drm/i915: Increase the RC6p threshold.

commit 0920a487 upstream.

This increases GEN6_RC6p_THRESHOLD from 100000 to 150000. For some
reason this avoids the gen6_gt_check_fifodbg.isra warnings and
associated GPU lockups, which makes my ivy bridge machine stable.
Signed-off-by: Stéphane Marchesin <marcheu@chromium.org>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -8059,7 +8059,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	I915_WRITE(GEN6_RC_SLEEP, 0);
 	I915_WRITE(GEN6_RC1e_THRESHOLD, 1000);
 	I915_WRITE(GEN6_RC6_THRESHOLD, 50000);
-	I915_WRITE(GEN6_RC6p_THRESHOLD, 100000);
+	I915_WRITE(GEN6_RC6p_THRESHOLD, 150000);
 	I915_WRITE(GEN6_RC6pp_THRESHOLD, 64000); /* unused */
 
 	if (intel_enable_rc6(dev_priv->dev))