1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * fence-chain: chain fences together in a timeline
4 *
5 * Copyright (C) 2018 Advanced Micro Devices, Inc.
6 * Authors:
7 *	Christian K��nig <christian.koenig@amd.com>
8 */
9
10#ifndef __LINUX_DMA_FENCE_CHAIN_H
11#define __LINUX_DMA_FENCE_CHAIN_H
12
13#include <linux/dma-fence.h>
14#include <linux/irq_work.h>
15#include <linux/slab.h>
16
17/**
18 * struct dma_fence_chain - fence to represent an node of a fence chain
19 * @base: fence base class
20 * @prev: previous fence of the chain
21 * @prev_seqno: original previous seqno before garbage collection
22 * @fence: encapsulated fence
23 * @lock: spinlock for fence handling
24 */
25struct dma_fence_chain {
26	struct dma_fence base;
27	struct dma_fence __rcu *prev;
28	u64 prev_seqno;
29	struct dma_fence *fence;
30	union {
31		/**
32		 * @cb: callback for signaling
33		 *
34		 * This is used to add the callback for signaling the
35		 * complection of the fence chain. Never used at the same time
36		 * as the irq work.
37		 */
38		struct dma_fence_cb cb;
39
40		/**
41		 * @work: irq work item for signaling
42		 *
43		 * Irq work structure to allow us to add the callback without
44		 * running into lock inversion. Never used at the same time as
45		 * the callback.
46		 */
47		struct irq_work work;
48	};
49	spinlock_t lock;
50};
51
52
53/**
54 * to_dma_fence_chain - cast a fence to a dma_fence_chain
55 * @fence: fence to cast to a dma_fence_array
56 *
57 * Returns NULL if the fence is not a dma_fence_chain,
58 * or the dma_fence_chain otherwise.
59 */
60static inline struct dma_fence_chain *
61to_dma_fence_chain(struct dma_fence *fence)
62{
63	if (!fence || !dma_fence_is_chain(fence))
64		return NULL;
65
66	return container_of(fence, struct dma_fence_chain, base);
67}
68
69/**
70 * dma_fence_chain_contained - return the contained fence
71 * @fence: the fence to test
72 *
73 * If the fence is a dma_fence_chain the function returns the fence contained
74 * inside the chain object, otherwise it returns the fence itself.
75 */
76static inline struct dma_fence *
77dma_fence_chain_contained(struct dma_fence *fence)
78{
79	struct dma_fence_chain *chain = to_dma_fence_chain(fence);
80
81	return chain ? chain->fence : fence;
82}
83
84/**
85 * dma_fence_chain_alloc
86 *
87 * Returns a new struct dma_fence_chain object or NULL on failure.
88 */
89static inline struct dma_fence_chain *dma_fence_chain_alloc(void)
90{
91	return kmalloc(sizeof(struct dma_fence_chain), GFP_KERNEL);
92};
93
94/**
95 * dma_fence_chain_free
96 * @chain: chain node to free
97 *
98 * Frees up an allocated but not used struct dma_fence_chain object. This
99 * doesn't need an RCU grace period since the fence was never initialized nor
100 * published. After dma_fence_chain_init() has been called the fence must be
101 * released by calling dma_fence_put(), and not through this function.
102 */
103static inline void dma_fence_chain_free(struct dma_fence_chain *chain)
104{
105	kfree(chain);
106};
107
108/**
109 * dma_fence_chain_for_each - iterate over all fences in chain
110 * @iter: current fence
111 * @head: starting point
112 *
113 * Iterate over all fences in the chain. We keep a reference to the current
114 * fence while inside the loop which must be dropped when breaking out.
115 *
116 * For a deep dive iterator see dma_fence_unwrap_for_each().
117 */
118#define dma_fence_chain_for_each(iter, head)	\
119	for (iter = dma_fence_get(head); iter; \
120	     iter = dma_fence_chain_walk(iter))
121
122struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence);
123int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno);
124void dma_fence_chain_init(struct dma_fence_chain *chain,
125			  struct dma_fence *prev,
126			  struct dma_fence *fence,
127			  uint64_t seqno);
128
129#endif /* __LINUX_DMA_FENCE_CHAIN_H */
130