--- /dev/null
+From 9adab8b5a7fde248504f484e197589f3e3c922e2 Mon Sep 17 00:00:00 2001
+From: Chris Wilson <chris@chris-wilson.co.uk>
+Date: Wed, 9 May 2012 21:45:43 +0100
+Subject: drm/i915: Avoid a double-read of PCH_IIR during interrupt handling
+
+From: Chris Wilson <chris@chris-wilson.co.uk>
+
+commit 9adab8b5a7fde248504f484e197589f3e3c922e2 upstream.
+
+Currently the code re-reads PCH_IIR during the hotplug interrupt
+processing. Not only is this a wasted read, but introduces a potential
+for handling a spurious interrupt as we then may not clear all the
+interrupts processed (since the re-read IIR may contains more interrupts
+asserted than we clear using the result of the original read).
+
+Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
+Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
+Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/gpu/drm/i915/i915_irq.c | 9 +++------
+ 1 file changed, 3 insertions(+), 6 deletions(-)
+
+--- a/drivers/gpu/drm/i915/i915_irq.c
++++ b/drivers/gpu/drm/i915/i915_irq.c
+@@ -422,14 +422,11 @@ static void gen6_pm_rps_work(struct work
+ mutex_unlock(&dev_priv->dev->struct_mutex);
+ }
+
+-static void pch_irq_handler(struct drm_device *dev)
++static void pch_irq_handler(struct drm_device *dev, u32 pch_iir)
+ {
+ drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+- u32 pch_iir;
+ int pipe;
+
+- pch_iir = I915_READ(SDEIIR);
+-
+ if (pch_iir & SDE_AUDIO_POWER_MASK)
+ DRM_DEBUG_DRIVER("PCH audio power change on port %d\n",
+ (pch_iir & SDE_AUDIO_POWER_MASK) >>
+@@ -527,7 +524,7 @@ static irqreturn_t ivybridge_irq_handler
+ if (de_iir & DE_PCH_EVENT_IVB) {
+ if (pch_iir & SDE_HOTPLUG_MASK_CPT)
+ queue_work(dev_priv->wq, &dev_priv->hotplug_work);
+- pch_irq_handler(dev);
++ pch_irq_handler(dev, pch_iir);
+ }
+
+ if (pm_iir & GEN6_PM_DEFERRED_EVENTS) {
+@@ -626,7 +623,7 @@ static irqreturn_t ironlake_irq_handler(
+ if (de_iir & DE_PCH_EVENT) {
+ if (pch_iir & hotplug_mask)
+ queue_work(dev_priv->wq, &dev_priv->hotplug_work);
+- pch_irq_handler(dev);
++ pch_irq_handler(dev, pch_iir);
+ }
+
+ if (de_iir & DE_PCU_EVENT) {