https://bugs.freedesktop.org/show_bug.cgi?id=66519
--- Comment #5 from Christian König deathsimple@vodafone.de --- Created attachment 81945 --> https://bugs.freedesktop.org/attachment.cgi?id=81945&action=edit Debugging patch
Please try the attached patch, it shouldn't fix the issue but instead outputs some debug messages ("IH: CP....") into dmesg.
If you don't see those messages try to but the system under some graphics load, for example start glxgears ten times simultaneously or something like that.