--- intel_ringbuffer.c.org	2013-01-18 14:33:31.647541129 +0800
+++ intel_ringbuffer.c	2013-01-18 18:27:58.433757169 +0800
@@ -252,42 +252,54 @@
 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
 	struct drm_i915_gem_object *obj = ring->obj;
 	u32 head;
-
-	/* Stop the ring if it's running. */
-	I915_WRITE_CTL(ring, 0);
-	I915_WRITE_HEAD(ring, 0);
-	ring->write_tail(ring, 0);
-
-	head = I915_READ_HEAD(ring) & HEAD_ADDR;
-
-	/* G45 ring initialization fails to reset head to zero */
-	if (head != 0) {
-		DRM_DEBUG_KMS("%s head not reset to zero "
-			      "ctl %08x head %08x tail %08x start %08x\n",
-			      ring->name,
-			      I915_READ_CTL(ring),
-			      I915_READ_HEAD(ring),
-			      I915_READ_TAIL(ring),
-			      I915_READ_START(ring));
-
+        int  i=0;
+	
+	for (i=0;i<120; i++) {
+		/* Stop the ring if it's running. */
+		I915_WRITE_CTL(ring, 0);
+		(void)I915_READ_CTL(ring);
 		I915_WRITE_HEAD(ring, 0);
+		ring->write_tail(ring, 0);
+
+		head = I915_READ_HEAD(ring) & HEAD_ADDR;
 
-		if (I915_READ_HEAD(ring) & HEAD_ADDR) {
-			DRM_ERROR("failed to set %s head to zero "
-				  "ctl %08x head %08x tail %08x start %08x\n",
-				  ring->name,
-				  I915_READ_CTL(ring),
-				  I915_READ_HEAD(ring),
-				  I915_READ_TAIL(ring),
-				  I915_READ_START(ring));
+		/* G45 ring initialization fails to reset head to zero */
+		if (head != 0) {
+			DRM_DEBUG_KMS("%s head not reset to zero "
+				      "ctl %08x head %08x tail %08x start %08x\n",
+				      ring->name,
+				      I915_READ_CTL(ring),
+				      I915_READ_HEAD(ring),
+				      I915_READ_TAIL(ring),
+				      I915_READ_START(ring));
+
+			I915_WRITE_HEAD(ring, 0);
+
+			if (I915_READ_HEAD(ring) & HEAD_ADDR) {
+				DRM_ERROR("failed to set %s head to zero "
+					  "ctl %08x head %08x tail %08x start %08x\n",
+					  ring->name,
+					  I915_READ_CTL(ring),
+					  I915_READ_HEAD(ring),
+					  I915_READ_TAIL(ring),
+					  I915_READ_START(ring));
+			}
 		}
-	}
+		else {
+		        printk(KERN_ALERT"in %s %d init successfully.",__FUNCTION__,i);	
+			break;
+		}
+
+        } 
 
 	/* 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);
+	if (I915_READ_START(ring) != obj->gtt_offset)
+		DRM_ERROR("failed to set %s start to GTT offset\n", ring->name);
+
 	I915_WRITE_CTL(ring,
 			((ring->size - PAGE_SIZE) & RING_NR_PAGES)
 			| RING_VALID);