/*
   * Watchdog driver for Atmel AT91SAM9x processors.
   *
   * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
   *
   * 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.
   */
  
  /*
   * The Watchdog Timer Mode Register can be only written to once. If the
   * timeout need to be set from Linux, be sure that the bootstrap or the
   * bootloader doesn't write to this register.
   */
  
  #include <linux/errno.h>
  #include <linux/fs.h>
  #include <linux/init.h>

  #include <linux/io.h>

  #include <linux/kernel.h>
  #include <linux/miscdevice.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  #include <linux/jiffies.h>
  #include <linux/timer.h>
  #include <linux/bitops.h>
  #include <linux/uaccess.h>

  #include "at91sam9_wdt.h"

  
  #define DRV_NAME "AT91SAM9 Watchdog"

  #define wdt_read(field) \
  	__raw_readl(at91wdt_private.base + field)
  #define wdt_write(field, val) \
  	__raw_writel((val), at91wdt_private.base + field)

  /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
   * use this to convert a watchdog
   * value from/to milliseconds.
   */
  #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
  #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
  
  /* Hardware timeout in seconds */
  #define WDT_HW_TIMEOUT 2
  
  /* Timer heartbeat (500ms) */
  #define WDT_TIMEOUT	(HZ/2)
  
  /* User land timeout */
  #define WDT_HEARTBEAT 15
  static int heartbeat = WDT_HEARTBEAT;
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  
  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 void at91_ping(unsigned long data);
  
  static struct {

  	void __iomem *base;

  	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
  	unsigned long open;
  	char expect_close;
  	struct timer_list timer;	/* The timer that pings the watchdog */
  } at91wdt_private;
  
  /* ......................................................................... */
  
  
  /*
   * Reload the watchdog timer.  (ie, pat the watchdog)
   */
  static inline void at91_wdt_reset(void)
  {

  	wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);

  }
  
  /*
   * Timer tick
   */
  static void at91_ping(unsigned long data)
  {
  	if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
  			(!nowayout && !at91wdt_private.open)) {
  		at91_wdt_reset();
  		mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
  	} else
  		printk(KERN_CRIT DRV_NAME": I will reset your machine !
  ");
  }
  
  /*
   * Watchdog device is opened, and watchdog starts running.
   */
  static int at91_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(0, &at91wdt_private.open))
  		return -EBUSY;
  
  	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
  	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
  
  	return nonseekable_open(inode, file);
  }
  
  /*
   * Close the watchdog device.
   */
  static int at91_wdt_close(struct inode *inode, struct file *file)
  {
  	clear_bit(0, &at91wdt_private.open);
  
  	/* stop internal ping */
  	if (!at91wdt_private.expect_close)
  		del_timer(&at91wdt_private.timer);
  
  	at91wdt_private.expect_close = 0;
  	return 0;
  }
  
  /*
   * Set the watchdog time interval in 1/256Hz (write-once)
   * Counter is 12 bit.
   */
  static int at91_wdt_settimeout(unsigned int timeout)
  {
  	unsigned int reg;
  	unsigned int mr;
  
  	/* Check if disabled */

  	mr = wdt_read(AT91_WDT_MR);

  	if (mr & AT91_WDT_WDDIS) {
  		printk(KERN_ERR DRV_NAME": sorry, watchdog is disabled
  ");
  		return -EIO;
  	}
  
  	/*
  	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
  	 *
  	 * Since WDV is a 12-bit counter, the maximum period is
  	 * 4096 / 256 = 16 seconds.
  	 */
  	reg = AT91_WDT_WDRSTEN	/* causes watchdog reset */
  		/* | AT91_WDT_WDRPROC	causes processor reset only */
  		| AT91_WDT_WDDBGHLT	/* disabled in debug mode */
  		| AT91_WDT_WDD		/* restart at any time */
  		| (timeout & AT91_WDT_WDV);  /* timer value */

  	wdt_write(AT91_WDT_MR, reg);

  
  	return 0;
  }
  
  static const struct watchdog_info at91_wdt_info = {
  	.identity	= DRV_NAME,

  	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
  						WDIOF_MAGICCLOSE,

  };
  
  /*
   * Handle commands from user-space.
   */
  static long at91_wdt_ioctl(struct file *file,
  		unsigned int cmd, unsigned long arg)
  {
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  	int new_value;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		return copy_to_user(argp, &at91_wdt_info,
  				    sizeof(at91_wdt_info)) ? -EFAULT : 0;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, p);
  
  	case WDIOC_KEEPALIVE:
  		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
  		return 0;
  
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_value, p))
  			return -EFAULT;
  
  		heartbeat = new_value;
  		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
  
  		return put_user(new_value, p);  /* return current value */
  
  	case WDIOC_GETTIMEOUT:
  		return put_user(heartbeat, p);
  	}
  	return -ENOTTY;
  }
  
  /*
   * Pat the watchdog whenever device is written to.
   */
  static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,

  								loff_t *ppos)

  {
  	if (!len)
  		return 0;
  
  	/* Scan for magic character */
  	if (!nowayout) {
  		size_t i;
  
  		at91wdt_private.expect_close = 0;
  
  		for (i = 0; i < len; i++) {
  			char c;
  			if (get_user(c, data + i))
  				return -EFAULT;
  			if (c == 'V') {
  				at91wdt_private.expect_close = 42;
  				break;
  			}
  		}
  	}
  
  	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
  
  	return len;
  }
  
  /* ......................................................................... */
  
  static const struct file_operations at91wdt_fops = {
  	.owner			= THIS_MODULE,
  	.llseek			= no_llseek,
  	.unlocked_ioctl	= at91_wdt_ioctl,
  	.open			= at91_wdt_open,
  	.release		= at91_wdt_close,
  	.write			= at91_wdt_write,
  };
  
  static struct miscdevice at91wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &at91wdt_fops,
  };
  
  static int __init at91wdt_probe(struct platform_device *pdev)
  {

  	struct resource	*r;

  	int res;
  
  	if (at91wdt_miscdev.parent)
  		return -EBUSY;
  	at91wdt_miscdev.parent = &pdev->dev;

  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!r)
  		return -ENODEV;
  	at91wdt_private.base = ioremap(r->start, resource_size(r));
  	if (!at91wdt_private.base) {
  		dev_err(&pdev->dev, "failed to map registers, aborting.
  ");
  		return -ENOMEM;
  	}

  	/* Set watchdog */
  	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
  	if (res)
  		return res;
  
  	res = misc_register(&at91wdt_miscdev);
  	if (res)
  		return res;
  
  	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
  	setup_timer(&at91wdt_private.timer, at91_ping, 0);
  	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
  
  	printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)
  ",
  		heartbeat, nowayout);
  
  	return 0;
  }
  
  static int __exit at91wdt_remove(struct platform_device *pdev)
  {
  	int res;
  
  	res = misc_deregister(&at91wdt_miscdev);
  	if (!res)
  		at91wdt_miscdev.parent = NULL;
  
  	return res;
  }

  static struct platform_driver at91wdt_driver = {
  	.remove		= __exit_p(at91wdt_remove),

  	.driver		= {
  		.name	= "at91_wdt",
  		.owner	= THIS_MODULE,
  	},
  };
  
  static int __init at91sam_wdt_init(void)
  {
  	return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
  }
  
  static void __exit at91sam_wdt_exit(void)
  {
  	platform_driver_unregister(&at91wdt_driver);
  }
  
  module_init(at91sam_wdt_init);
  module_exit(at91sam_wdt_exit);
  
  MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
  MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);