xref: /openbmc/linux/drivers/rtc/rtc-m41t94.c (revision d2912cb1)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Driver for ST M41T94 SPI RTC
4  *
5  * Copyright (C) 2008 Kim B. Heino
6  */
7 
8 #include <linux/module.h>
9 #include <linux/kernel.h>
10 #include <linux/platform_device.h>
11 #include <linux/rtc.h>
12 #include <linux/spi/spi.h>
13 #include <linux/bcd.h>
14 
15 #define M41T94_REG_SECONDS	0x01
16 #define M41T94_REG_MINUTES	0x02
17 #define M41T94_REG_HOURS	0x03
18 #define M41T94_REG_WDAY		0x04
19 #define M41T94_REG_DAY		0x05
20 #define M41T94_REG_MONTH	0x06
21 #define M41T94_REG_YEAR		0x07
22 #define M41T94_REG_HT		0x0c
23 
24 #define M41T94_BIT_HALT		0x40
25 #define M41T94_BIT_STOP		0x80
26 #define M41T94_BIT_CB		0x40
27 #define M41T94_BIT_CEB		0x80
28 
m41t94_set_time(struct device * dev,struct rtc_time * tm)29 static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
30 {
31 	struct spi_device *spi = to_spi_device(dev);
32 	u8 buf[8]; /* write cmd + 7 registers */
33 
34 	dev_dbg(dev, "%s secs=%d, mins=%d, "
35 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
36 		"write", tm->tm_sec, tm->tm_min,
37 		tm->tm_hour, tm->tm_mday,
38 		tm->tm_mon, tm->tm_year, tm->tm_wday);
39 
40 	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
41 	buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
42 	buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
43 	buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
44 	buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
45 	buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
46 	buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);
47 
48 	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
49 	if (tm->tm_year >= 100)
50 		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
51 	buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);
52 
53 	return spi_write(spi, buf, 8);
54 }
55 
m41t94_read_time(struct device * dev,struct rtc_time * tm)56 static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
57 {
58 	struct spi_device *spi = to_spi_device(dev);
59 	u8 buf[2];
60 	int ret, hour;
61 
62 	/* clear halt update bit */
63 	ret = spi_w8r8(spi, M41T94_REG_HT);
64 	if (ret < 0)
65 		return ret;
66 	if (ret & M41T94_BIT_HALT) {
67 		buf[0] = 0x80 | M41T94_REG_HT;
68 		buf[1] = ret & ~M41T94_BIT_HALT;
69 		spi_write(spi, buf, 2);
70 	}
71 
72 	/* clear stop bit */
73 	ret = spi_w8r8(spi, M41T94_REG_SECONDS);
74 	if (ret < 0)
75 		return ret;
76 	if (ret & M41T94_BIT_STOP) {
77 		buf[0] = 0x80 | M41T94_REG_SECONDS;
78 		buf[1] = ret & ~M41T94_BIT_STOP;
79 		spi_write(spi, buf, 2);
80 	}
81 
82 	tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
83 	tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
84 	hour = spi_w8r8(spi, M41T94_REG_HOURS);
85 	tm->tm_hour = bcd2bin(hour & 0x3f);
86 	tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
87 	tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
88 	tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
89 	tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
90 	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
91 		tm->tm_year += 100;
92 
93 	dev_dbg(dev, "%s secs=%d, mins=%d, "
94 		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
95 		"read", tm->tm_sec, tm->tm_min,
96 		tm->tm_hour, tm->tm_mday,
97 		tm->tm_mon, tm->tm_year, tm->tm_wday);
98 
99 	return 0;
100 }
101 
102 static const struct rtc_class_ops m41t94_rtc_ops = {
103 	.read_time	= m41t94_read_time,
104 	.set_time	= m41t94_set_time,
105 };
106 
107 static struct spi_driver m41t94_driver;
108 
m41t94_probe(struct spi_device * spi)109 static int m41t94_probe(struct spi_device *spi)
110 {
111 	struct rtc_device *rtc;
112 	int res;
113 
114 	spi->bits_per_word = 8;
115 	spi_setup(spi);
116 
117 	res = spi_w8r8(spi, M41T94_REG_SECONDS);
118 	if (res < 0) {
119 		dev_err(&spi->dev, "not found.\n");
120 		return res;
121 	}
122 
123 	rtc = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name,
124 					&m41t94_rtc_ops, THIS_MODULE);
125 	if (IS_ERR(rtc))
126 		return PTR_ERR(rtc);
127 
128 	spi_set_drvdata(spi, rtc);
129 
130 	return 0;
131 }
132 
133 static struct spi_driver m41t94_driver = {
134 	.driver = {
135 		.name	= "rtc-m41t94",
136 	},
137 	.probe	= m41t94_probe,
138 };
139 
140 module_spi_driver(m41t94_driver);
141 
142 MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
143 MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
144 MODULE_LICENSE("GPL");
145 MODULE_ALIAS("spi:rtc-m41t94");
146