rtc-r9701.c

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/*
 * Driver for Epson RTC-9701JE
 *
 * Copyright (C) 2008 Magnus Damm
 *
 * Based on 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.
 */

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

#define RSECCNT 0x00    /* Second Counter */
#define RMINCNT 0x01    /* Minute Counter */
#define RHRCNT  0x02    /* Hour Counter */
#define RWKCNT  0x03    /* Week Counter */
#define RDAYCNT 0x04    /* Day Counter */
#define RMONCNT 0x05    /* Month Counter */
#define RYRCNT  0x06    /* Year Counter */
#define R100CNT 0x07    /* Y100 Counter */
#define RMINAR  0x08    /* Minute Alarm */
#define RHRAR   0x09    /* Hour Alarm */
#define RWKAR   0x0a    /* Week/Day Alarm */
#define RTIMCNT 0x0c    /* Interval Timer */
#define REXT    0x0d    /* Extension Register */
#define RFLAG   0x0e    /* RTC Flag Register */
#define RCR 0x0f    /* RTC Control Register */

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

    buf[0] = address & 0x7f;
    buf[1] = data;

    return spi_write(spi, buf, ARRAY_SIZE(buf));
}

static int read_regs(struct device *dev, unsigned char *regs, int no_regs)
{
    struct spi_device *spi = to_spi_device(dev);
    u8 txbuf[1], rxbuf[1];
    int k, ret;

    ret = 0;

    for (k = 0; ret == 0 && k < no_regs; k++) {
        txbuf[0] = 0x80 | regs[k];
        ret = spi_write_then_read(spi, txbuf, 1, rxbuf, 1);
        regs[k] = rxbuf[0];
    }

    return ret;
}

static int r9701_get_datetime(struct device *dev, struct rtc_time *dt)
{
    int ret;
    unsigned char buf[] = { RSECCNT, RMINCNT, RHRCNT,
                RDAYCNT, RMONCNT, RYRCNT };

    ret = read_regs(dev, buf, ARRAY_SIZE(buf));
    if (ret)
        return ret;

    memset(dt, 0, sizeof(*dt));

    dt->tm_sec = bcd2bin(buf[0]); /* RSECCNT */
    dt->tm_min = bcd2bin(buf[1]); /* RMINCNT */
    dt->tm_hour = bcd2bin(buf[2]); /* RHRCNT */

    dt->tm_mday = bcd2bin(buf[3]); /* RDAYCNT */
    dt->tm_mon = bcd2bin(buf[4]) - 1; /* RMONCNT */
    dt->tm_year = bcd2bin(buf[5]) + 100; /* RYRCNT */

    /* the rtc device may contain illegal values on power up
     * according to the data sheet. make sure they are valid.
     */

    return rtc_valid_tm(dt);
}

static int r9701_set_datetime(struct device *dev, struct rtc_time *dt)
{
    int ret, year;

    year = dt->tm_year + 1900;
    if (year >= 2100 || year < 2000)
        return -EINVAL;

    ret = write_reg(dev, RHRCNT, bin2bcd(dt->tm_hour));
    ret = ret ? ret : write_reg(dev, RMINCNT, bin2bcd(dt->tm_min));
    ret = ret ? ret : write_reg(dev, RSECCNT, bin2bcd(dt->tm_sec));
    ret = ret ? ret : write_reg(dev, RDAYCNT, bin2bcd(dt->tm_mday));
    ret = ret ? ret : write_reg(dev, RMONCNT, bin2bcd(dt->tm_mon + 1));
    ret = ret ? ret : write_reg(dev, RYRCNT, bin2bcd(dt->tm_year - 100));
    ret = ret ? ret : write_reg(dev, RWKCNT, 1 << dt->tm_wday);

    return ret;
}

static const struct rtc_class_ops r9701_rtc_ops = {
    .read_time  = r9701_get_datetime,
    .set_time   = r9701_set_datetime,
};

static int __devinit r9701_probe(struct spi_device *spi)
{
    struct rtc_device *rtc;
    struct rtc_time dt;
    unsigned char tmp;
    int res;

    tmp = R100CNT;
    res = read_regs(&spi->dev, &tmp, 1);
    if (res || tmp != 0x20) {
        dev_err(&spi->dev, "cannot read RTC register\n");
        return -ENODEV;
    }

    /*
     * The device seems to be present. Now check if the registers
     * contain invalid values. If so, try to write a default date:
     * 2000/1/1 00:00:00
     */
    if (r9701_get_datetime(&spi->dev, &dt)) {
        dev_info(&spi->dev, "trying to repair invalid date/time\n");
        dt.tm_sec  = 0;
        dt.tm_min  = 0;
        dt.tm_hour = 0;
        dt.tm_mday = 1;
        dt.tm_mon  = 0;
        dt.tm_year = 100;

        if (r9701_set_datetime(&spi->dev, &dt) ||
                r9701_get_datetime(&spi->dev, &dt)) {
            dev_err(&spi->dev, "cannot repair RTC register\n");
            return -ENODEV;
        }
    }

    rtc = rtc_device_register("r9701",
                &spi->dev, &r9701_rtc_ops, THIS_MODULE);
    if (IS_ERR(rtc))
        return PTR_ERR(rtc);

    dev_set_drvdata(&spi->dev, rtc);

    return 0;
}

static int __devexit r9701_remove(struct spi_device *spi)
{
    struct rtc_device *rtc = dev_get_drvdata(&spi->dev);

    rtc_device_unregister(rtc);
    return 0;
}

static struct spi_driver r9701_driver = {
    .driver = {
        .name   = "rtc-r9701",
        .owner  = THIS_MODULE,
    },
    .probe  = r9701_probe,
    .remove = __devexit_p(r9701_remove),
};

module_spi_driver(r9701_driver);

MODULE_DESCRIPTION("r9701 spi RTC driver");
MODULE_AUTHOR("Magnus Damm <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-r9701");