/*
   * drivers/watchdog/m54xx_wdt.c
   *
   * Watchdog driver for ColdFire MCF547x & MCF548x processors
   * Copyright 2010 (c) Philippe De Muyter <phdm@macqel.be>
   *
   * Adapted from the IXP4xx watchdog driver, which carries these notices:
   *
   *  Author: Deepak Saxena <dsaxena@plexity.net>
   *
   *  Copyright 2004 (c) MontaVista, Software, Inc.
   *  Based on sa1100 driver, Copyright (C) 2000 Oleg Drokin <green@crimea.edu>
   *
   * This file is licensed under  the terms of the GNU General Public
   * License version 2. This program is licensed "as is" without any
   * warranty of any kind, whether express or implied.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>
  #include <linux/init.h>
  #include <linux/bitops.h>
  #include <linux/ioport.h>
  #include <linux/uaccess.h>
  
  #include <asm/coldfire.h>
  #include <asm/m54xxsim.h>
  #include <asm/m54xxgpt.h>
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  static unsigned int heartbeat = 30;	/* (secs) Default is 0.5 minute */
  static unsigned long wdt_status;
  
  #define	WDT_IN_USE		0
  #define	WDT_OK_TO_CLOSE		1
  
  static void wdt_enable(void)
  {
  	unsigned int gms0;
  
  	/* preserve GPIO usage, if any */
  	gms0 = __raw_readl(MCF_GPT_GMS0);
  	if (gms0 & MCF_GPT_GMS_TMS_GPIO)
  		gms0 &= (MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_GPIO_MASK
  							| MCF_GPT_GMS_OD);
  	else
  		gms0 = MCF_GPT_GMS_TMS_GPIO | MCF_GPT_GMS_OD;
  	__raw_writel(gms0, MCF_GPT_GMS0);
  	__raw_writel(MCF_GPT_GCIR_PRE(heartbeat*(MCF_BUSCLK/0xffff)) |
  			MCF_GPT_GCIR_CNT(0xffff), MCF_GPT_GCIR0);
  	gms0 |= MCF_GPT_GMS_OCPW(0xA5) | MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE;
  	__raw_writel(gms0, MCF_GPT_GMS0);
  }
  
  static void wdt_disable(void)
  {
  	unsigned int gms0;
  
  	/* disable watchdog */
  	gms0 = __raw_readl(MCF_GPT_GMS0);
  	gms0 &= ~(MCF_GPT_GMS_WDEN | MCF_GPT_GMS_CE);
  	__raw_writel(gms0, MCF_GPT_GMS0);
  }
  
  static void wdt_keepalive(void)
  {
  	unsigned int gms0;
  
  	gms0 = __raw_readl(MCF_GPT_GMS0);
  	gms0 |= MCF_GPT_GMS_OCPW(0xA5);
  	__raw_writel(gms0, MCF_GPT_GMS0);
  }
  
  static int m54xx_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(WDT_IN_USE, &wdt_status))
  		return -EBUSY;
  
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  	wdt_enable();
  	return nonseekable_open(inode, file);
  }
  
  static ssize_t m54xx_wdt_write(struct file *file, const char *data,
  						size_t len, loff_t *ppos)
  {
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  			for (i = 0; i != len; i++) {
  				char c;
  
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					set_bit(WDT_OK_TO_CLOSE, &wdt_status);
  			}
  		}
  		wdt_keepalive();
  	}
  	return len;
  }
  
  static const struct watchdog_info ident = {
  	.options	= WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT |
  				WDIOF_KEEPALIVEPING,
  	.identity	= "Coldfire M54xx Watchdog",
  };
  
  static long m54xx_wdt_ioctl(struct file *file, unsigned int cmd,
  							 unsigned long arg)
  {
  	int ret = -ENOTTY;
  	int time;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user((struct watchdog_info *)arg, &ident,
  				   sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  		ret = put_user(0, (int *)arg);
  		break;
  
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(0, (int *)arg);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		wdt_keepalive();
  		ret = 0;
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		ret = get_user(time, (int *)arg);
  		if (ret)
  			break;
  
  		if (time <= 0 || time > 30) {
  			ret = -EINVAL;
  			break;
  		}
  
  		heartbeat = time;
  		wdt_enable();
  		/* Fall through */
  
  	case WDIOC_GETTIMEOUT:
  		ret = put_user(heartbeat, (int *)arg);
  		break;
  	}
  	return ret;
  }
  
  static int m54xx_wdt_release(struct inode *inode, struct file *file)
  {
  	if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
  		wdt_disable();
  	else {
  		pr_crit("Device closed unexpectedly - timer will not stop
  ");
  		wdt_keepalive();
  	}
  	clear_bit(WDT_IN_USE, &wdt_status);
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	return 0;
  }
  
  
  static const struct file_operations m54xx_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= m54xx_wdt_write,
  	.unlocked_ioctl	= m54xx_wdt_ioctl,
  	.open		= m54xx_wdt_open,
  	.release	= m54xx_wdt_release,
  };
  
  static struct miscdevice m54xx_wdt_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &m54xx_wdt_fops,
  };
  
  static int __init m54xx_wdt_init(void)
  {
  	if (!request_mem_region(MCF_GPT_GCIR0, 4, "Coldfire M54xx Watchdog")) {
  		pr_warn("I/O region busy
  ");
  		return -EBUSY;
  	}
  	pr_info("driver is loaded
  ");
  
  	return misc_register(&m54xx_wdt_miscdev);
  }
  
  static void __exit m54xx_wdt_exit(void)
  {
  	misc_deregister(&m54xx_wdt_miscdev);
  	release_mem_region(MCF_GPT_GCIR0, 4);
  }
  
  module_init(m54xx_wdt_init);
  module_exit(m54xx_wdt_exit);
  
  MODULE_AUTHOR("Philippe De Muyter <phdm@macqel.be>");
  MODULE_DESCRIPTION("Coldfire M54xx Watchdog");
  
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds (default 30s)");
  
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
  
  MODULE_LICENSE("GPL");