drm/i915/ringbuffer: Simplify the ring irq refcounting

... and move it under the spinlock to gain the appropriate memory
barriers.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=32752
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 25 insertions, 39 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 3bff7fb72341..13cad981713b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -521,22 +521,20 @@ static bool
 render_ring_get_irq(struct intel_ring_buffer *ring)
 {
         struct drm_device *dev = ring->dev;
+        drm_i915_private_t *dev_priv = dev->dev_private;
 
         if (!dev->irq_enabled)
                 return false;
 
-        if (atomic_inc_return(&ring->irq_refcount) == 1) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->irq_lock);
+        if (ring->irq_refcount++ == 0) {
                 if (HAS_PCH_SPLIT(dev))
                         ironlake_enable_irq(dev_priv,
                                             GT_PIPE_NOTIFY | GT_USER_INTERRUPT);
                 else
                         i915_enable_irq(dev_priv, I915_USER_INTERRUPT);
-                spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
         }
+        spin_unlock(&dev_priv->irq_lock);
 
         return true;
 }
@@ -545,20 +543,18 @@ static void
 render_ring_put_irq(struct intel_ring_buffer *ring)
 {
         struct drm_device *dev = ring->dev;
+        drm_i915_private_t *dev_priv = dev->dev_private;
 
-        if (atomic_dec_and_test(&ring->irq_refcount)) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->irq_lock);
+        if (--ring->irq_refcount == 0) {
                 if (HAS_PCH_SPLIT(dev))
                         ironlake_disable_irq(dev_priv,
                                              GT_USER_INTERRUPT |
                                              GT_PIPE_NOTIFY);
                 else
                         i915_disable_irq(dev_priv, I915_USER_INTERRUPT);
-                spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
         }
+        spin_unlock(&dev_priv->irq_lock);
 }
 
 void intel_ring_setup_status_page(struct intel_ring_buffer *ring)
@@ -619,18 +615,15 @@ static bool
 ring_get_irq(struct intel_ring_buffer *ring, u32 flag)
 {
         struct drm_device *dev = ring->dev;
+        drm_i915_private_t *dev_priv = dev->dev_private;
 
         if (!dev->irq_enabled)
                return false;
 
-        if (atomic_inc_return(&ring->irq_refcount) == 1) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->irq_lock);
+        if (ring->irq_refcount++ == 0)
                 ironlake_enable_irq(dev_priv, flag);
-                spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
-        }
+        spin_unlock(&dev_priv->irq_lock);
 
         return true;
 }
@@ -639,35 +632,30 @@ static void
 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;
 
-        if (atomic_dec_and_test(&ring->irq_refcount)) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->irq_lock);
+        if (--ring->irq_refcount == 0)
                 ironlake_disable_irq(dev_priv, flag);
-                spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
-        }
+        spin_unlock(&dev_priv->irq_lock);
 }
 
 static bool
 gen6_ring_get_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;
 
         if (!dev->irq_enabled)
                return false;
 
-        if (atomic_inc_return(&ring->irq_refcount) == 1) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->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_irqrestore(&dev_priv->irq_lock, irqflags);
         }
+        spin_unlock(&dev_priv->irq_lock);
 
         return true;
 }
@@ -676,17 +664,15 @@ static void
 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;
 
-        if (atomic_dec_and_test(&ring->irq_refcount)) {
-                drm_i915_private_t *dev_priv = dev->dev_private;
-                unsigned long irqflags;
-
-                spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+        spin_lock(&dev_priv->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_irqrestore(&dev_priv->irq_lock, irqflags);
         }
+        spin_unlock(&dev_priv->irq_lock);
 }
 
 static bool
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 9b134b8643cb..6b1d9a5a7d07 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -55,11 +55,11 @@ struct  intel_ring_buffer {
         int             effective_size;
         struct intel_hw_status_page status_page;
 
+        u32             irq_refcount;
         u32             irq_mask;
         u32             irq_seqno;              /* last seq seem at irq time */
         u32             waiting_seqno;
         u32             sync_seqno[I915_NUM_RINGS-1];
-        atomic_t        irq_refcount;
         bool __must_check (*irq_get)(struct intel_ring_buffer *ring);
         void            (*irq_put)(struct intel_ring_buffer *ring);