xref: /openbmc/linux/drivers/pwm/core.c (revision 0984d159)
1 /*
2  * Generic pwmlib implementation
3  *
4  * Copyright (C) 2011 Sascha Hauer <s.hauer@pengutronix.de>
5  * Copyright (C) 2011-2012 Avionic Design GmbH
6  *
7  *  This program is free software; you can redistribute it and/or modify
8  *  it under the terms of the GNU General Public License as published by
9  *  the Free Software Foundation; either version 2, or (at your option)
10  *  any later version.
11  *
12  *  This program is distributed in the hope that it will be useful,
13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  *  GNU General Public License for more details.
16  *
17  *  You should have received a copy of the GNU General Public License
18  *  along with this program; see the file COPYING.  If not, write to
19  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
20  */
21 
22 #include <linux/module.h>
23 #include <linux/pwm.h>
24 #include <linux/radix-tree.h>
25 #include <linux/list.h>
26 #include <linux/mutex.h>
27 #include <linux/err.h>
28 #include <linux/slab.h>
29 #include <linux/device.h>
30 #include <linux/debugfs.h>
31 #include <linux/seq_file.h>
32 
33 #include <dt-bindings/pwm/pwm.h>
34 
35 #define MAX_PWMS 1024
36 
37 static DEFINE_MUTEX(pwm_lookup_lock);
38 static LIST_HEAD(pwm_lookup_list);
39 static DEFINE_MUTEX(pwm_lock);
40 static LIST_HEAD(pwm_chips);
41 static DECLARE_BITMAP(allocated_pwms, MAX_PWMS);
42 static RADIX_TREE(pwm_tree, GFP_KERNEL);
43 
44 static struct pwm_device *pwm_to_device(unsigned int pwm)
45 {
46 	return radix_tree_lookup(&pwm_tree, pwm);
47 }
48 
49 static int alloc_pwms(int pwm, unsigned int count)
50 {
51 	unsigned int from = 0;
52 	unsigned int start;
53 
54 	if (pwm >= MAX_PWMS)
55 		return -EINVAL;
56 
57 	if (pwm >= 0)
58 		from = pwm;
59 
60 	start = bitmap_find_next_zero_area(allocated_pwms, MAX_PWMS, from,
61 					   count, 0);
62 
63 	if (pwm >= 0 && start != pwm)
64 		return -EEXIST;
65 
66 	if (start + count > MAX_PWMS)
67 		return -ENOSPC;
68 
69 	return start;
70 }
71 
72 static void free_pwms(struct pwm_chip *chip)
73 {
74 	unsigned int i;
75 
76 	for (i = 0; i < chip->npwm; i++) {
77 		struct pwm_device *pwm = &chip->pwms[i];
78 
79 		radix_tree_delete(&pwm_tree, pwm->pwm);
80 	}
81 
82 	bitmap_clear(allocated_pwms, chip->base, chip->npwm);
83 
84 	kfree(chip->pwms);
85 	chip->pwms = NULL;
86 }
87 
88 static struct pwm_chip *pwmchip_find_by_name(const char *name)
89 {
90 	struct pwm_chip *chip;
91 
92 	if (!name)
93 		return NULL;
94 
95 	mutex_lock(&pwm_lock);
96 
97 	list_for_each_entry(chip, &pwm_chips, list) {
98 		const char *chip_name = dev_name(chip->dev);
99 
100 		if (chip_name && strcmp(chip_name, name) == 0) {
101 			mutex_unlock(&pwm_lock);
102 			return chip;
103 		}
104 	}
105 
106 	mutex_unlock(&pwm_lock);
107 
108 	return NULL;
109 }
110 
111 static int pwm_device_request(struct pwm_device *pwm, const char *label)
112 {
113 	int err;
114 
115 	if (test_bit(PWMF_REQUESTED, &pwm->flags))
116 		return -EBUSY;
117 
118 	if (!try_module_get(pwm->chip->ops->owner))
119 		return -ENODEV;
120 
121 	if (pwm->chip->ops->request) {
122 		err = pwm->chip->ops->request(pwm->chip, pwm);
123 		if (err) {
124 			module_put(pwm->chip->ops->owner);
125 			return err;
126 		}
127 	}
128 
129 	set_bit(PWMF_REQUESTED, &pwm->flags);
130 	pwm->label = label;
131 
132 	return 0;
133 }
134 
135 struct pwm_device *
136 of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
137 {
138 	struct pwm_device *pwm;
139 
140 	if (pc->of_pwm_n_cells < 3)
141 		return ERR_PTR(-EINVAL);
142 
143 	if (args->args[0] >= pc->npwm)
144 		return ERR_PTR(-EINVAL);
145 
146 	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
147 	if (IS_ERR(pwm))
148 		return pwm;
149 
150 	pwm->args.period = args->args[1];
151 
152 	if (args->args[2] & PWM_POLARITY_INVERTED)
153 		pwm->args.polarity = PWM_POLARITY_INVERSED;
154 	else
155 		pwm->args.polarity = PWM_POLARITY_NORMAL;
156 
157 	return pwm;
158 }
159 EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
160 
161 static struct pwm_device *
162 of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
163 {
164 	struct pwm_device *pwm;
165 
166 	if (pc->of_pwm_n_cells < 2)
167 		return ERR_PTR(-EINVAL);
168 
169 	if (args->args[0] >= pc->npwm)
170 		return ERR_PTR(-EINVAL);
171 
172 	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
173 	if (IS_ERR(pwm))
174 		return pwm;
175 
176 	pwm->args.period = args->args[1];
177 
178 	return pwm;
179 }
180 
181 static void of_pwmchip_add(struct pwm_chip *chip)
182 {
183 	if (!chip->dev || !chip->dev->of_node)
184 		return;
185 
186 	if (!chip->of_xlate) {
187 		chip->of_xlate = of_pwm_simple_xlate;
188 		chip->of_pwm_n_cells = 2;
189 	}
190 
191 	of_node_get(chip->dev->of_node);
192 }
193 
194 static void of_pwmchip_remove(struct pwm_chip *chip)
195 {
196 	if (chip->dev)
197 		of_node_put(chip->dev->of_node);
198 }
199 
200 /**
201  * pwm_set_chip_data() - set private chip data for a PWM
202  * @pwm: PWM device
203  * @data: pointer to chip-specific data
204  *
205  * Returns: 0 on success or a negative error code on failure.
206  */
207 int pwm_set_chip_data(struct pwm_device *pwm, void *data)
208 {
209 	if (!pwm)
210 		return -EINVAL;
211 
212 	pwm->chip_data = data;
213 
214 	return 0;
215 }
216 EXPORT_SYMBOL_GPL(pwm_set_chip_data);
217 
218 /**
219  * pwm_get_chip_data() - get private chip data for a PWM
220  * @pwm: PWM device
221  *
222  * Returns: A pointer to the chip-private data for the PWM device.
223  */
224 void *pwm_get_chip_data(struct pwm_device *pwm)
225 {
226 	return pwm ? pwm->chip_data : NULL;
227 }
228 EXPORT_SYMBOL_GPL(pwm_get_chip_data);
229 
230 static bool pwm_ops_check(const struct pwm_ops *ops)
231 {
232 	/* driver supports legacy, non-atomic operation */
233 	if (ops->config && ops->enable && ops->disable)
234 		return true;
235 
236 	/* driver supports atomic operation */
237 	if (ops->apply)
238 		return true;
239 
240 	return false;
241 }
242 
243 /**
244  * pwmchip_add_with_polarity() - register a new PWM chip
245  * @chip: the PWM chip to add
246  * @polarity: initial polarity of PWM channels
247  *
248  * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
249  * will be used. The initial polarity for all channels is specified by the
250  * @polarity parameter.
251  *
252  * Returns: 0 on success or a negative error code on failure.
253  */
254 int pwmchip_add_with_polarity(struct pwm_chip *chip,
255 			      enum pwm_polarity polarity)
256 {
257 	struct pwm_device *pwm;
258 	unsigned int i;
259 	int ret;
260 
261 	if (!chip || !chip->dev || !chip->ops || !chip->npwm)
262 		return -EINVAL;
263 
264 	if (!pwm_ops_check(chip->ops))
265 		return -EINVAL;
266 
267 	mutex_lock(&pwm_lock);
268 
269 	ret = alloc_pwms(chip->base, chip->npwm);
270 	if (ret < 0)
271 		goto out;
272 
273 	chip->pwms = kcalloc(chip->npwm, sizeof(*pwm), GFP_KERNEL);
274 	if (!chip->pwms) {
275 		ret = -ENOMEM;
276 		goto out;
277 	}
278 
279 	chip->base = ret;
280 
281 	for (i = 0; i < chip->npwm; i++) {
282 		pwm = &chip->pwms[i];
283 
284 		pwm->chip = chip;
285 		pwm->pwm = chip->base + i;
286 		pwm->hwpwm = i;
287 		pwm->state.polarity = polarity;
288 
289 		if (chip->ops->get_state)
290 			chip->ops->get_state(chip, pwm, &pwm->state);
291 
292 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
293 	}
294 
295 	bitmap_set(allocated_pwms, chip->base, chip->npwm);
296 
297 	INIT_LIST_HEAD(&chip->list);
298 	list_add(&chip->list, &pwm_chips);
299 
300 	ret = 0;
301 
302 	if (IS_ENABLED(CONFIG_OF))
303 		of_pwmchip_add(chip);
304 
305 	pwmchip_sysfs_export(chip);
306 
307 out:
308 	mutex_unlock(&pwm_lock);
309 	return ret;
310 }
311 EXPORT_SYMBOL_GPL(pwmchip_add_with_polarity);
312 
313 /**
314  * pwmchip_add() - register a new PWM chip
315  * @chip: the PWM chip to add
316  *
317  * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
318  * will be used. The initial polarity for all channels is normal.
319  *
320  * Returns: 0 on success or a negative error code on failure.
321  */
322 int pwmchip_add(struct pwm_chip *chip)
323 {
324 	return pwmchip_add_with_polarity(chip, PWM_POLARITY_NORMAL);
325 }
326 EXPORT_SYMBOL_GPL(pwmchip_add);
327 
328 /**
329  * pwmchip_remove() - remove a PWM chip
330  * @chip: the PWM chip to remove
331  *
332  * Removes a PWM chip. This function may return busy if the PWM chip provides
333  * a PWM device that is still requested.
334  *
335  * Returns: 0 on success or a negative error code on failure.
336  */
337 int pwmchip_remove(struct pwm_chip *chip)
338 {
339 	unsigned int i;
340 	int ret = 0;
341 
342 	mutex_lock(&pwm_lock);
343 
344 	for (i = 0; i < chip->npwm; i++) {
345 		struct pwm_device *pwm = &chip->pwms[i];
346 
347 		if (test_bit(PWMF_REQUESTED, &pwm->flags)) {
348 			ret = -EBUSY;
349 			goto out;
350 		}
351 	}
352 
353 	list_del_init(&chip->list);
354 
355 	if (IS_ENABLED(CONFIG_OF))
356 		of_pwmchip_remove(chip);
357 
358 	free_pwms(chip);
359 
360 	pwmchip_sysfs_unexport(chip);
361 
362 out:
363 	mutex_unlock(&pwm_lock);
364 	return ret;
365 }
366 EXPORT_SYMBOL_GPL(pwmchip_remove);
367 
368 /**
369  * pwm_request() - request a PWM device
370  * @pwm: global PWM device index
371  * @label: PWM device label
372  *
373  * This function is deprecated, use pwm_get() instead.
374  *
375  * Returns: A pointer to a PWM device or an ERR_PTR()-encoded error code on
376  * failure.
377  */
378 struct pwm_device *pwm_request(int pwm, const char *label)
379 {
380 	struct pwm_device *dev;
381 	int err;
382 
383 	if (pwm < 0 || pwm >= MAX_PWMS)
384 		return ERR_PTR(-EINVAL);
385 
386 	mutex_lock(&pwm_lock);
387 
388 	dev = pwm_to_device(pwm);
389 	if (!dev) {
390 		dev = ERR_PTR(-EPROBE_DEFER);
391 		goto out;
392 	}
393 
394 	err = pwm_device_request(dev, label);
395 	if (err < 0)
396 		dev = ERR_PTR(err);
397 
398 out:
399 	mutex_unlock(&pwm_lock);
400 
401 	return dev;
402 }
403 EXPORT_SYMBOL_GPL(pwm_request);
404 
405 /**
406  * pwm_request_from_chip() - request a PWM device relative to a PWM chip
407  * @chip: PWM chip
408  * @index: per-chip index of the PWM to request
409  * @label: a literal description string of this PWM
410  *
411  * Returns: A pointer to the PWM device at the given index of the given PWM
412  * chip. A negative error code is returned if the index is not valid for the
413  * specified PWM chip or if the PWM device cannot be requested.
414  */
415 struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
416 					 unsigned int index,
417 					 const char *label)
418 {
419 	struct pwm_device *pwm;
420 	int err;
421 
422 	if (!chip || index >= chip->npwm)
423 		return ERR_PTR(-EINVAL);
424 
425 	mutex_lock(&pwm_lock);
426 	pwm = &chip->pwms[index];
427 
428 	err = pwm_device_request(pwm, label);
429 	if (err < 0)
430 		pwm = ERR_PTR(err);
431 
432 	mutex_unlock(&pwm_lock);
433 	return pwm;
434 }
435 EXPORT_SYMBOL_GPL(pwm_request_from_chip);
436 
437 /**
438  * pwm_free() - free a PWM device
439  * @pwm: PWM device
440  *
441  * This function is deprecated, use pwm_put() instead.
442  */
443 void pwm_free(struct pwm_device *pwm)
444 {
445 	pwm_put(pwm);
446 }
447 EXPORT_SYMBOL_GPL(pwm_free);
448 
449 /**
450  * pwm_apply_state() - atomically apply a new state to a PWM device
451  * @pwm: PWM device
452  * @state: new state to apply. This can be adjusted by the PWM driver
453  *	   if the requested config is not achievable, for example,
454  *	   ->duty_cycle and ->period might be approximated.
455  */
456 int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
457 {
458 	int err;
459 
460 	if (!pwm || !state || !state->period ||
461 	    state->duty_cycle > state->period)
462 		return -EINVAL;
463 
464 	if (!memcmp(state, &pwm->state, sizeof(*state)))
465 		return 0;
466 
467 	if (pwm->chip->ops->apply) {
468 		err = pwm->chip->ops->apply(pwm->chip, pwm, state);
469 		if (err)
470 			return err;
471 
472 		pwm->state = *state;
473 	} else {
474 		/*
475 		 * FIXME: restore the initial state in case of error.
476 		 */
477 		if (state->polarity != pwm->state.polarity) {
478 			if (!pwm->chip->ops->set_polarity)
479 				return -ENOTSUPP;
480 
481 			/*
482 			 * Changing the polarity of a running PWM is
483 			 * only allowed when the PWM driver implements
484 			 * ->apply().
485 			 */
486 			if (pwm->state.enabled) {
487 				pwm->chip->ops->disable(pwm->chip, pwm);
488 				pwm->state.enabled = false;
489 			}
490 
491 			err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
492 							   state->polarity);
493 			if (err)
494 				return err;
495 
496 			pwm->state.polarity = state->polarity;
497 		}
498 
499 		if (state->period != pwm->state.period ||
500 		    state->duty_cycle != pwm->state.duty_cycle) {
501 			err = pwm->chip->ops->config(pwm->chip, pwm,
502 						     state->duty_cycle,
503 						     state->period);
504 			if (err)
505 				return err;
506 
507 			pwm->state.duty_cycle = state->duty_cycle;
508 			pwm->state.period = state->period;
509 		}
510 
511 		if (state->enabled != pwm->state.enabled) {
512 			if (state->enabled) {
513 				err = pwm->chip->ops->enable(pwm->chip, pwm);
514 				if (err)
515 					return err;
516 			} else {
517 				pwm->chip->ops->disable(pwm->chip, pwm);
518 			}
519 
520 			pwm->state.enabled = state->enabled;
521 		}
522 	}
523 
524 	return 0;
525 }
526 EXPORT_SYMBOL_GPL(pwm_apply_state);
527 
528 /**
529  * pwm_adjust_config() - adjust the current PWM config to the PWM arguments
530  * @pwm: PWM device
531  *
532  * This function will adjust the PWM config to the PWM arguments provided
533  * by the DT or PWM lookup table. This is particularly useful to adapt
534  * the bootloader config to the Linux one.
535  */
536 int pwm_adjust_config(struct pwm_device *pwm)
537 {
538 	struct pwm_state state;
539 	struct pwm_args pargs;
540 
541 	pwm_get_args(pwm, &pargs);
542 	pwm_get_state(pwm, &state);
543 
544 	/*
545 	 * If the current period is zero it means that either the PWM driver
546 	 * does not support initial state retrieval or the PWM has not yet
547 	 * been configured.
548 	 *
549 	 * In either case, we setup the new period and polarity, and assign a
550 	 * duty cycle of 0.
551 	 */
552 	if (!state.period) {
553 		state.duty_cycle = 0;
554 		state.period = pargs.period;
555 		state.polarity = pargs.polarity;
556 
557 		return pwm_apply_state(pwm, &state);
558 	}
559 
560 	/*
561 	 * Adjust the PWM duty cycle/period based on the period value provided
562 	 * in PWM args.
563 	 */
564 	if (pargs.period != state.period) {
565 		u64 dutycycle = (u64)state.duty_cycle * pargs.period;
566 
567 		do_div(dutycycle, state.period);
568 		state.duty_cycle = dutycycle;
569 		state.period = pargs.period;
570 	}
571 
572 	/*
573 	 * If the polarity changed, we should also change the duty cycle.
574 	 */
575 	if (pargs.polarity != state.polarity) {
576 		state.polarity = pargs.polarity;
577 		state.duty_cycle = state.period - state.duty_cycle;
578 	}
579 
580 	return pwm_apply_state(pwm, &state);
581 }
582 EXPORT_SYMBOL_GPL(pwm_adjust_config);
583 
584 static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
585 {
586 	struct pwm_chip *chip;
587 
588 	mutex_lock(&pwm_lock);
589 
590 	list_for_each_entry(chip, &pwm_chips, list)
591 		if (chip->dev && chip->dev->of_node == np) {
592 			mutex_unlock(&pwm_lock);
593 			return chip;
594 		}
595 
596 	mutex_unlock(&pwm_lock);
597 
598 	return ERR_PTR(-EPROBE_DEFER);
599 }
600 
601 /**
602  * of_pwm_get() - request a PWM via the PWM framework
603  * @np: device node to get the PWM from
604  * @con_id: consumer name
605  *
606  * Returns the PWM device parsed from the phandle and index specified in the
607  * "pwms" property of a device tree node or a negative error-code on failure.
608  * Values parsed from the device tree are stored in the returned PWM device
609  * object.
610  *
611  * If con_id is NULL, the first PWM device listed in the "pwms" property will
612  * be requested. Otherwise the "pwm-names" property is used to do a reverse
613  * lookup of the PWM index. This also means that the "pwm-names" property
614  * becomes mandatory for devices that look up the PWM device via the con_id
615  * parameter.
616  *
617  * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
618  * error code on failure.
619  */
620 struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
621 {
622 	struct pwm_device *pwm = NULL;
623 	struct of_phandle_args args;
624 	struct pwm_chip *pc;
625 	int index = 0;
626 	int err;
627 
628 	if (con_id) {
629 		index = of_property_match_string(np, "pwm-names", con_id);
630 		if (index < 0)
631 			return ERR_PTR(index);
632 	}
633 
634 	err = of_parse_phandle_with_args(np, "pwms", "#pwm-cells", index,
635 					 &args);
636 	if (err) {
637 		pr_debug("%s(): can't parse \"pwms\" property\n", __func__);
638 		return ERR_PTR(err);
639 	}
640 
641 	pc = of_node_to_pwmchip(args.np);
642 	if (IS_ERR(pc)) {
643 		pr_debug("%s(): PWM chip not found\n", __func__);
644 		pwm = ERR_CAST(pc);
645 		goto put;
646 	}
647 
648 	if (args.args_count != pc->of_pwm_n_cells) {
649 		pr_debug("%s: wrong #pwm-cells for %s\n", np->full_name,
650 			 args.np->full_name);
651 		pwm = ERR_PTR(-EINVAL);
652 		goto put;
653 	}
654 
655 	pwm = pc->of_xlate(pc, &args);
656 	if (IS_ERR(pwm))
657 		goto put;
658 
659 	/*
660 	 * If a consumer name was not given, try to look it up from the
661 	 * "pwm-names" property if it exists. Otherwise use the name of
662 	 * the user device node.
663 	 */
664 	if (!con_id) {
665 		err = of_property_read_string_index(np, "pwm-names", index,
666 						    &con_id);
667 		if (err < 0)
668 			con_id = np->name;
669 	}
670 
671 	pwm->label = con_id;
672 
673 put:
674 	of_node_put(args.np);
675 
676 	return pwm;
677 }
678 EXPORT_SYMBOL_GPL(of_pwm_get);
679 
680 /**
681  * pwm_add_table() - register PWM device consumers
682  * @table: array of consumers to register
683  * @num: number of consumers in table
684  */
685 void pwm_add_table(struct pwm_lookup *table, size_t num)
686 {
687 	mutex_lock(&pwm_lookup_lock);
688 
689 	while (num--) {
690 		list_add_tail(&table->list, &pwm_lookup_list);
691 		table++;
692 	}
693 
694 	mutex_unlock(&pwm_lookup_lock);
695 }
696 
697 /**
698  * pwm_remove_table() - unregister PWM device consumers
699  * @table: array of consumers to unregister
700  * @num: number of consumers in table
701  */
702 void pwm_remove_table(struct pwm_lookup *table, size_t num)
703 {
704 	mutex_lock(&pwm_lookup_lock);
705 
706 	while (num--) {
707 		list_del(&table->list);
708 		table++;
709 	}
710 
711 	mutex_unlock(&pwm_lookup_lock);
712 }
713 
714 /**
715  * pwm_get() - look up and request a PWM device
716  * @dev: device for PWM consumer
717  * @con_id: consumer name
718  *
719  * Lookup is first attempted using DT. If the device was not instantiated from
720  * a device tree, a PWM chip and a relative index is looked up via a table
721  * supplied by board setup code (see pwm_add_table()).
722  *
723  * Once a PWM chip has been found the specified PWM device will be requested
724  * and is ready to be used.
725  *
726  * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
727  * error code on failure.
728  */
729 struct pwm_device *pwm_get(struct device *dev, const char *con_id)
730 {
731 	struct pwm_device *pwm = ERR_PTR(-EPROBE_DEFER);
732 	const char *dev_id = dev ? dev_name(dev) : NULL;
733 	struct pwm_chip *chip = NULL;
734 	unsigned int best = 0;
735 	struct pwm_lookup *p, *chosen = NULL;
736 	unsigned int match;
737 
738 	/* look up via DT first */
739 	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
740 		return of_pwm_get(dev->of_node, con_id);
741 
742 	/*
743 	 * We look up the provider in the static table typically provided by
744 	 * board setup code. We first try to lookup the consumer device by
745 	 * name. If the consumer device was passed in as NULL or if no match
746 	 * was found, we try to find the consumer by directly looking it up
747 	 * by name.
748 	 *
749 	 * If a match is found, the provider PWM chip is looked up by name
750 	 * and a PWM device is requested using the PWM device per-chip index.
751 	 *
752 	 * The lookup algorithm was shamelessly taken from the clock
753 	 * framework:
754 	 *
755 	 * We do slightly fuzzy matching here:
756 	 *  An entry with a NULL ID is assumed to be a wildcard.
757 	 *  If an entry has a device ID, it must match
758 	 *  If an entry has a connection ID, it must match
759 	 * Then we take the most specific entry - with the following order
760 	 * of precedence: dev+con > dev only > con only.
761 	 */
762 	mutex_lock(&pwm_lookup_lock);
763 
764 	list_for_each_entry(p, &pwm_lookup_list, list) {
765 		match = 0;
766 
767 		if (p->dev_id) {
768 			if (!dev_id || strcmp(p->dev_id, dev_id))
769 				continue;
770 
771 			match += 2;
772 		}
773 
774 		if (p->con_id) {
775 			if (!con_id || strcmp(p->con_id, con_id))
776 				continue;
777 
778 			match += 1;
779 		}
780 
781 		if (match > best) {
782 			chosen = p;
783 
784 			if (match != 3)
785 				best = match;
786 			else
787 				break;
788 		}
789 	}
790 
791 	if (!chosen) {
792 		pwm = ERR_PTR(-ENODEV);
793 		goto out;
794 	}
795 
796 	chip = pwmchip_find_by_name(chosen->provider);
797 	if (!chip)
798 		goto out;
799 
800 	pwm = pwm_request_from_chip(chip, chosen->index, con_id ?: dev_id);
801 	if (IS_ERR(pwm))
802 		goto out;
803 
804 	pwm->args.period = chosen->period;
805 	pwm->args.polarity = chosen->polarity;
806 
807 out:
808 	mutex_unlock(&pwm_lookup_lock);
809 	return pwm;
810 }
811 EXPORT_SYMBOL_GPL(pwm_get);
812 
813 /**
814  * pwm_put() - release a PWM device
815  * @pwm: PWM device
816  */
817 void pwm_put(struct pwm_device *pwm)
818 {
819 	if (!pwm)
820 		return;
821 
822 	mutex_lock(&pwm_lock);
823 
824 	if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) {
825 		pr_warn("PWM device already freed\n");
826 		goto out;
827 	}
828 
829 	if (pwm->chip->ops->free)
830 		pwm->chip->ops->free(pwm->chip, pwm);
831 
832 	pwm->label = NULL;
833 
834 	module_put(pwm->chip->ops->owner);
835 out:
836 	mutex_unlock(&pwm_lock);
837 }
838 EXPORT_SYMBOL_GPL(pwm_put);
839 
840 static void devm_pwm_release(struct device *dev, void *res)
841 {
842 	pwm_put(*(struct pwm_device **)res);
843 }
844 
845 /**
846  * devm_pwm_get() - resource managed pwm_get()
847  * @dev: device for PWM consumer
848  * @con_id: consumer name
849  *
850  * This function performs like pwm_get() but the acquired PWM device will
851  * automatically be released on driver detach.
852  *
853  * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
854  * error code on failure.
855  */
856 struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id)
857 {
858 	struct pwm_device **ptr, *pwm;
859 
860 	ptr = devres_alloc(devm_pwm_release, sizeof(*ptr), GFP_KERNEL);
861 	if (!ptr)
862 		return ERR_PTR(-ENOMEM);
863 
864 	pwm = pwm_get(dev, con_id);
865 	if (!IS_ERR(pwm)) {
866 		*ptr = pwm;
867 		devres_add(dev, ptr);
868 	} else {
869 		devres_free(ptr);
870 	}
871 
872 	return pwm;
873 }
874 EXPORT_SYMBOL_GPL(devm_pwm_get);
875 
876 /**
877  * devm_of_pwm_get() - resource managed of_pwm_get()
878  * @dev: device for PWM consumer
879  * @np: device node to get the PWM from
880  * @con_id: consumer name
881  *
882  * This function performs like of_pwm_get() but the acquired PWM device will
883  * automatically be released on driver detach.
884  *
885  * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
886  * error code on failure.
887  */
888 struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
889 				   const char *con_id)
890 {
891 	struct pwm_device **ptr, *pwm;
892 
893 	ptr = devres_alloc(devm_pwm_release, sizeof(*ptr), GFP_KERNEL);
894 	if (!ptr)
895 		return ERR_PTR(-ENOMEM);
896 
897 	pwm = of_pwm_get(np, con_id);
898 	if (!IS_ERR(pwm)) {
899 		*ptr = pwm;
900 		devres_add(dev, ptr);
901 	} else {
902 		devres_free(ptr);
903 	}
904 
905 	return pwm;
906 }
907 EXPORT_SYMBOL_GPL(devm_of_pwm_get);
908 
909 static int devm_pwm_match(struct device *dev, void *res, void *data)
910 {
911 	struct pwm_device **p = res;
912 
913 	if (WARN_ON(!p || !*p))
914 		return 0;
915 
916 	return *p == data;
917 }
918 
919 /**
920  * devm_pwm_put() - resource managed pwm_put()
921  * @dev: device for PWM consumer
922  * @pwm: PWM device
923  *
924  * Release a PWM previously allocated using devm_pwm_get(). Calling this
925  * function is usually not needed because devm-allocated resources are
926  * automatically released on driver detach.
927  */
928 void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
929 {
930 	WARN_ON(devres_release(dev, devm_pwm_release, devm_pwm_match, pwm));
931 }
932 EXPORT_SYMBOL_GPL(devm_pwm_put);
933 
934 /**
935   * pwm_can_sleep() - report whether PWM access will sleep
936   * @pwm: PWM device
937   *
938   * Returns: True if accessing the PWM can sleep, false otherwise.
939   */
940 bool pwm_can_sleep(struct pwm_device *pwm)
941 {
942 	return true;
943 }
944 EXPORT_SYMBOL_GPL(pwm_can_sleep);
945 
946 #ifdef CONFIG_DEBUG_FS
947 static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
948 {
949 	unsigned int i;
950 
951 	for (i = 0; i < chip->npwm; i++) {
952 		struct pwm_device *pwm = &chip->pwms[i];
953 		struct pwm_state state;
954 
955 		pwm_get_state(pwm, &state);
956 
957 		seq_printf(s, " pwm-%-3d (%-20.20s):", i, pwm->label);
958 
959 		if (test_bit(PWMF_REQUESTED, &pwm->flags))
960 			seq_puts(s, " requested");
961 
962 		if (state.enabled)
963 			seq_puts(s, " enabled");
964 
965 		seq_printf(s, " period: %u ns", state.period);
966 		seq_printf(s, " duty: %u ns", state.duty_cycle);
967 		seq_printf(s, " polarity: %s",
968 			   state.polarity ? "inverse" : "normal");
969 
970 		seq_puts(s, "\n");
971 	}
972 }
973 
974 static void *pwm_seq_start(struct seq_file *s, loff_t *pos)
975 {
976 	mutex_lock(&pwm_lock);
977 	s->private = "";
978 
979 	return seq_list_start(&pwm_chips, *pos);
980 }
981 
982 static void *pwm_seq_next(struct seq_file *s, void *v, loff_t *pos)
983 {
984 	s->private = "\n";
985 
986 	return seq_list_next(v, &pwm_chips, pos);
987 }
988 
989 static void pwm_seq_stop(struct seq_file *s, void *v)
990 {
991 	mutex_unlock(&pwm_lock);
992 }
993 
994 static int pwm_seq_show(struct seq_file *s, void *v)
995 {
996 	struct pwm_chip *chip = list_entry(v, struct pwm_chip, list);
997 
998 	seq_printf(s, "%s%s/%s, %d PWM device%s\n", (char *)s->private,
999 		   chip->dev->bus ? chip->dev->bus->name : "no-bus",
1000 		   dev_name(chip->dev), chip->npwm,
1001 		   (chip->npwm != 1) ? "s" : "");
1002 
1003 	if (chip->ops->dbg_show)
1004 		chip->ops->dbg_show(chip, s);
1005 	else
1006 		pwm_dbg_show(chip, s);
1007 
1008 	return 0;
1009 }
1010 
1011 static const struct seq_operations pwm_seq_ops = {
1012 	.start = pwm_seq_start,
1013 	.next = pwm_seq_next,
1014 	.stop = pwm_seq_stop,
1015 	.show = pwm_seq_show,
1016 };
1017 
1018 static int pwm_seq_open(struct inode *inode, struct file *file)
1019 {
1020 	return seq_open(file, &pwm_seq_ops);
1021 }
1022 
1023 static const struct file_operations pwm_debugfs_ops = {
1024 	.owner = THIS_MODULE,
1025 	.open = pwm_seq_open,
1026 	.read = seq_read,
1027 	.llseek = seq_lseek,
1028 	.release = seq_release,
1029 };
1030 
1031 static int __init pwm_debugfs_init(void)
1032 {
1033 	debugfs_create_file("pwm", S_IFREG | S_IRUGO, NULL, NULL,
1034 			    &pwm_debugfs_ops);
1035 
1036 	return 0;
1037 }
1038 subsys_initcall(pwm_debugfs_init);
1039 #endif /* CONFIG_DEBUG_FS */
1040