1 /* drivers/rtc/rtc-max6902.c
2 *
3 * Copyright (C) 2006 8D Technologies inc.
4 * Copyright (C) 2004 Compulab Ltd.
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 * Driver for MAX6902 spi RTC
11 *
12 */
13
14 #include <linux/module.h>
15 #include <linux/kernel.h>
16 #include <linux/platform_device.h>
17 #include <linux/init.h>
18 #include <linux/rtc.h>
19 #include <linux/spi/spi.h>
20 #include <linux/bcd.h>
21
22 #define MAX6902_REG_SECONDS 0x01
23 #define MAX6902_REG_MINUTES 0x03
24 #define MAX6902_REG_HOURS 0x05
25 #define MAX6902_REG_DATE 0x07
26 #define MAX6902_REG_MONTH 0x09
27 #define MAX6902_REG_DAY 0x0B
28 #define MAX6902_REG_YEAR 0x0D
29 #define MAX6902_REG_CONTROL 0x0F
30 #define MAX6902_REG_CENTURY 0x13
31
max6902_set_reg(struct device * dev,unsigned char address,unsigned char data)32 static int max6902_set_reg(struct device *dev, unsigned char address,
33 unsigned char data)
34 {
35 struct spi_device *spi = to_spi_device(dev);
36 unsigned char buf[2];
37
38 /* MSB must be '0' to write */
39 buf[0] = address & 0x7f;
40 buf[1] = data;
41
42 return spi_write_then_read(spi, buf, 2, NULL, 0);
43 }
44
max6902_get_reg(struct device * dev,unsigned char address,unsigned char * data)45 static int max6902_get_reg(struct device *dev, unsigned char address,
46 unsigned char *data)
47 {
48 struct spi_device *spi = to_spi_device(dev);
49
50 /* Set MSB to indicate read */
51 *data = address | 0x80;
52
53 return spi_write_then_read(spi, data, 1, data, 1);
54 }
55
max6902_read_time(struct device * dev,struct rtc_time * dt)56 static int max6902_read_time(struct device *dev, struct rtc_time *dt)
57 {
58 int err, century;
59 struct spi_device *spi = to_spi_device(dev);
60 unsigned char buf[8];
61
62 buf[0] = 0xbf; /* Burst read */
63
64 err = spi_write_then_read(spi, buf, 1, buf, 8);
65 if (err != 0)
66 return err;
67
68 /* The chip sends data in this order:
69 * Seconds, Minutes, Hours, Date, Month, Day, Year */
70 dt->tm_sec = bcd2bin(buf[0]);
71 dt->tm_min = bcd2bin(buf[1]);
72 dt->tm_hour = bcd2bin(buf[2]);
73 dt->tm_mday = bcd2bin(buf[3]);
74 dt->tm_mon = bcd2bin(buf[4]) - 1;
75 dt->tm_wday = bcd2bin(buf[5]);
76 dt->tm_year = bcd2bin(buf[6]);
77
78 /* Read century */
79 err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
80 if (err != 0)
81 return err;
82
83 century = bcd2bin(buf[0]) * 100;
84
85 dt->tm_year += century;
86 dt->tm_year -= 1900;
87
88 return 0;
89 }
90
max6902_set_time(struct device * dev,struct rtc_time * dt)91 static int max6902_set_time(struct device *dev, struct rtc_time *dt)
92 {
93 dt->tm_year = dt->tm_year + 1900;
94
95 /* Remove write protection */
96 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0);
97
98 max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec));
99 max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min));
100 max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour));
101
102 max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday));
103 max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1));
104 max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday));
105 max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100));
106 max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100));
107
108 /* Compulab used a delay here. However, the datasheet
109 * does not mention a delay being required anywhere... */
110 /* delay(2000); */
111
112 /* Write protect */
113 max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80);
114
115 return 0;
116 }
117
118 static const struct rtc_class_ops max6902_rtc_ops = {
119 .read_time = max6902_read_time,
120 .set_time = max6902_set_time,
121 };
122
max6902_probe(struct spi_device * spi)123 static int max6902_probe(struct spi_device *spi)
124 {
125 struct rtc_device *rtc;
126 unsigned char tmp;
127 int res;
128
129 spi->mode = SPI_MODE_3;
130 spi->bits_per_word = 8;
131 spi_setup(spi);
132
133 res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
134 if (res != 0)
135 return res;
136
137 rtc = devm_rtc_device_register(&spi->dev, "max6902",
138 &max6902_rtc_ops, THIS_MODULE);
139 if (IS_ERR(rtc))
140 return PTR_ERR(rtc);
141
142 spi_set_drvdata(spi, rtc);
143 return 0;
144 }
145
146 static struct spi_driver max6902_driver = {
147 .driver = {
148 .name = "rtc-max6902",
149 },
150 .probe = max6902_probe,
151 };
152
153 module_spi_driver(max6902_driver);
154
155 MODULE_DESCRIPTION("max6902 spi RTC driver");
156 MODULE_AUTHOR("Raphael Assenat");
157 MODULE_LICENSE("GPL");
158 MODULE_ALIAS("spi:rtc-max6902");
159