frequent x crashes with gen6/sna

["Dieter Mummenschanz" <mummenschanz@gmx.net>]

hello,

using latest drm-core-next git from Dave Airlie as well as the latest xf86-video-intel git my system (Sandybridge Mobile (GT2+)) still hangs frequently right before X dies. This happens every time the GPU is under considerable stress, like decoding a va-api stream and running OpenGL apps at the same time.
syslog records the hang:

kernel: [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
kernel: [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
kernel: [drm:i915_wait_request] *ERROR* i915_wait_request returns -11 (awaiting 3263296 at 3263293, next 3263297)

after 3-4 seconds the system resumes normal following the X crash a couple of minutes later:
kernel: [drm:ironlake_update_pch_refclk] *ERROR* enabling SSC on PCH
kernel: [drm:ironlake_update_pch_refclk] *ERROR* enabling SSC on PCH

gpu related module opts are:
i915.i915_enable_rc6=1 pcie_aspm=force i915.i915_enable_fbc=1 i915.lvds_downclock=1

at least rc6 enabled is mandatory for me since I ran a mobile gpu.

any ideas?

regards
Dieter
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