/*
   * drivers/char/watchdog/sp805-wdt.c
   *
   * Watchdog driver for ARM SP805 watchdog module
   *
   * Copyright (C) 2010 ST Microelectronics
   * Viresh Kumar <viresh.linux@gmail.com>
   *
   * This file is licensed under the terms of the GNU General Public
   * License version 2 or later. This program is licensed "as is" without any
   * warranty of any kind, whether express or implied.
   */
  
  #include <linux/device.h>
  #include <linux/resource.h>
  #include <linux/amba/bus.h>
  #include <linux/bitops.h>
  #include <linux/clk.h>
  #include <linux/init.h>
  #include <linux/io.h>
  #include <linux/ioport.h>
  #include <linux/kernel.h>
  #include <linux/math64.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/pm.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  
  /* default timeout in seconds */
  #define DEFAULT_TIMEOUT		60
  
  #define MODULE_NAME		"sp805-wdt"
  
  /* watchdog register offsets and masks */
  #define WDTLOAD			0x000
  	#define LOAD_MIN	0x00000001
  	#define LOAD_MAX	0xFFFFFFFF
  #define WDTVALUE		0x004
  #define WDTCONTROL		0x008
  	/* control register masks */
  	#define	INT_ENABLE	(1 << 0)
  	#define	RESET_ENABLE	(1 << 1)
  #define WDTINTCLR		0x00C
  #define WDTRIS			0x010
  #define WDTMIS			0x014
  	#define INT_MASK	(1 << 0)
  #define WDTLOCK			0xC00
  	#define	UNLOCK		0x1ACCE551
  	#define	LOCK		0x00000001
  
  /**
   * struct sp805_wdt: sp805 wdt device structure
   * @wdd: instance of struct watchdog_device
   * @lock: spin lock protecting dev structure and io access
   * @base: base address of wdt
   * @clk: clock structure of wdt
   * @adev: amba device structure of wdt
   * @status: current status of wdt
   * @load_val: load value to be set for current timeout
   */
  struct sp805_wdt {
  	struct watchdog_device		wdd;
  	spinlock_t			lock;
  	void __iomem			*base;
  	struct clk			*clk;
  	struct amba_device		*adev;
  	unsigned int			load_val;
  };
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		"Set to 1 to keep watchdog running after device release");
  
  /* This routine finds load value that will reset system in required timout */
  static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
  {
  	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
  	u64 load, rate;
  
  	rate = clk_get_rate(wdt->clk);
  
  	/*
  	 * sp805 runs counter with given value twice, after the end of first
  	 * counter it gives an interrupt and then starts counter again. If
  	 * interrupt already occurred then it resets the system. This is why
  	 * load is half of what should be required.
  	 */
  	load = div_u64(rate, 2) * timeout - 1;
  
  	load = (load > LOAD_MAX) ? LOAD_MAX : load;
  	load = (load < LOAD_MIN) ? LOAD_MIN : load;
  
  	spin_lock(&wdt->lock);
  	wdt->load_val = load;
  	/* roundup timeout to closest positive integer value */
  	wdd->timeout = div_u64((load + 1) * 2 + (rate / 2), rate);
  	spin_unlock(&wdt->lock);
  
  	return 0;
  }
  
  /* returns number of seconds left for reset to occur */
  static unsigned int wdt_timeleft(struct watchdog_device *wdd)
  {
  	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
  	u64 load, rate;
  
  	rate = clk_get_rate(wdt->clk);
  
  	spin_lock(&wdt->lock);
  	load = readl_relaxed(wdt->base + WDTVALUE);
  
  	/*If the interrupt is inactive then time left is WDTValue + WDTLoad. */
  	if (!(readl_relaxed(wdt->base + WDTRIS) & INT_MASK))
  		load += wdt->load_val + 1;
  	spin_unlock(&wdt->lock);
  
  	return div_u64(load, rate);
  }
  
  static int wdt_config(struct watchdog_device *wdd, bool ping)
  {
  	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
  	int ret;
  
  	if (!ping) {
  
  		ret = clk_prepare_enable(wdt->clk);
  		if (ret) {
  			dev_err(&wdt->adev->dev, "clock enable fail");
  			return ret;
  		}
  	}
  
  	spin_lock(&wdt->lock);
  
  	writel_relaxed(UNLOCK, wdt->base + WDTLOCK);
  	writel_relaxed(wdt->load_val, wdt->base + WDTLOAD);
  
  	if (!ping) {
  		writel_relaxed(INT_MASK, wdt->base + WDTINTCLR);
  		writel_relaxed(INT_ENABLE | RESET_ENABLE, wdt->base +
  				WDTCONTROL);
  	}
  
  	writel_relaxed(LOCK, wdt->base + WDTLOCK);
  
  	/* Flush posted writes. */
  	readl_relaxed(wdt->base + WDTLOCK);
  	spin_unlock(&wdt->lock);
  
  	return 0;
  }
  
  static int wdt_ping(struct watchdog_device *wdd)
  {
  	return wdt_config(wdd, true);
  }
  
  /* enables watchdog timers reset */
  static int wdt_enable(struct watchdog_device *wdd)
  {
  	return wdt_config(wdd, false);
  }
  
  /* disables watchdog timers reset */
  static int wdt_disable(struct watchdog_device *wdd)
  {
  	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
  
  	spin_lock(&wdt->lock);
  
  	writel_relaxed(UNLOCK, wdt->base + WDTLOCK);
  	writel_relaxed(0, wdt->base + WDTCONTROL);
  	writel_relaxed(LOCK, wdt->base + WDTLOCK);
  
  	/* Flush posted writes. */
  	readl_relaxed(wdt->base + WDTLOCK);
  	spin_unlock(&wdt->lock);
  
  	clk_disable_unprepare(wdt->clk);
  
  	return 0;
  }
  
  static const struct watchdog_info wdt_info = {
  	.options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
  	.identity = MODULE_NAME,
  };
  
  static const struct watchdog_ops wdt_ops = {
  	.owner		= THIS_MODULE,
  	.start		= wdt_enable,
  	.stop		= wdt_disable,
  	.ping		= wdt_ping,
  	.set_timeout	= wdt_setload,
  	.get_timeleft	= wdt_timeleft,
  };
  
  static int
  sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
  {
  	struct sp805_wdt *wdt;
  	int ret = 0;
  
  	if (!devm_request_mem_region(&adev->dev, adev->res.start,
  				resource_size(&adev->res), "sp805_wdt")) {
  		dev_warn(&adev->dev, "Failed to get memory region resource
  ");
  		ret = -ENOENT;
  		goto err;
  	}
  
  	wdt = devm_kzalloc(&adev->dev, sizeof(*wdt), GFP_KERNEL);
  	if (!wdt) {
  		dev_warn(&adev->dev, "Kzalloc failed
  ");
  		ret = -ENOMEM;
  		goto err;
  	}
  
  	wdt->base = devm_ioremap(&adev->dev, adev->res.start,
  			resource_size(&adev->res));
  	if (!wdt->base) {
  		ret = -ENOMEM;
  		dev_warn(&adev->dev, "ioremap fail
  ");
  		goto err;
  	}
  
  	wdt->clk = devm_clk_get(&adev->dev, NULL);
  	if (IS_ERR(wdt->clk)) {
  		dev_warn(&adev->dev, "Clock not found
  ");
  		ret = PTR_ERR(wdt->clk);
  		goto err;
  	}
  
  	wdt->adev = adev;
  	wdt->wdd.info = &wdt_info;
  	wdt->wdd.ops = &wdt_ops;
  
  	spin_lock_init(&wdt->lock);
  	watchdog_set_nowayout(&wdt->wdd, nowayout);
  	watchdog_set_drvdata(&wdt->wdd, wdt);
  	wdt_setload(&wdt->wdd, DEFAULT_TIMEOUT);
  
  	ret = watchdog_register_device(&wdt->wdd);
  	if (ret) {
  		dev_err(&adev->dev, "watchdog_register_device() failed: %d
  ",
  				ret);
  		goto err;
  	}
  	amba_set_drvdata(adev, wdt);
  
  	dev_info(&adev->dev, "registration successful
  ");
  	return 0;
  
  err:
  	dev_err(&adev->dev, "Probe Failed!!!
  ");
  	return ret;
  }
  
  static int sp805_wdt_remove(struct amba_device *adev)
  {
  	struct sp805_wdt *wdt = amba_get_drvdata(adev);
  
  	watchdog_unregister_device(&wdt->wdd);
  	watchdog_set_drvdata(&wdt->wdd, NULL);
  
  	return 0;
  }
  
  static int __maybe_unused sp805_wdt_suspend(struct device *dev)
  {
  	struct sp805_wdt *wdt = dev_get_drvdata(dev);
  
  	if (watchdog_active(&wdt->wdd))
  		return wdt_disable(&wdt->wdd);
  
  	return 0;
  }
  
  static int __maybe_unused sp805_wdt_resume(struct device *dev)
  {
  	struct sp805_wdt *wdt = dev_get_drvdata(dev);
  
  	if (watchdog_active(&wdt->wdd))
  		return wdt_enable(&wdt->wdd);
  
  	return 0;
  }
  
  static SIMPLE_DEV_PM_OPS(sp805_wdt_dev_pm_ops, sp805_wdt_suspend,
  		sp805_wdt_resume);
  
  static struct amba_id sp805_wdt_ids[] = {
  	{
  		.id	= 0x00141805,
  		.mask	= 0x00ffffff,
  	},
  	{ 0, 0 },
  };
  
  MODULE_DEVICE_TABLE(amba, sp805_wdt_ids);
  
  static struct amba_driver sp805_wdt_driver = {
  	.drv = {
  		.name	= MODULE_NAME,
  		.pm	= &sp805_wdt_dev_pm_ops,
  	},
  	.id_table	= sp805_wdt_ids,
  	.probe		= sp805_wdt_probe,
  	.remove = sp805_wdt_remove,
  };
  
  module_amba_driver(sp805_wdt_driver);
  
  MODULE_AUTHOR("Viresh Kumar <viresh.linux@gmail.com>");
  MODULE_DESCRIPTION("ARM SP805 Watchdog Driver");
  MODULE_LICENSE("GPL");