/*
 * 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) 2014 Rose Technology
 * 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
 * recommended in .../Documentation/i2c/writing-clients.rst section
 * "Sending and receiving", using SMBus level communication is preferred.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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>
#ifdef CONFIG_RTC_DRV_DS1374_WDT
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/miscdevice.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>
#endif

#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_WDSTR	0x08 /* 1=INT, 0=RST */
#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);

#ifdef CONFIG_OF
static const struct of_device_id ds1374_of_match[] = {
	{ .compatible = "dallas,ds1374" },
	{ }
};
MODULE_DEVICE_TABLE(of, ds1374_of_match);
#endif

struct ds1374 {
	struct i2c_client *client;
	struct rtc_device *rtc;
	struct work_struct work;
#ifdef CONFIG_RTC_DRV_DS1374_WDT
	struct watchdog_device wdt;
#endif
	/* 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 (WARN_ON(nbytes > 4))
		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_time64_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_time64(time);

	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
}

#ifndef CONFIG_RTC_DRV_DS1374_WDT
/* 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_time64_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;

	new_alarm = rtc_tm_to_time64(&alarm->time);
	itime = rtc_tm_to_time64(&now);

	/* 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;
}
#endif

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);
}

#ifndef CONFIG_RTC_DRV_DS1374_WDT
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;
}
#endif

static const struct rtc_class_ops ds1374_rtc_ops = {
	.read_time = ds1374_read_time,
	.set_time = ds1374_set_time,
#ifndef CONFIG_RTC_DRV_DS1374_WDT
	.read_alarm = ds1374_read_alarm,
	.set_alarm = ds1374_set_alarm,
	.alarm_irq_enable = ds1374_alarm_irq_enable,
#endif
};

#ifdef CONFIG_RTC_DRV_DS1374_WDT
/*
 *****************************************************************************
 *
 * Watchdog Driver
 *
 *****************************************************************************
 */
/* Default margin */
#define TIMER_MARGIN_DEFAULT	32
#define TIMER_MARGIN_MIN	1
#define TIMER_MARGIN_MAX	4095 /* 24-bit value */

static int wdt_margin;
module_param(wdt_margin, int, 0);
MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 32s)");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default ="
		__MODULE_STRING(WATCHDOG_NOWAYOUT)")");

static const struct watchdog_info ds1374_wdt_info = {
	.identity       = "DS1374 Watchdog",
	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
						WDIOF_MAGICCLOSE,
};

static int ds1374_wdt_settimeout(struct watchdog_device *wdt, unsigned int timeout)
{
	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
	struct i2c_client *client = ds1374->client;
	int ret, cr;

	wdt->timeout = timeout;

	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
	if (cr < 0)
		return cr;

	/* Disable any existing watchdog/alarm before setting the new one */
	cr &= ~DS1374_REG_CR_WACE;

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

	/* Set new watchdog time */
	timeout = timeout * 4096;
	ret = ds1374_write_rtc(client, timeout, DS1374_REG_WDALM0, 3);
	if (ret)
		return ret;

	/* Enable watchdog timer */
	cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_WDALM;
	cr &= ~DS1374_REG_CR_WDSTR;/* for RST PIN */
	cr &= ~DS1374_REG_CR_AIE;

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

	return 0;
}

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static int ds1374_wdt_start(struct watchdog_device *wdt)
{
	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
	u32 val;

	return ds1374_read_rtc(ds1374->client, &val, DS1374_REG_WDALM0, 3);
}

static int ds1374_wdt_stop(struct watchdog_device *wdt)
{
	struct ds1374 *ds1374 = watchdog_get_drvdata(wdt);
	struct i2c_client *client = ds1374->client;
	int cr;

	cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
	if (cr < 0)
		return cr;

	/* Disable watchdog timer */
	cr &= ~DS1374_REG_CR_WACE;

	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
}

static const struct watchdog_ops ds1374_wdt_ops = {
	.owner          = THIS_MODULE,
	.start          = ds1374_wdt_start,
	.stop           = ds1374_wdt_stop,
	.set_timeout    = ds1374_wdt_settimeout,
};
#endif /*CONFIG_RTC_DRV_DS1374_WDT*/
/*
 *****************************************************************************
 *
 *	Driver Interface
 *
 *****************************************************************************
 */
static int ds1374_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct ds1374 *ds1374;
	int ret;

	ds1374 = devm_kzalloc(&client->dev, sizeof(struct ds1374), GFP_KERNEL);
	if (!ds1374)
		return -ENOMEM;

	ds1374->rtc = devm_rtc_allocate_device(&client->dev);
	if (IS_ERR(ds1374->rtc))
		return PTR_ERR(ds1374->rtc);

	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)
		return ret;

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

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

	ds1374->rtc->ops = &ds1374_rtc_ops;
	ds1374->rtc->range_max = U32_MAX;

	ret = devm_rtc_register_device(ds1374->rtc);
	if (ret)
		return ret;

#ifdef CONFIG_RTC_DRV_DS1374_WDT
	ds1374->wdt.info = &ds1374_wdt_info;
	ds1374->wdt.ops = &ds1374_wdt_ops;
	ds1374->wdt.timeout = TIMER_MARGIN_DEFAULT;
	ds1374->wdt.min_timeout = TIMER_MARGIN_MIN;
	ds1374->wdt.max_timeout = TIMER_MARGIN_MAX;

	watchdog_init_timeout(&ds1374->wdt, wdt_margin, &client->dev);
	watchdog_set_nowayout(&ds1374->wdt, nowayout);
	watchdog_stop_on_reboot(&ds1374->wdt);
	watchdog_stop_on_unregister(&ds1374->wdt);
	watchdog_set_drvdata(&ds1374->wdt, ds1374);
	ds1374_wdt_settimeout(&ds1374->wdt, ds1374->wdt.timeout);

	ret = devm_watchdog_register_device(&client->dev, &ds1374->wdt);
	if (ret)
		return ret;
#endif

	return 0;
}

static int 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);

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

	return 0;
}

#ifdef CONFIG_PM_SLEEP
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;
}
#endif

static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);

static struct i2c_driver ds1374_driver = {
	.driver = {
		.name = "rtc-ds1374",
		.of_match_table = of_match_ptr(ds1374_of_match),
		.pm = &ds1374_pm,
	},
	.probe = ds1374_probe,
	.remove = ds1374_remove,
	.id_table = ds1374_id,
};

module_i2c_driver(ds1374_driver);

MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
MODULE_LICENSE("GPL");