/* linux/drivers/char/watchdog/at91_wdt.c
 *
 * AT91SAM9261S Watchdog Timer Support
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
*/

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/config.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/arch/map.h>
#include <asm/hardware/clock.h>

#include <asm/arch/hardware.h>

#define DEFAULT_SLOW_CLOCK 32768
#define WDT_MR_WDD_MASK (0xfff << 16)
#define WDT_MR_WDV_MASK (0xfff << 0)

#define WDT_CR 0x00
#define WDT_MR 0x04
#define WDT_SR 0x08

#define WDT_MR_WDIDELHLT (0x1 << 29)
#define WDT_MR_WDDBGHLT  (0x1 << 28)

#define WDT_MR_WDDIS     (0x1 << 15)
#define WDT_MR_WDRPROC   (0x1 << 14)
#define WDT_MR_WDRSTEN   (0x1 << 13)
#define WDT_MR_WDFIEN    (0x1 << 12)

#define PFX "at91-wdt: "
#define AT91_WATCHDOG_DEFAULT_TIMEOUT	(15)

#define RSTC_MR_ERSTL	5  //the external reset length [ 2^(ERSTL+1) slow clock cycles ]

static int nowayout = WATCHDOG_NOWAYOUT;
static int wdt_timeout	= AT91_WATCHDOG_DEFAULT_TIMEOUT;
static int debug	= 0;

module_param(wdt_timeout,  int, 0);
module_param(nowayout,    int, 0);
module_param(debug,	  int, 0);

MODULE_PARM_DESC(wdt_timeout, "Watchdog wdt_timeout in seconds. default=" __MODULE_STRING(AT91_WATCHDOG_DEFAULT_TIMEOUT) ")");
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
MODULE_PARM_DESC(debug, "Watchdog debug, set to >1 for debug, (default 0)");


typedef enum close_state {
	CLOSE_STATE_NOT,
	CLOSE_STATE_ALLOW = 0x4321
} close_state_t;

static DECLARE_MUTEX(open_lock);

static struct resource	*wdt_mem;
static struct resource	*wdt_irq;
static void __iomem	*wdt_base;
static unsigned int	 wdt_count;
static close_state_t allow_close;

#define DBG(msg...) do { \
	if (debug) \
		printk(KERN_INFO msg); \
	} while(0)

static int at91wdt_seedwd(void)
{
	writel(0xa5000001, wdt_base + WDT_CR);
	return 0;
}

static int at91wdt_stop(void)
{
	unsigned long wtcon;

	wtcon = readl(wdt_base + WDT_MR);
	wtcon |= (WDT_MR_WDDIS);
	wtcon &= ~(WDT_MR_WDRSTEN);
	writel(wtcon, wdt_base + WDT_MR);

	return 0;
}

static int at91wdt_start(void)
{
	unsigned long wtcon;

	at91wdt_stop();

	wtcon = readl(wdt_base + WDT_MR);
	wtcon |= WDT_MR_WDRSTEN;
	wtcon &= ~WDT_MR_WDDIS;
	writel(wtcon, wdt_base + WDT_MR);

	DBG("%s: wdt_count=0x%08x, wtcon=%08lx\n",
	    __FUNCTION__, wdt_count, wtcon);

	return 0;
}

static int at91wdt_set_counter(int timeout)
{
	unsigned int freq = DEFAULT_SLOW_CLOCK;
	unsigned int count;
	unsigned long wtcon;

	if (timeout < 1)
		return -EINVAL;

	freq /= 128;
	count = timeout * freq;

	if (count >= 0x10000) {
		printk(KERN_ERR PFX "timeout %d too big\n", timeout);
		return -EINVAL;
	}

	wdt_timeout = timeout;
	wdt_count = count;

	wtcon = readl(wdt_base + WDT_MR);
	wtcon &= ~WDT_MR_WDV_MASK;
	wtcon |= count;
	writel(wtcon, wdt_base + WDT_MR);

	DBG("%s: count=%d, timeout=%d, freq=%d\n",
	   __FUNCTION__, count, timeout, freq);

	return 0;
}

static int at91wdt_open(struct inode *inode, struct file *file)
{
	if(down_trylock(&open_lock))
		return -EBUSY;

	if (nowayout) {
		__module_get(THIS_MODULE);
	} else {
		allow_close = CLOSE_STATE_ALLOW;
	}

	/* start the timer */
	at91wdt_start();
	return nonseekable_open(inode, file);
}

static int at91wdt_release(struct inode *inode, struct file *file)
{
	/*
	 *	Shut off the timer.
	 * 	Lock it in if it's a module and we set nowayout
	 */
	if (allow_close == CLOSE_STATE_ALLOW) {
		at91wdt_stop();
	} else {
		printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
		at91wdt_seedwd();
	}

	allow_close = CLOSE_STATE_NOT;
	up(&open_lock);
	return 0;
}

static ssize_t at91wdt_write(struct file *file, const char __user *data,
				size_t len, loff_t *ppos)
{
	/*
	 *	Refresh the timer.
	 */
	if(len) {
		if (!nowayout) {
			size_t i;

			/* In case it was set long ago */
			allow_close = CLOSE_STATE_NOT;

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

				if (get_user(c, data + i))
					return -EFAULT;
				if (c == 'V')
					allow_close = CLOSE_STATE_ALLOW;
			}
		}

		at91wdt_seedwd();
	}
	return len;
}

static struct watchdog_info at91_wdt_ident = {
	.options          = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
	.firmware_version =	0,
	.identity         =	"AT91SAM9261S Watchdog",
};

static int at91wdt_ioctl(struct inode *inode, struct file *file,
	unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_margin;

	switch (cmd) {
		default:
			return -ENOIOCTLCMD;

		case WDIOC_GETSUPPORT:
			return copy_to_user(argp, &at91_wdt_ident,
				sizeof(at91_wdt_ident)) ? -EFAULT : 0;

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

		case WDIOC_KEEPALIVE:
			at91wdt_seedwd();
			return 0;

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

			if (at91wdt_set_counter(new_margin))
				return -EINVAL;

			at91wdt_seedwd();
			return put_user(wdt_timeout, p);

		case WDIOC_GETTIMEOUT:
			return put_user(wdt_timeout, p);
	}
}

static struct file_operations at91wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= at91wdt_write,
	.ioctl		= at91wdt_ioctl,
	.open		= at91wdt_open,
	.release	= at91wdt_release,
};

static struct miscdevice at91wdt_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &at91wdt_fops,
};

static irqreturn_t at91wdt_irq(int irqno, void *param,
				  struct pt_regs *regs)
{
	printk(KERN_INFO PFX "Watchdog timer expired!\n");

	at91wdt_seedwd();
	return IRQ_HANDLED;
}

/* 
* Set the external reset length on pin NRST for exteral devices connected to  the system reset 
 */
static int at91rst_set_erstl(void)
{
	unsigned long rstc_mr;
	rstc_mr = readl(AT91C_VA_BASE_RSTC + 0x08);
	rstc_mr = (rstc_mr && 0x0fff0ff) || (RSTC_MR_ERSTL << 8)|| (0x0a5 << 24);
	writel(rstc_mr, AT91C_VA_BASE_RSTC + 0x08);

}
static int at91wdt_probe(struct platform_device *pdev)
{
	struct resource *res;
	int ret;

	DBG("%s: probe=%p\n", __FUNCTION__, pdev);

	wdt_base = AT91C_VA_BASE_WDT;
	DBG("probe: mapped wdt_base=%p\n", wdt_base);

	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (res == NULL) {
		printk(KERN_INFO PFX "failed to get irq resource\n");
		return -ENOENT;
	}

	ret = request_irq(res->start, at91wdt_irq, 0, pdev->name, pdev);
	if (ret != 0) {
		printk(KERN_INFO PFX "failed to install irq (%d)\n", ret);
		return ret;
	}

	readl(wdt_base + WDT_SR);
	writel(0x3fff2fff, wdt_base + WDT_MR);//reset WDT_MR just in case
	
	if (at91wdt_set_counter(wdt_timeout)) {
		at91wdt_set_counter(AT91_WATCHDOG_DEFAULT_TIMEOUT);
		printk(KERN_INFO PFX "wdt_timeout value out of range, default %d used\n",
			       AT91_WATCHDOG_DEFAULT_TIMEOUT);
	}

	ret = misc_register(&at91wdt_miscdev);
	if (ret) {
		printk (KERN_ERR PFX "cannot register miscdev on minor=%d (%d)\n",
			WATCHDOG_MINOR, ret);
		return ret;
	}

	at91wdt_stop();   
	at91rst_set_erstl();
	
	return 0;
}

static int at91wdt_remove(struct platform_device *dev)
{

	if (wdt_irq != NULL) {
		free_irq(wdt_irq->start, dev);
		wdt_irq = NULL;
	}

	misc_deregister(&at91wdt_miscdev);
	return 0;
}

static void at91wdt_shutdown(struct platform_device *dev)
{
	at91wdt_stop();	
}


static struct platform_driver at91wdt_driver = {
	.probe		= at91wdt_probe,
	.remove		= at91wdt_remove,
	.shutdown	= at91wdt_shutdown,
	.driver		= {
		.owner	= THIS_MODULE,
		.name	= "at91-wdt",
	},
};

static int __init watchdog_init(void)
{
	printk(KERN_INFO "AT91SAM9261S Watchdog Timer Initialization\n");
	return platform_driver_register(&at91wdt_driver);
}

static void __exit watchdog_exit(void)
{
	platform_driver_unregister(&at91wdt_driver);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("SOLOO");
MODULE_DESCRIPTION("AT91 Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);