drivers/watchdog/cadence_wdt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Cadence WDT driver - Used by Xilinx Zynq
  *
  * Copyright (C) 2010 - 2014 Xilinx, Inc.
  *
  */

 #include <linux/clk.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>

 #define CDNS_WDT_DEFAULT_TIMEOUT	10
 /* Supports 1 - 516 sec */
 #define CDNS_WDT_MIN_TIMEOUT	1
 #define CDNS_WDT_MAX_TIMEOUT	516

 /* Restart key */
 #define CDNS_WDT_RESTART_KEY 0x00001999

 /* Counter register access key */
 #define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000

 /* Counter value divisor */
 #define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000

 /* Clock prescaler value and selection */
 #define CDNS_WDT_PRESCALE_64	64
 #define CDNS_WDT_PRESCALE_512	512
 #define CDNS_WDT_PRESCALE_4096	4096
 #define CDNS_WDT_PRESCALE_SELECT_64	1
 #define CDNS_WDT_PRESCALE_SELECT_512	2
 #define CDNS_WDT_PRESCALE_SELECT_4096	3

 /* Input clock frequency */
 #define CDNS_WDT_CLK_10MHZ	10000000
 #define CDNS_WDT_CLK_75MHZ	75000000

 /* Counter maximum value */
 #define CDNS_WDT_COUNTER_MAX 0xFFF

 static int wdt_timeout;
 static int nowayout = WATCHDOG_NOWAYOUT;

 module_param(wdt_timeout, int, 0644);
 MODULE_PARM_DESC(wdt_timeout,
 		 "Watchdog time in seconds. (default="
 		 __MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");

 module_param(nowayout, int, 0644);
 MODULE_PARM_DESC(nowayout,
 		 "Watchdog cannot be stopped once started (default="
 		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

 /**
  * struct cdns_wdt - Watchdog device structure
  * @regs: baseaddress of device
  * @rst: reset flag
  * @clk: struct clk * of a clock source
  * @prescaler: for saving prescaler value
  * @ctrl_clksel: counter clock prescaler selection
  * @io_lock: spinlock for IO register access
  * @cdns_wdt_device: watchdog device structure
  *
  * Structure containing parameters specific to cadence watchdog.
  */
 struct cdns_wdt {
 	void __iomem		*regs;
 	bool			rst;
 	struct clk		*clk;
 	u32			prescaler;
 	u32			ctrl_clksel;
 	spinlock_t		io_lock;
 	struct watchdog_device	cdns_wdt_device;
 };

 /* Write access to Registers */
 static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
 {
 	writel_relaxed(val, wdt->regs + offset);
 }

 /*************************Register Map**************************************/

 /* Register Offsets for the WDT */
 #define CDNS_WDT_ZMR_OFFSET	0x0	/* Zero Mode Register */
 #define CDNS_WDT_CCR_OFFSET	0x4	/* Counter Control Register */
 #define CDNS_WDT_RESTART_OFFSET	0x8	/* Restart Register */
 #define CDNS_WDT_SR_OFFSET	0xC	/* Status Register */

 /*
  * Zero Mode Register - This register controls how the time out is indicated
  * and also contains the access code to allow writes to the register (0xABC).
  */
 #define CDNS_WDT_ZMR_WDEN_MASK	0x00000001 /* Enable the WDT */
 #define CDNS_WDT_ZMR_RSTEN_MASK	0x00000002 /* Enable the reset output */
 #define CDNS_WDT_ZMR_IRQEN_MASK	0x00000004 /* Enable IRQ output */
 #define CDNS_WDT_ZMR_RSTLEN_16	0x00000030 /* Reset pulse of 16 pclk cycles */
 #define CDNS_WDT_ZMR_ZKEY_VAL	0x00ABC000 /* Access key, 0xABC << 12 */
 /*
  * Counter Control register - This register controls how fast the timer runs
  * and the reset value and also contains the access code to allow writes to
  * the register.
  */
 #define CDNS_WDT_CCR_CRV_MASK	0x00003FFC /* Counter reset value */

 /**
  * cdns_wdt_stop - Stop the watchdog.
  *
  * @wdd: watchdog device
  *
  * Read the contents of the ZMR register, clear the WDEN bit
  * in the register and set the access key for successful write.
  *
  * Return: always 0
  */
 static int cdns_wdt_stop(struct watchdog_device *wdd)
 {
 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

 	spin_lock(&wdt->io_lock);
 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
 			  CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
 	spin_unlock(&wdt->io_lock);

 	return 0;
 }

 /**
  * cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
  *
  * @wdd: watchdog device
  *
  * Write the restart key value (0x00001999) to the restart register.
  *
  * Return: always 0
  */
 static int cdns_wdt_reload(struct watchdog_device *wdd)
 {
 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

 	spin_lock(&wdt->io_lock);
 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
 			  CDNS_WDT_RESTART_KEY);
 	spin_unlock(&wdt->io_lock);

 	return 0;
 }

 /**
  * cdns_wdt_start - Enable and start the watchdog.
  *
  * @wdd: watchdog device
  *
  * The counter value is calculated according to the formula:
  *		calculated count = (timeout * clock) / prescaler + 1.
  * The calculated count is divided by 0x1000 to obtain the field value
  * to write to counter control register.
  * Clears the contents of prescaler and counter reset value. Sets the
  * prescaler to 4096 and the calculated count and access key
  * to write to CCR Register.
  * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
  * or Interrupt signal(IRQEN) with a specified cycles and the access
  * key to write to ZMR Register.
  *
  * Return: always 0
  */
 static int cdns_wdt_start(struct watchdog_device *wdd)
 {
 	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
 	unsigned int data = 0;
 	unsigned short count;
 	unsigned long clock_f = clk_get_rate(wdt->clk);

 	/*
 	 * Counter value divisor to obtain the value of
 	 * counter reset to be written to control register.
 	 */
 	count = (wdd->timeout * (clock_f / wdt->prescaler)) /
 		 CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;

 	if (count > CDNS_WDT_COUNTER_MAX)
 		count = CDNS_WDT_COUNTER_MAX;

 	spin_lock(&wdt->io_lock);
 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
 			  CDNS_WDT_ZMR_ZKEY_VAL);

 	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;

 	/* Write counter access key first to be able write to register */
 	data = count | CDNS_WDT_REGISTER_ACCESS_KEY | wdt->ctrl_clksel;
 	cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
 	data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
 	       CDNS_WDT_ZMR_ZKEY_VAL;

 	/* Reset on timeout if specified in device tree. */
 	if (wdt->rst) {
 		data |= CDNS_WDT_ZMR_RSTEN_MASK;
 		data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
 	} else {
 		data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
 		data |= CDNS_WDT_ZMR_IRQEN_MASK;
 	}
 	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
 	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
 			  CDNS_WDT_RESTART_KEY);
 	spin_unlock(&wdt->io_lock);

 	return 0;
 }

 /**
  * cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
  *
  * @wdd: watchdog device
  * @new_time: new timeout value that needs to be set
  * Return: 0 on success
  *
  * Update the watchdog_device timeout with new value which is used when
  * cdns_wdt_start is called.
  */
 static int cdns_wdt_settimeout(struct watchdog_device *wdd,
 			       unsigned int new_time)
 {
 	wdd->timeout = new_time;

 	return cdns_wdt_start(wdd);
 }

 /**
  * cdns_wdt_irq_handler - Notifies of watchdog timeout.
  *
  * @irq: interrupt number
  * @dev_id: pointer to a platform device structure
  * Return: IRQ_HANDLED
  *
  * The handler is invoked when the watchdog times out and a
  * reset on timeout has not been enabled.
  */
 static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
 {
 	struct platform_device *pdev = dev_id;

 	dev_info(&pdev->dev,
 		 "Watchdog timed out. Internal reset not enabled\n");

 	return IRQ_HANDLED;
 }

 /*
  * Info structure used to indicate the features supported by the device
  * to the upper layers. This is defined in watchdog.h header file.
  */
 static const struct watchdog_info cdns_wdt_info = {
 	.identity	= "cdns_wdt watchdog",
 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 			  WDIOF_MAGICCLOSE,
 };

 /* Watchdog Core Ops */
 static const struct watchdog_ops cdns_wdt_ops = {
 	.owner = THIS_MODULE,
 	.start = cdns_wdt_start,
 	.stop = cdns_wdt_stop,
 	.ping = cdns_wdt_reload,
 	.set_timeout = cdns_wdt_settimeout,
 };

 /************************Platform Operations*****************************/
 /**
  * cdns_wdt_probe - Probe call for the device.
  *
  * @pdev: handle to the platform device structure.
  * Return: 0 on success, negative error otherwise.
  *
  * It does all the memory allocation and registration for the device.
  */
 static int cdns_wdt_probe(struct platform_device *pdev)
 {
 	struct resource *res;
 	int ret, irq;
 	unsigned long clock_f;
 	struct cdns_wdt *wdt;
 	struct watchdog_device *cdns_wdt_device;

 	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
 	if (!wdt)
 		return -ENOMEM;

 	cdns_wdt_device = &wdt->cdns_wdt_device;
 	cdns_wdt_device->info = &cdns_wdt_info;
 	cdns_wdt_device->ops = &cdns_wdt_ops;
 	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
 	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
 	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	wdt->regs = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(wdt->regs))
 		return PTR_ERR(wdt->regs);

 	/* Register the interrupt */
 	wdt->rst = of_property_read_bool(pdev->dev.of_node, "reset-on-timeout");
 	irq = platform_get_irq(pdev, 0);
 	if (!wdt->rst && irq >= 0) {
 		ret = devm_request_irq(&pdev->dev, irq, cdns_wdt_irq_handler, 0,
 				       pdev->name, pdev);
 		if (ret) {
 			dev_err(&pdev->dev,
 				"cannot register interrupt handler err=%d\n",
 				ret);
 			return ret;
 		}
 	}

 	/* Initialize the members of cdns_wdt structure */
 	cdns_wdt_device->parent = &pdev->dev;

 	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to set timeout value\n");
 		return ret;
 	}

 	watchdog_set_nowayout(cdns_wdt_device, nowayout);
 	watchdog_stop_on_reboot(cdns_wdt_device);
 	watchdog_set_drvdata(cdns_wdt_device, wdt);

 	wdt->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(wdt->clk)) {
 		dev_err(&pdev->dev, "input clock not found\n");
 		ret = PTR_ERR(wdt->clk);
 		return ret;
 	}

 	ret = clk_prepare_enable(wdt->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to enable clock\n");
 		return ret;
 	}

 	clock_f = clk_get_rate(wdt->clk);
 	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
 		wdt->prescaler = CDNS_WDT_PRESCALE_512;
 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
 	} else {
 		wdt->prescaler = CDNS_WDT_PRESCALE_4096;
 		wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
 	}

 	spin_lock_init(&wdt->io_lock);

 	ret = watchdog_register_device(cdns_wdt_device);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register wdt device\n");
 		goto err_clk_disable;
 	}
 	platform_set_drvdata(pdev, wdt);

 	dev_info(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
 		 wdt->regs, cdns_wdt_device->timeout,
 		 nowayout ? ", nowayout" : "");

 	return 0;

 err_clk_disable:
 	clk_disable_unprepare(wdt->clk);

 	return ret;
 }

 /**
  * cdns_wdt_remove - Probe call for the device.
  *
  * @pdev: handle to the platform device structure.
  * Return: 0 on success, otherwise negative error.
  *
  * Unregister the device after releasing the resources.
  */
 static int cdns_wdt_remove(struct platform_device *pdev)
 {
 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

 	cdns_wdt_stop(&wdt->cdns_wdt_device);
 	watchdog_unregister_device(&wdt->cdns_wdt_device);
 	clk_disable_unprepare(wdt->clk);

 	return 0;
 }

 /**
  * cdns_wdt_shutdown - Stop the device.
  *
  * @pdev: handle to the platform structure.
  *
  */
 static void cdns_wdt_shutdown(struct platform_device *pdev)
 {
 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

 	cdns_wdt_stop(&wdt->cdns_wdt_device);
 	clk_disable_unprepare(wdt->clk);
 }

 /**
  * cdns_wdt_suspend - Stop the device.
  *
  * @dev: handle to the device structure.
  * Return: 0 always.
  */
 static int __maybe_unused cdns_wdt_suspend(struct device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

 	if (watchdog_active(&wdt->cdns_wdt_device)) {
 		cdns_wdt_stop(&wdt->cdns_wdt_device);
 		clk_disable_unprepare(wdt->clk);
 	}

 	return 0;
 }

 /**
  * cdns_wdt_resume - Resume the device.
  *
  * @dev: handle to the device structure.
  * Return: 0 on success, errno otherwise.
  */
 static int __maybe_unused cdns_wdt_resume(struct device *dev)
 {
 	int ret;
 	struct platform_device *pdev = to_platform_device(dev);
 	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

 	if (watchdog_active(&wdt->cdns_wdt_device)) {
 		ret = clk_prepare_enable(wdt->clk);
 		if (ret) {
 			dev_err(dev, "unable to enable clock\n");
 			return ret;
 		}
 		cdns_wdt_start(&wdt->cdns_wdt_device);
 	}

 	return 0;
 }

 static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);

 static const struct of_device_id cdns_wdt_of_match[] = {
 	{ .compatible = "cdns,wdt-r1p2", },
 	{ /* end of table */ }
 };
 MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);

 /* Driver Structure */
 static struct platform_driver cdns_wdt_driver = {
 	.probe		= cdns_wdt_probe,
 	.remove		= cdns_wdt_remove,
 	.shutdown	= cdns_wdt_shutdown,
 	.driver		= {
 		.name	= "cdns-wdt",
 		.of_match_table = cdns_wdt_of_match,
 		.pm	= &cdns_wdt_pm_ops,
 	},
 };

 module_platform_driver(cdns_wdt_driver);

 MODULE_AUTHOR("Xilinx, Inc.");
 MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Cadence WDT driver - Used by Xilinx Zynq
	*
	* Copyright (C) 2010 - 2014 Xilinx, Inc.
	*
	*/

	#include <linux/clk.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/irq.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/watchdog.h>

	#define CDNS_WDT_DEFAULT_TIMEOUT 10
	/* Supports 1 - 516 sec */
	#define CDNS_WDT_MIN_TIMEOUT 1
	#define CDNS_WDT_MAX_TIMEOUT 516

	/* Restart key */
	#define CDNS_WDT_RESTART_KEY 0x00001999

	/* Counter register access key */
	#define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000

	/* Counter value divisor */
	#define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000

	/* Clock prescaler value and selection */
	#define CDNS_WDT_PRESCALE_64 64
	#define CDNS_WDT_PRESCALE_512 512
	#define CDNS_WDT_PRESCALE_4096 4096
	#define CDNS_WDT_PRESCALE_SELECT_64 1
	#define CDNS_WDT_PRESCALE_SELECT_512 2
	#define CDNS_WDT_PRESCALE_SELECT_4096 3

	/* Input clock frequency */
	#define CDNS_WDT_CLK_10MHZ 10000000
	#define CDNS_WDT_CLK_75MHZ 75000000

	/* Counter maximum value */
	#define CDNS_WDT_COUNTER_MAX 0xFFF

	static int wdt_timeout;
	static int nowayout = WATCHDOG_NOWAYOUT;

	module_param(wdt_timeout, int, 0644);
	MODULE_PARM_DESC(wdt_timeout,
	"Watchdog time in seconds. (default="
	__MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");

	module_param(nowayout, int, 0644);
	MODULE_PARM_DESC(nowayout,
	"Watchdog cannot be stopped once started (default="
	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

	/**
	* struct cdns_wdt - Watchdog device structure
	* @regs: baseaddress of device
	* @rst: reset flag
	* @clk: struct clk * of a clock source
	* @prescaler: for saving prescaler value
	* @ctrl_clksel: counter clock prescaler selection
	* @io_lock: spinlock for IO register access
	* @cdns_wdt_device: watchdog device structure
	*
	* Structure containing parameters specific to cadence watchdog.
	*/
	struct cdns_wdt {
	void __iomem *regs;
	bool rst;
	struct clk *clk;
	u32 prescaler;
	u32 ctrl_clksel;
	spinlock_t io_lock;
	struct watchdog_device cdns_wdt_device;
	};

	/* Write access to Registers */
	static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
	{
	writel_relaxed(val, wdt->regs + offset);
	}

	/***********************Register Map************************************/

	/* Register Offsets for the WDT */
	#define CDNS_WDT_ZMR_OFFSET 0x0 /* Zero Mode Register */
	#define CDNS_WDT_CCR_OFFSET 0x4 /* Counter Control Register */
	#define CDNS_WDT_RESTART_OFFSET 0x8 /* Restart Register */
	#define CDNS_WDT_SR_OFFSET 0xC /* Status Register */

	/*
	* Zero Mode Register - This register controls how the time out is indicated
	* and also contains the access code to allow writes to the register (0xABC).
	*/
	#define CDNS_WDT_ZMR_WDEN_MASK 0x00000001 /* Enable the WDT */
	#define CDNS_WDT_ZMR_RSTEN_MASK 0x00000002 /* Enable the reset output */
	#define CDNS_WDT_ZMR_IRQEN_MASK 0x00000004 /* Enable IRQ output */
	#define CDNS_WDT_ZMR_RSTLEN_16 0x00000030 /* Reset pulse of 16 pclk cycles */
	#define CDNS_WDT_ZMR_ZKEY_VAL 0x00ABC000 /* Access key, 0xABC << 12 */
	/*
	* Counter Control register - This register controls how fast the timer runs
	* and the reset value and also contains the access code to allow writes to
	* the register.
	*/
	#define CDNS_WDT_CCR_CRV_MASK 0x00003FFC /* Counter reset value */

	/**
	* cdns_wdt_stop - Stop the watchdog.
	*
	* @wdd: watchdog device
	*
	* Read the contents of the ZMR register, clear the WDEN bit
	* in the register and set the access key for successful write.
	*
	* Return: always 0
	*/
	static int cdns_wdt_stop(struct watchdog_device *wdd)
	{
	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

	spin_lock(&wdt->io_lock);
	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
	CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
	spin_unlock(&wdt->io_lock);

	return 0;
	}

	/**
	* cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
	*
	* @wdd: watchdog device
	*
	* Write the restart key value (0x00001999) to the restart register.
	*
	* Return: always 0
	*/
	static int cdns_wdt_reload(struct watchdog_device *wdd)
	{
	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

	spin_lock(&wdt->io_lock);
	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
	CDNS_WDT_RESTART_KEY);
	spin_unlock(&wdt->io_lock);

	return 0;
	}

	/**
	* cdns_wdt_start - Enable and start the watchdog.
	*
	* @wdd: watchdog device
	*
	* The counter value is calculated according to the formula:
	* calculated count = (timeout * clock) / prescaler + 1.
	* The calculated count is divided by 0x1000 to obtain the field value
	* to write to counter control register.
	* Clears the contents of prescaler and counter reset value. Sets the
	* prescaler to 4096 and the calculated count and access key
	* to write to CCR Register.
	* Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
	* or Interrupt signal(IRQEN) with a specified cycles and the access
	* key to write to ZMR Register.
	*
	* Return: always 0
	*/
	static int cdns_wdt_start(struct watchdog_device *wdd)
	{
	struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
	unsigned int data = 0;
	unsigned short count;
	unsigned long clock_f = clk_get_rate(wdt->clk);

	/*
	* Counter value divisor to obtain the value of
	* counter reset to be written to control register.
	*/
	count = (wdd->timeout * (clock_f / wdt->prescaler)) /
	CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;

	if (count > CDNS_WDT_COUNTER_MAX)
	count = CDNS_WDT_COUNTER_MAX;

	spin_lock(&wdt->io_lock);
	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
	CDNS_WDT_ZMR_ZKEY_VAL);

	count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;

	/* Write counter access key first to be able write to register */
	data = count \| CDNS_WDT_REGISTER_ACCESS_KEY \| wdt->ctrl_clksel;
	cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
	data = CDNS_WDT_ZMR_WDEN_MASK \| CDNS_WDT_ZMR_RSTLEN_16 \|
	CDNS_WDT_ZMR_ZKEY_VAL;

	/* Reset on timeout if specified in device tree. */
	if (wdt->rst) {
	data \|= CDNS_WDT_ZMR_RSTEN_MASK;
	data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
	} else {
	data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
	data \|= CDNS_WDT_ZMR_IRQEN_MASK;
	}
	cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
	cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
	CDNS_WDT_RESTART_KEY);
	spin_unlock(&wdt->io_lock);

	return 0;
	}

	/**
	* cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
	*
	* @wdd: watchdog device
	* @new_time: new timeout value that needs to be set
	* Return: 0 on success
	*
	* Update the watchdog_device timeout with new value which is used when
	* cdns_wdt_start is called.
	*/
	static int cdns_wdt_settimeout(struct watchdog_device *wdd,
	unsigned int new_time)
	{
	wdd->timeout = new_time;

	return cdns_wdt_start(wdd);
	}

	/**
	* cdns_wdt_irq_handler - Notifies of watchdog timeout.
	*
	* @irq: interrupt number
	* @dev_id: pointer to a platform device structure
	* Return: IRQ_HANDLED
	*
	* The handler is invoked when the watchdog times out and a
	* reset on timeout has not been enabled.
	*/
	static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
	{
	struct platform_device *pdev = dev_id;

	dev_info(&pdev->dev,
	"Watchdog timed out. Internal reset not enabled\n");

	return IRQ_HANDLED;
	}

	/*
	* Info structure used to indicate the features supported by the device
	* to the upper layers. This is defined in watchdog.h header file.
	*/
	static const struct watchdog_info cdns_wdt_info = {
	.identity = "cdns_wdt watchdog",
	.options = WDIOF_SETTIMEOUT \| WDIOF_KEEPALIVEPING \|
	WDIOF_MAGICCLOSE,
	};

	/* Watchdog Core Ops */
	static const struct watchdog_ops cdns_wdt_ops = {
	.owner = THIS_MODULE,
	.start = cdns_wdt_start,
	.stop = cdns_wdt_stop,
	.ping = cdns_wdt_reload,
	.set_timeout = cdns_wdt_settimeout,
	};

	/**********************Platform Operations***************************/
	/**
	* cdns_wdt_probe - Probe call for the device.
	*
	* @pdev: handle to the platform device structure.
	* Return: 0 on success, negative error otherwise.
	*
	* It does all the memory allocation and registration for the device.
	*/
	static int cdns_wdt_probe(struct platform_device *pdev)
	{
	struct resource *res;
	int ret, irq;
	unsigned long clock_f;
	struct cdns_wdt *wdt;
	struct watchdog_device *cdns_wdt_device;

	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
	if (!wdt)
	return -ENOMEM;

	cdns_wdt_device = &wdt->cdns_wdt_device;
	cdns_wdt_device->info = &cdns_wdt_info;
	cdns_wdt_device->ops = &cdns_wdt_ops;
	cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
	cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
	cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	wdt->regs = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(wdt->regs))
	return PTR_ERR(wdt->regs);

	/* Register the interrupt */
	wdt->rst = of_property_read_bool(pdev->dev.of_node, "reset-on-timeout");
	irq = platform_get_irq(pdev, 0);
	if (!wdt->rst && irq >= 0) {
	ret = devm_request_irq(&pdev->dev, irq, cdns_wdt_irq_handler, 0,
	pdev->name, pdev);
	if (ret) {
	dev_err(&pdev->dev,
	"cannot register interrupt handler err=%d\n",
	ret);
	return ret;
	}
	}

	/* Initialize the members of cdns_wdt structure */
	cdns_wdt_device->parent = &pdev->dev;

	ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
	if (ret) {
	dev_err(&pdev->dev, "unable to set timeout value\n");
	return ret;
	}

	watchdog_set_nowayout(cdns_wdt_device, nowayout);
	watchdog_stop_on_reboot(cdns_wdt_device);
	watchdog_set_drvdata(cdns_wdt_device, wdt);

	wdt->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(wdt->clk)) {
	dev_err(&pdev->dev, "input clock not found\n");
	ret = PTR_ERR(wdt->clk);
	return ret;
	}

	ret = clk_prepare_enable(wdt->clk);
	if (ret) {
	dev_err(&pdev->dev, "unable to enable clock\n");
	return ret;
	}

	clock_f = clk_get_rate(wdt->clk);
	if (clock_f <= CDNS_WDT_CLK_75MHZ) {
	wdt->prescaler = CDNS_WDT_PRESCALE_512;
	wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
	} else {
	wdt->prescaler = CDNS_WDT_PRESCALE_4096;
	wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
	}

	spin_lock_init(&wdt->io_lock);

	ret = watchdog_register_device(cdns_wdt_device);
	if (ret) {
	dev_err(&pdev->dev, "Failed to register wdt device\n");
	goto err_clk_disable;
	}
	platform_set_drvdata(pdev, wdt);

	dev_info(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
	wdt->regs, cdns_wdt_device->timeout,
	nowayout ? ", nowayout" : "");

	return 0;

	err_clk_disable:
	clk_disable_unprepare(wdt->clk);

	return ret;
	}

	/**
	* cdns_wdt_remove - Probe call for the device.
	*
	* @pdev: handle to the platform device structure.
	* Return: 0 on success, otherwise negative error.
	*
	* Unregister the device after releasing the resources.
	*/
	static int cdns_wdt_remove(struct platform_device *pdev)
	{
	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

	cdns_wdt_stop(&wdt->cdns_wdt_device);
	watchdog_unregister_device(&wdt->cdns_wdt_device);
	clk_disable_unprepare(wdt->clk);

	return 0;
	}

	/**
	* cdns_wdt_shutdown - Stop the device.
	*
	* @pdev: handle to the platform structure.
	*
	*/
	static void cdns_wdt_shutdown(struct platform_device *pdev)
	{
	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

	cdns_wdt_stop(&wdt->cdns_wdt_device);
	clk_disable_unprepare(wdt->clk);
	}

	/**
	* cdns_wdt_suspend - Stop the device.
	*
	* @dev: handle to the device structure.
	* Return: 0 always.
	*/
	static int __maybe_unused cdns_wdt_suspend(struct device *dev)
	{
	struct platform_device *pdev = to_platform_device(dev);
	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

	if (watchdog_active(&wdt->cdns_wdt_device)) {
	cdns_wdt_stop(&wdt->cdns_wdt_device);
	clk_disable_unprepare(wdt->clk);
	}

	return 0;
	}

	/**
	* cdns_wdt_resume - Resume the device.
	*
	* @dev: handle to the device structure.
	* Return: 0 on success, errno otherwise.
	*/
	static int __maybe_unused cdns_wdt_resume(struct device *dev)
	{
	int ret;
	struct platform_device *pdev = to_platform_device(dev);
	struct cdns_wdt *wdt = platform_get_drvdata(pdev);

	if (watchdog_active(&wdt->cdns_wdt_device)) {
	ret = clk_prepare_enable(wdt->clk);
	if (ret) {
	dev_err(dev, "unable to enable clock\n");
	return ret;
	}
	cdns_wdt_start(&wdt->cdns_wdt_device);
	}

	return 0;
	}

	static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);

	static const struct of_device_id cdns_wdt_of_match[] = {
	{ .compatible = "cdns,wdt-r1p2", },
	{ /* end of table */ }
	};
	MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);

	/* Driver Structure */
	static struct platform_driver cdns_wdt_driver = {
	.probe = cdns_wdt_probe,
	.remove = cdns_wdt_remove,
	.shutdown = cdns_wdt_shutdown,
	.driver = {
	.name = "cdns-wdt",
	.of_match_table = cdns_wdt_of_match,
	.pm = &cdns_wdt_pm_ops,
	},
	};

	module_platform_driver(cdns_wdt_driver);

	MODULE_AUTHOR("Xilinx, Inc.");
	MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
	MODULE_LICENSE("GPL");