(In reply to comment #11)
> 
> Sorry Alex, but is this intended (it is in the logs since 3.16+, too)?
> 
> [   11.316570] radeon 0000:01:00.0: (-1) pin WB bo failed
> [   11.316582] radeon 0000:01:00.0: f2fb0c00 unpin not necessary
> [   11.316601] radeon 0000:01:00.0: disabling GPU acceleration
> [   11.369220] radeon 0000:01:00.0: f6064000 unpin not necessary
> 
> [   11.433188] [TTM] Finalizing pool allocator
> [   11.433309] [TTM] Zone  kernel: Used memory at exit: 0 kiB
> [   11.433317] [TTM] Zone highmem: Used memory at exit: 0 kiB
> [   11.433320] [drm] radeon: ttm finalized
> 
> [   11.433325] [drm] Forcing AGP to PCIE mode
> 
> So, maybe GTT/GART grows to big?

AGP should work.  You'll have to bisect.  Anyway, this is not related to this
bug.  Please open a new one.