[PATCH v2] drm/scheduler: add documentation

Christian König christian.koenig at amd.com
Tue May 29 06:38:09 UTC 2018


Am 29.05.2018 um 07:53 schrieb Nayan Deshmukh:
> 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 at amd.com>
> Signed-off-by: Nayan Deshmukh <nayan26deshmukh at gmail.com>
> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

Reviewed-by: Christian König <christian.koenig at amd.com>

Going to push that into our branches later today,
Christian.

> ---
>   drivers/gpu/drm/scheduler/gpu_scheduler.c | 214 ++++++++++++++++++++++++------
>   include/drm/gpu_scheduler.h               | 153 +++++++++++++++++----
>   2 files changed, 296 insertions(+), 71 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> index 44d480768dfe..8c1e80c9b674 100644
> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> @@ -21,6 +21,29 @@
>    *
>    */
>   
> +/**
> + * DOC: Overview
> + *
> + * The GPU scheduler provides entities which allow userspace to push jobs
> + * into software queues which are then scheduled on a hardware run queue.
> + * The software queues have a priority among them. The scheduler selects the entities
> + * from the run queue using a FIFO. The scheduler provides dependency handling
> + * features among jobs. The driver is supposed to provide callback functions for
> + * backend operations to the scheduler like submitting a job to hardware run queue,
> + * returning the dependencies of a job etc.
> + *
> + * The organisation of the scheduler is the following:
> + *
> + * 1. Each hw run queue has one scheduler
> + * 2. Each scheduler has multiple run queues with different priorities
> + *    (e.g., HIGH_HW,HIGH_SW, KERNEL, NORMAL)
> + * 3. Each scheduler run queue has a queue of entities to schedule
> + * 4. Entities themselves maintain a queue of jobs that will be scheduled on
> + *    the hardware.
> + *
> + * The jobs in a entity are always scheduled in the order that they were pushed.
> + */
> +
>   #include <linux/kthread.h>
>   #include <linux/wait.h>
>   #include <linux/sched.h>
> @@ -39,7 +62,13 @@ static bool drm_sched_entity_is_ready(struct drm_sched_entity *entity);
>   static void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
>   static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb);
>   
> -/* Initialize a given run queue struct */
> +/**
> + * drm_sched_rq_init - initialize a given run queue struct
> + *
> + * @rq: scheduler run queue
> + *
> + * Initializes a scheduler runqueue.
> + */
>   static void drm_sched_rq_init(struct drm_sched_rq *rq)
>   {
>   	spin_lock_init(&rq->lock);
> @@ -47,6 +76,14 @@ static void drm_sched_rq_init(struct drm_sched_rq *rq)
>   	rq->current_entity = NULL;
>   }
>   
> +/**
> + * drm_sched_rq_add_entity - add an entity
> + *
> + * @rq: scheduler run queue
> + * @entity: scheduler entity
> + *
> + * Adds a scheduler entity to the run queue.
> + */
>   static void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
>   				    struct drm_sched_entity *entity)
>   {
> @@ -57,6 +94,14 @@ static void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
>   	spin_unlock(&rq->lock);
>   }
>   
> +/**
> + * drm_sched_rq_remove_entity - remove an entity
> + *
> + * @rq: scheduler run queue
> + * @entity: scheduler entity
> + *
> + * Removes a scheduler entity from the run queue.
> + */
>   static void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
>   				       struct drm_sched_entity *entity)
>   {
> @@ -70,9 +115,9 @@ static void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
>   }
>   
>   /**
> - * Select an entity which could provide a job to run
> + * drm_sched_rq_select_entity - Select an entity which could provide a job to run
>    *
> - * @rq		The run queue to check.
> + * @rq: scheduler run queue to check.
>    *
>    * Try to find a ready entity, returns NULL if none found.
>    */
> @@ -112,15 +157,16 @@ drm_sched_rq_select_entity(struct drm_sched_rq *rq)
>   }
>   
>   /**
> - * Init a context entity used by scheduler when submit to HW ring.
> + * drm_sched_entity_init - Init a context entity used by scheduler when
> + * submit to HW ring.
>    *
> - * @sched	The pointer to the scheduler
> - * @entity	The pointer to a valid drm_sched_entity
> - * @rq		The run queue this entity belongs
> - * @guilty      atomic_t set to 1 when a job on this queue
> - *              is found to be guilty causing a timeout
> + * @sched: scheduler instance
> + * @entity: scheduler entity to init
> + * @rq: the run queue this entity belongs
> + * @guilty: atomic_t set to 1 when a job on this queue
> + *          is found to be guilty causing a timeout
>    *
> - * return 0 if succeed. negative error code on failure
> + * Returns 0 on success or a negative error code on failure.
>   */
>   int drm_sched_entity_init(struct drm_gpu_scheduler *sched,
>   			  struct drm_sched_entity *entity,
> @@ -149,10 +195,10 @@ int drm_sched_entity_init(struct drm_gpu_scheduler *sched,
>   EXPORT_SYMBOL(drm_sched_entity_init);
>   
>   /**
> - * Query if entity is initialized
> + * drm_sched_entity_is_initialized - Query if entity is initialized
>    *
> - * @sched       Pointer to scheduler instance
> - * @entity	The pointer to a valid scheduler entity
> + * @sched: Pointer to scheduler instance
> + * @entity: The pointer to a valid scheduler entity
>    *
>    * return true if entity is initialized, false otherwise
>   */
> @@ -164,11 +210,11 @@ static bool drm_sched_entity_is_initialized(struct drm_gpu_scheduler *sched,
>   }
>   
>   /**
> - * Check if entity is idle
> + * drm_sched_entity_is_idle - Check if entity is idle
>    *
> - * @entity	The pointer to a valid scheduler entity
> + * @entity: scheduler entity
>    *
> - * Return true if entity don't has any unscheduled jobs.
> + * Returns true if the entity does not have any unscheduled jobs.
>    */
>   static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
>   {
> @@ -180,9 +226,9 @@ static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
>   }
>   
>   /**
> - * Check if entity is ready
> + * drm_sched_entity_is_ready - Check if entity is ready
>    *
> - * @entity	The pointer to a valid scheduler entity
> + * @entity: scheduler entity
>    *
>    * Return true if entity could provide a job.
>    */
> @@ -210,12 +256,12 @@ static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
>   
>   
>   /**
> - * Destroy a context entity
> + * drm_sched_entity_do_release - Destroy a context entity
>    *
> - * @sched       Pointer to scheduler instance
> - * @entity	The pointer to a valid scheduler entity
> + * @sched: scheduler instance
> + * @entity: scheduler entity
>    *
> - * Splitting drm_sched_entity_fini() into two functions, The first one is does the waiting,
> + * Splitting drm_sched_entity_fini() into two functions, The first one does the waiting,
>    * removes the entity from the runqueue and returns an error when the process was killed.
>    */
>   void drm_sched_entity_do_release(struct drm_gpu_scheduler *sched,
> @@ -237,12 +283,13 @@ void drm_sched_entity_do_release(struct drm_gpu_scheduler *sched,
>   EXPORT_SYMBOL(drm_sched_entity_do_release);
>   
>   /**
> - * Destroy a context entity
> + * drm_sched_entity_cleanup - Destroy a context entity
>    *
> - * @sched       Pointer to scheduler instance
> - * @entity	The pointer to a valid scheduler entity
> + * @sched: scheduler instance
> + * @entity: scheduler entity
>    *
> - * The second one then goes over the entity and signals all jobs with an error code.
> + * This should be called after @drm_sched_entity_do_release. It goes over the
> + * entity and signals all jobs with an error code if the process was killed.
>    */
>   void drm_sched_entity_cleanup(struct drm_gpu_scheduler *sched,
>   			   struct drm_sched_entity *entity)
> @@ -281,6 +328,14 @@ void drm_sched_entity_cleanup(struct drm_gpu_scheduler *sched,
>   }
>   EXPORT_SYMBOL(drm_sched_entity_cleanup);
>   
> +/**
> + * drm_sched_entity_fini - Destroy a context entity
> + *
> + * @sched: scheduler instance
> + * @entity: scheduler entity
> + *
> + * Calls drm_sched_entity_do_release() and drm_sched_entity_cleanup()
> + */
>   void drm_sched_entity_fini(struct drm_gpu_scheduler *sched,
>   				struct drm_sched_entity *entity)
>   {
> @@ -306,6 +361,15 @@ static void drm_sched_entity_clear_dep(struct dma_fence *f, struct dma_fence_cb
>   	dma_fence_put(f);
>   }
>   
> +/**
> + * drm_sched_entity_set_rq - Sets the run queue for an entity
> + *
> + * @entity: scheduler entity
> + * @rq: scheduler run queue
> + *
> + * Sets the run queue for an entity and removes the entity from the previous
> + * run queue in which was present.
> + */
>   void drm_sched_entity_set_rq(struct drm_sched_entity *entity,
>   			     struct drm_sched_rq *rq)
>   {
> @@ -325,6 +389,14 @@ void drm_sched_entity_set_rq(struct drm_sched_entity *entity,
>   }
>   EXPORT_SYMBOL(drm_sched_entity_set_rq);
>   
> +/**
> + * drm_sched_dependency_optimized
> + *
> + * @fence: the dependency fence
> + * @entity: the entity which depends on the above fence
> + *
> + * Returns true if the dependency can be optimized and false otherwise
> + */
>   bool drm_sched_dependency_optimized(struct dma_fence* fence,
>   				    struct drm_sched_entity *entity)
>   {
> @@ -413,9 +485,10 @@ drm_sched_entity_pop_job(struct drm_sched_entity *entity)
>   }
>   
>   /**
> - * Submit a job to the job queue
> + * drm_sched_entity_push_job - Submit a job to the entity's job queue
>    *
> - * @sched_job		The pointer to job required to submit
> + * @sched_job: job to submit
> + * @entity: scheduler entity
>    *
>    * Note: To guarantee that the order of insertion to queue matches
>    * the job's fence sequence number this function should be
> @@ -506,6 +579,13 @@ static void drm_sched_job_timedout(struct work_struct *work)
>   	job->sched->ops->timedout_job(job);
>   }
>   
> +/**
> + * drm_sched_hw_job_reset - stop the scheduler if it contains the bad job
> + *
> + * @sched: scheduler instance
> + * @bad: bad scheduler job
> + *
> + */
>   void drm_sched_hw_job_reset(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
>   {
>   	struct drm_sched_job *s_job;
> @@ -550,6 +630,12 @@ void drm_sched_hw_job_reset(struct drm_gpu_scheduler *sched, struct drm_sched_jo
>   }
>   EXPORT_SYMBOL(drm_sched_hw_job_reset);
>   
> +/**
> + * drm_sched_job_recovery - recover jobs after a reset
> + *
> + * @sched: scheduler instance
> + *
> + */
>   void drm_sched_job_recovery(struct drm_gpu_scheduler *sched)
>   {
>   	struct drm_sched_job *s_job, *tmp;
> @@ -599,10 +685,17 @@ void drm_sched_job_recovery(struct drm_gpu_scheduler *sched)
>   EXPORT_SYMBOL(drm_sched_job_recovery);
>   
>   /**
> - * Init a sched_job with basic field
> + * drm_sched_job_init - init a scheduler job
>    *
> - * Note: Refer to drm_sched_entity_push_job documentation
> + * @job: scheduler job to init
> + * @sched: scheduler instance
> + * @entity: scheduler entity to use
> + * @owner: job owner for debugging
> + *
> + * Refer to drm_sched_entity_push_job() documentation
>    * for locking considerations.
> + *
> + * Returns 0 for success, negative error code otherwise.
>    */
>   int drm_sched_job_init(struct drm_sched_job *job,
>   		       struct drm_gpu_scheduler *sched,
> @@ -626,7 +719,11 @@ int drm_sched_job_init(struct drm_sched_job *job,
>   EXPORT_SYMBOL(drm_sched_job_init);
>   
>   /**
> - * Return ture if we can push more jobs to the hw.
> + * drm_sched_ready - is the scheduler ready
> + *
> + * @sched: scheduler instance
> + *
> + * Return true if we can push more jobs to the hw, otherwise false.
>    */
>   static bool drm_sched_ready(struct drm_gpu_scheduler *sched)
>   {
> @@ -635,7 +732,10 @@ static bool drm_sched_ready(struct drm_gpu_scheduler *sched)
>   }
>   
>   /**
> - * Wake up the scheduler when it is ready
> + * drm_sched_wakeup - Wake up the scheduler when it is ready
> + *
> + * @sched: scheduler instance
> + *
>    */
>   static void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
>   {
> @@ -644,8 +744,12 @@ static void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
>   }
>   
>   /**
> - * Select next entity to process
> -*/
> + * drm_sched_select_entity - Select next entity to process
> + *
> + * @sched: scheduler instance
> + *
> + * Returns the entity to process or NULL if none are found.
> + */
>   static struct drm_sched_entity *
>   drm_sched_select_entity(struct drm_gpu_scheduler *sched)
>   {
> @@ -665,6 +769,14 @@ drm_sched_select_entity(struct drm_gpu_scheduler *sched)
>   	return entity;
>   }
>   
> +/**
> + * drm_sched_process_job - process a job
> + *
> + * @f: fence
> + * @cb: fence callbacks
> + *
> + * Called after job has finished execution.
> + */
>   static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
>   {
>   	struct drm_sched_fence *s_fence =
> @@ -680,6 +792,13 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
>   	wake_up_interruptible(&sched->wake_up_worker);
>   }
>   
> +/**
> + * drm_sched_blocked - check if the scheduler is blocked
> + *
> + * @sched: scheduler instance
> + *
> + * Returns true if blocked, otherwise false.
> + */
>   static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
>   {
>   	if (kthread_should_park()) {
> @@ -690,6 +809,13 @@ static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
>   	return false;
>   }
>   
> +/**
> + * drm_sched_main - main scheduler thread
> + *
> + * @param: scheduler instance
> + *
> + * Returns 0.
> + */
>   static int drm_sched_main(void *param)
>   {
>   	struct sched_param sparam = {.sched_priority = 1};
> @@ -744,15 +870,17 @@ static int drm_sched_main(void *param)
>   }
>   
>   /**
> - * Init a gpu scheduler instance
> + * drm_sched_init - Init a gpu scheduler instance
>    *
> - * @sched		The pointer to the scheduler
> - * @ops			The backend operations for this scheduler.
> - * @hw_submissions	Number of hw submissions to do.
> - * @name		Name used for debugging
> + * @sched: scheduler instance
> + * @ops: backend operations for this scheduler
> + * @hw_submission: number of hw submissions that can be in flight
> + * @hang_limit: number of times to allow a job to hang before dropping it
> + * @timeout: timeout value in jiffies for the scheduler
> + * @name: name used for debugging
>    *
>    * Return 0 on success, otherwise error code.
> -*/
> + */
>   int drm_sched_init(struct drm_gpu_scheduler *sched,
>   		   const struct drm_sched_backend_ops *ops,
>   		   unsigned hw_submission,
> @@ -788,9 +916,11 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
>   EXPORT_SYMBOL(drm_sched_init);
>   
>   /**
> - * Destroy a gpu scheduler
> + * drm_sched_fini - Destroy a gpu scheduler
> + *
> + * @sched: scheduler instance
>    *
> - * @sched	The pointer to the scheduler
> + * Tears down and cleans up the scheduler.
>    */
>   void drm_sched_fini(struct drm_gpu_scheduler *sched)
>   {
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index dec655894d08..496442f12bff 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/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;
> @@ -63,47 +83,96 @@ struct drm_sched_entity {
>   
>   	struct dma_fence		*dependency;
>   	struct dma_fence_cb		cb;
> -	atomic_t			*guilty; /* points to ctx's guilty */
> -	int            fini_status;
> -	struct dma_fence    *last_scheduled;
> +	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.
> -	 *
> -	 * When setting up an out fence for the job, you should use
> -	 * this, since it's available immediately upon
> -	 * drm_sched_job_init(), and the fence returned by the driver
> -	 * from run_job() won't be created until the dependencies have
> -	 * resolved.
> -	 */
> +        /**
> +         * @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
> +         * drm_sched_job_init(), and the fence returned by the driver
> +         * from run_job() won't be created until the dependencies have
> +         * resolved.
> +         */
>   	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;



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