/*
   * Watchdog driver for Cirrus Logic EP93xx family of devices.
   *
   * Copyright (c) 2004 Ray Lehtiniemi
   * Copyright (c) 2006 Tower Technologies
   * Based on ep93xx driver, bits from alim7101_wdt.c
   *
   * Authors: Ray Lehtiniemi <rayl@mail.com>,
   *	Alessandro Zummo <a.zummo@towertech.it>
   *
   * Copyright (c) 2012 H Hartley Sweeten <hsweeten@visionengravers.com>
   *	Convert to a platform device and use the watchdog framework API
   *
   * 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 watchdog fires after 250msec, which is a too short interval
   * for us to rely on the user space daemon alone. So we ping the
   * wdt each ~200msec and eventually stop doing it if the user space
   * daemon dies.
   *
   * TODO:
   *
   *	- Test last reset from watchdog status
   *	- Add a few missing ioctls
   */
  
  #include <linux/platform_device.h>
  #include <linux/module.h>
  #include <linux/watchdog.h>
  #include <linux/timer.h>
  #include <linux/io.h>
  
  #define WDT_VERSION	"0.4"
  
  /* default timeout (secs) */
  #define WDT_TIMEOUT 30
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
  
  static unsigned int timeout = WDT_TIMEOUT;
  module_param(timeout, uint, 0);
  MODULE_PARM_DESC(timeout,
  	"Watchdog timeout in seconds. (1<=timeout<=3600, default="
  				__MODULE_STRING(WDT_TIMEOUT) ")");
  
  static void __iomem *mmio_base;
  static struct timer_list timer;
  static unsigned long next_heartbeat;
  
  #define EP93XX_WATCHDOG		0x00
  #define EP93XX_WDSTATUS		0x04
  
  /* reset the wdt every ~200ms - the heartbeat of the device is 0.250 seconds*/
  #define WDT_INTERVAL (HZ/5)
  
  static void ep93xx_wdt_timer_ping(unsigned long data)
  {
  	if (time_before(jiffies, next_heartbeat))
  		writel(0x5555, mmio_base + EP93XX_WATCHDOG);
  
  	/* Re-set the timer interval */
  	mod_timer(&timer, jiffies + WDT_INTERVAL);
  }
  
  static int ep93xx_wdt_start(struct watchdog_device *wdd)
  {
  	next_heartbeat = jiffies + (timeout * HZ);
  
  	writel(0xaaaa, mmio_base + EP93XX_WATCHDOG);
  	mod_timer(&timer, jiffies + WDT_INTERVAL);
  
  	return 0;
  }
  
  static int ep93xx_wdt_stop(struct watchdog_device *wdd)
  {
  	del_timer_sync(&timer);
  	writel(0xaa55, mmio_base + EP93XX_WATCHDOG);
  
  	return 0;
  }
  
  static int ep93xx_wdt_keepalive(struct watchdog_device *wdd)
  {
  	/* user land ping */
  	next_heartbeat = jiffies + (timeout * HZ);
  
  	return 0;
  }
  
  static const struct watchdog_info ep93xx_wdt_ident = {
  	.options	= WDIOF_CARDRESET |
  			  WDIOF_MAGICCLOSE |
  			  WDIOF_KEEPALIVEPING,
  	.identity	= "EP93xx Watchdog",
  };
  
  static struct watchdog_ops ep93xx_wdt_ops = {
  	.owner		= THIS_MODULE,
  	.start		= ep93xx_wdt_start,
  	.stop		= ep93xx_wdt_stop,
  	.ping		= ep93xx_wdt_keepalive,
  };
  
  static struct watchdog_device ep93xx_wdt_wdd = {
  	.info		= &ep93xx_wdt_ident,
  	.ops		= &ep93xx_wdt_ops,
  };
  
  static int ep93xx_wdt_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	unsigned long val;
  	int err;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!res)
  		return -ENXIO;
  
  	if (!devm_request_mem_region(&pdev->dev, res->start,
  				     resource_size(res), pdev->name))
  		return -EBUSY;
  
  	mmio_base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
  	if (!mmio_base)
  		return -ENXIO;
  
  	if (timeout < 1 || timeout > 3600) {
  		timeout = WDT_TIMEOUT;
  		dev_warn(&pdev->dev,
  			"timeout value must be 1<=x<=3600, using %d
  ",
  			timeout);
  	}
  
  	val = readl(mmio_base + EP93XX_WATCHDOG);
  	ep93xx_wdt_wdd.bootstatus = (val & 0x01) ? WDIOF_CARDRESET : 0;
  	ep93xx_wdt_wdd.timeout = timeout;
  
  	watchdog_set_nowayout(&ep93xx_wdt_wdd, nowayout);
  
  	setup_timer(&timer, ep93xx_wdt_timer_ping, 1);
  
  	err = watchdog_register_device(&ep93xx_wdt_wdd);
  	if (err)
  		return err;
  
  	dev_info(&pdev->dev,
  		"EP93XX watchdog, driver version " WDT_VERSION "%s
  ",
  		(val & 0x08) ? " (nCS1 disable detected)" : "");
  
  	return 0;
  }
  
  static int ep93xx_wdt_remove(struct platform_device *pdev)
  {
  	watchdog_unregister_device(&ep93xx_wdt_wdd);
  	return 0;
  }
  
  static struct platform_driver ep93xx_wdt_driver = {
  	.driver		= {
  		.owner	= THIS_MODULE,
  		.name	= "ep93xx-wdt",
  	},
  	.probe		= ep93xx_wdt_probe,
  	.remove		= ep93xx_wdt_remove,
  };
  
  module_platform_driver(ep93xx_wdt_driver);
  
  MODULE_AUTHOR("Ray Lehtiniemi <rayl@mail.com>,"
  		"Alessandro Zummo <a.zummo@towertech.it>,"
  		"H Hartley Sweeten <hsweeten@visionengravers.com>");
  MODULE_DESCRIPTION("EP93xx Watchdog");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(WDT_VERSION);