https://bugzilla.kernel.org/show_bug.cgi?id=60523
--- Comment #11 from Tobias Droste tdroste@gmx.de --- Interesting fact #3:
it's also working if I only attach 1 monitor!
So it looks like power state 1, 2 and 4 are working correctly and power state 3 (no uvd and two monitors attached) is broken.