rtc-ds1390.c
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/*
* rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
*
* Copyright (C) 2008 Mercury IMC Ltd
* Written by Mark Jackson <mpfj@mimc.co.uk>
*
* 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.
*
* NOTE: Currently this driver only supports the bare minimum for read
* and write the RTC. The extra features provided by the chip family
* (alarms, trickle charger, different control registers) are unavailable.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#include <linux/slab.h>
#define DS1390_REG_100THS 0x00
#define DS1390_REG_SECONDS 0x01
#define DS1390_REG_MINUTES 0x02
#define DS1390_REG_HOURS 0x03
#define DS1390_REG_DAY 0x04
#define DS1390_REG_DATE 0x05
#define DS1390_REG_MONTH_CENT 0x06
#define DS1390_REG_YEAR 0x07
#define DS1390_REG_ALARM_100THS 0x08
#define DS1390_REG_ALARM_SECONDS 0x09
#define DS1390_REG_ALARM_MINUTES 0x0A
#define DS1390_REG_ALARM_HOURS 0x0B
#define DS1390_REG_ALARM_DAY_DATE 0x0C
#define DS1390_REG_CONTROL 0x0D
#define DS1390_REG_STATUS 0x0E
#define DS1390_REG_TRICKLE 0x0F
struct ds1390 {
struct rtc_device *rtc;
u8 txrx_buf[9]; /* cmd + 8 registers */
};
static int ds1390_get_reg(struct device *dev, unsigned char address,
unsigned char *data)
{
struct spi_device *spi = to_spi_device(dev);
struct ds1390 *chip = dev_get_drvdata(dev);
int status;
if (!data)
return -EINVAL;
/* Clear MSB to indicate read */
chip->txrx_buf[0] = address & 0x7f;
/* do the i/o */
status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
if (status != 0)
return status;
*data = chip->txrx_buf[1];
return 0;
}
static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
{
struct spi_device *spi = to_spi_device(dev);
struct ds1390 *chip = dev_get_drvdata(dev);
int status;
/* build the message */
chip->txrx_buf[0] = DS1390_REG_SECONDS;
/* do the i/o */
status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
if (status != 0)
return status;
/* The chip sends data in this order:
* Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
dt->tm_sec = bcd2bin(chip->txrx_buf[0]);
dt->tm_min = bcd2bin(chip->txrx_buf[1]);
dt->tm_hour = bcd2bin(chip->txrx_buf[2]);
dt->tm_wday = bcd2bin(chip->txrx_buf[3]);
dt->tm_mday = bcd2bin(chip->txrx_buf[4]);
/* mask off century bit */
dt->tm_mon = bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
/* adjust for century bit */
dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
return rtc_valid_tm(dt);
}
static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
{
struct spi_device *spi = to_spi_device(dev);
struct ds1390 *chip = dev_get_drvdata(dev);
/* build the message */
chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
chip->txrx_buf[2] = bin2bcd(dt->tm_min);
chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
((dt->tm_year > 99) ? 0x80 : 0x00);
chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
/* do the i/o */
return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
}
static const struct rtc_class_ops ds1390_rtc_ops = {
.read_time = ds1390_read_time,
.set_time = ds1390_set_time,
};
static int ds1390_probe(struct spi_device *spi)
{
unsigned char tmp;
struct ds1390 *chip;
int res;
spi->mode = SPI_MODE_3;
spi->bits_per_word = 8;
spi_setup(spi);
chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
if (!chip) {
dev_err(&spi->dev, "unable to allocate device memory\n");
return -ENOMEM;
}
spi_set_drvdata(spi, chip);
res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
if (res != 0) {
dev_err(&spi->dev, "unable to read device\n");
return res;
}
chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
&ds1390_rtc_ops, THIS_MODULE);
if (IS_ERR(chip->rtc)) {
dev_err(&spi->dev, "unable to register device\n");
res = PTR_ERR(chip->rtc);
}
return res;
}
static struct spi_driver ds1390_driver = {
.driver = {
.name = "rtc-ds1390",
.owner = THIS_MODULE,
},
.probe = ds1390_probe,
};
module_spi_driver(ds1390_driver);
MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-ds1390");