[RFC 22/23] drm/sched: Add helper for DRM cgroup controller weight notifications

[Tvrtko Ursulin]

To enable drivers which use the scheduler to easily connect with the DRM
cgroup controller we a add a helper to be used for registering for
scheduling weight notifications.

The scheduler itself straightforwardly "connects" with the concept of
scheduling weights, courtesy of the vruntime based design, where we can
trivially scale the runtime to vruntime factor by the scheduling weight on
top of the existing priority scaling.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
---
 drivers/gpu/drm/scheduler/sched_entity.c   | 16 ++++++++++++++++
 drivers/gpu/drm/scheduler/sched_internal.h | 12 +++++++++---
 include/drm/gpu_scheduler.h                |  7 +++++++
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 8729d3068449..4caf8c17090e 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -627,4 +627,20 @@ void drm_sched_cgroup_untrack_sched_entity(struct drm_file *file_priv,
 	spin_unlock(&file_priv->sched_entities.lock);
 }
 EXPORT_SYMBOL(drm_sched_cgroup_untrack_sched_entity);
+
+void drm_sched_cgroup_notify_weight(struct drm_file *file_priv,
+				    unsigned int weight)
+{
+	struct drm_sched_entity *entity;
+
+	spin_lock(&file_priv->sched_entities.lock);
+	list_for_each_entry(entity, &file_priv->sched_entities.list,
+			    drm_file_link) {
+		spin_lock(&entity->lock);
+		entity->cgroup_weight = weight;
+		spin_unlock(&entity->lock);
+	}
+	spin_unlock(&file_priv->sched_entities.lock);
+}
+EXPORT_SYMBOL(drm_sched_cgroup_notify_weight);
 #endif
diff --git a/drivers/gpu/drm/scheduler/sched_internal.h b/drivers/gpu/drm/scheduler/sched_internal.h
index 8d4bfe499b84..0310df87cb3c 100644
--- a/drivers/gpu/drm/scheduler/sched_internal.h
+++ b/drivers/gpu/drm/scheduler/sched_internal.h
@@ -3,6 +3,7 @@
 #ifndef _DRM_GPU_SCHEDULER_INTERNAL_H_
 #define _DRM_GPU_SCHEDULER_INTERNAL_H_
 
+#include <linux/cgroup_drm.h>
 #include <linux/ktime.h>
 #include <linux/kref.h>
 #include <linux/spinlock.h>
@@ -168,14 +169,19 @@ drm_sched_entity_update_vruntime(struct drm_sched_entity *entity)
 	};
 	struct drm_sched_entity_stats *stats = entity->stats;
 	ktime_t runtime, prev;
+	u64 runtime_ns;
 
 	spin_lock(&stats->lock);
 	prev = stats->prev_runtime;
 	runtime = stats->runtime;
 	stats->prev_runtime = runtime;
-	runtime = ktime_add_ns(stats->vruntime,
-			       ktime_to_ns(ktime_sub(runtime, prev)) <<
-			       shift[entity->priority]);
+	runtime_ns = ktime_to_ns(ktime_sub(runtime, prev)) <<
+		     shift[entity->priority];
+#if IS_ENABLED(CONFIG_CGROUP_DRM)
+	runtime_ns *= ((1 << DRM_CGROUP_WEIGHT_SHIFT) - entity->cgroup_weight);
+	runtime_ns >>= DRM_CGROUP_WEIGHT_SHIFT;
+#endif
+	runtime = ktime_add_ns(stats->vruntime, runtime_ns);
 	stats->vruntime = runtime;
 	spin_unlock(&stats->lock);
 
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index efd00059a814..292d9e03f055 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -146,6 +146,10 @@ struct drm_sched_entity {
 	 */
 	enum drm_sched_priority         priority;
 
+#if IS_ENABLED(CONFIG_CGROUP_DRM)
+	unsigned int			cgroup_weight;
+#endif
+
 	/**
 	 * @job_queue: the list of jobs of this entity.
 	 */
@@ -685,6 +689,9 @@ void drm_sched_cgroup_track_sched_entity(struct drm_file *file_priv,
 				  struct drm_sched_entity *entity);
 void drm_sched_cgroup_untrack_sched_entity(struct drm_file *file_priv,
 				    struct drm_sched_entity *entity);
+
+void drm_sched_cgroup_notify_weight(struct drm_file *file_priv,
+				    unsigned int weight);
 #else
 static inline void drm_sched_cgroup_init_drm_file(struct drm_file *file_priv)
 {
-- 
2.48.0