/*
   * Watchdog driver for Atmel AT32AP700X devices
   *
   * Copyright (C) 2005-2006 Atmel Corporation
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.

   *
   *
   * Errata: WDT Clear is blocked after WDT Reset
   *
   * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
   * register, preventing the program to clear the next Watchdog Timer Reset.
   *
   * If you still want to use the WDT after a WDT reset a small code can be
   * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
   * and use a GPIO pin to reset the system. This method requires that one of the
   * GPIO pins are available and connected externally to the RESET_N pin. After
   * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
   * the pin tristated with pullup.

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

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

  #include <linux/spinlock.h>

  #include <linux/slab.h>

  
  #define TIMEOUT_MIN		1

  #define TIMEOUT_MAX		2

  #define TIMEOUT_DEFAULT		TIMEOUT_MAX
  
  /* module parameters */
  static int timeout =  TIMEOUT_DEFAULT;
  module_param(timeout, int, 0);
  MODULE_PARM_DESC(timeout,
  		"Timeout value. Limited to be 1 or 2 seconds. (default="
  		__MODULE_STRING(TIMEOUT_DEFAULT) ")");

  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) ")");

  /* Watchdog registers and write/read macro */
  #define WDT_CTRL		0x00
  #define WDT_CTRL_EN		   0
  #define WDT_CTRL_PSEL		   8
  #define WDT_CTRL_KEY		  24
  
  #define WDT_CLR			0x04

  #define WDT_RCAUSE		0x10
  #define WDT_RCAUSE_POR		   0
  #define WDT_RCAUSE_EXT		   2
  #define WDT_RCAUSE_WDT		   3
  #define WDT_RCAUSE_JTAG		   4
  #define WDT_RCAUSE_SERP		   5

  #define WDT_BIT(name)		(1 << WDT_##name)

  #define WDT_BF(name, value)	((value) << WDT_##name)

  #define wdt_readl(dev, reg)				\

  	__raw_readl((dev)->regs + WDT_##reg)

  #define wdt_writel(dev, reg, value)			\

  	__raw_writel((value), (dev)->regs + WDT_##reg)
  
  struct wdt_at32ap700x {
  	void __iomem		*regs;

  	spinlock_t		io_lock;

  	int			timeout;

  	int			boot_status;

  	unsigned long		users;

  	struct miscdevice	miscdev;
  };
  
  static struct wdt_at32ap700x *wdt;

  static char expect_release;

  
  /*
   * Disable the watchdog.
   */

  static inline void at32_wdt_stop(void)

  {

  	unsigned long psel;

  	spin_lock(&wdt->io_lock);

  	psel = wdt_readl(wdt, CTRL) & WDT_BF(CTRL_PSEL, 0x0f);

  	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0x55));
  	wdt_writel(wdt, CTRL, psel | WDT_BF(CTRL_KEY, 0xaa));

  	spin_unlock(&wdt->io_lock);

  }
  
  /*
   * Enable and reset the watchdog.
   */

  static inline void at32_wdt_start(void)

  {
  	/* 0xf is 2^16 divider = 2 sec, 0xe is 2^15 divider = 1 sec */
  	unsigned long psel = (wdt->timeout > 1) ? 0xf : 0xe;

  	spin_lock(&wdt->io_lock);

  	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
  			| WDT_BF(CTRL_PSEL, psel)
  			| WDT_BF(CTRL_KEY, 0x55));
  	wdt_writel(wdt, CTRL, WDT_BIT(CTRL_EN)
  			| WDT_BF(CTRL_PSEL, psel)
  			| WDT_BF(CTRL_KEY, 0xaa));

  	spin_unlock(&wdt->io_lock);

  }
  
  /*
   * Pat the watchdog timer.
   */

  static inline void at32_wdt_pat(void)

  {

  	spin_lock(&wdt->io_lock);

  	wdt_writel(wdt, CLR, 0x42);

  	spin_unlock(&wdt->io_lock);

  }
  
  /*
   * Watchdog device is opened, and watchdog starts running.
   */
  static int at32_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(1, &wdt->users))
  		return -EBUSY;
  
  	at32_wdt_start();
  	return nonseekable_open(inode, file);
  }
  
  /*

   * Close the watchdog device.

   */
  static int at32_wdt_close(struct inode *inode, struct file *file)
  {

  	if (expect_release == 42) {
  		at32_wdt_stop();
  	} else {
  		dev_dbg(wdt->miscdev.parent,

  			"unexpected close, not stopping watchdog!
  ");

  		at32_wdt_pat();
  	}

  	clear_bit(1, &wdt->users);

  	expect_release = 0;

  	return 0;
  }
  
  /*
   * Change the watchdog time interval.
   */
  static int at32_wdt_settimeout(int time)
  {
  	/*
  	 * All counting occurs at 1 / SLOW_CLOCK (32 kHz) and max prescaler is
  	 * 2 ^ 16 allowing up to 2 seconds timeout.
  	 */
  	if ((time < TIMEOUT_MIN) || (time > TIMEOUT_MAX))
  		return -EINVAL;

  	/*
  	 * Set new watchdog time. It will be used when at32_wdt_start() is
  	 * called.
  	 */

  	wdt->timeout = time;
  	return 0;
  }

  /*
   * Get the watchdog status.
   */
  static int at32_wdt_get_status(void)
  {
  	int rcause;
  	int status = 0;
  
  	rcause = wdt_readl(wdt, RCAUSE);
  
  	switch (rcause) {
  	case WDT_BIT(RCAUSE_EXT):
  		status = WDIOF_EXTERN1;
  		break;
  	case WDT_BIT(RCAUSE_WDT):
  		status = WDIOF_CARDRESET;
  		break;
  	case WDT_BIT(RCAUSE_POR):  /* fall through */
  	case WDT_BIT(RCAUSE_JTAG): /* fall through */
  	case WDT_BIT(RCAUSE_SERP): /* fall through */
  	default:
  		break;
  	}
  
  	return status;
  }

  static const struct watchdog_info at32_wdt_info = {

  	.identity	= "at32ap700x watchdog",

  	.options	= WDIOF_SETTIMEOUT |
  			  WDIOF_KEEPALIVEPING |
  			  WDIOF_MAGICCLOSE,

  };
  
  /*
   * Handle commands from user-space.
   */

  static long at32_wdt_ioctl(struct file *file,
  				unsigned int cmd, unsigned long arg)

  {
  	int ret = -ENOTTY;
  	int time;
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;

  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user(argp, &at32_wdt_info,
  				sizeof(at32_wdt_info)) ? -EFAULT : 0;
  		break;

  	case WDIOC_GETSTATUS:

  		ret = put_user(0, p);
  		break;

  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(wdt->boot_status, p);
  		break;

  	case WDIOC_SETOPTIONS:
  		ret = get_user(time, p);
  		if (ret)
  			break;
  		if (time & WDIOS_DISABLECARD)
  			at32_wdt_stop();
  		if (time & WDIOS_ENABLECARD)
  			at32_wdt_start();
  		ret = 0;
  		break;

  	case WDIOC_KEEPALIVE:
  		at32_wdt_pat();
  		ret = 0;
  		break;
  	case WDIOC_SETTIMEOUT:
  		ret = get_user(time, p);
  		if (ret)
  			break;
  		ret = at32_wdt_settimeout(time);
  		if (ret)
  			break;
  		/* Enable new time value */
  		at32_wdt_start();
  		/* fall through */
  	case WDIOC_GETTIMEOUT:
  		ret = put_user(wdt->timeout, p);
  		break;

  	}
  
  	return ret;
  }

  static ssize_t at32_wdt_write(struct file *file, const char __user *data,
  				size_t len, loff_t *ppos)

  {

  	/* See if we got the magic character 'V' and reload the timer */
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			/*
  			 * note: just in case someone wrote the magic
  			 * character five months ago...
  			 */
  			expect_release = 0;
  
  			/*
  			 * scan to see whether or not we got the magic
  			 * character
  			 */
  			for (i = 0; i != len; i++) {
  				char c;

  				if (get_user(c, data + i))

  					return -EFAULT;
  				if (c == 'V')
  					expect_release = 42;
  			}
  		}
  		/* someone wrote to us, we should pat the watchdog */
  		at32_wdt_pat();
  	}

  	return len;
  }
  
  static const struct file_operations at32_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,

  	.unlocked_ioctl	= at32_wdt_ioctl,

  	.open		= at32_wdt_open,
  	.release	= at32_wdt_close,
  	.write		= at32_wdt_write,
  };
  
  static int __init at32_wdt_probe(struct platform_device *pdev)
  {
  	struct resource	*regs;
  	int ret;
  
  	if (wdt) {
  		dev_dbg(&pdev->dev, "only 1 wdt instance supported.
  ");
  		return -EBUSY;
  	}
  
  	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!regs) {
  		dev_dbg(&pdev->dev, "missing mmio resource
  ");
  		return -ENXIO;
  	}
  
  	wdt = kzalloc(sizeof(struct wdt_at32ap700x), GFP_KERNEL);
  	if (!wdt) {
  		dev_dbg(&pdev->dev, "no memory for wdt structure
  ");
  		return -ENOMEM;
  	}

  	wdt->regs = ioremap(regs->start, resource_size(regs));

  	if (!wdt->regs) {
  		ret = -ENOMEM;
  		dev_dbg(&pdev->dev, "could not map I/O memory
  ");
  		goto err_free;
  	}

  	spin_lock_init(&wdt->io_lock);

  	wdt->boot_status = at32_wdt_get_status();
  
  	/* Work-around for watchdog silicon errata. */
  	if (wdt->boot_status & WDIOF_CARDRESET) {
  		dev_info(&pdev->dev, "CPU must be reset with external "
  				"reset or POR due to silicon errata.
  ");
  		ret = -EIO;
  		goto err_iounmap;
  	} else {
  		wdt->users = 0;
  	}

  
  	wdt->miscdev.minor	= WATCHDOG_MINOR;
  	wdt->miscdev.name	= "watchdog";
  	wdt->miscdev.fops	= &at32_wdt_fops;
  	wdt->miscdev.parent	= &pdev->dev;
  
  	platform_set_drvdata(pdev, wdt);

  	if (at32_wdt_settimeout(timeout)) {
  		at32_wdt_settimeout(TIMEOUT_DEFAULT);

  		dev_dbg(&pdev->dev,
  			"default timeout invalid, set to %d sec.
  ",

  			TIMEOUT_DEFAULT);

  	}
  
  	ret = misc_register(&wdt->miscdev);
  	if (ret) {
  		dev_dbg(&pdev->dev, "failed to register wdt miscdev
  ");

  		goto err_register;

  	}

  	dev_info(&pdev->dev,
  		"AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)
  ",
  		wdt->regs, wdt->timeout, nowayout);

  
  	return 0;

  err_register:
  	platform_set_drvdata(pdev, NULL);

  err_iounmap:
  	iounmap(wdt->regs);
  err_free:

  	kfree(wdt);
  	wdt = NULL;
  	return ret;
  }
  
  static int __exit at32_wdt_remove(struct platform_device *pdev)
  {
  	if (wdt && platform_get_drvdata(pdev) == wdt) {

  		/* Stop the timer before we leave */
  		if (!nowayout)
  			at32_wdt_stop();

  		misc_deregister(&wdt->miscdev);

  		iounmap(wdt->regs);

  		kfree(wdt);
  		wdt = NULL;
  		platform_set_drvdata(pdev, NULL);
  	}

  	return 0;
  }
  
  static void at32_wdt_shutdown(struct platform_device *pdev)
  {
  	at32_wdt_stop();
  }
  
  #ifdef CONFIG_PM
  static int at32_wdt_suspend(struct platform_device *pdev, pm_message_t message)
  {
  	at32_wdt_stop();
  	return 0;
  }
  
  static int at32_wdt_resume(struct platform_device *pdev)
  {
  	if (wdt->users)
  		at32_wdt_start();
  	return 0;
  }

  #else
  #define at32_wdt_suspend NULL
  #define at32_wdt_resume NULL

  #endif

  /* work with hotplug and coldplug */
  MODULE_ALIAS("platform:at32_wdt");

  static struct platform_driver at32_wdt_driver = {
  	.remove		= __exit_p(at32_wdt_remove),

  	.suspend	= at32_wdt_suspend,
  	.resume		= at32_wdt_resume,

  	.driver		= {
  		.name	= "at32_wdt",
  		.owner	= THIS_MODULE,
  	},
  	.shutdown	= at32_wdt_shutdown,
  };
  
  static int __init at32_wdt_init(void)
  {
  	return platform_driver_probe(&at32_wdt_driver, at32_wdt_probe);
  }
  module_init(at32_wdt_init);
  
  static void __exit at32_wdt_exit(void)
  {
  	platform_driver_unregister(&at32_wdt_driver);
  }
  module_exit(at32_wdt_exit);

  MODULE_AUTHOR("Hans-Christian Egtvedt <egtvedt@samfundet.no>");

  MODULE_DESCRIPTION("Watchdog driver for Atmel AT32AP700X");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);