/* $NetBSD: hpet.c,v 1.18 2022/08/20 06:47:28 mlelstv Exp $ */

/*
 * Copyright (c) 2006 Nicolas Joly
 * 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * 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 FOUNDATION 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.
 */

/*
 * High Precision Event Timer.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: hpet.c,v 1.18 2022/08/20 06:47:28 mlelstv Exp $");

#include <sys/systm.h>
#include <sys/device.h>
#include <sys/module.h>

#include <sys/time.h>
#include <sys/timetc.h>

#include <sys/bus.h>
#include <sys/lock.h>

#include <machine/cpu_counter.h>

#include <dev/ic/hpetreg.h>
#include <dev/ic/hpetvar.h>

static u_int    hpet_get_timecount(struct timecounter *);
static bool     hpet_resume(device_t, const pmf_qual_t *);

static struct hpet_softc *hpet0 __read_mostly;

int
hpet_detach(device_t dv, int flags)
{
#if 0 /* XXX DELAY() is based off this, detaching is not a good idea. */
        struct hpet_softc *sc = device_private(dv);
        int rc;

        if ((rc = tc_detach(&sc->sc_tc)) != 0)
                return rc;

        pmf_device_deregister(dv);

        bus_space_write_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG, sc->sc_config);

        return 0;
#else
        return EBUSY;
#endif
}

void
hpet_attach_subr(device_t dv)
{
        struct hpet_softc *sc = device_private(dv);
        struct timecounter *tc;
        uint64_t tmp;
        uint32_t val, sval, eval;
        int i;

        tc = &sc->sc_tc;

        tc->tc_name = device_xname(dv);
        tc->tc_get_timecount = hpet_get_timecount;
        tc->tc_quality = 2000;

        tc->tc_counter_mask = 0xffffffff;

        /* Get frequency */
        sc->sc_period = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_PERIOD);
        if (sc->sc_period == 0 || sc->sc_period > HPET_PERIOD_MAX) {
                aprint_error_dev(dv, "invalid timer period\n");
                return;
        }

        /*
         * The following loop is a workaround for AMD SB700 based systems.
         * http://kerneltrap.org/mailarchive/git-commits-head/2008/8/17/2964724
         * http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a6825f1c1fa83b1e92b6715ee5771a4d6524d3b9
         */
        for (i = 0; bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG)
            == 0xffffffff; i++) {
                if (i >= 1000) {
                        aprint_error_dev(dv,
                            "HPET_CONFIG value = 0xffffffff\n");
                        return;
                }
        }

        tmp = (1000000000000000ULL * 2) / sc->sc_period;
        tc->tc_frequency = (tmp / 2) + (tmp & 1);

        /* Enable timer */
        val = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG);
        sc->sc_config = val;
        if ((val & HPET_CONFIG_ENABLE) == 0) {
                val |= HPET_CONFIG_ENABLE;
                bus_space_write_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG, val);
        }

        tc->tc_priv = sc;
        tc_init(tc);

        if (!pmf_device_register(dv, NULL, hpet_resume))
                aprint_error_dev(dv, "couldn't establish power handler\n");

        if (device_unit(dv) == 0)
                hpet0 = sc;

        /*
         * Determine approximately how long it takes to read the counter
         * register once, and compute an ajustment for hpet_delay() based on
         * that.
         */
        (void)bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        sval = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        for (i = 0; i < 998; i++)
                (void)bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        eval = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        val = eval - sval;
        sc->sc_adj = (int64_t)val * sc->sc_period / 1000;
}

static u_int
hpet_get_timecount(struct timecounter *tc)
{
        struct hpet_softc *sc = tc->tc_priv;

        return bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
}

static bool
hpet_resume(device_t dv, const pmf_qual_t *qual)
{
        struct hpet_softc *sc = device_private(dv);
        uint32_t val;

        val = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG);
        val |= HPET_CONFIG_ENABLE;
        bus_space_write_4(sc->sc_memt, sc->sc_memh, HPET_CONFIG, val);

        return true;
}

bool
hpet_delay_p(void)
{

        return hpet0 != NULL;
}

void
hpet_delay(unsigned int us)
{
        struct hpet_softc *sc;
        uint32_t ntick, otick;
        int64_t delta;

        /*
         * Read timer before slow division.  Convert microseconds to
         * femtoseconds, subtract the cost of 1 counter register access,
         * and convert to HPET units.
         */
        sc = hpet0;
        otick = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        delta = (((int64_t)us * 1000000000) - sc->sc_adj) / sc->sc_period;

        while (delta > 0) {
                SPINLOCK_BACKOFF_HOOK;
                ntick = bus_space_read_4(sc->sc_memt, sc->sc_memh,
                    HPET_MCOUNT_LO);
                delta -= (uint32_t)(ntick - otick);
                otick = ntick;
        }
}

uint64_t
hpet_tsc_freq(void)
{
        struct hpet_softc *sc;
        uint64_t td0, td, val, freq;
        uint32_t hd0, hd;
        int s;

        if (hpet0 == NULL || !cpu_hascounter())
                return 0;

        sc = hpet0;

        s = splhigh();
        (void)cpu_counter();
        (void)bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        hd0 = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        td0 = cpu_counter();
        splx(s);

        /*
         * Wait 1000000 HPET ticks (typically 50..100ms).
         *
         * This interval can produce an error of 1ppm (a few kHz
         * in estimated TSC frequency), however the HPET timer is
         * allowed to drift +/- 500ppm in that interval.
         *
         */
        hpet_delay(sc->sc_period / 1000);

        /*
         * Determine TSC freq by comparing how far the TSC and HPET have
         * advanced and round result to the nearest 1000.
         */
        s = splhigh();
        (void)cpu_counter();
        (void)bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        hd = bus_space_read_4(sc->sc_memt, sc->sc_memh, HPET_MCOUNT_LO);
        td = cpu_counter();
        splx(s);

        val = (uint64_t)(hd - hd0) * sc->sc_period / 100000000;
        freq = (td - td0) * 10000000 / val;
        return rounddown(freq + 500, 1000);
}

MODULE(MODULE_CLASS_DRIVER, hpet, NULL);

#ifdef _MODULE
#include "ioconf.c"
#endif

static int
hpet_modcmd(modcmd_t cmd, void *aux)
{
        int rv = 0;

        switch (cmd) {

        case MODULE_CMD_INIT:

#ifdef _MODULE
                rv = config_init_component(cfdriver_ioconf_hpet,
                    cfattach_ioconf_hpet, cfdata_ioconf_hpet);
#endif
                break;

        case MODULE_CMD_FINI:

#ifdef _MODULE
                rv = config_fini_component(cfdriver_ioconf_hpet,
                    cfattach_ioconf_hpet, cfdata_ioconf_hpet);
#endif
                break;

        default:
                rv = ENOTTY;
        }

        return rv;
}