[PATCH 32/39] drm/i915: Record space required for request emission

[Chris Wilson]

In the next patch, we will use deferred request emission. That requires
reserving sufficient space in the ringbuffer to emit the request, which
first requires us to know how large the request 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 e48de7bb83b4..dc8dbf815157 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -427,6 +427,7 @@ 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_request_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 d68e32c8224c..6bb1abd8f046 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1567,6 +1567,8 @@ static int gen8_emit_request(struct drm_i915_gem_request *request)
 	return intel_logical_ring_advance(request);
 }
 
+static const int gen8_emit_request_sz = 6 + WA_TAIL_DWORDS;
+
 static int gen8_emit_request_render(struct drm_i915_gem_request *request)
 {
 	struct intel_ring *ring = request->ring;
@@ -1598,6 +1600,8 @@ static int gen8_emit_request_render(struct drm_i915_gem_request *request)
 	return intel_logical_ring_advance(request);
 }
 
+static const int gen8_emit_request_render_sz = 8 + WA_TAIL_DWORDS;
+
 static int gen8_init_rcs_context(struct drm_i915_gem_request *req)
 {
 	int ret;
@@ -1672,6 +1676,7 @@ logical_ring_default_vfuncs(struct intel_engine_cs *engine)
 	engine->reset_hw = reset_common_ring;
 	engine->emit_flush = gen8_emit_flush;
 	engine->emit_request = gen8_emit_request;
+	engine->emit_request_sz = gen8_emit_request_sz;
 	engine->submit_request = execlists_submit_request;
 
 	engine->irq_enable = gen8_logical_ring_enable_irq;
@@ -1794,6 +1799,7 @@ 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_request = gen8_emit_request_render;
+	engine->emit_request_sz = gen8_emit_request_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 48a8dffbd90f..b538071c41f9 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1367,6 +1367,8 @@ static int i9xx_emit_request(struct drm_i915_gem_request *req)
 	return 0;
 }
 
+static const int i9xx_emit_request_sz = 4;
+
 /**
  * gen6_sema_emit_request - Update the semaphore mailbox registers
  *
@@ -1420,6 +1422,8 @@ static int gen8_render_emit_request(struct drm_i915_gem_request *req)
 	return 0;
 }
 
+static const int gen8_render_emit_request_sz = 8;
+
 /**
  * intel_ring_sync - sync the waiter to the signaller on seqno
  *
@@ -2656,8 +2660,21 @@ static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,
 	engine->reset_hw = reset_ring_common;
 
 	engine->emit_request = i9xx_emit_request;
-	if (i915.semaphores)
+	engine->emit_request_sz = i9xx_emit_request_sz;
+	if (i915.semaphores) {
+		int num_rings;
+
 		engine->emit_request = gen6_sema_emit_request;
+
+		num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
+		if (INTEL_GEN(dev_priv) >= 8) {
+			engine->emit_request_sz += num_rings * 6;
+		} else {
+			engine->emit_request_sz += num_rings * 3;
+			if (num_rings & 1)
+				engine->emit_request_sz++;
+		}
+	}
 	engine->submit_request = i9xx_submit_request;
 
 	if (INTEL_GEN(dev_priv) >= 8)
@@ -2685,9 +2702,17 @@ 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_request = gen8_render_emit_request;
+		engine->emit_request_sz = gen8_render_emit_request_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_request_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 5e1de04f8b3a..2c89252e38c2 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_request)(struct drm_i915_gem_request *req);
+	int		emit_request_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