/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2020 Jessica Clarke <jrtc27@FreeBSD.org>
 *
 * 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.
 */

/*
 * RTC for the goldfish virtual hardware platform implemented in QEMU,
 * initially for Android but now also used for RISC-V's virt machine.
 *
 * https://android.googlesource.com/platform/external/qemu/+/master/docs/GOLDFISH-VIRTUAL-HARDWARE.TXT
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/clock.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/types.h>

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

#include <machine/bus.h>
#include <machine/resource.h>
#include <sys/rman.h>

#include "clock_if.h"

#define GOLDFISH_RTC_TIME_LOW   0x00
#define GOLDFISH_RTC_TIME_HIGH  0x04

struct goldfish_rtc_softc {
        struct resource *res;
        int             rid;
        struct mtx      mtx;
};

static int
goldfish_rtc_probe(device_t dev)
{

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

        if (ofw_bus_is_compatible(dev, "google,goldfish-rtc")) {
                device_set_desc(dev, "Goldfish RTC");
                return (BUS_PROBE_DEFAULT);
        }

        return (ENXIO);
}

static int
goldfish_rtc_attach(device_t dev)
{
        struct goldfish_rtc_softc *sc;

        sc = device_get_softc(dev);

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

        mtx_init(&sc->mtx, device_get_nameunit(dev), NULL, MTX_DEF);

        /*
         * Register as a system realtime clock with 1 second resolution.
         */
        clock_register_flags(dev, 1000000, CLOCKF_SETTIME_NO_ADJ);
        clock_schedule(dev, 1);

        return (0);
}

static int
goldfish_rtc_detach(device_t dev)
{
        struct goldfish_rtc_softc *sc;

        sc = device_get_softc(dev);

        clock_unregister(dev);
        mtx_destroy(&sc->mtx);
        bus_release_resource(dev, SYS_RES_MEMORY, sc->rid, sc->res);

        return (0);
}

static int
goldfish_rtc_gettime(device_t dev, struct timespec *ts)
{
        struct goldfish_rtc_softc *sc;
        uint64_t low, high, nsec;

        sc = device_get_softc(dev);

        /*
         * Reading TIME_HIGH is defined in the documentation to give the high
         * 32 bits corresponding to the last TIME_LOW read, so must be done in
         * that order, but means we have atomicity guaranteed.
         */
        mtx_lock(&sc->mtx);
        low = bus_read_4(sc->res, GOLDFISH_RTC_TIME_LOW);
        high = bus_read_4(sc->res, GOLDFISH_RTC_TIME_HIGH);
        mtx_unlock(&sc->mtx);

        nsec = (high << 32) | low;
        ts->tv_sec = nsec / 1000000000;
        ts->tv_nsec = nsec % 1000000000;

        return (0);
}

static int
goldfish_rtc_settime(device_t dev, struct timespec *ts)
{
        struct goldfish_rtc_softc *sc;
        uint64_t nsec;

        sc = device_get_softc(dev);

        /*
         * We request a timespec with no resolution-adjustment.  That also
         * disables utc adjustment, so apply that ourselves.
         */
        ts->tv_sec -= utc_offset();
        nsec = (uint64_t)ts->tv_sec * 1000000000 + ts->tv_nsec;

        mtx_lock(&sc->mtx);
        bus_write_4(sc->res, GOLDFISH_RTC_TIME_HIGH, nsec >> 32);
        bus_write_4(sc->res, GOLDFISH_RTC_TIME_LOW, nsec);
        mtx_unlock(&sc->mtx);

        return (0);
}

static device_method_t goldfish_rtc_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         goldfish_rtc_probe),
        DEVMETHOD(device_attach,        goldfish_rtc_attach),
        DEVMETHOD(device_detach,        goldfish_rtc_detach),

        /* Clock interface */
        DEVMETHOD(clock_gettime,        goldfish_rtc_gettime),
        DEVMETHOD(clock_settime,        goldfish_rtc_settime),

        DEVMETHOD_END,
};

DEFINE_CLASS_0(goldfish_rtc, goldfish_rtc_driver, goldfish_rtc_methods,
    sizeof(struct goldfish_rtc_softc));

DRIVER_MODULE(goldfish_rtc, simplebus, goldfish_rtc_driver, NULL, NULL);