// SPDX-License-Identifier: GPL-2.0-only
/*
 * Syncpoint dma_fence implementation
 *
 * Copyright (c) 2020, NVIDIA Corporation.
 */

#include <linux/dma-fence.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/sync_file.h>

#include "fence.h"
#include "intr.h"
#include "syncpt.h"

static const char *host1x_syncpt_fence_get_driver_name(struct dma_fence *f)
{
        return "host1x";
}

static const char *host1x_syncpt_fence_get_timeline_name(struct dma_fence *f)
{
        return "syncpoint";
}

static struct host1x_syncpt_fence *to_host1x_fence(struct dma_fence *f)
{
        return container_of(f, struct host1x_syncpt_fence, base);
}

static bool host1x_syncpt_fence_enable_signaling(struct dma_fence *f)
{
        struct host1x_syncpt_fence *sf = to_host1x_fence(f);

        if (host1x_syncpt_is_expired(sf->sp, sf->threshold))
                return false;

        /* Reference for interrupt path. */
        dma_fence_get(f);

        /*
         * The dma_fence framework requires the fence driver to keep a
         * reference to any fences for which 'enable_signaling' has been
         * called (and that have not been signalled).
         *
         * We cannot currently always guarantee that all fences get signalled
         * or cancelled. As such, for such situations, set up a timeout, so
         * that long-lasting fences will get reaped eventually.
         */
        if (sf->timeout) {
                /* Reference for timeout path. */
                dma_fence_get(f);
                schedule_delayed_work(&sf->timeout_work, msecs_to_jiffies(30000));
        }

        host1x_intr_add_fence_locked(sf->sp->host, sf);

        /*
         * The fence may get signalled at any time after the above call,
         * so we need to initialize all state used by signalling
         * before it.
         */

        return true;
}

static const struct dma_fence_ops host1x_syncpt_fence_ops = {
        .get_driver_name = host1x_syncpt_fence_get_driver_name,
        .get_timeline_name = host1x_syncpt_fence_get_timeline_name,
        .enable_signaling = host1x_syncpt_fence_enable_signaling,
};

void host1x_fence_signal(struct host1x_syncpt_fence *f)
{
        if (atomic_xchg(&f->signaling, 1)) {
                /*
                 * Already on timeout path, but we removed the fence before
                 * timeout path could, so drop interrupt path reference.
                 */
                dma_fence_put(&f->base);
                return;
        }

        if (f->timeout && cancel_delayed_work(&f->timeout_work)) {
                /*
                 * We know that the timeout path will not be entered.
                 * Safe to drop the timeout path's reference now.
                 */
                dma_fence_put(&f->base);
        }

        dma_fence_signal_locked(&f->base);
        dma_fence_put(&f->base);
}

static void do_fence_timeout(struct work_struct *work)
{
        struct delayed_work *dwork = (struct delayed_work *)work;
        struct host1x_syncpt_fence *f =
                container_of(dwork, struct host1x_syncpt_fence, timeout_work);

        if (atomic_xchg(&f->signaling, 1)) {
                /* Already on interrupt path, drop timeout path reference if any. */
                if (f->timeout)
                        dma_fence_put(&f->base);
                return;
        }

        if (host1x_intr_remove_fence(f->sp->host, f)) {
                /*
                 * Managed to remove fence from queue, so it's safe to drop
                 * the interrupt path's reference.
                 */
                dma_fence_put(&f->base);
        }

        dma_fence_set_error(&f->base, -ETIMEDOUT);
        dma_fence_signal(&f->base);
        if (f->timeout)
                dma_fence_put(&f->base);
}

struct dma_fence *host1x_fence_create(struct host1x_syncpt *sp, u32 threshold,
                                      bool timeout)
{
        struct host1x_syncpt_fence *fence;

        fence = kzalloc_obj(*fence);
        if (!fence)
                return ERR_PTR(-ENOMEM);

        fence->sp = sp;
        fence->threshold = threshold;
        fence->timeout = timeout;

        dma_fence_init(&fence->base, &host1x_syncpt_fence_ops, &sp->fences.lock,
                       dma_fence_context_alloc(1), 0);

        INIT_DELAYED_WORK(&fence->timeout_work, do_fence_timeout);

        return &fence->base;
}
EXPORT_SYMBOL(host1x_fence_create);

void host1x_fence_cancel(struct dma_fence *f)
{
        struct host1x_syncpt_fence *sf = to_host1x_fence(f);

        schedule_delayed_work(&sf->timeout_work, 0);
        flush_delayed_work(&sf->timeout_work);
}
EXPORT_SYMBOL(host1x_fence_cancel);