// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * FIXME: add wdrtas_get_status and wdrtas_get_boot_status as soon as
   * RTAS calls are available
   */
  
  /*
   * RTAS watchdog driver
   *
   * (C) Copyright IBM Corp. 2005
   * device driver to exploit watchdog RTAS functions
   *
   * Authors : Utz Bacher <utz.bacher@de.ibm.com>

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

  #include <linux/uaccess.h>

  
  #include <asm/rtas.h>

  
  #define WDRTAS_MAGIC_CHAR		42
  #define WDRTAS_SUPPORTED_MASK		(WDIOF_SETTIMEOUT | \
  					 WDIOF_MAGICCLOSE)
  
  MODULE_AUTHOR("Utz Bacher <utz.bacher@de.ibm.com>");
  MODULE_DESCRIPTION("RTAS watchdog driver");
  MODULE_LICENSE("GPL");

  static bool wdrtas_nowayout = WATCHDOG_NOWAYOUT;

  static atomic_t wdrtas_miscdev_open = ATOMIC_INIT(0);

  static char wdrtas_expect_close;

  
  static int wdrtas_interval;
  
  #define WDRTAS_THERMAL_SENSOR		3
  static int wdrtas_token_get_sensor_state;
  #define WDRTAS_SURVEILLANCE_IND		9000
  static int wdrtas_token_set_indicator;
  #define WDRTAS_SP_SPI			28
  static int wdrtas_token_get_sp;
  static int wdrtas_token_event_scan;
  
  #define WDRTAS_DEFAULT_INTERVAL		300
  
  #define WDRTAS_LOGBUFFER_LEN		128
  static char wdrtas_logbuffer[WDRTAS_LOGBUFFER_LEN];
  
  
  /*** watchdog access functions */
  
  /**
   * wdrtas_set_interval - sets the watchdog interval
   * @interval: new interval
   *
   * returns 0 on success, <0 on failures
   *
   * wdrtas_set_interval sets the watchdog keepalive interval by calling the
   * RTAS function set-indicator (surveillance). The unit of interval is
   * seconds.
   */

  
  static int wdrtas_set_interval(int interval)

  {
  	long result;
  	static int print_msg = 10;
  
  	/* rtas uses minutes */
  	interval = (interval + 59) / 60;
  
  	result = rtas_call(wdrtas_token_set_indicator, 3, 1, NULL,
  			   WDRTAS_SURVEILLANCE_IND, 0, interval);

  	if (result < 0 && print_msg) {

  		pr_err("setting the watchdog to %i timeout failed: %li
  ",
  		       interval, result);

  		print_msg--;
  	}
  
  	return result;
  }

  #define WDRTAS_SP_SPI_LEN 4

  /**
   * wdrtas_get_interval - returns the current watchdog interval
   * @fallback_value: value (in seconds) to use, if the RTAS call fails
   *
   * returns the interval
   *
   * wdrtas_get_interval returns the current watchdog keepalive interval
   * as reported by the RTAS function ibm,get-system-parameter. The unit
   * of the return value is seconds.
   */

  static int wdrtas_get_interval(int fallback_value)

  {
  	long result;

  	char value[WDRTAS_SP_SPI_LEN];

  	spin_lock(&rtas_data_buf_lock);
  	memset(rtas_data_buf, 0, WDRTAS_SP_SPI_LEN);

  	result = rtas_call(wdrtas_token_get_sp, 3, 1, NULL,

  			   WDRTAS_SP_SPI, __pa(rtas_data_buf),
  			   WDRTAS_SP_SPI_LEN);
  
  	memcpy(value, rtas_data_buf, WDRTAS_SP_SPI_LEN);
  	spin_unlock(&rtas_data_buf_lock);

  	if (value[0] != 0 || value[1] != 2 || value[3] != 0 || result < 0) {

  		pr_warn("could not get sp_spi watchdog timeout (%li). Continuing
  ",
  			result);

  		return fallback_value;
  	}
  
  	/* rtas uses minutes */
  	return ((int)value[2]) * 60;
  }
  
  /**
   * wdrtas_timer_start - starts watchdog
   *
   * wdrtas_timer_start starts the watchdog by calling the RTAS function
   * set-interval (surveillance)
   */

  static void wdrtas_timer_start(void)

  {
  	wdrtas_set_interval(wdrtas_interval);
  }
  
  /**
   * wdrtas_timer_stop - stops watchdog
   *
   * wdrtas_timer_stop stops the watchdog timer by calling the RTAS function
   * set-interval (surveillance)
   */

  static void wdrtas_timer_stop(void)

  {
  	wdrtas_set_interval(0);
  }
  
  /**

   * wdrtas_timer_keepalive - resets watchdog timer to keep system alive
   *
   * wdrtas_timer_keepalive restarts the watchdog timer by calling the
   * RTAS function event-scan and repeats these calls as long as there are
   * events available. All events will be dumped.
   */

  static void wdrtas_timer_keepalive(void)

  {
  	long result;
  
  	do {
  		result = rtas_call(wdrtas_token_event_scan, 4, 1, NULL,
  				   RTAS_EVENT_SCAN_ALL_EVENTS, 0,
  				   (void *)__pa(wdrtas_logbuffer),
  				   WDRTAS_LOGBUFFER_LEN);
  		if (result < 0)

  			pr_err("event-scan failed: %li
  ", result);

  		if (result == 0)

  			print_hex_dump(KERN_INFO, "dumping event, data: ",
  				DUMP_PREFIX_OFFSET, 16, 1,
  				wdrtas_logbuffer, WDRTAS_LOGBUFFER_LEN, false);

  	} while (result == 0);
  }
  
  /**
   * wdrtas_get_temperature - returns current temperature
   *
   * returns temperature or <0 on failures
   *
   * wdrtas_get_temperature returns the current temperature in Fahrenheit. It
   * uses the RTAS call get-sensor-state, token 3 to do so
   */

  static int wdrtas_get_temperature(void)

  {

  	int result;

  	int temperature = 0;

  	result = rtas_get_sensor(WDRTAS_THERMAL_SENSOR, 0, &temperature);

  
  	if (result < 0)

  		pr_warn("reading the thermal sensor failed: %i
  ", result);

  	else
  		temperature = ((temperature * 9) / 5) + 32; /* fahrenheit */
  
  	return temperature;
  }
  
  /**
   * wdrtas_get_status - returns the status of the watchdog
   *
   * returns a bitmask of defines WDIOF_... as defined in
   * include/linux/watchdog.h
   */

  static int wdrtas_get_status(void)

  {
  	return 0; /* TODO */
  }
  
  /**
   * wdrtas_get_boot_status - returns the reason for the last boot
   *
   * returns a bitmask of defines WDIOF_... as defined in
   * include/linux/watchdog.h, indicating why the watchdog rebooted the system
   */

  static int wdrtas_get_boot_status(void)

  {
  	return 0; /* TODO */
  }
  
  /*** watchdog API and operations stuff */
  
  /* wdrtas_write - called when watchdog device is written to
   * @file: file structure
   * @buf: user buffer with data
   * @len: amount to data written
   * @ppos: position in file
   *
   * returns the number of successfully processed characters, which is always
   * the number of bytes passed to this function
   *
   * wdrtas_write processes all the data given to it and looks for the magic
   * character 'V'. This character allows the watchdog device to be closed
   * properly.
   */

  static ssize_t wdrtas_write(struct file *file, const char __user *buf,

  	     size_t len, loff_t *ppos)
  {
  	int i;
  	char c;
  
  	if (!len)
  		goto out;
  
  	if (!wdrtas_nowayout) {
  		wdrtas_expect_close = 0;
  		/* look for 'V' */
  		for (i = 0; i < len; i++) {
  			if (get_user(c, buf + i))
  				return -EFAULT;
  			/* allow to close device */
  			if (c == 'V')
  				wdrtas_expect_close = WDRTAS_MAGIC_CHAR;
  		}
  	}
  
  	wdrtas_timer_keepalive();
  
  out:
  	return len;
  }
  
  /**
   * wdrtas_ioctl - ioctl function for the watchdog device

   * @file: file structure
   * @cmd: command for ioctl
   * @arg: argument pointer
   *
   * returns 0 on success, <0 on failure
   *
   * wdrtas_ioctl implements the watchdog API ioctls
   */

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

  {

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

  	int i;

  	static const struct watchdog_info wdinfo = {

  		.options = WDRTAS_SUPPORTED_MASK,
  		.firmware_version = 0,

  		.identity = "wdrtas",

  	};
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		if (copy_to_user(argp, &wdinfo, sizeof(wdinfo)))
  			return -EFAULT;
  		return 0;
  
  	case WDIOC_GETSTATUS:
  		i = wdrtas_get_status();
  		return put_user(i, argp);
  
  	case WDIOC_GETBOOTSTATUS:
  		i = wdrtas_get_boot_status();
  		return put_user(i, argp);
  
  	case WDIOC_GETTEMP:
  		if (wdrtas_token_get_sensor_state == RTAS_UNKNOWN_SERVICE)
  			return -EOPNOTSUPP;
  
  		i = wdrtas_get_temperature();
  		return put_user(i, argp);
  
  	case WDIOC_SETOPTIONS:
  		if (get_user(i, argp))
  			return -EFAULT;
  		if (i & WDIOS_DISABLECARD)
  			wdrtas_timer_stop();
  		if (i & WDIOS_ENABLECARD) {
  			wdrtas_timer_keepalive();
  			wdrtas_timer_start();
  		}

  		/* not implemented. Done by H8

  		if (i & WDIOS_TEMPPANIC) {

  		} */

  		return 0;
  
  	case WDIOC_KEEPALIVE:
  		wdrtas_timer_keepalive();
  		return 0;
  
  	case WDIOC_SETTIMEOUT:
  		if (get_user(i, argp))
  			return -EFAULT;
  
  		if (wdrtas_set_interval(i))
  			return -EINVAL;
  
  		wdrtas_timer_keepalive();
  
  		if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE)
  			wdrtas_interval = i;
  		else
  			wdrtas_interval = wdrtas_get_interval(i);
  		/* fallthrough */
  
  	case WDIOC_GETTIMEOUT:
  		return put_user(wdrtas_interval, argp);
  
  	default:

  		return -ENOTTY;

  	}
  }
  
  /**
   * wdrtas_open - open function of watchdog device
   * @inode: inode structure
   * @file: file structure
   *
   * returns 0 on success, -EBUSY if the file has been opened already, <0 on
   * other failures
   *
   * function called when watchdog device is opened
   */

  static int wdrtas_open(struct inode *inode, struct file *file)

  {
  	/* only open once */
  	if (atomic_inc_return(&wdrtas_miscdev_open) > 1) {
  		atomic_dec(&wdrtas_miscdev_open);
  		return -EBUSY;
  	}
  
  	wdrtas_timer_start();
  	wdrtas_timer_keepalive();

  	return stream_open(inode, file);

  }
  
  /**
   * wdrtas_close - close function of watchdog device
   * @inode: inode structure
   * @file: file structure
   *
   * returns 0 on success
   *
   * close function. Always succeeds
   */

  static int wdrtas_close(struct inode *inode, struct file *file)

  {
  	/* only stop watchdog, if this was announced using 'V' before */
  	if (wdrtas_expect_close == WDRTAS_MAGIC_CHAR)
  		wdrtas_timer_stop();
  	else {

  		pr_warn("got unexpected close. Watchdog not stopped.
  ");

  		wdrtas_timer_keepalive();
  	}
  
  	wdrtas_expect_close = 0;
  	atomic_dec(&wdrtas_miscdev_open);
  	return 0;
  }
  
  /**
   * wdrtas_temp_read - gives back the temperature in fahrenheit
   * @file: file structure
   * @buf: user buffer
   * @count: number of bytes to be read
   * @ppos: position in file
   *
   * returns always 1 or -EFAULT in case of user space copy failures, <0 on
   * other failures
   *
   * wdrtas_temp_read gives the temperature to the users by copying this
   * value as one byte into the user space buffer. The unit is Fahrenheit...
   */

  static ssize_t wdrtas_temp_read(struct file *file, char __user *buf,

  		 size_t count, loff_t *ppos)
  {
  	int temperature = 0;
  
  	temperature = wdrtas_get_temperature();
  	if (temperature < 0)
  		return temperature;
  
  	if (copy_to_user(buf, &temperature, 1))
  		return -EFAULT;
  
  	return 1;
  }
  
  /**
   * wdrtas_temp_open - open function of temperature device
   * @inode: inode structure
   * @file: file structure
   *
   * returns 0 on success, <0 on failure
   *
   * function called when temperature device is opened
   */

  static int wdrtas_temp_open(struct inode *inode, struct file *file)

  {

  	return stream_open(inode, file);

  }
  
  /**
   * wdrtas_temp_close - close function of temperature device
   * @inode: inode structure
   * @file: file structure
   *
   * returns 0 on success
   *
   * close function. Always succeeds
   */

  static int wdrtas_temp_close(struct inode *inode, struct file *file)

  {
  	return 0;
  }
  
  /**
   * wdrtas_reboot - reboot notifier function
   * @nb: notifier block structure
   * @code: reboot code
   * @ptr: unused
   *
   * returns NOTIFY_DONE
   *
   * wdrtas_reboot stops the watchdog in case of a reboot
   */

  static int wdrtas_reboot(struct notifier_block *this,
  					unsigned long code, void *ptr)

  {

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

  		wdrtas_timer_stop();
  
  	return NOTIFY_DONE;
  }
  
  /*** initialization stuff */

  static const struct file_operations wdrtas_fops = {

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

  	.unlocked_ioctl	= wdrtas_ioctl,

  	.open		= wdrtas_open,
  	.release	= wdrtas_close,
  };
  
  static struct miscdevice wdrtas_miscdev = {
  	.minor =	WATCHDOG_MINOR,
  	.name =		"watchdog",
  	.fops =		&wdrtas_fops,
  };

  static const struct file_operations wdrtas_temp_fops = {

  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.read		= wdrtas_temp_read,
  	.open		= wdrtas_temp_open,
  	.release	= wdrtas_temp_close,
  };
  
  static struct miscdevice wdrtas_tempdev = {
  	.minor =	TEMP_MINOR,
  	.name =		"temperature",
  	.fops =		&wdrtas_temp_fops,
  };
  
  static struct notifier_block wdrtas_notifier = {
  	.notifier_call =	wdrtas_reboot,
  };
  
  /**
   * wdrtas_get_tokens - reads in RTAS tokens
   *

   * returns 0 on success, <0 on failure

   *
   * wdrtas_get_tokens reads in the tokens for the RTAS calls used in
   * this watchdog driver. It tolerates, if "get-sensor-state" and
   * "ibm,get-system-parameter" are not available.
   */

  static int wdrtas_get_tokens(void)

  {
  	wdrtas_token_get_sensor_state = rtas_token("get-sensor-state");
  	if (wdrtas_token_get_sensor_state == RTAS_UNKNOWN_SERVICE) {

  		pr_warn("couldn't get token for get-sensor-state. Trying to continue without temperature support.
  ");

  	}
  
  	wdrtas_token_get_sp = rtas_token("ibm,get-system-parameter");
  	if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE) {

  		pr_warn("couldn't get token for ibm,get-system-parameter. Trying to continue with a default timeout value of %i seconds.
  ",
  			WDRTAS_DEFAULT_INTERVAL);

  	}
  
  	wdrtas_token_set_indicator = rtas_token("set-indicator");
  	if (wdrtas_token_set_indicator == RTAS_UNKNOWN_SERVICE) {

  		pr_err("couldn't get token for set-indicator. Terminating watchdog code.
  ");

  		return -EIO;
  	}
  
  	wdrtas_token_event_scan = rtas_token("event-scan");
  	if (wdrtas_token_event_scan == RTAS_UNKNOWN_SERVICE) {

  		pr_err("couldn't get token for event-scan. Terminating watchdog code.
  ");

  		return -EIO;
  	}
  
  	return 0;
  }
  
  /**
   * wdrtas_unregister_devs - unregisters the misc dev handlers
   *
   * wdrtas_register_devs unregisters the watchdog and temperature watchdog
   * misc devs
   */

  static void wdrtas_unregister_devs(void)

  {
  	misc_deregister(&wdrtas_miscdev);
  	if (wdrtas_token_get_sensor_state != RTAS_UNKNOWN_SERVICE)
  		misc_deregister(&wdrtas_tempdev);
  }
  
  /**
   * wdrtas_register_devs - registers the misc dev handlers
   *

   * returns 0 on success, <0 on failure

   *
   * wdrtas_register_devs registers the watchdog and temperature watchdog
   * misc devs
   */

  static int wdrtas_register_devs(void)

  {
  	int result;
  
  	result = misc_register(&wdrtas_miscdev);
  	if (result) {

  		pr_err("couldn't register watchdog misc device. Terminating watchdog code.
  ");

  		return result;
  	}
  
  	if (wdrtas_token_get_sensor_state != RTAS_UNKNOWN_SERVICE) {
  		result = misc_register(&wdrtas_tempdev);
  		if (result) {

  			pr_warn("couldn't register watchdog temperature misc device. Continuing without temperature support.
  ");

  			wdrtas_token_get_sensor_state = RTAS_UNKNOWN_SERVICE;
  		}
  	}
  
  	return 0;
  }
  
  /**
   * wdrtas_init - init function of the watchdog driver
   *

   * returns 0 on success, <0 on failure

   *
   * registers the file handlers and the reboot notifier
   */

  static int __init wdrtas_init(void)

  {
  	if (wdrtas_get_tokens())
  		return -ENODEV;
  
  	if (wdrtas_register_devs())
  		return -ENODEV;
  
  	if (register_reboot_notifier(&wdrtas_notifier)) {

  		pr_err("could not register reboot notifier. Terminating watchdog code.
  ");

  		wdrtas_unregister_devs();
  		return -ENODEV;
  	}
  
  	if (wdrtas_token_get_sp == RTAS_UNKNOWN_SERVICE)
  		wdrtas_interval = WDRTAS_DEFAULT_INTERVAL;
  	else
  		wdrtas_interval = wdrtas_get_interval(WDRTAS_DEFAULT_INTERVAL);
  
  	return 0;
  }
  
  /**
   * wdrtas_exit - exit function of the watchdog driver
   *
   * unregisters the file handlers and the reboot notifier
   */

  static void __exit wdrtas_exit(void)

  {
  	if (!wdrtas_nowayout)
  		wdrtas_timer_stop();
  
  	wdrtas_unregister_devs();
  
  	unregister_reboot_notifier(&wdrtas_notifier);
  }
  
  module_init(wdrtas_init);
  module_exit(wdrtas_exit);