1/* rtc-ds1347.c
  2 *
  3 * Driver for Dallas Semiconductor DS1347 Low Current, SPI Compatible
  4 * Real Time Clock
  5 *
  6 * Author : Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License version 2 as
 10 * published by the Free Software Foundation.
 11 *
 12 */
 13
 14#include <linux/init.h>
 15#include <linux/module.h>
 16#include <linux/device.h>
 17#include <linux/platform_device.h>
 18#include <linux/rtc.h>
 19#include <linux/spi/spi.h>
 20#include <linux/bcd.h>
 21
 22/* Registers in ds1347 rtc */
 23
 24#define DS1347_SECONDS_REG	0x01
 25#define DS1347_MINUTES_REG	0x03
 26#define DS1347_HOURS_REG	0x05
 27#define DS1347_DATE_REG		0x07
 28#define DS1347_MONTH_REG	0x09
 29#define DS1347_DAY_REG		0x0B
 30#define DS1347_YEAR_REG		0x0D
 31#define DS1347_CONTROL_REG	0x0F
 32#define DS1347_STATUS_REG	0x17
 33#define DS1347_CLOCK_BURST	0x3F
 34
 35static int ds1347_read_reg(struct device *dev, unsigned char address,
 36				unsigned char *data)
 37{
 38	struct spi_device *spi = to_spi_device(dev);
 39
 40	*data = address | 0x80;
 41
 42	return spi_write_then_read(spi, data, 1, data, 1);
 43}
 44
 45static int ds1347_write_reg(struct device *dev, unsigned char address,
 46				unsigned char data)
 47{
 48	struct spi_device *spi = to_spi_device(dev);
 49	unsigned char buf[2];
 50
 51	buf[0] = address & 0x7F;
 52	buf[1] = data;
 53
 54	return spi_write_then_read(spi, buf, 2, NULL, 0);
 55}
 56
 57static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
 58{
 59	struct spi_device *spi = to_spi_device(dev);
 60	int err;
 61	unsigned char buf[8];
 62
 63	buf[0] = DS1347_CLOCK_BURST | 0x80;
 64
 65	err = spi_write_then_read(spi, buf, 1, buf, 8);
 66	if (err)
 67		return err;
 68
 69	dt->tm_sec = bcd2bin(buf[0]);
 70	dt->tm_min = bcd2bin(buf[1]);
 71	dt->tm_hour = bcd2bin(buf[2] & 0x3F);
 72	dt->tm_mday = bcd2bin(buf[3]);
 73	dt->tm_mon = bcd2bin(buf[4]) - 1;
 74	dt->tm_wday = bcd2bin(buf[5]) - 1;
 75	dt->tm_year = bcd2bin(buf[6]) + 100;
 76
 77	return rtc_valid_tm(dt);
 78}
 79
 80static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
 81{
 82	struct spi_device *spi = to_spi_device(dev);
 83	unsigned char buf[9];
 84
 85	buf[0] = DS1347_CLOCK_BURST & 0x7F;
 86	buf[1] = bin2bcd(dt->tm_sec);
 87	buf[2] = bin2bcd(dt->tm_min);
 88	buf[3] = (bin2bcd(dt->tm_hour) & 0x3F);
 89	buf[4] = bin2bcd(dt->tm_mday);
 90	buf[5] = bin2bcd(dt->tm_mon + 1);
 91	buf[6] = bin2bcd(dt->tm_wday + 1);
 92
 93	/* year in linux is from 1900 i.e in range of 100
 94	in rtc it is from 00 to 99 */
 95	dt->tm_year = dt->tm_year % 100;
 96
 97	buf[7] = bin2bcd(dt->tm_year);
 98	buf[8] = bin2bcd(0x00);
 99
100	/* write the rtc settings */
101	return spi_write_then_read(spi, buf, 9, NULL, 0);
102}
103
104static const struct rtc_class_ops ds1347_rtc_ops = {
105	.read_time = ds1347_read_time,
106	.set_time = ds1347_set_time,
107};
108
109static int ds1347_probe(struct spi_device *spi)
110{
111	struct rtc_device *rtc;
112	unsigned char data;
113	int res;
114
115	/* spi setup with ds1347 in mode 3 and bits per word as 8 */
116	spi->mode = SPI_MODE_3;
117	spi->bits_per_word = 8;
118	spi_setup(spi);
119
120	/* RTC Settings */
121	res = ds1347_read_reg(&spi->dev, DS1347_SECONDS_REG, &data);
122	if (res)
123		return res;
124
125	/* Disable the write protect of rtc */
126	ds1347_read_reg(&spi->dev, DS1347_CONTROL_REG, &data);
127	data = data & ~(1<<7);
128	ds1347_write_reg(&spi->dev, DS1347_CONTROL_REG, data);
129
130	/* Enable the oscillator , disable the oscillator stop flag,
131	 and glitch filter to reduce current consumption */
132	ds1347_read_reg(&spi->dev, DS1347_STATUS_REG, &data);
133	data = data & 0x1B;
134	ds1347_write_reg(&spi->dev, DS1347_STATUS_REG, data);
135
136	/* display the settings */
137	ds1347_read_reg(&spi->dev, DS1347_CONTROL_REG, &data);
138	dev_info(&spi->dev, "DS1347 RTC CTRL Reg = 0x%02x\n", data);
139
140	ds1347_read_reg(&spi->dev, DS1347_STATUS_REG, &data);
141	dev_info(&spi->dev, "DS1347 RTC Status Reg = 0x%02x\n", data);
142
143	rtc = devm_rtc_device_register(&spi->dev, "ds1347",
144				&ds1347_rtc_ops, THIS_MODULE);
145
146	if (IS_ERR(rtc))
147		return PTR_ERR(rtc);
148
149	spi_set_drvdata(spi, rtc);
150
151	return 0;
152}
153
154static struct spi_driver ds1347_driver = {
155	.driver = {
156		.name = "ds1347",
157		.owner = THIS_MODULE,
158	},
159	.probe = ds1347_probe,
160};
161
162module_spi_driver(ds1347_driver);
163
164MODULE_DESCRIPTION("DS1347 SPI RTC DRIVER");
165MODULE_AUTHOR("Raghavendra C Ganiga <ravi23ganiga@gmail.com>");
166MODULE_LICENSE("GPL v2");