linux/drivers/gpu/host1x/fence.c

// 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 DEFINE_SPINLOCK(lock);

struct host1x_syncpt_fence {
	struct dma_fence base;

	atomic_t signaling;

	struct host1x_syncpt *sp;
	u32 threshold;

	struct host1x_waitlist *waiter;
	void *waiter_ref;

	struct delayed_work timeout_work;
};

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);
	int err;

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

	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 provide a userspace API to create arbitrary syncpoint fences,
	 * so we cannot normally guarantee that all fences get signalled.
	 * As such, setup a timeout, so that long-lasting fences will get
	 * reaped eventually.
	 */
	schedule_delayed_work(&sf->timeout_work, msecs_to_jiffies(30000));

	err = host1x_intr_add_action(sf->sp->host, sf->sp, sf->threshold,
				     HOST1X_INTR_ACTION_SIGNAL_FENCE, f,
				     sf->waiter, &sf->waiter_ref);
	if (err) {
		cancel_delayed_work_sync(&sf->timeout_work);
		dma_fence_put(f);
		return false;
	}

	/* intr framework takes ownership of waiter */
	sf->waiter = NULL;

	/*
	 * 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 void host1x_syncpt_fence_release(struct dma_fence *f)
{
	struct host1x_syncpt_fence *sf = to_host1x_fence(f);

	if (sf->waiter)
		kfree(sf->waiter);

	dma_fence_free(f);
}

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,
	.release = host1x_syncpt_fence_release,
};

void host1x_fence_signal(struct host1x_syncpt_fence *f)
{
	if (atomic_xchg(&f->signaling, 1))
		return;

	/*
	 * Cancel pending timeout work - if it races, it will
	 * not get 'f->signaling' and return.
	 */
	cancel_delayed_work_sync(&f->timeout_work);

	host1x_intr_put_ref(f->sp->host, f->sp->id, f->waiter_ref, false);

	dma_fence_signal(&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))
		return;

	/*
	 * Cancel pending timeout work - if it races, it will
	 * not get 'f->signaling' and return.
	 */
	host1x_intr_put_ref(f->sp->host, f->sp->id, f->waiter_ref, true);

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

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

	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
	if (!fence)
		return ERR_PTR(-ENOMEM);

	fence->waiter = kzalloc(sizeof(*fence->waiter), GFP_KERNEL);
	if (!fence->waiter) {
		kfree(fence);
		return ERR_PTR(-ENOMEM);
	}

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

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

	INIT_DELAYED_WORK(&fence->timeout_work, do_fence_timeout);

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