// SPDX-License-Identifier: GPL-2.0+
/*
 * Watchdog driver for Conexant Digicolor
 *
 * Copyright (C) 2015 Paradox Innovation Ltd.
 *
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/watchdog.h>
#include <linux/platform_device.h>
#include <linux/of_address.h>

#define TIMER_A_CONTROL         0
#define TIMER_A_COUNT           4

#define TIMER_A_ENABLE_COUNT    BIT(0)
#define TIMER_A_ENABLE_WATCHDOG BIT(1)

struct dc_wdt {
        void __iomem            *base;
        struct clk              *clk;
        spinlock_t              lock;
};

static unsigned timeout;
module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");

static void dc_wdt_set(struct dc_wdt *wdt, u32 ticks)
{
        unsigned long flags;

        spin_lock_irqsave(&wdt->lock, flags);

        writel_relaxed(0, wdt->base + TIMER_A_CONTROL);
        writel_relaxed(ticks, wdt->base + TIMER_A_COUNT);
        writel_relaxed(TIMER_A_ENABLE_COUNT | TIMER_A_ENABLE_WATCHDOG,
                       wdt->base + TIMER_A_CONTROL);

        spin_unlock_irqrestore(&wdt->lock, flags);
}

static int dc_wdt_restart(struct watchdog_device *wdog, unsigned long action,
                          void *data)
{
        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);

        dc_wdt_set(wdt, 1);
        /* wait for reset to assert... */
        mdelay(500);

        return 0;
}

static int dc_wdt_start(struct watchdog_device *wdog)
{
        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);

        dc_wdt_set(wdt, wdog->timeout * clk_get_rate(wdt->clk));

        return 0;
}

static int dc_wdt_stop(struct watchdog_device *wdog)
{
        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);

        writel_relaxed(0, wdt->base + TIMER_A_CONTROL);

        return 0;
}

static int dc_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
{
        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);

        dc_wdt_set(wdt, t * clk_get_rate(wdt->clk));
        wdog->timeout = t;

        return 0;
}

static unsigned int dc_wdt_get_timeleft(struct watchdog_device *wdog)
{
        struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
        uint32_t count = readl_relaxed(wdt->base + TIMER_A_COUNT);

        return count / clk_get_rate(wdt->clk);
}

static const struct watchdog_ops dc_wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = dc_wdt_start,
        .stop           = dc_wdt_stop,
        .set_timeout    = dc_wdt_set_timeout,
        .get_timeleft   = dc_wdt_get_timeleft,
        .restart        = dc_wdt_restart,
};

static const struct watchdog_info dc_wdt_info = {
        .options        = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE
                        | WDIOF_KEEPALIVEPING,
        .identity       = "Conexant Digicolor Watchdog",
};

static struct watchdog_device dc_wdt_wdd = {
        .info           = &dc_wdt_info,
        .ops            = &dc_wdt_ops,
        .min_timeout    = 1,
};

static int dc_wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct dc_wdt *wdt;

        wdt = devm_kzalloc(dev, sizeof(struct dc_wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        wdt->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(wdt->base))
                return PTR_ERR(wdt->base);

        wdt->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(wdt->clk))
                return PTR_ERR(wdt->clk);
        dc_wdt_wdd.max_timeout = U32_MAX / clk_get_rate(wdt->clk);
        dc_wdt_wdd.timeout = dc_wdt_wdd.max_timeout;
        dc_wdt_wdd.parent = dev;

        spin_lock_init(&wdt->lock);

        watchdog_set_drvdata(&dc_wdt_wdd, wdt);
        watchdog_set_restart_priority(&dc_wdt_wdd, 128);
        watchdog_init_timeout(&dc_wdt_wdd, timeout, dev);
        watchdog_stop_on_reboot(&dc_wdt_wdd);
        return devm_watchdog_register_device(dev, &dc_wdt_wdd);
}

static const struct of_device_id dc_wdt_of_match[] = {
        { .compatible = "cnxt,cx92755-wdt", },
        {},
};
MODULE_DEVICE_TABLE(of, dc_wdt_of_match);

static struct platform_driver dc_wdt_driver = {
        .probe          = dc_wdt_probe,
        .driver = {
                .name =         "digicolor-wdt",
                .of_match_table = dc_wdt_of_match,
        },
};
module_platform_driver(dc_wdt_driver);

MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
MODULE_DESCRIPTION("Driver for Conexant Digicolor watchdog timer");
MODULE_LICENSE("GPL");