---

yaml
---
r: 345647
b: refs/heads/master
c: 633cf8f
h: refs/heads/master
i:
  345645: 0cb1c91
  345643: 5f670f2
  345639: 782b419
  345631: bb62c21
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a2165e312381f35b8abd7dcb8a8ab955bc60d867
+refs/heads/master: 633cf8f5056c3e72158e4dbc387b3d65926d2d55

trunk/drivers/gpu/drm/i915/i915_dma.c

@@ -141,7 +141,7 @@ void i915_kernel_lost_context(struct drm_device * dev)
 
 	ring->head = I915_READ_HEAD(ring) & HEAD_ADDR;
 	ring->tail = I915_READ_TAIL(ring) & TAIL_ADDR;
-	ring->space = ring->head - (ring->tail + 8);
+	ring->space = ring->head - (ring->tail + I915_RING_FREE_SPACE);
 	if (ring->space < 0)
 		ring->space += ring->size;
 

trunk/drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -45,7 +45,7 @@ struct pipe_control {
 
 static inline int ring_space(struct intel_ring_buffer *ring)
 {
-	int space = (ring->head & HEAD_ADDR) - (ring->tail + 8);
+	int space = (ring->head & HEAD_ADDR) - (ring->tail + I915_RING_FREE_SPACE);
 	if (space < 0)
 		space += ring->size;
 	return space;
@@ -1227,7 +1227,7 @@ static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
 		if (request->tail == -1)
 			continue;
 
-		space = request->tail - (ring->tail + 8);
+		space = request->tail - (ring->tail + I915_RING_FREE_SPACE);
 		if (space < 0)
 			space += ring->size;
 		if (space >= n) {

trunk/drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -1,6 +1,17 @@
 #ifndef _INTEL_RINGBUFFER_H_
 #define _INTEL_RINGBUFFER_H_
 
+/*
+ * Gen2 BSpec "1. Programming Environment" / 1.4.4.6 "Ring Buffer Use"
+ * Gen3 BSpec "vol1c Memory Interface Functions" / 2.3.4.5 "Ring Buffer Use"
+ * Gen4+ BSpec "vol1c Memory Interface and Command Stream" / 5.3.4.5 "Ring Buffer Use"
+ *
+ * "If the Ring Buffer Head Pointer and the Tail Pointer are on the same
+ * cacheline, the Head Pointer must not be greater than the Tail
+ * Pointer."
+ */
+#define I915_RING_FREE_SPACE 64
+
 struct  intel_hw_status_page {
 	u32		*page_addr;
 	unsigned int	gfx_addr;