Created attachment 79884 [details]
dmesg output when trying to switch back to radeon gpu.

I have two GPUs in my system:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Whistler [Radeon HD 6600M/6700M/7600M Series]

00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core
Processor Family Integrated Graphics Controller (rev 09)

This is a macbookpro8,2 and hence the gmuxer is controlled by the apple-gmux
driver.

If I suspend the system to ram whilst on the integrated gpu (i.e. the intel
gpu), then after resume switch back to the radeon, I get a GPU hang.

I've attached the dmesg output that I get when I try this.

I'm using linux 3.10-rc3.  I don't have X running when doing this
(vgaswitcheroo won't allow this).