Merge branch 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6

* 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
  drm/i915: Fix gen6 (SNB) missed BLT ring interrupts.

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b9fafe3b045b..9e34a1abeb61 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1740,6 +1740,16 @@ void ironlake_irq_preinstall(struct drm_device *dev)
                 INIT_WORK(&dev_priv->rps_work, gen6_pm_rps_work);
 
         I915_WRITE(HWSTAM, 0xeffe);
+        if (IS_GEN6(dev)) {
+                /* Workaround stalls observed on Sandy Bridge GPUs by
+                 * making the blitter command streamer generate a
+                 * write to the Hardware Status Page for
+                 * MI_USER_INTERRUPT.  This appears to serialize the
+                 * previous seqno write out before the interrupt
+                 * happens.
+                 */
+                I915_WRITE(GEN6_BLITTER_HWSTAM, ~GEN6_BLITTER_USER_INTERRUPT);
+        }
 
         /* XXX hotplug from PCH */