From: Oscar Mateo <oscar.ma...@intel.com>

Otherwise, we might receive a new interrupt before we have time to ack the first
one, eventually missing it.

According to BSPec, the right order should be:

1 - Disable Master Interrupt Control.
2 - Find the source(s) of the interrupt and clear the Interrupt Identity bits 
(IIR)
4 - Process the interrupt(s) that had bits set in the IIRs.
5 - Re-enable Master Interrupt Control.

We maintain the "disable SDE interrupts when handling" hack since apparently it 
works.

Spotted by Bob Beckett <robert.beck...@intel.com>.

Signed-off-by: Oscar Mateo <oscar.ma...@intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 5522cbf..4439e2d 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2165,30 +2165,30 @@ static irqreturn_t ironlake_irq_handler(int irq, void 
*arg)
 
        gt_iir = I915_READ(GTIIR);
        if (gt_iir) {
+               I915_WRITE(GTIIR, gt_iir);
+               ret = IRQ_HANDLED;
                if (INTEL_INFO(dev)->gen >= 6)
                        snb_gt_irq_handler(dev, dev_priv, gt_iir);
                else
                        ilk_gt_irq_handler(dev, dev_priv, gt_iir);
-               I915_WRITE(GTIIR, gt_iir);
-               ret = IRQ_HANDLED;
        }
 
        de_iir = I915_READ(DEIIR);
        if (de_iir) {
+               I915_WRITE(DEIIR, de_iir);
+               ret = IRQ_HANDLED;
                if (INTEL_INFO(dev)->gen >= 7)
                        ivb_display_irq_handler(dev, de_iir);
                else
                        ilk_display_irq_handler(dev, de_iir);
-               I915_WRITE(DEIIR, de_iir);
-               ret = IRQ_HANDLED;
        }
 
        if (INTEL_INFO(dev)->gen >= 6) {
                u32 pm_iir = I915_READ(GEN6_PMIIR);
                if (pm_iir) {
-                       gen6_rps_irq_handler(dev_priv, pm_iir);
                        I915_WRITE(GEN6_PMIIR, pm_iir);
                        ret = IRQ_HANDLED;
+                       gen6_rps_irq_handler(dev_priv, pm_iir);
                }
        }
 
-- 
1.9.0

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