Configuring the Bootloader

The Device Tree

  • Use the following command to list the available file’s within the boot media’s Boot partition (this is typically where binaries used for boot are stored):

    Target (U-Boot)
    ls mmc 0:1
    Example Output
    => ls mmc 0:1
       44   bootenv.txt
    52270   imx7d-phyboard-zeta-1110110c.dtb
    52286   imx7d-phyboard-zeta-2111101e.dtb
    52262   imx7d-phyboard-zeta-2111111e.dtb
    52286   imx7d-phyboard-zeta-2211101e.dtb
    52262   imx7d-phyboard-zeta-2211111e.dtb
    52238   imx7d-phyboard-zeta-kit.dtb
     2126   imx7d-phyboard-zeta-m4.dtbo
      240   imx7d-phyboard-zeta-peb-av-02-rev0.dtbo
     4652   imx7d-phyboard-zeta-peb-av-02.dtbo
     3577   imx7d-phyboard-zeta-peb-av-06.dtbo
     3256   imx7d-phyboard-zeta-peb-d-rpi.dtbo
    42848   imx7s-phyboard-zeta-kit.dtb
    52238   oftree
  9715904   zImage
            System Volume Information/

 15 file(s), 1 dir(s)

Working with Overlays

The PHYTEC BSP also comes with some device tree overlays to help evaluate certain interfaces and accessory hardware. The table “Linux Device Tree Summary in the Release Notes shows an overview of all available overlays.

Enable an Overlay

  • U-boot has an extra environment variable called “overlays” to apply device tree overlay files. We can enable device tree overlays with it like so:

Target (U-boot)
setenv overlays imx7d-phyboard-zeta-peb-d-rpi.dtbo
saveenv
boot

  • Moreover, it’s possible to enable multiple overlays by separating them with a space.

Target (U-boot)
setenv overlays imx7d-phyboard-zeta-peb-d-rpi.dtbo imx7d-phyboard-zeta-m4.dtbo
saveenv
boot

The saveenv command stores the boot environment to non-volatile memory. If you would like temporarily adjust the boot environment, you can omit the saveenv command and the boot environment will go back to the previously saved settings on the next boot.

Reset the U-Boot Environment to Default Settings

  • In order to revert the U-Boot environment back to its original settings, run the following:

Target (U-Boot)
env default -f -a
saveenv
boot