xref: /linux/drivers/rtc/rtc-m41t94.c (revision 60e13231561b3a4c5269bfa1ef6c0569ad6f28ec)
1 /*
2  * Driver for ST M41T94 SPI RTC
3  *
4  * Copyright (C) 2008 Kim B. Heino
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  */
10 
11 #include <linux/module.h>
12 #include <linux/kernel.h>
13 #include <linux/platform_device.h>
14 #include <linux/rtc.h>
15 #include <linux/spi/spi.h>
16 #include <linux/bcd.h>
17 
18 #define M41T94_REG_SECONDS	0x01
19 #define M41T94_REG_MINUTES	0x02
20 #define M41T94_REG_HOURS	0x03
21 #define M41T94_REG_WDAY		0x04
22 #define M41T94_REG_DAY		0x05
23 #define M41T94_REG_MONTH	0x06
24 #define M41T94_REG_YEAR		0x07
25 #define M41T94_REG_HT		0x0c
26 
27 #define M41T94_BIT_HALT		0x40
28 #define M41T94_BIT_STOP		0x80
29 #define M41T94_BIT_CB		0x40
30 #define M41T94_BIT_CEB		0x80
31 
32 static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
33 {
34 	struct spi_device *spi = to_spi_device(dev);
35 	u8 buf[8]; /* write cmd + 7 registers */
36 
37 	dev_dbg(dev, "%s secs=%d, mins=%d, "
38 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
39 		"write", tm->tm_sec, tm->tm_min,
40 		tm->tm_hour, tm->tm_mday,
41 		tm->tm_mon, tm->tm_year, tm->tm_wday);
42 
43 	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
44 	buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
45 	buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
46 	buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
47 	buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
48 	buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
49 	buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);
50 
51 	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
52 	if (tm->tm_year >= 100)
53 		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
54 	buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);
55 
56 	return spi_write(spi, buf, 8);
57 }
58 
59 static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
60 {
61 	struct spi_device *spi = to_spi_device(dev);
62 	u8 buf[2];
63 	int ret, hour;
64 
65 	/* clear halt update bit */
66 	ret = spi_w8r8(spi, M41T94_REG_HT);
67 	if (ret < 0)
68 		return ret;
69 	if (ret & M41T94_BIT_HALT) {
70 		buf[0] = 0x80 | M41T94_REG_HT;
71 		buf[1] = ret & ~M41T94_BIT_HALT;
72 		spi_write(spi, buf, 2);
73 	}
74 
75 	/* clear stop bit */
76 	ret = spi_w8r8(spi, M41T94_REG_SECONDS);
77 	if (ret < 0)
78 		return ret;
79 	if (ret & M41T94_BIT_STOP) {
80 		buf[0] = 0x80 | M41T94_REG_SECONDS;
81 		buf[1] = ret & ~M41T94_BIT_STOP;
82 		spi_write(spi, buf, 2);
83 	}
84 
85 	tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
86 	tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
87 	hour = spi_w8r8(spi, M41T94_REG_HOURS);
88 	tm->tm_hour = bcd2bin(hour & 0x3f);
89 	tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
90 	tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
91 	tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
92 	tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
93 	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
94 		tm->tm_year += 100;
95 
96 	dev_dbg(dev, "%s secs=%d, mins=%d, "
97 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
98 		"read", tm->tm_sec, tm->tm_min,
99 		tm->tm_hour, tm->tm_mday,
100 		tm->tm_mon, tm->tm_year, tm->tm_wday);
101 
102 	/* initial clock setting can be undefined */
103 	return rtc_valid_tm(tm);
104 }
105 
106 static const struct rtc_class_ops m41t94_rtc_ops = {
107 	.read_time	= m41t94_read_time,
108 	.set_time	= m41t94_set_time,
109 };
110 
111 static struct spi_driver m41t94_driver;
112 
113 static int __devinit m41t94_probe(struct spi_device *spi)
114 {
115 	struct rtc_device *rtc;
116 	int res;
117 
118 	spi->bits_per_word = 8;
119 	spi_setup(spi);
120 
121 	res = spi_w8r8(spi, M41T94_REG_SECONDS);
122 	if (res < 0) {
123 		dev_err(&spi->dev, "not found.\n");
124 		return res;
125 	}
126 
127 	rtc = rtc_device_register(m41t94_driver.driver.name,
128 		&spi->dev, &m41t94_rtc_ops, THIS_MODULE);
129 	if (IS_ERR(rtc))
130 		return PTR_ERR(rtc);
131 
132 	dev_set_drvdata(&spi->dev, rtc);
133 
134 	return 0;
135 }
136 
137 static int __devexit m41t94_remove(struct spi_device *spi)
138 {
139 	struct rtc_device *rtc = spi_get_drvdata(spi);
140 
141 	if (rtc)
142 		rtc_device_unregister(rtc);
143 
144 	return 0;
145 }
146 
147 static struct spi_driver m41t94_driver = {
148 	.driver = {
149 		.name	= "rtc-m41t94",
150 		.bus	= &spi_bus_type,
151 		.owner	= THIS_MODULE,
152 	},
153 	.probe	= m41t94_probe,
154 	.remove = __devexit_p(m41t94_remove),
155 };
156 
157 static __init int m41t94_init(void)
158 {
159 	return spi_register_driver(&m41t94_driver);
160 }
161 
162 module_init(m41t94_init);
163 
164 static __exit void m41t94_exit(void)
165 {
166 	spi_unregister_driver(&m41t94_driver);
167 }
168 
169 module_exit(m41t94_exit);
170 
171 MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
172 MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
173 MODULE_LICENSE("GPL");
174 MODULE_ALIAS("spi:rtc-m41t94");
175