(In reply to comment #35)
> Created attachment 91154 [details] [review] [review]
> possible fix
> 
> (In reply to comment #34)
> > 
> > $ lspci -nn | grep 'VGA'
> > 00:01.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc.
> > [AMD/ATI] Sumo [Radeon HD 6480G] [1002:9649]
> > 
> > [  188.599127] [drm] initializing kernel modesetting (SUMO 0x1002:0x9649
> > 0x17AA:0x21EA).
> > 
> > 
> > Thus, is's SUMO isn't it? Should I try to use "max_hw_contexts = 4" for the
> > SUMO case or that's unreasonable?
> 
> Your chip was misclassified.  The attached patch should fix it.

  Great! Now, it works! :)))

  Thank you so much.