootm_low"
2964		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2965		variable "bootm_mapsize" will override the value of
2966		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2967		then the value in "bootm_size" will be used instead.
2968
2969- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2970		Enable initrd_high functionality.  If defined then the
2971		initrd_high feature is enabled and the bootm ramdisk subcommand
2972		is enabled.
2973
2974- CONFIG_SYS_BOOT_GET_CMDLINE:
2975		Enables allocating and saving kernel cmdline in space between
2976		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2977
2978- CONFIG_SYS_BOOT_GET_KBD:
2979		Enables allocating and saving a kernel copy of the bd_info in
2980		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2981
2982- CONFIG_SYS_MAX_FLASH_BANKS:
2983		Max number of Flash memory banks
2984
2985- CONFIG_SYS_MAX_FLASH_SECT:
2986		Max number of sectors on a Flash chip
2987
2988- CONFIG_SYS_FLASH_ERASE_TOUT:
2989		Timeout for Flash erase operations (in ms)
2990
2991- CONFIG_SYS_FLASH_WRITE_TOUT:
2992		Timeout for Flash write operations (in ms)
2993
2994- CONFIG_SYS_FLASH_LOCK_TOUT
2995		Timeout for Flash set sector lock bit operation (in ms)
2996
2997- CONFIG_SYS_FLASH_UNLOCK_TOUT
2998		Timeout for Flash clear lock bits operation (in ms)
2999
3000- CONFIG_SYS_FLASH_PROTECTION
3001		If defined, hardware flash sectors protection is used
3002		instead of U-Boot software protection.
3003
3004- CONFIG_SYS_DIRECT_FLASH_TFTP:
3005
3006		Enable TFTP transfers directly to flash memory;
3007		without this option such a download has to be
3008		performed in two steps: (1) download to RAM, and (2)
3009		copy from RAM to flash.
3010
3011		The two-step approach is usually more reliable, since
3012		you can check if the download worked before you erase
3013		the flash, but in some situations (when system RAM is
3014		too limited to allow for a temporary copy of the
3015		downloaded image) this option may be very useful.
3016
3017- CONFIG_SYS_FLASH_CFI:
3018		Define if the flash driver uses extra elements in the
3019		common flash structure for storing flash geometry.
3020
3021- CONFIG_FLASH_CFI_DRIVER
3022		This option also enables the building of the cfi_flash driver
3023		in the drivers directory
3024
3025- CONFIG_FLASH_CFI_MTD
3026		This option enables the building of the cfi_mtd driver
3027		in the drivers directory. The driver exports CFI flash
3028		to the MTD layer.
3029
3030- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3031		Use buffered writes to flash.
3032
3033- CONFIG_FLASH_SPANSION_S29WS_N
3034		s29ws-n MirrorBit flash has non-standard addresses for buffered
3035		write commands.
3036
3037- CONFIG_SYS_FLASH_QUIET_TEST
3038		If this option is defined, the common CFI flash doesn't
3039		print it's warning upon not recognized FLASH banks. This
3040		is useful, if some of the configured banks are only
3041		optionally available.
3042
3043- CONFIG_FLASH_SHOW_PROGRESS
3044		If defined (must be an integer), print out countdown
3045		digits and dots.  Recommended value: 45 (9..1) for 80
3046		column displays, 15 (3..1) for 40 column displays.
3047
3048- CONFIG_FLASH_VERIFY
3049		If defined, the content of the flash (destination) is compared
3050		against the source after the write operation. An error message
3051		will be printed when the contents are not identical.
3052		Please note that this option is useless in nearly all cases,
3053		since such flash programming errors usually are detected earlier
3054		while unprotecting/erasing/programming. Please only enable
3055		this option if you really know what you are doing.
3056
3057- CONFIG_SYS_RX_ETH_BUFFER:
3058		Defines the number of Ethernet receive buffers. On some
3059		Ethernet controllers it is recommended to set this value
3060		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3061		buffers can be full shortly after enabling the interface
3062		on high Ethernet traffic.
3063		Defaults to 4 if not defined.
3064
3065- CONFIG_ENV_MAX_ENTRIES
3066
3067	Maximum number of entries in the hash table that is used
3068	internally to store the environment settings. The default
3069	setting is supposed to be generous and should work in most
3070	cases. This setting can be used to tune behaviour; see
3071	lib/hashtable.c for details.
3072
3073- CONFIG_ENV_FLAGS_LIST_DEFAULT
3074- CONFIG_ENV_FLAGS_LIST_STATIC
3075	Enable validation of the values given to environment variables when
3076	calling env set.  Variables can be restricted to only decimal,
3077	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3078	the variables can also be restricted to IP address or MAC address.
3079
3080	The format of the list is:
3081		type_attribute = [s|d|x|b|i|m]
3082		access_attribute = [a|r|o|c]
3083		attributes = type_attribute[access_attribute]
3084		entry = variable_name[:attributes]
3085		list = entry[,list]
3086
3087	The type attributes are:
3088		s - String (default)
3089		d - Decimal
3090		x - Hexadecimal
3091		b - Boolean ([1yYtT|0nNfF])
3092		i - IP address
3093		m - MAC address
3094
3095	The access attributes are:
3096		a - Any (default)
3097		r - Read-only
3098		o - Write-once
3099		c - Change-default
3100
3101	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3102		Define this to a list (string) to define the ".flags"
3103		environment variable in the default or embedded environment.
3104
3105	- CONFIG_ENV_FLAGS_LIST_STATIC
3106		Define this to a list (string) to define validation that
3107		should be done if an entry is not found in the ".flags"
3108		environment variable.  To override a setting in the static
3109		list, simply add an entry for the same variable name to the
3110		".flags" variable.
3111
3112	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3113	regular expression. This allows multiple variables to define the same
3114	flags without explicitly listing them for each variable.
3115
3116- CONFIG_ENV_ACCESS_IGNORE_FORCE
3117	If defined, don't allow the -f switch to env set override variable
3118	access flags.
3119
3120- CONFIG_USE_STDINT
3121	If stdint.h is available with your toolchain you can define this
3122	option to enable it. You can provide option 'USE_STDINT=1' when
3123	building U-Boot to enable this.
3124
3125The following definitions that deal with the placement and management
3126of environment data (variable area); in general, we support the
3127following configurations:
3128
3129- CONFIG_BUILD_ENVCRC:
3130
3131	Builds up envcrc with the target environment so that external utils
3132	may easily extract it and embed it in final U-Boot images.
3133
3134BE CAREFUL! The first access to the environment happens quite early
3135in U-Boot initialization (when we try to get the setting of for the
3136console baudrate). You *MUST* have mapped your NVRAM area then, or
3137U-Boot will hang.
3138
3139Please note that even with NVRAM we still use a copy of the
3140environment in RAM: we could work on NVRAM directly, but we want to
3141keep settings there always unmodified except somebody uses "saveenv"
3142to save the current settings.
3143
3144BE CAREFUL! For some special cases, the local device can not use
3145"saveenv" command. For example, the local device will get the
3146environment stored in a remote NOR flash by SRIO or PCIE link,
3147but it can not erase, write this NOR flash by SRIO or PCIE interface.
3148
3149- CONFIG_NAND_ENV_DST
3150
3151	Defines address in RAM to which the nand_spl code should copy the
3152	environment. If redundant environment is used, it will be copied to
3153	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3154
3155Please note that the environment is read-only until the monitor
3156has been relocated to RAM and a RAM copy of the environment has been
3157created; also, when using EEPROM you will have to use env_get_f()
3158until then to read environment variables.
3159
3160The environment is protected by a CRC32 checksum. Before the monitor
3161is relocated into RAM, as a result of a bad CRC you will be working
3162with the compiled-in default environment - *silently*!!! [This is
3163necessary, because the first environment variable we need is the
3164"baudrate" setting for the console - if we have a bad CRC, we don't
3165have any device yet where we could complain.]
3166
3167Note: once the monitor has been relocated, then it will complain if
3168the default environment is used; a new CRC is computed as soon as you
3169use the "saveenv" command to store a valid environment.
3170
3171- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3172		Echo the inverted Ethernet link state to the fault LED.
3173
3174		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3175		      also needs to be defined.
3176
3177- CONFIG_SYS_FAULT_MII_ADDR:
3178		MII address of the PHY to check for the Ethernet link state.
3179
3180- CONFIG_NS16550_MIN_FUNCTIONS:
3181		Define this if you desire to only have use of the NS16550_init
3182		and NS16550_putc functions for the serial driver located at
3183		drivers/serial/ns16550.c.  This option is useful for saving
3184		space for already greatly restricted images, including but not
3185		limited to NAND_SPL configurations.
3186
3187- CONFIG_DISPLAY_BOARDINFO
3188		Display information about the board that U-Boot is running on
3189		when U-Boot starts up. The board function checkboard() is called
3190		to do this.
3191
3192- CONFIG_DISPLAY_BOARDINFO_LATE
3193		Similar to the previous option, but display this information
3194		later, once stdio is running and output goes to the LCD, if
3195		present.
3196
3197- CONFIG_BOARD_SIZE_LIMIT:
3198		Maximum size of the U-Boot image. When defined, the
3199		build system checks that the actual size does not
3200		exceed it.
3201
3202Low Level (hardware related) configuration options:
3203---------------------------------------------------
3204
3205- CONFIG_SYS_CACHELINE_SIZE:
3206		Cache Line Size of the CPU.
3207
3208- CONFIG_SYS_CCSRBAR_DEFAULT:
3209		Default (power-on reset) physical address of CCSR on Freescale
3210		PowerPC SOCs.
3211
3212- CONFIG_SYS_CCSRBAR:
3213		Virtual address of CCSR.  On a 32-bit build, this is typically
3214		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3215
3216- CONFIG_SYS_CCSRBAR_PHYS:
3217		Physical address of CCSR.  CCSR can be relocated to a new
3218		physical address, if desired.  In this case, this macro should
3219		be set to that address.	 Otherwise, it should be set to the
3220		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3221		is typically relocated on 36-bit builds.  It is recommended
3222		that this macro be defined via the _HIGH and _LOW macros:
3223
3224		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3225			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3226
3227- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3228		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3229		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3230		used in assembly code, so it must not contain typecasts or
3231		integer size suffixes (e.g. "ULL").
3232
3233- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3234		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3235		used in assembly code, so it must not contain typecasts or
3236		integer size suffixes (e.g. "ULL").
3237
3238- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3239		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3240		forced to a value that ensures that CCSR is not relocated.
3241
3242- Floppy Disk Support:
3243		CONFIG_SYS_FDC_DRIVE_NUMBER
3244
3245		the default drive number (default value 0)
3246
3247		CONFIG_SYS_ISA_IO_STRIDE
3248
3249		defines the spacing between FDC chipset registers
3250		(default value 1)
3251
3252		CONFIG_SYS_ISA_IO_OFFSET
3253
3254		defines the offset of register from address. It
3255		depends on which part of the data bus is connected to
3256		the FDC chipset. (default value 0)
3257
3258		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3259		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3260		default value.
3261
3262		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3263		fdc_hw_init() is called at the beginning of the FDC
3264		setup. fdc_hw_init() must be provided by the board
3265		source code. It is used to make hardware-dependent
3266		initializations.
3267
3268- CONFIG_IDE_AHB:
3269		Most IDE controllers were designed to be connected with PCI
3270		interface. Only few of them were designed for AHB interface.
3271		When software is doing ATA command and data transfer to
3272		IDE devices through IDE-AHB controller, some additional
3273		registers accessing to these kind of IDE-AHB controller
3274		is required.
3275
3276- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3277		DO NOT CHANGE unless you know exactly what you're
3278		doing! (11-4) [MPC8xx systems only]
3279
3280- CONFIG_SYS_INIT_RAM_ADDR:
3281
3282		Start address of memory area that can be used for
3283		initial data and stack; please note that this must be
3284		writable memory that is working WITHOUT special
3285		initialization, i. e. you CANNOT use normal RAM which
3286		will become available only after programming the
3287		memory controller and running certain initialization
3288		sequences.
3289
3290		U-Boot uses the following memory types:
3291		- MPC8xx: IMMR (internal memory of the CPU)
3292
3293- CONFIG_SYS_GBL_DATA_OFFSET:
3294
3295		Offset of the initial data structure in the memory
3296		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3297		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3298		data is located at the end of the available space
3299		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3300		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3301		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3302		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3303
3304	Note:
3305		On the MPC824X (or other systems that use the data
3306		cache for initial memory) the address chosen for
3307		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3308		point to an otherwise UNUSED address space between
3309		the top of RAM and the start of the PCI space.
3310
3311- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3312
3313- CONFIG_SYS_OR_TIMING_SDRAM:
3314		SDRAM timing
3315
3316- CONFIG_SYS_MAMR_PTA:
3317		periodic timer for refresh
3318
3319- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3320  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3321  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3322  CONFIG_SYS_BR1_PRELIM:
3323		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3324
3325- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3326  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3327  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3328		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3329
3330- CONFIG_PCI_ENUM_ONLY
3331		Only scan through and get the devices on the buses.
3332		Don't do any setup work, presumably because someone or
3333		something has already done it, and we don't need to do it
3334		a second time.	Useful for platforms that are pre-booted
3335		by coreboot or similar.
3336
3337- CONFIG_PCI_INDIRECT_BRIDGE:
3338		Enable support for indirect PCI bridges.
3339
3340- CONFIG_SYS_SRIO:
3341		Chip has SRIO or not
3342
3343- CONFIG_SRIO1:
3344		Board has SRIO 1 port available
3345
3346- CONFIG_SRIO2:
3347		Board has SRIO 2 port available
3348
3349- CONFIG_SRIO_PCIE_BOOT_MASTER
3350		Board can support master function for Boot from SRIO and PCIE
3351
3352- CONFIG_SYS_SRIOn_MEM_VIRT:
3353		Virtual Address of SRIO port 'n' memory region
3354
3355- CONFIG_SYS_SRIOn_MEM_PHYS:
3356		Physical Address of SRIO port 'n' memory region
3357
3358- CONFIG_SYS_SRIOn_MEM_SIZE:
3359		Size of SRIO port 'n' memory region
3360
3361- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3362		Defined to tell the NAND controller that the NAND chip is using
3363		a 16 bit bus.
3364		Not all NAND drivers use this symbol.
3365		Example of drivers that use it:
3366		- drivers/mtd/nand/ndfc.c
3367		- drivers/mtd/nand/mxc_nand.c
3368
3369- CONFIG_SYS_NDFC_EBC0_CFG
3370		Sets the EBC0_CFG register for the NDFC. If not defined
3371		a default value will be used.
3372
3373- CONFIG_SPD_EEPROM
3374		Get DDR timing information from an I2C EEPROM. Common
3375		with pluggable memory modules such as SODIMMs
3376
3377  SPD_EEPROM_ADDRESS
3378		I2C address of the SPD EEPROM
3379
3380- CONFIG_SYS_SPD_BUS_NUM
3381		If SPD EEPROM is on an I2C bus other than the first
3382		one, specify here. Note that the value must resolve
3383		to something your driver can deal with.
3384
3385- CONFIG_SYS_DDR_RAW_TIMING
3386		Get DDR timing information from other than SPD. Common with
3387		soldered DDR chips onboard without SPD. DDR raw timing
3388		parameters are extracted from datasheet and hard-coded into
3389		header files or board specific files.
3390
3391- CONFIG_FSL_DDR_INTERACTIVE
3392		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3393
3394- CONFIG_FSL_DDR_SYNC_REFRESH
3395		Enable sync of refresh for multiple controllers.
3396
3397- CONFIG_FSL_DDR_BIST
3398		Enable built-in memory test for Freescale DDR controllers.
3399
3400- CONFIG_SYS_83XX_DDR_USES_CS0
3401		Only for 83xx systems. If specified, then DDR should
3402		be configured using CS0 and CS1 instead of CS2 and CS3.
3403
3404- CONFIG_RMII
3405		Enable RMII mode for all FECs.
3406		Note that this is a global option, we can't
3407		have one FEC in standard MII mode and another in RMII mode.
3408
3409- CONFIG_CRC32_VERIFY
3410		Add a verify option to the crc32 command.
3411		The syntax is:
3412
3413		=> crc32 -v <address> <count> <crc32>
3414
3415		Where address/count indicate a memory area
3416		and crc32 is the correct crc32 which the
3417		area should have.
3418
3419- CONFIG_LOOPW
3420		Add the "loopw" memory command. This only takes effect if
3421		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3422
3423- CONFIG_MX_CYCLIC
3424		Add the "mdc" and "mwc" memory commands. These are cyclic
3425		"md/mw" commands.
3426		Examples:
3427
3428		=> mdc.b 10 4 500
3429		This command will print 4 bytes (10,11,12,13) each 500 ms.
3430
3431		=> mwc.l 100 12345678 10
3432		This command will write 12345678 to address 100 all 10 ms.
3433
3434		This only takes effect if the memory commands are activated
3435		globally (CONFIG_CMD_MEMORY).
3436
3437- CONFIG_SKIP_LOWLEVEL_INIT
3438		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3439		low level initializations (like setting up the memory
3440		controller) are omitted and/or U-Boot does not
3441		relocate itself into RAM.
3442
3443		Normally this variable MUST NOT be defined. The only
3444		exception is when U-Boot is loaded (to RAM) by some
3445		other boot loader or by a debugger which performs
3446		these initializations itself.
3447
3448- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3449		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3450		to be skipped. The normal CP15 init (such as enabling the
3451		instruction cache) is still performed.
3452
3453- CONFIG_SPL_BUILD
3454		Modifies the behaviour of start.S when compiling a loader
3455		that is executed before the actual U-Boot. E.g. when
3456		compiling a NAND SPL.
3457
3458- CONFIG_TPL_BUILD
3459		Modifies the behaviour of start.S  when compiling a loader
3460		that is executed after the SPL and before the actual U-Boot.
3461		It is loaded by the SPL.
3462
3463- CONFIG_SYS_MPC85XX_NO_RESETVEC
3464		Only for 85xx systems. If this variable is specified, the section
3465		.resetvec is not kept and the section .bootpg is placed in the
3466		previous 4k of the .text section.
3467
3468- CONFIG_ARCH_MAP_SYSMEM
3469		Generally U-Boot (and in particular the md command) uses
3470		effective address. It is therefore not necessary to regard
3471		U-Boot address as virtual addresses that need to be translated
3472		to physical addresses. However, sandbox requires this, since
3473		it maintains its own little RAM buffer which contains all
3474		addressable memory. This option causes some memory accesses
3475		to be mapped through map_sysmem() / unmap_sysmem().
3476
3477- CONFIG_X86_RESET_VECTOR
3478		If defined, the x86 reset vector code is included. This is not
3479		needed when U-Boot is running from Coreboot.
3480
3481- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3482		Enables the RTC32K OSC on AM33xx based plattforms
3483
3484- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3485		Option to disable subpage write in NAND driver
3486		driver that uses this:
3487		drivers/mtd/nand/davinci_nand.c
3488
3489Freescale QE/FMAN Firmware Support:
3490-----------------------------------
3491
3492The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3493loading of "firmware", which is encoded in the QE firmware binary format.
3494This firmware often needs to be loaded during U-Boot booting, so macros
3495are used to identify the storage device (NOR flash, SPI, etc) and the address
3496within that device.
3497
3498- CONFIG_SYS_FMAN_FW_ADDR
3499	The address in the storage device where the FMAN microcode is located.  The
3500	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3501	is also specified.
3502
3503- CONFIG_SYS_QE_FW_ADDR
3504	The address in the storage device where the QE microcode is located.  The
3505	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3506	is also specified.
3507
3508- CONFIG_SYS_QE_FMAN_FW_LENGTH
3509	The maximum possible size of the firmware.  The firmware binary format
3510	has a field that specifies the actual size of the firmware, but it
3511	might not be possible to read any part of the firmware unless some
3512	local storage is allocated to hold the entire firmware first.
3513
3514- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3515	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3516	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3517	virtual address in NOR flash.
3518
3519- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3520	Specifies that QE/FMAN firmware is located in NAND flash.
3521	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3522
3523- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3524	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3525	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3526
3527- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3528	Specifies that QE/FMAN firmware is located in the remote (master)
3529	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3530	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3531	window->master inbound window->master LAW->the ucode address in
3532	master's memory space.
3533
3534Freescale Layerscape Management Complex Firmware Support:
3535---------------------------------------------------------
3536The Freescale Layerscape Management Complex (MC) supports the loading of
3537"firmware".
3538This firmware often needs to be loaded during U-Boot booting, so macros
3539are used to identify the storage device (NOR flash, SPI, etc) and the address
3540within that device.
3541
3542- CONFIG_FSL_MC_ENET
3543	Enable the MC driver for Layerscape SoCs.
3544
3545Freescale Layerscape Debug Server Support:
3546-------------------------------------------
3547The Freescale Layerscape Debug Server Support supports the loading of
3548"Debug Server firmware" and triggering SP boot-rom.
3549This firmware often needs to be loaded during U-Boot booting.
3550
3551- CONFIG_SYS_MC_RSV_MEM_ALIGN
3552	Define alignment of reserved memory MC requires
3553
3554Reproducible builds
3555-------------------
3556
3557In order to achieve reproducible builds, timestamps used in the U-Boot build
3558process have to be set to a fixed value.
3559
3560This is done using the SOURCE_DATE_EPOCH environment variable.
3561SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3562option for U-Boot or an environment variable in U-Boot.
3563
3564SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3565
3566Building the Software:
3567======================
3568
3569Building U-Boot has been tested in several native build environments
3570and in many different cross environments. Of course we cannot support
3571all possibly existing versions of cross development tools in all
3572(potentially obsolete) versions. In case of tool chain problems we
3573recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3574which is extensively used to build and test U-Boot.
3575
3576If you are not using a native environment, it is assumed that you
3577have GNU cross compiling tools available in your path. In this case,
3578you must set the environment variable CROSS_COMPILE in your shell.
3579Note that no changes to the Makefile or any other source files are
3580necessary. For example using the ELDK on a 4xx CPU, please enter:
3581
3582	$ CROSS_COMPILE=ppc_4xx-
3583	$ export CROSS_COMPILE
3584
3585Note: If you wish to generate Windows versions of the utilities in
3586      the tools directory you can use the MinGW toolchain
3587      (http://www.mingw.org).  Set your HOST tools to the MinGW
3588      toolchain and execute 'make tools'.  For example:
3589
3590       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3591
3592      Binaries such as tools/mkimage.exe will be created which can
3593      be executed on computers running Windows.
3594
3595U-Boot is intended to be simple to build. After installing the
3596sources you must configure U-Boot for one specific board type. This
3597is done by typing:
3598
3599	make NAME_defconfig
3600
3601where "NAME_defconfig" is the name of one of the existing configu-
3602rations; see boards.cfg for supported names.
3603
3604Note: for some board special configuration names may exist; check if
3605      additional information is available from the board vendor; for
3606      instance, the TQM823L systems are available without (standard)
3607      or with LCD support. You can select such additional "features"
3608      when choosing the configuration, i. e.
3609
3610      make TQM823L_defconfig
3611	- will configure for a plain TQM823L, i. e. no LCD support
3612
3613      make TQM823L_LCD_defconfig
3614	- will configure for a TQM823L with U-Boot console on LCD
3615
3616      etc.
3617
3618
3619Finally, type "make all", and you should get some working U-Boot
3620images ready for download to / installation on your system:
3621
3622- "u-boot.bin" is a raw binary image
3623- "u-boot" is an image in ELF binary format
3624- "u-boot.srec" is in Motorola S-Record format
3625
3626By default the build is performed locally and the objects are saved
3627in the source directory. One of the two methods can be used to change
3628this behavior and build U-Boot to some external directory:
3629
36301. Add O= to the make command line invocations:
3631
3632	make O=/tmp/build distclean
3633	make O=/tmp/build NAME_defconfig
3634	make O=/tmp/build all
3635
36362. Set environment variable KBUILD_OUTPUT to point to the desired location:
3637
3638	export KBUILD_OUTPUT=/tmp/build
3639	make distclean
3640	make NAME_defconfig
3641	make all
3642
3643Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3644variable.
3645
3646User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3647setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3648For example to treat all compiler warnings as errors:
3649
3650	make KCFLAGS=-Werror
3651
3652Please be aware that the Makefiles assume you are using GNU make, so
3653for instance on NetBSD you might need to use "gmake" instead of
3654native "make".
3655
3656
3657If the system board that you have is not listed, then you will need
3658to port U-Boot to your hardware platform. To do this, follow these
3659steps:
3660
36611.  Create a new directory to hold your board specific code. Add any
3662    files you need. In your board directory, you will need at least
3663    the "Makefile" and a "<board>.c".
36642.  Create a new configuration file "include/configs/<board>.h" for
3665    your board.
36663.  If you're porting U-Boot to a new CPU, then also create a new
3667    directory to hold your CPU specific code. Add any files you need.
36684.  Run "make <board>_defconfig" with your new name.
36695.  Type "make", and you should get a working "u-boot.srec" file
3670    to be installed on your target system.
36716.  Debug and solve any problems that might arise.
3672    [Of course, this last step is much harder than it sounds.]
3673
3674
3675Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3676==============================================================
3677
3678If you have modified U-Boot sources (for instance added a new board
3679or support for new devices, a new CPU, etc.) you are expected to
3680provide feedback to the other developers. The feedback normally takes
3681the form of a "patch", i. e. a context diff against a certain (latest
3682official or latest in the git repository) version of U-Boot sources.
3683
3684But before you submit such a patch, please verify that your modifi-
3685cation did not break existing code. At least make sure that *ALL* of
3686the supported boards compile WITHOUT ANY compiler warnings. To do so,
3687just run the buildman script (tools/buildman/buildman), which will
3688configure and build U-Boot for ALL supported system. Be warned, this
3689will take a while. Please see the buildman README, or run 'buildman -H'
3690for documentation.
3691
3692
3693See also "U-Boot Porting Guide" below.
3694
3695
3696Monitor Commands - Overview:
3697============================
3698
3699go	- start application at address 'addr'
3700run	- run commands in an environment variable
3701bootm	- boot application image from memory
3702bootp	- boot image via network using BootP/TFTP protocol
3703bootz   - boot zImage from memory
3704tftpboot- boot image via network using TFTP protocol
3705	       and env variables "ipaddr" and "serverip"
3706	       (and eventually "gatewayip")
3707tftpput - upload a file via network using TFTP protocol
3708rarpboot- boot image via network using RARP/TFTP protocol
3709diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3710loads	- load S-Record file over serial line
3711loadb	- load binary file over serial line (kermit mode)
3712md	- memory display
3713mm	- memory modify (auto-incrementing)
3714nm	- memory modify (constant address)
3715mw	- memory write (fill)
3716cp	- memory copy
3717cmp	- memory compare
3718crc32	- checksum calculation
3719i2c	- I2C sub-system
3720sspi	- SPI utility commands
3721base	- print or set address offset
3722printenv- print environment variables
3723setenv	- set environment variables
3724saveenv - save environment variables to persistent storage
3725protect - enable or disable FLASH write protection
3726erase	- erase FLASH memory
3727flinfo	- print FLASH memory information
3728nand	- NAND memory operations (see doc/README.nand)
3729bdinfo	- print Board Info structure
3730iminfo	- print header information for application image
3731coninfo - print console devices and informations
3732ide	- IDE sub-system
3733loop	- infinite loop on address range
3734loopw	- infinite write loop on address range
3735mtest	- simple RAM test
3736icache	- enable or disable instruction cache
3737dcache	- enable or disable data cache
3738reset	- Perform RESET of the CPU
3739echo	- echo args to console
3740version - print monitor version
3741help	- print online help
3742?	- alias for 'help'
3743
3744
3745Monitor Commands - Detailed Description:
3746========================================
3747
3748TODO.
3749
3750For now: just type "help <command>".
3751
3752
3753Environment Variables:
3754======================
3755
3756U-Boot supports user configuration using Environment Variables which
3757can be made persistent by saving to Flash memory.
3758
3759Environment Variables are set using "setenv", printed using
3760"printenv", and saved to Flash using "saveenv". Using "setenv"
3761without a value can be used to delete a variable from the
3762environment. As long as you don't save the environment you are
3763working with an in-memory copy. In case the Flash area containing the
3764environment is erased by accident, a default environment is provided.
3765
3766Some configuration options can be set using Environment Variables.
3767
3768List of environment variables (most likely not complete):
3769
3770  baudrate	- see CONFIG_BAUDRATE
3771
3772  bootdelay	- see CONFIG_BOOTDELAY
3773
3774  bootcmd	- see CONFIG_BOOTCOMMAND
3775
3776  bootargs	- Boot arguments when booting an RTOS image
3777
3778  bootfile	- Name of the image to load with TFTP
3779
3780  bootm_low	- Memory range available for image processing in the bootm
3781		  command can be restricted. This variable is given as
3782		  a hexadecimal number and defines lowest address allowed
3783		  for use by the bootm command. See also "bootm_size"
3784		  environment variable. Address defined by "bootm_low" is
3785		  also the base of the initial memory mapping for the Linux
3786		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3787		  bootm_mapsize.
3788
3789  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3790		  This variable is given as a hexadecimal number and it
3791		  defines the size of the memory region starting at base
3792		  address bootm_low that is accessible by the Linux kernel
3793		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3794		  as the default value if it is defined, and bootm_size is
3795		  used otherwise.
3796
3797  bootm_size	- Memory range available for image processing in the bootm
3798		  command can be restricted. This variable is given as
3799		  a hexadecimal number and defines the size of the region
3800		  allowed for use by the bootm command. See also "bootm_low"
3801		  environment variable.
3802
3803  updatefile	- Location of the software update file on a TFTP server, used
3804		  by the automatic software update feature. Please refer to
3805		  documentation in doc/README.update for more details.
3806
3807  autoload	- if set to "no" (any string beginning with 'n'),
3808		  "bootp" will just load perform a lookup of the
3809		  configuration from the BOOTP server, but not try to
3810		  load any image using TFTP
3811
3812  autostart	- if set to "yes", an image loaded using the "bootp",
3813		  "rarpboot", "tftpboot" or "diskboot" commands will
3814		  be automatically started (by internally calling
3815		  "bootm")
3816
3817		  If set to "no", a standalone image passed to the
3818		  "bootm" command will be copied to the load address
3819		  (and eventually uncompressed), but NOT be started.
3820		  This can be used to load and uncompress arbitrary
3821		  data.
3822
3823  fdt_high	- if set this restricts the maximum address that the
3824		  flattened device tree will be copied into upon boot.
3825		  For example, if you have a system with 1 GB memory
3826		  at physical address 0x10000000, while Linux kernel
3827		  only recognizes the first 704 MB as low memory, you
3828		  may need to set fdt_high as 0x3C000000 to have the
3829		  device tree blob be copied to the maximum address
3830		  of the 704 MB low memory, so that Linux kernel can
3831		  access it during the boot procedure.
3832
3833		  If this is set to the special value 0xFFFFFFFF then
3834		  the fdt will not be copied at all on boot.  For this
3835		  to work it must reside in writable memory, have
3836		  sufficient padding on the end of it for u-boot to
3837		  add the information it needs into it, and the memory
3838		  must be accessible by the kernel.
3839
3840  fdtcontroladdr- if set this is the address of the control flattened
3841		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3842		  defined.
3843
3844  i2cfast	- (PPC405GP|PPC405EP only)
3845		  if set to 'y' configures Linux I2C driver for fast
3846		  mode (400kHZ). This environment variable is used in
3847		  initialization code. So, for changes to be effective
3848		  it must be saved and board must be reset.
3849
3850  initrd_high	- restrict positioning of initrd images:
3851		  If this variable is not set, initrd images will be
3852		  copied to the highest possible address in RAM; this
3853		  is usually what you want since it allows for
3854		  maximum initrd size. If for some reason you want to
3855		  make sure that the initrd image is loaded below the
3856		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3857		  variable to a value of "no" or "off" or "0".
3858		  Alternatively, you can set it to a maximum upper
3859		  address to use (U-Boot will still check that it
3860		  does not overwrite the U-Boot stack and data).
3861
3862		  For instance, when you have a system with 16 MB
3863		  RAM, and want to reserve 4 MB from use by Linux,
3864		  you can do this by adding "mem=12M" to the value of
3865		  the "bootargs" variable. However, now you must make
3866		  sure that the initrd image is placed in the first
3867		  12 MB as well - this can be done with
3868
3869		  setenv initrd_high 00c00000
3870
3871		  If you set initrd_high to 0xFFFFFFFF, this is an
3872		  indication to U-Boot that all addresses are legal
3873		  for the Linux kernel, including addresses in flash
3874		  memory. In this case U-Boot will NOT COPY the
3875		  ramdisk at all. This may be useful to reduce the
3876		  boot time on your system, but requires that this
3877		  feature is supported by your Linux kernel.
3878
3879  ipaddr	- IP address; needed for tftpboot command
3880
3881  loadaddr	- Default load address for commands like "bootp",
3882		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3883
3884  loads_echo	- see CONFIG_LOADS_ECHO
3885
3886  serverip	- TFTP server IP address; needed for tftpboot command
3887
3888  bootretry	- see CONFIG_BOOT_RETRY_TIME
3889
3890  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3891
3892  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3893
3894  ethprime	- controls which interface is used first.
3895
3896  ethact	- controls which interface is currently active.
3897		  For example you can do the following
3898
3899		  => setenv ethact FEC
3900		  => ping 192.168.0.1 # traffic sent on FEC
3901		  => setenv ethact SCC
3902		  => ping 10.0.0.1 # traffic sent on SCC
3903
3904  ethrotate	- When set to "no" U-Boot does not go through all
3905		  available network interfaces.
3906		  It just stays at the currently selected interface.
3907
3908  netretry	- When set to "no" each network operation will
3909		  either succeed or fail without retrying.
3910		  When set to "once" the network operation will
3911		  fail when all the available network interfaces
3912		  are tried once without success.
3913		  Useful on scripts which control the retry operation
3914		  themselves.
3915
3916  npe_ucode	- set load address for the NPE microcode
3917
3918  silent_linux  - If set then Linux will be told to boot silently, by
3919		  changing the console to be empty. If "yes" it will be
3920		  made silent. If "no" it will not be made silent. If
3921		  unset, then it will be made silent if the U-Boot console
3922		  is silent.
3923
3924  tftpsrcp	- If this is set, the value is used for TFTP's
3925		  UDP source port.
3926
3927  tftpdstp	- If this is set, the value is used for TFTP's UDP
3928		  destination port instead of the Well Know Port 69.
3929
3930  tftpblocksize - Block size to use for TFTP transfers; if not set,
3931		  we use the TFTP server's default block size
3932
3933  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3934		  seconds, minimum value is 1000 = 1 second). Defines
3935		  when a packet is considered to be lost so it has to
3936		  be retransmitted. The default is 5000 = 5 seconds.
3937		  Lowering this value may make downloads succeed
3938		  faster in networks with high packet loss rates or
3939		  with unreliable TFTP servers.
3940
3941  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3942		  unit, minimum value = 0). Defines how many timeouts
3943		  can happen during a single file transfer before that
3944		  transfer is aborted. The default is 10, and 0 means
3945		  'no timeouts allowed'. Increasing this value may help
3946		  downloads succeed with high packet loss rates, or with
3947		  unreliable TFTP servers or client hardware.
3948
3949  vlan		- When set to a value < 4095 the traffic over
3950		  Ethernet is encapsulated/received over 802.1q
3951		  VLAN tagged frames.
3952
3953  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3954		  Unsigned value, in milliseconds. If not set, the period will
3955		  be either the default (28000), or a value based on
3956		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3957		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3958
3959The following image location variables contain the location of images
3960used in booting. The "Image" column gives the role of the image and is
3961not an environment variable name. The other columns are environment
3962variable names. "File Name" gives the name of the file on a TFTP
3963server, "RAM Address" gives the location in RAM the image will be
3964loaded to, and "Flash Location" gives the image's address in NOR
3965flash or offset in NAND flash.
3966
3967*Note* - these variables don't have to be defined for all boards, some
3968boards currently use other variables for these purposes, and some
3969boards use these variables for other purposes.
3970
3971Image		    File Name	     RAM Address       Flash Location
3972-----		    ---------	     -----------       --------------
3973u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3974Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3975device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3976ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3977
3978The following environment variables may be used and automatically
3979updated by the network boot commands ("bootp" and "rarpboot"),
3980depending the information provided by your boot server:
3981
3982  bootfile	- see above
3983  dnsip		- IP address of your Domain Name Server
3984  dnsip2	- IP address of your secondary Domain Name Server
3985  gatewayip	- IP address of the Gateway (Router) to use
3986  hostname	- Target hostname
3987  ipaddr	- see above
3988  netmask	- Subnet Mask
3989  rootpath	- Pathname of the root filesystem on the NFS server
3990  serverip	- see above
3991
3992
3993There are two special Environment Variables:
3994
3995  serial#	- contains hardware identification information such
3996		  as type string and/or serial number
3997  ethaddr	- Ethernet address
3998
3999These variables can be set only once (usually during manufacturing of
4000the board). U-Boot refuses to delete or overwrite these variables
4001once they have been set once.
4002
4003
4004Further special Environment Variables:
4005
4006  ver		- Contains the U-Boot version string as printed
4007		  with the "version" command. This variable is
4008		  readonly (see CONFIG_VERSION_VARIABLE).
4009
4010
4011Please note that changes to some configuration parameters may take
4012only effect after the next boot (yes, that's just like Windoze :-).
4013
4014
4015Callback functions for environment variables:
4016---------------------------------------------
4017
4018For some environment variables, the behavior of u-boot needs to change
4019when their values are changed.  This functionality allows functions to
4020be associated with arbitrary variables.  On creation, overwrite, or
4021deletion, the callback will provide the opportunity for some side
4022effect to happen or for the change to be rejected.
4023
4024The callbacks are named and associated with a function using the
4025U_BOOT_ENV_CALLBACK macro in your board or driver code.
4026
4027These callbacks are associated with variables in one of two ways.  The
4028static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4029in the board configuration to a string that defines a list of
4030associations.  The list must be in the following format:
4031
4032	entry = variable_name[:callback_name]
4033	list = entry[,list]
4034
4035If the callback name is not specified, then the callback is deleted.
4036Spaces are also allowed anywhere in the list.
4037
4038Callbacks can also be associated by defining the ".callbacks" variable
4039with the same list format above.  Any association in ".callbacks" will
4040override any association in the static list. You can define
4041CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4042".callbacks" environment variable in the default or embedded environment.
4043
4044If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4045regular expression. This allows multiple variables to be connected to
4046the same callback without explicitly listing them all out.
4047
4048
4049Command Line Parsing:
4050=====================
4051
4052There are two different command line parsers available with U-Boot:
4053the old "simple" one, and the much more powerful "hush" shell:
4054
4055Old, simple command line parser:
4056--------------------------------
4057
4058- supports environment variables (through setenv / saveenv commands)
4059- several commands on one line, separated by ';'
4060- variable substitution using "... ${name} ..." syntax
4061- special characters ('$', ';') can be escaped by prefixing with '\',
4062  for example:
4063	setenv bootcmd bootm \${address}
4064- You can also escape text by enclosing in single apostrophes, for example:
4065	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4066
4067Hush shell:
4068-----------
4069
4070- similar to Bourne shell, with control structures like
4071  if...then...else...fi, for...do...done; while...do...done,
4072  until...do...done, ...
4073- supports environment ("global") variables (through setenv / saveenv
4074  commands) and local shell variables (through standard shell syntax
4075  "name=value"); only environment variables can be used with "run"
4076  command
4077
4078General rules:
4079--------------
4080
4081(1) If a command line (or an environment variable executed by a "run"
4082    command) contains several commands separated by semicolon, and
4083    one of these commands fails, then the remaining commands will be
4084    executed anyway.
4085
4086(2) If you execute several variables with one call to run (i. e.
4087    calling run with a list of variables as arguments), any failing
4088    command will cause "run" to terminate, i. e. the remaining
4089    variables are not executed.
4090
4091Note for Redundant Ethernet Interfaces:
4092=======================================
4093
4094Some boards come with redundant Ethernet interfaces; U-Boot supports
4095such configurations and is capable of automatic selection of a
4096"working" interface when needed. MAC assignment works as follows:
4097
4098Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4099MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4100"eth1addr" (=>eth1), "eth2addr", ...
4101
4102If the network interface stores some valid MAC address (for instance
4103in SROM), this is used as default address if there is NO correspon-
4104ding setting in the environment; if the corresponding environment
4105variable is set, this overrides the settings in the card; that means:
4106
4107o If the SROM has a valid MAC address, and there is no address in the
4108  environment, the SROM's address is used.
4109
4110o If there is no valid address in the SROM, and a definition in the
4111  environment exists, then the value from the environment variable is
4112  used.
4113
4114o If both the SROM and the environment contain a MAC address, and
4115  both addresses are the same, this MAC address is used.
4116
4117o If both the SROM and the environment contain a MAC address, and the
4118  addresses differ, the value from the environment is used and a
4119  warning is printed.
4120
4121o If neither SROM nor the environment contain a MAC address, an error
4122  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4123  a random, locally-assigned MAC is used.
4124
4125If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4126will be programmed into hardware as part of the initialization process.	 This
4127may be skipped by setting the appropriate 'ethmacskip' environment variable.
4128The naming convention is as follows:
4129"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4130
4131Image Formats:
4132==============
4133
4134U-Boot is capable of booting (and performing other auxiliary operations on)
4135images in two formats:
4136
4137New uImage format (FIT)
4138-----------------------
4139
4140Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4141to Flattened Device Tree). It allows the use of images with multiple
4142components (several kernels, ramdisks, etc.), with contents protected by
4143SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4144
4145
4146Old uImage format
4147-----------------
4148
4149Old image format is based on binary files which can be basically anything,
4150preceded by a special header; see the definitions in include/image.h for
4151details; basically, the header defines the following image properties:
4152
4153* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4154  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4155  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4156  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4157  INTEGRITY).
4158* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4159  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4160  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4161* Compression Type (uncompressed, gzip, bzip2)
4162* Load Address
4163* Entry Point
4164* Image Name
4165* Image Timestamp
4166
4167The header is marked by a special Magic Number, and both the header
4168and the data portions of the image are secured against corruption by
4169CRC32 checksums.
4170
4171
4172Linux Support:
4173==============
4174
4175Although U-Boot should support any OS or standalone application
4176easily, the main focus has always been on Linux during the design of
4177U-Boot.
4178
4179U-Boot includes many features that so far have been part of some
4180special "boot loader" code within the Linux kernel. Also, any
4181"initrd" images to be used are no longer part of one big Linux image;
4182instead, kernel and "initrd" are separate images. This implementation
4183serves several purposes:
4184
4185- the same features can be used for other OS or standalone
4186  applications (for instance: using compressed images to reduce the
4187  Flash memory footprint)
4188
4189- it becomes much easier to port new Linux kernel versions because
4190  lots of low-level, hardware dependent stuff are done by U-Boot
4191
4192- the same Linux kernel image can now be used with different "initrd"
4193  images; of course this also means that different kernel images can
4194  be run with the same "initrd". This makes testing easier (you don't
4195  have to build a new "zImage.initrd" Linux image when you just
4196  change a file in your "initrd"). Also, a field-upgrade of the
4197  software is easier now.
4198
4199
4200Linux HOWTO:
4201============
4202
4203Porting Linux to U-Boot based systems:
4204---------------------------------------
4205
4206U-Boot cannot save you from doing all the necessary modifications to
4207configure the Linux device drivers for use with your target hardware
4208(no, we don't intend to provide a full virtual machine interface to
4209Linux :-).
4210
4211But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4212
4213Just make sure your machine specific header file (for instance
4214include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4215Information structure as we define in include/asm-<arch>/u-boot.h,
4216and make sure that your definition of IMAP_ADDR uses the same value
4217as your U-Boot configuration in CONFIG_SYS_IMMR.
4218
4219Note that U-Boot now has a driver model, a unified model for drivers.
4220If you are adding a new driver, plumb it into driver model. If there
4221is no uclass available, you are encouraged to create one. See
4222doc/driver-model.
4223
4224
4225Configuring the Linux kernel:
4226-----------------------------
4227
4228No specific requirements for U-Boot. Make sure you have some root
4229device (initial ramdisk, NFS) for your target system.
4230
4231
4232Building a Linux Image:
4233-----------------------
4234
4235With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4236not used. If you use recent kernel source, a new build target
4237"uImage" will exist which automatically builds an image usable by
4238U-Boot. Most older kernels also have support for a "pImage" target,
4239which was introduced for our predecessor project PPCBoot and uses a
4240100% compatible format.
4241
4242Example:
4243
4244	make TQM850L_defconfig
4245	make oldconfig
4246	make dep
4247	make uImage
4248
4249The "uImage" build target uses a special tool (in 'tools/mkimage') to
4250encapsulate a compressed Linux kernel image with header	 information,
4251CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4252
4253* build a standard "vmlinux" kernel image (in ELF binary format):
4254
4255* convert the kernel into a raw binary image:
4256
4257	${CROSS_COMPILE}-objcopy -O binary \
4258				 -R .note -R .comment \
4259				 -S vmlinux linux.bin
4260
4261* compress the binary image:
4262
4263	gzip -9 linux.bin
4264
4265* package compressed binary image for U-Boot:
4266
4267	mkimage -A ppc -O linux -T kernel -C gzip \
4268		-a 0 -e 0 -n "Linux Kernel Image" \
4269		-d linux.bin.gz uImage
4270
4271
4272The "mkimage" tool can also be used to create ramdisk images for use
4273with U-Boot, either separated from the Linux kernel image, or
4274combined into one file. "mkimage" encapsulates the images with a 64
4275byte header containing information about target architecture,
4276operating system, image type, compression method, entry points, time
4277stamp, CRC32 checksums, etc.
4278
4279"mkimage" can be called in two ways: to verify existing images and
4280print the header information, or to build new images.
4281
4282In the first form (with "-l" option) mkimage lists the information
4283contained in the header of an existing U-Boot image; this includes
4284checksum verification:
4285
4286	tools/mkimage -l image
4287	  -l ==> list image header information
4288
4289The second form (with "-d" option) is used to build a U-Boot image
4290from a "data file" which is used as image payload:
4291
4292	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4293		      -n name -d data_file image
4294	  -A ==> set architecture to 'arch'
4295	  -O ==> set operating system to 'os'
4296	  -T ==> set image type to 'type'
4297	  -C ==> set compression type 'comp'
4298	  -a ==> set load address to 'addr' (hex)
4299	  -e ==> set entry point to 'ep' (hex)
4300	  -n ==> set image name to 'name'
4301	  -d ==> use image data from 'datafile'
4302
4303Right now, all Linux kernels for PowerPC systems use the same load
4304address (0x00000000), but the entry point address depends on the
4305kernel version:
4306
4307- 2.2.x kernels have the entry point at 0x0000000C,
4308- 2.3.x and later kernels have the entry point at 0x00000000.
4309
4310So a typical call to build a U-Boot image would read:
4311
4312	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4313	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4314	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4315	> examples/uImage.TQM850L
4316	Image Name:   2.4.4 kernel for TQM850L
4317	Created:      Wed Jul 19 02:34:59 2000
4318	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4319	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4320	Load Address: 0x00000000
4321	Entry Point:  0x00000000
4322
4323To verify the contents of the image (or check for corruption):
4324
4325	-> tools/mkimage -l examples/uImage.TQM850L
4326	Image Name:   2.4.4 kernel for TQM850L
4327	Created:      Wed Jul 19 02:34:59 2000
4328	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4329	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4330	Load Address: 0x00000000
4331	Entry Point:  0x00000000
4332
4333NOTE: for embedded systems where boot time is critical you can trade
4334speed for memory and install an UNCOMPRESSED image instead: this
4335needs more space in Flash, but boots much faster since it does not
4336need to be uncompressed:
4337
4338	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4339	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4340	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4341	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4342	> examples/uImage.TQM850L-uncompressed
4343	Image Name:   2.4.4 kernel for TQM850L
4344	Created:      Wed Jul 19 02:34:59 2000
4345	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4346	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4347	Load Address: 0x00000000
4348	Entry Point:  0x00000000
4349
4350
4351Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4352when your kernel is intended to use an initial ramdisk:
4353
4354	-> tools/mkimage -n 'Simple Ramdisk Image' \
4355	> -A ppc -O linux -T ramdisk -C gzip \
4356	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4357	Image Name:   Simple Ramdisk Image
4358	Created:      Wed Jan 12 14:01:50 2000
4359	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4360	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4361	Load Address: 0x00000000
4362	Entry Point:  0x00000000
4363
4364The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4365option performs the converse operation of the mkimage's second form (the "-d"
4366option). Given an image built by mkimage, the dumpimage extracts a "data file"
4367from the image:
4368
4369	tools/dumpimage -i image -T type -p position data_file
4370	  -i ==> extract from the 'image' a specific 'data_file'
4371	  -T ==> set image type to 'type'
4372	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4373
4374
4375Installing a Linux Image:
4376-------------------------
4377
4378To downloading a U-Boot image over the serial (console) interface,
4379you must convert the image to S-Record format:
4380
4381	objcopy -I binary -O srec examples/image examples/image.srec
4382
4383The 'objcopy' does not understand the information in the U-Boot
4384image header, so the resulting S-Record file will be relative to
4385address 0x00000000. To load it to a given address, you need to
4386specify the target address as 'offset' parameter with the 'loads'
4387command.
4388
4389Example: install the image to address 0x40100000 (which on the
4390TQM8xxL is in the first Flash bank):
4391
4392	=> erase 40100000 401FFFFF
4393
4394	.......... done
4395	Erased 8 sectors
4396
4397	=> loads 40100000
4398	## Ready for S-Record download ...
4399	~>examples/image.srec
4400	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4401	...
4402	15989 15990 15991 15992
4403	[file transfer complete]
4404	[connected]
4405	## Start Addr = 0x00000000
4406
4407
4408You can check the success of the download using the 'iminfo' command;
4409this includes a checksum verification so you can be sure no data
4410corruption happened:
4411
4412	=> imi 40100000
4413
4414	## Checking Image at 40100000 ...
4415	   Image Name:	 2.2.13 for initrd on TQM850L
4416	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4417	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4418	   Load Address: 00000000
4419	   Entry Point:	 0000000c
4420	   Verifying Checksum ... OK
4421
4422
4423Boot Linux:
4424-----------
4425
4426The "bootm" command is used to boot an application that is stored in
4427memory (RAM or Flash). In case of a Linux kernel image, the contents
4428of the "bootargs" environment variable is passed to the kernel as
4429parameters. You can check and modify this variable using the
4430"printenv" and "setenv" commands:
4431
4432
4433	=> printenv bootargs
4434	bootargs=root=/dev/ram
4435
4436	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4437
4438	=> printenv bootargs
4439	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4440
4441	=> bootm 40020000
4442	## Booting Linux kernel at 40020000 ...
4443	   Image Name:	 2.2.13 for NFS on TQM850L
4444	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4445	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4446	   Load Address: 00000000
4447	   Entry Point:	 0000000c
4448	   Verifying Checksum ... OK
4449	   Uncompressing Kernel Image ... OK
4450	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
4451	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4452	time_init: decrementer frequency = 187500000/60
4453	Calibrating delay loop... 49.77 BogoMIPS
4454	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4455	...
4456
4457If you want to boot a Linux kernel with initial RAM disk, you pass
4458the memory addresses of both the kernel and the initrd image (PPBCOOT
4459format!) to the "bootm" command:
4460
4461	=> imi 40100000 40200000
4462
4463	## Checking Image at 40100000 ...
4464	   Image Name:	 2.2.13 for initrd on TQM850L
4465	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4466	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4467	   Load Address: 00000000
4468	   Entry Point:	 0000000c
4469	   Verifying Checksum ... OK
4470
4471	## Checking Image at 40200000 ...
4472	   Image Name:	 Simple Ramdisk Image
4473	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4474	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4475	   Load Address: 00000000
4476	   Entry Point:	 00000000
4477	   Verifying Checksum ... OK
4478
4479	=> bootm 40100000 40200000
4480	## Booting Linux kernel at 40100000 ...
4481	   Image Name:	 2.2.13 for initrd on TQM850L
4482	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4483	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4484	   Load Address: 00000000
4485	   Entry Point:	 0000000c
4486	   Verifying Checksum ... OK
4487	   Uncompressing Kernel Image ... OK
4488	## Loading RAMDisk Image at 40200000 ...
4489	   Image Name:	 Simple Ramdisk Image
4490	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4491	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4492	   Load Address: 00000000
4493	   Entry Point:	 00000000
4494	   Verifying Checksum ... OK
4495	   Loading Ramdisk ... OK
4496	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
4497	Boot arguments: root=/dev/ram
4498	time_init: decrementer frequency = 187500000/60
4499	Calibrating delay loop... 49.77 BogoMIPS
4500	...
4501	RAMDISK: Compressed image found at block 0
4502	VFS: Mounted root (ext2 filesystem).
4503
4504	bash#
4505
4506Boot Linux and pass a flat device tree:
4507-----------
4508
4509First, U-Boot must be compiled with the appropriate defines. See the section
4510titled "Linux Kernel Interface" above for a more in depth explanation. The
4511following is an example of how to start a kernel and pass an updated
4512flat device tree:
4513
4514=> print oftaddr
4515oftaddr=0x300000
4516=> print oft
4517oft=oftrees/mpc8540ads.dtb
4518=> tftp $oftaddr $oft
4519Speed: 1000, full duplex
4520Using TSEC0 device
4521TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4522Filename 'oftrees/mpc8540ads.dtb'.
4523Load address: 0x300000
4524Loading: #
4525done
4526Bytes transferred = 4106 (100a hex)
4527=> tftp $loadaddr $bootfile
4528Speed: 1000, full duplex
4529Using TSEC0 device
4530TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4531Filename 'uImage'.
4532Load address: 0x200000
4533Loading:############
4534done
4535Bytes transferred = 1029407 (fb51f hex)
4536=> print loadaddr
4537loadaddr=200000
4538=> print oftaddr
4539oftaddr=0x300000
4540=> bootm $loadaddr - $oftaddr
4541## Booting image at 00200000 ...
4542   Image Name:	 Linux-2.6.17-dirty
4543   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4544   Data Size:	 1029343 Bytes = 1005.2 kB
4545   Load Address: 00000000
4546   Entry Point:	 00000000
4547   Verifying Checksum ... OK
4548   Uncompressing Kernel Image ... OK
4549Booting using flat device tree at 0x300000
4550Using MPC85xx ADS machine description
4551Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4552[snip]
4553
4554
4555More About U-Boot Image Types:
4556------------------------------
4557
4558U-Boot supports the following image types:
4559
4560   "Standalone Programs" are directly runnable in the environment
4561	provided by U-Boot; it is expected that (if they behave
4562	well) you can continue to work in U-Boot after return from
4563	the Standalone Program.
4564   "OS Kernel Images" are usually images of some Embedded OS which
4565	will take over control completely. Usually these programs
4566	will install their own set of exception handlers, device
4567	drivers, set up the MMU, etc. - this means, that you cannot
4568	expect to re-enter U-Boot except by resetting the CPU.
4569   "RAMDisk Images" are more or less just data blocks, and their
4570	parameters (address, size) are passed to an OS kernel that is
4571	being started.
4572   "Multi-File Images" contain several images, typically an OS
4573	(Linux) kernel image and one or more data images like
4574	RAMDisks. This construct is useful for instance when you want
4575	to boot over the network using BOOTP etc., where the boot
4576	server provides just a single image file, but you want to get
4577	for instance an OS kernel and a RAMDisk image.
4578
4579	"Multi-File Images" start with a list of image sizes, each
4580	image size (in bytes) specified by an "uint32_t" in network
4581	byte order. This list is terminated by an "(uint32_t)0".
4582	Immediately after the terminating 0 follow the images, one by
4583	one, all aligned on "uint32_t" boundaries (size rounded up to
4584	a multiple of 4 bytes).
4585
4586   "Firmware Images" are binary images containing firmware (like
4587	U-Boot or FPGA images) which usually will be programmed to
4588	flash memory.
4589
4590   "Script files" are command sequences that will be executed by
4591	U-Boot's command interpreter; this feature is especially
4592	useful when you configure U-Boot to use a real shell (hush)
4593	as command interpreter.
4594
4595Booting the Linux zImage:
4596-------------------------
4597
4598On some platforms, it's possible to boot Linux zImage. This is done
4599using the "bootz" command. The syntax of "bootz" command is the same
4600as the syntax of "bootm" command.
4601
4602Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4603kernel with raw initrd images. The syntax is slightly different, the
4604address of the initrd must be augmented by it's size, in the following
4605format: "<initrd addres>:<initrd size>".
4606
4607
4608Standalone HOWTO:
4609=================
4610
4611One of the features of U-Boot is that you can dynamically load and
4612run "standalone" applications, which can use some resources of
4613U-Boot like console I/O functions or interrupt services.
4614
4615Two simple examples are included with the sources:
4616
4617"Hello World" Demo:
4618-------------------
4619
4620'examples/hello_world.c' contains a small "Hello World" Demo
4621application; it is automatically compiled when you build U-Boot.
4622It's configured to run at address 0x00040004, so you can play with it
4623like that:
4624
4625	=> loads
4626	## Ready for S-Record download ...
4627	~>examples/hello_world.srec
4628	1 2 3 4 5 6 7 8 9 10 11 ...
4629	[file transfer complete]
4630	[connected]
4631	## Start Addr = 0x00040004
4632
4633	=> go 40004 Hello World! This is a test.
4634	## Starting application at 0x00040004 ...
4635	Hello World
4636	argc = 7
4637	argv[0] = "40004"
4638	argv[1] = "Hello"
4639	argv[2] = "World!"
4640	argv[3] = "This"
4641	argv[4] = "is"
4642	argv[5] = "a"
4643	argv[6] = "test."
4644	argv[7] = "<NULL>"
4645	Hit any key to exit ...
4646
4647	## Application terminated, rc = 0x0
4648
4649Another example, which demonstrates how to register a CPM interrupt
4650handler with the U-Boot code, can be found in 'examples/timer.c'.
4651Here, a CPM timer is set up to generate an interrupt every second.
4652The interrupt service routine is trivial, just printing a '.'
4653character, but this is just a demo program. The application can be
4654controlled by the following keys:
4655
4656	? - print current values og the CPM Timer registers
4657	b - enable interrupts and start timer
4658	e - stop timer and disable interrupts
4659	q - quit application
4660
4661	=> loads
4662	## Ready for S-Record download ...
4663	~>examples/timer.srec
4664	1 2 3 4 5 6 7 8 9 10 11 ...
4665	[file transfer complete]
4666	[connected]
4667	## Start Addr = 0x00040004
4668
4669	=> go 40004
4670	## Starting application at 0x00040004 ...
4671	TIMERS=0xfff00980
4672	Using timer 1
4673	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4674
4675Hit 'b':
4676	[q, b, e, ?] Set interval 1000000 us
4677	Enabling timer
4678Hit '?':
4679	[q, b, e, ?] ........
4680	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4681Hit '?':
4682	[q, b, e, ?] .
4683	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4684Hit '?':
4685	[q, b, e, ?] .
4686	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4687Hit '?':
4688	[q, b, e, ?] .
4689	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4690Hit 'e':
4691	[q, b, e, ?] ...Stopping timer
4692Hit 'q':
4693	[q, b, e, ?] ## Application terminated, rc = 0x0
4694
4695
4696Minicom warning:
4697================
4698
4699Over time, many people have reported problems when trying to use the
4700"minicom" terminal emulation program for serial download. I (wd)
4701consider minicom to be broken, and recommend not to use it. Under
4702Unix, I recommend to use C-Kermit for general purpose use (and
4703especially for kermit binary protocol download ("loadb" command), and
4704use "cu" for S-Record download ("loads" command).  See
4705http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4706for help with kermit.
4707
4708
4709Nevertheless, if you absolutely want to use it try adding this
4710configuration to your "File transfer protocols" section:
4711
4712	   Name	   Program			Name U/D FullScr IO-Red. Multi
4713	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4714	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4715
4716
4717NetBSD Notes:
4718=============
4719
4720Starting at version 0.9.2, U-Boot supports NetBSD both as host
4721(build U-Boot) and target system (boots NetBSD/mpc8xx).
4722
4723Building requires a cross environment; it is known to work on
4724NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4725need gmake since the Makefiles are not compatible with BSD make).
4726Note that the cross-powerpc package does not install include files;
4727attempting to build U-Boot will fail because <machine/ansi.h> is
4728missing.  This file has to be installed and patched manually:
4729
4730	# cd /usr/pkg/cross/powerpc-netbsd/include
4731	# mkdir powerpc
4732	# ln -s powerpc machine
4733	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4734	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4735
4736Native builds *don't* work due to incompatibilities between native
4737and U-Boot include files.
4738
4739Booting assumes that (the first part of) the image booted is a
4740stage-2 loader which in turn loads and then invokes the kernel
4741proper. Loader sources will eventually appear in the NetBSD source
4742tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4743meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4744
4745
4746Implementation Internals:
4747=========================
4748
4749The following is not intended to be a complete description of every
4750implementation detail. However, it should help to understand the
4751inner workings of U-Boot and make it easier to port it to custom
4752hardware.
4753
4754
4755Initial Stack, Global Data:
4756---------------------------
4757
4758The implementation of U-Boot is complicated by the fact that U-Boot
4759starts running out of ROM (flash memory), usually without access to
4760system RAM (because the memory controller is not initialized yet).
4761This means that we don't have writable Data or BSS segments, and BSS
4762is not initialized as zero. To be able to get a C environment working
4763at all, we have to allocate at least a minimal stack. Implementation
4764options for this are defined and restricted by the CPU used: Some CPU
4765models provide on-chip memory (like the IMMR area on MPC8xx and
4766MPC826x processors), on others (parts of) the data cache can be
4767locked as (mis-) used as memory, etc.
4768
4769	Chris Hallinan posted a good summary of these issues to the
4770	U-Boot mailing list:
4771
4772	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4773	From: "Chris Hallinan" <clh@net1plus.com>
4774	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4775	...
4776
4777	Correct me if I'm wrong, folks, but the way I understand it
4778	is this: Using DCACHE as initial RAM for Stack, etc, does not
4779	require any physical RAM backing up the cache. The cleverness
4780	is that the cache is being used as a temporary supply of
4781	necessary storage before the SDRAM controller is setup. It's
4782	beyond the scope of this list to explain the details, but you
4783	can see how this works by studying the cache architecture and
4784	operation in the architecture and processor-specific manuals.
4785
4786	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4787	is another option for the system designer to use as an
4788	initial stack/RAM area prior to SDRAM being available. Either
4789	option should work for you. Using CS 4 should be fine if your
4790	board designers haven't used it for something that would
4791	cause you grief during the initial boot! It is frequently not
4792	used.
4793
4794	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4795	with your processor/board/system design. The default value
4796	you will find in any recent u-boot distribution in
4797	walnut.h should work for you. I'd set it to a value larger
4798	than your SDRAM module. If you have a 64MB SDRAM module, set
4799	it above 400_0000. Just make sure your board has no resources
4800	that are supposed to respond to that address! That code in
4801	start.S has been around a while and should work as is when
4802	you get the config right.
4803
4804	-Chris Hallinan
4805	DS4.COM, Inc.
4806
4807It is essential to remember this, since it has some impact on the C
4808code for the initialization procedures:
4809
4810* Initialized global data (data segment) is read-only. Do not attempt
4811  to write it.
4812
4813* Do not use any uninitialized global data (or implicitly initialized
4814  as zero data - BSS segment) at all - this is undefined, initiali-
4815  zation is performed later (when relocating to RAM).
4816
4817* Stack space is very limited. Avoid big data buffers or things like
4818  that.
4819
4820Having only the stack as writable memory limits means we cannot use
4821normal global data to share information between the code. But it
4822turned out that the implementation of U-Boot can be greatly
4823simplified by making a global data structure (gd_t) available to all
4824functions. We could pass a pointer to this data as argument to _all_
4825functions, but this would bloat the code. Instead we use a feature of
4826the GCC compiler (Global Register Variables) to share the data: we
4827place a pointer (gd) to the global data into a register which we
4828reserve for this purpose.
4829
4830When choosing a register for such a purpose we are restricted by the
4831relevant  (E)ABI  specifications for the current architecture, and by
4832GCC's implementation.
4833
4834For PowerPC, the following registers have specific use:
4835	R1:	stack pointer
4836	R2:	reserved for system use
4837	R3-R4:	parameter passing and return values
4838	R5-R10: parameter passing
4839	R13:	small data area pointer
4840	R30:	GOT pointer
4841	R31:	frame pointer
4842
4843	(U-Boot also uses R12 as internal GOT pointer. r12
4844	is a volatile register so r12 needs to be reset when
4845	going back and forth between asm and C)
4846
4847    ==> U-Boot will use R2 to hold a pointer to the global data
4848
4849    Note: on PPC, we could use a static initializer (since the
4850    address of the global data structure is known at compile time),
4851    but it turned out that reserving a register results in somewhat
4852    smaller code - although the code savings are not that big (on
4853    average for all boards 752 bytes for the whole U-Boot image,
4854    624 text + 127 data).
4855
4856On ARM, the following registers are used:
4857
4858	R0:	function argument word/integer result
4859	R1-R3:	function argument word
4860	R9:	platform specific
4861	R10:	stack limit (used only if stack checking is enabled)
4862	R11:	argument (frame) pointer
4863	R12:	temporary workspace
4864	R13:	stack pointer
4865	R14:	link register
4866	R15:	program counter
4867
4868    ==> U-Boot will use R9 to hold a pointer to the global data
4869
4870    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4871
4872On Nios II, the ABI is documented here:
4873	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4874
4875    ==> U-Boot will use gp to hold a pointer to the global data
4876
4877    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4878    to access small data sections, so gp is free.
4879
4880On NDS32, the following registers are used:
4881
4882	R0-R1:	argument/return
4883	R2-R5:	argument
4884	R15:	temporary register for assembler
4885	R16:	trampoline register
4886	R28:	frame pointer (FP)
4887	R29:	global pointer (GP)
4888	R30:	link register (LP)
4889	R31:	stack pointer (SP)
4890	PC:	program counter (PC)
4891
4892    ==> U-Boot will use R10 to hold a pointer to the global data
4893
4894NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4895or current versions of GCC may "optimize" the code too much.
4896
4897On RISC-V, the following registers are used:
4898
4899	x0: hard-wired zero (zero)
4900	x1: return address (ra)
4901	x2:	stack pointer (sp)
4902	x3:	global pointer (gp)
4903	x4:	thread pointer (tp)
4904	x5:	link register (t0)
4905	x8:	frame pointer (fp)
4906	x10-x11:	arguments/return values (a0-1)
4907	x12-x17:	arguments (a2-7)
4908	x28-31:	 temporaries (t3-6)
4909	pc:	program counter (pc)
4910
4911    ==> U-Boot will use gp to hold a pointer to the global data
4912
4913Memory Management:
4914------------------
4915
4916U-Boot runs in system state and uses physical addresses, i.e. the
4917MMU is not used either for address mapping nor for memory protection.
4918
4919The available memory is mapped to fixed addresses using the memory
4920controller. In this process, a contiguous block is formed for each
4921memory type (Flash, SDRAM, SRAM), even when it consists of several
4922physical memory banks.
4923
4924U-Boot is installed in the first 128 kB of the first Flash bank (on
4925TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4926booting and sizing and initializing DRAM, the code relocates itself
4927to the upper end of DRAM. Immediately below the U-Boot code some
4928memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4929configuration setting]. Below that, a structure with global Board
4930Info data is placed, followed by the stack (growing downward).
4931
4932Additionally, some exception handler code is copied to the low 8 kB
4933of DRAM (0x00000000 ... 0x00001FFF).
4934
4935So a typical memory configuration with 16 MB of DRAM could look like
4936this:
4937
4938	0x0000 0000	Exception Vector code
4939	      :
4940	0x0000 1FFF
4941	0x0000 2000	Free for Application Use
4942	      :
4943	      :
4944
4945	      :
4946	      :
4947	0x00FB FF20	Monitor Stack (Growing downward)
4948	0x00FB FFAC	Board Info Data and permanent copy of global data
4949	0x00FC 0000	Malloc Arena
4950	      :
4951	0x00FD FFFF
4952	0x00FE 0000	RAM Copy of Monitor Code
4953	...		eventually: LCD or video framebuffer
4954	...		eventually: pRAM (Protected RAM - unchanged by reset)
4955	0x00FF FFFF	[End of RAM]
4956
4957
4958System Initialization:
4959----------------------
4960
4961In the reset configuration, U-Boot starts at the reset entry point
4962(on most PowerPC systems at address 0x00000100). Because of the reset
4963configuration for CS0# this is a mirror of the on board Flash memory.
4964To be able to re-map memory U-Boot then jumps to its link address.
4965To be able to implement the initialization code in C, a (small!)
4966initial stack is set up in the internal Dual Ported RAM (in case CPUs
4967which provide such a feature like), or in a locked part of the data
4968cache. After that, U-Boot initializes the CPU core, the caches and
4969the SIU.
4970
4971Next, all (potentially) available memory banks are mapped using a
4972preliminary mapping. For example, we put them on 512 MB boundaries
4973(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4974on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4975programmed for SDRAM access. Using the temporary configuration, a
4976simple memory test is run that determines the size of the SDRAM
4977banks.
4978
4979When there is more than one SDRAM bank, and the banks are of
4980different size, the largest is mapped first. For equal size, the first
4981bank (CS2#) is mapped first. The first mapping is always for address
49820x00000000, with any additional banks following immediately to create
4983contiguous memory starting from 0.
4984
4985Then, the monitor installs itself at the upper end of the SDRAM area
4986and allocates memory for use by malloc() and for the global Board
4987Info data; also, the exception vector code is copied to the low RAM
4988pages, and the final stack is set up.
4989
4990Only after this relocation will you have a "normal" C environment;
4991until that you are restricted in several ways, mostly because you are
4992running from ROM, and because the code will have to be relocated to a
4993new address in RAM.
4994
4995
4996U-Boot Porting Guide:
4997----------------------
4998
4999[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5000list, October 2002]
5001
5002
5003int main(int argc, char *argv[])
5004{
5005	sighandler_t no_more_time;
5006
5007	signal(SIGALRM, no_more_time);
5008	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5009
5010	if (available_money > available_manpower) {
5011		Pay consultant to port U-Boot;
5012		return 0;
5013	}
5014
5015	Download latest U-Boot source;
5016
5017	Subscribe to u-boot mailing list;
5018
5019	if (clueless)
5020		email("Hi, I am new to U-Boot, how do I get started?");
5021
5022	while (learning) {
5023		Read the README file in the top level directory;
5024		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5025		Read applicable doc/*.README;
5026		Read the source, Luke;
5027		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5028	}
5029
5030	if (available_money > toLocalCurrency ($2500))
5031		Buy a BDI3000;
5032	else
5033		Add a lot of aggravation and time;
5034
5035	if (a similar board exists) {	/* hopefully... */
5036		cp -a board/<similar> board/<myboard>
5037		cp include/configs/<similar>.h include/configs/<myboard>.h
5038	} else {
5039		Create your own board support subdirectory;
5040		Create your own board include/configs/<myboard>.h file;
5041	}
5042	Edit new board/<myboard> files
5043	Edit new include/configs/<myboard>.h
5044
5045	while (!accepted) {
5046		while (!running) {
5047			do {
5048				Add / modify source code;
5049			} until (compiles);
5050			Debug;
5051			if (clueless)
5052				email("Hi, I am having problems...");
5053		}
5054		Send patch file to the U-Boot email list;
5055		if (reasonable critiques)
5056			Incorporate improvements from email list code review;
5057		else
5058			Defend code as written;
5059	}
5060
5061	return 0;
5062}
5063
5064void no_more_time (int sig)
5065{
5066      hire_a_guru();
5067}
5068
5069
5070Coding Standards:
5071-----------------
5072
5073All contributions to U-Boot should conform to the Linux kernel
5074coding style; see the kernel coding style guide at
5075https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
5076script "scripts/Lindent" in your Linux kernel source directory.
5077
5078Source files originating from a different project (for example the
5079MTD subsystem) are generally exempt from these guidelines and are not
5080reformatted to ease subsequent migration to newer versions of those
5081sources.
5082
5083Please note that U-Boot is implemented in C (and to some small parts in
5084Assembler); no C++ is used, so please do not use C++ style comments (//)
5085in your code.
5086
5087Please also stick to the following formatting rules:
5088- remove any trailing white space
5089- use TAB characters for indentation and vertical alignment, not spaces
5090- make sure NOT to use DOS '\r\n' line feeds
5091- do not add more than 2 consecutive empty lines to source files
5092- do not add trailing empty lines to source files
5093
5094Submissions which do not conform to the standards may be returned
5095with a request to reformat the changes.
5096
5097
5098Submitting Patches:
5099-------------------
5100
5101Since the number of patches for U-Boot is growing, we need to
5102establish some rules. Submissions which do not conform to these rules
5103may be rejected, even when they contain important and valuable stuff.
5104
5105Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5106
5107Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5108see https://lists.denx.de/listinfo/u-boot
5109
5110When you send a patch, please include the following information with
5111it:
5112
5113* For bug fixes: a description of the bug and how your patch fixes
5114  this bug. Please try to include a way of demonstrating that the
5115  patch actually fixes something.
5116
5117* For new features: a description of the feature and your
5118  implementation.
5119
5120* A CHANGELOG entry as plaintext (separate from the patch)
5121
5122* For major contributions, add a MAINTAINERS file with your
5123  information and associated file and directory references.
5124
5125* When you add support for a new board, don't forget to add a
5126  maintainer e-mail address to the boards.cfg file, too.
5127
5128* If your patch adds new configuration options, don't forget to
5129  document these in the README file.
5130
5131* The patch itself. If you are using git (which is *strongly*
5132  recommended) you can easily generate the patch using the
5133  "git format-patch". If you then use "git send-email" to send it to
5134  the U-Boot mailing list, you will avoid most of the common problems
5135  with some other mail clients.
5136
5137  If you cannot use git, use "diff -purN OLD NEW". If your version of
5138  diff does not support these options, then get the latest version of
5139  GNU diff.
5140
5141  The current directory when running this command shall be the parent
5142  directory of the U-Boot source tree (i. e. please make sure that
5143  your patch includes sufficient directory information for the
5144  affected files).
5145
5146  We prefer patches as plain text. MIME attachments are discouraged,
5147  and compressed attachments must not be used.
5148
5149* If one logical set of modifications affects or creates several
5150  files, all these changes shall be submitted in a SINGLE patch file.
5151
5152* Changesets that contain different, unrelated modifications shall be
5153  submitted as SEPARATE patches, one patch per changeset.
5154
5155
5156Notes:
5157
5158* Before sending the patch, run the buildman script on your patched
5159  source tree and make sure that no errors or warnings are reported
5160  for any of the boards.
5161
5162* Keep your modifications to the necessary minimum: A patch
5163  containing several unrelated changes or arbitrary reformats will be
5164  returned with a request to re-formatting / split it.
5165
5166* If you modify existing code, make sure that your new code does not
5167  add to the memory footprint of the code ;-) Small is beautiful!
5168  When adding new features, these should compile conditionally only
5169  (using #ifdef), and the resulting code with the new feature
5170  disabled must not need more memory than the old code without your
5171  modification.
5172
5173* Remember that there is a size limit of 100 kB per message on the
5174  u-boot mailing list. Bigger patches will be moderated. If they are
5175  reasonable and not too big, they will be acknowledged. But patches
5176  bigger than the size limit should be avoided.
5177