/*
   * drivers/char/watchdog/max63xx_wdt.c
   *
   * Driver for max63{69,70,71,72,73,74} watchdog timers
   *
   * Copyright (C) 2009 Marc Zyngier <maz@misterjones.org>
   *
   * 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.
   *
   * This driver assumes the watchdog pins are memory mapped (as it is
   * the case for the Arcom Zeus). Should it be connected over GPIOs or
   * another interface, some abstraction will have to be introduced.
   */
  
  #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/platform_device.h>
  #include <linux/spinlock.h>
  #include <linux/uaccess.h>
  #include <linux/io.h>
  #include <linux/device.h>

  #include <linux/slab.h>

  
  #define DEFAULT_HEARTBEAT 60
  #define MAX_HEARTBEAT     60
  
  static int heartbeat = DEFAULT_HEARTBEAT;
  static int nowayout  = WATCHDOG_NOWAYOUT;
  
  /*
   * Memory mapping: a single byte, 3 first lower bits to select bit 3
   * to ping the watchdog.
   */
  #define MAX6369_WDSET	(7 << 0)

  #define MAX6369_WDI	(1 << 3)

  
  static DEFINE_SPINLOCK(io_lock);
  
  static unsigned long wdt_status;
  #define WDT_IN_USE	0
  #define WDT_RUNNING	1
  #define WDT_OK_TO_CLOSE 2
  
  static int nodelay;
  static struct resource	*wdt_mem;
  static void __iomem	*wdt_base;
  static struct platform_device *max63xx_pdev;
  
  /*
   * The timeout values used are actually the absolute minimum the chip
   * offers. Typical values on my board are slightly over twice as long
   * (10s setting ends up with a 25s timeout), and can be up to 3 times
   * the nominal setting (according to the datasheet). So please take
   * these values with a grain of salt. Same goes for the initial delay
   * "feature". Only max6373/74 have a few settings without this initial
   * delay (selected with the "nodelay" parameter).
   *
   * I also decided to remove from the tables any timeout smaller than a
   * second, as it looked completly overkill...
   */
  
  /* Timeouts in second */
  struct max63xx_timeout {
  	u8 wdset;
  	u8 tdelay;
  	u8 twd;
  };
  
  static struct max63xx_timeout max6369_table[] = {
  	{ 5,  1,  1 },
  	{ 6, 10, 10 },
  	{ 7, 60, 60 },
  	{ },
  };
  
  static struct max63xx_timeout max6371_table[] = {
  	{ 6, 60,  3 },
  	{ 7, 60, 60 },
  	{ },
  };
  
  static struct max63xx_timeout max6373_table[] = {
  	{ 2, 60,  1 },
  	{ 5,  0,  1 },
  	{ 1,  3,  3 },
  	{ 7, 60, 10 },
  	{ 6,  0, 10 },
  	{ },
  };
  
  static struct max63xx_timeout *current_timeout;
  
  static struct max63xx_timeout *
  max63xx_select_timeout(struct max63xx_timeout *table, int value)
  {
  	while (table->twd) {
  		if (value <= table->twd) {
  			if (nodelay && table->tdelay == 0)
  				return table;
  
  			if (!nodelay)
  				return table;
  		}
  
  		table++;
  	}
  
  	return NULL;
  }
  
  static void max63xx_wdt_ping(void)
  {
  	u8 val;
  
  	spin_lock(&io_lock);
  
  	val = __raw_readb(wdt_base);
  
  	__raw_writeb(val | MAX6369_WDI, wdt_base);
  	__raw_writeb(val & ~MAX6369_WDI, wdt_base);
  
  	spin_unlock(&io_lock);
  }
  
  static void max63xx_wdt_enable(struct max63xx_timeout *entry)
  {
  	u8 val;
  
  	if (test_and_set_bit(WDT_RUNNING, &wdt_status))
  		return;
  
  	spin_lock(&io_lock);
  
  	val = __raw_readb(wdt_base);
  	val &= ~MAX6369_WDSET;
  	val |= entry->wdset;
  	__raw_writeb(val, wdt_base);
  
  	spin_unlock(&io_lock);
  
  	/* check for a edge triggered startup */
  	if (entry->tdelay == 0)
  		max63xx_wdt_ping();
  }
  
  static void max63xx_wdt_disable(void)
  {

  	u8 val;

  	spin_lock(&io_lock);

  	val = __raw_readb(wdt_base);
  	val &= ~MAX6369_WDSET;
  	val |= 3;
  	__raw_writeb(val, wdt_base);

  
  	spin_unlock(&io_lock);
  
  	clear_bit(WDT_RUNNING, &wdt_status);
  }
  
  static int max63xx_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(WDT_IN_USE, &wdt_status))
  		return -EBUSY;
  
  	max63xx_wdt_enable(current_timeout);
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	return nonseekable_open(inode, file);
  }
  
  static ssize_t max63xx_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);
  			}
  		}
  
  		max63xx_wdt_ping();
  	}
  
  	return len;
  }
  
  static const struct watchdog_info ident = {
  	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
  	.identity = "max63xx Watchdog",
  };
  
  static long max63xx_wdt_ioctl(struct file *file, unsigned int cmd,
  			      unsigned long arg)
  {
  	int ret = -ENOTTY;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		ret = copy_to_user((struct watchdog_info *)arg, &ident,
  				   sizeof(ident)) ? -EFAULT : 0;
  		break;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		ret = put_user(0, (int *)arg);
  		break;
  
  	case WDIOC_KEEPALIVE:
  		max63xx_wdt_ping();
  		ret = 0;
  		break;
  
  	case WDIOC_GETTIMEOUT:
  		ret = put_user(heartbeat, (int *)arg);
  		break;
  	}
  	return ret;
  }
  
  static int max63xx_wdt_release(struct inode *inode, struct file *file)
  {
  	if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
  		max63xx_wdt_disable();
  	else
  		dev_crit(&max63xx_pdev->dev,
  			 "device closed unexpectedly - timer will not stop
  ");
  
  	clear_bit(WDT_IN_USE, &wdt_status);
  	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
  
  	return 0;
  }
  
  static const struct file_operations max63xx_wdt_fops = {
  	.owner		= THIS_MODULE,
  	.llseek		= no_llseek,
  	.write		= max63xx_wdt_write,
  	.unlocked_ioctl	= max63xx_wdt_ioctl,
  	.open		= max63xx_wdt_open,
  	.release	= max63xx_wdt_release,
  };
  
  static struct miscdevice max63xx_wdt_miscdev = {
  	.minor	= WATCHDOG_MINOR,
  	.name	= "watchdog",
  	.fops	= &max63xx_wdt_fops,
  };
  
  static int __devinit max63xx_wdt_probe(struct platform_device *pdev)
  {
  	int ret = 0;
  	int size;

  	struct device *dev = &pdev->dev;
  	struct max63xx_timeout *table;
  
  	table = (struct max63xx_timeout *)pdev->id_entry->driver_data;
  
  	if (heartbeat < 1 || heartbeat > MAX_HEARTBEAT)
  		heartbeat = DEFAULT_HEARTBEAT;
  
  	dev_info(dev, "requesting %ds heartbeat
  ", heartbeat);
  	current_timeout = max63xx_select_timeout(table, heartbeat);
  
  	if (!current_timeout) {
  		dev_err(dev, "unable to satisfy heartbeat request
  ");
  		return -EINVAL;
  	}
  
  	dev_info(dev, "using %ds heartbeat with %ds initial delay
  ",
  		 current_timeout->twd, current_timeout->tdelay);
  
  	heartbeat = current_timeout->twd;
  
  	max63xx_pdev = pdev;

  	wdt_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (wdt_mem == NULL) {

  		dev_err(dev, "failed to get memory region resource
  ");
  		return -ENOENT;
  	}

  	size = resource_size(wdt_mem);
  	if (!request_mem_region(wdt_mem->start, size, pdev->name)) {

  		dev_err(dev, "failed to get memory region
  ");
  		return -ENOENT;
  	}

  	wdt_base = ioremap(wdt_mem->start, size);

  	if (!wdt_base) {
  		dev_err(dev, "failed to map memory region
  ");
  		ret = -ENOMEM;
  		goto out_request;
  	}
  
  	ret = misc_register(&max63xx_wdt_miscdev);
  	if (ret < 0) {
  		dev_err(dev, "cannot register misc device
  ");
  		goto out_unmap;
  	}
  
  	return 0;
  
  out_unmap:
  	iounmap(wdt_base);
  out_request:

  	release_mem_region(wdt_mem->start, size);
  	wdt_mem = NULL;

  
  	return ret;
  }
  
  static int __devexit max63xx_wdt_remove(struct platform_device *pdev)
  {
  	misc_deregister(&max63xx_wdt_miscdev);
  	if (wdt_mem) {

  		release_mem_region(wdt_mem->start, resource_size(wdt_mem));

  		wdt_mem = NULL;
  	}
  
  	if (wdt_base)
  		iounmap(wdt_base);
  
  	return 0;
  }
  
  static struct platform_device_id max63xx_id_table[] = {
  	{ "max6369_wdt", (kernel_ulong_t)max6369_table, },
  	{ "max6370_wdt", (kernel_ulong_t)max6369_table, },
  	{ "max6371_wdt", (kernel_ulong_t)max6371_table, },
  	{ "max6372_wdt", (kernel_ulong_t)max6371_table, },
  	{ "max6373_wdt", (kernel_ulong_t)max6373_table, },
  	{ "max6374_wdt", (kernel_ulong_t)max6373_table, },
  	{ },
  };
  MODULE_DEVICE_TABLE(platform, max63xx_id_table);
  
  static struct platform_driver max63xx_wdt_driver = {
  	.probe		= max63xx_wdt_probe,
  	.remove		= __devexit_p(max63xx_wdt_remove),
  	.id_table	= max63xx_id_table,
  	.driver		= {
  		.name	= "max63xx_wdt",
  		.owner	= THIS_MODULE,
  	},
  };

  module_platform_driver(max63xx_wdt_driver);

  
  MODULE_AUTHOR("Marc Zyngier <maz@misterjones.org>");
  MODULE_DESCRIPTION("max63xx Watchdog Driver");
  
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat,
  		 "Watchdog heartbeat period in seconds from 1 to "
  		 __MODULE_STRING(MAX_HEARTBEAT) ", default "
  		 __MODULE_STRING(DEFAULT_HEARTBEAT));
  
  module_param(nowayout, int, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  module_param(nodelay, int, 0);
  MODULE_PARM_DESC(nodelay,
  		 "Force selection of a timeout setting without initial delay "
  		 "(max6373/74 only, default=0)");
  
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);