/*
   * Watchdog driver for SiByte SB1 SoCs
   *
   * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@lsi.com>
   *
   * This driver is intended to make the second of two hardware watchdogs
   * on the Sibyte 12XX and 11XX SoCs available to the user.  There are two
   * such devices available on the SoC, but it seems that there isn't an
   * enumeration class for watchdogs in Linux like there is for RTCs.
   * The second is used rather than the first because it uses IRQ 1,
   * thereby avoiding all that IRQ 0 problematic nonsense.
   *
   * I have not tried this driver on a 1480 processor; it might work
   * just well enough to really screw things up.
   *
   * It is a simple timer, and there is an interrupt that is raised the
   * first time the timer expires.  The second time it expires, the chip
   * is reset and there is no way to redirect that NMI.  Which could
   * be problematic in some cases where this chip is sitting on the HT
   * bus and has just taken responsibility for providing a cache block.
   * Since the reset can't be redirected to the external reset pin, it is
   * possible that other HT connected processors might hang and not reset.
   * For Linux, a soft reset would probably be even worse than a hard reset.
   * There you have it.
   *
   * The timer takes 23 bits of a 64 bit register (?) as a count value,
   * and decrements the count every microsecond, for a max value of
   * 0x7fffff usec or about 8.3ish seconds.
   *
   * This watchdog borrows some user semantics from the softdog driver,
   * in that if you close the fd, it leaves the watchdog running, unless
   * you previously wrote a 'V' to the fd, in which case it disables
   * the watchdog when you close the fd like some other drivers.
   *
   * Based on various other watchdog drivers, which are probably all
   * loosely based on something Alan Cox wrote years ago.
   *
   *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   *						All Rights Reserved.
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	version 1 or 2 as published by the Free Software Foundation.
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/io.h>
  #include <linux/uaccess.h>
  #include <linux/fs.h>
  #include <linux/reboot.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/interrupt.h>
  
  #include <asm/sibyte/sb1250.h>
  #include <asm/sibyte/sb1250_regs.h>
  #include <asm/sibyte/sb1250_int.h>
  #include <asm/sibyte/sb1250_scd.h>
  
  static DEFINE_SPINLOCK(sbwd_lock);
  
  /*
   * set the initial count value of a timer
   *
   * wdog is the iomem address of the cfg register
   */
  void sbwdog_set(char __iomem *wdog, unsigned long t)
  {
  	spin_lock(&sbwd_lock);
  	__raw_writeb(0, wdog);
  	__raw_writeq(t & 0x7fffffUL, wdog - 0x10);
  	spin_unlock(&sbwd_lock);
  }
  
  /*
   * cause the timer to [re]load it's initial count and start counting
   * all over again
   *
   * wdog is the iomem address of the cfg register
   */
  void sbwdog_pet(char __iomem *wdog)
  {
  	spin_lock(&sbwd_lock);
  	__raw_writeb(__raw_readb(wdog) | 1, wdog);
  	spin_unlock(&sbwd_lock);
  }
  
  static unsigned long sbwdog_gate; /* keeps it to one thread only */
  static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));
  static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));
  static unsigned long timeout = 0x7fffffUL;	/* useconds: 8.3ish secs. */
  static int expect_close;
  
  static const struct watchdog_info ident = {
  	.options	= WDIOF_CARDRESET | WDIOF_SETTIMEOUT |
  					WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  	.identity	= "SiByte Watchdog",
  };
  
  /*
   * Allow only a single thread to walk the dog
   */
  static int sbwdog_open(struct inode *inode, struct file *file)
  {
  	nonseekable_open(inode, file);
  	if (test_and_set_bit(0, &sbwdog_gate))
  		return -EBUSY;
  	__module_get(THIS_MODULE);
  
  	/*
  	 * Activate the timer
  	 */
  	sbwdog_set(user_dog, timeout);
  	__raw_writeb(1, user_dog);
  
  	return 0;
  }
  
  /*
   * Put the dog back in the kennel.
   */
  static int sbwdog_release(struct inode *inode, struct file *file)
  {
  	if (expect_close == 42) {
  		__raw_writeb(0, user_dog);
  		module_put(THIS_MODULE);
  	} else {
  		pr_crit("%s: Unexpected close, not stopping watchdog!
  ",
  			ident.identity);
  		sbwdog_pet(user_dog);
  	}
  	clear_bit(0, &sbwdog_gate);
  	expect_close = 0;
  
  	return 0;
  }
  
  /*
   * 42 - the answer
   */
  static ssize_t sbwdog_write(struct file *file, const char __user *data,
  			size_t len, loff_t *ppos)
  {
  	int i;
  
  	if (len) {
  		/*
  		 * restart the timer
  		 */
  		expect_close = 0;
  
  		for (i = 0; i != len; i++) {
  			char c;
  
  			if (get_user(c, data + i))
  				return -EFAULT;
  			if (c == 'V')
  				expect_close = 42;
  		}
  		sbwdog_pet(user_dog);
  	}
  
  	return len;
  }
  
  static long sbwdog_ioctl(struct file *file, unsigned int cmd,
  						unsigned long arg)
  {
  	int ret = -ENOTTY;
  	unsigned long time;
  	void __user *argp = (void __user *)arg;
  	int __user *p = argp;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(0, p);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		sbwdog_pet(user_dog);
  		ret = 0;
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		ret = get_user(time, p);
  		if (ret)
  			break;
  
  		time *= 1000000;
  		if (time > 0x7fffffUL) {
  			ret = -EINVAL;
  			break;
  		}
  		timeout = time;
  		sbwdog_set(user_dog, timeout);
  		sbwdog_pet(user_dog);
  
  	case WDIOC_GETTIMEOUT:
  		/*
  		 * get the remaining count from the ... count register
  		 * which is 1*8 before the config register
  		 */
  		ret = put_user((u32)__raw_readq(user_dog - 8) / 1000000, p);
  		break;
  	}
  	return ret;
  }
  
  /*
   *	Notifier for system down
   */
  static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code,
  								void *erf)
  {
  	if (code == SYS_DOWN || code == SYS_HALT) {
  		/*
  		 * sit and sit
  		 */
  		__raw_writeb(0, user_dog);
  		__raw_writeb(0, kern_dog);
  	}
  
  	return NOTIFY_DONE;
  }
  
  static const struct file_operations sbwdog_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= sbwdog_write,
  	.unlocked_ioctl	= sbwdog_ioctl,
  	.open		= sbwdog_open,
  	.release	= sbwdog_release,
  };
  
  static struct miscdevice sbwdog_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &sbwdog_fops,
  };
  
  static struct notifier_block sbwdog_notifier = {
  	.notifier_call	= sbwdog_notify_sys,
  };
  
  /*
   * interrupt handler
   *
   * doesn't do a whole lot for user, but oh so cleverly written so kernel
   * code can use it to re-up the watchdog, thereby saving the kernel from
   * having to create and maintain a timer, just to tickle another timer,
   * which is just so wrong.
   */
  irqreturn_t sbwdog_interrupt(int irq, void *addr)
  {
  	unsigned long wd_init;
  	char *wd_cfg_reg = (char *)addr;
  	u8 cfg;
  
  	cfg = __raw_readb(wd_cfg_reg);
  	wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff;
  
  	/*
  	 * if it's the second watchdog timer, it's for those users
  	 */
  	if (wd_cfg_reg == user_dog)
  		pr_crit("%s in danger of initiating system reset "
  			"in %ld.%01ld seconds
  ",
  			ident.identity,
  			wd_init / 1000000, (wd_init / 100000) % 10);
  	else
  		cfg |= 1;
  
  	__raw_writeb(cfg, wd_cfg_reg);
  
  	return IRQ_HANDLED;
  }
  
  static int __init sbwdog_init(void)
  {
  	int ret;
  
  	/*
  	 * register a reboot notifier
  	 */
  	ret = register_reboot_notifier(&sbwdog_notifier);
  	if (ret) {
  		pr_err("%s: cannot register reboot notifier (err=%d)
  ",
  		       ident.identity, ret);
  		return ret;
  	}
  
  	/*
  	 * get the resources
  	 */
  
  	ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
  		ident.identity, (void *)user_dog);
  	if (ret) {
  		pr_err("%s: failed to request irq 1 - %d
  ",
  		       ident.identity, ret);
  		goto out;
  	}
  
  	ret = misc_register(&sbwdog_miscdev);
  	if (ret == 0) {
  		pr_info("%s: timeout is %ld.%ld secs
  ",
  			ident.identity,
  			timeout / 1000000, (timeout / 100000) % 10);
  		return 0;
  	}
  	free_irq(1, (void *)user_dog);
  out:
  	unregister_reboot_notifier(&sbwdog_notifier);
  
  	return ret;
  }
  
  static void __exit sbwdog_exit(void)
  {
  	misc_deregister(&sbwdog_miscdev);
  	free_irq(1, (void *)user_dog);
  	unregister_reboot_notifier(&sbwdog_notifier);
  }
  
  module_init(sbwdog_init);
  module_exit(sbwdog_exit);
  
  MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
  MODULE_DESCRIPTION("SiByte Watchdog");
  
  module_param(timeout, ulong, 0);
  MODULE_PARM_DESC(timeout,
        "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");
  
  MODULE_LICENSE("GPL");
  
  /*
   * example code that can be put in a platform code area to utilize the
   * first watchdog timer for the kernels own purpose.
  
  void platform_wd_setup(void)
  {
  	int ret;
  
  	ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
  		"Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0));
  	if (ret) {
  		pr_crit("Watchdog IRQ zero(0) failed to be requested - %d
  ", ret);
  	}
  }
  
  
   */