// SPDX-License-Identifier: GPL-2.0-only
/*
 * sl28cpld watchdog driver
 *
 * Copyright 2020 Kontron Europe GmbH
 */

#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

/*
 * Watchdog timer block registers.
 */
#define WDT_CTRL                        0x00
#define  WDT_CTRL_EN                    BIT(0)
#define  WDT_CTRL_LOCK                  BIT(2)
#define  WDT_CTRL_ASSERT_SYS_RESET      BIT(6)
#define  WDT_CTRL_ASSERT_WDT_TIMEOUT    BIT(7)
#define WDT_TIMEOUT                     0x01
#define WDT_KICK                        0x02
#define  WDT_KICK_VALUE                 0x6b
#define WDT_COUNT                       0x03

#define WDT_DEFAULT_TIMEOUT             10

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static int timeout;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Initial watchdog timeout in seconds");

struct sl28cpld_wdt {
        struct watchdog_device wdd;
        struct regmap *regmap;
        u32 offset;
        bool assert_wdt_timeout;
};

static int sl28cpld_wdt_ping(struct watchdog_device *wdd)
{
        struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);

        return regmap_write(wdt->regmap, wdt->offset + WDT_KICK,
                            WDT_KICK_VALUE);
}

static int sl28cpld_wdt_start(struct watchdog_device *wdd)
{
        struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
        unsigned int val;

        val = WDT_CTRL_EN | WDT_CTRL_ASSERT_SYS_RESET;
        if (wdt->assert_wdt_timeout)
                val |= WDT_CTRL_ASSERT_WDT_TIMEOUT;
        if (nowayout)
                val |= WDT_CTRL_LOCK;

        return regmap_update_bits(wdt->regmap, wdt->offset + WDT_CTRL,
                                  val, val);
}

static int sl28cpld_wdt_stop(struct watchdog_device *wdd)
{
        struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);

        return regmap_update_bits(wdt->regmap, wdt->offset + WDT_CTRL,
                                  WDT_CTRL_EN, 0);
}

static unsigned int sl28cpld_wdt_get_timeleft(struct watchdog_device *wdd)
{
        struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
        unsigned int val;
        int ret;

        ret = regmap_read(wdt->regmap, wdt->offset + WDT_COUNT, &val);
        if (ret)
                return 0;

        return val;
}

static int sl28cpld_wdt_set_timeout(struct watchdog_device *wdd,
                                    unsigned int timeout)
{
        struct sl28cpld_wdt *wdt = watchdog_get_drvdata(wdd);
        int ret;

        ret = regmap_write(wdt->regmap, wdt->offset + WDT_TIMEOUT, timeout);
        if (ret)
                return ret;

        wdd->timeout = timeout;

        return 0;
}

static const struct watchdog_info sl28cpld_wdt_info = {
        .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
        .identity = "sl28cpld watchdog",
};

static const struct watchdog_ops sl28cpld_wdt_ops = {
        .owner = THIS_MODULE,
        .start = sl28cpld_wdt_start,
        .stop = sl28cpld_wdt_stop,
        .ping = sl28cpld_wdt_ping,
        .set_timeout = sl28cpld_wdt_set_timeout,
        .get_timeleft = sl28cpld_wdt_get_timeleft,
};

static int sl28cpld_wdt_probe(struct platform_device *pdev)
{
        struct watchdog_device *wdd;
        struct sl28cpld_wdt *wdt;
        unsigned int status;
        unsigned int val;
        int ret;

        if (!pdev->dev.parent)
                return -ENODEV;

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

        wdt->regmap = dev_get_regmap(pdev->dev.parent, NULL);
        if (!wdt->regmap)
                return -ENODEV;

        ret = device_property_read_u32(&pdev->dev, "reg", &wdt->offset);
        if (ret)
                return -EINVAL;

        wdt->assert_wdt_timeout = device_property_read_bool(&pdev->dev,
                                                            "kontron,assert-wdt-timeout-pin");

        /* initialize struct watchdog_device */
        wdd = &wdt->wdd;
        wdd->parent = &pdev->dev;
        wdd->info = &sl28cpld_wdt_info;
        wdd->ops = &sl28cpld_wdt_ops;
        wdd->min_timeout = 1;
        wdd->max_timeout = 255;

        watchdog_set_drvdata(wdd, wdt);
        watchdog_stop_on_reboot(wdd);

        /*
         * Read the status early, in case of an error, we haven't modified the
         * hardware.
         */
        ret = regmap_read(wdt->regmap, wdt->offset + WDT_CTRL, &status);
        if (ret)
                return ret;

        /*
         * Initial timeout value, may be overwritten by device tree or module
         * parameter in watchdog_init_timeout().
         *
         * Reading a zero here means that either the hardware has a default
         * value of zero (which is very unlikely and definitely a hardware
         * bug) or the bootloader set it to zero. In any case, we handle
         * this case gracefully and set out own timeout.
         */
        ret = regmap_read(wdt->regmap, wdt->offset + WDT_TIMEOUT, &val);
        if (ret)
                return ret;

        if (val)
                wdd->timeout = val;
        else
                wdd->timeout = WDT_DEFAULT_TIMEOUT;

        watchdog_init_timeout(wdd, timeout, &pdev->dev);
        sl28cpld_wdt_set_timeout(wdd, wdd->timeout);

        /* if the watchdog is locked, we set nowayout */
        if (status & WDT_CTRL_LOCK)
                nowayout = true;
        watchdog_set_nowayout(wdd, nowayout);

        /*
         * If watchdog is already running, keep it enabled, but make
         * sure its mode is set correctly.
         */
        if (status & WDT_CTRL_EN) {
                sl28cpld_wdt_start(wdd);
                set_bit(WDOG_HW_RUNNING, &wdd->status);
        }

        ret = devm_watchdog_register_device(&pdev->dev, wdd);
        if (ret < 0)
                return ret;

        dev_info(&pdev->dev, "initial timeout %d sec%s\n",
                 wdd->timeout, nowayout ? ", nowayout" : "");

        return 0;
}

static const struct of_device_id sl28cpld_wdt_of_match[] = {
        { .compatible = "kontron,sl28cpld-wdt" },
        {}
};
MODULE_DEVICE_TABLE(of, sl28cpld_wdt_of_match);

static struct platform_driver sl28cpld_wdt_driver = {
        .probe = sl28cpld_wdt_probe,
        .driver = {
                .name = "sl28cpld-wdt",
                .of_match_table = sl28cpld_wdt_of_match,
        },
};
module_platform_driver(sl28cpld_wdt_driver);

MODULE_DESCRIPTION("sl28cpld Watchdog Driver");
MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
MODULE_LICENSE("GPL");