/*
 * 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 <uapi/linux/sched/types.h>
#include <drm/drmP.h>
#include <drm/gpu_scheduler.h>
#include <drm/spsc_queue.h>

#define CREATE_TRACE_POINTS
#include "gpu_scheduler_trace.h"

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

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

static void drm_sched_expel_job_unlocked(struct drm_sched_job *s_job);

/**
 * drm_sched_rq_init - initialize a given run queue struct
 *
 * @rq: scheduler run queue
 *
 * Initializes a scheduler runqueue.
 */
static void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
                              struct drm_sched_rq *rq)
{
        lockinit(&rq->lock, "gsrql", 0, LK_CANRECURSE);
        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;
        lockmgr(&rq->lock, LK_EXCLUSIVE);
        list_add_tail(&entity->list, &rq->entities);
        lockmgr(&rq->lock, LK_RELEASE);
}

/**
 * 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;
        lockmgr(&rq->lock, LK_EXCLUSIVE);
        list_del_init(&entity->list);
        if (rq->current_entity == entity)
                rq->current_entity = NULL;
        lockmgr(&rq->lock, LK_RELEASE);
}

/**
 * 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;

        lockmgr(&rq->lock, LK_EXCLUSIVE);

        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;
                                lockmgr(&rq->lock, LK_RELEASE);
                                return entity;
                        }
                }
        }

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

                if (drm_sched_entity_is_ready(entity)) {
                        rq->current_entity = entity;
                        lockmgr(&rq->lock, LK_RELEASE);
                        return entity;
                }

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

        lockmgr(&rq->lock, LK_RELEASE);

        return NULL;
}

/**
 * drm_sched_dependency_optimized
 *
 * @fence: the dependency fence
 * @entity: the entity which depends on the above fence
 *
 * Returns true if the dependency can be optimized and false otherwise
 */
bool drm_sched_dependency_optimized(struct dma_fence* fence,
                                    struct drm_sched_entity *entity)
{
        struct drm_gpu_scheduler *sched = entity->rq->sched;
        struct drm_sched_fence *s_fence;

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

        return false;
}
EXPORT_SYMBOL(drm_sched_dependency_optimized);

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

/* job_finish is called after hw fence signaled
 */
static void drm_sched_job_finish(struct work_struct *work)
{
        struct drm_sched_job *s_job = container_of(work, struct drm_sched_job,
                                                   finish_work);
        struct drm_gpu_scheduler *sched = s_job->sched;

        /*
         * Canceling the timeout without removing our job from the ring mirror
         * list is safe, as we will only end up in this worker if our jobs
         * finished fence has been signaled. So even if some another worker
         * manages to find this job as the next job in the list, the fence
         * signaled check below will prevent the timeout to be restarted.
         */
        cancel_delayed_work_sync(&sched->work_tdr);

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        /* remove job from ring_mirror_list */
        list_del_init(&s_job->node);
        /* queue TDR for next job */
        drm_sched_start_timeout(sched);
        lockmgr(&sched->job_list_lock, LK_RELEASE);

        dma_fence_put(&s_job->s_fence->finished);
        sched->ops->free_job(s_job);
}

static void drm_sched_job_finish_cb(struct dma_fence *f,
                                    struct dma_fence_cb *cb)
{
        struct drm_sched_job *job = container_of(cb, struct drm_sched_job,
                                                 finish_cb);
        schedule_work(&job->finish_work);
}

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

        dma_fence_add_callback(&s_job->s_fence->finished, &s_job->finish_cb,
                               drm_sched_job_finish_cb);

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_add_tail(&s_job->node, &sched->ring_mirror_list);
        drm_sched_start_timeout(sched);
        lockmgr(&sched->job_list_lock, LK_RELEASE);
}

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

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

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_for_each_entry_reverse(job, &sched->ring_mirror_list, node) {
                struct drm_sched_fence *fence = job->s_fence;

                if (!dma_fence_remove_callback(fence->parent, &fence->cb))
                        goto already_signaled;
        }

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

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

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_for_each_entry(job, &sched->ring_mirror_list, node) {
                struct drm_sched_fence *fence = job->s_fence;

                if (!fence->parent || !list_empty(&fence->cb.node))
                        continue;

                r = dma_fence_add_callback(fence->parent, &fence->cb,
                                           drm_sched_process_job);
                if (r)
                        drm_sched_process_job(fence->parent, &fence->cb);

already_signaled:
                ;
        }
        lockmgr(&sched->job_list_lock, LK_RELEASE);
}

/**
 * drm_sched_hw_job_reset - stop the scheduler if it contains the bad job
 *
 * @sched: scheduler instance
 * @bad: bad scheduler job
 *
 */
void drm_sched_hw_job_reset(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
{
        struct drm_sched_job *s_job;
        struct drm_sched_entity *entity, *tmp;
        int i;

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_for_each_entry_reverse(s_job, &sched->ring_mirror_list, node) {
                if (s_job->s_fence->parent &&
                    dma_fence_remove_callback(s_job->s_fence->parent,
                                              &s_job->s_fence->cb)) {
                        dma_fence_put(s_job->s_fence->parent);
                        s_job->s_fence->parent = NULL;
                        atomic_dec(&sched->hw_rq_count);
                }
        }
        lockmgr(&sched->job_list_lock, LK_RELEASE);

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

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

/**
 * drm_sched_job_recovery - recover jobs after a reset
 *
 * @sched: scheduler instance
 *
 */
void drm_sched_job_recovery(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_job *s_job, *tmp;
        bool found_guilty = false;
        int r;

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
                struct drm_sched_fence *s_fence = s_job->s_fence;
                struct dma_fence *fence;
                uint64_t guilty_context;

                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);

                lockmgr(&sched->job_list_lock, LK_RELEASE);
                fence = sched->ops->run_job(s_job);
                atomic_inc(&sched->hw_rq_count);

                if (fence) {
                        s_fence->parent = dma_fence_get(fence);
                        r = dma_fence_add_callback(fence, &s_fence->cb,
                                                   drm_sched_process_job);
                        if (r == -ENOENT)
                                drm_sched_process_job(fence, &s_fence->cb);
                        else if (r)
                                DRM_ERROR("fence add callback failed (%d)\n",
                                          r);
                        dma_fence_put(fence);
                } else {
                        if (s_fence->finished.error < 0)
                                drm_sched_expel_job_unlocked(s_job);
                        drm_sched_process_job(NULL, &s_fence->cb);
                }
                lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        }
        drm_sched_start_timeout(sched);
        lockmgr(&sched->job_list_lock, LK_RELEASE);
}
EXPORT_SYMBOL(drm_sched_job_recovery);

/**
 * drm_sched_job_init - init a scheduler job
 *
 * @job: scheduler job to init
 * @entity: scheduler entity to use
 * @owner: job owner for debugging
 *
 * Refer to drm_sched_entity_push_job() documentation
 * for locking considerations.
 *
 * Returns 0 for success, negative error code otherwise.
 */
int drm_sched_job_init(struct drm_sched_job *job,
                       struct drm_sched_entity *entity,
                       void *owner)
{
        struct drm_gpu_scheduler *sched;

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

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

        INIT_WORK(&job->finish_work, drm_sched_job_finish);
        INIT_LIST_HEAD(&job->node);

        return 0;
}
EXPORT_SYMBOL(drm_sched_job_init);

/**
 * drm_sched_ready - is the scheduler ready
 *
 * @sched: scheduler instance
 *
 * Return true if we can push more jobs to the hw, otherwise false.
 */
static bool drm_sched_ready(struct drm_gpu_scheduler *sched)
{
        return atomic_read(&sched->hw_rq_count) <
                sched->hw_submission_limit;
}

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

/**
 * drm_sched_select_entity - Select next entity to process
 *
 * @sched: scheduler instance
 *
 * Returns the entity to process or NULL if none are found.
 */
static struct drm_sched_entity *
drm_sched_select_entity(struct drm_gpu_scheduler *sched)
{
        struct drm_sched_entity *entity;
        int i;

        if (!drm_sched_ready(sched))
                return NULL;

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

        return entity;
}

/**
 * drm_sched_process_job - process a job
 *
 * @f: fence
 * @cb: fence callbacks
 *
 * Called after job has finished execution.
 */
static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
{
        struct drm_sched_fence *s_fence =
                container_of(cb, struct drm_sched_fence, cb);
        struct drm_gpu_scheduler *sched = s_fence->sched;

        dma_fence_get(&s_fence->finished);
        atomic_dec(&sched->hw_rq_count);
        atomic_dec(&sched->num_jobs);
        drm_sched_fence_finished(s_fence);

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

/**
 * drm_sched_blocked - check if the scheduler is blocked
 *
 * @sched: scheduler instance
 *
 * Returns true if blocked, otherwise false.
 */
static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
{
        if (kthread_should_park()) {
                kthread_parkme();
                return true;
        }

        return false;
}

/**
 * drm_sched_main - main scheduler thread
 *
 * @param: scheduler instance
 *
 * Returns 0.
 */
static int drm_sched_main(void *param)
{
#if 0
        struct sched_param sparam = {.sched_priority = 1};
#endif
        struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
        int r;

#if 0
        sched_setscheduler(current, SCHED_FIFO, &sparam);
#endif

        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;

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

                if (!entity)
                        continue;

                sched_job = drm_sched_entity_pop_job(entity);
                if (!sched_job)
                        continue;

                s_fence = sched_job->s_fence;

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

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

                if (fence) {
                        s_fence->parent = dma_fence_get(fence);
                        r = dma_fence_add_callback(fence, &s_fence->cb,
                                                   drm_sched_process_job);
                        if (r == -ENOENT)
                                drm_sched_process_job(fence, &s_fence->cb);
                        else if (r)
                                DRM_ERROR("fence add callback failed (%d)\n",
                                          r);
                        dma_fence_put(fence);
                } else {
                        if (s_fence->finished.error < 0)
                                drm_sched_expel_job_unlocked(sched_job);
                        drm_sched_process_job(NULL, &s_fence->cb);
                }

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

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

        lockmgr(&sched->job_list_lock, LK_EXCLUSIVE);
        list_del_init(&s_job->node);
        lockmgr(&sched->job_list_lock, LK_RELEASE);
}

/**
 * drm_sched_init - Init a gpu scheduler instance
 *
 * @sched: scheduler instance
 * @ops: backend operations for this scheduler
 * @hw_submission: number of hw submissions that can be in flight
 * @hang_limit: number of times to allow a job to hang before dropping it
 * @timeout: timeout value in jiffies for the scheduler
 * @name: name used for debugging
 *
 * Return 0 on success, otherwise error code.
 */
int drm_sched_init(struct drm_gpu_scheduler *sched,
                   const struct drm_sched_backend_ops *ops,
                   unsigned hw_submission,
                   unsigned hang_limit,
                   long timeout,
                   const char *name)
{
        int i;
        sched->ops = ops;
        sched->hw_submission_limit = hw_submission;
        sched->name = name;
        sched->timeout = timeout;
        sched->hang_limit = hang_limit;
        for (i = DRM_SCHED_PRIORITY_MIN; i < DRM_SCHED_PRIORITY_MAX; i++)
                drm_sched_rq_init(sched, &sched->sched_rq[i]);

        init_waitqueue_head(&sched->wake_up_worker);
        init_waitqueue_head(&sched->job_scheduled);
        INIT_LIST_HEAD(&sched->ring_mirror_list);
        lockinit(&sched->job_list_lock, "gssjll", 0, LK_CANRECURSE);
        atomic_set(&sched->hw_rq_count, 0);
        INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
        atomic_set(&sched->num_jobs, 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)) {
                DRM_ERROR("Failed to create scheduler for %s.\n", name);
                return PTR_ERR(sched->thread);
        }

        return 0;
}
EXPORT_SYMBOL(drm_sched_init);

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