/* Copyright (c) 2014, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>

#define WDT_RST         0x0
#define WDT_EN          0x8
#define WDT_BITE_TIME   0x24

struct qcom_wdt {
        struct watchdog_device  wdd;
        struct clk              *clk;
        unsigned long           rate;
        struct notifier_block   restart_nb;
        void __iomem            *base;
};

static inline
struct qcom_wdt *to_qcom_wdt(struct watchdog_device *wdd)
{
        return container_of(wdd, struct qcom_wdt, wdd);
}

static int qcom_wdt_start(struct watchdog_device *wdd)
{
        struct qcom_wdt *wdt = to_qcom_wdt(wdd);

        writel(0, wdt->base + WDT_EN);
        writel(1, wdt->base + WDT_RST);
        writel(wdd->timeout * wdt->rate, wdt->base + WDT_BITE_TIME);
        writel(1, wdt->base + WDT_EN);
        return 0;
}

static int qcom_wdt_stop(struct watchdog_device *wdd)
{
        struct qcom_wdt *wdt = to_qcom_wdt(wdd);

        writel(0, wdt->base + WDT_EN);
        return 0;
}

static int qcom_wdt_ping(struct watchdog_device *wdd)
{
        struct qcom_wdt *wdt = to_qcom_wdt(wdd);

        writel(1, wdt->base + WDT_RST);
        return 0;
}

static int qcom_wdt_set_timeout(struct watchdog_device *wdd,
                                unsigned int timeout)
{
        wdd->timeout = timeout;
        return qcom_wdt_start(wdd);
}

static const struct watchdog_ops qcom_wdt_ops = {
        .start          = qcom_wdt_start,
        .stop           = qcom_wdt_stop,
        .ping           = qcom_wdt_ping,
        .set_timeout    = qcom_wdt_set_timeout,
        .owner          = THIS_MODULE,
};

static const struct watchdog_info qcom_wdt_info = {
        .options        = WDIOF_KEEPALIVEPING
                        | WDIOF_MAGICCLOSE
                        | WDIOF_SETTIMEOUT,
        .identity       = KBUILD_MODNAME,
};

static int qcom_wdt_restart(struct notifier_block *nb, unsigned long action,
                            void *data)
{
        struct qcom_wdt *wdt = container_of(nb, struct qcom_wdt, restart_nb);
        u32 timeout;

        /*
         * Trigger watchdog bite:
         *    Setup BITE_TIME to be 128ms, and enable WDT.
         */
        timeout = 128 * wdt->rate / 1000;

        writel(0, wdt->base + WDT_EN);
        writel(1, wdt->base + WDT_RST);
        writel(timeout, wdt->base + WDT_BITE_TIME);
        writel(1, wdt->base + WDT_EN);

        /*
         * Actually make sure the above sequence hits hardware before sleeping.
         */
        wmb();

        msleep(150);
        return NOTIFY_DONE;
}

static int qcom_wdt_probe(struct platform_device *pdev)
{
        struct qcom_wdt *wdt;
        struct resource *res;
        int ret;

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

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

        wdt->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(wdt->clk)) {
                dev_err(&pdev->dev, "failed to get input clock\n");
                return PTR_ERR(wdt->clk);
        }

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

        /*
         * We use the clock rate to calculate the max timeout, so ensure it's
         * not zero to avoid a divide-by-zero exception.
         *
         * WATCHDOG_CORE assumes units of seconds, if the WDT is clocked such
         * that it would bite before a second elapses it's usefulness is
         * limited.  Bail if this is the case.
         */
        wdt->rate = clk_get_rate(wdt->clk);
        if (wdt->rate == 0 ||
            wdt->rate > 0x10000000U) {
                dev_err(&pdev->dev, "invalid clock rate\n");
                ret = -EINVAL;
                goto err_clk_unprepare;
        }

        wdt->wdd.dev = &pdev->dev;
        wdt->wdd.info = &qcom_wdt_info;
        wdt->wdd.ops = &qcom_wdt_ops;
        wdt->wdd.min_timeout = 1;
        wdt->wdd.max_timeout = 0x10000000U / wdt->rate;

        /*
         * If 'timeout-sec' unspecified in devicetree, assume a 30 second
         * default, unless the max timeout is less than 30 seconds, then use
         * the max instead.
         */
        wdt->wdd.timeout = min(wdt->wdd.max_timeout, 30U);
        watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);

        ret = watchdog_register_device(&wdt->wdd);
        if (ret) {
                dev_err(&pdev->dev, "failed to register watchdog\n");
                goto err_clk_unprepare;
        }

        /*
         * WDT restart notifier has priority 0 (use as a last resort)
         */
        wdt->restart_nb.notifier_call = qcom_wdt_restart;
        ret = register_restart_handler(&wdt->restart_nb);
        if (ret)
                dev_err(&pdev->dev, "failed to setup restart handler\n");

        platform_set_drvdata(pdev, wdt);
        return 0;

err_clk_unprepare:
        clk_disable_unprepare(wdt->clk);
        return ret;
}

static int qcom_wdt_remove(struct platform_device *pdev)
{
        struct qcom_wdt *wdt = platform_get_drvdata(pdev);

        unregister_restart_handler(&wdt->restart_nb);
        watchdog_unregister_device(&wdt->wdd);
        clk_disable_unprepare(wdt->clk);
        return 0;
}

static const struct of_device_id qcom_wdt_of_table[] = {
        { .compatible = "qcom,kpss-wdt-msm8960", },
        { .compatible = "qcom,kpss-wdt-apq8064", },
        { .compatible = "qcom,kpss-wdt-ipq8064", },
        { },
};
MODULE_DEVICE_TABLE(of, qcom_wdt_of_table);

static struct platform_driver qcom_watchdog_driver = {
        .probe  = qcom_wdt_probe,
        .remove = qcom_wdt_remove,
        .driver = {
                .name           = KBUILD_MODNAME,
                .of_match_table = qcom_wdt_of_table,
        },
};
module_platform_driver(qcom_watchdog_driver);

MODULE_DESCRIPTION("QCOM KPSS Watchdog Driver");
MODULE_LICENSE("GPL v2");