rtc-bq32k.c

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/*
 * Driver for TI BQ32000 RTC.
 *
 * Copyright (C) 2009 Semihalf.
 *
 * 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/i2c.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/bcd.h>

#define BQ32K_SECONDS       0x00    /* Seconds register address */
#define BQ32K_SECONDS_MASK  0x7F    /* Mask over seconds value */
#define BQ32K_STOP      0x80    /* Oscillator Stop flat */

#define BQ32K_MINUTES       0x01    /* Minutes register address */
#define BQ32K_MINUTES_MASK  0x7F    /* Mask over minutes value */
#define BQ32K_OF        0x80    /* Oscillator Failure flag */

#define BQ32K_HOURS_MASK    0x3F    /* Mask over hours value */
#define BQ32K_CENT      0x40    /* Century flag */
#define BQ32K_CENT_EN       0x80    /* Century flag enable bit */

struct bq32k_regs {
    uint8_t     seconds;
    uint8_t     minutes;
    uint8_t     cent_hours;
    uint8_t     day;
    uint8_t     date;
    uint8_t     month;
    uint8_t     years;
};

static struct i2c_driver bq32k_driver;

static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct i2c_msg msgs[] = {
        {
            .addr = client->addr,
            .flags = 0,
            .len = 1,
            .buf = &off,
        }, {
            .addr = client->addr,
            .flags = I2C_M_RD,
            .len = len,
            .buf = data,
        }
    };

    if (i2c_transfer(client->adapter, msgs, 2) == 2)
        return 0;

    return -EIO;
}

static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
{
    struct i2c_client *client = to_i2c_client(dev);
    uint8_t buffer[len + 1];

    buffer[0] = off;
    memcpy(&buffer[1], data, len);

    if (i2c_master_send(client, buffer, len + 1) == len + 1)
        return 0;

    return -EIO;
}

static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
    struct bq32k_regs regs;
    int error;

    error = bq32k_read(dev, &regs, 0, sizeof(regs));
    if (error)
        return error;

    tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
    tm->tm_min = bcd2bin(regs.minutes & BQ32K_SECONDS_MASK);
    tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
    tm->tm_mday = bcd2bin(regs.date);
    tm->tm_wday = bcd2bin(regs.day) - 1;
    tm->tm_mon = bcd2bin(regs.month) - 1;
    tm->tm_year = bcd2bin(regs.years) +
                ((regs.cent_hours & BQ32K_CENT) ? 100 : 0);

    return rtc_valid_tm(tm);
}

static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
    struct bq32k_regs regs;

    regs.seconds = bin2bcd(tm->tm_sec);
    regs.minutes = bin2bcd(tm->tm_min);
    regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
    regs.day = bin2bcd(tm->tm_wday + 1);
    regs.date = bin2bcd(tm->tm_mday);
    regs.month = bin2bcd(tm->tm_mon + 1);

    if (tm->tm_year >= 100) {
        regs.cent_hours |= BQ32K_CENT;
        regs.years = bin2bcd(tm->tm_year - 100);
    } else
        regs.years = bin2bcd(tm->tm_year);

    return bq32k_write(dev, &regs, 0, sizeof(regs));
}

static const struct rtc_class_ops bq32k_rtc_ops = {
    .read_time  = bq32k_rtc_read_time,
    .set_time   = bq32k_rtc_set_time,
};

static int bq32k_probe(struct i2c_client *client,
                const struct i2c_device_id *id)
{
    struct device *dev = &client->dev;
    struct rtc_device *rtc;
    uint8_t reg;
    int error;

    if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
        return -ENODEV;

    /* Check Oscillator Stop flag */
    error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
    if (!error && (reg & BQ32K_STOP)) {
        dev_warn(dev, "Oscillator was halted. Restarting...\n");
        reg &= ~BQ32K_STOP;
        error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
    }
    if (error)
        return error;

    /* Check Oscillator Failure flag */
    error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
    if (!error && (reg & BQ32K_OF)) {
        dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
        reg &= ~BQ32K_OF;
        error = bq32k_write(dev, &reg, BQ32K_MINUTES, 1);
    }
    if (error)
        return error;

    rtc = rtc_device_register(bq32k_driver.driver.name, &client->dev,
                        &bq32k_rtc_ops, THIS_MODULE);
    if (IS_ERR(rtc))
        return PTR_ERR(rtc);

    i2c_set_clientdata(client, rtc);

    return 0;
}

static int __devexit bq32k_remove(struct i2c_client *client)
{
    struct rtc_device *rtc = i2c_get_clientdata(client);

    rtc_device_unregister(rtc);
    return 0;
}

static const struct i2c_device_id bq32k_id[] = {
    { "bq32000", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, bq32k_id);

static struct i2c_driver bq32k_driver = {
    .driver = {
        .name   = "bq32k",
        .owner  = THIS_MODULE,
    },
    .probe      = bq32k_probe,
    .remove     = __devexit_p(bq32k_remove),
    .id_table   = bq32k_id,
};

module_i2c_driver(bq32k_driver);

MODULE_AUTHOR("Semihalf, Piotr Ziecik <[email protected]>");
MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
MODULE_LICENSE("GPL");