Using Linux 4.12.3 on a netbook with AMD A4-1200 Kabini APU and the amdgpu
driver:

Upon resuming from suspend-to-RAM, the LVDS display will become all while.

This situation will persist until a reboot, even after turning it off and on
again with xrandr.

Backlight control works fine at all times. External displays (VGA, HDMI) are
not affected. The radeon driver does not have this problem.

I noticed that in bug 42960 a very similar issue was fixed in radeon, but am
currently unsure whether the fix made it into amdgpu too.