/*
 * 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/wait.h>
#include <linux/sched.h>
#include <drm/drmP.h>
#include "gpu_scheduler.h"

#define CREATE_TRACE_POINTS
#include "gpu_sched_trace.h"

static bool amd_sched_entity_is_ready(struct amd_sched_entity *entity);
static void amd_sched_wakeup(struct amd_gpu_scheduler *sched);

struct kmem_cache *sched_fence_slab;
atomic_t sched_fence_slab_ref = ATOMIC_INIT(0);

/* Initialize a given run queue struct */
static void amd_sched_rq_init(struct amd_sched_rq *rq)
{
        spin_lock_init(&rq->lock);
        INIT_LIST_HEAD(&rq->entities);
        rq->current_entity = NULL;
}

static void amd_sched_rq_add_entity(struct amd_sched_rq *rq,
                                    struct amd_sched_entity *entity)
{
        if (!list_empty(&entity->list))
                return;
        spin_lock(&rq->lock);
        list_add_tail(&entity->list, &rq->entities);
        spin_unlock(&rq->lock);
}

static void amd_sched_rq_remove_entity(struct amd_sched_rq *rq,
                                       struct amd_sched_entity *entity)
{
        if (list_empty(&entity->list))
                return;
        spin_lock(&rq->lock);
        list_del_init(&entity->list);
        if (rq->current_entity == entity)
                rq->current_entity = NULL;
        spin_unlock(&rq->lock);
}

/**
 * Select an entity which could provide a job to run
 *
 * @rq          The run queue to check.
 *
 * Try to find a ready entity, returns NULL if none found.
 */
static struct amd_sched_entity *
amd_sched_rq_select_entity(struct amd_sched_rq *rq)
{
        struct amd_sched_entity *entity;

        spin_lock(&rq->lock);

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

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

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

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

        spin_unlock(&rq->lock);

        return NULL;
}

/**
 * Init a context entity used by scheduler when submit to HW ring.
 *
 * @sched       The pointer to the scheduler
 * @entity      The pointer to a valid amd_sched_entity
 * @rq          The run queue this entity belongs
 * @kernel      If this is an entity for the kernel
 * @jobs        The max number of jobs in the job queue
 *
 * return 0 if succeed. negative error code on failure
*/
int amd_sched_entity_init(struct amd_gpu_scheduler *sched,
                          struct amd_sched_entity *entity,
                          struct amd_sched_rq *rq,
                          uint32_t jobs)
{
        int r;

        if (!(sched && entity && rq))
                return -EINVAL;

        memset(entity, 0, sizeof(struct amd_sched_entity));
        INIT_LIST_HEAD(&entity->list);
        entity->rq = rq;
        entity->sched = sched;

        spin_lock_init(&entity->queue_lock);
        r = kfifo_alloc(&entity->job_queue, jobs * sizeof(void *), GFP_KERNEL);
        if (r)
                return r;

        atomic_set(&entity->fence_seq, 0);
        entity->fence_context = fence_context_alloc(1);

        return 0;
}

/**
 * Query if entity is initialized
 *
 * @sched       Pointer to scheduler instance
 * @entity      The pointer to a valid scheduler entity
 *
 * return true if entity is initialized, false otherwise
*/
static bool amd_sched_entity_is_initialized(struct amd_gpu_scheduler *sched,
                                            struct amd_sched_entity *entity)
{
        return entity->sched == sched &&
                entity->rq != NULL;
}

/**
 * Check if entity is idle
 *
 * @entity      The pointer to a valid scheduler entity
 *
 * Return true if entity don't has any unscheduled jobs.
 */
static bool amd_sched_entity_is_idle(struct amd_sched_entity *entity)
{
        rmb();
        if (kfifo_is_empty(&entity->job_queue))
                return true;

        return false;
}

/**
 * Check if entity is ready
 *
 * @entity      The pointer to a valid scheduler entity
 *
 * Return true if entity could provide a job.
 */
static bool amd_sched_entity_is_ready(struct amd_sched_entity *entity)
{
        if (kfifo_is_empty(&entity->job_queue))
                return false;

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

        return true;
}

/**
 * Destroy a context entity
 *
 * @sched       Pointer to scheduler instance
 * @entity      The pointer to a valid scheduler entity
 *
 * Cleanup and free the allocated resources.
 */
void amd_sched_entity_fini(struct amd_gpu_scheduler *sched,
                           struct amd_sched_entity *entity)
{
        struct amd_sched_rq *rq = entity->rq;

        if (!amd_sched_entity_is_initialized(sched, entity))
                return;

        /**
         * The client will not queue more IBs during this fini, consume existing
         * queued IBs
        */
        wait_event(sched->job_scheduled, amd_sched_entity_is_idle(entity));

        amd_sched_rq_remove_entity(rq, entity);
        kfifo_free(&entity->job_queue);
}

static void amd_sched_entity_wakeup(struct fence *f, struct fence_cb *cb)
{
        struct amd_sched_entity *entity =
                container_of(cb, struct amd_sched_entity, cb);
        entity->dependency = NULL;
        fence_put(f);
        amd_sched_wakeup(entity->sched);
}

static bool amd_sched_entity_add_dependency_cb(struct amd_sched_entity *entity)
{
        struct amd_gpu_scheduler *sched = entity->sched;
        struct fence * fence = entity->dependency;
        struct amd_sched_fence *s_fence;

        if (fence->context == entity->fence_context) {
                /* We can ignore fences from ourself */
                fence_put(entity->dependency);
                return false;
        }

        s_fence = to_amd_sched_fence(fence);
        if (s_fence && s_fence->sched == sched) {
                /* Fence is from the same scheduler */
                if (test_bit(AMD_SCHED_FENCE_SCHEDULED_BIT, &fence->flags)) {
                        /* Ignore it when it is already scheduled */
                        fence_put(entity->dependency);
                        return false;
                }

                /* Wait for fence to be scheduled */
                entity->cb.func = amd_sched_entity_wakeup;
                list_add_tail(&entity->cb.node, &s_fence->scheduled_cb);
                return true;
        }

        if (!fence_add_callback(entity->dependency, &entity->cb,
                                amd_sched_entity_wakeup))
                return true;

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

static struct amd_sched_job *
amd_sched_entity_pop_job(struct amd_sched_entity *entity)
{
        struct amd_gpu_scheduler *sched = entity->sched;
        struct amd_sched_job *sched_job;

        if (!kfifo_out_peek(&entity->job_queue, &sched_job, sizeof(sched_job)))
                return NULL;

        while ((entity->dependency = sched->ops->dependency(sched_job)))
                if (amd_sched_entity_add_dependency_cb(entity))
                        return NULL;

        return sched_job;
}

/**
 * Helper to submit a job to the job queue
 *
 * @sched_job           The pointer to job required to submit
 *
 * Returns true if we could submit the job.
 */
static bool amd_sched_entity_in(struct amd_sched_job *sched_job)
{
        struct amd_gpu_scheduler *sched = sched_job->sched;
        struct amd_sched_entity *entity = sched_job->s_entity;
        bool added, first = false;

        spin_lock(&entity->queue_lock);
        added = kfifo_in(&entity->job_queue, &sched_job,
                        sizeof(sched_job)) == sizeof(sched_job);

        if (added && kfifo_len(&entity->job_queue) == sizeof(sched_job))
                first = true;

        spin_unlock(&entity->queue_lock);

        /* first job wakes up scheduler */
        if (first) {
                /* Add the entity to the run queue */
                amd_sched_rq_add_entity(entity->rq, entity);
                amd_sched_wakeup(sched);
        }
        return added;
}

/**
 * Submit a job to the job queue
 *
 * @sched_job           The pointer to job required to submit
 *
 * Returns 0 for success, negative error code otherwise.
 */
void amd_sched_entity_push_job(struct amd_sched_job *sched_job)
{
        struct amd_sched_entity *entity = sched_job->s_entity;

        trace_amd_sched_job(sched_job);
        wait_event(entity->sched->job_scheduled,
                   amd_sched_entity_in(sched_job));
}

/**
 * Return ture if we can push more jobs to the hw.
 */
static bool amd_sched_ready(struct amd_gpu_scheduler *sched)
{
        return atomic_read(&sched->hw_rq_count) <
                sched->hw_submission_limit;
}

/**
 * Wake up the scheduler when it is ready
 */
static void amd_sched_wakeup(struct amd_gpu_scheduler *sched)
{
        if (amd_sched_ready(sched))
                wake_up_interruptible(&sched->wake_up_worker);
}

/**
 * Select next entity to process
*/
static struct amd_sched_entity *
amd_sched_select_entity(struct amd_gpu_scheduler *sched)
{
        struct amd_sched_entity *entity;
        int i;

        if (!amd_sched_ready(sched))
                return NULL;

        /* Kernel run queue has higher priority than normal run queue*/
        for (i = 0; i < AMD_SCHED_MAX_PRIORITY; i++) {
                entity = amd_sched_rq_select_entity(&sched->sched_rq[i]);
                if (entity)
                        break;
        }

        return entity;
}

static void amd_sched_process_job(struct fence *f, struct fence_cb *cb)
{
        struct amd_sched_fence *s_fence =
                container_of(cb, struct amd_sched_fence, cb);
        struct amd_gpu_scheduler *sched = s_fence->sched;
        unsigned long flags;

        atomic_dec(&sched->hw_rq_count);
        amd_sched_fence_signal(s_fence);
        if (sched->timeout != MAX_SCHEDULE_TIMEOUT) {
                cancel_delayed_work(&s_fence->dwork);
                spin_lock_irqsave(&sched->fence_list_lock, flags);
                list_del_init(&s_fence->list);
                spin_unlock_irqrestore(&sched->fence_list_lock, flags);
        }
        trace_amd_sched_process_job(s_fence);
        fence_put(&s_fence->base);
        wake_up_interruptible(&sched->wake_up_worker);
}

static void amd_sched_fence_work_func(struct work_struct *work)
{
        struct amd_sched_fence *s_fence =
                container_of(work, struct amd_sched_fence, dwork.work);
        struct amd_gpu_scheduler *sched = s_fence->sched;
        struct amd_sched_fence *entity, *tmp;
        unsigned long flags;

        DRM_ERROR("[%s] scheduler is timeout!\n", sched->name);

        /* Clean all pending fences */
        spin_lock_irqsave(&sched->fence_list_lock, flags);
        list_for_each_entry_safe(entity, tmp, &sched->fence_list, list) {
                DRM_ERROR("  fence no %d\n", entity->base.seqno);
                cancel_delayed_work(&entity->dwork);
                list_del_init(&entity->list);
                fence_put(&entity->base);
        }
        spin_unlock_irqrestore(&sched->fence_list_lock, flags);
}

static int amd_sched_main(void *param)
{
        struct sched_param sparam = {.sched_priority = 1};
        struct amd_gpu_scheduler *sched = (struct amd_gpu_scheduler *)param;
        int r, count;

        spin_lock_init(&sched->fence_list_lock);
        INIT_LIST_HEAD(&sched->fence_list);
        sched_setscheduler(current, SCHED_FIFO, &sparam);

        while (!kthread_should_stop()) {
                struct amd_sched_entity *entity;
                struct amd_sched_fence *s_fence;
                struct amd_sched_job *sched_job;
                struct fence *fence;
                unsigned long flags;

                wait_event_interruptible(sched->wake_up_worker,
                        (entity = amd_sched_select_entity(sched)) ||
                        kthread_should_stop());

                if (!entity)
                        continue;

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

                s_fence = sched_job->s_fence;

                if (sched->timeout != MAX_SCHEDULE_TIMEOUT) {
                        INIT_DELAYED_WORK(&s_fence->dwork, amd_sched_fence_work_func);
                        schedule_delayed_work(&s_fence->dwork, sched->timeout);
                        spin_lock_irqsave(&sched->fence_list_lock, flags);
                        list_add_tail(&s_fence->list, &sched->fence_list);
                        spin_unlock_irqrestore(&sched->fence_list_lock, flags);
                }

                atomic_inc(&sched->hw_rq_count);
                fence = sched->ops->run_job(sched_job);
                amd_sched_fence_scheduled(s_fence);
                if (fence) {
                        r = fence_add_callback(fence, &s_fence->cb,
                                               amd_sched_process_job);
                        if (r == -ENOENT)
                                amd_sched_process_job(fence, &s_fence->cb);
                        else if (r)
                                DRM_ERROR("fence add callback failed (%d)\n", r);
                        fence_put(fence);
                } else {
                        DRM_ERROR("Failed to run job!\n");
                        amd_sched_process_job(NULL, &s_fence->cb);
                }

                count = kfifo_out(&entity->job_queue, &sched_job,
                                sizeof(sched_job));
                WARN_ON(count != sizeof(sched_job));
                wake_up(&sched->job_scheduled);
        }
        return 0;
}

/**
 * Init a gpu scheduler instance
 *
 * @sched               The pointer to the scheduler
 * @ops                 The backend operations for this scheduler.
 * @hw_submissions      Number of hw submissions to do.
 * @name                Name used for debugging
 *
 * Return 0 on success, otherwise error code.
*/
int amd_sched_init(struct amd_gpu_scheduler *sched,
                   struct amd_sched_backend_ops *ops,
                   unsigned hw_submission, long timeout, const char *name)
{
        int i;
        sched->ops = ops;
        sched->hw_submission_limit = hw_submission;
        sched->name = name;
        sched->timeout = timeout;
        for (i = 0; i < AMD_SCHED_MAX_PRIORITY; i++)
                amd_sched_rq_init(&sched->sched_rq[i]);

        init_waitqueue_head(&sched->wake_up_worker);
        init_waitqueue_head(&sched->job_scheduled);
        atomic_set(&sched->hw_rq_count, 0);
        if (atomic_inc_return(&sched_fence_slab_ref) == 1) {
                sched_fence_slab = kmem_cache_create(
                        "amd_sched_fence", sizeof(struct amd_sched_fence), 0,
                        SLAB_HWCACHE_ALIGN, NULL);
                if (!sched_fence_slab)
                        return -ENOMEM;
        }

        /* Each scheduler will run on a seperate kernel thread */
        sched->thread = kthread_run(amd_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;
}

/**
 * Destroy a gpu scheduler
 *
 * @sched       The pointer to the scheduler
 */
void amd_sched_fini(struct amd_gpu_scheduler *sched)
{
        if (sched->thread)
                kthread_stop(sched->thread);
        if (atomic_dec_and_test(&sched_fence_slab_ref))
                kmem_cache_destroy(sched_fence_slab);
}