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

#include <drm/drm_print.h>
#include <drm/drm_gem.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)

/**
 * 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->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_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)
{
        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_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);
}

/**
 * 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->pending_list))
                queue_delayed_work(sched->timeout_wq, &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(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_cleanup_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) {
                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)
{
        drm_sched_increase_karma_ext(bad, 1);
}
EXPORT_SYMBOL(drm_sched_increase_karma);

void drm_sched_reset_karma(struct drm_sched_job *bad)
{
        drm_sched_increase_karma_ext(bad, 0);
}
EXPORT_SYMBOL(drm_sched_reset_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
 * pending 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->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)) {
                        atomic_dec(&sched->hw_rq_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
 * @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->pending_list, list) {
                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_job_done_cb);
                        if (r == -ENOENT)
                                drm_sched_job_done(s_job);
                        else if (r)
                                DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
                                          r);
                } else
                        drm_sched_job_done(s_job);
        }

        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 relaunch jobs from the pending list
 *
 * @sched: scheduler instance
 *
 */
void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
{
        drm_sched_resubmit_jobs_ext(sched, INT_MAX);
}
EXPORT_SYMBOL(drm_sched_resubmit_jobs);

/**
 * drm_sched_resubmit_jobs_ext - helper to relunch certain number of jobs from mirror ring list
 *
 * @sched: scheduler instance
 * @max: job numbers to relaunch
 *
 */
void drm_sched_resubmit_jobs_ext(struct drm_gpu_scheduler *sched, int max)
{
        struct drm_sched_job *s_job, *tmp;
        uint64_t guilty_context;
        bool found_guilty = false;
        struct dma_fence *fence;
        int i = 0;

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

                if (i >= max)
                        break;

                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);
                i++;

                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_ext);

/**
 * 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.
 *
 * 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.
 *
 * 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,
                       void *owner)
{
        drm_sched_entity_select_rq(entity);
        if (!entity->rq)
                return -ENOENT;

        job->entity = entity;
        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);

        sched = entity->rq->sched;

        job->sched = sched;
        job->s_priority = entity->rq - sched->sched_rq;
        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_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)
{
        struct dma_resv_iter cursor;
        struct dma_fence *fence;
        int ret;

        dma_resv_for_each_fence(&cursor, obj->resv, write, 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_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_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_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
                entity = drm_sched_rq_select_entity(&sched->sched_rq[i]);
                if (entity)
                        break;
        }

        return entity;
}

/**
 * drm_sched_get_cleanup_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_cleanup_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) {
                        next->s_fence->scheduled.timestamp =
                                job->s_fence->finished.timestamp;
                        /* 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_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);

                if (!entity)
                        continue;

                sched_job = drm_sched_entity_pop_job(entity);

                if (!sched_job) {
                        complete(&entity->entity_idle);
                        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);
                complete(&entity->entity_idle);
                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_job_done_cb);
                        if (r == -ENOENT)
                                drm_sched_job_done(sched_job);
                        else if (r)
                                DRM_DEV_ERROR(sched->dev, "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_job_done(sched_job);
                }

                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
 * @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
 *
 * 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, struct workqueue_struct *timeout_wq,
                   atomic_t *score, const char *name, struct device *dev)
{
        int i, ret;
        sched->ops = ops;
        sched->hw_submission_limit = hw_submission;
        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;
        for (i = DRM_SCHED_PRIORITY_MIN; i < DRM_SCHED_PRIORITY_COUNT; 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->pending_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_DEV_ERROR(sched->dev, "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)
{
        struct drm_sched_entity *s_entity;
        int i;

        if (sched->thread)
                kthread_stop(sched->thread);

        for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
                struct drm_sched_rq *rq = &sched->sched_rq[i];

                if (!rq)
                        continue;

                spin_lock(&rq->lock);
                list_for_each_entry(s_entity, &rq->entities, list)
                        /*
                         * Prevents reinsertion and marks job_queue as idle,
                         * it will removed from rq in drm_sched_entity_fini
                         * eventually
                         */
                        s_entity->stopped = true;
                spin_unlock(&rq->lock);

        }

        /* 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);

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

/**
 * drm_sched_increase_karma_ext - Update sched_entity guilty flag
 *
 * @bad: The job guilty of time out
 * @type: type for increase/reset karma
 *
 */
void drm_sched_increase_karma_ext(struct drm_sched_job *bad, int type)
{
        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) {
                if (type == 0)
                        atomic_set(&bad->karma, 0);
                else if (type == 1)
                        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 (entity->guilty)
                                                atomic_set(entity->guilty, type);
                                        break;
                                }
                        }
                        spin_unlock(&rq->lock);
                        if (&entity->list != &rq->entities)
                                break;
                }
        }
}
EXPORT_SYMBOL(drm_sched_increase_karma_ext);