This is a stub describing how TPL, VPL, and SPL load the next boot stages on a detail level for users.
For sure we will need a few patches on top to catch the whole complexity.
Signed-off-by: Heinrich Schuchardt heinrich.schuchardt@canonical.com --- v3: Call TPL Tertiary Program Loader, VPL Verifying Program Loader Put Power PC flow into an info box to stick out Add link to Falcon Mode Fix typos v2: Mention that PowerPC uses a different naming convention. Group boot devices by type Correct reference to UBI Fix typos --- doc/usage/index.rst | 1 + doc/usage/spl_boot.rst | 323 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 324 insertions(+) create mode 100644 doc/usage/spl_boot.rst
diff --git a/doc/usage/index.rst b/doc/usage/index.rst index 3326ec82ff..f45a7f5502 100644 --- a/doc/usage/index.rst +++ b/doc/usage/index.rst @@ -4,6 +4,7 @@ Use U-Boot .. toctree:: :maxdepth: 1
+ spl_boot blkmap dfu environment diff --git a/doc/usage/spl_boot.rst b/doc/usage/spl_boot.rst new file mode 100644 index 0000000000..ad6bf0ab69 --- /dev/null +++ b/doc/usage/spl_boot.rst @@ -0,0 +1,323 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +Booting from TPL/SPL +==================== + +The main U-Boot binary may be too large to be loaded directly by the Boot ROM. +This was the original driver for splitting up U-Boot into multiple boot stages. + +U-Boot typically goes through the following boot phases where TPL, VPL, and SPL +are optional. While many boards use SPL only few use TPL. + +TPL + Tertiary Program Loader. Very early init, as tiny as possible. This loads SPL + (or VPL if enabled). + +VPL + Verifying Program Loader. Optional verification step, which can select one of + several SPL binaries, if A/B verified boot is enabled. Implementation of the + VPL logic is work-in-progress. For now it just boots into SPL. + +SPL + Secondary Program Loader. Sets up SDRAM and loads U-Boot proper. It may also + load other firmware components. + +U-Boot + U-Boot proper, containing the command line and the logic to load an + operating system, e.g. via UEFI. + +.. note:: + + The naming convention on the PowerPC architecture deviates from the other + archtitectures. Here the boot sequence is SPL->TPL->U-Boot. + +Only main U-Boot has a command line interface. + +Further usages for U-Boot SPL comprise: + +* launching BL31 of ARM Trusted Firmware which invokes U-Boot as BL33 +* launching EDK II +* launching Linux, e.g. :doc:`Falcon Mode' <../develop/falcon>` +* launching RISC-V OpenSBI which invokes main U-Boot + +Target binaries +--------------- + +Binaries loaded by SPL/TPL can be: + +* raw binaries where the entry address equals the start address. This is the + only binary format supported by TPL. +* :doc:`FIT <fit/index>` images +* legacy U-Boot images + +Configuration +~~~~~~~~~~~~~ + +Raw images are only supported in SPL if CONFIG_SPL_RAW_IMAGE_SUPPORT=y. + +CONFIG_SPL_FIT=y and CONFIG_SPL_LOAD_FIT=y are needed to load FIT images. + +CONFIG_SPL_LEGACY_IMAGE_FORMAT=y is needed to load legacy U-Boot images. +CONFIG_SPL_LEGACY_IMAGE_CRC_CHECK=y enables checking the CRC32 of legacy U-Boot +images. + +Image load methods +------------------ + +The image boot methods available for a board must be defined in two places: + +The board code implements a function board_boot_order() enumerating up to +five boot methods and the sequence in which they are tried. (The maximum +number of boot methods is currently hard coded as variable spl_boot_list[]). +If there is only one boot method function, spl_boot_device() may be implemented +instead. + +The configuration controls which of these boot methods are actually available. + +Loading from block devices +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +MMC1, MMC2, MMC2_2 + These methods read an image from SD card or eMMC. The first digit after + 'MMC' indicates the device number. Required configuration settings include: + + * CONFIG_SPL_MMC=y or CONFIG_TPL_MMC=y + + To use a PCI connected MMC controller you need to additionally specify: + + * CONFIG_SPL_PCI=y + + * CONFIG_SPL_PCI_PNP=y + + * CONFIG_MMC=y + + * CONFIG_MMC_PCI=y + + * CONFIG_MMC_SDHCI=y + + To load from a file system use: + + * CONFIG_SPL_FS_FAT=y or CONFIG_SPL_FS_EXT=y + + * CONFIG_SPL_FS_LOAD_PAYLOAD_NAME="<filepath>" + +NVMe + This methods load the image from an NVMe drive. + Required configuration settings include: + + * CONFIG_SPL_PCI=y + + * CONFIG_SPL_PCI_PNP=y + + * CONFIG_SPL_NVME=y + + * CONFIG_SPL_NVME_PCI=y + + * CONFIG_SPL_NVME_BOOT_DEVICE (number of the NVMe device) + + * CONFIG_SYS_NVME_BOOT_PARTITION (partition to read from) + + To load from a file system use: + + * CONFIG_SPL_FS_FAT=y or CONFIG_SPL_FS_EXT=y + + * CONFIG_SPL_FS_LOAD_PAYLOAD_NAME="<filepath>" + +SATA + This method reads an image from a SATA drive. + Required configuration settings include: + + * CONFIG_SPL_SATA=y or CONFIG_TPL_SATA=y + + To use a PCIe connecte SATA controller you additionally need: + + * CONFIG_SPL_PCI=y + + * CONFIG_SPL_SATA=y + + * CONFIG_SPL_AHCI_PCI=y + + * CONFIG_SPL_PCI_PNP=y + + To load from a file system use: + + * CONFIG_SPL_FS_FAT=y + + * CONFIG_SYS_SATA_FAT_BOOT_PARTITION=<partition number> + + * CONFIG_SPL_FS_LOAD_PAYLOAD_NAME="<filepath>" + +USB + The USB method loads an image from a USB block device. + Required configuration settings include: + + * CONFIG_SPL_USB_HOST=y + + * CONFIG_SPL_USB_STORAGE=y + + To use a PCI connected USB 3.0 controller you additionally need: + + * CONFIG_SPL_FS_FAT=y + + * CONFIG_SPL_PCI=y + + * CONFIG_SPL_PCI_PNP=y + + * CONFIG_USB=y + + * CONFIG_USB_XHCI_HCD=y + + * CONFIG_USB_XHCI_PCI=y + + To load from a file system use: + + * CONFIG_SPL_FS_FAT=y or CONFIG_SPL_FS_EXT=y + + * CONFIG_SYS_USB_FAT_BOOT_PARTITION=<partition number> + + * CONFIG_SPL_FS_LOAD_PAYLOAD_NAME="<filepath>" + +Loading from flash devices +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +NAND + This method loads the image from NAND flash. To read from raw NAND the + following configuration settings are required: + + * CONFIG_SPL_NAND_SUPPORT=y or CONFIG_TPL_NAND_SUPPORT=y + + If CONFIG_SPL_NAND_RAW_ONLY=y only raw images can be loaded. + + For using UBI (Unsorted Block Images) volumes to read from NAND the + following configuration settings are required: + + * CONFIG_SPL_UBI=y or CONFIG_TPL_UBI=y + + The UBI volume to read can either be specified + + * by name using CONFIG_SPL_UBI_LOAD_BY_VOLNAME or + + * by number using CONFIG_SPL_UBI_LOAD_MONITOR_ID. + +NOR + This method loads the image from NOR flash. + Required configuration settings include: + + * CONFIG_SPL_NOR_SUPPORT=y or CONFIG_TPL_NOR_SUPPORT=y + +OneNAND + This methods loads the image from a OneNAND device. To read from raw OneNAND + the following configuration settings are required: + + * CONFIG_SPL_ONENAND_SUPPORT=y or CONFIG_TPL_ONENAND_SUPPORT=y + + For using the Ubi file system to read from NAND the following configuration + settings are required: + + * CONFIG_SPL_UBI=y or CONFIG_TPL_UBI=y + +SPI + This method loads an image form SPI NOR flash. + Required configuration settings include: + + * CONFIG_SPL_DM_SPI=y + + * CONFIG_SPL_SPI_FLASH=y + + * CONFIG_SPI_LOAD=y or CONFIG_TPL_SPI_LOAD=y + + +Sunxi SPI + This method which is specific to Allwinner SoCs loads an image form SPI NOR + flash. Required configuration settings include: + + * CONFIG_SPL_SPI_SUNXI=y + +Loading from other devices +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +BOOTROM + The binary is loaded by the boot ROM. + Required configuration settings include: + + * CONFIG_SPL_BOOTROM_SUPPORT=y or CONFIG_TPL_BOOTROM_SUPPORT=y + +DFU + :doc:`Device Firmware Upgrade <dfu>` is used to load the binary into RAM. + Required configuration settings include: + + * CONFIG_DFU=y + + * CONFIG_SPL_RAM_SUPPORT=y or CONFIG TPL_RAM_SUPPORT=y + +Ethernet + This method loads an image over Ethernet. The BOOTP protocol is used to find + a TFTP server and binary name. The binary is downloaded via the TFTP + protocol. Required configuration settings include: + + * CONFIG_SPL_NET=y or CONFIG_TPL_NET=y + + * CONFIG_SPL_ETH_DEVICE=y or CONFIG_DM_USB_GADGET=y + +FEL + This method does not actually load an image for U-Boot. + FEL is a routine contained in the boot ROM of Allwinner SoCs which serves + for the initial programming or recovery via USB + +RAM + This method uses an image preloaded into RAM. + Required configuration settings include: + + * CONFIG_SPL_RAM_SUPPORT=y or CONFIG_TPL_RAM_SUPPORT=y + + * CONFIG_RAM_DEVICE=y + +Sandbox file + On the sandbox this method loads an image from the host file system. + +Sandbox image + On the sandbox this method loads an image from the host file system. + +Semihosting + When running in an ARM or RISC-V virtual machine the semihosting method can + be used to load an image from the host file system. + Required configuration settings include: + + * CONFIG_SPL_SEMIHOSTING=y + + * CONFIG_SPL_SEMIHOSTING_FALLBACK=y + + * CONFIG_SPL_FS_LOAD_PAYLOAD_NAME=<path to file> + +UART + This method loads an image via the Y-Modem protocol from the UART. + Required configuration settings include: + + * CONFIG_SPL_YMODEM_SUPPORT=y or CONFIG_TPL_YMODEM_SUPPORT=y + +USB SDP + This method loads the image using the Serial Download Protocol as + implemented by the boot ROM of the i.MX family of SoCs. + + Required configuration settings include: + + * CONFIG_SPL_SERIAL=y + + * CONFIG_SPL_USB_SDP_SUPPORT=y or CONFIG_TPL_USB_SDP_SUPPORT + +VBE Simple + This method is used by the VPL stage to extract the next stage image from + the loaded image. + + Required configuration settings include: + + * CONFIG_VPL=y + + * CONFIG_SPL_BOOTMETH_VBE_SIMPLE_FW=y or CONFIG_TPL_BOOTMETH_VBE_SIMPLE_FW=y + +XIP + This method executes an image in place. + + Required configuration settings include: + + * CONFIG_SPL_XIP_SUPPORT