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606b23ad ML |
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/fence.h> | |
24 | #include <linux/dma-buf.h> | |
25 | ||
26 | enum seqno_fence_condition { | |
27 | SEQNO_FENCE_WAIT_GEQUAL, | |
28 | SEQNO_FENCE_WAIT_NONZERO | |
29 | }; | |
30 | ||
31 | struct seqno_fence { | |
32 | struct fence base; | |
33 | ||
34 | const struct fence_ops *ops; | |
35 | struct dma_buf *sync_buf; | |
36 | uint32_t seqno_ofs; | |
37 | enum seqno_fence_condition condition; | |
38 | }; | |
39 | ||
40 | extern const struct 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 | */ | |
49 | static inline struct seqno_fence * | |
50 | to_seqno_fence(struct 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 | |
1f58d946 | 65 | * @cond: fence wait condition |
606b23ad ML |
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 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 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 | */ | |
94 | static inline void | |
95 | seqno_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 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 fence_init for get_driver_name, so needs to be | |
107 | * initialized first | |
108 | */ | |
109 | fence->ops = ops; | |
110 | 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 */ |