/*
 * 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/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;
};

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);

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

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

        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;
}

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

        watchdog_unregister_device(&xdev->xilinx_wdt_wdd);

        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");