Comment # 18 on bug 1222156 from Stefan Dirsch

@Togan

You're using 

  radeon.si_support=0 amdgpu.si_support=1

right? I believe with that radeon kernel module is still being loaded but
doesn't initialize anything. So just amdgpu is active in that case.

Usage of radeonsi DRI driver for 2D acceleration in Xserver is hardcoded. So
this stays.

radeonsi also stays for Mesa, because that's the radeon driver for current AMD
Radeon cards and r300 and r600 is only for older cards.

So could be that latest radeonsi Mesa driver triggers a bug in latest radeon
kernel module.