// SPDX-License-Identifier: GPL-2.0+

  /*
   * Watchdog driver for Atmel AT91RM9200 (Thunder)
   *
   *  Copyright (C) 2003 SAN People (Pty) Ltd
   *

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/bitops.h>

  #include <linux/delay.h>

  #include <linux/errno.h>
  #include <linux/fs.h>
  #include <linux/init.h>

  #include <linux/io.h>

  #include <linux/kernel.h>

  #include <linux/mfd/syscon.h>
  #include <linux/mfd/syscon/atmel-st.h>

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

  #include <linux/platform_device.h>

  #include <linux/reboot.h>

  #include <linux/regmap.h>

  #include <linux/types.h>
  #include <linux/watchdog.h>

  #include <linux/uaccess.h>

  #include <linux/of.h>
  #include <linux/of_device.h>

  #define WDT_DEFAULT_TIME	5	/* seconds */
  #define WDT_MAX_TIME		256	/* seconds */

  
  static int wdt_time = WDT_DEFAULT_TIME;

  static bool nowayout = WATCHDOG_NOWAYOUT;

  static struct regmap *regmap_st;

  
  module_param(wdt_time, int, 0);

  MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="
  				__MODULE_STRING(WDT_DEFAULT_TIME) ")");

  #ifdef CONFIG_WATCHDOG_NOWAYOUT

  module_param(nowayout, bool, 0);

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

  #endif

  
  
  static unsigned long at91wdt_busy;
  
  /* ......................................................................... */

  static int at91rm9200_restart(struct notifier_block *this,
  					unsigned long mode, void *cmd)
  {
  	/*
  	 * Perform a hardware reset with the use of the Watchdog timer.
  	 */
  	regmap_write(regmap_st, AT91_ST_WDMR,
  		     AT91_ST_RSTEN | AT91_ST_EXTEN | 1);
  	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
  
  	mdelay(2000);
  
  	pr_emerg("Unable to restart system
  ");
  	return NOTIFY_DONE;
  }
  
  static struct notifier_block at91rm9200_restart_nb = {
  	.notifier_call = at91rm9200_restart,
  	.priority = 192,
  };

  /*
   * Disable the watchdog.
   */

  static inline void at91_wdt_stop(void)

  {

  	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN);

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

  static inline void at91_wdt_start(void)

  {

  	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN |

  				(((65536 * wdt_time) >> 8) & AT91_ST_WDV));

  	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);

  }
  
  /*
   * Reload the watchdog timer.  (ie, pat the watchdog)
   */

  static inline void at91_wdt_reload(void)

  {

  	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);

  }
  
  /* ......................................................................... */
  
  /*
   * Watchdog device is opened, and watchdog starts running.
   */
  static int at91_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(0, &at91wdt_busy))
  		return -EBUSY;
  
  	at91_wdt_start();

  	return stream_open(inode, file);

  }
  
  /*
   * Close the watchdog device.
   * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
   *  disabled.
   */
  static int at91_wdt_close(struct inode *inode, struct file *file)
  {

  	/* Disable the watchdog when file is closed */

  	if (!nowayout)

  		at91_wdt_stop();

  
  	clear_bit(0, &at91wdt_busy);
  	return 0;
  }
  
  /*
   * Change the watchdog time interval.
   */
  static int at91_wdt_settimeout(int new_time)
  {
  	/*

  	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz

  	 *
  	 * Since WDV is a 16-bit counter, the maximum period is

  	 * 65536 / 256 = 256 seconds.

  	 */
  	if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
  		return -EINVAL;

  	/* Set new watchdog time. It will be used when
  	   at91_wdt_start() is called. */

  	wdt_time = new_time;
  	return 0;
  }

  static const struct watchdog_info at91_wdt_info = {

  	.identity	= "at91 watchdog",
  	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
  };
  
  /*
   * Handle commands from user-space.
   */

  static long at91_wdt_ioctl(struct file *file,

  					unsigned int cmd, unsigned long arg)

  {
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  	int new_value;

  	switch (cmd) {

  	case WDIOC_GETSUPPORT:
  		return copy_to_user(argp, &at91_wdt_info,
  				sizeof(at91_wdt_info)) ? -EFAULT : 0;

  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, p);
  	case WDIOC_SETOPTIONS:
  		if (get_user(new_value, p))
  			return -EFAULT;
  		if (new_value & WDIOS_DISABLECARD)
  			at91_wdt_stop();
  		if (new_value & WDIOS_ENABLECARD)

  			at91_wdt_start();

  		return 0;

  	case WDIOC_KEEPALIVE:
  		at91_wdt_reload();	/* pat the watchdog */
  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_value, p))
  			return -EFAULT;
  		if (at91_wdt_settimeout(new_value))
  			return -EINVAL;
  		/* Enable new time value */
  		at91_wdt_start();
  		/* Return current value */
  		return put_user(wdt_time, p);
  	case WDIOC_GETTIMEOUT:
  		return put_user(wdt_time, p);

  	default:
  		return -ENOTTY;

  	}
  }
  
  /*
   * Pat the watchdog whenever device is written to.
   */

  static ssize_t at91_wdt_write(struct file *file, const char *data,
  						size_t len, loff_t *ppos)

  {
  	at91_wdt_reload();		/* pat the watchdog */
  	return len;
  }
  
  /* ......................................................................... */

  static const struct file_operations at91wdt_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,

  	.unlocked_ioctl	= at91_wdt_ioctl,

  	.open		= at91_wdt_open,
  	.release	= at91_wdt_close,
  	.write		= at91_wdt_write,
  };
  
  static struct miscdevice at91wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &at91wdt_fops,
  };

  static int at91wdt_probe(struct platform_device *pdev)

  {

  	struct device *dev = &pdev->dev;
  	struct device *parent;

  	int res;

  	if (at91wdt_miscdev.parent)

  		return -EBUSY;

  	at91wdt_miscdev.parent = &pdev->dev;

  	parent = dev->parent;
  	if (!parent) {
  		dev_err(dev, "no parent
  ");
  		return -ENODEV;
  	}
  
  	regmap_st = syscon_node_to_regmap(parent->of_node);

  	if (IS_ERR(regmap_st))

  		return -ENODEV;

  	res = misc_register(&at91wdt_miscdev);
  	if (res)
  		return res;

  	res = register_restart_handler(&at91rm9200_restart_nb);
  	if (res)
  		dev_warn(dev, "failed to register restart handler
  ");

  	pr_info("AT91 Watchdog Timer enabled (%d seconds%s)
  ",
  		wdt_time, nowayout ? ", nowayout" : "");

  	return 0;
  }

  static int at91wdt_remove(struct platform_device *pdev)

  {

  	struct device *dev = &pdev->dev;

  	int res;

  	res = unregister_restart_handler(&at91rm9200_restart_nb);
  	if (res)
  		dev_warn(dev, "failed to unregister restart handler
  ");

  	misc_deregister(&at91wdt_miscdev);
  	at91wdt_miscdev.parent = NULL;

  
  	return res;
  }
  
  static void at91wdt_shutdown(struct platform_device *pdev)
  {
  	at91_wdt_stop();
  }
  
  #ifdef CONFIG_PM
  
  static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
  {
  	at91_wdt_stop();
  	return 0;
  }
  
  static int at91wdt_resume(struct platform_device *pdev)
  {
  	if (at91wdt_busy)
  		at91_wdt_start();

  	return 0;

  }
  
  #else
  #define at91wdt_suspend NULL
  #define at91wdt_resume	NULL
  #endif

  static const struct of_device_id at91_wdt_dt_ids[] = {
  	{ .compatible = "atmel,at91rm9200-wdt" },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids);

  static struct platform_driver at91wdt_driver = {
  	.probe		= at91wdt_probe,

  	.remove		= at91wdt_remove,

  	.shutdown	= at91wdt_shutdown,
  	.suspend	= at91wdt_suspend,
  	.resume		= at91wdt_resume,
  	.driver		= {

  		.name	= "atmel_st_watchdog",

  		.of_match_table = at91_wdt_dt_ids,

  	},
  };
  
  static int __init at91_wdt_init(void)
  {

  	/* Check that the heartbeat value is within range;
  	   if not reset to the default */

  	if (at91_wdt_settimeout(wdt_time)) {
  		at91_wdt_settimeout(WDT_DEFAULT_TIME);

  		pr_info("wdt_time value must be 1 <= wdt_time <= 256, using %d
  ",
  			wdt_time);

  	}
  
  	return platform_driver_register(&at91wdt_driver);
  }

  static void __exit at91_wdt_exit(void)
  {

  	platform_driver_unregister(&at91wdt_driver);

  }
  
  module_init(at91_wdt_init);
  module_exit(at91_wdt_exit);
  
  MODULE_AUTHOR("Andrew Victor");
  MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("platform:atmel_st_watchdog");