/*
   * Copyright (c) 2009 Nuvoton technology corporation.
   *
   * Wan ZongShun <mcuos.com@gmail.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation;version 2 of the License.
   *
   */
  
  #include <linux/bitops.h>
  #include <linux/errno.h>
  #include <linux/fs.h>
  #include <linux/init.h>
  #include <linux/io.h>
  #include <linux/clk.h>
  #include <linux/kernel.h>
  #include <linux/miscdevice.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/interrupt.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  #include <linux/uaccess.h>
  
  #define REG_WTCR		0x1c
  #define WTCLK			(0x01 << 10)
  #define WTE			(0x01 << 7)	/*wdt enable*/
  #define WTIS			(0x03 << 4)
  #define WTIF			(0x01 << 3)
  #define WTRF			(0x01 << 2)
  #define WTRE			(0x01 << 1)
  #define WTR			(0x01 << 0)
  /*
   * The watchdog time interval can be calculated via following formula:
   * WTIS		real time interval (formula)
   * 0x00		((2^ 14 ) * ((external crystal freq) / 256))seconds
   * 0x01		((2^ 16 ) * ((external crystal freq) / 256))seconds
   * 0x02		((2^ 18 ) * ((external crystal freq) / 256))seconds
   * 0x03		((2^ 20 ) * ((external crystal freq) / 256))seconds
   *
   * The external crystal freq is 15Mhz in the nuc900 evaluation board.
   * So 0x00 = +-0.28 seconds, 0x01 = +-1.12 seconds, 0x02 = +-4.48 seconds,
   * 0x03 = +- 16.92 seconds..
   */
  #define WDT_HW_TIMEOUT		0x02
  #define WDT_TIMEOUT		(HZ/2)
  #define WDT_HEARTBEAT		15
  
  static int heartbeat = WDT_HEARTBEAT;
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  struct nuc900_wdt {
  	struct clk	 *wdt_clock;
  	struct platform_device *pdev;
  	void __iomem	 *wdt_base;
  	char		 expect_close;
  	struct timer_list timer;
  	spinlock_t       wdt_lock;
  	unsigned long next_heartbeat;
  };
  
  static unsigned long nuc900wdt_busy;
  static struct nuc900_wdt *nuc900_wdt;
  
  static inline void nuc900_wdt_keepalive(void)
  {
  	unsigned int val;
  
  	spin_lock(&nuc900_wdt->wdt_lock);
  
  	val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
  	val |= (WTR | WTIF);
  	__raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
  
  	spin_unlock(&nuc900_wdt->wdt_lock);
  }
  
  static inline void nuc900_wdt_start(void)
  {
  	unsigned int val;
  
  	spin_lock(&nuc900_wdt->wdt_lock);
  
  	val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
  	val |= (WTRE | WTE | WTR | WTCLK | WTIF);
  	val &= ~WTIS;
  	val |= (WDT_HW_TIMEOUT << 0x04);
  	__raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
  
  	spin_unlock(&nuc900_wdt->wdt_lock);
  
  	nuc900_wdt->next_heartbeat = jiffies + heartbeat * HZ;
  	mod_timer(&nuc900_wdt->timer, jiffies + WDT_TIMEOUT);
  }
  
  static inline void nuc900_wdt_stop(void)
  {
  	unsigned int val;
  
  	del_timer(&nuc900_wdt->timer);
  
  	spin_lock(&nuc900_wdt->wdt_lock);
  
  	val = __raw_readl(nuc900_wdt->wdt_base + REG_WTCR);
  	val &= ~WTE;
  	__raw_writel(val, nuc900_wdt->wdt_base + REG_WTCR);
  
  	spin_unlock(&nuc900_wdt->wdt_lock);
  }
  
  static inline void nuc900_wdt_ping(void)
  {
  	nuc900_wdt->next_heartbeat = jiffies + heartbeat * HZ;
  }
  
  static int nuc900_wdt_open(struct inode *inode, struct file *file)
  {
  
  	if (test_and_set_bit(0, &nuc900wdt_busy))
  		return -EBUSY;
  
  	nuc900_wdt_start();
  
  	return nonseekable_open(inode, file);
  }
  
  static int nuc900_wdt_close(struct inode *inode, struct file *file)
  {
  	if (nuc900_wdt->expect_close == 42)
  		nuc900_wdt_stop();
  	else {
  		dev_crit(&nuc900_wdt->pdev->dev,
  			"Unexpected close, not stopping watchdog!
  ");
  		nuc900_wdt_ping();
  	}
  
  	nuc900_wdt->expect_close = 0;
  	clear_bit(0, &nuc900wdt_busy);
  	return 0;
  }
  
  static const struct watchdog_info nuc900_wdt_info = {
  	.identity	= "nuc900 watchdog",
  	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
  						WDIOF_MAGICCLOSE,
  };
  
  static long nuc900_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, &nuc900_wdt_info,
  				sizeof(nuc900_wdt_info)) ? -EFAULT : 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		return put_user(0, p);
  
  	case WDIOC_KEEPALIVE:
  		nuc900_wdt_ping();
  		return 0;
  
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_value, p))
  			return -EFAULT;
  
  		heartbeat = new_value;
  		nuc900_wdt_ping();
  
  		return put_user(new_value, p);
  	case WDIOC_GETTIMEOUT:
  		return put_user(heartbeat, p);
  	default:
  		return -ENOTTY;
  	}
  }
  
  static ssize_t nuc900_wdt_write(struct file *file, const char __user *data,
  						size_t len, loff_t *ppos)
  {
  	if (!len)
  		return 0;
  
  	/* Scan for magic character */
  	if (!nowayout) {
  		size_t i;
  
  		nuc900_wdt->expect_close = 0;
  
  		for (i = 0; i < len; i++) {
  			char c;
  			if (get_user(c, data + i))
  				return -EFAULT;
  			if (c == 'V') {
  				nuc900_wdt->expect_close = 42;
  				break;
  			}
  		}
  	}
  
  	nuc900_wdt_ping();
  	return len;
  }
  
  static void nuc900_wdt_timer_ping(unsigned long data)
  {
  	if (time_before(jiffies, nuc900_wdt->next_heartbeat)) {
  		nuc900_wdt_keepalive();
  		mod_timer(&nuc900_wdt->timer, jiffies + WDT_TIMEOUT);
  	} else
  		dev_warn(&nuc900_wdt->pdev->dev, "Will reset the machine !
  ");
  }
  
  static const struct file_operations nuc900wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.unlocked_ioctl	= nuc900_wdt_ioctl,
  	.open		= nuc900_wdt_open,
  	.release	= nuc900_wdt_close,
  	.write		= nuc900_wdt_write,
  };
  
  static struct miscdevice nuc900wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &nuc900wdt_fops,
  };
  
  static int nuc900wdt_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	int ret = 0;
  
  	nuc900_wdt = devm_kzalloc(&pdev->dev, sizeof(*nuc900_wdt),
  				GFP_KERNEL);
  	if (!nuc900_wdt)
  		return -ENOMEM;
  
  	nuc900_wdt->pdev = pdev;
  
  	spin_lock_init(&nuc900_wdt->wdt_lock);
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	nuc900_wdt->wdt_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(nuc900_wdt->wdt_base))
  		return PTR_ERR(nuc900_wdt->wdt_base);
  
  	nuc900_wdt->wdt_clock = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(nuc900_wdt->wdt_clock)) {
  		dev_err(&pdev->dev, "failed to find watchdog clock source
  ");
  		return PTR_ERR(nuc900_wdt->wdt_clock);
  	}
  
  	clk_enable(nuc900_wdt->wdt_clock);
  
  	setup_timer(&nuc900_wdt->timer, nuc900_wdt_timer_ping, 0);
  
  	ret = misc_register(&nuc900wdt_miscdev);
  	if (ret) {
  		dev_err(&pdev->dev, "err register miscdev on minor=%d (%d)
  ",
  			WATCHDOG_MINOR, ret);
  		goto err_clk;
  	}
  
  	return 0;
  
  err_clk:
  	clk_disable(nuc900_wdt->wdt_clock);
  	return ret;
  }
  
  static int nuc900wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&nuc900wdt_miscdev);
  
  	clk_disable(nuc900_wdt->wdt_clock);
  
  	return 0;
  }
  
  static struct platform_driver nuc900wdt_driver = {
  	.probe		= nuc900wdt_probe,
  	.remove		= nuc900wdt_remove,
  	.driver		= {
  		.name	= "nuc900-wdt",
  		.owner	= THIS_MODULE,
  	},
  };
  
  module_platform_driver(nuc900wdt_driver);
  
  MODULE_AUTHOR("Wan ZongShun <mcuos.com@gmail.com>");
  MODULE_DESCRIPTION("Watchdog driver for NUC900");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:nuc900-wdt");