drm/i915: Defer breadcrumb emission

Move the actual emission of the breadcrumb for closing the request from
i915_add_request() to the submit callback. (It can be moved later when
required.) This allows us to defer the allocation of the global_seqno
from request construction to actual submission, allowing us to emit the
requests out of order (wrt to the order of their construction, they
still will only be executed one all of their dependencies are resolved
including that all earlier requests on their timeline have been
submitted.) We have to specialise how we then emit the request in order
to write into the preallocated space, rather than at the tail of the
ringbuffer (which will have been advanced by the addition of new
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/20161028125858.23563-29-chris@chris-wilson.co.uk

1 files changed, 57 insertions, 112 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ae9cf6bb4def..16244775b9d1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1213,90 +1213,62 @@ static void render_ring_cleanup(struct intel_engine_cs *engine)
 	i915_vma_unpin_and_release(&dev_priv->semaphore);
 }
 
-static int gen8_rcs_signal(struct drm_i915_gem_request *req)
+static u32 *gen8_rcs_signal(struct drm_i915_gem_request *req, u32 *out)
 {
-	struct intel_ring *ring = req->ring;
 	struct drm_i915_private *dev_priv = req->i915;
 	struct intel_engine_cs *waiter;
 	enum intel_engine_id id;
-	int ret, num_rings;
-
-	num_rings = INTEL_INFO(dev_priv)->num_rings;
-	ret = intel_ring_begin(req, (num_rings-1) * 8);
-	if (ret)
-		return ret;
 
 	for_each_engine(waiter, dev_priv, id) {
 		u64 gtt_offset = req->engine->semaphore.signal_ggtt[id];
 		if (gtt_offset == MI_SEMAPHORE_SYNC_INVALID)
 			continue;
 
-		intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(6));
-		intel_ring_emit(ring,
-				PIPE_CONTROL_GLOBAL_GTT_IVB |
-				PIPE_CONTROL_QW_WRITE |
-				PIPE_CONTROL_CS_STALL);
-		intel_ring_emit(ring, lower_32_bits(gtt_offset));
-		intel_ring_emit(ring, upper_32_bits(gtt_offset));
-		intel_ring_emit(ring, req->global_seqno);
-		intel_ring_emit(ring, 0);
-		intel_ring_emit(ring,
-				MI_SEMAPHORE_SIGNAL |
-				MI_SEMAPHORE_TARGET(waiter->hw_id));
-		intel_ring_emit(ring, 0);
+		*out++ = GFX_OP_PIPE_CONTROL(6);
+		*out++ = (PIPE_CONTROL_GLOBAL_GTT_IVB |
+			  PIPE_CONTROL_QW_WRITE |
+			  PIPE_CONTROL_CS_STALL);
+		*out++ = lower_32_bits(gtt_offset);
+		*out++ = upper_32_bits(gtt_offset);
+		*out++ = req->global_seqno;
+		*out++ = 0;
+		*out++ = (MI_SEMAPHORE_SIGNAL |
+			  MI_SEMAPHORE_TARGET(waiter->hw_id));
+		*out++ = 0;
 	}
-	intel_ring_advance(ring);
 
-	return 0;
+	return out;
 }
 
-static int gen8_xcs_signal(struct drm_i915_gem_request *req)
+static u32 *gen8_xcs_signal(struct drm_i915_gem_request *req, u32 *out)
 {
-	struct intel_ring *ring = req->ring;
 	struct drm_i915_private *dev_priv = req->i915;
 	struct intel_engine_cs *waiter;
 	enum intel_engine_id id;
-	int ret, num_rings;
-
-	num_rings = INTEL_INFO(dev_priv)->num_rings;
-	ret = intel_ring_begin(req, (num_rings-1) * 6);
-	if (ret)
-		return ret;
 
 	for_each_engine(waiter, dev_priv, id) {
 		u64 gtt_offset = req->engine->semaphore.signal_ggtt[id];
 		if (gtt_offset == MI_SEMAPHORE_SYNC_INVALID)
 			continue;
 
-		intel_ring_emit(ring,
-				(MI_FLUSH_DW + 1) | MI_FLUSH_DW_OP_STOREDW);
-		intel_ring_emit(ring,
-				lower_32_bits(gtt_offset) |
-				MI_FLUSH_DW_USE_GTT);
-		intel_ring_emit(ring, upper_32_bits(gtt_offset));
-		intel_ring_emit(ring, req->global_seqno);
-		intel_ring_emit(ring,
-				MI_SEMAPHORE_SIGNAL |
-				MI_SEMAPHORE_TARGET(waiter->hw_id));
-		intel_ring_emit(ring, 0);
+		*out++ = (MI_FLUSH_DW + 1) | MI_FLUSH_DW_OP_STOREDW;
+		*out++ = lower_32_bits(gtt_offset) | MI_FLUSH_DW_USE_GTT;
+		*out++ = upper_32_bits(gtt_offset);
+		*out++ = req->global_seqno;
+		*out++ = (MI_SEMAPHORE_SIGNAL |
+			  MI_SEMAPHORE_TARGET(waiter->hw_id));
+		*out++ = 0;
 	}
-	intel_ring_advance(ring);
 
-	return 0;
+	return out;
 }
 
-static int gen6_signal(struct drm_i915_gem_request *req)
+static u32 *gen6_signal(struct drm_i915_gem_request *req, u32 *out)
 {
-	struct intel_ring *ring = req->ring;
 	struct drm_i915_private *dev_priv = req->i915;
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
-	int ret, num_rings;
-
-	num_rings = INTEL_INFO(dev_priv)->num_rings;
-	ret = intel_ring_begin(req, round_up((num_rings-1) * 3, 2));
-	if (ret)
-		return ret;
+	int num_rings = 0;
 
 	for_each_engine(engine, dev_priv, id) {
 		i915_reg_t mbox_reg;
@@ -1306,46 +1278,34 @@ static int gen6_signal(struct drm_i915_gem_request *req)
 
 		mbox_reg = req->engine->semaphore.mbox.signal[engine->hw_id];
 		if (i915_mmio_reg_valid(mbox_reg)) {
-			intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
-			intel_ring_emit_reg(ring, mbox_reg);
-			intel_ring_emit(ring, req->global_seqno);
+			*out++ = MI_LOAD_REGISTER_IMM(1);
+			*out++ = i915_mmio_reg_offset(mbox_reg);
+			*out++ = req->global_seqno;
+			num_rings++;
 		}
 	}
+	if (num_rings & 1)
+		*out++ = MI_NOOP;
 
-	/* If num_dwords was rounded, make sure the tail pointer is correct */
-	if (num_rings % 2 == 0)
-		intel_ring_emit(ring, MI_NOOP);
-	intel_ring_advance(ring);
-
-	return 0;
+	return out;
 }
 
 static void i9xx_submit_request(struct drm_i915_gem_request *request)
 {
 	struct drm_i915_private *dev_priv = request->i915;
 
-	I915_WRITE_TAIL(request->engine,
-			intel_ring_offset(request->ring, request->tail));
+	I915_WRITE_TAIL(request->engine, request->tail);
 }
 
-static int i9xx_emit_breadcrumb(struct drm_i915_gem_request *req)
+static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req,
+				 u32 *out)
 {
-	struct intel_ring *ring = req->ring;
-	int ret;
-
-	ret = intel_ring_begin(req, 4);
-	if (ret)
-		return ret;
-
-	intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
-	intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
-	intel_ring_emit(ring, req->global_seqno);
-	intel_ring_emit(ring, MI_USER_INTERRUPT);
-	intel_ring_advance(ring);
-
-	req->tail = ring->tail;
+	*out++ = MI_STORE_DWORD_INDEX;
+	*out++ = I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT;
+	*out++ = req->global_seqno;
+	*out++ = MI_USER_INTERRUPT;
 
-	return 0;
+	req->tail = intel_ring_offset(req->ring, out);
 }
 
 static const int i9xx_emit_breadcrumb_sz = 4;
@@ -1358,49 +1318,34 @@ static const int i9xx_emit_breadcrumb_sz = 4;
  * Update the mailbox registers in the *other* rings with the current seqno.
  * This acts like a signal in the canonical semaphore.
  */
-static int gen6_sema_emit_breadcrumb(struct drm_i915_gem_request *req)
+static void gen6_sema_emit_breadcrumb(struct drm_i915_gem_request *req,
+				      u32 *out)
 {
-	int ret;
-
-	ret = req->engine->semaphore.signal(req);
-	if (ret)
-		return ret;
-
-	return i9xx_emit_breadcrumb(req);
+	return i9xx_emit_breadcrumb(req,
+				    req->engine->semaphore.signal(req, out));
 }
 
-static int gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req)
+static void gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req,
+					u32 *out)
 {
 	struct intel_engine_cs *engine = req->engine;
-	struct intel_ring *ring = req->ring;
-	int ret;
 
-	if (engine->semaphore.signal) {
-		ret = engine->semaphore.signal(req);
-		if (ret)
-			return ret;
-	}
-
-	ret = intel_ring_begin(req, 8);
-	if (ret)
-		return ret;
+	if (engine->semaphore.signal)
+		out = engine->semaphore.signal(req, out);
 
-	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(6));
-	intel_ring_emit(ring, (PIPE_CONTROL_GLOBAL_GTT_IVB |
+	*out++ = GFX_OP_PIPE_CONTROL(6);
+	*out++ = (PIPE_CONTROL_GLOBAL_GTT_IVB |
 			       PIPE_CONTROL_CS_STALL |
-			       PIPE_CONTROL_QW_WRITE));
-	intel_ring_emit(ring, intel_hws_seqno_address(engine));
-	intel_ring_emit(ring, 0);
-	intel_ring_emit(ring, req->global_seqno);
+			       PIPE_CONTROL_QW_WRITE);
+	*out++ = intel_hws_seqno_address(engine);
+	*out++ = 0;
+	*out++ = req->global_seqno;
 	/* We're thrashing one dword of HWS. */
-	intel_ring_emit(ring, 0);
-	intel_ring_emit(ring, MI_USER_INTERRUPT);
-	intel_ring_emit(ring, MI_NOOP);
-	intel_ring_advance(ring);
-
-	req->tail = ring->tail;
+	*out++ = 0;
+	*out++ = MI_USER_INTERRUPT;
+	*out++ = MI_NOOP;
 
-	return 0;
+	req->tail = intel_ring_offset(req->ring, out);
 }
 
 static const int gen8_render_emit_breadcrumb_sz = 8;