https://bugs.freedesktop.org/show_bug.cgi?id=66963
--- Comment #191 from Sergey orbitgray@ukr.net --- (In reply to comment #190)
Are you sure you have acceleration enabled, the behaviour you describe matches what I found when started testing that branch (grep dmesg for "*ERROR* radeon: ring 3 test failed (0xCAFEDEAD)").
Looks like you are right. I have the same error. Thanks. Will try your patch.