summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/drm_exec.c
blob: ff69cf0fb42aab8e23ea128c81feef2883d95947 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
// SPDX-License-Identifier: GPL-2.0 OR MIT

#include <drm/drm_exec.h>
#include <drm/drm_gem.h>
#include <linux/dma-resv.h>

/**
 * DOC: Overview
 *
 * This component mainly abstracts the retry loop necessary for locking
 * multiple GEM objects while preparing hardware operations (e.g. command
 * submissions, page table updates etc..).
 *
 * If a contention is detected while locking a GEM object the cleanup procedure
 * unlocks all previously locked GEM objects and locks the contended one first
 * before locking any further objects.
 *
 * After an object is locked fences slots can optionally be reserved on the
 * dma_resv object inside the GEM object.
 *
 * A typical usage pattern should look like this::
 *
 *	struct drm_gem_object *obj;
 *	struct drm_exec exec;
 *	unsigned long index;
 *	int ret;
 *
 *	drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT);
 *	drm_exec_until_all_locked(&exec) {
 *		ret = drm_exec_prepare_obj(&exec, boA, 1);
 *		drm_exec_retry_on_contention(&exec);
 *		if (ret)
 *			goto error;
 *
 *		ret = drm_exec_prepare_obj(&exec, boB, 1);
 *		drm_exec_retry_on_contention(&exec);
 *		if (ret)
 *			goto error;
 *	}
 *
 *	drm_exec_for_each_locked_object(&exec, index, obj) {
 *		dma_resv_add_fence(obj->resv, fence, DMA_RESV_USAGE_READ);
 *		...
 *	}
 *	drm_exec_fini(&exec);
 *
 * See struct dma_exec for more details.
 */

/* Dummy value used to initially enter the retry loop */
#define DRM_EXEC_DUMMY ((void *)~0)

/* Unlock all objects and drop references */
static void drm_exec_unlock_all(struct drm_exec *exec)
{
	struct drm_gem_object *obj;
	unsigned long index;

	drm_exec_for_each_locked_object(exec, index, obj) {
		dma_resv_unlock(obj->resv);
		drm_gem_object_put(obj);
	}

	drm_gem_object_put(exec->prelocked);
	exec->prelocked = NULL;
}

/**
 * drm_exec_init - initialize a drm_exec object
 * @exec: the drm_exec object to initialize
 * @flags: controls locking behavior, see DRM_EXEC_* defines
 *
 * Initialize the object and make sure that we can track locked objects.
 */
void drm_exec_init(struct drm_exec *exec, uint32_t flags)
{
	exec->flags = flags;
	exec->objects = kmalloc(PAGE_SIZE, GFP_KERNEL);

	/* If allocation here fails, just delay that till the first use */
	exec->max_objects = exec->objects ? PAGE_SIZE / sizeof(void *) : 0;
	exec->num_objects = 0;
	exec->contended = DRM_EXEC_DUMMY;
	exec->prelocked = NULL;
}
EXPORT_SYMBOL(drm_exec_init);

/**
 * drm_exec_fini - finalize a drm_exec object
 * @exec: the drm_exec object to finalize
 *
 * Unlock all locked objects, drop the references to objects and free all memory
 * used for tracking the state.
 */
void drm_exec_fini(struct drm_exec *exec)
{
	drm_exec_unlock_all(exec);
	kvfree(exec->objects);
	if (exec->contended != DRM_EXEC_DUMMY) {
		drm_gem_object_put(exec->contended);
		ww_acquire_fini(&exec->ticket);
	}
}
EXPORT_SYMBOL(drm_exec_fini);

/**
 * drm_exec_cleanup - cleanup when contention is detected
 * @exec: the drm_exec object to cleanup
 *
 * Cleanup the current state and return true if we should stay inside the retry
 * loop, false if there wasn't any contention detected and we can keep the
 * objects locked.
 */
bool drm_exec_cleanup(struct drm_exec *exec)
{
	if (likely(!exec->contended)) {
		ww_acquire_done(&exec->ticket);
		return false;
	}

	if (likely(exec->contended == DRM_EXEC_DUMMY)) {
		exec->contended = NULL;
		ww_acquire_init(&exec->ticket, &reservation_ww_class);
		return true;
	}

	drm_exec_unlock_all(exec);
	exec->num_objects = 0;
	return true;
}
EXPORT_SYMBOL(drm_exec_cleanup);

/* Track the locked object in the array */
static int drm_exec_obj_locked(struct drm_exec *exec,
			       struct drm_gem_object *obj)
{
	if (unlikely(exec->num_objects == exec->max_objects)) {
		size_t size = exec->max_objects * sizeof(void *);
		void *tmp;

		tmp = kvrealloc(exec->objects, size, size + PAGE_SIZE,
				GFP_KERNEL);
		if (!tmp)
			return -ENOMEM;

		exec->objects = tmp;
		exec->max_objects += PAGE_SIZE / sizeof(void *);
	}
	drm_gem_object_get(obj);
	exec->objects[exec->num_objects++] = obj;

	return 0;
}

/* Make sure the contended object is locked first */
static int drm_exec_lock_contended(struct drm_exec *exec)
{
	struct drm_gem_object *obj = exec->contended;
	int ret;

	if (likely(!obj))
		return 0;

	/* Always cleanup the contention so that error handling can kick in */
	exec->contended = NULL;
	if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT) {
		ret = dma_resv_lock_slow_interruptible(obj->resv,
						       &exec->ticket);
		if (unlikely(ret))
			goto error_dropref;
	} else {
		dma_resv_lock_slow(obj->resv, &exec->ticket);
	}

	ret = drm_exec_obj_locked(exec, obj);
	if (unlikely(ret))
		goto error_unlock;

	exec->prelocked = obj;
	return 0;

error_unlock:
	dma_resv_unlock(obj->resv);

error_dropref:
	drm_gem_object_put(obj);
	return ret;
}

/**
 * drm_exec_lock_obj - lock a GEM object for use
 * @exec: the drm_exec object with the state
 * @obj: the GEM object to lock
 *
 * Lock a GEM object for use and grab a reference to it.
 *
 * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
 * already locked (can be suppressed by setting the DRM_EXEC_IGNORE_DUPLICATES
 * flag), -ENOMEM when memory allocation failed and zero for success.
 */
int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
{
	int ret;

	ret = drm_exec_lock_contended(exec);
	if (unlikely(ret))
		return ret;

	if (exec->prelocked == obj) {
		drm_gem_object_put(exec->prelocked);
		exec->prelocked = NULL;
		return 0;
	}

	if (exec->flags & DRM_EXEC_INTERRUPTIBLE_WAIT)
		ret = dma_resv_lock_interruptible(obj->resv, &exec->ticket);
	else
		ret = dma_resv_lock(obj->resv, &exec->ticket);

	if (unlikely(ret == -EDEADLK)) {
		drm_gem_object_get(obj);
		exec->contended = obj;
		return -EDEADLK;
	}

	if (unlikely(ret == -EALREADY) &&
	    exec->flags & DRM_EXEC_IGNORE_DUPLICATES)
		return 0;

	if (unlikely(ret))
		return ret;

	ret = drm_exec_obj_locked(exec, obj);
	if (ret)
		goto error_unlock;

	return 0;

error_unlock:
	dma_resv_unlock(obj->resv);
	return ret;
}
EXPORT_SYMBOL(drm_exec_lock_obj);

/**
 * drm_exec_unlock_obj - unlock a GEM object in this exec context
 * @exec: the drm_exec object with the state
 * @obj: the GEM object to unlock
 *
 * Unlock the GEM object and remove it from the collection of locked objects.
 * Should only be used to unlock the most recently locked objects. It's not time
 * efficient to unlock objects locked long ago.
 */
void drm_exec_unlock_obj(struct drm_exec *exec, struct drm_gem_object *obj)
{
	unsigned int i;

	for (i = exec->num_objects; i--;) {
		if (exec->objects[i] == obj) {
			dma_resv_unlock(obj->resv);
			for (++i; i < exec->num_objects; ++i)
				exec->objects[i - 1] = exec->objects[i];
			--exec->num_objects;
			drm_gem_object_put(obj);
			return;
		}

	}
}
EXPORT_SYMBOL(drm_exec_unlock_obj);

/**
 * drm_exec_prepare_obj - prepare a GEM object for use
 * @exec: the drm_exec object with the state
 * @obj: the GEM object to prepare
 * @num_fences: how many fences to reserve
 *
 * Prepare a GEM object for use by locking it and reserving fence slots.
 *
 * Returns: -EDEADLK if a contention is detected, -EALREADY when object is
 * already locked, -ENOMEM when memory allocation failed and zero for success.
 */
int drm_exec_prepare_obj(struct drm_exec *exec, struct drm_gem_object *obj,
			 unsigned int num_fences)
{
	int ret;

	ret = drm_exec_lock_obj(exec, obj);
	if (ret)
		return ret;

	ret = dma_resv_reserve_fences(obj->resv, num_fences);
	if (ret) {
		drm_exec_unlock_obj(exec, obj);
		return ret;
	}

	return 0;
}
EXPORT_SYMBOL(drm_exec_prepare_obj);

/**
 * drm_exec_prepare_array - helper to prepare an array of objects
 * @exec: the drm_exec object with the state
 * @objects: array of GEM object to prepare
 * @num_objects: number of GEM objects in the array
 * @num_fences: number of fences to reserve on each GEM object
 *
 * Prepares all GEM objects in an array, aborts on first error.
 * Reserves @num_fences on each GEM object after locking it.
 *
 * Returns: -EDEADLOCK on contention, -EALREADY when object is already locked,
 * -ENOMEM when memory allocation failed and zero for success.
 */
int drm_exec_prepare_array(struct drm_exec *exec,
			   struct drm_gem_object **objects,
			   unsigned int num_objects,
			   unsigned int num_fences)
{
	int ret;

	for (unsigned int i = 0; i < num_objects; ++i) {
		ret = drm_exec_prepare_obj(exec, objects[i], num_fences);
		if (unlikely(ret))
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL(drm_exec_prepare_array);

MODULE_DESCRIPTION("DRM execution context");
MODULE_LICENSE("Dual MIT/GPL");