/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2019 Intel Corporation
 */

#include <linux/workqueue.h>

#include "i915_drv.h" /* for_each_engine() */
#include "i915_request.h"
#include "intel_engine_heartbeat.h"
#include "intel_gt.h"
#include "intel_gt_pm.h"
#include "intel_gt_requests.h"
#include "intel_timeline.h"

static bool retire_requests(struct intel_timeline *tl)
{
        struct i915_request *rq, *rn;

        list_for_each_entry_safe(rq, rn, &tl->requests, link)
                if (!i915_request_retire(rq))
                        return false;

        /* And check nothing new was submitted */
        return !i915_active_fence_isset(&tl->last_request);
}

static bool engine_active(const struct intel_engine_cs *engine)
{
        return !list_empty(&engine->kernel_context->timeline->requests);
}

static bool flush_submission(struct intel_gt *gt, long timeout)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
        bool active = false;

        if (!timeout)
                return false;

        if (!intel_gt_pm_is_awake(gt))
                return false;

        for_each_engine(engine, gt, id) {
                intel_engine_flush_submission(engine);

                /* Flush the background retirement and idle barriers */
                flush_work(&engine->retire_work);
                flush_delayed_work(&engine->wakeref.work);

                /* Is the idle barrier still outstanding? */
                active |= engine_active(engine);
        }

        return active;
}

static void engine_retire(struct work_struct *work)
{
        struct intel_engine_cs *engine =
                container_of(work, typeof(*engine), retire_work);
        struct intel_timeline *tl = xchg(&engine->retire, NULL);

        do {
                struct intel_timeline *next = xchg(&tl->retire, NULL);

                /*
                 * Our goal here is to retire _idle_ timelines as soon as
                 * possible (as they are idle, we do not expect userspace
                 * to be cleaning up anytime soon).
                 *
                 * If the timeline is currently locked, either it is being
                 * retired elsewhere or about to be!
                 */
                if (mutex_trylock(&tl->mutex)) {
                        retire_requests(tl);
                        mutex_unlock(&tl->mutex);
                }
                intel_timeline_put(tl);

                GEM_BUG_ON(!next);
                tl = ptr_mask_bits(next, 1);
        } while (tl);
}

static bool add_retire(struct intel_engine_cs *engine,
                       struct intel_timeline *tl)
{
#define STUB ((struct intel_timeline *)1)
        struct intel_timeline *first;

        /*
         * We open-code a llist here to include the additional tag [BIT(0)]
         * so that we know when the timeline is already on a
         * retirement queue: either this engine or another.
         */

        if (cmpxchg(&tl->retire, NULL, STUB)) /* already queued */
                return false;

        intel_timeline_get(tl);
        first = READ_ONCE(engine->retire);
        do
                tl->retire = ptr_pack_bits(first, 1, 1);
        while (!try_cmpxchg(&engine->retire, &first, tl));

        return !first;
}

void intel_engine_add_retire(struct intel_engine_cs *engine,
                             struct intel_timeline *tl)
{
        /* We don't deal well with the engine disappearing beneath us */
        GEM_BUG_ON(intel_engine_is_virtual(engine));

        if (add_retire(engine, tl))
                schedule_work(&engine->retire_work);
}

void intel_engine_init_retire(struct intel_engine_cs *engine)
{
        INIT_WORK(&engine->retire_work, engine_retire);
}

void intel_engine_fini_retire(struct intel_engine_cs *engine)
{
        flush_work(&engine->retire_work);
        GEM_BUG_ON(engine->retire);
}

long intel_gt_retire_requests_timeout(struct intel_gt *gt, long timeout)
{
        struct intel_gt_timelines *timelines = &gt->timelines;
        struct intel_timeline *tl, *tn;
        unsigned long active_count = 0;
        LIST_HEAD(free);

        flush_submission(gt, timeout); /* kick the ksoftirqd tasklets */
        spin_lock(&timelines->lock);
        list_for_each_entry_safe(tl, tn, &timelines->active_list, link) {
                if (!mutex_trylock(&tl->mutex)) {
                        active_count++; /* report busy to caller, try again? */
                        continue;
                }

                intel_timeline_get(tl);
                GEM_BUG_ON(!atomic_read(&tl->active_count));
                atomic_inc(&tl->active_count); /* pin the list element */
                spin_unlock(&timelines->lock);

                if (timeout > 0) {
                        struct dma_fence *fence;

                        fence = i915_active_fence_get(&tl->last_request);
                        if (fence) {
                                mutex_unlock(&tl->mutex);

                                timeout = dma_fence_wait_timeout(fence,
                                                                 true,
                                                                 timeout);
                                dma_fence_put(fence);

                                /* Retirement is best effort */
                                if (!mutex_trylock(&tl->mutex)) {
                                        active_count++;
                                        goto out_active;
                                }
                        }
                }

                if (!retire_requests(tl))
                        active_count++;
                mutex_unlock(&tl->mutex);

out_active:     spin_lock(&timelines->lock);

                /* Resume list iteration after reacquiring spinlock */
                list_safe_reset_next(tl, tn, link);
                if (atomic_dec_and_test(&tl->active_count))
                        list_del(&tl->link);

                /* Defer the final release to after the spinlock */
                if (refcount_dec_and_test(&tl->kref.refcount)) {
                        GEM_BUG_ON(atomic_read(&tl->active_count));
                        list_add(&tl->link, &free);
                }
        }
        spin_unlock(&timelines->lock);

        list_for_each_entry_safe(tl, tn, &free, link)
                __intel_timeline_free(&tl->kref);

        if (flush_submission(gt, timeout)) /* Wait, there's more! */
                active_count++;

        return active_count ? timeout : 0;
}

int intel_gt_wait_for_idle(struct intel_gt *gt, long timeout)
{
        /* If the device is asleep, we have no requests outstanding */
        if (!intel_gt_pm_is_awake(gt))
                return 0;

        while ((timeout = intel_gt_retire_requests_timeout(gt, timeout)) > 0) {
                cond_resched();
                if (signal_pending(current))
                        return -EINTR;
        }

        return timeout;
}

static void retire_work_handler(struct work_struct *work)
{
        struct intel_gt *gt =
                container_of(work, typeof(*gt), requests.retire_work.work);

        schedule_delayed_work(&gt->requests.retire_work,
                              round_jiffies_up_relative(HZ));
        intel_gt_retire_requests(gt);
}

void intel_gt_init_requests(struct intel_gt *gt)
{
        INIT_DELAYED_WORK(&gt->requests.retire_work, retire_work_handler);
}

void intel_gt_park_requests(struct intel_gt *gt)
{
        cancel_delayed_work(&gt->requests.retire_work);
}

void intel_gt_unpark_requests(struct intel_gt *gt)
{
        schedule_delayed_work(&gt->requests.retire_work,
                              round_jiffies_up_relative(HZ));
}

void intel_gt_fini_requests(struct intel_gt *gt)
{
        /* Wait until the work is marked as finished before unloading! */
        cancel_delayed_work_sync(&gt->requests.retire_work);
}