rtc-ds3234.c

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/* rtc-ds3234.c
 *
 * Driver for Dallas Semiconductor (DS3234) SPI RTC with Integrated Crystal
 * and SRAM.
 *
 * Copyright (C) 2008 MIMOMax Wireless 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.
 *
 */

#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>

#define DS3234_REG_SECONDS  0x00
#define DS3234_REG_MINUTES  0x01
#define DS3234_REG_HOURS    0x02
#define DS3234_REG_DAY      0x03
#define DS3234_REG_DATE     0x04
#define DS3234_REG_MONTH    0x05
#define DS3234_REG_YEAR     0x06
#define DS3234_REG_CENTURY  (1 << 7) /* Bit 7 of the Month register */

#define DS3234_REG_CONTROL  0x0E
#define DS3234_REG_CONT_STAT    0x0F

static int ds3234_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 '1' to indicate write */
    buf[0] = address | 0x80;
    buf[1] = data;

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

static int ds3234_get_reg(struct device *dev, unsigned char address,
                unsigned char *data)
{
    struct spi_device *spi = to_spi_device(dev);

    *data = address & 0x7f;

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

static int ds3234_read_time(struct device *dev, struct rtc_time *dt)
{
    int err;
    unsigned char buf[8];
    struct spi_device *spi = to_spi_device(dev);

    buf[0] = 0x00; /* Start address */

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

    /* Seconds, Minutes, Hours, Day, Date, Month, Year */
    dt->tm_sec  = bcd2bin(buf[0]);
    dt->tm_min  = bcd2bin(buf[1]);
    dt->tm_hour = bcd2bin(buf[2] & 0x3f);
    dt->tm_wday = bcd2bin(buf[3]) - 1; /* 0 = Sun */
    dt->tm_mday = bcd2bin(buf[4]);
    dt->tm_mon  = bcd2bin(buf[5] & 0x1f) - 1; /* 0 = Jan */
    dt->tm_year     = bcd2bin(buf[6] & 0xff) + 100; /* Assume 20YY */

    return rtc_valid_tm(dt);
}

static int ds3234_set_time(struct device *dev, struct rtc_time *dt)
{
    ds3234_set_reg(dev, DS3234_REG_SECONDS, bin2bcd(dt->tm_sec));
    ds3234_set_reg(dev, DS3234_REG_MINUTES, bin2bcd(dt->tm_min));
    ds3234_set_reg(dev, DS3234_REG_HOURS, bin2bcd(dt->tm_hour) & 0x3f);

    /* 0 = Sun */
    ds3234_set_reg(dev, DS3234_REG_DAY, bin2bcd(dt->tm_wday + 1));
    ds3234_set_reg(dev, DS3234_REG_DATE, bin2bcd(dt->tm_mday));

    /* 0 = Jan */
    ds3234_set_reg(dev, DS3234_REG_MONTH, bin2bcd(dt->tm_mon + 1));

    /* Assume 20YY although we just want to make sure not to go negative. */
    if (dt->tm_year > 100)
        dt->tm_year -= 100;

    ds3234_set_reg(dev, DS3234_REG_YEAR, bin2bcd(dt->tm_year));

    return 0;
}

static const struct rtc_class_ops ds3234_rtc_ops = {
    .read_time  = ds3234_read_time,
    .set_time   = ds3234_set_time,
};

static int __devinit ds3234_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 = ds3234_get_reg(&spi->dev, DS3234_REG_SECONDS, &tmp);
    if (res != 0)
        return res;

    /* Control settings
     *
     * CONTROL_REG
     * BIT 7    6   5   4   3   2   1   0
     *     EOSC BBSQW   CONV    RS2 RS1 INTCN   A2IE    A1IE
     *
     *     0    0   0   1   1   1   0   0
     *
     * CONTROL_STAT_REG
     * BIT 7    6   5   4   3   2   1   0
     *     OSF  BB32kHz CRATE1  CRATE0  EN32kHz BSY A2F A1F
     *
     *     1    0   0   0   1   0   0   0
     */
    ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
    ds3234_set_reg(&spi->dev, DS3234_REG_CONTROL, tmp & 0x1c);

    ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
    ds3234_set_reg(&spi->dev, DS3234_REG_CONT_STAT, tmp & 0x88);

    /* Print our settings */
    ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
    dev_info(&spi->dev, "Control Reg: 0x%02x\n", tmp);

    ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
    dev_info(&spi->dev, "Ctrl/Stat Reg: 0x%02x\n", tmp);

    rtc = rtc_device_register("ds3234",
                &spi->dev, &ds3234_rtc_ops, THIS_MODULE);
    if (IS_ERR(rtc))
        return PTR_ERR(rtc);

    dev_set_drvdata(&spi->dev, rtc);

    return 0;
}

static int __devexit ds3234_remove(struct spi_device *spi)
{
    struct rtc_device *rtc = spi_get_drvdata(spi);

    rtc_device_unregister(rtc);
    return 0;
}

static struct spi_driver ds3234_driver = {
    .driver = {
        .name    = "ds3234",
        .owner  = THIS_MODULE,
    },
    .probe   = ds3234_probe,
    .remove = __devexit_p(ds3234_remove),
};

module_spi_driver(ds3234_driver);

MODULE_DESCRIPTION("DS3234 SPI RTC driver");
MODULE_AUTHOR("Dennis Aberilla <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:ds3234");