rtc-ds1374.c

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/*
 * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
 *
 * Based on code by Randy Vinson <[email protected]>,
 * which was based on the m41t00.c by Mark Greer <[email protected]>.
 *
 * Copyright (C) 2006-2007 Freescale Semiconductor
 *
 * 2005 (c) MontaVista Software, Inc. This file is licensed under
 * the terms of the GNU General Public License version 2. This program
 * is licensed "as is" without any warranty of any kind, whether express
 * or implied.
 */
/*
 * 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>
#include <linux/pm.h>

#define DS1374_REG_TOD0     0x00 /* Time of Day */
#define DS1374_REG_TOD1     0x01
#define DS1374_REG_TOD2     0x02
#define DS1374_REG_TOD3     0x03
#define DS1374_REG_WDALM0   0x04 /* Watchdog/Alarm */
#define DS1374_REG_WDALM1   0x05
#define DS1374_REG_WDALM2   0x06
#define DS1374_REG_CR       0x07 /* Control */
#define DS1374_REG_CR_AIE   0x01 /* Alarm Int. Enable */
#define DS1374_REG_CR_WDALM 0x20 /* 1=Watchdog, 0=Alarm */
#define DS1374_REG_CR_WACE  0x40 /* WD/Alarm counter enable */
#define DS1374_REG_SR       0x08 /* Status */
#define DS1374_REG_SR_OSF   0x80 /* Oscillator Stop Flag */
#define DS1374_REG_SR_AF    0x01 /* Alarm Flag */
#define DS1374_REG_TCR      0x09 /* Trickle Charge */

static const struct i2c_device_id ds1374_id[] = {
    { "ds1374", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, ds1374_id);

struct ds1374 {
    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 ds1374_driver;

static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
                           int reg, int nbytes)
{
    u8 buf[4];
    int ret;
    int i;

    if (nbytes > 4) {
        WARN_ON(1);
        return -EINVAL;
    }

    ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);

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

    for (i = nbytes - 1, *time = 0; i >= 0; i--)
        *time = (*time << 8) | buf[i];

    return 0;
}

static int ds1374_write_rtc(struct i2c_client *client, u32 time,
                            int reg, int nbytes)
{
    u8 buf[4];
    int i;

    if (nbytes > 4) {
        WARN_ON(1);
        return -EINVAL;
    }

    for (i = 0; i < nbytes; i++) {
        buf[i] = time & 0xff;
        time >>= 8;
    }

    return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
}

static int ds1374_check_rtc_status(struct i2c_client *client)
{
    int ret = 0;
    int control, stat;

    stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
    if (stat < 0)
        return stat;

    if (stat & DS1374_REG_SR_OSF)
        dev_warn(&client->dev,
                 "oscillator discontinuity flagged, "
                 "time unreliable\n");

    stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);

    ret = i2c_smbus_write_byte_data(client, DS1374_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, DS1374_REG_CR);
    if (control < 0)
        return control;

    control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
    return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
}

static int ds1374_read_time(struct device *dev, struct rtc_time *time)
{
    struct i2c_client *client = to_i2c_client(dev);
    u32 itime;
    int ret;

    ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
    if (!ret)
        rtc_time_to_tm(itime, time);

    return ret;
}

static int ds1374_set_time(struct device *dev, struct rtc_time *time)
{
    struct i2c_client *client = to_i2c_client(dev);
    unsigned long itime;

    rtc_tm_to_time(time, &itime);
    return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
}

/* The ds1374 has a decrementer for an alarm, rather than a comparator.
 * If the time of day is changed, then the alarm will need to be
 * reset.
 */
static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds1374 *ds1374 = i2c_get_clientdata(client);
    u32 now, cur_alarm;
    int cr, sr;
    int ret = 0;

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

    mutex_lock(&ds1374->mutex);

    cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
    if (ret < 0)
        goto out;

    sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
    if (ret < 0)
        goto out;

    ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
    if (ret)
        goto out;

    ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
    if (ret)
        goto out;

    rtc_time_to_tm(now + cur_alarm, &alarm->time);
    alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
    alarm->pending = !!(sr & DS1374_REG_SR_AF);

out:
    mutex_unlock(&ds1374->mutex);
    return ret;
}

static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds1374 *ds1374 = i2c_get_clientdata(client);
    struct rtc_time now;
    unsigned long new_alarm, itime;
    int cr;
    int ret = 0;

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

    ret = ds1374_read_time(dev, &now);
    if (ret < 0)
        return ret;

    rtc_tm_to_time(&alarm->time, &new_alarm);
    rtc_tm_to_time(&now, &itime);

    /* This can happen due to races, in addition to dates that are
     * truly in the past.  To avoid requiring the caller to check for
     * races, dates in the past are assumed to be in the recent past
     * (i.e. not something that we'd rather the caller know about via
     * an error), and the alarm is set to go off as soon as possible.
     */
    if (time_before_eq(new_alarm, itime))
        new_alarm = 1;
    else
        new_alarm -= itime;

    mutex_lock(&ds1374->mutex);

    ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
    if (ret < 0)
        goto out;

    /* Disable any existing alarm before setting the new one
     * (or lack thereof). */
    cr &= ~DS1374_REG_CR_WACE;

    ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
    if (ret < 0)
        goto out;

    ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
    if (ret)
        goto out;

    if (alarm->enabled) {
        cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
        cr &= ~DS1374_REG_CR_WDALM;

        ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
    }

out:
    mutex_unlock(&ds1374->mutex);
    return ret;
}

static irqreturn_t ds1374_irq(int irq, void *dev_id)
{
    struct i2c_client *client = dev_id;
    struct ds1374 *ds1374 = i2c_get_clientdata(client);

    disable_irq_nosync(irq);
    schedule_work(&ds1374->work);
    return IRQ_HANDLED;
}

static void ds1374_work(struct work_struct *work)
{
    struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
    struct i2c_client *client = ds1374->client;
    int stat, control;

    mutex_lock(&ds1374->mutex);

    stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
    if (stat < 0)
        goto unlock;

    if (stat & DS1374_REG_SR_AF) {
        stat &= ~DS1374_REG_SR_AF;
        i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);

        control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
        if (control < 0)
            goto out;

        control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
        i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);

        rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
    }

out:
    if (!ds1374->exiting)
        enable_irq(client->irq);
unlock:
    mutex_unlock(&ds1374->mutex);
}

static int ds1374_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ds1374 *ds1374 = i2c_get_clientdata(client);
    int ret;

    mutex_lock(&ds1374->mutex);

    ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
    if (ret < 0)
        goto out;

    if (enabled) {
        ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
        ret &= ~DS1374_REG_CR_WDALM;
    } else {
        ret &= ~DS1374_REG_CR_WACE;
    }
    ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);

out:
    mutex_unlock(&ds1374->mutex);
    return ret;
}

static const struct rtc_class_ops ds1374_rtc_ops = {
    .read_time = ds1374_read_time,
    .set_time = ds1374_set_time,
    .read_alarm = ds1374_read_alarm,
    .set_alarm = ds1374_set_alarm,
    .alarm_irq_enable = ds1374_alarm_irq_enable,
};

static int ds1374_probe(struct i2c_client *client,
            const struct i2c_device_id *id)
{
    struct ds1374 *ds1374;
    int ret;

    ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
    if (!ds1374)
        return -ENOMEM;

    ds1374->client = client;
    i2c_set_clientdata(client, ds1374);

    INIT_WORK(&ds1374->work, ds1374_work);
    mutex_init(&ds1374->mutex);

    ret = ds1374_check_rtc_status(client);
    if (ret)
        goto out_free;

    if (client->irq > 0) {
        ret = request_irq(client->irq, ds1374_irq, 0,
                          "ds1374", client);
        if (ret) {
            dev_err(&client->dev, "unable to request IRQ\n");
            goto out_free;
        }

        device_set_wakeup_capable(&client->dev, 1);
    }

    ds1374->rtc = rtc_device_register(client->name, &client->dev,
                                      &ds1374_rtc_ops, THIS_MODULE);
    if (IS_ERR(ds1374->rtc)) {
        ret = PTR_ERR(ds1374->rtc);
        dev_err(&client->dev, "unable to register the class device\n");
        goto out_irq;
    }

    return 0;

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

out_free:
    kfree(ds1374);
    return ret;
}

static int __devexit ds1374_remove(struct i2c_client *client)
{
    struct ds1374 *ds1374 = i2c_get_clientdata(client);

    if (client->irq > 0) {
        mutex_lock(&ds1374->mutex);
        ds1374->exiting = 1;
        mutex_unlock(&ds1374->mutex);

        free_irq(client->irq, client);
        cancel_work_sync(&ds1374->work);
    }

    rtc_device_unregister(ds1374->rtc);
    kfree(ds1374);
    return 0;
}

#ifdef CONFIG_PM
static int ds1374_suspend(struct device *dev)
{
    struct i2c_client *client = to_i2c_client(dev);

    if (client->irq >= 0 && device_may_wakeup(&client->dev))
        enable_irq_wake(client->irq);
    return 0;
}

static int ds1374_resume(struct device *dev)
{
    struct i2c_client *client = to_i2c_client(dev);

    if (client->irq >= 0 && device_may_wakeup(&client->dev))
        disable_irq_wake(client->irq);
    return 0;
}

static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);

#define DS1374_PM (&ds1374_pm)
#else
#define DS1374_PM NULL
#endif

static struct i2c_driver ds1374_driver = {
    .driver = {
        .name = "rtc-ds1374",
        .owner = THIS_MODULE,
        .pm = DS1374_PM,
    },
    .probe = ds1374_probe,
    .remove = __devexit_p(ds1374_remove),
    .id_table = ds1374_id,
};

module_i2c_driver(ds1374_driver);

MODULE_AUTHOR("Scott Wood <[email protected]>");
MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
MODULE_LICENSE("GPL");