text: // SPDX-License-Identifier: GPL-2.0+
  /*
   * drivers/watchdog/ar7_wdt.c
   *
   * Copyright (C) 2007 Nicolas Thill <nico@openwrt.org>
   * Copyright (c) 2005 Enrik Berkhan <Enrik.Berkhan@akk.org>
   *
   * Some code taken from:
   * National Semiconductor SCx200 Watchdog support
   * Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/errno.h>
  #include <linux/miscdevice.h>
  #include <linux/platform_device.h>
  #include <linux/watchdog.h>
  #include <linux/fs.h>
  #include <linux/ioport.h>
  #include <linux/io.h>
  #include <linux/uaccess.h>
  #include <linux/clk.h>
  
  #include <asm/addrspace.h>
  #include <asm/mach-ar7/ar7.h>
  
  #define LONGNAME "TI AR7 Watchdog Timer"
  
  MODULE_AUTHOR("Nicolas Thill <nico@openwrt.org>");
  MODULE_DESCRIPTION(LONGNAME);
  MODULE_LICENSE("GPL");
  
  static int margin = 60;
  module_param(margin, int, 0);
  MODULE_PARM_DESC(margin, "Watchdog margin in seconds");
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
  
  #define READ_REG(x) readl((void __iomem *)&(x))
  #define WRITE_REG(x, v) writel((v), (void __iomem *)&(x))
  
  struct ar7_wdt {
  	u32 kick_lock;
  	u32 kick;
  	u32 change_lock;
  	u32 change;
  	u32 disable_lock;
  	u32 disable;
  	u32 prescale_lock;
  	u32 prescale;
  };
  
  static unsigned long wdt_is_open;
  static unsigned expect_close;
  static DEFINE_SPINLOCK(wdt_lock);
  
  /* XXX currently fixed, allows max margin ~68.72 secs */
  #define prescale_value 0xffff
  
  /* Resource of the WDT registers */
  static struct resource *ar7_regs_wdt;
  /* Pointer to the remapped WDT IO space */
  static struct ar7_wdt *ar7_wdt;
  
  static struct clk *vbus_clk;
  
  static void ar7_wdt_kick(u32 value)
  {
  	WRITE_REG(ar7_wdt->kick_lock, 0x5555);
  	if ((READ_REG(ar7_wdt->kick_lock) & 3) == 1) {
  		WRITE_REG(ar7_wdt->kick_lock, 0xaaaa);
  		if ((READ_REG(ar7_wdt->kick_lock) & 3) == 3) {
  			WRITE_REG(ar7_wdt->kick, value);
  			return;
  		}
  	}
  	pr_err("failed to unlock WDT kick reg\n");
  }
  
  static void ar7_wdt_prescale(u32 value)
  {
  	WRITE_REG(ar7_wdt->prescale_lock, 0x5a5a);
  	if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 1) {
  		WRITE_REG(ar7_wdt->prescale_lock, 0xa5a5);
  		if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 3) {
  			WRITE_REG(ar7_wdt->prescale, value);
  			return;
  		}
  	}
  	pr_err("failed to unlock WDT prescale reg\n");
  }
  
  static void ar7_wdt_change(u32 value)
  {
  	WRITE_REG(ar7_wdt->change_lock, 0x6666);
  	if ((READ_REG(ar7_wdt->change_lock) & 3) == 1) {
  		WRITE_REG(ar7_wdt->change_lock, 0xbbbb);
  		if ((READ_REG(ar7_wdt->change_lock) & 3) == 3) {
  			WRITE_REG(ar7_wdt->change, value);
  			return;
  		}
  	}
  	pr_err("failed to unlock WDT change reg\n");
  }
  
  static void ar7_wdt_disable(u32 value)
  {
  	WRITE_REG(ar7_wdt->disable_lock, 0x7777);
  	if ((READ_REG(ar7_wdt->disable_lock) & 3) == 1) {
  		WRITE_REG(ar7_wdt->disable_lock, 0xcccc);
  		if ((READ_REG(ar7_wdt->disable_lock) & 3) == 2) {
  			WRITE_REG(ar7_wdt->disable_lock, 0xdddd);
  			if ((READ_REG(ar7_wdt->disable_lock) & 3) == 3) {
  				WRITE_REG(ar7_wdt->disable, value);
  				return;
  			}
  		}
  	}
  	pr_err("failed to unlock WDT disable reg\n");
  }
  
  static void ar7_wdt_update_margin(int new_margin)
  {
  	u32 change;
  	u32 vbus_rate;
  
  	vbus_rate = clk_get_rate(vbus_clk);
  	change = new_margin * (vbus_rate / prescale_value);
  	if (change < 1)
  		change = 1;
  	if (change > 0xffff)
  		change = 0xffff;
  	ar7_wdt_change(change);
  	margin = change * prescale_value / vbus_rate;
  	pr_info("timer margin %d seconds (prescale %d, change %d, freq %d)\n",
  		margin, prescale_value, change, vbus_rate);
  }
  
  static void ar7_wdt_enable_wdt(void)
  {
  	pr_debug("enabling watchdog timer\n");
  	ar7_wdt_disable(1);
  	ar7_wdt_kick(1);
  }
  
  static void ar7_wdt_disable_wdt(void)
  {
  	pr_debug("disabling watchdog timer\n");
  	ar7_wdt_disable(0);
  }
  
  static int ar7_wdt_open(struct inode *inode, struct file *file)
  {
  	/* only allow one at a time */
  	if (test_and_set_bit(0, &wdt_is_open))
  		return -EBUSY;
  	ar7_wdt_enable_wdt();
  	expect_close = 0;
  
  	return stream_open(inode, file);
  }
  
  static int ar7_wdt_release(struct inode *inode, struct file *file)
  {
  	if (!expect_close)
  		pr_warn("watchdog device closed unexpectedly, will not disable the watchdog timer\n");
  	else if (!nowayout)
  		ar7_wdt_disable_wdt();
  	clear_bit(0, &wdt_is_open);
  	return 0;
  }
  
  static ssize_t ar7_wdt_write(struct file *file, const char *data,
  			     size_t len, loff_t *ppos)
  {
  	/* check for a magic close character */
  	if (len) {
  		size_t i;
  
  		spin_lock(&wdt_lock);
  		ar7_wdt_kick(1);
  		spin_unlock(&wdt_lock);
  
  		expect_close = 0;
  		for (i = 0; i < len; ++i) {
  			char c;
  			if (get_user(c, data + i))
  				return -EFAULT;
  			if (c == 'V')
  				expect_close = 1;
  		}
  
  	}
  	return len;
  }
  
  static long ar7_wdt_ioctl(struct file *file,
  					unsigned int cmd, unsigned long arg)
  {
  	static const struct watchdog_info ident = {
  		.identity = LONGNAME,
  		.firmware_version = 1,
  		.options = (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
  						WDIOF_MAGICCLOSE),
  	};
  	int new_margin;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		if (copy_to_user((struct watchdog_info *)arg, &ident,
  				sizeof(ident)))
  			return -EFAULT;
  		return 0;
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		if (put_user(0, (int *)arg))
  			return -EFAULT;
  		return 0;
  	case WDIOC_KEEPALIVE:
  		ar7_wdt_kick(1);
  		return 0;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_margin, (int *)arg))
  			return -EFAULT;
  		if (new_margin < 1)
  			return -EINVAL;
  
  		spin_lock(&wdt_lock);
  		ar7_wdt_update_margin(new_margin);
  		ar7_wdt_kick(1);
  		spin_unlock(&wdt_lock);
  		/* Fall through */
  
  	case WDIOC_GETTIMEOUT:
  		if (put_user(margin, (int *)arg))
  			return -EFAULT;
  		return 0;
  	default:
  		return -ENOTTY;
  	}
  }
  
  static const struct file_operations ar7_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.write		= ar7_wdt_write,
  	.unlocked_ioctl	= ar7_wdt_ioctl,
  	.open		= ar7_wdt_open,
  	.release	= ar7_wdt_release,
  	.llseek		= no_llseek,
  };
  
  static struct miscdevice ar7_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &ar7_wdt_fops,
  };
  
  static int ar7_wdt_probe(struct platform_device *pdev)
  {
  	int rc;
  
  	ar7_regs_wdt =
  		platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
  	ar7_wdt = devm_ioremap_resource(&pdev->dev, ar7_regs_wdt);
  	if (IS_ERR(ar7_wdt))
  		return PTR_ERR(ar7_wdt);
  
  	vbus_clk = clk_get(NULL, "vbus");
  	if (IS_ERR(vbus_clk)) {
  		pr_err("could not get vbus clock\n");
  		return PTR_ERR(vbus_clk);
  	}
  
  	ar7_wdt_disable_wdt();
  	ar7_wdt_prescale(prescale_value);
  	ar7_wdt_update_margin(margin);
  
  	rc = misc_register(&ar7_wdt_miscdev);
  	if (rc) {
  		pr_err("unable to register misc device\n");
  		goto out;
  	}
  	return 0;
  
  out:
  	clk_put(vbus_clk);
  	vbus_clk = NULL;
  	return rc;
  }
  
  static int ar7_wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&ar7_wdt_miscdev);
  	clk_put(vbus_clk);
  	vbus_clk = NULL;
  	return 0;
  }
  
  static void ar7_wdt_shutdown(struct platform_device *pdev)
  {
  	if (!nowayout)
  		ar7_wdt_disable_wdt();
  }
  
  static struct platform_driver ar7_wdt_driver = {
  	.probe = ar7_wdt_probe,
  	.remove = ar7_wdt_remove,
  	.shutdown = ar7_wdt_shutdown,
  	.driver = {
  		.name = "ar7_wdt",
  	},
  };
  
  module_platform_driver(ar7_wdt_driver);
  