drm/i915: Fix IRQ stall issue on Ironlake

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@kernel.org>
Signed-off-by: Zou, Nanhai <nanhai.zou@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index c3ceffa46ea0e2dfdfc600e7440f1750376eb1f9..aa7fd82aa6eb343afa3fdb4b7088104f311f00d9 100644 (file)
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -254,10 +254,15 @@ 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);
 
@@ -290,6 +295,9 @@ 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;
 }