/*-
 * Copyright (c) 2017 Andrew Turner
 * All rights reserved.
 *
 * This software was developed by SRI International and the University of
 * Cambridge Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
 * ("CTSRD"), as part of the DARPA CRASH research programme.
 *
 * 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/systm.h>
#include <sys/bus.h>
#include <sys/clock.h>
#include <sys/efi.h>
#include <sys/kernel.h>
#include <sys/module.h>

#include "clock_if.h"

static bool efirtc_zeroes_subseconds;
static struct timespec efirtc_resadj;

static const u_int us_per_s  = 1000000;
static const u_int ns_per_s  = 1000000000;
static const u_int ns_per_us = 1000;

static void
efirtc_identify(driver_t *driver, device_t parent)
{

        /* Don't add the driver unless we have working runtime services. */
        if (efi_rt_ok() != 0)
                return;
        if (device_find_child(parent, "efirtc", DEVICE_UNIT_ANY) != NULL)
                return;
        if (BUS_ADD_CHILD(parent, 0, "efirtc", DEVICE_UNIT_ANY) == NULL)
                device_printf(parent, "add child failed\n");
}

static int
efirtc_probe(device_t dev)
{
        struct efi_tm tm;
        int error;

        /*
         * Check whether we can read the time.  This will stop us from attaching
         * when there is EFI Runtime support but the gettime function is
         * unimplemented, e.g. on some builds of U-Boot.
         */
        if ((error = efi_get_time(&tm)) != 0) {
                if (bootverbose)
                        device_printf(dev, "cannot read EFI realtime clock, "
                            "error %d\n", error);
                return (error);
        }
        device_set_desc(dev, "EFI Realtime Clock");
        return (BUS_PROBE_DEFAULT);
}

static int
efirtc_attach(device_t dev)
{
        struct efi_tmcap tmcap;
        long res;
        int error;

        bzero(&tmcap, sizeof(tmcap));
        if ((error = efi_get_time_capabilities(&tmcap)) != 0) {
                device_printf(dev, "cannot get EFI time capabilities");
                return (error);
        }

        /* Translate resolution in Hz to tick length in usec. */
        if (tmcap.tc_res == 0)
                res = us_per_s; /* 0 is insane, assume 1 Hz. */
        else if (tmcap.tc_res > us_per_s)
                res = 1; /* 1us is the best we can represent */
        else
                res = us_per_s / tmcap.tc_res;

        /* Clock rounding adjustment is 1/2 of resolution, in nsec. */
        efirtc_resadj.tv_nsec = (res * ns_per_us) / 2;

        /* Does the clock zero the subseconds when time is set? */
        efirtc_zeroes_subseconds = tmcap.tc_stz;

        /*
         * Register.  If the clock zeroes out the subseconds when it's set,
         * schedule the SetTime calls to happen just before top-of-second.
         */
        clock_register_flags(dev, res, CLOCKF_SETTIME_NO_ADJ);
        if (efirtc_zeroes_subseconds)
                clock_schedule(dev, ns_per_s - ns_per_us);

        return (0);
}

static int
efirtc_detach(device_t dev)
{

        clock_unregister(dev);
        return (0);
}

static int
efirtc_gettime(device_t dev, struct timespec *ts)
{
        struct clocktime ct;
        struct efi_tm tm;
        int error;

        error = efi_get_time(&tm);
        if (error != 0)
                return (error);

        ct.sec = tm.tm_sec;
        ct.min = tm.tm_min;
        ct.hour = tm.tm_hour;
        ct.day = tm.tm_mday;
        ct.mon = tm.tm_mon;
        ct.year = tm.tm_year;
        ct.nsec = tm.tm_nsec;

        clock_dbgprint_ct(dev, CLOCK_DBG_READ, &ct);
        return (clock_ct_to_ts(&ct, ts));
}

static int
efirtc_settime(device_t dev, struct timespec *ts)
{
        struct clocktime ct;
        struct efi_tm tm;

        /*
         * We request a timespec with no resolution-adjustment so that we can
         * apply it ourselves based on whether or not the clock zeroes the
         * sub-second part of the time when setting the time.
         */
        ts->tv_sec -= utc_offset();
        if (!efirtc_zeroes_subseconds)
                timespecadd(ts, &efirtc_resadj, ts);
        
        clock_ts_to_ct(ts, &ct);
        clock_dbgprint_ct(dev, CLOCK_DBG_WRITE, &ct);

        bzero(&tm, sizeof(tm));
        tm.tm_sec = ct.sec;
        tm.tm_min = ct.min;
        tm.tm_hour = ct.hour;
        tm.tm_mday = ct.day;
        tm.tm_mon = ct.mon;
        tm.tm_year = ct.year;
        tm.tm_nsec = ct.nsec;

        return (efi_set_time(&tm));
}

static device_method_t efirtc_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,      efirtc_identify),
        DEVMETHOD(device_probe,         efirtc_probe),
        DEVMETHOD(device_attach,        efirtc_attach),
        DEVMETHOD(device_detach,        efirtc_detach),

        /* Clock interface */
        DEVMETHOD(clock_gettime,        efirtc_gettime),
        DEVMETHOD(clock_settime,        efirtc_settime),

        DEVMETHOD_END
};

static driver_t efirtc_driver = {
        "efirtc",
        efirtc_methods,
        0
};

DRIVER_MODULE(efirtc, nexus, efirtc_driver, 0, 0);
MODULE_VERSION(efirtc, 1);
MODULE_DEPEND(efirtc, efirt, 1, 1, 1);