diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 2be0db187ee6..b65a411aa7ce 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -582,6 +582,8 @@ void intel_engine_init_execlists(struct intel_engine_cs *engine)
 
 	execlists->queue_priority_hint = INT_MIN;
 	execlists->queue = RB_ROOT_CACHED;
+
+	i915_sched_init_ipi(&execlists->ipi);
 }
 
 static void cleanup_status_page(struct intel_engine_cs *engine)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
index 0b026cde9f09..48a91c0dbad6 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c
@@ -114,8 +114,7 @@ static void heartbeat(struct work_struct *wrk)
 			 * but all other contexts, including the kernel
 			 * context are stuck waiting for the signal.
 			 */
-		} else if (intel_engine_has_scheduler(engine) &&
-			   rq->sched.attr.priority < I915_PRIORITY_BARRIER) {
+		} else if (rq->sched.attr.priority < I915_PRIORITY_BARRIER) {
 			/*
 			 * Gradually raise the priority of the heartbeat to
 			 * give high priority work [which presumably desires
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index 7cc5f4ca3f56..7159f9575e65 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -20,6 +20,7 @@
 #include "i915_gem.h"
 #include "i915_pmu.h"
 #include "i915_priolist_types.h"
+#include "i915_scheduler_types.h"
 #include "i915_selftest.h"
 #include "intel_breadcrumbs_types.h"
 #include "intel_sseu.h"
@@ -257,6 +258,8 @@ struct intel_engine_execlists {
 	struct rb_root_cached queue;
 	struct rb_root_cached virtual;
 
+	struct i915_sched_ipi ipi;
+
 	/**
 	 * @csb_write: control register for Context Switch buffer
 	 *
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 84a55df88687..035e4be5d573 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -17,7 +17,25 @@ static struct i915_global_scheduler {
 	struct kmem_cache *slab_priorities;
 } global;
 
-static DEFINE_SPINLOCK(schedule_lock);
+/*
+ * Virtual engines complicate acquiring the engine timeline lock,
+ * as their rq->engine pointer is not stable until under that
+ * engine lock. The simple ploy we use is to take the lock then
+ * check that the rq still belongs to the newly locked engine.
+ */
+#define lock_engine_irqsave(rq, flags) ({ \
+	struct i915_request * const rq__ = (rq); \
+	struct intel_engine_cs *engine__ = READ_ONCE(rq__->engine); \
+\
+	spin_lock_irqsave(&engine__->active.lock, (flags)); \
+	while (engine__ != READ_ONCE((rq__)->engine)) { \
+		spin_unlock(&engine__->active.lock); \
+		engine__ = READ_ONCE(rq__->engine); \
+		spin_lock(&engine__->active.lock); \
+	} \
+\
+	engine__; \
+})
 
 static struct i915_sched_node *node_get(struct i915_sched_node *node)
 {
@@ -30,17 +48,104 @@ static void node_put(struct i915_sched_node *node)
 	i915_request_put(container_of(node, struct i915_request, sched));
 }
 
+static inline int rq_prio(const struct i915_request *rq)
+{
+	return READ_ONCE(rq->sched.attr.priority);
+}
+
+static int ipi_get_prio(struct i915_request *rq)
+{
+	if (READ_ONCE(rq->sched.ipi_priority) == I915_PRIORITY_INVALID)
+		return I915_PRIORITY_INVALID;
+
+	return xchg(&rq->sched.ipi_priority, I915_PRIORITY_INVALID);
+}
+
+static void ipi_schedule(struct work_struct *wrk)
+{
+	struct i915_sched_ipi *ipi = container_of(wrk, typeof(*ipi), work);
+	struct i915_request *rq = xchg(&ipi->list, NULL);
+
+	do {
+		struct i915_request *rn = xchg(&rq->sched.ipi_link, NULL);
+		int prio;
+
+		prio = ipi_get_prio(rq);
+
+		/*
+		 * For cross-engine scheduling to work we rely on one of two
+		 * things:
+		 *
+		 * a) The requests are using dma-fence fences and so will not
+		 * be scheduled until the previous engine is completed, and
+		 * so we cannot cross back onto the original engine and end up
+		 * queuing an earlier request after the first (due to the
+		 * interrupted DFS).
+		 *
+		 * b) The requests are using semaphores and so may be already
+		 * be in flight, in which case if we cross back onto the same
+		 * engine, we will already have put the interrupted DFS into
+		 * the priolist, and the continuation will now be queued
+		 * afterwards [out-of-order]. However, since we are using
+		 * semaphores in this case, we also perform yield on semaphore
+		 * waits and so will reorder the requests back into the correct
+		 * sequence. This occurrence (of promoting a request chain
+		 * that crosses the engines using semaphores back unto itself)
+		 * should be unlikely enough that it probably does not matter...
+		 */
+		local_bh_disable();
+		i915_request_set_priority(rq, prio);
+		local_bh_enable();
+
+		i915_request_put(rq);
+		rq = ptr_mask_bits(rn, 1);
+	} while (rq);
+}
+
+void i915_sched_init_ipi(struct i915_sched_ipi *ipi)
+{
+	INIT_WORK(&ipi->work, ipi_schedule);
+	ipi->list = NULL;
+}
+
+static void __ipi_add(struct i915_request *rq)
+{
+#define STUB ((struct i915_request *)1)
+	struct intel_engine_cs *engine = READ_ONCE(rq->engine);
+	struct i915_request *first;
+
+	if (!i915_request_get_rcu(rq))
+		return;
+
+	/*
+	 * We only want to add the request once into the ipi.list (or else
+	 * the chain will be broken). The worker must be guaranteed to run
+	 * at least once for every call to ipi_add, but it is allowed to
+	 * coalesce multiple ipi_add into a single pass using the final
+	 * property value.
+	 */
+	if (__i915_request_is_complete(rq) ||
+	    cmpxchg(&rq->sched.ipi_link, NULL, STUB)) { /* already queued */
+		i915_request_put(rq);
+		return;
+	}
+
+	/* Carefully insert ourselves into the head of the llist */
+	first = READ_ONCE(engine->execlists.ipi.list);
+	do {
+		rq->sched.ipi_link = ptr_pack_bits(first, 1, 1);
+	} while (!try_cmpxchg(&engine->execlists.ipi.list, &first, rq));
+
+	if (!first)
+		queue_work(system_unbound_wq, &engine->execlists.ipi.work);
+}
+
 static const struct i915_request *
 node_to_request(const struct i915_sched_node *node)
 {
 	return container_of(node, const struct i915_request, sched);
 }
 
-static inline bool node_started(const struct i915_sched_node *node)
-{
-	return i915_request_started(node_to_request(node));
-}
-
 static inline bool node_signaled(const struct i915_sched_node *node)
 {
 	return i915_request_completed(node_to_request(node));
@@ -137,42 +242,6 @@ void __i915_priolist_free(struct i915_priolist *p)
 	kmem_cache_free(global.slab_priorities, p);
 }
 
-struct sched_cache {
-	struct list_head *priolist;
-};
-
-static struct intel_engine_cs *
-sched_lock_engine(const struct i915_sched_node *node,
-		  struct intel_engine_cs *locked,
-		  struct sched_cache *cache)
-{
-	const struct i915_request *rq = node_to_request(node);
-	struct intel_engine_cs *engine;
-
-	GEM_BUG_ON(!locked);
-
-	/*
-	 * Virtual engines complicate acquiring the engine timeline lock,
-	 * as their rq->engine pointer is not stable until under that
-	 * engine lock. The simple ploy we use is to take the lock then
-	 * check that the rq still belongs to the newly locked engine.
-	 */
-	while (locked != (engine = READ_ONCE(rq->engine))) {
-		spin_unlock(&locked->active.lock);
-		memset(cache, 0, sizeof(*cache));
-		spin_lock(&engine->active.lock);
-		locked = engine;
-	}
-
-	GEM_BUG_ON(locked != engine);
-	return locked;
-}
-
-static inline int rq_prio(const struct i915_request *rq)
-{
-	return rq->sched.attr.priority;
-}
-
 static inline bool need_preempt(int prio, int active)
 {
 	/*
@@ -198,19 +267,17 @@ static void kick_submission(struct intel_engine_cs *engine,
 	if (prio <= engine->execlists.queue_priority_hint)
 		return;
 
-	rcu_read_lock();
-
 	/* Nothing currently active? We're overdue for a submission! */
 	inflight = execlists_active(&engine->execlists);
 	if (!inflight)
-		goto unlock;
+		return;
 
 	/*
 	 * If we are already the currently executing context, don't
 	 * bother evaluating if we should preempt ourselves.
 	 */
 	if (inflight->context == rq->context)
-		goto unlock;
+		return;
 
 	ENGINE_TRACE(engine,
 		     "bumping queue-priority-hint:%d for rq:%llx:%lld, inflight:%llx:%lld prio %d\n",
@@ -222,30 +289,28 @@ static void kick_submission(struct intel_engine_cs *engine,
 	engine->execlists.queue_priority_hint = prio;
 	if (need_preempt(prio, rq_prio(inflight)))
 		tasklet_hi_schedule(&engine->execlists.tasklet);
-
-unlock:
-	rcu_read_unlock();
 }
 
-static void __i915_schedule(struct i915_sched_node *node, int prio)
+static void ipi_priority(struct i915_request *rq, int prio)
 {
-	struct intel_engine_cs *engine;
-	struct i915_dependency *dep, *p;
-	struct i915_dependency stack;
-	struct sched_cache cache;
+	int old = READ_ONCE(rq->sched.ipi_priority);
+
+	do {
+		if (prio <= old)
+			return;
+	} while (!try_cmpxchg(&rq->sched.ipi_priority, &old, prio));
+
+	__ipi_add(rq);
+}
+
+static void __i915_request_set_priority(struct i915_request *rq, int prio)
+{
+	struct intel_engine_cs *engine = rq->engine;
+	struct i915_request *rn;
+	struct list_head *plist;
 	LIST_HEAD(dfs);
 
-	/* Needed in order to use the temporary link inside i915_dependency */
-	lockdep_assert_held(&schedule_lock);
-	GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
-
-	if (node_signaled(node))
-		return;
-
-	prio = max(prio, node->attr.priority);
-
-	stack.signaler = node;
-	list_add(&stack.dfs_link, &dfs);
+	list_add(&rq->sched.dfs, &dfs);
 
 	/*
 	 * Recursively bump all dependent priorities to match the new request.
@@ -265,66 +330,41 @@ static void __i915_schedule(struct i915_sched_node *node, int prio)
 	 * end result is a topological list of requests in reverse order, the
 	 * last element in the list is the request we must execute first.
 	 */
-	list_for_each_entry(dep, &dfs, dfs_link) {
-		struct i915_sched_node *node = dep->signaler;
+	list_for_each_entry(rq, &dfs, sched.dfs) {
+		struct i915_dependency *p;
 
-		/* If we are already flying, we know we have no signalers */
-		if (node_started(node))
-			continue;
+		/* Also release any children on this engine that are ready */
+		GEM_BUG_ON(rq->engine != engine);
 
-		/*
-		 * Within an engine, there can be no cycle, but we may
-		 * refer to the same dependency chain multiple times
-		 * (redundant dependencies are not eliminated) and across
-		 * engines.
-		 */
-		list_for_each_entry(p, &node->signalers_list, signal_link) {
-			GEM_BUG_ON(p == dep); /* no cycles! */
+		for_each_signaler(p, rq) {
+			struct i915_request *s =
+				container_of(p->signaler, typeof(*s), sched);
 
-			if (node_signaled(p->signaler))
+			GEM_BUG_ON(s == rq);
+
+			if (rq_prio(s) >= prio)
 				continue;
 
-			if (prio > READ_ONCE(p->signaler->attr.priority))
-				list_move_tail(&p->dfs_link, &dfs);
+			if (__i915_request_is_complete(s))
+				continue;
+
+			if (s->engine != rq->engine) {
+				ipi_priority(s, prio);
+				continue;
+			}
+
+			list_move_tail(&s->sched.dfs, &dfs);
 		}
 	}
 
-	/*
-	 * If we didn't need to bump any existing priorities, and we haven't
-	 * yet submitted this request (i.e. there is no potential race with
-	 * execlists_submit_request()), we can set our own priority and skip
-	 * acquiring the engine locks.
-	 */
-	if (node->attr.priority == I915_PRIORITY_INVALID) {
-		GEM_BUG_ON(!list_empty(&node->link));
-		node->attr.priority = prio;
+	plist = i915_sched_lookup_priolist(engine, prio);
 
-		if (stack.dfs_link.next == stack.dfs_link.prev)
-			return;
+	/* Fifo and depth-first replacement ensure our deps execute first */
+	list_for_each_entry_safe_reverse(rq, rn, &dfs, sched.dfs) {
+		GEM_BUG_ON(rq->engine != engine);
 
-		__list_del_entry(&stack.dfs_link);
-	}
-
-	memset(&cache, 0, sizeof(cache));
-	engine = node_to_request(node)->engine;
-	spin_lock(&engine->active.lock);
-
-	/* Fifo and depth-first replacement ensure our deps execute before us */
-	engine = sched_lock_engine(node, engine, &cache);
-	list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {
-		INIT_LIST_HEAD(&dep->dfs_link);
-
-		node = dep->signaler;
-		engine = sched_lock_engine(node, engine, &cache);
-		lockdep_assert_held(&engine->active.lock);
-
-		/* Recheck after acquiring the engine->timeline.lock */
-		if (prio <= node->attr.priority || node_signaled(node))
-			continue;
-
-		GEM_BUG_ON(node_to_request(node)->engine != engine);
-
-		WRITE_ONCE(node->attr.priority, prio);
+		INIT_LIST_HEAD(&rq->sched.dfs);
+		WRITE_ONCE(rq->sched.attr.priority, prio);
 
 		/*
 		 * Once the request is ready, it will be placed into the
@@ -334,32 +374,79 @@ static void __i915_schedule(struct i915_sched_node *node, int prio)
 		 * any preemption required, be dealt with upon submission.
 		 * See engine->submit_request()
 		 */
-		if (list_empty(&node->link))
+		if (!i915_request_is_ready(rq))
 			continue;
 
-		if (i915_request_in_priority_queue(node_to_request(node))) {
-			if (!cache.priolist)
-				cache.priolist =
-					i915_sched_lookup_priolist(engine,
-								   prio);
-			list_move_tail(&node->link, cache.priolist);
-		}
+		if (i915_request_in_priority_queue(rq))
+			list_move_tail(&rq->sched.link, plist);
 
-		/* Defer (tasklet) submission until after all of our updates. */
-		kick_submission(engine, node_to_request(node), prio);
+		/* Defer (tasklet) submission until after all updates. */
+		kick_submission(engine, rq, prio);
 	}
-
-	spin_unlock(&engine->active.lock);
 }
 
+#define all_signalers_checked(p, rq) \
+	list_entry_is_head(p, &(rq)->sched.signalers_list, signal_link)
+
 void i915_request_set_priority(struct i915_request *rq, int prio)
 {
-	if (!i915_request_use_scheduler(rq))
+	struct intel_engine_cs *engine;
+	unsigned long flags;
+
+	if (prio <= rq_prio(rq))
 		return;
 
-	spin_lock_irq(&schedule_lock);
-	__i915_schedule(&rq->sched, prio);
-	spin_unlock_irq(&schedule_lock);
+	/*
+	 * If we are setting the priority before being submitted, see if we
+	 * can quickly adjust our own priority in-situ and avoid taking
+	 * the contended engine->active.lock. If we need priority inheritance,
+	 * take the slow route.
+	 */
+	if (rq_prio(rq) == I915_PRIORITY_INVALID) {
+		struct i915_dependency *p;
+
+		rcu_read_lock();
+		for_each_signaler(p, rq) {
+			struct i915_request *s =
+				container_of(p->signaler, typeof(*s), sched);
+
+			if (rq_prio(s) >= prio)
+				continue;
+
+			if (__i915_request_is_complete(s))
+				continue;
+
+			break;
+		}
+		rcu_read_unlock();
+
+		/* Update priority in place if no PI required */
+		if (all_signalers_checked(p, rq) &&
+		    cmpxchg(&rq->sched.attr.priority,
+			    I915_PRIORITY_INVALID,
+			    prio) == I915_PRIORITY_INVALID)
+			return;
+	}
+
+	engine = lock_engine_irqsave(rq, flags);
+	if (prio <= rq_prio(rq))
+		goto unlock;
+
+	if (__i915_request_is_complete(rq))
+		goto unlock;
+
+	if (!intel_engine_has_scheduler(engine)) {
+		rq->sched.attr.priority = prio;
+		goto unlock;
+	}
+
+	rcu_read_lock();
+	__i915_request_set_priority(rq, prio);
+	rcu_read_unlock();
+	GEM_BUG_ON(rq_prio(rq) != prio);
+
+unlock:
+	spin_unlock_irqrestore(&engine->active.lock, flags);
 }
 
 void i915_sched_node_init(struct i915_sched_node *node)
@@ -369,6 +456,9 @@ void i915_sched_node_init(struct i915_sched_node *node)
 	INIT_LIST_HEAD(&node->signalers_list);
 	INIT_LIST_HEAD(&node->waiters_list);
 	INIT_LIST_HEAD(&node->link);
+	INIT_LIST_HEAD(&node->dfs);
+
+	node->ipi_link = NULL;
 
 	i915_sched_node_reinit(node);
 }
@@ -379,6 +469,9 @@ void i915_sched_node_reinit(struct i915_sched_node *node)
 	node->semaphores = 0;
 	node->flags = 0;
 
+	GEM_BUG_ON(node->ipi_link);
+	node->ipi_priority = I915_PRIORITY_INVALID;
+
 	GEM_BUG_ON(!list_empty(&node->signalers_list));
 	GEM_BUG_ON(!list_empty(&node->waiters_list));
 	GEM_BUG_ON(!list_empty(&node->link));
@@ -414,7 +507,6 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
 	spin_lock(&signal->lock);
 
 	if (!node_signaled(signal)) {
-		INIT_LIST_HEAD(&dep->dfs_link);
 		dep->signaler = signal;
 		dep->waiter = node_get(node);
 		dep->flags = flags;
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index a045be784c67..2870fa3e089e 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -14,6 +14,7 @@
 #include "i915_scheduler_types.h"
 
 struct drm_printer;
+struct intel_engine_cs;
 
 #define priolist_for_each_request(it, plist) \
 	list_for_each_entry(it, &(plist)->requests, sched.link)
@@ -35,6 +36,8 @@ int i915_sched_node_add_dependency(struct i915_sched_node *node,
 
 void i915_sched_node_retire(struct i915_sched_node *node);
 
+void i915_sched_init_ipi(struct i915_sched_ipi *ipi);
+
 void i915_request_set_priority(struct i915_request *request, int prio);
 
 struct list_head *
diff --git a/drivers/gpu/drm/i915/i915_scheduler_types.h b/drivers/gpu/drm/i915/i915_scheduler_types.h
index 623bf41fcf35..2a5265d9aff1 100644
--- a/drivers/gpu/drm/i915/i915_scheduler_types.h
+++ b/drivers/gpu/drm/i915/i915_scheduler_types.h
@@ -8,13 +8,17 @@
 #define _I915_SCHEDULER_TYPES_H_
 
 #include <linux/list.h>
+#include <linux/workqueue.h>
 
-#include "gt/intel_engine_types.h"
 #include "i915_priolist_types.h"
 
-struct drm_i915_private;
 struct i915_request;
-struct intel_engine_cs;
+
+/* Inter-engine scheduling delegation */
+struct i915_sched_ipi {
+	struct i915_request *list;
+	struct work_struct work;
+};
 
 struct i915_sched_attr {
 	/**
@@ -61,13 +65,19 @@ struct i915_sched_attr {
  */
 struct i915_sched_node {
 	spinlock_t lock; /* protect the lists */
+
 	struct list_head signalers_list; /* those before us, we depend upon */
 	struct list_head waiters_list; /* those after us, they depend upon us */
-	struct list_head link;
+	struct list_head link; /* guarded by engine->active.lock */
+	struct list_head dfs; /* guarded by engine->active.lock */
 	struct i915_sched_attr attr;
-	unsigned int flags;
+	unsigned long flags;
 #define I915_SCHED_HAS_EXTERNAL_CHAIN	BIT(0)
-	intel_engine_mask_t semaphores;
+	unsigned long semaphores;
+
+	/* handle being scheduled for PI from outside of our active.lock */
+	struct i915_request *ipi_link;
+	int ipi_priority;
 };
 
 struct i915_dependency {
@@ -75,7 +85,6 @@ struct i915_dependency {
 	struct i915_sched_node *waiter;
 	struct list_head signal_link;
 	struct list_head wait_link;
-	struct list_head dfs_link;
 	struct rcu_head rcu;
 	unsigned long flags;
 #define I915_DEPENDENCY_ALLOC		BIT(0)
