/*
   * Blackfin On-Chip Watchdog Driver

   *
   * Originally based on softdog.c

   * Copyright 2006-2010 Analog Devices Inc.

   * Copyright 2006-2007 Michele d'Amico

   * Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>

   *
   * Enter bugs at http://blackfin.uclinux.org/
   *
   * Licensed under the GPL-2 or later.
   */
  
  #include <linux/platform_device.h>
  #include <linux/module.h>
  #include <linux/moduleparam.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/interrupt.h>

  #include <linux/uaccess.h>

  #include <asm/blackfin.h>

  #include <asm/bfin_watchdog.h>

  #define stamp(fmt, args...) \
  	pr_debug("%s:%i: " fmt "
  ", __func__, __LINE__, ## args)

  #define stampit() stamp("here i am")

  #define pr_devinit(fmt, args...) \
  	({ static const __devinitconst char __fmt[] = fmt; \
  	printk(__fmt, ## args); })
  #define pr_init(fmt, args...) \
  	({ static const __initconst char __fmt[] = fmt; \
  	printk(__fmt, ## args); })

  
  #define WATCHDOG_NAME "bfin-wdt"
  #define PFX WATCHDOG_NAME ": "
  
  /* The BF561 has two watchdogs (one per core), but since Linux
   * only runs on core A, we'll just work with that one.
   */
  #ifdef BF561_FAMILY
  # define bfin_read_WDOG_CTL()    bfin_read_WDOGA_CTL()
  # define bfin_read_WDOG_CNT()    bfin_read_WDOGA_CNT()
  # define bfin_read_WDOG_STAT()   bfin_read_WDOGA_STAT()
  # define bfin_write_WDOG_CTL(x)  bfin_write_WDOGA_CTL(x)
  # define bfin_write_WDOG_CNT(x)  bfin_write_WDOGA_CNT(x)
  # define bfin_write_WDOG_STAT(x) bfin_write_WDOGA_STAT(x)
  #endif

  /* some defaults */
  #define WATCHDOG_TIMEOUT 20
  
  static unsigned int timeout = WATCHDOG_TIMEOUT;
  static int nowayout = WATCHDOG_NOWAYOUT;

  static const struct watchdog_info bfin_wdt_info;

  static unsigned long open_check;
  static char expect_close;

  static DEFINE_SPINLOCK(bfin_wdt_spinlock);

  
  /**
   *	bfin_wdt_keepalive - Keep the Userspace Watchdog Alive
   *

   *	The Userspace watchdog got a KeepAlive: schedule the next timeout.

   */
  static int bfin_wdt_keepalive(void)
  {
  	stampit();
  	bfin_write_WDOG_STAT(0);
  	return 0;
  }
  
  /**
   *	bfin_wdt_stop - Stop the Watchdog
   *
   *	Stops the on-chip watchdog.
   */
  static int bfin_wdt_stop(void)
  {
  	stampit();
  	bfin_write_WDOG_CTL(WDEN_DISABLE);
  	return 0;
  }
  
  /**
   *	bfin_wdt_start - Start the Watchdog
   *
   *	Starts the on-chip watchdog.  Automatically loads WDOG_CNT
   *	into WDOG_STAT for us.
   */
  static int bfin_wdt_start(void)
  {
  	stampit();
  	bfin_write_WDOG_CTL(WDEN_ENABLE | ICTL_RESET);
  	return 0;
  }
  
  /**
   *	bfin_wdt_running - Check Watchdog status
   *
   *	See if the watchdog is running.
   */
  static int bfin_wdt_running(void)
  {
  	stampit();
  	return ((bfin_read_WDOG_CTL() & WDEN_MASK) != WDEN_DISABLE);
  }
  
  /**
   *	bfin_wdt_set_timeout - Set the Userspace Watchdog timeout
   *	@t: new timeout value (in seconds)
   *
   *	Translate the specified timeout in seconds into System Clock
   *	terms which is what the on-chip Watchdog requires.
   */
  static int bfin_wdt_set_timeout(unsigned long t)
  {

  	u32 cnt, max_t, sclk;

  	unsigned long flags;

  	sclk = get_sclk();
  	max_t = -1 / sclk;
  	cnt = t * sclk;
  	stamp("maxtimeout=%us newtimeout=%lus (cnt=%#x)", max_t, t, cnt);

  	if (t > max_t) {

  		printk(KERN_WARNING PFX "timeout value is too large
  ");
  		return -EINVAL;
  	}
  
  	spin_lock_irqsave(&bfin_wdt_spinlock, flags);
  	{
  		int run = bfin_wdt_running();
  		bfin_wdt_stop();
  		bfin_write_WDOG_CNT(cnt);

  		if (run)
  			bfin_wdt_start();

  	}
  	spin_unlock_irqrestore(&bfin_wdt_spinlock, flags);
  
  	timeout = t;
  
  	return 0;
  }
  
  /**
   *	bfin_wdt_open - Open the Device
   *	@inode: inode of device
   *	@file: file handle of device
   *
   *	Watchdog device is opened and started.
   */
  static int bfin_wdt_open(struct inode *inode, struct file *file)
  {
  	stampit();
  
  	if (test_and_set_bit(0, &open_check))
  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	bfin_wdt_keepalive();
  	bfin_wdt_start();
  
  	return nonseekable_open(inode, file);
  }
  
  /**
   *	bfin_wdt_close - Close the Device
   *	@inode: inode of device
   *	@file: file handle of device
   *
   *	Watchdog device is closed and stopped.
   */
  static int bfin_wdt_release(struct inode *inode, struct file *file)
  {
  	stampit();

  	if (expect_close == 42)

  		bfin_wdt_stop();

  	else {
  		printk(KERN_CRIT PFX
  			"Unexpected close, not stopping watchdog!
  ");

  		bfin_wdt_keepalive();
  	}

  	expect_close = 0;
  	clear_bit(0, &open_check);

  	return 0;
  }
  
  /**
   *	bfin_wdt_write - Write to Device
   *	@file: file handle of device
   *	@buf: buffer to write
   *	@count: length of buffer
   *	@ppos: offset
   *
   *	Pings the watchdog on write.
   */
  static ssize_t bfin_wdt_write(struct file *file, const char __user *data,

  						size_t len, loff_t *ppos)

  {
  	stampit();
  
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			/* In case it was set long ago */
  			expect_close = 0;
  
  			for (i = 0; i != len; i++) {
  				char c;
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}
  		bfin_wdt_keepalive();
  	}
  
  	return len;
  }
  
  /**
   *	bfin_wdt_ioctl - Query Device

   *	@file: file handle of device
   *	@cmd: watchdog command
   *	@arg: argument
   *
   *	Query basic information from the device or ping it, as outlined by the
   *	watchdog API.
   */

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

  {
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  
  	stampit();
  
  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		if (copy_to_user(argp, &bfin_wdt_info, sizeof(bfin_wdt_info)))
  			return -EFAULT;
  		else

  			return 0;

  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(!!(_bfin_swrst & SWRST_RESET_WDOG), p);

  	case WDIOC_SETOPTIONS: {
  		unsigned long flags;
  		int options, ret = -EINVAL;
  
  		if (get_user(options, p))
  			return -EFAULT;
  
  		spin_lock_irqsave(&bfin_wdt_spinlock, flags);
  		if (options & WDIOS_DISABLECARD) {
  			bfin_wdt_stop();
  			ret = 0;

  		}

  		if (options & WDIOS_ENABLECARD) {
  			bfin_wdt_start();
  			ret = 0;

  		}

  		spin_unlock_irqrestore(&bfin_wdt_spinlock, flags);
  		return ret;
  	}

  	case WDIOC_KEEPALIVE:
  		bfin_wdt_keepalive();
  		return 0;
  	case WDIOC_SETTIMEOUT: {
  		int new_timeout;
  
  		if (get_user(new_timeout, p))
  			return -EFAULT;
  		if (bfin_wdt_set_timeout(new_timeout))
  			return -EINVAL;
  	}
  	/* Fall */
  	case WDIOC_GETTIMEOUT:
  		return put_user(timeout, p);

  	default:
  		return -ENOTTY;

  	}
  }

  #ifdef CONFIG_PM
  static int state_before_suspend;
  
  /**
   *	bfin_wdt_suspend - suspend the watchdog
   *	@pdev: device being suspended
   *	@state: requested suspend state
   *
   *	Remember if the watchdog was running and stop it.
   *	TODO: is this even right?  Doesn't seem to be any
   *	      standard in the watchdog world ...
   */
  static int bfin_wdt_suspend(struct platform_device *pdev, pm_message_t state)
  {
  	stampit();
  
  	state_before_suspend = bfin_wdt_running();
  	bfin_wdt_stop();
  
  	return 0;
  }
  
  /**
   *	bfin_wdt_resume - resume the watchdog
   *	@pdev: device being resumed
   *
   *	If the watchdog was running, turn it back on.
   */
  static int bfin_wdt_resume(struct platform_device *pdev)
  {
  	stampit();
  
  	if (state_before_suspend) {
  		bfin_wdt_set_timeout(timeout);
  		bfin_wdt_start();
  	}
  
  	return 0;
  }
  #else
  # define bfin_wdt_suspend NULL
  # define bfin_wdt_resume NULL
  #endif

  static const struct file_operations bfin_wdt_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,

  	.write		= bfin_wdt_write,

  	.unlocked_ioctl	= bfin_wdt_ioctl,
  	.open		= bfin_wdt_open,
  	.release	= bfin_wdt_release,

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

  static const struct watchdog_info bfin_wdt_info = {

  	.identity = "Blackfin Watchdog",
  	.options  = WDIOF_SETTIMEOUT |

  		    WDIOF_KEEPALIVEPING |
  		    WDIOF_MAGICCLOSE,

  };

  /**

   *	bfin_wdt_probe - Initialize module

   *

   *	Registers the misc device.  Actual device

   *	initialization is handled by bfin_wdt_open().
   */

  static int __devinit bfin_wdt_probe(struct platform_device *pdev)
  {
  	int ret;

  	ret = misc_register(&bfin_wdt_miscdev);
  	if (ret) {

  		pr_devinit(KERN_ERR PFX
  			"cannot register miscdev on minor=%d (err=%d)
  ",
  				WATCHDOG_MINOR, ret);

  		return ret;
  	}
  
  	pr_devinit(KERN_INFO PFX "initialized: timeout=%d sec (nowayout=%d)
  ",
  	       timeout, nowayout);
  
  	return 0;
  }
  
  /**
   *	bfin_wdt_remove - Initialize module
   *

   *	Unregisters the misc device.  Actual device

   *	deinitialization is handled by bfin_wdt_close().
   */
  static int __devexit bfin_wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&bfin_wdt_miscdev);

  	return 0;
  }

  /**
   *	bfin_wdt_shutdown - Soft Shutdown Handler
   *
   *	Handles the soft shutdown event.
   */
  static void bfin_wdt_shutdown(struct platform_device *pdev)
  {
  	stampit();
  
  	bfin_wdt_stop();
  }

  static struct platform_device *bfin_wdt_device;
  
  static struct platform_driver bfin_wdt_driver = {
  	.probe     = bfin_wdt_probe,
  	.remove    = __devexit_p(bfin_wdt_remove),

  	.shutdown  = bfin_wdt_shutdown,

  	.suspend   = bfin_wdt_suspend,
  	.resume    = bfin_wdt_resume,
  	.driver    = {
  		.name  = WATCHDOG_NAME,
  		.owner = THIS_MODULE,
  	},
  };
  
  /**
   *	bfin_wdt_init - Initialize module
   *
   *	Checks the module params and registers the platform device & driver.
   *	Real work is in the platform probe function.
   */

  static int __init bfin_wdt_init(void)
  {
  	int ret;
  
  	stampit();
  
  	/* Check that the timeout value is within range */
  	if (bfin_wdt_set_timeout(timeout))
  		return -EINVAL;
  
  	/* Since this is an on-chip device and needs no board-specific
  	 * resources, we'll handle all the platform device stuff here.
  	 */

  	ret = platform_driver_register(&bfin_wdt_driver);

  	if (ret) {

  		pr_init(KERN_ERR PFX "unable to register driver
  ");

  		return ret;
  	}

  	bfin_wdt_device = platform_device_register_simple(WATCHDOG_NAME,
  								-1, NULL, 0);

  	if (IS_ERR(bfin_wdt_device)) {
  		pr_init(KERN_ERR PFX "unable to register device
  ");
  		platform_driver_unregister(&bfin_wdt_driver);
  		return PTR_ERR(bfin_wdt_device);

  	}

  	return 0;
  }
  
  /**
   *	bfin_wdt_exit - Deinitialize module
   *

   *	Back out the platform device & driver steps.  Real work is in the
   *	platform remove function.

   */
  static void __exit bfin_wdt_exit(void)
  {

  	platform_device_unregister(bfin_wdt_device);
  	platform_driver_unregister(&bfin_wdt_driver);

  }
  
  module_init(bfin_wdt_init);
  module_exit(bfin_wdt_exit);
  
  MODULE_AUTHOR("Michele d'Amico, Mike Frysinger <vapier@gentoo.org>");
  MODULE_DESCRIPTION("Blackfin Watchdog Device Driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
  
  module_param(timeout, uint, 0);

  MODULE_PARM_DESC(timeout,
  	"Watchdog timeout in seconds. (1<=timeout<=((2^32)/SCLK), default="
  		__MODULE_STRING(WATCHDOG_TIMEOUT) ")");

  
  module_param(nowayout, int, 0);

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