https://bugs.freedesktop.org/show_bug.cgi?id=67800
--- Comment #6 from Kertesz Laszlo laszlo.kertesz@gmail.com --- I recompiled the kernel (from linus' git) with these patches applied:
http://lists.freedesktop.org/archives/dri-devel/2013-August/043145.html I also disabled C6 state from BIOS.
I had no freezes since then. I still have to test some longer idle times (i had ~3 hours maximum so far), but it seems promising.