aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-ds1307.c
blob: fec13e7d48ef300f1ce5e2424ef87ee1ba25ce35 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
/*
 * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
 *
 *  Copyright (C) 2005 James Chapman (ds1337 core)
 *  Copyright (C) 2006 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/rtc.h>
#include <linux/bcd.h>



/* We can't determine type by probing, but if we expect pre-Linux code
 * to have set the chip up as a clock (turning on the oscillator and
 * setting the date and time), Linux can ignore the non-clock features.
 * That's a natural job for a factory or repair bench.
 */
enum ds_type {
	ds_1307,
	ds_1337,
	ds_1338,
	ds_1339,
	ds_1340,
	m41t00,
	// rs5c372 too?  different address...
};


/* RTC registers don't differ much, except for the century flag */
#define DS1307_REG_SECS		0x00	/* 00-59 */
#	define DS1307_BIT_CH		0x80
#	define DS1340_BIT_nEOSC		0x80
#define DS1307_REG_MIN		0x01	/* 00-59 */
#define DS1307_REG_HOUR		0x02	/* 00-23, or 1-12{am,pm} */
#	define DS1307_BIT_12HR		0x40	/* in REG_HOUR */
#	define DS1307_BIT_PM		0x20	/* in REG_HOUR */
#	define DS1340_BIT_CENTURY_EN	0x80	/* in REG_HOUR */
#	define DS1340_BIT_CENTURY	0x40	/* in REG_HOUR */
#define DS1307_REG_WDAY		0x03	/* 01-07 */
#define DS1307_REG_MDAY		0x04	/* 01-31 */
#define DS1307_REG_MONTH	0x05	/* 01-12 */
#	define DS1337_BIT_CENTURY	0x80	/* in REG_MONTH */
#define DS1307_REG_YEAR		0x06	/* 00-99 */

/* Other registers (control, status, alarms, trickle charge, NVRAM, etc)
 * start at 7, and they differ a LOT. Only control and status matter for
 * basic RTC date and time functionality; be careful using them.
 */
#define DS1307_REG_CONTROL	0x07		/* or ds1338 */
#	define DS1307_BIT_OUT		0x80
#	define DS1338_BIT_OSF		0x20
#	define DS1307_BIT_SQWE		0x10
#	define DS1307_BIT_RS1		0x02
#	define DS1307_BIT_RS0		0x01
#define DS1337_REG_CONTROL	0x0e
#	define DS1337_BIT_nEOSC		0x80
#	define DS1339_BIT_BBSQI		0x20
#	define DS1337_BIT_RS2		0x10
#	define DS1337_BIT_RS1		0x08
#	define DS1337_BIT_INTCN		0x04
#	define DS1337_BIT_A2IE		0x02
#	define DS1337_BIT_A1IE		0x01
#define DS1340_REG_CONTROL	0x07
#	define DS1340_BIT_OUT		0x80
#	define DS1340_BIT_FT		0x40
#	define DS1340_BIT_CALIB_SIGN	0x20
#	define DS1340_M_CALIBRATION	0x1f
#define DS1340_REG_FLAG		0x09
#	define DS1340_BIT_OSF		0x80
#define DS1337_REG_STATUS	0x0f
#	define DS1337_BIT_OSF		0x80
#	define DS1337_BIT_A2I		0x02
#	define DS1337_BIT_A1I		0x01
#define DS1339_REG_ALARM1_SECS	0x07
#define DS1339_REG_TRICKLE	0x10



struct ds1307 {
	u8			regs[11];
	enum ds_type		type;
	unsigned long		flags;
#define HAS_NVRAM	0		/* bit 0 == sysfs file active */
#define HAS_ALARM	1		/* bit 1 == irq claimed */
	struct i2c_client	*client;
	struct rtc_device	*rtc;
	struct work_struct	work;
};

struct chip_desc {
	unsigned		nvram56:1;
	unsigned		alarm:1;
};

static const struct chip_desc chips[] = {
[ds_1307] = {
	.nvram56	= 1,
},
[ds_1337] = {
	.alarm		= 1,
},
[ds_1338] = {
	.nvram56	= 1,
},
[ds_1339] = {
	.alarm		= 1,
},
[ds_1340] = {
},
[m41t00] = {
}, };

static const struct i2c_device_id ds1307_id[] = {
	{ "ds1307", ds_1307 },
	{ "ds1337", ds_1337 },
	{ "ds1338", ds_1338 },
	{ "ds1339", ds_1339 },
	{ "ds1340", ds_1340 },
	{ "m41t00", m41t00 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, ds1307_id);

/*----------------------------------------------------------------------*/

/*
 * The IRQ logic includes a "real" handler running in IRQ context just
 * long enough to schedule this workqueue entry.   We need a task context
 * to talk to the RTC, since I2C I/O calls require that; and disable the
 * IRQ until we clear its status on the chip, so that this handler can
 * work with any type of triggering (not just falling edge).
 *
 * The ds1337 and ds1339 both have two alarms, but we only use the first
 * one (with a "seconds" field).  For ds1337 we expect nINTA is our alarm
 * signal; ds1339 chips have only one alarm signal.
 */
static void ds1307_work(struct work_struct *work)
{
	struct ds1307		*ds1307;
	struct i2c_client	*client;
	struct mutex		*lock;
	int			stat, control;

	ds1307 = container_of(work, struct ds1307, work);
	client = ds1307->client;
	lock = &ds1307->rtc->ops_lock;

	mutex_lock(lock);
	stat = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
	if (stat < 0)
		goto out;

	if (stat & DS1337_BIT_A1I) {
		stat &= ~DS1337_BIT_A1I;
		i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, stat);

		control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
		if (control < 0)
			goto out;

		control &= ~DS1337_BIT_A1IE;
		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);

		/* rtc_update_irq() assumes that it is called
		 * from IRQ-disabled context.
		 */
		local_irq_disable();
		rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
		local_irq_enable();
	}

out:
	if (test_bit(HAS_ALARM, &ds1307->flags))
		enable_irq(client->irq);
	mutex_unlock(lock);
}

static irqreturn_t ds1307_irq(int irq, void *dev_id)
{
	struct i2c_client	*client = dev_id;
	struct ds1307		*ds1307 = i2c_get_clientdata(client);

	disable_irq_nosync(irq);
	schedule_work(&ds1307->work);
	return IRQ_HANDLED;
}

/*----------------------------------------------------------------------*/

static int ds1307_get_time(struct device *dev, struct rtc_time *t)
{
	struct ds1307	*ds1307 = dev_get_drvdata(dev);
	int		tmp;

	/* read the RTC date and time registers all at once */
	tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
		DS1307_REG_SECS, 7, ds1307->regs);
	if (tmp != 7) {
		dev_err(dev, "%s error %d\n", "read", tmp);
		return -EIO;
	}

	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
			"read",
			ds1307->regs[0], ds1307->regs[1],
			ds1307->regs[2], ds1307->regs[3],
			ds1307->regs[4], ds1307->regs[5],
			ds1307->regs[6]);

	t->tm_sec = bcd2bin(ds1307->regs[DS1307_REG_SECS] & 0x7f);
	t->tm_min = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f);
	tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;
	t->tm_hour = bcd2bin(tmp);
	t->tm_wday = bcd2bin(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
	t->tm_mday = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
	tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;
	t->tm_mon = bcd2bin(tmp) - 1;

	/* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */
	t->tm_year = bcd2bin(ds1307->regs[DS1307_REG_YEAR]) + 100;

	dev_dbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
		"read", t->tm_sec, t->tm_min,
		t->tm_hour, t->tm_mday,
		t->tm_mon, t->tm_year, t->tm_wday);

	/* initial clock setting can be undefined */
	return rtc_valid_tm(t);
}

static int ds1307_set_time(struct device *dev, struct rtc_time *t)
{
	struct ds1307	*ds1307 = dev_get_drvdata(dev);
	int		result;
	int		tmp;
	u8		*buf = ds1307->regs;

	dev_dbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
		"write", t->tm_sec, t->tm_min,
		t->tm_hour, t->tm_mday,
		t->tm_mon, t->tm_year, t->tm_wday);

	buf[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
	buf[DS1307_REG_MIN] = bin2bcd(t->tm_min);
	buf[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
	buf[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
	buf[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
	buf[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);

	/* assume 20YY not 19YY */
	tmp = t->tm_year - 100;
	buf[DS1307_REG_YEAR] = bin2bcd(tmp);

	switch (ds1307->type) {
	case ds_1337:
	case ds_1339:
		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
		break;
	case ds_1340:
		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
				| DS1340_BIT_CENTURY;
		break;
	default:
		break;
	}

	dev_dbg(dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
		"write", buf[0], buf[1], buf[2], buf[3],
		buf[4], buf[5], buf[6]);

	result = i2c_smbus_write_i2c_block_data(ds1307->client, 0, 7, buf);
	if (result < 0) {
		dev_err(dev, "%s error %d\n", "write", result);
		return result;
	}
	return 0;
}

static int ds1307_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client       *client = to_i2c_client(dev);
	struct ds1307		*ds1307 = i2c_get_clientdata(client);
	int			ret;

	if (!test_bit(HAS_ALARM, &ds1307->flags))
		return -EINVAL;

	/* read all ALARM1, ALARM2, and status registers at once */
	ret = i2c_smbus_read_i2c_block_data(client,
			DS1339_REG_ALARM1_SECS, 9, ds1307->regs);
	if (ret != 9) {
		dev_err(dev, "%s error %d\n", "alarm read", ret);
		return -EIO;
	}

	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x\n",
			"alarm read",
			ds1307->regs[0], ds1307->regs[1],
			ds1307->regs[2], ds1307->regs[3],
			ds1307->regs[4], ds1307->regs[5],
			ds1307->regs[6], ds1307->regs[7],
			ds1307->regs[8]);

	/* report alarm time (ALARM1); assume 24 hour and day-of-month modes,
	 * and that all four fields are checked matches
	 */
	t->time.tm_sec = bcd2bin(ds1307->regs[0] & 0x7f);
	t->time.tm_min = bcd2bin(ds1307->regs[1] & 0x7f);
	t->time.tm_hour = bcd2bin(ds1307->regs[2] & 0x3f);
	t->time.tm_mday = bcd2bin(ds1307->regs[3] & 0x3f);
	t->time.tm_mon = -1;
	t->time.tm_year = -1;
	t->time.tm_wday = -1;
	t->time.tm_yday = -1;
	t->time.tm_isdst = -1;

	/* ... and status */
	t->enabled = !!(ds1307->regs[7] & DS1337_BIT_A1IE);
	t->pending = !!(ds1307->regs[8] & DS1337_BIT_A1I);

	dev_dbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, enabled=%d, pending=%d\n",
		"alarm read", t->time.tm_sec, t->time.tm_min,
		t->time.tm_hour, t->time.tm_mday,
		t->enabled, t->pending);

	return 0;
}

static int ds1307_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client       *client = to_i2c_client(dev);
	struct ds1307		*ds1307 = i2c_get_clientdata(client);
	unsigned char		*buf = ds1307->regs;
	u8			control, status;
	int			ret;

	if (!test_bit(HAS_ALARM, &ds1307->flags))
		return -EINVAL;

	dev_dbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, enabled=%d, pending=%d\n",
		"alarm set", t->time.tm_sec, t->time.tm_min,
		t->time.tm_hour, t->time.tm_mday,
		t->enabled, t->pending);

	/* read current status of both alarms and the chip */
	ret = i2c_smbus_read_i2c_block_data(client,
			DS1339_REG_ALARM1_SECS, 9, buf);
	if (ret != 9) {
		dev_err(dev, "%s error %d\n", "alarm write", ret);
		return -EIO;
	}
	control = ds1307->regs[7];
	status = ds1307->regs[8];

	dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x\n",
			"alarm set (old status)",
			ds1307->regs[0], ds1307->regs[1],
			ds1307->regs[2], ds1307->regs[3],
			ds1307->regs[4], ds1307->regs[5],
			ds1307->regs[6], control, status);

	/* set ALARM1, using 24 hour and day-of-month modes */
	buf[0] = bin2bcd(t->time.tm_sec);
	buf[1] = bin2bcd(t->time.tm_min);
	buf[2] = bin2bcd(t->time.tm_hour);
	buf[3] = bin2bcd(t->time.tm_mday);

	/* set ALARM2 to non-garbage */
	buf[4] = 0;
	buf[5] = 0;
	buf[6] = 0;

	/* optionally enable ALARM1 */
	buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
	if (t->enabled) {
		dev_dbg(dev, "alarm IRQ armed\n");
		buf[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
	}
	buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);

	ret = i2c_smbus_write_i2c_block_data(client,
			DS1339_REG_ALARM1_SECS, 9, buf);
	if (ret < 0) {
		dev_err(dev, "can't set alarm time\n");
		return ret;
	}

	return 0;
}

static int ds1307_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
	struct i2c_client	*client = to_i2c_client(dev);
	struct ds1307		*ds1307 = i2c_get_clientdata(client);
	int			ret;

	switch (cmd) {
	case RTC_AIE_OFF:
		if (!test_bit(HAS_ALARM, &ds1307->flags))
			return -ENOTTY;

		ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
		if (ret < 0)
			return ret;

		ret &= ~DS1337_BIT_A1IE;

		ret = i2c_smbus_write_byte_data(client,
						DS1337_REG_CONTROL, ret);
		if (ret < 0)
			return ret;

		break;

	case RTC_AIE_ON:
		if (!test_bit(HAS_ALARM, &ds1307->flags))
			return -ENOTTY;

		ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
		if (ret < 0)
			return ret;

		ret |= DS1337_BIT_A1IE;

		ret = i2c_smbus_write_byte_data(client,
						DS1337_REG_CONTROL, ret);
		if (ret < 0)
			return ret;

		break;

	default:
		return -ENOIOCTLCMD;
	}

	return 0;
}

static const struct rtc_class_ops ds13xx_rtc_ops = {
	.read_time	= ds1307_get_time,
	.set_time	= ds1307_set_time,
	.read_alarm	= ds1307_read_alarm,
	.set_alarm	= ds1307_set_alarm,
	.ioctl		= ds1307_ioctl,
};

/*----------------------------------------------------------------------*/

#define NVRAM_SIZE	56

static ssize_t
ds1307_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
		char *buf, loff_t off, size_t count)
{
	struct i2c_client	*client;
	struct ds1307		*ds1307;
	int			result;

	client = kobj_to_i2c_client(kobj);
	ds1307 = i2c_get_clientdata(client);

	if (unlikely(off >= NVRAM_SIZE))
		return 0;
	if ((off + count) > NVRAM_SIZE)
		count = NVRAM_SIZE - off;
	if (unlikely(!count))
		return count;

	result = i2c_smbus_read_i2c_block_data(client, 8 + off, count, buf);
	if (result < 0)
		dev_err(&client->dev, "%s error %d\n", "nvram read", result);
	return result;
}

static ssize_t
ds1307_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
		char *buf, loff_t off, size_t count)
{
	struct i2c_client	*client;
	int			result;

	client = kobj_to_i2c_client(kobj);

	if (unlikely(off >= NVRAM_SIZE))
		return -EFBIG;
	if ((off + count) > NVRAM_SIZE)
		count = NVRAM_SIZE - off;
	if (unlikely(!count))
		return count;

	result = i2c_smbus_write_i2c_block_data(client, 8 + off, count, buf);
	if (result < 0) {
		dev_err(&client->dev, "%s error %d\n", "nvram write", result);
		return result;
	}
	return count;
}

static struct bin_attribute nvram = {
	.attr = {
		.name	= "nvram",
		.mode	= S_IRUGO | S_IWUSR,
	},

	.read	= ds1307_nvram_read,
	.write	= ds1307_nvram_write,
	.size	= NVRAM_SIZE,
};

/*----------------------------------------------------------------------*/

static struct i2c_driver ds1307_driver;

static int __devinit ds1307_probe(struct i2c_client *client,
				  const struct i2c_device_id *id)
{
	struct ds1307		*ds1307;
	int			err = -ENODEV;
	int			tmp;
	const struct chip_desc	*chip = &chips[id->driver_data];
	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
	int			want_irq = false;
	unsigned char		*buf;

	if (!i2c_check_functionality(adapter,
			I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
			I2C_FUNC_SMBUS_I2C_BLOCK))
		return -EIO;

	if (!(ds1307 = kzalloc(sizeof(struct ds1307), GFP_KERNEL)))
		return -ENOMEM;

	ds1307->client = client;
	i2c_set_clientdata(client, ds1307);
	ds1307->type = id->driver_data;
	buf = ds1307->regs;

	switch (ds1307->type) {
	case ds_1337:
	case ds_1339:
		/* has IRQ? */
		if (ds1307->client->irq > 0 && chip->alarm) {
			INIT_WORK(&ds1307->work, ds1307_work);
			want_irq = true;
		}
		/* get registers that the "rtc" read below won't read... */
		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
				DS1337_REG_CONTROL, 2, buf);
		if (tmp != 2) {
			pr_debug("read error %d\n", tmp);
			err = -EIO;
			goto exit_free;
		}

		/* oscillator off?  turn it on, so clock can tick. */
		if (ds1307->regs[0] & DS1337_BIT_nEOSC)
			ds1307->regs[0] &= ~DS1337_BIT_nEOSC;

		/* Using IRQ?  Disable the square wave and both alarms.
		 * For ds1339, be sure alarms can trigger when we're
		 * running on Vbackup (BBSQI); we assume ds1337 will
		 * ignore that bit
		 */
		if (want_irq) {
			ds1307->regs[0] |= DS1337_BIT_INTCN | DS1339_BIT_BBSQI;
			ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
		}

		i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
							ds1307->regs[0]);

		/* oscillator fault?  clear flag, and warn */
		if (ds1307->regs[1] & DS1337_BIT_OSF) {
			i2c_smbus_write_byte_data(client, DS1337_REG_STATUS,
				ds1307->regs[1] & ~DS1337_BIT_OSF);
			dev_warn(&client->dev, "SET TIME!\n");
		}
		break;
	default:
		break;
	}

read_rtc:
	/* read RTC registers */
	tmp = i2c_smbus_read_i2c_block_data(ds1307->client, 0, 8, buf);
	if (tmp != 8) {
		pr_debug("read error %d\n", tmp);
		err = -EIO;
		goto exit_free;
	}

	/* minimal sanity checking; some chips (like DS1340) don't
	 * specify the extra bits as must-be-zero, but there are
	 * still a few values that are clearly out-of-range.
	 */
	tmp = ds1307->regs[DS1307_REG_SECS];
	switch (ds1307->type) {
	case ds_1307:
	case m41t00:
		/* clock halted?  turn it on, so clock can tick. */
		if (tmp & DS1307_BIT_CH) {
			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
			dev_warn(&client->dev, "SET TIME!\n");
			goto read_rtc;
		}
		break;
	case ds_1338:
		/* clock halted?  turn it on, so clock can tick. */
		if (tmp & DS1307_BIT_CH)
			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);

		/* oscillator fault?  clear flag, and warn */
		if (ds1307->regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
			i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,
					ds1307->regs[DS1307_REG_CONTROL]
					& ~DS1338_BIT_OSF);
			dev_warn(&client->dev, "SET TIME!\n");
			goto read_rtc;
		}
		break;
	case ds_1340:
		/* clock halted?  turn it on, so clock can tick. */
		if (tmp & DS1340_BIT_nEOSC)
			i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);

		tmp = i2c_smbus_read_byte_data(client, DS1340_REG_FLAG);
		if (tmp < 0) {
			pr_debug("read error %d\n", tmp);
			err = -EIO;
			goto exit_free;
		}

		/* oscillator fault?  clear flag, and warn */
		if (tmp & DS1340_BIT_OSF) {
			i2c_smbus_write_byte_data(client, DS1340_REG_FLAG, 0);
			dev_warn(&client->dev, "SET TIME!\n");
		}
		break;
	case ds_1337:
	case ds_1339:
		break;
	}

	tmp = ds1307->regs[DS1307_REG_SECS];
	tmp = bcd2bin(tmp & 0x7f);
	if (tmp > 60)
		goto exit_bad;
	tmp = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f);
	if (tmp > 60)
		goto exit_bad;

	tmp = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
	if (tmp == 0 || tmp > 31)
		goto exit_bad;

	tmp = bcd2bin(ds1307->regs[DS1307_REG_MONTH] & 0x1f);
	if (tmp == 0 || tmp > 12)
		goto exit_bad;

	tmp = ds1307->regs[DS1307_REG_HOUR];
	switch (ds1307->type) {
	case ds_1340:
	case m41t00:
		/* NOTE: ignores century bits; fix before deploying
		 * systems that will run through year 2100.
		 */
		break;
	default:
		if (!(tmp & DS1307_BIT_12HR))
			break;

		/* Be sure we're in 24 hour mode.  Multi-master systems
		 * take note...
		 */
		tmp = bcd2bin(tmp & 0x1f);
		if (tmp == 12)
			tmp = 0;
		if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
			tmp += 12;
		i2c_smbus_write_byte_data(client,
				DS1307_REG_HOUR,
				bin2bcd(tmp));
	}

	ds1307->rtc = rtc_device_register(client->name, &client->dev,
				&ds13xx_rtc_ops, THIS_MODULE);
	if (IS_ERR(ds1307->rtc)) {
		err = PTR_ERR(ds1307->rtc);
		dev_err(&client->dev,
			"unable to register the class device\n");
		goto exit_free;
	}

	if (want_irq) {
		err = request_irq(client->irq, ds1307_irq, 0,
			  ds1307->rtc->name, client);
		if (err) {
			dev_err(&client->dev,
				"unable to request IRQ!\n");
			goto exit_irq;
		}
		set_bit(HAS_ALARM, &ds1307->flags);
		dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
	}

	if (chip->nvram56) {
		err = sysfs_create_bin_file(&client->dev.kobj, &nvram);
		if (err == 0) {
			set_bit(HAS_NVRAM, &ds1307->flags);
			dev_info(&client->dev, "56 bytes nvram\n");
		}
	}

	return 0;

exit_bad:
	dev_dbg(&client->dev, "%s: %02x %02x %02x %02x %02x %02x %02x\n",
			"bogus register",
			ds1307->regs[0], ds1307->regs[1],
			ds1307->regs[2], ds1307->regs[3],
			ds1307->regs[4], ds1307->regs[5],
			ds1307->regs[6]);
exit_irq:
	if (ds1307->rtc)
		rtc_device_unregister(ds1307->rtc);
exit_free:
	kfree(ds1307);
	return err;
}

static int __devexit ds1307_remove(struct i2c_client *client)
{
	struct ds1307		*ds1307 = i2c_get_clientdata(client);

	if (test_and_clear_bit(HAS_ALARM, &ds1307->flags)) {
		free_irq(client->irq, client);
		cancel_work_sync(&ds1307->work);
	}

	if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))
		sysfs_remove_bin_file(&client->dev.kobj, &nvram);

	rtc_device_unregister(ds1307->rtc);
	kfree(ds1307);
	return 0;
}

static struct i2c_driver ds1307_driver = {
	.driver = {
		.name	= "rtc-ds1307",
		.owner	= THIS_MODULE,
	},
	.probe		= ds1307_probe,
	.remove		= __devexit_p(ds1307_remove),
	.id_table	= ds1307_id,
};

static int __init ds1307_init(void)
{
	return i2c_add_driver(&ds1307_driver);
}
module_init(ds1307_init);

static void __exit ds1307_exit(void)
{
	i2c_del_driver(&ds1307_driver);
}
module_exit(ds1307_exit);

MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
MODULE_LICENSE("GPL");