drm/i915: correctly order the ring init sequence

[pandora-kernel.git] / drivers / gpu / drm / i915 / intel_ringbuffer.c

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 4983e59..19085c0 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -263,8 +263,6 @@ static int init_ring_common(struct intel_ring_buffer *ring)
        I915_WRITE_HEAD(ring, 0);
        ring->write_tail(ring, 0);
 
-       /* Initialize the ring. */
-       I915_WRITE_START(ring, obj->gtt_offset);
        head = I915_READ_HEAD(ring) & HEAD_ADDR;
 
        /* G45 ring initialization fails to reset head to zero */
@@ -290,6 +288,11 @@ static int init_ring_common(struct intel_ring_buffer *ring)
                }
        }
 
+       /* Initialize the ring. This must happen _after_ we've cleared the ring
+        * registers with the above sequence (the readback of the HEAD registers
+        * also enforces ordering), otherwise the hw might lose the new ring
+        * register values. */
+       I915_WRITE_START(ring, obj->gtt_offset);
        I915_WRITE_CTL(ring,
                        ((ring->size - PAGE_SIZE) & RING_NR_PAGES)
                        | RING_VALID);