1/* 2 * seqno-fence, using a dma-buf to synchronize fencing 3 * 4 * Copyright (C) 2012 Texas Instruments 5 * Copyright (C) 2012 Canonical Ltd 6 * Authors: 7 * Rob Clark <robdclark@gmail.com> 8 * Maarten Lankhorst <maarten.lankhorst@canonical.com> 9 * 10 * This program is free software; you can redistribute it and/or modify it 11 * under the terms of the GNU General Public License version 2 as published by 12 * the Free Software Foundation. 13 * 14 * This program is distributed in the hope that it will be useful, but WITHOUT 15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 17 * more details. 18 */ 19 20#ifndef __LINUX_SEQNO_FENCE_H 21#define __LINUX_SEQNO_FENCE_H 22 23#include <linux/dma-fence.h> 24#include <linux/dma-buf.h> 25 26enum seqno_fence_condition { 27 SEQNO_FENCE_WAIT_GEQUAL, 28 SEQNO_FENCE_WAIT_NONZERO 29}; 30 31struct seqno_fence { 32 struct dma_fence base; 33 34 const struct dma_fence_ops *ops; 35 struct dma_buf *sync_buf; 36 uint32_t seqno_ofs; 37 enum seqno_fence_condition condition; 38}; 39 40extern const struct dma_fence_ops seqno_fence_ops; 41 42/** 43 * to_seqno_fence - cast a fence to a seqno_fence 44 * @fence: fence to cast to a seqno_fence 45 * 46 * Returns NULL if the fence is not a seqno_fence, 47 * or the seqno_fence otherwise. 48 */ 49static inline struct seqno_fence * 50to_seqno_fence(struct dma_fence *fence) 51{ 52 if (fence->ops != &seqno_fence_ops) 53 return NULL; 54 return container_of(fence, struct seqno_fence, base); 55} 56 57/** 58 * seqno_fence_init - initialize a seqno fence 59 * @fence: seqno_fence to initialize 60 * @lock: pointer to spinlock to use for fence 61 * @sync_buf: buffer containing the memory location to signal on 62 * @context: the execution context this fence is a part of 63 * @seqno_ofs: the offset within @sync_buf 64 * @seqno: the sequence # to signal on 65 * @cond: fence wait condition 66 * @ops: the fence_ops for operations on this seqno fence 67 * 68 * This function initializes a struct seqno_fence with passed parameters, 69 * and takes a reference on sync_buf which is released on fence destruction. 70 * 71 * A seqno_fence is a dma_fence which can complete in software when 72 * enable_signaling is called, but it also completes when 73 * (s32)((sync_buf)[seqno_ofs] - seqno) >= 0 is true 74 * 75 * The seqno_fence will take a refcount on the sync_buf until it's 76 * destroyed, but actual lifetime of sync_buf may be longer if one of the 77 * callers take a reference to it. 78 * 79 * Certain hardware have instructions to insert this type of wait condition 80 * in the command stream, so no intervention from software would be needed. 81 * This type of fence can be destroyed before completed, however a reference 82 * on the sync_buf dma-buf can be taken. It is encouraged to re-use the same 83 * dma-buf for sync_buf, since mapping or unmapping the sync_buf to the 84 * device's vm can be expensive. 85 * 86 * It is recommended for creators of seqno_fence to call dma_fence_signal() 87 * before destruction. This will prevent possible issues from wraparound at 88 * time of issue vs time of check, since users can check dma_fence_is_signaled() 89 * before submitting instructions for the hardware to wait on the fence. 90 * However, when ops.enable_signaling is not called, it doesn't have to be 91 * done as soon as possible, just before there's any real danger of seqno 92 * wraparound. 93 */ 94static inline void 95seqno_fence_init(struct seqno_fence *fence, spinlock_t *lock, 96 struct dma_buf *sync_buf, uint32_t context, 97 uint32_t seqno_ofs, uint32_t seqno, 98 enum seqno_fence_condition cond, 99 const struct dma_fence_ops *ops) 100{ 101 BUG_ON(!fence || !sync_buf || !ops); 102 BUG_ON(!ops->wait || !ops->enable_signaling || 103 !ops->get_driver_name || !ops->get_timeline_name); 104 105 /* 106 * ops is used in dma_fence_init for get_driver_name, so needs to be 107 * initialized first 108 */ 109 fence->ops = ops; 110 dma_fence_init(&fence->base, &seqno_fence_ops, lock, context, seqno); 111 get_dma_buf(sync_buf); 112 fence->sync_buf = sync_buf; 113 fence->seqno_ofs = seqno_ofs; 114 fence->condition = cond; 115} 116 117#endif /* __LINUX_SEQNO_FENCE_H */ 118