xref: /openbmc/linux/drivers/rtc/rtc-ds1307.c (revision 2fa49589)
1 /*
2  * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
3  *
4  *  Copyright (C) 2005 James Chapman (ds1337 core)
5  *  Copyright (C) 2006 David Brownell
6  *  Copyright (C) 2009 Matthias Fuchs (rx8025 support)
7  *  Copyright (C) 2012 Bertrand Achard (nvram access fixes)
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  */
13 
14 #include <linux/acpi.h>
15 #include <linux/bcd.h>
16 #include <linux/i2c.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/of_device.h>
20 #include <linux/rtc/ds1307.h>
21 #include <linux/rtc.h>
22 #include <linux/slab.h>
23 #include <linux/string.h>
24 #include <linux/hwmon.h>
25 #include <linux/hwmon-sysfs.h>
26 #include <linux/clk-provider.h>
27 #include <linux/regmap.h>
28 
29 /*
30  * We can't determine type by probing, but if we expect pre-Linux code
31  * to have set the chip up as a clock (turning on the oscillator and
32  * setting the date and time), Linux can ignore the non-clock features.
33  * That's a natural job for a factory or repair bench.
34  */
35 enum ds_type {
36 	ds_1307,
37 	ds_1308,
38 	ds_1337,
39 	ds_1338,
40 	ds_1339,
41 	ds_1340,
42 	ds_1341,
43 	ds_1388,
44 	ds_3231,
45 	m41t0,
46 	m41t00,
47 	m41t11,
48 	mcp794xx,
49 	rx_8025,
50 	rx_8130,
51 	last_ds_type /* always last */
52 	/* rs5c372 too?  different address... */
53 };
54 
55 /* RTC registers don't differ much, except for the century flag */
56 #define DS1307_REG_SECS		0x00	/* 00-59 */
57 #	define DS1307_BIT_CH		0x80
58 #	define DS1340_BIT_nEOSC		0x80
59 #	define MCP794XX_BIT_ST		0x80
60 #define DS1307_REG_MIN		0x01	/* 00-59 */
61 #	define M41T0_BIT_OF		0x80
62 #define DS1307_REG_HOUR		0x02	/* 00-23, or 1-12{am,pm} */
63 #	define DS1307_BIT_12HR		0x40	/* in REG_HOUR */
64 #	define DS1307_BIT_PM		0x20	/* in REG_HOUR */
65 #	define DS1340_BIT_CENTURY_EN	0x80	/* in REG_HOUR */
66 #	define DS1340_BIT_CENTURY	0x40	/* in REG_HOUR */
67 #define DS1307_REG_WDAY		0x03	/* 01-07 */
68 #	define MCP794XX_BIT_VBATEN	0x08
69 #define DS1307_REG_MDAY		0x04	/* 01-31 */
70 #define DS1307_REG_MONTH	0x05	/* 01-12 */
71 #	define DS1337_BIT_CENTURY	0x80	/* in REG_MONTH */
72 #define DS1307_REG_YEAR		0x06	/* 00-99 */
73 
74 /*
75  * Other registers (control, status, alarms, trickle charge, NVRAM, etc)
76  * start at 7, and they differ a LOT. Only control and status matter for
77  * basic RTC date and time functionality; be careful using them.
78  */
79 #define DS1307_REG_CONTROL	0x07		/* or ds1338 */
80 #	define DS1307_BIT_OUT		0x80
81 #	define DS1338_BIT_OSF		0x20
82 #	define DS1307_BIT_SQWE		0x10
83 #	define DS1307_BIT_RS1		0x02
84 #	define DS1307_BIT_RS0		0x01
85 #define DS1337_REG_CONTROL	0x0e
86 #	define DS1337_BIT_nEOSC		0x80
87 #	define DS1339_BIT_BBSQI		0x20
88 #	define DS3231_BIT_BBSQW		0x40 /* same as BBSQI */
89 #	define DS1337_BIT_RS2		0x10
90 #	define DS1337_BIT_RS1		0x08
91 #	define DS1337_BIT_INTCN		0x04
92 #	define DS1337_BIT_A2IE		0x02
93 #	define DS1337_BIT_A1IE		0x01
94 #define DS1340_REG_CONTROL	0x07
95 #	define DS1340_BIT_OUT		0x80
96 #	define DS1340_BIT_FT		0x40
97 #	define DS1340_BIT_CALIB_SIGN	0x20
98 #	define DS1340_M_CALIBRATION	0x1f
99 #define DS1340_REG_FLAG		0x09
100 #	define DS1340_BIT_OSF		0x80
101 #define DS1337_REG_STATUS	0x0f
102 #	define DS1337_BIT_OSF		0x80
103 #	define DS3231_BIT_EN32KHZ	0x08
104 #	define DS1337_BIT_A2I		0x02
105 #	define DS1337_BIT_A1I		0x01
106 #define DS1339_REG_ALARM1_SECS	0x07
107 
108 #define DS13XX_TRICKLE_CHARGER_MAGIC	0xa0
109 
110 #define RX8025_REG_CTRL1	0x0e
111 #	define RX8025_BIT_2412		0x20
112 #define RX8025_REG_CTRL2	0x0f
113 #	define RX8025_BIT_PON		0x10
114 #	define RX8025_BIT_VDET		0x40
115 #	define RX8025_BIT_XST		0x20
116 
117 #define M41TXX_REG_CONTROL	0x07
118 #	define M41TXX_BIT_OUT		BIT(7)
119 #	define M41TXX_BIT_FT		BIT(6)
120 #	define M41TXX_BIT_CALIB_SIGN	BIT(5)
121 #	define M41TXX_M_CALIBRATION	GENMASK(4, 0)
122 
123 /* negative offset step is -2.034ppm */
124 #define M41TXX_NEG_OFFSET_STEP_PPB	2034
125 /* positive offset step is +4.068ppm */
126 #define M41TXX_POS_OFFSET_STEP_PPB	4068
127 /* Min and max values supported with 'offset' interface by M41TXX */
128 #define M41TXX_MIN_OFFSET	((-31) * M41TXX_NEG_OFFSET_STEP_PPB)
129 #define M41TXX_MAX_OFFSET	((31) * M41TXX_POS_OFFSET_STEP_PPB)
130 
131 struct ds1307 {
132 	enum ds_type		type;
133 	unsigned long		flags;
134 #define HAS_NVRAM	0		/* bit 0 == sysfs file active */
135 #define HAS_ALARM	1		/* bit 1 == irq claimed */
136 	struct device		*dev;
137 	struct regmap		*regmap;
138 	const char		*name;
139 	struct rtc_device	*rtc;
140 #ifdef CONFIG_COMMON_CLK
141 	struct clk_hw		clks[2];
142 #endif
143 };
144 
145 struct chip_desc {
146 	unsigned		alarm:1;
147 	u16			nvram_offset;
148 	u16			nvram_size;
149 	u8			offset; /* register's offset */
150 	u8			century_reg;
151 	u8			century_enable_bit;
152 	u8			century_bit;
153 	u8			bbsqi_bit;
154 	irq_handler_t		irq_handler;
155 	const struct rtc_class_ops *rtc_ops;
156 	u16			trickle_charger_reg;
157 	u8			(*do_trickle_setup)(struct ds1307 *, u32,
158 						    bool);
159 };
160 
161 static int ds1307_get_time(struct device *dev, struct rtc_time *t);
162 static int ds1307_set_time(struct device *dev, struct rtc_time *t);
163 static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t);
164 static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t);
165 static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled);
166 static u8 do_trickle_setup_ds1339(struct ds1307 *, u32 ohms, bool diode);
167 static irqreturn_t rx8130_irq(int irq, void *dev_id);
168 static int rx8130_read_alarm(struct device *dev, struct rtc_wkalrm *t);
169 static int rx8130_set_alarm(struct device *dev, struct rtc_wkalrm *t);
170 static int rx8130_alarm_irq_enable(struct device *dev, unsigned int enabled);
171 static irqreturn_t mcp794xx_irq(int irq, void *dev_id);
172 static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t);
173 static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t);
174 static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled);
175 static int m41txx_rtc_read_offset(struct device *dev, long *offset);
176 static int m41txx_rtc_set_offset(struct device *dev, long offset);
177 
178 static const struct rtc_class_ops rx8130_rtc_ops = {
179 	.read_time      = ds1307_get_time,
180 	.set_time       = ds1307_set_time,
181 	.read_alarm     = rx8130_read_alarm,
182 	.set_alarm      = rx8130_set_alarm,
183 	.alarm_irq_enable = rx8130_alarm_irq_enable,
184 };
185 
186 static const struct rtc_class_ops mcp794xx_rtc_ops = {
187 	.read_time      = ds1307_get_time,
188 	.set_time       = ds1307_set_time,
189 	.read_alarm     = mcp794xx_read_alarm,
190 	.set_alarm      = mcp794xx_set_alarm,
191 	.alarm_irq_enable = mcp794xx_alarm_irq_enable,
192 };
193 
194 static const struct rtc_class_ops m41txx_rtc_ops = {
195 	.read_time      = ds1307_get_time,
196 	.set_time       = ds1307_set_time,
197 	.read_alarm	= ds1337_read_alarm,
198 	.set_alarm	= ds1337_set_alarm,
199 	.alarm_irq_enable = ds1307_alarm_irq_enable,
200 	.read_offset	= m41txx_rtc_read_offset,
201 	.set_offset	= m41txx_rtc_set_offset,
202 };
203 
204 static const struct chip_desc chips[last_ds_type] = {
205 	[ds_1307] = {
206 		.nvram_offset	= 8,
207 		.nvram_size	= 56,
208 	},
209 	[ds_1308] = {
210 		.nvram_offset	= 8,
211 		.nvram_size	= 56,
212 	},
213 	[ds_1337] = {
214 		.alarm		= 1,
215 		.century_reg	= DS1307_REG_MONTH,
216 		.century_bit	= DS1337_BIT_CENTURY,
217 	},
218 	[ds_1338] = {
219 		.nvram_offset	= 8,
220 		.nvram_size	= 56,
221 	},
222 	[ds_1339] = {
223 		.alarm		= 1,
224 		.century_reg	= DS1307_REG_MONTH,
225 		.century_bit	= DS1337_BIT_CENTURY,
226 		.bbsqi_bit	= DS1339_BIT_BBSQI,
227 		.trickle_charger_reg = 0x10,
228 		.do_trickle_setup = &do_trickle_setup_ds1339,
229 	},
230 	[ds_1340] = {
231 		.century_reg	= DS1307_REG_HOUR,
232 		.century_enable_bit = DS1340_BIT_CENTURY_EN,
233 		.century_bit	= DS1340_BIT_CENTURY,
234 		.do_trickle_setup = &do_trickle_setup_ds1339,
235 		.trickle_charger_reg = 0x08,
236 	},
237 	[ds_1341] = {
238 		.century_reg	= DS1307_REG_MONTH,
239 		.century_bit	= DS1337_BIT_CENTURY,
240 	},
241 	[ds_1388] = {
242 		.offset		= 1,
243 		.trickle_charger_reg = 0x0a,
244 	},
245 	[ds_3231] = {
246 		.alarm		= 1,
247 		.century_reg	= DS1307_REG_MONTH,
248 		.century_bit	= DS1337_BIT_CENTURY,
249 		.bbsqi_bit	= DS3231_BIT_BBSQW,
250 	},
251 	[rx_8130] = {
252 		.alarm		= 1,
253 		/* this is battery backed SRAM */
254 		.nvram_offset	= 0x20,
255 		.nvram_size	= 4,	/* 32bit (4 word x 8 bit) */
256 		.offset		= 0x10,
257 		.irq_handler = rx8130_irq,
258 		.rtc_ops = &rx8130_rtc_ops,
259 	},
260 	[m41t0] = {
261 		.rtc_ops	= &m41txx_rtc_ops,
262 	},
263 	[m41t00] = {
264 		.rtc_ops	= &m41txx_rtc_ops,
265 	},
266 	[m41t11] = {
267 		/* this is battery backed SRAM */
268 		.nvram_offset	= 8,
269 		.nvram_size	= 56,
270 		.rtc_ops	= &m41txx_rtc_ops,
271 	},
272 	[mcp794xx] = {
273 		.alarm		= 1,
274 		/* this is battery backed SRAM */
275 		.nvram_offset	= 0x20,
276 		.nvram_size	= 0x40,
277 		.irq_handler = mcp794xx_irq,
278 		.rtc_ops = &mcp794xx_rtc_ops,
279 	},
280 };
281 
282 static const struct i2c_device_id ds1307_id[] = {
283 	{ "ds1307", ds_1307 },
284 	{ "ds1308", ds_1308 },
285 	{ "ds1337", ds_1337 },
286 	{ "ds1338", ds_1338 },
287 	{ "ds1339", ds_1339 },
288 	{ "ds1388", ds_1388 },
289 	{ "ds1340", ds_1340 },
290 	{ "ds1341", ds_1341 },
291 	{ "ds3231", ds_3231 },
292 	{ "m41t0", m41t0 },
293 	{ "m41t00", m41t00 },
294 	{ "m41t11", m41t11 },
295 	{ "mcp7940x", mcp794xx },
296 	{ "mcp7941x", mcp794xx },
297 	{ "pt7c4338", ds_1307 },
298 	{ "rx8025", rx_8025 },
299 	{ "isl12057", ds_1337 },
300 	{ "rx8130", rx_8130 },
301 	{ }
302 };
303 MODULE_DEVICE_TABLE(i2c, ds1307_id);
304 
305 #ifdef CONFIG_OF
306 static const struct of_device_id ds1307_of_match[] = {
307 	{
308 		.compatible = "dallas,ds1307",
309 		.data = (void *)ds_1307
310 	},
311 	{
312 		.compatible = "dallas,ds1308",
313 		.data = (void *)ds_1308
314 	},
315 	{
316 		.compatible = "dallas,ds1337",
317 		.data = (void *)ds_1337
318 	},
319 	{
320 		.compatible = "dallas,ds1338",
321 		.data = (void *)ds_1338
322 	},
323 	{
324 		.compatible = "dallas,ds1339",
325 		.data = (void *)ds_1339
326 	},
327 	{
328 		.compatible = "dallas,ds1388",
329 		.data = (void *)ds_1388
330 	},
331 	{
332 		.compatible = "dallas,ds1340",
333 		.data = (void *)ds_1340
334 	},
335 	{
336 		.compatible = "dallas,ds1341",
337 		.data = (void *)ds_1341
338 	},
339 	{
340 		.compatible = "maxim,ds3231",
341 		.data = (void *)ds_3231
342 	},
343 	{
344 		.compatible = "st,m41t0",
345 		.data = (void *)m41t0
346 	},
347 	{
348 		.compatible = "st,m41t00",
349 		.data = (void *)m41t00
350 	},
351 	{
352 		.compatible = "st,m41t11",
353 		.data = (void *)m41t11
354 	},
355 	{
356 		.compatible = "microchip,mcp7940x",
357 		.data = (void *)mcp794xx
358 	},
359 	{
360 		.compatible = "microchip,mcp7941x",
361 		.data = (void *)mcp794xx
362 	},
363 	{
364 		.compatible = "pericom,pt7c4338",
365 		.data = (void *)ds_1307
366 	},
367 	{
368 		.compatible = "epson,rx8025",
369 		.data = (void *)rx_8025
370 	},
371 	{
372 		.compatible = "isil,isl12057",
373 		.data = (void *)ds_1337
374 	},
375 	{
376 		.compatible = "epson,rx8130",
377 		.data = (void *)rx_8130
378 	},
379 	{ }
380 };
381 MODULE_DEVICE_TABLE(of, ds1307_of_match);
382 #endif
383 
384 #ifdef CONFIG_ACPI
385 static const struct acpi_device_id ds1307_acpi_ids[] = {
386 	{ .id = "DS1307", .driver_data = ds_1307 },
387 	{ .id = "DS1308", .driver_data = ds_1308 },
388 	{ .id = "DS1337", .driver_data = ds_1337 },
389 	{ .id = "DS1338", .driver_data = ds_1338 },
390 	{ .id = "DS1339", .driver_data = ds_1339 },
391 	{ .id = "DS1388", .driver_data = ds_1388 },
392 	{ .id = "DS1340", .driver_data = ds_1340 },
393 	{ .id = "DS1341", .driver_data = ds_1341 },
394 	{ .id = "DS3231", .driver_data = ds_3231 },
395 	{ .id = "M41T0", .driver_data = m41t0 },
396 	{ .id = "M41T00", .driver_data = m41t00 },
397 	{ .id = "M41T11", .driver_data = m41t11 },
398 	{ .id = "MCP7940X", .driver_data = mcp794xx },
399 	{ .id = "MCP7941X", .driver_data = mcp794xx },
400 	{ .id = "PT7C4338", .driver_data = ds_1307 },
401 	{ .id = "RX8025", .driver_data = rx_8025 },
402 	{ .id = "ISL12057", .driver_data = ds_1337 },
403 	{ .id = "RX8130", .driver_data = rx_8130 },
404 	{ }
405 };
406 MODULE_DEVICE_TABLE(acpi, ds1307_acpi_ids);
407 #endif
408 
409 /*
410  * The ds1337 and ds1339 both have two alarms, but we only use the first
411  * one (with a "seconds" field).  For ds1337 we expect nINTA is our alarm
412  * signal; ds1339 chips have only one alarm signal.
413  */
414 static irqreturn_t ds1307_irq(int irq, void *dev_id)
415 {
416 	struct ds1307		*ds1307 = dev_id;
417 	struct mutex		*lock = &ds1307->rtc->ops_lock;
418 	int			stat, ret;
419 
420 	mutex_lock(lock);
421 	ret = regmap_read(ds1307->regmap, DS1337_REG_STATUS, &stat);
422 	if (ret)
423 		goto out;
424 
425 	if (stat & DS1337_BIT_A1I) {
426 		stat &= ~DS1337_BIT_A1I;
427 		regmap_write(ds1307->regmap, DS1337_REG_STATUS, stat);
428 
429 		ret = regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
430 					 DS1337_BIT_A1IE, 0);
431 		if (ret)
432 			goto out;
433 
434 		rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
435 	}
436 
437 out:
438 	mutex_unlock(lock);
439 
440 	return IRQ_HANDLED;
441 }
442 
443 /*----------------------------------------------------------------------*/
444 
445 static int ds1307_get_time(struct device *dev, struct rtc_time *t)
446 {
447 	struct ds1307	*ds1307 = dev_get_drvdata(dev);
448 	int		tmp, ret;
449 	const struct chip_desc *chip = &chips[ds1307->type];
450 	u8 regs[7];
451 
452 	/* read the RTC date and time registers all at once */
453 	ret = regmap_bulk_read(ds1307->regmap, chip->offset, regs,
454 			       sizeof(regs));
455 	if (ret) {
456 		dev_err(dev, "%s error %d\n", "read", ret);
457 		return ret;
458 	}
459 
460 	dev_dbg(dev, "%s: %7ph\n", "read", regs);
461 
462 	/* if oscillator fail bit is set, no data can be trusted */
463 	if (ds1307->type == m41t0 &&
464 	    regs[DS1307_REG_MIN] & M41T0_BIT_OF) {
465 		dev_warn_once(dev, "oscillator failed, set time!\n");
466 		return -EINVAL;
467 	}
468 
469 	t->tm_sec = bcd2bin(regs[DS1307_REG_SECS] & 0x7f);
470 	t->tm_min = bcd2bin(regs[DS1307_REG_MIN] & 0x7f);
471 	tmp = regs[DS1307_REG_HOUR] & 0x3f;
472 	t->tm_hour = bcd2bin(tmp);
473 	t->tm_wday = bcd2bin(regs[DS1307_REG_WDAY] & 0x07) - 1;
474 	t->tm_mday = bcd2bin(regs[DS1307_REG_MDAY] & 0x3f);
475 	tmp = regs[DS1307_REG_MONTH] & 0x1f;
476 	t->tm_mon = bcd2bin(tmp) - 1;
477 	t->tm_year = bcd2bin(regs[DS1307_REG_YEAR]) + 100;
478 
479 	if (regs[chip->century_reg] & chip->century_bit &&
480 	    IS_ENABLED(CONFIG_RTC_DRV_DS1307_CENTURY))
481 		t->tm_year += 100;
482 
483 	dev_dbg(dev, "%s secs=%d, mins=%d, "
484 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
485 		"read", t->tm_sec, t->tm_min,
486 		t->tm_hour, t->tm_mday,
487 		t->tm_mon, t->tm_year, t->tm_wday);
488 
489 	return 0;
490 }
491 
492 static int ds1307_set_time(struct device *dev, struct rtc_time *t)
493 {
494 	struct ds1307	*ds1307 = dev_get_drvdata(dev);
495 	const struct chip_desc *chip = &chips[ds1307->type];
496 	int		result;
497 	int		tmp;
498 	u8		regs[7];
499 
500 	dev_dbg(dev, "%s secs=%d, mins=%d, "
501 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
502 		"write", t->tm_sec, t->tm_min,
503 		t->tm_hour, t->tm_mday,
504 		t->tm_mon, t->tm_year, t->tm_wday);
505 
506 	if (t->tm_year < 100)
507 		return -EINVAL;
508 
509 #ifdef CONFIG_RTC_DRV_DS1307_CENTURY
510 	if (t->tm_year > (chip->century_bit ? 299 : 199))
511 		return -EINVAL;
512 #else
513 	if (t->tm_year > 199)
514 		return -EINVAL;
515 #endif
516 
517 	regs[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
518 	regs[DS1307_REG_MIN] = bin2bcd(t->tm_min);
519 	regs[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
520 	regs[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
521 	regs[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
522 	regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);
523 
524 	/* assume 20YY not 19YY */
525 	tmp = t->tm_year - 100;
526 	regs[DS1307_REG_YEAR] = bin2bcd(tmp);
527 
528 	if (chip->century_enable_bit)
529 		regs[chip->century_reg] |= chip->century_enable_bit;
530 	if (t->tm_year > 199 && chip->century_bit)
531 		regs[chip->century_reg] |= chip->century_bit;
532 
533 	if (ds1307->type == mcp794xx) {
534 		/*
535 		 * these bits were cleared when preparing the date/time
536 		 * values and need to be set again before writing the
537 		 * regsfer out to the device.
538 		 */
539 		regs[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
540 		regs[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
541 	}
542 
543 	dev_dbg(dev, "%s: %7ph\n", "write", regs);
544 
545 	result = regmap_bulk_write(ds1307->regmap, chip->offset, regs,
546 				   sizeof(regs));
547 	if (result) {
548 		dev_err(dev, "%s error %d\n", "write", result);
549 		return result;
550 	}
551 	return 0;
552 }
553 
554 static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
555 {
556 	struct ds1307		*ds1307 = dev_get_drvdata(dev);
557 	int			ret;
558 	u8			regs[9];
559 
560 	if (!test_bit(HAS_ALARM, &ds1307->flags))
561 		return -EINVAL;
562 
563 	/* read all ALARM1, ALARM2, and status registers at once */
564 	ret = regmap_bulk_read(ds1307->regmap, DS1339_REG_ALARM1_SECS,
565 			       regs, sizeof(regs));
566 	if (ret) {
567 		dev_err(dev, "%s error %d\n", "alarm read", ret);
568 		return ret;
569 	}
570 
571 	dev_dbg(dev, "%s: %4ph, %3ph, %2ph\n", "alarm read",
572 		&regs[0], &regs[4], &regs[7]);
573 
574 	/*
575 	 * report alarm time (ALARM1); assume 24 hour and day-of-month modes,
576 	 * and that all four fields are checked matches
577 	 */
578 	t->time.tm_sec = bcd2bin(regs[0] & 0x7f);
579 	t->time.tm_min = bcd2bin(regs[1] & 0x7f);
580 	t->time.tm_hour = bcd2bin(regs[2] & 0x3f);
581 	t->time.tm_mday = bcd2bin(regs[3] & 0x3f);
582 
583 	/* ... and status */
584 	t->enabled = !!(regs[7] & DS1337_BIT_A1IE);
585 	t->pending = !!(regs[8] & DS1337_BIT_A1I);
586 
587 	dev_dbg(dev, "%s secs=%d, mins=%d, "
588 		"hours=%d, mday=%d, enabled=%d, pending=%d\n",
589 		"alarm read", t->time.tm_sec, t->time.tm_min,
590 		t->time.tm_hour, t->time.tm_mday,
591 		t->enabled, t->pending);
592 
593 	return 0;
594 }
595 
596 static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
597 {
598 	struct ds1307		*ds1307 = dev_get_drvdata(dev);
599 	unsigned char		regs[9];
600 	u8			control, status;
601 	int			ret;
602 
603 	if (!test_bit(HAS_ALARM, &ds1307->flags))
604 		return -EINVAL;
605 
606 	dev_dbg(dev, "%s secs=%d, mins=%d, "
607 		"hours=%d, mday=%d, enabled=%d, pending=%d\n",
608 		"alarm set", t->time.tm_sec, t->time.tm_min,
609 		t->time.tm_hour, t->time.tm_mday,
610 		t->enabled, t->pending);
611 
612 	/* read current status of both alarms and the chip */
613 	ret = regmap_bulk_read(ds1307->regmap, DS1339_REG_ALARM1_SECS, regs,
614 			       sizeof(regs));
615 	if (ret) {
616 		dev_err(dev, "%s error %d\n", "alarm write", ret);
617 		return ret;
618 	}
619 	control = regs[7];
620 	status = regs[8];
621 
622 	dev_dbg(dev, "%s: %4ph, %3ph, %02x %02x\n", "alarm set (old status)",
623 		&regs[0], &regs[4], control, status);
624 
625 	/* set ALARM1, using 24 hour and day-of-month modes */
626 	regs[0] = bin2bcd(t->time.tm_sec);
627 	regs[1] = bin2bcd(t->time.tm_min);
628 	regs[2] = bin2bcd(t->time.tm_hour);
629 	regs[3] = bin2bcd(t->time.tm_mday);
630 
631 	/* set ALARM2 to non-garbage */
632 	regs[4] = 0;
633 	regs[5] = 0;
634 	regs[6] = 0;
635 
636 	/* disable alarms */
637 	regs[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
638 	regs[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);
639 
640 	ret = regmap_bulk_write(ds1307->regmap, DS1339_REG_ALARM1_SECS, regs,
641 				sizeof(regs));
642 	if (ret) {
643 		dev_err(dev, "can't set alarm time\n");
644 		return ret;
645 	}
646 
647 	/* optionally enable ALARM1 */
648 	if (t->enabled) {
649 		dev_dbg(dev, "alarm IRQ armed\n");
650 		regs[7] |= DS1337_BIT_A1IE;	/* only ALARM1 is used */
651 		regmap_write(ds1307->regmap, DS1337_REG_CONTROL, regs[7]);
652 	}
653 
654 	return 0;
655 }
656 
657 static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled)
658 {
659 	struct ds1307		*ds1307 = dev_get_drvdata(dev);
660 
661 	if (!test_bit(HAS_ALARM, &ds1307->flags))
662 		return -ENOTTY;
663 
664 	return regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
665 				  DS1337_BIT_A1IE,
666 				  enabled ? DS1337_BIT_A1IE : 0);
667 }
668 
669 static const struct rtc_class_ops ds13xx_rtc_ops = {
670 	.read_time	= ds1307_get_time,
671 	.set_time	= ds1307_set_time,
672 	.read_alarm	= ds1337_read_alarm,
673 	.set_alarm	= ds1337_set_alarm,
674 	.alarm_irq_enable = ds1307_alarm_irq_enable,
675 };
676 
677 /*----------------------------------------------------------------------*/
678 
679 /*
680  * Alarm support for rx8130 devices.
681  */
682 
683 #define RX8130_REG_ALARM_MIN		0x07
684 #define RX8130_REG_ALARM_HOUR		0x08
685 #define RX8130_REG_ALARM_WEEK_OR_DAY	0x09
686 #define RX8130_REG_EXTENSION		0x0c
687 #define RX8130_REG_EXTENSION_WADA	BIT(3)
688 #define RX8130_REG_FLAG			0x0d
689 #define RX8130_REG_FLAG_AF		BIT(3)
690 #define RX8130_REG_CONTROL0		0x0e
691 #define RX8130_REG_CONTROL0_AIE		BIT(3)
692 
693 static irqreturn_t rx8130_irq(int irq, void *dev_id)
694 {
695 	struct ds1307           *ds1307 = dev_id;
696 	struct mutex            *lock = &ds1307->rtc->ops_lock;
697 	u8 ctl[3];
698 	int ret;
699 
700 	mutex_lock(lock);
701 
702 	/* Read control registers. */
703 	ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
704 			       sizeof(ctl));
705 	if (ret < 0)
706 		goto out;
707 	if (!(ctl[1] & RX8130_REG_FLAG_AF))
708 		goto out;
709 	ctl[1] &= ~RX8130_REG_FLAG_AF;
710 	ctl[2] &= ~RX8130_REG_CONTROL0_AIE;
711 
712 	ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
713 				sizeof(ctl));
714 	if (ret < 0)
715 		goto out;
716 
717 	rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
718 
719 out:
720 	mutex_unlock(lock);
721 
722 	return IRQ_HANDLED;
723 }
724 
725 static int rx8130_read_alarm(struct device *dev, struct rtc_wkalrm *t)
726 {
727 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
728 	u8 ald[3], ctl[3];
729 	int ret;
730 
731 	if (!test_bit(HAS_ALARM, &ds1307->flags))
732 		return -EINVAL;
733 
734 	/* Read alarm registers. */
735 	ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_ALARM_MIN, ald,
736 			       sizeof(ald));
737 	if (ret < 0)
738 		return ret;
739 
740 	/* Read control registers. */
741 	ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
742 			       sizeof(ctl));
743 	if (ret < 0)
744 		return ret;
745 
746 	t->enabled = !!(ctl[2] & RX8130_REG_CONTROL0_AIE);
747 	t->pending = !!(ctl[1] & RX8130_REG_FLAG_AF);
748 
749 	/* Report alarm 0 time assuming 24-hour and day-of-month modes. */
750 	t->time.tm_sec = -1;
751 	t->time.tm_min = bcd2bin(ald[0] & 0x7f);
752 	t->time.tm_hour = bcd2bin(ald[1] & 0x7f);
753 	t->time.tm_wday = -1;
754 	t->time.tm_mday = bcd2bin(ald[2] & 0x7f);
755 	t->time.tm_mon = -1;
756 	t->time.tm_year = -1;
757 	t->time.tm_yday = -1;
758 	t->time.tm_isdst = -1;
759 
760 	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d enabled=%d\n",
761 		__func__, t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
762 		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled);
763 
764 	return 0;
765 }
766 
767 static int rx8130_set_alarm(struct device *dev, struct rtc_wkalrm *t)
768 {
769 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
770 	u8 ald[3], ctl[3];
771 	int ret;
772 
773 	if (!test_bit(HAS_ALARM, &ds1307->flags))
774 		return -EINVAL;
775 
776 	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
777 		"enabled=%d pending=%d\n", __func__,
778 		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
779 		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
780 		t->enabled, t->pending);
781 
782 	/* Read control registers. */
783 	ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
784 			       sizeof(ctl));
785 	if (ret < 0)
786 		return ret;
787 
788 	ctl[0] &= ~RX8130_REG_EXTENSION_WADA;
789 	ctl[1] |= RX8130_REG_FLAG_AF;
790 	ctl[2] &= ~RX8130_REG_CONTROL0_AIE;
791 
792 	ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
793 				sizeof(ctl));
794 	if (ret < 0)
795 		return ret;
796 
797 	/* Hardware alarm precision is 1 minute! */
798 	ald[0] = bin2bcd(t->time.tm_min);
799 	ald[1] = bin2bcd(t->time.tm_hour);
800 	ald[2] = bin2bcd(t->time.tm_mday);
801 
802 	ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_ALARM_MIN, ald,
803 				sizeof(ald));
804 	if (ret < 0)
805 		return ret;
806 
807 	if (!t->enabled)
808 		return 0;
809 
810 	ctl[2] |= RX8130_REG_CONTROL0_AIE;
811 
812 	return regmap_bulk_write(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
813 				 sizeof(ctl));
814 }
815 
816 static int rx8130_alarm_irq_enable(struct device *dev, unsigned int enabled)
817 {
818 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
819 	int ret, reg;
820 
821 	if (!test_bit(HAS_ALARM, &ds1307->flags))
822 		return -EINVAL;
823 
824 	ret = regmap_read(ds1307->regmap, RX8130_REG_CONTROL0, &reg);
825 	if (ret < 0)
826 		return ret;
827 
828 	if (enabled)
829 		reg |= RX8130_REG_CONTROL0_AIE;
830 	else
831 		reg &= ~RX8130_REG_CONTROL0_AIE;
832 
833 	return regmap_write(ds1307->regmap, RX8130_REG_CONTROL0, reg);
834 }
835 
836 /*----------------------------------------------------------------------*/
837 
838 /*
839  * Alarm support for mcp794xx devices.
840  */
841 
842 #define MCP794XX_REG_CONTROL		0x07
843 #	define MCP794XX_BIT_ALM0_EN	0x10
844 #	define MCP794XX_BIT_ALM1_EN	0x20
845 #define MCP794XX_REG_ALARM0_BASE	0x0a
846 #define MCP794XX_REG_ALARM0_CTRL	0x0d
847 #define MCP794XX_REG_ALARM1_BASE	0x11
848 #define MCP794XX_REG_ALARM1_CTRL	0x14
849 #	define MCP794XX_BIT_ALMX_IF	BIT(3)
850 #	define MCP794XX_BIT_ALMX_C0	BIT(4)
851 #	define MCP794XX_BIT_ALMX_C1	BIT(5)
852 #	define MCP794XX_BIT_ALMX_C2	BIT(6)
853 #	define MCP794XX_BIT_ALMX_POL	BIT(7)
854 #	define MCP794XX_MSK_ALMX_MATCH	(MCP794XX_BIT_ALMX_C0 | \
855 					 MCP794XX_BIT_ALMX_C1 | \
856 					 MCP794XX_BIT_ALMX_C2)
857 
858 static irqreturn_t mcp794xx_irq(int irq, void *dev_id)
859 {
860 	struct ds1307           *ds1307 = dev_id;
861 	struct mutex            *lock = &ds1307->rtc->ops_lock;
862 	int reg, ret;
863 
864 	mutex_lock(lock);
865 
866 	/* Check and clear alarm 0 interrupt flag. */
867 	ret = regmap_read(ds1307->regmap, MCP794XX_REG_ALARM0_CTRL, &reg);
868 	if (ret)
869 		goto out;
870 	if (!(reg & MCP794XX_BIT_ALMX_IF))
871 		goto out;
872 	reg &= ~MCP794XX_BIT_ALMX_IF;
873 	ret = regmap_write(ds1307->regmap, MCP794XX_REG_ALARM0_CTRL, reg);
874 	if (ret)
875 		goto out;
876 
877 	/* Disable alarm 0. */
878 	ret = regmap_update_bits(ds1307->regmap, MCP794XX_REG_CONTROL,
879 				 MCP794XX_BIT_ALM0_EN, 0);
880 	if (ret)
881 		goto out;
882 
883 	rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
884 
885 out:
886 	mutex_unlock(lock);
887 
888 	return IRQ_HANDLED;
889 }
890 
891 static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
892 {
893 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
894 	u8 regs[10];
895 	int ret;
896 
897 	if (!test_bit(HAS_ALARM, &ds1307->flags))
898 		return -EINVAL;
899 
900 	/* Read control and alarm 0 registers. */
901 	ret = regmap_bulk_read(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
902 			       sizeof(regs));
903 	if (ret)
904 		return ret;
905 
906 	t->enabled = !!(regs[0] & MCP794XX_BIT_ALM0_EN);
907 
908 	/* Report alarm 0 time assuming 24-hour and day-of-month modes. */
909 	t->time.tm_sec = bcd2bin(regs[3] & 0x7f);
910 	t->time.tm_min = bcd2bin(regs[4] & 0x7f);
911 	t->time.tm_hour = bcd2bin(regs[5] & 0x3f);
912 	t->time.tm_wday = bcd2bin(regs[6] & 0x7) - 1;
913 	t->time.tm_mday = bcd2bin(regs[7] & 0x3f);
914 	t->time.tm_mon = bcd2bin(regs[8] & 0x1f) - 1;
915 	t->time.tm_year = -1;
916 	t->time.tm_yday = -1;
917 	t->time.tm_isdst = -1;
918 
919 	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
920 		"enabled=%d polarity=%d irq=%d match=%lu\n", __func__,
921 		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
922 		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled,
923 		!!(regs[6] & MCP794XX_BIT_ALMX_POL),
924 		!!(regs[6] & MCP794XX_BIT_ALMX_IF),
925 		(regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);
926 
927 	return 0;
928 }
929 
930 /*
931  * We may have a random RTC weekday, therefore calculate alarm weekday based
932  * on current weekday we read from the RTC timekeeping regs
933  */
934 static int mcp794xx_alm_weekday(struct device *dev, struct rtc_time *tm_alarm)
935 {
936 	struct rtc_time tm_now;
937 	int days_now, days_alarm, ret;
938 
939 	ret = ds1307_get_time(dev, &tm_now);
940 	if (ret)
941 		return ret;
942 
943 	days_now = div_s64(rtc_tm_to_time64(&tm_now), 24 * 60 * 60);
944 	days_alarm = div_s64(rtc_tm_to_time64(tm_alarm), 24 * 60 * 60);
945 
946 	return (tm_now.tm_wday + days_alarm - days_now) % 7 + 1;
947 }
948 
949 static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t)
950 {
951 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
952 	unsigned char regs[10];
953 	int wday, ret;
954 
955 	if (!test_bit(HAS_ALARM, &ds1307->flags))
956 		return -EINVAL;
957 
958 	wday = mcp794xx_alm_weekday(dev, &t->time);
959 	if (wday < 0)
960 		return wday;
961 
962 	dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
963 		"enabled=%d pending=%d\n", __func__,
964 		t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
965 		t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
966 		t->enabled, t->pending);
967 
968 	/* Read control and alarm 0 registers. */
969 	ret = regmap_bulk_read(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
970 			       sizeof(regs));
971 	if (ret)
972 		return ret;
973 
974 	/* Set alarm 0, using 24-hour and day-of-month modes. */
975 	regs[3] = bin2bcd(t->time.tm_sec);
976 	regs[4] = bin2bcd(t->time.tm_min);
977 	regs[5] = bin2bcd(t->time.tm_hour);
978 	regs[6] = wday;
979 	regs[7] = bin2bcd(t->time.tm_mday);
980 	regs[8] = bin2bcd(t->time.tm_mon + 1);
981 
982 	/* Clear the alarm 0 interrupt flag. */
983 	regs[6] &= ~MCP794XX_BIT_ALMX_IF;
984 	/* Set alarm match: second, minute, hour, day, date, month. */
985 	regs[6] |= MCP794XX_MSK_ALMX_MATCH;
986 	/* Disable interrupt. We will not enable until completely programmed */
987 	regs[0] &= ~MCP794XX_BIT_ALM0_EN;
988 
989 	ret = regmap_bulk_write(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
990 				sizeof(regs));
991 	if (ret)
992 		return ret;
993 
994 	if (!t->enabled)
995 		return 0;
996 	regs[0] |= MCP794XX_BIT_ALM0_EN;
997 	return regmap_write(ds1307->regmap, MCP794XX_REG_CONTROL, regs[0]);
998 }
999 
1000 static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
1001 {
1002 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
1003 
1004 	if (!test_bit(HAS_ALARM, &ds1307->flags))
1005 		return -EINVAL;
1006 
1007 	return regmap_update_bits(ds1307->regmap, MCP794XX_REG_CONTROL,
1008 				  MCP794XX_BIT_ALM0_EN,
1009 				  enabled ? MCP794XX_BIT_ALM0_EN : 0);
1010 }
1011 
1012 static int m41txx_rtc_read_offset(struct device *dev, long *offset)
1013 {
1014 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
1015 	unsigned int ctrl_reg;
1016 	u8 val;
1017 
1018 	regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
1019 
1020 	val = ctrl_reg & M41TXX_M_CALIBRATION;
1021 
1022 	/* check if positive */
1023 	if (ctrl_reg & M41TXX_BIT_CALIB_SIGN)
1024 		*offset = (val * M41TXX_POS_OFFSET_STEP_PPB);
1025 	else
1026 		*offset = -(val * M41TXX_NEG_OFFSET_STEP_PPB);
1027 
1028 	return 0;
1029 }
1030 
1031 static int m41txx_rtc_set_offset(struct device *dev, long offset)
1032 {
1033 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
1034 	unsigned int ctrl_reg;
1035 
1036 	if ((offset < M41TXX_MIN_OFFSET) || (offset > M41TXX_MAX_OFFSET))
1037 		return -ERANGE;
1038 
1039 	if (offset >= 0) {
1040 		ctrl_reg = DIV_ROUND_CLOSEST(offset,
1041 					     M41TXX_POS_OFFSET_STEP_PPB);
1042 		ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
1043 	} else {
1044 		ctrl_reg = DIV_ROUND_CLOSEST(abs(offset),
1045 					     M41TXX_NEG_OFFSET_STEP_PPB);
1046 	}
1047 
1048 	return regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL,
1049 				  M41TXX_M_CALIBRATION | M41TXX_BIT_CALIB_SIGN,
1050 				  ctrl_reg);
1051 }
1052 
1053 static ssize_t frequency_test_store(struct device *dev,
1054 				    struct device_attribute *attr,
1055 				    const char *buf, size_t count)
1056 {
1057 	struct ds1307 *ds1307 = dev_get_drvdata(dev->parent);
1058 	bool freq_test_en;
1059 	int ret;
1060 
1061 	ret = kstrtobool(buf, &freq_test_en);
1062 	if (ret) {
1063 		dev_err(dev, "Failed to store RTC Frequency Test attribute\n");
1064 		return ret;
1065 	}
1066 
1067 	regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL, M41TXX_BIT_FT,
1068 			   freq_test_en ? M41TXX_BIT_FT : 0);
1069 
1070 	return count;
1071 }
1072 
1073 static ssize_t frequency_test_show(struct device *dev,
1074 				   struct device_attribute *attr,
1075 				   char *buf)
1076 {
1077 	struct ds1307 *ds1307 = dev_get_drvdata(dev->parent);
1078 	unsigned int ctrl_reg;
1079 
1080 	regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
1081 
1082 	return scnprintf(buf, PAGE_SIZE, (ctrl_reg & M41TXX_BIT_FT) ? "on\n" :
1083 			"off\n");
1084 }
1085 
1086 static DEVICE_ATTR_RW(frequency_test);
1087 
1088 static struct attribute *rtc_freq_test_attrs[] = {
1089 	&dev_attr_frequency_test.attr,
1090 	NULL,
1091 };
1092 
1093 static const struct attribute_group rtc_freq_test_attr_group = {
1094 	.attrs		= rtc_freq_test_attrs,
1095 };
1096 
1097 static int ds1307_add_frequency_test(struct ds1307 *ds1307)
1098 {
1099 	int err;
1100 
1101 	switch (ds1307->type) {
1102 	case m41t0:
1103 	case m41t00:
1104 	case m41t11:
1105 		err = rtc_add_group(ds1307->rtc, &rtc_freq_test_attr_group);
1106 		if (err)
1107 			return err;
1108 		break;
1109 	default:
1110 		break;
1111 	}
1112 
1113 	return 0;
1114 }
1115 
1116 /*----------------------------------------------------------------------*/
1117 
1118 static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
1119 			     size_t bytes)
1120 {
1121 	struct ds1307 *ds1307 = priv;
1122 	const struct chip_desc *chip = &chips[ds1307->type];
1123 
1124 	return regmap_bulk_read(ds1307->regmap, chip->nvram_offset + offset,
1125 				val, bytes);
1126 }
1127 
1128 static int ds1307_nvram_write(void *priv, unsigned int offset, void *val,
1129 			      size_t bytes)
1130 {
1131 	struct ds1307 *ds1307 = priv;
1132 	const struct chip_desc *chip = &chips[ds1307->type];
1133 
1134 	return regmap_bulk_write(ds1307->regmap, chip->nvram_offset + offset,
1135 				 val, bytes);
1136 }
1137 
1138 /*----------------------------------------------------------------------*/
1139 
1140 static u8 do_trickle_setup_ds1339(struct ds1307 *ds1307,
1141 				  u32 ohms, bool diode)
1142 {
1143 	u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
1144 		DS1307_TRICKLE_CHARGER_NO_DIODE;
1145 
1146 	switch (ohms) {
1147 	case 250:
1148 		setup |= DS1307_TRICKLE_CHARGER_250_OHM;
1149 		break;
1150 	case 2000:
1151 		setup |= DS1307_TRICKLE_CHARGER_2K_OHM;
1152 		break;
1153 	case 4000:
1154 		setup |= DS1307_TRICKLE_CHARGER_4K_OHM;
1155 		break;
1156 	default:
1157 		dev_warn(ds1307->dev,
1158 			 "Unsupported ohm value %u in dt\n", ohms);
1159 		return 0;
1160 	}
1161 	return setup;
1162 }
1163 
1164 static u8 ds1307_trickle_init(struct ds1307 *ds1307,
1165 			      const struct chip_desc *chip)
1166 {
1167 	u32 ohms;
1168 	bool diode = true;
1169 
1170 	if (!chip->do_trickle_setup)
1171 		return 0;
1172 
1173 	if (device_property_read_u32(ds1307->dev, "trickle-resistor-ohms",
1174 				     &ohms))
1175 		return 0;
1176 
1177 	if (device_property_read_bool(ds1307->dev, "trickle-diode-disable"))
1178 		diode = false;
1179 
1180 	return chip->do_trickle_setup(ds1307, ohms, diode);
1181 }
1182 
1183 /*----------------------------------------------------------------------*/
1184 
1185 #if IS_REACHABLE(CONFIG_HWMON)
1186 
1187 /*
1188  * Temperature sensor support for ds3231 devices.
1189  */
1190 
1191 #define DS3231_REG_TEMPERATURE	0x11
1192 
1193 /*
1194  * A user-initiated temperature conversion is not started by this function,
1195  * so the temperature is updated once every 64 seconds.
1196  */
1197 static int ds3231_hwmon_read_temp(struct device *dev, s32 *mC)
1198 {
1199 	struct ds1307 *ds1307 = dev_get_drvdata(dev);
1200 	u8 temp_buf[2];
1201 	s16 temp;
1202 	int ret;
1203 
1204 	ret = regmap_bulk_read(ds1307->regmap, DS3231_REG_TEMPERATURE,
1205 			       temp_buf, sizeof(temp_buf));
1206 	if (ret)
1207 		return ret;
1208 	/*
1209 	 * Temperature is represented as a 10-bit code with a resolution of
1210 	 * 0.25 degree celsius and encoded in two's complement format.
1211 	 */
1212 	temp = (temp_buf[0] << 8) | temp_buf[1];
1213 	temp >>= 6;
1214 	*mC = temp * 250;
1215 
1216 	return 0;
1217 }
1218 
1219 static ssize_t ds3231_hwmon_show_temp(struct device *dev,
1220 				      struct device_attribute *attr, char *buf)
1221 {
1222 	int ret;
1223 	s32 temp;
1224 
1225 	ret = ds3231_hwmon_read_temp(dev, &temp);
1226 	if (ret)
1227 		return ret;
1228 
1229 	return sprintf(buf, "%d\n", temp);
1230 }
1231 static SENSOR_DEVICE_ATTR(temp1_input, 0444, ds3231_hwmon_show_temp,
1232 			  NULL, 0);
1233 
1234 static struct attribute *ds3231_hwmon_attrs[] = {
1235 	&sensor_dev_attr_temp1_input.dev_attr.attr,
1236 	NULL,
1237 };
1238 ATTRIBUTE_GROUPS(ds3231_hwmon);
1239 
1240 static void ds1307_hwmon_register(struct ds1307 *ds1307)
1241 {
1242 	struct device *dev;
1243 
1244 	if (ds1307->type != ds_3231)
1245 		return;
1246 
1247 	dev = devm_hwmon_device_register_with_groups(ds1307->dev, ds1307->name,
1248 						     ds1307,
1249 						     ds3231_hwmon_groups);
1250 	if (IS_ERR(dev)) {
1251 		dev_warn(ds1307->dev, "unable to register hwmon device %ld\n",
1252 			 PTR_ERR(dev));
1253 	}
1254 }
1255 
1256 #else
1257 
1258 static void ds1307_hwmon_register(struct ds1307 *ds1307)
1259 {
1260 }
1261 
1262 #endif /* CONFIG_RTC_DRV_DS1307_HWMON */
1263 
1264 /*----------------------------------------------------------------------*/
1265 
1266 /*
1267  * Square-wave output support for DS3231
1268  * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3231.pdf
1269  */
1270 #ifdef CONFIG_COMMON_CLK
1271 
1272 enum {
1273 	DS3231_CLK_SQW = 0,
1274 	DS3231_CLK_32KHZ,
1275 };
1276 
1277 #define clk_sqw_to_ds1307(clk)	\
1278 	container_of(clk, struct ds1307, clks[DS3231_CLK_SQW])
1279 #define clk_32khz_to_ds1307(clk)	\
1280 	container_of(clk, struct ds1307, clks[DS3231_CLK_32KHZ])
1281 
1282 static int ds3231_clk_sqw_rates[] = {
1283 	1,
1284 	1024,
1285 	4096,
1286 	8192,
1287 };
1288 
1289 static int ds1337_write_control(struct ds1307 *ds1307, u8 mask, u8 value)
1290 {
1291 	struct mutex *lock = &ds1307->rtc->ops_lock;
1292 	int ret;
1293 
1294 	mutex_lock(lock);
1295 	ret = regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
1296 				 mask, value);
1297 	mutex_unlock(lock);
1298 
1299 	return ret;
1300 }
1301 
1302 static unsigned long ds3231_clk_sqw_recalc_rate(struct clk_hw *hw,
1303 						unsigned long parent_rate)
1304 {
1305 	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
1306 	int control, ret;
1307 	int rate_sel = 0;
1308 
1309 	ret = regmap_read(ds1307->regmap, DS1337_REG_CONTROL, &control);
1310 	if (ret)
1311 		return ret;
1312 	if (control & DS1337_BIT_RS1)
1313 		rate_sel += 1;
1314 	if (control & DS1337_BIT_RS2)
1315 		rate_sel += 2;
1316 
1317 	return ds3231_clk_sqw_rates[rate_sel];
1318 }
1319 
1320 static long ds3231_clk_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
1321 				      unsigned long *prate)
1322 {
1323 	int i;
1324 
1325 	for (i = ARRAY_SIZE(ds3231_clk_sqw_rates) - 1; i >= 0; i--) {
1326 		if (ds3231_clk_sqw_rates[i] <= rate)
1327 			return ds3231_clk_sqw_rates[i];
1328 	}
1329 
1330 	return 0;
1331 }
1332 
1333 static int ds3231_clk_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
1334 				   unsigned long parent_rate)
1335 {
1336 	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
1337 	int control = 0;
1338 	int rate_sel;
1339 
1340 	for (rate_sel = 0; rate_sel < ARRAY_SIZE(ds3231_clk_sqw_rates);
1341 			rate_sel++) {
1342 		if (ds3231_clk_sqw_rates[rate_sel] == rate)
1343 			break;
1344 	}
1345 
1346 	if (rate_sel == ARRAY_SIZE(ds3231_clk_sqw_rates))
1347 		return -EINVAL;
1348 
1349 	if (rate_sel & 1)
1350 		control |= DS1337_BIT_RS1;
1351 	if (rate_sel & 2)
1352 		control |= DS1337_BIT_RS2;
1353 
1354 	return ds1337_write_control(ds1307, DS1337_BIT_RS1 | DS1337_BIT_RS2,
1355 				control);
1356 }
1357 
1358 static int ds3231_clk_sqw_prepare(struct clk_hw *hw)
1359 {
1360 	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
1361 
1362 	return ds1337_write_control(ds1307, DS1337_BIT_INTCN, 0);
1363 }
1364 
1365 static void ds3231_clk_sqw_unprepare(struct clk_hw *hw)
1366 {
1367 	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
1368 
1369 	ds1337_write_control(ds1307, DS1337_BIT_INTCN, DS1337_BIT_INTCN);
1370 }
1371 
1372 static int ds3231_clk_sqw_is_prepared(struct clk_hw *hw)
1373 {
1374 	struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
1375 	int control, ret;
1376 
1377 	ret = regmap_read(ds1307->regmap, DS1337_REG_CONTROL, &control);
1378 	if (ret)
1379 		return ret;
1380 
1381 	return !(control & DS1337_BIT_INTCN);
1382 }
1383 
1384 static const struct clk_ops ds3231_clk_sqw_ops = {
1385 	.prepare = ds3231_clk_sqw_prepare,
1386 	.unprepare = ds3231_clk_sqw_unprepare,
1387 	.is_prepared = ds3231_clk_sqw_is_prepared,
1388 	.recalc_rate = ds3231_clk_sqw_recalc_rate,
1389 	.round_rate = ds3231_clk_sqw_round_rate,
1390 	.set_rate = ds3231_clk_sqw_set_rate,
1391 };
1392 
1393 static unsigned long ds3231_clk_32khz_recalc_rate(struct clk_hw *hw,
1394 						  unsigned long parent_rate)
1395 {
1396 	return 32768;
1397 }
1398 
1399 static int ds3231_clk_32khz_control(struct ds1307 *ds1307, bool enable)
1400 {
1401 	struct mutex *lock = &ds1307->rtc->ops_lock;
1402 	int ret;
1403 
1404 	mutex_lock(lock);
1405 	ret = regmap_update_bits(ds1307->regmap, DS1337_REG_STATUS,
1406 				 DS3231_BIT_EN32KHZ,
1407 				 enable ? DS3231_BIT_EN32KHZ : 0);
1408 	mutex_unlock(lock);
1409 
1410 	return ret;
1411 }
1412 
1413 static int ds3231_clk_32khz_prepare(struct clk_hw *hw)
1414 {
1415 	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
1416 
1417 	return ds3231_clk_32khz_control(ds1307, true);
1418 }
1419 
1420 static void ds3231_clk_32khz_unprepare(struct clk_hw *hw)
1421 {
1422 	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
1423 
1424 	ds3231_clk_32khz_control(ds1307, false);
1425 }
1426 
1427 static int ds3231_clk_32khz_is_prepared(struct clk_hw *hw)
1428 {
1429 	struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
1430 	int status, ret;
1431 
1432 	ret = regmap_read(ds1307->regmap, DS1337_REG_STATUS, &status);
1433 	if (ret)
1434 		return ret;
1435 
1436 	return !!(status & DS3231_BIT_EN32KHZ);
1437 }
1438 
1439 static const struct clk_ops ds3231_clk_32khz_ops = {
1440 	.prepare = ds3231_clk_32khz_prepare,
1441 	.unprepare = ds3231_clk_32khz_unprepare,
1442 	.is_prepared = ds3231_clk_32khz_is_prepared,
1443 	.recalc_rate = ds3231_clk_32khz_recalc_rate,
1444 };
1445 
1446 static struct clk_init_data ds3231_clks_init[] = {
1447 	[DS3231_CLK_SQW] = {
1448 		.name = "ds3231_clk_sqw",
1449 		.ops = &ds3231_clk_sqw_ops,
1450 	},
1451 	[DS3231_CLK_32KHZ] = {
1452 		.name = "ds3231_clk_32khz",
1453 		.ops = &ds3231_clk_32khz_ops,
1454 	},
1455 };
1456 
1457 static int ds3231_clks_register(struct ds1307 *ds1307)
1458 {
1459 	struct device_node *node = ds1307->dev->of_node;
1460 	struct clk_onecell_data	*onecell;
1461 	int i;
1462 
1463 	onecell = devm_kzalloc(ds1307->dev, sizeof(*onecell), GFP_KERNEL);
1464 	if (!onecell)
1465 		return -ENOMEM;
1466 
1467 	onecell->clk_num = ARRAY_SIZE(ds3231_clks_init);
1468 	onecell->clks = devm_kcalloc(ds1307->dev, onecell->clk_num,
1469 				     sizeof(onecell->clks[0]), GFP_KERNEL);
1470 	if (!onecell->clks)
1471 		return -ENOMEM;
1472 
1473 	for (i = 0; i < ARRAY_SIZE(ds3231_clks_init); i++) {
1474 		struct clk_init_data init = ds3231_clks_init[i];
1475 
1476 		/*
1477 		 * Interrupt signal due to alarm conditions and square-wave
1478 		 * output share same pin, so don't initialize both.
1479 		 */
1480 		if (i == DS3231_CLK_SQW && test_bit(HAS_ALARM, &ds1307->flags))
1481 			continue;
1482 
1483 		/* optional override of the clockname */
1484 		of_property_read_string_index(node, "clock-output-names", i,
1485 					      &init.name);
1486 		ds1307->clks[i].init = &init;
1487 
1488 		onecell->clks[i] = devm_clk_register(ds1307->dev,
1489 						     &ds1307->clks[i]);
1490 		if (IS_ERR(onecell->clks[i]))
1491 			return PTR_ERR(onecell->clks[i]);
1492 	}
1493 
1494 	if (!node)
1495 		return 0;
1496 
1497 	of_clk_add_provider(node, of_clk_src_onecell_get, onecell);
1498 
1499 	return 0;
1500 }
1501 
1502 static void ds1307_clks_register(struct ds1307 *ds1307)
1503 {
1504 	int ret;
1505 
1506 	if (ds1307->type != ds_3231)
1507 		return;
1508 
1509 	ret = ds3231_clks_register(ds1307);
1510 	if (ret) {
1511 		dev_warn(ds1307->dev, "unable to register clock device %d\n",
1512 			 ret);
1513 	}
1514 }
1515 
1516 #else
1517 
1518 static void ds1307_clks_register(struct ds1307 *ds1307)
1519 {
1520 }
1521 
1522 #endif /* CONFIG_COMMON_CLK */
1523 
1524 static const struct regmap_config regmap_config = {
1525 	.reg_bits = 8,
1526 	.val_bits = 8,
1527 };
1528 
1529 static int ds1307_probe(struct i2c_client *client,
1530 			const struct i2c_device_id *id)
1531 {
1532 	struct ds1307		*ds1307;
1533 	int			err = -ENODEV;
1534 	int			tmp;
1535 	const struct chip_desc	*chip;
1536 	bool			want_irq;
1537 	bool			ds1307_can_wakeup_device = false;
1538 	unsigned char		regs[8];
1539 	struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
1540 	u8			trickle_charger_setup = 0;
1541 
1542 	ds1307 = devm_kzalloc(&client->dev, sizeof(struct ds1307), GFP_KERNEL);
1543 	if (!ds1307)
1544 		return -ENOMEM;
1545 
1546 	dev_set_drvdata(&client->dev, ds1307);
1547 	ds1307->dev = &client->dev;
1548 	ds1307->name = client->name;
1549 
1550 	ds1307->regmap = devm_regmap_init_i2c(client, &regmap_config);
1551 	if (IS_ERR(ds1307->regmap)) {
1552 		dev_err(ds1307->dev, "regmap allocation failed\n");
1553 		return PTR_ERR(ds1307->regmap);
1554 	}
1555 
1556 	i2c_set_clientdata(client, ds1307);
1557 
1558 	if (client->dev.of_node) {
1559 		ds1307->type = (enum ds_type)
1560 			of_device_get_match_data(&client->dev);
1561 		chip = &chips[ds1307->type];
1562 	} else if (id) {
1563 		chip = &chips[id->driver_data];
1564 		ds1307->type = id->driver_data;
1565 	} else {
1566 		const struct acpi_device_id *acpi_id;
1567 
1568 		acpi_id = acpi_match_device(ACPI_PTR(ds1307_acpi_ids),
1569 					    ds1307->dev);
1570 		if (!acpi_id)
1571 			return -ENODEV;
1572 		chip = &chips[acpi_id->driver_data];
1573 		ds1307->type = acpi_id->driver_data;
1574 	}
1575 
1576 	want_irq = client->irq > 0 && chip->alarm;
1577 
1578 	if (!pdata)
1579 		trickle_charger_setup = ds1307_trickle_init(ds1307, chip);
1580 	else if (pdata->trickle_charger_setup)
1581 		trickle_charger_setup = pdata->trickle_charger_setup;
1582 
1583 	if (trickle_charger_setup && chip->trickle_charger_reg) {
1584 		trickle_charger_setup |= DS13XX_TRICKLE_CHARGER_MAGIC;
1585 		dev_dbg(ds1307->dev,
1586 			"writing trickle charger info 0x%x to 0x%x\n",
1587 			trickle_charger_setup, chip->trickle_charger_reg);
1588 		regmap_write(ds1307->regmap, chip->trickle_charger_reg,
1589 			     trickle_charger_setup);
1590 	}
1591 
1592 #ifdef CONFIG_OF
1593 /*
1594  * For devices with no IRQ directly connected to the SoC, the RTC chip
1595  * can be forced as a wakeup source by stating that explicitly in
1596  * the device's .dts file using the "wakeup-source" boolean property.
1597  * If the "wakeup-source" property is set, don't request an IRQ.
1598  * This will guarantee the 'wakealarm' sysfs entry is available on the device,
1599  * if supported by the RTC.
1600  */
1601 	if (chip->alarm && of_property_read_bool(client->dev.of_node,
1602 						 "wakeup-source"))
1603 		ds1307_can_wakeup_device = true;
1604 #endif
1605 
1606 	switch (ds1307->type) {
1607 	case ds_1337:
1608 	case ds_1339:
1609 	case ds_1341:
1610 	case ds_3231:
1611 		/* get registers that the "rtc" read below won't read... */
1612 		err = regmap_bulk_read(ds1307->regmap, DS1337_REG_CONTROL,
1613 				       regs, 2);
1614 		if (err) {
1615 			dev_dbg(ds1307->dev, "read error %d\n", err);
1616 			goto exit;
1617 		}
1618 
1619 		/* oscillator off?  turn it on, so clock can tick. */
1620 		if (regs[0] & DS1337_BIT_nEOSC)
1621 			regs[0] &= ~DS1337_BIT_nEOSC;
1622 
1623 		/*
1624 		 * Using IRQ or defined as wakeup-source?
1625 		 * Disable the square wave and both alarms.
1626 		 * For some variants, be sure alarms can trigger when we're
1627 		 * running on Vbackup (BBSQI/BBSQW)
1628 		 */
1629 		if (want_irq || ds1307_can_wakeup_device) {
1630 			regs[0] |= DS1337_BIT_INTCN | chip->bbsqi_bit;
1631 			regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);
1632 		}
1633 
1634 		regmap_write(ds1307->regmap, DS1337_REG_CONTROL,
1635 			     regs[0]);
1636 
1637 		/* oscillator fault?  clear flag, and warn */
1638 		if (regs[1] & DS1337_BIT_OSF) {
1639 			regmap_write(ds1307->regmap, DS1337_REG_STATUS,
1640 				     regs[1] & ~DS1337_BIT_OSF);
1641 			dev_warn(ds1307->dev, "SET TIME!\n");
1642 		}
1643 		break;
1644 
1645 	case rx_8025:
1646 		err = regmap_bulk_read(ds1307->regmap,
1647 				       RX8025_REG_CTRL1 << 4 | 0x08, regs, 2);
1648 		if (err) {
1649 			dev_dbg(ds1307->dev, "read error %d\n", err);
1650 			goto exit;
1651 		}
1652 
1653 		/* oscillator off?  turn it on, so clock can tick. */
1654 		if (!(regs[1] & RX8025_BIT_XST)) {
1655 			regs[1] |= RX8025_BIT_XST;
1656 			regmap_write(ds1307->regmap,
1657 				     RX8025_REG_CTRL2 << 4 | 0x08,
1658 				     regs[1]);
1659 			dev_warn(ds1307->dev,
1660 				 "oscillator stop detected - SET TIME!\n");
1661 		}
1662 
1663 		if (regs[1] & RX8025_BIT_PON) {
1664 			regs[1] &= ~RX8025_BIT_PON;
1665 			regmap_write(ds1307->regmap,
1666 				     RX8025_REG_CTRL2 << 4 | 0x08,
1667 				     regs[1]);
1668 			dev_warn(ds1307->dev, "power-on detected\n");
1669 		}
1670 
1671 		if (regs[1] & RX8025_BIT_VDET) {
1672 			regs[1] &= ~RX8025_BIT_VDET;
1673 			regmap_write(ds1307->regmap,
1674 				     RX8025_REG_CTRL2 << 4 | 0x08,
1675 				     regs[1]);
1676 			dev_warn(ds1307->dev, "voltage drop detected\n");
1677 		}
1678 
1679 		/* make sure we are running in 24hour mode */
1680 		if (!(regs[0] & RX8025_BIT_2412)) {
1681 			u8 hour;
1682 
1683 			/* switch to 24 hour mode */
1684 			regmap_write(ds1307->regmap,
1685 				     RX8025_REG_CTRL1 << 4 | 0x08,
1686 				     regs[0] | RX8025_BIT_2412);
1687 
1688 			err = regmap_bulk_read(ds1307->regmap,
1689 					       RX8025_REG_CTRL1 << 4 | 0x08,
1690 					       regs, 2);
1691 			if (err) {
1692 				dev_dbg(ds1307->dev, "read error %d\n", err);
1693 				goto exit;
1694 			}
1695 
1696 			/* correct hour */
1697 			hour = bcd2bin(regs[DS1307_REG_HOUR]);
1698 			if (hour == 12)
1699 				hour = 0;
1700 			if (regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
1701 				hour += 12;
1702 
1703 			regmap_write(ds1307->regmap,
1704 				     DS1307_REG_HOUR << 4 | 0x08, hour);
1705 		}
1706 		break;
1707 	default:
1708 		break;
1709 	}
1710 
1711 read_rtc:
1712 	/* read RTC registers */
1713 	err = regmap_bulk_read(ds1307->regmap, chip->offset, regs,
1714 			       sizeof(regs));
1715 	if (err) {
1716 		dev_dbg(ds1307->dev, "read error %d\n", err);
1717 		goto exit;
1718 	}
1719 
1720 	/*
1721 	 * minimal sanity checking; some chips (like DS1340) don't
1722 	 * specify the extra bits as must-be-zero, but there are
1723 	 * still a few values that are clearly out-of-range.
1724 	 */
1725 	tmp = regs[DS1307_REG_SECS];
1726 	switch (ds1307->type) {
1727 	case ds_1307:
1728 	case m41t0:
1729 	case m41t00:
1730 	case m41t11:
1731 		/* clock halted?  turn it on, so clock can tick. */
1732 		if (tmp & DS1307_BIT_CH) {
1733 			regmap_write(ds1307->regmap, DS1307_REG_SECS, 0);
1734 			dev_warn(ds1307->dev, "SET TIME!\n");
1735 			goto read_rtc;
1736 		}
1737 		break;
1738 	case ds_1308:
1739 	case ds_1338:
1740 		/* clock halted?  turn it on, so clock can tick. */
1741 		if (tmp & DS1307_BIT_CH)
1742 			regmap_write(ds1307->regmap, DS1307_REG_SECS, 0);
1743 
1744 		/* oscillator fault?  clear flag, and warn */
1745 		if (regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
1746 			regmap_write(ds1307->regmap, DS1307_REG_CONTROL,
1747 				     regs[DS1307_REG_CONTROL] &
1748 				     ~DS1338_BIT_OSF);
1749 			dev_warn(ds1307->dev, "SET TIME!\n");
1750 			goto read_rtc;
1751 		}
1752 		break;
1753 	case ds_1340:
1754 		/* clock halted?  turn it on, so clock can tick. */
1755 		if (tmp & DS1340_BIT_nEOSC)
1756 			regmap_write(ds1307->regmap, DS1307_REG_SECS, 0);
1757 
1758 		err = regmap_read(ds1307->regmap, DS1340_REG_FLAG, &tmp);
1759 		if (err) {
1760 			dev_dbg(ds1307->dev, "read error %d\n", err);
1761 			goto exit;
1762 		}
1763 
1764 		/* oscillator fault?  clear flag, and warn */
1765 		if (tmp & DS1340_BIT_OSF) {
1766 			regmap_write(ds1307->regmap, DS1340_REG_FLAG, 0);
1767 			dev_warn(ds1307->dev, "SET TIME!\n");
1768 		}
1769 		break;
1770 	case mcp794xx:
1771 		/* make sure that the backup battery is enabled */
1772 		if (!(regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
1773 			regmap_write(ds1307->regmap, DS1307_REG_WDAY,
1774 				     regs[DS1307_REG_WDAY] |
1775 				     MCP794XX_BIT_VBATEN);
1776 		}
1777 
1778 		/* clock halted?  turn it on, so clock can tick. */
1779 		if (!(tmp & MCP794XX_BIT_ST)) {
1780 			regmap_write(ds1307->regmap, DS1307_REG_SECS,
1781 				     MCP794XX_BIT_ST);
1782 			dev_warn(ds1307->dev, "SET TIME!\n");
1783 			goto read_rtc;
1784 		}
1785 
1786 		break;
1787 	default:
1788 		break;
1789 	}
1790 
1791 	tmp = regs[DS1307_REG_HOUR];
1792 	switch (ds1307->type) {
1793 	case ds_1340:
1794 	case m41t0:
1795 	case m41t00:
1796 	case m41t11:
1797 		/*
1798 		 * NOTE: ignores century bits; fix before deploying
1799 		 * systems that will run through year 2100.
1800 		 */
1801 		break;
1802 	case rx_8025:
1803 		break;
1804 	default:
1805 		if (!(tmp & DS1307_BIT_12HR))
1806 			break;
1807 
1808 		/*
1809 		 * Be sure we're in 24 hour mode.  Multi-master systems
1810 		 * take note...
1811 		 */
1812 		tmp = bcd2bin(tmp & 0x1f);
1813 		if (tmp == 12)
1814 			tmp = 0;
1815 		if (regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
1816 			tmp += 12;
1817 		regmap_write(ds1307->regmap, chip->offset + DS1307_REG_HOUR,
1818 			     bin2bcd(tmp));
1819 	}
1820 
1821 	if (want_irq || ds1307_can_wakeup_device) {
1822 		device_set_wakeup_capable(ds1307->dev, true);
1823 		set_bit(HAS_ALARM, &ds1307->flags);
1824 	}
1825 
1826 	ds1307->rtc = devm_rtc_allocate_device(ds1307->dev);
1827 	if (IS_ERR(ds1307->rtc))
1828 		return PTR_ERR(ds1307->rtc);
1829 
1830 	if (ds1307_can_wakeup_device && !want_irq) {
1831 		dev_info(ds1307->dev,
1832 			 "'wakeup-source' is set, request for an IRQ is disabled!\n");
1833 		/* We cannot support UIE mode if we do not have an IRQ line */
1834 		ds1307->rtc->uie_unsupported = 1;
1835 	}
1836 
1837 	if (want_irq) {
1838 		err = devm_request_threaded_irq(ds1307->dev, client->irq, NULL,
1839 						chip->irq_handler ?: ds1307_irq,
1840 						IRQF_SHARED | IRQF_ONESHOT,
1841 						ds1307->name, ds1307);
1842 		if (err) {
1843 			client->irq = 0;
1844 			device_set_wakeup_capable(ds1307->dev, false);
1845 			clear_bit(HAS_ALARM, &ds1307->flags);
1846 			dev_err(ds1307->dev, "unable to request IRQ!\n");
1847 		} else {
1848 			dev_dbg(ds1307->dev, "got IRQ %d\n", client->irq);
1849 		}
1850 	}
1851 
1852 	ds1307->rtc->ops = chip->rtc_ops ?: &ds13xx_rtc_ops;
1853 	err = ds1307_add_frequency_test(ds1307);
1854 	if (err)
1855 		return err;
1856 
1857 	err = rtc_register_device(ds1307->rtc);
1858 	if (err)
1859 		return err;
1860 
1861 	if (chip->nvram_size) {
1862 		struct nvmem_config nvmem_cfg = {
1863 			.name = "ds1307_nvram",
1864 			.word_size = 1,
1865 			.stride = 1,
1866 			.size = chip->nvram_size,
1867 			.reg_read = ds1307_nvram_read,
1868 			.reg_write = ds1307_nvram_write,
1869 			.priv = ds1307,
1870 		};
1871 
1872 		ds1307->rtc->nvram_old_abi = true;
1873 		rtc_nvmem_register(ds1307->rtc, &nvmem_cfg);
1874 	}
1875 
1876 	ds1307_hwmon_register(ds1307);
1877 	ds1307_clks_register(ds1307);
1878 
1879 	return 0;
1880 
1881 exit:
1882 	return err;
1883 }
1884 
1885 static struct i2c_driver ds1307_driver = {
1886 	.driver = {
1887 		.name	= "rtc-ds1307",
1888 		.of_match_table = of_match_ptr(ds1307_of_match),
1889 		.acpi_match_table = ACPI_PTR(ds1307_acpi_ids),
1890 	},
1891 	.probe		= ds1307_probe,
1892 	.id_table	= ds1307_id,
1893 };
1894 
1895 module_i2c_driver(ds1307_driver);
1896 
1897 MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
1898 MODULE_LICENSE("GPL");
1899