/*-
 * Copyright (c) 2000, 2001 Michael Smith
 * Copyright (c) 2000 BSDi
 * 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 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.
 *
 * $FreeBSD: src/sys/dev/acpica/acpi_timer.c,v 1.35 2004/07/22 05:42:14 njl Exp $
 */
#include "opt_acpi.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/sysctl.h>
#include <sys/systimer.h>

#include "acpi.h"
#include "accommon.h"
#include "acpivar.h"

/*
 * A timecounter based on the free-running ACPI timer.
 *
 * Based on the i386-only mp_clock.c by <phk@FreeBSD.ORG>.
 */

/* Hooks for the ACPICA debugging infrastructure */
#define _COMPONENT      ACPI_TIMER
ACPI_MODULE_NAME("TIMER")

#define ACPI_TIMER32_MASK       ((1UL << 32) - 1)
#define ACPI_TIMER32_HIBITS     (~ACPI_TIMER32_MASK)
#define ACPI_TIMER24_MASK       ((1UL << 24) - 1)
#define ACPI_TIMER24_HIBITS     (~ACPI_TIMER24_MASK)

static device_t                 acpi_timer_dev;
static uint32_t                 acpi_timer_resolution;
static uint32_t                 acpi_timer_offset;

static sysclock_t acpi_timer_get_timecount(void);
static sysclock_t acpi_timer_get_timecount24(void);
static sysclock_t acpi_timer_get_timecount_safe(void);
static void acpi_timer_construct(struct cputimer *timer, sysclock_t oldclock);

static struct cputimer acpi_cputimer = {
        .next           = SLIST_ENTRY_INITIALIZER,
        .name           = "ACPI",
        .pri            = CPUTIMER_PRI_ACPI,
        .type           = CPUTIMER_ACPI,
        .count          = acpi_timer_get_timecount_safe,
        .fromhz         = cputimer_default_fromhz,
        .fromus         = cputimer_default_fromus,
        .construct      = acpi_timer_construct,
        .destruct       = cputimer_default_destruct,
        .freq           = ACPI_PM_TIMER_FREQUENCY
};

static int      acpi_timer_identify(driver_t *driver, device_t parent);
static int      acpi_timer_probe(device_t dev);
static int      acpi_timer_attach(device_t dev);
static int      acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS);
static int      acpi_timer_test(void);

static device_method_t acpi_timer_methods[] = {
    DEVMETHOD(device_identify,  acpi_timer_identify),
    DEVMETHOD(device_probe,     acpi_timer_probe),
    DEVMETHOD(device_attach,    acpi_timer_attach),

    DEVMETHOD_END
};

static driver_t acpi_timer_driver = {
    "acpi_timer",
    acpi_timer_methods,
    0,
    .gpri = KOBJ_GPRI_ACPI+2
};

static devclass_t acpi_timer_devclass;
DRIVER_MODULE(acpi_timer, acpi, acpi_timer_driver, acpi_timer_devclass, NULL, NULL);
MODULE_DEPEND(acpi_timer, acpi, 1, 1, 1);

/*
 * Fetch current time value from hardware that may not correctly
 * latch the counter.  We need to read until we have three monotonic
 * samples and then use the middle one, otherwise we are not protected
 * against the fact that the bits can be wrong in two directions.  If
 * we only cared about monosity, two reads would be enough.
 */
static __always_inline uint32_t
_acpi_get_timer_safe(void)
{
    uint32_t u1, u2, u3;

    AcpiGetTimer(&u2);
    AcpiGetTimer(&u3);
    do {
        u1 = u2;
        u2 = u3;
        AcpiGetTimer(&u3);
    } while (u1 > u2 || u2 > u3);

    return (u2 + acpi_timer_offset);
}

static __always_inline uint32_t
_acpi_get_timer(void)
{
    uint32_t u1;

    AcpiGetTimer(&u1);
    return (u1 + acpi_timer_offset);
}

/*
 * Locate the ACPI timer using the FADT, set up and allocate the I/O resources
 * we will be using.
 */
static int
acpi_timer_identify(driver_t *driver, device_t parent)
{
    device_t dev;

    /*
     * Just try once, do nothing if the 'acpi' bus is rescanned.
     */
    if (device_get_state(parent) == DS_ATTACHED)
        return (0);

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);

    if (acpi_disabled("timer") || (acpi_quirks & ACPI_Q_TIMER) ||
        acpi_timer_dev)
        return (ENXIO);

    if ((dev = BUS_ADD_CHILD(parent, parent, 0, "acpi_timer", 0)) == NULL) {
        device_printf(parent, "could not add acpi_timer0\n");
        return (ENXIO);
    }
    acpi_timer_dev = dev;

    return (0);
}

static int
acpi_timer_probe(device_t dev)
{
    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);

    if (dev != acpi_timer_dev)
        return (ENXIO);

    if (ACPI_FAILURE(AcpiGetTimerResolution(&acpi_timer_resolution)))
        return (ENXIO);

    return (0);
}

static int
acpi_timer_attach(device_t dev)
{
    char desc[40];
    int i, j;

    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);

    /*
     * If all tests of the counter succeed, use the ACPI-fast method.  If
     * at least one failed, default to using the safe routine, which reads
     * the timer multiple times to get a consistent value before returning.
     */
    j = 0;
    for (i = 0; i < 10; i++)
        j += acpi_timer_test();
    if (j == 10) {
        /* Reliable hardware */
        if (acpi_timer_resolution == 32) {
            acpi_cputimer.name = "ACPI-fast";
            acpi_cputimer.count = acpi_timer_get_timecount;
        } else {
            acpi_cputimer.name = "ACPI-fast24";
            acpi_cputimer.count = acpi_timer_get_timecount24;
        }
    } else {
        if (acpi_timer_resolution == 32)
            acpi_cputimer.name = "ACPI-safe";
        else
            acpi_cputimer.name = "ACPI-safe24";
        acpi_cputimer.count = acpi_timer_get_timecount_safe;
    }

    ksprintf(desc, "%u-bit timer at 3.579545MHz", acpi_timer_resolution);
    device_set_desc_copy(dev, desc);

    cputimer_register(&acpi_cputimer);
    cputimer_select(&acpi_cputimer, 0);

    return (0);
}

/*
 * Construct the timer.  Adjust the base so the system clock does not
 * jump weirdly.  We want it to remain monotonic, so setup acpi_timer_offset
 * such that the low 24 or 32 bits continues sequencing relative to the low
 * bits of oldclock.
 */
static void
acpi_timer_construct(struct cputimer *timer, sysclock_t oldclock)
{
    acpi_timer_offset = 0;
    acpi_timer_offset = (uint32_t)oldclock - _acpi_get_timer_safe();
    timer->base = oldclock;
}

static sysclock_t
acpi_timer_get_timecount24(void)
{
    sysclock_t last_counter;
    sysclock_t next_counter;
    uint32_t counter;

    last_counter = acpi_cputimer.base;
    for (;;) {
        cpu_ccfence();
        counter = _acpi_get_timer() & (uint32_t)ACPI_TIMER24_MASK;
        next_counter = (last_counter & ACPI_TIMER24_HIBITS) | counter;
        if (counter < (last_counter & ACPI_TIMER24_MASK))
            next_counter += (1LU << 24);
        if (atomic_fcmpset_long(&acpi_cputimer.base, &last_counter,
                                next_counter)) {
            break;
        }
    }
    return next_counter;
}

static sysclock_t
acpi_timer_get_timecount(void)
{
    sysclock_t last_counter;
    sysclock_t next_counter;
    uint32_t counter;

    last_counter = acpi_cputimer.base;
    for (;;) {
        cpu_ccfence();
        counter = _acpi_get_timer();
        next_counter = (last_counter & ACPI_TIMER32_HIBITS) | counter;
        if (counter < (last_counter & ACPI_TIMER32_MASK))
            next_counter += (1LU << 32);
        if (atomic_fcmpset_long(&acpi_cputimer.base, &last_counter,
                                next_counter)) {
            break;
        }
    }
    return next_counter;
}

static sysclock_t
acpi_timer_get_timecount_safe(void)
{
    sysclock_t last_counter;
    sysclock_t next_counter;
    uint32_t counter;

    last_counter = acpi_cputimer.base;
    for (;;) {
        cpu_ccfence();
        counter = _acpi_get_timer_safe();
        if (acpi_timer_resolution == 32) {
            next_counter = (last_counter & ACPI_TIMER32_HIBITS) | counter;
            if (counter < (last_counter & ACPI_TIMER32_MASK))
                next_counter += (1LU << 32);
        } else {
            counter &= (uint32_t)ACPI_TIMER24_MASK;
            next_counter = (last_counter & ACPI_TIMER24_HIBITS) | counter;
            if (counter < (last_counter & ACPI_TIMER24_MASK))
                next_counter += (1LU << 24);
        }
        if (atomic_fcmpset_long(&acpi_cputimer.base, &last_counter,
                                next_counter)) {
            break;
        }
    }
    return next_counter;
}

/*
 * Timecounter freqency adjustment interface.
 */
static int
acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS)
{
    int error;
    u_int freq;

    if (acpi_cputimer.freq == 0)
        return (EOPNOTSUPP);
    freq = acpi_cputimer.freq;
    error = sysctl_handle_int(oidp, &freq, 0, req);
    if (error == 0 && req->newptr != NULL)
        cputimer_set_frequency(&acpi_cputimer, freq);

    return (error);
}

SYSCTL_PROC(_machdep, OID_AUTO, acpi_timer_freq, CTLTYPE_INT | CTLFLAG_RW,
    0, sizeof(u_int), acpi_timer_sysctl_freq, "I", "ACPI timer frequency");

/*
 * Some ACPI timers are known or believed to suffer from implementation
 * problems which can lead to erroneous values being read.  This function
 * tests for consistent results from the timer and returns 1 if it believes
 * the timer is consistent, otherwise it returns 0.
 *
 * It appears the cause is that the counter is not latched to the PCI bus
 * clock when read:
 *
 * ] 20. ACPI Timer Errata
 * ]
 * ]   Problem: The power management timer may return improper result when
 * ]   read. Although the timer value settles properly after incrementing,
 * ]   while incrementing there is a 3nS window every 69.8nS where the
 * ]   timer value is indeterminate (a 4.2% chance that the data will be
 * ]   incorrect when read). As a result, the ACPI free running count up
 * ]   timer specification is violated due to erroneous reads.  Implication:
 * ]   System hangs due to the "inaccuracy" of the timer when used by
 * ]   software for time critical events and delays.
 * ]
 * ] Workaround: Read the register twice and compare.
 * ] Status: This will not be fixed in the PIIX4 or PIIX4E, it is fixed
 * ] in the PIIX4M.
 */

static int
acpi_timer_test(void)
{
    uint32_t    last, this;
    int         min, max, max2, n, delta;
    register_t  s;

    min = INT32_MAX;
    max = max2 = 0;

    /* Test the timer with interrupts disabled to get accurate results. */
#if defined(__x86_64__)
    s = read_rflags();
#else
#error "no read_*flags"
#endif
    cpu_disable_intr();
    AcpiGetTimer(&last);
    for (n = 0; n < 2000; n++) {
        AcpiGetTimer(&this);
        delta = acpi_TimerDelta(this, last);
        if (delta > max) {
            max2 = max;
            max = delta;
        } else if (delta > max2) {
            max2 = delta;
        }
        if (delta < min)
            min = delta;
        last = this;
    }
    /* cpu_enable_intr(); restored to original by write_rflags() */
#if defined(__x86_64__)
    write_rflags(s);
#else
#error "no read_*flags"
#endif

    delta = max2 - min;
    if ((max - min > 8 || delta > 3) && vmm_guest == VMM_GUEST_NONE)
        n = 0;
    else if (min < 0 || max == 0 || max2 == 0)
        n = 0;
    else
        n = 1;
    if (bootverbose) {
        kprintf("ACPI timer looks %s min = %d, max = %d, width = %d\n",
                n ? "GOOD" : "BAD ",
                min, max, max - min);
    }

    return (n);
}