/*
   *      sunxi Watchdog Driver
   *
   *      Copyright (c) 2013 Carlo Caione
   *                    2012 Henrik Nordstrom
   *
   *      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.
   *
   *      Based on xen_wdt.c
   *      (c) Copyright 2010 Novell, Inc.
   */
  
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
  #include <linux/types.h>
  #include <linux/watchdog.h>
  
  #define WDT_MAX_TIMEOUT         16
  #define WDT_MIN_TIMEOUT         1
  #define WDT_MODE_TIMEOUT(n)     ((n) << 3)
  #define WDT_TIMEOUT_MASK        WDT_MODE_TIMEOUT(0x0F)
  
  #define WDT_CTRL                0x00
  #define WDT_CTRL_RELOAD         ((1 << 0) | (0x0a57 << 1))
  
  #define WDT_MODE                0x04
  #define WDT_MODE_EN             (1 << 0)
  #define WDT_MODE_RST_EN         (1 << 1)
  
  #define DRV_NAME		"sunxi-wdt"
  #define DRV_VERSION		"1.0"
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  static unsigned int timeout = WDT_MAX_TIMEOUT;
  
  struct sunxi_wdt_dev {
  	struct watchdog_device wdt_dev;
  	void __iomem *wdt_base;
  };
  
  /*
   * wdt_timeout_map maps the watchdog timer interval value in seconds to
   * the value of the register WDT_MODE bit 3:6
   *
   * [timeout seconds] = register value
   *
   */
  
  static const int wdt_timeout_map[] = {
  	[1] = 0b0001,  /* 1s  */
  	[2] = 0b0010,  /* 2s  */
  	[3] = 0b0011,  /* 3s  */
  	[4] = 0b0100,  /* 4s  */
  	[5] = 0b0101,  /* 5s  */
  	[6] = 0b0110,  /* 6s  */
  	[8] = 0b0111,  /* 8s  */
  	[10] = 0b1000, /* 10s */
  	[12] = 0b1001, /* 12s */
  	[14] = 0b1010, /* 14s */
  	[16] = 0b1011, /* 16s */
  };
  
  static int sunxi_wdt_ping(struct watchdog_device *wdt_dev)
  {
  	struct sunxi_wdt_dev *sunxi_wdt = watchdog_get_drvdata(wdt_dev);
  	void __iomem *wdt_base = sunxi_wdt->wdt_base;
  
  	iowrite32(WDT_CTRL_RELOAD, wdt_base + WDT_CTRL);
  
  	return 0;
  }
  
  static int sunxi_wdt_set_timeout(struct watchdog_device *wdt_dev,
  		unsigned int timeout)
  {
  	struct sunxi_wdt_dev *sunxi_wdt = watchdog_get_drvdata(wdt_dev);
  	void __iomem *wdt_base = sunxi_wdt->wdt_base;
  	u32 reg;
  
  	if (wdt_timeout_map[timeout] == 0)
  		timeout++;
  
  	sunxi_wdt->wdt_dev.timeout = timeout;
  
  	reg = ioread32(wdt_base + WDT_MODE);
  	reg &= ~WDT_TIMEOUT_MASK;
  	reg |= WDT_MODE_TIMEOUT(wdt_timeout_map[timeout]);
  	iowrite32(reg, wdt_base + WDT_MODE);
  
  	sunxi_wdt_ping(wdt_dev);
  
  	return 0;
  }
  
  static int sunxi_wdt_stop(struct watchdog_device *wdt_dev)
  {
  	struct sunxi_wdt_dev *sunxi_wdt = watchdog_get_drvdata(wdt_dev);
  	void __iomem *wdt_base = sunxi_wdt->wdt_base;
  
  	iowrite32(0, wdt_base + WDT_MODE);
  
  	return 0;
  }
  
  static int sunxi_wdt_start(struct watchdog_device *wdt_dev)
  {
  	u32 reg;
  	struct sunxi_wdt_dev *sunxi_wdt = watchdog_get_drvdata(wdt_dev);
  	void __iomem *wdt_base = sunxi_wdt->wdt_base;
  	int ret;
  
  	ret = sunxi_wdt_set_timeout(&sunxi_wdt->wdt_dev,
  			sunxi_wdt->wdt_dev.timeout);
  	if (ret < 0)
  		return ret;
  
  	reg = ioread32(wdt_base + WDT_MODE);
  	reg |= (WDT_MODE_RST_EN | WDT_MODE_EN);
  	iowrite32(reg, wdt_base + WDT_MODE);
  
  	return 0;
  }
  
  static const struct watchdog_info sunxi_wdt_info = {
  	.identity	= DRV_NAME,
  	.options	= WDIOF_SETTIMEOUT |
  			  WDIOF_KEEPALIVEPING |
  			  WDIOF_MAGICCLOSE,
  };
  
  static const struct watchdog_ops sunxi_wdt_ops = {
  	.owner		= THIS_MODULE,
  	.start		= sunxi_wdt_start,
  	.stop		= sunxi_wdt_stop,
  	.ping		= sunxi_wdt_ping,
  	.set_timeout	= sunxi_wdt_set_timeout,
  };
  
  static int sunxi_wdt_probe(struct platform_device *pdev)
  {
  	struct sunxi_wdt_dev *sunxi_wdt;
  	struct resource *res;
  	int err;
  
  	sunxi_wdt = devm_kzalloc(&pdev->dev, sizeof(*sunxi_wdt), GFP_KERNEL);
  	if (!sunxi_wdt)
  		return -EINVAL;
  
  	platform_set_drvdata(pdev, sunxi_wdt);
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	sunxi_wdt->wdt_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(sunxi_wdt->wdt_base))
  		return PTR_ERR(sunxi_wdt->wdt_base);
  
  	sunxi_wdt->wdt_dev.info = &sunxi_wdt_info;
  	sunxi_wdt->wdt_dev.ops = &sunxi_wdt_ops;
  	sunxi_wdt->wdt_dev.timeout = WDT_MAX_TIMEOUT;
  	sunxi_wdt->wdt_dev.max_timeout = WDT_MAX_TIMEOUT;
  	sunxi_wdt->wdt_dev.min_timeout = WDT_MIN_TIMEOUT;
  	sunxi_wdt->wdt_dev.parent = &pdev->dev;
  
  	watchdog_init_timeout(&sunxi_wdt->wdt_dev, timeout, &pdev->dev);
  	watchdog_set_nowayout(&sunxi_wdt->wdt_dev, nowayout);
  
  	watchdog_set_drvdata(&sunxi_wdt->wdt_dev, sunxi_wdt);
  
  	sunxi_wdt_stop(&sunxi_wdt->wdt_dev);
  
  	err = watchdog_register_device(&sunxi_wdt->wdt_dev);
  	if (unlikely(err))
  		return err;
  
  	dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)",
  			sunxi_wdt->wdt_dev.timeout, nowayout);
  
  	return 0;
  }
  
  static int sunxi_wdt_remove(struct platform_device *pdev)
  {
  	struct sunxi_wdt_dev *sunxi_wdt = platform_get_drvdata(pdev);
  
  	watchdog_unregister_device(&sunxi_wdt->wdt_dev);
  	watchdog_set_drvdata(&sunxi_wdt->wdt_dev, NULL);
  
  	return 0;
  }
  
  static void sunxi_wdt_shutdown(struct platform_device *pdev)
  {
  	struct sunxi_wdt_dev *sunxi_wdt = platform_get_drvdata(pdev);
  
  	sunxi_wdt_stop(&sunxi_wdt->wdt_dev);
  }
  
  static const struct of_device_id sunxi_wdt_dt_ids[] = {
  	{ .compatible = "allwinner,sun4i-wdt" },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, sunxi_wdt_dt_ids);
  
  static struct platform_driver sunxi_wdt_driver = {
  	.probe		= sunxi_wdt_probe,
  	.remove		= sunxi_wdt_remove,
  	.shutdown	= sunxi_wdt_shutdown,
  	.driver		= {
  		.owner		= THIS_MODULE,
  		.name		= DRV_NAME,
  		.of_match_table	= sunxi_wdt_dt_ids,
  	},
  };
  
  module_platform_driver(sunxi_wdt_driver);
  
  module_param(timeout, uint, 0);
  MODULE_PARM_DESC(timeout, "Watchdog heartbeat in seconds");
  
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  		"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Carlo Caione <carlo.caione@gmail.com>");
  MODULE_AUTHOR("Henrik Nordstrom <henrik@henriknordstrom.net>");
  MODULE_DESCRIPTION("sunxi WatchDog Timer Driver");
  MODULE_VERSION(DRV_VERSION);