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
32static 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
45static 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
56static 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 rtc_valid_tm(dt);
89}
90
91static 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
118static const struct rtc_class_ops max6902_rtc_ops = {
119	.read_time	= max6902_read_time,
120	.set_time	= max6902_set_time,
121};
122
123static 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
146static struct spi_driver max6902_driver = {
147	.driver = {
148		.name	= "rtc-max6902",
149		.owner	= THIS_MODULE,
150	},
151	.probe	= max6902_probe,
152};
153
154module_spi_driver(max6902_driver);
155
156MODULE_DESCRIPTION("max6902 spi RTC driver");
157MODULE_AUTHOR("Raphael Assenat");
158MODULE_LICENSE("GPL");
159MODULE_ALIAS("spi:rtc-max6902");
160