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/*

 * Fence mechanism for dma-buf and to allow for asynchronous dma access

 *

 * Copyright (C) 2012 Canonical Ltd

 * Copyright (C) 2012 Texas Instruments

 *

 * Authors:

 * Rob Clark 

 * Maarten Lankhorst 

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published by

 * the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for

 * more details.

 */

#include 

#include 

#include 

#include 

/*

 * fence context counter: each execution context should have its own

 * fence context, this allows checking if fences belong to the same

 * context or not. One device can have multiple separate contexts,

 * and they're used if some engine can run independently of another.

 */

static atomic_t fence_context_counter = ATOMIC_INIT(0);

/**

 * fence_context_alloc - allocate an array of fence contexts

 * @num:	[in]	amount of contexts to allocate

 *

 * This function will return the first index of the number of fences allocated.

 * The fence context is used for setting fence->context to a unique number.

 */

unsigned fence_context_alloc(unsigned num)

{

	BUG_ON(!num);

	return atomic_add_return(num, &fence_context_counter) - num;

}

EXPORT_SYMBOL(fence_context_alloc);

/**

 * fence_signal_locked - signal completion of a fence

 * @fence: the fence to signal

 *

 * Signal completion for software callbacks on a fence, this will unblock

 * fence_wait() calls and run all the callbacks added with

 * fence_add_callback(). Can be called multiple times, but since a fence

 * can only go from unsignaled to signaled state, it will only be effective

 * the first time.

 *

 * Unlike fence_signal, this function must be called with fence->lock held.

 */

int fence_signal_locked(struct fence *fence)

{

	struct fence_cb *cur, *tmp;

	int ret = 0;

	if (WARN_ON(!fence))

		return -EINVAL;

	if (!ktime_to_ns(fence->timestamp)) {

		fence->timestamp = ktime_get();

		smp_mb__before_atomic();

	}

	if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {

		ret = -EINVAL;

		/*

		 * we might have raced with the unlocked fence_signal,

		 * still run through all callbacks

		 */

    }

	list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {

		list_del_init(&cur->node);

		cur->func(fence, cur);

	}

	return ret;

}

EXPORT_SYMBOL(fence_signal_locked);

/**

 * fence_signal - signal completion of a fence

 * @fence: the fence to signal

 *

 * Signal completion for software callbacks on a fence, this will unblock

 * fence_wait() calls and run all the callbacks added with

 * fence_add_callback(). Can be called multiple times, but since a fence

 * can only go from unsignaled to signaled state, it will only be effective

 * the first time.

 */

int fence_signal(struct fence *fence)

{

	unsigned long flags;

	if (!fence)

		return -EINVAL;

	if (!ktime_to_ns(fence->timestamp)) {

		fence->timestamp = ktime_get();

		smp_mb__before_atomic();

	}

	if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		return -EINVAL;

	if (test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {

		struct fence_cb *cur, *tmp;

		spin_lock_irqsave(fence->lock, flags);

		list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {

			list_del_init(&cur->node);

			cur->func(fence, cur);

		}

		spin_unlock_irqrestore(fence->lock, flags);

	}

	return 0;

}

EXPORT_SYMBOL(fence_signal);

/**

 * fence_wait_timeout - sleep until the fence gets signaled

 * or until timeout elapses

 * @fence:	[in]	the fence to wait on

 * @intr:	[in]	if true, do an interruptible wait

 * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT

 *

 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the

 * remaining timeout in jiffies on success. Other error values may be

 * returned on custom implementations.

 *

 * Performs a synchronous wait on this fence. It is assumed the caller

 * directly or indirectly (buf-mgr between reservation and committing)

 * holds a reference to the fence, otherwise the fence might be

 * freed before return, resulting in undefined behavior.

 */

signed long

fence_wait_timeout(struct fence *fence, bool intr, signed long timeout)

{

	signed long ret;

	if (WARN_ON(timeout < 0))

		return -EINVAL;

	if (timeout == 0)

		return fence_is_signaled(fence);

    ret = fence->ops->wait(fence, intr, timeout);

    return ret;

}

EXPORT_SYMBOL(fence_wait_timeout);

void fence_release(struct kref *kref)

{

	struct fence *fence =

			container_of(kref, struct fence, refcount);

	BUG_ON(!list_empty(&fence->cb_list));

	if (fence->ops->release)

		fence->ops->release(fence);

	else

		fence_free(fence);

}

EXPORT_SYMBOL(fence_release);

void fence_free(struct fence *fence)

{

	kfree_rcu(fence, rcu);

}

EXPORT_SYMBOL(fence_free);

/**

 * fence_enable_sw_signaling - enable signaling on fence

 * @fence:	[in]	the fence to enable

 *

 * this will request for sw signaling to be enabled, to make the fence

 * complete as soon as possible

 */

void fence_enable_sw_signaling(struct fence *fence)

{

	unsigned long flags;

	if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&

	    !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {

		spin_lock_irqsave(fence->lock, flags);

		if (!fence->ops->enable_signaling(fence))

			fence_signal_locked(fence);

		spin_unlock_irqrestore(fence->lock, flags);

	}

}

EXPORT_SYMBOL(fence_enable_sw_signaling);

/**

 * fence_add_callback - add a callback to be called when the fence

 * is signaled

 * @fence:	[in]	the fence to wait on

 * @cb:		[in]	the callback to register

 * @func:	[in]	the function to call

 *

 * cb will be initialized by fence_add_callback, no initialization

 * by the caller is required. Any number of callbacks can be registered

 * to a fence, but a callback can only be registered to one fence at a time.

 *

 * Note that the callback can be called from an atomic context.  If

 * fence is already signaled, this function will return -ENOENT (and

 * *not* call the callback)

 *

 * Add a software callback to the fence. Same restrictions apply to

 * refcount as it does to fence_wait, however the caller doesn't need to

 * keep a refcount to fence afterwards: when software access is enabled,

 * the creator of the fence is required to keep the fence alive until

 * after it signals with fence_signal. The callback itself can be called

 * from irq context.

 *

 */

int fence_add_callback(struct fence *fence, struct fence_cb *cb,

		       fence_func_t func)

{

	unsigned long flags;

	int ret = 0;

	bool was_set;

	if (WARN_ON(!fence || !func))

		return -EINVAL;

	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {

		INIT_LIST_HEAD(&cb->node);

		return -ENOENT;

	}

	spin_lock_irqsave(fence->lock, flags);

	was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);

	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		ret = -ENOENT;

	else if (!was_set) {

		if (!fence->ops->enable_signaling(fence)) {

			fence_signal_locked(fence);

			ret = -ENOENT;

		}

	}

	if (!ret) {

		cb->func = func;

		list_add_tail(&cb->node, &fence->cb_list);

	} else

		INIT_LIST_HEAD(&cb->node);

	spin_unlock_irqrestore(fence->lock, flags);

	return ret;

}

EXPORT_SYMBOL(fence_add_callback);

/**

 * fence_remove_callback - remove a callback from the signaling list

 * @fence:	[in]	the fence to wait on

 * @cb:		[in]	the callback to remove

 *

 * Remove a previously queued callback from the fence. This function returns

 * true if the callback is successfully removed, or false if the fence has

 * already been signaled.

 *

 * *WARNING*:

 * Cancelling a callback should only be done if you really know what you're

 * doing, since deadlocks and race conditions could occur all too easily. For

 * this reason, it should only ever be done on hardware lockup recovery,

 * with a reference held to the fence.

 */

bool

fence_remove_callback(struct fence *fence, struct fence_cb *cb)

{

	unsigned long flags;

	bool ret;

	spin_lock_irqsave(fence->lock, flags);

	ret = !list_empty(&cb->node);

	if (ret)

		list_del_init(&cb->node);

	spin_unlock_irqrestore(fence->lock, flags);

	return ret;

}

EXPORT_SYMBOL(fence_remove_callback);

struct default_wait_cb {

	struct fence_cb base;

	struct task_struct *task;

};

static bool

fence_test_signaled_any(struct fence **fences, uint32_t count)

{

	int i;

	for (i = 0; i < count; ++i) {

		struct fence *fence = fences[i];

		if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))

			return true;

	}

	return false;

}

/**

 * fence_wait_any_timeout - sleep until any fence gets signaled

 * or until timeout elapses

 * @fences:	[in]	array of fences to wait on

 * @count:	[in]	number of fences to wait on

 * @intr:	[in]	if true, do an interruptible wait

 * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT

 *

 * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if

 * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies

 * on success.

 *

 * Synchronous waits for the first fence in the array to be signaled. The

 * caller needs to hold a reference to all fences in the array, otherwise a

 * fence might be freed before return, resulting in undefined behavior.

 */

/**

 * fence_init - Initialize a custom fence.

 * @fence:	[in]	the fence to initialize

 * @ops:	[in]	the fence_ops for operations on this fence

 * @lock:	[in]	the irqsafe spinlock to use for locking this fence

 * @context:	[in]	the execution context this fence is run on

 * @seqno:	[in]	a linear increasing sequence number for this context

 *

 * Initializes an allocated fence, the caller doesn't have to keep its

 * refcount after committing with this fence, but it will need to hold a

 * refcount again if fence_ops.enable_signaling gets called. This can

 * be used for other implementing other types of fence.

 *

 * context and seqno are used for easy comparison between fences, allowing

 * to check which fence is later by simply using fence_later.

 */

void

fence_init(struct fence *fence, const struct fence_ops *ops,

	     spinlock_t *lock, unsigned context, unsigned seqno)

{

	BUG_ON(!lock);

	BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||

	       !ops->get_driver_name || !ops->get_timeline_name);

	kref_init(&fence->refcount);

	fence->ops = ops;

	INIT_LIST_HEAD(&fence->cb_list);

	fence->lock = lock;

	fence->context = context;

	fence->seqno = seqno;

	fence->flags = 0UL;

}

EXPORT_SYMBOL(fence_init);