diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index a2c2c3ab5fb0ce..ebd71b487220ae 100644
--- a/drivers/gpu/drm/i915/i915_timeline.h
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -83,6 +83,25 @@ void i915_timeline_init(struct drm_i915_private *i915,
 			const char *name);
 void i915_timeline_fini(struct i915_timeline *tl);
 
+static inline void
+i915_timeline_set_subclass(struct i915_timeline *timeline,
+			   unsigned int subclass)
+{
+	lockdep_set_subclass(&timeline->lock, subclass);
+
+	/*
+	 * Due to an interesting quirk in lockdep's internal debug tracking,
+	 * after setting a subclass we must ensure the lock is used. Otherwise,
+	 * nr_unused_locks is incremented once too often.
+	 */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	local_irq_disable();
+	lock_map_acquire(&timeline->lock.dep_map);
+	lock_map_release(&timeline->lock.dep_map);
+	local_irq_enable();
+#endif
+}
+
 struct i915_timeline *
 i915_timeline_create(struct drm_i915_private *i915, const char *name);
 
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index bc147d9e6c9227..885a901b6e1337 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -485,7 +485,7 @@ static void intel_engine_init_execlist(struct intel_engine_cs *engine)
 void intel_engine_setup_common(struct intel_engine_cs *engine)
 {
 	i915_timeline_init(engine->i915, &engine->timeline, engine->name);
-	lockdep_set_subclass(&engine->timeline.lock, TIMELINE_ENGINE);
+	i915_timeline_set_subclass(&engine->timeline, TIMELINE_ENGINE);
 
 	intel_engine_init_execlist(engine);
 	intel_engine_init_hangcheck(engine);
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index 22a73da45ad58b..d0c44c18db429c 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -200,7 +200,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 	engine->base.submit_request = mock_submit_request;
 
 	i915_timeline_init(i915, &engine->base.timeline, engine->base.name);
-	lockdep_set_subclass(&engine->base.timeline.lock, TIMELINE_ENGINE);
+	i915_timeline_set_subclass(&engine->base.timeline, TIMELINE_ENGINE);
 
 	intel_engine_init_breadcrumbs(&engine->base);
 	engine->base.breadcrumbs.mock = true; /* prevent touching HW for irqs */