https://bugs.freedesktop.org/show_bug.cgi?id=94511
--- Comment #3 from Christian König deathsimple@vodafone.de --- Most likely the name of the problem here is AGP.
We already tried a couple of different workarounds but it is quite hard to get fully stable with UVD.
Try to disable AGP with radeon.agpmode=-1 and see if that helps.