[Intel-gfx] [PATCH 3/3] drm/i915: Treat ringbuffer writes as write to normal memory

[Chris Wilson]

Ringbuffers are now being written to either through LLC or WC paths, so
treating them as simply iomem is no longer adequate. However, for the
older !llc hardware, the hardware is documentated as treating the TAIL
register update as serialising, so we can relax the barriers when filling
the rings (but even if it were not, it is still an uncached register write
and so serialising anyway.).

For simplicity, let's ignore the iomem annotation.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_lrc.c        |  7 +------
 drivers/gpu/drm/i915/intel_lrc.h        |  6 +++---
 drivers/gpu/drm/i915/intel_ringbuffer.c |  7 +------
 drivers/gpu/drm/i915/intel_ringbuffer.h | 17 ++++++++++++-----
 4 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index d38746c5370d..10020505be75 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -713,13 +713,8 @@ intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
 
 static void __wrap_ring_buffer(struct intel_ringbuffer *ringbuf)
 {
-	uint32_t __iomem *virt;
 	int rem = ringbuf->size - ringbuf->tail;
-
-	virt = ringbuf->virtual_start + ringbuf->tail;
-	rem /= 4;
-	while (rem--)
-		iowrite32(MI_NOOP, virt++);
+	memset(ringbuf->virtual_start + ringbuf->tail, 0, rem);
 
 	ringbuf->tail = 0;
 	intel_ring_update_space(ringbuf);
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 64f89f9982a2..8b56fb934763 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -53,8 +53,9 @@ int logical_ring_flush_all_caches(struct drm_i915_gem_request *req);
  */
 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.
@@ -63,8 +64,7 @@ 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.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 49aa52440db2..0eaaab92dea0 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2180,13 +2180,8 @@ static int ring_wait_for_space(struct intel_engine_cs *ring, int n)
 
 static void __wrap_ring_buffer(struct intel_ringbuffer *ringbuf)
 {
-	uint32_t __iomem *virt;
 	int rem = ringbuf->size - ringbuf->tail;
-
-	virt = ringbuf->virtual_start + ringbuf->tail;
-	rem /= 4;
-	while (rem--)
-		iowrite32(MI_NOOP, virt++);
+	memset(ringbuf->virtual_start + ringbuf->tail, 0, rem);
 
 	ringbuf->tail = 0;
 	intel_ring_update_space(ringbuf);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 2e85fda94963..ff290765e6c9 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -427,17 +427,24 @@ int intel_ring_alloc_request_extras(struct drm_i915_gem_request *request);
 
 int __must_check intel_ring_begin(struct drm_i915_gem_request *req, int n);
 int __must_check intel_ring_cacheline_align(struct drm_i915_gem_request *req);
+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);
-- 
2.6.1