Configuring the Bootloader
Change the Device Tree
By default, U-Boot loads the dtb file named k3-am62a7-phyboard-lyra-rdk.dtb as the active device tree during boot. In order to instruct U-Boot to load a different device tree by a different name, reference the following steps:
Power on the board and press any key to stop autoboot and enter U-Boot.
Type the following commands:
Target (U-Boot)setenv default_device_tree <dtb name> saveenv reset
U-Boot will now load the dtb file named ‘<dtb name>’ automatically during subsequent boots (just replace with the appropriate file name when you run the command).
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
Our U-Boot has an extra environment variable to apply overlays. Therefore, set the environment variable “overlays” with one of the available overlay name and boot.
setenv overlays k3-am62-phyboard-lyra-vm016-mipi.dtbo
boot
Moreover, it’s possible to enable multiple overlays by seperating them with a space.
setenv overlays k3-am62-phyboard-lyra-vm016-mipi.dtbo k3-am62-phyboard-lyra-gpio-fan.dtbo
boot
Permanent Solution
The previous section only enables overlays for the current boot. Run “saveenv” after setting the environment variable will store it permantly on the storage device currently booted from.
setenv overlays k3-am62-phyboard-lyra-vm016-mipi.dtbo
saveenv
boot
To undo the permantly stored overlay, set the “overlays” environment without any parameter and overwrite it to the storage.
setenv overlays
saveenv
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:
env default -f -a
saveenv
boot