/*
 * Copyright (c) 2003,2004 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * 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. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 */

/*
 * WARNING!  THE SYSTIMER MODULE DOES NOT OPERATE OR DISPATCH WITH THE
 * MP LOCK HELD.  ALL CODE USING THIS MODULE MUST BE MP-SAFE.
 *
 * This code implements a fine-grained per-cpu system timer which is
 * ultimately based on a hardware timer.  The hardware timer abstraction
 * is sufficiently disconnected from this code to support both per-cpu
 * hardware timers or a single system-wide hardware timer.
 *
 * WARNING!  During early boot if a new system timer is selected, existing
 * timeouts will not be effected and will thus occur slower or faster.
 * periodic timers will be adjusted at the next periodic load.
 *
 * Notes on machine-dependant code (in arch/arch/systimer.c)
 *
 * cputimer_intr_reload()       Reload the one-shot (per-cpu basis)
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/thread.h>
#include <sys/globaldata.h>
#include <sys/systimer.h>
#include <sys/thread2.h>

/*
 * Execute ready systimers.  Called directly from the platform-specific
 * one-shot timer clock interrupt (e.g. clkintr()) or via an IPI.  May
 * be called simultaniously on multiple cpus and always operations on 
 * the current cpu's queue.  Systimer functions are responsible for calling
 * hardclock, statclock, and other finely-timed routines.
 */
void
systimer_intr(sysclock_t *timep, int in_ipi, struct intrframe *frame)
{
    globaldata_t gd = mycpu;
    sysclock_t time = *timep;
    systimer_t info;

    if (gd->gd_syst_nest)
        return;

    crit_enter();
    ++gd->gd_syst_nest;
    while ((info = TAILQ_FIRST(&gd->gd_systimerq)) != NULL) {
        /*
         * If we haven't reached the requested time, tell the cputimer
         * how much is left and break out.
         */
        if ((ssysclock_t)(info->time - time) > 0) {
            cputimer_intr_reload(info->time - time);
            break;
        }

        /*
         * Dequeue and execute, detect a loss of the systimer.  Note
         * that the in-progress systimer pointer can only be used to
         * detect a loss of the systimer, it is only useful within
         * this code sequence and becomes stale otherwise.
         */
        info->flags &= ~SYSTF_ONQUEUE;
        TAILQ_REMOVE(info->queue, info, node);
        gd->gd_systimer_inprog = info;
        crit_exit();
        info->func(info, in_ipi, frame);
        crit_enter();

        /*
         * The caller may deleted or even re-queue the systimer itself
         * with a delete/add sequence.  If the caller does not mess with
         * the systimer we will requeue the periodic interval automatically.
         *
         * If this is a non-queued periodic interrupt, do not allow multiple
         * events to build up (used for things like the callout timer to
         * prevent premature timeouts due to long interrupt disablements,
         * BIOS 8254 glitching, and so forth).  However, we still want to
         * keep things synchronized between cpus for efficient handling of
         * the timer interrupt so jump in multiples of the periodic rate.
         */
        if (gd->gd_systimer_inprog == info && info->periodic) {
            if (info->which != sys_cputimer) {
                info->periodic = sys_cputimer->fromhz(info->freq);
                info->which = sys_cputimer;
            }
            info->time += info->periodic;
            if ((info->flags & SYSTF_NONQUEUED) &&
                (ssysclock_t)(info->time - time) <= 0
            ) {
                info->time += roundup(time - info->time, info->periodic);
            }
            systimer_add(info);
        }
        gd->gd_systimer_inprog = NULL;
    }
    --gd->gd_syst_nest;
    crit_exit();
}

void
systimer_intr_enable(void)
{
    cputimer_intr_enable();
}

/*
 * MPSAFE
 */
void
systimer_add(systimer_t info)
{
    struct globaldata *gd = mycpu;

    KKASSERT((info->flags & SYSTF_ONQUEUE) == 0);
    crit_enter();
    if (info->gd == gd) {
        systimer_t scan1;
        systimer_t scan2;
        scan1 = TAILQ_FIRST(&gd->gd_systimerq);
        if (scan1 == NULL || (ssysclock_t)(scan1->time - info->time) > 0) {
            cputimer_intr_reload(info->time - sys_cputimer->count());
            TAILQ_INSERT_HEAD(&gd->gd_systimerq, info, node);
        } else {
            scan2 = TAILQ_LAST(&gd->gd_systimerq, systimerq);
            for (;;) {
                if (scan1 == NULL) {
                    TAILQ_INSERT_TAIL(&gd->gd_systimerq, info, node);
                    break;
                }
                if (info->flags & SYSTF_FIRST) {
                        /*
                         * When coincident events occur, the event being
                         * added wants to be placed before the others.
                         */
                        if ((ssysclock_t)(scan1->time - info->time) >= 0) {
                            TAILQ_INSERT_BEFORE(scan1, info, node);
                            break;
                        }
                        if ((ssysclock_t)(scan2->time - info->time) < 0) {
                            TAILQ_INSERT_AFTER(&gd->gd_systimerq, scan2,
                                               info, node);
                            break;
                        }
                } else {
                        /*
                         * When coincident events occur, the event being
                         * added should be placed after the others.  This
                         * is the default.
                         */
                        if ((ssysclock_t)(scan1->time - info->time) > 0) {
                            TAILQ_INSERT_BEFORE(scan1, info, node);
                            break;
                        }
                        if ((ssysclock_t)(scan2->time - info->time) <= 0) {
                            TAILQ_INSERT_AFTER(&gd->gd_systimerq, scan2,
                                                info, node);
                            break;
                        }
                }
                scan1 = TAILQ_NEXT(scan1, node);
                scan2 = TAILQ_PREV(scan2, systimerq, node);
            }
        }
        info->flags = (info->flags | SYSTF_ONQUEUE) & ~SYSTF_IPIRUNNING;
        info->queue = &gd->gd_systimerq;
    } else {
        KKASSERT((info->flags & SYSTF_IPIRUNNING) == 0);
        info->flags |= SYSTF_IPIRUNNING;
        lwkt_send_ipiq(info->gd, (ipifunc1_t)systimer_add, info);
    }
    crit_exit();
}

/*
 * systimer_del()
 *
 *      Delete a system timer.  Only the owning cpu can delete a timer.
 *
 * MPSAFE
 */
void
systimer_del(systimer_t info)
{
    struct globaldata *gd = info->gd;

    KKASSERT(gd == mycpu && (info->flags & SYSTF_IPIRUNNING) == 0);

    crit_enter();

    if (info->flags & SYSTF_ONQUEUE) {
        TAILQ_REMOVE(info->queue, info, node);
        info->flags &= ~SYSTF_ONQUEUE;
    }

    /*
     * Deal with dispatch races by clearing the in-progress systimer
     * pointer.  Only a direct pointer comparison can be used, the
     * actual contents of the structure gd_systimer_inprog points to,
     * if not equal to info, may be stale.
     */
    if (gd->gd_systimer_inprog == info)
        gd->gd_systimer_inprog = NULL;

    crit_exit();
}

/*
 * systimer_init_periodic*()
 *
 *      Initialize a periodic timer at the specified frequency and add
 *      it to the system.  The frequency is uncompensated and approximate.
 *
 *      Try to synchronize multiple registrations of the same or similar
 *      frequencies so the hardware interrupt is able to dispatch several
 *      together.  We do this by adjusting the phase of the initial timeout.
 *      This helps SMP.  Note that we are not attempting to synchronize to
 *      the realtime clock.
 *
 *      This synchronization is also depended upon for statclock, hardclock,
 *      and schedclock.
 */
static __inline
void
_systimer_init_periodic(systimer_t info, systimer_func_t func, void *data,
                        int64_t freq, int flags)
{
    sysclock_t base_count;

    if (sys_cputimer->sync_base == 0)
        sys_cputimer->sync_base = sys_cputimer->count();

    bzero(info, sizeof(struct systimer));

    if ((flags & SYSTF_100KHZSYNC) && freq <= 100000)
            info->periodic = sys_cputimer->fromhz(100000) * (100000 / freq);
    if ((flags & SYSTF_MSSYNC) && freq <= 1000)
            info->periodic = sys_cputimer->fromhz(1000) * (1000 / freq);
    else
            info->periodic = sys_cputimer->fromhz(freq);

    base_count = sys_cputimer->count();
    base_count = base_count -
                 (base_count - sys_cputimer->sync_base) % info->periodic;
    info->time = base_count + info->periodic;
    if (flags & SYSTF_OFFSETCPU)
            info->time += mycpu->gd_cpuid * info->periodic / ncpus;
    if (flags & SYSTF_OFFSET50)
            info->time += info->periodic / 2;
    info->func = func;
    info->data = data;
    info->freq = freq;
    info->which = sys_cputimer;
    info->gd = mycpu;
    info->flags |= flags;
    systimer_add(info);
}

void
systimer_init_periodic(systimer_t info, systimer_func_t func, void *data,
                       int64_t freq)
{
        _systimer_init_periodic(info, func, data, freq, 0);
}

void
systimer_init_periodic_nq(systimer_t info, systimer_func_t func, void *data,
                          int64_t freq)
{
        _systimer_init_periodic(info, func, data, freq, SYSTF_NONQUEUED);
}

/*
 * These provide systimers whos periods are in perfect multiples of 1ms
 * or 0.1uS.  This is used in situations where the caller wants to gang
 * multiple systimers together whos periods may have some coincident events,
 * in order for those coincident events to generate only one interrupt.
 *
 * This also allows the caller to make event ordering assumptions for
 * said coincident events.
 */
void
systimer_init_periodic_nq1khz(systimer_t info, systimer_func_t func,
                              void *data, int64_t freq)
{
        _systimer_init_periodic(info, func, data, freq,
                                SYSTF_NONQUEUED | SYSTF_MSSYNC);
}

void
systimer_init_periodic_nq100khz(systimer_t info, systimer_func_t func,
                                void *data, int64_t freq)
{
        _systimer_init_periodic(info, func, data, freq,
                                SYSTF_NONQUEUED | SYSTF_100KHZSYNC);
}

void
systimer_init_periodic_flags(systimer_t info, systimer_func_t func,
                                void *data, int64_t freq, int flags)
{
        _systimer_init_periodic(info, func, data, freq, flags);
}


/*
 * Adjust the periodic interval for a periodic timer which is already
 * running.  The current timeout is not effected.
 */
void
systimer_adjust_periodic(systimer_t info, int64_t freq)
{
    crit_enter();
    info->periodic = sys_cputimer->fromhz(freq);
    info->freq = freq;
    info->which = sys_cputimer;
    crit_exit();
}

/*
 * systimer_init_oneshot()
 *
 *      Initialize a periodic timer at the specified frequency and add
 *      it to the system.  The frequency is uncompensated and approximate.
 */
void
systimer_init_oneshot(systimer_t info, systimer_func_t func,
                      void *data, int64_t us)
{
    bzero(info, sizeof(struct systimer));
    info->time = sys_cputimer->count() + sys_cputimer->fromus(us);
    info->func = func;
    info->data = data;
    info->which = sys_cputimer;
    info->gd = mycpu;
    info->us = us;
    systimer_add(info);
}

/*
 * sys_cputimer was changed, recalculate all existing systimers and kick the
 * new interrupt.
 */
static void
systimer_changed_pcpu(void *arg __unused)
{
    globaldata_t gd = mycpu;
    systimer_t info;

    crit_enter();
again:
    TAILQ_FOREACH(info, &gd->gd_systimerq, node) {
        if (info->which == sys_cputimer)
                continue;
        TAILQ_REMOVE(&gd->gd_systimerq, info, node);
        info->flags &= ~SYSTF_ONQUEUE;
        if (info->periodic) {
                _systimer_init_periodic(info, info->func, info->data,
                                        info->freq, info->flags);
        } else {
                info->time = sys_cputimer->count() +
                             sys_cputimer->fromus(info->us);
                systimer_add(info);
        }
        goto again;
    }
    cputimer_intr_reload(1);
    crit_exit();
}

void
systimer_changed(void)
{
    globaldata_t gd = mycpu;
    int i;

    systimer_changed_pcpu(NULL);
    for (i = 0; i < ncpus; ++i) {
        if (i != gd->gd_cpuid) {
                lwkt_send_ipiq(globaldata_find(i),
                               systimer_changed_pcpu, NULL);
        }
    }
}