1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
4 *
5 * Based on code by Randy Vinson <rvinson@mvista.com>,
6 * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
7 *
8 * Copyright (C) 2014 Rose Technology
9 * Copyright (C) 2006-2007 Freescale Semiconductor
10 * Copyright (c) 2005 MontaVista Software, Inc.
11 */
12/*
13 * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
14 * recommended in .../Documentation/i2c/writing-clients.rst section
15 * "Sending and receiving", using SMBus level communication is preferred.
16 */
17
18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/interrupt.h>
23#include <linux/i2c.h>
24#include <linux/rtc.h>
25#include <linux/bcd.h>
26#include <linux/workqueue.h>
27#include <linux/slab.h>
28#include <linux/pm.h>
29#ifdef CONFIG_RTC_DRV_DS1374_WDT
30#include <linux/fs.h>
31#include <linux/ioctl.h>
32#include <linux/miscdevice.h>
33#include <linux/reboot.h>
34#include <linux/watchdog.h>
35#endif
36
37#define DS1374_REG_TOD0		0x00 /* Time of Day */
38#define DS1374_REG_TOD1		0x01
39#define DS1374_REG_TOD2		0x02
40#define DS1374_REG_TOD3		0x03
41#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
42#define DS1374_REG_WDALM1	0x05
43#define DS1374_REG_WDALM2	0x06
44#define DS1374_REG_CR		0x07 /* Control */
45#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
46#define DS1374_REG_CR_WDSTR	0x08 /* 1=INT, 0=RST */
47#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
48#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
49#define DS1374_REG_SR		0x08 /* Status */
50#define DS1374_REG_SR_OSF	0x80 /* Oscillator Stop Flag */
51#define DS1374_REG_SR_AF	0x01 /* Alarm Flag */
52#define DS1374_REG_TCR		0x09 /* Trickle Charge */
53
54static const struct i2c_device_id ds1374_id[] = {
55	{ "ds1374", 0 },
56	{ }
57};
58MODULE_DEVICE_TABLE(i2c, ds1374_id);
59
60#ifdef CONFIG_OF
61static const struct of_device_id ds1374_of_match[] = {
62	{ .compatible = "dallas,ds1374" },
63	{ }
64};
65MODULE_DEVICE_TABLE(of, ds1374_of_match);
66#endif
67
68struct ds1374 {
69	struct i2c_client *client;
70	struct rtc_device *rtc;
71	struct work_struct work;
72#ifdef CONFIG_RTC_DRV_DS1374_WDT
73	struct watchdog_device wdt;
74#endif
75	/* The mutex protects alarm operations, and prevents a race
76	 * between the enable_irq() in the workqueue and the free_irq()
77	 * in the remove function.
78	 */
79	struct mutex mutex;
80	int exiting;
81};
82
83static struct i2c_driver ds1374_driver;
84
85static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
86			   int reg, int nbytes)
87{
88	u8 buf[4];
89	int ret;
90	int i;
91
92	if (WARN_ON(nbytes > 4))
93		return -EINVAL;
94
95	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
96
97	if (ret < 0)
98		return ret;
99	if (ret < nbytes)
100		return -EIO;
101
102	for (i = nbytes - 1, *time = 0; i >= 0; i--)
103		*time = (*time << 8) | buf[i];
104
105	return 0;
106}
107
108static int ds1374_write_rtc(struct i2c_client *client, u32 time,
109			    int reg, int nbytes)
110{
111	u8 buf[4];
112	int i;
113
114	if (nbytes > 4) {
115		WARN_ON(1);
116		return -EINVAL;
117	}
118
119	for (i = 0; i < nbytes; i++) {
120		buf[i] = time & 0xff;
121		time >>= 8;
122	}
123
124	return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
125}
126
127static int ds1374_check_rtc_status(struct i2c_client *client)
128{
129	int ret = 0;
130	int control, stat;
131
132	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
133	if (stat < 0)
134		return stat;
135
136	if (stat & DS1374_REG_SR_OSF)
137		dev_warn(&client->dev,
138			 "oscillator discontinuity flagged, time unreliable\n");
139
140	stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
141
142	ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
143	if (ret < 0)
144		return ret;
145
146	/* If the alarm is pending, clear it before requesting
147	 * the interrupt, so an interrupt event isn't reported
148	 * before everything is initialized.
149	 */
150
151	control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
152	if (control < 0)
153		return control;
154
155	control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
156	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
157}
158
159static int ds1374_read_time(struct device *dev, struct rtc_time *time)
160{
161	struct i2c_client *client = to_i2c_client(dev);
162	u32 itime;
163	int ret;
164
165	ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
166	if (!ret)
167		rtc_time64_to_tm(itime, time);
168
169	return ret;
170}
171
172static int ds1374_set_time(struct device *dev, struct rtc_time *time)
173{
174	struct i2c_client *client = to_i2c_client(dev);
175	unsigned long itime = rtc_tm_to_time64(time);
176
177	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
178}
179
180#ifndef CONFIG_RTC_DRV_DS1374_WDT
181/* The ds1374 has a decrementer for an alarm, rather than a comparator.
182 * If the time of day is changed, then the alarm will need to be
183 * reset.
184 */
185static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
186{
187	struct i2c_client *client = to_i2c_client(dev);
188	struct ds1374 *ds1374 = i2c_get_clientdata(client);
189	u32 now, cur_alarm;
190	int cr, sr;
191	int ret = 0;
192
193	if (client->irq <= 0)
194		return -EINVAL;
195
196	mutex_lock(&ds1374->mutex);
197
198	cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
199	if (ret < 0)
200		goto out;
201
202	sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
203	if (ret < 0)
204		goto out;
205
206	ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
207	if (ret)
208		goto out;
209
210	ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
211	if (ret)
212		goto out;
213
214	rtc_time64_to_tm(now + cur_alarm, &alarm->time);
215	alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
216	alarm->pending = !!(sr & DS1374_REG_SR_AF);
217
218out:
219	mutex_unlock(&ds1374->mutex);
220	return ret;
221}
222
223static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
224{
225	struct i2c_client *client = to_i2c_client(dev);
226	struct ds1374 *ds1374 = i2c_get_clientdata(client);
227	struct rtc_time now;
228	unsigned long new_alarm, itime;
229	int cr;
230	int ret = 0;
231
232	if (client->irq <= 0)
233		return -EINVAL;
234
235	ret = ds1374_read_time(dev, &now);
236	if (ret < 0)
237		return ret;
238
239	new_alarm = rtc_tm_to_time64(&alarm->time);
240	itime = rtc_tm_to_time64(&now);
241
242	/* This can happen due to races, in addition to dates that are
243	 * truly in the past.  To avoid requiring the caller to check for
244	 * races, dates in the past are assumed to be in the recent past
245	 * (i.e. not something that we'd rather the caller know about via
246	 * an error), and the alarm is set to go off as soon as possible.
247	 */
248	if (time_before_eq(new_alarm, itime))
249		new_alarm = 1;
250	else
251		new_alarm -= itime;
252
253	mutex_lock(&ds1374->mutex);
254
255	ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
256	if (ret < 0)
257		goto out;
258
259	/* Disable any existing alarm before setting the new one
260	 * (or lack thereof). */
261	cr &= ~DS1374_REG_CR_WACE;
262
263	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
264	if (ret < 0)
265		goto out;
266
267	ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
268	if (ret)
269		goto out;
270
271	if (alarm->enabled) {
272		cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
273		cr &= ~DS1374_REG_CR_WDALM;
274
275		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
276	}
277
278out:
279	mutex_unlock(&ds1374->mutex);
280	return ret;
281}
282#endif
283
284static irqreturn_t ds1374_irq(int irq, void *dev_id)
285{
286	struct i2c_client *client = dev_id;
287	struct ds1374 *ds1374 = i2c_get_clientdata(client);
288
289	disable_irq_nosync(irq);
290	schedule_work(&ds1374->work);
291	return IRQ_HANDLED;
292}
293
294static void ds1374_work(struct work_struct *work)
295{
296	struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
297	struct i2c_client *client = ds1374->client;
298	int stat, control;
299
300	mutex_lock(&ds1374->mutex);
301
302	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
303	if (stat < 0)
304		goto unlock;
305
306	if (stat & DS1374_REG_SR_AF) {
307		stat &= ~DS1374_REG_SR_AF;
308		i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
309
310		control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
311		if (control < 0)
312			goto out;
313
314		control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
315		i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
316
317		rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
318	}
319
320out:
321	if (!ds1374->exiting)
322		enable_irq(client->irq);
323unlock:
324	mutex_unlock(&ds1374->mutex);
325}
326
327#ifndef CONFIG_RTC_DRV_DS1374_WDT
328static int ds1374_alarm_irq_enable(struct device *dev, unsigned int enabled)
329{
330	struct i2c_client *client = to_i2c_client(dev);
331	struct ds1374 *ds1374 = i2c_get_clientdata(client);
332	int ret;
333
334	mutex_lock(&ds1374->mutex);
335
336	ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
337	if (ret < 0)
338		goto out;
339
340	if (enabled) {
341		ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
342		ret &= ~DS1374_REG_CR_WDALM;
343	} else {
344		ret &= ~DS1374_REG_CR_WACE;
345	}
346	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
347
348out:
349	mutex_unlock(&ds1374->mutex);
350	return ret;
351}
352#endif
353
354static const struct rtc_class_ops ds1374_rtc_ops = {
355	.read_time = ds1374_read_time,
356	.set_time = ds1374_set_time,
357#ifndef CONFIG_RTC_DRV_DS1374_WDT
358	.read_alarm = ds1374_read_alarm,
359	.set_alarm = ds1374_set_alarm,
360	.alarm_irq_enable = ds1374_alarm_irq_enable,
361#endif
362};
363
364#ifdef CONFIG_RTC_DRV_DS1374_WDT
365/*
366 *****************************************************************************
367 *
368 * Watchdog Driver
369 *
370 *****************************************************************************
371 */
372/* Default margin */
373#define TIMER_MARGIN_DEFAULT	32
374#define TIMER_MARGIN_MIN	1
375#define TIMER_MARGIN_MAX	4095 /* 24-bit value */
376
377static int wdt_margin;
378module_param(wdt_margin, int, 0);
379MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 32s)");
380
381static bool nowayout = WATCHDOG_NOWAYOUT;
382module_param(nowayout, bool, 0);
383MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default ="
384		__MODULE_STRING(WATCHDOG_NOWAYOUT)")");
385
386static const struct watchdog_info ds1374_wdt_info = {
387	.identity       = "DS1374 Watchdog",
388	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
389						WDIOF_MAGICCLOSE,
390};
391
392static int ds1374_wdt_settimeout(struct watchdog_device *wdt, unsigned int timeout)
393{
394	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
395	struct i2c_client *client = ds1374->client;
396	int ret, cr;
397
398	wdt->timeout = timeout;
399
400	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
401	if (cr < 0)
402		return cr;
403
404	/* Disable any existing watchdog/alarm before setting the new one */
405	cr &= ~DS1374_REG_CR_WACE;
406
407	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
408	if (ret < 0)
409		return ret;
410
411	/* Set new watchdog time */
412	timeout = timeout * 4096;
413	ret = ds1374_write_rtc(client, timeout, DS1374_REG_WDALM0, 3);
414	if (ret)
415		return ret;
416
417	/* Enable watchdog timer */
418	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
419	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
420	cr &= ~DS1374_REG_CR_AIE;
421
422	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
423	if (ret < 0)
424		return ret;
425
426	return 0;
427}
428
429/*
430 * Reload the watchdog timer.  (ie, pat the watchdog)
431 */
432static int ds1374_wdt_start(struct watchdog_device *wdt)
433{
434	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
435	u32 val;
436
437	return ds1374_read_rtc(ds1374->client, &val, DS1374_REG_WDALM0, 3);
438}
439
440static int ds1374_wdt_stop(struct watchdog_device *wdt)
441{
442	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
443	struct i2c_client *client = ds1374->client;
444	int cr;
445
446	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
447	if (cr < 0)
448		return cr;
449
450	/* Disable watchdog timer */
451	cr &= ~DS1374_REG_CR_WACE;
452
453	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
454}
455
456static const struct watchdog_ops ds1374_wdt_ops = {
457	.owner          = THIS_MODULE,
458	.start          = ds1374_wdt_start,
459	.stop           = ds1374_wdt_stop,
460	.set_timeout    = ds1374_wdt_settimeout,
461};
462#endif /*CONFIG_RTC_DRV_DS1374_WDT*/
463/*
464 *****************************************************************************
465 *
466 *	Driver Interface
467 *
468 *****************************************************************************
469 */
470static int ds1374_probe(struct i2c_client *client)
471{
472	struct ds1374 *ds1374;
473	int ret;
474
475	ds1374 = devm_kzalloc(&client->dev, sizeof(struct ds1374), GFP_KERNEL);
476	if (!ds1374)
477		return -ENOMEM;
478
479	ds1374->rtc = devm_rtc_allocate_device(&client->dev);
480	if (IS_ERR(ds1374->rtc))
481		return PTR_ERR(ds1374->rtc);
482
483	ds1374->client = client;
484	i2c_set_clientdata(client, ds1374);
485
486	INIT_WORK(&ds1374->work, ds1374_work);
487	mutex_init(&ds1374->mutex);
488
489	ret = ds1374_check_rtc_status(client);
490	if (ret)
491		return ret;
492
493	if (client->irq > 0) {
494		ret = devm_request_irq(&client->dev, client->irq, ds1374_irq, 0,
495					"ds1374", client);
496		if (ret) {
497			dev_err(&client->dev, "unable to request IRQ\n");
498			return ret;
499		}
500
501		device_set_wakeup_capable(&client->dev, 1);
502	}
503
504	ds1374->rtc->ops = &ds1374_rtc_ops;
505	ds1374->rtc->range_max = U32_MAX;
506
507	ret = devm_rtc_register_device(ds1374->rtc);
508	if (ret)
509		return ret;
510
511#ifdef CONFIG_RTC_DRV_DS1374_WDT
512	ds1374->wdt.info = &ds1374_wdt_info;
513	ds1374->wdt.ops = &ds1374_wdt_ops;
514	ds1374->wdt.timeout = TIMER_MARGIN_DEFAULT;
515	ds1374->wdt.min_timeout = TIMER_MARGIN_MIN;
516	ds1374->wdt.max_timeout = TIMER_MARGIN_MAX;
517
518	watchdog_init_timeout(&ds1374->wdt, wdt_margin, &client->dev);
519	watchdog_set_nowayout(&ds1374->wdt, nowayout);
520	watchdog_stop_on_reboot(&ds1374->wdt);
521	watchdog_stop_on_unregister(&ds1374->wdt);
522	watchdog_set_drvdata(&ds1374->wdt, ds1374);
523	ds1374_wdt_settimeout(&ds1374->wdt, ds1374->wdt.timeout);
524
525	ret = devm_watchdog_register_device(&client->dev, &ds1374->wdt);
526	if (ret)
527		return ret;
528#endif
529
530	return 0;
531}
532
533static void ds1374_remove(struct i2c_client *client)
534{
535	struct ds1374 *ds1374 = i2c_get_clientdata(client);
536
537	if (client->irq > 0) {
538		mutex_lock(&ds1374->mutex);
539		ds1374->exiting = 1;
540		mutex_unlock(&ds1374->mutex);
541
542		devm_free_irq(&client->dev, client->irq, client);
543		cancel_work_sync(&ds1374->work);
544	}
545}
546
547#ifdef CONFIG_PM_SLEEP
548static int ds1374_suspend(struct device *dev)
549{
550	struct i2c_client *client = to_i2c_client(dev);
551
552	if (client->irq > 0 && device_may_wakeup(&client->dev))
553		enable_irq_wake(client->irq);
554	return 0;
555}
556
557static int ds1374_resume(struct device *dev)
558{
559	struct i2c_client *client = to_i2c_client(dev);
560
561	if (client->irq > 0 && device_may_wakeup(&client->dev))
562		disable_irq_wake(client->irq);
563	return 0;
564}
565#endif
566
567static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);
568
569static struct i2c_driver ds1374_driver = {
570	.driver = {
571		.name = "rtc-ds1374",
572		.of_match_table = of_match_ptr(ds1374_of_match),
573		.pm = &ds1374_pm,
574	},
575	.probe = ds1374_probe,
576	.remove = ds1374_remove,
577	.id_table = ds1374_id,
578};
579
580module_i2c_driver(ds1374_driver);
581
582MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
583MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
584MODULE_LICENSE("GPL");
585