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/*

 * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C

 *

 * Based on code by Randy Vinson <rvinson@mvista.com>,

 * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.

 *

 * 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>

#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 */

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);

        new_alarm -= 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 (new_alarm <= 0)

                new_alarm = 1;

        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)

                return;

        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() assumes that it is called

                 * from IRQ-disabled context.

                 */

                local_irq_disable();

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

                local_irq_enable();

        }

out:

        if (!ds1374->exiting)

                enable_irq(client->irq);

        mutex_unlock(&ds1374->mutex);

}

static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)

{

        struct i2c_client *client = to_i2c_client(dev);

        struct ds1374 *ds1374 = i2c_get_clientdata(client);

        int ret = -ENOIOCTLCMD;

        mutex_lock(&ds1374->mutex);

        switch (cmd) {

        case RTC_AIE_OFF:

                ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);

                if (ret < 0)

                        goto out;

                ret &= ~DS1374_REG_CR_WACE;

                ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);

                if (ret < 0)

                        goto out;

                break;

        case RTC_AIE_ON:

                ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);

                if (ret < 0)

                        goto out;

                ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;

                ret &= ~DS1374_REG_CR_WDALM;

                ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);

                if (ret < 0)

                        goto out;

                break;

        }

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,

        .ioctl = ds1374_ioctl,

};

static int ds1374_probe(struct i2c_client *client)

{

        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;

                }

        }

        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:

        i2c_set_clientdata(client, NULL);

        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);

                flush_scheduled_work();

        }

        rtc_device_unregister(ds1374->rtc);

        i2c_set_clientdata(client, NULL);

        kfree(ds1374);

        return 0;

}

static struct i2c_driver ds1374_driver = {

        .driver = {

                .name = "rtc-ds1374",

                .owner = THIS_MODULE,

        },

        .probe = ds1374_probe,

        .remove = __devexit_p(ds1374_remove),

};

static int __init ds1374_init(void)

{

        return i2c_add_driver(&ds1374_driver);

}

static void __exit ds1374_exit(void)

{

        i2c_del_driver(&ds1374_driver);

}

module_init(ds1374_init);

module_exit(ds1374_exit);

MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");

MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");

MODULE_LICENSE("GPL");