rtc-max6902.c

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/* drivers/rtc/rtc-max6902.c
 *
 * Copyright (C) 2006 8D Technologies inc.
 * Copyright (C) 2004 Compulab Ltd.
 *
 * 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.
 *
 * Driver for MAX6902 spi RTC
 *
 */

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

#define MAX6902_REG_SECONDS     0x01
#define MAX6902_REG_MINUTES     0x03
#define MAX6902_REG_HOURS       0x05
#define MAX6902_REG_DATE        0x07
#define MAX6902_REG_MONTH       0x09
#define MAX6902_REG_DAY         0x0B
#define MAX6902_REG_YEAR        0x0D
#define MAX6902_REG_CONTROL     0x0F
#define MAX6902_REG_CENTURY     0x13

static int max6902_set_reg(struct device *dev, unsigned char address,
                unsigned char data)
{
    struct spi_device *spi = to_spi_device(dev);
    unsigned char buf[2];

    /* MSB must be '0' to write */
    buf[0] = address & 0x7f;
    buf[1] = data;

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

static int max6902_get_reg(struct device *dev, unsigned char address,
                unsigned char *data)
{
    struct spi_device *spi = to_spi_device(dev);

    /* Set MSB to indicate read */
    *data = address | 0x80;

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

static int max6902_read_time(struct device *dev, struct rtc_time *dt)
{
    int err, century;
    struct spi_device *spi = to_spi_device(dev);
    unsigned char buf[8];

    buf[0] = 0xbf;  /* Burst read */

    err = spi_write_then_read(spi, buf, 1, buf, 8);
    if (err != 0)
        return err;

    /* The chip sends data in this order:
     * Seconds, Minutes, Hours, Date, Month, Day, Year */
    dt->tm_sec  = bcd2bin(buf[0]);
    dt->tm_min  = bcd2bin(buf[1]);
    dt->tm_hour = bcd2bin(buf[2]);
    dt->tm_mday = bcd2bin(buf[3]);
    dt->tm_mon  = bcd2bin(buf[4]) - 1;
    dt->tm_wday = bcd2bin(buf[5]);
    dt->tm_year = bcd2bin(buf[6]);

    /* Read century */
    err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
    if (err != 0)
        return err;

    century = bcd2bin(buf[0]) * 100;

    dt->tm_year += century;
    dt->tm_year -= 1900;

    return rtc_valid_tm(dt);
}

static int max6902_set_time(struct device *dev, struct rtc_time *dt)
{
    dt->tm_year = dt->tm_year + 1900;

    /* Remove write protection */
    max6902_set_reg(dev, 0xF, 0);

    max6902_set_reg(dev, 0x01, bin2bcd(dt->tm_sec));
    max6902_set_reg(dev, 0x03, bin2bcd(dt->tm_min));
    max6902_set_reg(dev, 0x05, bin2bcd(dt->tm_hour));

    max6902_set_reg(dev, 0x07, bin2bcd(dt->tm_mday));
    max6902_set_reg(dev, 0x09, bin2bcd(dt->tm_mon + 1));
    max6902_set_reg(dev, 0x0B, bin2bcd(dt->tm_wday));
    max6902_set_reg(dev, 0x0D, bin2bcd(dt->tm_year % 100));
    max6902_set_reg(dev, 0x13, bin2bcd(dt->tm_year / 100));

    /* Compulab used a delay here. However, the datasheet
     * does not mention a delay being required anywhere... */
    /* delay(2000); */

    /* Write protect */
    max6902_set_reg(dev, 0xF, 0x80);

    return 0;
}

static const struct rtc_class_ops max6902_rtc_ops = {
    .read_time  = max6902_read_time,
    .set_time   = max6902_set_time,
};

static int __devinit max6902_probe(struct spi_device *spi)
{
    struct rtc_device *rtc;
    unsigned char tmp;
    int res;

    spi->mode = SPI_MODE_3;
    spi->bits_per_word = 8;
    spi_setup(spi);

    res = max6902_get_reg(&spi->dev, MAX6902_REG_SECONDS, &tmp);
    if (res != 0)
        return res;

    rtc = rtc_device_register("max6902",
                &spi->dev, &max6902_rtc_ops, THIS_MODULE);
    if (IS_ERR(rtc))
        return PTR_ERR(rtc);

    dev_set_drvdata(&spi->dev, rtc);
    return 0;
}

static int __devexit max6902_remove(struct spi_device *spi)
{
    struct rtc_device *rtc = dev_get_drvdata(&spi->dev);

    rtc_device_unregister(rtc);
    return 0;
}

static struct spi_driver max6902_driver = {
    .driver = {
        .name   = "rtc-max6902",
        .owner  = THIS_MODULE,
    },
    .probe  = max6902_probe,
    .remove = __devexit_p(max6902_remove),
};

module_spi_driver(max6902_driver);

MODULE_DESCRIPTION ("max6902 spi RTC driver");
MODULE_AUTHOR ("Raphael Assenat");
MODULE_LICENSE ("GPL");
MODULE_ALIAS("spi:rtc-max6902");