drm/i915: Consolidate the timeline->barrier

The timeline is strictly ordered, so by inserting the timeline->barrier
request into the timeline->last_request it naturally provides the same
barrier. Consolidate the pair of barriers into one as they serve the
same purpose.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190408091728.20207-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_context.c

@@ -1167,7 +1167,7 @@ static int
 gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
 {
 	struct drm_i915_private *i915 = ce->engine->i915;
-	struct i915_request *rq, *prev;
+	struct i915_request *rq;
 	intel_wakeref_t wakeref;
 	int ret;
 
@@ -1192,16 +1192,7 @@ gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
 	}
 
 	/* Queue this switch after all other activity by this context. */
-	prev = i915_active_request_raw(&ce->ring->timeline->last_request,
-				       &i915->drm.struct_mutex);
-	if (prev && !i915_request_completed(prev)) {
-		ret = i915_request_await_dma_fence(rq, &prev->fence);
-		if (ret < 0)
-			goto out_add;
-	}
-
-	/* Order all following requests to be after. */
-	ret = i915_timeline_set_barrier(ce->ring->timeline, rq);
+	ret = i915_active_request_set(&ce->ring->timeline->last_request, rq);
 	if (ret)
 		goto out_add;
 

drivers/gpu/drm/i915/i915_request.c

@@ -584,11 +584,6 @@ i915_request_alloc_slow(struct intel_context *ce)
 	return kmem_cache_alloc(global.slab_requests, GFP_KERNEL);
 }
 
-static int add_timeline_barrier(struct i915_request *rq)
-{
-	return i915_request_await_active_request(rq, &rq->timeline->barrier);
-}
-
 /**
  * i915_request_alloc - allocate a request structure
  *
@@ -738,10 +733,6 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
 	 */
 	rq->head = rq->ring->emit;
 
-	ret = add_timeline_barrier(rq);
-	if (ret)
-		goto err_unwind;
-
 	ret = engine->request_alloc(rq);
 	if (ret)
 		goto err_unwind;

drivers/gpu/drm/i915/i915_timeline.c

@@ -253,7 +253,6 @@ int i915_timeline_init(struct drm_i915_private *i915,
 	spin_lock_init(&timeline->lock);
 	mutex_init(&timeline->mutex);
 
-	INIT_ACTIVE_REQUEST(&timeline->barrier);
 	INIT_ACTIVE_REQUEST(&timeline->last_request);
 	INIT_LIST_HEAD(&timeline->requests);
 
@@ -326,7 +325,6 @@ void i915_timeline_fini(struct i915_timeline *timeline)
 {
 	GEM_BUG_ON(timeline->pin_count);
 	GEM_BUG_ON(!list_empty(&timeline->requests));
-	GEM_BUG_ON(i915_active_request_isset(&timeline->barrier));
 
 	i915_syncmap_free(&timeline->sync);
 

drivers/gpu/drm/i915/i915_timeline.h

@@ -110,19 +110,4 @@ void i915_timelines_init(struct drm_i915_private *i915);
 void i915_timelines_park(struct drm_i915_private *i915);
 void i915_timelines_fini(struct drm_i915_private *i915);
 
-/**
- * i915_timeline_set_barrier - orders submission between different timelines
- * @timeline: timeline to set the barrier on
- * @rq: request after which new submissions can proceed
- *
- * Sets the passed in request as the serialization point for all subsequent
- * submissions on @timeline. Subsequent requests will not be submitted to GPU
- * until the barrier has been completed.
- */
-static inline int
-i915_timeline_set_barrier(struct i915_timeline *tl, struct i915_request *rq)
-{
-	return i915_active_request_set(&tl->barrier, rq);
-}
-
 #endif

drivers/gpu/drm/i915/i915_timeline_types.h

@@ -61,16 +61,6 @@ struct i915_timeline {
 	 */
 	struct i915_syncmap *sync;
 
-	/**
-	 * Barrier provides the ability to serialize ordering between different
-	 * timelines.
-	 *
-	 * Users can call i915_timeline_set_barrier which will make all
-	 * subsequent submissions to this timeline be executed only after the
-	 * barrier has been completed.
-	 */
-	struct i915_active_request barrier;
-
 	struct list_head link;
 	struct drm_i915_private *i915;
 

drivers/gpu/drm/i915/selftests/mock_timeline.c

@@ -16,7 +16,6 @@ void mock_timeline_init(struct i915_timeline *timeline, u64 context)
 	spin_lock_init(&timeline->lock);
 	mutex_init(&timeline->mutex);
 
-	INIT_ACTIVE_REQUEST(&timeline->barrier);
 	INIT_ACTIVE_REQUEST(&timeline->last_request);
 	INIT_LIST_HEAD(&timeline->requests);