/*
   *  Copyright (C) 2010, Paul Cercueil <paul@crapouillou.net>
   *  JZ4740 Watchdog driver
   *
   *  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.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  675 Mass Ave, Cambridge, MA 02139, USA.
   *
   */
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/watchdog.h>
  #include <linux/init.h>
  #include <linux/platform_device.h>
  #include <linux/io.h>
  #include <linux/device.h>
  #include <linux/clk.h>
  #include <linux/slab.h>
  #include <linux/err.h>
  
  #include <asm/mach-jz4740/timer.h>
  
  #define JZ_REG_WDT_TIMER_DATA     0x0
  #define JZ_REG_WDT_COUNTER_ENABLE 0x4
  #define JZ_REG_WDT_TIMER_COUNTER  0x8
  #define JZ_REG_WDT_TIMER_CONTROL  0xC
  
  #define JZ_WDT_CLOCK_PCLK 0x1
  #define JZ_WDT_CLOCK_RTC  0x2
  #define JZ_WDT_CLOCK_EXT  0x4
  
  #define JZ_WDT_CLOCK_DIV_SHIFT   3
  
  #define JZ_WDT_CLOCK_DIV_1    (0 << JZ_WDT_CLOCK_DIV_SHIFT)
  #define JZ_WDT_CLOCK_DIV_4    (1 << JZ_WDT_CLOCK_DIV_SHIFT)
  #define JZ_WDT_CLOCK_DIV_16   (2 << JZ_WDT_CLOCK_DIV_SHIFT)
  #define JZ_WDT_CLOCK_DIV_64   (3 << JZ_WDT_CLOCK_DIV_SHIFT)
  #define JZ_WDT_CLOCK_DIV_256  (4 << JZ_WDT_CLOCK_DIV_SHIFT)
  #define JZ_WDT_CLOCK_DIV_1024 (5 << JZ_WDT_CLOCK_DIV_SHIFT)
  
  #define DEFAULT_HEARTBEAT 5
  #define MAX_HEARTBEAT     2048
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		 "Watchdog cannot be stopped once started (default="
  		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  static unsigned int heartbeat = DEFAULT_HEARTBEAT;
  module_param(heartbeat, uint, 0);
  MODULE_PARM_DESC(heartbeat,
  		"Watchdog heartbeat period in seconds from 1 to "
  		__MODULE_STRING(MAX_HEARTBEAT) ", default "
  		__MODULE_STRING(DEFAULT_HEARTBEAT));
  
  struct jz4740_wdt_drvdata {
  	struct watchdog_device wdt;
  	void __iomem *base;
  	struct clk *rtc_clk;
  };
  
  static int jz4740_wdt_ping(struct watchdog_device *wdt_dev)
  {
  	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
  
  	writew(0x0, drvdata->base + JZ_REG_WDT_TIMER_COUNTER);
  	return 0;
  }
  
  static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
  				    unsigned int new_timeout)
  {
  	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
  	unsigned int rtc_clk_rate;
  	unsigned int timeout_value;
  	unsigned short clock_div = JZ_WDT_CLOCK_DIV_1;
  
  	rtc_clk_rate = clk_get_rate(drvdata->rtc_clk);
  
  	timeout_value = rtc_clk_rate * new_timeout;
  	while (timeout_value > 0xffff) {
  		if (clock_div == JZ_WDT_CLOCK_DIV_1024) {
  			/* Requested timeout too high;
  			* use highest possible value. */
  			timeout_value = 0xffff;
  			break;
  		}
  		timeout_value >>= 2;
  		clock_div += (1 << JZ_WDT_CLOCK_DIV_SHIFT);
  	}
  
  	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
  	writew(clock_div, drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
  
  	writew((u16)timeout_value, drvdata->base + JZ_REG_WDT_TIMER_DATA);
  	writew(0x0, drvdata->base + JZ_REG_WDT_TIMER_COUNTER);
  	writew(clock_div | JZ_WDT_CLOCK_RTC,
  		drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
  
  	writeb(0x1, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
  
  	wdt_dev->timeout = new_timeout;
  	return 0;
  }
  
  static int jz4740_wdt_start(struct watchdog_device *wdt_dev)
  {
  	jz4740_timer_enable_watchdog();
  	jz4740_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
  
  	return 0;
  }
  
  static int jz4740_wdt_stop(struct watchdog_device *wdt_dev)
  {
  	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
  
  	jz4740_timer_disable_watchdog();
  	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
  
  	return 0;
  }
  
  static const struct watchdog_info jz4740_wdt_info = {
  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  	.identity = "jz4740 Watchdog",
  };
  
  static const struct watchdog_ops jz4740_wdt_ops = {
  	.owner = THIS_MODULE,
  	.start = jz4740_wdt_start,
  	.stop = jz4740_wdt_stop,
  	.ping = jz4740_wdt_ping,
  	.set_timeout = jz4740_wdt_set_timeout,
  };
  
  static int jz4740_wdt_probe(struct platform_device *pdev)
  {
  	struct jz4740_wdt_drvdata *drvdata;
  	struct watchdog_device *jz4740_wdt;
  	struct resource	*res;
  	int ret;
  
  	drvdata = devm_kzalloc(&pdev->dev, sizeof(struct jz4740_wdt_drvdata),
  			       GFP_KERNEL);
  	if (!drvdata) {
  		dev_err(&pdev->dev, "Unable to alloacate watchdog device
  ");
  		return -ENOMEM;
  	}
  
  	if (heartbeat < 1 || heartbeat > MAX_HEARTBEAT)
  		heartbeat = DEFAULT_HEARTBEAT;
  
  	jz4740_wdt = &drvdata->wdt;
  	jz4740_wdt->info = &jz4740_wdt_info;
  	jz4740_wdt->ops = &jz4740_wdt_ops;
  	jz4740_wdt->timeout = heartbeat;
  	jz4740_wdt->min_timeout = 1;
  	jz4740_wdt->max_timeout = MAX_HEARTBEAT;
  	watchdog_set_nowayout(jz4740_wdt, nowayout);
  	watchdog_set_drvdata(jz4740_wdt, drvdata);
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	drvdata->base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(drvdata->base)) {
  		ret = PTR_ERR(drvdata->base);
  		goto err_out;
  	}
  
  	drvdata->rtc_clk = clk_get(&pdev->dev, "rtc");
  	if (IS_ERR(drvdata->rtc_clk)) {
  		dev_err(&pdev->dev, "cannot find RTC clock
  ");
  		ret = PTR_ERR(drvdata->rtc_clk);
  		goto err_out;
  	}
  
  	ret = watchdog_register_device(&drvdata->wdt);
  	if (ret < 0)
  		goto err_disable_clk;
  
  	platform_set_drvdata(pdev, drvdata);
  	return 0;
  
  err_disable_clk:
  	clk_put(drvdata->rtc_clk);
  err_out:
  	return ret;
  }
  
  static int jz4740_wdt_remove(struct platform_device *pdev)
  {
  	struct jz4740_wdt_drvdata *drvdata = platform_get_drvdata(pdev);
  
  	jz4740_wdt_stop(&drvdata->wdt);
  	watchdog_unregister_device(&drvdata->wdt);
  	clk_put(drvdata->rtc_clk);
  
  	return 0;
  }
  
  static struct platform_driver jz4740_wdt_driver = {
  	.probe = jz4740_wdt_probe,
  	.remove = jz4740_wdt_remove,
  	.driver = {
  		.name = "jz4740-wdt",
  		.owner	= THIS_MODULE,
  	},
  };
  
  module_platform_driver(jz4740_wdt_driver);
  
  MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
  MODULE_DESCRIPTION("jz4740 Watchdog Driver");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:jz4740-wdt");