/*
   * Atheros AR71XX/AR724X/AR913X built-in hardware watchdog timer.
   *
   * Copyright (C) 2008-2011 Gabor Juhos <juhosg@openwrt.org>
   * Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
   *
   * This driver was based on: drivers/watchdog/ixp4xx_wdt.c
   *	Author: Deepak Saxena <dsaxena@plexity.net>
   *	Copyright 2004 (c) MontaVista, Software, Inc.
   *
   * which again was based on sa1100 driver,
   *	Copyright (C) 2000 Oleg Drokin <green@crimea.edu>
   *
   * 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.
   *
   */
  
  #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/miscdevice.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/of.h>
  #include <linux/of_platform.h>
  
  #define DRIVER_NAME	"ath79-wdt"
  
  #define WDT_TIMEOUT	15	/* seconds */
  
  #define WDOG_REG_CTRL		0x00
  #define WDOG_REG_TIMER		0x04
  
  #define WDOG_CTRL_LAST_RESET	BIT(31)
  #define WDOG_CTRL_ACTION_MASK	3
  #define WDOG_CTRL_ACTION_NONE	0	/* no action */
  #define WDOG_CTRL_ACTION_GPI	1	/* general purpose interrupt */
  #define WDOG_CTRL_ACTION_NMI	2	/* NMI */
  #define WDOG_CTRL_ACTION_FCR	3	/* full chip reset */
  
  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) ")");
  
  static int timeout = WDT_TIMEOUT;
  module_param(timeout, int, 0);
  MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
  			  "(default=" __MODULE_STRING(WDT_TIMEOUT) "s)");
  
  static unsigned long wdt_flags;
  
  #define WDT_FLAGS_BUSY		0
  #define WDT_FLAGS_EXPECT_CLOSE	1
  
  static struct clk *wdt_clk;
  static unsigned long wdt_freq;
  static int boot_status;
  static int max_timeout;
  static void __iomem *wdt_base;
  
  static inline void ath79_wdt_wr(unsigned reg, u32 val)
  {
  	iowrite32(val, wdt_base + reg);
  }
  
  static inline u32 ath79_wdt_rr(unsigned reg)
  {
  	return ioread32(wdt_base + reg);
  }
  
  static inline void ath79_wdt_keepalive(void)
  {
  	ath79_wdt_wr(WDOG_REG_TIMER, wdt_freq * timeout);
  	/* flush write */
  	ath79_wdt_rr(WDOG_REG_TIMER);
  }
  
  static inline void ath79_wdt_enable(void)
  {
  	ath79_wdt_keepalive();
  
  	/*
  	 * Updating the TIMER register requires a few microseconds
  	 * on the AR934x SoCs at least. Use a small delay to ensure
  	 * that the TIMER register is updated within the hardware
  	 * before enabling the watchdog.
  	 */
  	udelay(2);
  
  	ath79_wdt_wr(WDOG_REG_CTRL, WDOG_CTRL_ACTION_FCR);
  	/* flush write */
  	ath79_wdt_rr(WDOG_REG_CTRL);
  }
  
  static inline void ath79_wdt_disable(void)
  {
  	ath79_wdt_wr(WDOG_REG_CTRL, WDOG_CTRL_ACTION_NONE);
  	/* flush write */
  	ath79_wdt_rr(WDOG_REG_CTRL);
  }
  
  static int ath79_wdt_set_timeout(int val)
  {
  	if (val < 1 || val > max_timeout)
  		return -EINVAL;
  
  	timeout = val;
  	ath79_wdt_keepalive();
  
  	return 0;
  }
  
  static int ath79_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(WDT_FLAGS_BUSY, &wdt_flags))
  		return -EBUSY;
  
  	clear_bit(WDT_FLAGS_EXPECT_CLOSE, &wdt_flags);
  	ath79_wdt_enable();
  
  	return nonseekable_open(inode, file);
  }
  
  static int ath79_wdt_release(struct inode *inode, struct file *file)
  {
  	if (test_bit(WDT_FLAGS_EXPECT_CLOSE, &wdt_flags))
  		ath79_wdt_disable();
  	else {
  		pr_crit("device closed unexpectedly, watchdog timer will not stop!
  ");
  		ath79_wdt_keepalive();
  	}
  
  	clear_bit(WDT_FLAGS_BUSY, &wdt_flags);
  	clear_bit(WDT_FLAGS_EXPECT_CLOSE, &wdt_flags);
  
  	return 0;
  }
  
  static ssize_t ath79_wdt_write(struct file *file, const char *data,
  				size_t len, loff_t *ppos)
  {
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			clear_bit(WDT_FLAGS_EXPECT_CLOSE, &wdt_flags);
  
  			for (i = 0; i != len; i++) {
  				char c;
  
  				if (get_user(c, data + i))
  					return -EFAULT;
  
  				if (c == 'V')
  					set_bit(WDT_FLAGS_EXPECT_CLOSE,
  						&wdt_flags);
  			}
  		}
  
  		ath79_wdt_keepalive();
  	}
  
  	return len;
  }
  
  static const struct watchdog_info ath79_wdt_info = {
  	.options		= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
  				  WDIOF_MAGICCLOSE | WDIOF_CARDRESET,
  	.firmware_version	= 0,
  	.identity		= "ATH79 watchdog",
  };
  
  static long ath79_wdt_ioctl(struct file *file, unsigned int cmd,
  			    unsigned long arg)
  {
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  	int err;
  	int t;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		err = copy_to_user(argp, &ath79_wdt_info,
  				   sizeof(ath79_wdt_info)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  		err = put_user(0, p);
  		break;
  
  	case WDIOC_GETBOOTSTATUS:
  		err = put_user(boot_status, p);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		ath79_wdt_keepalive();
  		err = 0;
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		err = get_user(t, p);
  		if (err)
  			break;
  
  		err = ath79_wdt_set_timeout(t);
  		if (err)
  			break;
  
  		/* fallthrough */
  	case WDIOC_GETTIMEOUT:
  		err = put_user(timeout, p);
  		break;
  
  	default:
  		err = -ENOTTY;
  		break;
  	}
  
  	return err;
  }
  
  static const struct file_operations ath79_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= ath79_wdt_write,
  	.unlocked_ioctl	= ath79_wdt_ioctl,
  	.open		= ath79_wdt_open,
  	.release	= ath79_wdt_release,
  };
  
  static struct miscdevice ath79_wdt_miscdev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &ath79_wdt_fops,
  };
  
  static int ath79_wdt_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	u32 ctrl;
  	int err;
  
  	if (wdt_base)
  		return -EBUSY;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	wdt_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(wdt_base))
  		return PTR_ERR(wdt_base);
  
  	wdt_clk = devm_clk_get(&pdev->dev, "wdt");
  	if (IS_ERR(wdt_clk))
  		return PTR_ERR(wdt_clk);
  
  	err = clk_enable(wdt_clk);
  	if (err)
  		return err;
  
  	wdt_freq = clk_get_rate(wdt_clk);
  	if (!wdt_freq) {
  		err = -EINVAL;
  		goto err_clk_disable;
  	}
  
  	max_timeout = (0xfffffffful / wdt_freq);
  	if (timeout < 1 || timeout > max_timeout) {
  		timeout = max_timeout;
  		dev_info(&pdev->dev,
  			"timeout value must be 0 < timeout < %d, using %d
  ",
  			max_timeout, timeout);
  	}
  
  	ctrl = ath79_wdt_rr(WDOG_REG_CTRL);
  	boot_status = (ctrl & WDOG_CTRL_LAST_RESET) ? WDIOF_CARDRESET : 0;
  
  	err = misc_register(&ath79_wdt_miscdev);
  	if (err) {
  		dev_err(&pdev->dev,
  			"unable to register misc device, err=%d
  ", err);
  		goto err_clk_disable;
  	}
  
  	return 0;
  
  err_clk_disable:
  	clk_disable(wdt_clk);
  	return err;
  }
  
  static int ath79_wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&ath79_wdt_miscdev);
  	clk_disable(wdt_clk);
  	return 0;
  }
  
  static void ath97_wdt_shutdown(struct platform_device *pdev)
  {
  	ath79_wdt_disable();
  }
  
  #ifdef CONFIG_OF
  static const struct of_device_id ath79_wdt_match[] = {
  	{ .compatible = "qca,ar7130-wdt" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, ath79_wdt_match);
  #endif
  
  static struct platform_driver ath79_wdt_driver = {
  	.probe		= ath79_wdt_probe,
  	.remove		= ath79_wdt_remove,
  	.shutdown	= ath97_wdt_shutdown,
  	.driver		= {
  		.name	= DRIVER_NAME,
  		.owner	= THIS_MODULE,
  		.of_match_table = of_match_ptr(ath79_wdt_match),
  	},
  };
  
  module_platform_driver(ath79_wdt_driver);
  
  MODULE_DESCRIPTION("Atheros AR71XX/AR724X/AR913X hardware watchdog driver");
  MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org");
  MODULE_AUTHOR("Imre Kaloz <kaloz@openwrt.org");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("platform:" DRIVER_NAME);