Linux 6.14-rc3

[linux.git] / drivers / gpu / drm / scheduler / sched_main.c

/*
 * 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 an entity are always scheduled in the order in which they were pushed.
 *
 * Note that once a job was taken from the entities queue and pushed to the
 * hardware, i.e. the pending queue, the entity must not be referenced anymore
 * through the jobs entity pointer.
 */

/**
 * DOC: Flow Control
 *
 * The DRM GPU scheduler provides a flow control mechanism to regulate the rate
 * in which the jobs fetched from scheduler entities are executed.
 *
 * In this context the &drm_gpu_scheduler keeps track of a driver specified
 * credit limit representing the capacity of this scheduler and a credit count;
 * every &drm_sched_job carries a driver specified number of credits.
 *
 * Once a job is executed (but not yet finished), the job's credits contribute
 * to the scheduler's credit count until the job is finished. If by executing
 * one more job the scheduler's credit count would exceed the scheduler's
 * credit limit, the job won't be executed. Instead, the scheduler will wait
 * until the credit count has decreased enough to not overflow its credit limit.
 * This implies waiting for previously executed jobs.
 *
 * Optionally, drivers may register a callback (update_job_credits) provided by
 * struct drm_sched_backend_ops to update the job's credits dynamically. The
 * scheduler executes this callback every time the scheduler considers a job for
 * execution and subsequently checks whether the job fits the scheduler's credit
 * limit.
 */

#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/dma-resv.h>
#include <uapi/linux/sched/types.h>

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

#define CREATE_TRACE_POINTS
#include "gpu_scheduler_trace.h"

#ifdef CONFIG_LOCKDEP
static struct lockdep_map drm_sched_lockdep_map = {
        .name = "drm_sched_lockdep_map"
};
#endif

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

int drm_sched_policy = DRM_SCHED_POLICY_FIFO;

/**
 * DOC: sched_policy (int)
 * Used to override default entities scheduling policy in a run queue.
 */
MODULE_PARM_DESC(sched_policy, "Specify the scheduling policy for entities on a run-queue, " __stringify(DRM_SCHED_POLICY_RR) " = Round Robin, " __stringify(DRM_SCHED_POLICY_FIFO) " = FIFO (default).");
module_param_named(sched_policy, drm_sched_policy, int, 0444);

static u32 drm_sched_available_credits(struct drm_gpu_scheduler *sched)
{
        u32 credits;

        drm_WARN_ON(sched, check_sub_overflow(sched->credit_limit,
                                              atomic_read(&sched->credit_count),
                                              &credits));

        return credits;
}

/**
 * drm_sched_can_queue -- Can we queue more to the hardware?
 * @sched: scheduler instance
 * @entity: the scheduler entity
 *
 * Return true if we can push at least one more job from @entity, false
 * otherwise.
 */
static bool drm_sched_can_queue(struct drm_gpu_scheduler *sched,
                                struct drm_sched_entity *entity)
{
        struct drm_sched_job *s_job;

        s_job = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
        if (!s_job)
                return false;

        if (sched->ops->update_job_credits) {
                s_job->credits = sched->ops->update_job_credits(s_job);

                drm_WARN(sched, !s_job->credits,
                         "Jobs with zero credits bypass job-flow control.\n");
        }

        /* If a job exceeds the credit limit, truncate it to the credit limit
         * itself to guarantee forward progress.
         */
        if (drm_WARN(sched, s_job->credits > sched->credit_limit,
                     "Jobs may not exceed the credit limit, truncate.\n"))
                s_job->credits = sched->credit_limit;

        return drm_sched_available_credits(sched) >= s_job->credits;
}

static __always_inline bool drm_sched_entity_compare_before(struct rb_node *a,
                                                            const struct rb_node *b)
{
        struct drm_sched_entity *ent_a =  rb_entry((a), struct drm_sched_entity, rb_tree_node);
        struct drm_sched_entity *ent_b =  rb_entry((b), struct drm_sched_entity, rb_tree_node);

        return ktime_before(ent_a->oldest_job_waiting, ent_b->oldest_job_waiting);
}

static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
                                            struct drm_sched_rq *rq)
{
        if (!RB_EMPTY_NODE(&entity->rb_tree_node)) {
                rb_erase_cached(&entity->rb_tree_node, &rq->rb_tree_root);
                RB_CLEAR_NODE(&entity->rb_tree_node);
        }
}

void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
                                     struct drm_sched_rq *rq,
                                     ktime_t ts)
{
        /*
         * Both locks need to be grabbed, one to protect from entity->rq change
         * for entity from within concurrent drm_sched_entity_select_rq and the
         * other to update the rb tree structure.
         */
        lockdep_assert_held(&entity->lock);
        lockdep_assert_held(&rq->lock);

        drm_sched_rq_remove_fifo_locked(entity, rq);

        entity->oldest_job_waiting = ts;

        rb_add_cached(&entity->rb_tree_node, &rq->rb_tree_root,
                      drm_sched_entity_compare_before);
}

/**
 * drm_sched_rq_init - initialize a given run queue struct
 *
 * @sched: scheduler instance to associate with this run queue
 * @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->rb_tree_root = RB_ROOT_CACHED;
        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)
{
        lockdep_assert_held(&entity->lock);
        lockdep_assert_held(&rq->lock);

        if (!list_empty(&entity->list))
                return;

        atomic_inc(rq->sched->score);
        list_add_tail(&entity->list, &rq->entities);
}

/**
 * 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)
{
        lockdep_assert_held(&entity->lock);

        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;

        if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
                drm_sched_rq_remove_fifo_locked(entity, rq);

        spin_unlock(&rq->lock);
}

/**
 * drm_sched_rq_select_entity_rr - Select an entity which could provide a job to run
 *
 * @sched: the gpu scheduler
 * @rq: scheduler run queue to check.
 *
 * Try to find the next ready entity.
 *
 * Return an entity if one is found; return an error-pointer (!NULL) if an
 * entity was ready, but the scheduler had insufficient credits to accommodate
 * its job; return NULL, if no ready entity was found.
 */
static struct drm_sched_entity *
drm_sched_rq_select_entity_rr(struct drm_gpu_scheduler *sched,
                              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)) {
                                /* If we can't queue yet, preserve the current
                                 * entity in terms of fairness.
                                 */
                                if (!drm_sched_can_queue(sched, entity)) {
                                        spin_unlock(&rq->lock);
                                        return ERR_PTR(-ENOSPC);
                                }

                                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)) {
                        /* If we can't queue yet, preserve the current entity in
                         * terms of fairness.
                         */
                        if (!drm_sched_can_queue(sched, entity)) {
                                spin_unlock(&rq->lock);
                                return ERR_PTR(-ENOSPC);
                        }

                        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_rq_select_entity_fifo - Select an entity which provides a job to run
 *
 * @sched: the gpu scheduler
 * @rq: scheduler run queue to check.
 *
 * Find oldest waiting ready entity.
 *
 * Return an entity if one is found; return an error-pointer (!NULL) if an
 * entity was ready, but the scheduler had insufficient credits to accommodate
 * its job; return NULL, if no ready entity was found.
 */
static struct drm_sched_entity *
drm_sched_rq_select_entity_fifo(struct drm_gpu_scheduler *sched,
                                struct drm_sched_rq *rq)
{
        struct rb_node *rb;

        spin_lock(&rq->lock);
        for (rb = rb_first_cached(&rq->rb_tree_root); rb; rb = rb_next(rb)) {
                struct drm_sched_entity *entity;

                entity = rb_entry(rb, struct drm_sched_entity, rb_tree_node);
                if (drm_sched_entity_is_ready(entity)) {
                        /* If we can't queue yet, preserve the current entity in
                         * terms of fairness.
                         */
                        if (!drm_sched_can_queue(sched, entity)) {
                                spin_unlock(&rq->lock);
                                return ERR_PTR(-ENOSPC);
                        }

                        reinit_completion(&entity->entity_idle);
                        break;
                }
        }
        spin_unlock(&rq->lock);

        return rb ? rb_entry(rb, struct drm_sched_entity, rb_tree_node) : NULL;
}

/**
 * drm_sched_run_job_queue - enqueue run-job work
 * @sched: scheduler instance
 */
static void drm_sched_run_job_queue(struct drm_gpu_scheduler *sched)
{
        if (!READ_ONCE(sched->pause_submit))
                queue_work(sched->submit_wq, &sched->work_run_job);
}

/**
 * __drm_sched_run_free_queue - enqueue free-job work
 * @sched: scheduler instance
 */
static void __drm_sched_run_free_queue(struct drm_gpu_scheduler *sched)
{
        if (!READ_ONCE(sched->pause_submit))
                queue_work(sched->submit_wq, &sched->work_free_job);
}

/**
 * drm_sched_run_free_queue - enqueue free-job work if ready
 * @sched: scheduler instance
 */
static void drm_sched_run_free_queue(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_job *job;

        spin_lock(&sched->job_list_lock);
        job = list_first_entry_or_null(&sched->pending_list,
                                       struct drm_sched_job, list);
        if (job && dma_fence_is_signaled(&job->s_fence->finished))
                __drm_sched_run_free_queue(sched);
        spin_unlock(&sched->job_list_lock);
}

/**
 * drm_sched_job_done - complete a job
 * @s_job: pointer to the job which is done
 *
 * Finish the job's fence and wake up the worker thread.
 */
static void drm_sched_job_done(struct drm_sched_job *s_job, int result)
{
        struct drm_sched_fence *s_fence = s_job->s_fence;
        struct drm_gpu_scheduler *sched = s_fence->sched;

        atomic_sub(s_job->credits, &sched->credit_count);
        atomic_dec(sched->score);

        trace_drm_sched_process_job(s_fence);

        dma_fence_get(&s_fence->finished);
        drm_sched_fence_finished(s_fence, result);
        dma_fence_put(&s_fence->finished);
        __drm_sched_run_free_queue(sched);
}

/**
 * drm_sched_job_done_cb - the callback for a done job
 * @f: fence
 * @cb: fence callbacks
 */
static void drm_sched_job_done_cb(struct dma_fence *f, struct dma_fence_cb *cb)
{
        struct drm_sched_job *s_job = container_of(cb, struct drm_sched_job, cb);

        drm_sched_job_done(s_job, f->error);
}

/**
 * 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)
{
        lockdep_assert_held(&sched->job_list_lock);

        if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
            !list_empty(&sched->pending_list))
                mod_delayed_work(sched->timeout_wq, &sched->work_tdr, sched->timeout);
}

static void drm_sched_start_timeout_unlocked(struct drm_gpu_scheduler *sched)
{
        spin_lock(&sched->job_list_lock);
        drm_sched_start_timeout(sched);
        spin_unlock(&sched->job_list_lock);
}

/**
 * drm_sched_tdr_queue_imm: - immediately start job timeout handler
 *
 * @sched: scheduler for which the timeout handling should be started.
 *
 * Start timeout handling immediately for the named scheduler.
 */
void drm_sched_tdr_queue_imm(struct drm_gpu_scheduler *sched)
{
        spin_lock(&sched->job_list_lock);
        sched->timeout = 0;
        drm_sched_start_timeout(sched);
        spin_unlock(&sched->job_list_lock);
}
EXPORT_SYMBOL(drm_sched_tdr_queue_imm);

/**
 * 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)
{
        if (sched->timeout_wq)
                mod_delayed_work(sched->timeout_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(sched->timeout_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->pending_list))
                cancel_delayed_work(&sched->work_tdr);
        else
                mod_delayed_work(sched->timeout_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->list, &sched->pending_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;
        enum drm_gpu_sched_stat status = DRM_GPU_SCHED_STAT_NOMINAL;

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

        /* Protects against concurrent deletion in drm_sched_get_finished_job */
        spin_lock(&sched->job_list_lock);
        job = list_first_entry_or_null(&sched->pending_list,
                                       struct drm_sched_job, list);

        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->list);
                spin_unlock(&sched->job_list_lock);

                status = 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);
        }

        if (status != DRM_GPU_SCHED_STAT_ENODEV)
                drm_sched_start_timeout_unlocked(sched);
}

/**
 * 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
 * pending list any more.
 *
 * This function is typically used for reset recovery (see the docu of
 * drm_sched_backend_ops.timedout_job() for details). Do not call it for
 * scheduler teardown, i.e., before calling drm_sched_fini().
 */
void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
{
        struct drm_sched_job *s_job, *tmp;

        drm_sched_wqueue_stop(sched);

        /*
         * Reinsert back the bad job here - now it's safe as
         * drm_sched_get_finished_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_finished_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->list, &sched->pending_list);

        /*
         * Iterate the job list from later to  earlier one and either deactive
         * their HW callbacks or remove them from pending 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->pending_list,
                                         list) {
                if (s_job->s_fence->parent &&
                    dma_fence_remove_callback(s_job->s_fence->parent,
                                              &s_job->cb)) {
                        dma_fence_put(s_job->s_fence->parent);
                        s_job->s_fence->parent = NULL;
                        atomic_sub(s_job->credits, &sched->credit_count);
                } else {
                        /*
                         * remove job from pending_list.
                         * Locking here is for concurrent resume timeout
                         */
                        spin_lock(&sched->job_list_lock);
                        list_del_init(&s_job->list);
                        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_start - recover jobs after a reset
 *
 * @sched: scheduler instance
 * @errno: error to set on the pending fences
 *
 * This function is typically used for reset recovery (see the docu of
 * drm_sched_backend_ops.timedout_job() for details). Do not call it for
 * scheduler startup. The scheduler itself is fully operational after
 * drm_sched_init() succeeded.
 */
void drm_sched_start(struct drm_gpu_scheduler *sched, int errno)
{
        struct drm_sched_job *s_job, *tmp;

        /*
         * 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->pending_list, list) {
                struct dma_fence *fence = s_job->s_fence->parent;

                atomic_add(s_job->credits, &sched->credit_count);

                if (!fence) {
                        drm_sched_job_done(s_job, errno ?: -ECANCELED);
                        continue;
                }

                if (dma_fence_add_callback(fence, &s_job->cb,
                                           drm_sched_job_done_cb))
                        drm_sched_job_done(s_job, fence->error ?: errno);
        }

        drm_sched_start_timeout_unlocked(sched);
        drm_sched_wqueue_start(sched);
}
EXPORT_SYMBOL(drm_sched_start);

/**
 * drm_sched_resubmit_jobs - Deprecated, don't use in new code!
 *
 * @sched: scheduler instance
 *
 * Re-submitting jobs was a concept AMD came up as cheap way to implement
 * recovery after a job timeout.
 *
 * This turned out to be not working very well. First of all there are many
 * problem with the dma_fence implementation and requirements. Either the
 * implementation is risking deadlocks with core memory management or violating
 * documented implementation details of the dma_fence object.
 *
 * Drivers can still save and restore their state for recovery operations, but
 * we shouldn't make this a general scheduler feature around the dma_fence
 * interface.
 */
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->pending_list, list) {
                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);

                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 = dma_fence_get(fence);

                        /* Drop for orignal kref_init */
                        dma_fence_put(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
 * @credits: the number of credits this job contributes to the schedulers
 * credit limit
 * @owner: job owner for debugging
 *
 * Refer to drm_sched_entity_push_job() documentation
 * for locking considerations.
 *
 * Drivers must make sure drm_sched_job_cleanup() if this function returns
 * successfully, even when @job is aborted before drm_sched_job_arm() is called.
 *
 * Note that this function does not assign a valid value to each struct member
 * of struct drm_sched_job. Take a look at that struct's documentation to see
 * who sets which struct member with what lifetime.
 *
 * WARNING: amdgpu abuses &drm_sched.ready to signal when the hardware
 * has died, which can mean that there's no valid runqueue for a @entity.
 * This function returns -ENOENT in this case (which probably should be -EIO as
 * a more meanigful return value).
 *
 * Returns 0 for success, negative error code otherwise.
 */
int drm_sched_job_init(struct drm_sched_job *job,
                       struct drm_sched_entity *entity,
                       u32 credits, void *owner)
{
        if (!entity->rq) {
                /* This will most likely be followed by missing frames
                 * or worse--a blank screen--leave a trail in the
                 * logs, so this can be debugged easier.
                 */
                drm_err(job->sched, "%s: entity has no rq!\n", __func__);
                return -ENOENT;
        }

        if (unlikely(!credits)) {
                pr_err("*ERROR* %s: credits cannot be 0!\n", __func__);
                return -EINVAL;
        }

        /*
         * We don't know for sure how the user has allocated. Thus, zero the
         * struct so that unallowed (i.e., too early) usage of pointers that
         * this function does not set is guaranteed to lead to a NULL pointer
         * exception instead of UB.
         */
        memset(job, 0, sizeof(*job));

        job->entity = entity;
        job->credits = credits;
        job->s_fence = drm_sched_fence_alloc(entity, owner);
        if (!job->s_fence)
                return -ENOMEM;

        INIT_LIST_HEAD(&job->list);

        xa_init_flags(&job->dependencies, XA_FLAGS_ALLOC);

        return 0;
}
EXPORT_SYMBOL(drm_sched_job_init);

/**
 * drm_sched_job_arm - arm a scheduler job for execution
 * @job: scheduler job to arm
 *
 * This arms a scheduler job for execution. Specifically it initializes the
 * &drm_sched_job.s_fence of @job, so that it can be attached to struct dma_resv
 * or other places that need to track the completion of this job.
 *
 * Refer to drm_sched_entity_push_job() documentation for locking
 * considerations.
 *
 * This can only be called if drm_sched_job_init() succeeded.
 */
void drm_sched_job_arm(struct drm_sched_job *job)
{
        struct drm_gpu_scheduler *sched;
        struct drm_sched_entity *entity = job->entity;

        BUG_ON(!entity);
        drm_sched_entity_select_rq(entity);
        sched = entity->rq->sched;

        job->sched = sched;
        job->s_priority = entity->priority;
        job->id = atomic64_inc_return(&sched->job_id_count);

        drm_sched_fence_init(job->s_fence, job->entity);
}
EXPORT_SYMBOL(drm_sched_job_arm);

/**
 * drm_sched_job_add_dependency - adds the fence as a job dependency
 * @job: scheduler job to add the dependencies to
 * @fence: the dma_fence to add to the list of dependencies.
 *
 * Note that @fence is consumed in both the success and error cases.
 *
 * Returns:
 * 0 on success, or an error on failing to expand the array.
 */
int drm_sched_job_add_dependency(struct drm_sched_job *job,
                                 struct dma_fence *fence)
{
        struct dma_fence *entry;
        unsigned long index;
        u32 id = 0;
        int ret;

        if (!fence)
                return 0;

        /* Deduplicate if we already depend on a fence from the same context.
         * This lets the size of the array of deps scale with the number of
         * engines involved, rather than the number of BOs.
         */
        xa_for_each(&job->dependencies, index, entry) {
                if (entry->context != fence->context)
                        continue;

                if (dma_fence_is_later(fence, entry)) {
                        dma_fence_put(entry);
                        xa_store(&job->dependencies, index, fence, GFP_KERNEL);
                } else {
                        dma_fence_put(fence);
                }
                return 0;
        }

        ret = xa_alloc(&job->dependencies, &id, fence, xa_limit_32b, GFP_KERNEL);
        if (ret != 0)
                dma_fence_put(fence);

        return ret;
}
EXPORT_SYMBOL(drm_sched_job_add_dependency);

/**
 * drm_sched_job_add_syncobj_dependency - adds a syncobj's fence as a job dependency
 * @job: scheduler job to add the dependencies to
 * @file: drm file private pointer
 * @handle: syncobj handle to lookup
 * @point: timeline point
 *
 * This adds the fence matching the given syncobj to @job.
 *
 * Returns:
 * 0 on success, or an error on failing to expand the array.
 */
int drm_sched_job_add_syncobj_dependency(struct drm_sched_job *job,
                                         struct drm_file *file,
                                         u32 handle,
                                         u32 point)
{
        struct dma_fence *fence;
        int ret;

        ret = drm_syncobj_find_fence(file, handle, point, 0, &fence);
        if (ret)
                return ret;

        return drm_sched_job_add_dependency(job, fence);
}
EXPORT_SYMBOL(drm_sched_job_add_syncobj_dependency);

/**
 * drm_sched_job_add_resv_dependencies - add all fences from the resv to the job
 * @job: scheduler job to add the dependencies to
 * @resv: the dma_resv object to get the fences from
 * @usage: the dma_resv_usage to use to filter the fences
 *
 * This adds all fences matching the given usage from @resv to @job.
 * Must be called with the @resv lock held.
 *
 * Returns:
 * 0 on success, or an error on failing to expand the array.
 */
int drm_sched_job_add_resv_dependencies(struct drm_sched_job *job,
                                        struct dma_resv *resv,
                                        enum dma_resv_usage usage)
{
        struct dma_resv_iter cursor;
        struct dma_fence *fence;
        int ret;

        dma_resv_assert_held(resv);

        dma_resv_for_each_fence(&cursor, resv, usage, fence) {
                /* Make sure to grab an additional ref on the added fence */
                dma_fence_get(fence);
                ret = drm_sched_job_add_dependency(job, fence);
                if (ret) {
                        dma_fence_put(fence);
                        return ret;
                }
        }
        return 0;
}
EXPORT_SYMBOL(drm_sched_job_add_resv_dependencies);

/**
 * drm_sched_job_add_implicit_dependencies - adds implicit dependencies as job
 *   dependencies
 * @job: scheduler job to add the dependencies to
 * @obj: the gem object to add new dependencies from.
 * @write: whether the job might write the object (so we need to depend on
 * shared fences in the reservation object).
 *
 * This should be called after drm_gem_lock_reservations() on your array of
 * GEM objects used in the job but before updating the reservations with your
 * own fences.
 *
 * Returns:
 * 0 on success, or an error on failing to expand the array.
 */
int drm_sched_job_add_implicit_dependencies(struct drm_sched_job *job,
                                            struct drm_gem_object *obj,
                                            bool write)
{
        return drm_sched_job_add_resv_dependencies(job, obj->resv,
                                                   dma_resv_usage_rw(write));
}
EXPORT_SYMBOL(drm_sched_job_add_implicit_dependencies);

/**
 * drm_sched_job_cleanup - clean up scheduler job resources
 * @job: scheduler job to clean up
 *
 * Cleans up the resources allocated with drm_sched_job_init().
 *
 * Drivers should call this from their error unwind code if @job is aborted
 * before drm_sched_job_arm() is called.
 *
 * After that point of no return @job is committed to be executed by the
 * scheduler, and this function should be called from the
 * &drm_sched_backend_ops.free_job callback.
 */
void drm_sched_job_cleanup(struct drm_sched_job *job)
{
        struct dma_fence *fence;
        unsigned long index;

        if (kref_read(&job->s_fence->finished.refcount)) {
                /* drm_sched_job_arm() has been called */
                dma_fence_put(&job->s_fence->finished);
        } else {
                /* aborted job before committing to run it */
                drm_sched_fence_free(job->s_fence);
        }

        job->s_fence = NULL;

        xa_for_each(&job->dependencies, index, fence) {
                dma_fence_put(fence);
        }
        xa_destroy(&job->dependencies);

}
EXPORT_SYMBOL(drm_sched_job_cleanup);

/**
 * drm_sched_wakeup - Wake up the scheduler if it is ready to queue
 * @sched: scheduler instance
 *
 * Wake up the scheduler if we can queue jobs.
 */
void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
{
        drm_sched_run_job_queue(sched);
}

/**
 * drm_sched_select_entity - Select next entity to process
 *
 * @sched: scheduler instance
 *
 * Return an entity to process or NULL if none are found.
 *
 * Note, that we break out of the for-loop when "entity" is non-null, which can
 * also be an error-pointer--this assures we don't process lower priority
 * run-queues. See comments in the respectively called functions.
 */
static struct drm_sched_entity *
drm_sched_select_entity(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_entity *entity;
        int i;

        /* Start with the highest priority.
         */
        for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
                entity = drm_sched_policy == DRM_SCHED_POLICY_FIFO ?
                        drm_sched_rq_select_entity_fifo(sched, sched->sched_rq[i]) :
                        drm_sched_rq_select_entity_rr(sched, sched->sched_rq[i]);
                if (entity)
                        break;
        }

        return IS_ERR(entity) ? NULL : entity;
}

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

        spin_lock(&sched->job_list_lock);

        job = list_first_entry_or_null(&sched->pending_list,
                                       struct drm_sched_job, list);

        if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
                /* remove job from pending_list */
                list_del_init(&job->list);

                /* cancel this job's TO timer */
                cancel_delayed_work(&sched->work_tdr);
                /* make the scheduled timestamp more accurate */
                next = list_first_entry_or_null(&sched->pending_list,
                                                typeof(*next), list);

                if (next) {
                        if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
                                     &next->s_fence->scheduled.flags))
                                next->s_fence->scheduled.timestamp =
                                        dma_fence_timestamp(&job->s_fence->finished);
                        /* start TO timer for next job */
                        drm_sched_start_timeout(sched);
                }
        } else {
                job = NULL;
        }

        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_free_job_work - worker to call free_job
 *
 * @w: free job work
 */
static void drm_sched_free_job_work(struct work_struct *w)
{
        struct drm_gpu_scheduler *sched =
                container_of(w, struct drm_gpu_scheduler, work_free_job);
        struct drm_sched_job *job;

        if (READ_ONCE(sched->pause_submit))
                return;

        job = drm_sched_get_finished_job(sched);
        if (job)
                sched->ops->free_job(job);

        drm_sched_run_free_queue(sched);
        drm_sched_run_job_queue(sched);
}

/**
 * drm_sched_run_job_work - worker to call run_job
 *
 * @w: run job work
 */
static void drm_sched_run_job_work(struct work_struct *w)
{
        struct drm_gpu_scheduler *sched =
                container_of(w, struct drm_gpu_scheduler, work_run_job);
        struct drm_sched_entity *entity;
        struct dma_fence *fence;
        struct drm_sched_fence *s_fence;
        struct drm_sched_job *sched_job;
        int r;

        if (READ_ONCE(sched->pause_submit))
                return;

        /* Find entity with a ready job */
        entity = drm_sched_select_entity(sched);
        if (!entity)
                return; /* No more work */

        sched_job = drm_sched_entity_pop_job(entity);
        if (!sched_job) {
                complete_all(&entity->entity_idle);
                drm_sched_run_job_queue(sched);
                return;
        }

        s_fence = sched_job->s_fence;

        atomic_add(sched_job->credits, &sched->credit_count);
        drm_sched_job_begin(sched_job);

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

        if (!IS_ERR_OR_NULL(fence)) {
                /* Drop for original kref_init of the fence */
                dma_fence_put(fence);

                r = dma_fence_add_callback(fence, &sched_job->cb,
                                           drm_sched_job_done_cb);
                if (r == -ENOENT)
                        drm_sched_job_done(sched_job, fence->error);
                else if (r)
                        DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n", r);
        } else {
                drm_sched_job_done(sched_job, IS_ERR(fence) ?
                                   PTR_ERR(fence) : 0);
        }

        wake_up(&sched->job_scheduled);
        drm_sched_run_job_queue(sched);
}

/**
 * drm_sched_init - Init a gpu scheduler instance
 *
 * @sched: scheduler instance
 * @ops: backend operations for this scheduler
 * @submit_wq: workqueue to use for submission. If NULL, an ordered wq is
 *             allocated and used
 * @num_rqs: number of runqueues, one for each priority, up to DRM_SCHED_PRIORITY_COUNT
 * @credit_limit: the number of credits this scheduler can hold from all jobs
 * @hang_limit: number of times to allow a job to hang before dropping it
 * @timeout: timeout value in jiffies for the scheduler
 * @timeout_wq: workqueue to use for timeout work. If NULL, the system_wq is
 *              used
 * @score: optional score atomic shared with other schedulers
 * @name: name used for debugging
 * @dev: target &struct device
 *
 * Return 0 on success, otherwise error code.
 */
int drm_sched_init(struct drm_gpu_scheduler *sched,
                   const struct drm_sched_backend_ops *ops,
                   struct workqueue_struct *submit_wq,
                   u32 num_rqs, u32 credit_limit, unsigned int hang_limit,
                   long timeout, struct workqueue_struct *timeout_wq,
                   atomic_t *score, const char *name, struct device *dev)
{
        int i;

        sched->ops = ops;
        sched->credit_limit = credit_limit;
        sched->name = name;
        sched->timeout = timeout;
        sched->timeout_wq = timeout_wq ? : system_wq;
        sched->hang_limit = hang_limit;
        sched->score = score ? score : &sched->_score;
        sched->dev = dev;

        if (num_rqs > DRM_SCHED_PRIORITY_COUNT) {
                /* This is a gross violation--tell drivers what the  problem is.
                 */
                drm_err(sched, "%s: num_rqs cannot be greater than DRM_SCHED_PRIORITY_COUNT\n",
                        __func__);
                return -EINVAL;
        } else if (sched->sched_rq) {
                /* Not an error, but warn anyway so drivers can
                 * fine-tune their DRM calling order, and return all
                 * is good.
                 */
                drm_warn(sched, "%s: scheduler already initialized!\n", __func__);
                return 0;
        }

        if (submit_wq) {
                sched->submit_wq = submit_wq;
                sched->own_submit_wq = false;
        } else {
#ifdef CONFIG_LOCKDEP
                sched->submit_wq = alloc_ordered_workqueue_lockdep_map(name,
                                                                       WQ_MEM_RECLAIM,
                                                                       &drm_sched_lockdep_map);
#else
                sched->submit_wq = alloc_ordered_workqueue(name, WQ_MEM_RECLAIM);
#endif
                if (!sched->submit_wq)
                        return -ENOMEM;

                sched->own_submit_wq = true;
        }

        sched->sched_rq = kmalloc_array(num_rqs, sizeof(*sched->sched_rq),
                                        GFP_KERNEL | __GFP_ZERO);
        if (!sched->sched_rq)
                goto Out_check_own;
        sched->num_rqs = num_rqs;
        for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
                sched->sched_rq[i] = kzalloc(sizeof(*sched->sched_rq[i]), GFP_KERNEL);
                if (!sched->sched_rq[i])
                        goto Out_unroll;
                drm_sched_rq_init(sched, sched->sched_rq[i]);
        }

        init_waitqueue_head(&sched->job_scheduled);
        INIT_LIST_HEAD(&sched->pending_list);
        spin_lock_init(&sched->job_list_lock);
        atomic_set(&sched->credit_count, 0);
        INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
        INIT_WORK(&sched->work_run_job, drm_sched_run_job_work);
        INIT_WORK(&sched->work_free_job, drm_sched_free_job_work);
        atomic_set(&sched->_score, 0);
        atomic64_set(&sched->job_id_count, 0);
        sched->pause_submit = false;

        sched->ready = true;
        return 0;
Out_unroll:
        for (--i ; i >= DRM_SCHED_PRIORITY_KERNEL; i--)
                kfree(sched->sched_rq[i]);

        kfree(sched->sched_rq);
        sched->sched_rq = NULL;
Out_check_own:
        if (sched->own_submit_wq)
                destroy_workqueue(sched->submit_wq);
        drm_err(sched, "%s: Failed to setup GPU scheduler--out of memory\n", __func__);
        return -ENOMEM;
}
EXPORT_SYMBOL(drm_sched_init);

/**
 * drm_sched_fini - Destroy a gpu scheduler
 *
 * @sched: scheduler instance
 *
 * Tears down and cleans up the scheduler.
 *
 * This stops submission of new jobs to the hardware through
 * drm_sched_backend_ops.run_job(). Consequently, drm_sched_backend_ops.free_job()
 * will not be called for all jobs still in drm_gpu_scheduler.pending_list.
 * There is no solution for this currently. Thus, it is up to the driver to make
 * sure that:
 *
 *  a) drm_sched_fini() is only called after for all submitted jobs
 *     drm_sched_backend_ops.free_job() has been called or that
 *  b) the jobs for which drm_sched_backend_ops.free_job() has not been called
 *     after drm_sched_fini() ran are freed manually.
 *
 * FIXME: Take care of the above problem and prevent this function from leaking
 * the jobs in drm_gpu_scheduler.pending_list under any circumstances.
 */
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_entity *s_entity;
        int i;

        drm_sched_wqueue_stop(sched);

        for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
                struct drm_sched_rq *rq = sched->sched_rq[i];

                spin_lock(&rq->lock);
                list_for_each_entry(s_entity, &rq->entities, list)
                        /*
                         * Prevents reinsertion and marks job_queue as idle,
                         * it will be removed from the rq in drm_sched_entity_fini()
                         * eventually
                         */
                        s_entity->stopped = true;
                spin_unlock(&rq->lock);
                kfree(sched->sched_rq[i]);
        }

        /* Wakeup everyone stuck in drm_sched_entity_flush for this scheduler */
        wake_up_all(&sched->job_scheduled);

        /* Confirm no work left behind accessing device structures */
        cancel_delayed_work_sync(&sched->work_tdr);

        if (sched->own_submit_wq)
                destroy_workqueue(sched->submit_wq);
        sched->ready = false;
        kfree(sched->sched_rq);
        sched->sched_rq = NULL;
}
EXPORT_SYMBOL(drm_sched_fini);

/**
 * 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 change @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_HIGH; i < sched->num_rqs; 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 (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_wqueue_ready - Is the scheduler ready for submission
 *
 * @sched: scheduler instance
 *
 * Returns true if submission is ready
 */
bool drm_sched_wqueue_ready(struct drm_gpu_scheduler *sched)
{
        return sched->ready;
}
EXPORT_SYMBOL(drm_sched_wqueue_ready);

/**
 * drm_sched_wqueue_stop - stop scheduler submission
 * @sched: scheduler instance
 *
 * Stops the scheduler from pulling new jobs from entities. It also stops
 * freeing jobs automatically through drm_sched_backend_ops.free_job().
 */
void drm_sched_wqueue_stop(struct drm_gpu_scheduler *sched)
{
        WRITE_ONCE(sched->pause_submit, true);
        cancel_work_sync(&sched->work_run_job);
        cancel_work_sync(&sched->work_free_job);
}
EXPORT_SYMBOL(drm_sched_wqueue_stop);

/**
 * drm_sched_wqueue_start - start scheduler submission
 * @sched: scheduler instance
 *
 * Restarts the scheduler after drm_sched_wqueue_stop() has stopped it.
 *
 * This function is not necessary for 'conventional' startup. The scheduler is
 * fully operational after drm_sched_init() succeeded.
 */
void drm_sched_wqueue_start(struct drm_gpu_scheduler *sched)
{
        WRITE_ONCE(sched->pause_submit, false);
        queue_work(sched->submit_wq, &sched->work_run_job);
        queue_work(sched->submit_wq, &sched->work_free_job);
}
EXPORT_SYMBOL(drm_sched_wqueue_start);