linux - drivers/rtc/rtc-max6902.c

154 lines · 3.7 KiB

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
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
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
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
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
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");