drm/i915: Track requests inside each intel_ring

By tracking each request occupying space inside an individual
intel_ring, we can greatly simplify the logic of tracking available
space and not worry about other timelines. (Each ring is an ordered
timeline of committed requests.)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470293567-10811-17-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_request.c

@@ -180,6 +180,7 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
 	 * Note this requires that we are always called in request
 	 * completion order.
 	 */
+	list_del(&request->ring_link);
 	request->ring->last_retired_head = request->postfix;
 
 	/* Walk through the active list, calling retire on each. This allows
@@ -487,6 +488,7 @@ void __i915_add_request(struct drm_i915_gem_request *request,
 	request->previous_seqno = engine->last_submitted_seqno;
 	smp_store_mb(engine->last_submitted_seqno, request->fence.seqno);
 	list_add_tail(&request->link, &engine->request_list);
+	list_add_tail(&request->ring_link, &ring->request_list);
 
 	/* Record the position of the start of the request so that
 	 * should we detect the updated seqno part-way through the

drivers/gpu/drm/i915/i915_gem_request.h

@@ -109,6 +109,9 @@ struct drm_i915_gem_request {
 	/** engine->request_list entry for this request */
 	struct list_head link;
 
+	/** ring->request_list entry for this request */
+	struct list_head ring_link;
+
 	struct drm_i915_file_private *file_priv;
 	/** file_priv list entry for this request */
 	struct list_head client_list;

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2046,6 +2046,8 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size)
 	ring->engine = engine;
 	list_add(&ring->link, &engine->buffers);
 
+	INIT_LIST_HEAD(&ring->request_list);
+
 	ring->size = size;
 	/* Workaround an erratum on the i830 which causes a hang if
 	 * the TAIL pointer points to within the last 2 cachelines
@@ -2266,7 +2268,6 @@ int intel_ring_alloc_request_extras(struct drm_i915_gem_request *request)
 static int wait_for_space(struct drm_i915_gem_request *req, int bytes)
 {
 	struct intel_ring *ring = req->ring;
-	struct intel_engine_cs *engine = req->engine;
 	struct drm_i915_gem_request *target;
 
 	intel_ring_update_space(ring);
@@ -2284,17 +2285,9 @@ static int wait_for_space(struct drm_i915_gem_request *req, int bytes)
 	 */
 	GEM_BUG_ON(!req->reserved_space);
 
-	list_for_each_entry(target, &engine->request_list, link) {
+	list_for_each_entry(target, &ring->request_list, ring_link) {
 		unsigned space;
 
-		/*
-		 * The request queue is per-engine, so can contain requests
-		 * from multiple ringbuffers. Here, we must ignore any that
-		 * aren't from the ringbuffer we're considering.
-		 */
-		if (target->ring != ring)
-			continue;
-
 		/* Would completion of this request free enough space? */
 		space = __intel_ring_space(target->postfix, ring->tail,
 					   ring->size);
@@ -2302,7 +2295,7 @@ static int wait_for_space(struct drm_i915_gem_request *req, int bytes)
 			break;
 	}
 
-	if (WARN_ON(&target->link == &engine->request_list))
+	if (WARN_ON(&target->ring_link == &ring->request_list))
 		return -ENOSPC;
 
 	return i915_wait_request(target);

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -90,6 +90,8 @@ struct intel_ring {
 	struct intel_engine_cs *engine;
 	struct list_head link;
 
+	struct list_head request_list;
+
 	u32 head;
 	u32 tail;
 	int space;