1/*
2 * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
3 *
4 * Based on code by Randy Vinson <rvinson@mvista.com>,
5 * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
6 *
7 * Copyright (C) 2014 Rose Technology
8 * Copyright (C) 2006-2007 Freescale Semiconductor
9 *
10 * 2005 (c) MontaVista Software, Inc. This file is licensed under
11 * the terms of the GNU General Public License version 2. This program
12 * is licensed "as is" without any warranty of any kind, whether express
13 * or implied.
14 */
15/*
16 * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
17 * recommended in .../Documentation/i2c/writing-clients.rst section
18 * "Sending and receiving", using SMBus level communication is preferred.
19 */
20
21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23#include <linux/kernel.h>
24#include <linux/module.h>
25#include <linux/interrupt.h>
26#include <linux/i2c.h>
27#include <linux/rtc.h>
28#include <linux/bcd.h>
29#include <linux/workqueue.h>
30#include <linux/slab.h>
31#include <linux/pm.h>
32#ifdef CONFIG_RTC_DRV_DS1374_WDT
33#include <linux/fs.h>
34#include <linux/ioctl.h>
35#include <linux/miscdevice.h>
36#include <linux/reboot.h>
37#include <linux/watchdog.h>
38#endif
39
40#define DS1374_REG_TOD0		0x00 /* Time of Day */
41#define DS1374_REG_TOD1		0x01
42#define DS1374_REG_TOD2		0x02
43#define DS1374_REG_TOD3		0x03
44#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
45#define DS1374_REG_WDALM1	0x05
46#define DS1374_REG_WDALM2	0x06
47#define DS1374_REG_CR		0x07 /* Control */
48#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
49#define DS1374_REG_CR_WDSTR	0x08 /* 1=INT, 0=RST */
50#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
51#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
52#define DS1374_REG_SR		0x08 /* Status */
53#define DS1374_REG_SR_OSF	0x80 /* Oscillator Stop Flag */
54#define DS1374_REG_SR_AF	0x01 /* Alarm Flag */
55#define DS1374_REG_TCR		0x09 /* Trickle Charge */
56
57static const struct i2c_device_id ds1374_id[] = {
58	{ "ds1374", 0 },
59	{ }
60};
61MODULE_DEVICE_TABLE(i2c, ds1374_id);
62
63#ifdef CONFIG_OF
64static const struct of_device_id ds1374_of_match[] = {
65	{ .compatible = "dallas,ds1374" },
66	{ }
67};
68MODULE_DEVICE_TABLE(of, ds1374_of_match);
69#endif
70
71struct ds1374 {
72	struct i2c_client *client;
73	struct rtc_device *rtc;
74	struct work_struct work;
75#ifdef CONFIG_RTC_DRV_DS1374_WDT
76	struct watchdog_device wdt;
77#endif
78	/* The mutex protects alarm operations, and prevents a race
79	 * between the enable_irq() in the workqueue and the free_irq()
80	 * in the remove function.
81	 */
82	struct mutex mutex;
83	int exiting;
84};
85
86static struct i2c_driver ds1374_driver;
87
88static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
89			   int reg, int nbytes)
90{
91	u8 buf[4];
92	int ret;
93	int i;
94
95	if (WARN_ON(nbytes > 4))
96		return -EINVAL;
97
98	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
99
100	if (ret < 0)
101		return ret;
102	if (ret < nbytes)
103		return -EIO;
104
105	for (i = nbytes - 1, *time = 0; i >= 0; i--)
106		*time = (*time << 8) | buf[i];
107
108	return 0;
109}
110
111static int ds1374_write_rtc(struct i2c_client *client, u32 time,
112			    int reg, int nbytes)
113{
114	u8 buf[4];
115	int i;
116
117	if (nbytes > 4) {
118		WARN_ON(1);
119		return -EINVAL;
120	}
121
122	for (i = 0; i < nbytes; i++) {
123		buf[i] = time & 0xff;
124		time >>= 8;
125	}
126
127	return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
128}
129
130static int ds1374_check_rtc_status(struct i2c_client *client)
131{
132	int ret = 0;
133	int control, stat;
134
135	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
136	if (stat < 0)
137		return stat;
138
139	if (stat & DS1374_REG_SR_OSF)
140		dev_warn(&client->dev,
141			 "oscillator discontinuity flagged, time unreliable\n");
142
143	stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
144
145	ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
146	if (ret < 0)
147		return ret;
148
149	/* If the alarm is pending, clear it before requesting
150	 * the interrupt, so an interrupt event isn't reported
151	 * before everything is initialized.
152	 */
153
154	control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
155	if (control < 0)
156		return control;
157
158	control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
159	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
160}
161
162static int ds1374_read_time(struct device *dev, struct rtc_time *time)
163{
164	struct i2c_client *client = to_i2c_client(dev);
165	u32 itime;
166	int ret;
167
168	ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
169	if (!ret)
170		rtc_time64_to_tm(itime, time);
171
172	return ret;
173}
174
175static int ds1374_set_time(struct device *dev, struct rtc_time *time)
176{
177	struct i2c_client *client = to_i2c_client(dev);
178	unsigned long itime = rtc_tm_to_time64(time);
179
180	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
181}
182
183#ifndef CONFIG_RTC_DRV_DS1374_WDT
184/* The ds1374 has a decrementer for an alarm, rather than a comparator.
185 * If the time of day is changed, then the alarm will need to be
186 * reset.
187 */
188static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
189{
190	struct i2c_client *client = to_i2c_client(dev);
191	struct ds1374 *ds1374 = i2c_get_clientdata(client);
192	u32 now, cur_alarm;
193	int cr, sr;
194	int ret = 0;
195
196	if (client->irq <= 0)
197		return -EINVAL;
198
199	mutex_lock(&ds1374->mutex);
200
201	cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
202	if (ret < 0)
203		goto out;
204
205	sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
206	if (ret < 0)
207		goto out;
208
209	ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
210	if (ret)
211		goto out;
212
213	ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
214	if (ret)
215		goto out;
216
217	rtc_time64_to_tm(now + cur_alarm, &alarm->time);
218	alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
219	alarm->pending = !!(sr & DS1374_REG_SR_AF);
220
221out:
222	mutex_unlock(&ds1374->mutex);
223	return ret;
224}
225
226static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
227{
228	struct i2c_client *client = to_i2c_client(dev);
229	struct ds1374 *ds1374 = i2c_get_clientdata(client);
230	struct rtc_time now;
231	unsigned long new_alarm, itime;
232	int cr;
233	int ret = 0;
234
235	if (client->irq <= 0)
236		return -EINVAL;
237
238	ret = ds1374_read_time(dev, &now);
239	if (ret < 0)
240		return ret;
241
242	new_alarm = rtc_tm_to_time64(&alarm->time);
243	itime = rtc_tm_to_time64(&now);
244
245	/* This can happen due to races, in addition to dates that are
246	 * truly in the past.  To avoid requiring the caller to check for
247	 * races, dates in the past are assumed to be in the recent past
248	 * (i.e. not something that we'd rather the caller know about via
249	 * an error), and the alarm is set to go off as soon as possible.
250	 */
251	if (time_before_eq(new_alarm, itime))
252		new_alarm = 1;
253	else
254		new_alarm -= itime;
255
256	mutex_lock(&ds1374->mutex);
257
258	ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
259	if (ret < 0)
260		goto out;
261
262	/* Disable any existing alarm before setting the new one
263	 * (or lack thereof). */
264	cr &= ~DS1374_REG_CR_WACE;
265
266	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
267	if (ret < 0)
268		goto out;
269
270	ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
271	if (ret)
272		goto out;
273
274	if (alarm->enabled) {
275		cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
276		cr &= ~DS1374_REG_CR_WDALM;
277
278		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
279	}
280
281out:
282	mutex_unlock(&ds1374->mutex);
283	return ret;
284}
285#endif
286
287static irqreturn_t ds1374_irq(int irq, void *dev_id)
288{
289	struct i2c_client *client = dev_id;
290	struct ds1374 *ds1374 = i2c_get_clientdata(client);
291
292	disable_irq_nosync(irq);
293	schedule_work(&ds1374->work);
294	return IRQ_HANDLED;
295}
296
297static void ds1374_work(struct work_struct *work)
298{
299	struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
300	struct i2c_client *client = ds1374->client;
301	int stat, control;
302
303	mutex_lock(&ds1374->mutex);
304
305	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
306	if (stat < 0)
307		goto unlock;
308
309	if (stat & DS1374_REG_SR_AF) {
310		stat &= ~DS1374_REG_SR_AF;
311		i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
312
313		control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
314		if (control < 0)
315			goto out;
316
317		control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
318		i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
319
320		rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
321	}
322
323out:
324	if (!ds1374->exiting)
325		enable_irq(client->irq);
326unlock:
327	mutex_unlock(&ds1374->mutex);
328}
329
330#ifndef CONFIG_RTC_DRV_DS1374_WDT
331static int ds1374_alarm_irq_enable(struct device *dev, unsigned int enabled)
332{
333	struct i2c_client *client = to_i2c_client(dev);
334	struct ds1374 *ds1374 = i2c_get_clientdata(client);
335	int ret;
336
337	mutex_lock(&ds1374->mutex);
338
339	ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
340	if (ret < 0)
341		goto out;
342
343	if (enabled) {
344		ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
345		ret &= ~DS1374_REG_CR_WDALM;
346	} else {
347		ret &= ~DS1374_REG_CR_WACE;
348	}
349	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
350
351out:
352	mutex_unlock(&ds1374->mutex);
353	return ret;
354}
355#endif
356
357static const struct rtc_class_ops ds1374_rtc_ops = {
358	.read_time = ds1374_read_time,
359	.set_time = ds1374_set_time,
360#ifndef CONFIG_RTC_DRV_DS1374_WDT
361	.read_alarm = ds1374_read_alarm,
362	.set_alarm = ds1374_set_alarm,
363	.alarm_irq_enable = ds1374_alarm_irq_enable,
364#endif
365};
366
367#ifdef CONFIG_RTC_DRV_DS1374_WDT
368/*
369 *****************************************************************************
370 *
371 * Watchdog Driver
372 *
373 *****************************************************************************
374 */
375/* Default margin */
376#define TIMER_MARGIN_DEFAULT	32
377#define TIMER_MARGIN_MIN	1
378#define TIMER_MARGIN_MAX	4095 /* 24-bit value */
379
380static int wdt_margin;
381module_param(wdt_margin, int, 0);
382MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 32s)");
383
384static bool nowayout = WATCHDOG_NOWAYOUT;
385module_param(nowayout, bool, 0);
386MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default ="
387		__MODULE_STRING(WATCHDOG_NOWAYOUT)")");
388
389static const struct watchdog_info ds1374_wdt_info = {
390	.identity       = "DS1374 Watchdog",
391	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
392						WDIOF_MAGICCLOSE,
393};
394
395static int ds1374_wdt_settimeout(struct watchdog_device *wdt, unsigned int timeout)
396{
397	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
398	struct i2c_client *client = ds1374->client;
399	int ret, cr;
400
401	wdt->timeout = timeout;
402
403	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
404	if (cr < 0)
405		return cr;
406
407	/* Disable any existing watchdog/alarm before setting the new one */
408	cr &= ~DS1374_REG_CR_WACE;
409
410	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
411	if (ret < 0)
412		return ret;
413
414	/* Set new watchdog time */
415	timeout = timeout * 4096;
416	ret = ds1374_write_rtc(client, timeout, DS1374_REG_WDALM0, 3);
417	if (ret)
418		return ret;
419
420	/* Enable watchdog timer */
421	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
422	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
423	cr &= ~DS1374_REG_CR_AIE;
424
425	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
426	if (ret < 0)
427		return ret;
428
429	return 0;
430}
431
432/*
433 * Reload the watchdog timer.  (ie, pat the watchdog)
434 */
435static int ds1374_wdt_start(struct watchdog_device *wdt)
436{
437	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
438	u32 val;
439
440	return ds1374_read_rtc(ds1374->client, &val, DS1374_REG_WDALM0, 3);
441}
442
443static int ds1374_wdt_stop(struct watchdog_device *wdt)
444{
445	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
446	struct i2c_client *client = ds1374->client;
447	int cr;
448
449	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
450	if (cr < 0)
451		return cr;
452
453	/* Disable watchdog timer */
454	cr &= ~DS1374_REG_CR_WACE;
455
456	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
457}
458
459static const struct watchdog_ops ds1374_wdt_ops = {
460	.owner          = THIS_MODULE,
461	.start          = ds1374_wdt_start,
462	.stop           = ds1374_wdt_stop,
463	.set_timeout    = ds1374_wdt_settimeout,
464};
465#endif /*CONFIG_RTC_DRV_DS1374_WDT*/
466/*
467 *****************************************************************************
468 *
469 *	Driver Interface
470 *
471 *****************************************************************************
472 */
473static int ds1374_probe(struct i2c_client *client,
474			const struct i2c_device_id *id)
475{
476	struct ds1374 *ds1374;
477	int ret;
478
479	ds1374 = devm_kzalloc(&client->dev, sizeof(struct ds1374), GFP_KERNEL);
480	if (!ds1374)
481		return -ENOMEM;
482
483	ds1374->rtc = devm_rtc_allocate_device(&client->dev);
484	if (IS_ERR(ds1374->rtc))
485		return PTR_ERR(ds1374->rtc);
486
487	ds1374->client = client;
488	i2c_set_clientdata(client, ds1374);
489
490	INIT_WORK(&ds1374->work, ds1374_work);
491	mutex_init(&ds1374->mutex);
492
493	ret = ds1374_check_rtc_status(client);
494	if (ret)
495		return ret;
496
497	if (client->irq > 0) {
498		ret = devm_request_irq(&client->dev, client->irq, ds1374_irq, 0,
499					"ds1374", client);
500		if (ret) {
501			dev_err(&client->dev, "unable to request IRQ\n");
502			return ret;
503		}
504
505		device_set_wakeup_capable(&client->dev, 1);
506	}
507
508	ds1374->rtc->ops = &ds1374_rtc_ops;
509	ds1374->rtc->range_max = U32_MAX;
510
511	ret = rtc_register_device(ds1374->rtc);
512	if (ret)
513		return ret;
514
515#ifdef CONFIG_RTC_DRV_DS1374_WDT
516	ds1374->wdt.info = &ds1374_wdt_info;
517	ds1374->wdt.ops = &ds1374_wdt_ops;
518	ds1374->wdt.timeout = TIMER_MARGIN_DEFAULT;
519	ds1374->wdt.min_timeout = TIMER_MARGIN_MIN;
520	ds1374->wdt.max_timeout = TIMER_MARGIN_MAX;
521
522	watchdog_init_timeout(&ds1374->wdt, wdt_margin, &client->dev);
523	watchdog_set_nowayout(&ds1374->wdt, nowayout);
524	watchdog_stop_on_reboot(&ds1374->wdt);
525	watchdog_stop_on_unregister(&ds1374->wdt);
526	watchdog_set_drvdata(&ds1374->wdt, ds1374);
527	ds1374_wdt_settimeout(&ds1374->wdt, ds1374->wdt.timeout);
528
529	ret = devm_watchdog_register_device(&client->dev, &ds1374->wdt);
530	if (ret)
531		return ret;
532#endif
533
534	return 0;
535}
536
537static int ds1374_remove(struct i2c_client *client)
538{
539	struct ds1374 *ds1374 = i2c_get_clientdata(client);
540
541	if (client->irq > 0) {
542		mutex_lock(&ds1374->mutex);
543		ds1374->exiting = 1;
544		mutex_unlock(&ds1374->mutex);
545
546		devm_free_irq(&client->dev, client->irq, client);
547		cancel_work_sync(&ds1374->work);
548	}
549
550	return 0;
551}
552
553#ifdef CONFIG_PM_SLEEP
554static int ds1374_suspend(struct device *dev)
555{
556	struct i2c_client *client = to_i2c_client(dev);
557
558	if (client->irq > 0 && device_may_wakeup(&client->dev))
559		enable_irq_wake(client->irq);
560	return 0;
561}
562
563static int ds1374_resume(struct device *dev)
564{
565	struct i2c_client *client = to_i2c_client(dev);
566
567	if (client->irq > 0 && device_may_wakeup(&client->dev))
568		disable_irq_wake(client->irq);
569	return 0;
570}
571#endif
572
573static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);
574
575static struct i2c_driver ds1374_driver = {
576	.driver = {
577		.name = "rtc-ds1374",
578		.of_match_table = of_match_ptr(ds1374_of_match),
579		.pm = &ds1374_pm,
580	},
581	.probe = ds1374_probe,
582	.remove = ds1374_remove,
583	.id_table = ds1374_id,
584};
585
586module_i2c_driver(ds1374_driver);
587
588MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
589MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
590MODULE_LICENSE("GPL");
591