/*

   * Watchdog timer for PowerPC Book-E systems
   *
   * Author: Matthew McClintock

   * Maintainer: Kumar Gala <galak@kernel.crashing.org>

   *

   * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.

   *
   * 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;  either version 2 of the  License, or (at your
   * option) any later version.
   */

  #include <linux/module.h>
  #include <linux/fs.h>

  #include <linux/smp.h>

  #include <linux/miscdevice.h>
  #include <linux/notifier.h>
  #include <linux/watchdog.h>

  #include <linux/uaccess.h>

  
  #include <asm/reg_booke.h>

  #include <asm/system.h>

  #include <asm/time.h>
  #include <asm/div64.h>

  /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.

   * Also, the wdt_period sets the watchdog timer period timeout.
   * For E500 cpus the wdt_period sets which bit changing from 0->1 will
   * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
   * first time nothing will happen, the second time a watchdog exception will
   * occur, and the final time the board will reset.
   */

  u32 booke_wdt_enabled;

  u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;

  
  #ifdef	CONFIG_FSL_BOOKE

  #define WDTP(x)		((((x)&0x3)<<30)|(((x)&0x3c)<<15))

  #define WDTP_MASK	(WDTP(0x3f))

  #else
  #define WDTP(x)		(TCR_WP(x))

  #define WDTP_MASK	(TCR_WP_MASK)

  #endif

  static DEFINE_SPINLOCK(booke_wdt_lock);

  /* For the specified period, determine the number of seconds
   * corresponding to the reset time.  There will be a watchdog
   * exception at approximately 3/5 of this time.
   *
   * The formula to calculate this is given by:
   * 2.5 * (2^(63-period+1)) / timebase_freq
   *
   * In order to simplify things, we assume that period is
   * at least 1.  This will still result in a very long timeout.
   */
  static unsigned long long period_to_sec(unsigned int period)
  {
  	unsigned long long tmp = 1ULL << (64 - period);
  	unsigned long tmp2 = ppc_tb_freq;
  
  	/* tmp may be a very large number and we don't want to overflow,
  	 * so divide the timebase freq instead of multiplying tmp
  	 */
  	tmp2 = tmp2 / 5 * 2;
  
  	do_div(tmp, tmp2);
  	return tmp;
  }
  
  /*
   * This procedure will find the highest period which will give a timeout
   * greater than the one required. e.g. for a bus speed of 66666666 and
   * and a parameter of 2 secs, then this procedure will return a value of 38.
   */
  static unsigned int sec_to_period(unsigned int secs)
  {
  	unsigned int period;
  	for (period = 63; period > 0; period--) {
  		if (period_to_sec(period) >= secs)
  			return period;
  	}
  	return 0;
  }

  static void __booke_wdt_set(void *data)
  {
  	u32 val;
  
  	val = mfspr(SPRN_TCR);
  	val &= ~WDTP_MASK;
  	val |= WDTP(booke_wdt_period);
  
  	mtspr(SPRN_TCR, val);
  }
  
  static void booke_wdt_set(void)
  {
  	on_each_cpu(__booke_wdt_set, NULL, 0);
  }

  static void __booke_wdt_ping(void *data)

  {
  	mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
  }

  static void booke_wdt_ping(void)
  {

  	on_each_cpu(__booke_wdt_ping, NULL, 0);

  }
  
  static void __booke_wdt_enable(void *data)

  {
  	u32 val;

  	/* clear status before enabling watchdog */

  	__booke_wdt_ping(NULL);

  	val = mfspr(SPRN_TCR);

  	val &= ~WDTP_MASK;

  	val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(booke_wdt_period));

  
  	mtspr(SPRN_TCR, val);
  }

  /**
   * booke_wdt_disable - disable the watchdog on the given CPU
   *
   * This function is called on each CPU.  It disables the watchdog on that CPU.
   *
   * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
   * effectively disable the watchdog by setting its period to the maximum value.
   */
  static void __booke_wdt_disable(void *data)
  {
  	u32 val;
  
  	val = mfspr(SPRN_TCR);
  	val &= ~(TCR_WIE | WDTP_MASK);
  	mtspr(SPRN_TCR, val);
  
  	/* clear status to make sure nothing is pending */
  	__booke_wdt_ping(NULL);
  
  }

  static ssize_t booke_wdt_write(struct file *file, const char __user *buf,

  				size_t count, loff_t *ppos)
  {
  	booke_wdt_ping();
  	return count;
  }

  static struct watchdog_info ident = {

  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
  	.identity = "PowerPC Book-E Watchdog",

  };

  static long booke_wdt_ioctl(struct file *file,
  				unsigned int cmd, unsigned long arg)

  {
  	u32 tmp = 0;

  	u32 __user *p = (u32 __user *)arg;

  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:

  		if (copy_to_user((void *)arg, &ident, sizeof(ident)))

  			return -EFAULT;
  	case WDIOC_GETSTATUS:

  		return put_user(0, p);

  	case WDIOC_GETBOOTSTATUS:
  		/* XXX: something is clearing TSR */
  		tmp = mfspr(SPRN_TSR) & TSR_WRS(3);

  		/* returns CARDRESET if last reset was caused by the WDT */
  		return (tmp ? WDIOF_CARDRESET : 0);

  	case WDIOC_SETOPTIONS:
  		if (get_user(tmp, p))
  			return -EINVAL;
  		if (tmp == WDIOS_ENABLECARD) {
  			booke_wdt_ping();
  			break;
  		} else
  			return -EINVAL;
  		return 0;

  	case WDIOC_KEEPALIVE:
  		booke_wdt_ping();
  		return 0;
  	case WDIOC_SETTIMEOUT:

  		if (get_user(tmp, p))

  			return -EFAULT;

  #ifdef	CONFIG_FSL_BOOKE
  		/* period of 1 gives the largest possible timeout */
  		if (tmp > period_to_sec(1))
  			return -EINVAL;
  		booke_wdt_period = sec_to_period(tmp);
  #else
  		booke_wdt_period = tmp;
  #endif

  		booke_wdt_set();

  		return 0;
  	case WDIOC_GETTIMEOUT:

  		return put_user(booke_wdt_period, p);

  	default:

  		return -ENOTTY;

  	}
  
  	return 0;
  }

  /* wdt_is_active stores wether or not the /dev/watchdog device is opened */
  static unsigned long wdt_is_active;

  static int booke_wdt_open(struct inode *inode, struct file *file)

  {

  	/* /dev/watchdog can only be opened once */
  	if (test_and_set_bit(0, &wdt_is_active))
  		return -EBUSY;

  	spin_lock(&booke_wdt_lock);

  	if (booke_wdt_enabled == 0) {
  		booke_wdt_enabled = 1;

  		on_each_cpu(__booke_wdt_enable, NULL, 0);

  		pr_debug("booke_wdt: watchdog enabled (timeout = %llu sec)
  ",
  			period_to_sec(booke_wdt_period));

  	}

  	spin_unlock(&booke_wdt_lock);

  	return nonseekable_open(inode, file);

  }

  static int booke_wdt_release(struct inode *inode, struct file *file)
  {

  #ifndef CONFIG_WATCHDOG_NOWAYOUT
  	/* Normally, the watchdog is disabled when /dev/watchdog is closed, but
  	 * if CONFIG_WATCHDOG_NOWAYOUT is defined, then it means that the
  	 * watchdog should remain enabled.  So we disable it only if
  	 * CONFIG_WATCHDOG_NOWAYOUT is not defined.
  	 */

  	on_each_cpu(__booke_wdt_disable, NULL, 0);
  	booke_wdt_enabled = 0;

  	pr_debug("booke_wdt: watchdog disabled
  ");

  #endif
  
  	clear_bit(0, &wdt_is_active);

  
  	return 0;
  }

  static const struct file_operations booke_wdt_fops = {

  	.owner = THIS_MODULE,
  	.llseek = no_llseek,
  	.write = booke_wdt_write,

  	.unlocked_ioctl = booke_wdt_ioctl,

  	.open = booke_wdt_open,

  	.release = booke_wdt_release,

  };
  
  static struct miscdevice booke_wdt_miscdev = {

  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &booke_wdt_fops,

  };
  
  static void __exit booke_wdt_exit(void)
  {
  	misc_deregister(&booke_wdt_miscdev);
  }

  static int __init booke_wdt_init(void)
  {
  	int ret = 0;

  	pr_info("booke_wdt: powerpc book-e watchdog driver loaded
  ");

  	ident.firmware_version = cur_cpu_spec->pvr_value;

  
  	ret = misc_register(&booke_wdt_miscdev);
  	if (ret) {

  		pr_err("booke_wdt: cannot register device (minor=%u, ret=%i)
  ",
  		       WATCHDOG_MINOR, ret);

  		return ret;
  	}

  	spin_lock(&booke_wdt_lock);

  	if (booke_wdt_enabled == 1) {

  		pr_info("booke_wdt: watchdog enabled (timeout = %llu sec)
  ",
  			period_to_sec(booke_wdt_period));

  		on_each_cpu(__booke_wdt_enable, NULL, 0);

  	}

  	spin_unlock(&booke_wdt_lock);

  
  	return ret;
  }

  
  module_init(booke_wdt_init);
  module_exit(booke_wdt_exit);
  
  MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
  MODULE_LICENSE("GPL");