/*
 * 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/export.h>
#include <linux/slab.h>
#include <linux/completion.h>

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

#include "sched_internal.h"

#include "gpu_scheduler_trace.h"

/**
 * 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 that the &sched_list must have at least one element to schedule the entity.
 *
 * For changing @priority later on at runtime see
 * drm_sched_entity_set_priority(). For changing the set of schedulers
 * @sched_list at runtime see drm_sched_entity_modify_sched().
 *
 * An entity is cleaned up by calling drm_sched_entity_fini(). See also
 * drm_sched_entity_destroy().
 *
 * 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->last_user = current->group_leader;
        /*
         * It's perfectly valid to initialize an entity without having a valid
         * scheduler attached. It's just not valid to use the scheduler before it
         * is initialized itself.
         */
        entity->sched_list = num_sched_list > 1 ? sched_list : NULL;
        RCU_INIT_POINTER(entity->last_scheduled, NULL);
        RB_CLEAR_NODE(&entity->rb_tree_node);

        if (num_sched_list && !sched_list[0]->sched_rq) {
                /* Since every entry covered by num_sched_list
                 * should be non-NULL and therefore we warn drivers
                 * not to do this and to fix their DRM calling order.
                 */
                pr_warn("%s: called with uninitialized scheduler\n", __func__);
        } else if (num_sched_list) {
                /* The "priority" of an entity cannot exceed the number of run-queues of a
                 * scheduler. Protect against num_rqs being 0, by converting to signed. Choose
                 * the lowest priority available.
                 */
                if (entity->priority >= sched_list[0]->num_rqs) {
                        dev_err(sched_list[0]->dev, "entity has out-of-bounds priority: %u. num_rqs: %u\n",
                                entity->priority, sched_list[0]->num_rqs);
                        entity->priority = max_t(s32, (s32) sched_list[0]->num_rqs - 1,
                                                 (s32) DRM_SCHED_PRIORITY_KERNEL);
                }
                entity->rq = sched_list[0]->sched_rq[entity->priority];
        }

        init_completion(&entity->entity_idle);

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

        spin_lock_init(&entity->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
 *
 * Note that this must be called under the same common lock for @entity as
 * drm_sched_job_arm() and drm_sched_entity_push_job(), or the driver needs to
 * guarantee through some other means that this is never called while new jobs
 * can be pushed to @entity.
 */
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);

        spin_lock(&entity->lock);
        entity->sched_list = sched_list;
        entity->num_sched_list = num_sched_list;
        spin_unlock(&entity->lock);
}
EXPORT_SYMBOL(drm_sched_entity_modify_sched);

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 ||
            entity->stopped)
                return true;

        return false;
}

/**
 * drm_sched_entity_error - return error of last scheduled job
 * @entity: scheduler entity to check
 *
 * Opportunistically return the error of the last scheduled job. Result can
 * change any time when new jobs are pushed to the hw.
 */
int drm_sched_entity_error(struct drm_sched_entity *entity)
{
        struct dma_fence *fence;
        int r;

        rcu_read_lock();
        fence = rcu_dereference(entity->last_scheduled);
        r = fence ? fence->error : 0;
        rcu_read_unlock();

        return r;
}
EXPORT_SYMBOL(drm_sched_entity_error);

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

static void drm_sched_entity_kill_jobs_work(struct work_struct *wrk)
{
        struct drm_sched_job *job = container_of(wrk, typeof(*job), work);
        struct dma_fence *f;
        unsigned long index;

        /* Wait for all dependencies to avoid data corruptions */
        xa_for_each(&job->dependencies, index, f) {
                struct drm_sched_fence *s_fence = to_drm_sched_fence(f);

                if (s_fence && f == &s_fence->scheduled) {
                        /* The dependencies array had a reference on the scheduled
                         * fence, and the finished fence refcount might have
                         * dropped to zero. Use dma_fence_get_rcu() so we get
                         * a NULL fence in that case.
                         */
                        f = dma_fence_get_rcu(&s_fence->finished);

                        /* Now that we have a reference on the finished fence,
                         * we can release the reference the dependencies array
                         * had on the scheduled fence.
                         */
                        dma_fence_put(&s_fence->scheduled);
                }

                xa_erase(&job->dependencies, index);
                if (f && !dma_fence_add_callback(f, &job->finish_cb,
                                                 drm_sched_entity_kill_jobs_cb))
                        return;

                dma_fence_put(f);
        }

        drm_sched_fence_scheduled(job->s_fence, NULL);
        drm_sched_fence_finished(job->s_fence, -ESRCH);
        WARN_ON(job->s_fence->parent);
        job->sched->ops->free_job(job);
}

/* 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);

        dma_fence_put(f);

        INIT_WORK(&job->work, drm_sched_entity_kill_jobs_work);
        schedule_work(&job->work);
}

/* Remove the entity from the scheduler and kill all pending jobs */
static void drm_sched_entity_kill(struct drm_sched_entity *entity)
{
        struct drm_sched_job *job;
        struct dma_fence *prev;

        if (!entity->rq)
                return;

        spin_lock(&entity->lock);
        entity->stopped = true;
        drm_sched_rq_remove_entity(entity->rq, entity);
        spin_unlock(&entity->lock);

        /* Make sure this entity is not used by the scheduler at the moment */
        wait_for_completion(&entity->entity_idle);

        /* The entity is guaranteed to not be used by the scheduler */
        prev = rcu_dereference_check(entity->last_scheduled, true);
        dma_fence_get(prev);
        while ((job = drm_sched_entity_queue_pop(entity))) {
                struct drm_sched_fence *s_fence = job->s_fence;

                dma_fence_get(&s_fence->finished);
                if (!prev ||
                    dma_fence_add_callback(prev, &job->finish_cb,
                                           drm_sched_entity_kill_jobs_cb)) {
                        /*
                         * Adding callback above failed.
                         * dma_fence_put() checks for NULL.
                         */
                        dma_fence_put(prev);
                        drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb);
                }

                prev = &s_fence->finished;
        }
        dma_fence_put(prev);
}

/**
 * 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 jobs during this fini - consume
         * existing queued ones, 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 a killed process disallow further enqueueing of jobs. */
        last_user = cmpxchg(&entity->last_user, current->group_leader, NULL);
        if (last_user == current->group_leader &&
            (current->flags & PF_EXITING) && (current->exit_code == SIGKILL))
                drm_sched_entity_kill(entity);

        return ret;
}
EXPORT_SYMBOL(drm_sched_entity_flush);

/**
 * drm_sched_entity_fini - Destroy a context entity
 *
 * @entity: scheduler entity
 *
 * Cleanups up @entity which has been initialized by drm_sched_entity_init().
 *
 * If there are potentially job still in flight or getting newly queued
 * drm_sched_entity_flush() must be called first. This function then 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)
{
        /*
         * If consumption of existing jobs wasn't completed forcefully remove
         * them. Also makes sure that the scheduler won't touch this entity any
         * more.
         */
        drm_sched_entity_kill(entity);

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

        dma_fence_put(rcu_dereference_check(entity->last_scheduled, true));
        RCU_INIT_POINTER(entity->last_scheduled, NULL);
}
EXPORT_SYMBOL(drm_sched_entity_fini);

/**
 * drm_sched_entity_destroy - Destroy a context entity
 * @entity: scheduler entity
 *
 * Calls drm_sched_entity_flush() and drm_sched_entity_fini() as a
 * convenience wrapper.
 */
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_wakeup - callback to clear the entity's dependency and
 * wake up the 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);

        entity->dependency = NULL;
        dma_fence_put(f);
        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 runqueues used for the entity.
 */
void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
                                   enum drm_sched_priority priority)
{
        spin_lock(&entity->lock);
        entity->priority = priority;
        spin_unlock(&entity->lock);
}
EXPORT_SYMBOL(drm_sched_entity_set_priority);

/*
 * 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_sched_job *sched_job)
{
        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 (!fence->error && s_fence && s_fence->sched == sched &&
            !test_bit(DRM_SCHED_FENCE_DONT_PIPELINE, &fence->flags)) {

                /*
                 * 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 (trace_drm_sched_job_unschedulable_enabled() &&
            !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &entity->dependency->flags))
                trace_drm_sched_job_unschedulable(sched_job, entity->dependency);

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

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

static struct dma_fence *
drm_sched_job_dependency(struct drm_sched_job *job,
                         struct drm_sched_entity *entity)
{
        struct dma_fence *f;

        /* We keep the fence around, so we can iterate over all dependencies
         * in drm_sched_entity_kill_jobs_cb() to ensure all deps are signaled
         * before killing the job.
         */
        f = xa_load(&job->dependencies, job->last_dependency);
        if (f) {
                job->last_dependency++;
                return dma_fence_get(f);
        }

        if (job->sched->ops->prepare_job)
                return job->sched->ops->prepare_job(job, entity);

        return NULL;
}

struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
{
        struct drm_sched_job *sched_job;

        sched_job = drm_sched_entity_queue_peek(entity);
        if (!sched_job)
                return NULL;

        while ((entity->dependency =
                        drm_sched_job_dependency(sched_job, entity))) {
                if (drm_sched_entity_add_dependency_cb(entity, sched_job))
                        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(rcu_dereference_check(entity->last_scheduled, true));
        rcu_assign_pointer(entity->last_scheduled,
                           dma_fence_get(&sched_job->s_fence->finished));

        /*
         * If the queue is empty we allow drm_sched_entity_select_rq() to
         * locklessly access ->last_scheduled. This only works if we set the
         * pointer before we dequeue and if we a write barrier here.
         */
        smp_wmb();

        spsc_queue_pop(&entity->job_queue);

        /*
         * Update the entity's location in the min heap according to
         * the timestamp of the next job, if any.
         */
        if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) {
                struct drm_sched_job *next;

                next = drm_sched_entity_queue_peek(entity);
                if (next) {
                        struct drm_sched_rq *rq;

                        spin_lock(&entity->lock);
                        rq = entity->rq;
                        spin_lock(&rq->lock);
                        drm_sched_rq_update_fifo_locked(entity, rq,
                                                        next->submit_ts);
                        spin_unlock(&rq->lock);
                        spin_unlock(&entity->lock);
                }
        }

        /* Jobs and entities might have different lifecycles. Since we're
         * removing the job from the entities queue, set the jobs entity pointer
         * to NULL to prevent any future access of the entity through this job.
         */
        sched_job->entity = NULL;

        return sched_job;
}

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;

        /* single possible engine and already selected */
        if (!entity->sched_list)
                return;

        /* queue non-empty, stay on the same engine */
        if (spsc_queue_count(&entity->job_queue))
                return;

        /*
         * Only when the queue is empty are we guaranteed that
         * drm_sched_run_job_work() cannot change entity->last_scheduled. To
         * enforce ordering we need a read barrier here. See
         * drm_sched_entity_pop_job() for the other side.
         */
        smp_rmb();

        fence = rcu_dereference_check(entity->last_scheduled, true);

        /* stay on the same engine if the previous job hasn't finished */
        if (fence && !dma_fence_is_signaled(fence))
                return;

        spin_lock(&entity->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;
        }

        if (entity->num_sched_list == 1)
                entity->sched_list = NULL;

        spin_unlock(&entity->lock);
}

/**
 * drm_sched_entity_push_job - Submit a job to the entity's job queue
 * @sched_job: job to submit
 *
 * 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_arm()
 * under common lock for the struct drm_sched_entity that was set up for
 * @sched_job in drm_sched_job_init().
 */
void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
{
        struct drm_sched_entity *entity = sched_job->entity;
        bool first;
        ktime_t submit_ts;

        trace_drm_sched_job_queue(sched_job, entity);

        if (trace_drm_sched_job_add_dep_enabled()) {
                struct dma_fence *entry;
                unsigned long index;

                xa_for_each(&sched_job->dependencies, index, entry)
                        trace_drm_sched_job_add_dep(sched_job, entry);
        }
        atomic_inc(entity->rq->sched->score);
        WRITE_ONCE(entity->last_user, current->group_leader);

        /*
         * After the sched_job is pushed into the entity queue, it may be
         * completed and freed up at any time. We can no longer access it.
         * Make sure to set the submit_ts first, to avoid a race.
         */
        sched_job->submit_ts = submit_ts = ktime_get();
        first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);

        /* first job wakes up scheduler */
        if (first) {
                struct drm_gpu_scheduler *sched;
                struct drm_sched_rq *rq;

                /* Add the entity to the run queue */
                spin_lock(&entity->lock);
                if (entity->stopped) {
                        spin_unlock(&entity->lock);

                        DRM_ERROR("Trying to push to a killed entity\n");
                        return;
                }

                rq = entity->rq;
                sched = rq->sched;

                spin_lock(&rq->lock);
                drm_sched_rq_add_entity(rq, entity);

                if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
                        drm_sched_rq_update_fifo_locked(entity, rq, submit_ts);

                spin_unlock(&rq->lock);
                spin_unlock(&entity->lock);

                drm_sched_wakeup(sched);
        }
}
EXPORT_SYMBOL(drm_sched_entity_push_job);