/* $NetBSD: acpi_timer.c,v 1.27 2021/07/25 01:43:08 jmcneill Exp $ */

/*-
 * Copyright (c) 2006 Matthias Drochner <drochner@NetBSD.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 NETBSD FOUNDATION, INC. 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: acpi_timer.c,v 1.27 2021/07/25 01:43:08 jmcneill Exp $");

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

#include <dev/acpi/acpivar.h>
#include <dev/acpi/acpi_timer.h>

#include <machine/acpi_machdep.h>

#if (!ACPI_REDUCED_HARDWARE)
static int      acpitimer_test(void);

static struct timecounter acpi_timecounter = {
        .tc_get_timecount = acpitimer_read_safe,
        .tc_counter_mask = 0x00ffffff,
        .tc_frequency = ACPI_PM_TIMER_FREQUENCY,
        .tc_name = "ACPI-Safe",
        .tc_quality = 900,
};

static bool
acpitimer_supported(void)
{
        return AcpiGbl_FADT.PmTimerLength != 0;
}
#endif

int
acpitimer_init(struct acpi_softc *sc)
{
#if (!ACPI_REDUCED_HARDWARE)
        ACPI_TABLE_WAET *waet;
        ACPI_STATUS rv;
        uint32_t bits;
        int i, j;

        if (!acpitimer_supported())
                return -1;

        rv = AcpiGetTimerResolution(&bits);

        if (ACPI_FAILURE(rv))
                return -1;

        if (bits == 32)
                acpi_timecounter.tc_counter_mask = 0xffffffff;

        for (i = j = 0; i < 10; i++)
                j += acpitimer_test();

        rv = AcpiGetTable(ACPI_SIG_WAET, 0, (ACPI_TABLE_HEADER **)&waet);
        if (ACPI_SUCCESS(rv)) {
                /*
                 * Windows ACPI Emulated Devices Table (WAET) has a hint
                 * to let the OS know that a single read of the PM timer
                 * provides a reliable value.
                 */
                if ((waet->Flags & ACPI_WAET_TIMER_ONE_READ) != 0) {
                        j += 10;
                }
        }

        if (j >= 10) {
                acpi_timecounter.tc_name = "ACPI-Fast";
                acpi_timecounter.tc_get_timecount = acpitimer_read_fast;
                acpi_timecounter.tc_quality = 1000;
        }

        tc_init(&acpi_timecounter);

        aprint_debug_dev(sc->sc_dev, "%s %d-bit timer\n",
            acpi_timecounter.tc_name, bits);

        return 0;
#else
        return -1;
#endif
}

int
acpitimer_detach(void)
{
#if (!ACPI_REDUCED_HARDWARE)
        if (!acpitimer_supported())
                return -1;

        return tc_detach(&acpi_timecounter);
#else
        return -1;
#endif
}

#if (!ACPI_REDUCED_HARDWARE)
u_int
acpitimer_read_fast(struct timecounter *tc)
{
        uint32_t t;

        (void)AcpiGetTimer(&t);

        return t;
}

/*
 * Some chipsets (PIIX4 variants) do not latch correctly;
 * there is a chance that a transition is hit.
 */
u_int
acpitimer_read_safe(struct timecounter *tc)
{
        uint32_t t1, t2, t3;

        (void)AcpiGetTimer(&t2);
        (void)AcpiGetTimer(&t3);

        do {
                t1 = t2;
                t2 = t3;

                (void)AcpiGetTimer(&t3);

        } while ((t1 > t2) || (t2 > t3));

        return t2;
}

uint32_t
acpitimer_delta(uint32_t end, uint32_t start)
{
        const u_int mask = acpi_timecounter.tc_counter_mask;
        uint32_t delta;

        if (end >= start)
                delta = end - start;
        else
                delta = ((mask - start) + end + 1) & mask;

        return delta;
}

#define N 2000

static int
acpitimer_test(void)
{
        uint32_t last, this, delta;
        int minl, maxl, n;

        minl = 10000000;
        maxl = 0;

        acpi_md_OsDisableInterrupt();

        (void)AcpiGetTimer(&last);

        for (n = 0; n < N; n++) {

                (void)AcpiGetTimer(&this);

                delta = acpitimer_delta(this, last);

                if (delta > maxl)
                        maxl = delta;
                else if (delta < minl)
                        minl = delta;

                last = this;
        }

        acpi_md_OsEnableInterrupt();

        if (maxl - minl > 2 )
                n = 0;
        else if (minl < 0 || maxl == 0)
                n = 0;
        else
                n = 1;

        return n;
}
#endif