/*
 * Copyright (c) 2026, Chloe M.
 * Provided under the BSD-3 clause.
 *
 * Description:  MP bringup
 * Author:       Chloe M.
 */

#include <stdef.h>
#include <hal/mp.h>
#include <hal/prim.h>
#include <ex/trace.h>
#include <machine/irqchip.h>
#include <machine/hpet.h>
#include <machine/lapic.h>
#include <units.h>

/* Limit used to prevent log spam */
#define MP_LOG_CAP 4
#define MP_DEBUG 1

/* Local APIC flags */
#define LAPIC_ONLINE_CAPABLE BIT(1)

#define DTRACE(Fmt, ...) \
    TRACE("[ MP ]: " Fmt, ##__VA_ARGS__)

#if MP_DEBUG
#define MP_DTRACE(...)                  \
    if (ProcessorsUp < MP_LOG_CAP) {    \
        DTRACE(__VA_ARGS__);            \
    }
#else
#define MP_DTRACE(...) (VOID)0
#endif  /* MP_DEBUG */

static USIZE ProcessorsUp = 0;

/*
 * Bring up a single application processor
 *
 * @Lapic: Local APIC of processor to bring up
 */
static VOID
ApKick(ACPI_LOCAL_APIC *Lapic)
{
    UQUAD UsecCur, UsecGoal;
    ULONG BspId;

    if (Lapic == NULL) {
        return;
    }

    /* Don't nuke ourselves */
    BspId = MdLapicId();
    if (Lapic->ApicId == BspId) {
        return;
    }

    /*
     * Some processor entries may not be "online capable", if we
     * encounter such entries, ignore it.
     */
    if (!ISSET(Lapic->Flags, LAPIC_ONLINE_CAPABLE)) {
        return;
    }

    /* Send an INIT IPI to the processor */
    MdLapicSendIpi(
        0,
        Lapic->ApicId,
        0,
        IPI_XND_NONE,
        IPI_DELMOD_INIT
    );

    /* MP spec states to wait 10 usec */
    UsecCur = MdHpetTimeUsec();
    UsecGoal = UsecCur + (USEC_PER_MSEC * 10);
    while (MdHpetTimeUsec() < UsecGoal) {
        HalCpuSpinWait();
    }

    DTRACE("sent init to apic%d\n", Lapic->ApicId);
    ++ProcessorsUp;
}

VOID
HalMpBringUp(VOID)
{
    ACPI_LOCAL_APIC *LocalApic;
    USIZE Idx;

    /* Bring up each AP */
    for (Idx = 0;; ++Idx) {
        LocalApic = MdLapicByIndex(Idx);
        if (LocalApic == NULL) {
            break;
        }

        ApKick(LocalApic);
    }
}