[Intel-gfx] [PATCH 4/6] drm/i915: Fix IRQ stall issue on Ironlake

[Zhenyu Wang]

From: Zou, Nanhai <nanhai.zou at intel.com>

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.

Cc: Stable Team <stable at kernel.org>
Signed-off-by: Zou, Nanhai <nanhai.zou at intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index f1fbfdd..417ba99 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -268,10 +268,15 @@ irqreturn_t igdng_irq_handler(struct drm_device *dev)
 {
 	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);
 
@@ -307,6 +312,9 @@ irqreturn_t igdng_irq_handler(struct drm_device *dev)
 		gt_iir = new_gt_iir;
 	}
 
+	I915_WRITE(DEIER, de_ier);
+	(void)I915_READ(DEIER);
+
 	return ret;
 }
 
-- 
1.6.2.5