Comment # 1 on bug 109375 from Rafał Miłecki

For a comparison: behavior with the commit 262485a50fd4~1 (before the
regression):

Before suspend:
> cat /sys/class/backlight/amdgpu_bl0/{actual_brightness,brightness}
255
255

After resume:
> cat /sys/class/backlight/amdgpu_bl0/{actual_brightness,brightness}
250
255

Looks like a problem with amdgpu restoring backlight after resume.