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