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seqno-fence.h
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/* * 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/fence.h> #include <linux/dma-buf.h> enum seqno_fence_condition { SEQNO_FENCE_WAIT_GEQUAL, SEQNO_FENCE_WAIT_NONZERO }; struct seqno_fence { struct fence base; const struct fence_ops *ops; struct dma_buf *sync_buf; uint32_t seqno_ofs; enum seqno_fence_condition condition; }; extern const struct 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 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 fence_signal * before destruction. This will prevent possible issues from wraparound at * time of issue vs time of check, since users can check 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 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 fence_init for get_driver_name, so needs to be * initialized first */ fence->ops = ops; 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 */