https://bugzilla.kernel.org/show_bug.cgi?id=210263
jaromir.obr@gmail.com changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |jaromir.obr@gmail.com
--- Comment #6 from jaromir.obr@gmail.com --- @Fabian I have the same experience. I was running kernel 5.13 on Ubuntu 21.10 and when I upgraded to mainline kernel 5.15.13 (using https://github.com/pimlie/ubuntu-mainline-kernel.sh), the service "systemd-backlight@backlight:amdgpu_bl0.service" starts as expected and backlight seems to be restored.
With kernel 5.13 it failed: "Failed to start Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0" and I was not able to start it manually.