summaryrefslogtreecommitdiff
path: root/drivers/rtc/rtc-rs5c372.c
blob: b4c5d016eca32c10838c352859ff1b73fbcb4556 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * An I2C driver for Ricoh RS5C372, R2025S/D and RV5C38[67] RTCs
 *
 * Copyright (C) 2005 Pavel Mironchik <pmironchik@optifacio.net>
 * Copyright (C) 2006 Tower Technologies
 * Copyright (C) 2008 Paul Mundt
 */

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

/*
 * Ricoh has a family of I2C based RTCs, which differ only slightly from
 * each other.  Differences center on pinout (e.g. how many interrupts,
 * output clock, etc) and how the control registers are used.  The '372
 * is significant only because that's the one this driver first supported.
 */
#define RS5C372_REG_SECS	0
#define RS5C372_REG_MINS	1
#define RS5C372_REG_HOURS	2
#define RS5C372_REG_WDAY	3
#define RS5C372_REG_DAY		4
#define RS5C372_REG_MONTH	5
#define RS5C372_REG_YEAR	6
#define RS5C372_REG_TRIM	7
#	define RS5C372_TRIM_XSL		0x80		/* only if RS5C372[a|b] */
#	define RS5C372_TRIM_MASK	0x7F
#	define R2221TL_TRIM_DEV		(1 << 7)	/* only if R2221TL */
#	define RS5C372_TRIM_DECR	(1 << 6)

#define RS5C_REG_ALARM_A_MIN	8			/* or ALARM_W */
#define RS5C_REG_ALARM_A_HOURS	9
#define RS5C_REG_ALARM_A_WDAY	10

#define RS5C_REG_ALARM_B_MIN	11			/* or ALARM_D */
#define RS5C_REG_ALARM_B_HOURS	12
#define RS5C_REG_ALARM_B_WDAY	13			/* (ALARM_B only) */

#define RS5C_REG_CTRL1		14
#	define RS5C_CTRL1_AALE		(1 << 7)	/* or WALE */
#	define RS5C_CTRL1_BALE		(1 << 6)	/* or DALE */
#	define RV5C387_CTRL1_24		(1 << 5)
#	define RS5C372A_CTRL1_SL1	(1 << 5)
#	define RS5C_CTRL1_CT_MASK	(7 << 0)
#	define RS5C_CTRL1_CT0		(0 << 0)	/* no periodic irq */
#	define RS5C_CTRL1_CT4		(4 << 0)	/* 1 Hz level irq */
#define RS5C_REG_CTRL2		15
#	define RS5C372_CTRL2_24		(1 << 5)
#	define RS5C_CTRL2_XSTP		(1 << 4)	/* only if !R2x2x */
#	define R2x2x_CTRL2_VDET		(1 << 6)	/* only if  R2x2x */
#	define R2x2x_CTRL2_XSTP		(1 << 5)	/* only if  R2x2x */
#	define R2x2x_CTRL2_PON		(1 << 4)	/* only if  R2x2x */
#	define RS5C_CTRL2_CTFG		(1 << 2)
#	define RS5C_CTRL2_AAFG		(1 << 1)	/* or WAFG */
#	define RS5C_CTRL2_BAFG		(1 << 0)	/* or DAFG */


/* to read (style 1) or write registers starting at R */
#define RS5C_ADDR(R)		(((R) << 4) | 0)


enum rtc_type {
	rtc_undef = 0,
	rtc_r2025sd,
	rtc_r2221tl,
	rtc_rs5c372a,
	rtc_rs5c372b,
	rtc_rv5c386,
	rtc_rv5c387a,
};

static const struct i2c_device_id rs5c372_id[] = {
	{ "r2025sd", rtc_r2025sd },
	{ "r2221tl", rtc_r2221tl },
	{ "rs5c372a", rtc_rs5c372a },
	{ "rs5c372b", rtc_rs5c372b },
	{ "rv5c386", rtc_rv5c386 },
	{ "rv5c387a", rtc_rv5c387a },
	{ }
};
MODULE_DEVICE_TABLE(i2c, rs5c372_id);

static const __maybe_unused struct of_device_id rs5c372_of_match[] = {
	{
		.compatible = "ricoh,r2025sd",
		.data = (void *)rtc_r2025sd
	},
	{
		.compatible = "ricoh,r2221tl",
		.data = (void *)rtc_r2221tl
	},
	{
		.compatible = "ricoh,rs5c372a",
		.data = (void *)rtc_rs5c372a
	},
	{
		.compatible = "ricoh,rs5c372b",
		.data = (void *)rtc_rs5c372b
	},
	{
		.compatible = "ricoh,rv5c386",
		.data = (void *)rtc_rv5c386
	},
	{
		.compatible = "ricoh,rv5c387a",
		.data = (void *)rtc_rv5c387a
	},
	{ }
};
MODULE_DEVICE_TABLE(of, rs5c372_of_match);

/* REVISIT:  this assumes that:
 *  - we're in the 21st century, so it's safe to ignore the century
 *    bit for rv5c38[67] (REG_MONTH bit 7);
 *  - we should use ALARM_A not ALARM_B (may be wrong on some boards)
 */
struct rs5c372 {
	struct i2c_client	*client;
	struct rtc_device	*rtc;
	enum rtc_type		type;
	unsigned		time24:1;
	unsigned		has_irq:1;
	unsigned		smbus:1;
	char			buf[17];
	char			*regs;
};

static int rs5c_get_regs(struct rs5c372 *rs5c)
{
	struct i2c_client	*client = rs5c->client;
	struct i2c_msg		msgs[] = {
		{
			.addr = client->addr,
			.flags = I2C_M_RD,
			.len = sizeof(rs5c->buf),
			.buf = rs5c->buf
		},
	};

	/* This implements the third reading method from the datasheet, using
	 * an internal address that's reset after each transaction (by STOP)
	 * to 0x0f ... so we read extra registers, and skip the first one.
	 *
	 * The first method doesn't work with the iop3xx adapter driver, on at
	 * least 80219 chips; this works around that bug.
	 *
	 * The third method on the other hand doesn't work for the SMBus-only
	 * configurations, so we use the first method there, stripping off
	 * the extra register in the process.
	 */
	if (rs5c->smbus) {
		int addr = RS5C_ADDR(RS5C372_REG_SECS);
		int size = sizeof(rs5c->buf) - 1;

		if (i2c_smbus_read_i2c_block_data(client, addr, size,
						  rs5c->buf + 1) != size) {
			dev_warn(&client->dev, "can't read registers\n");
			return -EIO;
		}
	} else {
		if ((i2c_transfer(client->adapter, msgs, 1)) != 1) {
			dev_warn(&client->dev, "can't read registers\n");
			return -EIO;
		}
	}

	dev_dbg(&client->dev,
		"%3ph (%02x) %3ph (%02x), %3ph, %3ph; %02x %02x\n",
		rs5c->regs + 0, rs5c->regs[3],
		rs5c->regs + 4, rs5c->regs[7],
		rs5c->regs + 8, rs5c->regs + 11,
		rs5c->regs[14], rs5c->regs[15]);

	return 0;
}

static unsigned rs5c_reg2hr(struct rs5c372 *rs5c, unsigned reg)
{
	unsigned	hour;

	if (rs5c->time24)
		return bcd2bin(reg & 0x3f);

	hour = bcd2bin(reg & 0x1f);
	if (hour == 12)
		hour = 0;
	if (reg & 0x20)
		hour += 12;
	return hour;
}

static unsigned rs5c_hr2reg(struct rs5c372 *rs5c, unsigned hour)
{
	if (rs5c->time24)
		return bin2bcd(hour);

	if (hour > 12)
		return 0x20 | bin2bcd(hour - 12);
	if (hour == 12)
		return 0x20 | bin2bcd(12);
	if (hour == 0)
		return bin2bcd(12);
	return bin2bcd(hour);
}

static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct rs5c372	*rs5c = i2c_get_clientdata(client);
	int		status = rs5c_get_regs(rs5c);
	unsigned char ctrl2 = rs5c->regs[RS5C_REG_CTRL2];

	if (status < 0)
		return status;

	switch (rs5c->type) {
	case rtc_r2025sd:
	case rtc_r2221tl:
		if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
		    (rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
			dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
			return -EINVAL;
		}
		break;
	default:
		if (ctrl2 & RS5C_CTRL2_XSTP) {
			dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
			return -EINVAL;
		}
	}

	tm->tm_sec = bcd2bin(rs5c->regs[RS5C372_REG_SECS] & 0x7f);
	tm->tm_min = bcd2bin(rs5c->regs[RS5C372_REG_MINS] & 0x7f);
	tm->tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C372_REG_HOURS]);

	tm->tm_wday = bcd2bin(rs5c->regs[RS5C372_REG_WDAY] & 0x07);
	tm->tm_mday = bcd2bin(rs5c->regs[RS5C372_REG_DAY] & 0x3f);

	/* tm->tm_mon is zero-based */
	tm->tm_mon = bcd2bin(rs5c->regs[RS5C372_REG_MONTH] & 0x1f) - 1;

	/* year is 1900 + tm->tm_year */
	tm->tm_year = bcd2bin(rs5c->regs[RS5C372_REG_YEAR]) + 100;

	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
		"mday=%d, mon=%d, year=%d, wday=%d\n",
		__func__,
		tm->tm_sec, tm->tm_min, tm->tm_hour,
		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

	return 0;
}

static int rs5c372_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct rs5c372	*rs5c = i2c_get_clientdata(client);
	unsigned char	buf[7];
	unsigned char	ctrl2;
	int		addr;

	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d "
		"mday=%d, mon=%d, year=%d, wday=%d\n",
		__func__,
		tm->tm_sec, tm->tm_min, tm->tm_hour,
		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

	addr   = RS5C_ADDR(RS5C372_REG_SECS);
	buf[0] = bin2bcd(tm->tm_sec);
	buf[1] = bin2bcd(tm->tm_min);
	buf[2] = rs5c_hr2reg(rs5c, tm->tm_hour);
	buf[3] = bin2bcd(tm->tm_wday);
	buf[4] = bin2bcd(tm->tm_mday);
	buf[5] = bin2bcd(tm->tm_mon + 1);
	buf[6] = bin2bcd(tm->tm_year - 100);

	if (i2c_smbus_write_i2c_block_data(client, addr, sizeof(buf), buf) < 0) {
		dev_dbg(&client->dev, "%s: write error in line %i\n",
			__func__, __LINE__);
		return -EIO;
	}

	addr = RS5C_ADDR(RS5C_REG_CTRL2);
	ctrl2 = i2c_smbus_read_byte_data(client, addr);

	/* clear rtc warning bits */
	switch (rs5c->type) {
	case rtc_r2025sd:
	case rtc_r2221tl:
		ctrl2 &= ~(R2x2x_CTRL2_VDET | R2x2x_CTRL2_PON);
		if (rs5c->type == rtc_r2025sd)
			ctrl2 |= R2x2x_CTRL2_XSTP;
		else
			ctrl2 &= ~R2x2x_CTRL2_XSTP;
		break;
	default:
		ctrl2 &= ~RS5C_CTRL2_XSTP;
		break;
	}

	if (i2c_smbus_write_byte_data(client, addr, ctrl2) < 0) {
		dev_dbg(&client->dev, "%s: write error in line %i\n",
			__func__, __LINE__);
		return -EIO;
	}

	return 0;
}

#if IS_ENABLED(CONFIG_RTC_INTF_PROC)
#define	NEED_TRIM
#endif

#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)
#define	NEED_TRIM
#endif

#ifdef	NEED_TRIM
static int rs5c372_get_trim(struct i2c_client *client, int *osc, int *trim)
{
	struct rs5c372 *rs5c372 = i2c_get_clientdata(client);
	u8 tmp = rs5c372->regs[RS5C372_REG_TRIM];

	if (osc) {
		if (rs5c372->type == rtc_rs5c372a || rs5c372->type == rtc_rs5c372b)
			*osc = (tmp & RS5C372_TRIM_XSL) ? 32000 : 32768;
		else
			*osc = 32768;
	}

	if (trim) {
		dev_dbg(&client->dev, "%s: raw trim=%x\n", __func__, tmp);
		tmp &= RS5C372_TRIM_MASK;
		if (tmp & 0x3e) {
			int t = tmp & 0x3f;

			if (tmp & 0x40)
				t = (~t | (s8)0xc0) + 1;
			else
				t = t - 1;

			tmp = t * 2;
		} else
			tmp = 0;
		*trim = tmp;
	}

	return 0;
}
#endif

static int rs5c_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct i2c_client	*client = to_i2c_client(dev);
	struct rs5c372		*rs5c = i2c_get_clientdata(client);
	unsigned char		buf;
	int			status, addr;

	buf = rs5c->regs[RS5C_REG_CTRL1];

	if (!rs5c->has_irq)
		return -EINVAL;

	status = rs5c_get_regs(rs5c);
	if (status < 0)
		return status;

	addr = RS5C_ADDR(RS5C_REG_CTRL1);
	if (enabled)
		buf |= RS5C_CTRL1_AALE;
	else
		buf &= ~RS5C_CTRL1_AALE;

	if (i2c_smbus_write_byte_data(client, addr, buf) < 0) {
		dev_warn(dev, "can't update alarm\n");
		status = -EIO;
	} else
		rs5c->regs[RS5C_REG_CTRL1] = buf;

	return status;
}


/* NOTE:  Since RTC_WKALM_{RD,SET} were originally defined for EFI,
 * which only exposes a polled programming interface; and since
 * these calls map directly to those EFI requests; we don't demand
 * we have an IRQ for this chip when we go through this API.
 *
 * The older x86_pc derived RTC_ALM_{READ,SET} calls require irqs
 * though, managed through RTC_AIE_{ON,OFF} requests.
 */

static int rs5c_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client	*client = to_i2c_client(dev);
	struct rs5c372		*rs5c = i2c_get_clientdata(client);
	int			status;

	status = rs5c_get_regs(rs5c);
	if (status < 0)
		return status;

	/* report alarm time */
	t->time.tm_sec = 0;
	t->time.tm_min = bcd2bin(rs5c->regs[RS5C_REG_ALARM_A_MIN] & 0x7f);
	t->time.tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C_REG_ALARM_A_HOURS]);

	/* ... and status */
	t->enabled = !!(rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE);
	t->pending = !!(rs5c->regs[RS5C_REG_CTRL2] & RS5C_CTRL2_AAFG);

	return 0;
}

static int rs5c_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
	struct i2c_client	*client = to_i2c_client(dev);
	struct rs5c372		*rs5c = i2c_get_clientdata(client);
	int			status, addr, i;
	unsigned char		buf[3];

	/* only handle up to 24 hours in the future, like RTC_ALM_SET */
	if (t->time.tm_mday != -1
			|| t->time.tm_mon != -1
			|| t->time.tm_year != -1)
		return -EINVAL;

	/* REVISIT: round up tm_sec */

	/* if needed, disable irq (clears pending status) */
	status = rs5c_get_regs(rs5c);
	if (status < 0)
		return status;
	if (rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE) {
		addr = RS5C_ADDR(RS5C_REG_CTRL1);
		buf[0] = rs5c->regs[RS5C_REG_CTRL1] & ~RS5C_CTRL1_AALE;
		if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0) {
			dev_dbg(dev, "can't disable alarm\n");
			return -EIO;
		}
		rs5c->regs[RS5C_REG_CTRL1] = buf[0];
	}

	/* set alarm */
	buf[0] = bin2bcd(t->time.tm_min);
	buf[1] = rs5c_hr2reg(rs5c, t->time.tm_hour);
	buf[2] = 0x7f;	/* any/all days */

	for (i = 0; i < sizeof(buf); i++) {
		addr = RS5C_ADDR(RS5C_REG_ALARM_A_MIN + i);
		if (i2c_smbus_write_byte_data(client, addr, buf[i]) < 0) {
			dev_dbg(dev, "can't set alarm time\n");
			return -EIO;
		}
	}

	/* ... and maybe enable its irq */
	if (t->enabled) {
		addr = RS5C_ADDR(RS5C_REG_CTRL1);
		buf[0] = rs5c->regs[RS5C_REG_CTRL1] | RS5C_CTRL1_AALE;
		if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0)
			dev_warn(dev, "can't enable alarm\n");
		rs5c->regs[RS5C_REG_CTRL1] = buf[0];
	}

	return 0;
}

#if IS_ENABLED(CONFIG_RTC_INTF_PROC)

static int rs5c372_rtc_proc(struct device *dev, struct seq_file *seq)
{
	int err, osc, trim;

	err = rs5c372_get_trim(to_i2c_client(dev), &osc, &trim);
	if (err == 0) {
		seq_printf(seq, "crystal\t\t: %d.%03d KHz\n",
				osc / 1000, osc % 1000);
		seq_printf(seq, "trim\t\t: %d\n", trim);
	}

	return 0;
}

#else
#define	rs5c372_rtc_proc	NULL
#endif

#ifdef CONFIG_RTC_INTF_DEV
static int rs5c372_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
	struct rs5c372	*rs5c = i2c_get_clientdata(to_i2c_client(dev));
	unsigned char	ctrl2;
	int		addr;
	unsigned int	flags;

	dev_dbg(dev, "%s: cmd=%x\n", __func__, cmd);

	addr = RS5C_ADDR(RS5C_REG_CTRL2);
	ctrl2 = i2c_smbus_read_byte_data(rs5c->client, addr);

	switch (cmd) {
	case RTC_VL_READ:
		flags = 0;

		switch (rs5c->type) {
		case rtc_r2025sd:
		case rtc_r2221tl:
			if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
				(rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
				flags |= RTC_VL_DATA_INVALID;
			}
			if (ctrl2 & R2x2x_CTRL2_VDET)
				flags |= RTC_VL_BACKUP_LOW;
			break;
		default:
			if (ctrl2 & RS5C_CTRL2_XSTP)
				flags |= RTC_VL_DATA_INVALID;
			break;
		}

		return put_user(flags, (unsigned int __user *)arg);
	case RTC_VL_CLR:
		/* clear VDET bit */
		if (rs5c->type == rtc_r2025sd || rs5c->type == rtc_r2221tl) {
			ctrl2 &= ~R2x2x_CTRL2_VDET;
			if (i2c_smbus_write_byte_data(rs5c->client, addr, ctrl2) < 0) {
				dev_dbg(&rs5c->client->dev, "%s: write error in line %i\n",
						__func__, __LINE__);
				return -EIO;
			}
		}
		return 0;
	default:
		return -ENOIOCTLCMD;
	}
	return 0;
}
#else
#define rs5c372_ioctl	NULL
#endif

static int rs5c372_read_offset(struct device *dev, long *offset)
{
	struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
	u8 val = rs5c->regs[RS5C372_REG_TRIM];
	long ppb_per_step = 0;
	bool decr = val & RS5C372_TRIM_DECR;

	switch (rs5c->type) {
	case rtc_r2221tl:
		ppb_per_step = val & R2221TL_TRIM_DEV ? 1017 : 3051;
		break;
	case rtc_rs5c372a:
	case rtc_rs5c372b:
		ppb_per_step = val & RS5C372_TRIM_XSL ? 3125 : 3051;
		break;
	default:
		ppb_per_step = 3051;
		break;
	}

	/* Only bits[0:5] repsents the time counts */
	val &= 0x3F;

	/* If bits[1:5] are all 0, it means no increment or decrement */
	if (!(val & 0x3E)) {
		*offset = 0;
	} else {
		if (decr)
			*offset = -(((~val) & 0x3F) + 1) * ppb_per_step;
		else
			*offset = (val - 1) * ppb_per_step;
	}

	return 0;
}

static int rs5c372_set_offset(struct device *dev, long offset)
{
	struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
	int addr = RS5C_ADDR(RS5C372_REG_TRIM);
	u8 val = 0;
	u8 tmp = 0;
	long ppb_per_step = 3051;
	long steps = LONG_MIN;

	switch (rs5c->type) {
	case rtc_rs5c372a:
	case rtc_rs5c372b:
		tmp = rs5c->regs[RS5C372_REG_TRIM];
		if (tmp & RS5C372_TRIM_XSL) {
			ppb_per_step = 3125;
			val |= RS5C372_TRIM_XSL;
		}
		break;
	case rtc_r2221tl:
		/*
		 * Check if it is possible to use high resolution mode (DEV=1).
		 * In this mode, the minimum resolution is 2 / (32768 * 20 * 3),
		 * which is about 1017 ppb.
		 */
		steps = DIV_ROUND_CLOSEST(offset, 1017);
		if (steps >= -0x3E && steps <= 0x3E) {
			ppb_per_step = 1017;
			val |= R2221TL_TRIM_DEV;
		} else {
			/*
			 * offset is out of the range of high resolution mode.
			 * Try to use low resolution mode (DEV=0). In this mode,
			 * the minimum resolution is 2 / (32768 * 20), which is
			 * about 3051 ppb.
			 */
			steps = LONG_MIN;
		}
		break;
	default:
		break;
	}

	if (steps == LONG_MIN) {
		steps = DIV_ROUND_CLOSEST(offset, ppb_per_step);
		if (steps > 0x3E || steps < -0x3E)
			return -ERANGE;
	}

	if (steps > 0) {
		val |= steps + 1;
	} else {
		val |= RS5C372_TRIM_DECR;
		val |= (~(-steps - 1)) & 0x3F;
	}

	if (!steps || !(val & 0x3E)) {
		/*
		 * if offset is too small, set oscillation adjustment register
		 * or time trimming register with its default value whic means
		 * no increment or decrement. But for rs5c372[a|b], the XSL bit
		 * should be kept unchanged.
		 */
		if (rs5c->type == rtc_rs5c372a || rs5c->type == rtc_rs5c372b)
			val &= RS5C372_TRIM_XSL;
		else
			val = 0;
	}

	dev_dbg(&rs5c->client->dev, "write 0x%x for offset %ld\n", val, offset);

	if (i2c_smbus_write_byte_data(rs5c->client, addr, val) < 0) {
		dev_err(&rs5c->client->dev, "failed to write 0x%x to reg %d\n", val, addr);
		return -EIO;
	}

	rs5c->regs[RS5C372_REG_TRIM] = val;

	return 0;
}

static const struct rtc_class_ops rs5c372_rtc_ops = {
	.proc		= rs5c372_rtc_proc,
	.read_time	= rs5c372_rtc_read_time,
	.set_time	= rs5c372_rtc_set_time,
	.read_alarm	= rs5c_read_alarm,
	.set_alarm	= rs5c_set_alarm,
	.alarm_irq_enable = rs5c_rtc_alarm_irq_enable,
	.ioctl		= rs5c372_ioctl,
	.read_offset    = rs5c372_read_offset,
	.set_offset     = rs5c372_set_offset,
};

#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)

static ssize_t rs5c372_sysfs_show_trim(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	int err, trim;

	err = rs5c372_get_trim(to_i2c_client(dev), NULL, &trim);
	if (err)
		return err;

	return sprintf(buf, "%d\n", trim);
}
static DEVICE_ATTR(trim, S_IRUGO, rs5c372_sysfs_show_trim, NULL);

static ssize_t rs5c372_sysfs_show_osc(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	int err, osc;

	err = rs5c372_get_trim(to_i2c_client(dev), &osc, NULL);
	if (err)
		return err;

	return sprintf(buf, "%d.%03d KHz\n", osc / 1000, osc % 1000);
}
static DEVICE_ATTR(osc, S_IRUGO, rs5c372_sysfs_show_osc, NULL);

static int rs5c_sysfs_register(struct device *dev)
{
	int err;

	err = device_create_file(dev, &dev_attr_trim);
	if (err)
		return err;
	err = device_create_file(dev, &dev_attr_osc);
	if (err)
		device_remove_file(dev, &dev_attr_trim);

	return err;
}

static void rs5c_sysfs_unregister(struct device *dev)
{
	device_remove_file(dev, &dev_attr_trim);
	device_remove_file(dev, &dev_attr_osc);
}

#else
static int rs5c_sysfs_register(struct device *dev)
{
	return 0;
}

static void rs5c_sysfs_unregister(struct device *dev)
{
	/* nothing */
}
#endif	/* SYSFS */

static struct i2c_driver rs5c372_driver;

static int rs5c_oscillator_setup(struct rs5c372 *rs5c372)
{
	unsigned char buf[2];
	int addr, i, ret = 0;

	addr   = RS5C_ADDR(RS5C_REG_CTRL1);
	buf[0] = rs5c372->regs[RS5C_REG_CTRL1];
	buf[1] = rs5c372->regs[RS5C_REG_CTRL2];

	switch (rs5c372->type) {
	case rtc_r2025sd:
		if (buf[1] & R2x2x_CTRL2_XSTP)
			return ret;
		break;
	case rtc_r2221tl:
		if (!(buf[1] & R2x2x_CTRL2_XSTP))
			return ret;
		break;
	default:
		if (!(buf[1] & RS5C_CTRL2_XSTP))
			return ret;
		break;
	}

	/* use 24hr mode */
	switch (rs5c372->type) {
	case rtc_rs5c372a:
	case rtc_rs5c372b:
		buf[1] |= RS5C372_CTRL2_24;
		rs5c372->time24 = 1;
		break;
	case rtc_r2025sd:
	case rtc_r2221tl:
	case rtc_rv5c386:
	case rtc_rv5c387a:
		buf[0] |= RV5C387_CTRL1_24;
		rs5c372->time24 = 1;
		break;
	default:
		/* impossible */
		break;
	}

	for (i = 0; i < sizeof(buf); i++) {
		addr = RS5C_ADDR(RS5C_REG_CTRL1 + i);
		ret = i2c_smbus_write_byte_data(rs5c372->client, addr, buf[i]);
		if (unlikely(ret < 0))
			return ret;
	}

	rs5c372->regs[RS5C_REG_CTRL1] = buf[0];
	rs5c372->regs[RS5C_REG_CTRL2] = buf[1];

	return 0;
}

static int rs5c372_probe(struct i2c_client *client)
{
	int err = 0;
	int smbus_mode = 0;
	struct rs5c372 *rs5c372;

	dev_dbg(&client->dev, "%s\n", __func__);

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
			I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK)) {
		/*
		 * If we don't have any master mode adapter, try breaking
		 * it down in to the barest of capabilities.
		 */
		if (i2c_check_functionality(client->adapter,
				I2C_FUNC_SMBUS_BYTE_DATA |
				I2C_FUNC_SMBUS_I2C_BLOCK))
			smbus_mode = 1;
		else {
			/* Still no good, give up */
			err = -ENODEV;
			goto exit;
		}
	}

	rs5c372 = devm_kzalloc(&client->dev, sizeof(struct rs5c372),
				GFP_KERNEL);
	if (!rs5c372) {
		err = -ENOMEM;
		goto exit;
	}

	rs5c372->client = client;
	i2c_set_clientdata(client, rs5c372);
	if (client->dev.of_node) {
		rs5c372->type = (enum rtc_type)
			of_device_get_match_data(&client->dev);
	} else {
		const struct i2c_device_id *id = i2c_match_id(rs5c372_id, client);
		rs5c372->type = id->driver_data;
	}

	/* we read registers 0x0f then 0x00-0x0f; skip the first one */
	rs5c372->regs = &rs5c372->buf[1];
	rs5c372->smbus = smbus_mode;

	err = rs5c_get_regs(rs5c372);
	if (err < 0)
		goto exit;

	/* clock may be set for am/pm or 24 hr time */
	switch (rs5c372->type) {
	case rtc_rs5c372a:
	case rtc_rs5c372b:
		/* alarm uses ALARM_A; and nINTRA on 372a, nINTR on 372b.
		 * so does periodic irq, except some 327a modes.
		 */
		if (rs5c372->regs[RS5C_REG_CTRL2] & RS5C372_CTRL2_24)
			rs5c372->time24 = 1;
		break;
	case rtc_r2025sd:
	case rtc_r2221tl:
	case rtc_rv5c386:
	case rtc_rv5c387a:
		if (rs5c372->regs[RS5C_REG_CTRL1] & RV5C387_CTRL1_24)
			rs5c372->time24 = 1;
		/* alarm uses ALARM_W; and nINTRB for alarm and periodic
		 * irq, on both 386 and 387
		 */
		break;
	default:
		dev_err(&client->dev, "unknown RTC type\n");
		goto exit;
	}

	/* if the oscillator lost power and no other software (like
	 * the bootloader) set it up, do it here.
	 *
	 * The R2025S/D does this a little differently than the other
	 * parts, so we special case that..
	 */
	err = rs5c_oscillator_setup(rs5c372);
	if (unlikely(err < 0)) {
		dev_err(&client->dev, "setup error\n");
		goto exit;
	}

	dev_info(&client->dev, "%s found, %s\n",
			({ char *s; switch (rs5c372->type) {
			case rtc_r2025sd:	s = "r2025sd"; break;
			case rtc_r2221tl:	s = "r2221tl"; break;
			case rtc_rs5c372a:	s = "rs5c372a"; break;
			case rtc_rs5c372b:	s = "rs5c372b"; break;
			case rtc_rv5c386:	s = "rv5c386"; break;
			case rtc_rv5c387a:	s = "rv5c387a"; break;
			default:		s = "chip"; break;
			}; s;}),
			rs5c372->time24 ? "24hr" : "am/pm"
			);

	/* REVISIT use client->irq to register alarm irq ... */
	rs5c372->rtc = devm_rtc_device_register(&client->dev,
					rs5c372_driver.driver.name,
					&rs5c372_rtc_ops, THIS_MODULE);

	if (IS_ERR(rs5c372->rtc)) {
		err = PTR_ERR(rs5c372->rtc);
		goto exit;
	}

	err = rs5c_sysfs_register(&client->dev);
	if (err)
		goto exit;

	return 0;

exit:
	return err;
}

static void rs5c372_remove(struct i2c_client *client)
{
	rs5c_sysfs_unregister(&client->dev);
}

static struct i2c_driver rs5c372_driver = {
	.driver		= {
		.name	= "rtc-rs5c372",
		.of_match_table = of_match_ptr(rs5c372_of_match),
	},
	.probe_new	= rs5c372_probe,
	.remove		= rs5c372_remove,
	.id_table	= rs5c372_id,
};

module_i2c_driver(rs5c372_driver);

MODULE_AUTHOR(
		"Pavel Mironchik <pmironchik@optifacio.net>, "
		"Alessandro Zummo <a.zummo@towertech.it>, "
		"Paul Mundt <lethal@linux-sh.org>");
MODULE_DESCRIPTION("Ricoh RS5C372 RTC driver");
MODULE_LICENSE("GPL");