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some device information that cannot be recovered if overwritten.
compatible
property which indicates which device driver should be used to implement the features provided by that node. We also use the FDT to pass provide configuration and verified boot information from U-Boot to the kernel. There is a different FDT for each board type, and even for each SKU (since a particular manufacturing run may change the chips that are used in some cases).cros_bundle_firmware
This is a tool for creating a firmware image and writing it to your board. It can handle the following tasks:
To create an image for a particular board, use:
cros_bundle_firmware -b <board> -o <filename>
This will generate an image <filename>
for the board. The tool finds files it needs in /build/<board>/firmware
, things like u-boot.bin
, the device tree source files (in dts subdir) and so on. There are options to specify each of these manually if you want to, and this is what the ebuild does. However, it does make for a very long command line. If you are unsure what files it is picking up, use -v3.
By default cros_bundle_firmware
is quiet. Unless there are warnings/errors, all you will see is progress, and a command prompt when done. Use -v2, -v3 or even -v4 to change that.
Things you can do with this tool, which involve adding options:
-u u-boot.bin
-U /build/<board>/firmware/u-boot.bin
-d my-board.dts
-I arch/arm/dts -I board/samsung/dts
-w sd:.
.
means to write to the only SD card connected to your machine. You can explicitly name the card if you like. Try -w sd
to get a list of options.-w usb
-s
-O <dir>
A full list of options is below, or use the --help flag.
Usage: cros_bundle_firmware [options] Options: -h, --help show this help message and exit --add-config-str=ADD_CONFIG_STR Add a /config string to the U-Boot fdt --add-config-int=ADD_CONFIG_INT Add a /config integer to the U-Boot fdt -b BOARD, --board=BOARD Board name to use (e.g. tegra2_kaen) --bootcmd=BOOTCMD Set U-Boot boot command --bootsecure Boot command is simple (no arguments) and not interruptible -c BCT, --bct=BCT Path to BCT source file: only one can be given -d FDT, --dt=FDT Path to fdt binary blob .dtb file to use --bl1=EXYNOS_BL1 Exynos preboot (BL1) file --bl2=EXYNOS_BL2 Exynos Secondary Program Loader (SPL / BL2) file --hwid=HARDWARE_ID Hardware ID string to use -B BMPBLK, --bmpblk=BMPBLK Bitmap block to use -F FLASH_DEST, --flash=FLASH_DEST Create a flasher to flash the device (spi, mmc) -k KEY, --key=KEY Path to signing key directory (default to dev key) -I INCLUDEDIRS, --includedir=INCLUDEDIRS Include directory to search for files -m, --map Output a flash map summary -o OUTPUT, --output=OUTPUT Filename of final output image -O OUTDIR, --outdir=OUTDIR Path to directory to use for intermediate and output files -p, --preserve Preserve temporary output directory -P POSTLOAD, --postload=POSTLOAD Path to post-load portion of U-Boot (u-boot-post.bin) -s, --small Create/write only the signed U-Boot binary (not the full image) -S SEABIOS, --seabios=SEABIOS Legacy BIOS (SeaBIOS) -u UBOOT, --uboot=UBOOT Executable bootloader file (U-Boot) -U UBOOT_FLASHER, --uboot-flasher=UBOOT_FLASHER Executable bootloader file (U-Boot) to use for flashing (defaults to the same as --uboot) -C COREBOOT, --coreboot=COREBOOT Executable lowlevel init file (coreboot) -v VERBOSITY, --verbosity=VERBOSITY Control verbosity: 0=silent, 1=progress, 3=full, 4=debug -w WRITE, --write=WRITE Write firmware to device (usb, sd)
cros_write_firmware
If you already have an image, you can use this tool to write it to an SD card or over USB. However, you might find ‘cros_bundle_firmware -w
’ more flexible.
cros_write_firmware -b daisy -i <image> -w sd:.
You can do this without USB download using an SD card if you like. Please follow these steps:
Get an SD card and put it into your card reader. The contents of this will be overwritten.
Get the latest source:
$ repo sync
Build everything
$ build_packages --board daisy
$ emerge-daisy chromeos-u-boot
$ emerge-daisy sys-boot/chromeos-bootimage
Write the firmware to your SD card (-F means to create an automatic flasher)
$ cros_bundle_firmware --add-config-int load_env 1 -b daisy -w sd:. -F spi # Add '-d exynos5250-snow' for snow
Insert the SD card into your daisy board
Hold down the button which is labelled T20_REC / FW_DEBUG / DFU_REC depending on whether you are using Servo 2, Daisy or Min-Servo.
Press COLD_RST_L / KBC_RST / C_RST, then PWR_BUTTON to switch on, to boot from the SD card.
When it starts up, you should see a console on your servo UART, and it will start flashing your board.
When finished, type ‘reset’ into the terminal, or press COLD_RST_L / KBC_RST / C_RST again, then PWR_BUTTON to switch on.
Steps 8 can also be done via servod:
dut-control fw_up:on fw_up cold_reset:on cold_reset cold_reset:off cold_reset \ pwr_button:press pwr_button sleep:2 pwr_button:release pwr_button \ cold_reset:off cold_reset fw_up:off fw_up cpu_uart_en:on
Building from the firmware branch
The ToT is not guaranteed to build usable firmware for older boards, so it is often necessary to retrieve an old branch to do so. These steps were used to build the Link firmware from source:
This should create image-link.bin
in /build/link/firmware
under the chroot.
Using flashrom
The flashrom
command can be run from a root shell on the device, or it can be used from a development PC connected via servo. See here for more detailed instructions on usage.
Using the SPI flash emulator
The instructions in this section assume that you have a Dediprog EM100 hooked up to the system. This hardware allows for downloading a new firmware image to the board in mere seconds, rather than waiting a few minutes to reflash a physical SPI memory device.
To build a new firmware image, write it to your em100 and reset your link (using servo2):
$ USE=dev emerge-link chromeos-u-boot $ cros_bundle_firmware -b link --bootcmd vboot_twostop -w em100
(the ‘dev’ flag reduces the 870KB of spew from the U-Boot ebuild, printing only warnings and errors)
If you want a U-Boot serial console, but don't want to coreboot to print out all its serial info, you can build a coreboot WITHOUT the USE=pcserial
flag, and then:
$ cros_bundle_firmware -b link --add-node-enable console 1 --bootcmd vboot_twostop -w em100
This enables the console node in the device tree, thus turning on the serial console in U-Boot.