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

/*-
* Copyright (c) 2006 Matthias Drochner <[email protected]>
* 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