summaryrefslogtreecommitdiffstats
path: root/drivers/rtc/rtc-max6916.c
blob: 623ab27b2757cda88eb75486a88e87369f0034bc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
/* rtc-max6916.c
 *
 * Driver for MAXIM  max6916 Low Current, SPI Compatible
 * Real Time Clock
 *
 * Author : Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>

/* Registers in max6916 rtc */

#define MAX6916_SECONDS_REG	0x01
#define MAX6916_MINUTES_REG	0x02
#define MAX6916_HOURS_REG	0x03
#define MAX6916_DATE_REG	0x04
#define MAX6916_MONTH_REG	0x05
#define MAX6916_DAY_REG	0x06
#define MAX6916_YEAR_REG	0x07
#define MAX6916_CONTROL_REG	0x08
#define MAX6916_STATUS_REG	0x0C
#define MAX6916_CLOCK_BURST	0x3F

static int max6916_read_reg(struct device *dev, unsigned char address,
			    unsigned char *data)
{
	struct spi_device *spi = to_spi_device(dev);

	*data = address | 0x80;

	return spi_write_then_read(spi, data, 1, data, 1);
}

static int max6916_write_reg(struct device *dev, unsigned char address,
			     unsigned char data)
{
	struct spi_device *spi = to_spi_device(dev);
	unsigned char buf[2];

	buf[0] = address & 0x7F;
	buf[1] = data;

	return spi_write_then_read(spi, buf, 2, NULL, 0);
}

static int max6916_read_time(struct device *dev, struct rtc_time *dt)
{
	struct spi_device *spi = to_spi_device(dev);
	int err;
	unsigned char buf[8];

	buf[0] = MAX6916_CLOCK_BURST | 0x80;

	err = spi_write_then_read(spi, buf, 1, buf, 8);

	if (err)
		return err;

	dt->tm_sec = bcd2bin(buf[0]);
	dt->tm_min = bcd2bin(buf[1]);
	dt->tm_hour = bcd2bin(buf[2] & 0x3F);
	dt->tm_mday = bcd2bin(buf[3]);
	dt->tm_mon = bcd2bin(buf[4]) - 1;
	dt->tm_wday = bcd2bin(buf[5]) - 1;
	dt->tm_year = bcd2bin(buf[6]) + 100;

	return rtc_valid_tm(dt);
}

static int max6916_set_time(struct device *dev, struct rtc_time *dt)
{
	struct spi_device *spi = to_spi_device(dev);
	unsigned char buf[9];

	if (dt->tm_year < 100 || dt->tm_year > 199) {
		dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n",
			dt->tm_year + 1900);
	return -EINVAL;
	}

	buf[0] = MAX6916_CLOCK_BURST & 0x7F;
	buf[1] = bin2bcd(dt->tm_sec);
	buf[2] = bin2bcd(dt->tm_min);
	buf[3] = (bin2bcd(dt->tm_hour) & 0X3F);
	buf[4] = bin2bcd(dt->tm_mday);
	buf[5] = bin2bcd(dt->tm_mon + 1);
	buf[6] = bin2bcd(dt->tm_wday + 1);
	buf[7] = bin2bcd(dt->tm_year % 100);
	buf[8] = bin2bcd(0x00);

	/* write the rtc settings */
	return spi_write_then_read(spi, buf, 9, NULL, 0);
}

static const struct rtc_class_ops max6916_rtc_ops = {
	.read_time = max6916_read_time,
	.set_time = max6916_set_time,
};

static int max6916_probe(struct spi_device *spi)
{
	struct rtc_device *rtc;
	unsigned char data;
	int res;

	/* spi setup with max6916 in mode 3 and bits per word as 8 */
	spi->mode = SPI_MODE_3;
	spi->bits_per_word = 8;
	spi_setup(spi);

	/* RTC Settings */
	res = max6916_read_reg(&spi->dev, MAX6916_SECONDS_REG, &data);
	if (res)
		return res;

	/* Disable the write protect of rtc */
	max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
	data = data & ~(1 << 7);
	max6916_write_reg(&spi->dev, MAX6916_CONTROL_REG, data);

	/*Enable oscillator,disable oscillator stop flag, glitch filter*/
	max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
	data = data & 0x1B;
	max6916_write_reg(&spi->dev, MAX6916_STATUS_REG, data);

	/* display the settings */
	max6916_read_reg(&spi->dev, MAX6916_CONTROL_REG, &data);
	dev_info(&spi->dev, "MAX6916 RTC CTRL Reg = 0x%02x\n", data);

	max6916_read_reg(&spi->dev, MAX6916_STATUS_REG, &data);
	dev_info(&spi->dev, "MAX6916 RTC Status Reg = 0x%02x\n", data);

	rtc = devm_rtc_device_register(&spi->dev, "max6916",
				       &max6916_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc))
		return PTR_ERR(rtc);

	spi_set_drvdata(spi, rtc);

	return 0;
}

static struct spi_driver max6916_driver = {
	.driver = {
		.name = "max6916",
	},
	.probe = max6916_probe,
};
module_spi_driver(max6916_driver);

MODULE_DESCRIPTION("MAX6916 SPI RTC DRIVER");
MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@gmail.com>");
MODULE_LICENSE("GPL v2");
OpenPOWER on IntegriCloud