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
29static 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
56static 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
102static const struct rtc_class_ops m41t94_rtc_ops = {
103	.read_time	= m41t94_read_time,
104	.set_time	= m41t94_set_time,
105};
106
107static struct spi_driver m41t94_driver;
108
109static 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
133static struct spi_driver m41t94_driver = {
134	.driver = {
135		.name	= "rtc-m41t94",
136	},
137	.probe	= m41t94_probe,
138};
139
140module_spi_driver(m41t94_driver);
141
142MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
143MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
144MODULE_LICENSE("GPL");
145MODULE_ALIAS("spi:rtc-m41t94");
146