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/*
 * Moschip MCS814x Watchdog driver
 *
 * Copyright (C) 2012, Florian Fainelli <florian@openwrt.org>
 *
 * 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.
 *
 * 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.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/io.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/of.h>

#define WDT_COUNT       0x00
#define WDT_CTRL        0x04
#define  WDT_CTRL_EN    0x1

/* watchdog frequency */
#define WDT_MAX_VALUE   (0xffffffff)

struct mcs814x_wdt {
        void __iomem            *regs;
        spinlock_t              lock;
        struct watchdog_device  wdt_dev;
        struct clk              *clk;
};

static int mcs814x_wdt_start(struct watchdog_device *dev)
{
        struct mcs814x_wdt *wdt = watchdog_get_drvdata(dev);
        u32 reg;

        spin_lock(&wdt->lock);
        reg = readl_relaxed(wdt->regs + WDT_CTRL);
        reg |= WDT_CTRL_EN;
        writel_relaxed(reg, wdt->regs + WDT_CTRL);
        spin_unlock(&wdt->lock);

        return 0;
}

static int mcs814x_wdt_stop(struct watchdog_device *dev)
{
        struct mcs814x_wdt *wdt = watchdog_get_drvdata(dev);
        u32 reg;

        spin_lock(&wdt->lock);
        reg = readl_relaxed(wdt->regs + WDT_CTRL);
        reg &= ~WDT_CTRL_EN;
        writel_relaxed(reg, wdt->regs + WDT_CTRL);
        spin_unlock(&wdt->lock);

        return 0;
}

static int mcs814x_wdt_set_timeout(struct watchdog_device *dev,
                                unsigned int new_timeout)
{
        struct mcs814x_wdt *wdt = watchdog_get_drvdata(dev);

        spin_lock(&wdt->lock);
        /* watchdog counts upward and rollover (0xfffffff -> 0)
         * triggers the reboot
         */
        writel_relaxed(WDT_MAX_VALUE - (new_timeout * clk_get_rate(wdt->clk)),
                wdt->regs + WDT_COUNT);
        spin_unlock(&wdt->lock);

        return 0;
}

static int mcs814x_wdt_ping(struct watchdog_device *dev)
{
        /* restart the watchdog */
        mcs814x_wdt_stop(dev);
        mcs814x_wdt_set_timeout(dev, dev->timeout);
        mcs814x_wdt_start(dev);

        return 0;
}

static const struct watchdog_info mcs814x_wdt_ident = {
        .options        = WDIOF_CARDRESET | WDIOF_SETTIMEOUT |
                          WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
        .identity       = "MCS814x Watchdog",
};

static struct watchdog_ops mcs814x_wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = mcs814x_wdt_start,
        .stop           = mcs814x_wdt_stop,
        .set_timeout    = mcs814x_wdt_set_timeout,
        .ping           = mcs814x_wdt_ping,
};

static int mcs814x_wdt_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct mcs814x_wdt *wdt;
        int ret;
        struct clk *clk;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

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

        wdt = kzalloc(sizeof(*wdt), GFP_KERNEL);
        if (!wdt) {
                ret = -ENOMEM;
                goto out_clk;
        }

        spin_lock_init(&wdt->lock);
        wdt->clk = clk;
        wdt->wdt_dev.info = &mcs814x_wdt_ident;
        wdt->wdt_dev.ops = &mcs814x_wdt_ops;
        wdt->wdt_dev.min_timeout = 1;
        /* approximately 10995 secs */
        wdt->wdt_dev.max_timeout = (WDT_MAX_VALUE / clk_get_rate(clk));

        platform_set_drvdata(pdev, wdt);

        /* only ioremap registers, because the register is shared */
        wdt->regs = devm_ioremap(&pdev->dev, res->start, resource_size(res));
        if (!wdt->regs) {
                ret = -ENOMEM;
                goto out;
        }

        watchdog_set_drvdata(&wdt->wdt_dev, wdt);

        ret = watchdog_register_device(&wdt->wdt_dev);
        if (ret) {
                dev_err(&pdev->dev, "cannot register watchdog: %d\n", ret);
                goto out;
        }

        dev_info(&pdev->dev, "registered\n");
        return 0;

out:
        platform_set_drvdata(pdev, NULL);
        kfree(wdt);
out_clk:
        clk_put(clk);
        return ret;
}

static int mcs814x_wdt_remove(struct platform_device *pdev)
{
        struct mcs814x_wdt *wdt = platform_get_drvdata(pdev);

        clk_put(wdt->clk);
        watchdog_unregister_device(&wdt->wdt_dev);
        watchdog_set_drvdata(&wdt->wdt_dev, NULL);
        kfree(wdt);
        platform_set_drvdata(pdev, NULL);

        return 0;
}

static const struct of_device_id mcs814x_wdt_ids[] = {
        { .compatible = "moschip,mcs814x-wdt", },
        { /* sentinel */ },
};

static struct platform_driver mcs814x_wdt_driver = {
        .driver = {
                .name   = "mcs814x-wdt",
                .owner  = THIS_MODULE,
                .of_match_table = mcs814x_wdt_ids,
        },
        .probe          = mcs814x_wdt_probe,
        .remove         = mcs814x_wdt_remove,
};

module_platform_driver(mcs814x_wdt_driver);

MODULE_AUTHOR("Florian Fainelli <florian@openwrt.org>");
MODULE_DESCRIPTION("Moschip MCS814x Watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:mcs814x-wdt");