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drm/scheduler: add documentation

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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>
This commit is contained in:
Nayan Deshmukh 2018-05-29 11:23:07 +05:30 committed by Alex Deucher
parent fe78627d43
commit 2d33948e4e
2 changed files with 296 additions and 71 deletions
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214
drivers/gpu/drm/scheduler/gpu_scheduler.c
View File

@ -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 The pointer to the scheduler
* @sched: scheduler instance
*
* Tears down and cleans up the scheduler.
*/
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{

153
include/drm/gpu_scheduler.h
View File

@ -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;