Boot Yocto image von SD Card in armStone MX8MP

  • Hi @everyone :)

    Ich bin neu hier in der Forum

    Ich möchte gern mein eigene Yocto Image die in einem SD-Card ist als Image für den SBC booten.

    In der SD-Card ist kein Bootloader image? Nur ein Yocto image? Brauche ich denn ein U-Boot image für den spezifische Board? Soll diese U-Boot image in einer Partition von der SD-Card sein?

  • Hello,

    please communicate in English for this Forum, as others might need a solution for the same issue.

    Translated question:


    I would like to boot my Yocto image from SD-Card.

    There is no bootloader image in the SD-Card. Do I need a U-Boot specific to the board and should the U-Boot image be in a partition of the SD-Card?

    Our boards usually boot from the onboard eMMC, so the U-Boot image for the early startup is in the Bootpartition from the eMMC.

    If you want to boot your Yocto root filesystem and/or the Linux kernel with Device-Tree from the SD-Card, you can do so by entering some commands in U-Boot:

    1. setenv mmcdev 2 // Sets the current mmc device for the following commands to SD-Card
    2. run .kernel_mmc // In boot process the kernel will be loaded from current mmc device (SD-Card now)
    3. run .fdt_mmc // Same for Device-Tree
    4. run .rootfs_mmc // Same for RootFS
    5. saveenv // Write the new environments into the eMMC, so they remain after a powercycle

    If you just want to boot your Yocto rootFS, you can leave out the commands run .kernel_mmc and run .fdt_mmc.

    If you want to set the boot medium to the eMMC again, you can do this with the same commands, just with setenv mmcdev 0.

    The U-Boot expects on the boot medium a FAT partition, which includes Device-Trees and the kernel image, and an ext4 partition, which contains the root filesystem. It may be that you need to edit the environments in the U-Boot, if your SD-Card has another partiton layout.

    I hope I could clarify the boot process for you.

    Your F&S Support Team