xref: /openbmc/linux/drivers/reset/core.c (revision 82003e04)
1 /*
2  * Reset Controller framework
3  *
4  * Copyright 2013 Philipp Zabel, Pengutronix
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  */
11 #include <linux/atomic.h>
12 #include <linux/device.h>
13 #include <linux/err.h>
14 #include <linux/export.h>
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/of.h>
18 #include <linux/reset.h>
19 #include <linux/reset-controller.h>
20 #include <linux/slab.h>
21 
22 static DEFINE_MUTEX(reset_list_mutex);
23 static LIST_HEAD(reset_controller_list);
24 
25 /**
26  * struct reset_control - a reset control
27  * @rcdev: a pointer to the reset controller device
28  *         this reset control belongs to
29  * @list: list entry for the rcdev's reset controller list
30  * @id: ID of the reset controller in the reset
31  *      controller device
32  * @refcnt: Number of gets of this reset_control
33  * @shared: Is this a shared (1), or an exclusive (0) reset_control?
34  * @deassert_cnt: Number of times this reset line has been deasserted
35  */
36 struct reset_control {
37 	struct reset_controller_dev *rcdev;
38 	struct list_head list;
39 	unsigned int id;
40 	unsigned int refcnt;
41 	int shared;
42 	atomic_t deassert_count;
43 };
44 
45 /**
46  * of_reset_simple_xlate - translate reset_spec to the reset line number
47  * @rcdev: a pointer to the reset controller device
48  * @reset_spec: reset line specifier as found in the device tree
49  * @flags: a flags pointer to fill in (optional)
50  *
51  * This simple translation function should be used for reset controllers
52  * with 1:1 mapping, where reset lines can be indexed by number without gaps.
53  */
54 static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
55 			  const struct of_phandle_args *reset_spec)
56 {
57 	if (reset_spec->args[0] >= rcdev->nr_resets)
58 		return -EINVAL;
59 
60 	return reset_spec->args[0];
61 }
62 
63 /**
64  * reset_controller_register - register a reset controller device
65  * @rcdev: a pointer to the initialized reset controller device
66  */
67 int reset_controller_register(struct reset_controller_dev *rcdev)
68 {
69 	if (!rcdev->of_xlate) {
70 		rcdev->of_reset_n_cells = 1;
71 		rcdev->of_xlate = of_reset_simple_xlate;
72 	}
73 
74 	INIT_LIST_HEAD(&rcdev->reset_control_head);
75 
76 	mutex_lock(&reset_list_mutex);
77 	list_add(&rcdev->list, &reset_controller_list);
78 	mutex_unlock(&reset_list_mutex);
79 
80 	return 0;
81 }
82 EXPORT_SYMBOL_GPL(reset_controller_register);
83 
84 /**
85  * reset_controller_unregister - unregister a reset controller device
86  * @rcdev: a pointer to the reset controller device
87  */
88 void reset_controller_unregister(struct reset_controller_dev *rcdev)
89 {
90 	mutex_lock(&reset_list_mutex);
91 	list_del(&rcdev->list);
92 	mutex_unlock(&reset_list_mutex);
93 }
94 EXPORT_SYMBOL_GPL(reset_controller_unregister);
95 
96 static void devm_reset_controller_release(struct device *dev, void *res)
97 {
98 	reset_controller_unregister(*(struct reset_controller_dev **)res);
99 }
100 
101 /**
102  * devm_reset_controller_register - resource managed reset_controller_register()
103  * @dev: device that is registering this reset controller
104  * @rcdev: a pointer to the initialized reset controller device
105  *
106  * Managed reset_controller_register(). For reset controllers registered by
107  * this function, reset_controller_unregister() is automatically called on
108  * driver detach. See reset_controller_register() for more information.
109  */
110 int devm_reset_controller_register(struct device *dev,
111 				   struct reset_controller_dev *rcdev)
112 {
113 	struct reset_controller_dev **rcdevp;
114 	int ret;
115 
116 	rcdevp = devres_alloc(devm_reset_controller_release, sizeof(*rcdevp),
117 			      GFP_KERNEL);
118 	if (!rcdevp)
119 		return -ENOMEM;
120 
121 	ret = reset_controller_register(rcdev);
122 	if (!ret) {
123 		*rcdevp = rcdev;
124 		devres_add(dev, rcdevp);
125 	} else {
126 		devres_free(rcdevp);
127 	}
128 
129 	return ret;
130 }
131 EXPORT_SYMBOL_GPL(devm_reset_controller_register);
132 
133 /**
134  * reset_control_reset - reset the controlled device
135  * @rstc: reset controller
136  *
137  * Calling this on a shared reset controller is an error.
138  */
139 int reset_control_reset(struct reset_control *rstc)
140 {
141 	if (WARN_ON(IS_ERR_OR_NULL(rstc)) ||
142 	    WARN_ON(rstc->shared))
143 		return -EINVAL;
144 
145 	if (rstc->rcdev->ops->reset)
146 		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
147 
148 	return -ENOTSUPP;
149 }
150 EXPORT_SYMBOL_GPL(reset_control_reset);
151 
152 /**
153  * reset_control_assert - asserts the reset line
154  * @rstc: reset controller
155  *
156  * Calling this on an exclusive reset controller guarantees that the reset
157  * will be asserted. When called on a shared reset controller the line may
158  * still be deasserted, as long as other users keep it so.
159  *
160  * For shared reset controls a driver cannot expect the hw's registers and
161  * internal state to be reset, but must be prepared for this to happen.
162  */
163 int reset_control_assert(struct reset_control *rstc)
164 {
165 	if (WARN_ON(IS_ERR_OR_NULL(rstc)))
166 		return -EINVAL;
167 
168 	if (!rstc->rcdev->ops->assert)
169 		return -ENOTSUPP;
170 
171 	if (rstc->shared) {
172 		if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
173 			return -EINVAL;
174 
175 		if (atomic_dec_return(&rstc->deassert_count) != 0)
176 			return 0;
177 	}
178 
179 	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
180 }
181 EXPORT_SYMBOL_GPL(reset_control_assert);
182 
183 /**
184  * reset_control_deassert - deasserts the reset line
185  * @rstc: reset controller
186  *
187  * After calling this function, the reset is guaranteed to be deasserted.
188  */
189 int reset_control_deassert(struct reset_control *rstc)
190 {
191 	if (WARN_ON(IS_ERR_OR_NULL(rstc)))
192 		return -EINVAL;
193 
194 	if (!rstc->rcdev->ops->deassert)
195 		return -ENOTSUPP;
196 
197 	if (rstc->shared) {
198 		if (atomic_inc_return(&rstc->deassert_count) != 1)
199 			return 0;
200 	}
201 
202 	return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
203 }
204 EXPORT_SYMBOL_GPL(reset_control_deassert);
205 
206 /**
207  * reset_control_status - returns a negative errno if not supported, a
208  * positive value if the reset line is asserted, or zero if the reset
209  * line is not asserted.
210  * @rstc: reset controller
211  */
212 int reset_control_status(struct reset_control *rstc)
213 {
214 	if (WARN_ON(IS_ERR_OR_NULL(rstc)))
215 		return -EINVAL;
216 
217 	if (rstc->rcdev->ops->status)
218 		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
219 
220 	return -ENOTSUPP;
221 }
222 EXPORT_SYMBOL_GPL(reset_control_status);
223 
224 static struct reset_control *__reset_control_get(
225 				struct reset_controller_dev *rcdev,
226 				unsigned int index, int shared)
227 {
228 	struct reset_control *rstc;
229 
230 	lockdep_assert_held(&reset_list_mutex);
231 
232 	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
233 		if (rstc->id == index) {
234 			if (WARN_ON(!rstc->shared || !shared))
235 				return ERR_PTR(-EBUSY);
236 
237 			rstc->refcnt++;
238 			return rstc;
239 		}
240 	}
241 
242 	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
243 	if (!rstc)
244 		return ERR_PTR(-ENOMEM);
245 
246 	try_module_get(rcdev->owner);
247 
248 	rstc->rcdev = rcdev;
249 	list_add(&rstc->list, &rcdev->reset_control_head);
250 	rstc->id = index;
251 	rstc->refcnt = 1;
252 	rstc->shared = shared;
253 
254 	return rstc;
255 }
256 
257 static void __reset_control_put(struct reset_control *rstc)
258 {
259 	lockdep_assert_held(&reset_list_mutex);
260 
261 	if (--rstc->refcnt)
262 		return;
263 
264 	module_put(rstc->rcdev->owner);
265 
266 	list_del(&rstc->list);
267 	kfree(rstc);
268 }
269 
270 struct reset_control *__of_reset_control_get(struct device_node *node,
271 				     const char *id, int index, int shared)
272 {
273 	struct reset_control *rstc;
274 	struct reset_controller_dev *r, *rcdev;
275 	struct of_phandle_args args;
276 	int rstc_id;
277 	int ret;
278 
279 	if (!node)
280 		return ERR_PTR(-EINVAL);
281 
282 	if (id) {
283 		index = of_property_match_string(node,
284 						 "reset-names", id);
285 		if (index < 0)
286 			return ERR_PTR(-ENOENT);
287 	}
288 
289 	ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
290 					 index, &args);
291 	if (ret)
292 		return ERR_PTR(ret);
293 
294 	mutex_lock(&reset_list_mutex);
295 	rcdev = NULL;
296 	list_for_each_entry(r, &reset_controller_list, list) {
297 		if (args.np == r->of_node) {
298 			rcdev = r;
299 			break;
300 		}
301 	}
302 	of_node_put(args.np);
303 
304 	if (!rcdev) {
305 		mutex_unlock(&reset_list_mutex);
306 		return ERR_PTR(-EPROBE_DEFER);
307 	}
308 
309 	if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
310 		mutex_unlock(&reset_list_mutex);
311 		return ERR_PTR(-EINVAL);
312 	}
313 
314 	rstc_id = rcdev->of_xlate(rcdev, &args);
315 	if (rstc_id < 0) {
316 		mutex_unlock(&reset_list_mutex);
317 		return ERR_PTR(rstc_id);
318 	}
319 
320 	/* reset_list_mutex also protects the rcdev's reset_control list */
321 	rstc = __reset_control_get(rcdev, rstc_id, shared);
322 
323 	mutex_unlock(&reset_list_mutex);
324 
325 	return rstc;
326 }
327 EXPORT_SYMBOL_GPL(__of_reset_control_get);
328 
329 /**
330  * reset_control_put - free the reset controller
331  * @rstc: reset controller
332  */
333 
334 void reset_control_put(struct reset_control *rstc)
335 {
336 	if (IS_ERR(rstc))
337 		return;
338 
339 	mutex_lock(&reset_list_mutex);
340 	__reset_control_put(rstc);
341 	mutex_unlock(&reset_list_mutex);
342 }
343 EXPORT_SYMBOL_GPL(reset_control_put);
344 
345 static void devm_reset_control_release(struct device *dev, void *res)
346 {
347 	reset_control_put(*(struct reset_control **)res);
348 }
349 
350 struct reset_control *__devm_reset_control_get(struct device *dev,
351 				     const char *id, int index, int shared)
352 {
353 	struct reset_control **ptr, *rstc;
354 
355 	ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
356 			   GFP_KERNEL);
357 	if (!ptr)
358 		return ERR_PTR(-ENOMEM);
359 
360 	rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
361 				      id, index, shared);
362 	if (!IS_ERR(rstc)) {
363 		*ptr = rstc;
364 		devres_add(dev, ptr);
365 	} else {
366 		devres_free(ptr);
367 	}
368 
369 	return rstc;
370 }
371 EXPORT_SYMBOL_GPL(__devm_reset_control_get);
372 
373 /**
374  * device_reset - find reset controller associated with the device
375  *                and perform reset
376  * @dev: device to be reset by the controller
377  *
378  * Convenience wrapper for reset_control_get() and reset_control_reset().
379  * This is useful for the common case of devices with single, dedicated reset
380  * lines.
381  */
382 int device_reset(struct device *dev)
383 {
384 	struct reset_control *rstc;
385 	int ret;
386 
387 	rstc = reset_control_get(dev, NULL);
388 	if (IS_ERR(rstc))
389 		return PTR_ERR(rstc);
390 
391 	ret = reset_control_reset(rstc);
392 
393 	reset_control_put(rstc);
394 
395 	return ret;
396 }
397 EXPORT_SYMBOL_GPL(device_reset);
398