summaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-ds1307.c
blob: a705e6490808f277e21102bf208a5e77c1d35bb1 (plain)
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
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
/*
 * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
 *
 *  Copyright (C) 2005 James Chapman (ds1337 core)
 *  Copyright (C) 2006 David Brownell
 *  Copyright (C) 2009 Matthias Fuchs (rx8025 support)
 *  Copyright (C) 2012 Bertrand Achard (nvram access fixes)
 *
 * 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/bcd.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/of_irq.h>
#include <linux/pm_wakeirq.h>
#include <linux/rtc/ds1307.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/string.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,
	ds_1388,
	ds_3231,
	m41t00,
	mcp794xx,
	rx_8025,
	last_ds_type /* always last */
	/* 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 MCP794XX_BIT_ST		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 MCP794XX_BIT_VBATEN	0x08
#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 DS3231_BIT_BBSQW		0x40 /* same as BBSQI */
#	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 DS13XX_TRICKLE_CHARGER_MAGIC	0xa0

#define RX8025_REG_CTRL1	0x0e
#	define RX8025_BIT_2412		0x20
#define RX8025_REG_CTRL2	0x0f
#	define RX8025_BIT_PON		0x10
#	define RX8025_BIT_VDET		0x40
#	define RX8025_BIT_XST		0x20


struct ds1307 {
	u8			offset; /* register's offset */
	u8			regs[11];
	u16			nvram_offset;
	struct bin_attribute	*nvram;
	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;
	int			wakeirq;
	s32 (*read_block_data)(const struct i2c_client *client, u8 command,
			       u8 length, u8 *values);
	s32 (*write_block_data)(const struct i2c_client *client, u8 command,
				u8 length, const u8 *values);
};

struct chip_desc {
	unsigned		alarm:1;
	u16			nvram_offset;
	u16			nvram_size;
	u16			trickle_charger_reg;
	u8			trickle_charger_setup;
	u8			(*do_trickle_setup)(struct i2c_client *, uint32_t, bool);
};

static u8 do_trickle_setup_ds1339(struct i2c_client *,
				  uint32_t ohms, bool diode);

static struct chip_desc chips[last_ds_type] = {
	[ds_1307] = {
		.nvram_offset	= 8,
		.nvram_size	= 56,
	},
	[ds_1337] = {
		.alarm		= 1,
	},
	[ds_1338] = {
		.nvram_offset	= 8,
		.nvram_size	= 56,
	},
	[ds_1339] = {
		.alarm		= 1,
		.trickle_charger_reg = 0x10,
		.do_trickle_setup = &do_trickle_setup_ds1339,
	},
	[ds_1340] = {
		.trickle_charger_reg = 0x08,
	},
	[ds_1388] = {
		.trickle_charger_reg = 0x0a,
	},
	[ds_3231] = {
		.alarm		= 1,
	},
	[mcp794xx] = {
		.alarm		= 1,
		/* this is battery backed SRAM */
		.nvram_offset	= 0x20,
		.nvram_size	= 0x40,
	},
};

static const struct i2c_device_id ds1307_id[] = {
	{ "ds1307", ds_1307 },
	{ "ds1337", ds_1337 },
	{ "ds1338", ds_1338 },
	{ "ds1339", ds_1339 },
	{ "ds1388", ds_1388 },
	{ "ds1340", ds_1340 },
	{ "ds3231", ds_3231 },
	{ "m41t00", m41t00 },
	{ "mcp7940x", mcp794xx },
	{ "mcp7941x", mcp794xx },
	{ "pt7c4338", ds_1307 },
	{ "rx8025", rx_8025 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, ds1307_id);

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

#define BLOCK_DATA_MAX_TRIES 10

static s32 ds1307_read_block_data_once(const struct i2c_client *client,
				       u8 command, u8 length, u8 *values)
{
	s32 i, data;

	for (i = 0; i < length; i++) {
		data = i2c_smbus_read_byte_data(client, command + i);
		if (data < 0)
			return data;
		values[i] = data;
	}
	return i;
}

static s32 ds1307_read_block_data(const struct i2c_client *client, u8 command,
				  u8 length, u8 *values)
{
	u8 oldvalues[255];
	s32 ret;
	int tries = 0;

	dev_dbg(&client->dev, "ds1307_read_block_data (length=%d)\n", length);
	ret = ds1307_read_block_data_once(client, command, length, values);
	if (ret < 0)
		return ret;
	do {
		if (++tries > BLOCK_DATA_MAX_TRIES) {
			dev_err(&client->dev,
				"ds1307_read_block_data failed\n");
			return -EIO;
		}
		memcpy(oldvalues, values, length);
		ret = ds1307_read_block_data_once(client, command, length,
						  values);
		if (ret < 0)
			return ret;
	} while (memcmp(oldvalues, values, length));
	return length;
}

static s32 ds1307_write_block_data(const struct i2c_client *client, u8 command,
				   u8 length, const u8 *values)
{
	u8 currvalues[255];
	int tries = 0;

	dev_dbg(&client->dev, "ds1307_write_block_data (length=%d)\n", length);
	do {
		s32 i, ret;

		if (++tries > BLOCK_DATA_MAX_TRIES) {
			dev_err(&client->dev,
				"ds1307_write_block_data failed\n");
			return -EIO;
		}
		for (i = 0; i < length; i++) {
			ret = i2c_smbus_write_byte_data(client, command + i,
							values[i]);
			if (ret < 0)
				return ret;
		}
		ret = ds1307_read_block_data_once(client, command, length,
						  currvalues);
		if (ret < 0)
			return ret;
	} while (memcmp(currvalues, values, length));
	return length;
}

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

/* These RTC devices are not designed to be connected to a SMbus adapter.
   SMbus limits block operations length to 32 bytes, whereas it's not
   limited on I2C buses. As a result, accesses may exceed 32 bytes;
   in that case, split them into smaller blocks */

static s32 ds1307_native_smbus_write_block_data(const struct i2c_client *client,
				u8 command, u8 length, const u8 *values)
{
	u8 suboffset = 0;

	if (length <= I2C_SMBUS_BLOCK_MAX)
		return i2c_smbus_write_i2c_block_data(client,
					command, length, values);

	while (suboffset < length) {
		s32 retval = i2c_smbus_write_i2c_block_data(client,
				command + suboffset,
				min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
				values + suboffset);
		if (retval < 0)
			return retval;

		suboffset += I2C_SMBUS_BLOCK_MAX;
	}
	return length;
}

static s32 ds1307_native_smbus_read_block_data(const struct i2c_client *client,
				u8 command, u8 length, u8 *values)
{
	u8 suboffset = 0;

	if (length <= I2C_SMBUS_BLOCK_MAX)
		return i2c_smbus_read_i2c_block_data(client,
					command, length, values);

	while (suboffset < length) {
		s32 retval = i2c_smbus_read_i2c_block_data(client,
				command + suboffset,
				min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
				values + suboffset);
		if (retval < 0)
			return retval;

		suboffset += I2C_SMBUS_BLOCK_MAX;
	}
	return length;
}

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

/*
 * 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 irqreturn_t ds1307_irq(int irq, void *dev_id)
{
	struct i2c_client	*client = dev_id;
	struct ds1307		*ds1307 = i2c_get_clientdata(client);
	struct mutex		*lock = &ds1307->rtc->ops_lock;
	int			stat, control;

	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(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
	}

out:
	mutex_unlock(lock);

	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 = ds1307->read_block_data(ds1307->client,
		ds1307->offset, 7, ds1307->regs);
	if (tmp != 7) {
		dev_err(dev, "%s error %d\n", "read", tmp);
		return -EIO;
	}

	dev_dbg(dev, "%s: %7ph\n", "read", ds1307->regs);

	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:
	case ds_3231:
		buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
		break;
	case ds_1340:
		buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
				| DS1340_BIT_CENTURY;
		break;
	case mcp794xx:
		/*
		 * these bits were cleared when preparing the date/time
		 * values and need to be set again before writing the
		 * buffer out to the device.
		 */
		buf[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
		buf[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
		break;
	default:
		break;
	}

	dev_dbg(dev, "%s: %7ph\n", "write", buf);

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

static int ds1337_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 = ds1307->read_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 ds1337_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 = ds1307->read_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 = ds1307->write_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_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	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 -ENOTTY;

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

	if (enabled)
		ret |= DS1337_BIT_A1IE;
	else
		ret &= ~DS1337_BIT_A1IE;

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

	return 0;
}

static const struct rtc_class_ops ds13xx_rtc_ops = {
	.read_time	= ds1307_get_time,
	.set_time	= ds1307_set_time,
	.read_alarm	= ds1337_read_alarm,
	.set_alarm	= ds1337_set_alarm,
	.alarm_irq_enable = ds1307_alarm_irq_enable,
};

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

/*
 * Alarm support for mcp794xx devices.
 */

#define MCP794XX_REG_CONTROL		0x07
#	define MCP794XX_BIT_ALM0_EN	0x10
#	define MCP794XX_BIT_ALM1_EN	0x20
#define MCP794XX_REG_ALARM0_BASE	0x0a
#define MCP794XX_REG_ALARM0_CTRL	0x0d
#define MCP794XX_REG_ALARM1_BASE	0x11
#define MCP794XX_REG_ALARM1_CTRL	0x14
#	define MCP794XX_BIT_ALMX_IF	(1 << 3)
#	define MCP794XX_BIT_ALMX_C0	(1 << 4)
#	define MCP794XX_BIT_ALMX_C1	(1 << 5)
#	define MCP794XX_BIT_ALMX_C2	(1 << 6)
#	define MCP794XX_BIT_ALMX_POL	(1 << 7)
#	define MCP794XX_MSK_ALMX_MATCH	(MCP794XX_BIT_ALMX_C0 | \
					 MCP794XX_BIT_ALMX_C1 | \
					 MCP794XX_BIT_ALMX_C2)

static irqreturn_t mcp794xx_irq(int irq, void *dev_id)
{
	struct i2c_client       *client = dev_id;
	struct ds1307           *ds1307 = i2c_get_clientdata(client);
	struct mutex            *lock = &ds1307->rtc->ops_lock;
	int reg, ret;

	mutex_lock(lock);

	/* Check and clear alarm 0 interrupt flag. */
	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_ALARM0_CTRL);
	if (reg < 0)
		goto out;
	if (!(reg & MCP794XX_BIT_ALMX_IF))
		goto out;
	reg &= ~MCP794XX_BIT_ALMX_IF;
	ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_ALARM0_CTRL, reg);
	if (ret < 0)
		goto out;

	/* Disable alarm 0. */
	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
	if (reg < 0)
		goto out;
	reg &= ~MCP794XX_BIT_ALM0_EN;
	ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
	if (ret < 0)
		goto out;

	rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);

out:
	mutex_unlock(lock);

	return IRQ_HANDLED;
}

static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct ds1307 *ds1307 = i2c_get_clientdata(client);
	u8 *regs = ds1307->regs;
	int ret;

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

	/* Read control and alarm 0 registers. */
	ret = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
	if (ret < 0)
		return ret;

	t->enabled = !!(regs[0] & MCP794XX_BIT_ALM0_EN);

	/* Report alarm 0 time assuming 24-hour and day-of-month modes. */
	t->time.tm_sec = bcd2bin(ds1307->regs[3] & 0x7f);
	t->time.tm_min = bcd2bin(ds1307->regs[4] & 0x7f);
	t->time.tm_hour = bcd2bin(ds1307->regs[5] & 0x3f);
	t->time.tm_wday = bcd2bin(ds1307->regs[6] & 0x7) - 1;
	t->time.tm_mday = bcd2bin(ds1307->regs[7] & 0x3f);
	t->time.tm_mon = bcd2bin(ds1307->regs[8] & 0x1f) - 1;
	t->time.tm_year = -1;
	t->time.tm_yday = -1;
	t->time.tm_isdst = -1;

	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
		"enabled=%d polarity=%d irq=%d match=%d\n", __func__,
		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled,
		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_POL),
		!!(ds1307->regs[6] & MCP794XX_BIT_ALMX_IF),
		(ds1307->regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);

	return 0;
}

static int mcp794xx_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 *regs = ds1307->regs;
	int ret;

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

	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
		"enabled=%d pending=%d\n", __func__,
		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
		t->enabled, t->pending);

	/* Read control and alarm 0 registers. */
	ret = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
	if (ret < 0)
		return ret;

	/* Set alarm 0, using 24-hour and day-of-month modes. */
	regs[3] = bin2bcd(t->time.tm_sec);
	regs[4] = bin2bcd(t->time.tm_min);
	regs[5] = bin2bcd(t->time.tm_hour);
	regs[6] = bin2bcd(t->time.tm_wday) + 1;
	regs[7] = bin2bcd(t->time.tm_mday);
	regs[8] = bin2bcd(t->time.tm_mon) + 1;

	/* Clear the alarm 0 interrupt flag. */
	regs[6] &= ~MCP794XX_BIT_ALMX_IF;
	/* Set alarm match: second, minute, hour, day, date, month. */
	regs[6] |= MCP794XX_MSK_ALMX_MATCH;
	/* Disable interrupt. We will not enable until completely programmed */
	regs[0] &= ~MCP794XX_BIT_ALM0_EN;

	ret = ds1307->write_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
	if (ret < 0)
		return ret;

	if (!t->enabled)
		return 0;
	regs[0] |= MCP794XX_BIT_ALM0_EN;
	return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, regs[0]);
}

static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct ds1307 *ds1307 = i2c_get_clientdata(client);
	int reg;

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

	reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
	if (reg < 0)
		return reg;

	if (enabled)
		reg |= MCP794XX_BIT_ALM0_EN;
	else
		reg &= ~MCP794XX_BIT_ALM0_EN;

	return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
}

static const struct rtc_class_ops mcp794xx_rtc_ops = {
	.read_time	= ds1307_get_time,
	.set_time	= ds1307_set_time,
	.read_alarm	= mcp794xx_read_alarm,
	.set_alarm	= mcp794xx_set_alarm,
	.alarm_irq_enable = mcp794xx_alarm_irq_enable,
};

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

static ssize_t
ds1307_nvram_read(struct file *filp, 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);

	result = ds1307->read_block_data(client, ds1307->nvram_offset + 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 file *filp, 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);

	result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
								count, buf);
	if (result < 0) {
		dev_err(&client->dev, "%s error %d\n", "nvram write", result);
		return result;
	}
	return count;
}


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

static u8 do_trickle_setup_ds1339(struct i2c_client *client,
				  uint32_t ohms, bool diode)
{
	u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
		DS1307_TRICKLE_CHARGER_NO_DIODE;

	switch (ohms) {
	case 250:
		setup |= DS1307_TRICKLE_CHARGER_250_OHM;
		break;
	case 2000:
		setup |= DS1307_TRICKLE_CHARGER_2K_OHM;
		break;
	case 4000:
		setup |= DS1307_TRICKLE_CHARGER_4K_OHM;
		break;
	default:
		dev_warn(&client->dev,
			 "Unsupported ohm value %u in dt\n", ohms);
		return 0;
	}
	return setup;
}

static void ds1307_trickle_of_init(struct i2c_client *client,
				   struct chip_desc *chip)
{
	uint32_t ohms = 0;
	bool diode = true;

	if (!chip->do_trickle_setup)
		goto out;
	if (of_property_read_u32(client->dev.of_node, "trickle-resistor-ohms" , &ohms))
		goto out;
	if (of_property_read_bool(client->dev.of_node, "trickle-diode-disable"))
		diode = false;
	chip->trickle_charger_setup = chip->do_trickle_setup(client,
							     ohms, diode);
out:
	return;
}

static int ds1307_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct ds1307		*ds1307;
	int			err = -ENODEV;
	int			tmp;
	struct chip_desc	*chip = &chips[id->driver_data];
	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
	bool			want_irq = false;
	unsigned char		*buf;
	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
	irq_handler_t	irq_handler = ds1307_irq;

	static const int	bbsqi_bitpos[] = {
		[ds_1337] = 0,
		[ds_1339] = DS1339_BIT_BBSQI,
		[ds_3231] = DS3231_BIT_BBSQW,
	};
	const struct rtc_class_ops *rtc_ops = &ds13xx_rtc_ops;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)
	    && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
		return -EIO;

	ds1307 = devm_kzalloc(&client->dev, sizeof(struct ds1307), GFP_KERNEL);
	if (!ds1307)
		return -ENOMEM;

	i2c_set_clientdata(client, ds1307);

	ds1307->client	= client;
	ds1307->type	= id->driver_data;

	if (!pdata && client->dev.of_node)
		ds1307_trickle_of_init(client, chip);
	else if (pdata && pdata->trickle_charger_setup)
		chip->trickle_charger_setup = pdata->trickle_charger_setup;

	if (chip->trickle_charger_setup && chip->trickle_charger_reg) {
		dev_dbg(&client->dev, "writing trickle charger info 0x%x to 0x%x\n",
		    DS13XX_TRICKLE_CHARGER_MAGIC | chip->trickle_charger_setup,
		    chip->trickle_charger_reg);
		i2c_smbus_write_byte_data(client, chip->trickle_charger_reg,
		    DS13XX_TRICKLE_CHARGER_MAGIC |
		    chip->trickle_charger_setup);
	}

	buf = ds1307->regs;
	if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK)) {
		ds1307->read_block_data = ds1307_native_smbus_read_block_data;
		ds1307->write_block_data = ds1307_native_smbus_write_block_data;
	} else {
		ds1307->read_block_data = ds1307_read_block_data;
		ds1307->write_block_data = ds1307_write_block_data;
	}

	switch (ds1307->type) {
	case ds_1337:
	case ds_1339:
	case ds_3231:
		/* get registers that the "rtc" read below won't read... */
		tmp = ds1307->read_block_data(ds1307->client,
				DS1337_REG_CONTROL, 2, buf);
		if (tmp != 2) {
			dev_dbg(&client->dev, "read error %d\n", tmp);
			err = -EIO;
			goto exit;
		}

		/* 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 some variants, be sure alarms can trigger when we're
		 * running on Vbackup (BBSQI/BBSQW)
		 */
		if (ds1307->client->irq > 0 && chip->alarm) {
			ds1307->regs[0] |= DS1337_BIT_INTCN
					| bbsqi_bitpos[ds1307->type];
			ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);

			want_irq = true;
		}

		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;

	case rx_8025:
		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
				RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
		if (tmp != 2) {
			dev_dbg(&client->dev, "read error %d\n", tmp);
			err = -EIO;
			goto exit;
		}

		/* oscillator off?  turn it on, so clock can tick. */
		if (!(ds1307->regs[1] & RX8025_BIT_XST)) {
			ds1307->regs[1] |= RX8025_BIT_XST;
			i2c_smbus_write_byte_data(client,
						  RX8025_REG_CTRL2 << 4 | 0x08,
						  ds1307->regs[1]);
			dev_warn(&client->dev,
				 "oscillator stop detected - SET TIME!\n");
		}

		if (ds1307->regs[1] & RX8025_BIT_PON) {
			ds1307->regs[1] &= ~RX8025_BIT_PON;
			i2c_smbus_write_byte_data(client,
						  RX8025_REG_CTRL2 << 4 | 0x08,
						  ds1307->regs[1]);
			dev_warn(&client->dev, "power-on detected\n");
		}

		if (ds1307->regs[1] & RX8025_BIT_VDET) {
			ds1307->regs[1] &= ~RX8025_BIT_VDET;
			i2c_smbus_write_byte_data(client,
						  RX8025_REG_CTRL2 << 4 | 0x08,
						  ds1307->regs[1]);
			dev_warn(&client->dev, "voltage drop detected\n");
		}

		/* make sure we are running in 24hour mode */
		if (!(ds1307->regs[0] & RX8025_BIT_2412)) {
			u8 hour;

			/* switch to 24 hour mode */
			i2c_smbus_write_byte_data(client,
						  RX8025_REG_CTRL1 << 4 | 0x08,
						  ds1307->regs[0] |
						  RX8025_BIT_2412);

			tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
					RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
			if (tmp != 2) {
				dev_dbg(&client->dev, "read error %d\n", tmp);
				err = -EIO;
				goto exit;
			}

			/* correct hour */
			hour = bcd2bin(ds1307->regs[DS1307_REG_HOUR]);
			if (hour == 12)
				hour = 0;
			if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
				hour += 12;

			i2c_smbus_write_byte_data(client,
						  DS1307_REG_HOUR << 4 | 0x08,
						  hour);
		}
		break;
	case ds_1388:
		ds1307->offset = 1; /* Seconds starts at 1 */
		break;
	case mcp794xx:
		rtc_ops = &mcp794xx_rtc_ops;
		if (ds1307->client->irq > 0 && chip->alarm) {
			irq_handler = mcp794xx_irq;
			want_irq = true;
		}
		break;
	default:
		break;
	}

read_rtc:
	/* read RTC registers */
	tmp = ds1307->read_block_data(ds1307->client, ds1307->offset, 8, buf);
	if (tmp != 8) {
		dev_dbg(&client->dev, "read error %d\n", tmp);
		err = -EIO;
		goto exit;
	}

	/*
	 * 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) {
			dev_dbg(&client->dev, "read error %d\n", tmp);
			err = -EIO;
			goto exit;
		}

		/* 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 mcp794xx:
		/* make sure that the backup battery is enabled */
		if (!(ds1307->regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
			i2c_smbus_write_byte_data(client, DS1307_REG_WDAY,
					ds1307->regs[DS1307_REG_WDAY]
					| MCP794XX_BIT_VBATEN);
		}

		/* clock halted?  turn it on, so clock can tick. */
		if (!(tmp & MCP794XX_BIT_ST)) {
			i2c_smbus_write_byte_data(client, DS1307_REG_SECS,
					MCP794XX_BIT_ST);
			dev_warn(&client->dev, "SET TIME!\n");
			goto read_rtc;
		}

		break;
	default:
		break;
	}

	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;
	case rx_8025:
		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->offset + DS1307_REG_HOUR,
				bin2bcd(tmp));
	}

	device_set_wakeup_capable(&client->dev, want_irq);
	ds1307->rtc = devm_rtc_device_register(&client->dev, client->name,
				rtc_ops, THIS_MODULE);
	if (IS_ERR(ds1307->rtc)) {
		return PTR_ERR(ds1307->rtc);
	}

	if (want_irq) {
		struct device_node *node = client->dev.of_node;

		err = devm_request_threaded_irq(&client->dev,
						client->irq, NULL, irq_handler,
						IRQF_SHARED | IRQF_ONESHOT,
						ds1307->rtc->name, client);
		if (err) {
			client->irq = 0;
			dev_err(&client->dev, "unable to request IRQ!\n");
			goto no_irq;
		}

		set_bit(HAS_ALARM, &ds1307->flags);
		dev_dbg(&client->dev, "got IRQ %d\n", client->irq);

		/* Currently supported by OF code only! */
		if (!node)
			goto no_irq;

		err = of_irq_get(node, 1);
		if (err <= 0) {
			if (err == -EPROBE_DEFER)
				goto exit;
			goto no_irq;
		}
		ds1307->wakeirq = err;

		err = dev_pm_set_dedicated_wake_irq(&client->dev,
						    ds1307->wakeirq);
		if (err) {
			dev_err(&client->dev, "unable to setup wakeIRQ %d!\n",
				err);
			goto exit;
		}
	}

no_irq:
	if (chip->nvram_size) {

		ds1307->nvram = devm_kzalloc(&client->dev,
					sizeof(struct bin_attribute),
					GFP_KERNEL);
		if (!ds1307->nvram) {
			dev_err(&client->dev, "cannot allocate memory for nvram sysfs\n");
		} else {

			ds1307->nvram->attr.name = "nvram";
			ds1307->nvram->attr.mode = S_IRUGO | S_IWUSR;

			sysfs_bin_attr_init(ds1307->nvram);

			ds1307->nvram->read = ds1307_nvram_read;
			ds1307->nvram->write = ds1307_nvram_write;
			ds1307->nvram->size = chip->nvram_size;
			ds1307->nvram_offset = chip->nvram_offset;

			err = sysfs_create_bin_file(&client->dev.kobj,
						    ds1307->nvram);
			if (err) {
				dev_err(&client->dev,
					"unable to create sysfs file: %s\n",
					ds1307->nvram->attr.name);
			} else {
				set_bit(HAS_NVRAM, &ds1307->flags);
				dev_info(&client->dev, "%zu bytes nvram\n",
					 ds1307->nvram->size);
			}
		}
	}

	return 0;

exit:
	return err;
}

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

	if (ds1307->wakeirq)
		dev_pm_clear_wake_irq(&client->dev);

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

	return 0;
}

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

module_i2c_driver(ds1307_driver);

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