1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index a2c2c3ab5fb0..ebd71b487220 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);