9 config SPL_DFU_NO_RESET
14 depends on SUPPORT_SPL
17 If you want to build SPL as well as the normal image, say Y.
20 bool "Support SPL based upon the common SPL framework"
24 Enable the SPL framework under common/spl/. This framework
25 supports MMC, NAND and YMODEM and other methods loading of U-Boot
26 and the Linux Kernel. If unsure, say Y.
29 hex "Maximum size of SPL image"
31 default 69632 if ARCH_MX6 && !MX6_OCRAM_256KB
32 default 200704 if ARCH_MX6 && MX6_OCRAM_256KB
35 Specifies the maximum length of the U-Boot SPL image.
36 If this value is zero, it is ignored.
38 config SPL_SIZE_LIMIT_SUBTRACT_GD
39 bool "SPL image size check: provide space for global data"
40 depends on SPL_SIZE_LIMIT > 0
42 If enabled, aligned size of global data is reserved in
43 SPL_SIZE_LIMIT check to ensure such an image does not overflow SRAM
44 if SPL_SIZE_LIMIT describes the size of SRAM available for SPL when
45 pre-reloc global data is put into this SRAM, too.
47 config SPL_SIZE_LIMIT_SUBTRACT_MALLOC
48 bool "SPL image size check: provide space for malloc() pool before relocation"
49 depends on SPL_SIZE_LIMIT > 0
51 If enabled, SPL_SYS_MALLOC_F_LEN is reserved in SPL_SIZE_LIMIT check
52 to ensure such an image does not overflow SRAM if SPL_SIZE_LIMIT
53 describes the size of SRAM available for SPL when pre-reloc malloc
54 pool is put into this SRAM, too.
56 config SPL_SIZE_LIMIT_PROVIDE_STACK
57 hex "SPL image size check: provide stack space before relocation"
58 depends on SPL_SIZE_LIMIT > 0
61 If set, this size is reserved in SPL_SIZE_LIMIT check to ensure such
62 an image does not overflow SRAM if SPL_SIZE_LIMIT describes the size
63 of SRAM available for SPL when the stack required before reolcation
66 config SPL_SYS_STACK_F_CHECK_BYTE
70 Constant used to check the stack
72 config SPL_SYS_REPORT_STACK_F_USAGE
73 depends on SPL_SIZE_LIMIT_PROVIDE_STACK != 0
74 bool "Check and report stack usage in SPL before relocation"
76 If this option is enabled, the initial SPL stack is filled with 0xaa
77 very early, up to the size configured with
78 SPL_SIZE_LIMIT_PROVIDE_STACK.
79 Later when SPL is done using this initial stack and switches to a
80 stack in DRAM, the actually used size of this initial stack is
81 reported by examining the memory and searching for the lowest
82 occurrence of non 0xaa bytes.
83 This default implementation works for stacks growing down only.
85 menu "PowerPC SPL Boot options"
86 depends on PPC && (SUPPORT_SPL && !SPL_FRAMEWORK)
89 bool "Load SPL from NAND flash"
92 bool "Load SPL from SD Card / eMMC"
95 bool "Load SPL from SPI flash"
98 bool "Create SPL in Freescale PBI format"
100 Create boot binary having SPL binary in PBI format concatenated with
106 bool "Pass hand-off information from SPL to U-Boot proper"
109 It is useful to be able to pass information from SPL to U-Boot
110 proper to preserve state that is known in SPL and is needed in U-Boot.
111 Enable this to locate the handoff information in U-Boot proper, early
112 in boot. It is available in gd->handoff. The state state is set up
113 in SPL (or TPL if that is being used).
118 bool "Pass hand-off information from SPL to U-Boot proper"
119 depends on HANDOFF && SPL_BLOBLIST
122 This option enables SPL to write handoff information. This can be
123 used to pass information like the size of SDRAM from SPL to U-Boot
124 proper. Also SPL can receive information from TPL in the same place
128 string "Linker script for the SPL stage"
129 default "arch/$(ARCH)/cpu/u-boot-spl.lds"
131 The SPL stage will usually require a different linker-script
132 (as it runs from a different memory region) than the regular
133 U-Boot stage. Set this to the path of the linker-script to
138 default ISW_ENTRY_ADDR if AM43XX || AM33XX || OMAP54XX || ARCH_KEYSTONE
139 default 0x10060 if MACH_SUN50I || MACH_SUN50I_H5 || MACH_SUN9I
140 default 0x20060 if MACH_SUN50I_H6
141 default 0x00060 if ARCH_SUNXI
144 The address in memory that SPL will be running from.
146 config SPL_BOARD_INIT
147 bool "Call board-specific initialization in SPL"
149 If this option is enabled, U-Boot will call the function
150 spl_board_init() from board_init_r(). This function should be
151 provided by the board.
153 config SPL_BOOTROM_SUPPORT
154 bool "Support returning to the BOOTROM"
156 Some platforms (e.g. the Rockchip RK3368) provide support in their
157 ROM for loading the next boot-stage after performing basic setup
160 Enable this option, to return to the BOOTROM through the
161 BOOT_DEVICE_BOOTROM (or fall-through to the next boot device in the
162 boot device list, if not implemented for a given board)
164 config SPL_BOOTCOUNT_LIMIT
165 bool "Support bootcount in SPL"
166 depends on SPL_ENV_SUPPORT
168 On some boards, which use 'falcon' mode, it is necessary to check
169 and increment the number of boot attempts. Such boards do not
170 use proper U-Boot for normal boot flow and hence needs those
171 adjustments to be done in the SPL.
173 config SPL_RAW_IMAGE_SUPPORT
174 bool "Support SPL loading and booting of RAW images"
175 default n if (ARCH_MX6 && (SPL_MMC_SUPPORT || SPL_SATA_SUPPORT))
176 default y if !TI_SECURE_DEVICE
178 SPL will support loading and booting a RAW image when this option
179 is y. If this is not set, SPL will move on to other available
180 boot media to find a suitable image.
182 config SPL_LEGACY_IMAGE_SUPPORT
183 bool "Support SPL loading and booting of Legacy images"
184 default y if !TI_SECURE_DEVICE && !SPL_LOAD_FIT
186 SPL will support loading and booting Legacy images when this option
187 is y. If this is not set, SPL will move on to other available
188 boot media to find a suitable image.
190 config SPL_LEGACY_IMAGE_CRC_CHECK
191 bool "Check CRC of Legacy images"
192 depends on SPL_LEGACY_IMAGE_SUPPORT
193 select SPL_CRC32_SUPPORT
195 Enable this to check the CRC of Legacy images. While this increases
196 reliability, it affects both code size and boot duration.
197 If disabled, Legacy images are booted if the image magic and size
198 are correct, without further integrity checks.
200 config SPL_SYS_MALLOC_SIMPLE
202 prompt "Only use malloc_simple functions in the SPL"
204 Say Y here to only use the *_simple malloc functions from
205 malloc_simple.c, rather then using the versions from dlmalloc.c;
206 this will make the SPL binary smaller at the cost of more heap
207 usage as the *_simple malloc functions do not re-use free-ed mem.
209 config TPL_SYS_MALLOC_SIMPLE
211 prompt "Only use malloc_simple functions in the TPL"
214 Say Y here to only use the *_simple malloc functions from
215 malloc_simple.c, rather then using the versions from dlmalloc.c;
216 this will make the TPL binary smaller at the cost of more heap
217 usage as the *_simple malloc functions do not re-use free-ed mem.
220 bool "Enable SDRAM location for SPL stack"
222 SPL starts off execution in SRAM and thus typically has only a small
223 stack available. Since SPL sets up DRAM while in its board_init_f()
224 function, it is possible for the stack to move there before
225 board_init_r() is reached. This option enables a special SDRAM
226 location for the SPL stack. U-Boot SPL switches to this after
227 board_init_f() completes, and before board_init_r() starts.
229 config SPL_STACK_R_ADDR
230 depends on SPL_STACK_R
231 hex "SDRAM location for SPL stack"
232 default 0x82000000 if ARCH_OMAP2PLUS
234 Specify the address in SDRAM for the SPL stack. This will be set up
235 before board_init_r() is called.
237 config SPL_STACK_R_MALLOC_SIMPLE_LEN
238 depends on SPL_STACK_R && SPL_SYS_MALLOC_SIMPLE
239 hex "Size of malloc_simple heap after switching to DRAM SPL stack"
242 Specify the amount of the stack to use as memory pool for
243 malloc_simple after switching the stack to DRAM. This may be set
244 to give board_init_r() a larger heap then the initial heap in
245 SRAM which is limited to SYS_MALLOC_F_LEN bytes.
247 config SPL_SEPARATE_BSS
248 bool "BSS section is in a different memory region from text"
250 Some platforms need a large BSS region in SPL and can provide this
251 because RAM is already set up. In this case BSS can be moved to RAM.
252 This option should then be enabled so that the correct device tree
253 location is used. Normally we put the device tree at the end of BSS
254 but with this option enabled, it goes at _image_binary_end.
256 config SPL_BANNER_PRINT
257 bool "Enable output of the SPL banner 'U-Boot SPL ...'"
260 If this option is enabled, SPL will print the banner with version
261 info. Disabling this option could be useful to reduce TPL boot time
262 (e.g. approx. 6 ms faster, when output on i.MX6 with 115200 baud).
264 config TPL_BANNER_PRINT
265 bool "Enable output of the TPL banner 'U-Boot TPL ...'"
269 If this option is enabled, SPL will not print the banner with version
270 info. Disabling this option could be useful to reduce SPL boot time
271 (e.g. approx. 6 ms faster, when output on i.MX6 with 115200 baud).
274 depends on ARM && !ARM64
275 bool "Allows initializing BSS early before entering board_init_f"
277 On some platform we have sufficient memory available early on to
278 allow setting up and using a basic BSS prior to entering
279 board_init_f. Activating this option will also de-activate the
280 clearing of BSS during the SPL relocation process, thus allowing
281 to carry state from board_init_f to board_init_r by way of BSS.
283 config SPL_DISPLAY_PRINT
284 bool "Display a board-specific message in SPL"
286 If this option is enabled, U-Boot will call the function
287 spl_display_print() immediately after displaying the SPL console
288 banner ("U-Boot SPL ..."). This function should be provided by
291 config SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR
292 bool "MMC raw mode: by sector"
293 default y if ARCH_SUNXI || ARCH_DAVINCI || ARCH_UNIPHIER || \
294 ARCH_MX6 || ARCH_MX7 || \
295 ARCH_ROCKCHIP || ARCH_MVEBU || ARCH_SOCFPGA || \
296 ARCH_AT91 || ARCH_ZYNQ || ARCH_KEYSTONE || OMAP34XX || \
297 OMAP44XX || OMAP54XX || AM33XX || AM43XX
299 Use sector number for specifying U-Boot location on MMC/SD in
302 config SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR
303 hex "Address on the MMC to load U-Boot from"
304 depends on SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR
305 default 0x50 if ARCH_SUNXI
306 default 0x75 if ARCH_DAVINCI
307 default 0x8a if ARCH_MX6 || ARCH_MX7
308 default 0x100 if ARCH_UNIPHIER
309 default 0x140 if ARCH_MVEBU
310 default 0x200 if ARCH_SOCFPGA || ARCH_AT91
311 default 0x300 if ARCH_ZYNQ || ARCH_KEYSTONE || OMAP34XX || OMAP44XX || \
312 OMAP54XX || AM33XX || AM43XX || ARCH_K3
313 default 0x4000 if ARCH_ROCKCHIP
315 Address on the MMC to load U-Boot from, when the MMC is being used
316 in raw mode. Units: MMC sectors (1 sector = 512 bytes).
318 config SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION
319 bool "MMC Raw mode: by partition"
321 Use a partition for loading U-Boot when using MMC/SD in raw mode.
323 config SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
324 hex "Partition to use to load U-Boot from"
325 depends on SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION
328 Partition on the MMC to load U-Boot from when the MMC is being
331 config SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION_TYPE
332 bool "MMC raw mode: by partition type"
333 depends on DOS_PARTITION && SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION
335 Use partition type for specifying U-Boot partition on MMC/SD in
336 raw mode. U-Boot will be loaded from the first partition of this
339 config SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION_TYPE
340 hex "Partition Type on the MMC to load U-Boot from"
341 depends on SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION_TYPE
343 Partition Type on the MMC to load U-Boot from, when the MMC is being
346 config SPL_CRC32_SUPPORT
348 default y if SPL_LEGACY_IMAGE_SUPPORT
350 Enable this to support CRC32 in uImages or FIT images within SPL.
351 This is a 32-bit checksum value that can be used to verify images.
352 For FIT images, this is the least secure type of checksum, suitable
353 for detected accidental image corruption. For secure applications you
354 should consider SHA1 or SHA256.
356 config SPL_MD5_SUPPORT
360 Enable this to support MD5 in FIT images within SPL. An MD5
361 checksum is a 128-bit hash value used to check that the image
362 contents have not been corrupted. Note that MD5 is not considered
363 secure as it is possible (with a brute-force attack) to adjust the
364 image while still retaining the same MD5 hash value. For secure
365 applications where images may be changed maliciously, you should
366 consider SHA1 or SHA256.
368 config SPL_SHA1_SUPPORT
373 Enable this to support SHA1 in FIT images within SPL. A SHA1
374 checksum is a 160-bit (20-byte) hash value used to check that the
375 image contents have not been corrupted or maliciously altered.
376 While SHA1 is fairly secure it is coming to the end of its life
377 due to the expanding computing power available to brute-force
378 attacks. For more security, consider SHA256.
380 config SPL_SHA256_SUPPORT
381 bool "Support SHA256"
385 Enable this to support SHA256 in FIT images within SPL. A SHA256
386 checksum is a 256-bit (32-byte) hash value used to check that the
387 image contents have not been corrupted. SHA256 is recommended for
388 use in secure applications since (as at 2016) there is no known
389 feasible attack that could produce a 'collision' with differing
390 input data. Use this for the highest security. Note that only the
391 SHA256 variant is supported: SHA512 and others are not currently
394 config SPL_FIT_IMAGE_TINY
395 bool "Remove functionality from SPL FIT loading to reduce size"
397 default y if MACH_SUN50I || MACH_SUN50I_H5 || MACH_SUN50I_H6
398 default y if ARCH_IMX8M
400 Enable this to reduce the size of the FIT image loading code
401 in SPL, if space for the SPL binary is very tight.
403 This removes the detection of image types (which forces the
404 first image to be treated as having a U-Boot style calling
405 convention) and skips the recording of each loaded payload
406 (i.e. loadable) into the FDT (modifying the loaded FDT to
407 ensure this information is available to the next image
410 config SPL_CPU_SUPPORT
411 bool "Support CPU drivers"
413 Enable this to support CPU drivers in SPL. These drivers can set
414 up CPUs and provide information about them such as the model and
415 name. This can be useful in SPL since setting up the CPUs earlier
416 may improve boot performance. Enable this option to build the
417 drivers in drivers/cpu as part of an SPL build.
419 config SPL_CRYPTO_SUPPORT
420 bool "Support crypto drivers"
422 Enable crypto drivers in SPL. These drivers can be used to
423 accelerate secure boot processing in secure applications. Enable
424 this option to build the drivers in drivers/crypto as part of an
427 config SPL_HASH_SUPPORT
428 bool "Support hashing drivers"
432 Enable hashing drivers in SPL. These drivers can be used to
433 accelerate secure boot processing in secure applications. Enable
434 this option to build system-specific drivers for hash acceleration
435 as part of an SPL build.
437 config TPL_HASH_SUPPORT
438 bool "Support hashing drivers in TPL"
443 Enable hashing drivers in SPL. These drivers can be used to
444 accelerate secure boot processing in secure applications. Enable
445 this option to build system-specific drivers for hash acceleration
446 as part of an SPL build.
448 config SPL_DMA_SUPPORT
449 bool "Support DMA drivers"
451 Enable DMA (direct-memory-access) drivers in SPL. These drivers
452 can be used to handle memory-to-peripheral data transfer without
453 the CPU moving the data. Enable this option to build the drivers
454 in drivers/dma as part of an SPL build.
456 config SPL_DRIVERS_MISC_SUPPORT
457 bool "Support misc drivers"
459 Enable miscellaneous drivers in SPL. These drivers perform various
460 tasks that don't fall nicely into other categories, Enable this
461 option to build the drivers in drivers/misc as part of an SPL
462 build, for those that support building in SPL (not all drivers do).
464 config SPL_ENV_SUPPORT
465 bool "Support an environment"
467 Enable environment support in SPL. The U-Boot environment provides
468 a number of settings (essentially name/value pairs) which can
469 control many aspects of U-Boot's operation. Normally this is not
470 needed in SPL as it has a much simpler task with less
471 configuration. But some boards use this to support 'Falcon' boot
472 on EXT2 and FAT, where SPL boots directly into Linux without
473 starting U-Boot first. Enabling this option will make env_get()
474 and env_set() available in SPL.
477 bool "Support save environment"
478 depends on SPL_ENV_SUPPORT
479 select SPL_MMC_WRITE if ENV_IS_IN_MMC
481 Enable save environment support in SPL after setenv. By default
482 the saveenv option is not provided in SPL, but some boards need
483 this support in 'Falcon' boot, where SPL need to boot from
484 different images based on environment variable set by OS. For
485 example OS may set "reboot_image" environment variable to
486 "recovery" inorder to boot recovery image by SPL. The SPL read
487 "reboot_image" and act accordingly and change the reboot_image
488 to default mode using setenv and save the environment.
490 config SPL_ETH_SUPPORT
491 bool "Support Ethernet"
492 depends on SPL_ENV_SUPPORT
494 Enable access to the network subsystem and associated Ethernet
495 drivers in SPL. This permits SPL to load U-Boot over an Ethernet
496 link rather than from an on-board peripheral. Environment support
497 is required since the network stack uses a number of environment
498 variables. See also SPL_NET_SUPPORT.
501 bool "Support EXT filesystems"
503 Enable support for EXT2/3/4 filesystems with SPL. This permits
504 U-Boot (or Linux in Falcon mode) to be loaded from an EXT
505 filesystem from within SPL. Support for the underlying block
506 device (e.g. MMC or USB) must be enabled separately.
509 bool "Support FAT filesystems"
512 Enable support for FAT and VFAT filesystems with SPL. This
513 permits U-Boot (or Linux in Falcon mode) to be loaded from a FAT
514 filesystem from within SPL. Support for the underlying block
515 device (e.g. MMC or USB) must be enabled separately.
518 bool "Support write for FAT filesystems"
520 Enable write support for FAT and VFAT filesystems with SPL.
521 Support for the underlying block device (e.g. MMC or USB) must be
524 config SPL_FPGA_SUPPORT
527 Enable support for FPGAs in SPL. Field-programmable Gate Arrays
528 provide software-configurable hardware which is typically used to
529 implement peripherals (such as UARTs, LCD displays, MMC) or
530 accelerate custom processing functions, such as image processing
531 or machine learning. Sometimes it is useful to program the FPGA
532 as early as possible during boot, and this option can enable that
535 config SPL_GPIO_SUPPORT
536 bool "Support GPIO in SPL"
538 Enable support for GPIOs (General-purpose Input/Output) in SPL.
539 GPIOs allow U-Boot to read the state of an input line (high or
540 low) and set the state of an output line. This can be used to
541 drive LEDs, control power to various system parts and read user
542 input. GPIOs can be useful in SPL to enable a 'sign-of-life' LED,
543 for example. Enable this option to build the drivers in
544 drivers/gpio as part of an SPL build.
546 config SPL_I2C_SUPPORT
549 Enable support for the I2C (Inter-Integrated Circuit) bus in SPL.
550 I2C works with a clock and data line which can be driven by a
551 one or more masters or slaves. It is a fairly complex bus but is
552 widely used as it only needs two lines for communication. Speeds of
553 400kbps are typical but up to 3.4Mbps is supported by some
554 hardware. I2C can be useful in SPL to configure power management
555 ICs (PMICs) before raising the CPU clock speed, for example.
556 Enable this option to build the drivers in drivers/i2c as part of
559 config SPL_LIBCOMMON_SUPPORT
560 bool "Support common libraries"
562 Enable support for common U-Boot libraries within SPL. These
563 libraries include common code to deal with U-Boot images,
564 environment and USB, for example. This option is enabled on many
565 boards. Enable this option to build the code in common/ as part of
568 config SPL_LIBDISK_SUPPORT
569 bool "Support disk partitions"
572 Enable support for disk partitions within SPL. 'Disk' is something
573 of a misnomer as it includes non-spinning media such as flash (as
574 used in MMC and USB sticks). Partitions provide a way for a disk
575 to be split up into separate regions, with a partition table placed
576 at the start or end which describes the location and size of each
577 'partition'. These partitions are typically uses as individual block
578 devices, typically with an EXT2 or FAT filesystem in each. This
579 option enables whatever partition support has been enabled in
580 U-Boot to also be used in SPL. It brings in the code in disk/.
582 config SPL_LIBGENERIC_SUPPORT
583 bool "Support generic libraries"
585 Enable support for generic U-Boot libraries within SPL. These
586 libraries include generic code to deal with device tree, hashing,
587 printf(), compression and the like. This option is enabled on many
588 boards. Enable this option to build the code in lib/ as part of an
591 config SPL_DM_MAILBOX
592 bool "Support Mailbox"
594 Enable support for Mailbox within SPL. This enable the inter
595 processor communication protocols tobe used within SPL. Enable
596 this option to build the drivers in drivers/mailbox as part of
599 config SPL_MMC_SUPPORT
602 select HAVE_BLOCK_DEVICE
604 Enable support for MMC (Multimedia Card) within SPL. This enables
605 the MMC protocol implementation and allows any enabled drivers to
606 be used within SPL. MMC can be used with or without disk partition
607 support depending on the application (SPL_LIBDISK_SUPPORT). Enable
608 this option to build the drivers in drivers/mmc as part of an SPL
611 config SPL_FORCE_MMC_BOOT
612 bool "Force SPL booting from MMC"
613 depends on SPL_MMC_SUPPORT
616 Force SPL to use MMC device for Linux kernel booting even when the
617 SoC ROM recognized boot medium is not eMMC/SD. This is crucial for
618 factory or 'falcon mode' booting.
621 bool "Tiny MMC framework in SPL"
622 depends on SPL_MMC_SUPPORT
625 Enable MMC framework tinification support. This option is useful if
626 if your SPL is extremely size constrained. Heed the warning, enable
627 this option if and only if you know exactly what you are doing, if
628 you are reading this help text, you most likely have no idea :-)
630 The MMC framework is reduced to bare minimum to be useful. No malloc
631 support is needed for the MMC framework operation with this option
632 enabled. The framework supports exactly one MMC device and exactly
633 one MMC driver. The MMC driver can be adjusted to avoid any malloc
634 operations too, which can remove the need for malloc support in SPL
635 and thus further reduce footprint.
638 bool "MMC/SD/SDIO card support for write operations in SPL"
639 depends on SPL_MMC_SUPPORT
642 Enable write access to MMC and SD Cards in SPL
645 config SPL_MPC8XXX_INIT_DDR_SUPPORT
646 bool "Support MPC8XXX DDR init"
648 Enable support for DDR-SDRAM (double-data-rate synchronous dynamic
649 random-access memory) on the MPC8XXX family within SPL. This
650 allows DRAM to be set up before loading U-Boot into that DRAM,
653 config SPL_MTD_SUPPORT
654 bool "Support MTD drivers"
656 Enable support for MTD (Memory Technology Device) within SPL. MTD
657 provides a block interface over raw NAND and can also be used with
658 SPI flash. This allows SPL to load U-Boot from supported MTD
659 devices. See SPL_NAND_SUPPORT and SPL_ONENAND_SUPPORT for how
660 to enable specific MTD drivers.
662 config SPL_MUSB_NEW_SUPPORT
663 bool "Support new Mentor Graphics USB"
665 Enable support for Mentor Graphics USB in SPL. This is a new
666 driver used by some boards. Enable this option to build
667 the drivers in drivers/usb/musb-new as part of an SPL build. The
668 old drivers are in drivers/usb/musb.
670 config SPL_NAND_SUPPORT
671 bool "Support NAND flash"
673 Enable support for NAND (Negative AND) flash in SPL. NAND flash
674 can be used to allow SPL to load U-Boot from supported devices.
675 This enables the drivers in drivers/mtd/nand/raw as part of an SPL
681 Enable support for loading payloads from UBI. See
682 README.ubispl for more info.
685 config SPL_UBI_LOAD_BY_VOLNAME
686 bool "Support loading volumes by name"
688 This enables support for loading UBI volumes by name. When this
689 is set, CONFIG_SPL_UBI_LOAD_MONITOR_VOLNAME can be used to
690 configure the volume name from which to load U-Boot.
692 config SPL_UBI_MAX_VOL_LEBS
693 int "Maximum number of LEBs per volume"
696 The maximum number of logical eraseblocks which a static volume
697 to load can contain. Used for sizing the scan data structure.
699 config SPL_UBI_MAX_PEB_SIZE
700 int "Maximum PEB size"
703 The maximum physical erase block size.
705 config SPL_UBI_MAX_PEBS
706 int "Maximum number of PEBs"
709 The maximum physical erase block size. If not overridden by
710 board code, this value will be used as the actual number of PEBs.
712 config SPL_UBI_PEB_OFFSET
713 int "Offset to first UBI PEB"
716 The offset in number of PEBs from the start of flash to the first
717 PEB part of the UBI image.
719 config SPL_UBI_VID_OFFSET
720 int "Offset to VID header"
723 config SPL_UBI_LEB_START
724 int "Offset to LEB in PEB"
727 The offset in bytes to the LEB within a PEB.
729 config SPL_UBI_INFO_ADDR
730 hex "Address to place UBI scan info"
733 Address for ubispl to place the scan info. Read README.ubispl to
734 determine the required size
736 config SPL_UBI_VOL_IDS
737 int "Maximum volume id"
740 The maximum volume id which can be loaded. Used for sizing the
743 config SPL_UBI_LOAD_MONITOR_ID
744 int "id of U-Boot volume"
747 The UBI volume id from which to load U-Boot
749 config SPL_UBI_LOAD_MONITOR_VOLNAME
750 string "volume name of U-Boot volume"
751 depends on SPL_UBI_LOAD_BY_VOLNAME
753 The UBI volume name from which to load U-Boot
755 config SPL_UBI_LOAD_KERNEL_ID
756 int "id of kernel volume"
757 depends on SPL_OS_BOOT && SPL_UBI
759 The UBI volume id from which to load the kernel
761 config SPL_UBI_LOAD_ARGS_ID
762 int "id of kernel args volume"
763 depends on SPL_OS_BOOT && SPL_UBI
765 The UBI volume id from which to load the device tree
767 config UBI_SPL_SILENCE_MSG
768 bool "silence UBI SPL messages"
771 Disable messages from UBI SPL. This leaves warnings
776 config SPL_NET_SUPPORT
777 bool "Support networking"
779 Enable support for network devices (such as Ethernet) in SPL.
780 This permits SPL to load U-Boot over a network link rather than
781 from an on-board peripheral. Environment support is required since
782 the network stack uses a number of environment variables. See also
786 config SPL_NET_VCI_STRING
787 string "BOOTP Vendor Class Identifier string sent by SPL"
789 As defined by RFC 2132 the vendor class identifier field can be
790 sent by the client to identify the vendor type and configuration
791 of a client. This is often used in practice to allow for the DHCP
792 server to specify different files to load depending on if the ROM,
793 SPL or U-Boot itself makes the request
794 endif # if SPL_NET_SUPPORT
796 config SPL_NO_CPU_SUPPORT
797 bool "Drop CPU code in SPL"
799 This is specific to the ARM926EJ-S CPU. It disables the standard
800 start.S start-up code, presumably so that a replacement can be
801 used on that CPU. You should not enable it unless you know what
804 config SPL_NOR_SUPPORT
805 bool "Support NOR flash"
807 Enable support for loading U-Boot from memory-mapped NOR (Negative
808 OR) flash in SPL. NOR flash is slow to write but fast to read, and
809 a memory-mapped device makes it very easy to access. Loading from
810 NOR is typically achieved with just a memcpy().
812 config SPL_XIP_SUPPORT
816 Enable support for execute in place of U-Boot or kernel image. There
817 is no need to copy image from flash to ram if flash supports execute
818 in place. Its very useful in systems having enough flash but not
819 enough ram to load the image.
821 config SPL_ONENAND_SUPPORT
822 bool "Support OneNAND flash"
824 Enable support for OneNAND (Negative AND) flash in SPL. OneNAND is
825 a type of NAND flash and therefore can be used to allow SPL to
826 load U-Boot from supported devices. This enables the drivers in
827 drivers/mtd/onenand as part of an SPL build.
830 bool "Activate Falcon Mode"
831 depends on !TI_SECURE_DEVICE
834 Enable booting directly to an OS from SPL.
835 for more info read doc/README.falcon
839 hex "addr, where OS is found"
840 depends on SPL_NOR_SUPPORT
842 Specify the address, where the OS image is found, which
849 default "tpl/u-boot-with-tpl.bin" if TPL
852 Payload for SPL boot. For backward compatibility, default to
853 u-boot.bin, i.e. RAW image without any header. In case of
854 TPL, tpl/u-boot-with-tpl.bin. For new boards, suggest to
858 bool "Support PCI drivers"
860 Enable support for PCI in SPL. For platforms that need PCI to boot,
861 or must perform some init using PCI in SPL, this provides the
862 necessary driver support. This enables the drivers in drivers/pci
863 as part of an SPL build.
865 config SPL_PCH_SUPPORT
866 bool "Support PCH drivers"
868 Enable support for PCH (Platform Controller Hub) devices in SPL.
869 These are used to set up GPIOs and the SPI peripheral early in
870 boot. This enables the drivers in drivers/pch as part of an SPL
873 config SPL_POST_MEM_SUPPORT
874 bool "Support POST drivers"
876 Enable support for POST (Power-on Self Test) in SPL. POST is a
877 procedure that checks that the hardware (CPU or board) appears to
878 be functionally correctly. It is a sanity check that can be
879 performed before booting. This enables the drivers in post/drivers
880 as part of an SPL build.
883 bool "Support reset drivers"
886 Enable support for reset control in SPL.
887 That can be useful in SPL to handle IP reset in driver, as in U-Boot,
888 by using the generic reset API provided by driver model.
889 This enables the drivers in drivers/reset as part of an SPL build.
891 config SPL_POWER_SUPPORT
892 bool "Support power drivers"
894 Enable support for power control in SPL. This includes support
895 for PMICs (Power-management Integrated Circuits) and some of the
896 features provided by PMICs. In particular, voltage regulators can
897 be used to enable/disable power and vary its voltage. That can be
898 useful in SPL to turn on boot peripherals and adjust CPU voltage
899 so that the clock speed can be increased. This enables the drivers
900 in drivers/power, drivers/power/pmic and drivers/power/regulator
901 as part of an SPL build.
903 config SPL_POWER_DOMAIN
904 bool "Support power domain drivers"
906 Enable support for power domain control in SPL. Many SoCs allow
907 power to be applied to or removed from portions of the SoC (power
908 domains). This may be used to save power. This API provides the
909 means to control such power management hardware. This enables
910 the drivers in drivers/power/domain as part of a SPL build.
912 config SPL_RAM_SUPPORT
913 bool "Support booting from RAM"
914 default y if MICROBLAZE || ARCH_SOCFPGA || TEGRA || ARCH_ZYNQ
916 Enable booting of an image in RAM. The image can be preloaded or
917 it can be loaded by SPL directly into RAM (e.g. using USB).
919 config SPL_RAM_DEVICE
920 bool "Support booting from preloaded image in RAM"
921 depends on SPL_RAM_SUPPORT
922 default y if MICROBLAZE || ARCH_SOCFPGA || TEGRA || ARCH_ZYNQ
924 Enable booting of an image already loaded in RAM. The image has to
925 be already in memory when SPL takes over, e.g. loaded by the boot
928 config SPL_REMOTEPROC
929 bool "Support REMOTEPROCS"
931 Enable support for REMOTEPROCs in SPL. This permits to load
932 a remote processor firmware in SPL.
934 config SPL_RTC_SUPPORT
935 bool "Support RTC drivers"
937 Enable RTC (Real-time Clock) support in SPL. This includes support
938 for reading and setting the time. Some RTC devices also have some
939 non-volatile (battery-backed) memory which is accessible if
940 needed. This enables the drivers in drivers/rtc as part of an SPL
943 config SPL_SATA_SUPPORT
944 bool "Support loading from SATA"
946 Enable support for SATA (Serial AT attachment) in SPL. This allows
947 use of SATA devices such as hard drives and flash drivers for
948 loading U-Boot. SATA is used in higher-end embedded systems and
949 can provide higher performance than MMC , at somewhat higher
950 expense and power consumption. This enables loading from SATA
951 using a configured device.
953 config SPL_SATA_RAW_U_BOOT_USE_SECTOR
954 bool "SATA raw mode: by sector"
955 depends on SPL_SATA_SUPPORT
957 Use sector number for specifying U-Boot location on SATA disk in
960 config SPL_SATA_RAW_U_BOOT_SECTOR
961 hex "Sector on the SATA disk to load U-Boot from"
962 depends on SPL_SATA_RAW_U_BOOT_USE_SECTOR
964 Sector on the SATA disk to load U-Boot from, when the SATA disk is being
965 used in raw mode. Units: SATA disk sectors (1 sector = 512 bytes).
967 config SPL_SERIAL_SUPPORT
968 bool "Support serial"
972 Enable support for serial in SPL. This allows use of a serial UART
973 for displaying messages while SPL is running. It also brings in
974 printf() and panic() functions. This should normally be enabled
975 unless there are space reasons not to. Even then, consider
976 enabling SPL_USE_TINY_PRINTF which is a small printf() version.
978 config SPL_SPI_FLASH_SUPPORT
979 bool "Support SPI flash drivers"
981 Enable support for using SPI flash in SPL, and loading U-Boot from
982 SPI flash. SPI flash (Serial Peripheral Bus flash) is named after
983 the SPI bus that is used to connect it to a system. It is a simple
984 but fast bidirectional 4-wire bus (clock, chip select and two data
985 lines). This enables the drivers in drivers/mtd/spi as part of an
986 SPL build. This normally requires SPL_SPI_SUPPORT.
988 if SPL_SPI_FLASH_SUPPORT
990 config SPL_SPI_FLASH_TINY
991 bool "Enable low footprint SPL SPI Flash support"
992 depends on !SPI_FLASH_BAR
993 default y if SPI_FLASH
995 Enable lightweight SPL SPI Flash support that supports just reading
996 data/images from flash. No support to write/erase flash. Enable
997 this if you have SPL size limitations and don't need full
998 fledged SPI flash support.
1000 config SPL_SPI_FLASH_SFDP_SUPPORT
1001 bool "SFDP table parsing support for SPI NOR flashes"
1002 depends on !SPI_FLASH_BAR && !SPL_SPI_FLASH_TINY
1004 Enable support for parsing and auto discovery of parameters for
1005 SPI NOR flashes using Serial Flash Discoverable Parameters (SFDP)
1006 tables as per JESD216 standard in SPL.
1009 bool "Support loading from SPI flash"
1011 Enable support for loading next stage, U-Boot or otherwise, from
1012 SPI NOR in U-Boot SPL.
1014 endif # SPL_SPI_FLASH_SUPPORT
1016 config SYS_SPI_U_BOOT_OFFS
1017 hex "address of u-boot payload in SPI flash"
1019 depends on SPL_SPI_LOAD || SPL_SPI_SUNXI
1021 Address within SPI-Flash from where the u-boot payload is fetched
1024 config SPL_SPI_SUPPORT
1025 bool "Support SPI drivers"
1027 Enable support for using SPI in SPL. This is used for connecting
1028 to SPI flash for loading U-Boot. See SPL_SPI_FLASH_SUPPORT for
1029 more details on that. The SPI driver provides the transport for
1030 data between the SPI flash and the CPU. This option can be used to
1031 enable SPI drivers that are needed for other purposes also, such
1035 bool "Driver support for thermal devices"
1037 Enable support for temperature-sensing devices. Some SoCs have on-chip
1038 temperature sensors to permit warnings, speed throttling or even
1039 automatic power-off when the temperature gets too high or low. Other
1040 devices may be discrete but connected on a suitable bus.
1042 config SPL_USB_HOST_SUPPORT
1043 bool "Support USB host drivers"
1044 select HAVE_BLOCK_DEVICE
1046 Enable access to USB (Universal Serial Bus) host devices so that
1047 SPL can load U-Boot from a connected USB peripheral, such as a USB
1048 flash stick. While USB takes a little longer to start up than most
1049 buses, it is very flexible since many different types of storage
1050 device can be attached. This option enables the drivers in
1051 drivers/usb/host as part of an SPL build.
1053 config SPL_USB_STORAGE
1054 bool "Support loading from USB"
1055 depends on SPL_USB_HOST_SUPPORT && !(BLK && !DM_USB)
1057 Enable support for USB devices in SPL. This allows use of USB
1058 devices such as hard drives and flash drivers for loading U-Boot.
1059 The actual drivers are enabled separately using the normal U-Boot
1060 config options. This enables loading from USB using a configured
1063 config SPL_USB_GADGET
1064 bool "Suppport USB Gadget drivers"
1066 Enable USB Gadget API which allows to enable USB device functions
1071 config SPL_USB_ETHER
1072 bool "Support USB Ethernet drivers"
1074 Enable access to the USB network subsystem and associated
1075 drivers in SPL. This permits SPL to load U-Boot over a
1076 USB-connected Ethernet link (such as a USB Ethernet dongle) rather
1077 than from an onboard peripheral. Environment support is required
1078 since the network stack uses a number of environment variables.
1079 See also SPL_NET_SUPPORT and SPL_ETH_SUPPORT.
1082 bool "Support DFU (Device Firmware Upgrade)"
1083 select SPL_HASH_SUPPORT
1084 select SPL_DFU_NO_RESET
1085 depends on SPL_RAM_SUPPORT
1087 This feature enables the DFU (Device Firmware Upgrade) in SPL with
1088 RAM memory device support. The ROM code will load and execute
1089 the SPL built with dfu. The user can load binaries (u-boot/kernel) to
1090 selected device partition from host-pc using dfu-utils.
1091 This feature is useful to flash the binaries to factory or bare-metal
1092 boards using USB interface.
1095 bool "DFU device selection"
1100 depends on SPL_DFU && SPL_RAM_SUPPORT
1102 select RAM/DDR memory device for loading binary images
1103 (u-boot/kernel) to the selected device partition using
1104 DFU and execute the u-boot/kernel from RAM.
1108 config SPL_USB_SDP_SUPPORT
1109 bool "Support SDP (Serial Download Protocol)"
1111 Enable Serial Download Protocol (SDP) device support in SPL. This
1112 allows to download images into memory and execute (jump to) them
1113 using the same protocol as implemented by the i.MX family's boot ROM.
1116 config SPL_WATCHDOG_SUPPORT
1117 bool "Support watchdog drivers"
1118 imply SPL_WDT if !HW_WATCHDOG
1120 Enable support for watchdog drivers in SPL. A watchdog is
1121 typically a hardware peripheral which can reset the system when it
1122 detects no activity for a while (such as a software crash). This
1123 enables the drivers in drivers/watchdog as part of an SPL build.
1125 config SPL_YMODEM_SUPPORT
1126 bool "Support loading using Ymodem"
1127 depends on SPL_SERIAL_SUPPORT
1129 While loading from serial is slow it can be a useful backup when
1130 there is no other option. The Ymodem protocol provides a reliable
1131 means of transmitting U-Boot over a serial line for using in SPL,
1132 with a checksum to ensure correctness.
1135 bool "Support ARM Trusted Firmware"
1138 ATF(ARM Trusted Firmware) is a component for ARM AArch64 which
1139 is loaded by SPL (which is considered as BL2 in ATF terminology).
1140 More detail at: https://github.com/ARM-software/arm-trusted-firmware
1142 config SPL_ATF_NO_PLATFORM_PARAM
1143 bool "Pass no platform parameter"
1146 While we expect to call a pointer to a valid FDT (or NULL)
1147 as the platform parameter to an ATF, some ATF versions are
1148 not U-Boot aware and have an insufficiently robust parameter
1149 validation to gracefully reject a FDT being passed.
1151 If this option is enabled, the spl_atf os-type handler will
1152 always pass NULL for the platform parameter.
1154 If your ATF is affected, say Y.
1156 config SPL_AM33XX_ENABLE_RTC32K_OSC
1157 bool "Enable the RTC32K OSC on AM33xx based platforms"
1160 Enable access to the AM33xx RTC and select the external 32kHz clock
1164 bool "Support OP-TEE Trusted OS"
1167 OP-TEE is an open source Trusted OS which is loaded by SPL.
1168 More detail at: https://github.com/OP-TEE/optee_os
1171 bool "Support RISC-V OpenSBI"
1172 depends on RISCV && SPL_RISCV_MMODE && RISCV_SMODE
1174 OpenSBI is an open-source implementation of the RISC-V Supervisor Binary
1175 Interface (SBI) specification. U-Boot supports the OpenSBI FW_DYNAMIC
1176 firmware. It is loaded and started by U-Boot SPL.
1178 More details are available at https://github.com/riscv/opensbi and
1179 https://github.com/riscv/riscv-sbi-doc
1181 config SPL_OPENSBI_LOAD_ADDR
1182 hex "OpenSBI load address"
1183 depends on SPL_OPENSBI
1185 Load address of the OpenSBI binary.
1189 depends on SUPPORT_TPL
1192 If you want to build TPL as well as the normal image and SPL, say Y.
1197 bool "Pass hand-off information from TPL to SPL and U-Boot proper"
1198 depends on HANDOFF && TPL_BLOBLIST
1201 This option enables TPL to write handoff information. This can be
1202 used to pass information like the size of SDRAM from TPL to U-Boot
1203 proper. The information is also available to SPL if it is useful
1206 config TPL_BOARD_INIT
1207 bool "Call board-specific initialization in TPL"
1209 If this option is enabled, U-Boot will call the function
1210 spl_board_init() from board_init_r(). This function should be
1211 provided by the board.
1214 string "Linker script for the TPL stage"
1216 default "arch/arm/cpu/armv8/u-boot-spl.lds" if ARM64
1217 default "arch/$(ARCH)/cpu/u-boot-spl.lds"
1219 The TPL stage will usually require a different linker-script
1220 (as it runs from a different memory region) than the regular
1221 U-Boot stage. Set this to the path of the linker-script to
1224 May be left empty to trigger the Makefile infrastructure to
1225 fall back to the linker-script used for the SPL stage.
1227 config TPL_NEEDS_SEPARATE_TEXT_BASE
1228 bool "TPL needs a separate text-base"
1232 Enable, if the TPL stage should not inherit its text-base
1233 from the SPL stage. When enabled, a base address for the
1234 .text sections of the TPL stage has to be set below.
1236 config TPL_NEEDS_SEPARATE_STACK
1237 bool "TPL needs a separate initial stack-pointer"
1241 Enable, if the TPL stage should not inherit its initial
1242 stack-pointer from the settings for the SPL stage.
1244 config TPL_TEXT_BASE
1245 hex "Base address for the .text section of the TPL stage"
1246 depends on TPL_NEEDS_SEPARATE_TEXT_BASE
1248 The base address for the .text section of the TPL stage.
1251 int "Maximum size (in bytes) for the TPL stage"
1255 The maximum size (in bytes) of the TPL stage.
1258 hex "Address of the initial stack-pointer for the TPL stage"
1259 depends on TPL_NEEDS_SEPARATE_STACK
1261 The address of the initial stack-pointer for the TPL stage.
1262 Usually this will be the (aligned) top-of-stack.
1264 config TPL_BOOTROM_SUPPORT
1265 bool "Support returning to the BOOTROM (from TPL)"
1267 Some platforms (e.g. the Rockchip RK3368) provide support in their
1268 ROM for loading the next boot-stage after performing basic setup
1271 Enable this option, to return to the BOOTROM through the
1272 BOOT_DEVICE_BOOTROM (or fall-through to the next boot device in the
1273 boot device list, if not implemented for a given board)
1275 config TPL_DRIVERS_MISC_SUPPORT
1276 bool "Support misc drivers in TPL"
1278 Enable miscellaneous drivers in TPL. These drivers perform various
1279 tasks that don't fall nicely into other categories, Enable this
1280 option to build the drivers in drivers/misc as part of an TPL
1281 build, for those that support building in TPL (not all drivers do).
1283 config TPL_ENV_SUPPORT
1284 bool "Support an environment"
1286 Enable environment support in TPL. See SPL_ENV_SUPPORT for details.
1288 config TPL_GPIO_SUPPORT
1289 bool "Support GPIO in TPL"
1291 Enable support for GPIOs (General-purpose Input/Output) in TPL.
1292 GPIOs allow U-Boot to read the state of an input line (high or
1293 low) and set the state of an output line. This can be used to
1294 drive LEDs, control power to various system parts and read user
1295 input. GPIOs can be useful in TPL to enable a 'sign-of-life' LED,
1296 for example. Enable this option to build the drivers in
1297 drivers/gpio as part of an TPL build.
1299 config TPL_I2C_SUPPORT
1302 Enable support for the I2C bus in TPL. See SPL_I2C_SUPPORT for
1305 config TPL_LIBCOMMON_SUPPORT
1306 bool "Support common libraries"
1308 Enable support for common U-Boot libraries within TPL. See
1309 SPL_LIBCOMMON_SUPPORT for details.
1311 config TPL_LIBGENERIC_SUPPORT
1312 bool "Support generic libraries"
1314 Enable support for generic U-Boot libraries within TPL. See
1315 SPL_LIBGENERIC_SUPPORT for details.
1317 config TPL_MPC8XXX_INIT_DDR_SUPPORT
1318 bool "Support MPC8XXX DDR init"
1320 Enable support for DDR-SDRAM on the MPC8XXX family within TPL. See
1321 SPL_MPC8XXX_INIT_DDR_SUPPORT for details.
1323 config TPL_MMC_SUPPORT
1327 Enable support for MMC within TPL. See SPL_MMC_SUPPORT for details.
1329 config TPL_NAND_SUPPORT
1330 bool "Support NAND flash"
1332 Enable support for NAND in TPL. See SPL_NAND_SUPPORT for details.
1335 bool "Support PCI drivers"
1337 Enable support for PCI in TPL. For platforms that need PCI to boot,
1338 or must perform some init using PCI in SPL, this provides the
1339 necessary driver support. This enables the drivers in drivers/pci
1340 as part of a TPL build.
1342 config TPL_PCH_SUPPORT
1343 bool "Support PCH drivers"
1345 Enable support for PCH (Platform Controller Hub) devices in TPL.
1346 These are used to set up GPIOs and the SPI peripheral early in
1347 boot. This enables the drivers in drivers/pch as part of a TPL
1350 config TPL_RAM_SUPPORT
1351 bool "Support booting from RAM"
1353 Enable booting of an image in RAM. The image can be preloaded or
1354 it can be loaded by TPL directly into RAM (e.g. using USB).
1356 config TPL_RAM_DEVICE
1357 bool "Support booting from preloaded image in RAM"
1358 depends on TPL_RAM_SUPPORT
1360 Enable booting of an image already loaded in RAM. The image has to
1361 be already in memory when TPL takes over, e.g. loaded by the boot
1364 config TPL_RTC_SUPPORT
1365 bool "Support RTC drivers"
1367 Enable RTC (Real-time Clock) support in TPL. This includes support
1368 for reading and setting the time. Some RTC devices also have some
1369 non-volatile (battery-backed) memory which is accessible if
1370 needed. This enables the drivers in drivers/rtc as part of an TPL
1373 config TPL_SERIAL_SUPPORT
1374 bool "Support serial"
1378 Enable support for serial in TPL. See SPL_SERIAL_SUPPORT for
1381 config TPL_SPI_FLASH_SUPPORT
1382 bool "Support SPI flash drivers"
1384 Enable support for using SPI flash in TPL. See SPL_SPI_FLASH_SUPPORT
1388 bool "Support loading from SPI flash"
1389 depends on TPL_SPI_FLASH_SUPPORT
1391 Enable support for loading next stage, U-Boot or otherwise, from
1392 SPI NOR in U-Boot TPL.
1394 config TPL_SPI_SUPPORT
1395 bool "Support SPI drivers"
1397 Enable support for using SPI in TPL. See SPL_SPI_SUPPORT for
1400 config TPL_YMODEM_SUPPORT
1401 bool "Support loading using Ymodem"
1402 depends on TPL_SERIAL_SUPPORT
1404 While loading from serial is slow it can be a useful backup when
1405 there is no other option. The Ymodem protocol provides a reliable
1406 means of transmitting U-Boot over a serial line for using in TPL,
1407 with a checksum to ensure correctness.
1411 config SPL_AT91_MCK_BYPASS
1412 bool "Use external clock signal as a source of main clock for AT91 platforms"
1413 depends on ARCH_AT91
1416 Use external 8 to 24 Mhz clock signal as source of main clock instead
1417 of an external crystal oscillator.
1418 This option disables the internal driving on the XOUT pin.
1419 The external source has to provide a stable clock on the XIN pin.
1420 If this option is disabled, the SoC expects a crystal oscillator
1421 that needs driving on both XIN and XOUT lines.