i915: Protect vblank IRQ reg access with spinlock

This uses the same spinlock as the user_irq code as it shares the same
register, ensuring that interrupt registers are updated atomically.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 40 insertions, 29 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index baae511c785b..671dd79d0aac 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -481,22 +481,24 @@ static int i915_emit_irq(struct drm_device * dev)
 void i915_user_irq_get(struct drm_device *dev)
 {
         drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+        unsigned long irqflags;
 
-        spin_lock(&dev_priv->user_irq_lock);
+        spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
         if (dev->irq_enabled && (++dev_priv->user_irq_refcount == 1))
                 i915_enable_irq(dev_priv, I915_USER_INTERRUPT);
-        spin_unlock(&dev_priv->user_irq_lock);
+        spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 }
 
 void i915_user_irq_put(struct drm_device *dev)
 {
         drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+        unsigned long irqflags;
 
-        spin_lock(&dev_priv->user_irq_lock);
+        spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
         BUG_ON(dev->irq_enabled && dev_priv->user_irq_refcount <= 0);
         if (dev->irq_enabled && (--dev_priv->user_irq_refcount == 0))
                 i915_disable_irq(dev_priv, I915_USER_INTERRUPT);
-        spin_unlock(&dev_priv->user_irq_lock);
+        spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 }
 
 static int i915_wait_irq(struct drm_device * dev, int irq_nr)
@@ -584,33 +586,37 @@ int i915_enable_vblank(struct drm_device *dev, int plane)
         int pipe = i915_get_pipe(dev, plane);
         u32     pipestat_reg = 0;
         u32     pipestat;
+        u32     interrupt = 0;
+        unsigned long irqflags;
 
         switch (pipe) {
         case 0:
                 pipestat_reg = PIPEASTAT;
-                i915_enable_irq(dev_priv, I915_DISPLAY_PIPE_A_EVENT_INTERRUPT);
+                interrupt = I915_DISPLAY_PIPE_A_EVENT_INTERRUPT;
                 break;
         case 1:
                 pipestat_reg = PIPEBSTAT;
-                i915_enable_irq(dev_priv, I915_DISPLAY_PIPE_B_EVENT_INTERRUPT);
+                interrupt = I915_DISPLAY_PIPE_B_EVENT_INTERRUPT;
                 break;
         default:
                 DRM_ERROR("tried to enable vblank on non-existent pipe %d\n",
                           pipe);
-                break;
+                return 0;
         }
 
-        if (pipestat_reg) {
-                pipestat = I915_READ(pipestat_reg);
-                if (IS_I965G(dev))
-                        pipestat |= PIPE_START_VBLANK_INTERRUPT_ENABLE;
-                else
-                        pipestat |= PIPE_VBLANK_INTERRUPT_ENABLE;
-                /* Clear any stale interrupt status */
-                pipestat |= (PIPE_START_VBLANK_INTERRUPT_STATUS |
-                             PIPE_VBLANK_INTERRUPT_STATUS);
-                I915_WRITE(pipestat_reg, pipestat);
-        }
+        spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
+        pipestat = I915_READ(pipestat_reg);
+        if (IS_I965G(dev))
+                pipestat |= PIPE_START_VBLANK_INTERRUPT_ENABLE;
+        else
+                pipestat |= PIPE_VBLANK_INTERRUPT_ENABLE;
+        /* Clear any stale interrupt status */
+        pipestat |= (PIPE_START_VBLANK_INTERRUPT_STATUS |
+                     PIPE_VBLANK_INTERRUPT_STATUS);
+        I915_WRITE(pipestat_reg, pipestat);
+        (void) I915_READ(pipestat_reg); /* Posting read */
+        i915_enable_irq(dev_priv, interrupt);
+        spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 
         return 0;
 }
@@ -621,31 +627,36 @@ void i915_disable_vblank(struct drm_device *dev, int plane)
         int pipe = i915_get_pipe(dev, plane);
         u32     pipestat_reg = 0;
         u32     pipestat;
+        u32     interrupt = 0;
+        unsigned long irqflags;
 
         switch (pipe) {
         case 0:
                 pipestat_reg = PIPEASTAT;
-                i915_disable_irq(dev_priv, I915_DISPLAY_PIPE_A_EVENT_INTERRUPT);
+                interrupt = I915_DISPLAY_PIPE_A_EVENT_INTERRUPT;
                 break;
         case 1:
                 pipestat_reg = PIPEBSTAT;
-                i915_disable_irq(dev_priv, I915_DISPLAY_PIPE_B_EVENT_INTERRUPT);
+                interrupt = I915_DISPLAY_PIPE_B_EVENT_INTERRUPT;
                 break;
         default:
                 DRM_ERROR("tried to disable vblank on non-existent pipe %d\n",
                           pipe);
+                return;
                 break;
         }
 
-        if (pipestat_reg) {
-                pipestat = I915_READ(pipestat_reg);
-                pipestat &= ~(PIPE_START_VBLANK_INTERRUPT_ENABLE |
-                              PIPE_VBLANK_INTERRUPT_ENABLE);
-                /* Clear any stale interrupt status */
-                pipestat |= (PIPE_START_VBLANK_INTERRUPT_STATUS |
-                             PIPE_VBLANK_INTERRUPT_STATUS);
-                I915_WRITE(pipestat_reg, pipestat);
-        }
+        spin_lock_irqsave(&dev_priv->user_irq_lock, irqflags);
+        i915_disable_irq(dev_priv, interrupt);
+        pipestat = I915_READ(pipestat_reg);
+        pipestat &= ~(PIPE_START_VBLANK_INTERRUPT_ENABLE |
+                      PIPE_VBLANK_INTERRUPT_ENABLE);
+        /* Clear any stale interrupt status */
+        pipestat |= (PIPE_START_VBLANK_INTERRUPT_STATUS |
+                     PIPE_VBLANK_INTERRUPT_STATUS);
+        I915_WRITE(pipestat_reg, pipestat);
+        (void) I915_READ(pipestat_reg); /* Posting read */
+        spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 }
 
 /* Set the vblank monitor pipe