2 files changed, 11 insertions, 13 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 89a65be8a3f..31cd7e33e82 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;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 3126c268198..d2cd0f1efee 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -30,8 +30,9 @@ struct  intel_ring_buffer {
         struct          drm_device *dev;
         struct          drm_gem_object *gem_object;
 
-        unsigned int    head;
-        unsigned int    tail;
+        u32             actual_head;
+        u32             head;
+        u32             tail;
         int             space;
         struct intel_hw_status_page status_page;