xref: /openbmc/u-boot/README (revision 32151d40)
1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the Git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136  /arm			Files generic to ARM architecture
137  /m68k			Files generic to m68k architecture
138  /microblaze		Files generic to microblaze architecture
139  /mips			Files generic to MIPS architecture
140  /nds32		Files generic to NDS32 architecture
141  /nios2		Files generic to Altera NIOS2 architecture
142  /openrisc		Files generic to OpenRISC architecture
143  /powerpc		Files generic to PowerPC architecture
144  /riscv		Files generic to RISC-V architecture
145  /sandbox		Files generic to HW-independent "sandbox"
146  /sh			Files generic to SH architecture
147  /x86			Files generic to x86 architecture
148/api			Machine/arch independent API for external apps
149/board			Board dependent files
150/cmd			U-Boot commands functions
151/common			Misc architecture independent functions
152/configs		Board default configuration files
153/disk			Code for disk drive partition handling
154/doc			Documentation (don't expect too much)
155/drivers		Commonly used device drivers
156/dts			Contains Makefile for building internal U-Boot fdt.
157/examples		Example code for standalone applications, etc.
158/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159/include		Header Files
160/lib			Library routines generic to all architectures
161/Licenses		Various license files
162/net			Networking code
163/post			Power On Self Test
164/scripts		Various build scripts and Makefiles
165/test			Various unit test files
166/tools			Tools to build S-Record or U-Boot images, etc.
167
168Software Configuration:
169=======================
170
171Configuration is usually done using C preprocessor defines; the
172rationale behind that is to avoid dead code whenever possible.
173
174There are two classes of configuration variables:
175
176* Configuration _OPTIONS_:
177  These are selectable by the user and have names beginning with
178  "CONFIG_".
179
180* Configuration _SETTINGS_:
181  These depend on the hardware etc. and should not be meddled with if
182  you don't know what you're doing; they have names beginning with
183  "CONFIG_SYS_".
184
185Previously, all configuration was done by hand, which involved creating
186symbolic links and editing configuration files manually. More recently,
187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188allowing you to use the "make menuconfig" command to configure your
189build.
190
191
192Selection of Processor Architecture and Board Type:
193---------------------------------------------------
194
195For all supported boards there are ready-to-use default
196configurations available; just type "make <board_name>_defconfig".
197
198Example: For a TQM823L module type:
199
200	cd u-boot
201	make TQM823L_defconfig
202
203Note: If you're looking for the default configuration file for a board
204you're sure used to be there but is now missing, check the file
205doc/README.scrapyard for a list of no longer supported boards.
206
207Sandbox Environment:
208--------------------
209
210U-Boot can be built natively to run on a Linux host using the 'sandbox'
211board. This allows feature development which is not board- or architecture-
212specific to be undertaken on a native platform. The sandbox is also used to
213run some of U-Boot's tests.
214
215See board/sandbox/README.sandbox for more details.
216
217
218Board Initialisation Flow:
219--------------------------
220
221This is the intended start-up flow for boards. This should apply for both
222SPL and U-Boot proper (i.e. they both follow the same rules).
223
224Note: "SPL" stands for "Secondary Program Loader," which is explained in
225more detail later in this file.
226
227At present, SPL mostly uses a separate code path, but the function names
228and roles of each function are the same. Some boards or architectures
229may not conform to this.  At least most ARM boards which use
230CONFIG_SPL_FRAMEWORK conform to this.
231
232Execution typically starts with an architecture-specific (and possibly
233CPU-specific) start.S file, such as:
234
235	- arch/arm/cpu/armv7/start.S
236	- arch/powerpc/cpu/mpc83xx/start.S
237	- arch/mips/cpu/start.S
238
239and so on. From there, three functions are called; the purpose and
240limitations of each of these functions are described below.
241
242lowlevel_init():
243	- purpose: essential init to permit execution to reach board_init_f()
244	- no global_data or BSS
245	- there is no stack (ARMv7 may have one but it will soon be removed)
246	- must not set up SDRAM or use console
247	- must only do the bare minimum to allow execution to continue to
248		board_init_f()
249	- this is almost never needed
250	- return normally from this function
251
252board_init_f():
253	- purpose: set up the machine ready for running board_init_r():
254		i.e. SDRAM and serial UART
255	- global_data is available
256	- stack is in SRAM
257	- BSS is not available, so you cannot use global/static variables,
258		only stack variables and global_data
259
260	Non-SPL-specific notes:
261	- dram_init() is called to set up DRAM. If already done in SPL this
262		can do nothing
263
264	SPL-specific notes:
265	- you can override the entire board_init_f() function with your own
266		version as needed.
267	- preloader_console_init() can be called here in extremis
268	- should set up SDRAM, and anything needed to make the UART work
269	- these is no need to clear BSS, it will be done by crt0.S
270	- must return normally from this function (don't call board_init_r()
271		directly)
272
273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274this point the stack and global_data are relocated to below
275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276memory.
277
278board_init_r():
279	- purpose: main execution, common code
280	- global_data is available
281	- SDRAM is available
282	- BSS is available, all static/global variables can be used
283	- execution eventually continues to main_loop()
284
285	Non-SPL-specific notes:
286	- U-Boot is relocated to the top of memory and is now running from
287		there.
288
289	SPL-specific notes:
290	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292	- preloader_console_init() can be called here - typically this is
293		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294		spl_board_init() function containing this call
295	- loads U-Boot or (in falcon mode) Linux
296
297
298
299Configuration Options:
300----------------------
301
302Configuration depends on the combination of board and CPU type; all
303such information is kept in a configuration file
304"include/configs/<board_name>.h".
305
306Example: For a TQM823L module, all configuration settings are in
307"include/configs/TQM823L.h".
308
309
310Many of the options are named exactly as the corresponding Linux
311kernel configuration options. The intention is to make it easier to
312build a config tool - later.
313
314- ARM Platform Bus Type(CCI):
315		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316		provides full cache coherency between two clusters of multi-core
317		CPUs and I/O coherency for devices and I/O masters
318
319		CONFIG_SYS_FSL_HAS_CCI400
320
321		Defined For SoC that has cache coherent interconnect
322		CCN-400
323
324		CONFIG_SYS_FSL_HAS_CCN504
325
326		Defined for SoC that has cache coherent interconnect CCN-504
327
328The following options need to be configured:
329
330- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331
332- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333
334- 85xx CPU Options:
335		CONFIG_SYS_PPC64
336
337		Specifies that the core is a 64-bit PowerPC implementation (implements
338		the "64" category of the Power ISA). This is necessary for ePAPR
339		compliance, among other possible reasons.
340
341		CONFIG_SYS_FSL_TBCLK_DIV
342
343		Defines the core time base clock divider ratio compared to the
344		system clock.  On most PQ3 devices this is 8, on newer QorIQ
345		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
346
347		CONFIG_SYS_FSL_PCIE_COMPAT
348
349		Defines the string to utilize when trying to match PCIe device
350		tree nodes for the given platform.
351
352		CONFIG_SYS_FSL_ERRATUM_A004510
353
354		Enables a workaround for erratum A004510.  If set,
355		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
356		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
357
358		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
359		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
360
361		Defines one or two SoC revisions (low 8 bits of SVR)
362		for which the A004510 workaround should be applied.
363
364		The rest of SVR is either not relevant to the decision
365		of whether the erratum is present (e.g. p2040 versus
366		p2041) or is implied by the build target, which controls
367		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
368
369		See Freescale App Note 4493 for more information about
370		this erratum.
371
372		CONFIG_A003399_NOR_WORKAROUND
373		Enables a workaround for IFC erratum A003399. It is only
374		required during NOR boot.
375
376		CONFIG_A008044_WORKAROUND
377		Enables a workaround for T1040/T1042 erratum A008044. It is only
378		required during NAND boot and valid for Rev 1.0 SoC revision
379
380		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
381
382		This is the value to write into CCSR offset 0x18600
383		according to the A004510 workaround.
384
385		CONFIG_SYS_FSL_DSP_DDR_ADDR
386		This value denotes start offset of DDR memory which is
387		connected exclusively to the DSP cores.
388
389		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
390		This value denotes start offset of M2 memory
391		which is directly connected to the DSP core.
392
393		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
394		This value denotes start offset of M3 memory which is directly
395		connected to the DSP core.
396
397		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
398		This value denotes start offset of DSP CCSR space.
399
400		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
401		Single Source Clock is clocking mode present in some of FSL SoC's.
402		In this mode, a single differential clock is used to supply
403		clocks to the sysclock, ddrclock and usbclock.
404
405		CONFIG_SYS_CPC_REINIT_F
406		This CONFIG is defined when the CPC is configured as SRAM at the
407		time of U-Boot entry and is required to be re-initialized.
408
409		CONFIG_DEEP_SLEEP
410		Indicates this SoC supports deep sleep feature. If deep sleep is
411		supported, core will start to execute uboot when wakes up.
412
413- Generic CPU options:
414		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
415
416		Defines the endianess of the CPU. Implementation of those
417		values is arch specific.
418
419		CONFIG_SYS_FSL_DDR
420		Freescale DDR driver in use. This type of DDR controller is
421		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
422		SoCs.
423
424		CONFIG_SYS_FSL_DDR_ADDR
425		Freescale DDR memory-mapped register base.
426
427		CONFIG_SYS_FSL_DDR_EMU
428		Specify emulator support for DDR. Some DDR features such as
429		deskew training are not available.
430
431		CONFIG_SYS_FSL_DDRC_GEN1
432		Freescale DDR1 controller.
433
434		CONFIG_SYS_FSL_DDRC_GEN2
435		Freescale DDR2 controller.
436
437		CONFIG_SYS_FSL_DDRC_GEN3
438		Freescale DDR3 controller.
439
440		CONFIG_SYS_FSL_DDRC_GEN4
441		Freescale DDR4 controller.
442
443		CONFIG_SYS_FSL_DDRC_ARM_GEN3
444		Freescale DDR3 controller for ARM-based SoCs.
445
446		CONFIG_SYS_FSL_DDR1
447		Board config to use DDR1. It can be enabled for SoCs with
448		Freescale DDR1 or DDR2 controllers, depending on the board
449		implemetation.
450
451		CONFIG_SYS_FSL_DDR2
452		Board config to use DDR2. It can be enabled for SoCs with
453		Freescale DDR2 or DDR3 controllers, depending on the board
454		implementation.
455
456		CONFIG_SYS_FSL_DDR3
457		Board config to use DDR3. It can be enabled for SoCs with
458		Freescale DDR3 or DDR3L controllers.
459
460		CONFIG_SYS_FSL_DDR3L
461		Board config to use DDR3L. It can be enabled for SoCs with
462		DDR3L controllers.
463
464		CONFIG_SYS_FSL_DDR4
465		Board config to use DDR4. It can be enabled for SoCs with
466		DDR4 controllers.
467
468		CONFIG_SYS_FSL_IFC_BE
469		Defines the IFC controller register space as Big Endian
470
471		CONFIG_SYS_FSL_IFC_LE
472		Defines the IFC controller register space as Little Endian
473
474		CONFIG_SYS_FSL_IFC_CLK_DIV
475		Defines divider of platform clock(clock input to IFC controller).
476
477		CONFIG_SYS_FSL_LBC_CLK_DIV
478		Defines divider of platform clock(clock input to eLBC controller).
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SPL_FSL_PBL
490		It adds a target to create boot binary having SPL binary in PBI format
491		concatenated with u-boot binary.
492
493		CONFIG_SYS_FSL_DDR_BE
494		Defines the DDR controller register space as Big Endian
495
496		CONFIG_SYS_FSL_DDR_LE
497		Defines the DDR controller register space as Little Endian
498
499		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500		Physical address from the view of DDR controllers. It is the
501		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
502		it could be different for ARM SoCs.
503
504		CONFIG_SYS_FSL_DDR_INTLV_256B
505		DDR controller interleaving on 256-byte. This is a special
506		interleaving mode, handled by Dickens for Freescale layerscape
507		SoCs with ARM core.
508
509		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510		Number of controllers used as main memory.
511
512		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513		Number of controllers used for other than main memory.
514
515		CONFIG_SYS_FSL_HAS_DP_DDR
516		Defines the SoC has DP-DDR used for DPAA.
517
518		CONFIG_SYS_FSL_SEC_BE
519		Defines the SEC controller register space as Big Endian
520
521		CONFIG_SYS_FSL_SEC_LE
522		Defines the SEC controller register space as Little Endian
523
524- MIPS CPU options:
525		CONFIG_SYS_INIT_SP_OFFSET
526
527		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528		pointer. This is needed for the temporary stack before
529		relocation.
530
531		CONFIG_SYS_MIPS_CACHE_MODE
532
533		Cache operation mode for the MIPS CPU.
534		See also arch/mips/include/asm/mipsregs.h.
535		Possible values are:
536			CONF_CM_CACHABLE_NO_WA
537			CONF_CM_CACHABLE_WA
538			CONF_CM_UNCACHED
539			CONF_CM_CACHABLE_NONCOHERENT
540			CONF_CM_CACHABLE_CE
541			CONF_CM_CACHABLE_COW
542			CONF_CM_CACHABLE_CUW
543			CONF_CM_CACHABLE_ACCELERATED
544
545		CONFIG_SYS_XWAY_EBU_BOOTCFG
546
547		Special option for Lantiq XWAY SoCs for booting from NOR flash.
548		See also arch/mips/cpu/mips32/start.S.
549
550		CONFIG_XWAY_SWAP_BYTES
551
552		Enable compilation of tools/xway-swap-bytes needed for Lantiq
553		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
554		be swapped if a flash programmer is used.
555
556- ARM options:
557		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
558
559		Select high exception vectors of the ARM core, e.g., do not
560		clear the V bit of the c1 register of CP15.
561
562		COUNTER_FREQUENCY
563		Generic timer clock source frequency.
564
565		COUNTER_FREQUENCY_REAL
566		Generic timer clock source frequency if the real clock is
567		different from COUNTER_FREQUENCY, and can only be determined
568		at run time.
569
570- Tegra SoC options:
571		CONFIG_TEGRA_SUPPORT_NON_SECURE
572
573		Support executing U-Boot in non-secure (NS) mode. Certain
574		impossible actions will be skipped if the CPU is in NS mode,
575		such as ARM architectural timer initialization.
576
577- Linux Kernel Interface:
578		CONFIG_CLOCKS_IN_MHZ
579
580		U-Boot stores all clock information in Hz
581		internally. For binary compatibility with older Linux
582		kernels (which expect the clocks passed in the
583		bd_info data to be in MHz) the environment variable
584		"clocks_in_mhz" can be defined so that U-Boot
585		converts clock data to MHZ before passing it to the
586		Linux kernel.
587		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
588		"clocks_in_mhz=1" is automatically included in the
589		default environment.
590
591		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
592
593		When transferring memsize parameter to Linux, some versions
594		expect it to be in bytes, others in MB.
595		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
596
597		CONFIG_OF_LIBFDT
598
599		New kernel versions are expecting firmware settings to be
600		passed using flattened device trees (based on open firmware
601		concepts).
602
603		CONFIG_OF_LIBFDT
604		 * New libfdt-based support
605		 * Adds the "fdt" command
606		 * The bootm command automatically updates the fdt
607
608		OF_TBCLK - The timebase frequency.
609		OF_STDOUT_PATH - The path to the console device
610
611		boards with QUICC Engines require OF_QE to set UCC MAC
612		addresses
613
614		CONFIG_OF_BOARD_SETUP
615
616		Board code has addition modification that it wants to make
617		to the flat device tree before handing it off to the kernel
618
619		CONFIG_OF_SYSTEM_SETUP
620
621		Other code has addition modification that it wants to make
622		to the flat device tree before handing it off to the kernel.
623		This causes ft_system_setup() to be called before booting
624		the kernel.
625
626		CONFIG_OF_IDE_FIXUP
627
628		U-Boot can detect if an IDE device is present or not.
629		If not, and this new config option is activated, U-Boot
630		removes the ATA node from the DTS before booting Linux,
631		so the Linux IDE driver does not probe the device and
632		crash. This is needed for buggy hardware (uc101) where
633		no pull down resistor is connected to the signal IDE5V_DD7.
634
635		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
636
637		This setting is mandatory for all boards that have only one
638		machine type and must be used to specify the machine type
639		number as it appears in the ARM machine registry
640		(see http://www.arm.linux.org.uk/developer/machines/).
641		Only boards that have multiple machine types supported
642		in a single configuration file and the machine type is
643		runtime discoverable, do not have to use this setting.
644
645- vxWorks boot parameters:
646
647		bootvx constructs a valid bootline using the following
648		environments variables: bootdev, bootfile, ipaddr, netmask,
649		serverip, gatewayip, hostname, othbootargs.
650		It loads the vxWorks image pointed bootfile.
651
652		Note: If a "bootargs" environment is defined, it will overwride
653		the defaults discussed just above.
654
655- Cache Configuration:
656		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
657		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
658		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
659
660- Cache Configuration for ARM:
661		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
662				      controller
663		CONFIG_SYS_PL310_BASE - Physical base address of PL310
664					controller register space
665
666- Serial Ports:
667		CONFIG_PL010_SERIAL
668
669		Define this if you want support for Amba PrimeCell PL010 UARTs.
670
671		CONFIG_PL011_SERIAL
672
673		Define this if you want support for Amba PrimeCell PL011 UARTs.
674
675		CONFIG_PL011_CLOCK
676
677		If you have Amba PrimeCell PL011 UARTs, set this variable to
678		the clock speed of the UARTs.
679
680		CONFIG_PL01x_PORTS
681
682		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
683		define this to a list of base addresses for each (supported)
684		port. See e.g. include/configs/versatile.h
685
686		CONFIG_SERIAL_HW_FLOW_CONTROL
687
688		Define this variable to enable hw flow control in serial driver.
689		Current user of this option is drivers/serial/nsl16550.c driver
690
691- Console Baudrate:
692		CONFIG_BAUDRATE - in bps
693		Select one of the baudrates listed in
694		CONFIG_SYS_BAUDRATE_TABLE, see below.
695
696- Autoboot Command:
697		CONFIG_BOOTCOMMAND
698		Only needed when CONFIG_BOOTDELAY is enabled;
699		define a command string that is automatically executed
700		when no character is read on the console interface
701		within "Boot Delay" after reset.
702
703		CONFIG_RAMBOOT and CONFIG_NFSBOOT
704		The value of these goes into the environment as
705		"ramboot" and "nfsboot" respectively, and can be used
706		as a convenience, when switching between booting from
707		RAM and NFS.
708
709- Pre-Boot Commands:
710		CONFIG_PREBOOT
711
712		When this option is #defined, the existence of the
713		environment variable "preboot" will be checked
714		immediately before starting the CONFIG_BOOTDELAY
715		countdown and/or running the auto-boot command resp.
716		entering interactive mode.
717
718		This feature is especially useful when "preboot" is
719		automatically generated or modified. For an example
720		see the LWMON board specific code: here "preboot" is
721		modified when the user holds down a certain
722		combination of keys on the (special) keyboard when
723		booting the systems
724
725- Serial Download Echo Mode:
726		CONFIG_LOADS_ECHO
727		If defined to 1, all characters received during a
728		serial download (using the "loads" command) are
729		echoed back. This might be needed by some terminal
730		emulations (like "cu"), but may as well just take
731		time on others. This setting #define's the initial
732		value of the "loads_echo" environment variable.
733
734- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
735		CONFIG_KGDB_BAUDRATE
736		Select one of the baudrates listed in
737		CONFIG_SYS_BAUDRATE_TABLE, see below.
738
739- Removal of commands
740		If no commands are needed to boot, you can disable
741		CONFIG_CMDLINE to remove them. In this case, the command line
742		will not be available, and when U-Boot wants to execute the
743		boot command (on start-up) it will call board_run_command()
744		instead. This can reduce image size significantly for very
745		simple boot procedures.
746
747- Regular expression support:
748		CONFIG_REGEX
749		If this variable is defined, U-Boot is linked against
750		the SLRE (Super Light Regular Expression) library,
751		which adds regex support to some commands, as for
752		example "env grep" and "setexpr".
753
754- Device tree:
755		CONFIG_OF_CONTROL
756		If this variable is defined, U-Boot will use a device tree
757		to configure its devices, instead of relying on statically
758		compiled #defines in the board file. This option is
759		experimental and only available on a few boards. The device
760		tree is available in the global data as gd->fdt_blob.
761
762		U-Boot needs to get its device tree from somewhere. This can
763		be done using one of the three options below:
764
765		CONFIG_OF_EMBED
766		If this variable is defined, U-Boot will embed a device tree
767		binary in its image. This device tree file should be in the
768		board directory and called <soc>-<board>.dts. The binary file
769		is then picked up in board_init_f() and made available through
770		the global data structure as gd->fdt_blob.
771
772		CONFIG_OF_SEPARATE
773		If this variable is defined, U-Boot will build a device tree
774		binary. It will be called u-boot.dtb. Architecture-specific
775		code will locate it at run-time. Generally this works by:
776
777			cat u-boot.bin u-boot.dtb >image.bin
778
779		and in fact, U-Boot does this for you, creating a file called
780		u-boot-dtb.bin which is useful in the common case. You can
781		still use the individual files if you need something more
782		exotic.
783
784		CONFIG_OF_BOARD
785		If this variable is defined, U-Boot will use the device tree
786		provided by the board at runtime instead of embedding one with
787		the image. Only boards defining board_fdt_blob_setup() support
788		this option (see include/fdtdec.h file).
789
790- Watchdog:
791		CONFIG_WATCHDOG
792		If this variable is defined, it enables watchdog
793		support for the SoC. There must be support in the SoC
794		specific code for a watchdog. For the 8xx
795		CPUs, the SIU Watchdog feature is enabled in the SYPCR
796		register.  When supported for a specific SoC is
797		available, then no further board specific code should
798		be needed to use it.
799
800		CONFIG_HW_WATCHDOG
801		When using a watchdog circuitry external to the used
802		SoC, then define this variable and provide board
803		specific code for the "hw_watchdog_reset" function.
804
805		CONFIG_AT91_HW_WDT_TIMEOUT
806		specify the timeout in seconds. default 2 seconds.
807
808- Real-Time Clock:
809
810		When CONFIG_CMD_DATE is selected, the type of the RTC
811		has to be selected, too. Define exactly one of the
812		following options:
813
814		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
815		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
816		CONFIG_RTC_MC146818	- use MC146818 RTC
817		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
818		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
819		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
820		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
821		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
822		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
823		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
824		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
825		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
826					  RV3029 RTC.
827
828		Note that if the RTC uses I2C, then the I2C interface
829		must also be configured. See I2C Support, below.
830
831- GPIO Support:
832		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
833
834		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
835		chip-ngpio pairs that tell the PCA953X driver the number of
836		pins supported by a particular chip.
837
838		Note that if the GPIO device uses I2C, then the I2C interface
839		must also be configured. See I2C Support, below.
840
841- I/O tracing:
842		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
843		accesses and can checksum them or write a list of them out
844		to memory. See the 'iotrace' command for details. This is
845		useful for testing device drivers since it can confirm that
846		the driver behaves the same way before and after a code
847		change. Currently this is supported on sandbox and arm. To
848		add support for your architecture, add '#include <iotrace.h>'
849		to the bottom of arch/<arch>/include/asm/io.h and test.
850
851		Example output from the 'iotrace stats' command is below.
852		Note that if the trace buffer is exhausted, the checksum will
853		still continue to operate.
854
855			iotrace is enabled
856			Start:  10000000	(buffer start address)
857			Size:   00010000	(buffer size)
858			Offset: 00000120	(current buffer offset)
859			Output: 10000120	(start + offset)
860			Count:  00000018	(number of trace records)
861			CRC32:  9526fb66	(CRC32 of all trace records)
862
863- Timestamp Support:
864
865		When CONFIG_TIMESTAMP is selected, the timestamp
866		(date and time) of an image is printed by image
867		commands like bootm or iminfo. This option is
868		automatically enabled when you select CONFIG_CMD_DATE .
869
870- Partition Labels (disklabels) Supported:
871		Zero or more of the following:
872		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
873		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
874		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
875				       bootloader.  Note 2TB partition limit; see
876				       disk/part_efi.c
877		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
878
879		If IDE or SCSI support is enabled (CONFIG_IDE or
880		CONFIG_SCSI) you must configure support for at
881		least one non-MTD partition type as well.
882
883- IDE Reset method:
884		CONFIG_IDE_RESET_ROUTINE - this is defined in several
885		board configurations files but used nowhere!
886
887		CONFIG_IDE_RESET - is this is defined, IDE Reset will
888		be performed by calling the function
889			ide_set_reset(int reset)
890		which has to be defined in a board specific file
891
892- ATAPI Support:
893		CONFIG_ATAPI
894
895		Set this to enable ATAPI support.
896
897- LBA48 Support
898		CONFIG_LBA48
899
900		Set this to enable support for disks larger than 137GB
901		Also look at CONFIG_SYS_64BIT_LBA.
902		Whithout these , LBA48 support uses 32bit variables and will 'only'
903		support disks up to 2.1TB.
904
905		CONFIG_SYS_64BIT_LBA:
906			When enabled, makes the IDE subsystem use 64bit sector addresses.
907			Default is 32bit.
908
909- SCSI Support:
910		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
911		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
912		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
913		maximum numbers of LUNs, SCSI ID's and target
914		devices.
915
916		The environment variable 'scsidevs' is set to the number of
917		SCSI devices found during the last scan.
918
919- NETWORK Support (PCI):
920		CONFIG_E1000
921		Support for Intel 8254x/8257x gigabit chips.
922
923		CONFIG_E1000_SPI
924		Utility code for direct access to the SPI bus on Intel 8257x.
925		This does not do anything useful unless you set at least one
926		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
927
928		CONFIG_E1000_SPI_GENERIC
929		Allow generic access to the SPI bus on the Intel 8257x, for
930		example with the "sspi" command.
931
932		CONFIG_EEPRO100
933		Support for Intel 82557/82559/82559ER chips.
934		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
935		write routine for first time initialisation.
936
937		CONFIG_TULIP
938		Support for Digital 2114x chips.
939		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
940		modem chip initialisation (KS8761/QS6611).
941
942		CONFIG_NATSEMI
943		Support for National dp83815 chips.
944
945		CONFIG_NS8382X
946		Support for National dp8382[01] gigabit chips.
947
948- NETWORK Support (other):
949
950		CONFIG_DRIVER_AT91EMAC
951		Support for AT91RM9200 EMAC.
952
953			CONFIG_RMII
954			Define this to use reduced MII inteface
955
956			CONFIG_DRIVER_AT91EMAC_QUIET
957			If this defined, the driver is quiet.
958			The driver doen't show link status messages.
959
960		CONFIG_CALXEDA_XGMAC
961		Support for the Calxeda XGMAC device
962
963		CONFIG_LAN91C96
964		Support for SMSC's LAN91C96 chips.
965
966			CONFIG_LAN91C96_USE_32_BIT
967			Define this to enable 32 bit addressing
968
969		CONFIG_SMC91111
970		Support for SMSC's LAN91C111 chip
971
972			CONFIG_SMC91111_BASE
973			Define this to hold the physical address
974			of the device (I/O space)
975
976			CONFIG_SMC_USE_32_BIT
977			Define this if data bus is 32 bits
978
979			CONFIG_SMC_USE_IOFUNCS
980			Define this to use i/o functions instead of macros
981			(some hardware wont work with macros)
982
983		CONFIG_DRIVER_TI_EMAC
984		Support for davinci emac
985
986			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
987			Define this if you have more then 3 PHYs.
988
989		CONFIG_FTGMAC100
990		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
991
992			CONFIG_FTGMAC100_EGIGA
993			Define this to use GE link update with gigabit PHY.
994			Define this if FTGMAC100 is connected to gigabit PHY.
995			If your system has 10/100 PHY only, it might not occur
996			wrong behavior. Because PHY usually return timeout or
997			useless data when polling gigabit status and gigabit
998			control registers. This behavior won't affect the
999			correctnessof 10/100 link speed update.
1000
1001		CONFIG_SH_ETHER
1002		Support for Renesas on-chip Ethernet controller
1003
1004			CONFIG_SH_ETHER_USE_PORT
1005			Define the number of ports to be used
1006
1007			CONFIG_SH_ETHER_PHY_ADDR
1008			Define the ETH PHY's address
1009
1010			CONFIG_SH_ETHER_CACHE_WRITEBACK
1011			If this option is set, the driver enables cache flush.
1012
1013- PWM Support:
1014		CONFIG_PWM_IMX
1015		Support for PWM module on the imx6.
1016
1017- TPM Support:
1018		CONFIG_TPM
1019		Support TPM devices.
1020
1021		CONFIG_TPM_TIS_INFINEON
1022		Support for Infineon i2c bus TPM devices. Only one device
1023		per system is supported at this time.
1024
1025			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1026			Define the burst count bytes upper limit
1027
1028		CONFIG_TPM_ST33ZP24
1029		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1030
1031			CONFIG_TPM_ST33ZP24_I2C
1032			Support for STMicroelectronics ST33ZP24 I2C devices.
1033			Requires TPM_ST33ZP24 and I2C.
1034
1035			CONFIG_TPM_ST33ZP24_SPI
1036			Support for STMicroelectronics ST33ZP24 SPI devices.
1037			Requires TPM_ST33ZP24 and SPI.
1038
1039		CONFIG_TPM_ATMEL_TWI
1040		Support for Atmel TWI TPM device. Requires I2C support.
1041
1042		CONFIG_TPM_TIS_LPC
1043		Support for generic parallel port TPM devices. Only one device
1044		per system is supported at this time.
1045
1046			CONFIG_TPM_TIS_BASE_ADDRESS
1047			Base address where the generic TPM device is mapped
1048			to. Contemporary x86 systems usually map it at
1049			0xfed40000.
1050
1051		CONFIG_TPM
1052		Define this to enable the TPM support library which provides
1053		functional interfaces to some TPM commands.
1054		Requires support for a TPM device.
1055
1056		CONFIG_TPM_AUTH_SESSIONS
1057		Define this to enable authorized functions in the TPM library.
1058		Requires CONFIG_TPM and CONFIG_SHA1.
1059
1060- USB Support:
1061		At the moment only the UHCI host controller is
1062		supported (PIP405, MIP405); define
1063		CONFIG_USB_UHCI to enable it.
1064		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1065		and define CONFIG_USB_STORAGE to enable the USB
1066		storage devices.
1067		Note:
1068		Supported are USB Keyboards and USB Floppy drives
1069		(TEAC FD-05PUB).
1070
1071		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1072		txfilltuning field in the EHCI controller on reset.
1073
1074		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1075		HW module registers.
1076
1077- USB Device:
1078		Define the below if you wish to use the USB console.
1079		Once firmware is rebuilt from a serial console issue the
1080		command "setenv stdin usbtty; setenv stdout usbtty" and
1081		attach your USB cable. The Unix command "dmesg" should print
1082		it has found a new device. The environment variable usbtty
1083		can be set to gserial or cdc_acm to enable your device to
1084		appear to a USB host as a Linux gserial device or a
1085		Common Device Class Abstract Control Model serial device.
1086		If you select usbtty = gserial you should be able to enumerate
1087		a Linux host by
1088		# modprobe usbserial vendor=0xVendorID product=0xProductID
1089		else if using cdc_acm, simply setting the environment
1090		variable usbtty to be cdc_acm should suffice. The following
1091		might be defined in YourBoardName.h
1092
1093			CONFIG_USB_DEVICE
1094			Define this to build a UDC device
1095
1096			CONFIG_USB_TTY
1097			Define this to have a tty type of device available to
1098			talk to the UDC device
1099
1100			CONFIG_USBD_HS
1101			Define this to enable the high speed support for usb
1102			device and usbtty. If this feature is enabled, a routine
1103			int is_usbd_high_speed(void)
1104			also needs to be defined by the driver to dynamically poll
1105			whether the enumeration has succeded at high speed or full
1106			speed.
1107
1108			CONFIG_SYS_CONSOLE_IS_IN_ENV
1109			Define this if you want stdin, stdout &/or stderr to
1110			be set to usbtty.
1111
1112		If you have a USB-IF assigned VendorID then you may wish to
1113		define your own vendor specific values either in BoardName.h
1114		or directly in usbd_vendor_info.h. If you don't define
1115		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1116		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1117		should pretend to be a Linux device to it's target host.
1118
1119			CONFIG_USBD_MANUFACTURER
1120			Define this string as the name of your company for
1121			- CONFIG_USBD_MANUFACTURER "my company"
1122
1123			CONFIG_USBD_PRODUCT_NAME
1124			Define this string as the name of your product
1125			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1126
1127			CONFIG_USBD_VENDORID
1128			Define this as your assigned Vendor ID from the USB
1129			Implementors Forum. This *must* be a genuine Vendor ID
1130			to avoid polluting the USB namespace.
1131			- CONFIG_USBD_VENDORID 0xFFFF
1132
1133			CONFIG_USBD_PRODUCTID
1134			Define this as the unique Product ID
1135			for your device
1136			- CONFIG_USBD_PRODUCTID 0xFFFF
1137
1138- ULPI Layer Support:
1139		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1140		the generic ULPI layer. The generic layer accesses the ULPI PHY
1141		via the platform viewport, so you need both the genric layer and
1142		the viewport enabled. Currently only Chipidea/ARC based
1143		viewport is supported.
1144		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1145		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1146		If your ULPI phy needs a different reference clock than the
1147		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1148		the appropriate value in Hz.
1149
1150- MMC Support:
1151		The MMC controller on the Intel PXA is supported. To
1152		enable this define CONFIG_MMC. The MMC can be
1153		accessed from the boot prompt by mapping the device
1154		to physical memory similar to flash. Command line is
1155		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1156		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1157
1158		CONFIG_SH_MMCIF
1159		Support for Renesas on-chip MMCIF controller
1160
1161			CONFIG_SH_MMCIF_ADDR
1162			Define the base address of MMCIF registers
1163
1164			CONFIG_SH_MMCIF_CLK
1165			Define the clock frequency for MMCIF
1166
1167		CONFIG_SUPPORT_EMMC_BOOT
1168		Enable some additional features of the eMMC boot partitions.
1169
1170- USB Device Firmware Update (DFU) class support:
1171		CONFIG_DFU_OVER_USB
1172		This enables the USB portion of the DFU USB class
1173
1174		CONFIG_DFU_MMC
1175		This enables support for exposing (e)MMC devices via DFU.
1176
1177		CONFIG_DFU_NAND
1178		This enables support for exposing NAND devices via DFU.
1179
1180		CONFIG_DFU_RAM
1181		This enables support for exposing RAM via DFU.
1182		Note: DFU spec refer to non-volatile memory usage, but
1183		allow usages beyond the scope of spec - here RAM usage,
1184		one that would help mostly the developer.
1185
1186		CONFIG_SYS_DFU_DATA_BUF_SIZE
1187		Dfu transfer uses a buffer before writing data to the
1188		raw storage device. Make the size (in bytes) of this buffer
1189		configurable. The size of this buffer is also configurable
1190		through the "dfu_bufsiz" environment variable.
1191
1192		CONFIG_SYS_DFU_MAX_FILE_SIZE
1193		When updating files rather than the raw storage device,
1194		we use a static buffer to copy the file into and then write
1195		the buffer once we've been given the whole file.  Define
1196		this to the maximum filesize (in bytes) for the buffer.
1197		Default is 4 MiB if undefined.
1198
1199		DFU_DEFAULT_POLL_TIMEOUT
1200		Poll timeout [ms], is the timeout a device can send to the
1201		host. The host must wait for this timeout before sending
1202		a subsequent DFU_GET_STATUS request to the device.
1203
1204		DFU_MANIFEST_POLL_TIMEOUT
1205		Poll timeout [ms], which the device sends to the host when
1206		entering dfuMANIFEST state. Host waits this timeout, before
1207		sending again an USB request to the device.
1208
1209- Journaling Flash filesystem support:
1210		CONFIG_JFFS2_NAND
1211		Define these for a default partition on a NAND device
1212
1213		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1214		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1215		Define these for a default partition on a NOR device
1216
1217- Keyboard Support:
1218		See Kconfig help for available keyboard drivers.
1219
1220		CONFIG_KEYBOARD
1221
1222		Define this to enable a custom keyboard support.
1223		This simply calls drv_keyboard_init() which must be
1224		defined in your board-specific files. This option is deprecated
1225		and is only used by novena. For new boards, use driver model
1226		instead.
1227
1228- Video support:
1229		CONFIG_FSL_DIU_FB
1230		Enable the Freescale DIU video driver.	Reference boards for
1231		SOCs that have a DIU should define this macro to enable DIU
1232		support, and should also define these other macros:
1233
1234			CONFIG_SYS_DIU_ADDR
1235			CONFIG_VIDEO
1236			CONFIG_CFB_CONSOLE
1237			CONFIG_VIDEO_SW_CURSOR
1238			CONFIG_VGA_AS_SINGLE_DEVICE
1239			CONFIG_VIDEO_LOGO
1240			CONFIG_VIDEO_BMP_LOGO
1241
1242		The DIU driver will look for the 'video-mode' environment
1243		variable, and if defined, enable the DIU as a console during
1244		boot.  See the documentation file doc/README.video for a
1245		description of this variable.
1246
1247- LCD Support:	CONFIG_LCD
1248
1249		Define this to enable LCD support (for output to LCD
1250		display); also select one of the supported displays
1251		by defining one of these:
1252
1253		CONFIG_ATMEL_LCD:
1254
1255			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1256
1257		CONFIG_NEC_NL6448AC33:
1258
1259			NEC NL6448AC33-18. Active, color, single scan.
1260
1261		CONFIG_NEC_NL6448BC20
1262
1263			NEC NL6448BC20-08. 6.5", 640x480.
1264			Active, color, single scan.
1265
1266		CONFIG_NEC_NL6448BC33_54
1267
1268			NEC NL6448BC33-54. 10.4", 640x480.
1269			Active, color, single scan.
1270
1271		CONFIG_SHARP_16x9
1272
1273			Sharp 320x240. Active, color, single scan.
1274			It isn't 16x9, and I am not sure what it is.
1275
1276		CONFIG_SHARP_LQ64D341
1277
1278			Sharp LQ64D341 display, 640x480.
1279			Active, color, single scan.
1280
1281		CONFIG_HLD1045
1282
1283			HLD1045 display, 640x480.
1284			Active, color, single scan.
1285
1286		CONFIG_OPTREX_BW
1287
1288			Optrex	 CBL50840-2 NF-FW 99 22 M5
1289			or
1290			Hitachi	 LMG6912RPFC-00T
1291			or
1292			Hitachi	 SP14Q002
1293
1294			320x240. Black & white.
1295
1296		CONFIG_LCD_ALIGNMENT
1297
1298		Normally the LCD is page-aligned (typically 4KB). If this is
1299		defined then the LCD will be aligned to this value instead.
1300		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1301		here, since it is cheaper to change data cache settings on
1302		a per-section basis.
1303
1304
1305		CONFIG_LCD_ROTATION
1306
1307		Sometimes, for example if the display is mounted in portrait
1308		mode or even if it's mounted landscape but rotated by 180degree,
1309		we need to rotate our content of the display relative to the
1310		framebuffer, so that user can read the messages which are
1311		printed out.
1312		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1313		initialized with a given rotation from "vl_rot" out of
1314		"vidinfo_t" which is provided by the board specific code.
1315		The value for vl_rot is coded as following (matching to
1316		fbcon=rotate:<n> linux-kernel commandline):
1317		0 = no rotation respectively 0 degree
1318		1 = 90 degree rotation
1319		2 = 180 degree rotation
1320		3 = 270 degree rotation
1321
1322		If CONFIG_LCD_ROTATION is not defined, the console will be
1323		initialized with 0degree rotation.
1324
1325		CONFIG_LCD_BMP_RLE8
1326
1327		Support drawing of RLE8-compressed bitmaps on the LCD.
1328
1329		CONFIG_I2C_EDID
1330
1331		Enables an 'i2c edid' command which can read EDID
1332		information over I2C from an attached LCD display.
1333
1334- Splash Screen Support: CONFIG_SPLASH_SCREEN
1335
1336		If this option is set, the environment is checked for
1337		a variable "splashimage". If found, the usual display
1338		of logo, copyright and system information on the LCD
1339		is suppressed and the BMP image at the address
1340		specified in "splashimage" is loaded instead. The
1341		console is redirected to the "nulldev", too. This
1342		allows for a "silent" boot where a splash screen is
1343		loaded very quickly after power-on.
1344
1345		CONFIG_SPLASHIMAGE_GUARD
1346
1347		If this option is set, then U-Boot will prevent the environment
1348		variable "splashimage" from being set to a problematic address
1349		(see doc/README.displaying-bmps).
1350		This option is useful for targets where, due to alignment
1351		restrictions, an improperly aligned BMP image will cause a data
1352		abort. If you think you will not have problems with unaligned
1353		accesses (for example because your toolchain prevents them)
1354		there is no need to set this option.
1355
1356		CONFIG_SPLASH_SCREEN_ALIGN
1357
1358		If this option is set the splash image can be freely positioned
1359		on the screen. Environment variable "splashpos" specifies the
1360		position as "x,y". If a positive number is given it is used as
1361		number of pixel from left/top. If a negative number is given it
1362		is used as number of pixel from right/bottom. You can also
1363		specify 'm' for centering the image.
1364
1365		Example:
1366		setenv splashpos m,m
1367			=> image at center of screen
1368
1369		setenv splashpos 30,20
1370			=> image at x = 30 and y = 20
1371
1372		setenv splashpos -10,m
1373			=> vertically centered image
1374			   at x = dspWidth - bmpWidth - 9
1375
1376- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1377
1378		If this option is set, additionally to standard BMP
1379		images, gzipped BMP images can be displayed via the
1380		splashscreen support or the bmp command.
1381
1382- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1383
1384		If this option is set, 8-bit RLE compressed BMP images
1385		can be displayed via the splashscreen support or the
1386		bmp command.
1387
1388- Compression support:
1389		CONFIG_GZIP
1390
1391		Enabled by default to support gzip compressed images.
1392
1393		CONFIG_BZIP2
1394
1395		If this option is set, support for bzip2 compressed
1396		images is included. If not, only uncompressed and gzip
1397		compressed images are supported.
1398
1399		NOTE: the bzip2 algorithm requires a lot of RAM, so
1400		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1401		be at least 4MB.
1402
1403- MII/PHY support:
1404		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1405
1406		The clock frequency of the MII bus
1407
1408		CONFIG_PHY_RESET_DELAY
1409
1410		Some PHY like Intel LXT971A need extra delay after
1411		reset before any MII register access is possible.
1412		For such PHY, set this option to the usec delay
1413		required. (minimum 300usec for LXT971A)
1414
1415		CONFIG_PHY_CMD_DELAY (ppc4xx)
1416
1417		Some PHY like Intel LXT971A need extra delay after
1418		command issued before MII status register can be read
1419
1420- IP address:
1421		CONFIG_IPADDR
1422
1423		Define a default value for the IP address to use for
1424		the default Ethernet interface, in case this is not
1425		determined through e.g. bootp.
1426		(Environment variable "ipaddr")
1427
1428- Server IP address:
1429		CONFIG_SERVERIP
1430
1431		Defines a default value for the IP address of a TFTP
1432		server to contact when using the "tftboot" command.
1433		(Environment variable "serverip")
1434
1435		CONFIG_KEEP_SERVERADDR
1436
1437		Keeps the server's MAC address, in the env 'serveraddr'
1438		for passing to bootargs (like Linux's netconsole option)
1439
1440- Gateway IP address:
1441		CONFIG_GATEWAYIP
1442
1443		Defines a default value for the IP address of the
1444		default router where packets to other networks are
1445		sent to.
1446		(Environment variable "gatewayip")
1447
1448- Subnet mask:
1449		CONFIG_NETMASK
1450
1451		Defines a default value for the subnet mask (or
1452		routing prefix) which is used to determine if an IP
1453		address belongs to the local subnet or needs to be
1454		forwarded through a router.
1455		(Environment variable "netmask")
1456
1457- Multicast TFTP Mode:
1458		CONFIG_MCAST_TFTP
1459
1460		Defines whether you want to support multicast TFTP as per
1461		rfc-2090; for example to work with atftp.  Lets lots of targets
1462		tftp down the same boot image concurrently.  Note: the Ethernet
1463		driver in use must provide a function: mcast() to join/leave a
1464		multicast group.
1465
1466- BOOTP Recovery Mode:
1467		CONFIG_BOOTP_RANDOM_DELAY
1468
1469		If you have many targets in a network that try to
1470		boot using BOOTP, you may want to avoid that all
1471		systems send out BOOTP requests at precisely the same
1472		moment (which would happen for instance at recovery
1473		from a power failure, when all systems will try to
1474		boot, thus flooding the BOOTP server. Defining
1475		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1476		inserted before sending out BOOTP requests. The
1477		following delays are inserted then:
1478
1479		1st BOOTP request:	delay 0 ... 1 sec
1480		2nd BOOTP request:	delay 0 ... 2 sec
1481		3rd BOOTP request:	delay 0 ... 4 sec
1482		4th and following
1483		BOOTP requests:		delay 0 ... 8 sec
1484
1485		CONFIG_BOOTP_ID_CACHE_SIZE
1486
1487		BOOTP packets are uniquely identified using a 32-bit ID. The
1488		server will copy the ID from client requests to responses and
1489		U-Boot will use this to determine if it is the destination of
1490		an incoming response. Some servers will check that addresses
1491		aren't in use before handing them out (usually using an ARP
1492		ping) and therefore take up to a few hundred milliseconds to
1493		respond. Network congestion may also influence the time it
1494		takes for a response to make it back to the client. If that
1495		time is too long, U-Boot will retransmit requests. In order
1496		to allow earlier responses to still be accepted after these
1497		retransmissions, U-Boot's BOOTP client keeps a small cache of
1498		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1499		cache. The default is to keep IDs for up to four outstanding
1500		requests. Increasing this will allow U-Boot to accept offers
1501		from a BOOTP client in networks with unusually high latency.
1502
1503- DHCP Advanced Options:
1504		You can fine tune the DHCP functionality by defining
1505		CONFIG_BOOTP_* symbols:
1506
1507		CONFIG_BOOTP_NISDOMAIN
1508		CONFIG_BOOTP_BOOTFILESIZE
1509		CONFIG_BOOTP_SEND_HOSTNAME
1510		CONFIG_BOOTP_NTPSERVER
1511		CONFIG_BOOTP_TIMEOFFSET
1512		CONFIG_BOOTP_VENDOREX
1513		CONFIG_BOOTP_MAY_FAIL
1514
1515		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1516		environment variable, not the BOOTP server.
1517
1518		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1519		after the configured retry count, the call will fail
1520		instead of starting over.  This can be used to fail over
1521		to Link-local IP address configuration if the DHCP server
1522		is not available.
1523
1524		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1525		to do a dynamic update of a DNS server. To do this, they
1526		need the hostname of the DHCP requester.
1527		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1528		of the "hostname" environment variable is passed as
1529		option 12 to the DHCP server.
1530
1531		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1532
1533		A 32bit value in microseconds for a delay between
1534		receiving a "DHCP Offer" and sending the "DHCP Request".
1535		This fixes a problem with certain DHCP servers that don't
1536		respond 100% of the time to a "DHCP request". E.g. On an
1537		AT91RM9200 processor running at 180MHz, this delay needed
1538		to be *at least* 15,000 usec before a Windows Server 2003
1539		DHCP server would reply 100% of the time. I recommend at
1540		least 50,000 usec to be safe. The alternative is to hope
1541		that one of the retries will be successful but note that
1542		the DHCP timeout and retry process takes a longer than
1543		this delay.
1544
1545 - Link-local IP address negotiation:
1546		Negotiate with other link-local clients on the local network
1547		for an address that doesn't require explicit configuration.
1548		This is especially useful if a DHCP server cannot be guaranteed
1549		to exist in all environments that the device must operate.
1550
1551		See doc/README.link-local for more information.
1552
1553 - MAC address from environment variables
1554
1555		FDT_SEQ_MACADDR_FROM_ENV
1556
1557		Fix-up device tree with MAC addresses fetched sequentially from
1558		environment variables. This config work on assumption that
1559		non-usable ethernet node of device-tree are either not present
1560		or their status has been marked as "disabled".
1561
1562 - CDP Options:
1563		CONFIG_CDP_DEVICE_ID
1564
1565		The device id used in CDP trigger frames.
1566
1567		CONFIG_CDP_DEVICE_ID_PREFIX
1568
1569		A two character string which is prefixed to the MAC address
1570		of the device.
1571
1572		CONFIG_CDP_PORT_ID
1573
1574		A printf format string which contains the ascii name of
1575		the port. Normally is set to "eth%d" which sets
1576		eth0 for the first Ethernet, eth1 for the second etc.
1577
1578		CONFIG_CDP_CAPABILITIES
1579
1580		A 32bit integer which indicates the device capabilities;
1581		0x00000010 for a normal host which does not forwards.
1582
1583		CONFIG_CDP_VERSION
1584
1585		An ascii string containing the version of the software.
1586
1587		CONFIG_CDP_PLATFORM
1588
1589		An ascii string containing the name of the platform.
1590
1591		CONFIG_CDP_TRIGGER
1592
1593		A 32bit integer sent on the trigger.
1594
1595		CONFIG_CDP_POWER_CONSUMPTION
1596
1597		A 16bit integer containing the power consumption of the
1598		device in .1 of milliwatts.
1599
1600		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1601
1602		A byte containing the id of the VLAN.
1603
1604- Status LED:	CONFIG_LED_STATUS
1605
1606		Several configurations allow to display the current
1607		status using a LED. For instance, the LED will blink
1608		fast while running U-Boot code, stop blinking as
1609		soon as a reply to a BOOTP request was received, and
1610		start blinking slow once the Linux kernel is running
1611		(supported by a status LED driver in the Linux
1612		kernel). Defining CONFIG_LED_STATUS enables this
1613		feature in U-Boot.
1614
1615		Additional options:
1616
1617		CONFIG_LED_STATUS_GPIO
1618		The status LED can be connected to a GPIO pin.
1619		In such cases, the gpio_led driver can be used as a
1620		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1621		to include the gpio_led driver in the U-Boot binary.
1622
1623		CONFIG_GPIO_LED_INVERTED_TABLE
1624		Some GPIO connected LEDs may have inverted polarity in which
1625		case the GPIO high value corresponds to LED off state and
1626		GPIO low value corresponds to LED on state.
1627		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1628		with a list of GPIO LEDs that have inverted polarity.
1629
1630- I2C Support:	CONFIG_SYS_I2C
1631
1632		This enable the NEW i2c subsystem, and will allow you to use
1633		i2c commands at the u-boot command line (as long as you set
1634		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1635		based realtime clock chips or other i2c devices. See
1636		common/cmd_i2c.c for a description of the command line
1637		interface.
1638
1639		ported i2c driver to the new framework:
1640		- drivers/i2c/soft_i2c.c:
1641		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1642		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1643		    for defining speed and slave address
1644		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1645		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1646		    for defining speed and slave address
1647		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1648		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1649		    for defining speed and slave address
1650		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1651		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1652		    for defining speed and slave address
1653
1654		- drivers/i2c/fsl_i2c.c:
1655		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1656		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1657		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1658		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1659		    bus.
1660		  - If your board supports a second fsl i2c bus, define
1661		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1662		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1663		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1664		    second bus.
1665
1666		- drivers/i2c/tegra_i2c.c:
1667		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1668		  - This driver adds 4 i2c buses with a fix speed from
1669		    100000 and the slave addr 0!
1670
1671		- drivers/i2c/ppc4xx_i2c.c
1672		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1673		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1674		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1675
1676		- drivers/i2c/i2c_mxc.c
1677		  - activate this driver with CONFIG_SYS_I2C_MXC
1678		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1679		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1680		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1681		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1682		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1683		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1684		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1685		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1686		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1687		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1688		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1689		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1690		If those defines are not set, default value is 100000
1691		for speed, and 0 for slave.
1692
1693		- drivers/i2c/rcar_i2c.c:
1694		  - activate this driver with CONFIG_SYS_I2C_RCAR
1695		  - This driver adds 4 i2c buses
1696
1697		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1698		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1699		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1700		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1701		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1702		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1703		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1704		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1705		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1706
1707		- drivers/i2c/sh_i2c.c:
1708		  - activate this driver with CONFIG_SYS_I2C_SH
1709		  - This driver adds from 2 to 5 i2c buses
1710
1711		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1712		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1713		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1714		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1715		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1716		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1717		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1718		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1719		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1720		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1721		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1722
1723		- drivers/i2c/omap24xx_i2c.c
1724		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1725		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1726		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1727		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1728		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1729		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1730		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1731		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1732		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1733		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1734		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1735
1736		- drivers/i2c/zynq_i2c.c
1737		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1738		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1739		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1740
1741		- drivers/i2c/s3c24x0_i2c.c:
1742		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1743		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1744		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1745		    with a fix speed from 100000 and the slave addr 0!
1746
1747		- drivers/i2c/ihs_i2c.c
1748		  - activate this driver with CONFIG_SYS_I2C_IHS
1749		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1750		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1751		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1752		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1753		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1754		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1755		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1756		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1757		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1758		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1759		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1760		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1761		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1762		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1763		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1764		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1765		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1766		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1767		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1768		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1769		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1770
1771		additional defines:
1772
1773		CONFIG_SYS_NUM_I2C_BUSES
1774		Hold the number of i2c buses you want to use.
1775
1776		CONFIG_SYS_I2C_DIRECT_BUS
1777		define this, if you don't use i2c muxes on your hardware.
1778		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1779		omit this define.
1780
1781		CONFIG_SYS_I2C_MAX_HOPS
1782		define how many muxes are maximal consecutively connected
1783		on one i2c bus. If you not use i2c muxes, omit this
1784		define.
1785
1786		CONFIG_SYS_I2C_BUSES
1787		hold a list of buses you want to use, only used if
1788		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1789		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1790		CONFIG_SYS_NUM_I2C_BUSES = 9:
1791
1792		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1793					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1794					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1795					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1796					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1797					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1798					{1, {I2C_NULL_HOP}}, \
1799					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1800					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1801					}
1802
1803		which defines
1804			bus 0 on adapter 0 without a mux
1805			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1806			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1807			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1808			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1809			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1810			bus 6 on adapter 1 without a mux
1811			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1812			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1813
1814		If you do not have i2c muxes on your board, omit this define.
1815
1816- Legacy I2C Support:
1817		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1818		then the following macros need to be defined (examples are
1819		from include/configs/lwmon.h):
1820
1821		I2C_INIT
1822
1823		(Optional). Any commands necessary to enable the I2C
1824		controller or configure ports.
1825
1826		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1827
1828		I2C_ACTIVE
1829
1830		The code necessary to make the I2C data line active
1831		(driven).  If the data line is open collector, this
1832		define can be null.
1833
1834		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1835
1836		I2C_TRISTATE
1837
1838		The code necessary to make the I2C data line tri-stated
1839		(inactive).  If the data line is open collector, this
1840		define can be null.
1841
1842		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1843
1844		I2C_READ
1845
1846		Code that returns true if the I2C data line is high,
1847		false if it is low.
1848
1849		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1850
1851		I2C_SDA(bit)
1852
1853		If <bit> is true, sets the I2C data line high. If it
1854		is false, it clears it (low).
1855
1856		eg: #define I2C_SDA(bit) \
1857			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1858			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1859
1860		I2C_SCL(bit)
1861
1862		If <bit> is true, sets the I2C clock line high. If it
1863		is false, it clears it (low).
1864
1865		eg: #define I2C_SCL(bit) \
1866			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1867			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1868
1869		I2C_DELAY
1870
1871		This delay is invoked four times per clock cycle so this
1872		controls the rate of data transfer.  The data rate thus
1873		is 1 / (I2C_DELAY * 4). Often defined to be something
1874		like:
1875
1876		#define I2C_DELAY  udelay(2)
1877
1878		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1879
1880		If your arch supports the generic GPIO framework (asm/gpio.h),
1881		then you may alternatively define the two GPIOs that are to be
1882		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1883		have GPIO-based defaults assigned to them as appropriate.
1884
1885		You should define these to the GPIO value as given directly to
1886		the generic GPIO functions.
1887
1888		CONFIG_SYS_I2C_INIT_BOARD
1889
1890		When a board is reset during an i2c bus transfer
1891		chips might think that the current transfer is still
1892		in progress. On some boards it is possible to access
1893		the i2c SCLK line directly, either by using the
1894		processor pin as a GPIO or by having a second pin
1895		connected to the bus. If this option is defined a
1896		custom i2c_init_board() routine in boards/xxx/board.c
1897		is run early in the boot sequence.
1898
1899		CONFIG_I2C_MULTI_BUS
1900
1901		This option allows the use of multiple I2C buses, each of which
1902		must have a controller.	 At any point in time, only one bus is
1903		active.	 To switch to a different bus, use the 'i2c dev' command.
1904		Note that bus numbering is zero-based.
1905
1906		CONFIG_SYS_I2C_NOPROBES
1907
1908		This option specifies a list of I2C devices that will be skipped
1909		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1910		is set, specify a list of bus-device pairs.  Otherwise, specify
1911		a 1D array of device addresses
1912
1913		e.g.
1914			#undef	CONFIG_I2C_MULTI_BUS
1915			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1916
1917		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1918
1919			#define CONFIG_I2C_MULTI_BUS
1920			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1921
1922		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1923
1924		CONFIG_SYS_SPD_BUS_NUM
1925
1926		If defined, then this indicates the I2C bus number for DDR SPD.
1927		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1928
1929		CONFIG_SYS_RTC_BUS_NUM
1930
1931		If defined, then this indicates the I2C bus number for the RTC.
1932		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1933
1934		CONFIG_SOFT_I2C_READ_REPEATED_START
1935
1936		defining this will force the i2c_read() function in
1937		the soft_i2c driver to perform an I2C repeated start
1938		between writing the address pointer and reading the
1939		data.  If this define is omitted the default behaviour
1940		of doing a stop-start sequence will be used.  Most I2C
1941		devices can use either method, but some require one or
1942		the other.
1943
1944- SPI Support:	CONFIG_SPI
1945
1946		Enables SPI driver (so far only tested with
1947		SPI EEPROM, also an instance works with Crystal A/D and
1948		D/As on the SACSng board)
1949
1950		CONFIG_SOFT_SPI
1951
1952		Enables a software (bit-bang) SPI driver rather than
1953		using hardware support. This is a general purpose
1954		driver that only requires three general I/O port pins
1955		(two outputs, one input) to function. If this is
1956		defined, the board configuration must define several
1957		SPI configuration items (port pins to use, etc). For
1958		an example, see include/configs/sacsng.h.
1959
1960		CONFIG_HARD_SPI
1961
1962		Enables a hardware SPI driver for general-purpose reads
1963		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1964		must define a list of chip-select function pointers.
1965		Currently supported on some MPC8xxx processors.	 For an
1966		example, see include/configs/mpc8349emds.h.
1967
1968		CONFIG_SYS_SPI_MXC_WAIT
1969		Timeout for waiting until spi transfer completed.
1970		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1971
1972- FPGA Support: CONFIG_FPGA
1973
1974		Enables FPGA subsystem.
1975
1976		CONFIG_FPGA_<vendor>
1977
1978		Enables support for specific chip vendors.
1979		(ALTERA, XILINX)
1980
1981		CONFIG_FPGA_<family>
1982
1983		Enables support for FPGA family.
1984		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1985
1986		CONFIG_FPGA_COUNT
1987
1988		Specify the number of FPGA devices to support.
1989
1990		CONFIG_SYS_FPGA_PROG_FEEDBACK
1991
1992		Enable printing of hash marks during FPGA configuration.
1993
1994		CONFIG_SYS_FPGA_CHECK_BUSY
1995
1996		Enable checks on FPGA configuration interface busy
1997		status by the configuration function. This option
1998		will require a board or device specific function to
1999		be written.
2000
2001		CONFIG_FPGA_DELAY
2002
2003		If defined, a function that provides delays in the FPGA
2004		configuration driver.
2005
2006		CONFIG_SYS_FPGA_CHECK_CTRLC
2007		Allow Control-C to interrupt FPGA configuration
2008
2009		CONFIG_SYS_FPGA_CHECK_ERROR
2010
2011		Check for configuration errors during FPGA bitfile
2012		loading. For example, abort during Virtex II
2013		configuration if the INIT_B line goes low (which
2014		indicated a CRC error).
2015
2016		CONFIG_SYS_FPGA_WAIT_INIT
2017
2018		Maximum time to wait for the INIT_B line to de-assert
2019		after PROB_B has been de-asserted during a Virtex II
2020		FPGA configuration sequence. The default time is 500
2021		ms.
2022
2023		CONFIG_SYS_FPGA_WAIT_BUSY
2024
2025		Maximum time to wait for BUSY to de-assert during
2026		Virtex II FPGA configuration. The default is 5 ms.
2027
2028		CONFIG_SYS_FPGA_WAIT_CONFIG
2029
2030		Time to wait after FPGA configuration. The default is
2031		200 ms.
2032
2033- Configuration Management:
2034		CONFIG_BUILD_TARGET
2035
2036		Some SoCs need special image types (e.g. U-Boot binary
2037		with a special header) as build targets. By defining
2038		CONFIG_BUILD_TARGET in the SoC / board header, this
2039		special image will be automatically built upon calling
2040		make / buildman.
2041
2042		CONFIG_IDENT_STRING
2043
2044		If defined, this string will be added to the U-Boot
2045		version information (U_BOOT_VERSION)
2046
2047- Vendor Parameter Protection:
2048
2049		U-Boot considers the values of the environment
2050		variables "serial#" (Board Serial Number) and
2051		"ethaddr" (Ethernet Address) to be parameters that
2052		are set once by the board vendor / manufacturer, and
2053		protects these variables from casual modification by
2054		the user. Once set, these variables are read-only,
2055		and write or delete attempts are rejected. You can
2056		change this behaviour:
2057
2058		If CONFIG_ENV_OVERWRITE is #defined in your config
2059		file, the write protection for vendor parameters is
2060		completely disabled. Anybody can change or delete
2061		these parameters.
2062
2063		Alternatively, if you define _both_ an ethaddr in the
2064		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2065		Ethernet address is installed in the environment,
2066		which can be changed exactly ONCE by the user. [The
2067		serial# is unaffected by this, i. e. it remains
2068		read-only.]
2069
2070		The same can be accomplished in a more flexible way
2071		for any variable by configuring the type of access
2072		to allow for those variables in the ".flags" variable
2073		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2074
2075- Protected RAM:
2076		CONFIG_PRAM
2077
2078		Define this variable to enable the reservation of
2079		"protected RAM", i. e. RAM which is not overwritten
2080		by U-Boot. Define CONFIG_PRAM to hold the number of
2081		kB you want to reserve for pRAM. You can overwrite
2082		this default value by defining an environment
2083		variable "pram" to the number of kB you want to
2084		reserve. Note that the board info structure will
2085		still show the full amount of RAM. If pRAM is
2086		reserved, a new environment variable "mem" will
2087		automatically be defined to hold the amount of
2088		remaining RAM in a form that can be passed as boot
2089		argument to Linux, for instance like that:
2090
2091			setenv bootargs ... mem=\${mem}
2092			saveenv
2093
2094		This way you can tell Linux not to use this memory,
2095		either, which results in a memory region that will
2096		not be affected by reboots.
2097
2098		*WARNING* If your board configuration uses automatic
2099		detection of the RAM size, you must make sure that
2100		this memory test is non-destructive. So far, the
2101		following board configurations are known to be
2102		"pRAM-clean":
2103
2104			IVMS8, IVML24, SPD8xx,
2105			HERMES, IP860, RPXlite, LWMON,
2106			FLAGADM
2107
2108- Access to physical memory region (> 4GB)
2109		Some basic support is provided for operations on memory not
2110		normally accessible to U-Boot - e.g. some architectures
2111		support access to more than 4GB of memory on 32-bit
2112		machines using physical address extension or similar.
2113		Define CONFIG_PHYSMEM to access this basic support, which
2114		currently only supports clearing the memory.
2115
2116- Error Recovery:
2117		CONFIG_NET_RETRY_COUNT
2118
2119		This variable defines the number of retries for
2120		network operations like ARP, RARP, TFTP, or BOOTP
2121		before giving up the operation. If not defined, a
2122		default value of 5 is used.
2123
2124		CONFIG_ARP_TIMEOUT
2125
2126		Timeout waiting for an ARP reply in milliseconds.
2127
2128		CONFIG_NFS_TIMEOUT
2129
2130		Timeout in milliseconds used in NFS protocol.
2131		If you encounter "ERROR: Cannot umount" in nfs command,
2132		try longer timeout such as
2133		#define CONFIG_NFS_TIMEOUT 10000UL
2134
2135- Command Interpreter:
2136		CONFIG_SYS_PROMPT_HUSH_PS2
2137
2138		This defines the secondary prompt string, which is
2139		printed when the command interpreter needs more input
2140		to complete a command. Usually "> ".
2141
2142	Note:
2143
2144		In the current implementation, the local variables
2145		space and global environment variables space are
2146		separated. Local variables are those you define by
2147		simply typing `name=value'. To access a local
2148		variable later on, you have write `$name' or
2149		`${name}'; to execute the contents of a variable
2150		directly type `$name' at the command prompt.
2151
2152		Global environment variables are those you use
2153		setenv/printenv to work with. To run a command stored
2154		in such a variable, you need to use the run command,
2155		and you must not use the '$' sign to access them.
2156
2157		To store commands and special characters in a
2158		variable, please use double quotation marks
2159		surrounding the whole text of the variable, instead
2160		of the backslashes before semicolons and special
2161		symbols.
2162
2163- Command Line Editing and History:
2164		CONFIG_CMDLINE_PS_SUPPORT
2165
2166		Enable support for changing the command prompt string
2167		at run-time. Only static string is supported so far.
2168		The string is obtained from environment variables PS1
2169		and PS2.
2170
2171- Default Environment:
2172		CONFIG_EXTRA_ENV_SETTINGS
2173
2174		Define this to contain any number of null terminated
2175		strings (variable = value pairs) that will be part of
2176		the default environment compiled into the boot image.
2177
2178		For example, place something like this in your
2179		board's config file:
2180
2181		#define CONFIG_EXTRA_ENV_SETTINGS \
2182			"myvar1=value1\0" \
2183			"myvar2=value2\0"
2184
2185		Warning: This method is based on knowledge about the
2186		internal format how the environment is stored by the
2187		U-Boot code. This is NOT an official, exported
2188		interface! Although it is unlikely that this format
2189		will change soon, there is no guarantee either.
2190		You better know what you are doing here.
2191
2192		Note: overly (ab)use of the default environment is
2193		discouraged. Make sure to check other ways to preset
2194		the environment like the "source" command or the
2195		boot command first.
2196
2197		CONFIG_DELAY_ENVIRONMENT
2198
2199		Normally the environment is loaded when the board is
2200		initialised so that it is available to U-Boot. This inhibits
2201		that so that the environment is not available until
2202		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2203		this is instead controlled by the value of
2204		/config/load-environment.
2205
2206- Serial Flash support
2207		Usage requires an initial 'sf probe' to define the serial
2208		flash parameters, followed by read/write/erase/update
2209		commands.
2210
2211		The following defaults may be provided by the platform
2212		to handle the common case when only a single serial
2213		flash is present on the system.
2214
2215		CONFIG_SF_DEFAULT_BUS		Bus identifier
2216		CONFIG_SF_DEFAULT_CS		Chip-select
2217		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2218		CONFIG_SF_DEFAULT_SPEED		in Hz
2219
2220
2221- TFTP Fixed UDP Port:
2222		CONFIG_TFTP_PORT
2223
2224		If this is defined, the environment variable tftpsrcp
2225		is used to supply the TFTP UDP source port value.
2226		If tftpsrcp isn't defined, the normal pseudo-random port
2227		number generator is used.
2228
2229		Also, the environment variable tftpdstp is used to supply
2230		the TFTP UDP destination port value.  If tftpdstp isn't
2231		defined, the normal port 69 is used.
2232
2233		The purpose for tftpsrcp is to allow a TFTP server to
2234		blindly start the TFTP transfer using the pre-configured
2235		target IP address and UDP port. This has the effect of
2236		"punching through" the (Windows XP) firewall, allowing
2237		the remainder of the TFTP transfer to proceed normally.
2238		A better solution is to properly configure the firewall,
2239		but sometimes that is not allowed.
2240
2241- Show boot progress:
2242		CONFIG_SHOW_BOOT_PROGRESS
2243
2244		Defining this option allows to add some board-
2245		specific code (calling a user-provided function
2246		"show_boot_progress(int)") that enables you to show
2247		the system's boot progress on some display (for
2248		example, some LED's) on your board. At the moment,
2249		the following checkpoints are implemented:
2250
2251
2252Legacy uImage format:
2253
2254  Arg	Where			When
2255    1	common/cmd_bootm.c	before attempting to boot an image
2256   -1	common/cmd_bootm.c	Image header has bad	 magic number
2257    2	common/cmd_bootm.c	Image header has correct magic number
2258   -2	common/cmd_bootm.c	Image header has bad	 checksum
2259    3	common/cmd_bootm.c	Image header has correct checksum
2260   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2261    4	common/cmd_bootm.c	Image data   has correct checksum
2262   -4	common/cmd_bootm.c	Image is for unsupported architecture
2263    5	common/cmd_bootm.c	Architecture check OK
2264   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2265    6	common/cmd_bootm.c	Image Type check OK
2266   -6	common/cmd_bootm.c	gunzip uncompression error
2267   -7	common/cmd_bootm.c	Unimplemented compression type
2268    7	common/cmd_bootm.c	Uncompression OK
2269    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2270   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2271
2272    9	common/image.c		Start initial ramdisk verification
2273  -10	common/image.c		Ramdisk header has bad	   magic number
2274  -11	common/image.c		Ramdisk header has bad	   checksum
2275   10	common/image.c		Ramdisk header is OK
2276  -12	common/image.c		Ramdisk data   has bad	   checksum
2277   11	common/image.c		Ramdisk data   has correct checksum
2278   12	common/image.c		Ramdisk verification complete, start loading
2279  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2280   13	common/image.c		Start multifile image verification
2281   14	common/image.c		No initial ramdisk, no multifile, continue.
2282
2283   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2284
2285  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2286  -31	post/post.c		POST test failed, detected by post_output_backlog()
2287  -32	post/post.c		POST test failed, detected by post_run_single()
2288
2289   34	common/cmd_doc.c	before loading a Image from a DOC device
2290  -35	common/cmd_doc.c	Bad usage of "doc" command
2291   35	common/cmd_doc.c	correct usage of "doc" command
2292  -36	common/cmd_doc.c	No boot device
2293   36	common/cmd_doc.c	correct boot device
2294  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2295   37	common/cmd_doc.c	correct chip ID found, device available
2296  -38	common/cmd_doc.c	Read Error on boot device
2297   38	common/cmd_doc.c	reading Image header from DOC device OK
2298  -39	common/cmd_doc.c	Image header has bad magic number
2299   39	common/cmd_doc.c	Image header has correct magic number
2300  -40	common/cmd_doc.c	Error reading Image from DOC device
2301   40	common/cmd_doc.c	Image header has correct magic number
2302   41	common/cmd_ide.c	before loading a Image from a IDE device
2303  -42	common/cmd_ide.c	Bad usage of "ide" command
2304   42	common/cmd_ide.c	correct usage of "ide" command
2305  -43	common/cmd_ide.c	No boot device
2306   43	common/cmd_ide.c	boot device found
2307  -44	common/cmd_ide.c	Device not available
2308   44	common/cmd_ide.c	Device available
2309  -45	common/cmd_ide.c	wrong partition selected
2310   45	common/cmd_ide.c	partition selected
2311  -46	common/cmd_ide.c	Unknown partition table
2312   46	common/cmd_ide.c	valid partition table found
2313  -47	common/cmd_ide.c	Invalid partition type
2314   47	common/cmd_ide.c	correct partition type
2315  -48	common/cmd_ide.c	Error reading Image Header on boot device
2316   48	common/cmd_ide.c	reading Image Header from IDE device OK
2317  -49	common/cmd_ide.c	Image header has bad magic number
2318   49	common/cmd_ide.c	Image header has correct magic number
2319  -50	common/cmd_ide.c	Image header has bad	 checksum
2320   50	common/cmd_ide.c	Image header has correct checksum
2321  -51	common/cmd_ide.c	Error reading Image from IDE device
2322   51	common/cmd_ide.c	reading Image from IDE device OK
2323   52	common/cmd_nand.c	before loading a Image from a NAND device
2324  -53	common/cmd_nand.c	Bad usage of "nand" command
2325   53	common/cmd_nand.c	correct usage of "nand" command
2326  -54	common/cmd_nand.c	No boot device
2327   54	common/cmd_nand.c	boot device found
2328  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2329   55	common/cmd_nand.c	correct chip ID found, device available
2330  -56	common/cmd_nand.c	Error reading Image Header on boot device
2331   56	common/cmd_nand.c	reading Image Header from NAND device OK
2332  -57	common/cmd_nand.c	Image header has bad magic number
2333   57	common/cmd_nand.c	Image header has correct magic number
2334  -58	common/cmd_nand.c	Error reading Image from NAND device
2335   58	common/cmd_nand.c	reading Image from NAND device OK
2336
2337  -60	common/env_common.c	Environment has a bad CRC, using default
2338
2339   64	net/eth.c		starting with Ethernet configuration.
2340  -64	net/eth.c		no Ethernet found.
2341   65	net/eth.c		Ethernet found.
2342
2343  -80	common/cmd_net.c	usage wrong
2344   80	common/cmd_net.c	before calling net_loop()
2345  -81	common/cmd_net.c	some error in net_loop() occurred
2346   81	common/cmd_net.c	net_loop() back without error
2347  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2348   82	common/cmd_net.c	trying automatic boot
2349   83	common/cmd_net.c	running "source" command
2350  -83	common/cmd_net.c	some error in automatic boot or "source" command
2351   84	common/cmd_net.c	end without errors
2352
2353FIT uImage format:
2354
2355  Arg	Where			When
2356  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2357 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2358  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2359 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2360  102	common/cmd_bootm.c	Kernel unit name specified
2361 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2362  103	common/cmd_bootm.c	Found configuration node
2363  104	common/cmd_bootm.c	Got kernel subimage node offset
2364 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2365  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2366 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2367  106	common/cmd_bootm.c	Architecture check OK
2368 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2369  107	common/cmd_bootm.c	Kernel subimage type OK
2370 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2371  108	common/cmd_bootm.c	Got kernel subimage data/size
2372 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2373 -109	common/cmd_bootm.c	Can't get kernel subimage type
2374 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2375 -111	common/cmd_bootm.c	Can't get kernel subimage os
2376 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2377 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2378
2379  120	common/image.c		Start initial ramdisk verification
2380 -120	common/image.c		Ramdisk FIT image has incorrect format
2381  121	common/image.c		Ramdisk FIT image has correct format
2382  122	common/image.c		No ramdisk subimage unit name, using configuration
2383 -122	common/image.c		Can't get configuration for ramdisk subimage
2384  123	common/image.c		Ramdisk unit name specified
2385 -124	common/image.c		Can't get ramdisk subimage node offset
2386  125	common/image.c		Got ramdisk subimage node offset
2387 -125	common/image.c		Ramdisk subimage hash verification failed
2388  126	common/image.c		Ramdisk subimage hash verification OK
2389 -126	common/image.c		Ramdisk subimage for unsupported architecture
2390  127	common/image.c		Architecture check OK
2391 -127	common/image.c		Can't get ramdisk subimage data/size
2392  128	common/image.c		Got ramdisk subimage data/size
2393  129	common/image.c		Can't get ramdisk load address
2394 -129	common/image.c		Got ramdisk load address
2395
2396 -130	common/cmd_doc.c	Incorrect FIT image format
2397  131	common/cmd_doc.c	FIT image format OK
2398
2399 -140	common/cmd_ide.c	Incorrect FIT image format
2400  141	common/cmd_ide.c	FIT image format OK
2401
2402 -150	common/cmd_nand.c	Incorrect FIT image format
2403  151	common/cmd_nand.c	FIT image format OK
2404
2405- Standalone program support:
2406		CONFIG_STANDALONE_LOAD_ADDR
2407
2408		This option defines a board specific value for the
2409		address where standalone program gets loaded, thus
2410		overwriting the architecture dependent default
2411		settings.
2412
2413- Frame Buffer Address:
2414		CONFIG_FB_ADDR
2415
2416		Define CONFIG_FB_ADDR if you want to use specific
2417		address for frame buffer.  This is typically the case
2418		when using a graphics controller has separate video
2419		memory.  U-Boot will then place the frame buffer at
2420		the given address instead of dynamically reserving it
2421		in system RAM by calling lcd_setmem(), which grabs
2422		the memory for the frame buffer depending on the
2423		configured panel size.
2424
2425		Please see board_init_f function.
2426
2427- Automatic software updates via TFTP server
2428		CONFIG_UPDATE_TFTP
2429		CONFIG_UPDATE_TFTP_CNT_MAX
2430		CONFIG_UPDATE_TFTP_MSEC_MAX
2431
2432		These options enable and control the auto-update feature;
2433		for a more detailed description refer to doc/README.update.
2434
2435- MTD Support (mtdparts command, UBI support)
2436		CONFIG_MTD_DEVICE
2437
2438		Adds the MTD device infrastructure from the Linux kernel.
2439		Needed for mtdparts command support.
2440
2441		CONFIG_MTD_PARTITIONS
2442
2443		Adds the MTD partitioning infrastructure from the Linux
2444		kernel. Needed for UBI support.
2445
2446- UBI support
2447		CONFIG_MTD_UBI_WL_THRESHOLD
2448		This parameter defines the maximum difference between the highest
2449		erase counter value and the lowest erase counter value of eraseblocks
2450		of UBI devices. When this threshold is exceeded, UBI starts performing
2451		wear leveling by means of moving data from eraseblock with low erase
2452		counter to eraseblocks with high erase counter.
2453
2454		The default value should be OK for SLC NAND flashes, NOR flashes and
2455		other flashes which have eraseblock life-cycle 100000 or more.
2456		However, in case of MLC NAND flashes which typically have eraseblock
2457		life-cycle less than 10000, the threshold should be lessened (e.g.,
2458		to 128 or 256, although it does not have to be power of 2).
2459
2460		default: 4096
2461
2462		CONFIG_MTD_UBI_BEB_LIMIT
2463		This option specifies the maximum bad physical eraseblocks UBI
2464		expects on the MTD device (per 1024 eraseblocks). If the
2465		underlying flash does not admit of bad eraseblocks (e.g. NOR
2466		flash), this value is ignored.
2467
2468		NAND datasheets often specify the minimum and maximum NVM
2469		(Number of Valid Blocks) for the flashes' endurance lifetime.
2470		The maximum expected bad eraseblocks per 1024 eraseblocks
2471		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2472		which gives 20 for most NANDs (MaxNVB is basically the total
2473		count of eraseblocks on the chip).
2474
2475		To put it differently, if this value is 20, UBI will try to
2476		reserve about 1.9% of physical eraseblocks for bad blocks
2477		handling. And that will be 1.9% of eraseblocks on the entire
2478		NAND chip, not just the MTD partition UBI attaches. This means
2479		that if you have, say, a NAND flash chip admits maximum 40 bad
2480		eraseblocks, and it is split on two MTD partitions of the same
2481		size, UBI will reserve 40 eraseblocks when attaching a
2482		partition.
2483
2484		default: 20
2485
2486		CONFIG_MTD_UBI_FASTMAP
2487		Fastmap is a mechanism which allows attaching an UBI device
2488		in nearly constant time. Instead of scanning the whole MTD device it
2489		only has to locate a checkpoint (called fastmap) on the device.
2490		The on-flash fastmap contains all information needed to attach
2491		the device. Using fastmap makes only sense on large devices where
2492		attaching by scanning takes long. UBI will not automatically install
2493		a fastmap on old images, but you can set the UBI parameter
2494		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2495		that fastmap-enabled images are still usable with UBI implementations
2496		without	fastmap support. On typical flash devices the whole fastmap
2497		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2498
2499		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2500		Set this parameter to enable fastmap automatically on images
2501		without a fastmap.
2502		default: 0
2503
2504		CONFIG_MTD_UBI_FM_DEBUG
2505		Enable UBI fastmap debug
2506		default: 0
2507
2508- SPL framework
2509		CONFIG_SPL
2510		Enable building of SPL globally.
2511
2512		CONFIG_SPL_LDSCRIPT
2513		LDSCRIPT for linking the SPL binary.
2514
2515		CONFIG_SPL_MAX_FOOTPRINT
2516		Maximum size in memory allocated to the SPL, BSS included.
2517		When defined, the linker checks that the actual memory
2518		used by SPL from _start to __bss_end does not exceed it.
2519		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2520		must not be both defined at the same time.
2521
2522		CONFIG_SPL_MAX_SIZE
2523		Maximum size of the SPL image (text, data, rodata, and
2524		linker lists sections), BSS excluded.
2525		When defined, the linker checks that the actual size does
2526		not exceed it.
2527
2528		CONFIG_SPL_TEXT_BASE
2529		TEXT_BASE for linking the SPL binary.
2530
2531		CONFIG_SPL_RELOC_TEXT_BASE
2532		Address to relocate to.  If unspecified, this is equal to
2533		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2534
2535		CONFIG_SPL_BSS_START_ADDR
2536		Link address for the BSS within the SPL binary.
2537
2538		CONFIG_SPL_BSS_MAX_SIZE
2539		Maximum size in memory allocated to the SPL BSS.
2540		When defined, the linker checks that the actual memory used
2541		by SPL from __bss_start to __bss_end does not exceed it.
2542		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2543		must not be both defined at the same time.
2544
2545		CONFIG_SPL_STACK
2546		Adress of the start of the stack SPL will use
2547
2548		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2549		When defined, SPL will panic() if the image it has
2550		loaded does not have a signature.
2551		Defining this is useful when code which loads images
2552		in SPL cannot guarantee that absolutely all read errors
2553		will be caught.
2554		An example is the LPC32XX MLC NAND driver, which will
2555		consider that a completely unreadable NAND block is bad,
2556		and thus should be skipped silently.
2557
2558		CONFIG_SPL_RELOC_STACK
2559		Adress of the start of the stack SPL will use after
2560		relocation.  If unspecified, this is equal to
2561		CONFIG_SPL_STACK.
2562
2563		CONFIG_SYS_SPL_MALLOC_START
2564		Starting address of the malloc pool used in SPL.
2565		When this option is set the full malloc is used in SPL and
2566		it is set up by spl_init() and before that, the simple malloc()
2567		can be used if CONFIG_SYS_MALLOC_F is defined.
2568
2569		CONFIG_SYS_SPL_MALLOC_SIZE
2570		The size of the malloc pool used in SPL.
2571
2572		CONFIG_SPL_OS_BOOT
2573		Enable booting directly to an OS from SPL.
2574		See also: doc/README.falcon
2575
2576		CONFIG_SPL_DISPLAY_PRINT
2577		For ARM, enable an optional function to print more information
2578		about the running system.
2579
2580		CONFIG_SPL_INIT_MINIMAL
2581		Arch init code should be built for a very small image
2582
2583		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2584		Partition on the MMC to load U-Boot from when the MMC is being
2585		used in raw mode
2586
2587		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2588		Sector to load kernel uImage from when MMC is being
2589		used in raw mode (for Falcon mode)
2590
2591		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2592		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2593		Sector and number of sectors to load kernel argument
2594		parameters from when MMC is being used in raw mode
2595		(for falcon mode)
2596
2597		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2598		Partition on the MMC to load U-Boot from when the MMC is being
2599		used in fs mode
2600
2601		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2602		Filename to read to load U-Boot when reading from filesystem
2603
2604		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2605		Filename to read to load kernel uImage when reading
2606		from filesystem (for Falcon mode)
2607
2608		CONFIG_SPL_FS_LOAD_ARGS_NAME
2609		Filename to read to load kernel argument parameters
2610		when reading from filesystem (for Falcon mode)
2611
2612		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2613		Set this for NAND SPL on PPC mpc83xx targets, so that
2614		start.S waits for the rest of the SPL to load before
2615		continuing (the hardware starts execution after just
2616		loading the first page rather than the full 4K).
2617
2618		CONFIG_SPL_SKIP_RELOCATE
2619		Avoid SPL relocation
2620
2621		CONFIG_SPL_NAND_BASE
2622		Include nand_base.c in the SPL.  Requires
2623		CONFIG_SPL_NAND_DRIVERS.
2624
2625		CONFIG_SPL_NAND_DRIVERS
2626		SPL uses normal NAND drivers, not minimal drivers.
2627
2628		CONFIG_SPL_NAND_ECC
2629		Include standard software ECC in the SPL
2630
2631		CONFIG_SPL_NAND_SIMPLE
2632		Support for NAND boot using simple NAND drivers that
2633		expose the cmd_ctrl() interface.
2634
2635		CONFIG_SPL_UBI
2636		Support for a lightweight UBI (fastmap) scanner and
2637		loader
2638
2639		CONFIG_SPL_NAND_RAW_ONLY
2640		Support to boot only raw u-boot.bin images. Use this only
2641		if you need to save space.
2642
2643		CONFIG_SPL_COMMON_INIT_DDR
2644		Set for common ddr init with serial presence detect in
2645		SPL binary.
2646
2647		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2648		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2649		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2650		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2651		CONFIG_SYS_NAND_ECCBYTES
2652		Defines the size and behavior of the NAND that SPL uses
2653		to read U-Boot
2654
2655		CONFIG_SPL_NAND_BOOT
2656		Add support NAND boot
2657
2658		CONFIG_SYS_NAND_U_BOOT_OFFS
2659		Location in NAND to read U-Boot from
2660
2661		CONFIG_SYS_NAND_U_BOOT_DST
2662		Location in memory to load U-Boot to
2663
2664		CONFIG_SYS_NAND_U_BOOT_SIZE
2665		Size of image to load
2666
2667		CONFIG_SYS_NAND_U_BOOT_START
2668		Entry point in loaded image to jump to
2669
2670		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2671		Define this if you need to first read the OOB and then the
2672		data. This is used, for example, on davinci platforms.
2673
2674		CONFIG_SPL_RAM_DEVICE
2675		Support for running image already present in ram, in SPL binary
2676
2677		CONFIG_SPL_PAD_TO
2678		Image offset to which the SPL should be padded before appending
2679		the SPL payload. By default, this is defined as
2680		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2681		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2682		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2683
2684		CONFIG_SPL_TARGET
2685		Final target image containing SPL and payload.  Some SPLs
2686		use an arch-specific makefile fragment instead, for
2687		example if more than one image needs to be produced.
2688
2689		CONFIG_SPL_FIT_PRINT
2690		Printing information about a FIT image adds quite a bit of
2691		code to SPL. So this is normally disabled in SPL. Use this
2692		option to re-enable it. This will affect the output of the
2693		bootm command when booting a FIT image.
2694
2695- TPL framework
2696		CONFIG_TPL
2697		Enable building of TPL globally.
2698
2699		CONFIG_TPL_PAD_TO
2700		Image offset to which the TPL should be padded before appending
2701		the TPL payload. By default, this is defined as
2702		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2703		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2704		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2705
2706- Interrupt support (PPC):
2707
2708		There are common interrupt_init() and timer_interrupt()
2709		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2710		for CPU specific initialization. interrupt_init_cpu()
2711		should set decrementer_count to appropriate value. If
2712		CPU resets decrementer automatically after interrupt
2713		(ppc4xx) it should set decrementer_count to zero.
2714		timer_interrupt() calls timer_interrupt_cpu() for CPU
2715		specific handling. If board has watchdog / status_led
2716		/ other_activity_monitor it works automatically from
2717		general timer_interrupt().
2718
2719
2720Board initialization settings:
2721------------------------------
2722
2723During Initialization u-boot calls a number of board specific functions
2724to allow the preparation of board specific prerequisites, e.g. pin setup
2725before drivers are initialized. To enable these callbacks the
2726following configuration macros have to be defined. Currently this is
2727architecture specific, so please check arch/your_architecture/lib/board.c
2728typically in board_init_f() and board_init_r().
2729
2730- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2731- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2732- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2733- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2734
2735Configuration Settings:
2736-----------------------
2737
2738- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2739		Optionally it can be defined to support 64-bit memory commands.
2740
2741- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2742		undefine this when you're short of memory.
2743
2744- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2745		width of the commands listed in the 'help' command output.
2746
2747- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2748		prompt for user input.
2749
2750- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2751
2752- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2753
2754- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2755
2756- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2757		the application (usually a Linux kernel) when it is
2758		booted
2759
2760- CONFIG_SYS_BAUDRATE_TABLE:
2761		List of legal baudrate settings for this board.
2762
2763- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2764		Begin and End addresses of the area used by the
2765		simple memory test.
2766
2767- CONFIG_SYS_MEMTEST_SCRATCH:
2768		Scratch address used by the alternate memory test
2769		You only need to set this if address zero isn't writeable
2770
2771- CONFIG_SYS_MEM_RESERVE_SECURE
2772		Only implemented for ARMv8 for now.
2773		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2774		is substracted from total RAM and won't be reported to OS.
2775		This memory can be used as secure memory. A variable
2776		gd->arch.secure_ram is used to track the location. In systems
2777		the RAM base is not zero, or RAM is divided into banks,
2778		this variable needs to be recalcuated to get the address.
2779
2780- CONFIG_SYS_MEM_TOP_HIDE:
2781		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2782		this specified memory area will get subtracted from the top
2783		(end) of RAM and won't get "touched" at all by U-Boot. By
2784		fixing up gd->ram_size the Linux kernel should gets passed
2785		the now "corrected" memory size and won't touch it either.
2786		This should work for arch/ppc and arch/powerpc. Only Linux
2787		board ports in arch/powerpc with bootwrapper support that
2788		recalculate the memory size from the SDRAM controller setup
2789		will have to get fixed in Linux additionally.
2790
2791		This option can be used as a workaround for the 440EPx/GRx
2792		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2793		be touched.
2794
2795		WARNING: Please make sure that this value is a multiple of
2796		the Linux page size (normally 4k). If this is not the case,
2797		then the end address of the Linux memory will be located at a
2798		non page size aligned address and this could cause major
2799		problems.
2800
2801- CONFIG_SYS_LOADS_BAUD_CHANGE:
2802		Enable temporary baudrate change while serial download
2803
2804- CONFIG_SYS_SDRAM_BASE:
2805		Physical start address of SDRAM. _Must_ be 0 here.
2806
2807- CONFIG_SYS_FLASH_BASE:
2808		Physical start address of Flash memory.
2809
2810- CONFIG_SYS_MONITOR_BASE:
2811		Physical start address of boot monitor code (set by
2812		make config files to be same as the text base address
2813		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2814		CONFIG_SYS_FLASH_BASE when booting from flash.
2815
2816- CONFIG_SYS_MONITOR_LEN:
2817		Size of memory reserved for monitor code, used to
2818		determine _at_compile_time_ (!) if the environment is
2819		embedded within the U-Boot image, or in a separate
2820		flash sector.
2821
2822- CONFIG_SYS_MALLOC_LEN:
2823		Size of DRAM reserved for malloc() use.
2824
2825- CONFIG_SYS_MALLOC_F_LEN
2826		Size of the malloc() pool for use before relocation. If
2827		this is defined, then a very simple malloc() implementation
2828		will become available before relocation. The address is just
2829		below the global data, and the stack is moved down to make
2830		space.
2831
2832		This feature allocates regions with increasing addresses
2833		within the region. calloc() is supported, but realloc()
2834		is not available. free() is supported but does nothing.
2835		The memory will be freed (or in fact just forgotten) when
2836		U-Boot relocates itself.
2837
2838- CONFIG_SYS_MALLOC_SIMPLE
2839		Provides a simple and small malloc() and calloc() for those
2840		boards which do not use the full malloc in SPL (which is
2841		enabled with CONFIG_SYS_SPL_MALLOC_START).
2842
2843- CONFIG_SYS_NONCACHED_MEMORY:
2844		Size of non-cached memory area. This area of memory will be
2845		typically located right below the malloc() area and mapped
2846		uncached in the MMU. This is useful for drivers that would
2847		otherwise require a lot of explicit cache maintenance. For
2848		some drivers it's also impossible to properly maintain the
2849		cache. For example if the regions that need to be flushed
2850		are not a multiple of the cache-line size, *and* padding
2851		cannot be allocated between the regions to align them (i.e.
2852		if the HW requires a contiguous array of regions, and the
2853		size of each region is not cache-aligned), then a flush of
2854		one region may result in overwriting data that hardware has
2855		written to another region in the same cache-line. This can
2856		happen for example in network drivers where descriptors for
2857		buffers are typically smaller than the CPU cache-line (e.g.
2858		16 bytes vs. 32 or 64 bytes).
2859
2860		Non-cached memory is only supported on 32-bit ARM at present.
2861
2862- CONFIG_SYS_BOOTM_LEN:
2863		Normally compressed uImages are limited to an
2864		uncompressed size of 8 MBytes. If this is not enough,
2865		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2866		to adjust this setting to your needs.
2867
2868- CONFIG_SYS_BOOTMAPSZ:
2869		Maximum size of memory mapped by the startup code of
2870		the Linux kernel; all data that must be processed by
2871		the Linux kernel (bd_info, boot arguments, FDT blob if
2872		used) must be put below this limit, unless "bootm_low"
2873		environment variable is defined and non-zero. In such case
2874		all data for the Linux kernel must be between "bootm_low"
2875		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2876		variable "bootm_mapsize" will override the value of
2877		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2878		then the value in "bootm_size" will be used instead.
2879
2880- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2881		Enable initrd_high functionality.  If defined then the
2882		initrd_high feature is enabled and the bootm ramdisk subcommand
2883		is enabled.
2884
2885- CONFIG_SYS_BOOT_GET_CMDLINE:
2886		Enables allocating and saving kernel cmdline in space between
2887		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2888
2889- CONFIG_SYS_BOOT_GET_KBD:
2890		Enables allocating and saving a kernel copy of the bd_info in
2891		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2892
2893- CONFIG_SYS_MAX_FLASH_BANKS:
2894		Max number of Flash memory banks
2895
2896- CONFIG_SYS_MAX_FLASH_SECT:
2897		Max number of sectors on a Flash chip
2898
2899- CONFIG_SYS_FLASH_ERASE_TOUT:
2900		Timeout for Flash erase operations (in ms)
2901
2902- CONFIG_SYS_FLASH_WRITE_TOUT:
2903		Timeout for Flash write operations (in ms)
2904
2905- CONFIG_SYS_FLASH_LOCK_TOUT
2906		Timeout for Flash set sector lock bit operation (in ms)
2907
2908- CONFIG_SYS_FLASH_UNLOCK_TOUT
2909		Timeout for Flash clear lock bits operation (in ms)
2910
2911- CONFIG_SYS_FLASH_PROTECTION
2912		If defined, hardware flash sectors protection is used
2913		instead of U-Boot software protection.
2914
2915- CONFIG_SYS_DIRECT_FLASH_TFTP:
2916
2917		Enable TFTP transfers directly to flash memory;
2918		without this option such a download has to be
2919		performed in two steps: (1) download to RAM, and (2)
2920		copy from RAM to flash.
2921
2922		The two-step approach is usually more reliable, since
2923		you can check if the download worked before you erase
2924		the flash, but in some situations (when system RAM is
2925		too limited to allow for a temporary copy of the
2926		downloaded image) this option may be very useful.
2927
2928- CONFIG_SYS_FLASH_CFI:
2929		Define if the flash driver uses extra elements in the
2930		common flash structure for storing flash geometry.
2931
2932- CONFIG_FLASH_CFI_DRIVER
2933		This option also enables the building of the cfi_flash driver
2934		in the drivers directory
2935
2936- CONFIG_FLASH_CFI_MTD
2937		This option enables the building of the cfi_mtd driver
2938		in the drivers directory. The driver exports CFI flash
2939		to the MTD layer.
2940
2941- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2942		Use buffered writes to flash.
2943
2944- CONFIG_FLASH_SPANSION_S29WS_N
2945		s29ws-n MirrorBit flash has non-standard addresses for buffered
2946		write commands.
2947
2948- CONFIG_SYS_FLASH_QUIET_TEST
2949		If this option is defined, the common CFI flash doesn't
2950		print it's warning upon not recognized FLASH banks. This
2951		is useful, if some of the configured banks are only
2952		optionally available.
2953
2954- CONFIG_FLASH_SHOW_PROGRESS
2955		If defined (must be an integer), print out countdown
2956		digits and dots.  Recommended value: 45 (9..1) for 80
2957		column displays, 15 (3..1) for 40 column displays.
2958
2959- CONFIG_FLASH_VERIFY
2960		If defined, the content of the flash (destination) is compared
2961		against the source after the write operation. An error message
2962		will be printed when the contents are not identical.
2963		Please note that this option is useless in nearly all cases,
2964		since such flash programming errors usually are detected earlier
2965		while unprotecting/erasing/programming. Please only enable
2966		this option if you really know what you are doing.
2967
2968- CONFIG_SYS_RX_ETH_BUFFER:
2969		Defines the number of Ethernet receive buffers. On some
2970		Ethernet controllers it is recommended to set this value
2971		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2972		buffers can be full shortly after enabling the interface
2973		on high Ethernet traffic.
2974		Defaults to 4 if not defined.
2975
2976- CONFIG_ENV_MAX_ENTRIES
2977
2978	Maximum number of entries in the hash table that is used
2979	internally to store the environment settings. The default
2980	setting is supposed to be generous and should work in most
2981	cases. This setting can be used to tune behaviour; see
2982	lib/hashtable.c for details.
2983
2984- CONFIG_ENV_FLAGS_LIST_DEFAULT
2985- CONFIG_ENV_FLAGS_LIST_STATIC
2986	Enable validation of the values given to environment variables when
2987	calling env set.  Variables can be restricted to only decimal,
2988	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2989	the variables can also be restricted to IP address or MAC address.
2990
2991	The format of the list is:
2992		type_attribute = [s|d|x|b|i|m]
2993		access_attribute = [a|r|o|c]
2994		attributes = type_attribute[access_attribute]
2995		entry = variable_name[:attributes]
2996		list = entry[,list]
2997
2998	The type attributes are:
2999		s - String (default)
3000		d - Decimal
3001		x - Hexadecimal
3002		b - Boolean ([1yYtT|0nNfF])
3003		i - IP address
3004		m - MAC address
3005
3006	The access attributes are:
3007		a - Any (default)
3008		r - Read-only
3009		o - Write-once
3010		c - Change-default
3011
3012	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3013		Define this to a list (string) to define the ".flags"
3014		environment variable in the default or embedded environment.
3015
3016	- CONFIG_ENV_FLAGS_LIST_STATIC
3017		Define this to a list (string) to define validation that
3018		should be done if an entry is not found in the ".flags"
3019		environment variable.  To override a setting in the static
3020		list, simply add an entry for the same variable name to the
3021		".flags" variable.
3022
3023	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3024	regular expression. This allows multiple variables to define the same
3025	flags without explicitly listing them for each variable.
3026
3027- CONFIG_ENV_ACCESS_IGNORE_FORCE
3028	If defined, don't allow the -f switch to env set override variable
3029	access flags.
3030
3031- CONFIG_USE_STDINT
3032	If stdint.h is available with your toolchain you can define this
3033	option to enable it. You can provide option 'USE_STDINT=1' when
3034	building U-Boot to enable this.
3035
3036The following definitions that deal with the placement and management
3037of environment data (variable area); in general, we support the
3038following configurations:
3039
3040- CONFIG_BUILD_ENVCRC:
3041
3042	Builds up envcrc with the target environment so that external utils
3043	may easily extract it and embed it in final U-Boot images.
3044
3045BE CAREFUL! The first access to the environment happens quite early
3046in U-Boot initialization (when we try to get the setting of for the
3047console baudrate). You *MUST* have mapped your NVRAM area then, or
3048U-Boot will hang.
3049
3050Please note that even with NVRAM we still use a copy of the
3051environment in RAM: we could work on NVRAM directly, but we want to
3052keep settings there always unmodified except somebody uses "saveenv"
3053to save the current settings.
3054
3055BE CAREFUL! For some special cases, the local device can not use
3056"saveenv" command. For example, the local device will get the
3057environment stored in a remote NOR flash by SRIO or PCIE link,
3058but it can not erase, write this NOR flash by SRIO or PCIE interface.
3059
3060- CONFIG_NAND_ENV_DST
3061
3062	Defines address in RAM to which the nand_spl code should copy the
3063	environment. If redundant environment is used, it will be copied to
3064	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3065
3066Please note that the environment is read-only until the monitor
3067has been relocated to RAM and a RAM copy of the environment has been
3068created; also, when using EEPROM you will have to use env_get_f()
3069until then to read environment variables.
3070
3071The environment is protected by a CRC32 checksum. Before the monitor
3072is relocated into RAM, as a result of a bad CRC you will be working
3073with the compiled-in default environment - *silently*!!! [This is
3074necessary, because the first environment variable we need is the
3075"baudrate" setting for the console - if we have a bad CRC, we don't
3076have any device yet where we could complain.]
3077
3078Note: once the monitor has been relocated, then it will complain if
3079the default environment is used; a new CRC is computed as soon as you
3080use the "saveenv" command to store a valid environment.
3081
3082- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3083		Echo the inverted Ethernet link state to the fault LED.
3084
3085		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3086		      also needs to be defined.
3087
3088- CONFIG_SYS_FAULT_MII_ADDR:
3089		MII address of the PHY to check for the Ethernet link state.
3090
3091- CONFIG_NS16550_MIN_FUNCTIONS:
3092		Define this if you desire to only have use of the NS16550_init
3093		and NS16550_putc functions for the serial driver located at
3094		drivers/serial/ns16550.c.  This option is useful for saving
3095		space for already greatly restricted images, including but not
3096		limited to NAND_SPL configurations.
3097
3098- CONFIG_DISPLAY_BOARDINFO
3099		Display information about the board that U-Boot is running on
3100		when U-Boot starts up. The board function checkboard() is called
3101		to do this.
3102
3103- CONFIG_DISPLAY_BOARDINFO_LATE
3104		Similar to the previous option, but display this information
3105		later, once stdio is running and output goes to the LCD, if
3106		present.
3107
3108- CONFIG_BOARD_SIZE_LIMIT:
3109		Maximum size of the U-Boot image. When defined, the
3110		build system checks that the actual size does not
3111		exceed it.
3112
3113Low Level (hardware related) configuration options:
3114---------------------------------------------------
3115
3116- CONFIG_SYS_CACHELINE_SIZE:
3117		Cache Line Size of the CPU.
3118
3119- CONFIG_SYS_CCSRBAR_DEFAULT:
3120		Default (power-on reset) physical address of CCSR on Freescale
3121		PowerPC SOCs.
3122
3123- CONFIG_SYS_CCSRBAR:
3124		Virtual address of CCSR.  On a 32-bit build, this is typically
3125		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3126
3127- CONFIG_SYS_CCSRBAR_PHYS:
3128		Physical address of CCSR.  CCSR can be relocated to a new
3129		physical address, if desired.  In this case, this macro should
3130		be set to that address.	 Otherwise, it should be set to the
3131		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3132		is typically relocated on 36-bit builds.  It is recommended
3133		that this macro be defined via the _HIGH and _LOW macros:
3134
3135		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3136			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3137
3138- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3139		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3140		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3141		used in assembly code, so it must not contain typecasts or
3142		integer size suffixes (e.g. "ULL").
3143
3144- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3145		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3146		used in assembly code, so it must not contain typecasts or
3147		integer size suffixes (e.g. "ULL").
3148
3149- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3150		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3151		forced to a value that ensures that CCSR is not relocated.
3152
3153- Floppy Disk Support:
3154		CONFIG_SYS_FDC_DRIVE_NUMBER
3155
3156		the default drive number (default value 0)
3157
3158		CONFIG_SYS_ISA_IO_STRIDE
3159
3160		defines the spacing between FDC chipset registers
3161		(default value 1)
3162
3163		CONFIG_SYS_ISA_IO_OFFSET
3164
3165		defines the offset of register from address. It
3166		depends on which part of the data bus is connected to
3167		the FDC chipset. (default value 0)
3168
3169		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3170		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3171		default value.
3172
3173		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3174		fdc_hw_init() is called at the beginning of the FDC
3175		setup. fdc_hw_init() must be provided by the board
3176		source code. It is used to make hardware-dependent
3177		initializations.
3178
3179- CONFIG_IDE_AHB:
3180		Most IDE controllers were designed to be connected with PCI
3181		interface. Only few of them were designed for AHB interface.
3182		When software is doing ATA command and data transfer to
3183		IDE devices through IDE-AHB controller, some additional
3184		registers accessing to these kind of IDE-AHB controller
3185		is required.
3186
3187- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3188		DO NOT CHANGE unless you know exactly what you're
3189		doing! (11-4) [MPC8xx systems only]
3190
3191- CONFIG_SYS_INIT_RAM_ADDR:
3192
3193		Start address of memory area that can be used for
3194		initial data and stack; please note that this must be
3195		writable memory that is working WITHOUT special
3196		initialization, i. e. you CANNOT use normal RAM which
3197		will become available only after programming the
3198		memory controller and running certain initialization
3199		sequences.
3200
3201		U-Boot uses the following memory types:
3202		- MPC8xx: IMMR (internal memory of the CPU)
3203
3204- CONFIG_SYS_GBL_DATA_OFFSET:
3205
3206		Offset of the initial data structure in the memory
3207		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3208		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3209		data is located at the end of the available space
3210		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3211		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3212		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3213		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3214
3215	Note:
3216		On the MPC824X (or other systems that use the data
3217		cache for initial memory) the address chosen for
3218		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3219		point to an otherwise UNUSED address space between
3220		the top of RAM and the start of the PCI space.
3221
3222- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3223
3224- CONFIG_SYS_OR_TIMING_SDRAM:
3225		SDRAM timing
3226
3227- CONFIG_SYS_MAMR_PTA:
3228		periodic timer for refresh
3229
3230- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3231  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3232  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3233  CONFIG_SYS_BR1_PRELIM:
3234		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3235
3236- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3237  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3238  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3239		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3240
3241- CONFIG_PCI_ENUM_ONLY
3242		Only scan through and get the devices on the buses.
3243		Don't do any setup work, presumably because someone or
3244		something has already done it, and we don't need to do it
3245		a second time.	Useful for platforms that are pre-booted
3246		by coreboot or similar.
3247
3248- CONFIG_PCI_INDIRECT_BRIDGE:
3249		Enable support for indirect PCI bridges.
3250
3251- CONFIG_SYS_SRIO:
3252		Chip has SRIO or not
3253
3254- CONFIG_SRIO1:
3255		Board has SRIO 1 port available
3256
3257- CONFIG_SRIO2:
3258		Board has SRIO 2 port available
3259
3260- CONFIG_SRIO_PCIE_BOOT_MASTER
3261		Board can support master function for Boot from SRIO and PCIE
3262
3263- CONFIG_SYS_SRIOn_MEM_VIRT:
3264		Virtual Address of SRIO port 'n' memory region
3265
3266- CONFIG_SYS_SRIOn_MEM_PHYS:
3267		Physical Address of SRIO port 'n' memory region
3268
3269- CONFIG_SYS_SRIOn_MEM_SIZE:
3270		Size of SRIO port 'n' memory region
3271
3272- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3273		Defined to tell the NAND controller that the NAND chip is using
3274		a 16 bit bus.
3275		Not all NAND drivers use this symbol.
3276		Example of drivers that use it:
3277		- drivers/mtd/nand/ndfc.c
3278		- drivers/mtd/nand/mxc_nand.c
3279
3280- CONFIG_SYS_NDFC_EBC0_CFG
3281		Sets the EBC0_CFG register for the NDFC. If not defined
3282		a default value will be used.
3283
3284- CONFIG_SPD_EEPROM
3285		Get DDR timing information from an I2C EEPROM. Common
3286		with pluggable memory modules such as SODIMMs
3287
3288  SPD_EEPROM_ADDRESS
3289		I2C address of the SPD EEPROM
3290
3291- CONFIG_SYS_SPD_BUS_NUM
3292		If SPD EEPROM is on an I2C bus other than the first
3293		one, specify here. Note that the value must resolve
3294		to something your driver can deal with.
3295
3296- CONFIG_SYS_DDR_RAW_TIMING
3297		Get DDR timing information from other than SPD. Common with
3298		soldered DDR chips onboard without SPD. DDR raw timing
3299		parameters are extracted from datasheet and hard-coded into
3300		header files or board specific files.
3301
3302- CONFIG_FSL_DDR_INTERACTIVE
3303		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3304
3305- CONFIG_FSL_DDR_SYNC_REFRESH
3306		Enable sync of refresh for multiple controllers.
3307
3308- CONFIG_FSL_DDR_BIST
3309		Enable built-in memory test for Freescale DDR controllers.
3310
3311- CONFIG_SYS_83XX_DDR_USES_CS0
3312		Only for 83xx systems. If specified, then DDR should
3313		be configured using CS0 and CS1 instead of CS2 and CS3.
3314
3315- CONFIG_RMII
3316		Enable RMII mode for all FECs.
3317		Note that this is a global option, we can't
3318		have one FEC in standard MII mode and another in RMII mode.
3319
3320- CONFIG_CRC32_VERIFY
3321		Add a verify option to the crc32 command.
3322		The syntax is:
3323
3324		=> crc32 -v <address> <count> <crc32>
3325
3326		Where address/count indicate a memory area
3327		and crc32 is the correct crc32 which the
3328		area should have.
3329
3330- CONFIG_LOOPW
3331		Add the "loopw" memory command. This only takes effect if
3332		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3333
3334- CONFIG_MX_CYCLIC
3335		Add the "mdc" and "mwc" memory commands. These are cyclic
3336		"md/mw" commands.
3337		Examples:
3338
3339		=> mdc.b 10 4 500
3340		This command will print 4 bytes (10,11,12,13) each 500 ms.
3341
3342		=> mwc.l 100 12345678 10
3343		This command will write 12345678 to address 100 all 10 ms.
3344
3345		This only takes effect if the memory commands are activated
3346		globally (CONFIG_CMD_MEMORY).
3347
3348- CONFIG_SKIP_LOWLEVEL_INIT
3349		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3350		low level initializations (like setting up the memory
3351		controller) are omitted and/or U-Boot does not
3352		relocate itself into RAM.
3353
3354		Normally this variable MUST NOT be defined. The only
3355		exception is when U-Boot is loaded (to RAM) by some
3356		other boot loader or by a debugger which performs
3357		these initializations itself.
3358
3359- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3360		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3361		to be skipped. The normal CP15 init (such as enabling the
3362		instruction cache) is still performed.
3363
3364- CONFIG_SPL_BUILD
3365		Modifies the behaviour of start.S when compiling a loader
3366		that is executed before the actual U-Boot. E.g. when
3367		compiling a NAND SPL.
3368
3369- CONFIG_TPL_BUILD
3370		Modifies the behaviour of start.S  when compiling a loader
3371		that is executed after the SPL and before the actual U-Boot.
3372		It is loaded by the SPL.
3373
3374- CONFIG_SYS_MPC85XX_NO_RESETVEC
3375		Only for 85xx systems. If this variable is specified, the section
3376		.resetvec is not kept and the section .bootpg is placed in the
3377		previous 4k of the .text section.
3378
3379- CONFIG_ARCH_MAP_SYSMEM
3380		Generally U-Boot (and in particular the md command) uses
3381		effective address. It is therefore not necessary to regard
3382		U-Boot address as virtual addresses that need to be translated
3383		to physical addresses. However, sandbox requires this, since
3384		it maintains its own little RAM buffer which contains all
3385		addressable memory. This option causes some memory accesses
3386		to be mapped through map_sysmem() / unmap_sysmem().
3387
3388- CONFIG_X86_RESET_VECTOR
3389		If defined, the x86 reset vector code is included. This is not
3390		needed when U-Boot is running from Coreboot.
3391
3392- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3393		Option to disable subpage write in NAND driver
3394		driver that uses this:
3395		drivers/mtd/nand/davinci_nand.c
3396
3397Freescale QE/FMAN Firmware Support:
3398-----------------------------------
3399
3400The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3401loading of "firmware", which is encoded in the QE firmware binary format.
3402This firmware often needs to be loaded during U-Boot booting, so macros
3403are used to identify the storage device (NOR flash, SPI, etc) and the address
3404within that device.
3405
3406- CONFIG_SYS_FMAN_FW_ADDR
3407	The address in the storage device where the FMAN microcode is located.  The
3408	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3409	is also specified.
3410
3411- CONFIG_SYS_QE_FW_ADDR
3412	The address in the storage device where the QE microcode is located.  The
3413	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3414	is also specified.
3415
3416- CONFIG_SYS_QE_FMAN_FW_LENGTH
3417	The maximum possible size of the firmware.  The firmware binary format
3418	has a field that specifies the actual size of the firmware, but it
3419	might not be possible to read any part of the firmware unless some
3420	local storage is allocated to hold the entire firmware first.
3421
3422- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3423	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3424	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3425	virtual address in NOR flash.
3426
3427- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3428	Specifies that QE/FMAN firmware is located in NAND flash.
3429	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3430
3431- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3432	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3433	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3434
3435- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3436	Specifies that QE/FMAN firmware is located in the remote (master)
3437	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3438	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3439	window->master inbound window->master LAW->the ucode address in
3440	master's memory space.
3441
3442Freescale Layerscape Management Complex Firmware Support:
3443---------------------------------------------------------
3444The Freescale Layerscape Management Complex (MC) supports the loading of
3445"firmware".
3446This firmware often needs to be loaded during U-Boot booting, so macros
3447are used to identify the storage device (NOR flash, SPI, etc) and the address
3448within that device.
3449
3450- CONFIG_FSL_MC_ENET
3451	Enable the MC driver for Layerscape SoCs.
3452
3453Freescale Layerscape Debug Server Support:
3454-------------------------------------------
3455The Freescale Layerscape Debug Server Support supports the loading of
3456"Debug Server firmware" and triggering SP boot-rom.
3457This firmware often needs to be loaded during U-Boot booting.
3458
3459- CONFIG_SYS_MC_RSV_MEM_ALIGN
3460	Define alignment of reserved memory MC requires
3461
3462Reproducible builds
3463-------------------
3464
3465In order to achieve reproducible builds, timestamps used in the U-Boot build
3466process have to be set to a fixed value.
3467
3468This is done using the SOURCE_DATE_EPOCH environment variable.
3469SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3470option for U-Boot or an environment variable in U-Boot.
3471
3472SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3473
3474Building the Software:
3475======================
3476
3477Building U-Boot has been tested in several native build environments
3478and in many different cross environments. Of course we cannot support
3479all possibly existing versions of cross development tools in all
3480(potentially obsolete) versions. In case of tool chain problems we
3481recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3482which is extensively used to build and test U-Boot.
3483
3484If you are not using a native environment, it is assumed that you
3485have GNU cross compiling tools available in your path. In this case,
3486you must set the environment variable CROSS_COMPILE in your shell.
3487Note that no changes to the Makefile or any other source files are
3488necessary. For example using the ELDK on a 4xx CPU, please enter:
3489
3490	$ CROSS_COMPILE=ppc_4xx-
3491	$ export CROSS_COMPILE
3492
3493Note: If you wish to generate Windows versions of the utilities in
3494      the tools directory you can use the MinGW toolchain
3495      (http://www.mingw.org).  Set your HOST tools to the MinGW
3496      toolchain and execute 'make tools'.  For example:
3497
3498       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3499
3500      Binaries such as tools/mkimage.exe will be created which can
3501      be executed on computers running Windows.
3502
3503U-Boot is intended to be simple to build. After installing the
3504sources you must configure U-Boot for one specific board type. This
3505is done by typing:
3506
3507	make NAME_defconfig
3508
3509where "NAME_defconfig" is the name of one of the existing configu-
3510rations; see boards.cfg for supported names.
3511
3512Note: for some board special configuration names may exist; check if
3513      additional information is available from the board vendor; for
3514      instance, the TQM823L systems are available without (standard)
3515      or with LCD support. You can select such additional "features"
3516      when choosing the configuration, i. e.
3517
3518      make TQM823L_defconfig
3519	- will configure for a plain TQM823L, i. e. no LCD support
3520
3521      make TQM823L_LCD_defconfig
3522	- will configure for a TQM823L with U-Boot console on LCD
3523
3524      etc.
3525
3526
3527Finally, type "make all", and you should get some working U-Boot
3528images ready for download to / installation on your system:
3529
3530- "u-boot.bin" is a raw binary image
3531- "u-boot" is an image in ELF binary format
3532- "u-boot.srec" is in Motorola S-Record format
3533
3534By default the build is performed locally and the objects are saved
3535in the source directory. One of the two methods can be used to change
3536this behavior and build U-Boot to some external directory:
3537
35381. Add O= to the make command line invocations:
3539
3540	make O=/tmp/build distclean
3541	make O=/tmp/build NAME_defconfig
3542	make O=/tmp/build all
3543
35442. Set environment variable KBUILD_OUTPUT to point to the desired location:
3545
3546	export KBUILD_OUTPUT=/tmp/build
3547	make distclean
3548	make NAME_defconfig
3549	make all
3550
3551Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3552variable.
3553
3554User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3555setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3556For example to treat all compiler warnings as errors:
3557
3558	make KCFLAGS=-Werror
3559
3560Please be aware that the Makefiles assume you are using GNU make, so
3561for instance on NetBSD you might need to use "gmake" instead of
3562native "make".
3563
3564
3565If the system board that you have is not listed, then you will need
3566to port U-Boot to your hardware platform. To do this, follow these
3567steps:
3568
35691.  Create a new directory to hold your board specific code. Add any
3570    files you need. In your board directory, you will need at least
3571    the "Makefile" and a "<board>.c".
35722.  Create a new configuration file "include/configs/<board>.h" for
3573    your board.
35743.  If you're porting U-Boot to a new CPU, then also create a new
3575    directory to hold your CPU specific code. Add any files you need.
35764.  Run "make <board>_defconfig" with your new name.
35775.  Type "make", and you should get a working "u-boot.srec" file
3578    to be installed on your target system.
35796.  Debug and solve any problems that might arise.
3580    [Of course, this last step is much harder than it sounds.]
3581
3582
3583Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3584==============================================================
3585
3586If you have modified U-Boot sources (for instance added a new board
3587or support for new devices, a new CPU, etc.) you are expected to
3588provide feedback to the other developers. The feedback normally takes
3589the form of a "patch", i. e. a context diff against a certain (latest
3590official or latest in the git repository) version of U-Boot sources.
3591
3592But before you submit such a patch, please verify that your modifi-
3593cation did not break existing code. At least make sure that *ALL* of
3594the supported boards compile WITHOUT ANY compiler warnings. To do so,
3595just run the buildman script (tools/buildman/buildman), which will
3596configure and build U-Boot for ALL supported system. Be warned, this
3597will take a while. Please see the buildman README, or run 'buildman -H'
3598for documentation.
3599
3600
3601See also "U-Boot Porting Guide" below.
3602
3603
3604Monitor Commands - Overview:
3605============================
3606
3607go	- start application at address 'addr'
3608run	- run commands in an environment variable
3609bootm	- boot application image from memory
3610bootp	- boot image via network using BootP/TFTP protocol
3611bootz   - boot zImage from memory
3612tftpboot- boot image via network using TFTP protocol
3613	       and env variables "ipaddr" and "serverip"
3614	       (and eventually "gatewayip")
3615tftpput - upload a file via network using TFTP protocol
3616rarpboot- boot image via network using RARP/TFTP protocol
3617diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3618loads	- load S-Record file over serial line
3619loadb	- load binary file over serial line (kermit mode)
3620md	- memory display
3621mm	- memory modify (auto-incrementing)
3622nm	- memory modify (constant address)
3623mw	- memory write (fill)
3624cp	- memory copy
3625cmp	- memory compare
3626crc32	- checksum calculation
3627i2c	- I2C sub-system
3628sspi	- SPI utility commands
3629base	- print or set address offset
3630printenv- print environment variables
3631setenv	- set environment variables
3632saveenv - save environment variables to persistent storage
3633protect - enable or disable FLASH write protection
3634erase	- erase FLASH memory
3635flinfo	- print FLASH memory information
3636nand	- NAND memory operations (see doc/README.nand)
3637bdinfo	- print Board Info structure
3638iminfo	- print header information for application image
3639coninfo - print console devices and informations
3640ide	- IDE sub-system
3641loop	- infinite loop on address range
3642loopw	- infinite write loop on address range
3643mtest	- simple RAM test
3644icache	- enable or disable instruction cache
3645dcache	- enable or disable data cache
3646reset	- Perform RESET of the CPU
3647echo	- echo args to console
3648version - print monitor version
3649help	- print online help
3650?	- alias for 'help'
3651
3652
3653Monitor Commands - Detailed Description:
3654========================================
3655
3656TODO.
3657
3658For now: just type "help <command>".
3659
3660
3661Environment Variables:
3662======================
3663
3664U-Boot supports user configuration using Environment Variables which
3665can be made persistent by saving to Flash memory.
3666
3667Environment Variables are set using "setenv", printed using
3668"printenv", and saved to Flash using "saveenv". Using "setenv"
3669without a value can be used to delete a variable from the
3670environment. As long as you don't save the environment you are
3671working with an in-memory copy. In case the Flash area containing the
3672environment is erased by accident, a default environment is provided.
3673
3674Some configuration options can be set using Environment Variables.
3675
3676List of environment variables (most likely not complete):
3677
3678  baudrate	- see CONFIG_BAUDRATE
3679
3680  bootdelay	- see CONFIG_BOOTDELAY
3681
3682  bootcmd	- see CONFIG_BOOTCOMMAND
3683
3684  bootargs	- Boot arguments when booting an RTOS image
3685
3686  bootfile	- Name of the image to load with TFTP
3687
3688  bootm_low	- Memory range available for image processing in the bootm
3689		  command can be restricted. This variable is given as
3690		  a hexadecimal number and defines lowest address allowed
3691		  for use by the bootm command. See also "bootm_size"
3692		  environment variable. Address defined by "bootm_low" is
3693		  also the base of the initial memory mapping for the Linux
3694		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3695		  bootm_mapsize.
3696
3697  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3698		  This variable is given as a hexadecimal number and it
3699		  defines the size of the memory region starting at base
3700		  address bootm_low that is accessible by the Linux kernel
3701		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3702		  as the default value if it is defined, and bootm_size is
3703		  used otherwise.
3704
3705  bootm_size	- Memory range available for image processing in the bootm
3706		  command can be restricted. This variable is given as
3707		  a hexadecimal number and defines the size of the region
3708		  allowed for use by the bootm command. See also "bootm_low"
3709		  environment variable.
3710
3711  updatefile	- Location of the software update file on a TFTP server, used
3712		  by the automatic software update feature. Please refer to
3713		  documentation in doc/README.update for more details.
3714
3715  autoload	- if set to "no" (any string beginning with 'n'),
3716		  "bootp" will just load perform a lookup of the
3717		  configuration from the BOOTP server, but not try to
3718		  load any image using TFTP
3719
3720  autostart	- if set to "yes", an image loaded using the "bootp",
3721		  "rarpboot", "tftpboot" or "diskboot" commands will
3722		  be automatically started (by internally calling
3723		  "bootm")
3724
3725		  If set to "no", a standalone image passed to the
3726		  "bootm" command will be copied to the load address
3727		  (and eventually uncompressed), but NOT be started.
3728		  This can be used to load and uncompress arbitrary
3729		  data.
3730
3731  fdt_high	- if set this restricts the maximum address that the
3732		  flattened device tree will be copied into upon boot.
3733		  For example, if you have a system with 1 GB memory
3734		  at physical address 0x10000000, while Linux kernel
3735		  only recognizes the first 704 MB as low memory, you
3736		  may need to set fdt_high as 0x3C000000 to have the
3737		  device tree blob be copied to the maximum address
3738		  of the 704 MB low memory, so that Linux kernel can
3739		  access it during the boot procedure.
3740
3741		  If this is set to the special value 0xFFFFFFFF then
3742		  the fdt will not be copied at all on boot.  For this
3743		  to work it must reside in writable memory, have
3744		  sufficient padding on the end of it for u-boot to
3745		  add the information it needs into it, and the memory
3746		  must be accessible by the kernel.
3747
3748  fdtcontroladdr- if set this is the address of the control flattened
3749		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3750		  defined.
3751
3752  i2cfast	- (PPC405GP|PPC405EP only)
3753		  if set to 'y' configures Linux I2C driver for fast
3754		  mode (400kHZ). This environment variable is used in
3755		  initialization code. So, for changes to be effective
3756		  it must be saved and board must be reset.
3757
3758  initrd_high	- restrict positioning of initrd images:
3759		  If this variable is not set, initrd images will be
3760		  copied to the highest possible address in RAM; this
3761		  is usually what you want since it allows for
3762		  maximum initrd size. If for some reason you want to
3763		  make sure that the initrd image is loaded below the
3764		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3765		  variable to a value of "no" or "off" or "0".
3766		  Alternatively, you can set it to a maximum upper
3767		  address to use (U-Boot will still check that it
3768		  does not overwrite the U-Boot stack and data).
3769
3770		  For instance, when you have a system with 16 MB
3771		  RAM, and want to reserve 4 MB from use by Linux,
3772		  you can do this by adding "mem=12M" to the value of
3773		  the "bootargs" variable. However, now you must make
3774		  sure that the initrd image is placed in the first
3775		  12 MB as well - this can be done with
3776
3777		  setenv initrd_high 00c00000
3778
3779		  If you set initrd_high to 0xFFFFFFFF, this is an
3780		  indication to U-Boot that all addresses are legal
3781		  for the Linux kernel, including addresses in flash
3782		  memory. In this case U-Boot will NOT COPY the
3783		  ramdisk at all. This may be useful to reduce the
3784		  boot time on your system, but requires that this
3785		  feature is supported by your Linux kernel.
3786
3787  ipaddr	- IP address; needed for tftpboot command
3788
3789  loadaddr	- Default load address for commands like "bootp",
3790		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3791
3792  loads_echo	- see CONFIG_LOADS_ECHO
3793
3794  serverip	- TFTP server IP address; needed for tftpboot command
3795
3796  bootretry	- see CONFIG_BOOT_RETRY_TIME
3797
3798  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3799
3800  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3801
3802  ethprime	- controls which interface is used first.
3803
3804  ethact	- controls which interface is currently active.
3805		  For example you can do the following
3806
3807		  => setenv ethact FEC
3808		  => ping 192.168.0.1 # traffic sent on FEC
3809		  => setenv ethact SCC
3810		  => ping 10.0.0.1 # traffic sent on SCC
3811
3812  ethrotate	- When set to "no" U-Boot does not go through all
3813		  available network interfaces.
3814		  It just stays at the currently selected interface.
3815
3816  netretry	- When set to "no" each network operation will
3817		  either succeed or fail without retrying.
3818		  When set to "once" the network operation will
3819		  fail when all the available network interfaces
3820		  are tried once without success.
3821		  Useful on scripts which control the retry operation
3822		  themselves.
3823
3824  npe_ucode	- set load address for the NPE microcode
3825
3826  silent_linux  - If set then Linux will be told to boot silently, by
3827		  changing the console to be empty. If "yes" it will be
3828		  made silent. If "no" it will not be made silent. If
3829		  unset, then it will be made silent if the U-Boot console
3830		  is silent.
3831
3832  tftpsrcp	- If this is set, the value is used for TFTP's
3833		  UDP source port.
3834
3835  tftpdstp	- If this is set, the value is used for TFTP's UDP
3836		  destination port instead of the Well Know Port 69.
3837
3838  tftpblocksize - Block size to use for TFTP transfers; if not set,
3839		  we use the TFTP server's default block size
3840
3841  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3842		  seconds, minimum value is 1000 = 1 second). Defines
3843		  when a packet is considered to be lost so it has to
3844		  be retransmitted. The default is 5000 = 5 seconds.
3845		  Lowering this value may make downloads succeed
3846		  faster in networks with high packet loss rates or
3847		  with unreliable TFTP servers.
3848
3849  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3850		  unit, minimum value = 0). Defines how many timeouts
3851		  can happen during a single file transfer before that
3852		  transfer is aborted. The default is 10, and 0 means
3853		  'no timeouts allowed'. Increasing this value may help
3854		  downloads succeed with high packet loss rates, or with
3855		  unreliable TFTP servers or client hardware.
3856
3857  vlan		- When set to a value < 4095 the traffic over
3858		  Ethernet is encapsulated/received over 802.1q
3859		  VLAN tagged frames.
3860
3861  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3862		  Unsigned value, in milliseconds. If not set, the period will
3863		  be either the default (28000), or a value based on
3864		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3865		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3866
3867The following image location variables contain the location of images
3868used in booting. The "Image" column gives the role of the image and is
3869not an environment variable name. The other columns are environment
3870variable names. "File Name" gives the name of the file on a TFTP
3871server, "RAM Address" gives the location in RAM the image will be
3872loaded to, and "Flash Location" gives the image's address in NOR
3873flash or offset in NAND flash.
3874
3875*Note* - these variables don't have to be defined for all boards, some
3876boards currently use other variables for these purposes, and some
3877boards use these variables for other purposes.
3878
3879Image		    File Name	     RAM Address       Flash Location
3880-----		    ---------	     -----------       --------------
3881u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3882Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3883device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3884ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3885
3886The following environment variables may be used and automatically
3887updated by the network boot commands ("bootp" and "rarpboot"),
3888depending the information provided by your boot server:
3889
3890  bootfile	- see above
3891  dnsip		- IP address of your Domain Name Server
3892  dnsip2	- IP address of your secondary Domain Name Server
3893  gatewayip	- IP address of the Gateway (Router) to use
3894  hostname	- Target hostname
3895  ipaddr	- see above
3896  netmask	- Subnet Mask
3897  rootpath	- Pathname of the root filesystem on the NFS server
3898  serverip	- see above
3899
3900
3901There are two special Environment Variables:
3902
3903  serial#	- contains hardware identification information such
3904		  as type string and/or serial number
3905  ethaddr	- Ethernet address
3906
3907These variables can be set only once (usually during manufacturing of
3908the board). U-Boot refuses to delete or overwrite these variables
3909once they have been set once.
3910
3911
3912Further special Environment Variables:
3913
3914  ver		- Contains the U-Boot version string as printed
3915		  with the "version" command. This variable is
3916		  readonly (see CONFIG_VERSION_VARIABLE).
3917
3918
3919Please note that changes to some configuration parameters may take
3920only effect after the next boot (yes, that's just like Windoze :-).
3921
3922
3923Callback functions for environment variables:
3924---------------------------------------------
3925
3926For some environment variables, the behavior of u-boot needs to change
3927when their values are changed.  This functionality allows functions to
3928be associated with arbitrary variables.  On creation, overwrite, or
3929deletion, the callback will provide the opportunity for some side
3930effect to happen or for the change to be rejected.
3931
3932The callbacks are named and associated with a function using the
3933U_BOOT_ENV_CALLBACK macro in your board or driver code.
3934
3935These callbacks are associated with variables in one of two ways.  The
3936static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3937in the board configuration to a string that defines a list of
3938associations.  The list must be in the following format:
3939
3940	entry = variable_name[:callback_name]
3941	list = entry[,list]
3942
3943If the callback name is not specified, then the callback is deleted.
3944Spaces are also allowed anywhere in the list.
3945
3946Callbacks can also be associated by defining the ".callbacks" variable
3947with the same list format above.  Any association in ".callbacks" will
3948override any association in the static list. You can define
3949CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3950".callbacks" environment variable in the default or embedded environment.
3951
3952If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3953regular expression. This allows multiple variables to be connected to
3954the same callback without explicitly listing them all out.
3955
3956
3957Command Line Parsing:
3958=====================
3959
3960There are two different command line parsers available with U-Boot:
3961the old "simple" one, and the much more powerful "hush" shell:
3962
3963Old, simple command line parser:
3964--------------------------------
3965
3966- supports environment variables (through setenv / saveenv commands)
3967- several commands on one line, separated by ';'
3968- variable substitution using "... ${name} ..." syntax
3969- special characters ('$', ';') can be escaped by prefixing with '\',
3970  for example:
3971	setenv bootcmd bootm \${address}
3972- You can also escape text by enclosing in single apostrophes, for example:
3973	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3974
3975Hush shell:
3976-----------
3977
3978- similar to Bourne shell, with control structures like
3979  if...then...else...fi, for...do...done; while...do...done,
3980  until...do...done, ...
3981- supports environment ("global") variables (through setenv / saveenv
3982  commands) and local shell variables (through standard shell syntax
3983  "name=value"); only environment variables can be used with "run"
3984  command
3985
3986General rules:
3987--------------
3988
3989(1) If a command line (or an environment variable executed by a "run"
3990    command) contains several commands separated by semicolon, and
3991    one of these commands fails, then the remaining commands will be
3992    executed anyway.
3993
3994(2) If you execute several variables with one call to run (i. e.
3995    calling run with a list of variables as arguments), any failing
3996    command will cause "run" to terminate, i. e. the remaining
3997    variables are not executed.
3998
3999Note for Redundant Ethernet Interfaces:
4000=======================================
4001
4002Some boards come with redundant Ethernet interfaces; U-Boot supports
4003such configurations and is capable of automatic selection of a
4004"working" interface when needed. MAC assignment works as follows:
4005
4006Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4007MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4008"eth1addr" (=>eth1), "eth2addr", ...
4009
4010If the network interface stores some valid MAC address (for instance
4011in SROM), this is used as default address if there is NO correspon-
4012ding setting in the environment; if the corresponding environment
4013variable is set, this overrides the settings in the card; that means:
4014
4015o If the SROM has a valid MAC address, and there is no address in the
4016  environment, the SROM's address is used.
4017
4018o If there is no valid address in the SROM, and a definition in the
4019  environment exists, then the value from the environment variable is
4020  used.
4021
4022o If both the SROM and the environment contain a MAC address, and
4023  both addresses are the same, this MAC address is used.
4024
4025o If both the SROM and the environment contain a MAC address, and the
4026  addresses differ, the value from the environment is used and a
4027  warning is printed.
4028
4029o If neither SROM nor the environment contain a MAC address, an error
4030  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4031  a random, locally-assigned MAC is used.
4032
4033If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4034will be programmed into hardware as part of the initialization process.	 This
4035may be skipped by setting the appropriate 'ethmacskip' environment variable.
4036The naming convention is as follows:
4037"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4038
4039Image Formats:
4040==============
4041
4042U-Boot is capable of booting (and performing other auxiliary operations on)
4043images in two formats:
4044
4045New uImage format (FIT)
4046-----------------------
4047
4048Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4049to Flattened Device Tree). It allows the use of images with multiple
4050components (several kernels, ramdisks, etc.), with contents protected by
4051SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4052
4053
4054Old uImage format
4055-----------------
4056
4057Old image format is based on binary files which can be basically anything,
4058preceded by a special header; see the definitions in include/image.h for
4059details; basically, the header defines the following image properties:
4060
4061* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4062  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4063  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4064  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4065  INTEGRITY).
4066* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4067  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4068  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4069* Compression Type (uncompressed, gzip, bzip2)
4070* Load Address
4071* Entry Point
4072* Image Name
4073* Image Timestamp
4074
4075The header is marked by a special Magic Number, and both the header
4076and the data portions of the image are secured against corruption by
4077CRC32 checksums.
4078
4079
4080Linux Support:
4081==============
4082
4083Although U-Boot should support any OS or standalone application
4084easily, the main focus has always been on Linux during the design of
4085U-Boot.
4086
4087U-Boot includes many features that so far have been part of some
4088special "boot loader" code within the Linux kernel. Also, any
4089"initrd" images to be used are no longer part of one big Linux image;
4090instead, kernel and "initrd" are separate images. This implementation
4091serves several purposes:
4092
4093- the same features can be used for other OS or standalone
4094  applications (for instance: using compressed images to reduce the
4095  Flash memory footprint)
4096
4097- it becomes much easier to port new Linux kernel versions because
4098  lots of low-level, hardware dependent stuff are done by U-Boot
4099
4100- the same Linux kernel image can now be used with different "initrd"
4101  images; of course this also means that different kernel images can
4102  be run with the same "initrd". This makes testing easier (you don't
4103  have to build a new "zImage.initrd" Linux image when you just
4104  change a file in your "initrd"). Also, a field-upgrade of the
4105  software is easier now.
4106
4107
4108Linux HOWTO:
4109============
4110
4111Porting Linux to U-Boot based systems:
4112---------------------------------------
4113
4114U-Boot cannot save you from doing all the necessary modifications to
4115configure the Linux device drivers for use with your target hardware
4116(no, we don't intend to provide a full virtual machine interface to
4117Linux :-).
4118
4119But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4120
4121Just make sure your machine specific header file (for instance
4122include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4123Information structure as we define in include/asm-<arch>/u-boot.h,
4124and make sure that your definition of IMAP_ADDR uses the same value
4125as your U-Boot configuration in CONFIG_SYS_IMMR.
4126
4127Note that U-Boot now has a driver model, a unified model for drivers.
4128If you are adding a new driver, plumb it into driver model. If there
4129is no uclass available, you are encouraged to create one. See
4130doc/driver-model.
4131
4132
4133Configuring the Linux kernel:
4134-----------------------------
4135
4136No specific requirements for U-Boot. Make sure you have some root
4137device (initial ramdisk, NFS) for your target system.
4138
4139
4140Building a Linux Image:
4141-----------------------
4142
4143With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4144not used. If you use recent kernel source, a new build target
4145"uImage" will exist which automatically builds an image usable by
4146U-Boot. Most older kernels also have support for a "pImage" target,
4147which was introduced for our predecessor project PPCBoot and uses a
4148100% compatible format.
4149
4150Example:
4151
4152	make TQM850L_defconfig
4153	make oldconfig
4154	make dep
4155	make uImage
4156
4157The "uImage" build target uses a special tool (in 'tools/mkimage') to
4158encapsulate a compressed Linux kernel image with header	 information,
4159CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4160
4161* build a standard "vmlinux" kernel image (in ELF binary format):
4162
4163* convert the kernel into a raw binary image:
4164
4165	${CROSS_COMPILE}-objcopy -O binary \
4166				 -R .note -R .comment \
4167				 -S vmlinux linux.bin
4168
4169* compress the binary image:
4170
4171	gzip -9 linux.bin
4172
4173* package compressed binary image for U-Boot:
4174
4175	mkimage -A ppc -O linux -T kernel -C gzip \
4176		-a 0 -e 0 -n "Linux Kernel Image" \
4177		-d linux.bin.gz uImage
4178
4179
4180The "mkimage" tool can also be used to create ramdisk images for use
4181with U-Boot, either separated from the Linux kernel image, or
4182combined into one file. "mkimage" encapsulates the images with a 64
4183byte header containing information about target architecture,
4184operating system, image type, compression method, entry points, time
4185stamp, CRC32 checksums, etc.
4186
4187"mkimage" can be called in two ways: to verify existing images and
4188print the header information, or to build new images.
4189
4190In the first form (with "-l" option) mkimage lists the information
4191contained in the header of an existing U-Boot image; this includes
4192checksum verification:
4193
4194	tools/mkimage -l image
4195	  -l ==> list image header information
4196
4197The second form (with "-d" option) is used to build a U-Boot image
4198from a "data file" which is used as image payload:
4199
4200	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4201		      -n name -d data_file image
4202	  -A ==> set architecture to 'arch'
4203	  -O ==> set operating system to 'os'
4204	  -T ==> set image type to 'type'
4205	  -C ==> set compression type 'comp'
4206	  -a ==> set load address to 'addr' (hex)
4207	  -e ==> set entry point to 'ep' (hex)
4208	  -n ==> set image name to 'name'
4209	  -d ==> use image data from 'datafile'
4210
4211Right now, all Linux kernels for PowerPC systems use the same load
4212address (0x00000000), but the entry point address depends on the
4213kernel version:
4214
4215- 2.2.x kernels have the entry point at 0x0000000C,
4216- 2.3.x and later kernels have the entry point at 0x00000000.
4217
4218So a typical call to build a U-Boot image would read:
4219
4220	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4221	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4222	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4223	> examples/uImage.TQM850L
4224	Image Name:   2.4.4 kernel for TQM850L
4225	Created:      Wed Jul 19 02:34:59 2000
4226	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4227	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4228	Load Address: 0x00000000
4229	Entry Point:  0x00000000
4230
4231To verify the contents of the image (or check for corruption):
4232
4233	-> tools/mkimage -l examples/uImage.TQM850L
4234	Image Name:   2.4.4 kernel for TQM850L
4235	Created:      Wed Jul 19 02:34:59 2000
4236	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4237	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4238	Load Address: 0x00000000
4239	Entry Point:  0x00000000
4240
4241NOTE: for embedded systems where boot time is critical you can trade
4242speed for memory and install an UNCOMPRESSED image instead: this
4243needs more space in Flash, but boots much faster since it does not
4244need to be uncompressed:
4245
4246	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4247	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4248	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4249	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4250	> examples/uImage.TQM850L-uncompressed
4251	Image Name:   2.4.4 kernel for TQM850L
4252	Created:      Wed Jul 19 02:34:59 2000
4253	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4254	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4255	Load Address: 0x00000000
4256	Entry Point:  0x00000000
4257
4258
4259Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4260when your kernel is intended to use an initial ramdisk:
4261
4262	-> tools/mkimage -n 'Simple Ramdisk Image' \
4263	> -A ppc -O linux -T ramdisk -C gzip \
4264	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4265	Image Name:   Simple Ramdisk Image
4266	Created:      Wed Jan 12 14:01:50 2000
4267	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4268	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4269	Load Address: 0x00000000
4270	Entry Point:  0x00000000
4271
4272The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4273option performs the converse operation of the mkimage's second form (the "-d"
4274option). Given an image built by mkimage, the dumpimage extracts a "data file"
4275from the image:
4276
4277	tools/dumpimage -i image -T type -p position data_file
4278	  -i ==> extract from the 'image' a specific 'data_file'
4279	  -T ==> set image type to 'type'
4280	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4281
4282
4283Installing a Linux Image:
4284-------------------------
4285
4286To downloading a U-Boot image over the serial (console) interface,
4287you must convert the image to S-Record format:
4288
4289	objcopy -I binary -O srec examples/image examples/image.srec
4290
4291The 'objcopy' does not understand the information in the U-Boot
4292image header, so the resulting S-Record file will be relative to
4293address 0x00000000. To load it to a given address, you need to
4294specify the target address as 'offset' parameter with the 'loads'
4295command.
4296
4297Example: install the image to address 0x40100000 (which on the
4298TQM8xxL is in the first Flash bank):
4299
4300	=> erase 40100000 401FFFFF
4301
4302	.......... done
4303	Erased 8 sectors
4304
4305	=> loads 40100000
4306	## Ready for S-Record download ...
4307	~>examples/image.srec
4308	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4309	...
4310	15989 15990 15991 15992
4311	[file transfer complete]
4312	[connected]
4313	## Start Addr = 0x00000000
4314
4315
4316You can check the success of the download using the 'iminfo' command;
4317this includes a checksum verification so you can be sure no data
4318corruption happened:
4319
4320	=> imi 40100000
4321
4322	## Checking Image at 40100000 ...
4323	   Image Name:	 2.2.13 for initrd on TQM850L
4324	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4325	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4326	   Load Address: 00000000
4327	   Entry Point:	 0000000c
4328	   Verifying Checksum ... OK
4329
4330
4331Boot Linux:
4332-----------
4333
4334The "bootm" command is used to boot an application that is stored in
4335memory (RAM or Flash). In case of a Linux kernel image, the contents
4336of the "bootargs" environment variable is passed to the kernel as
4337parameters. You can check and modify this variable using the
4338"printenv" and "setenv" commands:
4339
4340
4341	=> printenv bootargs
4342	bootargs=root=/dev/ram
4343
4344	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4345
4346	=> printenv bootargs
4347	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4348
4349	=> bootm 40020000
4350	## Booting Linux kernel at 40020000 ...
4351	   Image Name:	 2.2.13 for NFS on TQM850L
4352	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4353	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4354	   Load Address: 00000000
4355	   Entry Point:	 0000000c
4356	   Verifying Checksum ... OK
4357	   Uncompressing Kernel Image ... OK
4358	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
4359	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4360	time_init: decrementer frequency = 187500000/60
4361	Calibrating delay loop... 49.77 BogoMIPS
4362	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4363	...
4364
4365If you want to boot a Linux kernel with initial RAM disk, you pass
4366the memory addresses of both the kernel and the initrd image (PPBCOOT
4367format!) to the "bootm" command:
4368
4369	=> imi 40100000 40200000
4370
4371	## Checking Image at 40100000 ...
4372	   Image Name:	 2.2.13 for initrd on TQM850L
4373	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4374	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4375	   Load Address: 00000000
4376	   Entry Point:	 0000000c
4377	   Verifying Checksum ... OK
4378
4379	## Checking Image at 40200000 ...
4380	   Image Name:	 Simple Ramdisk Image
4381	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4382	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4383	   Load Address: 00000000
4384	   Entry Point:	 00000000
4385	   Verifying Checksum ... OK
4386
4387	=> bootm 40100000 40200000
4388	## Booting Linux kernel at 40100000 ...
4389	   Image Name:	 2.2.13 for initrd on TQM850L
4390	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4391	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4392	   Load Address: 00000000
4393	   Entry Point:	 0000000c
4394	   Verifying Checksum ... OK
4395	   Uncompressing Kernel Image ... OK
4396	## Loading RAMDisk Image at 40200000 ...
4397	   Image Name:	 Simple Ramdisk Image
4398	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4399	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4400	   Load Address: 00000000
4401	   Entry Point:	 00000000
4402	   Verifying Checksum ... OK
4403	   Loading Ramdisk ... OK
4404	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
4405	Boot arguments: root=/dev/ram
4406	time_init: decrementer frequency = 187500000/60
4407	Calibrating delay loop... 49.77 BogoMIPS
4408	...
4409	RAMDISK: Compressed image found at block 0
4410	VFS: Mounted root (ext2 filesystem).
4411
4412	bash#
4413
4414Boot Linux and pass a flat device tree:
4415-----------
4416
4417First, U-Boot must be compiled with the appropriate defines. See the section
4418titled "Linux Kernel Interface" above for a more in depth explanation. The
4419following is an example of how to start a kernel and pass an updated
4420flat device tree:
4421
4422=> print oftaddr
4423oftaddr=0x300000
4424=> print oft
4425oft=oftrees/mpc8540ads.dtb
4426=> tftp $oftaddr $oft
4427Speed: 1000, full duplex
4428Using TSEC0 device
4429TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4430Filename 'oftrees/mpc8540ads.dtb'.
4431Load address: 0x300000
4432Loading: #
4433done
4434Bytes transferred = 4106 (100a hex)
4435=> tftp $loadaddr $bootfile
4436Speed: 1000, full duplex
4437Using TSEC0 device
4438TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4439Filename 'uImage'.
4440Load address: 0x200000
4441Loading:############
4442done
4443Bytes transferred = 1029407 (fb51f hex)
4444=> print loadaddr
4445loadaddr=200000
4446=> print oftaddr
4447oftaddr=0x300000
4448=> bootm $loadaddr - $oftaddr
4449## Booting image at 00200000 ...
4450   Image Name:	 Linux-2.6.17-dirty
4451   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4452   Data Size:	 1029343 Bytes = 1005.2 kB
4453   Load Address: 00000000
4454   Entry Point:	 00000000
4455   Verifying Checksum ... OK
4456   Uncompressing Kernel Image ... OK
4457Booting using flat device tree at 0x300000
4458Using MPC85xx ADS machine description
4459Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4460[snip]
4461
4462
4463More About U-Boot Image Types:
4464------------------------------
4465
4466U-Boot supports the following image types:
4467
4468   "Standalone Programs" are directly runnable in the environment
4469	provided by U-Boot; it is expected that (if they behave
4470	well) you can continue to work in U-Boot after return from
4471	the Standalone Program.
4472   "OS Kernel Images" are usually images of some Embedded OS which
4473	will take over control completely. Usually these programs
4474	will install their own set of exception handlers, device
4475	drivers, set up the MMU, etc. - this means, that you cannot
4476	expect to re-enter U-Boot except by resetting the CPU.
4477   "RAMDisk Images" are more or less just data blocks, and their
4478	parameters (address, size) are passed to an OS kernel that is
4479	being started.
4480   "Multi-File Images" contain several images, typically an OS
4481	(Linux) kernel image and one or more data images like
4482	RAMDisks. This construct is useful for instance when you want
4483	to boot over the network using BOOTP etc., where the boot
4484	server provides just a single image file, but you want to get
4485	for instance an OS kernel and a RAMDisk image.
4486
4487	"Multi-File Images" start with a list of image sizes, each
4488	image size (in bytes) specified by an "uint32_t" in network
4489	byte order. This list is terminated by an "(uint32_t)0".
4490	Immediately after the terminating 0 follow the images, one by
4491	one, all aligned on "uint32_t" boundaries (size rounded up to
4492	a multiple of 4 bytes).
4493
4494   "Firmware Images" are binary images containing firmware (like
4495	U-Boot or FPGA images) which usually will be programmed to
4496	flash memory.
4497
4498   "Script files" are command sequences that will be executed by
4499	U-Boot's command interpreter; this feature is especially
4500	useful when you configure U-Boot to use a real shell (hush)
4501	as command interpreter.
4502
4503Booting the Linux zImage:
4504-------------------------
4505
4506On some platforms, it's possible to boot Linux zImage. This is done
4507using the "bootz" command. The syntax of "bootz" command is the same
4508as the syntax of "bootm" command.
4509
4510Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4511kernel with raw initrd images. The syntax is slightly different, the
4512address of the initrd must be augmented by it's size, in the following
4513format: "<initrd addres>:<initrd size>".
4514
4515
4516Standalone HOWTO:
4517=================
4518
4519One of the features of U-Boot is that you can dynamically load and
4520run "standalone" applications, which can use some resources of
4521U-Boot like console I/O functions or interrupt services.
4522
4523Two simple examples are included with the sources:
4524
4525"Hello World" Demo:
4526-------------------
4527
4528'examples/hello_world.c' contains a small "Hello World" Demo
4529application; it is automatically compiled when you build U-Boot.
4530It's configured to run at address 0x00040004, so you can play with it
4531like that:
4532
4533	=> loads
4534	## Ready for S-Record download ...
4535	~>examples/hello_world.srec
4536	1 2 3 4 5 6 7 8 9 10 11 ...
4537	[file transfer complete]
4538	[connected]
4539	## Start Addr = 0x00040004
4540
4541	=> go 40004 Hello World! This is a test.
4542	## Starting application at 0x00040004 ...
4543	Hello World
4544	argc = 7
4545	argv[0] = "40004"
4546	argv[1] = "Hello"
4547	argv[2] = "World!"
4548	argv[3] = "This"
4549	argv[4] = "is"
4550	argv[5] = "a"
4551	argv[6] = "test."
4552	argv[7] = "<NULL>"
4553	Hit any key to exit ...
4554
4555	## Application terminated, rc = 0x0
4556
4557Another example, which demonstrates how to register a CPM interrupt
4558handler with the U-Boot code, can be found in 'examples/timer.c'.
4559Here, a CPM timer is set up to generate an interrupt every second.
4560The interrupt service routine is trivial, just printing a '.'
4561character, but this is just a demo program. The application can be
4562controlled by the following keys:
4563
4564	? - print current values og the CPM Timer registers
4565	b - enable interrupts and start timer
4566	e - stop timer and disable interrupts
4567	q - quit application
4568
4569	=> loads
4570	## Ready for S-Record download ...
4571	~>examples/timer.srec
4572	1 2 3 4 5 6 7 8 9 10 11 ...
4573	[file transfer complete]
4574	[connected]
4575	## Start Addr = 0x00040004
4576
4577	=> go 40004
4578	## Starting application at 0x00040004 ...
4579	TIMERS=0xfff00980
4580	Using timer 1
4581	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4582
4583Hit 'b':
4584	[q, b, e, ?] Set interval 1000000 us
4585	Enabling timer
4586Hit '?':
4587	[q, b, e, ?] ........
4588	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4589Hit '?':
4590	[q, b, e, ?] .
4591	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4592Hit '?':
4593	[q, b, e, ?] .
4594	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4595Hit '?':
4596	[q, b, e, ?] .
4597	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4598Hit 'e':
4599	[q, b, e, ?] ...Stopping timer
4600Hit 'q':
4601	[q, b, e, ?] ## Application terminated, rc = 0x0
4602
4603
4604Minicom warning:
4605================
4606
4607Over time, many people have reported problems when trying to use the
4608"minicom" terminal emulation program for serial download. I (wd)
4609consider minicom to be broken, and recommend not to use it. Under
4610Unix, I recommend to use C-Kermit for general purpose use (and
4611especially for kermit binary protocol download ("loadb" command), and
4612use "cu" for S-Record download ("loads" command).  See
4613http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4614for help with kermit.
4615
4616
4617Nevertheless, if you absolutely want to use it try adding this
4618configuration to your "File transfer protocols" section:
4619
4620	   Name	   Program			Name U/D FullScr IO-Red. Multi
4621	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4622	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4623
4624
4625NetBSD Notes:
4626=============
4627
4628Starting at version 0.9.2, U-Boot supports NetBSD both as host
4629(build U-Boot) and target system (boots NetBSD/mpc8xx).
4630
4631Building requires a cross environment; it is known to work on
4632NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4633need gmake since the Makefiles are not compatible with BSD make).
4634Note that the cross-powerpc package does not install include files;
4635attempting to build U-Boot will fail because <machine/ansi.h> is
4636missing.  This file has to be installed and patched manually:
4637
4638	# cd /usr/pkg/cross/powerpc-netbsd/include
4639	# mkdir powerpc
4640	# ln -s powerpc machine
4641	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4642	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4643
4644Native builds *don't* work due to incompatibilities between native
4645and U-Boot include files.
4646
4647Booting assumes that (the first part of) the image booted is a
4648stage-2 loader which in turn loads and then invokes the kernel
4649proper. Loader sources will eventually appear in the NetBSD source
4650tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4651meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4652
4653
4654Implementation Internals:
4655=========================
4656
4657The following is not intended to be a complete description of every
4658implementation detail. However, it should help to understand the
4659inner workings of U-Boot and make it easier to port it to custom
4660hardware.
4661
4662
4663Initial Stack, Global Data:
4664---------------------------
4665
4666The implementation of U-Boot is complicated by the fact that U-Boot
4667starts running out of ROM (flash memory), usually without access to
4668system RAM (because the memory controller is not initialized yet).
4669This means that we don't have writable Data or BSS segments, and BSS
4670is not initialized as zero. To be able to get a C environment working
4671at all, we have to allocate at least a minimal stack. Implementation
4672options for this are defined and restricted by the CPU used: Some CPU
4673models provide on-chip memory (like the IMMR area on MPC8xx and
4674MPC826x processors), on others (parts of) the data cache can be
4675locked as (mis-) used as memory, etc.
4676
4677	Chris Hallinan posted a good summary of these issues to the
4678	U-Boot mailing list:
4679
4680	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4681	From: "Chris Hallinan" <clh@net1plus.com>
4682	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4683	...
4684
4685	Correct me if I'm wrong, folks, but the way I understand it
4686	is this: Using DCACHE as initial RAM for Stack, etc, does not
4687	require any physical RAM backing up the cache. The cleverness
4688	is that the cache is being used as a temporary supply of
4689	necessary storage before the SDRAM controller is setup. It's
4690	beyond the scope of this list to explain the details, but you
4691	can see how this works by studying the cache architecture and
4692	operation in the architecture and processor-specific manuals.
4693
4694	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4695	is another option for the system designer to use as an
4696	initial stack/RAM area prior to SDRAM being available. Either
4697	option should work for you. Using CS 4 should be fine if your
4698	board designers haven't used it for something that would
4699	cause you grief during the initial boot! It is frequently not
4700	used.
4701
4702	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4703	with your processor/board/system design. The default value
4704	you will find in any recent u-boot distribution in
4705	walnut.h should work for you. I'd set it to a value larger
4706	than your SDRAM module. If you have a 64MB SDRAM module, set
4707	it above 400_0000. Just make sure your board has no resources
4708	that are supposed to respond to that address! That code in
4709	start.S has been around a while and should work as is when
4710	you get the config right.
4711
4712	-Chris Hallinan
4713	DS4.COM, Inc.
4714
4715It is essential to remember this, since it has some impact on the C
4716code for the initialization procedures:
4717
4718* Initialized global data (data segment) is read-only. Do not attempt
4719  to write it.
4720
4721* Do not use any uninitialized global data (or implicitly initialized
4722  as zero data - BSS segment) at all - this is undefined, initiali-
4723  zation is performed later (when relocating to RAM).
4724
4725* Stack space is very limited. Avoid big data buffers or things like
4726  that.
4727
4728Having only the stack as writable memory limits means we cannot use
4729normal global data to share information between the code. But it
4730turned out that the implementation of U-Boot can be greatly
4731simplified by making a global data structure (gd_t) available to all
4732functions. We could pass a pointer to this data as argument to _all_
4733functions, but this would bloat the code. Instead we use a feature of
4734the GCC compiler (Global Register Variables) to share the data: we
4735place a pointer (gd) to the global data into a register which we
4736reserve for this purpose.
4737
4738When choosing a register for such a purpose we are restricted by the
4739relevant  (E)ABI  specifications for the current architecture, and by
4740GCC's implementation.
4741
4742For PowerPC, the following registers have specific use:
4743	R1:	stack pointer
4744	R2:	reserved for system use
4745	R3-R4:	parameter passing and return values
4746	R5-R10: parameter passing
4747	R13:	small data area pointer
4748	R30:	GOT pointer
4749	R31:	frame pointer
4750
4751	(U-Boot also uses R12 as internal GOT pointer. r12
4752	is a volatile register so r12 needs to be reset when
4753	going back and forth between asm and C)
4754
4755    ==> U-Boot will use R2 to hold a pointer to the global data
4756
4757    Note: on PPC, we could use a static initializer (since the
4758    address of the global data structure is known at compile time),
4759    but it turned out that reserving a register results in somewhat
4760    smaller code - although the code savings are not that big (on
4761    average for all boards 752 bytes for the whole U-Boot image,
4762    624 text + 127 data).
4763
4764On ARM, the following registers are used:
4765
4766	R0:	function argument word/integer result
4767	R1-R3:	function argument word
4768	R9:	platform specific
4769	R10:	stack limit (used only if stack checking is enabled)
4770	R11:	argument (frame) pointer
4771	R12:	temporary workspace
4772	R13:	stack pointer
4773	R14:	link register
4774	R15:	program counter
4775
4776    ==> U-Boot will use R9 to hold a pointer to the global data
4777
4778    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4779
4780On Nios II, the ABI is documented here:
4781	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4782
4783    ==> U-Boot will use gp to hold a pointer to the global data
4784
4785    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4786    to access small data sections, so gp is free.
4787
4788On NDS32, the following registers are used:
4789
4790	R0-R1:	argument/return
4791	R2-R5:	argument
4792	R15:	temporary register for assembler
4793	R16:	trampoline register
4794	R28:	frame pointer (FP)
4795	R29:	global pointer (GP)
4796	R30:	link register (LP)
4797	R31:	stack pointer (SP)
4798	PC:	program counter (PC)
4799
4800    ==> U-Boot will use R10 to hold a pointer to the global data
4801
4802NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4803or current versions of GCC may "optimize" the code too much.
4804
4805On RISC-V, the following registers are used:
4806
4807	x0: hard-wired zero (zero)
4808	x1: return address (ra)
4809	x2:	stack pointer (sp)
4810	x3:	global pointer (gp)
4811	x4:	thread pointer (tp)
4812	x5:	link register (t0)
4813	x8:	frame pointer (fp)
4814	x10-x11:	arguments/return values (a0-1)
4815	x12-x17:	arguments (a2-7)
4816	x28-31:	 temporaries (t3-6)
4817	pc:	program counter (pc)
4818
4819    ==> U-Boot will use gp to hold a pointer to the global data
4820
4821Memory Management:
4822------------------
4823
4824U-Boot runs in system state and uses physical addresses, i.e. the
4825MMU is not used either for address mapping nor for memory protection.
4826
4827The available memory is mapped to fixed addresses using the memory
4828controller. In this process, a contiguous block is formed for each
4829memory type (Flash, SDRAM, SRAM), even when it consists of several
4830physical memory banks.
4831
4832U-Boot is installed in the first 128 kB of the first Flash bank (on
4833TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4834booting and sizing and initializing DRAM, the code relocates itself
4835to the upper end of DRAM. Immediately below the U-Boot code some
4836memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4837configuration setting]. Below that, a structure with global Board
4838Info data is placed, followed by the stack (growing downward).
4839
4840Additionally, some exception handler code is copied to the low 8 kB
4841of DRAM (0x00000000 ... 0x00001FFF).
4842
4843So a typical memory configuration with 16 MB of DRAM could look like
4844this:
4845
4846	0x0000 0000	Exception Vector code
4847	      :
4848	0x0000 1FFF
4849	0x0000 2000	Free for Application Use
4850	      :
4851	      :
4852
4853	      :
4854	      :
4855	0x00FB FF20	Monitor Stack (Growing downward)
4856	0x00FB FFAC	Board Info Data and permanent copy of global data
4857	0x00FC 0000	Malloc Arena
4858	      :
4859	0x00FD FFFF
4860	0x00FE 0000	RAM Copy of Monitor Code
4861	...		eventually: LCD or video framebuffer
4862	...		eventually: pRAM (Protected RAM - unchanged by reset)
4863	0x00FF FFFF	[End of RAM]
4864
4865
4866System Initialization:
4867----------------------
4868
4869In the reset configuration, U-Boot starts at the reset entry point
4870(on most PowerPC systems at address 0x00000100). Because of the reset
4871configuration for CS0# this is a mirror of the on board Flash memory.
4872To be able to re-map memory U-Boot then jumps to its link address.
4873To be able to implement the initialization code in C, a (small!)
4874initial stack is set up in the internal Dual Ported RAM (in case CPUs
4875which provide such a feature like), or in a locked part of the data
4876cache. After that, U-Boot initializes the CPU core, the caches and
4877the SIU.
4878
4879Next, all (potentially) available memory banks are mapped using a
4880preliminary mapping. For example, we put them on 512 MB boundaries
4881(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4882on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4883programmed for SDRAM access. Using the temporary configuration, a
4884simple memory test is run that determines the size of the SDRAM
4885banks.
4886
4887When there is more than one SDRAM bank, and the banks are of
4888different size, the largest is mapped first. For equal size, the first
4889bank (CS2#) is mapped first. The first mapping is always for address
48900x00000000, with any additional banks following immediately to create
4891contiguous memory starting from 0.
4892
4893Then, the monitor installs itself at the upper end of the SDRAM area
4894and allocates memory for use by malloc() and for the global Board
4895Info data; also, the exception vector code is copied to the low RAM
4896pages, and the final stack is set up.
4897
4898Only after this relocation will you have a "normal" C environment;
4899until that you are restricted in several ways, mostly because you are
4900running from ROM, and because the code will have to be relocated to a
4901new address in RAM.
4902
4903
4904U-Boot Porting Guide:
4905----------------------
4906
4907[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4908list, October 2002]
4909
4910
4911int main(int argc, char *argv[])
4912{
4913	sighandler_t no_more_time;
4914
4915	signal(SIGALRM, no_more_time);
4916	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4917
4918	if (available_money > available_manpower) {
4919		Pay consultant to port U-Boot;
4920		return 0;
4921	}
4922
4923	Download latest U-Boot source;
4924
4925	Subscribe to u-boot mailing list;
4926
4927	if (clueless)
4928		email("Hi, I am new to U-Boot, how do I get started?");
4929
4930	while (learning) {
4931		Read the README file in the top level directory;
4932		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4933		Read applicable doc/*.README;
4934		Read the source, Luke;
4935		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4936	}
4937
4938	if (available_money > toLocalCurrency ($2500))
4939		Buy a BDI3000;
4940	else
4941		Add a lot of aggravation and time;
4942
4943	if (a similar board exists) {	/* hopefully... */
4944		cp -a board/<similar> board/<myboard>
4945		cp include/configs/<similar>.h include/configs/<myboard>.h
4946	} else {
4947		Create your own board support subdirectory;
4948		Create your own board include/configs/<myboard>.h file;
4949	}
4950	Edit new board/<myboard> files
4951	Edit new include/configs/<myboard>.h
4952
4953	while (!accepted) {
4954		while (!running) {
4955			do {
4956				Add / modify source code;
4957			} until (compiles);
4958			Debug;
4959			if (clueless)
4960				email("Hi, I am having problems...");
4961		}
4962		Send patch file to the U-Boot email list;
4963		if (reasonable critiques)
4964			Incorporate improvements from email list code review;
4965		else
4966			Defend code as written;
4967	}
4968
4969	return 0;
4970}
4971
4972void no_more_time (int sig)
4973{
4974      hire_a_guru();
4975}
4976
4977
4978Coding Standards:
4979-----------------
4980
4981All contributions to U-Boot should conform to the Linux kernel
4982coding style; see the kernel coding style guide at
4983https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4984script "scripts/Lindent" in your Linux kernel source directory.
4985
4986Source files originating from a different project (for example the
4987MTD subsystem) are generally exempt from these guidelines and are not
4988reformatted to ease subsequent migration to newer versions of those
4989sources.
4990
4991Please note that U-Boot is implemented in C (and to some small parts in
4992Assembler); no C++ is used, so please do not use C++ style comments (//)
4993in your code.
4994
4995Please also stick to the following formatting rules:
4996- remove any trailing white space
4997- use TAB characters for indentation and vertical alignment, not spaces
4998- make sure NOT to use DOS '\r\n' line feeds
4999- do not add more than 2 consecutive empty lines to source files
5000- do not add trailing empty lines to source files
5001
5002Submissions which do not conform to the standards may be returned
5003with a request to reformat the changes.
5004
5005
5006Submitting Patches:
5007-------------------
5008
5009Since the number of patches for U-Boot is growing, we need to
5010establish some rules. Submissions which do not conform to these rules
5011may be rejected, even when they contain important and valuable stuff.
5012
5013Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5014
5015Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5016see https://lists.denx.de/listinfo/u-boot
5017
5018When you send a patch, please include the following information with
5019it:
5020
5021* For bug fixes: a description of the bug and how your patch fixes
5022  this bug. Please try to include a way of demonstrating that the
5023  patch actually fixes something.
5024
5025* For new features: a description of the feature and your
5026  implementation.
5027
5028* A CHANGELOG entry as plaintext (separate from the patch)
5029
5030* For major contributions, add a MAINTAINERS file with your
5031  information and associated file and directory references.
5032
5033* When you add support for a new board, don't forget to add a
5034  maintainer e-mail address to the boards.cfg file, too.
5035
5036* If your patch adds new configuration options, don't forget to
5037  document these in the README file.
5038
5039* The patch itself. If you are using git (which is *strongly*
5040  recommended) you can easily generate the patch using the
5041  "git format-patch". If you then use "git send-email" to send it to
5042  the U-Boot mailing list, you will avoid most of the common problems
5043  with some other mail clients.
5044
5045  If you cannot use git, use "diff -purN OLD NEW". If your version of
5046  diff does not support these options, then get the latest version of
5047  GNU diff.
5048
5049  The current directory when running this command shall be the parent
5050  directory of the U-Boot source tree (i. e. please make sure that
5051  your patch includes sufficient directory information for the
5052  affected files).
5053
5054  We prefer patches as plain text. MIME attachments are discouraged,
5055  and compressed attachments must not be used.
5056
5057* If one logical set of modifications affects or creates several
5058  files, all these changes shall be submitted in a SINGLE patch file.
5059
5060* Changesets that contain different, unrelated modifications shall be
5061  submitted as SEPARATE patches, one patch per changeset.
5062
5063
5064Notes:
5065
5066* Before sending the patch, run the buildman script on your patched
5067  source tree and make sure that no errors or warnings are reported
5068  for any of the boards.
5069
5070* Keep your modifications to the necessary minimum: A patch
5071  containing several unrelated changes or arbitrary reformats will be
5072  returned with a request to re-formatting / split it.
5073
5074* If you modify existing code, make sure that your new code does not
5075  add to the memory footprint of the code ;-) Small is beautiful!
5076  When adding new features, these should compile conditionally only
5077  (using #ifdef), and the resulting code with the new feature
5078  disabled must not need more memory than the old code without your
5079  modification.
5080
5081* Remember that there is a size limit of 100 kB per message on the
5082  u-boot mailing list. Bigger patches will be moderated. If they are
5083  reasonable and not too big, they will be acknowledged. But patches
5084  bigger than the size limit should be avoided.
5085