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>

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index baae511..671dd79 100644 (file)
--- 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