/*
   * 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/err.h>

  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/types.h>
  #include <linux/kernel.h>

  #include <linux/watchdog.h>

  #include <linux/bitops.h>
  #include <linux/platform_device.h>
  #include <linux/spinlock.h>

  #include <linux/io.h>

  #include <linux/slab.h>

  
  #define DEFAULT_HEARTBEAT 60
  #define MAX_HEARTBEAT     60

  static unsigned int heartbeat = DEFAULT_HEARTBEAT;

  static bool 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)

  #define MAX6369_WDSET_DISABLED	3

  static int nodelay;

  
  struct max63xx_wdt {
  	struct watchdog_device wdd;
  	const struct max63xx_timeout *timeout;
  
  	/* memory mapping */
  	void __iomem *base;
  	spinlock_t lock;
  
  	/* WDI and WSET bits write access routines */
  	void (*ping)(struct max63xx_wdt *wdt);
  	void (*set)(struct max63xx_wdt *wdt, u8 set);
  };

  
  /*
   * 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 {

  	const u8 wdset;
  	const u8 tdelay;
  	const u8 twd;

  };

  static const struct max63xx_timeout max6369_table[] = {

  	{ 5,  1,  1 },
  	{ 6, 10, 10 },
  	{ 7, 60, 60 },
  	{ },
  };

  static const struct max63xx_timeout max6371_table[] = {

  	{ 6, 60,  3 },
  	{ 7, 60, 60 },
  	{ },
  };

  static const struct max63xx_timeout max6373_table[] = {

  	{ 2, 60,  1 },
  	{ 5,  0,  1 },
  	{ 1,  3,  3 },
  	{ 7, 60, 10 },
  	{ 6,  0, 10 },
  	{ },
  };

  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 int max63xx_wdt_ping(struct watchdog_device *wdd)

  {

  	struct max63xx_wdt *wdt = watchdog_get_drvdata(wdd);

  	wdt->ping(wdt);

  	return 0;

  }

  static int max63xx_wdt_start(struct watchdog_device *wdd)

  {

  	struct max63xx_wdt *wdt = watchdog_get_drvdata(wdd);

  	wdt->set(wdt, wdt->timeout->wdset);

  
  	/* check for a edge triggered startup */

  	if (wdt->timeout->tdelay == 0)
  		wdt->ping(wdt);

  	return 0;

  }

  static int max63xx_wdt_stop(struct watchdog_device *wdd)

  {

  	struct max63xx_wdt *wdt = watchdog_get_drvdata(wdd);

  	wdt->set(wdt, MAX6369_WDSET_DISABLED);

  	return 0;

  }

  static const struct watchdog_ops max63xx_wdt_ops = {
  	.owner = THIS_MODULE,
  	.start = max63xx_wdt_start,
  	.stop = max63xx_wdt_stop,
  	.ping = max63xx_wdt_ping,

  };

  static const struct watchdog_info max63xx_wdt_info = {
  	.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  	.identity = "max63xx Watchdog",

  };

  static void max63xx_mmap_ping(struct max63xx_wdt *wdt)
  {
  	u8 val;
  
  	spin_lock(&wdt->lock);
  
  	val = __raw_readb(wdt->base);
  
  	__raw_writeb(val | MAX6369_WDI, wdt->base);
  	__raw_writeb(val & ~MAX6369_WDI, wdt->base);
  
  	spin_unlock(&wdt->lock);
  }
  
  static void max63xx_mmap_set(struct max63xx_wdt *wdt, u8 set)
  {
  	u8 val;
  
  	spin_lock(&wdt->lock);
  
  	val = __raw_readb(wdt->base);
  	val &= ~MAX6369_WDSET;
  	val |= set & MAX6369_WDSET;
  	__raw_writeb(val, wdt->base);
  
  	spin_unlock(&wdt->lock);
  }
  
  static int max63xx_mmap_init(struct platform_device *p, struct max63xx_wdt *wdt)
  {
  	struct resource *mem = platform_get_resource(p, IORESOURCE_MEM, 0);
  
  	wdt->base = devm_ioremap_resource(&p->dev, mem);
  	if (IS_ERR(wdt->base))
  		return PTR_ERR(wdt->base);
  
  	spin_lock_init(&wdt->lock);
  
  	wdt->ping = max63xx_mmap_ping;
  	wdt->set = max63xx_mmap_set;
  	return 0;
  }

  static int max63xx_wdt_probe(struct platform_device *pdev)

  {

  	struct max63xx_wdt *wdt;

  	struct max63xx_timeout *table;

  	int err;
  
  	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
  	if (!wdt)
  		return -ENOMEM;

  
  	table = (struct max63xx_timeout *)pdev->id_entry->driver_data;
  
  	if (heartbeat < 1 || heartbeat > MAX_HEARTBEAT)
  		heartbeat = DEFAULT_HEARTBEAT;

  	wdt->timeout = max63xx_select_timeout(table, heartbeat);
  	if (!wdt->timeout) {
  		dev_err(&pdev->dev, "unable to satisfy %ds heartbeat request
  ",
  			heartbeat);

  		return -EINVAL;
  	}

  	err = max63xx_mmap_init(pdev, wdt);
  	if (err)
  		return err;
  
  	platform_set_drvdata(pdev, &wdt->wdd);
  	watchdog_set_drvdata(&wdt->wdd, wdt);

  	wdt->wdd.parent = &pdev->dev;
  	wdt->wdd.timeout = wdt->timeout->twd;
  	wdt->wdd.info = &max63xx_wdt_info;
  	wdt->wdd.ops = &max63xx_wdt_ops;

  	watchdog_set_nowayout(&wdt->wdd, nowayout);

  	err = watchdog_register_device(&wdt->wdd);
  	if (err)
  		return err;

  	dev_info(&pdev->dev, "using %ds heartbeat with %ds initial delay
  ",
  		 wdt->timeout->twd, wdt->timeout->tdelay);
  	return 0;

  }

  static int max63xx_wdt_remove(struct platform_device *pdev)

  {

  	struct watchdog_device *wdd = platform_get_drvdata(pdev);
  
  	watchdog_unregister_device(wdd);

  	return 0;
  }

  static const 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		= max63xx_wdt_remove,

  	.id_table	= max63xx_id_table,
  	.driver		= {
  		.name	= "max63xx_wdt",

  	},
  };

  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, bool, 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 v2");