/*
 * 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.
 *
 */

#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/completion.h>

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

#include "gpu_scheduler_trace.h"

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

/**
 * drm_sched_entity_init - Init a context entity used by scheduler when
 * submit to HW ring.
 *
 * @entity: scheduler entity to init
 * @priority: priority of the entity
 * @sched_list: the list of drm scheds on which jobs from this
 *           entity can be submitted
 * @num_sched_list: number of drm sched in sched_list
 * @guilty: atomic_t set to 1 when a job on this queue
 *          is found to be guilty causing a timeout
 *
 * Note: the sched_list should have at least one element to schedule
 *       the entity
 *
 * Returns 0 on success or a negative error code on failure.
 */
int drm_sched_entity_init(struct drm_sched_entity *entity,
                          enum drm_sched_priority priority,
                          struct drm_gpu_scheduler **sched_list,
                          unsigned int num_sched_list,
                          atomic_t *guilty)
{
        if (!(entity && sched_list && (num_sched_list == 0 || sched_list[0])))
                return -EINVAL;

        memset(entity, 0, sizeof(struct drm_sched_entity));
        INIT_LIST_HEAD(&entity->list);
        entity->rq = NULL;
        entity->guilty = guilty;
        entity->num_sched_list = num_sched_list;
        entity->priority = priority;
        entity->sched_list = num_sched_list > 1 ? sched_list : NULL;
        entity->last_scheduled = NULL;

        if(num_sched_list)
                entity->rq = &sched_list[0]->sched_rq[entity->priority];

        init_completion(&entity->entity_idle);

        /* We start in an idle state. */
        complete(&entity->entity_idle);

        spin_lock_init(&entity->rq_lock);
        spsc_queue_init(&entity->job_queue);

        atomic_set(&entity->fence_seq, 0);
        entity->fence_context = dma_fence_context_alloc(2);

        return 0;
}
EXPORT_SYMBOL(drm_sched_entity_init);

/**
 * drm_sched_entity_modify_sched - Modify sched of an entity
 * @entity: scheduler entity to init
 * @sched_list: the list of new drm scheds which will replace
 *               existing entity->sched_list
 * @num_sched_list: number of drm sched in sched_list
 */
void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
                                    struct drm_gpu_scheduler **sched_list,
                                    unsigned int num_sched_list)
{
        WARN_ON(!num_sched_list || !sched_list);

        entity->sched_list = sched_list;
        entity->num_sched_list = num_sched_list;
}
EXPORT_SYMBOL(drm_sched_entity_modify_sched);

/**
 * drm_sched_entity_is_idle - Check if entity is idle
 *
 * @entity: scheduler entity
 *
 * Returns true if the entity does not have any unscheduled jobs.
 */
static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
{
        rmb(); /* for list_empty to work without lock */

        if (list_empty(&entity->list) ||
            spsc_queue_count(&entity->job_queue) == 0)
                return true;

        return false;
}

/**
 * drm_sched_entity_is_ready - Check if entity is ready
 *
 * @entity: scheduler entity
 *
 * Return true if entity could provide a job.
 */
bool drm_sched_entity_is_ready(struct drm_sched_entity *entity)
{
        if (spsc_queue_peek(&entity->job_queue) == NULL)
                return false;

        if (READ_ONCE(entity->dependency))
                return false;

        return true;
}

/**
 * drm_sched_entity_flush - Flush a context entity
 *
 * @entity: scheduler entity
 * @timeout: time to wait in for Q to become empty in jiffies.
 *
 * Splitting drm_sched_entity_fini() into two functions, The first one does the
 * waiting, removes the entity from the runqueue and returns an error when the
 * process was killed.
 *
 * Returns the remaining time in jiffies left from the input timeout
 */
long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
{
        struct drm_gpu_scheduler *sched;
        struct task_struct *last_user;
        long ret = timeout;

        if (!entity->rq)
                return 0;

        sched = entity->rq->sched;
        /**
         * The client will not queue more IBs during this fini, consume existing
         * queued IBs or discard them on SIGKILL
         */
        if (current->flags & PF_EXITING) {
                if (timeout)
                        ret = wait_event_timeout(
                                        sched->job_scheduled,
                                        drm_sched_entity_is_idle(entity),
                                        timeout);
        } else {
                wait_event_killable(sched->job_scheduled,
                                    drm_sched_entity_is_idle(entity));
        }

        /* For killed process disable any more IBs enqueue right now */
        last_user = cmpxchg(&entity->last_user, current->group_leader, NULL);
        if ((!last_user || last_user == current->group_leader) &&
            (current->flags & PF_EXITING) && (current->exit_code == SIGKILL)) {
                spin_lock(&entity->rq_lock);
                entity->stopped = true;
                drm_sched_rq_remove_entity(entity->rq, entity);
                spin_unlock(&entity->rq_lock);
        }

        return ret;
}
EXPORT_SYMBOL(drm_sched_entity_flush);

/**
 * drm_sched_entity_kill_jobs - helper for drm_sched_entity_kill_jobs
 *
 * @f: signaled fence
 * @cb: our callback structure
 *
 * Signal the scheduler finished fence when the entity in question is killed.
 */
static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
                                          struct dma_fence_cb *cb)
{
        struct drm_sched_job *job = container_of(cb, struct drm_sched_job,
                                                 finish_cb);

        drm_sched_fence_finished(job->s_fence);
        WARN_ON(job->s_fence->parent);
        job->sched->ops->free_job(job);
}

/**
 * drm_sched_entity_kill_jobs - Make sure all remaining jobs are killed
 *
 * @entity: entity which is cleaned up
 *
 * Makes sure that all remaining jobs in an entity are killed before it is
 * destroyed.
 */
static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
{
        struct drm_sched_job *job;
        int r;

        while ((job = to_drm_sched_job(spsc_queue_pop(&entity->job_queue)))) {
                struct drm_sched_fence *s_fence = job->s_fence;

                drm_sched_fence_scheduled(s_fence);
                dma_fence_set_error(&s_fence->finished, -ESRCH);

                /*
                 * When pipe is hanged by older entity, new entity might
                 * not even have chance to submit it's first job to HW
                 * and so entity->last_scheduled will remain NULL
                 */
                if (!entity->last_scheduled) {
                        drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
                        continue;
                }

                r = dma_fence_add_callback(entity->last_scheduled,
                                           &job->finish_cb,
                                           drm_sched_entity_kill_jobs_cb);
                if (r == -ENOENT)
                        drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
                else if (r)
                        DRM_ERROR("fence add callback failed (%d)\n", r);
        }
}

/**
 * drm_sched_entity_cleanup - Destroy a context entity
 *
 * @entity: scheduler entity
 *
 * This should be called after @drm_sched_entity_do_release. It goes over the
 * entity and signals all jobs with an error code if the process was killed.
 *
 */
void drm_sched_entity_fini(struct drm_sched_entity *entity)
{
        struct drm_gpu_scheduler *sched = NULL;

        if (entity->rq) {
                sched = entity->rq->sched;
                drm_sched_rq_remove_entity(entity->rq, entity);
        }

        /* Consumption of existing IBs wasn't completed. Forcefully
         * remove them here.
         */
        if (spsc_queue_count(&entity->job_queue)) {
                if (sched) {
                        /*
                         * Wait for thread to idle to make sure it isn't processing
                         * this entity.
                         */
                        wait_for_completion(&entity->entity_idle);

                }
                if (entity->dependency) {
                        dma_fence_remove_callback(entity->dependency,
                                                  &entity->cb);
                        dma_fence_put(entity->dependency);
                        entity->dependency = NULL;
                }

                drm_sched_entity_kill_jobs(entity);
        }

        dma_fence_put(entity->last_scheduled);
        entity->last_scheduled = NULL;
}
EXPORT_SYMBOL(drm_sched_entity_fini);

/**
 * drm_sched_entity_fini - Destroy a context entity
 *
 * @entity: scheduler entity
 *
 * Calls drm_sched_entity_do_release() and drm_sched_entity_cleanup()
 */
void drm_sched_entity_destroy(struct drm_sched_entity *entity)
{
        drm_sched_entity_flush(entity, MAX_WAIT_SCHED_ENTITY_Q_EMPTY);
        drm_sched_entity_fini(entity);
}
EXPORT_SYMBOL(drm_sched_entity_destroy);

/*
 * drm_sched_entity_clear_dep - callback to clear the entities dependency
 */
static void drm_sched_entity_clear_dep(struct dma_fence *f,
                                       struct dma_fence_cb *cb)
{
        struct drm_sched_entity *entity =
                container_of(cb, struct drm_sched_entity, cb);

        entity->dependency = NULL;
        dma_fence_put(f);
}

/*
 * drm_sched_entity_clear_dep - callback to clear the entities dependency and
 * wake up scheduler
 */
static void drm_sched_entity_wakeup(struct dma_fence *f,
                                    struct dma_fence_cb *cb)
{
        struct drm_sched_entity *entity =
                container_of(cb, struct drm_sched_entity, cb);

        drm_sched_entity_clear_dep(f, cb);
        drm_sched_wakeup(entity->rq->sched);
}

/**
 * drm_sched_entity_set_priority - Sets priority of the entity
 *
 * @entity: scheduler entity
 * @priority: scheduler priority
 *
 * Update the priority of runqueus used for the entity.
 */
void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
                                   enum drm_sched_priority priority)
{
        spin_lock(&entity->rq_lock);
        entity->priority = priority;
        spin_unlock(&entity->rq_lock);
}
EXPORT_SYMBOL(drm_sched_entity_set_priority);

/**
 * drm_sched_entity_add_dependency_cb - add callback for the entities dependency
 *
 * @entity: entity with dependency
 *
 * Add a callback to the current dependency of the entity to wake up the
 * scheduler when the entity becomes available.
 */
static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity)
{
        struct drm_gpu_scheduler *sched = entity->rq->sched;
        struct dma_fence *fence = entity->dependency;
        struct drm_sched_fence *s_fence;

        if (fence->context == entity->fence_context ||
            fence->context == entity->fence_context + 1) {
                /*
                 * Fence is a scheduled/finished fence from a job
                 * which belongs to the same entity, we can ignore
                 * fences from ourself
                 */
                dma_fence_put(entity->dependency);
                return false;
        }

        s_fence = to_drm_sched_fence(fence);
        if (s_fence && s_fence->sched == sched) {

                /*
                 * Fence is from the same scheduler, only need to wait for
                 * it to be scheduled
                 */
                fence = dma_fence_get(&s_fence->scheduled);
                dma_fence_put(entity->dependency);
                entity->dependency = fence;
                if (!dma_fence_add_callback(fence, &entity->cb,
                                            drm_sched_entity_clear_dep))
                        return true;

                /* Ignore it when it is already scheduled */
                dma_fence_put(fence);
                return false;
        }

        if (!dma_fence_add_callback(entity->dependency, &entity->cb,
                                    drm_sched_entity_wakeup))
                return true;

        dma_fence_put(entity->dependency);
        return false;
}

/**
 * drm_sched_entity_pop_job - get a ready to be scheduled job from the entity
 *
 * @entity: entity to get the job from
 *
 * Process all dependencies and try to get one job from the entities queue.
 */
struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
{
        struct drm_gpu_scheduler *sched = entity->rq->sched;
        struct drm_sched_job *sched_job;

        sched_job = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
        if (!sched_job)
                return NULL;

        while ((entity->dependency =
                        sched->ops->dependency(sched_job, entity))) {
                trace_drm_sched_job_wait_dep(sched_job, entity->dependency);

                if (drm_sched_entity_add_dependency_cb(entity))
                        return NULL;
        }

        /* skip jobs from entity that marked guilty */
        if (entity->guilty && atomic_read(entity->guilty))
                dma_fence_set_error(&sched_job->s_fence->finished, -ECANCELED);

        dma_fence_put(entity->last_scheduled);
        entity->last_scheduled = dma_fence_get(&sched_job->s_fence->finished);

        spsc_queue_pop(&entity->job_queue);
        return sched_job;
}

/**
 * drm_sched_entity_select_rq - select a new rq for the entity
 *
 * @entity: scheduler entity
 *
 * Check all prerequisites and select a new rq for the entity for load
 * balancing.
 */
void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
{
        struct dma_fence *fence;
        struct drm_gpu_scheduler *sched;
        struct drm_sched_rq *rq;

        if (spsc_queue_count(&entity->job_queue) || entity->num_sched_list <= 1)
                return;

        fence = READ_ONCE(entity->last_scheduled);
        if (fence && !dma_fence_is_signaled(fence))
                return;

        spin_lock(&entity->rq_lock);
        sched = drm_sched_pick_best(entity->sched_list, entity->num_sched_list);
        rq = sched ? &sched->sched_rq[entity->priority] : NULL;
        if (rq != entity->rq) {
                drm_sched_rq_remove_entity(entity->rq, entity);
                entity->rq = rq;
        }

        spin_unlock(&entity->rq_lock);
}

/**
 * drm_sched_entity_push_job - Submit a job to the entity's job queue
 *
 * @sched_job: job to submit
 * @entity: scheduler entity
 *
 * Note: To guarantee that the order of insertion to queue matches
 * the job's fence sequence number this function should be
 * called with drm_sched_job_init under common lock.
 *
 * Returns 0 for success, negative error code otherwise.
 */
void drm_sched_entity_push_job(struct drm_sched_job *sched_job,
                               struct drm_sched_entity *entity)
{
        bool first;

        trace_drm_sched_job(sched_job, entity);
        atomic_inc(&entity->rq->sched->score);
        WRITE_ONCE(entity->last_user, current->group_leader);
        first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);

        /* first job wakes up scheduler */
        if (first) {
                /* Add the entity to the run queue */
                spin_lock(&entity->rq_lock);
                if (entity->stopped) {
                        spin_unlock(&entity->rq_lock);

                        DRM_ERROR("Trying to push to a killed entity\n");
                        return;
                }
                drm_sched_rq_add_entity(entity->rq, entity);
                spin_unlock(&entity->rq_lock);
                drm_sched_wakeup(entity->rq->sched);
        }
}
EXPORT_SYMBOL(drm_sched_entity_push_job);