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 <[email protected]>
 *
 * 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 __devinit 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 = kzalloc(sizeof *chip, GFP_KERNEL);
    if (!chip) {
        dev_err(&spi->dev, "unable to allocate device memory\n");
        return -ENOMEM;
    }
    dev_set_drvdata(&spi->dev, chip);

    res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
    if (res != 0) {
        dev_err(&spi->dev, "unable to read device\n");
        kfree(chip);
        return res;
    }

    chip->rtc = rtc_device_register("ds1390",
                &spi->dev, &ds1390_rtc_ops, THIS_MODULE);
    if (IS_ERR(chip->rtc)) {
        dev_err(&spi->dev, "unable to register device\n");
        res = PTR_ERR(chip->rtc);
        kfree(chip);
    }

    return res;
}

static int __devexit ds1390_remove(struct spi_device *spi)
{
    struct ds1390 *chip = spi_get_drvdata(spi);

    rtc_device_unregister(chip->rtc);
    kfree(chip);

    return 0;
}

static struct spi_driver ds1390_driver = {
    .driver = {
        .name   = "rtc-ds1390",
        .owner  = THIS_MODULE,
    },
    .probe  = ds1390_probe,
    .remove = __devexit_p(ds1390_remove),
};

module_spi_driver(ds1390_driver);

MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
MODULE_AUTHOR("Mark Jackson <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-ds1390");