1 #include <linux/kernel.h>
2 #include <linux/module.h>
3 #include <linux/irq.h>
4 #include <linux/spinlock.h>
5
6 #include <asm/gpio.h>
7
8
9 /* Optional implementation infrastructure for GPIO interfaces.
10 *
11 * Platforms may want to use this if they tend to use very many GPIOs
12 * that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
13 *
14 * When kernel footprint or instruction count is an issue, simpler
15 * implementations may be preferred. The GPIO programming interface
16 * allows for inlining speed-critical get/set operations for common
17 * cases, so that access to SOC-integrated GPIOs can sometimes cost
18 * only an instruction or two per bit.
19 */
20
21
22 /* When debugging, extend minimal trust to callers and platform code.
23 * Also emit diagnostic messages that may help initial bringup, when
24 * board setup or driver bugs are most common.
25 *
26 * Otherwise, minimize overhead in what may be bitbanging codepaths.
27 */
28 #ifdef DEBUG
29 #define extra_checks 1
30 #else
31 #define extra_checks 0
32 #endif
33
34 /* gpio_lock prevents conflicts during gpio_desc[] table updates.
35 * While any GPIO is requested, its gpio_chip is not removable;
36 * each GPIO's "requested" flag serves as a lock and refcount.
37 */
38 static DEFINE_SPINLOCK(gpio_lock);
39
40 struct gpio_desc {
41 struct gpio_chip *chip;
42 unsigned long flags;
43 /* flag symbols are bit numbers */
44 #define FLAG_REQUESTED 0
45 #define FLAG_IS_OUT 1
46
47 #ifdef CONFIG_DEBUG_FS
48 const char *label;
49 #endif
50 };
51 static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
52
53 static inline void desc_set_label(struct gpio_desc *d, const char *label)
54 {
55 #ifdef CONFIG_DEBUG_FS
56 d->label = label;
57 #endif
58 }
59
60 /* Warn when drivers omit gpio_request() calls -- legal but ill-advised
61 * when setting direction, and otherwise illegal. Until board setup code
62 * and drivers use explicit requests everywhere (which won't happen when
63 * those calls have no teeth) we can't avoid autorequesting. This nag
64 * message should motivate switching to explicit requests...
65 */
66 static void gpio_ensure_requested(struct gpio_desc *desc)
67 {
68 if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
69 pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
70 desc_set_label(desc, "[auto]");
71 }
72 }
73
74 /* caller holds gpio_lock *OR* gpio is marked as requested */
75 static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
76 {
77 return gpio_desc[gpio].chip;
78 }
79
80 /**
81 * gpiochip_add() - register a gpio_chip
82 * @chip: the chip to register, with chip->base initialized
83 * Context: potentially before irqs or kmalloc will work
84 *
85 * Returns a negative errno if the chip can't be registered, such as
86 * because the chip->base is invalid or already associated with a
87 * different chip. Otherwise it returns zero as a success code.
88 */
89 int gpiochip_add(struct gpio_chip *chip)
90 {
91 unsigned long flags;
92 int status = 0;
93 unsigned id;
94
95 /* NOTE chip->base negative is reserved to mean a request for
96 * dynamic allocation. We don't currently support that.
97 */
98
99 if (chip->base < 0 || (chip->base + chip->ngpio) >= ARCH_NR_GPIOS) {
100 status = -EINVAL;
101 goto fail;
102 }
103
104 spin_lock_irqsave(&gpio_lock, flags);
105
106 /* these GPIO numbers must not be managed by another gpio_chip */
107 for (id = chip->base; id < chip->base + chip->ngpio; id++) {
108 if (gpio_desc[id].chip != NULL) {
109 status = -EBUSY;
110 break;
111 }
112 }
113 if (status == 0) {
114 for (id = chip->base; id < chip->base + chip->ngpio; id++) {
115 gpio_desc[id].chip = chip;
116 gpio_desc[id].flags = 0;
117 }
118 }
119
120 spin_unlock_irqrestore(&gpio_lock, flags);
121 fail:
122 /* failures here can mean systems won't boot... */
123 if (status)
124 pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
125 chip->base, chip->base + chip->ngpio,
126 chip->label ? : "generic");
127 return status;
128 }
129 EXPORT_SYMBOL_GPL(gpiochip_add);
130
131 /**
132 * gpiochip_remove() - unregister a gpio_chip
133 * @chip: the chip to unregister
134 *
135 * A gpio_chip with any GPIOs still requested may not be removed.
136 */
137 int gpiochip_remove(struct gpio_chip *chip)
138 {
139 unsigned long flags;
140 int status = 0;
141 unsigned id;
142
143 spin_lock_irqsave(&gpio_lock, flags);
144
145 for (id = chip->base; id < chip->base + chip->ngpio; id++) {
146 if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
147 status = -EBUSY;
148 break;
149 }
150 }
151 if (status == 0) {
152 for (id = chip->base; id < chip->base + chip->ngpio; id++)
153 gpio_desc[id].chip = NULL;
154 }
155
156 spin_unlock_irqrestore(&gpio_lock, flags);
157 return status;
158 }
159 EXPORT_SYMBOL_GPL(gpiochip_remove);
160
161
162 /* These "optional" allocation calls help prevent drivers from stomping
163 * on each other, and help provide better diagnostics in debugfs.
164 * They're called even less than the "set direction" calls.
165 */
166 int gpio_request(unsigned gpio, const char *label)
167 {
168 struct gpio_desc *desc;
169 int status = -EINVAL;
170 unsigned long flags;
171
172 spin_lock_irqsave(&gpio_lock, flags);
173
174 if (gpio >= ARCH_NR_GPIOS)
175 goto done;
176 desc = &gpio_desc[gpio];
177 if (desc->chip == NULL)
178 goto done;
179
180 /* NOTE: gpio_request() can be called in early boot,
181 * before IRQs are enabled.
182 */
183
184 if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
185 desc_set_label(desc, label ? : "?");
186 status = 0;
187 } else
188 status = -EBUSY;
189
190 done:
191 if (status)
192 pr_debug("gpio_request: gpio-%d (%s) status %d\n",
193 gpio, label ? : "?", status);
194 spin_unlock_irqrestore(&gpio_lock, flags);
195 return status;
196 }
197 EXPORT_SYMBOL_GPL(gpio_request);
198
199 void gpio_free(unsigned gpio)
200 {
201 unsigned long flags;
202 struct gpio_desc *desc;
203
204 if (gpio >= ARCH_NR_GPIOS) {
205 WARN_ON(extra_checks);
206 return;
207 }
208
209 spin_lock_irqsave(&gpio_lock, flags);
210
211 desc = &gpio_desc[gpio];
212 if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags))
213 desc_set_label(desc, NULL);
214 else
215 WARN_ON(extra_checks);
216
217 spin_unlock_irqrestore(&gpio_lock, flags);
218 }
219 EXPORT_SYMBOL_GPL(gpio_free);
220
221
222 /**
223 * gpiochip_is_requested - return string iff signal was requested
224 * @chip: controller managing the signal
225 * @offset: of signal within controller's 0..(ngpio - 1) range
226 *
227 * Returns NULL if the GPIO is not currently requested, else a string.
228 * If debugfs support is enabled, the string returned is the label passed
229 * to gpio_request(); otherwise it is a meaningless constant.
230 *
231 * This function is for use by GPIO controller drivers. The label can
232 * help with diagnostics, and knowing that the signal is used as a GPIO
233 * can help avoid accidentally multiplexing it to another controller.
234 */
235 const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
236 {
237 unsigned gpio = chip->base + offset;
238
239 if (gpio >= ARCH_NR_GPIOS || gpio_desc[gpio].chip != chip)
240 return NULL;
241 if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
242 return NULL;
243 #ifdef CONFIG_DEBUG_FS
244 return gpio_desc[gpio].label;
245 #else
246 return "?";
247 #endif
248 }
249 EXPORT_SYMBOL_GPL(gpiochip_is_requested);
250
251
252 /* Drivers MUST set GPIO direction before making get/set calls. In
253 * some cases this is done in early boot, before IRQs are enabled.
254 *
255 * As a rule these aren't called more than once (except for drivers
256 * using the open-drain emulation idiom) so these are natural places
257 * to accumulate extra debugging checks. Note that we can't (yet)
258 * rely on gpio_request() having been called beforehand.
259 */
260
261 int gpio_direction_input(unsigned gpio)
262 {
263 unsigned long flags;
264 struct gpio_chip *chip;
265 struct gpio_desc *desc = &gpio_desc[gpio];
266 int status = -EINVAL;
267
268 spin_lock_irqsave(&gpio_lock, flags);
269
270 if (gpio >= ARCH_NR_GPIOS)
271 goto fail;
272 chip = desc->chip;
273 if (!chip || !chip->get || !chip->direction_input)
274 goto fail;
275 gpio -= chip->base;
276 if (gpio >= chip->ngpio)
277 goto fail;
278 gpio_ensure_requested(desc);
279
280 /* now we know the gpio is valid and chip won't vanish */
281
282 spin_unlock_irqrestore(&gpio_lock, flags);
283
284 might_sleep_if(extra_checks && chip->can_sleep);
285
286 status = chip->direction_input(chip, gpio);
287 if (status == 0)
288 clear_bit(FLAG_IS_OUT, &desc->flags);
289 return status;
290 fail:
291 spin_unlock_irqrestore(&gpio_lock, flags);
292 if (status)
293 pr_debug("%s: gpio-%d status %d\n",
294 __FUNCTION__, gpio, status);
295 return status;
296 }
297 EXPORT_SYMBOL_GPL(gpio_direction_input);
298
299 int gpio_direction_output(unsigned gpio, int value)
300 {
301 unsigned long flags;
302 struct gpio_chip *chip;
303 struct gpio_desc *desc = &gpio_desc[gpio];
304 int status = -EINVAL;
305
306 spin_lock_irqsave(&gpio_lock, flags);
307
308 if (gpio >= ARCH_NR_GPIOS)
309 goto fail;
310 chip = desc->chip;
311 if (!chip || !chip->set || !chip->direction_output)
312 goto fail;
313 gpio -= chip->base;
314 if (gpio >= chip->ngpio)
315 goto fail;
316 gpio_ensure_requested(desc);
317
318 /* now we know the gpio is valid and chip won't vanish */
319
320 spin_unlock_irqrestore(&gpio_lock, flags);
321
322 might_sleep_if(extra_checks && chip->can_sleep);
323
324 status = chip->direction_output(chip, gpio, value);
325 if (status == 0)
326 set_bit(FLAG_IS_OUT, &desc->flags);
327 return status;
328 fail:
329 spin_unlock_irqrestore(&gpio_lock, flags);
330 if (status)
331 pr_debug("%s: gpio-%d status %d\n",
332 __FUNCTION__, gpio, status);
333 return status;
334 }
335 EXPORT_SYMBOL_GPL(gpio_direction_output);
336
337
338 /* I/O calls are only valid after configuration completed; the relevant
339 * "is this a valid GPIO" error checks should already have been done.
340 *
341 * "Get" operations are often inlinable as reading a pin value register,
342 * and masking the relevant bit in that register.
343 *
344 * When "set" operations are inlinable, they involve writing that mask to
345 * one register to set a low value, or a different register to set it high.
346 * Otherwise locking is needed, so there may be little value to inlining.
347 *
348 *------------------------------------------------------------------------
349 *
350 * IMPORTANT!!! The hot paths -- get/set value -- assume that callers
351 * have requested the GPIO. That can include implicit requesting by
352 * a direction setting call. Marking a gpio as requested locks its chip
353 * in memory, guaranteeing that these table lookups need no more locking
354 * and that gpiochip_remove() will fail.
355 *
356 * REVISIT when debugging, consider adding some instrumentation to ensure
357 * that the GPIO was actually requested.
358 */
359
360 /**
361 * __gpio_get_value() - return a gpio's value
362 * @gpio: gpio whose value will be returned
363 * Context: any
364 *
365 * This is used directly or indirectly to implement gpio_get_value().
366 * It returns the zero or nonzero value provided by the associated
367 * gpio_chip.get() method; or zero if no such method is provided.
368 */
369 int __gpio_get_value(unsigned gpio)
370 {
371 struct gpio_chip *chip;
372
373 chip = gpio_to_chip(gpio);
374 WARN_ON(extra_checks && chip->can_sleep);
375 return chip->get ? chip->get(chip, gpio - chip->base) : 0;
376 }
377 EXPORT_SYMBOL_GPL(__gpio_get_value);
378
379 /**
380 * __gpio_set_value() - assign a gpio's value
381 * @gpio: gpio whose value will be assigned
382 * @value: value to assign
383 * Context: any
384 *
385 * This is used directly or indirectly to implement gpio_set_value().
386 * It invokes the associated gpio_chip.set() method.
387 */
388 void __gpio_set_value(unsigned gpio, int value)
389 {
390 struct gpio_chip *chip;
391
392 chip = gpio_to_chip(gpio);
393 WARN_ON(extra_checks && chip->can_sleep);
394 chip->set(chip, gpio - chip->base, value);
395 }
396 EXPORT_SYMBOL_GPL(__gpio_set_value);
397
398 /**
399 * __gpio_cansleep() - report whether gpio value access will sleep
400 * @gpio: gpio in question
401 * Context: any
402 *
403 * This is used directly or indirectly to implement gpio_cansleep(). It
404 * returns nonzero if access reading or writing the GPIO value can sleep.
405 */
406 int __gpio_cansleep(unsigned gpio)
407 {
408 struct gpio_chip *chip;
409
410 /* only call this on GPIOs that are valid! */
411 chip = gpio_to_chip(gpio);
412
413 return chip->can_sleep;
414 }
415 EXPORT_SYMBOL_GPL(__gpio_cansleep);
416
417
418
419 /* There's no value in making it easy to inline GPIO calls that may sleep.
420 * Common examples include ones connected to I2C or SPI chips.
421 */
422
423 int gpio_get_value_cansleep(unsigned gpio)
424 {
425 struct gpio_chip *chip;
426
427 might_sleep_if(extra_checks);
428 chip = gpio_to_chip(gpio);
429 return chip->get(chip, gpio - chip->base);
430 }
431 EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);
432
433 void gpio_set_value_cansleep(unsigned gpio, int value)
434 {
435 struct gpio_chip *chip;
436
437 might_sleep_if(extra_checks);
438 chip = gpio_to_chip(gpio);
439 chip->set(chip, gpio - chip->base, value);
440 }
441 EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);
442
443
444 #ifdef CONFIG_DEBUG_FS
445
446 #include <linux/debugfs.h>
447 #include <linux/seq_file.h>
448
449
450 static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
451 {
452 unsigned i;
453 unsigned gpio = chip->base;
454 struct gpio_desc *gdesc = &gpio_desc[gpio];
455 int is_out;
456
457 for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
458 if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
459 continue;
460
461 is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
462 seq_printf(s, " gpio-%-3d (%-12s) %s %s",
463 gpio, gdesc->label,
464 is_out ? "out" : "in ",
465 chip->get
466 ? (chip->get(chip, i) ? "hi" : "lo")
467 : "? ");
468
469 if (!is_out) {
470 int irq = gpio_to_irq(gpio);
471 struct irq_desc *desc = irq_desc + irq;
472
473 /* This races with request_irq(), set_irq_type(),
474 * and set_irq_wake() ... but those are "rare".
475 *
476 * More significantly, trigger type flags aren't
477 * currently maintained by genirq.
478 */
479 if (irq >= 0 && desc->action) {
480 char *trigger;
481
482 switch (desc->status & IRQ_TYPE_SENSE_MASK) {
483 case IRQ_TYPE_NONE:
484 trigger = "(default)";
485 break;
486 case IRQ_TYPE_EDGE_FALLING:
487 trigger = "edge-falling";
488 break;
489 case IRQ_TYPE_EDGE_RISING:
490 trigger = "edge-rising";
491 break;
492 case IRQ_TYPE_EDGE_BOTH:
493 trigger = "edge-both";
494 break;
495 case IRQ_TYPE_LEVEL_HIGH:
496 trigger = "level-high";
497 break;
498 case IRQ_TYPE_LEVEL_LOW:
499 trigger = "level-low";
500 break;
501 default:
502 trigger = "?trigger?";
503 break;
504 }
505
506 seq_printf(s, " irq-%d %s%s",
507 irq, trigger,
508 (desc->status & IRQ_WAKEUP)
509 ? " wakeup" : "");
510 }
511 }
512
513 seq_printf(s, "\n");
514 }
515 }
516
517 static int gpiolib_show(struct seq_file *s, void *unused)
518 {
519 struct gpio_chip *chip = NULL;
520 unsigned gpio;
521 int started = 0;
522
523 /* REVISIT this isn't locked against gpio_chip removal ... */
524
525 for (gpio = 0; gpio < ARCH_NR_GPIOS; gpio++) {
526 if (chip == gpio_desc[gpio].chip)
527 continue;
528 chip = gpio_desc[gpio].chip;
529 if (!chip)
530 continue;
531
532 seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
533 started ? "\n" : "",
534 chip->base, chip->base + chip->ngpio - 1,
535 chip->label ? : "generic",
536 chip->can_sleep ? ", can sleep" : "");
537 started = 1;
538 if (chip->dbg_show)
539 chip->dbg_show(s, chip);
540 else
541 gpiolib_dbg_show(s, chip);
542 }
543 return 0;
544 }
545
546 static int gpiolib_open(struct inode *inode, struct file *file)
547 {
548 return single_open(file, gpiolib_show, NULL);
549 }
550
551 static struct file_operations gpiolib_operations = {
552 .open = gpiolib_open,
553 .read = seq_read,
554 .llseek = seq_lseek,
555 .release = single_release,
556 };
557
558 static int __init gpiolib_debugfs_init(void)
559 {
560 /* /sys/kernel/debug/gpio */
561 (void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
562 NULL, NULL, &gpiolib_operations);
563 return 0;
564 }
565 subsys_initcall(gpiolib_debugfs_init);
566
567 #endif /* DEBUG_FS */
568
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