https://bugs.freedesktop.org/show_bug.cgi?id=99710
--- Comment #13 from Sandeep sandy.8925@gmail.com --- Ok fine - I tested wtih amdgpu.dpm=0 and no hangs after 2 whole levels of Left 4 Dead 2.
Looks like DPM is the problem - seems to be a regression, since it was working fine with DPM 2-3 months ago.