/*

   * drivers/watchdog/shwdt.c

   *
   * Watchdog driver for integrated watchdog in the SuperH processors.
   *

   * Copyright (C) 2001 - 2010  Paul Mundt <lethal@linux-sh.org>

   *
   * 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.
   *
   * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
   *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
   *
   * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
   *     Added expect close support, made emulated timeout runtime changeable
   *     general cleanups, add some ioctls
   */

  #include <linux/module.h>
  #include <linux/moduleparam.h>

  #include <linux/platform_device.h>

  #include <linux/init.h>
  #include <linux/types.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/reboot.h>
  #include <linux/notifier.h>
  #include <linux/ioport.h>
  #include <linux/fs.h>

  #include <linux/mm.h>

  #include <linux/slab.h>

  #include <linux/io.h>
  #include <linux/uaccess.h>

  #include <asm/watchdog.h>

  #define DRV_NAME "sh-wdt"

  
  /*
   * Default clock division ratio is 5.25 msecs. For an additional table of
   * values, consult the asm-sh/watchdog.h. Overload this at module load
   * time.
   *
   * In order for this to work reliably we need to have HZ set to 1000 or
   * something quite higher than 100 (or we need a proper high-res timer
   * implementation that will deal with this properly), otherwise the 10ms
   * resolution of a jiffy is enough to trigger the overflow. For things like
   * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
   * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
   * necssary.
   *
   * As a result of this timing problem, the only modes that are particularly
   * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
   * overflow periods respectively.
   *
   * Also, since we can't really expect userspace to be responsive enough

   * before the overflow happens, we maintain two separate timers .. One in

   * the kernel for clearing out WOVF every 2ms or so (again, this depends on
   * HZ == 1000), and another for monitoring userspace writes to the WDT device.
   *
   * As such, we currently use a configurable heartbeat interval which defaults
   * to 30s. In this case, the userspace daemon is only responsible for periodic
   * writes to the device before the next heartbeat is scheduled. If the daemon
   * misses its deadline, the kernel timer will allow the WDT to overflow.
   */
  static int clock_division_ratio = WTCSR_CKS_4096;

  #define next_ping_period(cks)	msecs_to_jiffies(cks - 4)

  static const struct watchdog_info sh_wdt_info;

  static struct platform_device *sh_wdt_dev;

  static DEFINE_SPINLOCK(shwdt_lock);

  
  #define WATCHDOG_HEARTBEAT 30			/* 30 sec default heartbeat */
  static int heartbeat = WATCHDOG_HEARTBEAT;	/* in seconds */

  static int nowayout = WATCHDOG_NOWAYOUT;

  static unsigned long next_heartbeat;
  
  struct sh_wdt {
  	void __iomem		*base;
  	struct device		*dev;

  	struct timer_list	timer;
  
  	unsigned long		enabled;
  	char			expect_close;
  };
  
  static void sh_wdt_start(struct sh_wdt *wdt)

  {

  	unsigned long flags;

  	u8 csr;

  	spin_lock_irqsave(&shwdt_lock, flags);

  
  	next_heartbeat = jiffies + (heartbeat * HZ);

  	mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));

  
  	csr = sh_wdt_read_csr();
  	csr |= WTCSR_WT | clock_division_ratio;
  	sh_wdt_write_csr(csr);
  
  	sh_wdt_write_cnt(0);
  
  	/*
  	 * These processors have a bit of an inconsistent initialization
  	 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
  	 * RSTCSR register was removed.
  	 *
  	 * On the SH-2 however, in addition with bits being in different
  	 * locations, we must deal with RSTCSR outright..
  	 */
  	csr = sh_wdt_read_csr();
  	csr |= WTCSR_TME;
  	csr &= ~WTCSR_RSTS;
  	sh_wdt_write_csr(csr);
  
  #ifdef CONFIG_CPU_SH2

  	csr = sh_wdt_read_rstcsr();
  	csr &= ~RSTCSR_RSTS;
  	sh_wdt_write_rstcsr(csr);
  #endif

  	spin_unlock_irqrestore(&shwdt_lock, flags);

  }

  static void sh_wdt_stop(struct sh_wdt *wdt)

  {

  	unsigned long flags;

  	u8 csr;

  	spin_lock_irqsave(&shwdt_lock, flags);

  	del_timer(&wdt->timer);

  
  	csr = sh_wdt_read_csr();
  	csr &= ~WTCSR_TME;
  	sh_wdt_write_csr(csr);

  	spin_unlock_irqrestore(&shwdt_lock, flags);

  }

  static inline void sh_wdt_keepalive(struct sh_wdt *wdt)

  {

  	unsigned long flags;

  	spin_lock_irqsave(&shwdt_lock, flags);

  	next_heartbeat = jiffies + (heartbeat * HZ);

  	spin_unlock_irqrestore(&shwdt_lock, flags);

  }

  static int sh_wdt_set_heartbeat(int t)
  {

  	unsigned long flags;
  
  	if (unlikely(t < 1 || t > 3600)) /* arbitrary upper limit */

  		return -EINVAL;

  	spin_lock_irqsave(&shwdt_lock, flags);

  	heartbeat = t;

  	spin_unlock_irqrestore(&shwdt_lock, flags);

  	return 0;
  }

  static void sh_wdt_ping(unsigned long data)
  {

  	struct sh_wdt *wdt = (struct sh_wdt *)data;

  	unsigned long flags;

  	spin_lock_irqsave(&shwdt_lock, flags);

  	if (time_before(jiffies, next_heartbeat)) {

  		u8 csr;

  
  		csr = sh_wdt_read_csr();
  		csr &= ~WTCSR_IOVF;
  		sh_wdt_write_csr(csr);
  
  		sh_wdt_write_cnt(0);

  		mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));

  	} else

  		dev_warn(wdt->dev, "Heartbeat lost! Will not ping "
  		         "the watchdog
  ");

  	spin_unlock_irqrestore(&shwdt_lock, flags);

  }

  static int sh_wdt_open(struct inode *inode, struct file *file)
  {

  	struct sh_wdt *wdt = platform_get_drvdata(sh_wdt_dev);
  
  	if (test_and_set_bit(0, &wdt->enabled))

  		return -EBUSY;
  	if (nowayout)
  		__module_get(THIS_MODULE);

  	file->private_data = wdt;
  
  	sh_wdt_start(wdt);

  
  	return nonseekable_open(inode, file);
  }

  static int sh_wdt_close(struct inode *inode, struct file *file)
  {

  	struct sh_wdt *wdt = file->private_data;
  
  	if (wdt->expect_close == 42) {
  		sh_wdt_stop(wdt);

  	} else {

  		dev_crit(wdt->dev, "Unexpected close, not "
  		         "stopping watchdog!
  ");
  		sh_wdt_keepalive(wdt);

  	}

  	clear_bit(0, &wdt->enabled);
  	wdt->expect_close = 0;

  
  	return 0;
  }

  static ssize_t sh_wdt_write(struct file *file, const char *buf,
  			    size_t count, loff_t *ppos)
  {

  	struct sh_wdt *wdt = file->private_data;

  	if (count) {
  		if (!nowayout) {
  			size_t i;

  			wdt->expect_close = 0;

  
  			for (i = 0; i != count; i++) {
  				char c;
  				if (get_user(c, buf + i))
  					return -EFAULT;
  				if (c == 'V')

  					wdt->expect_close = 42;

  			}
  		}

  		sh_wdt_keepalive(wdt);

  	}
  
  	return count;
  }

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

  {

  	struct sh_wdt *wdt = file->private_data;

  	int new_heartbeat;
  	int options, retval = -EINVAL;
  
  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		return copy_to_user((struct watchdog_info *)arg,
  			  &sh_wdt_info, sizeof(sh_wdt_info)) ? -EFAULT : 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, (int *)arg);

  	case WDIOC_SETOPTIONS:
  		if (get_user(options, (int *)arg))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD) {

  			sh_wdt_stop(wdt);

  			retval = 0;
  		}
  
  		if (options & WDIOS_ENABLECARD) {

  			sh_wdt_start(wdt);

  			retval = 0;
  		}

  		return retval;

  	case WDIOC_KEEPALIVE:

  		sh_wdt_keepalive(wdt);

  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_heartbeat, (int *)arg))
  			return -EFAULT;
  
  		if (sh_wdt_set_heartbeat(new_heartbeat))
  			return -EINVAL;

  		sh_wdt_keepalive(wdt);

  		/* Fall */
  	case WDIOC_GETTIMEOUT:
  		return put_user(heartbeat, (int *)arg);

  	default:
  		return -ENOTTY;
  	}

  	return 0;
  }

  static int sh_wdt_notify_sys(struct notifier_block *this,
  			     unsigned long code, void *unused)
  {

  	struct sh_wdt *wdt = platform_get_drvdata(sh_wdt_dev);

  	if (code == SYS_DOWN || code == SYS_HALT)

  		sh_wdt_stop(wdt);

  
  	return NOTIFY_DONE;
  }

  static const struct file_operations sh_wdt_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= sh_wdt_write,

  	.unlocked_ioctl	= sh_wdt_ioctl,

  	.open		= sh_wdt_open,
  	.release	= sh_wdt_close,
  };

  static const struct watchdog_info sh_wdt_info = {

  	.options		= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
  				  WDIOF_MAGICCLOSE,

  	.firmware_version	= 1,
  	.identity		= "SH WDT",
  };
  
  static struct notifier_block sh_wdt_notifier = {
  	.notifier_call		= sh_wdt_notify_sys,
  };
  
  static struct miscdevice sh_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &sh_wdt_fops,
  };

  static int __devinit sh_wdt_probe(struct platform_device *pdev)

  {

  	struct sh_wdt *wdt;
  	struct resource *res;

  	int rc;

  	/*
  	 * As this driver only covers the global watchdog case, reject
  	 * any attempts to register per-CPU watchdogs.
  	 */
  	if (pdev->id != -1)
  		return -EINVAL;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (unlikely(!res))
  		return -EINVAL;
  
  	if (!devm_request_mem_region(&pdev->dev, res->start,
  				     resource_size(res), DRV_NAME))
  		return -EBUSY;
  
  	wdt = devm_kzalloc(&pdev->dev, sizeof(struct sh_wdt), GFP_KERNEL);
  	if (unlikely(!wdt)) {
  		rc = -ENOMEM;
  		goto out_release;

  	}

  	wdt->dev = &pdev->dev;
  
  	wdt->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
  	if (unlikely(!wdt->base)) {
  		rc = -ENXIO;
  		goto out_err;

  	}

  	rc = register_reboot_notifier(&sh_wdt_notifier);

  	if (unlikely(rc)) {

  		dev_err(&pdev->dev,

  			"Can't register reboot notifier (err=%d)
  ", rc);

  		goto out_unmap;

  	}

  	sh_wdt_miscdev.parent = wdt->dev;

  	rc = misc_register(&sh_wdt_miscdev);

  	if (unlikely(rc)) {

  		dev_err(&pdev->dev,

  			"Can't register miscdev on minor=%d (err=%d)
  ",
  						sh_wdt_miscdev.minor, rc);

  		goto out_unreg;

  	}

  	init_timer(&wdt->timer);
  	wdt->timer.function	= sh_wdt_ping;
  	wdt->timer.data		= (unsigned long)wdt;
  	wdt->timer.expires	= next_ping_period(clock_division_ratio);
  
  	platform_set_drvdata(pdev, wdt);
  	sh_wdt_dev = pdev;
  
  	dev_info(&pdev->dev, "initialized.
  ");

  
  	return 0;

  
  out_unreg:
  	unregister_reboot_notifier(&sh_wdt_notifier);
  out_unmap:
  	devm_iounmap(&pdev->dev, wdt->base);
  out_err:
  	devm_kfree(&pdev->dev, wdt);
  out_release:
  	devm_release_mem_region(&pdev->dev, res->start, resource_size(res));
  
  	return rc;

  }

  static int __devexit sh_wdt_remove(struct platform_device *pdev)

  {

  	struct sh_wdt *wdt = platform_get_drvdata(pdev);
  	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  
  	platform_set_drvdata(pdev, NULL);

  	misc_deregister(&sh_wdt_miscdev);

  
  	sh_wdt_dev = NULL;

  	unregister_reboot_notifier(&sh_wdt_notifier);

  	devm_release_mem_region(&pdev->dev, res->start, resource_size(res));
  	devm_iounmap(&pdev->dev, wdt->base);
  	devm_kfree(&pdev->dev, wdt);
  
  	return 0;
  }
  
  static struct platform_driver sh_wdt_driver = {
  	.driver		= {
  		.name	= DRV_NAME,
  		.owner	= THIS_MODULE,
  	},
  
  	.probe	= sh_wdt_probe,
  	.remove	= __devexit_p(sh_wdt_remove),
  };
  
  static int __init sh_wdt_init(void)
  {
  	int rc;
  
  	if (unlikely(clock_division_ratio < 0x5 ||
  		     clock_division_ratio > 0x7)) {
  		clock_division_ratio = WTCSR_CKS_4096;
  
  		pr_info("%s: divisor must be 0x5<=x<=0x7, using %d
  ",
  			 DRV_NAME, clock_division_ratio);
  	}
  
  	rc = sh_wdt_set_heartbeat(heartbeat);
  	if (unlikely(rc)) {
  		heartbeat = WATCHDOG_HEARTBEAT;
  
  		pr_info("%s: heartbeat value must be 1<=x<=3600, using %d
  ",
  			DRV_NAME, heartbeat);
  	}
  
  	pr_info("%s: configured with heartbeat=%d sec (nowayout=%d)
  ",
  		DRV_NAME, heartbeat, nowayout);
  
  	return platform_driver_register(&sh_wdt_driver);

  }

  static void __exit sh_wdt_exit(void)
  {
  	platform_driver_unregister(&sh_wdt_driver);
  }
  module_init(sh_wdt_init);
  module_exit(sh_wdt_exit);

  MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
  MODULE_DESCRIPTION("SuperH watchdog driver");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("platform:" DRV_NAME);

  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
  
  module_param(clock_division_ratio, int, 0);

  MODULE_PARM_DESC(clock_division_ratio,
  	"Clock division ratio. Valid ranges are from 0x5 (1.31ms) "

  	"to 0x7 (5.25ms). (default=" __MODULE_STRING(WTCSR_CKS_4096) ")");

  
  module_param(heartbeat, int, 0);

  MODULE_PARM_DESC(heartbeat,
  	"Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default="
  				__MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

  
  module_param(nowayout, int, 0);

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