[Intel-gfx] [PATCH] drm/i915/execlists: Track begin/end of execlists submission sequences

[Chris Wilson]

We would like to start doing some bookkeeping at the beginning, between
contexts and at the end of execlists submission. We already mark the
beginning and end using EXECLISTS_ACTIVE_USER, to provide an indication
when the HW is idle. This give us a pair of sequence points we can then
expand on for further bookkeeping.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Francisco Jerez <currojerez at riseup.net>
---
 drivers/gpu/drm/i915/intel_lrc.c        | 42 ++++++++++++++++++++++++---------
 drivers/gpu/drm/i915/intel_ringbuffer.h | 11 ++++++++-
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 654634254b64..61fb1387feb3 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -374,6 +374,19 @@ execlists_context_status_change(struct i915_request *rq, unsigned long status)
 				   status, rq);
 }
 
+static inline void
+execlists_user_begin(struct intel_engine_execlists *execlists,
+		     const struct execlist_port *port)
+{
+	execlists_set_active_once(execlists, EXECLISTS_ACTIVE_USER);
+}
+
+static inline void
+execlists_user_end(struct intel_engine_execlists *execlists)
+{
+	execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
+}
+
 static inline void
 execlists_context_schedule_in(struct i915_request *rq)
 {
@@ -710,7 +723,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 	spin_unlock_irq(&engine->timeline->lock);
 
 	if (submit) {
-		execlists_set_active(execlists, EXECLISTS_ACTIVE_USER);
+		execlists_user_begin(execlists, execlists->port);
 		execlists_submit_ports(engine);
 	}
 
@@ -741,7 +754,7 @@ execlists_cancel_port_requests(struct intel_engine_execlists * const execlists)
 		port++;
 	}
 
-	execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
+	execlists_user_end(execlists);
 }
 
 static void clear_gtiir(struct intel_engine_cs *engine)
@@ -872,7 +885,7 @@ static void execlists_submission_tasklet(unsigned long data)
 {
 	struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
 	struct intel_engine_execlists * const execlists = &engine->execlists;
-	struct execlist_port * const port = execlists->port;
+	struct execlist_port *port = execlists->port;
 	struct drm_i915_private *dev_priv = engine->i915;
 	bool fw = false;
 
@@ -1010,9 +1023,19 @@ static void execlists_submission_tasklet(unsigned long data)
 
 			GEM_BUG_ON(count == 0);
 			if (--count == 0) {
+				/*
+				 * On the final event corresponding to the
+				 * submission of this context, we expect either
+				 * an element-switch event or a completion
+				 * event (and on completion, the active-idle
+				 * marker). No more preemptions, lite-restore
+				 * or otherwise
+				 */
 				GEM_BUG_ON(status & GEN8_CTX_STATUS_PREEMPTED);
 				GEM_BUG_ON(port_isset(&port[1]) &&
 					   !(status & GEN8_CTX_STATUS_ELEMENT_SWITCH));
+				GEM_BUG_ON(!port_isset(&port[1]) &&
+					   !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
 				GEM_BUG_ON(!i915_request_completed(rq));
 				execlists_context_schedule_out(rq);
 				trace_i915_request_out(rq);
@@ -1021,17 +1044,14 @@ static void execlists_submission_tasklet(unsigned long data)
 				GEM_TRACE("%s completed ctx=%d\n",
 					  engine->name, port->context_id);
 
-				execlists_port_complete(execlists, port);
+				port = execlists_port_complete(execlists, port);
+				if (port_isset(port))
+					execlists_user_begin(execlists, port);
+				else
+					execlists_user_end(execlists);
 			} else {
 				port_set(port, port_pack(rq, count));
 			}
-
-			/* After the final element, the hw should be idle */
-			GEM_BUG_ON(port_count(port) == 0 &&
-				   !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
-			if (port_count(port) == 0)
-				execlists_clear_active(execlists,
-						       EXECLISTS_ACTIVE_USER);
 		}
 
 		if (head != execlists->csb_head) {
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index a02c7b3b9d55..2e20627e254b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -638,6 +638,13 @@ execlists_set_active(struct intel_engine_execlists *execlists,
 	__set_bit(bit, (unsigned long *)&execlists->active);
 }
 
+static inline bool
+execlists_set_active_once(struct intel_engine_execlists *execlists,
+			  unsigned int bit)
+{
+	return !__test_and_set_bit(bit, (unsigned long *)&execlists->active);
+}
+
 static inline void
 execlists_clear_active(struct intel_engine_execlists *execlists,
 		       unsigned int bit)
@@ -664,7 +671,7 @@ execlists_num_ports(const struct intel_engine_execlists * const execlists)
 	return execlists->port_mask + 1;
 }
 
-static inline void
+static inline struct execlist_port *
 execlists_port_complete(struct intel_engine_execlists * const execlists,
 			struct execlist_port * const port)
 {
@@ -675,6 +682,8 @@ execlists_port_complete(struct intel_engine_execlists * const execlists,
 
 	memmove(port, port + 1, m * sizeof(struct execlist_port));
 	memset(port + m, 0, sizeof(struct execlist_port));
+
+	return port;
 }
 
 static inline unsigned int
-- 
2.16.3