aboutsummaryrefslogtreecommitdiffstats
path: root/target/linux/brcm2708/patches-4.19/950-0341-rtc-rv3028-add-new-driver.patch
blob: 6a00e82300f72b47e1f483b7082cd15689c678ad (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
From bb0e317bfc453877805a12f975490ad38b6413f1 Mon Sep 17 00:00:00 2001
From: Alexandre Belloni <alexandre.belloni@bootlin.com>
Date: Wed, 13 Feb 2019 00:21:36 +0100
Subject: [PATCH] rtc: rv3028: add new driver

upstream commit e6e7376cfd7b3f9b63de3a22792f64d9bfb2ab53.

Add a driver for the MicroCrystal RV-3028. It is a SMT Real-Time Clock
Module that incorporates an integrated CMOS circuit together with an XTAL.
It has an i2c interface.

The driver handles date/time, alarms, trickle charging, timestamping,
frequency offset correction, EEPROM and NVRAM.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 Documentation/devicetree/bindings/rtc/rtc.txt |  69 ++
 drivers/rtc/Kconfig                           |   9 +
 drivers/rtc/Makefile                          |   1 +
 drivers/rtc/rtc-rv3028.c                      | 733 ++++++++++++++++++
 4 files changed, 812 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rtc/rtc.txt
 create mode 100644 drivers/rtc/rtc-rv3028.c

--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/rtc.txt
@@ -0,0 +1,69 @@
+Generic device tree bindings for Real Time Clock devices
+========================================================
+
+This document describes generic bindings which can be used to describe Real Time
+Clock devices in a device tree.
+
+Required properties
+-------------------
+
+- compatible : name of RTC device following generic names recommended practice.
+
+For other required properties e.g. to describe register sets,
+clocks, etc. check the binding documentation of the specific driver.
+
+Optional properties
+-------------------
+
+- start-year : if provided, the default hardware range supported by the RTC is
+               shifted so the first usable year is the specified one.
+
+The following properties may not be supported by all drivers. However, if a
+driver wants to support one of the below features, it should adapt the bindings
+below.
+- trickle-resistor-ohms :   Selected resistor for trickle charger. Should be given
+                            if trickle charger should be enabled
+- trickle-diode-disable :   Do not use internal trickle charger diode Should be
+                            given if internal trickle charger diode should be
+                            disabled
+- wakeup-source :           Enables wake up of host system on alarm
+- quartz-load-femtofarads : The capacitive load of the quartz(x-tal),
+                            expressed in femto Farad (fF).
+                            The default value shall be listed (if optional),
+                            and likewise all valid values.
+
+Trivial RTCs
+------------
+
+This is a list of trivial RTC devices that have simple device tree
+bindings, consisting only of a compatible field, an address and
+possibly an interrupt line.
+
+
+Compatible		Vendor / Chip
+==========		=============
+abracon,abb5zes3	AB-RTCMC-32.768kHz-B5ZE-S3: Real Time Clock/Calendar Module with I2C Interface
+dallas,ds1374		I2C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output
+dallas,ds1672		Dallas DS1672 Real-time Clock
+dallas,ds3232		Extremely Accurate I²C RTC with Integrated Crystal and SRAM
+epson,rx8010		I2C-BUS INTERFACE REAL TIME CLOCK MODULE
+epson,rx8581		I2C-BUS INTERFACE REAL TIME CLOCK MODULE
+emmicro,em3027		EM Microelectronic EM3027 Real-time Clock
+isil,isl1208		Intersil ISL1208 Low Power RTC with Battery Backed SRAM
+isil,isl1218		Intersil ISL1218 Low Power RTC with Battery Backed SRAM
+isil,isl12022		Intersil ISL12022 Real-time Clock
+microcrystal,rv3028	Real Time Clock Module with I2C-Bus
+microcrystal,rv3029	Real Time Clock Module with I2C-Bus
+microcrystal,rv8523	Real Time Clock
+nxp,pcf2127		Real-time clock
+nxp,pcf2129		Real-time clock
+nxp,pcf8563		Real-time clock/calendar
+pericom,pt7c4338	Real-time Clock Module
+ricoh,r2025sd		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,r2221tl		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rs5c372a		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rs5c372b		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rv5c386		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+ricoh,rv5c387a		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
+sii,s35390a		2-wire CMOS real-time clock
+whwave,sd3078		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -625,6 +625,15 @@ config RTC_DRV_EM3027
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-em3027.
 
+config RTC_DRV_RV3028
+	tristate "Micro Crystal RV3028"
+	help
+	  If you say yes here you get support for the Micro Crystal
+	  RV3028.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-rv3028.
+
 config RTC_DRV_RV8803
 	tristate "Micro Crystal RV8803, Epson RX8900"
 	help
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -136,6 +136,7 @@ obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_RTD119X)	+= rtc-rtd119x.o
+obj-$(CONFIG_RTC_DRV_RV3028)	+= rtc-rv3028.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o
--- /dev/null
+++ b/drivers/rtc/rtc-rv3028.c
@@ -0,0 +1,733 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC driver for the Micro Crystal RV3028
+ *
+ * Copyright (C) 2019 Micro Crystal SA
+ *
+ * Alexandre Belloni <alexandre.belloni@bootlin.com>
+ *
+ */
+
+#include <linux/bcd.h>
+#include <linux/bitops.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/log2.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include "rtc-core.h"
+
+#define RV3028_SEC			0x00
+#define RV3028_MIN			0x01
+#define RV3028_HOUR			0x02
+#define RV3028_WDAY			0x03
+#define RV3028_DAY			0x04
+#define RV3028_MONTH			0x05
+#define RV3028_YEAR			0x06
+#define RV3028_ALARM_MIN		0x07
+#define RV3028_ALARM_HOUR		0x08
+#define RV3028_ALARM_DAY		0x09
+#define RV3028_STATUS			0x0E
+#define RV3028_CTRL1			0x0F
+#define RV3028_CTRL2			0x10
+#define RV3028_EVT_CTRL			0x13
+#define RV3028_TS_COUNT			0x14
+#define RV3028_TS_SEC			0x15
+#define RV3028_RAM1			0x1F
+#define RV3028_EEPROM_ADDR		0x25
+#define RV3028_EEPROM_DATA		0x26
+#define RV3028_EEPROM_CMD		0x27
+#define RV3028_CLKOUT			0x35
+#define RV3028_OFFSET			0x36
+#define RV3028_BACKUP			0x37
+
+#define RV3028_STATUS_PORF		BIT(0)
+#define RV3028_STATUS_EVF		BIT(1)
+#define RV3028_STATUS_AF		BIT(2)
+#define RV3028_STATUS_TF		BIT(3)
+#define RV3028_STATUS_UF		BIT(4)
+#define RV3028_STATUS_BSF		BIT(5)
+#define RV3028_STATUS_CLKF		BIT(6)
+#define RV3028_STATUS_EEBUSY		BIT(7)
+
+#define RV3028_CTRL1_EERD		BIT(3)
+#define RV3028_CTRL1_WADA		BIT(5)
+
+#define RV3028_CTRL2_RESET		BIT(0)
+#define RV3028_CTRL2_12_24		BIT(1)
+#define RV3028_CTRL2_EIE		BIT(2)
+#define RV3028_CTRL2_AIE		BIT(3)
+#define RV3028_CTRL2_TIE		BIT(4)
+#define RV3028_CTRL2_UIE		BIT(5)
+#define RV3028_CTRL2_TSE		BIT(7)
+
+#define RV3028_EVT_CTRL_TSR		BIT(2)
+
+#define RV3028_EEPROM_CMD_WRITE		0x21
+#define RV3028_EEPROM_CMD_READ		0x22
+
+#define RV3028_EEBUSY_POLL		10000
+#define RV3028_EEBUSY_TIMEOUT		100000
+
+#define RV3028_BACKUP_TCE		BIT(5)
+#define RV3028_BACKUP_TCR_MASK		GENMASK(1,0)
+
+#define OFFSET_STEP_PPT			953674
+
+enum rv3028_type {
+	rv_3028,
+};
+
+struct rv3028_data {
+	struct regmap *regmap;
+	struct rtc_device *rtc;
+	enum rv3028_type type;
+};
+
+static u16 rv3028_trickle_resistors[] = {1000, 3000, 6000, 11000};
+
+static ssize_t timestamp0_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
+
+	regmap_update_bits(rv3028->regmap, RV3028_EVT_CTRL, RV3028_EVT_CTRL_TSR,
+			   RV3028_EVT_CTRL_TSR);
+
+	return count;
+};
+
+static ssize_t timestamp0_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
+	struct rtc_time tm;
+	int ret, count;
+	u8 date[6];
+
+	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
+	if (ret)
+		return ret;
+
+	if (!count)
+		return 0;
+
+	ret = regmap_bulk_read(rv3028->regmap, RV3028_TS_SEC, date,
+			       sizeof(date));
+	if (ret)
+		return ret;
+
+	tm.tm_sec = bcd2bin(date[0]);
+	tm.tm_min = bcd2bin(date[1]);
+	tm.tm_hour = bcd2bin(date[2]);
+	tm.tm_mday = bcd2bin(date[3]);
+	tm.tm_mon = bcd2bin(date[4]) - 1;
+	tm.tm_year = bcd2bin(date[5]) + 100;
+
+	ret = rtc_valid_tm(&tm);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%llu\n",
+		       (unsigned long long)rtc_tm_to_time64(&tm));
+};
+
+static DEVICE_ATTR_RW(timestamp0);
+
+static ssize_t timestamp0_count_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
+	int ret, count;
+
+	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%u\n", count);
+};
+
+static DEVICE_ATTR_RO(timestamp0_count);
+
+static struct attribute *rv3028_attrs[] = {
+	&dev_attr_timestamp0.attr,
+	&dev_attr_timestamp0_count.attr,
+	NULL
+};
+
+static const struct attribute_group rv3028_attr_group = {
+	.attrs	= rv3028_attrs,
+};
+
+static irqreturn_t rv3028_handle_irq(int irq, void *dev_id)
+{
+	struct rv3028_data *rv3028 = dev_id;
+	unsigned long events = 0;
+	u32 status = 0, ctrl = 0;
+
+	if (regmap_read(rv3028->regmap, RV3028_STATUS, &status) < 0 ||
+	   status == 0) {
+		return IRQ_NONE;
+	}
+
+	if (status & RV3028_STATUS_PORF)
+		dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");
+
+	if (status & RV3028_STATUS_TF) {
+		status |= RV3028_STATUS_TF;
+		ctrl |= RV3028_CTRL2_TIE;
+		events |= RTC_PF;
+	}
+
+	if (status & RV3028_STATUS_AF) {
+		status |= RV3028_STATUS_AF;
+		ctrl |= RV3028_CTRL2_AIE;
+		events |= RTC_AF;
+	}
+
+	if (status & RV3028_STATUS_UF) {
+		status |= RV3028_STATUS_UF;
+		ctrl |= RV3028_CTRL2_UIE;
+		events |= RTC_UF;
+	}
+
+	if (events) {
+		rtc_update_irq(rv3028->rtc, 1, events);
+		regmap_update_bits(rv3028->regmap, RV3028_STATUS, status, 0);
+		regmap_update_bits(rv3028->regmap, RV3028_CTRL2, ctrl, 0);
+	}
+
+	if (status & RV3028_STATUS_EVF) {
+		sysfs_notify(&rv3028->rtc->dev.kobj, NULL,
+			     dev_attr_timestamp0.attr.name);
+		dev_warn(&rv3028->rtc->dev, "event detected");
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int rv3028_get_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	u8 date[7];
+	int ret, status;
+
+	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
+	if (ret < 0)
+		return ret;
+
+	if (status & RV3028_STATUS_PORF) {
+		dev_warn(dev, "Voltage low, data is invalid.\n");
+		return -EINVAL;
+	}
+
+	ret = regmap_bulk_read(rv3028->regmap, RV3028_SEC, date, sizeof(date));
+	if (ret)
+		return ret;
+
+	tm->tm_sec  = bcd2bin(date[RV3028_SEC] & 0x7f);
+	tm->tm_min  = bcd2bin(date[RV3028_MIN] & 0x7f);
+	tm->tm_hour = bcd2bin(date[RV3028_HOUR] & 0x3f);
+	tm->tm_wday = ilog2(date[RV3028_WDAY] & 0x7f);
+	tm->tm_mday = bcd2bin(date[RV3028_DAY] & 0x3f);
+	tm->tm_mon  = bcd2bin(date[RV3028_MONTH] & 0x1f) - 1;
+	tm->tm_year = bcd2bin(date[RV3028_YEAR]) + 100;
+
+	return 0;
+}
+
+static int rv3028_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	u8 date[7];
+	int ret;
+
+	date[RV3028_SEC]   = bin2bcd(tm->tm_sec);
+	date[RV3028_MIN]   = bin2bcd(tm->tm_min);
+	date[RV3028_HOUR]  = bin2bcd(tm->tm_hour);
+	date[RV3028_WDAY]  = 1 << (tm->tm_wday);
+	date[RV3028_DAY]   = bin2bcd(tm->tm_mday);
+	date[RV3028_MONTH] = bin2bcd(tm->tm_mon + 1);
+	date[RV3028_YEAR]  = bin2bcd(tm->tm_year - 100);
+
+	/*
+	 * Writing to the Seconds register has the same effect as setting RESET
+	 * bit to 1
+	 */
+	ret = regmap_bulk_write(rv3028->regmap, RV3028_SEC, date,
+				sizeof(date));
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
+				 RV3028_STATUS_PORF, 0);
+
+	return ret;
+}
+
+static int rv3028_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	u8 alarmvals[3];
+	int status, ctrl, ret;
+
+	ret = regmap_bulk_read(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
+			       sizeof(alarmvals));
+	if (ret)
+		return ret;
+
+	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_read(rv3028->regmap, RV3028_CTRL2, &ctrl);
+	if (ret < 0)
+		return ret;
+
+	alrm->time.tm_sec  = 0;
+	alrm->time.tm_min  = bcd2bin(alarmvals[0] & 0x7f);
+	alrm->time.tm_hour = bcd2bin(alarmvals[1] & 0x3f);
+	alrm->time.tm_mday = bcd2bin(alarmvals[2] & 0x3f);
+
+	alrm->enabled = !!(ctrl & RV3028_CTRL2_AIE);
+	alrm->pending = (status & RV3028_STATUS_AF) && alrm->enabled;
+
+	return 0;
+}
+
+static int rv3028_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	u8 alarmvals[3];
+	u8 ctrl = 0;
+	int ret;
+
+	/* The alarm has no seconds, round up to nearest minute */
+	if (alrm->time.tm_sec) {
+		time64_t alarm_time = rtc_tm_to_time64(&alrm->time);
+
+		alarm_time += 60 - alrm->time.tm_sec;
+		rtc_time64_to_tm(alarm_time, &alrm->time);
+	}
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
+				 RV3028_CTRL2_AIE | RV3028_CTRL2_UIE, 0);
+	if (ret)
+		return ret;
+
+	alarmvals[0] = bin2bcd(alrm->time.tm_min);
+	alarmvals[1] = bin2bcd(alrm->time.tm_hour);
+	alarmvals[2] = bin2bcd(alrm->time.tm_mday);
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
+				 RV3028_STATUS_AF, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_write(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
+				sizeof(alarmvals));
+	if (ret)
+		return ret;
+
+	if (alrm->enabled) {
+		if (rv3028->rtc->uie_rtctimer.enabled)
+			ctrl |= RV3028_CTRL2_UIE;
+		if (rv3028->rtc->aie_timer.enabled)
+			ctrl |= RV3028_CTRL2_AIE;
+	}
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
+				 RV3028_CTRL2_UIE | RV3028_CTRL2_AIE, ctrl);
+
+	return ret;
+}
+
+static int rv3028_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	int ctrl = 0, ret;
+
+	if (enabled) {
+		if (rv3028->rtc->uie_rtctimer.enabled)
+			ctrl |= RV3028_CTRL2_UIE;
+		if (rv3028->rtc->aie_timer.enabled)
+			ctrl |= RV3028_CTRL2_AIE;
+	}
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
+				 RV3028_STATUS_AF | RV3028_STATUS_UF, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
+				 RV3028_CTRL2_UIE | RV3028_CTRL2_AIE, ctrl);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int rv3028_read_offset(struct device *dev, long *offset)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	int ret, value, steps;
+
+	ret = regmap_read(rv3028->regmap, RV3028_OFFSET, &value);
+	if (ret < 0)
+		return ret;
+
+	steps = sign_extend32(value << 1, 8);
+
+	ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &value);
+	if (ret < 0)
+		return ret;
+
+	steps += value >> 7;
+
+	*offset = DIV_ROUND_CLOSEST(steps * OFFSET_STEP_PPT, 1000);
+
+	return 0;
+}
+
+static int rv3028_set_offset(struct device *dev, long offset)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	int ret;
+
+	offset = clamp(offset, -244141L, 243187L) * 1000;
+	offset = DIV_ROUND_CLOSEST(offset, OFFSET_STEP_PPT);
+
+	ret = regmap_write(rv3028->regmap, RV3028_OFFSET, offset >> 1);
+	if (ret < 0)
+		return ret;
+
+	return regmap_update_bits(rv3028->regmap, RV3028_BACKUP, BIT(7),
+				  offset << 7);
+}
+
+static int rv3028_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
+	int status, ret = 0;
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
+		if (ret < 0)
+			return ret;
+
+		if (status & RV3028_STATUS_PORF)
+			dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");
+
+		status &= RV3028_STATUS_PORF;
+
+		if (copy_to_user((void __user *)arg, &status, sizeof(int)))
+			return -EFAULT;
+
+		return 0;
+
+	case RTC_VL_CLR:
+		ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
+					 RV3028_STATUS_PORF, 0);
+
+		return ret;
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+static int rv3028_nvram_write(void *priv, unsigned int offset, void *val,
+			      size_t bytes)
+{
+	return regmap_bulk_write(priv, RV3028_RAM1 + offset, val, bytes);
+}
+
+static int rv3028_nvram_read(void *priv, unsigned int offset, void *val,
+			     size_t bytes)
+{
+	return regmap_bulk_read(priv, RV3028_RAM1 + offset, val, bytes);
+}
+
+static int rv3028_eeprom_write(void *priv, unsigned int offset, void *val,
+			       size_t bytes)
+{
+	u32 status, ctrl1;
+	int i, ret, err;
+	u8 *buf = val;
+
+	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
+	if (ret)
+		return ret;
+
+	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
+		ret = regmap_update_bits(priv, RV3028_CTRL1,
+					 RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
+		if (ret)
+			return ret;
+
+		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
+					       !(status & RV3028_STATUS_EEBUSY),
+					       RV3028_EEBUSY_POLL,
+					       RV3028_EEBUSY_TIMEOUT);
+		if (ret)
+			goto restore_eerd;
+	}
+
+	for (i = 0; i < bytes; i++) {
+		ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_write(priv, RV3028_EEPROM_DATA, buf[i]);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_write(priv, RV3028_EEPROM_CMD,
+				   RV3028_EEPROM_CMD_WRITE);
+		if (ret)
+			goto restore_eerd;
+
+		usleep_range(RV3028_EEBUSY_POLL, RV3028_EEBUSY_TIMEOUT);
+
+		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
+					       !(status & RV3028_STATUS_EEBUSY),
+					       RV3028_EEBUSY_POLL,
+					       RV3028_EEBUSY_TIMEOUT);
+		if (ret)
+			goto restore_eerd;
+	}
+
+restore_eerd:
+	if (!(ctrl1 & RV3028_CTRL1_EERD))
+	{
+		err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
+					 0);
+		if (err && !ret)
+			ret = err;
+	}
+
+	return ret;
+}
+
+static int rv3028_eeprom_read(void *priv, unsigned int offset, void *val,
+			      size_t bytes)
+{
+	u32 status, ctrl1, data;
+	int i, ret, err;
+	u8 *buf = val;
+
+	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
+	if (ret)
+		return ret;
+
+	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
+		ret = regmap_update_bits(priv, RV3028_CTRL1,
+					 RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
+		if (ret)
+			return ret;
+
+		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
+					       !(status & RV3028_STATUS_EEBUSY),
+					       RV3028_EEBUSY_POLL,
+					       RV3028_EEBUSY_TIMEOUT);
+		if (ret)
+			goto restore_eerd;
+	}
+
+	for (i = 0; i < bytes; i++) {
+		ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_write(priv, RV3028_EEPROM_CMD,
+				   RV3028_EEPROM_CMD_READ);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
+					       !(status & RV3028_STATUS_EEBUSY),
+					       RV3028_EEBUSY_POLL,
+					       RV3028_EEBUSY_TIMEOUT);
+		if (ret)
+			goto restore_eerd;
+
+		ret = regmap_read(priv, RV3028_EEPROM_DATA, &data);
+		if (ret)
+			goto restore_eerd;
+		buf[i] = data;
+	}
+
+restore_eerd:
+	if (!(ctrl1 & RV3028_CTRL1_EERD))
+	{
+		err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
+					 0);
+		if (err && !ret)
+			ret = err;
+	}
+
+	return ret;
+}
+
+static struct rtc_class_ops rv3028_rtc_ops = {
+	.read_time = rv3028_get_time,
+	.set_time = rv3028_set_time,
+	.read_offset = rv3028_read_offset,
+	.set_offset = rv3028_set_offset,
+	.ioctl = rv3028_ioctl,
+};
+
+static const struct regmap_config regmap_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+        .max_register = 0x37,
+};
+
+static int rv3028_probe(struct i2c_client *client)
+{
+	struct rv3028_data *rv3028;
+	int ret, status;
+	u32 ohms;
+	struct nvmem_config nvmem_cfg = {
+		.name = "rv3028_nvram",
+		.word_size = 1,
+		.stride = 1,
+		.size = 2,
+		.type = NVMEM_TYPE_BATTERY_BACKED,
+		.reg_read = rv3028_nvram_read,
+		.reg_write = rv3028_nvram_write,
+	};
+	struct nvmem_config eeprom_cfg = {
+		.name = "rv3028_eeprom",
+		.word_size = 1,
+		.stride = 1,
+		.size = 43,
+		.type = NVMEM_TYPE_EEPROM,
+		.reg_read = rv3028_eeprom_read,
+		.reg_write = rv3028_eeprom_write,
+	};
+
+	rv3028 = devm_kzalloc(&client->dev, sizeof(struct rv3028_data),
+			      GFP_KERNEL);
+	if (!rv3028)
+		return -ENOMEM;
+
+	rv3028->regmap = devm_regmap_init_i2c(client, &regmap_config);
+
+	i2c_set_clientdata(client, rv3028);
+
+	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
+	if (ret < 0)
+		return ret;
+
+	if (status & RV3028_STATUS_PORF)
+		dev_warn(&client->dev, "Voltage low, data loss detected.\n");
+
+	if (status & RV3028_STATUS_AF)
+		dev_warn(&client->dev, "An alarm may have been missed.\n");
+
+	rv3028->rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(rv3028->rtc)) {
+		return PTR_ERR(rv3028->rtc);
+	}
+
+	if (client->irq > 0) {
+		ret = devm_request_threaded_irq(&client->dev, client->irq,
+						NULL, rv3028_handle_irq,
+						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+						"rv3028", rv3028);
+		if (ret) {
+			dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
+			client->irq = 0;
+		} else {
+			rv3028_rtc_ops.read_alarm = rv3028_get_alarm;
+			rv3028_rtc_ops.set_alarm = rv3028_set_alarm;
+			rv3028_rtc_ops.alarm_irq_enable = rv3028_alarm_irq_enable;
+		}
+	}
+
+	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL1,
+				 RV3028_CTRL1_WADA, RV3028_CTRL1_WADA);
+	if (ret)
+		return ret;
+
+	/* setup timestamping */
+	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
+				 RV3028_CTRL2_EIE | RV3028_CTRL2_TSE,
+				 RV3028_CTRL2_EIE | RV3028_CTRL2_TSE);
+	if (ret)
+		return ret;
+
+	/* setup trickle charger */
+	if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
+				      &ohms)) {
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
+			if (ohms == rv3028_trickle_resistors[i])
+				break;
+
+		if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
+			ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
+						 RV3028_BACKUP_TCE |
+						 RV3028_BACKUP_TCR_MASK,
+						 RV3028_BACKUP_TCE | i);
+			if (ret)
+				return ret;
+		} else {
+			dev_warn(&client->dev, "invalid trickle resistor value\n");
+		}
+	}
+
+	ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
+	if (ret)
+		return ret;
+
+	rv3028->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	rv3028->rtc->range_max = RTC_TIMESTAMP_END_2099;
+	rv3028->rtc->ops = &rv3028_rtc_ops;
+	ret = rtc_register_device(rv3028->rtc);
+	if (ret)
+		return ret;
+
+	nvmem_cfg.priv = rv3028->regmap;
+	rtc_nvmem_register(rv3028->rtc, &nvmem_cfg);
+	eeprom_cfg.priv = rv3028->regmap;
+	rtc_nvmem_register(rv3028->rtc, &eeprom_cfg);
+
+	rv3028->rtc->max_user_freq = 1;
+
+	return 0;
+}
+
+static const struct of_device_id rv3028_of_match[] = {
+	{ .compatible = "microcrystal,rv3028", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rv3028_of_match);
+
+static struct i2c_driver rv3028_driver = {
+	.driver = {
+		.name = "rtc-rv3028",
+		.of_match_table = of_match_ptr(rv3028_of_match),
+	},
+	.probe_new	= rv3028_probe,
+};
+module_i2c_driver(rv3028_driver);
+
+MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@bootlin.com>");
+MODULE_DESCRIPTION("Micro Crystal RV3028 RTC driver");
+MODULE_LICENSE("GPL v2");