/*
   *  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.
   *
   *  Copyright (C) 2010 John Crispin <blogic@openwrt.org>
   *  Based on EP93xx wdt driver
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/of_platform.h>
  #include <linux/uaccess.h>
  #include <linux/clk.h>
  #include <linux/io.h>
  
  #include <lantiq_soc.h>
  
  /*
   * Section 3.4 of the datasheet
   * The password sequence protects the WDT control register from unintended
   * write actions, which might cause malfunction of the WDT.
   *
   * essentially the following two magic passwords need to be written to allow
   * IO access to the WDT core
   */
  #define LTQ_WDT_PW1		0x00BE0000
  #define LTQ_WDT_PW2		0x00DC0000
  
  #define LTQ_WDT_CR		0x0	/* watchdog control register */
  #define LTQ_WDT_SR		0x8	/* watchdog status register */
  
  #define LTQ_WDT_SR_EN		(0x1 << 31)	/* enable bit */
  #define LTQ_WDT_SR_PWD		(0x3 << 26)	/* turn on power */
  #define LTQ_WDT_SR_CLKDIV	(0x3 << 24)	/* turn on clock and set */
  						/* divider to 0x40000 */
  #define LTQ_WDT_DIVIDER		0x40000
  #define LTQ_MAX_TIMEOUT		((1 << 16) - 1)	/* the reload field is 16 bit */
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  
  static void __iomem *ltq_wdt_membase;
  static unsigned long ltq_io_region_clk_rate;
  
  static unsigned long ltq_wdt_bootstatus;
  static unsigned long ltq_wdt_in_use;
  static int ltq_wdt_timeout = 30;
  static int ltq_wdt_ok_to_close;
  
  static void
  ltq_wdt_enable(void)
  {
  	unsigned long int timeout = ltq_wdt_timeout *
  			(ltq_io_region_clk_rate / LTQ_WDT_DIVIDER) + 0x1000;
  	if (timeout > LTQ_MAX_TIMEOUT)
  		timeout = LTQ_MAX_TIMEOUT;
  
  	/* write the first password magic */
  	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
  	/* write the second magic plus the configuration and new timeout */
  	ltq_w32(LTQ_WDT_SR_EN | LTQ_WDT_SR_PWD | LTQ_WDT_SR_CLKDIV |
  		LTQ_WDT_PW2 | timeout, ltq_wdt_membase + LTQ_WDT_CR);
  }
  
  static void
  ltq_wdt_disable(void)
  {
  	/* write the first password magic */
  	ltq_w32(LTQ_WDT_PW1, ltq_wdt_membase + LTQ_WDT_CR);
  	/*
  	 * write the second password magic with no config
  	 * this turns the watchdog off
  	 */
  	ltq_w32(LTQ_WDT_PW2, ltq_wdt_membase + LTQ_WDT_CR);
  }
  
  static ssize_t
  ltq_wdt_write(struct file *file, const char __user *data,
  		size_t len, loff_t *ppos)
  {
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			ltq_wdt_ok_to_close = 0;
  			for (i = 0; i != len; i++) {
  				char c;
  
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					ltq_wdt_ok_to_close = 1;
  				else
  					ltq_wdt_ok_to_close = 0;
  			}
  		}
  		ltq_wdt_enable();
  	}
  
  	return len;
  }
  
  static struct watchdog_info ident = {
  	.options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
  			WDIOF_CARDRESET,
  	.identity = "ltq_wdt",
  };
  
  static long
  ltq_wdt_ioctl(struct file *file,
  		unsigned int cmd, unsigned long arg)
  {
  	int ret = -ENOTTY;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
  				sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(ltq_wdt_bootstatus, (int __user *)arg);
  		break;
  
  	case WDIOC_GETSTATUS:
  		ret = put_user(0, (int __user *)arg);
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		ret = get_user(ltq_wdt_timeout, (int __user *)arg);
  		if (!ret)
  			ltq_wdt_enable();
  		/* intentional drop through */
  	case WDIOC_GETTIMEOUT:
  		ret = put_user(ltq_wdt_timeout, (int __user *)arg);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		ltq_wdt_enable();
  		ret = 0;
  		break;
  	}
  	return ret;
  }
  
  static int
  ltq_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(0, &ltq_wdt_in_use))
  		return -EBUSY;
  	ltq_wdt_in_use = 1;
  	ltq_wdt_enable();
  
  	return nonseekable_open(inode, file);
  }
  
  static int
  ltq_wdt_release(struct inode *inode, struct file *file)
  {
  	if (ltq_wdt_ok_to_close)
  		ltq_wdt_disable();
  	else
  		pr_err("watchdog closed without warning
  ");
  	ltq_wdt_ok_to_close = 0;
  	clear_bit(0, &ltq_wdt_in_use);
  
  	return 0;
  }
  
  static const struct file_operations ltq_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.write		= ltq_wdt_write,
  	.unlocked_ioctl	= ltq_wdt_ioctl,
  	.open		= ltq_wdt_open,
  	.release	= ltq_wdt_release,
  	.llseek		= no_llseek,
  };
  
  static struct miscdevice ltq_wdt_miscdev = {
  	.minor	= WATCHDOG_MINOR,
  	.name	= "watchdog",
  	.fops	= &ltq_wdt_fops,
  };
  
  static int
  ltq_wdt_probe(struct platform_device *pdev)
  {
  	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	struct clk *clk;
  
  	if (!res) {
  		dev_err(&pdev->dev, "cannot obtain I/O memory region");
  		return -ENOENT;
  	}
  
  	ltq_wdt_membase = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(ltq_wdt_membase))
  		return PTR_ERR(ltq_wdt_membase);
  
  	/* we do not need to enable the clock as it is always running */
  	clk = clk_get_io();
  	if (IS_ERR(clk)) {
  		dev_err(&pdev->dev, "Failed to get clock
  ");
  		return -ENOENT;
  	}
  	ltq_io_region_clk_rate = clk_get_rate(clk);
  	clk_put(clk);
  
  	/* find out if the watchdog caused the last reboot */
  	if (ltq_reset_cause() == LTQ_RST_CAUSE_WDTRST)
  		ltq_wdt_bootstatus = WDIOF_CARDRESET;
  
  	dev_info(&pdev->dev, "Init done
  ");
  	return misc_register(&ltq_wdt_miscdev);
  }
  
  static int
  ltq_wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&ltq_wdt_miscdev);
  
  	return 0;
  }
  
  static const struct of_device_id ltq_wdt_match[] = {
  	{ .compatible = "lantiq,wdt" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, ltq_wdt_match);
  
  static struct platform_driver ltq_wdt_driver = {
  	.probe = ltq_wdt_probe,
  	.remove = ltq_wdt_remove,
  	.driver = {
  		.name = "wdt",
  		.owner = THIS_MODULE,
  		.of_match_table = ltq_wdt_match,
  	},
  };
  
  module_platform_driver(ltq_wdt_driver);
  
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
  MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
  MODULE_DESCRIPTION("Lantiq SoC Watchdog");
  MODULE_LICENSE("GPL");