// SPDX-License-Identifier: GPL-2.0
/*
 * Watchdog driver for the MEN z069 IP-Core
 *
 * Copyright (C) 2018 Johannes Thumshirn <jth@kernel.org>
 */
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mcb.h>
#include <linux/module.h>
#include <linux/watchdog.h>

struct men_z069_drv {
        struct watchdog_device wdt;
        void __iomem *base;
        struct resource *mem;
};

#define MEN_Z069_WTR                    0x10
#define MEN_Z069_WTR_WDEN               BIT(15)
#define MEN_Z069_WTR_WDET_MASK          0x7fff
#define MEN_Z069_WVR                    0x14

#define MEN_Z069_TIMER_FREQ             500 /* 500 Hz */
#define MEN_Z069_WDT_COUNTER_MIN        1
#define MEN_Z069_WDT_COUNTER_MAX        0x7fff
#define MEN_Z069_DEFAULT_TIMEOUT        30

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 men_z069_wdt_start(struct watchdog_device *wdt)
{
        struct men_z069_drv *drv = watchdog_get_drvdata(wdt);
        u16 val;

        val = readw(drv->base + MEN_Z069_WTR);
        val |= MEN_Z069_WTR_WDEN;
        writew(val, drv->base + MEN_Z069_WTR);

        return 0;
}

static int men_z069_wdt_stop(struct watchdog_device *wdt)
{
        struct men_z069_drv *drv = watchdog_get_drvdata(wdt);
        u16 val;

        val = readw(drv->base + MEN_Z069_WTR);
        val &= ~MEN_Z069_WTR_WDEN;
        writew(val, drv->base + MEN_Z069_WTR);

        return 0;
}

static int men_z069_wdt_ping(struct watchdog_device *wdt)
{
        struct men_z069_drv *drv = watchdog_get_drvdata(wdt);
        u16 val;

        /* The watchdog trigger value toggles between 0x5555 and 0xaaaa */
        val = readw(drv->base + MEN_Z069_WVR);
        val ^= 0xffff;
        writew(val, drv->base + MEN_Z069_WVR);

        return 0;
}

static int men_z069_wdt_set_timeout(struct watchdog_device *wdt,
                                    unsigned int timeout)
{
        struct men_z069_drv *drv = watchdog_get_drvdata(wdt);
        u16 reg, val, ena;

        wdt->timeout = timeout;
        val = timeout * MEN_Z069_TIMER_FREQ;

        reg = readw(drv->base + MEN_Z069_WTR);
        ena = reg & MEN_Z069_WTR_WDEN;
        reg = ena | val;
        writew(reg, drv->base + MEN_Z069_WTR);

        return 0;
}

static const struct watchdog_info men_z069_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
        .identity = "MEN z069 Watchdog",
};

static const struct watchdog_ops men_z069_ops = {
        .owner = THIS_MODULE,
        .start = men_z069_wdt_start,
        .stop = men_z069_wdt_stop,
        .ping = men_z069_wdt_ping,
        .set_timeout = men_z069_wdt_set_timeout,
};

static int men_z069_probe(struct mcb_device *dev,
                          const struct mcb_device_id *id)
{
        struct men_z069_drv *drv;
        struct resource *mem;

        drv = devm_kzalloc(&dev->dev, sizeof(struct men_z069_drv), GFP_KERNEL);
        if (!drv)
                return -ENOMEM;

        mem = mcb_request_mem(dev, "z069-wdt");
        if (IS_ERR(mem))
                return PTR_ERR(mem);

        drv->base = devm_ioremap(&dev->dev, mem->start, resource_size(mem));
        if (drv->base == NULL)
                goto release_mem;

        drv->mem = mem;
        drv->wdt.info = &men_z069_info;
        drv->wdt.ops = &men_z069_ops;
        drv->wdt.timeout = MEN_Z069_DEFAULT_TIMEOUT;
        drv->wdt.min_timeout = 1;
        drv->wdt.max_timeout = MEN_Z069_WDT_COUNTER_MAX / MEN_Z069_TIMER_FREQ;

        watchdog_init_timeout(&drv->wdt, 0, &dev->dev);
        watchdog_set_nowayout(&drv->wdt, nowayout);
        watchdog_set_drvdata(&drv->wdt, drv);
        drv->wdt.parent = &dev->dev;
        mcb_set_drvdata(dev, drv);

        return watchdog_register_device(&drv->wdt);

release_mem:
        mcb_release_mem(mem);
        return -ENOMEM;
}

static void men_z069_remove(struct mcb_device *dev)
{
        struct men_z069_drv *drv = mcb_get_drvdata(dev);

        watchdog_unregister_device(&drv->wdt);
        mcb_release_mem(drv->mem);
}

static const struct mcb_device_id men_z069_ids[] = {
        { .device = 0x45 },
        { }
};
MODULE_DEVICE_TABLE(mcb, men_z069_ids);

static struct mcb_driver men_z069_driver = {
        .driver = {
                .name = "z069-wdt",
        },
        .probe = men_z069_probe,
        .remove = men_z069_remove,
        .id_table = men_z069_ids,
};
module_mcb_driver(men_z069_driver);

MODULE_AUTHOR("Johannes Thumshirn <jth@kernel.org>");
MODULE_DESCRIPTION("Watchdog driver for the MEN z069 IP-Core");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("mcb:16z069");
MODULE_IMPORT_NS("MCB");