/*
   * Watchdog driver for Cirrus Logic EP93xx family of devices.
   *
   * Copyright (c) 2004 Ray Lehtiniemi
   * Copyright (c) 2006 Tower Technologies
   * Based on ep93xx driver, bits from alim7101_wdt.c
   *
   * Authors: Ray Lehtiniemi <rayl@mail.com>,
   *	Alessandro Zummo <a.zummo@towertech.it>
   *
   * 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.
   *
   * This watchdog fires after 250msec, which is a too short interval
   * for us to rely on the user space daemon alone. So we ping the
   * wdt each ~200msec and eventually stop doing it if the user space
   * daemon dies.
   *
   * TODO:
   *
   *	- Test last reset from watchdog status
   *	- Add a few missing ioctls
   */
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/timer.h>

  #include <linux/uaccess.h>

  #include <linux/io.h>

  #include <mach/hardware.h>

  
  #define WDT_VERSION	"0.3"
  #define PFX		"ep93xx_wdt: "
  
  /* default timeout (secs) */
  #define WDT_TIMEOUT 30
  
  static int nowayout = WATCHDOG_NOWAYOUT;
  static int timeout = WDT_TIMEOUT;
  
  static struct timer_list timer;
  static unsigned long next_heartbeat;
  static unsigned long wdt_status;
  static unsigned long boot_status;
  
  #define WDT_IN_USE		0
  #define WDT_OK_TO_CLOSE		1
  
  #define EP93XX_WDT_REG(x)	(EP93XX_WATCHDOG_BASE + (x))
  #define EP93XX_WDT_WATCHDOG	EP93XX_WDT_REG(0x00)
  #define EP93XX_WDT_WDSTATUS	EP93XX_WDT_REG(0x04)
  
  /* reset the wdt every ~200ms */
  #define WDT_INTERVAL (HZ/5)
  
  static void wdt_enable(void)
  {
  	__raw_writew(0xaaaa, EP93XX_WDT_WATCHDOG);
  }
  
  static void wdt_disable(void)
  {
  	__raw_writew(0xaa55, EP93XX_WDT_WATCHDOG);
  }
  
  static inline void wdt_ping(void)
  {
  	__raw_writew(0x5555, EP93XX_WDT_WATCHDOG);
  }
  
  static void wdt_startup(void)
  {
  	next_heartbeat = jiffies + (timeout * HZ);
  
  	wdt_enable();
  	mod_timer(&timer, jiffies + WDT_INTERVAL);
  }
  
  static void wdt_shutdown(void)
  {
  	del_timer_sync(&timer);
  	wdt_disable();
  }
  
  static void wdt_keepalive(void)
  {
  	/* user land ping */
  	next_heartbeat = jiffies + (timeout * HZ);
  }
  
  static int ep93xx_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(WDT_IN_USE, &wdt_status))
  		return -EBUSY;
  
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	wdt_startup();
  
  	return nonseekable_open(inode, file);
  }
  
  static ssize_t
  ep93xx_wdt_write(struct file *file, const char __user *data, size_t len,
  		 loff_t *ppos)
  {

  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  			for (i = 0; i != len; i++) {
  				char c;
  
  				if (get_user(c, data + i))
  					return -EFAULT;
  
  				if (c == 'V')
  					set_bit(WDT_OK_TO_CLOSE, &wdt_status);
  				else
  					clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  			}
  		}
  		wdt_keepalive();
  	}
  
  	return len;
  }

  static const struct watchdog_info ident = {

  	.options = WDIOF_CARDRESET | WDIOF_MAGICCLOSE,
  	.identity = "EP93xx Watchdog",
  };

  static long ep93xx_wdt_ioctl(struct file *file,
  					unsigned int cmd, unsigned long arg)

  {

  	int ret = -ENOTTY;

  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
  				sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  		ret = put_user(0, (int __user *)arg);
  		break;
  
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(boot_status, (int __user *)arg);
  		break;

  	case WDIOC_KEEPALIVE:
  		wdt_keepalive();
  		ret = 0;
  		break;

  
  	case WDIOC_GETTIMEOUT:
  		/* actually, it is 0.250 seconds.... */
  		ret = put_user(1, (int __user *)arg);
  		break;

  	}
  	return ret;
  }
  
  static int ep93xx_wdt_release(struct inode *inode, struct file *file)
  {
  	if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
  		wdt_shutdown();
  	else

  		printk(KERN_CRIT PFX
  			"Device closed unexpectedly - timer will not stop
  ");

  
  	clear_bit(WDT_IN_USE, &wdt_status);
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	return 0;
  }

  static const struct file_operations ep93xx_wdt_fops = {

  	.owner		= THIS_MODULE,
  	.write		= ep93xx_wdt_write,

  	.unlocked_ioctl	= ep93xx_wdt_ioctl,

  	.open		= ep93xx_wdt_open,
  	.release	= ep93xx_wdt_release,

  	.llseek		= no_llseek,

  };
  
  static struct miscdevice ep93xx_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &ep93xx_wdt_fops,
  };
  
  static void ep93xx_timer_ping(unsigned long data)
  {
  	if (time_before(jiffies, next_heartbeat))
  		wdt_ping();
  
  	/* Re-set the timer interval */
  	mod_timer(&timer, jiffies + WDT_INTERVAL);
  }
  
  static int __init ep93xx_wdt_init(void)
  {
  	int err;
  
  	err = misc_register(&ep93xx_wdt_miscdev);
  
  	boot_status = __raw_readl(EP93XX_WDT_WATCHDOG) & 0x01 ? 1 : 0;
  
  	printk(KERN_INFO PFX "EP93XX watchdog, driver version "
  		WDT_VERSION "%s
  ",
  		(__raw_readl(EP93XX_WDT_WATCHDOG) & 0x08)
  		? " (nCS1 disable detected)" : "");
  
  	if (timeout < 1 || timeout > 3600) {
  		timeout = WDT_TIMEOUT;
  		printk(KERN_INFO PFX
  			"timeout value must be 1<=x<=3600, using %d
  ",
  			timeout);
  	}
  
  	setup_timer(&timer, ep93xx_timer_ping, 1);
  	return err;
  }
  
  static void __exit ep93xx_wdt_exit(void)
  {
  	wdt_shutdown();
  	misc_deregister(&ep93xx_wdt_miscdev);
  }
  
  module_init(ep93xx_wdt_init);
  module_exit(ep93xx_wdt_exit);
  
  module_param(nowayout, int, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
  
  module_param(timeout, int, 0);

  MODULE_PARM_DESC(timeout,
  	"Watchdog timeout in seconds. (1<=timeout<=3600, default="

  				__MODULE_STRING(WDT_TIMEOUT) ")");

  
  MODULE_AUTHOR("Ray Lehtiniemi <rayl@mail.com>,"
  		"Alessandro Zummo <a.zummo@towertech.it>");
  MODULE_DESCRIPTION("EP93xx Watchdog");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(WDT_VERSION);
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);