1 // SPDX-License-Identifier: MIT
2 /*
3 * Copyright © 2021 Intel Corporation
4 */
5
6 #include <linux/dma-fence.h>
7 #include <linux/slab.h>
8
9 #include <drm/ttm/ttm_bo.h>
10
11 #include "i915_deps.h"
12
13 /**
14 * DOC: Set of utilities to dynamically collect dependencies into a
15 * structure which is fed into the GT migration code.
16 *
17 * Once we can do async unbinding, this is also needed to coalesce
18 * the migration fence with the unbind fences if these are coalesced
19 * post-migration.
20 *
21 * While collecting the individual dependencies, we store the refcounted
22 * struct dma_fence pointers in a realloc-managed pointer array, since
23 * that can be easily fed into a dma_fence_array. Other options are
24 * available, like for example an xarray for similarity with drm/sched.
25 * Can be changed easily if needed.
26 *
27 * A struct i915_deps need to be initialized using i915_deps_init().
28 * If i915_deps_add_dependency() or i915_deps_add_resv() return an
29 * error code they will internally call i915_deps_fini(), which frees
30 * all internal references and allocations.
31 */
32
33 /* Min number of fence pointers in the array when an allocation occurs. */
34 #define I915_DEPS_MIN_ALLOC_CHUNK 8U
35
i915_deps_reset_fences(struct i915_deps * deps)36 static void i915_deps_reset_fences(struct i915_deps *deps)
37 {
38 if (deps->fences != &deps->single)
39 kfree(deps->fences);
40 deps->num_deps = 0;
41 deps->fences_size = 1;
42 deps->fences = &deps->single;
43 }
44
45 /**
46 * i915_deps_init - Initialize an i915_deps structure
47 * @deps: Pointer to the i915_deps structure to initialize.
48 * @gfp: The allocation mode for subsequenst allocations.
49 */
i915_deps_init(struct i915_deps * deps,gfp_t gfp)50 void i915_deps_init(struct i915_deps *deps, gfp_t gfp)
51 {
52 deps->fences = NULL;
53 deps->gfp = gfp;
54 i915_deps_reset_fences(deps);
55 }
56
57 /**
58 * i915_deps_fini - Finalize an i915_deps structure
59 * @deps: Pointer to the i915_deps structure to finalize.
60 *
61 * This function drops all fence references taken, conditionally frees and
62 * then resets the fences array.
63 */
i915_deps_fini(struct i915_deps * deps)64 void i915_deps_fini(struct i915_deps *deps)
65 {
66 unsigned int i;
67
68 for (i = 0; i < deps->num_deps; ++i)
69 dma_fence_put(deps->fences[i]);
70
71 if (deps->fences != &deps->single)
72 kfree(deps->fences);
73 }
74
i915_deps_grow(struct i915_deps * deps,struct dma_fence * fence,const struct ttm_operation_ctx * ctx)75 static int i915_deps_grow(struct i915_deps *deps, struct dma_fence *fence,
76 const struct ttm_operation_ctx *ctx)
77 {
78 int ret;
79
80 if (deps->num_deps >= deps->fences_size) {
81 unsigned int new_size = 2 * deps->fences_size;
82 struct dma_fence **new_fences;
83
84 new_size = max(new_size, I915_DEPS_MIN_ALLOC_CHUNK);
85 new_fences = kmalloc_array(new_size, sizeof(*new_fences), deps->gfp);
86 if (!new_fences)
87 goto sync;
88
89 memcpy(new_fences, deps->fences,
90 deps->fences_size * sizeof(*new_fences));
91 swap(new_fences, deps->fences);
92 if (new_fences != &deps->single)
93 kfree(new_fences);
94 deps->fences_size = new_size;
95 }
96 deps->fences[deps->num_deps++] = dma_fence_get(fence);
97 return 0;
98
99 sync:
100 if (ctx->no_wait_gpu && !dma_fence_is_signaled(fence)) {
101 ret = -EBUSY;
102 goto unref;
103 }
104
105 ret = dma_fence_wait(fence, ctx->interruptible);
106 if (ret)
107 goto unref;
108
109 ret = fence->error;
110 if (ret)
111 goto unref;
112
113 return 0;
114
115 unref:
116 i915_deps_fini(deps);
117 return ret;
118 }
119
120 /**
121 * i915_deps_sync - Wait for all the fences in the dependency collection
122 * @deps: Pointer to the i915_deps structure the fences of which to wait for.
123 * @ctx: Pointer to a struct ttm_operation_ctx indicating how the waits
124 * should be performed.
125 *
126 * This function waits for fences in the dependency collection. If it
127 * encounters an error during the wait or a fence error, the wait for
128 * further fences is aborted and the error returned.
129 *
130 * Return: Zero if successful, Negative error code on error.
131 */
i915_deps_sync(const struct i915_deps * deps,const struct ttm_operation_ctx * ctx)132 int i915_deps_sync(const struct i915_deps *deps, const struct ttm_operation_ctx *ctx)
133 {
134 struct dma_fence **fences = deps->fences;
135 unsigned int i;
136 int ret = 0;
137
138 for (i = 0; i < deps->num_deps; ++i, ++fences) {
139 if (ctx->no_wait_gpu && !dma_fence_is_signaled(*fences)) {
140 ret = -EBUSY;
141 break;
142 }
143
144 ret = dma_fence_wait(*fences, ctx->interruptible);
145 if (!ret)
146 ret = (*fences)->error;
147 if (ret)
148 break;
149 }
150
151 return ret;
152 }
153
154 /**
155 * i915_deps_add_dependency - Add a fence to the dependency collection
156 * @deps: Pointer to the i915_deps structure a fence is to be added to.
157 * @fence: The fence to add.
158 * @ctx: Pointer to a struct ttm_operation_ctx indicating how waits are to
159 * be performed if waiting.
160 *
161 * Adds a fence to the dependency collection, and takes a reference on it.
162 * If the fence context is not zero and there was a later fence from the
163 * same fence context already added, then the fence is not added to the
164 * dependency collection. If the fence context is not zero and there was
165 * an earlier fence already added, then the fence will replace the older
166 * fence from the same context and the reference on the earlier fence will
167 * be dropped.
168 * If there is a failure to allocate memory to accommodate the new fence to
169 * be added, the new fence will instead be waited for and an error may
170 * be returned; depending on the value of @ctx, or if there was a fence
171 * error. If an error was returned, the dependency collection will be
172 * finalized and all fence reference dropped.
173 *
174 * Return: 0 if success. Negative error code on error.
175 */
i915_deps_add_dependency(struct i915_deps * deps,struct dma_fence * fence,const struct ttm_operation_ctx * ctx)176 int i915_deps_add_dependency(struct i915_deps *deps,
177 struct dma_fence *fence,
178 const struct ttm_operation_ctx *ctx)
179 {
180 unsigned int i;
181 int ret;
182
183 if (!fence)
184 return 0;
185
186 if (dma_fence_is_signaled(fence)) {
187 ret = fence->error;
188 if (ret)
189 i915_deps_fini(deps);
190 return ret;
191 }
192
193 for (i = 0; i < deps->num_deps; ++i) {
194 struct dma_fence *entry = deps->fences[i];
195
196 if (!entry->context || entry->context != fence->context)
197 continue;
198
199 if (dma_fence_is_later(fence, entry)) {
200 dma_fence_put(entry);
201 deps->fences[i] = dma_fence_get(fence);
202 }
203
204 return 0;
205 }
206
207 return i915_deps_grow(deps, fence, ctx);
208 }
209
210 /**
211 * i915_deps_add_resv - Add the fences of a reservation object to a dependency
212 * collection.
213 * @deps: Pointer to the i915_deps structure a fence is to be added to.
214 * @resv: The reservation object, then fences of which to add.
215 * @ctx: Pointer to a struct ttm_operation_ctx indicating how waits are to
216 * be performed if waiting.
217 *
218 * Calls i915_deps_add_depencency() on the indicated fences of @resv.
219 *
220 * Return: Zero on success. Negative error code on error.
221 */
i915_deps_add_resv(struct i915_deps * deps,struct dma_resv * resv,const struct ttm_operation_ctx * ctx)222 int i915_deps_add_resv(struct i915_deps *deps, struct dma_resv *resv,
223 const struct ttm_operation_ctx *ctx)
224 {
225 struct dma_resv_iter iter;
226 struct dma_fence *fence;
227
228 dma_resv_assert_held(resv);
229 dma_resv_for_each_fence(&iter, resv, dma_resv_usage_rw(true), fence) {
230 int ret = i915_deps_add_dependency(deps, fence, ctx);
231
232 if (ret)
233 return ret;
234 }
235
236 return 0;
237 }
238