/*
 * Copyright (c) 2017-2019 François Tigeot <ftigeot@wolfpond.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 unmodified, 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 ``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 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 <linux/hrtimer.h>
#include <linux/bug.h>

#include <sys/systimer.h>
#include <sys/taskqueue.h>

static void
__hrtimer_function(systimer_t info, int in_ipi, struct intrframe *frame)
{
        struct hrtimer *timer = info->data;
        struct taskqueue *tq = taskqueue_thread[mycpuid];

        BUG_ON(taskqueue_enqueue(tq, &timer->task) != 0);
}

static void
__hrtimer_task(void *arg, int pending)
{
        struct hrtimer *timer = arg;
        enum hrtimer_restart restart;

        lwkt_gettoken(&timer->timer_token);
        timer->running = true;
        if (timer->cancel) {
                timer->running = false;
                timer->active = false;
                goto done;
        }
        lwkt_reltoken(&timer->timer_token);
        KKASSERT(timer->function != NULL);
        restart = timer->function(timer);
        lwkt_gettoken(&timer->timer_token);
        timer->running = false;
        timer->active = false;
        if (!timer->cancel && restart == HRTIMER_RESTART) {
                KKASSERT(timer->is_rel);
                timer->active = true;
                systimer_init_oneshot(&timer->st, __hrtimer_function,
                    timer, timer->timeout_us);
        }
done:
        lwkt_reltoken(&timer->timer_token);
}

void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                           enum hrtimer_mode mode)
{
        BUG_ON(clock_id != CLOCK_MONOTONIC);

        memset(timer, 0, sizeof(struct hrtimer));
        timer->clock_id = clock_id;
        timer->ht_mode = mode;
        timer->active = false;
        timer->running = false;
        timer->cancel = false;
        timer->gd = NULL;
        TASK_INIT(&timer->task, 1, __hrtimer_task, timer);
        lwkt_token_init(&timer->timer_token, "timer token");
}

void
hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
                       u64 range_ns, const enum hrtimer_mode mode)
{
        if (mode == HRTIMER_MODE_ABS) {
                struct timespec ts;
                ktime_t curtime;

                timer->is_rel = false;
                nanouptime(&ts);
                curtime = ts.tv_sec * 1000000000 + ts.tv_nsec;
                if (curtime > tim)
                        timer->timeout_us = 500;
                else
                        timer->timeout_us = (tim - curtime) / 1000;
        } else {
                timer->timeout_us = tim / 1000;
                timer->is_rel = true;
        }
        /* Prevent arbitrarily short timeouts from being scheduled. */
        timer->timeout_us = max(500, timer->timeout_us);

        lwkt_gettoken(&timer->timer_token);

        timer->cancel = false;
        timer->running = false;
        timer->active = true;
        timer->gd = mycpu;
        systimer_init_oneshot(&timer->st, __hrtimer_function, timer,
            timer->timeout_us);

        lwkt_reltoken(&timer->timer_token);
}

int
hrtimer_cancel(struct hrtimer *timer)
{
        int ret = 0;

        lwkt_gettoken(&timer->timer_token);
        if (timer->active) {
                struct taskqueue *tq = taskqueue_thread[timer->gd->gd_cpuid];
                bool running = timer->running;

                ret = 1;
                timer->cancel = true;
                lwkt_reltoken(&timer->timer_token);
                if (running) {
                        /* Nothing */
                } else if (timer->gd == mycpu) {
                        systimer_del(&timer->st);
                } else {
                        struct globaldata *oldcpu = mycpu;
                        lwkt_setcpu_self(timer->gd);
                        systimer_del(&timer->st);
                        lwkt_setcpu_self(oldcpu);
                }
                while (taskqueue_cancel(tq, &timer->task, NULL))
                        taskqueue_drain(tq, &timer->task);
        } else {
                lwkt_reltoken(&timer->timer_token);
        }
        return ret;
}

/* Returns non-zero if the timer is queued or running */
bool
hrtimer_active(const struct hrtimer *const_timer)
{
        bool ret;
        struct hrtimer *timer = __DECONST(struct hrtimer *, const_timer);

        lwkt_gettoken(&timer->timer_token);
        ret = timer->active;
        lwkt_reltoken(&timer->timer_token);
        return ret;
}