[intel] Use IMR instead of IER to pend interrupts during ISR

Noting that the interrupt mask register was more reliable than the interrupt
enable register for managing interrupts in user_irq_on/user_irq_off, this
patch replaces the remaining IER frobbing with IMR instead.

The test which exposes IER related failures is:

$ glxgears & glxgears & glxgears
(reposition the glxgears windows away from the upper left corner)
$ while :; do x11perf -rect100 -reps 800 -repeat 1; sleep 1; done &
$ while :; do runoa; runet; done &

diff --git a/shared-core/i915_irq.c b/shared-core/i915_irq.c
index c0abcbd..a55497a 100644 (file)
--- a/shared-core/i915_irq.c
+++ b/shared-core/i915_irq.c
@@ -451,7 +451,7 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
        int vblank = 0;
 
        if (dev->pdev->msi_enabled)
-               I915_WRITE(I915REG_INT_ENABLE_R, 0);
+               I915_WRITE(I915REG_INT_MASK_R, ~0);
        iir = I915_READ(I915REG_INT_IDENTITY_R);
 #if 0
        DRM_DEBUG("flag=%08x\n", iir);
@@ -464,9 +464,11 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
                           I915_READ(I915REG_INT_ENABLE_R),
                           I915_READ(I915REG_PIPEASTAT),
                           I915_READ(I915REG_PIPEBSTAT));
-               if (dev->pdev->msi_enabled)
-                       I915_WRITE(I915REG_INT_ENABLE_R,
-                                  I915_INTERRUPT_ENABLE_MASK);
+               if (dev->pdev->msi_enabled) {
+                       I915_WRITE(I915REG_INT_MASK_R,
+                                  dev_priv->irq_mask_reg);
+                       (void) I915_READ(I915REG_INT_MASK_R);
+               }
                return IRQ_NONE;
        }
 
@@ -484,6 +486,8 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
        }
 
        I915_WRITE(I915REG_INT_IDENTITY_R, iir);
+       if (dev->pdev->msi_enabled)
+               I915_WRITE(I915REG_INT_MASK_R, dev_priv->irq_mask_reg);
        (void) I915_READ(I915REG_INT_IDENTITY_R); /* Flush posted writes */
 
        if (dev_priv->sarea_priv)
@@ -512,8 +516,6 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
                        drm_locked_tasklet(dev, i915_vblank_tasklet);
        }
 
-       if (dev->pdev->msi_enabled)
-               I915_WRITE(I915REG_INT_ENABLE_R, I915_INTERRUPT_ENABLE_MASK);
        return IRQ_HANDLED;
 }
 
@@ -543,6 +545,7 @@ void i915_user_irq_on(drm_i915_private_t *dev_priv)
                if ((dev_priv->irq_mask_reg & I915_USER_INTERRUPT) != 0) {
                        dev_priv->irq_mask_reg &= ~I915_USER_INTERRUPT;
                        I915_WRITE(I915REG_INT_MASK_R, dev_priv->irq_mask_reg);
+                       I915_WRITE(I915REG_INT_IDENTITY_R, I915_USER_INTERRUPT);
                        (void) I915_READ (I915REG_INT_MASK_R);
                }
        }
@@ -740,7 +743,7 @@ static void i915_enable_interrupt (struct drm_device *dev)
 {
        drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
        
-       dev_priv->irq_mask_reg = I915_INTERRUPT_ENABLE_MASK;
+       dev_priv->irq_mask_reg = ~0;
        I915_WRITE(I915REG_INT_MASK_R, dev_priv->irq_mask_reg);
        I915_WRITE(I915REG_INT_ENABLE_R, I915_INTERRUPT_ENABLE_MASK);
        (void) I915_READ (I915REG_INT_ENABLE_R);