[PATCH 05/26] drm/i915: Lift timeline ordering to await_dma_fence

[Chris Wilson]

Currently we filter out repeated use of the same timeline in the low
level i915_gem_request_await_request(), after having added the
dependency on the old request. However, we can lift this to
i915_gem_request_await_dma_fence() (before the dependency is added)
using the observation that requests along the same timeline are
explicitly ordered via i915_add_request (along with the dependencies).

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 9a52383002b0..97e1062ecbd8 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -679,6 +679,7 @@ i915_gem_request_await_request(struct drm_i915_gem_request *to,
 	int ret;
 
 	GEM_BUG_ON(to == from);
+	GEM_BUG_ON(to->timeline == from->timeline);
 
 	if (i915_gem_request_completed(from))
 		return 0;
@@ -691,9 +692,6 @@ i915_gem_request_await_request(struct drm_i915_gem_request *to,
 			return ret;
 	}
 
-	if (to->timeline == from->timeline)
-		return 0;
-
 	if (to->engine == from->engine) {
 		ret = i915_sw_fence_await_sw_fence_gfp(&to->submit,
 						       &from->submit,
@@ -759,6 +757,13 @@ i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
 		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 			continue;
 
+		/* Requests on the same timeline are explicitly ordered, along
+		 * with their dependencies, by i915_add_request() which ensures
+		 * that requests are submitted in-order through each ring.
+		 */
+		if (fence->context == req->fence.context)
+			continue;
+
 		if (dma_fence_is_i915(fence))
 			ret = i915_gem_request_await_request(req,
 							     to_request(fence));
-- 
2.11.0