[PATCH 6/7] drm/i915: Priority boost for waiting clients

[Chris Wilson]

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_request.c   |  1 +
 drivers/gpu/drm/i915/i915_scheduler.c | 34 ++++++++++++++++++++++-----
 drivers/gpu/drm/i915/i915_scheduler.h |  5 +++-
 3 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index e33cdd95bdc3..1a211e7b662f 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1289,6 +1289,7 @@ long i915_request_wait(struct i915_request *rq,
 		add_wait_queue(errq, &reset);
 
 	intel_wait_init(&wait);
+	i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT);
 
 restart:
 	do {
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 749a192b4628..2da651db5029 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -239,7 +239,8 @@ sched_lock_engine(struct i915_sched_node *node, struct intel_engine_cs *locked)
 	return engine;
 }
 
-void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+static void __i915_schedule(struct i915_request *rq,
+			    const struct i915_sched_attr *attr)
 {
 	struct list_head *uninitialized_var(pl);
 	struct intel_engine_cs *engine, *last;
@@ -248,6 +249,8 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
 	const int prio = attr->priority;
 	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 (i915_request_completed(rq))
@@ -256,9 +259,6 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
 	if (prio <= READ_ONCE(rq->sched.attr.priority))
 		return;
 
-	/* Needed in order to use the temporary link inside i915_dependency */
-	spin_lock(&schedule_lock);
-
 	stack.signaler = &rq->sched;
 	list_add(&stack.dfs_link, &dfs);
 
@@ -312,7 +312,7 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
 		rq->sched.attr = *attr;
 
 		if (stack.dfs_link.next == stack.dfs_link.prev)
-			goto out_unlock;
+			return;
 
 		__list_del_entry(&stack.dfs_link);
 	}
@@ -350,7 +350,29 @@ void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
 	}
 
 	spin_unlock_irq(&engine->timeline.lock);
+}
 
-out_unlock:
+void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+{
+	spin_lock(&schedule_lock);
+	__i915_schedule(rq, attr);
 	spin_unlock(&schedule_lock);
 }
+
+void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump)
+{
+	struct i915_sched_attr attr;
+
+	GEM_BUG_ON(bump & I915_PRIORITY_MASK);
+
+	if (READ_ONCE(rq->sched.attr.priority) == I915_PRIORITY_INVALID)
+		return;
+
+	spin_lock_bh(&schedule_lock);
+
+	attr = rq->sched.attr;
+	attr.priority |= bump;
+	__i915_schedule(rq, &attr);
+
+	spin_unlock_bh(&schedule_lock);
+}
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index 9b21ff72f619..e5120ef974d4 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -24,12 +24,13 @@ enum {
 	I915_PRIORITY_INVALID = INT_MIN
 };
 
-#define I915_USER_PRIORITY_SHIFT 1
+#define I915_USER_PRIORITY_SHIFT 2
 #define I915_USER_PRIORITY(x) ((x) << I915_USER_PRIORITY_SHIFT)
 
 #define I915_PRIORITY_COUNT BIT(I915_USER_PRIORITY_SHIFT)
 #define I915_PRIORITY_MASK (-I915_PRIORITY_COUNT)
 
+#define I915_PRIORITY_WAIT BIT(1)
 #define I915_PRIORITY_NEWCLIENT BIT(0)
 
 struct i915_sched_attr {
@@ -99,6 +100,8 @@ void i915_sched_node_fini(struct drm_i915_private *i915,
 void i915_schedule(struct i915_request *request,
 		   const struct i915_sched_attr *attr);
 
+void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump);
+
 struct list_head *
 i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio);
 
-- 
2.18.0