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
28static 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
41static 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
52static 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
87static 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
114static const struct rtc_class_ops max6902_rtc_ops = {
115	.read_time	= max6902_read_time,
116	.set_time	= max6902_set_time,
117};
118
119static 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
142static struct spi_driver max6902_driver = {
143	.driver = {
144		.name	= "rtc-max6902",
145	},
146	.probe	= max6902_probe,
147};
148
149module_spi_driver(max6902_driver);
150
151MODULE_DESCRIPTION("max6902 spi RTC driver");
152MODULE_AUTHOR("Raphael Assenat");
153MODULE_LICENSE("GPL");
154MODULE_ALIAS("spi:rtc-max6902");
155