drm/i915: Keep track of reserved execlist portselist2elist

To further enchance port processing, keep track of
reserved ports. This way we can iterate only the used subset
of port space. Note that we lift the responsibility of
execlists_submit_request() to inspect hw availability and
always do dequeuing. This is to ensure that only the irq
handler will be responsible for keeping track of available ports.

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>

5 files changed, 117 insertions, 67 deletions

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 0dfb03a0cee4..fdda3a1835ad 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -662,12 +662,19 @@ static void port_assign(struct execlist_port *port,
 static bool i915_guc_dequeue(struct intel_engine_cs *engine)
 {
 	struct intel_engine_execlist * const el = &engine->execlist;
-	struct execlist_port *port = execlist_port_head(el);
-	const struct execlist_port * const last_port = execlist_port_tail(el);
-	struct drm_i915_gem_request *last = port_request(port);
+	struct execlist_port *port;
+	struct drm_i915_gem_request *last;
 	struct rb_node *rb;
 	bool submit = false;
 
+	if (execlist_active_ports(el)) {
+		port = execlist_port_tail(el);
+		last = port_request(port);
+	} else {
+		port = NULL;
+		last = NULL;
+	}
+
 	spin_lock_irq(&engine->timeline->lock);
 	rb = el->first;
 	GEM_BUG_ON(rb_first(&el->queue) != rb);
@@ -675,9 +682,12 @@ static bool i915_guc_dequeue(struct intel_engine_cs *engine)
 		struct i915_priolist *p = rb_entry(rb, typeof(*p), node);
 		struct drm_i915_gem_request *rq, *rn;
 
+		if (!port)
+			port = execlist_request_port(el);
+
 		list_for_each_entry_safe(rq, rn, &p->requests, priotree.link) {
 			if (last && rq->ctx != last->ctx) {
-				if (port == last_port) {
+				if (!execlist_inactive_ports(el)) {
 					__list_del_many(&p->requests,
 							&rq->priotree.link);
 					goto done;
@@ -686,7 +696,8 @@ static bool i915_guc_dequeue(struct intel_engine_cs *engine)
 				if (submit)
 					port_assign(port, last);
 
-				port = execlist_port_next(el, port);
+				port = execlist_request_port(el);
+				GEM_BUG_ON(port_isset(port));
 			}
 
 			INIT_LIST_HEAD(&rq->priotree.link);
@@ -717,26 +728,22 @@ static void i915_guc_irq_handler(unsigned long data)
 {
 	struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
 	struct intel_engine_execlist * const el = &engine->execlist;
-	struct execlist_port *port = execlist_port_head(el);
-	const struct execlist_port * const last_port = execlist_port_tail(el);
-	struct drm_i915_gem_request *rq;
-	bool submit;
 
 	do {
-		rq = port_request(port);
-		while (rq && i915_gem_request_completed(rq)) {
+		while (execlist_active_ports(el)) {
+			struct execlist_port *port = execlist_port_head(el);
+			struct drm_i915_gem_request *rq = port_request(port);
+
+			if (!i915_gem_request_completed(rq))
+				break;
+
 			trace_i915_gem_request_out(rq);
 			i915_gem_request_put(rq);
 
-			port = execlist_port_complete(el, port);
-
-			rq = port_request(port);
+			execlist_release_port(el, port);
 		}
 
-		submit = false;
-		if (!port_count(last_port))
-			submit = i915_guc_dequeue(engine);
-	} while (submit);
+	} while (execlist_inactive_ports(el) && i915_guc_dequeue(engine));
 }
 
 /*
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 1919ac0b7b0f..de4e608786a8 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1312,7 +1312,7 @@ gen8_cs_irq_handler(struct intel_engine_cs *engine, u32 iir, int test_shift)
 	bool tasklet = false;
 
 	if (iir & (GT_CONTEXT_SWITCH_INTERRUPT << test_shift)) {
-		if (port_count(execlist_port_head(el))) {
+		if (execlist_active_ports(el)) {
 			__set_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
 			tasklet = true;
 		}
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 4b9eaec50070..b09212bb66b4 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -389,6 +389,7 @@ static void intel_engine_init_execlist(struct intel_engine_cs *engine)
 	GEM_BUG_ON(el->port_mask >= EXECLIST_MAX_PORTS);
 
 	el->port_head = 0;
+	el->port_count = 0;
 
 	el->queue = RB_ROOT;
 	el->first = NULL;
@@ -1345,8 +1346,8 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 	if (test_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted))
 		return false;
 
-	/* Both ports drained, no more ELSP submission? */
-	if (port_request(execlist_port_head(&engine->execlist)))
+	/* All ports drained, no more ELSP submission? */
+	if (execlist_active_ports(&engine->execlist))
 		return false;
 
 	/* ELSP is empty, but there are ready requests? */
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 1a1c68c53fbd..18a87cf56b81 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -344,23 +344,27 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 	struct execlist_port *port;
 	unsigned int n;
 
+	for (n = 0; n < execlist_inactive_ports(el); n++) {
+		writel(0, elsp);
+		writel(0, elsp);
+	}
+
 	for_each_execlist_port_reverse(el, port, n) {
 		struct drm_i915_gem_request *rq;
 		unsigned int count;
 		u64 desc;
 
 		rq = port_unpack(port, &count);
-		if (rq) {
-			GEM_BUG_ON(count > !n);
-			if (!count++)
-				execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
-			port_set(port, port_pack(rq, count));
-			desc = execlists_update_context(rq);
-			GEM_DEBUG_EXEC(port->context_id = upper_32_bits(desc));
-		} else {
-			GEM_BUG_ON(!n);
-			desc = 0;
-		}
+
+		GEM_BUG_ON(!rq);
+		GEM_BUG_ON(count > !n);
+
+		if (!count++)
+			execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
+
+		port_set(port, port_pack(rq, count));
+		desc = execlists_update_context(rq);
+		GEM_DEBUG_EXEC(port->context_id = upper_32_bits(desc));
 
 		writel(upper_32_bits(desc), elsp);
 		writel(lower_32_bits(desc), elsp);
@@ -398,15 +402,16 @@ static void port_assign(struct execlist_port *port,
 
 static void execlists_dequeue(struct intel_engine_cs *engine)
 {
-	struct drm_i915_gem_request *last;
 	struct intel_engine_execlist * const el = &engine->execlist;
-	struct execlist_port *port = execlist_port_head(el);
-	const struct execlist_port * const last_port = execlist_port_tail(el);
+	struct execlist_port *port;
+	struct drm_i915_gem_request *last;
 	struct rb_node *rb;
 	bool submit = false;
 
-	last = port_request(port);
-	if (last)
+	if (execlist_active_ports(el)) {
+		port = execlist_port_tail(el);
+		last = port_request(port);
+
 		/* WaIdleLiteRestore:bdw,skl
 		 * Apply the wa NOOPs to prevent ring:HEAD == req:TAIL
 		 * as we resubmit the request. See gen8_emit_breadcrumb()
@@ -414,6 +419,10 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 		 * request.
 		 */
 		last->tail = last->wa_tail;
+	} else {
+		port = NULL;
+		last = NULL;
+	}
 
 	/* Hardware submission is through 2 ports. Conceptually each port
 	 * has a (RING_START, RING_HEAD, RING_TAIL) tuple. RING_START is
@@ -443,6 +452,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 		struct i915_priolist *p = rb_entry(rb, typeof(*p), node);
 		struct drm_i915_gem_request *rq, *rn;
 
+		if (!port)
+			port = execlist_request_port(el);
+
 		list_for_each_entry_safe(rq, rn, &p->requests, priotree.link) {
 			/*
 			 * Can we combine this request with the current port?
@@ -461,7 +473,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 				 * combine this request with the last, then we
 				 * are done.
 				 */
-				if (port == last_port) {
+				if (!execlist_inactive_ports(el)) {
 					__list_del_many(&p->requests,
 							&rq->priotree.link);
 					goto done;
@@ -486,8 +498,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 				if (submit)
 					port_assign(port, last);
 
-				port = execlist_port_next(el, port);
-
+				port = execlist_request_port(el);
 				GEM_BUG_ON(port_isset(port));
 			}
 
@@ -518,9 +529,12 @@ done:
 
 static bool execlists_elsp_ready(struct intel_engine_execlist * const el)
 {
-	struct execlist_port * const port = execlist_port_head(el);
+	const unsigned int active = execlist_active_ports(el);
+
+	if (!active)
+		return true;
 
-	return port_count(port) + port_count(execlist_port_next(el, port)) < 2;
+	return port_count(execlist_port_tail(el)) + active < 2;
 }
 
 /*
@@ -531,7 +545,6 @@ static void intel_lrc_irq_handler(unsigned long data)
 {
 	struct intel_engine_cs * const engine = (struct intel_engine_cs *)data;
 	struct intel_engine_execlist * const el = &engine->execlist;
-	struct execlist_port *port = execlist_port_head(el);
 	struct drm_i915_private *dev_priv = engine->i915;
 
 	/* We can skip acquiring intel_runtime_pm_get() here as it was taken
@@ -571,6 +584,7 @@ static void intel_lrc_irq_handler(unsigned long data)
 		tail = GEN8_CSB_WRITE_PTR(head);
 		head = GEN8_CSB_READ_PTR(head);
 		while (head != tail) {
+			struct execlist_port *port;
 			struct drm_i915_gem_request *rq;
 			unsigned int status;
 			unsigned int count;
@@ -599,6 +613,7 @@ static void intel_lrc_irq_handler(unsigned long data)
 			if (!(status & GEN8_CTX_STATUS_COMPLETED_MASK))
 				continue;
 
+			port = execlist_port_head(el);
 			/* Check the context/desc id for this event matches */
 			GEM_DEBUG_BUG_ON(readl(buf + 2 * head + 1) !=
 					 port->context_id);
@@ -613,13 +628,13 @@ static void intel_lrc_irq_handler(unsigned long data)
 				trace_i915_gem_request_out(rq);
 				i915_gem_request_put(rq);
 
-				port = execlist_port_complete(el, port);
+				execlist_release_port(el, port);
 			} else {
 				port_set(port, port_pack(rq, count));
 			}
 
 			/* After the final element, the hw should be idle */
-			GEM_BUG_ON(port_count(port) == 0 &&
+			GEM_BUG_ON(execlist_active_ports(el) == 0 &&
 				   !(status & GEN8_CTX_STATUS_ACTIVE_IDLE));
 		}
 
@@ -709,10 +724,8 @@ static void execlists_submit_request(struct drm_i915_gem_request *request)
 
 	if (insert_request(engine,
 			   &request->priotree,
-			   request->priotree.priority)) {
-		if (execlists_elsp_ready(el))
-			tasklet_hi_schedule(&el->irq_tasklet);
-	}
+			   request->priotree.priority))
+		tasklet_hi_schedule(&el->irq_tasklet);
 
 	GEM_BUG_ON(!el->first);
 	GEM_BUG_ON(list_empty(&request->priotree.link));
@@ -1334,7 +1347,6 @@ static void reset_common_ring(struct intel_engine_cs *engine,
 			      struct drm_i915_gem_request *request)
 {
 	struct intel_engine_execlist * const el = &engine->execlist;
-	struct execlist_port *port = execlist_port_head(el);
 	struct intel_context *ce;
 
 	/*
@@ -1351,12 +1363,16 @@ static void reset_common_ring(struct intel_engine_cs *engine,
 		return;
 	}
 
-	if (request->ctx != port_request(port)->ctx) {
-		i915_gem_request_put(port_request(port));
-		execlist_port_complete(el, port);
-	}
+	if (execlist_active_ports(el)) {
+		struct execlist_port *port = execlist_port_head(el);
 
-	GEM_BUG_ON(request->ctx != port_request(port)->ctx);
+		if (request->ctx != port_request(port)->ctx) {
+			i915_gem_request_put(port_request(port));
+			execlist_release_port(el, port);
+		}
+
+		GEM_BUG_ON(request->ctx != port_request(port)->ctx);
+	}
 
 	/* If the request was innocent, we leave the request in the ELSP
 	 * and will try to replay it on restarting. The context image may
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 13d8e1115f3b..9c377f6eb8fe 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -249,6 +249,11 @@ struct intel_engine_execlist {
 	unsigned int port_head;
 
 	/**
+	 * @port_count: reserved ports
+	 */
+	unsigned int port_count;
+
+	/**
 	 * @queue: queue of requests, in priority lists
 	 */
 	struct rb_root queue;
@@ -510,44 +515,65 @@ struct intel_engine_cs {
 
 #define for_each_execlist_port(el__, port__, n__) \
 	for ((n__) = 0; \
-	     (port__) = &(el__)->port[__port_idx((el__)->port_head, (n__), (el__)->port_mask)], (n__) < (el__)->port_mask + 1; \
+	     (port__) = &(el__)->port[__port_idx((el__)->port_head, (n__), (el__)->port_mask)], (n__) < (el__)->port_count; \
 	     (n__)++)
 
 #define for_each_execlist_port_reverse(el__, port__, n__) \
-	for ((n__) = (el__)->port_mask + 1; \
+	for ((n__) = (el__)->port_count; \
 	     (port__) = &(el__)->port[__port_idx((el__)->port_head - 1, (n__), (el__)->port_mask)], (n__)--;)
 
 static inline struct execlist_port *
 execlist_port_head(struct intel_engine_execlist * const el)
 {
+	GEM_DEBUG_BUG_ON(!el->port_count);
+
 	return &el->port[el->port_head];
 }
 
 static inline struct execlist_port *
 execlist_port_tail(struct intel_engine_execlist * const el)
 {
-	return &el->port[__port_idx(el->port_head, el->port_mask, el->port_mask)];
+	GEM_DEBUG_BUG_ON(!el->port_count);
+
+	return &el->port[__port_idx(el->port_head, el->port_count - 1, el->port_mask)];
 }
 
-static inline struct execlist_port *
-execlist_port_next(struct intel_engine_execlist * const el,
-		   const struct execlist_port * const port)
+static inline unsigned int
+execlist_active_ports(const struct intel_engine_execlist * const el)
 {
-	const unsigned int i = port_index(port, el);
+	return READ_ONCE(el->port_count);
+}
 
-	return &el->port[__port_idx(i, 1, el->port_mask)];
+static inline unsigned int
+execlist_inactive_ports(const struct intel_engine_execlist * const el)
+{
+	return el->port_mask + 1 - READ_ONCE(el->port_count);
 }
 
 static inline struct execlist_port *
-execlist_port_complete(struct intel_engine_execlist * const el,
-		       struct execlist_port * const port)
+execlist_request_port(struct intel_engine_execlist * const el)
+{
+	GEM_DEBUG_BUG_ON(el->port_count == el->port_mask + 1);
+
+	el->port_count++;
+
+	GEM_DEBUG_BUG_ON(port_isset(execlist_port_tail(el)));
+
+	return execlist_port_tail(el);
+}
+
+static inline void
+execlist_release_port(struct intel_engine_execlist * const el,
+		      struct execlist_port * const port)
 {
 	GEM_DEBUG_BUG_ON(port_index(port, el) != el->port_head);
+	GEM_DEBUG_BUG_ON(!port_isset(port));
+	GEM_DEBUG_BUG_ON(!el->port_count);
 
 	memset(port, 0, sizeof(struct execlist_port));
-	el->port_head = __port_idx(el->port_head, 1, el->port_mask);
 
-	return execlist_port_head(el);
+	el->port_head = __port_idx(el->port_head, 1, el->port_mask);
+	el->port_count--;
 }
 
 void execlist_cancel_port_requests(struct intel_engine_execlist * const el);