drm/i915: Don't mask EI UP interrupt on IVB|SNB
authorMika Kuoppala <mika.kuoppala@linux.intel.com>
Thu, 22 Aug 2013 18:09:00 +0000 (21:09 +0300)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Tue, 3 Sep 2013 09:10:54 +0000 (11:10 +0200)
commita9c1f90c8e1792127f8348c1cc2565b79b2ef20a
tree19df9921b837a6c4c4a1d937faf1524a4cf768a1
parentf33bcab9e816c5bf56b74c3007790f2a256910eb
drm/i915: Don't mask EI UP interrupt on IVB|SNB

Submitting a batchbuffer which simulates a gpu
hang by doing MI_BATCH_BUFFER_START into itself,
to test hangcheck, started to hard hang the whole box
(IVB). Bisecting lead to this commit:

commit 664b422c2966cd39b8f67e8d53a566ea8c877cd6
Author: Vinit Azad <vinit.azad@intel.com>
Date:   Wed Aug 14 13:34:33 2013 -0700

    drm/i915: Only unmask required PM interrupts

Experimenting with the mask register showed that
unmasking EI UP will prevent the hard hang in IVB and SNB.
HSW doesn't hang with EI UP masked.

Considering we are just disabling interrupts that aren't even
delivered to driver, this change is more likely to paper over some
weirdness in gpu's internal state machine. But until better
explanation can be found, let's trade little bit of power
for stability on these architectures.

v2: - Unmask EI_EXPIRED directly in I915_WRITE (Vinit)
v3: - Only unmask on SNB and IVB

Cc: Vinit Azad <vinit.azad@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Acked-by: Vinit Azad <vinit.azad@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/intel_pm.c