drm/i915: Stop passing caller's num_dwords to engine->semaphore.signal()

Rather than pass in the num_dwords that the caller wishes to use after
the signal command packet, split the breadcrumb emission into two phases
and have both the signal and breadcrumb individiually acquire space on
the ring. This makes the interface simpler for the reader, and will
simplify for patches.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-25-git-send-email-chris@chris-wilson.co.ukReviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470174640-18242-16-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1309,10 +1309,8 @@ static void render_ring_cleanup(struct intel_engine_cs *engine)
 	intel_fini_pipe_control(engine);
 }
 
-static int gen8_rcs_signal(struct drm_i915_gem_request *signaller_req,
-			   unsigned int num_dwords)
+static int gen8_rcs_signal(struct drm_i915_gem_request *signaller_req)
 {
-#define MBOX_UPDATE_DWORDS 8
 	struct intel_ring *signaller = signaller_req->ring;
 	struct drm_i915_private *dev_priv = signaller_req->i915;
 	struct intel_engine_cs *waiter;
@@ -1320,10 +1318,7 @@ static int gen8_rcs_signal(struct drm_i915_gem_request *signaller_req,
 	int ret, num_rings;
 
 	num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask);
-	num_dwords += (num_rings-1) * MBOX_UPDATE_DWORDS;
-#undef MBOX_UPDATE_DWORDS
-
-	ret = intel_ring_begin(signaller_req, num_dwords);
+	ret = intel_ring_begin(signaller_req, (num_rings-1) * 8);
 	if (ret)
 		return ret;
 
@@ -1347,14 +1342,13 @@ static int gen8_rcs_signal(struct drm_i915_gem_request *signaller_req,
 				MI_SEMAPHORE_TARGET(waiter->hw_id));
 		intel_ring_emit(signaller, 0);
 	}
+	intel_ring_advance(signaller);
 
 	return 0;
 }
 
-static int gen8_xcs_signal(struct drm_i915_gem_request *signaller_req,
-			   unsigned int num_dwords)
+static int gen8_xcs_signal(struct drm_i915_gem_request *signaller_req)
 {
-#define MBOX_UPDATE_DWORDS 6
 	struct intel_ring *signaller = signaller_req->ring;
 	struct drm_i915_private *dev_priv = signaller_req->i915;
 	struct intel_engine_cs *waiter;
@@ -1362,10 +1356,7 @@ static int gen8_xcs_signal(struct drm_i915_gem_request *signaller_req,
 	int ret, num_rings;
 
 	num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask);
-	num_dwords += (num_rings-1) * MBOX_UPDATE_DWORDS;
-#undef MBOX_UPDATE_DWORDS
-
-	ret = intel_ring_begin(signaller_req, num_dwords);
+	ret = intel_ring_begin(signaller_req, (num_rings-1) * 6);
 	if (ret)
 		return ret;
 
@@ -1387,12 +1378,12 @@ static int gen8_xcs_signal(struct drm_i915_gem_request *signaller_req,
 				MI_SEMAPHORE_TARGET(waiter->hw_id));
 		intel_ring_emit(signaller, 0);
 	}
+	intel_ring_advance(signaller);
 
 	return 0;
 }
 
-static int gen6_signal(struct drm_i915_gem_request *signaller_req,
-		       unsigned int num_dwords)
+static int gen6_signal(struct drm_i915_gem_request *signaller_req)
 {
 	struct intel_ring *signaller = signaller_req->ring;
 	struct drm_i915_private *dev_priv = signaller_req->i915;
@@ -1400,12 +1391,8 @@ static int gen6_signal(struct drm_i915_gem_request *signaller_req,
 	enum intel_engine_id id;
 	int ret, num_rings;
 
-#define MBOX_UPDATE_DWORDS 3
 	num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask);
-	num_dwords += round_up((num_rings-1) * MBOX_UPDATE_DWORDS, 2);
-#undef MBOX_UPDATE_DWORDS
-
-	ret = intel_ring_begin(signaller_req, num_dwords);
+	ret = intel_ring_begin(signaller_req, round_up((num_rings-1) * 3, 2));
 	if (ret)
 		return ret;
 
@@ -1423,6 +1410,7 @@ static int gen6_signal(struct drm_i915_gem_request *signaller_req,
 	/* If num_dwords was rounded, make sure the tail pointer is correct */
 	if (num_rings % 2 == 0)
 		intel_ring_emit(signaller, MI_NOOP);
+	intel_ring_advance(signaller);
 
 	return 0;
 }
@@ -1441,11 +1429,13 @@ static int gen6_emit_request(struct drm_i915_gem_request *req)
 	struct intel_ring *ring = req->ring;
 	int ret;
 
-	if (engine->semaphore.signal)
-		ret = engine->semaphore.signal(req, 4);
-	else
-		ret = intel_ring_begin(req, 4);
+	if (engine->semaphore.signal) {
+		ret = engine->semaphore.signal(req);
+		if (ret)
+			return ret;
+	}
 
+	ret = intel_ring_begin(req, 4);
 	if (ret)
 		return ret;
 
@@ -1466,10 +1456,13 @@ static int gen8_render_emit_request(struct drm_i915_gem_request *req)
 	struct intel_ring *ring = req->ring;
 	int ret;
 
-	if (engine->semaphore.signal)
-		ret = engine->semaphore.signal(req, 8);
-	else
-		ret = intel_ring_begin(req, 8);
+	if (engine->semaphore.signal) {
+		ret = engine->semaphore.signal(req);
+		if (ret)
+			return ret;
+	}
+
+	ret = intel_ring_begin(req, 8);
 	if (ret)
 		return ret;
 

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -280,9 +280,7 @@ struct intel_engine_cs {
 		int	(*sync_to)(struct drm_i915_gem_request *to_req,
 				   struct intel_engine_cs *from,
 				   u32 seqno);
-		int	(*signal)(struct drm_i915_gem_request *signaller_req,
-				  /* num_dwords needed by caller */
-				  unsigned int num_dwords);
+		int	(*signal)(struct drm_i915_gem_request *signaller_req);
 	} semaphore;
 
 	/* Execlists */