aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-m41t94.c
blob: c8c97a4169d4e22e46ed3aa6a7b0a72fa65ec4ba (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
/*
 * Driver for ST M41T94 SPI RTC
 *
 * Copyright (C) 2008 Kim B. Heino
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>

#define M41T94_REG_SECONDS	0x01
#define M41T94_REG_MINUTES	0x02
#define M41T94_REG_HOURS	0x03
#define M41T94_REG_WDAY		0x04
#define M41T94_REG_DAY		0x05
#define M41T94_REG_MONTH	0x06
#define M41T94_REG_YEAR		0x07
#define M41T94_REG_HT		0x0c

#define M41T94_BIT_HALT		0x40
#define M41T94_BIT_STOP		0x80
#define M41T94_BIT_CB		0x40
#define M41T94_BIT_CEB		0x80

static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
{
	struct spi_device *spi = to_spi_device(dev);
	u8 buf[8]; /* write cmd + 7 registers */

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

	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
	buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
	buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
	buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
	buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
	buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
	buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);

	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
	if (tm->tm_year >= 100)
		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
	buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);

	return spi_write(spi, buf, 8);
}

static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
{
	struct spi_device *spi = to_spi_device(dev);
	u8 buf[2];
	int ret, hour;

	/* clear halt update bit */
	ret = spi_w8r8(spi, M41T94_REG_HT);
	if (ret < 0)
		return ret;
	if (ret & M41T94_BIT_HALT) {
		buf[0] = 0x80 | M41T94_REG_HT;
		buf[1] = ret & ~M41T94_BIT_HALT;
		spi_write(spi, buf, 2);
	}

	/* clear stop bit */
	ret = spi_w8r8(spi, M41T94_REG_SECONDS);
	if (ret < 0)
		return ret;
	if (ret & M41T94_BIT_STOP) {
		buf[0] = 0x80 | M41T94_REG_SECONDS;
		buf[1] = ret & ~M41T94_BIT_STOP;
		spi_write(spi, buf, 2);
	}

	tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
	tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
	hour = spi_w8r8(spi, M41T94_REG_HOURS);
	tm->tm_hour = bcd2bin(hour & 0x3f);
	tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
	tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
	tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
	tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
		tm->tm_year += 100;

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

	/* initial clock setting can be undefined */
	return rtc_valid_tm(tm);
}

static const struct rtc_class_ops m41t94_rtc_ops = {
	.read_time	= m41t94_read_time,
	.set_time	= m41t94_set_time,
};

static struct spi_driver m41t94_driver;

static int __devinit m41t94_probe(struct spi_device *spi)
{
	struct rtc_device *rtc;
	int res;

	spi->bits_per_word = 8;
	spi_setup(spi);

	res = spi_w8r8(spi, M41T94_REG_SECONDS);
	if (res < 0) {
		dev_err(&spi->dev, "not found.\n");
		return res;
	}

	rtc = rtc_device_register(m41t94_driver.driver.name,
		&spi->dev, &m41t94_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc))
		return PTR_ERR(rtc);

	dev_set_drvdata(&spi->dev, rtc);

	return 0;
}

static int __devexit m41t94_remove(struct spi_device *spi)
{
	struct rtc_device *rtc = platform_get_drvdata(spi);

	if (rtc)
		rtc_device_unregister(rtc);

	return 0;
}

static struct spi_driver m41t94_driver = {
	.driver = {
		.name	= "rtc-m41t94",
		.bus	= &spi_bus_type,
		.owner	= THIS_MODULE,
	},
	.probe	= m41t94_probe,
	.remove = __devexit_p(m41t94_remove),
};

static __init int m41t94_init(void)
{
	return spi_register_driver(&m41t94_driver);
}

module_init(m41t94_init);

static __exit void m41t94_exit(void)
{
	spi_unregister_driver(&m41t94_driver);
}

module_exit(m41t94_exit);

MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-m41t94");