(In reply to Christian König from comment #3)
> That could just be a symptom of a hardware hang which isn't detected for
> some reason.
> 
> Please take a look at amdgpu_fence_info as well to see if there are any
> outstanding submissions.

If it's a hardware hang, wouldn't it also happen when using catalyst? It
doesn't happen there, so it should at least be possible to work around (if it
is a hardware problem).
I will continue investigating why this happens, but it does seem to me like
this, #91278, and #91676 all are caused by the same thing, but with different
log output depending on if you use drm-next-4.3 or drm-next-4.2.