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/*
 * Watchdog Device Driver for Xilinx axi/xps_timebase_wdt
 *
 * (C) Copyright 2013 - 2014 Xilinx, Inc.
 * (C) Copyright 2011 (Alejandro Cabrera <aldaya@gmail.com>)
 *
 * 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.
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ioport.h>
#include <linux/watchdog.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_address.h>

/* Register offsets for the Wdt device */
#define XWT_TWCSR0_OFFSET   0x0 /* Control/Status Register0 */
#define XWT_TWCSR1_OFFSET   0x4 /* Control/Status Register1 */
#define XWT_TBR_OFFSET      0x8 /* Timebase Register Offset */

/* Control/Status Register Masks  */
#define XWT_CSR0_WRS_MASK   0x00000008 /* Reset status */
#define XWT_CSR0_WDS_MASK   0x00000004 /* Timer state  */
#define XWT_CSR0_EWDT1_MASK 0x00000002 /* Enable bit 1 */

/* Control/Status Register 0/1 bits  */
#define XWT_CSRX_EWDT2_MASK 0x00000001 /* Enable bit 2 */

/* SelfTest constants */
#define XWT_MAX_SELFTEST_LOOP_COUNT 0x00010000
#define XWT_TIMER_FAILED            0xFFFFFFFF

#define WATCHDOG_NAME     "Xilinx Watchdog"

struct xwdt_device {
	void __iomem *base;
	u32 wdt_interval;
	spinlock_t spinlock;
	struct watchdog_device xilinx_wdt_wdd;
	struct clk		*clk;
};

static int xilinx_wdt_start(struct watchdog_device *wdd)
{
	u32 control_status_reg;
	struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

	spin_lock(&xdev->spinlock);

	/* Clean previous status and enable the watchdog timer */
	control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);
	control_status_reg |= (XWT_CSR0_WRS_MASK | XWT_CSR0_WDS_MASK);

	iowrite32((control_status_reg | XWT_CSR0_EWDT1_MASK),
		  xdev->base + XWT_TWCSR0_OFFSET);

	iowrite32(XWT_CSRX_EWDT2_MASK, xdev->base + XWT_TWCSR1_OFFSET);

	spin_unlock(&xdev->spinlock);

	return 0;
}

static int xilinx_wdt_stop(struct watchdog_device *wdd)
{
	u32 control_status_reg;
	struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

	spin_lock(&xdev->spinlock);

	control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);

	iowrite32((control_status_reg & ~XWT_CSR0_EWDT1_MASK),
		  xdev->base + XWT_TWCSR0_OFFSET);

	iowrite32(0, xdev->base + XWT_TWCSR1_OFFSET);

	spin_unlock(&xdev->spinlock);
	pr_info("Stopped!\n");

	return 0;
}

static int xilinx_wdt_keepalive(struct watchdog_device *wdd)
{
	u32 control_status_reg;
	struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

	spin_lock(&xdev->spinlock);

	control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);
	control_status_reg |= (XWT_CSR0_WRS_MASK | XWT_CSR0_WDS_MASK);
	iowrite32(control_status_reg, xdev->base + XWT_TWCSR0_OFFSET);

	spin_unlock(&xdev->spinlock);

	return 0;
}

static const struct watchdog_info xilinx_wdt_ident = {
	.options =  WDIOF_MAGICCLOSE |
		    WDIOF_KEEPALIVEPING,
	.firmware_version =	1,
	.identity =	WATCHDOG_NAME,
};

static const struct watchdog_ops xilinx_wdt_ops = {
	.owner = THIS_MODULE,
	.start = xilinx_wdt_start,
	.stop = xilinx_wdt_stop,
	.ping = xilinx_wdt_keepalive,
};

static u32 xwdt_selftest(struct xwdt_device *xdev)
{
	int i;
	u32 timer_value1;
	u32 timer_value2;

	spin_lock(&xdev->spinlock);

	timer_value1 = ioread32(xdev->base + XWT_TBR_OFFSET);
	timer_value2 = ioread32(xdev->base + XWT_TBR_OFFSET);

	for (i = 0;
		((i <= XWT_MAX_SELFTEST_LOOP_COUNT) &&
			(timer_value2 == timer_value1)); i++) {
		timer_value2 = ioread32(xdev->base + XWT_TBR_OFFSET);
	}

	spin_unlock(&xdev->spinlock);

	if (timer_value2 != timer_value1)
		return ~XWT_TIMER_FAILED;
	else
		return XWT_TIMER_FAILED;
}

static int xwdt_probe(struct platform_device *pdev)
{
	int rc;
	u32 pfreq = 0, enable_once = 0;
	struct resource *res;
	struct xwdt_device *xdev;
	struct watchdog_device *xilinx_wdt_wdd;

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

	xilinx_wdt_wdd = &xdev->xilinx_wdt_wdd;
	xilinx_wdt_wdd->info = &xilinx_wdt_ident;
	xilinx_wdt_wdd->ops = &xilinx_wdt_ops;
	xilinx_wdt_wdd->parent = &pdev->dev;

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

	rc = of_property_read_u32(pdev->dev.of_node, "clock-frequency", &pfreq);
	if (rc)
		dev_warn(&pdev->dev,
			 "The watchdog clock frequency cannot be obtained\n");

	rc = of_property_read_u32(pdev->dev.of_node, "xlnx,wdt-interval",
				  &xdev->wdt_interval);
	if (rc)
		dev_warn(&pdev->dev,
			 "Parameter \"xlnx,wdt-interval\" not found\n");

	rc = of_property_read_u32(pdev->dev.of_node, "xlnx,wdt-enable-once",
				  &enable_once);
	if (rc)
		dev_warn(&pdev->dev,
			 "Parameter \"xlnx,wdt-enable-once\" not found\n");

	watchdog_set_nowayout(xilinx_wdt_wdd, enable_once);

	/*
	 * Twice of the 2^wdt_interval / freq  because the first wdt overflow is
	 * ignored (interrupt), reset is only generated at second wdt overflow
	 */
	if (pfreq && xdev->wdt_interval)
		xilinx_wdt_wdd->timeout = 2 * ((1 << xdev->wdt_interval) /
					  pfreq);

	spin_lock_init(&xdev->spinlock);
	watchdog_set_drvdata(xilinx_wdt_wdd, xdev);

	xdev->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(xdev->clk)) {
		if (PTR_ERR(xdev->clk) == -ENOENT)
			xdev->clk = NULL;
		else
			return PTR_ERR(xdev->clk);
	}

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

	rc = xwdt_selftest(xdev);
	if (rc == XWT_TIMER_FAILED) {
		dev_err(&pdev->dev, "SelfTest routine error\n");
		goto err_clk_disable;
	}

	rc = watchdog_register_device(xilinx_wdt_wdd);
	if (rc) {
		dev_err(&pdev->dev, "Cannot register watchdog (err=%d)\n", rc);
		goto err_clk_disable;
	}

	dev_info(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds\n",
		 xdev->base, xilinx_wdt_wdd->timeout);

	platform_set_drvdata(pdev, xdev);

	return 0;
err_clk_disable:
	clk_disable_unprepare(xdev->clk);

	return rc;
}

static int xwdt_remove(struct platform_device *pdev)
{
	struct xwdt_device *xdev = platform_get_drvdata(pdev);

	watchdog_unregister_device(&xdev->xilinx_wdt_wdd);
	clk_disable_unprepare(xdev->clk);

	return 0;
}

/* Match table for of_platform binding */
static const struct of_device_id xwdt_of_match[] = {
	{ .compatible = "xlnx,xps-timebase-wdt-1.00.a", },
	{ .compatible = "xlnx,xps-timebase-wdt-1.01.a", },
	{},
};
MODULE_DEVICE_TABLE(of, xwdt_of_match);

static struct platform_driver xwdt_driver = {
	.probe       = xwdt_probe,
	.remove      = xwdt_remove,
	.driver = {
		.name  = WATCHDOG_NAME,
		.of_match_table = xwdt_of_match,
	},
};

module_platform_driver(xwdt_driver);

MODULE_AUTHOR("Alejandro Cabrera <aldaya@gmail.com>");
MODULE_DESCRIPTION("Xilinx Watchdog driver");
MODULE_LICENSE("GPL v2");