/*-
 * Copyright (c) 2018 Joyent, Inc.
 * Copyright (c) 2014 Tycho Nightingale <tycho.nightingale@pluribusnetworks.com>
 * Copyright (c) 2011 NetApp, Inc.
 * All rights reserved.
 * Copyright (c) 2018 Joyent, Inc.
 *
 * 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 NETAPP, INC ``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 NETAPP, INC 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.
 */
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */
/* This file is dual-licensed; see usr/src/contrib/bhyve/LICENSE */

/*
 * Copyright 2022 Oxide Computer Company
 */

#include <sys/cdefs.h>

#include <sys/param.h>
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/kernel.h>
#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/systm.h>

#include <machine/vmm.h>

#include "vatpic.h"
#include "vioapic.h"
#include "vatpit.h"

#define VATPIT_LOCK(vatpit)             mutex_enter(&((vatpit)->lock))
#define VATPIT_UNLOCK(vatpit)           mutex_exit(&((vatpit)->lock))
#define VATPIT_LOCKED(vatpit)           MUTEX_HELD(&((vatpit)->lock))

#define TIMER_SEL_MASK          0xc0
#define TIMER_RW_MASK           0x30
#define TIMER_MODE_MASK         0x0f
#define TIMER_SEL_READBACK      0xc0

#define TIMER_STS_OUT           0x80
#define TIMER_STS_NULLCNT       0x40

#define VALID_STATUS_BITS       (TIMER_STS_OUT | TIMER_STS_NULLCNT)

#define TIMER_RB_LCTR           0x20
#define TIMER_RB_LSTATUS        0x10
#define TIMER_RB_CTR_2          0x08
#define TIMER_RB_CTR_1          0x04
#define TIMER_RB_CTR_0          0x02

#define TMR2_OUT_STS            0x20

#define PIT_8254_FREQ           1193182
#define TIMER_DIV(freq, hz)     (((freq) + (hz) / 2) / (hz))

struct vatpit_callout_arg {
        struct vatpit   *vatpit;
        int             channel_num;
};

struct channel {
        uint8_t         mode;
        uint16_t        initial;        /* initial counter value */

        uint8_t         reg_cr[2];
        uint8_t         reg_ol[2];
        uint8_t         reg_status;

        bool            slatched;       /* status latched */
        bool            olatched;       /* output latched */
        bool            cr_sel;         /* read MSB from control register */
        bool            ol_sel;         /* read MSB from output latch */
        bool            fr_sel;         /* read MSB from free-running timer */

        hrtime_t        time_loaded;    /* time when counter was loaded */
        hrtime_t        time_target;    /* target time */
        uint64_t        total_target;

        struct callout  callout;
        struct vatpit_callout_arg callout_arg;
};

struct vatpit {
        struct vm       *vm;
        kmutex_t        lock;

        struct channel  channel[3];
};

static void pit_timer_start_cntr0(struct vatpit *vatpit);

static uint64_t
vatpit_delta_ticks(struct vatpit *vatpit, struct channel *c)
{
        const hrtime_t delta = gethrtime() - c->time_loaded;

        return (hrt_freq_count(delta, PIT_8254_FREQ));
}

static int
vatpit_get_out(struct vatpit *vatpit, int channel)
{
        struct channel *c;
        uint64_t delta_ticks;
        int out;

        c = &vatpit->channel[channel];

        switch (c->mode) {
        case TIMER_INTTC:
                delta_ticks = vatpit_delta_ticks(vatpit, c);
                out = (delta_ticks >= c->initial);
                break;
        default:
                out = 0;
                break;
        }

        return (out);
}

static void
vatpit_callout_handler(void *a)
{
        struct vatpit_callout_arg *arg = a;
        struct vatpit *vatpit;
        struct callout *callout;
        struct channel *c;

        vatpit = arg->vatpit;
        c = &vatpit->channel[arg->channel_num];
        callout = &c->callout;

        VATPIT_LOCK(vatpit);

        if (callout_pending(callout))           /* callout was reset */
                goto done;

        if (!callout_active(callout))           /* callout was stopped */
                goto done;

        callout_deactivate(callout);

        if (c->mode == TIMER_RATEGEN || c->mode == TIMER_SQWAVE) {
                pit_timer_start_cntr0(vatpit);
        } else {
                /*
                 * For non-periodic timers, clear the time target to distinguish
                 * between a fired timer (thus a zero value) and a pending one
                 * awaiting VM resumption (holding a non-zero value).
                 */
                c->time_target = 0;
        }

        (void) vatpic_pulse_irq(vatpit->vm, 0);
        (void) vioapic_pulse_irq(vatpit->vm, 2);

done:
        VATPIT_UNLOCK(vatpit);
}

static void
vatpit_callout_reset(struct vatpit *vatpit)
{
        struct channel *c = &vatpit->channel[0];

        ASSERT(VATPIT_LOCKED(vatpit));
        callout_reset_hrtime(&c->callout, c->time_target,
            vatpit_callout_handler, &c->callout_arg, C_ABSOLUTE);
}

static void
pit_timer_start_cntr0(struct vatpit *vatpit)
{
        struct channel *c = &vatpit->channel[0];

        if (c->initial == 0) {
                return;
        }

        c->total_target += c->initial;
        c->time_target = c->time_loaded +
            hrt_freq_interval(PIT_8254_FREQ, c->total_target);

        /*
         * If we are more than 'c->initial' ticks behind, reset the timer base
         * to fire at the next 'c->initial' interval boundary.
         */
        hrtime_t now = gethrtime();
        if (c->time_target < now) {
                const uint64_t ticks_behind =
                    hrt_freq_count(now - c->time_target, PIT_8254_FREQ);

                c->total_target += roundup(ticks_behind, c->initial);
                c->time_target = c->time_loaded +
                    hrt_freq_interval(PIT_8254_FREQ, c->total_target);
        }

        vatpit_callout_reset(vatpit);
}

static uint16_t
pit_update_counter(struct vatpit *vatpit, struct channel *c, bool latch)
{
        uint16_t lval;
        uint64_t delta_ticks;

        /* cannot latch a new value until the old one has been consumed */
        if (latch && c->olatched)
                return (0);

        if (c->initial == 0) {
                /*
                 * This is possibly an OS bug - reading the value of the timer
                 * without having set up the initial value.
                 *
                 * The original user-space version of this code set the timer to
                 * 100hz in this condition; do the same here.
                 */
                c->initial = TIMER_DIV(PIT_8254_FREQ, 100);
                c->time_loaded = gethrtime();
                c->reg_status &= ~TIMER_STS_NULLCNT;
        }

        delta_ticks = vatpit_delta_ticks(vatpit, c);
        lval = c->initial - delta_ticks % c->initial;

        if (latch) {
                c->olatched = true;
                c->ol_sel = true;
                c->reg_ol[1] = lval;            /* LSB */
                c->reg_ol[0] = lval >> 8;       /* MSB */
        }

        return (lval);
}

static int
pit_readback1(struct vatpit *vatpit, int channel, uint8_t cmd)
{
        struct channel *c;

        c = &vatpit->channel[channel];

        /*
         * Latch the count/status of the timer if not already latched.
         * N.B. that the count/status latch-select bits are active-low.
         */
        if ((cmd & TIMER_RB_LCTR) == 0 && !c->olatched) {
                (void) pit_update_counter(vatpit, c, true);
        }

        if ((cmd & TIMER_RB_LSTATUS) == 0 && !c->slatched) {
                c->slatched = true;
                /*
                 * For mode 0, see if the elapsed time is greater
                 * than the initial value - this results in the
                 * output pin being set to 1 in the status byte.
                 */
                if (c->mode == TIMER_INTTC && vatpit_get_out(vatpit, channel))
                        c->reg_status |= TIMER_STS_OUT;
                else
                        c->reg_status &= ~TIMER_STS_OUT;
        }

        return (0);
}

static int
pit_readback(struct vatpit *vatpit, uint8_t cmd)
{
        int error;

        /*
         * The readback command can apply to all timers.
         */
        error = 0;
        if (cmd & TIMER_RB_CTR_0)
                error = pit_readback1(vatpit, 0, cmd);
        if (!error && cmd & TIMER_RB_CTR_1)
                error = pit_readback1(vatpit, 1, cmd);
        if (!error && cmd & TIMER_RB_CTR_2)
                error = pit_readback1(vatpit, 2, cmd);

        return (error);
}

static int
vatpit_update_mode(struct vatpit *vatpit, uint8_t val)
{
        struct channel *c;
        int sel, rw;
        uint8_t mode;

        sel = val & TIMER_SEL_MASK;
        rw = val & TIMER_RW_MASK;
        mode = val & TIMER_MODE_MASK;

        /* Clear don't-care bit (M2) when M1 is set */
        if ((mode & TIMER_RATEGEN) != 0) {
                mode &= ~TIMER_SWSTROBE;
        }

        if (sel == TIMER_SEL_READBACK)
                return (pit_readback(vatpit, val));

        if (rw != TIMER_LATCH && rw != TIMER_16BIT)
                return (-1);

        if (rw != TIMER_LATCH) {
                /*
                 * Counter mode is not affected when issuing a
                 * latch command.
                 */
                if (mode != TIMER_INTTC &&
                    mode != TIMER_RATEGEN &&
                    mode != TIMER_SQWAVE &&
                    mode != TIMER_SWSTROBE)
                        return (-1);
        }

        c = &vatpit->channel[sel >> 6];
        if (rw == TIMER_LATCH) {
                (void) pit_update_counter(vatpit, c, true);
        } else {
                c->mode = mode;
                c->olatched = false;    /* reset latch after reprogramming */
                c->reg_status |= TIMER_STS_NULLCNT;
        }

        return (0);
}

int
vatpit_handler(void *arg, bool in, uint16_t port, uint8_t bytes, uint32_t *eax)
{
        struct vatpit *vatpit = arg;
        struct channel *c;
        uint8_t val;
        int error;

        if (bytes != 1)
                return (-1);

        val = *eax;

        if (port == TIMER_MODE) {
                if (in) {
                        /* Mode is write-only */
                        return (-1);
                }

                VATPIT_LOCK(vatpit);
                error = vatpit_update_mode(vatpit, val);
                VATPIT_UNLOCK(vatpit);

                return (error);
        }

        /* counter ports */
        KASSERT(port >= TIMER_CNTR0 && port <= TIMER_CNTR2,
            ("invalid port 0x%x", port));
        c = &vatpit->channel[port - TIMER_CNTR0];

        VATPIT_LOCK(vatpit);
        if (in && c->slatched) {
                /* Return the status byte if latched */
                *eax = c->reg_status;
                c->slatched = false;
                c->reg_status = 0;
        } else if (in) {
                /*
                 * The spec says that once the output latch is completely
                 * read it should revert to "following" the counter. Use
                 * the free running counter for this case (i.e. Linux
                 * TSC calibration). Assuming the access mode is 16-bit,
                 * toggle the MSB/LSB bit on each read.
                 */
                if (!c->olatched) {
                        uint16_t tmp;

                        tmp = pit_update_counter(vatpit, c, false);
                        if (c->fr_sel) {
                                tmp >>= 8;
                        }
                        tmp &= 0xff;
                        *eax = tmp;
                        c->fr_sel = !c->fr_sel;
                } else {
                        if (c->ol_sel) {
                                *eax = c->reg_ol[1];
                                c->ol_sel = false;
                        } else {
                                *eax = c->reg_ol[0];
                                c->olatched = false;
                        }
                }
        } else {
                if (!c->cr_sel) {
                        c->reg_cr[0] = *eax;
                        c->cr_sel = true;
                } else {
                        c->reg_cr[1] = *eax;
                        c->cr_sel = false;

                        c->reg_status &= ~TIMER_STS_NULLCNT;
                        c->fr_sel = false;
                        c->initial = c->reg_cr[0] | (uint16_t)c->reg_cr[1] << 8;
                        c->time_loaded = gethrtime();
                        /* Start an interval timer for channel 0 */
                        if (port == TIMER_CNTR0) {
                                c->time_target = c->time_loaded;
                                c->total_target = 0;
                                pit_timer_start_cntr0(vatpit);
                        }
                        if (c->initial == 0)
                                c->initial = 0xffff;
                }
        }
        VATPIT_UNLOCK(vatpit);

        return (0);
}

int
vatpit_nmisc_handler(void *arg, bool in, uint16_t port, uint8_t bytes,
    uint32_t *eax)
{
        struct vatpit *vatpit = arg;

        if (in) {
                        VATPIT_LOCK(vatpit);
                        if (vatpit_get_out(vatpit, 2))
                                *eax = TMR2_OUT_STS;
                        else
                                *eax = 0;

                        VATPIT_UNLOCK(vatpit);
        }

        return (0);
}

struct vatpit *
vatpit_init(struct vm *vm)
{
        struct vatpit *vatpit;
        struct vatpit_callout_arg *arg;
        int i;

        vatpit = kmem_zalloc(sizeof (struct vatpit), KM_SLEEP);
        vatpit->vm = vm;

        mutex_init(&vatpit->lock, NULL, MUTEX_ADAPTIVE, NULL);

        for (i = 0; i < 3; i++) {
                callout_init(&vatpit->channel[i].callout, 1);
                arg = &vatpit->channel[i].callout_arg;
                arg->vatpit = vatpit;
                arg->channel_num = i;
        }

        return (vatpit);
}

void
vatpit_cleanup(struct vatpit *vatpit)
{
        int i;

        for (i = 0; i < 3; i++)
                callout_drain(&vatpit->channel[i].callout);

        mutex_destroy(&vatpit->lock);
        kmem_free(vatpit, sizeof (*vatpit));
}

void
vatpit_localize_resources(struct vatpit *vatpit)
{
        for (uint_t i = 0; i < 3; i++) {
                /* Only localize channels which might be running */
                if (vatpit->channel[i].mode != 0) {
                        vmm_glue_callout_localize(&vatpit->channel[i].callout);
                }
        }
}

void
vatpit_pause(struct vatpit *vatpit)
{
        struct channel *c = &vatpit->channel[0];

        VATPIT_LOCK(vatpit);
        callout_stop(&c->callout);
        VATPIT_UNLOCK(vatpit);
}

void
vatpit_resume(struct vatpit *vatpit)
{
        struct channel *c = &vatpit->channel[0];

        VATPIT_LOCK(vatpit);
        ASSERT(!callout_active(&c->callout));
        if (c->time_target != 0) {
                vatpit_callout_reset(vatpit);
        }
        VATPIT_UNLOCK(vatpit);
}

static int
vatpit_data_read(void *datap, const vmm_data_req_t *req)
{
        VERIFY3U(req->vdr_class, ==, VDC_ATPIT);
        VERIFY3U(req->vdr_version, ==, 1);
        VERIFY3U(req->vdr_len, >=, sizeof (struct vdi_atpit_v1));

        struct vatpit *vatpit = datap;
        struct vdi_atpit_v1 *out = req->vdr_data;

        VATPIT_LOCK(vatpit);
        for (uint_t i = 0; i < 3; i++) {
                const struct channel *src = &vatpit->channel[i];
                struct vdi_atpit_channel_v1 *chan = &out->va_channel[i];

                chan->vac_initial = src->initial;
                chan->vac_reg_cr =
                    (src->reg_cr[0] | (uint16_t)src->reg_cr[1] << 8);
                chan->vac_reg_ol =
                    (src->reg_ol[0] | (uint16_t)src->reg_ol[1] << 8);
                chan->vac_reg_status = src->reg_status;
                chan->vac_mode = src->mode;
                chan->vac_status =
                    (src->slatched ? (1 << 0) : 0) |
                    (src->olatched ? (1 << 1) : 0) |
                    (src->cr_sel ? (1 << 2) : 0) |
                    (src->ol_sel ? (1 << 3) : 0) |
                    (src->fr_sel ? (1 << 4) : 0);
                /* Only channel 0 has the timer configured */
                if (i == 0 && src->time_target != 0) {
                        chan->vac_time_target =
                            vm_normalize_hrtime(vatpit->vm, src->time_target);
                } else {
                        chan->vac_time_target = 0;
                }
        }
        VATPIT_UNLOCK(vatpit);

        return (0);
}

static bool
vatpit_data_validate(const struct vdi_atpit_v1 *src)
{
        for (uint_t i = 0; i < 3; i++) {
                const struct vdi_atpit_channel_v1 *chan = &src->va_channel[i];

                if ((chan->vac_status & ~VALID_STATUS_BITS) != 0) {
                        return (false);
                }
        }
        return (true);
}

static int
vatpit_data_write(void *datap, const vmm_data_req_t *req)
{
        VERIFY3U(req->vdr_class, ==, VDC_ATPIT);
        VERIFY3U(req->vdr_version, ==, 1);
        VERIFY3U(req->vdr_len, >=, sizeof (struct vdi_atpit_v1));

        struct vatpit *vatpit = datap;
        const struct vdi_atpit_v1 *src = req->vdr_data;
        if (!vatpit_data_validate(src)) {
                return (EINVAL);
        }

        VATPIT_LOCK(vatpit);
        for (uint_t i = 0; i < 3; i++) {
                const struct vdi_atpit_channel_v1 *chan = &src->va_channel[i];
                struct channel *out = &vatpit->channel[i];

                out->initial = chan->vac_initial;
                out->reg_cr[0] = chan->vac_reg_cr;
                out->reg_cr[1] = chan->vac_reg_cr >> 8;
                out->reg_ol[0] = chan->vac_reg_ol;
                out->reg_ol[1] = chan->vac_reg_ol >> 8;
                out->reg_status = chan->vac_reg_status;
                out->mode = chan->vac_mode;
                out->slatched = (chan->vac_status & (1 << 0)) != 0;
                out->olatched = (chan->vac_status & (1 << 1)) != 0;
                out->cr_sel = (chan->vac_status & (1 << 2)) != 0;
                out->ol_sel = (chan->vac_status & (1 << 3)) != 0;
                out->fr_sel = (chan->vac_status & (1 << 4)) != 0;

                /* Only channel 0 has the timer configured */
                if (i != 0) {
                        continue;
                }

                struct callout *callout = &out->callout;
                if (callout_active(callout)) {
                        callout_deactivate(callout);
                }

                if (chan->vac_time_target == 0) {
                        out->time_loaded = 0;
                        out->time_target = 0;
                        continue;
                }

                /* back-calculate time_loaded for the appropriate interval */
                const uint64_t time_target =
                    vm_denormalize_hrtime(vatpit->vm, chan->vac_time_target);
                out->total_target = out->initial;
                out->time_target = time_target;
                out->time_loaded = time_target -
                    hrt_freq_interval(PIT_8254_FREQ, out->initial);

                if (!vm_is_paused(vatpit->vm)) {
                        vatpit_callout_reset(vatpit);
                }
        }
        VATPIT_UNLOCK(vatpit);

        return (0);
}

static const vmm_data_version_entry_t atpit_v1 = {
        .vdve_class = VDC_ATPIT,
        .vdve_version = 1,
        .vdve_len_expect = sizeof (struct vdi_atpit_v1),
        .vdve_readf = vatpit_data_read,
        .vdve_writef = vatpit_data_write,
};
VMM_DATA_VERSION(atpit_v1);