Free Electrons

Embedded Linux Experts

  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
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
#ifndef __LINUX_PWM_H
#define __LINUX_PWM_H

#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/of.h>

struct pwm_capture;
struct seq_file;

struct pwm_chip;

/**
 * enum pwm_polarity - polarity of a PWM signal
 * @PWM_POLARITY_NORMAL: a high signal for the duration of the duty-
 * cycle, followed by a low signal for the remainder of the pulse
 * period
 * @PWM_POLARITY_INVERSED: a low signal for the duration of the duty-
 * cycle, followed by a high signal for the remainder of the pulse
 * period
 */
enum pwm_polarity {
	PWM_POLARITY_NORMAL,
	PWM_POLARITY_INVERSED,
};

/**
 * struct pwm_args - board-dependent PWM arguments
 * @period: reference period
 * @polarity: reference polarity
 *
 * This structure describes board-dependent arguments attached to a PWM
 * device. These arguments are usually retrieved from the PWM lookup table or
 * device tree.
 *
 * Do not confuse this with the PWM state: PWM arguments represent the initial
 * configuration that users want to use on this PWM device rather than the
 * current PWM hardware state.
 */
struct pwm_args {
	unsigned int period;
	enum pwm_polarity polarity;
};

enum {
	PWMF_REQUESTED = 1 << 0,
	PWMF_EXPORTED = 1 << 1,
};

/*
 * struct pwm_state - state of a PWM channel
 * @period: PWM period (in nanoseconds)
 * @duty_cycle: PWM duty cycle (in nanoseconds)
 * @polarity: PWM polarity
 * @enabled: PWM enabled status
 */
struct pwm_state {
	unsigned int period;
	unsigned int duty_cycle;
	enum pwm_polarity polarity;
	bool enabled;
};

/**
 * struct pwm_device - PWM channel object
 * @label: name of the PWM device
 * @flags: flags associated with the PWM device
 * @hwpwm: per-chip relative index of the PWM device
 * @pwm: global index of the PWM device
 * @chip: PWM chip providing this PWM device
 * @chip_data: chip-private data associated with the PWM device
 * @args: PWM arguments
 * @state: curent PWM channel state
 */
struct pwm_device {
	const char *label;
	unsigned long flags;
	unsigned int hwpwm;
	unsigned int pwm;
	struct pwm_chip *chip;
	void *chip_data;

	struct pwm_args args;
	struct pwm_state state;
};

/**
 * pwm_get_state() - retrieve the current PWM state
 * @pwm: PWM device
 * @state: state to fill with the current PWM state
 */
static inline void pwm_get_state(const struct pwm_device *pwm,
				 struct pwm_state *state)
{
	*state = pwm->state;
}

static inline bool pwm_is_enabled(const struct pwm_device *pwm)
{
	struct pwm_state state;

	pwm_get_state(pwm, &state);

	return state.enabled;
}

static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
{
	if (pwm)
		pwm->state.period = period;
}

static inline unsigned int pwm_get_period(const struct pwm_device *pwm)
{
	struct pwm_state state;

	pwm_get_state(pwm, &state);

	return state.period;
}

static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
{
	if (pwm)
		pwm->state.duty_cycle = duty;
}

static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
{
	struct pwm_state state;

	pwm_get_state(pwm, &state);

	return state.duty_cycle;
}

static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
{
	struct pwm_state state;

	pwm_get_state(pwm, &state);

	return state.polarity;
}

static inline void pwm_get_args(const struct pwm_device *pwm,
				struct pwm_args *args)
{
	*args = pwm->args;
}

/**
 * pwm_init_state() - prepare a new state to be applied with pwm_apply_state()
 * @pwm: PWM device
 * @state: state to fill with the prepared PWM state
 *
 * This functions prepares a state that can later be tweaked and applied
 * to the PWM device with pwm_apply_state(). This is a convenient function
 * that first retrieves the current PWM state and the replaces the period
 * and polarity fields with the reference values defined in pwm->args.
 * Once the function returns, you can adjust the ->enabled and ->duty_cycle
 * fields according to your needs before calling pwm_apply_state().
 *
 * ->duty_cycle is initially set to zero to avoid cases where the current
 * ->duty_cycle value exceed the pwm_args->period one, which would trigger
 * an error if the user calls pwm_apply_state() without adjusting ->duty_cycle
 * first.
 */
static inline void pwm_init_state(const struct pwm_device *pwm,
				  struct pwm_state *state)
{
	struct pwm_args args;

	/* First get the current state. */
	pwm_get_state(pwm, state);

	/* Then fill it with the reference config */
	pwm_get_args(pwm, &args);

	state->period = args.period;
	state->polarity = args.polarity;
	state->duty_cycle = 0;
}

/**
 * pwm_get_relative_duty_cycle() - Get a relative duty cycle value
 * @state: PWM state to extract the duty cycle from
 * @scale: target scale of the relative duty cycle
 *
 * This functions converts the absolute duty cycle stored in @state (expressed
 * in nanosecond) into a value relative to the period.
 *
 * For example if you want to get the duty_cycle expressed in percent, call:
 *
 * pwm_get_state(pwm, &state);
 * duty = pwm_get_relative_duty_cycle(&state, 100);
 */
static inline unsigned int
pwm_get_relative_duty_cycle(const struct pwm_state *state, unsigned int scale)
{
	if (!state->period)
		return 0;

	return DIV_ROUND_CLOSEST_ULL((u64)state->duty_cycle * scale,
				     state->period);
}

/**
 * pwm_set_relative_duty_cycle() - Set a relative duty cycle value
 * @state: PWM state to fill
 * @duty_cycle: relative duty cycle value
 * @scale: scale in which @duty_cycle is expressed
 *
 * This functions converts a relative into an absolute duty cycle (expressed
 * in nanoseconds), and puts the result in state->duty_cycle.
 *
 * For example if you want to configure a 50% duty cycle, call:
 *
 * pwm_init_state(pwm, &state);
 * pwm_set_relative_duty_cycle(&state, 50, 100);
 * pwm_apply_state(pwm, &state);
 *
 * This functions returns -EINVAL if @duty_cycle and/or @scale are
 * inconsistent (@scale == 0 or @duty_cycle > @scale).
 */
static inline int
pwm_set_relative_duty_cycle(struct pwm_state *state, unsigned int duty_cycle,
			    unsigned int scale)
{
	if (!scale || duty_cycle > scale)
		return -EINVAL;

	state->duty_cycle = DIV_ROUND_CLOSEST_ULL((u64)duty_cycle *
						  state->period,
						  scale);

	return 0;
}

/**
 * struct pwm_ops - PWM controller operations
 * @request: optional hook for requesting a PWM
 * @free: optional hook for freeing a PWM
 * @config: configure duty cycles and period length for this PWM
 * @set_polarity: configure the polarity of this PWM
 * @capture: capture and report PWM signal
 * @enable: enable PWM output toggling
 * @disable: disable PWM output toggling
 * @apply: atomically apply a new PWM config. The state argument
 *	   should be adjusted with the real hardware config (if the
 *	   approximate the period or duty_cycle value, state should
 *	   reflect it)
 * @get_state: get the current PWM state. This function is only
 *	       called once per PWM device when the PWM chip is
 *	       registered.
 * @dbg_show: optional routine to show contents in debugfs
 * @owner: helps prevent removal of modules exporting active PWMs
 */
struct pwm_ops {
	int (*request)(struct pwm_chip *chip, struct pwm_device *pwm);
	void (*free)(struct pwm_chip *chip, struct pwm_device *pwm);
	int (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
		      int duty_ns, int period_ns);
	int (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm,
			    enum pwm_polarity polarity);
	int (*capture)(struct pwm_chip *chip, struct pwm_device *pwm,
		       struct pwm_capture *result, unsigned long timeout);
	int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
	void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
	int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
		     struct pwm_state *state);
	void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
			  struct pwm_state *state);
#ifdef CONFIG_DEBUG_FS
	void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
#endif
	struct module *owner;
};

/**
 * struct pwm_chip - abstract a PWM controller
 * @dev: device providing the PWMs
 * @list: list node for internal use
 * @ops: callbacks for this PWM controller
 * @base: number of first PWM controlled by this chip
 * @npwm: number of PWMs controlled by this chip
 * @pwms: array of PWM devices allocated by the framework
 * @of_xlate: request a PWM device given a device tree PWM specifier
 * @of_pwm_n_cells: number of cells expected in the device tree PWM specifier
 */
struct pwm_chip {
	struct device *dev;
	struct list_head list;
	const struct pwm_ops *ops;
	int base;
	unsigned int npwm;

	struct pwm_device *pwms;

	struct pwm_device * (*of_xlate)(struct pwm_chip *pc,
					const struct of_phandle_args *args);
	unsigned int of_pwm_n_cells;
};

/**
 * struct pwm_capture - PWM capture data
 * @period: period of the PWM signal (in nanoseconds)
 * @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
 */
struct pwm_capture {
	unsigned int period;
	unsigned int duty_cycle;
};

#if IS_ENABLED(CONFIG_PWM)
/* PWM user APIs */
struct pwm_device *pwm_request(int pwm_id, const char *label);
void pwm_free(struct pwm_device *pwm);
int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
int pwm_adjust_config(struct pwm_device *pwm);

/**
 * pwm_config() - change a PWM device configuration
 * @pwm: PWM device
 * @duty_ns: "on" time (in nanoseconds)
 * @period_ns: duration (in nanoseconds) of one cycle
 *
 * Returns: 0 on success or a negative error code on failure.
 */
static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
			     int period_ns)
{
	struct pwm_state state;

	if (!pwm)
		return -EINVAL;

	if (duty_ns < 0 || period_ns < 0)
		return -EINVAL;

	pwm_get_state(pwm, &state);
	if (state.duty_cycle == duty_ns && state.period == period_ns)
		return 0;

	state.duty_cycle = duty_ns;
	state.period = period_ns;
	return pwm_apply_state(pwm, &state);
}

/**
 * pwm_set_polarity() - configure the polarity of a PWM signal
 * @pwm: PWM device
 * @polarity: new polarity of the PWM signal
 *
 * Note that the polarity cannot be configured while the PWM device is
 * enabled.
 *
 * Returns: 0 on success or a negative error code on failure.
 */
static inline int pwm_set_polarity(struct pwm_device *pwm,
				   enum pwm_polarity polarity)
{
	struct pwm_state state;

	if (!pwm)
		return -EINVAL;

	pwm_get_state(pwm, &state);
	if (state.polarity == polarity)
		return 0;

	/*
	 * Changing the polarity of a running PWM without adjusting the
	 * dutycycle/period value is a bit risky (can introduce glitches).
	 * Return -EBUSY in this case.
	 * Note that this is allowed when using pwm_apply_state() because
	 * the user specifies all the parameters.
	 */
	if (state.enabled)
		return -EBUSY;

	state.polarity = polarity;
	return pwm_apply_state(pwm, &state);
}

/**
 * pwm_enable() - start a PWM output toggling
 * @pwm: PWM device
 *
 * Returns: 0 on success or a negative error code on failure.
 */
static inline int pwm_enable(struct pwm_device *pwm)
{
	struct pwm_state state;

	if (!pwm)
		return -EINVAL;

	pwm_get_state(pwm, &state);
	if (state.enabled)
		return 0;

	state.enabled = true;
	return pwm_apply_state(pwm, &state);
}

/**
 * pwm_disable() - stop a PWM output toggling
 * @pwm: PWM device
 */
static inline void pwm_disable(struct pwm_device *pwm)
{
	struct pwm_state state;

	if (!pwm)
		return;

	pwm_get_state(pwm, &state);
	if (!state.enabled)
		return;

	state.enabled = false;
	pwm_apply_state(pwm, &state);
}

/* PWM provider APIs */
int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
		unsigned long timeout);
int pwm_set_chip_data(struct pwm_device *pwm, void *data);
void *pwm_get_chip_data(struct pwm_device *pwm);

int pwmchip_add_with_polarity(struct pwm_chip *chip,
			      enum pwm_polarity polarity);
int pwmchip_add(struct pwm_chip *chip);
int pwmchip_remove(struct pwm_chip *chip);
struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
					 unsigned int index,
					 const char *label);

struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
		const struct of_phandle_args *args);

struct pwm_device *pwm_get(struct device *dev, const char *con_id);
struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id);
void pwm_put(struct pwm_device *pwm);

struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);
struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
				   const char *con_id);
void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
#else
static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
{
	return ERR_PTR(-ENODEV);
}

static inline void pwm_free(struct pwm_device *pwm)
{
}

static inline int pwm_apply_state(struct pwm_device *pwm,
				  const struct pwm_state *state)
{
	return -ENOTSUPP;
}

static inline int pwm_adjust_config(struct pwm_device *pwm)
{
	return -ENOTSUPP;
}

static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
			     int period_ns)
{
	return -EINVAL;
}

static inline int pwm_capture(struct pwm_device *pwm,
			      struct pwm_capture *result,
			      unsigned long timeout)
{
	return -EINVAL;
}

static inline int pwm_set_polarity(struct pwm_device *pwm,
				   enum pwm_polarity polarity)
{
	return -ENOTSUPP;
}

static inline int pwm_enable(struct pwm_device *pwm)
{
	return -EINVAL;
}

static inline void pwm_disable(struct pwm_device *pwm)
{
}

static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data)
{
	return -EINVAL;
}

static inline void *pwm_get_chip_data(struct pwm_device *pwm)
{
	return NULL;
}

static inline int pwmchip_add(struct pwm_chip *chip)
{
	return -EINVAL;
}

static inline int pwmchip_add_inversed(struct pwm_chip *chip)
{
	return -EINVAL;
}

static inline int pwmchip_remove(struct pwm_chip *chip)
{
	return -EINVAL;
}

static inline struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
						       unsigned int index,
						       const char *label)
{
	return ERR_PTR(-ENODEV);
}

static inline struct pwm_device *pwm_get(struct device *dev,
					 const char *consumer)
{
	return ERR_PTR(-ENODEV);
}

static inline struct pwm_device *of_pwm_get(struct device_node *np,
					    const char *con_id)
{
	return ERR_PTR(-ENODEV);
}

static inline void pwm_put(struct pwm_device *pwm)
{
}

static inline struct pwm_device *devm_pwm_get(struct device *dev,
					      const char *consumer)
{
	return ERR_PTR(-ENODEV);
}

static inline struct pwm_device *devm_of_pwm_get(struct device *dev,
						 struct device_node *np,
						 const char *con_id)
{
	return ERR_PTR(-ENODEV);
}

static inline void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
{
}
#endif

static inline void pwm_apply_args(struct pwm_device *pwm)
{
	struct pwm_state state = { };

	/*
	 * PWM users calling pwm_apply_args() expect to have a fresh config
	 * where the polarity and period are set according to pwm_args info.
	 * The problem is, polarity can only be changed when the PWM is
	 * disabled.
	 *
	 * PWM drivers supporting hardware readout may declare the PWM device
	 * as enabled, and prevent polarity setting, which changes from the
	 * existing behavior, where all PWM devices are declared as disabled
	 * at startup (even if they are actually enabled), thus authorizing
	 * polarity setting.
	 *
	 * To fulfill this requirement, we apply a new state which disables
	 * the PWM device and set the reference period and polarity config.
	 *
	 * Note that PWM users requiring a smooth handover between the
	 * bootloader and the kernel (like critical regulators controlled by
	 * PWM devices) will have to switch to the atomic API and avoid calling
	 * pwm_apply_args().
	 */

	state.enabled = false;
	state.polarity = pwm->args.polarity;
	state.period = pwm->args.period;

	pwm_apply_state(pwm, &state);
}

struct pwm_lookup {
	struct list_head list;
	const char *provider;
	unsigned int index;
	const char *dev_id;
	const char *con_id;
	unsigned int period;
	enum pwm_polarity polarity;
	const char *module; /* optional, may be NULL */
};

#define PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id,	\
			       _period, _polarity, _module)		\
	{								\
		.provider = _provider,					\
		.index = _index,					\
		.dev_id = _dev_id,					\
		.con_id = _con_id,					\
		.period = _period,					\
		.polarity = _polarity,					\
		.module = _module,					\
	}

#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
	PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id, _period, \
			       _polarity, NULL)

#if IS_ENABLED(CONFIG_PWM)
void pwm_add_table(struct pwm_lookup *table, size_t num);
void pwm_remove_table(struct pwm_lookup *table, size_t num);
#else
static inline void pwm_add_table(struct pwm_lookup *table, size_t num)
{
}

static inline void pwm_remove_table(struct pwm_lookup *table, size_t num)
{
}
#endif

#ifdef CONFIG_PWM_SYSFS
void pwmchip_sysfs_export(struct pwm_chip *chip);
void pwmchip_sysfs_unexport(struct pwm_chip *chip);
void pwmchip_sysfs_unexport_children(struct pwm_chip *chip);
#else
static inline void pwmchip_sysfs_export(struct pwm_chip *chip)
{
}

static inline void pwmchip_sysfs_unexport(struct pwm_chip *chip)
{
}

static inline void pwmchip_sysfs_unexport_children(struct pwm_chip *chip)
{
}
#endif /* CONFIG_PWM_SYSFS */

#endif /* __LINUX_PWM_H */