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
32static 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
59static 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
106static const struct rtc_class_ops m41t94_rtc_ops = {
107	.read_time	= m41t94_read_time,
108	.set_time	= m41t94_set_time,
109};
110
111static struct spi_driver m41t94_driver;
112
113static int 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 = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name,
128					&m41t94_rtc_ops, THIS_MODULE);
129	if (IS_ERR(rtc))
130		return PTR_ERR(rtc);
131
132	spi_set_drvdata(spi, rtc);
133
134	return 0;
135}
136
137static struct spi_driver m41t94_driver = {
138	.driver = {
139		.name	= "rtc-m41t94",
140	},
141	.probe	= m41t94_probe,
142};
143
144module_spi_driver(m41t94_driver);
145
146MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
147MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
148MODULE_LICENSE("GPL");
149MODULE_ALIAS("spi:rtc-m41t94");
150