Comment # 178 on bug 66963 from Thierry Vignaud

(In reply to comment #172)
> > Is there any patch I can try against 3.12.6?
> 
> You can try disabling additional dpm features as per comment 94.

The patch seems to fix the issue.
Booting with only the second half is not enough (the voltage_control & the
gfx_clock_gating changes):
I experienced black screen freeze on boot & disabled accel another time.