Commenting out
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/radeon/radeon_uvd.c?id=7050c6ef5f0e9bc5e6bf9eb035320b70f731b919#n130

or removing /lib/firmware/radeon/bonaire_uvd.bin fixes the problem on my
system.