/*
 * (C) Copyright 2016 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 */

#include <linux/slab.h>
#include <linux/fence.h>
#include <linux/reservation.h>

#include "i915_sw_fence.h"

static DEFINE_SPINLOCK(i915_sw_fence_lock);

static int __i915_sw_fence_notify(struct i915_sw_fence *fence,
                                  enum i915_sw_fence_notify state)
{
        i915_sw_fence_notify_t fn;

        fn = (i915_sw_fence_notify_t)(fence->flags & I915_SW_FENCE_MASK);
        return fn(fence, state);
}

static void i915_sw_fence_free(struct kref *kref)
{
        struct i915_sw_fence *fence = container_of(kref, typeof(*fence), kref);

        WARN_ON(atomic_read(&fence->pending) > 0);

        if (fence->flags & I915_SW_FENCE_MASK)
                __i915_sw_fence_notify(fence, FENCE_FREE);
        else
                kfree(fence);
}

static void i915_sw_fence_put(struct i915_sw_fence *fence)
{
        kref_put(&fence->kref, i915_sw_fence_free);
}

static struct i915_sw_fence *i915_sw_fence_get(struct i915_sw_fence *fence)
{
        kref_get(&fence->kref);
        return fence;
}

static void __i915_sw_fence_wake_up_all(struct i915_sw_fence *fence,
                                        struct list_head *continuation)
{
        wait_queue_head_t *x = &fence->wait;
        wait_queue_t *pos, *next;
        unsigned long flags;

        atomic_set_release(&fence->pending, -1); /* 0 -> -1 [done] */

        /*
         * To prevent unbounded recursion as we traverse the graph of
         * i915_sw_fences, we move the task_list from this, the next ready
         * fence, to the tail of the original fence's task_list
         * (and so added to the list to be woken).
         */

        spin_lock_irqsave_nested(&x->lock, flags, 1 + !!continuation);
        if (continuation) {
                list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
                        if (pos->func == autoremove_wake_function)
                                pos->func(pos, TASK_NORMAL, 0, continuation);
                        else
                                list_move_tail(&pos->task_list, continuation);
                }
        } else {
                LIST_HEAD(extra);

                do {
                        list_for_each_entry_safe(pos, next,
                                                 &x->task_list, task_list)
                                pos->func(pos, TASK_NORMAL, 0, &extra);

                        if (list_empty(&extra))
                                break;

                        list_splice_tail_init(&extra, &x->task_list);
                } while (1);
        }
        spin_unlock_irqrestore(&x->lock, flags);
}

static void __i915_sw_fence_complete(struct i915_sw_fence *fence,
                                     struct list_head *continuation)
{
        if (!atomic_dec_and_test(&fence->pending))
                return;

        if (fence->flags & I915_SW_FENCE_MASK &&
            __i915_sw_fence_notify(fence, FENCE_COMPLETE) != NOTIFY_DONE)
                return;

        __i915_sw_fence_wake_up_all(fence, continuation);
}

static void i915_sw_fence_complete(struct i915_sw_fence *fence)
{
        if (WARN_ON(i915_sw_fence_done(fence)))
                return;

        __i915_sw_fence_complete(fence, NULL);
}

static void i915_sw_fence_await(struct i915_sw_fence *fence)
{
        WARN_ON(atomic_inc_return(&fence->pending) <= 1);
}

void i915_sw_fence_init(struct i915_sw_fence *fence, i915_sw_fence_notify_t fn)
{
        BUG_ON((unsigned long)fn & ~I915_SW_FENCE_MASK);

        init_waitqueue_head(&fence->wait);
        kref_init(&fence->kref);
        atomic_set(&fence->pending, 1);
        fence->flags = (unsigned long)fn;
}

void i915_sw_fence_commit(struct i915_sw_fence *fence)
{
        i915_sw_fence_complete(fence);
        i915_sw_fence_put(fence);
}

static int i915_sw_fence_wake(wait_queue_t *wq, unsigned mode, int flags, void *key)
{
        list_del(&wq->task_list);
        __i915_sw_fence_complete(wq->private, key);
        i915_sw_fence_put(wq->private);
        return 0;
}

static bool __i915_sw_fence_check_if_after(struct i915_sw_fence *fence,
                                    const struct i915_sw_fence * const signaler)
{
        wait_queue_t *wq;

        if (__test_and_set_bit(I915_SW_FENCE_CHECKED_BIT, &fence->flags))
                return false;

        if (fence == signaler)
                return true;

        list_for_each_entry(wq, &fence->wait.task_list, task_list) {
                if (wq->func != i915_sw_fence_wake)
                        continue;

                if (__i915_sw_fence_check_if_after(wq->private, signaler))
                        return true;
        }

        return false;
}

static void __i915_sw_fence_clear_checked_bit(struct i915_sw_fence *fence)
{
        wait_queue_t *wq;

        if (!__test_and_clear_bit(I915_SW_FENCE_CHECKED_BIT, &fence->flags))
                return;

        list_for_each_entry(wq, &fence->wait.task_list, task_list) {
                if (wq->func != i915_sw_fence_wake)
                        continue;

                __i915_sw_fence_clear_checked_bit(wq->private);
        }
}

static bool i915_sw_fence_check_if_after(struct i915_sw_fence *fence,
                                  const struct i915_sw_fence * const signaler)
{
        unsigned long flags;
        bool err;

        if (!IS_ENABLED(CONFIG_I915_SW_FENCE_CHECK_DAG))
                return false;

        spin_lock_irqsave(&i915_sw_fence_lock, flags);
        err = __i915_sw_fence_check_if_after(fence, signaler);
        __i915_sw_fence_clear_checked_bit(fence);
        spin_unlock_irqrestore(&i915_sw_fence_lock, flags);

        return err;
}

int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
                                 struct i915_sw_fence *signaler,
                                 wait_queue_t *wq)
{
        unsigned long flags;
        int pending;

        if (i915_sw_fence_done(signaler))
                return 0;

        /* The dependency graph must be acyclic. */
        if (unlikely(i915_sw_fence_check_if_after(fence, signaler)))
                return -EINVAL;

        INIT_LIST_HEAD(&wq->task_list);
        wq->flags = 0;
        wq->func = i915_sw_fence_wake;
        wq->private = i915_sw_fence_get(fence);

        i915_sw_fence_await(fence);

        spin_lock_irqsave(&signaler->wait.lock, flags);
        if (likely(!i915_sw_fence_done(signaler))) {
                __add_wait_queue_tail(&signaler->wait, wq);
                pending = 1;
        } else {
                i915_sw_fence_wake(wq, 0, 0, NULL);
                pending = 0;
        }
        spin_unlock_irqrestore(&signaler->wait.lock, flags);

        return pending;
}

struct dma_fence_cb {
        struct fence_cb base;
        struct i915_sw_fence *fence;
        struct fence *dma;
        struct timer_list timer;
};

static void timer_i915_sw_fence_wake(unsigned long data)
{
        struct dma_fence_cb *cb = (struct dma_fence_cb *)data;

        printk(KERN_WARNING "asynchronous wait on fence %s:%s:%x timed out\n",
               cb->dma->ops->get_driver_name(cb->dma),
               cb->dma->ops->get_timeline_name(cb->dma),
               cb->dma->seqno);
        fence_put(cb->dma);
        cb->dma = NULL;

        i915_sw_fence_commit(cb->fence);
        cb->timer.function = NULL;
}

static void dma_i915_sw_fence_wake(struct fence *dma, struct fence_cb *data)
{
        struct dma_fence_cb *cb = container_of(data, typeof(*cb), base);

        del_timer_sync(&cb->timer);
        if (cb->timer.function)
                i915_sw_fence_commit(cb->fence);
        fence_put(cb->dma);

        kfree(cb);
}

int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
                                  struct fence *dma,
                                  unsigned long timeout,
                                  gfp_t gfp)
{
        struct dma_fence_cb *cb;
        int ret;

        if (fence_is_signaled(dma))
                return 0;

        cb = kmalloc(sizeof(*cb), gfp);
        if (!cb) {
                if (!gfpflags_allow_blocking(gfp))
                        return -ENOMEM;

                return fence_wait(dma, false);
        }

        cb->fence = i915_sw_fence_get(fence);
        i915_sw_fence_await(fence);

        cb->dma = NULL;
        __setup_timer(&cb->timer,
                      timer_i915_sw_fence_wake, (unsigned long)cb,
                      TIMER_IRQSAFE);
        if (timeout) {
                cb->dma = fence_get(dma);
                mod_timer(&cb->timer, round_jiffies_up(jiffies + timeout));
        }

        ret = fence_add_callback(dma, &cb->base, dma_i915_sw_fence_wake);
        if (ret == 0) {
                ret = 1;
        } else {
                dma_i915_sw_fence_wake(dma, &cb->base);
                if (ret == -ENOENT) /* fence already signaled */
                        ret = 0;
        }

        return ret;
}

int i915_sw_fence_await_reservation(struct i915_sw_fence *fence,
                                    struct reservation_object *resv,
                                    const struct fence_ops *exclude,
                                    bool write,
                                    unsigned long timeout,
                                    gfp_t gfp)
{
        struct fence *excl;
        int ret = 0, pending;

        if (write) {
                struct fence **shared;
                unsigned int count, i;

                ret = reservation_object_get_fences_rcu(resv,
                                                        &excl, &count, &shared);
                if (ret)
                        return ret;

                for (i = 0; i < count; i++) {
                        if (shared[i]->ops == exclude)
                                continue;

                        pending = i915_sw_fence_await_dma_fence(fence,
                                                                shared[i],
                                                                timeout,
                                                                gfp);
                        if (pending < 0) {
                                ret = pending;
                                break;
                        }

                        ret |= pending;
                }

                for (i = 0; i < count; i++)
                        fence_put(shared[i]);
                kfree(shared);
        } else {
                excl = reservation_object_get_excl_rcu(resv);
        }

        if (ret >= 0 && excl && excl->ops != exclude) {
                pending = i915_sw_fence_await_dma_fence(fence,
                                                        excl,
                                                        timeout,
                                                        gfp);
                if (pending < 0)
                        ret = pending;
                else
                        ret |= pending;
        }

        fence_put(excl);

        return ret;
}