1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * dma-fence-util: misc functions for dma_fence objects
4 *
5 * Copyright (C) 2022 Advanced Micro Devices, Inc.
6 * Authors:
7 * Christian König <christian.koenig@amd.com>
8 */
9
10 #include <linux/dma-fence.h>
11 #include <linux/dma-fence-array.h>
12 #include <linux/dma-fence-chain.h>
13 #include <linux/dma-fence-unwrap.h>
14 #include <linux/slab.h>
15
16 /* Internal helper to start new array iteration, don't use directly */
17 static struct dma_fence *
__dma_fence_unwrap_array(struct dma_fence_unwrap * cursor)18 __dma_fence_unwrap_array(struct dma_fence_unwrap *cursor)
19 {
20 cursor->array = dma_fence_chain_contained(cursor->chain);
21 cursor->index = 0;
22 return dma_fence_array_first(cursor->array);
23 }
24
25 /**
26 * dma_fence_unwrap_first - return the first fence from fence containers
27 * @head: the entrypoint into the containers
28 * @cursor: current position inside the containers
29 *
30 * Unwraps potential dma_fence_chain/dma_fence_array containers and return the
31 * first fence.
32 */
dma_fence_unwrap_first(struct dma_fence * head,struct dma_fence_unwrap * cursor)33 struct dma_fence *dma_fence_unwrap_first(struct dma_fence *head,
34 struct dma_fence_unwrap *cursor)
35 {
36 cursor->chain = dma_fence_get(head);
37 return __dma_fence_unwrap_array(cursor);
38 }
39 EXPORT_SYMBOL_GPL(dma_fence_unwrap_first);
40
41 /**
42 * dma_fence_unwrap_next - return the next fence from a fence containers
43 * @cursor: current position inside the containers
44 *
45 * Continue unwrapping the dma_fence_chain/dma_fence_array containers and return
46 * the next fence from them.
47 */
dma_fence_unwrap_next(struct dma_fence_unwrap * cursor)48 struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
49 {
50 struct dma_fence *tmp;
51
52 ++cursor->index;
53 tmp = dma_fence_array_next(cursor->array, cursor->index);
54 if (tmp)
55 return tmp;
56
57 cursor->chain = dma_fence_chain_walk(cursor->chain);
58 return __dma_fence_unwrap_array(cursor);
59 }
60 EXPORT_SYMBOL_GPL(dma_fence_unwrap_next);
61
62 /* Implementation for the dma_fence_merge() marco, don't use directly */
__dma_fence_unwrap_merge(unsigned int num_fences,struct dma_fence ** fences,struct dma_fence_unwrap * iter)63 struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
64 struct dma_fence **fences,
65 struct dma_fence_unwrap *iter)
66 {
67 struct dma_fence_array *result;
68 struct dma_fence *tmp, **array;
69 ktime_t timestamp;
70 unsigned int i;
71 size_t count;
72
73 count = 0;
74 timestamp = ns_to_ktime(0);
75 for (i = 0; i < num_fences; ++i) {
76 dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {
77 if (!dma_fence_is_signaled(tmp)) {
78 ++count;
79 } else {
80 ktime_t t = dma_fence_timestamp(tmp);
81
82 if (ktime_after(t, timestamp))
83 timestamp = t;
84 }
85 }
86 }
87
88 /*
89 * If we couldn't find a pending fence just return a private signaled
90 * fence with the timestamp of the last signaled one.
91 */
92 if (count == 0)
93 return dma_fence_allocate_private_stub(timestamp);
94
95 array = kmalloc_array(count, sizeof(*array), GFP_KERNEL);
96 if (!array)
97 return NULL;
98
99 /*
100 * This trashes the input fence array and uses it as position for the
101 * following merge loop. This works because the dma_fence_merge()
102 * wrapper macro is creating this temporary array on the stack together
103 * with the iterators.
104 */
105 for (i = 0; i < num_fences; ++i)
106 fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]);
107
108 count = 0;
109 do {
110 unsigned int sel;
111
112 restart:
113 tmp = NULL;
114 for (i = 0; i < num_fences; ++i) {
115 struct dma_fence *next;
116
117 while (fences[i] && dma_fence_is_signaled(fences[i]))
118 fences[i] = dma_fence_unwrap_next(&iter[i]);
119
120 next = fences[i];
121 if (!next)
122 continue;
123
124 /*
125 * We can't guarantee that inpute fences are ordered by
126 * context, but it is still quite likely when this
127 * function is used multiple times. So attempt to order
128 * the fences by context as we pass over them and merge
129 * fences with the same context.
130 */
131 if (!tmp || tmp->context > next->context) {
132 tmp = next;
133 sel = i;
134
135 } else if (tmp->context < next->context) {
136 continue;
137
138 } else if (dma_fence_is_later(tmp, next)) {
139 fences[i] = dma_fence_unwrap_next(&iter[i]);
140 goto restart;
141 } else {
142 fences[sel] = dma_fence_unwrap_next(&iter[sel]);
143 goto restart;
144 }
145 }
146
147 if (tmp) {
148 array[count++] = dma_fence_get(tmp);
149 fences[sel] = dma_fence_unwrap_next(&iter[sel]);
150 }
151 } while (tmp);
152
153 if (count == 0) {
154 tmp = dma_fence_allocate_private_stub(ktime_get());
155 goto return_tmp;
156 }
157
158 if (count == 1) {
159 tmp = array[0];
160 goto return_tmp;
161 }
162
163 result = dma_fence_array_create(count, array,
164 dma_fence_context_alloc(1),
165 1, false);
166 if (!result) {
167 tmp = NULL;
168 goto return_tmp;
169 }
170 return &result->base;
171
172 return_tmp:
173 kfree(array);
174 return tmp;
175 }
176 EXPORT_SYMBOL_GPL(__dma_fence_unwrap_merge);
177
