drm/i915: Simplify interrupt processing for IvyBridge

We can take advantage that the PCH_IIR is a subordinate register to
reduce one of the required IIR reads, and that we only need to clear
interrupts handled to reduce the writes. And by simply tidying the code
we can reduce the line count and hopefully make it more readable.

v2: Split out the bugfix from the refactoring.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -577,72 +577,61 @@ static irqreturn_t ivybridge_irq_handler(DRM_IRQ_ARGS)
 {
 	struct drm_device *dev = (struct drm_device *) arg;
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
-	int ret = IRQ_NONE;
-	u32 de_iir, gt_iir, de_ier, pch_iir, pm_iir;
+	u32 de_iir, gt_iir, de_ier, pm_iir;
+	irqreturn_t ret = IRQ_NONE;
+	int i;
 
 	atomic_inc(&dev_priv->irq_received);
 
 	/* disable master interrupt before clearing iir  */
 	de_ier = I915_READ(DEIER);
 	I915_WRITE(DEIER, de_ier & ~DE_MASTER_IRQ_CONTROL);
-	POSTING_READ(DEIER);
 
-	de_iir = I915_READ(DEIIR);
 	gt_iir = I915_READ(GTIIR);
-	pch_iir = I915_READ(SDEIIR);
-	pm_iir = I915_READ(GEN6_PMIIR);
-
-	if (de_iir == 0 && gt_iir == 0 && pch_iir == 0 && pm_iir == 0)
-		goto done;
-
-	ret = IRQ_HANDLED;
-
+	if (gt_iir) {
 		snb_gt_irq_handler(dev, dev_priv, gt_iir);
+		I915_WRITE(GTIIR, gt_iir);
+		ret = IRQ_HANDLED;
+	}
 
+	de_iir = I915_READ(DEIIR);
+	if (de_iir) {
 		if (de_iir & DE_GSE_IVB)
 			intel_opregion_gse_intr(dev);
 
-	if (de_iir & DE_PLANEA_FLIP_DONE_IVB) {
-		intel_prepare_page_flip(dev, 0);
-		intel_finish_page_flip_plane(dev, 0);
+		for (i = 0; i < 3; i++) {
+			if (de_iir & (DE_PLANEA_FLIP_DONE_IVB << (5 * i))) {
+				intel_prepare_page_flip(dev, i);
+				intel_finish_page_flip_plane(dev, i);
 			}
-
-	if (de_iir & DE_PLANEB_FLIP_DONE_IVB) {
-		intel_prepare_page_flip(dev, 1);
-		intel_finish_page_flip_plane(dev, 1);
+			if (de_iir & (DE_PIPEA_VBLANK_IVB << (5 * i)))
+				drm_handle_vblank(dev, i);
 		}
 
-	if (de_iir & DE_PLANEC_FLIP_DONE_IVB) {
-		intel_prepare_page_flip(dev, 2);
-		intel_finish_page_flip_plane(dev, 2);
-	}
-
-	if (de_iir & DE_PIPEA_VBLANK_IVB)
-		drm_handle_vblank(dev, 0);
-
-	if (de_iir & DE_PIPEB_VBLANK_IVB)
-		drm_handle_vblank(dev, 1);
-
-	if (de_iir & DE_PIPEC_VBLANK_IVB)
-		drm_handle_vblank(dev, 2);
-
 		/* check event from PCH */
 		if (de_iir & DE_PCH_EVENT_IVB) {
+			u32 pch_iir = I915_READ(SDEIIR);
+
 			if (pch_iir & SDE_HOTPLUG_MASK_CPT)
 				queue_work(dev_priv->wq, &dev_priv->hotplug_work);
 			pch_irq_handler(dev, pch_iir);
+
+			/* clear PCH hotplug event before clear CPU irq */
+			I915_WRITE(SDEIIR, pch_iir);
+		}
+
+		I915_WRITE(DEIIR, de_iir);
+		ret = IRQ_HANDLED;
 	}
 
+	pm_iir = I915_READ(GEN6_PMIIR);
+	if (pm_iir) {
 		if (pm_iir & GEN6_PM_DEFERRED_EVENTS)
 			gen6_queue_rps_work(dev_priv, pm_iir);
-
-	/* should clear PCH hotplug event before clear CPU irq */
-	I915_WRITE(SDEIIR, pch_iir);
-	I915_WRITE(GTIIR, gt_iir);
-	I915_WRITE(DEIIR, de_iir);
 		I915_WRITE(GEN6_PMIIR, pm_iir);
+		ret = IRQ_HANDLED;
+	}
 
-done:
 	I915_WRITE(DEIER, de_ier);
 	POSTING_READ(DEIER);