drm/i915: Make the ring IMR handling private

As the IMR for the USER interrupts are not modified elsewhere, we can
separate the spinlock used for these from that of hpd and pipestats.
Those two IMR are manipulated under an IRQ and so need heavier locking.
Reported-and-tested-by: Alexey Fisher <bug-track@fisher-privat.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -526,7 +526,7 @@ render_ring_get_irq(struct intel_ring_buffer *ring)
 	if (!dev->irq_enabled)
 		return false;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (ring->irq_refcount++ == 0) {
 		if (HAS_PCH_SPLIT(dev))
 			ironlake_enable_irq(dev_priv,
@@ -534,7 +534,7 @@ render_ring_get_irq(struct intel_ring_buffer *ring)
 		else
 			i915_enable_irq(dev_priv, I915_USER_INTERRUPT);
 	}
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 
 	return true;
 }
@@ -545,7 +545,7 @@ render_ring_put_irq(struct intel_ring_buffer *ring)
 	struct drm_device *dev = ring->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (--ring->irq_refcount == 0) {
 		if (HAS_PCH_SPLIT(dev))
 			ironlake_disable_irq(dev_priv,
@@ -554,7 +554,7 @@ render_ring_put_irq(struct intel_ring_buffer *ring)
 		else
 			i915_disable_irq(dev_priv, I915_USER_INTERRUPT);
 	}
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 }
 
 void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
@@ -620,10 +620,10 @@ ring_get_irq(struct intel_ring_buffer *ring, u32 flag)
 	if (!dev->irq_enabled)
 	       return false;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (ring->irq_refcount++ == 0)
 		ironlake_enable_irq(dev_priv, flag);
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 
 	return true;
 }
@@ -634,10 +634,10 @@ ring_put_irq(struct intel_ring_buffer *ring, u32 flag)
 	struct drm_device *dev = ring->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (--ring->irq_refcount == 0)
 		ironlake_disable_irq(dev_priv, flag);
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 }
 
 static bool
@@ -649,13 +649,13 @@ gen6_ring_get_irq(struct intel_ring_buffer *ring, u32 gflag, u32 rflag)
 	if (!dev->irq_enabled)
 	       return false;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (ring->irq_refcount++ == 0) {
 		ring->irq_mask &= ~rflag;
 		I915_WRITE_IMR(ring, ring->irq_mask);
 		ironlake_enable_irq(dev_priv, gflag);
 	}
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 
 	return true;
 }
@@ -666,13 +666,13 @@ gen6_ring_put_irq(struct intel_ring_buffer *ring, u32 gflag, u32 rflag)
 	struct drm_device *dev = ring->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
-	spin_lock(&dev_priv->irq_lock);
+	spin_lock(&ring->irq_lock);
 	if (--ring->irq_refcount == 0) {
 		ring->irq_mask |= rflag;
 		I915_WRITE_IMR(ring, ring->irq_mask);
 		ironlake_disable_irq(dev_priv, gflag);
 	}
-	spin_unlock(&dev_priv->irq_lock);
+	spin_unlock(&ring->irq_lock);
 }
 
 static bool
@@ -814,6 +814,8 @@ int intel_init_ring_buffer(struct drm_device *dev,
 	INIT_LIST_HEAD(&ring->active_list);
 	INIT_LIST_HEAD(&ring->request_list);
 	INIT_LIST_HEAD(&ring->gpu_write_list);
+
+	spin_lock_init(&ring->irq_lock);
 	ring->irq_mask = ~0;
 
 	if (I915_NEED_GFX_HWS(dev)) {

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -55,6 +55,7 @@ struct  intel_ring_buffer {
 	int		effective_size;
 	struct intel_hw_status_page status_page;
 
+	spinlock_t	irq_lock;
 	u32		irq_refcount;
 	u32		irq_mask;
 	u32		irq_seqno;		/* last seq seem at irq time */