/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* seqno-fence, using a dma-buf to synchronize fencing
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*
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* Copyright (C) 2012 Texas Instruments
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* Copyright (C) 2012 Canonical Ltd
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* Authors:
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* Rob Clark <robdclark@gmail.com>
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* Maarten Lankhorst <maarten.lankhorst@canonical.com>
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*/
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#ifndef __LINUX_SEQNO_FENCE_H
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#define __LINUX_SEQNO_FENCE_H
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#include <linux/dma-fence.h>
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#include <linux/dma-buf.h>
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enum seqno_fence_condition {
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SEQNO_FENCE_WAIT_GEQUAL,
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SEQNO_FENCE_WAIT_NONZERO
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};
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struct seqno_fence {
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struct dma_fence base;
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const struct dma_fence_ops *ops;
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struct dma_buf *sync_buf;
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uint32_t seqno_ofs;
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enum seqno_fence_condition condition;
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};
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extern const struct dma_fence_ops seqno_fence_ops;
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/**
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* to_seqno_fence - cast a fence to a seqno_fence
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* @fence: fence to cast to a seqno_fence
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*
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* Returns NULL if the fence is not a seqno_fence,
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* or the seqno_fence otherwise.
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*/
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static inline struct seqno_fence *
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to_seqno_fence(struct dma_fence *fence)
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{
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if (fence->ops != &seqno_fence_ops)
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return NULL;
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return container_of(fence, struct seqno_fence, base);
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}
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/**
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* seqno_fence_init - initialize a seqno fence
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* @fence: seqno_fence to initialize
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* @lock: pointer to spinlock to use for fence
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* @sync_buf: buffer containing the memory location to signal on
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* @context: the execution context this fence is a part of
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* @seqno_ofs: the offset within @sync_buf
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* @seqno: the sequence # to signal on
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* @cond: fence wait condition
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* @ops: the fence_ops for operations on this seqno fence
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*
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* This function initializes a struct seqno_fence with passed parameters,
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* and takes a reference on sync_buf which is released on fence destruction.
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*
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* A seqno_fence is a dma_fence which can complete in software when
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* enable_signaling is called, but it also completes when
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* (s32)((sync_buf)[seqno_ofs] - seqno) >= 0 is true
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*
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* The seqno_fence will take a refcount on the sync_buf until it's
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* destroyed, but actual lifetime of sync_buf may be longer if one of the
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* callers take a reference to it.
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*
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* Certain hardware have instructions to insert this type of wait condition
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* in the command stream, so no intervention from software would be needed.
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* This type of fence can be destroyed before completed, however a reference
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* on the sync_buf dma-buf can be taken. It is encouraged to re-use the same
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* dma-buf for sync_buf, since mapping or unmapping the sync_buf to the
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* device's vm can be expensive.
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*
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* It is recommended for creators of seqno_fence to call dma_fence_signal()
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* before destruction. This will prevent possible issues from wraparound at
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* time of issue vs time of check, since users can check dma_fence_is_signaled()
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* before submitting instructions for the hardware to wait on the fence.
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* However, when ops.enable_signaling is not called, it doesn't have to be
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* done as soon as possible, just before there's any real danger of seqno
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* wraparound.
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*/
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static inline void
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seqno_fence_init(struct seqno_fence *fence, spinlock_t *lock,
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struct dma_buf *sync_buf, uint32_t context,
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uint32_t seqno_ofs, uint32_t seqno,
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enum seqno_fence_condition cond,
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const struct dma_fence_ops *ops)
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{
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BUG_ON(!fence || !sync_buf || !ops);
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BUG_ON(!ops->wait || !ops->enable_signaling ||
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!ops->get_driver_name || !ops->get_timeline_name);
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/*
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* ops is used in dma_fence_init for get_driver_name, so needs to be
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* initialized first
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*/
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fence->ops = ops;
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dma_fence_init(&fence->base, &seqno_fence_ops, lock, context, seqno);
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get_dma_buf(sync_buf);
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fence->sync_buf = sync_buf;
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fence->seqno_ofs = seqno_ofs;
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fence->condition = cond;
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}
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#endif /* __LINUX_SEQNO_FENCE_H */
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