/*
 * Watchdog driver for the wm831x PMICs
 *
 * Copyright (C) 2009 Wolfson Microelectronics
 *
 * 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
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>
#include <linux/gpio.h>

#include <linux/mfd/wm831x/core.h>
#include <linux/mfd/wm831x/pdata.h>
#include <linux/mfd/wm831x/watchdog.h>

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

static unsigned long wm831x_wdt_users;
static struct miscdevice wm831x_wdt_miscdev;
static int wm831x_wdt_expect_close;
static DEFINE_MUTEX(wdt_mutex);
static struct wm831x *wm831x;
static unsigned int update_gpio;
static unsigned int update_state;

/* We can't use the sub-second values here but they're included
 * for completeness.  */
static struct {
	int time;  /* Seconds */
	u16 val;   /* WDOG_TO value */
} wm831x_wdt_cfgs[] = {
	{  1, 2 },
	{  2, 3 },
	{  4, 4 },
	{  8, 5 },
	{ 16, 6 },
	{ 32, 7 },
	{ 33, 7 },  /* Actually 32.768s so include both, others round down */
};

static int wm831x_wdt_set_timeout(struct wm831x *wm831x, u16 value)
{
	int ret;

	mutex_lock(&wdt_mutex);

	ret = wm831x_reg_unlock(wm831x);
	if (ret == 0) {
		ret = wm831x_set_bits(wm831x, WM831X_WATCHDOG,
				      WM831X_WDOG_TO_MASK, value);
		wm831x_reg_lock(wm831x);
	} else {
		dev_err(wm831x->dev, "Failed to unlock security key: %d\n",
			ret);
	}

	mutex_unlock(&wdt_mutex);

	return ret;
}

static int wm831x_wdt_start(struct wm831x *wm831x)
{
	int ret;

	mutex_lock(&wdt_mutex);

	ret = wm831x_reg_unlock(wm831x);
	if (ret == 0) {
		ret = wm831x_set_bits(wm831x, WM831X_WATCHDOG,
				      WM831X_WDOG_ENA, WM831X_WDOG_ENA);
		wm831x_reg_lock(wm831x);
	} else {
		dev_err(wm831x->dev, "Failed to unlock security key: %d\n",
			ret);
	}

	mutex_unlock(&wdt_mutex);

	return ret;
}

static int wm831x_wdt_stop(struct wm831x *wm831x)
{
	int ret;

	mutex_lock(&wdt_mutex);

	ret = wm831x_reg_unlock(wm831x);
	if (ret == 0) {
		ret = wm831x_set_bits(wm831x, WM831X_WATCHDOG,
				      WM831X_WDOG_ENA, 0);
		wm831x_reg_lock(wm831x);
	} else {
		dev_err(wm831x->dev, "Failed to unlock security key: %d\n",
			ret);
	}

	mutex_unlock(&wdt_mutex);

	return ret;
}

static int wm831x_wdt_kick(struct wm831x *wm831x)
{
	int ret;
	u16 reg;

	mutex_lock(&wdt_mutex);

	if (update_gpio) {
		gpio_set_value_cansleep(update_gpio, update_state);
		update_state = !update_state;
		ret = 0;
		goto out;
	}


	reg = wm831x_reg_read(wm831x, WM831X_WATCHDOG);

	if (!(reg & WM831X_WDOG_RST_SRC)) {
		dev_err(wm831x->dev, "Hardware watchdog update unsupported\n");
		ret = -EINVAL;
		goto out;
	}

	reg |= WM831X_WDOG_RESET;

	ret = wm831x_reg_unlock(wm831x);
	if (ret == 0) {
		ret = wm831x_reg_write(wm831x, WM831X_WATCHDOG, reg);
		wm831x_reg_lock(wm831x);
	} else {
		dev_err(wm831x->dev, "Failed to unlock security key: %d\n",
			ret);
	}

out:
	mutex_unlock(&wdt_mutex);

	return ret;
}

static int wm831x_wdt_open(struct inode *inode, struct file *file)
{
	int ret;

	if (!wm831x)
		return -ENODEV;

	if (test_and_set_bit(0, &wm831x_wdt_users))
		return -EBUSY;

	ret = wm831x_wdt_start(wm831x);
	if (ret != 0)
		return ret;

	return nonseekable_open(inode, file);
}

static int wm831x_wdt_release(struct inode *inode, struct file *file)
{
	if (wm831x_wdt_expect_close)
		wm831x_wdt_stop(wm831x);
	else {
		dev_warn(wm831x->dev, "Watchdog device closed uncleanly\n");
		wm831x_wdt_kick(wm831x);
	}

	clear_bit(0, &wm831x_wdt_users);

	return 0;
}

static ssize_t wm831x_wdt_write(struct file *file,
				const char __user *data, size_t count,
				loff_t *ppos)
{
	size_t i;

	if (count) {
		wm831x_wdt_kick(wm831x);

		if (!nowayout) {
			/* In case it was set long ago */
			wm831x_wdt_expect_close = 0;

			/* scan to see whether or not we got the magic
			   character */
			for (i = 0; i != count; i++) {
				char c;
				if (get_user(c, data + i))
					return -EFAULT;
				if (c == 'V')
					wm831x_wdt_expect_close = 42;
			}
		}
	}
	return count;
}

static const struct watchdog_info ident = {
	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
	.identity = "WM831x Watchdog",
};

static long wm831x_wdt_ioctl(struct file *file, unsigned int cmd,
			     unsigned long arg)
{
	int ret = -ENOTTY, time, i;
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	u16 reg;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
		break;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		ret = put_user(0, p);
		break;

	case WDIOC_SETOPTIONS:
	{
		int options;

		if (get_user(options, p))
			return -EFAULT;

		ret = -EINVAL;

		/* Setting both simultaneously means at least one must fail */
		if (options == WDIOS_DISABLECARD)
			ret = wm831x_wdt_start(wm831x);

		if (options == WDIOS_ENABLECARD)
			ret = wm831x_wdt_stop(wm831x);
		break;
	}

	case WDIOC_KEEPALIVE:
		ret = wm831x_wdt_kick(wm831x);
		break;

	case WDIOC_SETTIMEOUT:
		ret = get_user(time, p);
		if (ret)
			break;

		if (time == 0) {
			if (nowayout)
				ret = -EINVAL;
			else
				wm831x_wdt_stop(wm831x);
			break;
		}

		for (i = 0; i < ARRAY_SIZE(wm831x_wdt_cfgs); i++)
			if (wm831x_wdt_cfgs[i].time == time)
				break;
		if (i == ARRAY_SIZE(wm831x_wdt_cfgs))
			ret = -EINVAL;
		else
			ret = wm831x_wdt_set_timeout(wm831x,
						     wm831x_wdt_cfgs[i].val);
		break;

	case WDIOC_GETTIMEOUT:
		reg = wm831x_reg_read(wm831x, WM831X_WATCHDOG);
		reg &= WM831X_WDOG_TO_MASK;
		for (i = 0; i < ARRAY_SIZE(wm831x_wdt_cfgs); i++)
			if (wm831x_wdt_cfgs[i].val == reg)
				break;
		if (i == ARRAY_SIZE(wm831x_wdt_cfgs)) {
			dev_warn(wm831x->dev,
				 "Unknown watchdog configuration: %x\n", reg);
			ret = -EINVAL;
		} else
			ret = put_user(wm831x_wdt_cfgs[i].time, p);

	}

	return ret;
}

static const struct file_operations wm831x_wdt_fops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.write = wm831x_wdt_write,
	.unlocked_ioctl = wm831x_wdt_ioctl,
	.open = wm831x_wdt_open,
	.release = wm831x_wdt_release,
};

static struct miscdevice wm831x_wdt_miscdev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &wm831x_wdt_fops,
};

static int __devinit wm831x_wdt_probe(struct platform_device *pdev)
{
	struct wm831x_pdata *chip_pdata;
	struct wm831x_watchdog_pdata *pdata;
	int reg, ret;

	if (wm831x) {
		dev_err(&pdev->dev, "wm831x watchdog already registered\n");
		return -EBUSY;
	}

	wm831x = dev_get_drvdata(pdev->dev.parent);

	ret = wm831x_reg_read(wm831x, WM831X_WATCHDOG);
	if (ret < 0) {
		dev_err(wm831x->dev, "Failed to read watchdog status: %d\n",
			ret);
		goto err;
	}
	reg = ret;

	if (reg & WM831X_WDOG_DEBUG)
		dev_warn(wm831x->dev, "Watchdog is paused\n");

	/* Apply any configuration */
	if (pdev->dev.parent->platform_data) {
		chip_pdata = pdev->dev.parent->platform_data;
		pdata = chip_pdata->watchdog;
	} else {
		pdata = NULL;
	}

	if (pdata) {
		reg &= ~(WM831X_WDOG_SECACT_MASK | WM831X_WDOG_PRIMACT_MASK |
			 WM831X_WDOG_RST_SRC);

		reg |= pdata->primary << WM831X_WDOG_PRIMACT_SHIFT;
		reg |= pdata->secondary << WM831X_WDOG_SECACT_SHIFT;
		reg |= pdata->software << WM831X_WDOG_RST_SRC_SHIFT;

		if (pdata->update_gpio) {
			ret = gpio_request(pdata->update_gpio,
					   "Watchdog update");
			if (ret < 0) {
				dev_err(wm831x->dev,
					"Failed to request update GPIO: %d\n",
					ret);
				goto err;
			}

			ret = gpio_direction_output(pdata->update_gpio, 0);
			if (ret != 0) {
				dev_err(wm831x->dev,
					"gpio_direction_output returned: %d\n",
					ret);
				goto err_gpio;
			}

			update_gpio = pdata->update_gpio;

			/* Make sure the watchdog takes hardware updates */
			reg |= WM831X_WDOG_RST_SRC;
		}

		ret = wm831x_reg_unlock(wm831x);
		if (ret == 0) {
			ret = wm831x_reg_write(wm831x, WM831X_WATCHDOG, reg);
			wm831x_reg_lock(wm831x);
		} else {
			dev_err(wm831x->dev,
				"Failed to unlock security key: %d\n", ret);
			goto err_gpio;
		}
	}

	wm831x_wdt_miscdev.parent = &pdev->dev;

	ret = misc_register(&wm831x_wdt_miscdev);
	if (ret != 0) {
		dev_err(wm831x->dev, "Failed to register miscdev: %d\n", ret);
		goto err_gpio;
	}

	return 0;

err_gpio:
	if (update_gpio) {
		gpio_free(update_gpio);
		update_gpio = 0;
	}
err:
	return ret;
}

static int __devexit wm831x_wdt_remove(struct platform_device *pdev)
{
	if (update_gpio) {
		gpio_free(update_gpio);
		update_gpio = 0;
	}

	misc_deregister(&wm831x_wdt_miscdev);

	return 0;
}

static struct platform_driver wm831x_wdt_driver = {
	.probe = wm831x_wdt_probe,
	.remove = __devexit_p(wm831x_wdt_remove),
	.driver = {
		.name = "wm831x-watchdog",
	},
};

static int __init wm831x_wdt_init(void)
{
	return platform_driver_register(&wm831x_wdt_driver);
}
module_init(wm831x_wdt_init);

static void __exit wm831x_wdt_exit(void)
{
	platform_driver_unregister(&wm831x_wdt_driver);
}
module_exit(wm831x_wdt_exit);

MODULE_AUTHOR("Mark Brown");
MODULE_DESCRIPTION("WM831x Watchdog");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:wm831x-watchdog");