drm/i915: Manage PIPESTAT to control vblank interrupts instead of IMR.

The pipestat fields affect reporting of all vblank-related interrupts, so we
have to reset them during the irq_handler, and while enabling vblank
interrupts.  Otherwise, if a pipe status field had been set to non-zero
before enabling reporting, we would never see an interrupt again.

This patch adds i915_enable_pipestat and i915_disable_pipestat to abstract
out the steps needed to change the reported interrupts.
Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -132,6 +132,7 @@ typedef struct drm_i915_private {
 	int user_irq_refcount;
 	/** Cached value of IMR to avoid reads in updating the bitfield */
 	u32 irq_mask_reg;
+	u32 pipestat[2];
 
 	int tex_lru_log_granularity;
 	int allow_batchbuffer;
@@ -446,6 +447,13 @@ extern int i915_vblank_swap(struct drm_device *dev, void *data,
 			    struct drm_file *file_priv);
 extern void i915_enable_irq(drm_i915_private_t *dev_priv, u32 mask);
 
+void
+i915_enable_pipestat(drm_i915_private_t *dev_priv, int pipe, u32 mask);
+
+void
+i915_disable_pipestat(drm_i915_private_t *dev_priv, int pipe, u32 mask);
+
+
 /* i915_mem.c */
 extern int i915_mem_alloc(struct drm_device *dev, void *data,
 			  struct drm_file *file_priv);

drivers/gpu/drm/i915/i915_opregion.c

@@ -235,17 +235,15 @@ void opregion_enable_asle(struct drm_device *dev)
 	struct opregion_asle *asle = dev_priv->opregion.asle;
 
 	if (asle) {
-		u32 pipeb_stats = I915_READ(PIPEBSTAT);
 		if (IS_MOBILE(dev)) {
-			/* Many devices trigger events with a write to the
-			   legacy backlight controller, so we need to ensure
-			   that it's able to generate interrupts */
-			I915_WRITE(PIPEBSTAT, pipeb_stats |=
-				   I915_LEGACY_BLC_EVENT_ENABLE);
-			i915_enable_irq(dev_priv, I915_ASLE_INTERRUPT |
-					I915_DISPLAY_PIPE_B_EVENT_INTERRUPT);
-		} else
-			i915_enable_irq(dev_priv, I915_ASLE_INTERRUPT);
+			unsigned long irqflags;
+
+			spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
+			i915_enable_pipestat(dev_priv, 1,
+					     I915_LEGACY_BLC_EVENT_ENABLE);
+			spin_unlock_irqrestore(&dev_priv->user_irq_lock,
+					       irqflags);
+		}
 
 		asle->tche = ASLE_ALS_EN | ASLE_BLC_EN | ASLE_PFIT_EN |
 			ASLE_PFMB_EN;