rtc-m41t94.c

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/*
 * Driver for ST M41T94 SPI RTC
 *
 * Copyright (C) 2008 Kim B. Heino
 *
 * 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/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>

#define M41T94_REG_SECONDS  0x01
#define M41T94_REG_MINUTES  0x02
#define M41T94_REG_HOURS    0x03
#define M41T94_REG_WDAY     0x04
#define M41T94_REG_DAY      0x05
#define M41T94_REG_MONTH    0x06
#define M41T94_REG_YEAR     0x07
#define M41T94_REG_HT       0x0c

#define M41T94_BIT_HALT     0x40
#define M41T94_BIT_STOP     0x80
#define M41T94_BIT_CB       0x40
#define M41T94_BIT_CEB      0x80

static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
{
    struct spi_device *spi = to_spi_device(dev);
    u8 buf[8]; /* write cmd + 7 registers */

    dev_dbg(dev, "%s secs=%d, mins=%d, "
        "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
        "write", tm->tm_sec, tm->tm_min,
        tm->tm_hour, tm->tm_mday,
        tm->tm_mon, tm->tm_year, tm->tm_wday);

    buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
    buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
    buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
    buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
    buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
    buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
    buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);

    buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
    if (tm->tm_year >= 100)
        buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
    buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);

    return spi_write(spi, buf, 8);
}

static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
{
    struct spi_device *spi = to_spi_device(dev);
    u8 buf[2];
    int ret, hour;

    /* clear halt update bit */
    ret = spi_w8r8(spi, M41T94_REG_HT);
    if (ret < 0)
        return ret;
    if (ret & M41T94_BIT_HALT) {
        buf[0] = 0x80 | M41T94_REG_HT;
        buf[1] = ret & ~M41T94_BIT_HALT;
        spi_write(spi, buf, 2);
    }

    /* clear stop bit */
    ret = spi_w8r8(spi, M41T94_REG_SECONDS);
    if (ret < 0)
        return ret;
    if (ret & M41T94_BIT_STOP) {
        buf[0] = 0x80 | M41T94_REG_SECONDS;
        buf[1] = ret & ~M41T94_BIT_STOP;
        spi_write(spi, buf, 2);
    }

    tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
    tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
    hour = spi_w8r8(spi, M41T94_REG_HOURS);
    tm->tm_hour = bcd2bin(hour & 0x3f);
    tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
    tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
    tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
    tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
    if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
        tm->tm_year += 100;

    dev_dbg(dev, "%s secs=%d, mins=%d, "
        "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
        "read", tm->tm_sec, tm->tm_min,
        tm->tm_hour, tm->tm_mday,
        tm->tm_mon, tm->tm_year, tm->tm_wday);

    /* initial clock setting can be undefined */
    return rtc_valid_tm(tm);
}

static const struct rtc_class_ops m41t94_rtc_ops = {
    .read_time  = m41t94_read_time,
    .set_time   = m41t94_set_time,
};

static struct spi_driver m41t94_driver;

static int __devinit m41t94_probe(struct spi_device *spi)
{
    struct rtc_device *rtc;
    int res;

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

    res = spi_w8r8(spi, M41T94_REG_SECONDS);
    if (res < 0) {
        dev_err(&spi->dev, "not found.\n");
        return res;
    }

    rtc = rtc_device_register(m41t94_driver.driver.name,
        &spi->dev, &m41t94_rtc_ops, THIS_MODULE);
    if (IS_ERR(rtc))
        return PTR_ERR(rtc);

    dev_set_drvdata(&spi->dev, rtc);

    return 0;
}

static int __devexit m41t94_remove(struct spi_device *spi)
{
    struct rtc_device *rtc = spi_get_drvdata(spi);

    if (rtc)
        rtc_device_unregister(rtc);

    return 0;
}

static struct spi_driver m41t94_driver = {
    .driver = {
        .name   = "rtc-m41t94",
        .owner  = THIS_MODULE,
    },
    .probe  = m41t94_probe,
    .remove = __devexit_p(m41t94_remove),
};

module_spi_driver(m41t94_driver);

MODULE_AUTHOR("Kim B. Heino <[email protected]>");
MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-m41t94");