/*
 * Copyright 2015 Advanced Micro Devices, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 */

/**
 * 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>
#include <linux/completion.h>
#include <uapi/linux/sched/types.h>

#include <drm/drm_print.h>
#include <drm/gpu_scheduler.h>
#include <drm/spsc_queue.h>

#define CREATE_TRACE_POINTS
#include "gpu_scheduler_trace.h"

#define to_drm_sched_job(sched_job)             \
                container_of((sched_job), struct drm_sched_job, queue_node)

static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb);

/**
 * 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_gpu_scheduler *sched,
                              struct drm_sched_rq *rq)
{
        spin_lock_init(&rq->lock);
        INIT_LIST_HEAD(&rq->entities);
        rq->current_entity = NULL;
        rq->sched = sched;
}

/**
 * drm_sched_rq_add_entity - add an entity
 *
 * @rq: scheduler run queue
 * @entity: scheduler entity
 *
 * Adds a scheduler entity to the run queue.
 */
void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
                             struct drm_sched_entity *entity)
{
        if (!list_empty(&entity->list))
                return;
        spin_lock(&rq->lock);
        atomic_inc(&rq->sched->score);
        list_add_tail(&entity->list, &rq->entities);
        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.
 */
void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
                                struct drm_sched_entity *entity)
{
        if (list_empty(&entity->list))
                return;
        spin_lock(&rq->lock);
        atomic_dec(&rq->sched->score);
        list_del_init(&entity->list);
        if (rq->current_entity == entity)
                rq->current_entity = NULL;
        spin_unlock(&rq->lock);
}

/**
 * drm_sched_rq_select_entity - Select an entity which could provide a job to run
 *
 * @rq: scheduler run queue to check.
 *
 * Try to find a ready entity, returns NULL if none found.
 */
static struct drm_sched_entity *
drm_sched_rq_select_entity(struct drm_sched_rq *rq)
{
        struct drm_sched_entity *entity;

        spin_lock(&rq->lock);

        entity = rq->current_entity;
        if (entity) {
                list_for_each_entry_continue(entity, &rq->entities, list) {
                        if (drm_sched_entity_is_ready(entity)) {
                                rq->current_entity = entity;
                                reinit_completion(&entity->entity_idle);
                                spin_unlock(&rq->lock);
                                return entity;
                        }
                }
        }

        list_for_each_entry(entity, &rq->entities, list) {

                if (drm_sched_entity_is_ready(entity)) {
                        rq->current_entity = entity;
                        reinit_completion(&entity->entity_idle);
                        spin_unlock(&rq->lock);
                        return entity;
                }

                if (entity == rq->current_entity)
                        break;
        }

        spin_unlock(&rq->lock);

        return NULL;
}

/**
 * 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)
{
        struct drm_gpu_scheduler *sched = entity->rq->sched;
        struct drm_sched_fence *s_fence;

        if (!fence || dma_fence_is_signaled(fence))
                return false;
        if (fence->context == entity->fence_context)
                return true;
        s_fence = to_drm_sched_fence(fence);
        if (s_fence && s_fence->sched == sched)
                return true;

        return false;
}
EXPORT_SYMBOL(drm_sched_dependency_optimized);

/**
 * drm_sched_start_timeout - start timeout for reset worker
 *
 * @sched: scheduler instance to start the worker for
 *
 * Start the timeout for the given scheduler.
 */
static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
{
        if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
            !list_empty(&sched->ring_mirror_list))
                schedule_delayed_work(&sched->work_tdr, sched->timeout);
}

/**
 * drm_sched_fault - immediately start timeout handler
 *
 * @sched: scheduler where the timeout handling should be started.
 *
 * Start timeout handling immediately when the driver detects a hardware fault.
 */
void drm_sched_fault(struct drm_gpu_scheduler *sched)
{
        mod_delayed_work(system_wq, &sched->work_tdr, 0);
}
EXPORT_SYMBOL(drm_sched_fault);

/**
 * drm_sched_suspend_timeout - Suspend scheduler job timeout
 *
 * @sched: scheduler instance for which to suspend the timeout
 *
 * Suspend the delayed work timeout for the scheduler. This is done by
 * modifying the delayed work timeout to an arbitrary large value,
 * MAX_SCHEDULE_TIMEOUT in this case.
 *
 * Returns the timeout remaining
 *
 */
unsigned long drm_sched_suspend_timeout(struct drm_gpu_scheduler *sched)
{
        unsigned long sched_timeout, now = jiffies;

        sched_timeout = sched->work_tdr.timer.expires;

        /*
         * Modify the timeout to an arbitrarily large value. This also prevents
         * the timeout to be restarted when new submissions arrive
         */
        if (mod_delayed_work(system_wq, &sched->work_tdr, MAX_SCHEDULE_TIMEOUT)
                        && time_after(sched_timeout, now))
                return sched_timeout - now;
        else
                return sched->timeout;
}
EXPORT_SYMBOL(drm_sched_suspend_timeout);

/**
 * drm_sched_resume_timeout - Resume scheduler job timeout
 *
 * @sched: scheduler instance for which to resume the timeout
 * @remaining: remaining timeout
 *
 * Resume the delayed work timeout for the scheduler.
 */
void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,
                unsigned long remaining)
{
        spin_lock(&sched->job_list_lock);

        if (list_empty(&sched->ring_mirror_list))
                cancel_delayed_work(&sched->work_tdr);
        else
                mod_delayed_work(system_wq, &sched->work_tdr, remaining);

        spin_unlock(&sched->job_list_lock);
}
EXPORT_SYMBOL(drm_sched_resume_timeout);

static void drm_sched_job_begin(struct drm_sched_job *s_job)
{
        struct drm_gpu_scheduler *sched = s_job->sched;

        spin_lock(&sched->job_list_lock);
        list_add_tail(&s_job->node, &sched->ring_mirror_list);
        drm_sched_start_timeout(sched);
        spin_unlock(&sched->job_list_lock);
}

static void drm_sched_job_timedout(struct work_struct *work)
{
        struct drm_gpu_scheduler *sched;
        struct drm_sched_job *job;

        sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);

        /* Protects against concurrent deletion in drm_sched_get_cleanup_job */
        spin_lock(&sched->job_list_lock);
        job = list_first_entry_or_null(&sched->ring_mirror_list,
                                       struct drm_sched_job, node);

        if (job) {
                /*
                 * Remove the bad job so it cannot be freed by concurrent
                 * drm_sched_cleanup_jobs. It will be reinserted back after sched->thread
                 * is parked at which point it's safe.
                 */
                list_del_init(&job->node);
                spin_unlock(&sched->job_list_lock);

                job->sched->ops->timedout_job(job);

                /*
                 * Guilty job did complete and hence needs to be manually removed
                 * See drm_sched_stop doc.
                 */
                if (sched->free_guilty) {
                        job->sched->ops->free_job(job);
                        sched->free_guilty = false;
                }
        } else {
                spin_unlock(&sched->job_list_lock);
        }

        spin_lock(&sched->job_list_lock);
        drm_sched_start_timeout(sched);
        spin_unlock(&sched->job_list_lock);
}

 /**
  * drm_sched_increase_karma - Update sched_entity guilty flag
  *
  * @bad: The job guilty of time out
  *
  * Increment on every hang caused by the 'bad' job. If this exceeds the hang
  * limit of the scheduler then the respective sched entity is marked guilty and
  * jobs from it will not be scheduled further
  */
void drm_sched_increase_karma(struct drm_sched_job *bad)
{
        int i;
        struct drm_sched_entity *tmp;
        struct drm_sched_entity *entity;
        struct drm_gpu_scheduler *sched = bad->sched;

        /* don't increase @bad's karma if it's from KERNEL RQ,
         * because sometimes GPU hang would cause kernel jobs (like VM updating jobs)
         * corrupt but keep in mind that kernel jobs always considered good.
         */
        if (bad->s_priority != DRM_SCHED_PRIORITY_KERNEL) {
                atomic_inc(&bad->karma);
                for (i = DRM_SCHED_PRIORITY_MIN; i < DRM_SCHED_PRIORITY_KERNEL;
                     i++) {
                        struct drm_sched_rq *rq = &sched->sched_rq[i];

                        spin_lock(&rq->lock);
                        list_for_each_entry_safe(entity, tmp, &rq->entities, list) {
                                if (bad->s_fence->scheduled.context ==
                                    entity->fence_context) {
                                        if (atomic_read(&bad->karma) >
                                            bad->sched->hang_limit)
                                                if (entity->guilty)
                                                        atomic_set(entity->guilty, 1);
                                        break;
                                }
                        }
                        spin_unlock(&rq->lock);
                        if (&entity->list != &rq->entities)
                                break;
                }
        }
}
EXPORT_SYMBOL(drm_sched_increase_karma);

/**
 * drm_sched_stop - stop the scheduler
 *
 * @sched: scheduler instance
 * @bad: job which caused the time out
 *
 * Stop the scheduler and also removes and frees all completed jobs.
 * Note: bad job will not be freed as it might be used later and so it's
 * callers responsibility to release it manually if it's not part of the
 * mirror list any more.
 *
 */
void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
{
        struct drm_sched_job *s_job, *tmp;

        kthread_park(sched->thread);

        /*
         * Reinsert back the bad job here - now it's safe as
         * drm_sched_get_cleanup_job cannot race against us and release the
         * bad job at this point - we parked (waited for) any in progress
         * (earlier) cleanups and drm_sched_get_cleanup_job will not be called
         * now until the scheduler thread is unparked.
         */
        if (bad && bad->sched == sched)
                /*
                 * Add at the head of the queue to reflect it was the earliest
                 * job extracted.
                 */
                list_add(&bad->node, &sched->ring_mirror_list);

        /*
         * Iterate the job list from later to  earlier one and either deactive
         * their HW callbacks or remove them from mirror list if they already
         * signaled.
         * This iteration is thread safe as sched thread is stopped.
         */
        list_for_each_entry_safe_reverse(s_job, tmp, &sched->ring_mirror_list, node) {
                if (s_job->s_fence->parent &&
                    dma_fence_remove_callback(s_job->s_fence->parent,
                                              &s_job->cb)) {
                        atomic_dec(&sched->hw_rq_count);
                } else {
                        /*
                         * remove job from ring_mirror_list.
                         * Locking here is for concurrent resume timeout
                         */
                        spin_lock(&sched->job_list_lock);
                        list_del_init(&s_job->node);
                        spin_unlock(&sched->job_list_lock);

                        /*
                         * Wait for job's HW fence callback to finish using s_job
                         * before releasing it.
                         *
                         * Job is still alive so fence refcount at least 1
                         */
                        dma_fence_wait(&s_job->s_fence->finished, false);

                        /*
                         * We must keep bad job alive for later use during
                         * recovery by some of the drivers but leave a hint
                         * that the guilty job must be released.
                         */
                        if (bad != s_job)
                                sched->ops->free_job(s_job);
                        else
                                sched->free_guilty = true;
                }
        }

        /*
         * Stop pending timer in flight as we rearm it in  drm_sched_start. This
         * avoids the pending timeout work in progress to fire right away after
         * this TDR finished and before the newly restarted jobs had a
         * chance to complete.
         */
        cancel_delayed_work(&sched->work_tdr);
}

EXPORT_SYMBOL(drm_sched_stop);

/**
 * drm_sched_job_recovery - recover jobs after a reset
 *
 * @sched: scheduler instance
 * @full_recovery: proceed with complete sched restart
 *
 */
void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
{
        struct drm_sched_job *s_job, *tmp;
        int r;

        /*
         * Locking the list is not required here as the sched thread is parked
         * so no new jobs are being inserted or removed. Also concurrent
         * GPU recovers can't run in parallel.
         */
        list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
                struct dma_fence *fence = s_job->s_fence->parent;

                atomic_inc(&sched->hw_rq_count);

                if (!full_recovery)
                        continue;

                if (fence) {
                        r = dma_fence_add_callback(fence, &s_job->cb,
                                                   drm_sched_process_job);
                        if (r == -ENOENT)
                                drm_sched_process_job(fence, &s_job->cb);
                        else if (r)
                                DRM_ERROR("fence add callback failed (%d)\n",
                                          r);
                } else
                        drm_sched_process_job(NULL, &s_job->cb);
        }

        if (full_recovery) {
                spin_lock(&sched->job_list_lock);
                drm_sched_start_timeout(sched);
                spin_unlock(&sched->job_list_lock);
        }

        kthread_unpark(sched->thread);
}
EXPORT_SYMBOL(drm_sched_start);

/**
 * drm_sched_resubmit_jobs - helper to relunch job from mirror ring list
 *
 * @sched: scheduler instance
 *
 */
void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_job *s_job, *tmp;
        uint64_t guilty_context;
        bool found_guilty = false;
        struct dma_fence *fence;

        list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
                struct drm_sched_fence *s_fence = s_job->s_fence;

                if (!found_guilty && atomic_read(&s_job->karma) > sched->hang_limit) {
                        found_guilty = true;
                        guilty_context = s_job->s_fence->scheduled.context;
                }

                if (found_guilty && s_job->s_fence->scheduled.context == guilty_context)
                        dma_fence_set_error(&s_fence->finished, -ECANCELED);

                dma_fence_put(s_job->s_fence->parent);
                fence = sched->ops->run_job(s_job);

                if (IS_ERR_OR_NULL(fence)) {
                        if (IS_ERR(fence))
                                dma_fence_set_error(&s_fence->finished, PTR_ERR(fence));

                        s_job->s_fence->parent = NULL;
                } else {
                        s_job->s_fence->parent = fence;
                }


        }
}
EXPORT_SYMBOL(drm_sched_resubmit_jobs);

/**
 * drm_sched_job_init - init a scheduler job
 *
 * @job: scheduler job to init
 * @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_sched_entity *entity,
                       void *owner)
{
        struct drm_gpu_scheduler *sched;

        drm_sched_entity_select_rq(entity);
        if (!entity->rq)
                return -ENOENT;

        sched = entity->rq->sched;

        job->sched = sched;
        job->entity = entity;
        job->s_priority = entity->rq - sched->sched_rq;
        job->s_fence = drm_sched_fence_create(entity, owner);
        if (!job->s_fence)
                return -ENOMEM;
        job->id = atomic64_inc_return(&sched->job_id_count);

        INIT_LIST_HEAD(&job->node);

        return 0;
}
EXPORT_SYMBOL(drm_sched_job_init);

/**
 * drm_sched_job_cleanup - clean up scheduler job resources
 *
 * @job: scheduler job to clean up
 */
void drm_sched_job_cleanup(struct drm_sched_job *job)
{
        dma_fence_put(&job->s_fence->finished);
        job->s_fence = NULL;
}
EXPORT_SYMBOL(drm_sched_job_cleanup);

/**
 * 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)
{
        return atomic_read(&sched->hw_rq_count) <
                sched->hw_submission_limit;
}

/**
 * drm_sched_wakeup - Wake up the scheduler when it is ready
 *
 * @sched: scheduler instance
 *
 */
void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
{
        if (drm_sched_ready(sched))
                wake_up_interruptible(&sched->wake_up_worker);
}

/**
 * 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)
{
        struct drm_sched_entity *entity;
        int i;

        if (!drm_sched_ready(sched))
                return NULL;

        /* Kernel run queue has higher priority than normal run queue*/
        for (i = DRM_SCHED_PRIORITY_MAX - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
                entity = drm_sched_rq_select_entity(&sched->sched_rq[i]);
                if (entity)
                        break;
        }

        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_job *s_job = container_of(cb, struct drm_sched_job, cb);
        struct drm_sched_fence *s_fence = s_job->s_fence;
        struct drm_gpu_scheduler *sched = s_fence->sched;

        atomic_dec(&sched->hw_rq_count);
        atomic_dec(&sched->score);

        trace_drm_sched_process_job(s_fence);

        dma_fence_get(&s_fence->finished);
        drm_sched_fence_finished(s_fence);
        dma_fence_put(&s_fence->finished);
        wake_up_interruptible(&sched->wake_up_worker);
}

/**
 * drm_sched_get_cleanup_job - fetch the next finished job to be destroyed
 *
 * @sched: scheduler instance
 *
 * Returns the next finished job from the mirror list (if there is one)
 * ready for it to be destroyed.
 */
static struct drm_sched_job *
drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_job *job;

        /*
         * Don't destroy jobs while the timeout worker is running  OR thread
         * is being parked and hence assumed to not touch ring_mirror_list
         */
        if ((sched->timeout != MAX_SCHEDULE_TIMEOUT &&
            !cancel_delayed_work(&sched->work_tdr)) ||
            kthread_should_park())
                return NULL;

        spin_lock(&sched->job_list_lock);

        job = list_first_entry_or_null(&sched->ring_mirror_list,
                                       struct drm_sched_job, node);

        if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
                /* remove job from ring_mirror_list */
                list_del_init(&job->node);
        } else {
                job = NULL;
                /* queue timeout for next job */
                drm_sched_start_timeout(sched);
        }

        spin_unlock(&sched->job_list_lock);

        return job;
}

/**
 * drm_sched_pick_best - Get a drm sched from a sched_list with the least load
 * @sched_list: list of drm_gpu_schedulers
 * @num_sched_list: number of drm_gpu_schedulers in the sched_list
 *
 * Returns pointer of the sched with the least load or NULL if none of the
 * drm_gpu_schedulers are ready
 */
struct drm_gpu_scheduler *
drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
                     unsigned int num_sched_list)
{
        struct drm_gpu_scheduler *sched, *picked_sched = NULL;
        int i;
        unsigned int min_score = UINT_MAX, num_score;

        for (i = 0; i < num_sched_list; ++i) {
                sched = sched_list[i];

                if (!sched->ready) {
                        DRM_WARN("scheduler %s is not ready, skipping",
                                 sched->name);
                        continue;
                }

                num_score = atomic_read(&sched->score);
                if (num_score < min_score) {
                        min_score = num_score;
                        picked_sched = sched;
                }
        }

        return picked_sched;
}
EXPORT_SYMBOL(drm_sched_pick_best);

/**
 * 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()) {
                kthread_parkme();
                return true;
        }

        return false;
}

/**
 * drm_sched_main - main scheduler thread
 *
 * @param: scheduler instance
 *
 * Returns 0.
 */
static int drm_sched_main(void *param)
{
        struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
        int r;

        sched_set_fifo_low(current);

        while (!kthread_should_stop()) {
                struct drm_sched_entity *entity = NULL;
                struct drm_sched_fence *s_fence;
                struct drm_sched_job *sched_job;
                struct dma_fence *fence;
                struct drm_sched_job *cleanup_job = NULL;

                wait_event_interruptible(sched->wake_up_worker,
                                         (cleanup_job = drm_sched_get_cleanup_job(sched)) ||
                                         (!drm_sched_blocked(sched) &&
                                          (entity = drm_sched_select_entity(sched))) ||
                                         kthread_should_stop());

                if (cleanup_job) {
                        sched->ops->free_job(cleanup_job);
                        /* queue timeout for next job */
                        drm_sched_start_timeout(sched);
                }

                if (!entity)
                        continue;

                sched_job = drm_sched_entity_pop_job(entity);

                complete(&entity->entity_idle);

                if (!sched_job)
                        continue;

                s_fence = sched_job->s_fence;

                atomic_inc(&sched->hw_rq_count);
                drm_sched_job_begin(sched_job);

                trace_drm_run_job(sched_job, entity);
                fence = sched->ops->run_job(sched_job);
                drm_sched_fence_scheduled(s_fence);

                if (!IS_ERR_OR_NULL(fence)) {
                        s_fence->parent = dma_fence_get(fence);
                        r = dma_fence_add_callback(fence, &sched_job->cb,
                                                   drm_sched_process_job);
                        if (r == -ENOENT)
                                drm_sched_process_job(fence, &sched_job->cb);
                        else if (r)
                                DRM_ERROR("fence add callback failed (%d)\n",
                                          r);
                        dma_fence_put(fence);
                } else {
                        if (IS_ERR(fence))
                                dma_fence_set_error(&s_fence->finished, PTR_ERR(fence));

                        drm_sched_process_job(NULL, &sched_job->cb);
                }

                wake_up(&sched->job_scheduled);
        }
        return 0;
}

/**
 * drm_sched_init - Init a gpu scheduler instance
 *
 * @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,
                   unsigned hang_limit,
                   long timeout,
                   const char *name)
{
        int i, ret;
        sched->ops = ops;
        sched->hw_submission_limit = hw_submission;
        sched->name = name;
        sched->timeout = timeout;
        sched->hang_limit = hang_limit;
        for (i = DRM_SCHED_PRIORITY_MIN; i < DRM_SCHED_PRIORITY_MAX; i++)
                drm_sched_rq_init(sched, &sched->sched_rq[i]);

        init_waitqueue_head(&sched->wake_up_worker);
        init_waitqueue_head(&sched->job_scheduled);
        INIT_LIST_HEAD(&sched->ring_mirror_list);
        spin_lock_init(&sched->job_list_lock);
        atomic_set(&sched->hw_rq_count, 0);
        INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
        atomic_set(&sched->score, 0);
        atomic64_set(&sched->job_id_count, 0);

        /* Each scheduler will run on a seperate kernel thread */
        sched->thread = kthread_run(drm_sched_main, sched, sched->name);
        if (IS_ERR(sched->thread)) {
                ret = PTR_ERR(sched->thread);
                sched->thread = NULL;
                DRM_ERROR("Failed to create scheduler for %s.\n", name);
                return ret;
        }

        sched->ready = true;
        return 0;
}
EXPORT_SYMBOL(drm_sched_init);

/**
 * drm_sched_fini - Destroy a gpu scheduler
 *
 * @sched: scheduler instance
 *
 * Tears down and cleans up the scheduler.
 */
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
        if (sched->thread)
                kthread_stop(sched->thread);

        sched->ready = false;
}
EXPORT_SYMBOL(drm_sched_fini);