Merge commit 'v2.6.37-rc8' into perf/core

Merge reason: pick up latest -rc.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 11 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 89a65be8a3f3..31cd7e33e820 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -696,20 +696,17 @@ int intel_wait_ring_buffer(struct drm_device *dev,
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	u32 head;
 
-	head = intel_read_status_page(ring, 4);
-	if (head) {
-		ring->head = head & HEAD_ADDR;
-		ring->space = ring->head - (ring->tail + 8);
-		if (ring->space < 0)
-			ring->space += ring->size;
-		if (ring->space >= n)
-			return 0;
-	}
-
 	trace_i915_ring_wait_begin (dev);
 	end = jiffies + 3 * HZ;
 	do {
-		ring->head = I915_READ_HEAD(ring) & HEAD_ADDR;
+		/* If the reported head position has wrapped or hasn't advanced,
+		 * fallback to the slow and accurate path.
+		 */
+		head = intel_read_status_page(ring, 4);
+		if (head < ring->actual_head)
+			head = I915_READ_HEAD(ring);
+		ring->actual_head = head;
+		ring->head = head & HEAD_ADDR;
 		ring->space = ring->head - (ring->tail + 8);
 		if (ring->space < 0)
 			ring->space += ring->size;