[071/119] drm/i915: Fix IRQ stall issue on Ironlake

[Greg KH]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Nanhai Zou <nanhai.zou@xxxxxxxxx>

commit 2d109a845dd3074885db726892c629ab73dd0ed8 upstream.

The master irq control in DE must be disabled before irq handling,
and enable after the process. This fixes the irq stall issue on
Ironlake.

Signed-off-by: Nanhai Zou <nanhai.zou@xxxxxxxxx>
Signed-off-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/gpu/drm/i915/i915_irq.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -253,10 +253,15 @@ irqreturn_t igdng_irq_handler(struct drm
 {
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
 	int ret = IRQ_NONE;
-	u32 de_iir, gt_iir;
+	u32 de_iir, gt_iir, de_ier;
 	u32 new_de_iir, new_gt_iir;
 	struct drm_i915_master_private *master_priv;
 
+	/* disable master interrupt before clearing iir  */
+	de_ier = I915_READ(DEIER);
+	I915_WRITE(DEIER, de_ier & ~DE_MASTER_IRQ_CONTROL);
+	(void)I915_READ(DEIER);
+
 	de_iir = I915_READ(DEIIR);
 	gt_iir = I915_READ(GTIIR);
 
@@ -287,6 +292,9 @@ irqreturn_t igdng_irq_handler(struct drm
 		gt_iir = new_gt_iir;
 	}
 
+	I915_WRITE(DEIER, de_ier);
+	(void)I915_READ(DEIER);
+
 	return ret;
 }
 


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