[Intel-gfx] [PATCH 33/41] drm/i915: Record space required for breadcrumb emission

[Chris Wilson]

In the next patch, we will use deferred breadcrumb emission. That requires
reserving sufficient space in the ringbuffer to emit the breadcrumb, which
first requires us to know how large the breadcrumb is.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.c |  1 +
 drivers/gpu/drm/i915/intel_lrc.c        |  6 ++++++
 drivers/gpu/drm/i915/intel_ringbuffer.c | 29 +++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 5f1538b7f43c..af4827926d3b 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -434,6 +434,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 	 * away, e.g. because a GPU scheduler has deferred it.
 	 */
 	req->reserved_space = MIN_SPACE_FOR_ADD_REQUEST;
+	GEM_BUG_ON(req->reserved_space < engine->emit_breadcrumb_sz);
 
 	if (i915.enable_execlists)
 		ret = intel_logical_ring_alloc_request_extras(req);
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 57dba458f185..8229baebb2b3 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1590,6 +1590,8 @@ static int gen8_emit_breadcrumb(struct drm_i915_gem_request *request)
 	return intel_logical_ring_advance(request);
 }
 
+static const int gen8_emit_breadcrumb_sz = 6 + WA_TAIL_DWORDS;
+
 static int gen8_emit_breadcrumb_render(struct drm_i915_gem_request *request)
 {
 	struct intel_ring *ring = request->ring;
@@ -1621,6 +1623,8 @@ static int gen8_emit_breadcrumb_render(struct drm_i915_gem_request *request)
 	return intel_logical_ring_advance(request);
 }
 
+static const int gen8_emit_breadcrumb_render_sz = 8 + WA_TAIL_DWORDS;
+
 static int gen8_init_rcs_context(struct drm_i915_gem_request *req)
 {
 	int ret;
@@ -1695,6 +1699,7 @@ logical_ring_default_vfuncs(struct intel_engine_cs *engine)
 	engine->reset_hw = reset_common_ring;
 	engine->emit_flush = gen8_emit_flush;
 	engine->emit_breadcrumb = gen8_emit_breadcrumb;
+	engine->emit_breadcrumb_sz = gen8_emit_breadcrumb_sz;
 	engine->submit_request = execlists_submit_request;
 
 	engine->irq_enable = gen8_logical_ring_enable_irq;
@@ -1817,6 +1822,7 @@ int logical_render_ring_init(struct intel_engine_cs *engine)
 	engine->init_context = gen8_init_rcs_context;
 	engine->emit_flush = gen8_emit_flush_render;
 	engine->emit_breadcrumb = gen8_emit_breadcrumb_render;
+	engine->emit_breadcrumb_sz = gen8_emit_breadcrumb_render_sz;
 
 	ret = intel_engine_create_scratch(engine, 4096);
 	if (ret)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 6a0c75c5833b..95f8b3b13351 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1350,6 +1350,8 @@ static int i9xx_emit_breadcrumb(struct drm_i915_gem_request *req)
 	return 0;
 }
 
+static const int i9xx_emit_breadcrumb_sz = 4;
+
 /**
  * gen6_sema_emit_breadcrumb - Update the semaphore mailbox registers
  *
@@ -1403,6 +1405,8 @@ static int gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req)
 	return 0;
 }
 
+static const int gen8_render_emit_breadcrumb_sz = 8;
+
 /**
  * intel_ring_sync - sync the waiter to the signaller on seqno
  *
@@ -2640,8 +2644,21 @@ static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,
 	engine->reset_hw = reset_ring_common;
 
 	engine->emit_breadcrumb = i9xx_emit_breadcrumb;
-	if (i915.semaphores)
+	engine->emit_breadcrumb_sz = i9xx_emit_breadcrumb_sz;
+	if (i915.semaphores) {
+		int num_rings;
+
 		engine->emit_breadcrumb = gen6_sema_emit_breadcrumb;
+
+		num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
+		if (INTEL_GEN(dev_priv) >= 8) {
+			engine->emit_breadcrumb_sz += num_rings * 6;
+		} else {
+			engine->emit_breadcrumb_sz += num_rings * 3;
+			if (num_rings & 1)
+				engine->emit_breadcrumb_sz++;
+		}
+	}
 	engine->submit_request = i9xx_submit_request;
 
 	if (INTEL_GEN(dev_priv) >= 8)
@@ -2669,9 +2686,17 @@ int intel_init_render_ring_buffer(struct intel_engine_cs *engine)
 	if (INTEL_GEN(dev_priv) >= 8) {
 		engine->init_context = intel_rcs_ctx_init;
 		engine->emit_breadcrumb = gen8_render_emit_breadcrumb;
+		engine->emit_breadcrumb_sz = gen8_render_emit_breadcrumb_sz;
 		engine->emit_flush = gen8_render_ring_flush;
-		if (i915.semaphores)
+		if (i915.semaphores) {
+			int num_rings;
+
 			engine->semaphore.signal = gen8_rcs_signal;
+
+			num_rings =
+				hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
+			engine->emit_breadcrumb_sz += num_rings * 6;
+		}
 	} else if (INTEL_GEN(dev_priv) >= 6) {
 		engine->init_context = intel_rcs_ctx_init;
 		engine->emit_flush = gen7_render_ring_flush;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index a5ced1649ecd..7b7aaafac0da 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -256,6 +256,7 @@ struct intel_engine_cs {
 #define I915_DISPATCH_PINNED BIT(1)
 #define I915_DISPATCH_RS     BIT(2)
 	int		(*emit_breadcrumb)(struct drm_i915_gem_request *req);
+	int		emit_breadcrumb_sz;
 
 	/* Pass the request to the hardware queue (e.g. directly into
 	 * the legacy ringbuffer or to the end of an execlist).
-- 
2.9.3