// SPDX-License-Identifier: GPL-2.0-only
/*
 * drivers/char/watchdog/ixp4xx_wdt.c
 *
 * Watchdog driver for Intel IXP4xx network processors
 *
 * Author: Deepak Saxena <dsaxena@plexity.net>
 * Author: Linus Walleij <linus.walleij@linaro.org>
 *
 * Copyright 2004 (c) MontaVista, Software, Inc.
 * Based on sa1100 driver, Copyright (C) 2000 Oleg Drokin <green@crimea.edu>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/watchdog.h>
#include <linux/bits.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/soc/ixp4xx/cpu.h>

struct ixp4xx_wdt {
        struct watchdog_device wdd;
        void __iomem *base;
        unsigned long rate;
};

/* Fallback if we do not have a clock for this */
#define IXP4XX_TIMER_FREQ       66666000

/* Registers after the timer registers */
#define IXP4XX_OSWT_OFFSET      0x14  /* Watchdog Timer */
#define IXP4XX_OSWE_OFFSET      0x18  /* Watchdog Enable */
#define IXP4XX_OSWK_OFFSET      0x1C  /* Watchdog Key */
#define IXP4XX_OSST_OFFSET      0x20  /* Timer Status */

#define IXP4XX_OSST_TIMER_WDOG_PEND     0x00000008
#define IXP4XX_OSST_TIMER_WARM_RESET    0x00000010
#define IXP4XX_WDT_KEY                  0x0000482E
#define IXP4XX_WDT_RESET_ENABLE         0x00000001
#define IXP4XX_WDT_IRQ_ENABLE           0x00000002
#define IXP4XX_WDT_COUNT_ENABLE         0x00000004

static inline
struct ixp4xx_wdt *to_ixp4xx_wdt(struct watchdog_device *wdd)
{
        return container_of(wdd, struct ixp4xx_wdt, wdd);
}

static int ixp4xx_wdt_start(struct watchdog_device *wdd)
{
        struct ixp4xx_wdt *iwdt = to_ixp4xx_wdt(wdd);

        __raw_writel(IXP4XX_WDT_KEY, iwdt->base + IXP4XX_OSWK_OFFSET);
        __raw_writel(0, iwdt->base + IXP4XX_OSWE_OFFSET);
        __raw_writel(wdd->timeout * iwdt->rate,
                     iwdt->base + IXP4XX_OSWT_OFFSET);
        __raw_writel(IXP4XX_WDT_COUNT_ENABLE | IXP4XX_WDT_RESET_ENABLE,
                     iwdt->base + IXP4XX_OSWE_OFFSET);
        __raw_writel(0, iwdt->base + IXP4XX_OSWK_OFFSET);

        return 0;
}

static int ixp4xx_wdt_stop(struct watchdog_device *wdd)
{
        struct ixp4xx_wdt *iwdt = to_ixp4xx_wdt(wdd);

        __raw_writel(IXP4XX_WDT_KEY, iwdt->base + IXP4XX_OSWK_OFFSET);
        __raw_writel(0, iwdt->base + IXP4XX_OSWE_OFFSET);
        __raw_writel(0, iwdt->base + IXP4XX_OSWK_OFFSET);

        return 0;
}

static int ixp4xx_wdt_set_timeout(struct watchdog_device *wdd,
                                  unsigned int timeout)
{
        wdd->timeout = timeout;
        if (watchdog_active(wdd))
                ixp4xx_wdt_start(wdd);

        return 0;
}

static int ixp4xx_wdt_restart(struct watchdog_device *wdd,
                              unsigned long action, void *data)
{
        struct ixp4xx_wdt *iwdt = to_ixp4xx_wdt(wdd);

        __raw_writel(IXP4XX_WDT_KEY, iwdt->base + IXP4XX_OSWK_OFFSET);
        __raw_writel(0, iwdt->base + IXP4XX_OSWT_OFFSET);
        __raw_writel(IXP4XX_WDT_COUNT_ENABLE | IXP4XX_WDT_RESET_ENABLE,
                     iwdt->base + IXP4XX_OSWE_OFFSET);

        return 0;
}

static const struct watchdog_ops ixp4xx_wdt_ops = {
        .start = ixp4xx_wdt_start,
        .stop = ixp4xx_wdt_stop,
        .set_timeout = ixp4xx_wdt_set_timeout,
        .restart = ixp4xx_wdt_restart,
        .owner = THIS_MODULE,
};

/*
 * The A0 version of the IXP422 had a bug in the watchdog making
 * is useless, but we still need to use it to restart the system
 * as it is the only way, so in this special case we register a
 * "dummy" watchdog that doesn't really work, but will support
 * the restart operation.
 */
static int ixp4xx_wdt_dummy(struct watchdog_device *wdd)
{
        return 0;
}

static const struct watchdog_ops ixp4xx_wdt_restart_only_ops = {
        .start = ixp4xx_wdt_dummy,
        .stop = ixp4xx_wdt_dummy,
        .restart = ixp4xx_wdt_restart,
        .owner = THIS_MODULE,
};

static const struct watchdog_info ixp4xx_wdt_info = {
        .options = WDIOF_KEEPALIVEPING
                | WDIOF_MAGICCLOSE
                | WDIOF_SETTIMEOUT,
        .identity = KBUILD_MODNAME,
};

static int ixp4xx_wdt_probe(struct platform_device *pdev)
{
        static const struct watchdog_ops *iwdt_ops;
        struct device *dev = &pdev->dev;
        struct ixp4xx_wdt *iwdt;
        struct clk *clk;
        int ret;

        if (!(read_cpuid_id() & 0xf) && !cpu_is_ixp46x()) {
                dev_info(dev, "Rev. A0 IXP42x CPU detected - only restart supported\n");
                iwdt_ops = &ixp4xx_wdt_restart_only_ops;
        } else {
                iwdt_ops = &ixp4xx_wdt_ops;
        }

        iwdt = devm_kzalloc(dev, sizeof(*iwdt), GFP_KERNEL);
        if (!iwdt)
                return -ENOMEM;
        iwdt->base = (void __iomem *)dev->platform_data;

        /*
         * Retrieve rate from a fixed clock from the device tree if
         * the parent has that, else use the default clock rate.
         */
        clk = devm_clk_get_enabled(dev->parent, NULL);
        if (!IS_ERR(clk))
                iwdt->rate = clk_get_rate(clk);

        if (!iwdt->rate)
                iwdt->rate = IXP4XX_TIMER_FREQ;

        iwdt->wdd.info = &ixp4xx_wdt_info;
        iwdt->wdd.ops = iwdt_ops;
        iwdt->wdd.min_timeout = 1;
        iwdt->wdd.max_timeout = U32_MAX / iwdt->rate;
        iwdt->wdd.parent = dev;
        /* Default to 60 seconds */
        iwdt->wdd.timeout = 60U;
        watchdog_init_timeout(&iwdt->wdd, 0, dev);

        if (__raw_readl(iwdt->base + IXP4XX_OSST_OFFSET) &
            IXP4XX_OSST_TIMER_WARM_RESET)
                iwdt->wdd.bootstatus = WDIOF_CARDRESET;

        ret = devm_watchdog_register_device(dev, &iwdt->wdd);
        if (ret)
                return ret;

        dev_info(dev, "IXP4xx watchdog available\n");

        return 0;
}

static struct platform_driver ixp4xx_wdt_driver = {
        .probe = ixp4xx_wdt_probe,
        .driver = {
                .name   = "ixp4xx-watchdog",
        },
};
module_platform_driver(ixp4xx_wdt_driver);

MODULE_AUTHOR("Deepak Saxena <dsaxena@plexity.net>");
MODULE_DESCRIPTION("IXP4xx Network Processor Watchdog");
MODULE_LICENSE("GPL");