text: /*
   * 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 <robdclark@gmail.com>
   * Maarten Lankhorst <maarten.lankhorst@canonical.com>
   *
   * 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 <linux/slab.h>
  #include <linux/export.h>
  #include <linux/atomic.h>
  #include <linux/dma-fence.h>
  #include <linux/sched/signal.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/dma_fence.h>
  
  EXPORT_TRACEPOINT_SYMBOL(dma_fence_annotate_wait_on);
  EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
  EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
  
  /*
   * 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 atomic64_t dma_fence_context_counter = ATOMIC64_INIT(0);
  
  /**
   * dma_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.
   */
  u64 dma_fence_context_alloc(unsigned num)
  {
  	BUG_ON(!num);
  	return atomic64_add_return(num, &dma_fence_context_counter) - num;
  }
  EXPORT_SYMBOL(dma_fence_context_alloc);
  
  /**
   * dma_fence_signal_locked - signal completion of a fence
   * @fence: the fence to signal
   *
   * Signal completion for software callbacks on a fence, this will unblock
   * dma_fence_wait() calls and run all the callbacks added with
   * dma_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 dma_fence_signal, this function must be called with fence->lock held.
   */
  int dma_fence_signal_locked(struct dma_fence *fence)
  {
  	struct dma_fence_cb *cur, *tmp;
  	int ret = 0;
  
  	lockdep_assert_held(fence->lock);
  
  	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(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
  		ret = -EINVAL;
  
  		/*
  		 * we might have raced with the unlocked dma_fence_signal,
  		 * still run through all callbacks
  		 */
  	} else
  		trace_dma_fence_signaled(fence);
  
  	list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
  		list_del_init(&cur->node);
  		cur->func(fence, cur);
  	}
  	return ret;
  }
  EXPORT_SYMBOL(dma_fence_signal_locked);
  
  /**
   * dma_fence_signal - signal completion of a fence
   * @fence: the fence to signal
   *
   * Signal completion for software callbacks on a fence, this will unblock
   * dma_fence_wait() calls and run all the callbacks added with
   * dma_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 dma_fence_signal(struct dma_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(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		return -EINVAL;
  
  	trace_dma_fence_signaled(fence);
  
  	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
  		struct dma_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(dma_fence_signal);
  
  /**
   * dma_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
  dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
  {
  	signed long ret;
  
  	if (WARN_ON(timeout < 0))
  		return -EINVAL;
  
  	trace_dma_fence_wait_start(fence);
  	ret = fence->ops->wait(fence, intr, timeout);
  	trace_dma_fence_wait_end(fence);
  	return ret;
  }
  EXPORT_SYMBOL(dma_fence_wait_timeout);
  
  void dma_fence_release(struct kref *kref)
  {
  	struct dma_fence *fence =
  		container_of(kref, struct dma_fence, refcount);
  
  	trace_dma_fence_destroy(fence);
  
  	BUG_ON(!list_empty(&fence->cb_list));
  
  	if (fence->ops->release)
  		fence->ops->release(fence);
  	else
  		dma_fence_free(fence);
  }
  EXPORT_SYMBOL(dma_fence_release);
  
  void dma_fence_free(struct dma_fence *fence)
  {
  	kfree_rcu(fence, rcu);
  }
  EXPORT_SYMBOL(dma_fence_free);
  
  /**
   * dma_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 dma_fence_enable_sw_signaling(struct dma_fence *fence)
  {
  	unsigned long flags;
  
  	if (!test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
  			      &fence->flags) &&
  	    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
  		trace_dma_fence_enable_signal(fence);
  
  		spin_lock_irqsave(fence->lock, flags);
  
  		if (!fence->ops->enable_signaling(fence))
  			dma_fence_signal_locked(fence);
  
  		spin_unlock_irqrestore(fence->lock, flags);
  	}
  }
  EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
  
  /**
   * dma_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 dma_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 dma_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 dma_fence_signal. The callback itself can be called
   * from irq context.
   *
   */
  int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
  			   dma_fence_func_t func)
  {
  	unsigned long flags;
  	int ret = 0;
  	bool was_set;
  
  	if (WARN_ON(!fence || !func))
  		return -EINVAL;
  
  	if (test_bit(DMA_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(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
  				   &fence->flags);
  
  	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		ret = -ENOENT;
  	else if (!was_set) {
  		trace_dma_fence_enable_signal(fence);
  
  		if (!fence->ops->enable_signaling(fence)) {
  			dma_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(dma_fence_add_callback);
  
  /**
   * dma_fence_get_status - returns the status upon completion
   * @fence: [in]	the dma_fence to query
   *
   * This wraps dma_fence_get_status_locked() to return the error status
   * condition on a signaled fence. See dma_fence_get_status_locked() for more
   * details.
   *
   * Returns 0 if the fence has not yet been signaled, 1 if the fence has
   * been signaled without an error condition, or a negative error code
   * if the fence has been completed in err.
   */
  int dma_fence_get_status(struct dma_fence *fence)
  {
  	unsigned long flags;
  	int status;
  
  	spin_lock_irqsave(fence->lock, flags);
  	status = dma_fence_get_status_locked(fence);
  	spin_unlock_irqrestore(fence->lock, flags);
  
  	return status;
  }
  EXPORT_SYMBOL(dma_fence_get_status);
  
  /**
   * dma_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
  dma_fence_remove_callback(struct dma_fence *fence, struct dma_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(dma_fence_remove_callback);
  
  struct default_wait_cb {
  	struct dma_fence_cb base;
  	struct task_struct *task;
  };
  
  static void
  dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
  {
  	struct default_wait_cb *wait =
  		container_of(cb, struct default_wait_cb, base);
  
  	wake_up_state(wait->task, TASK_NORMAL);
  }
  
  /**
   * dma_fence_default_wait - default 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. If timeout is zero the value one is
   * returned if the fence is already signaled for consistency with other
   * functions taking a jiffies timeout.
   */
  signed long
  dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
  {
  	struct default_wait_cb cb;
  	unsigned long flags;
  	signed long ret = timeout ? timeout : 1;
  	bool was_set;
  
  	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		return ret;
  
  	spin_lock_irqsave(fence->lock, flags);
  
  	if (intr && signal_pending(current)) {
  		ret = -ERESTARTSYS;
  		goto out;
  	}
  
  	was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
  				   &fence->flags);
  
  	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		goto out;
  
  	if (!was_set) {
  		trace_dma_fence_enable_signal(fence);
  
  		if (!fence->ops->enable_signaling(fence)) {
  			dma_fence_signal_locked(fence);
  			goto out;
  		}
  	}
  
  	cb.base.func = dma_fence_default_wait_cb;
  	cb.task = current;
  	list_add(&cb.base.node, &fence->cb_list);
  
  	while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
  		if (intr)
  			__set_current_state(TASK_INTERRUPTIBLE);
  		else
  			__set_current_state(TASK_UNINTERRUPTIBLE);
  		spin_unlock_irqrestore(fence->lock, flags);
  
  		ret = schedule_timeout(ret);
  
  		spin_lock_irqsave(fence->lock, flags);
  		if (ret > 0 && intr && signal_pending(current))
  			ret = -ERESTARTSYS;
  	}
  
  	if (!list_empty(&cb.base.node))
  		list_del(&cb.base.node);
  	__set_current_state(TASK_RUNNING);
  
  out:
  	spin_unlock_irqrestore(fence->lock, flags);
  	return ret;
  }
  EXPORT_SYMBOL(dma_fence_default_wait);
  
  static bool
  dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
  			    uint32_t *idx)
  {
  	int i;
  
  	for (i = 0; i < count; ++i) {
  		struct dma_fence *fence = fences[i];
  		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
  			if (idx)
  				*idx = i;
  			return true;
  		}
  	}
  	return false;
  }
  
  /**
   * dma_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
   * @idx:       [out]	the first signaled fence index, meaningful only on
   *			positive return
   *
   * 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.
   */
  signed long
  dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
  			   bool intr, signed long timeout, uint32_t *idx)
  {
  	struct default_wait_cb *cb;
  	signed long ret = timeout;
  	unsigned i;
  
  	if (WARN_ON(!fences || !count || timeout < 0))
  		return -EINVAL;
  
  	if (timeout == 0) {
  		for (i = 0; i < count; ++i)
  			if (dma_fence_is_signaled(fences[i])) {
  				if (idx)
  					*idx = i;
  				return 1;
  			}
  
  		return 0;
  	}
  
  	cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
  	if (cb == NULL) {
  		ret = -ENOMEM;
  		goto err_free_cb;
  	}
  
  	for (i = 0; i < count; ++i) {
  		struct dma_fence *fence = fences[i];
  
  		if (fence->ops->wait != dma_fence_default_wait) {
  			ret = -EINVAL;
  			goto fence_rm_cb;
  		}
  
  		cb[i].task = current;
  		if (dma_fence_add_callback(fence, &cb[i].base,
  					   dma_fence_default_wait_cb)) {
  			/* This fence is already signaled */
  			if (idx)
  				*idx = i;
  			goto fence_rm_cb;
  		}
  	}
  
  	while (ret > 0) {
  		if (intr)
  			set_current_state(TASK_INTERRUPTIBLE);
  		else
  			set_current_state(TASK_UNINTERRUPTIBLE);
  
  		if (dma_fence_test_signaled_any(fences, count, idx))
  			break;
  
  		ret = schedule_timeout(ret);
  
  		if (ret > 0 && intr && signal_pending(current))
  			ret = -ERESTARTSYS;
  	}
  
  	__set_current_state(TASK_RUNNING);
  
  fence_rm_cb:
  	while (i-- > 0)
  		dma_fence_remove_callback(fences[i], &cb[i].base);
  
  err_free_cb:
  	kfree(cb);
  
  	return ret;
  }
  EXPORT_SYMBOL(dma_fence_wait_any_timeout);
  
  /**
   * dma_fence_init - Initialize a custom fence.
   * @fence:	[in]	the fence to initialize
   * @ops:	[in]	the dma_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 dma_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 dma_fence_later.
   */
  void
  dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
  	       spinlock_t *lock, u64 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;
  	fence->error = 0;
  
  	trace_dma_fence_init(fence);
  }
  EXPORT_SYMBOL(dma_fence_init);
  