VC4 configuration

config.txt

In the upstream kernel, graphics is already enabled in the device tree. The firmware requires one configuration option in config.txt to keep it from smashing the graphics state on undervoltage:

avoid_warnings=2

In the downstream kernel tree, vc4 is disabled by default and you need an overlay to enable it:

dtoverlay=vc4-kms-v3d
avoid_warnings=2

The VC4 graphics driver does not use any other config.txt entries for its configuration. It also doesn't use any of the memory reserved by the firmware under the gpu_mem configuration option, so keeping gpu_mem low will give Linux more space, including space for actual GPU operation.

Console resolution

The fbdev-style DRM console can have its boot-time resolution configured by adding a video= kernel parameter

For example:

video=HDMI-1:1024x768M@60m

To fake the EDID from HDMI to something else, so that X11 or other applications will also choose the same mode, you can force use of one of the kernel's built-in EDIDs:

drm_kms_helper.edid_firmware=edid/1920x1080.bin

There are also a 1680x1050.bin, 1280x1024.bin, and 1024x768.bin.

Screen rotation

There is no support for configuring console rotation at boot with the video= parameter. This should be added.

X screens can be rotated with a command like:

xrandr --output HDMI-1 --rotate right