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 *
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  */
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  */
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 */
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 	unsigned int i;
70 	size_t count;
71 
72 	count = 0;
73 	for (i = 0; i < num_fences; ++i) {
74 		dma_fence_unwrap_for_each(tmp, &iter[i], fences[i])
75 			if (!dma_fence_is_signaled(tmp))
76 				++count;
77 	}
78 
79 	if (count == 0)
80 		return dma_fence_get_stub();
81 
82 	array = kmalloc_array(count, sizeof(*array), GFP_KERNEL);
83 	if (!array)
84 		return NULL;
85 
86 	/*
87 	 * This trashes the input fence array and uses it as position for the
88 	 * following merge loop. This works because the dma_fence_merge()
89 	 * wrapper macro is creating this temporary array on the stack together
90 	 * with the iterators.
91 	 */
92 	for (i = 0; i < num_fences; ++i)
93 		fences[i] = dma_fence_unwrap_first(fences[i], &iter[i]);
94 
95 	count = 0;
96 	do {
97 		unsigned int sel;
98 
99 restart:
100 		tmp = NULL;
101 		for (i = 0; i < num_fences; ++i) {
102 			struct dma_fence *next;
103 
104 			while (fences[i] && dma_fence_is_signaled(fences[i]))
105 				fences[i] = dma_fence_unwrap_next(&iter[i]);
106 
107 			next = fences[i];
108 			if (!next)
109 				continue;
110 
111 			/*
112 			 * We can't guarantee that inpute fences are ordered by
113 			 * context, but it is still quite likely when this
114 			 * function is used multiple times. So attempt to order
115 			 * the fences by context as we pass over them and merge
116 			 * fences with the same context.
117 			 */
118 			if (!tmp || tmp->context > next->context) {
119 				tmp = next;
120 				sel = i;
121 
122 			} else if (tmp->context < next->context) {
123 				continue;
124 
125 			} else if (dma_fence_is_later(tmp, next)) {
126 				fences[i] = dma_fence_unwrap_next(&iter[i]);
127 				goto restart;
128 			} else {
129 				fences[sel] = dma_fence_unwrap_next(&iter[sel]);
130 				goto restart;
131 			}
132 		}
133 
134 		if (tmp) {
135 			array[count++] = dma_fence_get(tmp);
136 			fences[sel] = dma_fence_unwrap_next(&iter[sel]);
137 		}
138 	} while (tmp);
139 
140 	if (count == 0) {
141 		tmp = dma_fence_get_stub();
142 		goto return_tmp;
143 	}
144 
145 	if (count == 1) {
146 		tmp = array[0];
147 		goto return_tmp;
148 	}
149 
150 	result = dma_fence_array_create(count, array,
151 					dma_fence_context_alloc(1),
152 					1, false);
153 	if (!result) {
154 		tmp = NULL;
155 		goto return_tmp;
156 	}
157 	return &result->base;
158 
159 return_tmp:
160 	kfree(array);
161 	return tmp;
162 }
163 EXPORT_SYMBOL_GPL(__dma_fence_unwrap_merge);
164