/*
   * drivers/watchdog/shwdt.c
   *
   * Watchdog driver for integrated watchdog in the SuperH processors.
   *
   * Copyright (C) 2001 - 2012  Paul Mundt <lethal@linux-sh.org>
   *
   * 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.
   *
   * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
   *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
   *
   * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
   *     Added expect close support, made emulated timeout runtime changeable
   *     general cleanups, add some ioctls
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/init.h>
  #include <linux/types.h>
  #include <linux/spinlock.h>
  #include <linux/watchdog.h>
  #include <linux/pm_runtime.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/io.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <asm/watchdog.h>
  
  #define DRV_NAME "sh-wdt"
  
  /*
   * Default clock division ratio is 5.25 msecs. For an additional table of
   * values, consult the asm-sh/watchdog.h. Overload this at module load
   * time.
   *
   * In order for this to work reliably we need to have HZ set to 1000 or
   * something quite higher than 100 (or we need a proper high-res timer
   * implementation that will deal with this properly), otherwise the 10ms
   * resolution of a jiffy is enough to trigger the overflow. For things like
   * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
   * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
   * necssary.
   *
   * As a result of this timing problem, the only modes that are particularly
   * feasible are the 4096 and the 2048 divisors, which yield 5.25 and 2.62ms
   * overflow periods respectively.
   *
   * Also, since we can't really expect userspace to be responsive enough
   * before the overflow happens, we maintain two separate timers .. One in
   * the kernel for clearing out WOVF every 2ms or so (again, this depends on
   * HZ == 1000), and another for monitoring userspace writes to the WDT device.
   *
   * As such, we currently use a configurable heartbeat interval which defaults
   * to 30s. In this case, the userspace daemon is only responsible for periodic
   * writes to the device before the next heartbeat is scheduled. If the daemon
   * misses its deadline, the kernel timer will allow the WDT to overflow.
   */
  static int clock_division_ratio = WTCSR_CKS_4096;
  #define next_ping_period(cks)	(jiffies + msecs_to_jiffies(cks - 4))
  
  #define WATCHDOG_HEARTBEAT 30			/* 30 sec default heartbeat */
  static int heartbeat = WATCHDOG_HEARTBEAT;	/* in seconds */
  static bool nowayout = WATCHDOG_NOWAYOUT;
  static unsigned long next_heartbeat;
  
  struct sh_wdt {
  	void __iomem		*base;
  	struct device		*dev;
  	struct clk		*clk;
  	spinlock_t		lock;
  
  	struct timer_list	timer;
  };
  
  static int sh_wdt_start(struct watchdog_device *wdt_dev)
  {
  	struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
  	unsigned long flags;
  	u8 csr;
  
  	pm_runtime_get_sync(wdt->dev);
  	clk_enable(wdt->clk);
  
  	spin_lock_irqsave(&wdt->lock, flags);
  
  	next_heartbeat = jiffies + (heartbeat * HZ);
  	mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));
  
  	csr = sh_wdt_read_csr();
  	csr |= WTCSR_WT | clock_division_ratio;
  	sh_wdt_write_csr(csr);
  
  	sh_wdt_write_cnt(0);
  
  	/*
  	 * These processors have a bit of an inconsistent initialization
  	 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
  	 * RSTCSR register was removed.
  	 *
  	 * On the SH-2 however, in addition with bits being in different
  	 * locations, we must deal with RSTCSR outright..
  	 */
  	csr = sh_wdt_read_csr();
  	csr |= WTCSR_TME;
  	csr &= ~WTCSR_RSTS;
  	sh_wdt_write_csr(csr);
  
  #ifdef CONFIG_CPU_SH2
  	csr = sh_wdt_read_rstcsr();
  	csr &= ~RSTCSR_RSTS;
  	sh_wdt_write_rstcsr(csr);
  #endif
  	spin_unlock_irqrestore(&wdt->lock, flags);
  
  	return 0;
  }
  
  static int sh_wdt_stop(struct watchdog_device *wdt_dev)
  {
  	struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
  	unsigned long flags;
  	u8 csr;
  
  	spin_lock_irqsave(&wdt->lock, flags);
  
  	del_timer(&wdt->timer);
  
  	csr = sh_wdt_read_csr();
  	csr &= ~WTCSR_TME;
  	sh_wdt_write_csr(csr);
  
  	spin_unlock_irqrestore(&wdt->lock, flags);
  
  	clk_disable(wdt->clk);
  	pm_runtime_put_sync(wdt->dev);
  
  	return 0;
  }
  
  static int sh_wdt_keepalive(struct watchdog_device *wdt_dev)
  {
  	struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
  	unsigned long flags;
  
  	spin_lock_irqsave(&wdt->lock, flags);
  	next_heartbeat = jiffies + (heartbeat * HZ);
  	spin_unlock_irqrestore(&wdt->lock, flags);
  
  	return 0;
  }
  
  static int sh_wdt_set_heartbeat(struct watchdog_device *wdt_dev, unsigned t)
  {
  	struct sh_wdt *wdt = watchdog_get_drvdata(wdt_dev);
  	unsigned long flags;
  
  	if (unlikely(t < 1 || t > 3600)) /* arbitrary upper limit */
  		return -EINVAL;
  
  	spin_lock_irqsave(&wdt->lock, flags);
  	heartbeat = t;
  	wdt_dev->timeout = t;
  	spin_unlock_irqrestore(&wdt->lock, flags);
  
  	return 0;
  }
  
  static void sh_wdt_ping(unsigned long data)
  {
  	struct sh_wdt *wdt = (struct sh_wdt *)data;
  	unsigned long flags;
  
  	spin_lock_irqsave(&wdt->lock, flags);
  	if (time_before(jiffies, next_heartbeat)) {
  		u8 csr;
  
  		csr = sh_wdt_read_csr();
  		csr &= ~WTCSR_IOVF;
  		sh_wdt_write_csr(csr);
  
  		sh_wdt_write_cnt(0);
  
  		mod_timer(&wdt->timer, next_ping_period(clock_division_ratio));
  	} else
  		dev_warn(wdt->dev, "Heartbeat lost! Will not ping "
  		         "the watchdog
  ");
  	spin_unlock_irqrestore(&wdt->lock, flags);
  }
  
  static const struct watchdog_info sh_wdt_info = {
  	.options		= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
  				  WDIOF_MAGICCLOSE,
  	.firmware_version	= 1,
  	.identity		= "SH WDT",
  };
  
  static const struct watchdog_ops sh_wdt_ops = {
  	.owner		= THIS_MODULE,
  	.start		= sh_wdt_start,
  	.stop		= sh_wdt_stop,
  	.ping		= sh_wdt_keepalive,
  	.set_timeout	= sh_wdt_set_heartbeat,
  };
  
  static struct watchdog_device sh_wdt_dev = {
  	.info	= &sh_wdt_info,
  	.ops	= &sh_wdt_ops,
  };
  
  static int sh_wdt_probe(struct platform_device *pdev)
  {
  	struct sh_wdt *wdt;
  	struct resource *res;
  	int rc;
  
  	/*
  	 * As this driver only covers the global watchdog case, reject
  	 * any attempts to register per-CPU watchdogs.
  	 */
  	if (pdev->id != -1)
  		return -EINVAL;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (unlikely(!res))
  		return -EINVAL;
  
  	wdt = devm_kzalloc(&pdev->dev, sizeof(struct sh_wdt), GFP_KERNEL);
  	if (unlikely(!wdt))
  		return -ENOMEM;
  
  	wdt->dev = &pdev->dev;
  
  	wdt->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(wdt->clk)) {
  		/*
  		 * Clock framework support is optional, continue on
  		 * anyways if we don't find a matching clock.
  		 */
  		wdt->clk = NULL;
  	}
  
  	wdt->base = devm_ioremap_resource(wdt->dev, res);
  	if (IS_ERR(wdt->base))
  		return PTR_ERR(wdt->base);
  
  	watchdog_set_nowayout(&sh_wdt_dev, nowayout);
  	watchdog_set_drvdata(&sh_wdt_dev, wdt);
  
  	spin_lock_init(&wdt->lock);
  
  	rc = sh_wdt_set_heartbeat(&sh_wdt_dev, heartbeat);
  	if (unlikely(rc)) {
  		/* Default timeout if invalid */
  		sh_wdt_set_heartbeat(&sh_wdt_dev, WATCHDOG_HEARTBEAT);
  
  		dev_warn(&pdev->dev,
  			 "heartbeat value must be 1<=x<=3600, using %d
  ",
  			 sh_wdt_dev.timeout);
  	}
  
  	dev_info(&pdev->dev, "configured with heartbeat=%d sec (nowayout=%d)
  ",
  		 sh_wdt_dev.timeout, nowayout);
  
  	rc = watchdog_register_device(&sh_wdt_dev);
  	if (unlikely(rc)) {
  		dev_err(&pdev->dev, "Can't register watchdog (err=%d)
  ", rc);
  		return rc;
  	}
  
  	init_timer(&wdt->timer);
  	wdt->timer.function	= sh_wdt_ping;
  	wdt->timer.data		= (unsigned long)wdt;
  	wdt->timer.expires	= next_ping_period(clock_division_ratio);
  
  	platform_set_drvdata(pdev, wdt);
  
  	dev_info(&pdev->dev, "initialized.
  ");
  
  	pm_runtime_enable(&pdev->dev);
  
  	return 0;
  }
  
  static int sh_wdt_remove(struct platform_device *pdev)
  {
  	struct sh_wdt *wdt = platform_get_drvdata(pdev);
  
  	watchdog_unregister_device(&sh_wdt_dev);
  
  	pm_runtime_disable(&pdev->dev);
  
  	return 0;
  }
  
  static void sh_wdt_shutdown(struct platform_device *pdev)
  {
  	sh_wdt_stop(&sh_wdt_dev);
  }
  
  static struct platform_driver sh_wdt_driver = {
  	.driver		= {
  		.name	= DRV_NAME,
  		.owner	= THIS_MODULE,
  	},
  
  	.probe		= sh_wdt_probe,
  	.remove		= sh_wdt_remove,
  	.shutdown	= sh_wdt_shutdown,
  };
  
  static int __init sh_wdt_init(void)
  {
  	if (unlikely(clock_division_ratio < 0x5 ||
  		     clock_division_ratio > 0x7)) {
  		clock_division_ratio = WTCSR_CKS_4096;
  
  		pr_info("divisor must be 0x5<=x<=0x7, using %d
  ",
  			clock_division_ratio);
  	}
  
  	return platform_driver_register(&sh_wdt_driver);
  }
  
  static void __exit sh_wdt_exit(void)
  {
  	platform_driver_unregister(&sh_wdt_driver);
  }
  module_init(sh_wdt_init);
  module_exit(sh_wdt_exit);
  
  MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
  MODULE_DESCRIPTION("SuperH watchdog driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:" DRV_NAME);
  
  module_param(clock_division_ratio, int, 0);
  MODULE_PARM_DESC(clock_division_ratio,
  	"Clock division ratio. Valid ranges are from 0x5 (1.31ms) "
  	"to 0x7 (5.25ms). (default=" __MODULE_STRING(WTCSR_CKS_4096) ")");
  
  module_param(heartbeat, int, 0);
  MODULE_PARM_DESC(heartbeat,
  	"Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default="
  				__MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
  
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  	"Watchdog cannot be stopped once started (default="
  				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");