menu "Boot options" menu "Boot images" config ANDROID_BOOT_IMAGE bool "Enable support for Android Boot Images" default y if FASTBOOT help This enables support for booting images which use the Android image format header. config FIT bool "Support Flattened Image Tree" select HASH select MD5 select SHA1 imply SHA256 help This option allows you to boot the new uImage structure, Flattened Image Tree. FIT is formally a FDT, which can include images of various types (kernel, FDT blob, ramdisk, etc.) in a single blob. To boot this new uImage structure, pass the address of the blob to the "bootm" command. FIT is very flexible, supporting compression, multiple images, multiple configurations, verification through hashing and also verified boot (secure boot using RSA). config TIMESTAMP bool "Show image date and time when displaying image information" default y if CMD_DATE help When CONFIG_TIMESTAMP is selected, the timestamp (date and time) of an image is printed by image commands like bootm or iminfo. This is shown as 'Timestamp: xxx' and 'Created: xxx'. If this option is enabled, then U-Boot requires FITs to have a timestamp. If a FIT is loaded that does not, the message 'Wrong FIT format: no timestamp' is shown. if FIT config FIT_EXTERNAL_OFFSET hex "FIT external data offset" default 0x0 help This specifies a data offset in fit image. The offset is from data payload offset to the beginning of fit image header. When specifies a offset, specific data could be put in the hole between data payload and fit image header, such as CSF data on i.MX platform. config FIT_FULL_CHECK bool "Do a full check of the FIT before using it" default y help Enable this do a full check of the FIT to make sure it is valid. This helps to protect against carefully crafted FITs which take advantage of bugs or omissions in the code. This includes a bad structure, multiple root nodes and the like. config FIT_SIGNATURE bool "Enable signature verification of FIT uImages" depends on DM select HASH imply RSA imply RSA_VERIFY select IMAGE_SIGN_INFO select FIT_FULL_CHECK help This option enables signature verification of FIT uImages, using a hash signed and verified using RSA. If CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive hashing is available using hardware, then the RSA library will use it. See doc/uImage.FIT/signature.txt for more details. WARNING: When relying on signed FIT images with a required signature check the legacy image format is disabled by default, so that unsigned images cannot be loaded. If a board needs the legacy image format support in this case, enable it using CONFIG_LEGACY_IMAGE_FORMAT. config FIT_SIGNATURE_MAX_SIZE hex "Max size of signed FIT structures" depends on FIT_SIGNATURE default 0x10000000 help This option sets a max size in bytes for verified FIT uImages. A sane value of 256MB protects corrupted DTB structures from overlapping device memory. Assure this size does not extend past expected storage space. config FIT_RSASSA_PSS bool "Support rsassa-pss signature scheme of FIT image contents" depends on FIT_SIGNATURE help Enable this to support the pss padding algorithm as described in the rfc8017 (https://tools.ietf.org/html/rfc8017). config FIT_CIPHER bool "Enable ciphering data in a FIT uImages" depends on DM select AES help Enable the feature of data ciphering/unciphering in the tool mkimage and in the u-boot support of the FIT image. config FIT_VERBOSE bool "Show verbose messages when FIT images fail" help Generally a system will have valid FIT images so debug messages are a waste of code space. If you are debugging your images then you can enable this option to get more verbose information about failures. config FIT_BEST_MATCH bool "Select the best match for the kernel device tree" help When no configuration is explicitly selected, default to the one whose fdt's compatibility field best matches that of U-Boot itself. A match is considered "best" if it matches the most specific compatibility entry of U-Boot's fdt's root node. The order of entries in the configuration's fdt is ignored. config FIT_IMAGE_POST_PROCESS bool "Enable post-processing of FIT artifacts after loading by U-Boot" depends on TI_SECURE_DEVICE || SOCFPGA_SECURE_VAB_AUTH default y if TI_SECURE_DEVICE help Allows doing any sort of manipulation to blobs after they got extracted from FIT images like stripping off headers or modifying the size of the blob, verification, authentication, decryption etc. in a platform or board specific way. In order to use this feature a platform or board- specific implementation of board_fit_image_post_process() must be provided. Also, anything done during this post-processing step would need to be comprehended in how the images were prepared before being injected into the FIT creation (i.e. the blobs would have been pre- processed before being added to the FIT image). config FIT_PRINT bool "Support FIT printing" default y help Support printing the content of the fitImage in a verbose manner. if SPL config SPL_FIT bool "Support Flattened Image Tree within SPL" depends on SPL select SPL_HASH select SPL_OF_LIBFDT config SPL_FIT_PRINT bool "Support FIT printing within SPL" depends on SPL_FIT help Support printing the content of the fitImage in a verbose manner in SPL. config SPL_FIT_FULL_CHECK bool "Do a full check of the FIT before using it" help Enable this do a full check of the FIT to make sure it is valid. This helps to protect against carefully crafted FITs which take advantage of bugs or omissions in the code. This includes a bad structure, multiple root nodes and the like. config SPL_FIT_SIGNATURE bool "Enable signature verification of FIT firmware within SPL" depends on SPL_DM depends on SPL_LOAD_FIT || SPL_LOAD_FIT_FULL select FIT_SIGNATURE select SPL_FIT select SPL_CRYPTO select SPL_HASH imply SPL_RSA imply SPL_RSA_VERIFY select SPL_IMAGE_SIGN_INFO select SPL_FIT_FULL_CHECK config SPL_FIT_SIGNATURE_MAX_SIZE hex "Max size of signed FIT structures in SPL" depends on SPL_FIT_SIGNATURE default 0x10000000 help This option sets a max size in bytes for verified FIT uImages. A sane value of 256MB protects corrupted DTB structures from overlapping device memory. Assure this size does not extend past expected storage space. config SPL_FIT_RSASSA_PSS bool "Support rsassa-pss signature scheme of FIT image contents in SPL" depends on SPL_FIT_SIGNATURE help Enable this to support the pss padding algorithm as described in the rfc8017 (https://tools.ietf.org/html/rfc8017) in SPL. config SPL_LOAD_FIT bool "Enable SPL loading U-Boot as a FIT (basic fitImage features)" select SPL_FIT help Normally with the SPL framework a legacy image is generated as part of the build. This contains U-Boot along with information as to where it should be loaded. This option instead enables generation of a FIT (Flat Image Tree) which provides more flexibility. In particular it can handle selecting from multiple device tree and passing the correct one to U-Boot. This path has the following limitations: 1. "loadables" images, other than FDTs, which do not have a "load" property will not be loaded. This limitation also applies to FPGA images with the correct "compatible" string. 2. For FPGA images, the supported "compatible" list is in the doc/uImage.FIT/source_file_format.txt. 3. FDTs are only loaded for images with an "os" property of "u-boot". "linux" images are also supported with Falcon boot mode. config SPL_LOAD_FIT_ADDRESS hex "load address of fit image" depends on SPL_LOAD_FIT default 0x0 help Specify the load address of the fit image that will be loaded by SPL. config SPL_LOAD_FIT_APPLY_OVERLAY bool "Enable SPL applying DT overlays from FIT" depends on SPL_LOAD_FIT select OF_LIBFDT_OVERLAY help The device tree is loaded from the FIT image. Allow the SPL is to also load device-tree overlays from the FIT image an apply them over the device tree. config SPL_LOAD_FIT_APPLY_OVERLAY_BUF_SZ depends on SPL_LOAD_FIT_APPLY_OVERLAY default 0x10000 hex "size of temporary buffer used to load the overlays" help The size of the area where the overlays will be loaded and uncompress. Must be at least as large as biggest overlay (uncompressed) config SPL_LOAD_FIT_FULL bool "Enable SPL loading U-Boot as a FIT (full fitImage features)" select SPL_FIT help Normally with the SPL framework a legacy image is generated as part of the build. This contains U-Boot along with information as to where it should be loaded. This option instead enables generation of a FIT (Flat Image Tree) which provides more flexibility. In particular it can handle selecting from multiple device tree and passing the correct one to U-Boot. config SPL_FIT_IMAGE_POST_PROCESS bool "Enable post-processing of FIT artifacts after loading by the SPL" depends on SPL_LOAD_FIT default y if TI_SECURE_DEVICE help Allows doing any sort of manipulation to blobs after they got extracted from the U-Boot FIT image like stripping off headers or modifying the size of the blob, verification, authentication, decryption etc. in a platform or board specific way. In order to use this feature a platform or board-specific implementation of board_fit_image_post_process() must be provided. Also, anything done during this post-processing step would need to be comprehended in how the images were prepared before being injected into the FIT creation (i.e. the blobs would have been pre- processed before being added to the FIT image). config SPL_FIT_SOURCE string ".its source file for U-Boot FIT image" depends on SPL_FIT help Specifies a (platform specific) FIT source file to generate the U-Boot FIT image. This could specify further image to load and/or execute. config USE_SPL_FIT_GENERATOR bool "Use a script to generate the .its script" default y if SPL_FIT && (!ARCH_SUNXI && !RISCV) config SPL_FIT_GENERATOR string ".its file generator script for U-Boot FIT image" depends on USE_SPL_FIT_GENERATOR default "arch/arm/mach-rockchip/make_fit_atf.py" if SPL_LOAD_FIT && ARCH_ROCKCHIP default "arch/arm/mach-zynqmp/mkimage_fit_atf.sh" if SPL_LOAD_FIT && ARCH_ZYNQMP help Specifies a (platform specific) script file to generate the FIT source file used to build the U-Boot FIT image file. This gets passed a list of supported device tree file stub names to include in the generated image. endif # SPL if VPL config VPL_FIT bool "Support Flattened Image Tree within VPL" depends on VPL default y select VPL_HASH select VPL_OF_LIBFDT config VPL_FIT_PRINT bool "Support FIT printing within VPL" depends on VPL_FIT default y help Support printing the content of the fitImage in a verbose manner in VPL. config VPL_FIT_FULL_CHECK bool "Do a full check of the FIT before using it" default y help Enable this do a full check of the FIT to make sure it is valid. This helps to protect against carefully crafted FITs which take advantage of bugs or omissions in the code. This includes a bad structure, multiple root nodes and the like. config VPL_FIT_SIGNATURE bool "Enable signature verification of FIT firmware within VPL" depends on VPL_DM default y select FIT_SIGNATURE select VPL_FIT select VPL_CRYPTO select VPL_HASH imply VPL_RSA imply VPL_RSA_VERIFY select VPL_IMAGE_SIGN_INFO select VPL_FIT_FULL_CHECK config VPL_FIT_SIGNATURE_MAX_SIZE hex "Max size of signed FIT structures in VPL" depends on VPL_FIT_SIGNATURE default 0x10000000 help This option sets a max size in bytes for verified FIT uImages. A sane value of 256MB protects corrupted DTB structures from overlapping device memory. Assure this size does not extend past expected storage space. endif # VPL endif # FIT config PXE_UTILS bool select MENU help Utilities for parsing PXE file formats. config BOOTSTD bool "Standard boot support" default y depends on DM && OF_CONTROL && BLK help U-Boot supports a standard way of locating something to boot, typically an Operating System such as Linux, provided by a distro such as Arch Linux or Debian. Enable this to support iterating through available bootdevs and using bootmeths to find bootflows suitable for booting. Standard boot is not a standard way of booting, just a framework within U-Boot for supporting all the different ways that exist. Terminology: - bootdev - a device which can hold a distro (e.g. MMC) - bootmeth - a method to scan a bootdev to find bootflows (owned by U-Boot) - bootflow - a description of how to boot (owned by the distro) config BOOTSTD_FULL bool "Enhanced features for standard boot" default y if SANDBOX help This enables various useful features for standard boot, which are not essential for operation: - bootdev, bootmeth commands - extra features in the bootflow command - support for selecting the ordering of bootmeths ("bootmeth order") - support for selecting the ordering of bootdevs using the devicetree as well as the "boot_targets" environment variable config SPL_BOOTSTD bool "Standard boot support in VPL" depends on SPL && SPL_DM && SPL_OF_CONTROL && SPL_BLK default y if VPL help This enables standard boot in SPL. This is neeeded so that VBE (Verified Boot for Embedded) can be used, since it depends on standard boot. It is enabled by default since the main purpose of VPL is to handle the firmware part of VBE. config VPL_BOOTSTD bool "Standard boot support in VPL" depends on VPL && VPL_DM && VPL_OF_CONTROL && VPL_BLK default y help This enables standard boot in SPL. This is neeeded so that VBE (Verified Boot for Embedded) can be used, since it depends on standard boot. It is enabled by default since the main purpose of VPL is to handle the firmware part of VBE. if BOOTSTD config BOOTSTD_BOOTCOMMAND bool "Use bootstd to boot" default y if !DISTRO_DEFAULTS help Enable this to select a default boot-command suitable for booting with standard boot. This can be overridden by the board if needed, but the default command should be enough for most boards which use standard boot. For now this is only selected if distro boot is NOT used, since standard boot does not support all of the features of distro boot yet. config BOOTMETH_GLOBAL bool help Add support for global bootmeths. This feature is used by VBE and EFI bootmgr, since they take full control over which bootdevs are selected to boot. config BOOTMETH_DISTRO bool "Bootdev support for distro boot" select PXE_UTILS default y help Enables support for distro boot using bootdevs. This makes the bootdevs look for a 'extlinux/extlinux.conf' on each filesystem they scan. This provides a way to try out standard boot on an existing boot flow. config BOOTMETH_DISTRO_PXE bool "Bootdev support for distro boot over network" depends on CMD_PXE && CMD_NET && DM_ETH default y help Enables support for distro boot using bootdevs. This makes the bootdevs look for a 'extlinux/extlinux.conf' on the tftp server. This provides a way to try out standard boot on an existing boot flow. config BOOTMETH_EFILOADER bool "Bootdev support for EFI boot" depends on CMD_BOOTEFI default y help Enables support for EFI boot using bootdevs. This makes the bootdevs look for a 'boot.efi' on each filesystem they scan. The resulting file is booted after enabling U-Boot's EFI loader support. The depends on the architecture of the board: aa64 - aarch64 (ARM 64-bit) arm - ARM 32-bit ia32 - x86 32-bit x64 - x86 64-bit riscv32 - RISC-V 32-bit riscv64 - RISC-V 64-bit This provides a way to try out standard boot on an existing boot flow. config BOOTMETH_VBE bool "Bootdev support for Verified Boot for Embedded" depends on FIT default y select BOOTMETH_GLOBAL help Enables support for VBE boot. This is a standard boot method which supports selection of various firmware components, seleciton of an OS to boot as well as updating these using fwupd. config SPL_BOOTMETH_VBE bool "Bootdev support for Verified Boot for Embedded (SPL)" depends on SPL && FIT default y if VPL help Enables support for VBE boot. This is a standard boot method which supports selection of various firmware components, seleciton of an OS to boot as well as updating these using fwupd. config VPL_BOOTMETH_VBE bool "Bootdev support for Verified Boot for Embedded (VPL)" depends on VPL && FIT default y help Enables support for VBE boot. This is a standard boot method which supports selection of various firmware components, seleciton of an OS to boot as well as updating these using fwupd. if BOOTMETH_VBE config BOOTMETH_VBE_SIMPLE bool "Bootdev support for VBE 'simple' method" default y help Enables support for VBE 'simple' boot. This allows updating a single firmware image in boot media such as MMC. It does not support any sort of rollback, recovery or A/B boot. config BOOTMETH_VBE_SIMPLE_OS bool "Bootdev support for VBE 'simple' method OS phase" default y help Enables support for the OS parts of VBE 'simple' boot. This includes fixing up the device tree with the required VBE information, ready for booting into the OS. This option is only enabled for U-Boot proper, since it is the phase where device tree fixups happen. config SPL_BOOTMETH_VBE_SIMPLE bool "Bootdev support for VBE 'simple' method (SPL)" depends on SPL default y if VPL help Enables support for VBE 'simple' boot. This allows updating a single firmware image in boot media such as MMC. It does not support any sort of rollback, recovery or A/B boot. config VPL_BOOTMETH_VBE_SIMPLE bool "Bootdev support for VBE 'simple' method (VPL)" depends on VPL default y help Enables support for VBE 'simple' boot. This allows updating a single firmware image in boot media such as MMC. It does not support any sort of rollback, recovery or A/B boot. config SPL_BOOTMETH_VBE_SIMPLE_FW bool "Bootdev support for VBE 'simple' method firmware phase (SPL)" depends on VPL default y help Enables support for the firmware parts of VBE 'simple' boot. This includes an SPL loader which locates the correct U-Boot to boot into. This option should really only be enabled for VPL, since it is the phase where the SPL + U-Boot decision should be made. But for now, SPL does its own FIT-configuration selection. config VPL_BOOTMETH_VBE_SIMPLE_FW bool "Bootdev support for VBE 'simple' method firmware phase (VPL)" depends on VPL default y help Enables support for the firmware parts of VBE 'simple' boot. This includes an SPL loader which locates the correct SPL to boot into. This option enabled for VPL, since it is the phase where the SPL decision is made. endif # BOOTMETH_VBE config BOOTMETH_SANDBOX def_bool y depends on SANDBOX help This is a sandbox bootmeth driver used for testing. It always returns -ENOTSUPP when attempting to boot. config BOOTMETH_SCRIPT bool "Bootdev support for U-Boot scripts" default y if BOOTSTD_FULL help Enables support for booting a distro via a U-Boot script. This makes the bootdevs look for a 'boot/boot.scr' file which can be used to boot the distro. This provides a way to try out standard boot on an existing boot flow. It is not enabled by default to save space. endif config LEGACY_IMAGE_FORMAT bool "Enable support for the legacy image format" default y if !FIT_SIGNATURE && !TI_SECURE_DEVICE help This option enables the legacy image format. It is enabled by default for backward compatibility, unless FIT_SIGNATURE is set where it is disabled so that unsigned images cannot be loaded. If a board needs the legacy image format support in this case, enable it here. config SUPPORT_RAW_INITRD bool "Enable raw initrd images" help Note, defining the SUPPORT_RAW_INITRD allows user to supply kernel with raw initrd images. The syntax is slightly different, the address of the initrd must be augmented by it's size, in the following format: ":". config OF_BOARD_SETUP bool "Set up board-specific details in device tree before boot" depends on OF_LIBFDT help This causes U-Boot to call ft_board_setup() before booting into the Operating System. This function can set up various board-specific information in the device tree for use by the OS. The device tree is then passed to the OS. config OF_SYSTEM_SETUP bool "Set up system-specific details in device tree before boot" depends on OF_LIBFDT help This causes U-Boot to call ft_system_setup() before booting into the Operating System. This function can set up various system-specific information in the device tree for use by the OS. The device tree is then passed to the OS. config OF_STDOUT_VIA_ALIAS bool "Update the device-tree stdout alias from U-Boot" depends on OF_LIBFDT help This uses U-Boot's serial alias from the aliases node to update the device tree passed to the OS. The "linux,stdout-path" property in the chosen node is set to point to the correct serial node. This option currently references CONFIG_CONS_INDEX, which is incorrect when used with device tree as this option does not exist / should not be used. config HAVE_TEXT_BASE bool depends on !NIOS2 && !XTENSA depends on !EFI_APP default y config TEXT_BASE depends on HAVE_TEXT_BASE default 0x0 if POSITION_INDEPENDENT default 0x80800000 if ARCH_OMAP2PLUS || ARCH_K3 default 0x81700000 if MACH_SUNIV default 0x2a000000 if MACH_SUN9I default 0x4a000000 if SUNXI_MINIMUM_DRAM_MB >= 256 default 0x42e00000 if SUNXI_MINIMUM_DRAM_MB >= 64 hex "Text Base" help The address in memory that U-Boot will be running from, initially. config HAVE_SYS_MONITOR_BASE bool depends on ARC || MIPS || M68K || NIOS2 || PPC || XTENSA || X86 \ || ENV_IS_IN_FLASH || MTD_NOR_FLASH depends on !EFI_APP default y config SYS_MONITOR_BASE depends on HAVE_SYS_MONITOR_BASE hex "Physical start address of boot monitor code" default TEXT_BASE help The physical start address of boot monitor code (which is the same as CONFIG_TEXT_BASE when linking) and the same as CFG_SYS_FLASH_BASE when booting from flash. config SPL_SYS_MONITOR_BASE depends on MPC85xx && SPL && HAVE_SYS_MONITOR_BASE hex "Physical start address of SPL monitor code" default SPL_TEXT_BASE config TPL_SYS_MONITOR_BASE depends on MPC85xx && TPL && HAVE_SYS_MONITOR_BASE hex "Physical start address of TPL monitor code" config DYNAMIC_SYS_CLK_FREQ bool "Determine CPU clock frequency at run-time" help Implement a get_board_sys_clk function that will determine the CPU clock frequency at run time, rather than define it statically. config SYS_CLK_FREQ depends on !DYNAMIC_SYS_CLK_FREQ int "CPU clock frequency" default 125000000 if ARCH_LS1012A default 100000000 if ARCH_P2020 || ARCH_T1024 || ARCH_T1042 || \ ARCH_LS1021A || FSL_LSCH2 || FSL_LSCH3 default 66666666 if ARCH_P1010 || ARCH_P1020 || ARCH_T4240 default 66660000 if ARCH_T2080 default 33333333 if RCAR_GEN3 default 24000000 if ARCH_EXYNOS default 20000000 if RCAR_GEN2 default 0 help A static value for the CPU frequency. Note that if not required for a given SoC, this can be left at 0. config ARCH_FIXUP_FDT_MEMORY bool "Enable arch_fixup_memory_banks() call" default y help Enable FDT memory map syncup before OS boot. This feature can be used for booting OS with different memory setup where the part of the memory location should be used for different purpose. config CHROMEOS bool "Support booting Chrome OS" help Chrome OS requires U-Boot to set up a table indicating the boot mode (e.g. Developer mode) and a few other things. Enable this if you are booting on a Chromebook to avoid getting an error about an invalid firmware ID. config CHROMEOS_VBOOT bool "Support Chrome OS verified boot" help This is intended to enable the full Chrome OS verified boot support in U-Boot. It is not actually implemented in the U-Boot source code at present, so this option is always set to 'n'. It allows distinguishing between booting Chrome OS in a basic way (developer mode) and a full boot. config SYS_RAMBOOT bool config RAMBOOT_PBL bool "Freescale PBL(pre-boot loader) image format support" select SYS_RAMBOOT if PPC help Some SoCs use PBL to load RCW and/or pre-initialization instructions. For more details refer to doc/README.pblimage choice prompt "Freescale PBL load location" depends on RAMBOOT_PBL || ((TARGET_P1010RDB_PA || TARGET_P1010RDB_PB \ || TARGET_P1020RDB_PC || TARGET_P1020RDB_PD || TARGET_P2020RDB) \ && !CMD_NAND) config SDCARD bool "Freescale PBL is found on SD card" config SPIFLASH bool "Freescale PBL is found on SPI flash" endchoice config FSL_FIXED_MMC_LOCATION bool "PBL MMC is at a fixed location" depends on SDCARD && !RAMBOOT_PBL config ESDHC_HC_BLK_ADDR def_bool y depends on FSL_FIXED_MMC_LOCATION && (ARCH_BSC9131 || ARCH_BSC9132 || ARCH_P1010) help In High Capacity SD Cards (> 2 GBytes), the 32-bit source address and code length of these soc specify the memory address in block address format. Block length is fixed to 512 bytes as per the SD High Capacity specification. config SYS_FSL_PBL_PBI string "PBI(pre-boot instructions) commands for the PBL image" depends on RAMBOOT_PBL help PBI commands can be used to configure SoC before it starts the execution. Please refer doc/README.pblimage for more details. config SYS_FSL_PBL_RCW string "Aadditional RCW (Power on reset configuration) for the PBL image" depends on RAMBOOT_PBL help Enables addition of RCW (Power on reset configuration) in built image. Please refer doc/README.pblimage for more details. config SYS_BOOT_RAMDISK_HIGH depends on CMD_BOOTM || CMD_BOOTI || CMD_BOOTZ depends on !(NIOS2 || SANDBOX || SH || XTENSA) def_bool y help Enable initrd_high functionality. If defined then the initrd_high feature is enabled and the boot* ramdisk subcommand is enabled. endmenu # Boot images menu "Boot timing" config BOOTSTAGE bool "Boot timing and reporting" help Enable recording of boot time while booting. To use it, insert calls to bootstage_mark() with a suitable BOOTSTAGE_ID from bootstage.h. Only a single entry is recorded for each ID. You can give the entry a name with bootstage_mark_name(). You can also record elapsed time in a particular stage using bootstage_start() before starting and bootstage_accum() when finished. Bootstage will add up all the accumulated time and report it. Normally, IDs are defined in bootstage.h but a small number of additional 'user' IDs can be used by passing BOOTSTAGE_ID_ALLOC as the ID. Calls to show_boot_progress() will also result in log entries but these will not have names. config SPL_BOOTSTAGE bool "Boot timing and reported in SPL" depends on BOOTSTAGE && SPL help Enable recording of boot time in SPL. To make this visible to U-Boot proper, enable BOOTSTAGE_STASH as well. This will stash the timing information when SPL finishes and load it when U-Boot proper starts up. config TPL_BOOTSTAGE bool "Boot timing and reported in TPL" depends on BOOTSTAGE && TPL help Enable recording of boot time in SPL. To make this visible to U-Boot proper, enable BOOTSTAGE_STASH as well. This will stash the timing information when TPL finishes and load it when U-Boot proper starts up. config BOOTSTAGE_REPORT bool "Display a detailed boot timing report before booting the OS" depends on BOOTSTAGE help Enable output of a boot time report just before the OS is booted. This shows how long it took U-Boot to go through each stage of the boot process. The report looks something like this: Timer summary in microseconds: Mark Elapsed Stage 0 0 reset 3,575,678 3,575,678 board_init_f start 3,575,695 17 arch_cpu_init A9 3,575,777 82 arch_cpu_init done 3,659,598 83,821 board_init_r start 3,910,375 250,777 main_loop 29,916,167 26,005,792 bootm_start 30,361,327 445,160 start_kernel config BOOTSTAGE_RECORD_COUNT int "Number of boot stage records to store" depends on BOOTSTAGE default 30 help This is the size of the bootstage record list and is the maximum number of bootstage records that can be recorded. config SPL_BOOTSTAGE_RECORD_COUNT int "Number of boot stage records to store for SPL" depends on SPL_BOOTSTAGE default 5 help This is the size of the bootstage record list and is the maximum number of bootstage records that can be recorded. config TPL_BOOTSTAGE_RECORD_COUNT int "Number of boot stage records to store for TPL" depends on TPL_BOOTSTAGE default 5 help This is the size of the bootstage record list and is the maximum number of bootstage records that can be recorded. config BOOTSTAGE_FDT bool "Store boot timing information in the OS device tree" depends on BOOTSTAGE help Stash the bootstage information in the FDT. A root 'bootstage' node is created with each bootstage id as a child. Each child has a 'name' property and either 'mark' containing the mark time in microseconds, or 'accum' containing the accumulated time for that bootstage id in microseconds. For example: bootstage { 154 { name = "board_init_f"; mark = <3575678>; }; 170 { name = "lcd"; accum = <33482>; }; }; Code in the Linux kernel can find this in /proc/devicetree. config BOOTSTAGE_STASH bool "Stash the boot timing information in memory before booting OS" depends on BOOTSTAGE help Some OSes do not support device tree. Bootstage can instead write the boot timing information in a binary format at a given address. This happens through a call to bootstage_stash(), typically in the CPU's cleanup_before_linux() function. You can use the 'bootstage stash' and 'bootstage unstash' commands to do this on the command line. config BOOTSTAGE_STASH_ADDR hex "Address to stash boot timing information" default 0 help Provide an address which will not be overwritten by the OS when it starts, so that it can read this information when ready. config BOOTSTAGE_STASH_SIZE hex "Size of boot timing stash region" default 0x1000 help This should be large enough to hold the bootstage stash. A value of 4096 (4KiB) is normally plenty. config SHOW_BOOT_PROGRESS bool "Show boot progress in a board-specific manner" help Defining this option allows to add some board-specific code (calling a user-provided function show_boot_progress(int) that enables you to show the system's boot progress on some display (for example, some LEDs) on your board. At the moment, the following checkpoints are implemented: Legacy uImage format: Arg Where When 1 common/cmd_bootm.c before attempting to boot an image -1 common/cmd_bootm.c Image header has bad magic number 2 common/cmd_bootm.c Image header has correct magic number -2 common/cmd_bootm.c Image header has bad checksum 3 common/cmd_bootm.c Image header has correct checksum -3 common/cmd_bootm.c Image data has bad checksum 4 common/cmd_bootm.c Image data has correct checksum -4 common/cmd_bootm.c Image is for unsupported architecture 5 common/cmd_bootm.c Architecture check OK -5 common/cmd_bootm.c Wrong Image Type (not kernel, multi) 6 common/cmd_bootm.c Image Type check OK -6 common/cmd_bootm.c gunzip uncompression error -7 common/cmd_bootm.c Unimplemented compression type 7 common/cmd_bootm.c Uncompression OK 8 common/cmd_bootm.c No uncompress/copy overwrite error -9 common/cmd_bootm.c Unsupported OS (not Linux, BSD, VxWorks, QNX) 9 common/image.c Start initial ramdisk verification -10 common/image.c Ramdisk header has bad magic number -11 common/image.c Ramdisk header has bad checksum 10 common/image.c Ramdisk header is OK -12 common/image.c Ramdisk data has bad checksum 11 common/image.c Ramdisk data has correct checksum 12 common/image.c Ramdisk verification complete, start loading -13 common/image.c Wrong Image Type (not PPC Linux ramdisk) 13 common/image.c Start multifile image verification 14 common/image.c No initial ramdisk, no multifile, continue. 15 arch//lib/bootm.c All preparation done, transferring control to OS -30 arch/powerpc/lib/board.c Fatal error, hang the system -31 post/post.c POST test failed, detected by post_output_backlog() -32 post/post.c POST test failed, detected by post_run_single() 34 common/cmd_doc.c before loading a Image from a DOC device -35 common/cmd_doc.c Bad usage of "doc" command 35 common/cmd_doc.c correct usage of "doc" command -36 common/cmd_doc.c No boot device 36 common/cmd_doc.c correct boot device -37 common/cmd_doc.c Unknown Chip ID on boot device 37 common/cmd_doc.c correct chip ID found, device available -38 common/cmd_doc.c Read Error on boot device 38 common/cmd_doc.c reading Image header from DOC device OK -39 common/cmd_doc.c Image header has bad magic number 39 common/cmd_doc.c Image header has correct magic number -40 common/cmd_doc.c Error reading Image from DOC device 40 common/cmd_doc.c Image header has correct magic number 41 common/cmd_ide.c before loading a Image from a IDE device -42 common/cmd_ide.c Bad usage of "ide" command 42 common/cmd_ide.c correct usage of "ide" command -43 common/cmd_ide.c No boot device 43 common/cmd_ide.c boot device found -44 common/cmd_ide.c Device not available 44 common/cmd_ide.c Device available -45 common/cmd_ide.c wrong partition selected 45 common/cmd_ide.c partition selected -46 common/cmd_ide.c Unknown partition table 46 common/cmd_ide.c valid partition table found -47 common/cmd_ide.c Invalid partition type 47 common/cmd_ide.c correct partition type -48 common/cmd_ide.c Error reading Image Header on boot device 48 common/cmd_ide.c reading Image Header from IDE device OK -49 common/cmd_ide.c Image header has bad magic number 49 common/cmd_ide.c Image header has correct magic number -50 common/cmd_ide.c Image header has bad checksum 50 common/cmd_ide.c Image header has correct checksum -51 common/cmd_ide.c Error reading Image from IDE device 51 common/cmd_ide.c reading Image from IDE device OK 52 common/cmd_nand.c before loading a Image from a NAND device -53 common/cmd_nand.c Bad usage of "nand" command 53 common/cmd_nand.c correct usage of "nand" command -54 common/cmd_nand.c No boot device 54 common/cmd_nand.c boot device found -55 common/cmd_nand.c Unknown Chip ID on boot device 55 common/cmd_nand.c correct chip ID found, device available -56 common/cmd_nand.c Error reading Image Header on boot device 56 common/cmd_nand.c reading Image Header from NAND device OK -57 common/cmd_nand.c Image header has bad magic number 57 common/cmd_nand.c Image header has correct magic number -58 common/cmd_nand.c Error reading Image from NAND device 58 common/cmd_nand.c reading Image from NAND device OK -60 common/env_common.c Environment has a bad CRC, using default 64 net/eth.c starting with Ethernet configuration. -64 net/eth.c no Ethernet found. 65 net/eth.c Ethernet found. -80 common/cmd_net.c usage wrong 80 common/cmd_net.c before calling net_loop() -81 common/cmd_net.c some error in net_loop() occurred 81 common/cmd_net.c net_loop() back without error -82 common/cmd_net.c size == 0 (File with size 0 loaded) 82 common/cmd_net.c trying automatic boot 83 common/cmd_net.c running "source" command -83 common/cmd_net.c some error in automatic boot or "source" command 84 common/cmd_net.c end without errors FIT uImage format: Arg Where When 100 common/cmd_bootm.c Kernel FIT Image has correct format -100 common/cmd_bootm.c Kernel FIT Image has incorrect format 101 common/cmd_bootm.c No Kernel subimage unit name, using configuration -101 common/cmd_bootm.c Can't get configuration for kernel subimage 102 common/cmd_bootm.c Kernel unit name specified -103 common/cmd_bootm.c Can't get kernel subimage node offset 103 common/cmd_bootm.c Found configuration node 104 common/cmd_bootm.c Got kernel subimage node offset -104 common/cmd_bootm.c Kernel subimage hash verification failed 105 common/cmd_bootm.c Kernel subimage hash verification OK -105 common/cmd_bootm.c Kernel subimage is for unsupported architecture 106 common/cmd_bootm.c Architecture check OK -106 common/cmd_bootm.c Kernel subimage has wrong type 107 common/cmd_bootm.c Kernel subimage type OK -107 common/cmd_bootm.c Can't get kernel subimage data/size 108 common/cmd_bootm.c Got kernel subimage data/size -108 common/cmd_bootm.c Wrong image type (not legacy, FIT) -109 common/cmd_bootm.c Can't get kernel subimage type -110 common/cmd_bootm.c Can't get kernel subimage comp -111 common/cmd_bootm.c Can't get kernel subimage os -112 common/cmd_bootm.c Can't get kernel subimage load address -113 common/cmd_bootm.c Image uncompress/copy overwrite error 120 common/image.c Start initial ramdisk verification -120 common/image.c Ramdisk FIT image has incorrect format 121 common/image.c Ramdisk FIT image has correct format 122 common/image.c No ramdisk subimage unit name, using configuration -122 common/image.c Can't get configuration for ramdisk subimage 123 common/image.c Ramdisk unit name specified -124 common/image.c Can't get ramdisk subimage node offset 125 common/image.c Got ramdisk subimage node offset -125 common/image.c Ramdisk subimage hash verification failed 126 common/image.c Ramdisk subimage hash verification OK -126 common/image.c Ramdisk subimage for unsupported architecture 127 common/image.c Architecture check OK -127 common/image.c Can't get ramdisk subimage data/size 128 common/image.c Got ramdisk subimage data/size 129 common/image.c Can't get ramdisk load address -129 common/image.c Got ramdisk load address -130 common/cmd_doc.c Incorrect FIT image format 131 common/cmd_doc.c FIT image format OK -140 common/cmd_ide.c Incorrect FIT image format 141 common/cmd_ide.c FIT image format OK -150 common/cmd_nand.c Incorrect FIT image format 151 common/cmd_nand.c FIT image format OK config SPL_SHOW_BOOT_PROGRESS bool "Show boot progress in a board-specific manner in SPL" depends on SPL help Defining this option allows to add some board-specific code (calling a user-provided function show_boot_progress(int) that enables you to show the system's boot progress on some display (for example, some LEDs) on your board. For details see SHOW_BOOT_PROGRESS. endmenu menu "Boot media" config NOR_BOOT bool "Support for booting from NOR flash" depends on NOR help Enabling this will make a U-Boot binary that is capable of being booted via NOR. In this case we will enable certain pinmux early as the ROM only partially sets up pinmux. We also default to using NOR for environment. config NAND_BOOT bool "Support for booting from NAND flash" imply MTD_RAW_NAND help Enabling this will make a U-Boot binary that is capable of being booted via NAND flash. This is not a must, some SoCs need this, some not. config ONENAND_BOOT bool "Support for booting from ONENAND" imply MTD_RAW_NAND help Enabling this will make a U-Boot binary that is capable of being booted via ONENAND. This is not a must, some SoCs need this, some not. config QSPI_BOOT bool "Support for booting from QSPI flash" help Enabling this will make a U-Boot binary that is capable of being booted via QSPI flash. This is not a must, some SoCs need this, some not. config SATA_BOOT bool "Support for booting from SATA" help Enabling this will make a U-Boot binary that is capable of being booted via SATA. This is not a must, some SoCs need this, some not. config SD_BOOT bool "Support for booting from SD/EMMC" help Enabling this will make a U-Boot binary that is capable of being booted via SD/EMMC. This is not a must, some SoCs need this, some not. config SD_BOOT_QSPI bool "Support for booting from SD/EMMC and enable QSPI" help Enabling this will make a U-Boot binary that is capable of being booted via SD/EMMC while enabling QSPI on the platform as well. This is not a must, some SoCs need this, some not. config SPI_BOOT bool "Support for booting from SPI flash" help Enabling this will make a U-Boot binary that is capable of being booted via SPI flash. This is not a must, some SoCs need this, some not. endmenu menu "Autoboot options" config AUTOBOOT bool "Autoboot" default y help This enables the autoboot. See doc/README.autoboot for detail. config BOOTDELAY int "delay in seconds before automatically booting" default 2 depends on AUTOBOOT help Delay before automatically running bootcmd; set to 0 to autoboot with no delay, but you can stop it by key input. set to -1 to disable autoboot. set to -2 to autoboot with no delay and not check for abort If this value is >= 0 then it is also used for the default delay before starting the default entry in bootmenu. If it is < 0 then a default value of 10s is used. See doc/README.autoboot for details. config AUTOBOOT_KEYED bool "Stop autobooting via specific input key / string" help This option enables stopping (aborting) of the automatic boot feature only by issuing a specific input key or string. If not enabled, any input key will abort the U-Boot automatic booting process and bring the device to the U-Boot prompt for user input. config AUTOBOOT_FLUSH_STDIN bool "Enable flushing stdin before starting to read the password" depends on AUTOBOOT_KEYED && !SANDBOX help When this option is enabled stdin buffer will be flushed before starting to read the password. This can't be enabled for the sandbox as flushing stdin would break the autoboot unit tests. config AUTOBOOT_PROMPT string "Autoboot stop prompt" depends on AUTOBOOT_KEYED default "Autoboot in %d seconds\\n" help This string is displayed before the boot delay selected by CONFIG_BOOTDELAY starts. If it is not defined there is no output indicating that autoboot is in progress. Note that this define is used as the (only) argument to a printf() call, so it may contain '%' format specifications, provided that it also includes, sepearated by commas exactly like in a printf statement, the required arguments. It is the responsibility of the user to select only such arguments that are valid in the given context. config AUTOBOOT_ENCRYPTION bool "Enable encryption in autoboot stopping" depends on AUTOBOOT_KEYED help This option allows a string to be entered into U-Boot to stop the autoboot. The behavior depends whether CONFIG_CRYPT_PW from lib is enabled or not. In case CONFIG_CRYPT_PW is enabled, the string will be forwarded to the crypt-based functionality and be compared against the string in the environment variable 'bootstopkeycrypt'. In case CONFIG_CRYPT_PW is disabled the string itself is hashed and compared against the hash in the environment variable 'bootstopkeysha256'. If it matches in either case then boot stops and a command-line prompt is presented. This provides a way to ship a secure production device which can also be accessed at the U-Boot command line. config AUTOBOOT_SHA256_FALLBACK bool "Allow fallback from crypt-hashed password to sha256" depends on AUTOBOOT_ENCRYPTION && CRYPT_PW help This option adds support to fall back from crypt-hashed passwords to checking a SHA256 hashed password in case the 'bootstopusesha256' environment variable is set to 'true'. config AUTOBOOT_DELAY_STR string "Delay autobooting via specific input key / string" depends on AUTOBOOT_KEYED && !AUTOBOOT_ENCRYPTION help This option delays the automatic boot feature by issuing a specific input key or string. If CONFIG_AUTOBOOT_DELAY_STR or the environment variable "bootdelaykey" is specified and this string is received from console input before autoboot starts booting, U-Boot gives a command prompt. The U-Boot prompt will time out if CONFIG_BOOT_RETRY_TIME is used, otherwise it never times out. config AUTOBOOT_STOP_STR string "Stop autobooting via specific input key / string" depends on AUTOBOOT_KEYED && !AUTOBOOT_ENCRYPTION help This option enables stopping (aborting) of the automatic boot feature only by issuing a specific input key or string. If CONFIG_AUTOBOOT_STOP_STR or the environment variable "bootstopkey" is specified and this string is received from console input before autoboot starts booting, U-Boot gives a command prompt. The U-Boot prompt never times out, even if CONFIG_BOOT_RETRY_TIME is used. config AUTOBOOT_KEYED_CTRLC bool "Enable Ctrl-C autoboot interruption" depends on AUTOBOOT_KEYED && !AUTOBOOT_ENCRYPTION help This option allows for the boot sequence to be interrupted by ctrl-c, in addition to the "bootdelaykey" and "bootstopkey". Setting this variable provides an escape sequence from the limited "password" strings. config AUTOBOOT_NEVER_TIMEOUT bool "Make the password entry never time-out" depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION && CRYPT_PW help This option removes the timeout from the password entry when the user first presses the key before entering any other character. config AUTOBOOT_STOP_STR_ENABLE bool "Enable fixed string to stop autobooting" depends on AUTOBOOT_KEYED && AUTOBOOT_ENCRYPTION help This option enables the feature to add a fixed stop string that is defined at compile time. In every case it will be tried to load the stop string from the environment. In case this is enabled and there is no stop string in the environment, this will be used as default value. config AUTOBOOT_STOP_STR_CRYPT string "Stop autobooting via crypt-hashed password" depends on AUTOBOOT_STOP_STR_ENABLE && CRYPT_PW help This option adds the feature to only stop the autobooting, and therefore boot into the U-Boot prompt, when the input string / password matches a values that is hashed via one of the supported crypt-style password hashing options and saved in the environment variable "bootstopkeycrypt". config AUTOBOOT_STOP_STR_SHA256 string "Stop autobooting via SHA256 hashed password" depends on AUTOBOOT_STOP_STR_ENABLE help This option adds the feature to only stop the autobooting, and therefore boot into the U-Boot prompt, when the input string / password matches a values that is encypted via a SHA256 hash and saved in the environment variable "bootstopkeysha256". If the value in that variable includes a ":", the portion prior to the ":" will be treated as a salt value. config AUTOBOOT_USE_MENUKEY bool "Allow a specify key to run a menu from the environment" depends on !AUTOBOOT_KEYED help If a specific key is pressed to stop autoboot, then the commands in the environment variable 'menucmd' are executed before boot starts. config AUTOBOOT_MENUKEY int "ASCII value of boot key to show a menu" default 0 depends on AUTOBOOT_USE_MENUKEY help If this key is pressed to stop autoboot, then the commands in the environment variable 'menucmd' will be executed before boot starts. For example, 33 means "!" in ASCII, so pressing ! at boot would take this action. config AUTOBOOT_MENU_SHOW bool "Show a menu on boot" depends on CMD_BOOTMENU help This enables the boot menu, controlled by environment variables defined by the board. The menu starts after running the 'preboot' environmnent variable (if enabled) and before handling the boot delay. See README.bootmenu for more details. config BOOTMENU_DISABLE_UBOOT_CONSOLE bool "Disallow bootmenu to enter the U-Boot console" depends on AUTOBOOT_MENU_SHOW help If this option is enabled, user can not enter the U-Boot console from bootmenu. It increases the system security. config BOOT_RETRY bool "Boot retry feature" help Allow for having the U-Boot command prompt time out and attempt to boot again. If the environment variable "bootretry" is found then its value is used, otherwise the retry timeout is CONFIG_BOOT_RETRY_TIME. CONFIG_BOOT_RETRY_MIN is optional and defaults to CONFIG_BOOT_RETRY_TIME. All times are in seconds. config BOOT_RETRY_TIME int "Timeout in seconds before attempting to boot again" depends on BOOT_RETRY help Time in seconds before the U-Boot prompt will timeout and boot will be attempted again. config BOOT_RETRY_MIN int "Minimum timeout in seconds for 'bootretry'" depends on BOOT_RETRY default BOOT_RETRY_TIME help The minimum time in seconds that "bootretry" can be set to. config RESET_TO_RETRY bool "Reset the board to retry autoboot" depends on BOOT_RETRY help After the countdown timed out, the board will be reset to restart again. endmenu menu "Image support" config IMAGE_PRE_LOAD bool "Image pre-load support" help Enable an image pre-load stage in the SPL. This pre-load stage allows to do some manipulation or check (for example signature check) on an image before launching it. config SPL_IMAGE_PRE_LOAD bool "Image pre-load support within SPL" depends on SPL && IMAGE_PRE_LOAD help Enable an image pre-load stage in the SPL. This pre-load stage allows to do some manipulation or check (for example signature check) on an image before launching it. config IMAGE_PRE_LOAD_SIG bool "Image pre-load signature support" depends on IMAGE_PRE_LOAD select FIT_SIGNATURE select RSA select RSA_VERIFY_WITH_PKEY help Enable signature check support in the pre-load stage. For this feature a very simple header is added before the image with few fields: - a magic - the image size - the signature All other information (header size, type of signature, ...) are provided in the node /image/pre-load/sig of u-boot. config SPL_IMAGE_PRE_LOAD_SIG bool "Image pre-load signature support witin SPL" depends on SPL_IMAGE_PRE_LOAD && IMAGE_PRE_LOAD_SIG select SPL_FIT_SIGNATURE select SPL_RSA select SPL_RSA_VERIFY_WITH_PKEY help Enable signature check support in the pre-load stage in the SPL. For this feature a very simple header is added before the image with few fields: - a magic - the image size - the signature All other information (header size, type of signature, ...) are provided in the node /image/pre-load/sig of u-boot. endmenu config USE_BOOTARGS bool "Enable boot arguments" help Provide boot arguments to bootm command. Boot arguments are specified in CONFIG_BOOTARGS option. Enable this option to be able to specify CONFIG_BOOTARGS string. If this option is disabled, CONFIG_BOOTARGS will be undefined and won't take any space in U-Boot image. config BOOTARGS string "Boot arguments" depends on USE_BOOTARGS && !USE_DEFAULT_ENV_FILE help This can be used to pass arguments to the bootm command. The value of CONFIG_BOOTARGS goes into the environment value "bootargs". Note that this value will also override the "chosen" node in FDT blob. config BOOTARGS_SUBST bool "Support substituting strings in boot arguments" help This allows substituting string values in the boot arguments. These are applied after the commandline has been built. One use for this is to insert the root-disk UUID into the command line where bootargs contains "root=${uuid}" setenv bootargs "console= root=${uuid}" # Set the 'uuid' environment variable part uuid mmc 2:2 uuid # Command-line substitution will put the real uuid into the # kernel command line bootm config USE_BOOTCOMMAND bool "Enable a default value for bootcmd" help Provide a default value for the bootcmd entry in the environment. If autoboot is enabled this is what will be run automatically. Enable this option to be able to specify CONFIG_BOOTCOMMAND as a string. If this option is disabled, CONFIG_BOOTCOMMAND will be undefined and won't take any space in U-Boot image. config BOOTCOMMAND string "bootcmd value" depends on USE_BOOTCOMMAND && !USE_DEFAULT_ENV_FILE default "bootflow scan -lb" if BOOTSTD_BOOTCOMMAND && CMD_BOOTFLOW_FULL default "bootflow scan" if BOOTSTD_BOOTCOMMAND && !CMD_BOOTFLOW_FULL default "run distro_bootcmd" if !BOOTSTD_BOOTCOMMAND && DISTRO_DEFAULTS help This is the string of commands that will be used as bootcmd and if AUTOBOOT is set, automatically run. config USE_PREBOOT bool "Enable preboot" help When this option is enabled, the existence of the environment variable "preboot" will be checked immediately before starting the CONFIG_BOOTDELAY countdown and/or running the auto-boot command resp. entering interactive mode. This feature is especially useful when "preboot" is automatically generated or modified. For example, the boot code can modify the "preboot" when a user holds down a certain combination of keys. config PREBOOT string "preboot default value" depends on USE_PREBOOT && !USE_DEFAULT_ENV_FILE default "usb start" if USB_KEYBOARD default "" help This is the default of "preboot" environment variable. config PREBOOT_DEFINED bool default y if PREBOOT != "" config DEFAULT_FDT_FILE string "Default fdt file" help This option is used to set the default fdt file to boot OS. config SAVE_PREV_BL_FDT_ADDR depends on ARM bool "Saves fdt address, passed by the previous bootloader, to env var" help When u-boot is used as a chain-loaded bootloader (replacing OS kernel), enable this option to save fdt address, passed by the previous bootloader for future use. Address is saved to `prevbl_fdt_addr` environment variable. If no fdt was provided by previous bootloader, no env variables will be created. config SAVE_PREV_BL_INITRAMFS_START_ADDR depends on ARM bool "Saves initramfs address, passed by the previous bootloader, to env var" help When u-boot is used as a chain-loaded bootloader(replacing OS kernel), enable this option to save initramfs address, passed by the previous bootloader for future use. Address is saved to `prevbl_initrd_start_addr` environment variable. If no initramfs was provided by previous bootloader, no env variables will be created. endmenu # Booting