/*
   * mv64x60_wdt.c - MV64X60 (Marvell Discovery) watchdog userspace interface
   *
   * Author: James Chapman <jchapman@katalix.com>
   *
   * Platform-specific setup code should configure the dog to generate
   * interrupt or reset as required.  This code only enables/disables
   * and services the watchdog.
   *
   * Derived from mpc8xx_wdt.c, with the following copyright.

   *

   * 2002 (c) Florian Schirmer <jolt@tuxbox.org> 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.
   */

  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/miscdevice.h>
  #include <linux/module.h>
  #include <linux/watchdog.h>

  #include <linux/platform_device.h>

  #include <linux/mv643xx.h>

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

  #define MV64x60_WDT_WDC_OFFSET	0

  /*
   * The watchdog configuration register contains a pair of 2-bit fields,
   *   1.  a reload field, bits 27-26, which triggers a reload of
   *       the countdown register, and
   *   2.  an enable field, bits 25-24, which toggles between
   *       enabling and disabling the watchdog timer.
   * Bit 31 is a read-only field which indicates whether the
   * watchdog timer is currently enabled.
   *
   * The low 24 bits contain the timer reload value.
   */
  #define MV64x60_WDC_ENABLE_SHIFT	24
  #define MV64x60_WDC_SERVICE_SHIFT	26
  #define MV64x60_WDC_ENABLED_SHIFT	31
  
  #define MV64x60_WDC_ENABLED_TRUE	1
  #define MV64x60_WDC_ENABLED_FALSE	0

  
  /* Flags bits */
  #define MV64x60_WDOG_FLAG_OPENED	0

  
  static unsigned long wdt_flags;
  static int wdt_status;

  static void __iomem *mv64x60_wdt_regs;

  static int mv64x60_wdt_timeout;

  static int mv64x60_wdt_count;

  static unsigned int bus_clk;

  static char expect_close;

  static DEFINE_SPINLOCK(mv64x60_wdt_spinlock);

  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 int mv64x60_wdt_toggle_wdc(int enabled_predicate, int field_shift)

  {

  	u32 data;
  	u32 enabled;
  	int ret = 0;
  
  	spin_lock(&mv64x60_wdt_spinlock);
  	data = readl(mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
  	enabled = (data >> MV64x60_WDC_ENABLED_SHIFT) & 1;
  
  	/* only toggle the requested field if enabled state matches predicate */
  	if ((enabled ^ enabled_predicate) == 0) {
  		/* We write a 1, then a 2 -- to the appropriate field */
  		data = (1 << field_shift) | mv64x60_wdt_count;
  		writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
  
  		data = (2 << field_shift) | mv64x60_wdt_count;
  		writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
  		ret = 1;
  	}
  	spin_unlock(&mv64x60_wdt_spinlock);
  
  	return ret;

  }
  
  static void mv64x60_wdt_service(void)
  {

  	mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
  			       MV64x60_WDC_SERVICE_SHIFT);

  }

  static void mv64x60_wdt_handler_enable(void)

  {

  	if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_FALSE,
  				   MV64x60_WDC_ENABLE_SHIFT)) {
  		mv64x60_wdt_service();
  		printk(KERN_NOTICE "mv64x60_wdt: watchdog activated
  ");

  	}
  }

  static void mv64x60_wdt_handler_disable(void)

  {

  	if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
  				   MV64x60_WDC_ENABLE_SHIFT))
  		printk(KERN_NOTICE "mv64x60_wdt: watchdog deactivated
  ");

  }

  static void mv64x60_wdt_set_timeout(unsigned int timeout)

  {
  	/* maximum bus cycle count is 0xFFFFFFFF */
  	if (timeout > 0xFFFFFFFF / bus_clk)
  		timeout = 0xFFFFFFFF / bus_clk;

  	mv64x60_wdt_count = timeout * bus_clk >> 8;

  	mv64x60_wdt_timeout = timeout;

  }

  static int mv64x60_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(MV64x60_WDOG_FLAG_OPENED, &wdt_flags))
  		return -EBUSY;

  	if (nowayout)
  		__module_get(THIS_MODULE);

  	mv64x60_wdt_handler_enable();

  	return nonseekable_open(inode, file);

  }
  
  static int mv64x60_wdt_release(struct inode *inode, struct file *file)
  {

  	if (expect_close == 42)

  		mv64x60_wdt_handler_disable();

  	else {
  		printk(KERN_CRIT
  		       "mv64x60_wdt: unexpected close, not stopping timer!
  ");
  		mv64x60_wdt_service();
  	}
  	expect_close = 0;

  
  	clear_bit(MV64x60_WDOG_FLAG_OPENED, &wdt_flags);
  
  	return 0;
  }

  static ssize_t mv64x60_wdt_write(struct file *file, const char __user *data,

  				 size_t len, loff_t *ppos)

  {

  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			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;
  			}
  		}

  		mv64x60_wdt_service();

  	}

  
  	return len;
  }

  static long mv64x60_wdt_ioctl(struct file *file,
  					unsigned int cmd, unsigned long arg)

  {

  	int timeout;

  	int options;

  	void __user *argp = (void __user *)arg;

  	static const struct watchdog_info info = {

  		.options =	WDIOF_SETTIMEOUT	|

  				WDIOF_MAGICCLOSE	|

  				WDIOF_KEEPALIVEPING,

  		.firmware_version = 0,
  		.identity = "MV64x60 watchdog",
  	};
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:

  		if (copy_to_user(argp, &info, sizeof(info)))

  			return -EFAULT;
  		break;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:

  		if (put_user(wdt_status, (int __user *)argp))

  			return -EFAULT;
  		wdt_status &= ~WDIOF_KEEPALIVEPING;
  		break;
  
  	case WDIOC_GETTEMP:
  		return -EOPNOTSUPP;
  
  	case WDIOC_SETOPTIONS:

  		if (get_user(options, (int __user *)argp))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD)
  			mv64x60_wdt_handler_disable();
  
  		if (options & WDIOS_ENABLECARD)
  			mv64x60_wdt_handler_enable();
  		break;

  
  	case WDIOC_KEEPALIVE:
  		mv64x60_wdt_service();
  		wdt_status |= WDIOF_KEEPALIVEPING;
  		break;
  
  	case WDIOC_SETTIMEOUT:

  		if (get_user(timeout, (int __user *)argp))
  			return -EFAULT;
  		mv64x60_wdt_set_timeout(timeout);
  		/* Fall through */

  
  	case WDIOC_GETTIMEOUT:

  		if (put_user(mv64x60_wdt_timeout, (int __user *)argp))

  			return -EFAULT;
  		break;
  
  	default:

  		return -ENOTTY;

  	}
  
  	return 0;
  }

  static const struct file_operations mv64x60_wdt_fops = {

  	.owner = THIS_MODULE,
  	.llseek = no_llseek,
  	.write = mv64x60_wdt_write,

  	.unlocked_ioctl = mv64x60_wdt_ioctl,

  	.open = mv64x60_wdt_open,
  	.release = mv64x60_wdt_release,
  };
  
  static struct miscdevice mv64x60_wdt_miscdev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &mv64x60_wdt_fops,
  };

  static int __devinit mv64x60_wdt_probe(struct platform_device *dev)

  {

  	struct mv64x60_wdt_pdata *pdata = dev->dev.platform_data;

  	struct resource *r;

  	int timeout = 10;

  	bus_clk = 133;			/* in MHz */

  	if (pdata) {

  		timeout = pdata->timeout;

  		bus_clk = pdata->bus_clk;
  	}

  	/* Since bus_clk is truncated MHz, actual frequency could be
  	 * up to 1MHz higher.  Round up, since it's better to time out
  	 * too late than too soon.
  	 */
  	bus_clk++;
  	bus_clk *= 1000000;		/* convert to Hz */

  	r = platform_get_resource(dev, IORESOURCE_MEM, 0);
  	if (!r)
  		return -ENODEV;

  	mv64x60_wdt_regs = ioremap(r->start, resource_size(r));

  	if (mv64x60_wdt_regs == NULL)
  		return -ENOMEM;

  	mv64x60_wdt_set_timeout(timeout);

  	mv64x60_wdt_handler_disable();	/* in case timer was already running */

  	return misc_register(&mv64x60_wdt_miscdev);
  }

  static int __devexit mv64x60_wdt_remove(struct platform_device *dev)

  {
  	misc_deregister(&mv64x60_wdt_miscdev);

  	mv64x60_wdt_handler_disable();

  	iounmap(mv64x60_wdt_regs);

  	return 0;
  }

  static struct platform_driver mv64x60_wdt_driver = {

  	.probe = mv64x60_wdt_probe,
  	.remove = __devexit_p(mv64x60_wdt_remove),

  	.driver = {
  		.owner = THIS_MODULE,
  		.name = MV64x60_WDT_NAME,
  	},

  };

  static int __init mv64x60_wdt_init(void)
  {

  	printk(KERN_INFO "MV64x60 watchdog driver
  ");

  	return platform_driver_register(&mv64x60_wdt_driver);

  }
  
  static void __exit mv64x60_wdt_exit(void)
  {

  	platform_driver_unregister(&mv64x60_wdt_driver);

  }
  
  module_init(mv64x60_wdt_init);
  module_exit(mv64x60_wdt_exit);
  
  MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
  MODULE_DESCRIPTION("MV64x60 watchdog driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

  MODULE_ALIAS("platform:" MV64x60_WDT_NAME);