- Created by Manuela Strücker, last modified on 21 04, 2021
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Introduction
the industry standard "distro boot" boot flow for U-boot has been implemented as default by Xilinx. (see xilinx-wiki.atlassian "Using Distro Boot With Xilinx U-Boot")
The distro boot functionality is implemented as an extension of the existing U-Boot bootcmd functionality in U-Boot. It extends its functionality by redirecting the call to bootcmd to a call to the distro_bootcmd variable.
bootcmd=run distro_bootcmd
Distro_bootcmd and Boot_targets
The distro_bootcmd variable typically contains a sequence of commands that scans a pre-defined list of potential boot targets in search of boot collateral as shown below in an snippet of the printenv
scriptaddr=0x3000000 script_offset_f=fc0000 script_size_f=0x40000 boot_targets=qspi jtag mmc0 mmc1 qspi nand nor usb0 usb1 pxe dhcp distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done bootcmd_qspi=sf probe 0 0 0 && sf read ${scriptaddr} ${script_offset_f} ${script_size_f} && echo QSPI: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo QSPI: SCRIPT FAILED: continuing...; bootcmd_mmc0=devnum=0; run mmc_boot mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
The boot_targets list is defined in the platform definition in the U-Boot source tree.
Depending on the specifics of the target platform, the distro boot infrastructure can either use the boot_targets list to explicitly find specific boot collateral (eg. hard-coded loading once a valid boot target is located) or it can be used to locate some kind of decoupled configuration information.
Not all devices listed in the boot_target list are available. Which devices can be used depends on
- the target platform used
- the correct configuration of the hardware in Vivado
- the correct configuration of the u-boot and the device tree in Petalinux
Configuration examples can be found in the corresponding reference designs.
Boot Method Precedence
The order of precedence for searching for boot components is as follows
- extlinux.conf file (located in /extlinux/ or /boot/extlinux/)
- boot.scr file + image.ub file
- boot.scr file + individual files (Image, system.dtb, etc.)
In absence of a valid extlinux.conf file, U-Boot will scan the boot_targets list looking for a file named boot.scr.uimg or boot.scr (in that order) and run any commands located in the script file. If your environment requires a different sequence of commands or behaviour, you can edit the boot.scr file to suit your needs.
Using the boot.src method
Install u-boot-tools on Linux OS
Before using the mkimage function, the u-boot-tools needs to be installed.
sudo apt-get update sudo apt install u-boot-tools
Generate boot.script file from boot.scr file
For the modification of the boot.scr file convert the existing boot.scr file into an boot.script file:
dd if=boot.scr of=boot.script bs=72 skip=1
Modifying boot.script file
Modify the boot.script file based on your needs. For example, when booting image.ub from SD card, USB or QSPI flash, the following boot.script file should work after conversion into an boot.scr file. The boot.scr file could be located on all working boot_targets.
# This is a boot script for U-Boot # Generate boot.scr: # mkimage -c none -A arm -T script -d boot.script boot.scr # # Generate boot.script (for modifications in boot.scr): # dd if=boot.scr of=boot.script bs=72 skip=1 # ################ imageub_addr=0x10000000 # imageub_flash_addr=0x200000 imageub_flash_size=0xD90000 for boot_target in ${boot_targets}; do # Boot target is mmc0 or usb0: image.ub on mmc0 or usb0 if test "${boot_target}" = "${devtype}0"; then if test -e ${devtype} 0:${distro_bootpart} /image.ub; then fatload ${devtype} 0:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi # Boot target is mmc1 or usb1: image.ub on mmc1 or usb1 if test "${boot_target}" = "${devtype}1"; then if test -e ${devtype} 1:${distro_bootpart} /image.ub; then fatload ${devtype} 1:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi # Boot target is qspi: image.ub on qspi; image.ub is included in BOOT.bin if test "${boot_target}" = "qspi"; then sf probe 0 0 0; sf read ${imageub_addr} ${imageub_flash_addr} ${imageub_flash_size}; bootm ${imageub_addr}; fi done
Note
The alias name ${devnum}, used in Xilinx default files, does not work in all variants tested, therefore the ${devtype} boot_targets were split up
Generate boot.scr file from boot.script file
Please remember that the boot.script file needs to be converted back into the boot.scr file after the edits are complete
mkimage -c none -A arm -T script -d boot.script boot.scr
Distro Boot in SD-Boot mode
Boot Variants | SD-Card (mmc0) | USB-Stick (usb0) | QSPI-Flash | Comments |
---|---|---|---|---|
Variant 1 | BOOT.bin1 image.ub boot.scr Init.sh | -- | -- | recommended workflow |
Variant 2 | BOOT.bin1 image.ub Init.sh | -- | BOOT.bin2 | used boot.scr from QSPI-Flash and image.ub from SD card |
Variant 3 | BOOT.bin1 boot.scr Init.sh | -- | BOOT.bin2 | used boot.scr from SD card and image.ub from QSPI-Flash |
Variant 4 | BOOT.bin1 image.ub Init.sh | -- | BOOT.bin3 | used boot.scr from QSPI-Flash and image.ub from SD card |
File name | BOOT.bin1 | BOOT.bin2 | BOOT.bin3 | QSPI Flash Offset Address | RAM Load Address |
---|---|---|---|---|---|
fsbl.elf | x | x | x | -- | NA |
test_board.bit | x | x | x | -- | NA |
u-boot.elf | x | x | x | -- | NA |
image.ub | x | 0x200000 | 0x10000000 | ||
boot.scr | x | x | 0xfc0000 | 0x3000000 |
Note
When booting from a QSPI device, care must be taken to maintain a very specific scheme for where files are located both in the nonvolatile flash device as well as where they are loaded into DDR prior to hand-off to the robust operating system.
Variant 1 (Boot.bin, image.ub and boot.scr on SD card):
- Copy image.ub, boot.scr and Boot.bin on SD-Card.
- use files from (<project folder>/_binaries_<Article Name>)/boot_linux from generated binary folder,see: Get prebuilt boot binaries
- or use prebuilt file location, see <design_name>/prebuilt/readme_file_location.txt
- Set Boot Mode to SD-Boot.
- Depends on Carrier, see carrier TRM.
- Insert SD-Card in SD-Slot.
Variant 2 (Boot.bin on SD card; image.ub and boot.scr on USB):
- Copy image.ub on SD-Card.
- use files from (<project folder>/_binaries_<Article Name>)/boot_linux from generated binary folder,see: Get prebuilt boot binaries
- or use prebuilt file location, see <design_name>/prebuilt/readme_file_location.txt
- Copy boot.scr and Boot.bin on USB Stick
- Set Boot Mode to SD-Boot.
- Depends on Carrier, see carrier TRM.
- Insert SD-Card in SD-Slot.
- Insert USB-Stick in USB-Slot
Distro Boot in QSPI-Boot mode
Boot Variants | SD-Card (mmc0) | USB-Stick (usb0) | QSPI-Flash | Comments |
---|---|---|---|---|
Variant 1 | -- | -- | BOOT.bin2 zynq_fsbl_flash | Boot only from QSPI flash |
Variant 2 | image.ub boot.scr | -- | BOOT.bin1 zynq_fsbl_flash | used boot.scr and image.ub from SD card |
Variant 3 | BOOT.bin1 image.ub | -- | BOOT.bin3 zynq_fsbl_flash | used boot.scr from QSPI-Flash and image.ub from SD card |
File name | BOOT.bin1 | BOOT.bin2 | BOOT.bin3 | QSPI Flash Offset Address | RAM Load Address |
---|---|---|---|---|---|
fsbl.elf | x | x | x | -- | NA |
test_board.bit | x | x | x | -- | NA |
u-boot.elf | x | x | x | -- | NA |
image.ub | x | 0x200000 | 0x10000000 | ||
boot.scr | x | x | 0xfc0000 | 0x3000000 |
Note
When booting from a QSPI device, care must be taken to maintain a very specific scheme for where files are located both in the nonvolatile flash device as well as where they are loaded into DDR prior to hand-off to the robust operating system.
Variant 1 (Boot.bin on QSPI Flash; image.ub and boot.scr on SD card):
- Connect JTAG and power on carrier with module (boot mode set to SD boot and no SD card is inserted)
- Open Vivado Project with "vivado_open_existing_project_guimode.cmd" or if not created, create with "vivado_create_project_guimode.cmd"
- Type on Vivado TCL Console: TE::pr_program_flash -swapp u-boot
Note: To program with SDK/Vivado GUI, use special FSBL (zynq_fsbl_flash) on setup
optional "TE::pr_program_flash -swapp hello_te0715" possible - Copy boot.scr and image.ub on SD-Card
- use files from (<project folder>/_binaries_<Article Name>)/boot_linux from generated binary folder,see: Get prebuilt boot binaries
- or use prebuilt file location, see <design_name>/prebuilt/readme_file_location.txt
- Set boot mode to QSPI-Boot mode and insert SD card.
- Depends on Carrier, see carrier TRM.
Variant 2 (Boot.bin, image.ub and boot.scr on QSPI Flash):
- Connect JTAG and power on carrier with module (boot mode set to SD boot and no SD card is inserted)
- Open Vivado Project with "vivado_open_existing_project_guimode.cmd" or if not created, create with "vivado_create_project_guimode.cmd"
- Type on Vivado TCL Console: TE::pr_program_flash -swapp u-boot
Note: To program with SDK/Vivado GUI, use special FSBL (zynq_fsbl_flash) on setup
optional "TE::pr_program_flash -swapp hello_te0715" possible - Set boot mode to QSPI-Boot mode and start the board.
- Depends on Carrier, see carrier TRM.
Code Snippets for Boot.scr file
# Boot target is mmc0: image.ub on mmc0 if test "${boot_target}" = "mmc0"; then mmc dev 0 if test -e mmc 0:${distro_bootpart} /image.ub; then echo [TE_BOOT-20] boot_target is ${boot_target}. Found image.ub on mmc0:${distro_bootpart} ; fatload mmc 0:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi # Boot target is mmc1: image.ub on mmc1 if test "${boot_target}" = "mmc1"; then mmc dev 1 if test -e mmc 1:${distro_bootpart} /image.ub; then echo [TE_BOOT-21] boot_target is ${boot_target}. Found image.ub on mmc1:${distro_bootpart}; fatload mmc 1:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi
Note
The alias name ${devnum}, used in Xilinx default files, does not work in all variants tested, therefore the ${devtype} boot_targets were split up
# Boot target is mmc0 or usb0: image.ub on mmc0 or usb0 if test "${boot_target}" = "${devtype}0"; then if test -e ${devtype} 0:${distro_bootpart} /image.ub; then echo [TE_BOOT-20] boot_target is ${boot_target}. Found image.ub on ${devtype}0:${distro_bootpart} ; fatload ${devtype} 0:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi # Boot target is mmc1 or usb1: image.ub on mmc1 or usb1 if test "${boot_target}" = "${devtype}1"; then if test -e ${devtype} 1:${distro_bootpart} /image.ub; then echo [TE_BOOT-21] boot_target is ${boot_target}. Found image.ub on ${devtype}1:${distro_bootpart}; fatload ${devtype} 1:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi
Note
The alias name ${devnum}, used in Xilinx default files, does not work in all variants tested, therefore the ${devtype} boot_targets were split up
# image.ub on usb0 if test "${boot_target}" = "usb0"; then if test -e usb 0:${distro_bootpart} /image.ub; then echo [TE_BOOT-20] boot_target is ${boot_target}. Found image.ub on usb0:${distro_bootpart} ; fatload usb 0:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi # image.ub on usb1 if test "${boot_target}" = "usb1"; then if test -e usb 1:${distro_bootpart} /image.ub; then echo [TE_BOOT-21] boot_target is ${boot_target}. Found image.ub on usb1:${distro_bootpart}; fatload usb 1:${distro_bootpart} ${imageub_addr} image.ub; bootm ${imageub_addr}; fi fi
# Boot target is qspi: image.ub on qspi; image.ub is included in BOOT.bin if test "${boot_target}" = "qspi"; then echo [TE_BOOT-30] Try to use image.ub from ${boot_target}, load image.ub from qspi-flash address ${imageub_flash_addr}; echo [TE_BOOT-30] max. image.ub size is ${imageub_flash_size} ; sf probe 0 0 0; sf read ${imageub_addr} ${imageub_flash_addr} ${imageub_flash_size}; bootm ${imageub_addr}; fi
References
https://wiki.ubuntu.com/ARM/EditBootscr
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