drm/i915: Fix IRQ stall issue on Ironlake

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@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 7ebc84c2881e23547ffb7099294f58995dea1bfe..9431a727a9855a7385b2ab4c645f75d1267d2439 100644 (file)
--- 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_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);
 
@@ -287,6 +292,9 @@ 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;
 }