drm/scheduler: add documentation

convert existing raw comments into kernel-doc format as well
as add new documentation

v2: reword the overview
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Nayan Deshmukh <nayan26deshmukh@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>

include/drm/gpu_scheduler.h

@@ -43,13 +43,33 @@ enum drm_sched_priority {
 };
 
 /**
- * drm_sched_entity - A wrapper around a job queue (typically attached
- * to the DRM file_priv).
+ * struct drm_sched_entity - A wrapper around a job queue (typically
+ * attached to the DRM file_priv).
+ *
+ * @list: used to append this struct to the list of entities in the
+ *        runqueue.
+ * @rq: runqueue to which this entity belongs.
+ * @rq_lock: lock to modify the runqueue to which this entity belongs.
+ * @sched: the scheduler instance to which this entity is enqueued.
+ * @job_queue: the list of jobs of this entity.
+ * @fence_seq: a linearly increasing seqno incremented with each
+ *             new &drm_sched_fence which is part of the entity.
+ * @fence_context: a unique context for all the fences which belong
+ *                 to this entity.
+ *                 The &drm_sched_fence.scheduled uses the
+ *                 fence_context but &drm_sched_fence.finished uses
+ *                 fence_context + 1.
+ * @dependency: the dependency fence of the job which is on the top
+ *              of the job queue.
+ * @cb: callback for the dependency fence above.
+ * @guilty: points to ctx's guilty.
+ * @fini_status: contains the exit status in case the process was signalled.
+ * @last_scheduled: points to the finished fence of the last scheduled job.
  *
  * Entities will emit jobs in order to their corresponding hardware
  * ring, and the scheduler will alternate between entities based on
  * scheduling policy.
-*/
+ */
 struct drm_sched_entity {
 	struct list_head		list;
 	struct drm_sched_rq		*rq;
@@ -63,27 +83,41 @@ struct drm_sched_entity {
 
 	struct dma_fence		*dependency;
 	struct dma_fence_cb		cb;
-	atomic_t			*guilty; /* points to ctx's guilty */
+	atomic_t			*guilty;
 	int                             fini_status;
 	struct dma_fence                *last_scheduled;
 };
 
 /**
+ * struct drm_sched_rq - queue of entities to be scheduled.
+ *
+ * @lock: to modify the entities list.
+ * @entities: list of the entities to be scheduled.
+ * @current_entity: the entity which is to be scheduled.
+ *
  * Run queue is a set of entities scheduling command submissions for
  * one specific ring. It implements the scheduling policy that selects
  * the next entity to emit commands from.
-*/
+ */
 struct drm_sched_rq {
 	spinlock_t			lock;
 	struct list_head		entities;
 	struct drm_sched_entity		*current_entity;
 };
 
+/**
+ * struct drm_sched_fence - fences corresponding to the scheduling of a job.
+ */
 struct drm_sched_fence {
+        /**
+         * @scheduled: this fence is what will be signaled by the scheduler
+         * when the job is scheduled.
+         */
 	struct dma_fence		scheduled;
 
-	/* This fence is what will be signaled by the scheduler when
-	 * the job is completed.
+        /**
+         * @finished: this fence is what will be signaled by the scheduler
+         * when the job is completed.
          *
          * When setting up an out fence for the job, you should use
          * this, since it's available immediately upon
@@ -93,17 +127,52 @@ struct drm_sched_fence {
          */
 	struct dma_fence		finished;
 
+        /**
+         * @cb: the callback for the parent fence below.
+         */
 	struct dma_fence_cb		cb;
+        /**
+         * @parent: the fence returned by &drm_sched_backend_ops.run_job
+         * when scheduling the job on hardware. We signal the
+         * &drm_sched_fence.finished fence once parent is signalled.
+         */
 	struct dma_fence		*parent;
+        /**
+         * @sched: the scheduler instance to which the job having this struct
+         * belongs to.
+         */
 	struct drm_gpu_scheduler	*sched;
+        /**
+         * @lock: the lock used by the scheduled and the finished fences.
+         */
 	spinlock_t			lock;
+        /**
+         * @owner: job owner for debugging
+         */
 	void				*owner;
 };
 
 struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
 
 /**
- * drm_sched_job - A job to be run by an entity.
+ * struct drm_sched_job - A job to be run by an entity.
+ *
+ * @queue_node: used to append this struct to the queue of jobs in an entity.
+ * @sched: the scheduler instance on which this job is scheduled.
+ * @s_fence: contains the fences for the scheduling of job.
+ * @finish_cb: the callback for the finished fence.
+ * @finish_work: schedules the function @drm_sched_job_finish once the job has
+ *               finished to remove the job from the
+ *               @drm_gpu_scheduler.ring_mirror_list.
+ * @node: used to append this struct to the @drm_gpu_scheduler.ring_mirror_list.
+ * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the timeout
+ *            interval is over.
+ * @id: a unique id assigned to each job scheduled on the scheduler.
+ * @karma: increment on every hang caused by this job. If this exceeds the hang
+ *         limit of the scheduler then the job is marked guilty and will not
+ *         be scheduled further.
+ * @s_priority: the priority of the job.
+ * @entity: the entity to which this job belongs.
  *
  * A job is created by the driver using drm_sched_job_init(), and
  * should call drm_sched_entity_push_job() once it wants the scheduler
@@ -130,38 +199,64 @@ static inline bool drm_sched_invalidate_job(struct drm_sched_job *s_job,
 }
 
 /**
+ * struct drm_sched_backend_ops
+ *
  * Define the backend operations called by the scheduler,
- * these functions should be implemented in driver side
-*/
+ * these functions should be implemented in driver side.
+ */
 struct drm_sched_backend_ops {
-	/* Called when the scheduler is considering scheduling this
-	 * job next, to get another struct dma_fence for this job to
+	/**
+         * @dependency: Called when the scheduler is considering scheduling
+         * this job next, to get another struct dma_fence for this job to
 	 * block on.  Once it returns NULL, run_job() may be called.
 	 */
 	struct dma_fence *(*dependency)(struct drm_sched_job *sched_job,
 					struct drm_sched_entity *s_entity);
 
-	/* Called to execute the job once all of the dependencies have
-	 * been resolved.  This may be called multiple times, if
+	/**
+         * @run_job: Called to execute the job once all of the dependencies
+         * have been resolved.  This may be called multiple times, if
 	 * timedout_job() has happened and drm_sched_job_recovery()
 	 * decides to try it again.
 	 */
 	struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
 
-	/* Called when a job has taken too long to execute, to trigger
-	 * GPU recovery.
+	/**
+         * @timedout_job: Called when a job has taken too long to execute,
+         * to trigger GPU recovery.
 	 */
 	void (*timedout_job)(struct drm_sched_job *sched_job);
 
-	/* Called once the job's finished fence has been signaled and
-	 * it's time to clean it up.
+	/**
+         * @free_job: Called once the job's finished fence has been signaled
+         * and it's time to clean it up.
 	 */
 	void (*free_job)(struct drm_sched_job *sched_job);
 };
 
 /**
- * One scheduler is implemented for each hardware ring
-*/
+ * struct drm_gpu_scheduler
+ *
+ * @ops: backend operations provided by the driver.
+ * @hw_submission_limit: the max size of the hardware queue.
+ * @timeout: the time after which a job is removed from the scheduler.
+ * @name: name of the ring for which this scheduler is being used.
+ * @sched_rq: priority wise array of run queues.
+ * @wake_up_worker: the wait queue on which the scheduler sleeps until a job
+ *                  is ready to be scheduled.
+ * @job_scheduled: once @drm_sched_entity_do_release is called the scheduler
+ *                 waits on this wait queue until all the scheduled jobs are
+ *                 finished.
+ * @hw_rq_count: the number of jobs currently in the hardware queue.
+ * @job_id_count: used to assign unique id to the each job.
+ * @thread: the kthread on which the scheduler which run.
+ * @ring_mirror_list: the list of jobs which are currently in the job queue.
+ * @job_list_lock: lock to protect the ring_mirror_list.
+ * @hang_limit: once the hangs by a job crosses this limit then it is marked
+ *              guilty and it will be considered for scheduling further.
+ *
+ * One scheduler is implemented for each hardware ring.
+ */
 struct drm_gpu_scheduler {
 	const struct drm_sched_backend_ops	*ops;
 	uint32_t			hw_submission_limit;