/*
   * seqno-fence, using a dma-buf to synchronize fencing
   *
   * Copyright (C) 2012 Texas Instruments
   * Copyright (C) 2012 Canonical Ltd
   * 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.
   */
  
  #ifndef __LINUX_SEQNO_FENCE_H
  #define __LINUX_SEQNO_FENCE_H
  
  #include <linux/dma-fence.h>
  #include <linux/dma-buf.h>
  
  enum seqno_fence_condition {
  	SEQNO_FENCE_WAIT_GEQUAL,
  	SEQNO_FENCE_WAIT_NONZERO
  };
  
  struct seqno_fence {
  	struct dma_fence base;
  
  	const struct dma_fence_ops *ops;
  	struct dma_buf *sync_buf;
  	uint32_t seqno_ofs;
  	enum seqno_fence_condition condition;
  };
  
  extern const struct dma_fence_ops seqno_fence_ops;
  
  /**
   * to_seqno_fence - cast a fence to a seqno_fence
   * @fence: fence to cast to a seqno_fence
   *
   * Returns NULL if the fence is not a seqno_fence,
   * or the seqno_fence otherwise.
   */
  static inline struct seqno_fence *
  to_seqno_fence(struct dma_fence *fence)
  {
  	if (fence->ops != &seqno_fence_ops)
  		return NULL;
  	return container_of(fence, struct seqno_fence, base);
  }
  
  /**
   * seqno_fence_init - initialize a seqno fence
   * @fence: seqno_fence to initialize
   * @lock: pointer to spinlock to use for fence
   * @sync_buf: buffer containing the memory location to signal on
   * @context: the execution context this fence is a part of
   * @seqno_ofs: the offset within @sync_buf
   * @seqno: the sequence # to signal on
   * @cond: fence wait condition
   * @ops: the fence_ops for operations on this seqno fence
   *
   * This function initializes a struct seqno_fence with passed parameters,
   * and takes a reference on sync_buf which is released on fence destruction.
   *
   * A seqno_fence is a dma_fence which can complete in software when
   * enable_signaling is called, but it also completes when
   * (s32)((sync_buf)[seqno_ofs] - seqno) >= 0 is true
   *
   * The seqno_fence will take a refcount on the sync_buf until it's
   * destroyed, but actual lifetime of sync_buf may be longer if one of the
   * callers take a reference to it.
   *
   * Certain hardware have instructions to insert this type of wait condition
   * in the command stream, so no intervention from software would be needed.
   * This type of fence can be destroyed before completed, however a reference
   * on the sync_buf dma-buf can be taken. It is encouraged to re-use the same
   * dma-buf for sync_buf, since mapping or unmapping the sync_buf to the
   * device's vm can be expensive.
   *
   * It is recommended for creators of seqno_fence to call dma_fence_signal()
   * before destruction. This will prevent possible issues from wraparound at
   * time of issue vs time of check, since users can check dma_fence_is_signaled()
   * before submitting instructions for the hardware to wait on the fence.
   * However, when ops.enable_signaling is not called, it doesn't have to be
   * done as soon as possible, just before there's any real danger of seqno
   * wraparound.
   */
  static inline void
  seqno_fence_init(struct seqno_fence *fence, spinlock_t *lock,
  		 struct dma_buf *sync_buf,  uint32_t context,
  		 uint32_t seqno_ofs, uint32_t seqno,
  		 enum seqno_fence_condition cond,
  		 const struct dma_fence_ops *ops)
  {
  	BUG_ON(!fence || !sync_buf || !ops);
  	BUG_ON(!ops->wait || !ops->enable_signaling ||
  	       !ops->get_driver_name || !ops->get_timeline_name);
  
  	/*
  	 * ops is used in dma_fence_init for get_driver_name, so needs to be
  	 * initialized first
  	 */
  	fence->ops = ops;
  	dma_fence_init(&fence->base, &seqno_fence_ops, lock, context, seqno);
  	get_dma_buf(sync_buf);
  	fence->sync_buf = sync_buf;
  	fence->seqno_ofs = seqno_ofs;
  	fence->condition = cond;
  }
  
  #endif /* __LINUX_SEQNO_FENCE_H */