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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 <[email protected]>");
143MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
144MODULE_LICENSE("GPL");
145MODULE_ALIAS("spi:rtc-m41t94");