summaryrefslogtreecommitdiffstats
path: root/drivers/gpio/gpiolib.c
blob: 2ba6127c4fae5f2c7dcc8af3b39d021cc7a25c95 (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
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
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/irq.h>
#include <linux/spinlock.h>

#include <asm/gpio.h>


/* Optional implementation infrastructure for GPIO interfaces.
 *
 * Platforms may want to use this if they tend to use very many GPIOs
 * that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
 *
 * When kernel footprint or instruction count is an issue, simpler
 * implementations may be preferred.  The GPIO programming interface
 * allows for inlining speed-critical get/set operations for common
 * cases, so that access to SOC-integrated GPIOs can sometimes cost
 * only an instruction or two per bit.
 */


/* When debugging, extend minimal trust to callers and platform code.
 * Also emit diagnostic messages that may help initial bringup, when
 * board setup or driver bugs are most common.
 *
 * Otherwise, minimize overhead in what may be bitbanging codepaths.
 */
#ifdef	DEBUG
#define	extra_checks	1
#else
#define	extra_checks	0
#endif

/* gpio_lock prevents conflicts during gpio_desc[] table updates.
 * While any GPIO is requested, its gpio_chip is not removable;
 * each GPIO's "requested" flag serves as a lock and refcount.
 */
static DEFINE_SPINLOCK(gpio_lock);

struct gpio_desc {
	struct gpio_chip	*chip;
	unsigned long		flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED	0
#define FLAG_IS_OUT	1

#ifdef CONFIG_DEBUG_FS
	const char		*label;
#endif
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];

static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
	d->label = label;
#endif
}

/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
 * when setting direction, and otherwise illegal.  Until board setup code
 * and drivers use explicit requests everywhere (which won't happen when
 * those calls have no teeth) we can't avoid autorequesting.  This nag
 * message should motivate switching to explicit requests...
 */
static void gpio_ensure_requested(struct gpio_desc *desc)
{
	if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
		pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
		desc_set_label(desc, "[auto]");
		if (!try_module_get(desc->chip->owner))
			pr_err("GPIO-%d: module can't be gotten \n",
					(int)(desc - gpio_desc));
	}
}

/* caller holds gpio_lock *OR* gpio is marked as requested */
static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
{
	return gpio_desc[gpio].chip;
}

/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
static int gpiochip_find_base(int ngpio)
{
	int i;
	int spare = 0;
	int base = -ENOSPC;

	for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
		struct gpio_chip *chip = gpio_desc[i].chip;

		if (!chip) {
			spare++;
			if (spare == ngpio) {
				base = i;
				break;
			}
		} else {
			spare = 0;
			i -= chip->ngpio - 1;
		}
	}

	if (gpio_is_valid(base))
		pr_debug("%s: found new base at %d\n", __func__, base);
	return base;
}

/**
 * gpiochip_add() - register a gpio_chip
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs or kmalloc will work
 *
 * Returns a negative errno if the chip can't be registered, such as
 * because the chip->base is invalid or already associated with a
 * different chip.  Otherwise it returns zero as a success code.
 *
 * If chip->base is negative, this requests dynamic assignment of
 * a range of valid GPIOs.
 */
int gpiochip_add(struct gpio_chip *chip)
{
	unsigned long	flags;
	int		status = 0;
	unsigned	id;
	int		base = chip->base;

	if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio))
			&& base >= 0) {
		status = -EINVAL;
		goto fail;
	}

	spin_lock_irqsave(&gpio_lock, flags);

	if (base < 0) {
		base = gpiochip_find_base(chip->ngpio);
		if (base < 0) {
			status = base;
			goto fail_unlock;
		}
		chip->base = base;
	}

	/* these GPIO numbers must not be managed by another gpio_chip */
	for (id = base; id < base + chip->ngpio; id++) {
		if (gpio_desc[id].chip != NULL) {
			status = -EBUSY;
			break;
		}
	}
	if (status == 0) {
		for (id = base; id < base + chip->ngpio; id++) {
			gpio_desc[id].chip = chip;
			gpio_desc[id].flags = 0;
		}
	}

fail_unlock:
	spin_unlock_irqrestore(&gpio_lock, flags);
fail:
	/* failures here can mean systems won't boot... */
	if (status)
		pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
			chip->base, chip->base + chip->ngpio,
			chip->label ? : "generic");
	return status;
}
EXPORT_SYMBOL_GPL(gpiochip_add);

/**
 * gpiochip_remove() - unregister a gpio_chip
 * @chip: the chip to unregister
 *
 * A gpio_chip with any GPIOs still requested may not be removed.
 */
int gpiochip_remove(struct gpio_chip *chip)
{
	unsigned long	flags;
	int		status = 0;
	unsigned	id;

	spin_lock_irqsave(&gpio_lock, flags);

	for (id = chip->base; id < chip->base + chip->ngpio; id++) {
		if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
			status = -EBUSY;
			break;
		}
	}
	if (status == 0) {
		for (id = chip->base; id < chip->base + chip->ngpio; id++)
			gpio_desc[id].chip = NULL;
	}

	spin_unlock_irqrestore(&gpio_lock, flags);
	return status;
}
EXPORT_SYMBOL_GPL(gpiochip_remove);


/* These "optional" allocation calls help prevent drivers from stomping
 * on each other, and help provide better diagnostics in debugfs.
 * They're called even less than the "set direction" calls.
 */
int gpio_request(unsigned gpio, const char *label)
{
	struct gpio_desc	*desc;
	int			status = -EINVAL;
	unsigned long		flags;

	spin_lock_irqsave(&gpio_lock, flags);

	if (!gpio_is_valid(gpio))
		goto done;
	desc = &gpio_desc[gpio];
	if (desc->chip == NULL)
		goto done;

	if (!try_module_get(desc->chip->owner))
		goto done;

	/* NOTE:  gpio_request() can be called in early boot,
	 * before IRQs are enabled.
	 */

	if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
		desc_set_label(desc, label ? : "?");
		status = 0;
	} else {
		status = -EBUSY;
		module_put(desc->chip->owner);
	}

done:
	if (status)
		pr_debug("gpio_request: gpio-%d (%s) status %d\n",
			gpio, label ? : "?", status);
	spin_unlock_irqrestore(&gpio_lock, flags);
	return status;
}
EXPORT_SYMBOL_GPL(gpio_request);

void gpio_free(unsigned gpio)
{
	unsigned long		flags;
	struct gpio_desc	*desc;

	if (!gpio_is_valid(gpio)) {
		WARN_ON(extra_checks);
		return;
	}

	spin_lock_irqsave(&gpio_lock, flags);

	desc = &gpio_desc[gpio];
	if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags)) {
		desc_set_label(desc, NULL);
		module_put(desc->chip->owner);
	} else
		WARN_ON(extra_checks);

	spin_unlock_irqrestore(&gpio_lock, flags);
}
EXPORT_SYMBOL_GPL(gpio_free);


/**
 * gpiochip_is_requested - return string iff signal was requested
 * @chip: controller managing the signal
 * @offset: of signal within controller's 0..(ngpio - 1) range
 *
 * Returns NULL if the GPIO is not currently requested, else a string.
 * If debugfs support is enabled, the string returned is the label passed
 * to gpio_request(); otherwise it is a meaningless constant.
 *
 * This function is for use by GPIO controller drivers.  The label can
 * help with diagnostics, and knowing that the signal is used as a GPIO
 * can help avoid accidentally multiplexing it to another controller.
 */
const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
{
	unsigned gpio = chip->base + offset;

	if (!gpio_is_valid(gpio) || gpio_desc[gpio].chip != chip)
		return NULL;
	if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
		return NULL;
#ifdef CONFIG_DEBUG_FS
	return gpio_desc[gpio].label;
#else
	return "?";
#endif
}
EXPORT_SYMBOL_GPL(gpiochip_is_requested);


/* Drivers MUST set GPIO direction before making get/set calls.  In
 * some cases this is done in early boot, before IRQs are enabled.
 *
 * As a rule these aren't called more than once (except for drivers
 * using the open-drain emulation idiom) so these are natural places
 * to accumulate extra debugging checks.  Note that we can't (yet)
 * rely on gpio_request() having been called beforehand.
 */

int gpio_direction_input(unsigned gpio)
{
	unsigned long		flags;
	struct gpio_chip	*chip;
	struct gpio_desc	*desc = &gpio_desc[gpio];
	int			status = -EINVAL;

	spin_lock_irqsave(&gpio_lock, flags);

	if (!gpio_is_valid(gpio))
		goto fail;
	chip = desc->chip;
	if (!chip || !chip->get || !chip->direction_input)
		goto fail;
	gpio -= chip->base;
	if (gpio >= chip->ngpio)
		goto fail;
	gpio_ensure_requested(desc);

	/* now we know the gpio is valid and chip won't vanish */

	spin_unlock_irqrestore(&gpio_lock, flags);

	might_sleep_if(extra_checks && chip->can_sleep);

	status = chip->direction_input(chip, gpio);
	if (status == 0)
		clear_bit(FLAG_IS_OUT, &desc->flags);
	return status;
fail:
	spin_unlock_irqrestore(&gpio_lock, flags);
	if (status)
		pr_debug("%s: gpio-%d status %d\n",
			__FUNCTION__, gpio, status);
	return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_input);

int gpio_direction_output(unsigned gpio, int value)
{
	unsigned long		flags;
	struct gpio_chip	*chip;
	struct gpio_desc	*desc = &gpio_desc[gpio];
	int			status = -EINVAL;

	spin_lock_irqsave(&gpio_lock, flags);

	if (!gpio_is_valid(gpio))
		goto fail;
	chip = desc->chip;
	if (!chip || !chip->set || !chip->direction_output)
		goto fail;
	gpio -= chip->base;
	if (gpio >= chip->ngpio)
		goto fail;
	gpio_ensure_requested(desc);

	/* now we know the gpio is valid and chip won't vanish */

	spin_unlock_irqrestore(&gpio_lock, flags);

	might_sleep_if(extra_checks && chip->can_sleep);

	status = chip->direction_output(chip, gpio, value);
	if (status == 0)
		set_bit(FLAG_IS_OUT, &desc->flags);
	return status;
fail:
	spin_unlock_irqrestore(&gpio_lock, flags);
	if (status)
		pr_debug("%s: gpio-%d status %d\n",
			__FUNCTION__, gpio, status);
	return status;
}
EXPORT_SYMBOL_GPL(gpio_direction_output);


/* I/O calls are only valid after configuration completed; the relevant
 * "is this a valid GPIO" error checks should already have been done.
 *
 * "Get" operations are often inlinable as reading a pin value register,
 * and masking the relevant bit in that register.
 *
 * When "set" operations are inlinable, they involve writing that mask to
 * one register to set a low value, or a different register to set it high.
 * Otherwise locking is needed, so there may be little value to inlining.
 *
 *------------------------------------------------------------------------
 *
 * IMPORTANT!!!  The hot paths -- get/set value -- assume that callers
 * have requested the GPIO.  That can include implicit requesting by
 * a direction setting call.  Marking a gpio as requested locks its chip
 * in memory, guaranteeing that these table lookups need no more locking
 * and that gpiochip_remove() will fail.
 *
 * REVISIT when debugging, consider adding some instrumentation to ensure
 * that the GPIO was actually requested.
 */

/**
 * __gpio_get_value() - return a gpio's value
 * @gpio: gpio whose value will be returned
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_get_value().
 * It returns the zero or nonzero value provided by the associated
 * gpio_chip.get() method; or zero if no such method is provided.
 */
int __gpio_get_value(unsigned gpio)
{
	struct gpio_chip	*chip;

	chip = gpio_to_chip(gpio);
	WARN_ON(extra_checks && chip->can_sleep);
	return chip->get ? chip->get(chip, gpio - chip->base) : 0;
}
EXPORT_SYMBOL_GPL(__gpio_get_value);

/**
 * __gpio_set_value() - assign a gpio's value
 * @gpio: gpio whose value will be assigned
 * @value: value to assign
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_set_value().
 * It invokes the associated gpio_chip.set() method.
 */
void __gpio_set_value(unsigned gpio, int value)
{
	struct gpio_chip	*chip;

	chip = gpio_to_chip(gpio);
	WARN_ON(extra_checks && chip->can_sleep);
	chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(__gpio_set_value);

/**
 * __gpio_cansleep() - report whether gpio value access will sleep
 * @gpio: gpio in question
 * Context: any
 *
 * This is used directly or indirectly to implement gpio_cansleep().  It
 * returns nonzero if access reading or writing the GPIO value can sleep.
 */
int __gpio_cansleep(unsigned gpio)
{
	struct gpio_chip	*chip;

	/* only call this on GPIOs that are valid! */
	chip = gpio_to_chip(gpio);

	return chip->can_sleep;
}
EXPORT_SYMBOL_GPL(__gpio_cansleep);



/* There's no value in making it easy to inline GPIO calls that may sleep.
 * Common examples include ones connected to I2C or SPI chips.
 */

int gpio_get_value_cansleep(unsigned gpio)
{
	struct gpio_chip	*chip;

	might_sleep_if(extra_checks);
	chip = gpio_to_chip(gpio);
	return chip->get(chip, gpio - chip->base);
}
EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);

void gpio_set_value_cansleep(unsigned gpio, int value)
{
	struct gpio_chip	*chip;

	might_sleep_if(extra_checks);
	chip = gpio_to_chip(gpio);
	chip->set(chip, gpio - chip->base, value);
}
EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);


#ifdef CONFIG_DEBUG_FS

#include <linux/debugfs.h>
#include <linux/seq_file.h>


static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
	unsigned		i;
	unsigned		gpio = chip->base;
	struct gpio_desc	*gdesc = &gpio_desc[gpio];
	int			is_out;

	for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
		if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
			continue;

		is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
		seq_printf(s, " gpio-%-3d (%-12s) %s %s",
			gpio, gdesc->label,
			is_out ? "out" : "in ",
			chip->get
				? (chip->get(chip, i) ? "hi" : "lo")
				: "?  ");

		if (!is_out) {
			int		irq = gpio_to_irq(gpio);
			struct irq_desc	*desc = irq_desc + irq;

			/* This races with request_irq(), set_irq_type(),
			 * and set_irq_wake() ... but those are "rare".
			 *
			 * More significantly, trigger type flags aren't
			 * currently maintained by genirq.
			 */
			if (irq >= 0 && desc->action) {
				char *trigger;

				switch (desc->status & IRQ_TYPE_SENSE_MASK) {
				case IRQ_TYPE_NONE:
					trigger = "(default)";
					break;
				case IRQ_TYPE_EDGE_FALLING:
					trigger = "edge-falling";
					break;
				case IRQ_TYPE_EDGE_RISING:
					trigger = "edge-rising";
					break;
				case IRQ_TYPE_EDGE_BOTH:
					trigger = "edge-both";
					break;
				case IRQ_TYPE_LEVEL_HIGH:
					trigger = "level-high";
					break;
				case IRQ_TYPE_LEVEL_LOW:
					trigger = "level-low";
					break;
				default:
					trigger = "?trigger?";
					break;
				}

				seq_printf(s, " irq-%d %s%s",
					irq, trigger,
					(desc->status & IRQ_WAKEUP)
						? " wakeup" : "");
			}
		}

		seq_printf(s, "\n");
	}
}

static int gpiolib_show(struct seq_file *s, void *unused)
{
	struct gpio_chip	*chip = NULL;
	unsigned		gpio;
	int			started = 0;

	/* REVISIT this isn't locked against gpio_chip removal ... */

	for (gpio = 0; gpio_is_valid(gpio); gpio++) {
		if (chip == gpio_desc[gpio].chip)
			continue;
		chip = gpio_desc[gpio].chip;
		if (!chip)
			continue;

		seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
				started ? "\n" : "",
				chip->base, chip->base + chip->ngpio - 1,
				chip->label ? : "generic",
				chip->can_sleep ? ", can sleep" : "");
		started = 1;
		if (chip->dbg_show)
			chip->dbg_show(s, chip);
		else
			gpiolib_dbg_show(s, chip);
	}
	return 0;
}

static int gpiolib_open(struct inode *inode, struct file *file)
{
	return single_open(file, gpiolib_show, NULL);
}

static struct file_operations gpiolib_operations = {
	.open		= gpiolib_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init gpiolib_debugfs_init(void)
{
	/* /sys/kernel/debug/gpio */
	(void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
				NULL, NULL, &gpiolib_operations);
	return 0;
}
subsys_initcall(gpiolib_debugfs_init);

#endif	/* DEBUG_FS */
OpenPOWER on IntegriCloud