struct drm_i915_private *dev_priv = dev->dev_private;
int pipestat_reg = (pipe == 0 ? PIPEASTAT : PIPEBSTAT);
+ /* Clear existing vblank status. Note this will clear any other
+ * sticky status fields as well.
+ *
+ * This races with i915_driver_irq_handler() with the result
+ * that either function could miss a vblank event. Here it is not
+ * fatal, as we will either wait upon the next vblank interrupt or
+ * timeout. Generally speaking intel_wait_for_vblank() is only
+ * called during modeset at which time the GPU should be idle and
+ * should *not* be performing page flips and thus not waiting on
+ * vblanks...
+ * Currently, the result of us stealing a vblank from the irq
+ * handler is that a single frame will be skipped during swapbuffers.
+ */
+ I915_WRITE(pipestat_reg,
+ I915_READ(pipestat_reg) | PIPE_VBLANK_INTERRUPT_STATUS);
+
/* Wait for vblank interrupt bit to set */
if (wait_for((I915_READ(pipestat_reg) &
PIPE_VBLANK_INTERRUPT_STATUS),