drm/i915: Remove the definitions for Primary Ring Buffer

We only ever used the PRB0, neglecting the secondary ring buffers, and
now with the advent of multiple engines with separate ring buffers we
need to excise the anachronisms from our code (and be explicit about
which ring we mean where). This is doubly important in light of the
FORCEWAKE required to read ring buffer registers on SandyBridge.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 4a0664e..2103452 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -520,30 +520,30 @@
 }
 
 static u32
-i915_ringbuffer_last_batch(struct drm_device *dev)
+i915_ringbuffer_last_batch(struct drm_device *dev,
+			   struct intel_ring_buffer *ring)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 head, bbaddr;
-	u32 *ring;
+	u32 *val;
 
 	/* Locate the current position in the ringbuffer and walk back
 	 * to find the most recently dispatched batch buffer.
 	 */
 	bbaddr = 0;
-	head = I915_READ(PRB0_HEAD) & HEAD_ADDR;
-	ring = (u32 *)(dev_priv->render_ring.virtual_start + head);
+	head = I915_READ_HEAD(ring) & HEAD_ADDR;
+	val = (u32 *)(ring->virtual_start + head);
 
-	while (--ring >= (u32 *)dev_priv->render_ring.virtual_start) {
-		bbaddr = i915_get_bbaddr(dev, ring);
+	while (--val >= (u32 *)ring->virtual_start) {
+		bbaddr = i915_get_bbaddr(dev, val);
 		if (bbaddr)
 			break;
 	}
 
 	if (bbaddr == 0) {
-		ring = (u32 *)(dev_priv->render_ring.virtual_start
-				+ dev_priv->render_ring.size);
-		while (--ring >= (u32 *)dev_priv->render_ring.virtual_start) {
-			bbaddr = i915_get_bbaddr(dev, ring);
+		val = (u32 *)(ring->virtual_start + ring->size);
+		while (--val >= (u32 *)ring->virtual_start) {
+			bbaddr = i915_get_bbaddr(dev, val);
 			if (bbaddr)
 				break;
 		}
@@ -628,7 +628,7 @@
 		error->bbaddr = 0;
 	}
 
-	bbaddr = i915_ringbuffer_last_batch(dev);
+	bbaddr = i915_ringbuffer_last_batch(dev, &dev_priv->render_ring);
 
 	/* Grab the current batchbuffer, most likely to have crashed. */
 	batchbuffer[0] = NULL;
@@ -1398,10 +1398,10 @@
 				 * and break the hang. This should work on
 				 * all but the second generation chipsets.
 				 */
-				u32 tmp = I915_READ(PRB0_CTL);
+				struct intel_ring_buffer *ring = &dev_priv->render_ring;
+				u32 tmp = I915_READ_CTL(ring);
 				if (tmp & RING_WAIT) {
-					I915_WRITE(PRB0_CTL, tmp);
-					POSTING_READ(PRB0_CTL);
+					I915_WRITE_CTL(ring, tmp);
 					goto repeat;
 				}
 			}