Created attachment 97956 [details]
lspci

I have an Asus X550 series laptop with an AMD APU A8-5550M.
The integrated GPU is a 8550G and the dGPU is a 8670M.

After upgrading the kernel from 3.13.6 to 3.13.7 the machine becomes unbootable
and it freezes(black screen, possibly X not able to start). 

Setting radeon.runpm=0 at boot time doesn't help. 

After doing a bisect I've found the following commit to be the problematic one:

[drm/radeon] fix runpm disabling on non-PX harder.

Also, I have to mention that the bug seems to be reproducible on similar
hardware configurations, see: http://forums.gentoo.org/viewtopic-p-7529160.html