rtc-ds3232.c

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/*
 * RTC client/driver for the Maxim/Dallas DS3232 Real-Time Clock over I2C
 *
 * Copyright (C) 2009-2011 Freescale Semiconductor.
 * Author: Jack Lan <[email protected]>
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */
/*
 * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
 * recommened in .../Documentation/i2c/writing-clients section
 * "Sending and receiving", using SMBus level communication is preferred.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/i2c.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/workqueue.h>
#include <linux/slab.h>

#define DS3232_REG_SECONDS  0x00
#define DS3232_REG_MINUTES  0x01
#define DS3232_REG_HOURS    0x02
#define DS3232_REG_AMPM     0x02
#define DS3232_REG_DAY      0x03
#define DS3232_REG_DATE     0x04
#define DS3232_REG_MONTH    0x05
#define DS3232_REG_CENTURY  0x05
#define DS3232_REG_YEAR     0x06
#define DS3232_REG_ALARM1         0x07  /* Alarm 1 BASE */
#define DS3232_REG_ALARM2         0x0B  /* Alarm 2 BASE */
#define DS3232_REG_CR       0x0E    /* Control register */
#   define DS3232_REG_CR_nEOSC        0x80
#       define DS3232_REG_CR_INTCN        0x04
#       define DS3232_REG_CR_A2IE        0x02
#       define DS3232_REG_CR_A1IE        0x01

#define DS3232_REG_SR   0x0F    /* control/status register */
#   define DS3232_REG_SR_OSF   0x80
#       define DS3232_REG_SR_BSY   0x04
#       define DS3232_REG_SR_A2F   0x02
#       define DS3232_REG_SR_A1F   0x01

struct ds3232 {
    struct i2c_client *client;
    struct rtc_device *rtc;
    struct work_struct work;

    /* The mutex protects alarm operations, and prevents a race
     * between the enable_irq() in the workqueue and the free_irq()
     * in the remove function.
     */
    struct mutex mutex;
    int exiting;
};

static struct i2c_driver ds3232_driver;

static int ds3232_check_rtc_status(struct i2c_client *client)
{
    int ret = 0;
    int control, stat;

    stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
    if (stat < 0)
        return stat;

    if (stat & DS3232_REG_SR_OSF)
        dev_warn(&client->dev,
                "oscillator discontinuity flagged, "
                "time unreliable\n");

    stat &= ~(DS3232_REG_SR_OSF | DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);

    ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
    if (ret < 0)
        return ret;

    /* If the alarm is pending, clear it before requesting
     * the interrupt, so an interrupt event isn't reported
     * before everything is initialized.
     */

    control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
    if (control < 0)
        return control;

    control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
    control |= DS3232_REG_CR_INTCN;

    return i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
}

static int ds3232_read_time(struct device *dev, struct rtc_time *time)
{
    struct i2c_client *client = to_i2c_client(dev);
    int ret;
    u8 buf[7];
    unsigned int year, month, day, hour, minute, second;
    unsigned int week, twelve_hr, am_pm;
    unsigned int century, add_century = 0;

    ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_SECONDS, 7, buf);

    if (ret < 0)
        return ret;
    if (ret < 7)
        return -EIO;

    second = buf[0];
    minute = buf[1];
    hour = buf[2];
    week = buf[3];
    day = buf[4];
    month = buf[5];
    year = buf[6];

    /* Extract additional information for AM/PM and century */

    twelve_hr = hour & 0x40;
    am_pm = hour & 0x20;
    century = month & 0x80;

    /* Write to rtc_time structure */

    time->tm_sec = bcd2bin(second);
    time->tm_min = bcd2bin(minute);
    if (twelve_hr) {
        /* Convert to 24 hr */
        if (am_pm)
            time->tm_hour = bcd2bin(hour & 0x1F) + 12;
        else
            time->tm_hour = bcd2bin(hour & 0x1F);
    } else {
        time->tm_hour = bcd2bin(hour);
    }

    /* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
    time->tm_wday = bcd2bin(week) - 1;
    time->tm_mday = bcd2bin(day);
    /* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
    time->tm_mon = bcd2bin(month & 0x7F) - 1;
    if (century)
        add_century = 100;

    time->tm_year = bcd2bin(year) + add_century;

    return rtc_valid_tm(time);
}

static int ds3232_set_time(struct device *dev, struct rtc_time *time)
{
    struct i2c_client *client = to_i2c_client(dev);
    u8 buf[7];

    /* Extract time from rtc_time and load into ds3232*/

    buf[0] = bin2bcd(time->tm_sec);
    buf[1] = bin2bcd(time->tm_min);
    buf[2] = bin2bcd(time->tm_hour);
    /* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
    buf[3] = bin2bcd(time->tm_wday + 1);
    buf[4] = bin2bcd(time->tm_mday); /* Date */
    /* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
    buf[5] = bin2bcd(time->tm_mon + 1);
    if (time->tm_year >= 100) {
        buf[5] |= 0x80;
        buf[6] = bin2bcd(time->tm_year - 100);
    } else {
        buf[6] = bin2bcd(time->tm_year);
    }

    return i2c_smbus_write_i2c_block_data(client,
                          DS3232_REG_SECONDS, 7, buf);
}

/*
 * DS3232 has two alarm, we only use alarm1
 * According to linux specification, only support one-shot alarm
 * no periodic alarm mode
 */
static int ds3232_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds3232 *ds3232 = i2c_get_clientdata(client);
    int control, stat;
    int ret;
    u8 buf[4];

    mutex_lock(&ds3232->mutex);

    ret = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
    if (ret < 0)
        goto out;
    stat = ret;
    ret = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
    if (ret < 0)
        goto out;
    control = ret;
    ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
    if (ret < 0)
        goto out;

    alarm->time.tm_sec = bcd2bin(buf[0] & 0x7F);
    alarm->time.tm_min = bcd2bin(buf[1] & 0x7F);
    alarm->time.tm_hour = bcd2bin(buf[2] & 0x7F);
    alarm->time.tm_mday = bcd2bin(buf[3] & 0x7F);

    alarm->time.tm_mon = -1;
    alarm->time.tm_year = -1;
    alarm->time.tm_wday = -1;
    alarm->time.tm_yday = -1;
    alarm->time.tm_isdst = -1;

    alarm->enabled = !!(control & DS3232_REG_CR_A1IE);
    alarm->pending = !!(stat & DS3232_REG_SR_A1F);

    ret = 0;
out:
    mutex_unlock(&ds3232->mutex);
    return ret;
}

/*
 * linux rtc-module does not support wday alarm
 * and only 24h time mode supported indeed
 */
static int ds3232_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds3232 *ds3232 = i2c_get_clientdata(client);
    int control, stat;
    int ret;
    u8 buf[4];

    if (client->irq <= 0)
        return -EINVAL;

    mutex_lock(&ds3232->mutex);

    buf[0] = bin2bcd(alarm->time.tm_sec);
    buf[1] = bin2bcd(alarm->time.tm_min);
    buf[2] = bin2bcd(alarm->time.tm_hour);
    buf[3] = bin2bcd(alarm->time.tm_mday);

    /* clear alarm interrupt enable bit */
    ret = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
    if (ret < 0)
        goto out;
    control = ret;
    control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
    ret = i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
    if (ret < 0)
        goto out;

    /* clear any pending alarm flag */
    ret = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
    if (ret < 0)
        goto out;
    stat = ret;
    stat &= ~(DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);
    ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
    if (ret < 0)
        goto out;

    ret = i2c_smbus_write_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);

    if (alarm->enabled) {
        control |= DS3232_REG_CR_A1IE;
        ret = i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
    }
out:
    mutex_unlock(&ds3232->mutex);
    return ret;
}

static void ds3232_update_alarm(struct i2c_client *client)
{
    struct ds3232 *ds3232 = i2c_get_clientdata(client);
    int control;
    int ret;
    u8 buf[4];

    mutex_lock(&ds3232->mutex);

    ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
    if (ret < 0)
        goto unlock;

    buf[0] = bcd2bin(buf[0]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
                                0x80 : buf[0];
    buf[1] = bcd2bin(buf[1]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
                                0x80 : buf[1];
    buf[2] = bcd2bin(buf[2]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
                                0x80 : buf[2];
    buf[3] = bcd2bin(buf[3]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
                                0x80 : buf[3];

    ret = i2c_smbus_write_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
    if (ret < 0)
        goto unlock;

    control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
    if (control < 0)
        goto unlock;

    if (ds3232->rtc->irq_data & (RTC_AF | RTC_UF))
        /* enable alarm1 interrupt */
        control |= DS3232_REG_CR_A1IE;
    else
        /* disable alarm1 interrupt */
        control &= ~(DS3232_REG_CR_A1IE);
    i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);

unlock:
    mutex_unlock(&ds3232->mutex);
}

static int ds3232_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds3232 *ds3232 = i2c_get_clientdata(client);

    if (client->irq <= 0)
        return -EINVAL;

    if (enabled)
        ds3232->rtc->irq_data |= RTC_AF;
    else
        ds3232->rtc->irq_data &= ~RTC_AF;

    ds3232_update_alarm(client);
    return 0;
}

static irqreturn_t ds3232_irq(int irq, void *dev_id)
{
    struct i2c_client *client = dev_id;
    struct ds3232 *ds3232 = i2c_get_clientdata(client);

    disable_irq_nosync(irq);
    schedule_work(&ds3232->work);
    return IRQ_HANDLED;
}

static void ds3232_work(struct work_struct *work)
{
    struct ds3232 *ds3232 = container_of(work, struct ds3232, work);
    struct i2c_client *client = ds3232->client;
    int stat, control;

    mutex_lock(&ds3232->mutex);

    stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
    if (stat < 0)
        goto unlock;

    if (stat & DS3232_REG_SR_A1F) {
        control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
        if (control < 0)
            goto out;
        /* disable alarm1 interrupt */
        control &= ~(DS3232_REG_CR_A1IE);
        i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);

        /* clear the alarm pend flag */
        stat &= ~DS3232_REG_SR_A1F;
        i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);

        rtc_update_irq(ds3232->rtc, 1, RTC_AF | RTC_IRQF);
    }

out:
    if (!ds3232->exiting)
        enable_irq(client->irq);
unlock:
    mutex_unlock(&ds3232->mutex);
}

static const struct rtc_class_ops ds3232_rtc_ops = {
    .read_time = ds3232_read_time,
    .set_time = ds3232_set_time,
    .read_alarm = ds3232_read_alarm,
    .set_alarm = ds3232_set_alarm,
    .alarm_irq_enable = ds3232_alarm_irq_enable,
};

static int __devinit ds3232_probe(struct i2c_client *client,
        const struct i2c_device_id *id)
{
    struct ds3232 *ds3232;
    int ret;

    ds3232 = kzalloc(sizeof(struct ds3232), GFP_KERNEL);
    if (!ds3232)
        return -ENOMEM;

    ds3232->client = client;
    i2c_set_clientdata(client, ds3232);

    INIT_WORK(&ds3232->work, ds3232_work);
    mutex_init(&ds3232->mutex);

    ret = ds3232_check_rtc_status(client);
    if (ret)
        goto out_free;

    ds3232->rtc = rtc_device_register(client->name, &client->dev,
                      &ds3232_rtc_ops, THIS_MODULE);
    if (IS_ERR(ds3232->rtc)) {
        ret = PTR_ERR(ds3232->rtc);
        dev_err(&client->dev, "unable to register the class device\n");
        goto out_irq;
    }

    if (client->irq >= 0) {
        ret = request_irq(client->irq, ds3232_irq, 0,
                 "ds3232", client);
        if (ret) {
            dev_err(&client->dev, "unable to request IRQ\n");
            goto out_free;
        }
    }

    return 0;

out_irq:
    if (client->irq >= 0)
        free_irq(client->irq, client);

out_free:
    kfree(ds3232);
    return ret;
}

static int __devexit ds3232_remove(struct i2c_client *client)
{
    struct ds3232 *ds3232 = i2c_get_clientdata(client);

    if (client->irq >= 0) {
        mutex_lock(&ds3232->mutex);
        ds3232->exiting = 1;
        mutex_unlock(&ds3232->mutex);

        free_irq(client->irq, client);
        cancel_work_sync(&ds3232->work);
    }

    rtc_device_unregister(ds3232->rtc);
    kfree(ds3232);
    return 0;
}

static const struct i2c_device_id ds3232_id[] = {
    { "ds3232", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, ds3232_id);

static struct i2c_driver ds3232_driver = {
    .driver = {
        .name = "rtc-ds3232",
        .owner = THIS_MODULE,
    },
    .probe = ds3232_probe,
    .remove = __devexit_p(ds3232_remove),
    .id_table = ds3232_id,
};

module_i2c_driver(ds3232_driver);

MODULE_AUTHOR("Srikanth Srinivasan <[email protected]>");
MODULE_DESCRIPTION("Maxim/Dallas DS3232 RTC Driver");
MODULE_LICENSE("GPL");