https://bugs.freedesktop.org/show_bug.cgi?id=89536
--- Comment #8 from Michel Dänzer michel@daenzer.net --- (In reply to Rafael Ristovski from comment #7)
I just downgraded, PRIME worked flawlessly up until 3.19, I was able to test up until 3.17.6-1 since the next one after that was the latest kernel in the [testing] repo aka 3.19.2-1
Can you narrow it down further, ideally bisect?