Same issue here. Happens very often during firefox usage, but also on other ocasions.
[51278.392895] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
[51278.392901] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
[51278.397785] [drm] Enabling RC6 states: RC6 on, RC6p off, RC6pp off
Same issue here. Happens very often during firefox usage, but also on other ocasions.
[51278.392895] [drm:i915_ hangcheck_ hung] *ERROR* Hangcheck timer elapsed... GPU hung dri/0/i915_ error_state
[51278.392901] [drm] capturing error event; look for more information in /debug/
[51278.397785] [drm] Enabling RC6 states: RC6 on, RC6p off, RC6pp off