[Intel-gfx] [PATCH 47/49] drm/i915: Treat ringbuffer writes as write to normal memory

[Chris Wilson]

The hardware is documentated as treating the TAIL register update as
serialising, so we can relax the barriers when filling the rings.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_lrc.h        |  7 ++++---
 drivers/gpu/drm/i915/intel_ringbuffer.h | 17 ++++++++++++-----
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index b276e00773d9..979229970a91 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -50,8 +50,9 @@ int logical_ring_flush_all_caches(struct intel_ringbuffer *ringbuf,
  */
 static inline void intel_logical_ring_advance(struct intel_ringbuffer *ringbuf)
 {
-	ringbuf->tail &= ringbuf->size - 1;
+	intel_ringbuffer_advance(ringbuf);
 }
+
 /**
  * intel_logical_ring_emit() - write a DWORD to the ringbuffer.
  * @ringbuf: Ringbuffer to write to.
@@ -60,9 +61,9 @@ static inline void intel_logical_ring_advance(struct intel_ringbuffer *ringbuf)
 static inline void intel_logical_ring_emit(struct intel_ringbuffer *ringbuf,
 					   u32 data)
 {
-	iowrite32(data, ringbuf->virtual_start + ringbuf->tail);
-	ringbuf->tail += 4;
+	intel_ringbuffer_emit(ringbuf, data);
 }
+
 int intel_logical_ring_begin(struct intel_ringbuffer *ringbuf,
 			     struct intel_context *ctx,
 			     int num_dwords);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index dc9f5ac21833..b4d3dc1922f7 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -404,17 +404,24 @@ void intel_cleanup_ring_buffer(struct intel_engine_cs *ring);
 
 int __must_check intel_ring_begin(struct intel_engine_cs *ring, int n);
 int __must_check intel_ring_cacheline_align(struct intel_engine_cs *ring);
+static inline void intel_ringbuffer_emit(struct intel_ringbuffer *rb,
+					 u32 data)
+{
+	*(uint32_t __force *)(rb->virtual_start + rb->tail) = data;
+	rb->tail += 4;
+}
+static inline void intel_ringbuffer_advance(struct intel_ringbuffer *rb)
+{
+	rb->tail &= rb->size - 1;
+}
 static inline void intel_ring_emit(struct intel_engine_cs *ring,
 				   u32 data)
 {
-	struct intel_ringbuffer *ringbuf = ring->buffer;
-	iowrite32(data, ringbuf->virtual_start + ringbuf->tail);
-	ringbuf->tail += 4;
+	intel_ringbuffer_emit(ring->buffer, data);
 }
 static inline void intel_ring_advance(struct intel_engine_cs *ring)
 {
-	struct intel_ringbuffer *ringbuf = ring->buffer;
-	ringbuf->tail &= ringbuf->size - 1;
+	intel_ringbuffer_advance(ring->buffer);
 }
 int __intel_ring_space(int head, int tail, int size);
 void intel_ring_update_space(struct intel_ringbuffer *ringbuf);
-- 
2.1.4