1 // SPDX-License-Identifier: GPL-2.0-only
2 /* drivers/rtc/rtc-max6902.c
3  *
4  * Copyright (C) 2006 8D Technologies inc.
5  * Copyright (C) 2004 Compulab Ltd.
6  *
7  * Driver for MAX6902 spi RTC
8  */
9 
10 #include <linux/module.h>
11 #include <linux/kernel.h>
12 #include <linux/platform_device.h>
13 #include <linux/init.h>
14 #include <linux/rtc.h>
15 #include <linux/spi/spi.h>
16 #include <linux/bcd.h>
17 
18 #define MAX6902_REG_SECONDS		0x01
19 #define MAX6902_REG_MINUTES		0x03
20 #define MAX6902_REG_HOURS		0x05
21 #define MAX6902_REG_DATE		0x07
22 #define MAX6902_REG_MONTH		0x09
23 #define MAX6902_REG_DAY			0x0B
24 #define MAX6902_REG_YEAR		0x0D
25 #define MAX6902_REG_CONTROL		0x0F
26 #define MAX6902_REG_CENTURY		0x13
27 
max6902_set_reg(struct device * dev,unsigned char address,unsigned char data)28 static int max6902_set_reg(struct device *dev, unsigned char address,
29 				unsigned char data)
30 {
31 	struct spi_device *spi = to_spi_device(dev);
32 	unsigned char buf[2];
33 
34 	/* MSB must be '0' to write */
35 	buf[0] = address & 0x7f;
36 	buf[1] = data;
37 
38 	return spi_write_then_read(spi, buf, 2, NULL, 0);
39 }
40 
max6902_get_reg(struct device * dev,unsigned char address,unsigned char * data)41 static int max6902_get_reg(struct device *dev, unsigned char address,
42 				unsigned char *data)
43 {
44 	struct spi_device *spi = to_spi_device(dev);
45 
46 	/* Set MSB to indicate read */
47 	*data = address | 0x80;
48 
49 	return spi_write_then_read(spi, data, 1, data, 1);
50 }
51 
max6902_read_time(struct device * dev,struct rtc_time * dt)52 static int max6902_read_time(struct device *dev, struct rtc_time *dt)
53 {
54 	int err, century;
55 	struct spi_device *spi = to_spi_device(dev);
56 	unsigned char buf[8];
57 
58 	buf[0] = 0xbf;	/* Burst read */
59 
60 	err = spi_write_then_read(spi, buf, 1, buf, 8);
61 	if (err != 0)
62 		return err;
63 
64 	/* The chip sends data in this order:
65 	 * Seconds, Minutes, Hours, Date, Month, Day, Year */
66 	dt->tm_sec	= bcd2bin(buf[0]);
67 	dt->tm_min	= bcd2bin(buf[1]);
68 	dt->tm_hour	= bcd2bin(buf[2]);
69 	dt->tm_mday	= bcd2bin(buf[3]);
70 	dt->tm_mon	= bcd2bin(buf[4]) - 1;
71 	dt->tm_wday	= bcd2bin(buf[5]);
72 	dt->tm_year	= bcd2bin(buf[6]);
73 
74 	/* Read century */
75 	err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
76 	if (err != 0)
77 		return err;
78 
79 	century = bcd2bin(buf[0]) * 100;
80 
81 	dt->tm_year += century;
82 	dt->tm_year -= 1900;
83 
84 	return 0;
85 }
86 
max6902_set_time(struct device * dev,struct rtc_time * dt)87 static int max6902_set_time(struct device *dev, struct rtc_time *dt)
88 {
89 	dt->tm_year = dt->tm_year + 1900;
90 
91 	/* Remove write protection */
92 	max6902_set_reg(dev, MAX6902_REG_CONTROL, 0);
93 
94 	max6902_set_reg(dev, MAX6902_REG_SECONDS, bin2bcd(dt->tm_sec));
95 	max6902_set_reg(dev, MAX6902_REG_MINUTES, bin2bcd(dt->tm_min));
96 	max6902_set_reg(dev, MAX6902_REG_HOURS, bin2bcd(dt->tm_hour));
97 
98 	max6902_set_reg(dev, MAX6902_REG_DATE, bin2bcd(dt->tm_mday));
99 	max6902_set_reg(dev, MAX6902_REG_MONTH, bin2bcd(dt->tm_mon + 1));
100 	max6902_set_reg(dev, MAX6902_REG_DAY, bin2bcd(dt->tm_wday));
101 	max6902_set_reg(dev, MAX6902_REG_YEAR, bin2bcd(dt->tm_year % 100));
102 	max6902_set_reg(dev, MAX6902_REG_CENTURY, bin2bcd(dt->tm_year / 100));
103 
104 	/* Compulab used a delay here. However, the datasheet
105 	 * does not mention a delay being required anywhere... */
106 	/* delay(2000); */
107 
108 	/* Write protect */
109 	max6902_set_reg(dev, MAX6902_REG_CONTROL, 0x80);
110 
111 	return 0;
112 }
113 
114 static const struct rtc_class_ops max6902_rtc_ops = {
115 	.read_time	= max6902_read_time,
116 	.set_time	= max6902_set_time,
117 };
118 
max6902_probe(struct spi_device * spi)119 static int max6902_probe(struct spi_device *spi)
120 {
121 	struct rtc_device *rtc;
122 	unsigned char tmp;
123 	int res;
124 
125 	spi->mode = SPI_MODE_3;
126 	spi->bits_per_word = 8;
127 	spi_setup(spi);
128 
129 	res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
130 	if (res != 0)
131 		return res;
132 
133 	rtc = devm_rtc_device_register(&spi->dev, "max6902",
134 				&max6902_rtc_ops, THIS_MODULE);
135 	if (IS_ERR(rtc))
136 		return PTR_ERR(rtc);
137 
138 	spi_set_drvdata(spi, rtc);
139 	return 0;
140 }
141 
142 static struct spi_driver max6902_driver = {
143 	.driver = {
144 		.name	= "rtc-max6902",
145 	},
146 	.probe	= max6902_probe,
147 };
148 
149 module_spi_driver(max6902_driver);
150 
151 MODULE_DESCRIPTION("max6902 spi RTC driver");
152 MODULE_AUTHOR("Raphael Assenat");
153 MODULE_LICENSE("GPL");
154 MODULE_ALIAS("spi:rtc-max6902");
155