/*
   * Watchdog driver for SBC-FITPC2 board
   *
   * Author: Denis Turischev <denis@compulab.co.il>
   *
   * Adapted from the IXP2000 watchdog driver by Deepak Saxena.
   *
   * 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.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME " WATCHDOG: " fmt
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/ioport.h>
  #include <linux/delay.h>
  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/moduleparam.h>
  #include <linux/dmi.h>
  #include <linux/io.h>
  #include <linux/uaccess.h>

  static bool nowayout = WATCHDOG_NOWAYOUT;

  static unsigned int margin = 60;	/* (secs) Default is 1 minute */
  static unsigned long wdt_status;

  static DEFINE_MUTEX(wdt_lock);

  
  #define WDT_IN_USE		0
  #define WDT_OK_TO_CLOSE		1
  
  #define COMMAND_PORT		0x4c
  #define DATA_PORT		0x48
  
  #define IFACE_ON_COMMAND	1
  #define REBOOT_COMMAND		2

  #define WATCHDOG_NAME		"SBC-FITPC2 Watchdog"

  
  static void wdt_send_data(unsigned char command, unsigned char data)
  {

  	outb(data, DATA_PORT);

  	msleep(200);

  	outb(command, COMMAND_PORT);
  	msleep(100);

  }
  
  static void wdt_enable(void)
  {

  	mutex_lock(&wdt_lock);

  	wdt_send_data(IFACE_ON_COMMAND, 1);
  	wdt_send_data(REBOOT_COMMAND, margin);

  	mutex_unlock(&wdt_lock);

  }
  
  static void wdt_disable(void)
  {

  	mutex_lock(&wdt_lock);

  	wdt_send_data(IFACE_ON_COMMAND, 0);
  	wdt_send_data(REBOOT_COMMAND, 0);

  	mutex_unlock(&wdt_lock);

  }
  
  static int fitpc2_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(WDT_IN_USE, &wdt_status))
  		return -EBUSY;
  
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	wdt_enable();
  
  	return nonseekable_open(inode, file);
  }
  
  static ssize_t fitpc2_wdt_write(struct file *file, const char *data,
  						size_t len, loff_t *ppos)
  {
  	size_t i;
  
  	if (!len)
  		return 0;
  
  	if (nowayout) {
  		len = 0;
  		goto out;
  	}
  
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	for (i = 0; i != len; i++) {
  		char c;
  
  		if (get_user(c, data + i))
  			return -EFAULT;
  
  		if (c == 'V')
  			set_bit(WDT_OK_TO_CLOSE, &wdt_status);
  	}
  
  out:
  	wdt_enable();
  
  	return len;
  }

  static const struct watchdog_info ident = {

  	.options	= WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT |
  				WDIOF_KEEPALIVEPING,
  	.identity	= WATCHDOG_NAME,
  };
  
  
  static long fitpc2_wdt_ioctl(struct file *file, unsigned int cmd,
  							unsigned long arg)
  {
  	int ret = -ENOTTY;
  	int time;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user((struct watchdog_info *)arg, &ident,
  				   sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  		ret = put_user(0, (int *)arg);
  		break;
  
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(0, (int *)arg);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		wdt_enable();
  		ret = 0;
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		ret = get_user(time, (int *)arg);
  		if (ret)
  			break;
  
  		if (time < 31 || time > 255) {
  			ret = -EINVAL;
  			break;
  		}
  
  		margin = time;
  		wdt_enable();
  		/* Fall through */
  
  	case WDIOC_GETTIMEOUT:
  		ret = put_user(margin, (int *)arg);
  		break;
  	}
  
  	return ret;
  }
  
  static int fitpc2_wdt_release(struct inode *inode, struct file *file)
  {
  	if (test_bit(WDT_OK_TO_CLOSE, &wdt_status)) {
  		wdt_disable();
  		pr_info("Device disabled
  ");
  	} else {

  		pr_warn("Device closed unexpectedly - timer will not stop
  ");

  		wdt_enable();
  	}
  
  	clear_bit(WDT_IN_USE, &wdt_status);
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	return 0;
  }
  
  
  static const struct file_operations fitpc2_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= fitpc2_wdt_write,
  	.unlocked_ioctl	= fitpc2_wdt_ioctl,
  	.open		= fitpc2_wdt_open,
  	.release	= fitpc2_wdt_release,
  };
  
  static struct miscdevice fitpc2_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &fitpc2_wdt_fops,
  };
  
  static int __init fitpc2_wdt_init(void)
  {
  	int err;

  	const char *brd_name;

  	brd_name = dmi_get_system_info(DMI_BOARD_NAME);
  
  	if (!brd_name || !strstr(brd_name, "SBC-FITPC2"))

  		return -ENODEV;

  	pr_info("%s found
  ", brd_name);

  
  	if (!request_region(COMMAND_PORT, 1, WATCHDOG_NAME)) {
  		pr_err("I/O address 0x%04x already in use
  ", COMMAND_PORT);
  		return -EIO;
  	}
  
  	if (!request_region(DATA_PORT, 1, WATCHDOG_NAME)) {
  		pr_err("I/O address 0x%04x already in use
  ", DATA_PORT);
  		err = -EIO;
  		goto err_data_port;
  	}
  
  	if (margin < 31 || margin > 255) {

  		pr_err("margin must be in range 31 - 255 seconds, you tried to set %d
  ",
  		       margin);

  		err = -EINVAL;
  		goto err_margin;
  	}
  
  	err = misc_register(&fitpc2_wdt_miscdev);

  	if (err) {

  		pr_err("cannot register miscdev on minor=%d (err=%d)
  ",

  		       WATCHDOG_MINOR, err);

  		goto err_margin;
  	}
  
  	return 0;
  
  err_margin:
  	release_region(DATA_PORT, 1);
  err_data_port:
  	release_region(COMMAND_PORT, 1);
  
  	return err;
  }
  
  static void __exit fitpc2_wdt_exit(void)
  {
  	misc_deregister(&fitpc2_wdt_miscdev);
  	release_region(DATA_PORT, 1);
  	release_region(COMMAND_PORT, 1);
  }
  
  module_init(fitpc2_wdt_init);
  module_exit(fitpc2_wdt_exit);
  
  MODULE_AUTHOR("Denis Turischev <denis@compulab.co.il>");
  MODULE_DESCRIPTION("SBC-FITPC2 Watchdog");
  
  module_param(margin, int, 0);
  MODULE_PARM_DESC(margin, "Watchdog margin in seconds (default 60s)");

  module_param(nowayout, bool, 0);

  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
  
  MODULE_LICENSE("GPL");