aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-m41t80.c
blob: a82937e2f82405a0ecb1346bf667a5e6be2b8b2d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
/*
 * I2C client/driver for the ST M41T80 family of i2c rtc chips.
 *
 * Author: Alexander Bigga <ab@mycable.de>
 *
 * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
 *
 * 2006 (c) mycable GmbH
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bcd.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/string.h>
#ifdef CONFIG_RTC_DRV_M41T80_WDT
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/miscdevice.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>
#endif

#define M41T80_REG_SSEC	0
#define M41T80_REG_SEC	1
#define M41T80_REG_MIN	2
#define M41T80_REG_HOUR	3
#define M41T80_REG_WDAY	4
#define M41T80_REG_DAY	5
#define M41T80_REG_MON	6
#define M41T80_REG_YEAR	7
#define M41T80_REG_ALARM_MON	0xa
#define M41T80_REG_ALARM_DAY	0xb
#define M41T80_REG_ALARM_HOUR	0xc
#define M41T80_REG_ALARM_MIN	0xd
#define M41T80_REG_ALARM_SEC	0xe
#define M41T80_REG_FLAGS	0xf
#define M41T80_REG_SQW	0x13

#define M41T80_DATETIME_REG_SIZE	(M41T80_REG_YEAR + 1)
#define M41T80_ALARM_REG_SIZE	\
	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)

#define M41T80_SEC_ST		(1 << 7)	/* ST: Stop Bit */
#define M41T80_ALMON_AFE	(1 << 7)	/* AFE: AF Enable Bit */
#define M41T80_ALMON_SQWE	(1 << 6)	/* SQWE: SQW Enable Bit */
#define M41T80_ALHOUR_HT	(1 << 6)	/* HT: Halt Update Bit */
#define M41T80_FLAGS_AF		(1 << 6)	/* AF: Alarm Flag Bit */
#define M41T80_FLAGS_BATT_LOW	(1 << 4)	/* BL: Battery Low Bit */
#define M41T80_WATCHDOG_RB2	(1 << 7)	/* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB1	(1 << 1)	/* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB0	(1 << 0)	/* RB: Watchdog resolution */

#define M41T80_FEATURE_HT	(1 << 0)	/* Halt feature */
#define M41T80_FEATURE_BL	(1 << 1)	/* Battery low indicator */
#define M41T80_FEATURE_SQ	(1 << 2)	/* Squarewave feature */
#define M41T80_FEATURE_WD	(1 << 3)	/* Extra watchdog resolution */
#define M41T80_FEATURE_SQ_ALT	(1 << 4)	/* RSx bits are in reg 4 */

static DEFINE_MUTEX(m41t80_rtc_mutex);
static const struct i2c_device_id m41t80_id[] = {
	{ "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
	{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
	{ "m41t80", M41T80_FEATURE_SQ },
	{ "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
	{ "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
	{ "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
	{ }
};
MODULE_DEVICE_TABLE(i2c, m41t80_id);

struct m41t80_data {
	u8 features;
	struct rtc_device *rtc;
};

static int m41t80_get_datetime(struct i2c_client *client,
			       struct rtc_time *tm)
{
	u8 buf[M41T80_DATETIME_REG_SIZE], dt_addr[1] = { M41T80_REG_SEC };
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
			.buf	= buf + M41T80_REG_SEC,
		},
	};

	if (i2c_transfer(client->adapter, msgs, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}

	tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
	tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
	tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
	tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
	tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
	tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;

	/* assume 20YY not 19YY, and ignore the Century Bit */
	tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
	return rtc_valid_tm(tm);
}

/* Sets the given date and time to the real time clock. */
static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
{
	u8 wbuf[1 + M41T80_DATETIME_REG_SIZE];
	u8 *buf = &wbuf[1];
	u8 dt_addr[1] = { M41T80_REG_SEC };
	struct i2c_msg msgs_in[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= dt_addr,
		},
		{
			.addr	= client->addr,
			.flags	= I2C_M_RD,
			.len	= M41T80_DATETIME_REG_SIZE - M41T80_REG_SEC,
			.buf	= buf + M41T80_REG_SEC,
		},
	};
	struct i2c_msg msgs[] = {
		{
			.addr	= client->addr,
			.flags	= 0,
			.len	= 1 + M41T80_DATETIME_REG_SIZE,
			.buf	= wbuf,
		 },
	};

	/* Read current reg values into buf[1..7] */
	if (i2c_transfer(client->adapter, msgs_in, 2) < 0) {
		dev_err(&client->dev, "read error\n");
		return -EIO;
	}

	wbuf[0] = 0; /* offset into rtc's regs */
	/* Merge time-data and register flags into buf[0..7] */
	buf[M41T80_REG_SSEC] = 0;
	buf[M41T80_REG_SEC] =
		bin2bcd(tm->tm_sec) | (buf[M41T80_REG_SEC] & ~0x7f);
	buf[M41T80_REG_MIN] =
		bin2bcd(tm->tm_min) | (buf[M41T80_REG_MIN] & ~0x7f);
	buf[M41T80_REG_HOUR] =
		bin2bcd(tm->tm_hour) | (buf[M41T80_REG_HOUR] & ~0x3f);
	buf[M41T80_REG_WDAY] =
		(tm->tm_wday & 0x07) | (buf[M41T80_REG_WDAY] & ~0x07);
	buf[M41T80_REG_DAY] =
		bin2bcd(tm->tm_mday) | (buf[M41T80_REG_DAY] & ~0x3f);
	buf[M41T80_REG_MON] =
		bin2bcd(tm->tm_mon + 1) | (buf[M41T80_REG_MON] & ~0x1f);
	/* assume 20YY not 19YY */
	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year % 100);

	if (i2c_transfer(client->adapter, msgs, 1) != 1) {
		dev_err(&client->dev, "write error\n");
		return -EIO;
	}
	return 0;
}

#if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	u8 reg;

	if (clientdata->features & M41T80_FEATURE_BL) {
		reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
		seq_printf(seq, "battery\t\t: %s\n",
			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
	}
	return 0;
}
#else
#define m41t80_rtc_proc NULL
#endif

static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	return m41t80_get_datetime(to_i2c_client(dev), tm);
}

static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	return m41t80_set_datetime(to_i2c_client(dev), tm);
}

/*
 * XXX - m41t80 alarm functionality is reported broken.
 * until it is fixed, don't register alarm functions.
 */
static struct rtc_class_ops m41t80_rtc_ops = {
	.read_time = m41t80_rtc_read_time,
	.set_time = m41t80_rtc_set_time,
	.proc = m41t80_rtc_proc,
};

#if defined(CONFIG_RTC_INTF_SYSFS) || defined(CONFIG_RTC_INTF_SYSFS_MODULE)
static ssize_t m41t80_sysfs_show_flags(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	int val;

	val = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
	if (val < 0)
		return val;
	return sprintf(buf, "%#x\n", val);
}
static DEVICE_ATTR(flags, S_IRUGO, m41t80_sysfs_show_flags, NULL);

static ssize_t m41t80_sysfs_show_sqwfreq(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	int val, reg_sqw;

	if (!(clientdata->features & M41T80_FEATURE_SQ))
		return -EINVAL;

	reg_sqw = M41T80_REG_SQW;
	if (clientdata->features & M41T80_FEATURE_SQ_ALT)
		reg_sqw = M41T80_REG_WDAY;
	val = i2c_smbus_read_byte_data(client, reg_sqw);
	if (val < 0)
		return val;
	val = (val >> 4) & 0xf;
	switch (val) {
	case 0:
		break;
	case 1:
		val = 32768;
		break;
	default:
		val = 32768 >> val;
	}
	return sprintf(buf, "%d\n", val);
}
static ssize_t m41t80_sysfs_set_sqwfreq(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct m41t80_data *clientdata = i2c_get_clientdata(client);
	int almon, sqw, reg_sqw, rc;
	int val = simple_strtoul(buf, NULL, 0);

	if (!(clientdata->features & M41T80_FEATURE_SQ))
		return -EINVAL;

	if (val) {
		if (!is_power_of_2(val))
			return -EINVAL;
		val = ilog2(val);
		if (val == 15)
			val = 1;
		else if (val < 14)
			val = 15 - val;
		else
			return -EINVAL;
	}
	/* disable SQW, set SQW frequency & re-enable */
	almon = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
	if (almon < 0)
		return almon;
	reg_sqw = M41T80_REG_SQW;
	if (clientdata->features & M41T80_FEATURE_SQ_ALT)
		reg_sqw = M41T80_REG_WDAY;
	sqw = i2c_smbus_read_byte_data(client, reg_sqw);
	if (sqw < 0)
		return sqw;
	sqw = (sqw & 0x0f) | (val << 4);

	rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
				      almon & ~M41T80_ALMON_SQWE);
	if (rc < 0)
		return rc;

	if (val) {
		rc = i2c_smbus_write_byte_data(client, reg_sqw, sqw);
		if (rc < 0)
			return rc;

		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
					     almon | M41T80_ALMON_SQWE);
		if (rc <0)
			return rc;
	}
	return count;
}
static DEVICE_ATTR(sqwfreq, S_IRUGO | S_IWUSR,
		   m41t80_sysfs_show_sqwfreq, m41t80_sysfs_set_sqwfreq);

static struct attribute *attrs[] = {
	&dev_attr_flags.attr,
	&dev_attr_sqwfreq.attr,
	NULL,
};
static struct attribute_group attr_group = {
	.attrs = attrs,
};

static int m41t80_sysfs_register(struct device *dev)
{
	return sysfs_create_group(&dev->kobj, &attr_group);
}
#else
static int m41t80_sysfs_register(struct device *dev)
{
	return 0;
}
#endif

#ifdef CONFIG_RTC_DRV_M41T80_WDT
/*
 *****************************************************************************
 *
 * Watchdog Driver
 *
 *****************************************************************************
 */
static struct i2c_client *save_client;

/* Default margin */
#define WD_TIMO 60		/* 1..31 seconds */

static int wdt_margin = WD_TIMO;
module_param(wdt_margin, int, 0);
MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");

static unsigned long wdt_is_open;
static int boot_flag;

/**
 *	wdt_ping:
 *
 *	Reload counter one with the watchdog timeout. We don't bother reloading
 *	the cascade counter.
 */
static void wdt_ping(void)
{
	unsigned char i2c_data[2];
	struct i2c_msg msgs1[1] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 2,
			.buf	= i2c_data,
		},
	};
	struct m41t80_data *clientdata = i2c_get_clientdata(save_client);

	i2c_data[0] = 0x09;		/* watchdog register */

	if (wdt_margin > 31)
		i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
	else
		/*
		 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
		 */
		i2c_data[1] = wdt_margin<<2 | 0x82;

	/*
	 * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
	 * that would be an invalid resolution.
	 */
	if (clientdata->features & M41T80_FEATURE_WD)
		i2c_data[1] &= ~M41T80_WATCHDOG_RB2;

	i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *	wdt_disable:
 *
 *	disables watchdog.
 */
static void wdt_disable(void)
{
	unsigned char i2c_data[2], i2c_buf[0x10];
	struct i2c_msg msgs0[2] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 1,
			.buf	= i2c_data,
		},
		{
			.addr	= save_client->addr,
			.flags	= I2C_M_RD,
			.len	= 1,
			.buf	= i2c_buf,
		},
	};
	struct i2c_msg msgs1[1] = {
		{
			.addr	= save_client->addr,
			.flags	= 0,
			.len	= 2,
			.buf	= i2c_data,
		},
	};

	i2c_data[0] = 0x09;
	i2c_transfer(save_client->adapter, msgs0, 2);

	i2c_data[0] = 0x09;
	i2c_data[1] = 0x00;
	i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *	wdt_write:
 *	@file: file handle to the watchdog
 *	@buf: buffer to write (unused as data does not matter here
 *	@count: count of bytes
 *	@ppos: pointer to the position to write. No seeks allowed
 *
 *	A write to a watchdog device is defined as a keepalive signal. Any
 *	write of data will do, as we we don't define content meaning.
 */
static ssize_t wdt_write(struct file *file, const char __user *buf,
			 size_t count, loff_t *ppos)
{
	if (count) {
		wdt_ping();
		return 1;
	}
	return 0;
}

static ssize_t wdt_read(struct file *file, char __user *buf,
			size_t count, loff_t *ppos)
{
	return 0;
}

/**
 *	wdt_ioctl:
 *	@inode: inode of the device
 *	@file: file handle to the device
 *	@cmd: watchdog command
 *	@arg: argument pointer
 *
 *	The watchdog API defines a common set of functions for all watchdogs
 *	according to their available features. We only actually usefully support
 *	querying capabilities and current status.
 */
static int wdt_ioctl(struct file *file, unsigned int cmd,
		     unsigned long arg)
{
	int new_margin, rv;
	static struct watchdog_info ident = {
		.options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
			WDIOF_SETTIMEOUT,
		.firmware_version = 1,
		.identity = "M41T80 WTD"
	};

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		return copy_to_user((struct watchdog_info __user *)arg, &ident,
				    sizeof(ident)) ? -EFAULT : 0;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(boot_flag, (int __user *)arg);
	case WDIOC_KEEPALIVE:
		wdt_ping();
		return 0;
	case WDIOC_SETTIMEOUT:
		if (get_user(new_margin, (int __user *)arg))
			return -EFAULT;
		/* Arbitrary, can't find the card's limits */
		if (new_margin < 1 || new_margin > 124)
			return -EINVAL;
		wdt_margin = new_margin;
		wdt_ping();
		/* Fall */
	case WDIOC_GETTIMEOUT:
		return put_user(wdt_margin, (int __user *)arg);

	case WDIOC_SETOPTIONS:
		if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
			return -EFAULT;

		if (rv & WDIOS_DISABLECARD) {
			pr_info("disable watchdog\n");
			wdt_disable();
		}

		if (rv & WDIOS_ENABLECARD) {
			pr_info("enable watchdog\n");
			wdt_ping();
		}

		return -EINVAL;
	}
	return -ENOTTY;
}

static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
			       unsigned long arg)
{
	int ret;

	mutex_lock(&m41t80_rtc_mutex);
	ret = wdt_ioctl(file, cmd, arg);
	mutex_unlock(&m41t80_rtc_mutex);

	return ret;
}

/**
 *	wdt_open:
 *	@inode: inode of device
 *	@file: file handle to device
 *
 */
static int wdt_open(struct inode *inode, struct file *file)
{
	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
		mutex_lock(&m41t80_rtc_mutex);
		if (test_and_set_bit(0, &wdt_is_open)) {
			mutex_unlock(&m41t80_rtc_mutex);
			return -EBUSY;
		}
		/*
		 *	Activate
		 */
		wdt_is_open = 1;
		mutex_unlock(&m41t80_rtc_mutex);
		return nonseekable_open(inode, file);
	}
	return -ENODEV;
}

/**
 *	wdt_close:
 *	@inode: inode to board
 *	@file: file handle to board
 *
 */
static int wdt_release(struct inode *inode, struct file *file)
{
	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
		clear_bit(0, &wdt_is_open);
	return 0;
}

/**
 *	notify_sys:
 *	@this: our notifier block
 *	@code: the event being reported
 *	@unused: unused
 *
 *	Our notifier is called on system shutdowns. We want to turn the card
 *	off at reboot otherwise the machine will reboot again during memory
 *	test or worse yet during the following fsck. This would suck, in fact
 *	trust me - if it happens it does suck.
 */
static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
			  void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		/* Disable Watchdog */
		wdt_disable();
	return NOTIFY_DONE;
}

static const struct file_operations wdt_fops = {
	.owner	= THIS_MODULE,
	.read	= wdt_read,
	.unlocked_ioctl = wdt_unlocked_ioctl,
	.write	= wdt_write,
	.open	= wdt_open,
	.release = wdt_release,
	.llseek = no_llseek,
};

static struct miscdevice wdt_dev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &wdt_fops,
};

/*
 *	The WDT card needs to learn about soft shutdowns in order to
 *	turn the timebomb registers off.
 */
static struct notifier_block wdt_notifier = {
	.notifier_call = wdt_notify_sys,
};
#endif /* CONFIG_RTC_DRV_M41T80_WDT */

/*
 *****************************************************************************
 *
 *	Driver Interface
 *
 *****************************************************************************
 */
static int m41t80_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	int rc = 0;
	struct rtc_device *rtc = NULL;
	struct rtc_time tm;
	struct m41t80_data *clientdata = NULL;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C
				     | I2C_FUNC_SMBUS_BYTE_DATA))
		return -ENODEV;

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

	clientdata->features = id->driver_data;
	i2c_set_clientdata(client, clientdata);

	rtc = devm_rtc_device_register(&client->dev, client->name,
					&m41t80_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc))
		return PTR_ERR(rtc);

	clientdata->rtc = rtc;

	/* Make sure HT (Halt Update) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);

	if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
		if (clientdata->features & M41T80_FEATURE_HT) {
			m41t80_get_datetime(client, &tm);
			dev_info(&client->dev, "HT bit was set!\n");
			dev_info(&client->dev,
				 "Power Down at "
				 "%04i-%02i-%02i %02i:%02i:%02i\n",
				 tm.tm_year + 1900,
				 tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
				 tm.tm_min, tm.tm_sec);
		}
		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
					      rc & ~M41T80_ALHOUR_HT);
	}

	if (rc < 0) {
		dev_err(&client->dev, "Can't clear HT bit\n");
		return rc;
	}

	/* Make sure ST (stop) bit is cleared */
	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);

	if (rc >= 0 && rc & M41T80_SEC_ST)
		rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
					      rc & ~M41T80_SEC_ST);
	if (rc < 0) {
		dev_err(&client->dev, "Can't clear ST bit\n");
		return rc;
	}

	rc = m41t80_sysfs_register(&client->dev);
	if (rc)
		return rc;

#ifdef CONFIG_RTC_DRV_M41T80_WDT
	if (clientdata->features & M41T80_FEATURE_HT) {
		save_client = client;
		rc = misc_register(&wdt_dev);
		if (rc)
			return rc;
		rc = register_reboot_notifier(&wdt_notifier);
		if (rc) {
			misc_deregister(&wdt_dev);
			return rc;
		}
	}
#endif
	return 0;
}

static int m41t80_remove(struct i2c_client *client)
{
#ifdef CONFIG_RTC_DRV_M41T80_WDT
	struct m41t80_data *clientdata = i2c_get_clientdata(client);

	if (clientdata->features & M41T80_FEATURE_HT) {
		misc_deregister(&wdt_dev);
		unregister_reboot_notifier(&wdt_notifier);
	}
#endif

	return 0;
}

static struct i2c_driver m41t80_driver = {
	.driver = {
		.name = "rtc-m41t80",
	},
	.probe = m41t80_probe,
	.remove = m41t80_remove,
	.id_table = m41t80_id,
};

module_i2c_driver(m41t80_driver);

MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
MODULE_LICENSE("GPL");