/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2022 Michael J. Karels <karels@freebsd.org>
 * Copyright (c) 2012 Alexander Rybalko <ray@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/reboot.h>
#include <sys/rman.h>
#include <sys/systm.h>
#include <sys/watchdog.h>

#include <dev/ofw/openfirm.h>
#include <dev/ofw/ofw_bus.h>
#include <dev/ofw/ofw_bus_subr.h>

#include <dev/clk/clk.h>

#include <machine/bus.h>
#include <machine/machdep.h>

#define APPLE_WDOG_WD0_TIMER            0x0000
#define APPLE_WDOG_WD0_RESET            0x0004
#define APPLE_WDOG_WD0_INTR             0x0008
#define APPLE_WDOG_WD0_CNTL             0x000c

#define APPLE_WDOG_WD1_TIMER            0x0010
#define APPLE_WDOG_WD1_RESET            0x0014
#define APPLE_WDOG_WD1_CNTL             0x001c

#define APPLE_WDOG_WD2_TIMER            0x0020
#define APPLE_WDOG_WD2_RESET            0x0024
#define APPLE_WDOG_WD2_CNTL             0x002c

#define APPLE_WDOG_CNTL_INTENABLE       0x0001
#define APPLE_WDOG_CNTL_INTSTAT         0x0002
#define APPLE_WDOG_CNTL_RSTENABLE       0x0004

#define READ(_sc, _r) bus_space_read_4((_sc)->bst, (_sc)->bsh, (_r))
#define WRITE(_sc, _r, _v) bus_space_write_4((_sc)->bst, (_sc)->bsh, (_r), (_v))

struct apple_wdog_softc {
        device_t                dev;
        struct resource *       res;
        bus_space_tag_t         bst;
        bus_space_handle_t      bsh;
        clk_t                   clk;
        uint64_t                clk_freq;
        struct mtx              mtx;
};

static struct ofw_compat_data compat_data[] = {
        {"apple,wdt",           1},
        {NULL,                  0}
};

static void apple_wdog_watchdog_fn(void *private, u_int cmd, int *error);
static void apple_wdog_reboot_system(void *, int);

static int
apple_wdog_probe(device_t dev)
{

        if (!ofw_bus_status_okay(dev))
                return (ENXIO);

        if (ofw_bus_search_compatible(dev, compat_data)->ocd_data == 0)
                return (ENXIO);

        device_set_desc(dev, "Apple Watchdog");

        return (BUS_PROBE_DEFAULT);
}

static int
apple_wdog_attach(device_t dev)
{
        struct apple_wdog_softc *sc;
        int error, rid;

        sc = device_get_softc(dev);
        sc->dev = dev;

        rid = 0;
        sc->res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid, RF_ACTIVE);
        if (sc->res == NULL) {
                device_printf(dev, "could not allocate memory resource\n");
                return (ENXIO);
        }

        sc->bst = rman_get_bustag(sc->res);
        sc->bsh = rman_get_bushandle(sc->res);

        error = clk_get_by_ofw_index(dev, 0, 0, &sc->clk);
        if (error != 0) {
                device_printf(dev, "cannot get clock\n");
                goto fail;
        }
        error = clk_enable(sc->clk);
        if (error != 0) {
                device_printf(dev, "cannot enable clock\n");
                goto fail;
        }
        error = clk_get_freq(sc->clk, &sc->clk_freq);
        if (error != 0) {
                device_printf(dev, "cannot get base frequency\n");
                goto fail_clk;
        }

        mtx_init(&sc->mtx, "Apple Watchdog", "apple_wdog", MTX_DEF);
        EVENTHANDLER_REGISTER(watchdog_list, apple_wdog_watchdog_fn, sc, 0);
        EVENTHANDLER_REGISTER(shutdown_final, apple_wdog_reboot_system, sc,
            SHUTDOWN_PRI_LAST);

        /* Reset the watchdog timers. */
        WRITE(sc, APPLE_WDOG_WD0_CNTL, 0);
        WRITE(sc, APPLE_WDOG_WD1_CNTL, 0);

        return (0);

fail_clk:
        clk_disable(sc->clk);
fail:
        bus_release_resource(dev, SYS_RES_MEMORY, 0, sc->res);
        return (error);
}

static void
apple_wdog_watchdog_fn(void *private, u_int cmd, int *error)
{
        struct apple_wdog_softc *sc;
        uint64_t sec;
        uint32_t ticks, sec_max;

        sc = private;
        mtx_lock(&sc->mtx);

        cmd &= WD_INTERVAL;

        if (cmd > 0) {
                sec = ((uint64_t)1 << (cmd & WD_INTERVAL)) / 1000000000;
                sec_max = UINT_MAX / sc->clk_freq;
                if (sec == 0 || sec > sec_max) {
                        /*
                         * Can't arm
                         * disable watchdog as watchdog(9) requires
                         */
                        device_printf(sc->dev,
                            "Can't arm, timeout must be between 1-%d seconds\n",
                            sec_max);
                        WRITE(sc, APPLE_WDOG_WD1_CNTL, 0);
                        mtx_unlock(&sc->mtx);
                        *error = EINVAL;
                        return;
                }

                ticks = sec * sc->clk_freq;
                WRITE(sc, APPLE_WDOG_WD1_TIMER, 0);
                WRITE(sc, APPLE_WDOG_WD1_RESET, ticks);
                WRITE(sc, APPLE_WDOG_WD1_CNTL, APPLE_WDOG_CNTL_RSTENABLE);

                *error = 0;
        } else
                WRITE(sc, APPLE_WDOG_WD1_CNTL, 0);

        mtx_unlock(&sc->mtx);
}

static void
apple_wdog_reboot_system(void *private, int howto)
{
        struct apple_wdog_softc *sc = private;

        /* Only handle reset. */
        if ((howto & (RB_HALT | RB_POWEROFF)) != 0)
                return;

        printf("Resetting system ... ");

        WRITE(sc, APPLE_WDOG_WD1_CNTL, APPLE_WDOG_CNTL_RSTENABLE);
        WRITE(sc, APPLE_WDOG_WD1_RESET, 1);
        WRITE(sc, APPLE_WDOG_WD1_TIMER, 0);

        /* Wait for watchdog timeout; should take milliseconds. */
        DELAY(2000000);

        /* Not reached ... one hopes. */
        printf("failed to reset.\n");
}

static device_method_t apple_wdog_methods[] = {
        DEVMETHOD(device_probe, apple_wdog_probe),
        DEVMETHOD(device_attach, apple_wdog_attach),

        DEVMETHOD_END
};

static driver_t apple_wdog_driver = {
        "apple_wdog",
        apple_wdog_methods,
        sizeof(struct apple_wdog_softc),
};

DRIVER_MODULE(apple_wdog, simplebus, apple_wdog_driver, 0, 0);