/* Watchdog timer for machines with the CS5535/CS5536 companion chip
 *
 * Copyright (C) 2006-2007, Advanced Micro Devices, Inc.
 * Copyright (C) 2009  Andres Salomon <dilinger@collabora.co.uk>
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#include <linux/cs5535.h>

#define GEODEWDT_HZ 500
#define GEODEWDT_SCALE 6
#define GEODEWDT_MAX_SECONDS 131

#define WDT_FLAGS_OPEN 1
#define WDT_FLAGS_ORPHAN 2

#define DRV_NAME "geodewdt"
#define WATCHDOG_NAME "Geode GX/LX WDT"
#define WATCHDOG_TIMEOUT 60

static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. 1<= timeout <=131, default="
				__MODULE_STRING(WATCHDOG_TIMEOUT) ".");

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 struct platform_device *geodewdt_platform_device;
static unsigned long wdt_flags;
static struct cs5535_mfgpt_timer *wdt_timer;
static int safe_close;

static void geodewdt_ping(void)
{
	/* Stop the counter */
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);

	/* Reset the counter */
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);

	/* Enable the counter */
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
}

static void geodewdt_disable(void)
{
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
}

static int geodewdt_set_heartbeat(int val)
{
	if (val < 1 || val > GEODEWDT_MAX_SECONDS)
		return -EINVAL;

	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2, val * GEODEWDT_HZ);
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);

	timeout = val;
	return 0;
}

static int geodewdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(WDT_FLAGS_OPEN, &wdt_flags))
		return -EBUSY;

	if (!test_and_clear_bit(WDT_FLAGS_ORPHAN, &wdt_flags))
		__module_get(THIS_MODULE);

	geodewdt_ping();
	return nonseekable_open(inode, file);
}

static int geodewdt_release(struct inode *inode, struct file *file)
{
	if (safe_close) {
		geodewdt_disable();
		module_put(THIS_MODULE);
	} else {
		pr_crit("Unexpected close - watchdog is not stopping\n");
		geodewdt_ping();

		set_bit(WDT_FLAGS_ORPHAN, &wdt_flags);
	}

	clear_bit(WDT_FLAGS_OPEN, &wdt_flags);
	safe_close = 0;
	return 0;
}

static ssize_t geodewdt_write(struct file *file, const char __user *data,
				size_t len, loff_t *ppos)
{
	if (len) {
		if (!nowayout) {
			size_t i;
			safe_close = 0;

			for (i = 0; i != len; i++) {
				char c;

				if (get_user(c, data + i))
					return -EFAULT;

				if (c == 'V')
					safe_close = 1;
			}
		}

		geodewdt_ping();
	}
	return len;
}

static long geodewdt_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int interval;

	static const struct watchdog_info ident = {
		.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING
		| WDIOF_MAGICCLOSE,
		.firmware_version =     1,
		.identity =             WATCHDOG_NAME,
	};

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

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);

	case WDIOC_SETOPTIONS:
	{
		int options, ret = -EINVAL;

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

		if (options & WDIOS_DISABLECARD) {
			geodewdt_disable();
			ret = 0;
		}

		if (options & WDIOS_ENABLECARD) {
			geodewdt_ping();
			ret = 0;
		}

		return ret;
	}
	case WDIOC_KEEPALIVE:
		geodewdt_ping();
		return 0;

	case WDIOC_SETTIMEOUT:
		if (get_user(interval, p))
			return -EFAULT;

		if (geodewdt_set_heartbeat(interval))
			return -EINVAL;
	/* Fall through */
	case WDIOC_GETTIMEOUT:
		return put_user(timeout, p);

	default:
		return -ENOTTY;
	}

	return 0;
}

static const struct file_operations geodewdt_fops = {
	.owner          = THIS_MODULE,
	.llseek         = no_llseek,
	.write          = geodewdt_write,
	.unlocked_ioctl = geodewdt_ioctl,
	.open           = geodewdt_open,
	.release        = geodewdt_release,
};

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

static int __init geodewdt_probe(struct platform_device *dev)
{
	int ret;

	wdt_timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
	if (!wdt_timer) {
		pr_err("No timers were available\n");
		return -ENODEV;
	}

	/* Set up the timer */

	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP,
			  GEODEWDT_SCALE | (3 << 8));

	/* Set up comparator 2 to reset when the event fires */
	cs5535_mfgpt_toggle_event(wdt_timer, MFGPT_CMP2, MFGPT_EVENT_RESET, 1);

	/* Set up the initial timeout */

	cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2,
		timeout * GEODEWDT_HZ);

	ret = misc_register(&geodewdt_miscdev);

	return ret;
}

static int geodewdt_remove(struct platform_device *dev)
{
	misc_deregister(&geodewdt_miscdev);
	return 0;
}

static void geodewdt_shutdown(struct platform_device *dev)
{
	geodewdt_disable();
}

static struct platform_driver geodewdt_driver = {
	.remove		= geodewdt_remove,
	.shutdown	= geodewdt_shutdown,
	.driver		= {
		.name	= DRV_NAME,
	},
};

static int __init geodewdt_init(void)
{
	int ret;

	geodewdt_platform_device = platform_device_register_simple(DRV_NAME,
								-1, NULL, 0);
	if (IS_ERR(geodewdt_platform_device))
		return PTR_ERR(geodewdt_platform_device);

	ret = platform_driver_probe(&geodewdt_driver, geodewdt_probe);
	if (ret)
		goto err;

	return 0;
err:
	platform_device_unregister(geodewdt_platform_device);
	return ret;
}

static void __exit geodewdt_exit(void)
{
	platform_device_unregister(geodewdt_platform_device);
	platform_driver_unregister(&geodewdt_driver);
}

module_init(geodewdt_init);
module_exit(geodewdt_exit);

MODULE_AUTHOR("Advanced Micro Devices, Inc");
MODULE_DESCRIPTION("Geode GX/LX Watchdog Driver");
MODULE_LICENSE("GPL");