rtc-ds1374.c revision 9db8995be5e1869b5effa117909bc285e06fc09b 
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) 2006-2007 Freescale Semiconductor
8 *
9 * 2005 (c) MontaVista Software, Inc. This file is licensed under
10 * the terms of the GNU General Public License version 2. This program
11 * is licensed "as is" without any warranty of any kind, whether express
12 * or implied.
13 */
14/*
15 * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
16 * recommened in .../Documentation/i2c/writing-clients section
17 * "Sending and receiving", using SMBus level communication is preferred.
18 */
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
29#define DS1374_REG_TOD0		0x00 /* Time of Day */
30#define DS1374_REG_TOD1		0x01
31#define DS1374_REG_TOD2		0x02
32#define DS1374_REG_TOD3		0x03
33#define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
34#define DS1374_REG_WDALM1	0x05
35#define DS1374_REG_WDALM2	0x06
36#define DS1374_REG_CR		0x07 /* Control */
37#define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
38#define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
39#define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
40#define DS1374_REG_SR		0x08 /* Status */
41#define DS1374_REG_SR_OSF	0x80 /* Oscillator Stop Flag */
42#define DS1374_REG_SR_AF	0x01 /* Alarm Flag */
43#define DS1374_REG_TCR		0x09 /* Trickle Charge */
44
45static const struct i2c_device_id ds1374_id[] = {
46	{ "ds1374", 0 },
47	{ }
48};
49MODULE_DEVICE_TABLE(i2c, ds1374_id);
50
51struct ds1374 {
52	struct i2c_client *client;
53	struct rtc_device *rtc;
54	struct work_struct work;
55
56	/* The mutex protects alarm operations, and prevents a race
57	 * between the enable_irq() in the workqueue and the free_irq()
58	 * in the remove function.
59	 */
60	struct mutex mutex;
61	int exiting;
62};
63
64static struct i2c_driver ds1374_driver;
65
66static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
67                           int reg, int nbytes)
68{
69	u8 buf[4];
70	int ret;
71	int i;
72
73	if (nbytes > 4) {
74		WARN_ON(1);
75		return -EINVAL;
76	}
77
78	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
79
80	if (ret < 0)
81		return ret;
82	if (ret < nbytes)
83		return -EIO;
84
85	for (i = nbytes - 1, *time = 0; i >= 0; i--)
86		*time = (*time << 8) | buf[i];
87
88	return 0;
89}
90
91static int ds1374_write_rtc(struct i2c_client *client, u32 time,
92                            int reg, int nbytes)
93{
94	u8 buf[4];
95	int i;
96
97	if (nbytes > 4) {
98		WARN_ON(1);
99		return -EINVAL;
100	}
101
102	for (i = 0; i < nbytes; i++) {
103		buf[i] = time & 0xff;
104		time >>= 8;
105	}
106
107	return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
108}
109
110static int ds1374_check_rtc_status(struct i2c_client *client)
111{
112	int ret = 0;
113	int control, stat;
114
115	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
116	if (stat < 0)
117		return stat;
118
119	if (stat & DS1374_REG_SR_OSF)
120		dev_warn(&client->dev,
121		         "oscillator discontinuity flagged, "
122		         "time unreliable\n");
123
124	stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
125
126	ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
127	if (ret < 0)
128		return ret;
129
130	/* If the alarm is pending, clear it before requesting
131	 * the interrupt, so an interrupt event isn't reported
132	 * before everything is initialized.
133	 */
134
135	control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
136	if (control < 0)
137		return control;
138
139	control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
140	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
141}
142
143static int ds1374_read_time(struct device *dev, struct rtc_time *time)
144{
145	struct i2c_client *client = to_i2c_client(dev);
146	u32 itime;
147	int ret;
148
149	ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
150	if (!ret)
151		rtc_time_to_tm(itime, time);
152
153	return ret;
154}
155
156static int ds1374_set_time(struct device *dev, struct rtc_time *time)
157{
158	struct i2c_client *client = to_i2c_client(dev);
159	unsigned long itime;
160
161	rtc_tm_to_time(time, &itime);
162	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
163}
164
165/* The ds1374 has a decrementer for an alarm, rather than a comparator.
166 * If the time of day is changed, then the alarm will need to be
167 * reset.
168 */
169static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
170{
171	struct i2c_client *client = to_i2c_client(dev);
172	struct ds1374 *ds1374 = i2c_get_clientdata(client);
173	u32 now, cur_alarm;
174	int cr, sr;
175	int ret = 0;
176
177	if (client->irq <= 0)
178		return -EINVAL;
179
180	mutex_lock(&ds1374->mutex);
181
182	cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
183	if (ret < 0)
184		goto out;
185
186	sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
187	if (ret < 0)
188		goto out;
189
190	ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
191	if (ret)
192		goto out;
193
194	ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
195	if (ret)
196		goto out;
197
198	rtc_time_to_tm(now + cur_alarm, &alarm->time);
199	alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
200	alarm->pending = !!(sr & DS1374_REG_SR_AF);
201
202out:
203	mutex_unlock(&ds1374->mutex);
204	return ret;
205}
206
207static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
208{
209	struct i2c_client *client = to_i2c_client(dev);
210	struct ds1374 *ds1374 = i2c_get_clientdata(client);
211	struct rtc_time now;
212	unsigned long new_alarm, itime;
213	int cr;
214	int ret = 0;
215
216	if (client->irq <= 0)
217		return -EINVAL;
218
219	ret = ds1374_read_time(dev, &now);
220	if (ret < 0)
221		return ret;
222
223	rtc_tm_to_time(&alarm->time, &new_alarm);
224	rtc_tm_to_time(&now, &itime);
225
226	/* This can happen due to races, in addition to dates that are
227	 * truly in the past.  To avoid requiring the caller to check for
228	 * races, dates in the past are assumed to be in the recent past
229	 * (i.e. not something that we'd rather the caller know about via
230	 * an error), and the alarm is set to go off as soon as possible.
231	 */
232	if (time_before_eq(new_alarm, itime))
233		new_alarm = 1;
234	else
235		new_alarm -= itime;
236
237	mutex_lock(&ds1374->mutex);
238
239	ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
240	if (ret < 0)
241		goto out;
242
243	/* Disable any existing alarm before setting the new one
244	 * (or lack thereof). */
245	cr &= ~DS1374_REG_CR_WACE;
246
247	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
248	if (ret < 0)
249		goto out;
250
251	ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
252	if (ret)
253		goto out;
254
255	if (alarm->enabled) {
256		cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
257		cr &= ~DS1374_REG_CR_WDALM;
258
259		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
260	}
261
262out:
263	mutex_unlock(&ds1374->mutex);
264	return ret;
265}
266
267static irqreturn_t ds1374_irq(int irq, void *dev_id)
268{
269	struct i2c_client *client = dev_id;
270	struct ds1374 *ds1374 = i2c_get_clientdata(client);
271
272	disable_irq_nosync(irq);
273	schedule_work(&ds1374->work);
274	return IRQ_HANDLED;
275}
276
277static void ds1374_work(struct work_struct *work)
278{
279	struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
280	struct i2c_client *client = ds1374->client;
281	int stat, control;
282
283	mutex_lock(&ds1374->mutex);
284
285	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
286	if (stat < 0)
287		goto unlock;
288
289	if (stat & DS1374_REG_SR_AF) {
290		stat &= ~DS1374_REG_SR_AF;
291		i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
292
293		control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
294		if (control < 0)
295			goto out;
296
297		control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
298		i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
299
300		rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
301	}
302
303out:
304	if (!ds1374->exiting)
305		enable_irq(client->irq);
306unlock:
307	mutex_unlock(&ds1374->mutex);
308}
309
310static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
311{
312	struct i2c_client *client = to_i2c_client(dev);
313	struct ds1374 *ds1374 = i2c_get_clientdata(client);
314	int ret = -ENOIOCTLCMD;
315
316	mutex_lock(&ds1374->mutex);
317
318	switch (cmd) {
319	case RTC_AIE_OFF:
320		ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
321		if (ret < 0)
322			goto out;
323
324		ret &= ~DS1374_REG_CR_WACE;
325
326		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
327		if (ret < 0)
328			goto out;
329
330		break;
331
332	case RTC_AIE_ON:
333		ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
334		if (ret < 0)
335			goto out;
336
337		ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
338		ret &= ~DS1374_REG_CR_WDALM;
339
340		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
341		if (ret < 0)
342			goto out;
343
344		break;
345	}
346
347out:
348	mutex_unlock(&ds1374->mutex);
349	return ret;
350}
351
352static const struct rtc_class_ops ds1374_rtc_ops = {
353	.read_time = ds1374_read_time,
354	.set_time = ds1374_set_time,
355	.read_alarm = ds1374_read_alarm,
356	.set_alarm = ds1374_set_alarm,
357	.ioctl = ds1374_ioctl,
358};
359
360static int ds1374_probe(struct i2c_client *client,
361			const struct i2c_device_id *id)
362{
363	struct ds1374 *ds1374;
364	int ret;
365
366	ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
367	if (!ds1374)
368		return -ENOMEM;
369
370	ds1374->client = client;
371	i2c_set_clientdata(client, ds1374);
372
373	INIT_WORK(&ds1374->work, ds1374_work);
374	mutex_init(&ds1374->mutex);
375
376	ret = ds1374_check_rtc_status(client);
377	if (ret)
378		goto out_free;
379
380	if (client->irq > 0) {
381		ret = request_irq(client->irq, ds1374_irq, 0,
382		                  "ds1374", client);
383		if (ret) {
384			dev_err(&client->dev, "unable to request IRQ\n");
385			goto out_free;
386		}
387
388		device_set_wakeup_capable(&client->dev, 1);
389	}
390
391	ds1374->rtc = rtc_device_register(client->name, &client->dev,
392	                                  &ds1374_rtc_ops, THIS_MODULE);
393	if (IS_ERR(ds1374->rtc)) {
394		ret = PTR_ERR(ds1374->rtc);
395		dev_err(&client->dev, "unable to register the class device\n");
396		goto out_irq;
397	}
398
399	return 0;
400
401out_irq:
402	if (client->irq > 0)
403		free_irq(client->irq, client);
404
405out_free:
406	kfree(ds1374);
407	return ret;
408}
409
410static int __devexit ds1374_remove(struct i2c_client *client)
411{
412	struct ds1374 *ds1374 = i2c_get_clientdata(client);
413
414	if (client->irq > 0) {
415		mutex_lock(&ds1374->mutex);
416		ds1374->exiting = 1;
417		mutex_unlock(&ds1374->mutex);
418
419		free_irq(client->irq, client);
420		cancel_work_sync(&ds1374->work);
421	}
422
423	rtc_device_unregister(ds1374->rtc);
424	kfree(ds1374);
425	return 0;
426}
427
428#ifdef CONFIG_PM
429static int ds1374_suspend(struct i2c_client *client, pm_message_t state)
430{
431	if (client->irq >= 0 && device_may_wakeup(&client->dev))
432		enable_irq_wake(client->irq);
433	return 0;
434}
435
436static int ds1374_resume(struct i2c_client *client)
437{
438	if (client->irq >= 0 && device_may_wakeup(&client->dev))
439		disable_irq_wake(client->irq);
440	return 0;
441}
442#else
443#define ds1374_suspend	NULL
444#define ds1374_resume	NULL
445#endif
446
447static struct i2c_driver ds1374_driver = {
448	.driver = {
449		.name = "rtc-ds1374",
450		.owner = THIS_MODULE,
451	},
452	.probe = ds1374_probe,
453	.suspend = ds1374_suspend,
454	.resume = ds1374_resume,
455	.remove = __devexit_p(ds1374_remove),
456	.id_table = ds1374_id,
457};
458
459static int __init ds1374_init(void)
460{
461	return i2c_add_driver(&ds1374_driver);
462}
463
464static void __exit ds1374_exit(void)
465{
466	i2c_del_driver(&ds1374_driver);
467}
468
469module_init(ds1374_init);
470module_exit(ds1374_exit);
471
472MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
473MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
474MODULE_LICENSE("GPL");
475