summaryrefslogtreecommitdiffstats
path: root/drivers/reset/core.c
blob: 72b32bd1554963231504bfd13addc52260b01d97 (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
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
/*
 * Reset Controller framework
 *
 * Copyright 2013 Philipp Zabel, Pengutronix
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/reset.h>
#include <linux/reset-controller.h>
#include <linux/slab.h>

static DEFINE_MUTEX(reset_list_mutex);
static LIST_HEAD(reset_controller_list);

/**
 * struct reset_control - a reset control
 * @rcdev: a pointer to the reset controller device
 *         this reset control belongs to
 * @list: list entry for the rcdev's reset controller list
 * @id: ID of the reset controller in the reset
 *      controller device
 * @refcnt: Number of gets of this reset_control
 * @shared: Is this a shared (1), or an exclusive (0) reset_control?
 * @deassert_cnt: Number of times this reset line has been deasserted
 */
struct reset_control {
	struct reset_controller_dev *rcdev;
	struct list_head list;
	unsigned int id;
	unsigned int refcnt;
	int shared;
	atomic_t deassert_count;
};

/**
 * of_reset_simple_xlate - translate reset_spec to the reset line number
 * @rcdev: a pointer to the reset controller device
 * @reset_spec: reset line specifier as found in the device tree
 * @flags: a flags pointer to fill in (optional)
 *
 * This simple translation function should be used for reset controllers
 * with 1:1 mapping, where reset lines can be indexed by number without gaps.
 */
static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
			  const struct of_phandle_args *reset_spec)
{
	if (reset_spec->args[0] >= rcdev->nr_resets)
		return -EINVAL;

	return reset_spec->args[0];
}

/**
 * reset_controller_register - register a reset controller device
 * @rcdev: a pointer to the initialized reset controller device
 */
int reset_controller_register(struct reset_controller_dev *rcdev)
{
	if (!rcdev->of_xlate) {
		rcdev->of_reset_n_cells = 1;
		rcdev->of_xlate = of_reset_simple_xlate;
	}

	INIT_LIST_HEAD(&rcdev->reset_control_head);

	mutex_lock(&reset_list_mutex);
	list_add(&rcdev->list, &reset_controller_list);
	mutex_unlock(&reset_list_mutex);

	return 0;
}
EXPORT_SYMBOL_GPL(reset_controller_register);

/**
 * reset_controller_unregister - unregister a reset controller device
 * @rcdev: a pointer to the reset controller device
 */
void reset_controller_unregister(struct reset_controller_dev *rcdev)
{
	mutex_lock(&reset_list_mutex);
	list_del(&rcdev->list);
	mutex_unlock(&reset_list_mutex);
}
EXPORT_SYMBOL_GPL(reset_controller_unregister);

/**
 * reset_control_reset - reset the controlled device
 * @rstc: reset controller
 *
 * Calling this on a shared reset controller is an error.
 */
int reset_control_reset(struct reset_control *rstc)
{
	if (WARN_ON(rstc->shared))
		return -EINVAL;

	if (rstc->rcdev->ops->reset)
		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);

	return -ENOTSUPP;
}
EXPORT_SYMBOL_GPL(reset_control_reset);

/**
 * reset_control_assert - asserts the reset line
 * @rstc: reset controller
 *
 * Calling this on an exclusive reset controller guarantees that the reset
 * will be asserted. When called on a shared reset controller the line may
 * still be deasserted, as long as other users keep it so.
 *
 * For shared reset controls a driver cannot expect the hw's registers and
 * internal state to be reset, but must be prepared for this to happen.
 */
int reset_control_assert(struct reset_control *rstc)
{
	if (!rstc->rcdev->ops->assert)
		return -ENOTSUPP;

	if (rstc->shared) {
		if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
			return -EINVAL;

		if (atomic_dec_return(&rstc->deassert_count) != 0)
			return 0;
	}

	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_assert);

/**
 * reset_control_deassert - deasserts the reset line
 * @rstc: reset controller
 *
 * After calling this function, the reset is guaranteed to be deasserted.
 */
int reset_control_deassert(struct reset_control *rstc)
{
	if (!rstc->rcdev->ops->deassert)
		return -ENOTSUPP;

	if (rstc->shared) {
		if (atomic_inc_return(&rstc->deassert_count) != 1)
			return 0;
	}

	return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_deassert);

/**
 * reset_control_status - returns a negative errno if not supported, a
 * positive value if the reset line is asserted, or zero if the reset
 * line is not asserted.
 * @rstc: reset controller
 */
int reset_control_status(struct reset_control *rstc)
{
	if (rstc->rcdev->ops->status)
		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);

	return -ENOTSUPP;
}
EXPORT_SYMBOL_GPL(reset_control_status);

static struct reset_control *__reset_control_get(
				struct reset_controller_dev *rcdev,
				unsigned int index, int shared)
{
	struct reset_control *rstc;

	lockdep_assert_held(&reset_list_mutex);

	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
		if (rstc->id == index) {
			if (WARN_ON(!rstc->shared || !shared))
				return ERR_PTR(-EBUSY);

			rstc->refcnt++;
			return rstc;
		}
	}

	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
	if (!rstc)
		return ERR_PTR(-ENOMEM);

	try_module_get(rcdev->owner);

	rstc->rcdev = rcdev;
	list_add(&rstc->list, &rcdev->reset_control_head);
	rstc->id = index;
	rstc->refcnt = 1;
	rstc->shared = shared;

	return rstc;
}

static void __reset_control_put(struct reset_control *rstc)
{
	lockdep_assert_held(&reset_list_mutex);

	if (--rstc->refcnt)
		return;

	module_put(rstc->rcdev->owner);

	list_del(&rstc->list);
	kfree(rstc);
}

struct reset_control *__of_reset_control_get(struct device_node *node,
				     const char *id, int index, int shared)
{
	struct reset_control *rstc;
	struct reset_controller_dev *r, *rcdev;
	struct of_phandle_args args;
	int rstc_id;
	int ret;

	if (!node)
		return ERR_PTR(-EINVAL);

	if (id) {
		index = of_property_match_string(node,
						 "reset-names", id);
		if (index < 0)
			return ERR_PTR(-ENOENT);
	}

	ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
					 index, &args);
	if (ret)
		return ERR_PTR(ret);

	mutex_lock(&reset_list_mutex);
	rcdev = NULL;
	list_for_each_entry(r, &reset_controller_list, list) {
		if (args.np == r->of_node) {
			rcdev = r;
			break;
		}
	}
	of_node_put(args.np);

	if (!rcdev) {
		mutex_unlock(&reset_list_mutex);
		return ERR_PTR(-EPROBE_DEFER);
	}

	if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
		mutex_unlock(&reset_list_mutex);
		return ERR_PTR(-EINVAL);
	}

	rstc_id = rcdev->of_xlate(rcdev, &args);
	if (rstc_id < 0) {
		mutex_unlock(&reset_list_mutex);
		return ERR_PTR(rstc_id);
	}

	/* reset_list_mutex also protects the rcdev's reset_control list */
	rstc = __reset_control_get(rcdev, rstc_id, shared);

	mutex_unlock(&reset_list_mutex);

	return rstc;
}
EXPORT_SYMBOL_GPL(__of_reset_control_get);

/**
 * reset_control_put - free the reset controller
 * @rstc: reset controller
 */

void reset_control_put(struct reset_control *rstc)
{
	if (IS_ERR(rstc))
		return;

	mutex_lock(&reset_list_mutex);
	__reset_control_put(rstc);
	mutex_unlock(&reset_list_mutex);
}
EXPORT_SYMBOL_GPL(reset_control_put);

static void devm_reset_control_release(struct device *dev, void *res)
{
	reset_control_put(*(struct reset_control **)res);
}

struct reset_control *__devm_reset_control_get(struct device *dev,
				     const char *id, int index, int shared)
{
	struct reset_control **ptr, *rstc;

	ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
			   GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
				      id, index, shared);
	if (!IS_ERR(rstc)) {
		*ptr = rstc;
		devres_add(dev, ptr);
	} else {
		devres_free(ptr);
	}

	return rstc;
}
EXPORT_SYMBOL_GPL(__devm_reset_control_get);

/**
 * device_reset - find reset controller associated with the device
 *                and perform reset
 * @dev: device to be reset by the controller
 *
 * Convenience wrapper for reset_control_get() and reset_control_reset().
 * This is useful for the common case of devices with single, dedicated reset
 * lines.
 */
int device_reset(struct device *dev)
{
	struct reset_control *rstc;
	int ret;

	rstc = reset_control_get(dev, NULL);
	if (IS_ERR(rstc))
		return PTR_ERR(rstc);

	ret = reset_control_reset(rstc);

	reset_control_put(rstc);

	return ret;
}
EXPORT_SYMBOL_GPL(device_reset);
OpenPOWER on IntegriCloud