Kajzer, I don't think this has anything to do with the original problem
reported here anymore but should be tracked in a separate report.

(In reply to Kajzer from comment #269)
> # first bad commit: [02376d8282b88f07d0716da6155094c8760b1a13] drm/radeon:
> Allow write-combined CPU mappings of BOs in GTT (v2)
> 
> commit 02376d8282b88f07d0716da6155094c8760b1a13
> Author: Michel Dänzer <michel.daenzer@amd.com>
> Date:   Thu Jul 17 19:01:08 2014 +0900
> 
>     drm/radeon: Allow write-combined CPU mappings of BOs in GTT (v2)

Are you 100% (or at least 99.99...% :) sure that the problem doesn't happen
without this commit?