[PATCH 32/70] drm/i915: Treat ringbuffer writes as write to normal memory

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_lrc.h        |  6 +++---
 drivers/gpu/drm/i915/intel_ringbuffer.h | 17 ++++++++++++-----
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 0790e4b26b13..16c717672020 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -52,8 +52,9 @@ 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.
@@ -62,8 +63,7 @@ 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);
 }
 
 /* Logical Ring Contexts */
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 298b0ff46ecb..0899123c6bcc 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -404,17 +404,24 @@ int intel_ring_alloc_request_extras(struct drm_i915_gem_request *request);
 
 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

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