Comment # 64 on bug 60802 from Alexandre Demers

(In reply to comment #63)
> Created attachment 76592 [details] [review] [review]
> take 5
> 
> After further investigation this seems to be an alignment issue with large
> block sizes on the DMA engine on cayman.  For now just use the blitter for
> large block sizes.

It does the trick for now.