[Intel-gfx] [PATCH 18/37] drm/i915: Only clflush the context object when binding

[Chris Wilson]

We know that the only access to the context object is via the GPU, and
the only time when it can be out of the GPU domain is when it is swapped
out and unbound. Therefore we only need to clflush the object when
binding.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 19 +++++++------------
 drivers/gpu/drm/i915/intel_ringbuffer.c |  4 ++++
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 3857ce097c84..824dfe14bcd0 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -772,6 +772,13 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
 	if (skip_rcs_switch(ppgtt, engine, to))
 		return 0;
 
+	/* Clear this page out of any CPU caches for coherent swap-in/out. */
+	if (!(vma->flags & I915_VMA_GLOBAL_BIND)) {
+		ret = i915_gem_object_set_to_gtt_domain(vma->obj, false);
+		if (ret)
+			return ret;
+	}
+
 	/* Trying to pin first makes error handling easier. */
 	ret = i915_vma_pin(vma, 0, to->ggtt_alignment, PIN_GLOBAL);
 	if (ret)
@@ -786,18 +793,6 @@ static int do_rcs_switch(struct drm_i915_gem_request *req)
 	 */
 	from = engine->last_context;
 
-	/*
-	 * Clear this page out of any CPU caches for coherent swap-in/out. Note
-	 * that thanks to write = false in this call and us not setting any gpu
-	 * write domains when putting a context object onto the active list
-	 * (when switching away from it), this won't block.
-	 *
-	 * XXX: We need a real interface to do this instead of trickery.
-	 */
-	ret = i915_gem_object_set_to_gtt_domain(vma->obj, false);
-	if (ret)
-		goto err;
-
 	if (needs_pd_load_pre(ppgtt, engine, to)) {
 		/* Older GENs and non render rings still want the load first,
 		 * "PP_DCLV followed by PP_DIR_BASE register through Load
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 0bbf8500c174..27a284619a27 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2092,6 +2092,10 @@ static int intel_ring_context_pin(struct i915_gem_context *ctx,
 		return 0;
 
 	if (ce->state) {
+		ret = i915_gem_object_set_to_gtt_domain(ce->state->obj, false);
+		if (ret)
+			goto error;
+
 		ret = i915_vma_pin(ce->state, 0, ctx->ggtt_alignment,
 				   PIN_GLOBAL | PIN_HIGH);
 		if (ret)
-- 
2.8.1