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       1                 :            : /* SPDX-License-Identifier: GPL-2.0-only */
       2                 :            : /*
       3                 :            :  * seqno-fence, using a dma-buf to synchronize fencing
       4                 :            :  *
       5                 :            :  * Copyright (C) 2012 Texas Instruments
       6                 :            :  * Copyright (C) 2012 Canonical Ltd
       7                 :            :  * Authors:
       8                 :            :  *   Rob Clark <robdclark@gmail.com>
       9                 :            :  *   Maarten Lankhorst <maarten.lankhorst@canonical.com>
      10                 :            :  */
      11                 :            : 
      12                 :            : #ifndef __LINUX_SEQNO_FENCE_H
      13                 :            : #define __LINUX_SEQNO_FENCE_H
      14                 :            : 
      15                 :            : #include <linux/dma-fence.h>
      16                 :            : #include <linux/dma-buf.h>
      17                 :            : 
      18                 :            : enum seqno_fence_condition {
      19                 :            :         SEQNO_FENCE_WAIT_GEQUAL,
      20                 :            :         SEQNO_FENCE_WAIT_NONZERO
      21                 :            : };
      22                 :            : 
      23                 :            : struct seqno_fence {
      24                 :            :         struct dma_fence base;
      25                 :            : 
      26                 :            :         const struct dma_fence_ops *ops;
      27                 :            :         struct dma_buf *sync_buf;
      28                 :            :         uint32_t seqno_ofs;
      29                 :            :         enum seqno_fence_condition condition;
      30                 :            : };
      31                 :            : 
      32                 :            : extern const struct dma_fence_ops seqno_fence_ops;
      33                 :            : 
      34                 :            : /**
      35                 :            :  * to_seqno_fence - cast a fence to a seqno_fence
      36                 :            :  * @fence: fence to cast to a seqno_fence
      37                 :            :  *
      38                 :            :  * Returns NULL if the fence is not a seqno_fence,
      39                 :            :  * or the seqno_fence otherwise.
      40                 :            :  */
      41                 :            : static inline struct seqno_fence *
      42                 :            : to_seqno_fence(struct dma_fence *fence)
      43                 :            : {
      44                 :          0 :         if (fence->ops != &seqno_fence_ops)
      45                 :            :                 return NULL;
      46                 :            :         return container_of(fence, struct seqno_fence, base);
      47                 :            : }
      48                 :            : 
      49                 :            : /**
      50                 :            :  * seqno_fence_init - initialize a seqno fence
      51                 :            :  * @fence: seqno_fence to initialize
      52                 :            :  * @lock: pointer to spinlock to use for fence
      53                 :            :  * @sync_buf: buffer containing the memory location to signal on
      54                 :            :  * @context: the execution context this fence is a part of
      55                 :            :  * @seqno_ofs: the offset within @sync_buf
      56                 :            :  * @seqno: the sequence # to signal on
      57                 :            :  * @cond: fence wait condition
      58                 :            :  * @ops: the fence_ops for operations on this seqno fence
      59                 :            :  *
      60                 :            :  * This function initializes a struct seqno_fence with passed parameters,
      61                 :            :  * and takes a reference on sync_buf which is released on fence destruction.
      62                 :            :  *
      63                 :            :  * A seqno_fence is a dma_fence which can complete in software when
      64                 :            :  * enable_signaling is called, but it also completes when
      65                 :            :  * (s32)((sync_buf)[seqno_ofs] - seqno) >= 0 is true
      66                 :            :  *
      67                 :            :  * The seqno_fence will take a refcount on the sync_buf until it's
      68                 :            :  * destroyed, but actual lifetime of sync_buf may be longer if one of the
      69                 :            :  * callers take a reference to it.
      70                 :            :  *
      71                 :            :  * Certain hardware have instructions to insert this type of wait condition
      72                 :            :  * in the command stream, so no intervention from software would be needed.
      73                 :            :  * This type of fence can be destroyed before completed, however a reference
      74                 :            :  * on the sync_buf dma-buf can be taken. It is encouraged to re-use the same
      75                 :            :  * dma-buf for sync_buf, since mapping or unmapping the sync_buf to the
      76                 :            :  * device's vm can be expensive.
      77                 :            :  *
      78                 :            :  * It is recommended for creators of seqno_fence to call dma_fence_signal()
      79                 :            :  * before destruction. This will prevent possible issues from wraparound at
      80                 :            :  * time of issue vs time of check, since users can check dma_fence_is_signaled()
      81                 :            :  * before submitting instructions for the hardware to wait on the fence.
      82                 :            :  * However, when ops.enable_signaling is not called, it doesn't have to be
      83                 :            :  * done as soon as possible, just before there's any real danger of seqno
      84                 :            :  * wraparound.
      85                 :            :  */
      86                 :            : static inline void
      87                 :            : seqno_fence_init(struct seqno_fence *fence, spinlock_t *lock,
      88                 :            :                  struct dma_buf *sync_buf,  uint32_t context,
      89                 :            :                  uint32_t seqno_ofs, uint32_t seqno,
      90                 :            :                  enum seqno_fence_condition cond,
      91                 :            :                  const struct dma_fence_ops *ops)
      92                 :            : {
      93                 :            :         BUG_ON(!fence || !sync_buf || !ops);
      94                 :            :         BUG_ON(!ops->wait || !ops->enable_signaling ||
      95                 :            :                !ops->get_driver_name || !ops->get_timeline_name);
      96                 :            : 
      97                 :            :         /*
      98                 :            :          * ops is used in dma_fence_init for get_driver_name, so needs to be
      99                 :            :          * initialized first
     100                 :            :          */
     101                 :            :         fence->ops = ops;
     102                 :            :         dma_fence_init(&fence->base, &seqno_fence_ops, lock, context, seqno);
     103                 :            :         get_dma_buf(sync_buf);
     104                 :            :         fence->sync_buf = sync_buf;
     105                 :            :         fence->seqno_ofs = seqno_ofs;
     106                 :            :         fence->condition = cond;
     107                 :            : }
     108                 :            : 
     109                 :            : #endif /* __LINUX_SEQNO_FENCE_H */