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

#include <machine/lapic.h>
#include <machine/lapicreg.h>
#include <machine/msr.h>
#include <machine/cpuid.h>
#include <drivers/acpi/tables.h>
#include <drivers/acpi/acpi.h>
#include <mm/vmm.h>
#include <ex/trace.h>
#include <ke/knot.h>
#include <stdef.h>

/*
 * Trace only on the bootstrap processor but not on any others
 * to avoid log spam...
 */
#define DTRACE_BSP(Fmt, ...) do {                       \
        ULONG ApicBase;                                 \
                                                        \
        ApicBase = MdRdmsr(IA32_APIC_BASE_MSR);         \
        if (ISSET(ApicBase, BIT(8))) {                  \
            TRACE("[ LAPIC ]: " Fmt, ##__VA_ARGS__);    \
        }                                               \
    } while (0);

/*
 * Returns true if the Local APIC unit is supported on the
 * current processor.
 */
static BOOLEAN
LapicIsSupported(VOID)
{
    ULONG Edx, Unused;

    CPUID(1, Unused, Unused, Unused, Edx);
    return ISSET(Edx, BIT(9)) != 0;
}

/*
 * Returns true if the CPU can operate its Local APIC unit
 * in the newer x2APIC mode.
 */
static BOOLEAN
LapicHasX2Apic(VOID)
{
    ULONG Ecx, Unused;

    CPUID(1, Unused, Unused, Ecx, Unused);
    return ISSET(Ecx, BIT(21)) != 0;
}

/*
 * Enable the Local APIC unit
 */
static VOID
LapicEnable(VOID)
{
    UQUAD ApicBase;

    /* Hardware enable the Local APIC unit */
    ApicBase = MdRdmsr(IA32_APIC_BASE_MSR);
    ApicBase |= LAPIC_HW_ENABLE;
    MdWrmsr(IA32_APIC_BASE_MSR, ApicBase);
}

VOID
MdLapicInit(KPCR *Kpcr)
{
    ACPI_MADT *Madt;
    MCB *Mcb;

    if (Kpcr == NULL) {
        KeKnot(
            KNOT_MISC,
            "lapic: failed to initialize lapic driver\n"
        );
    }

    if (!LapicIsSupported()) {
        KeKnot(
            KNOT_MISSING_HARDWARE,
            "lapic: local apic not supported\n"
        );
    }

    /* Obtain the ACPI MADT table */
    Madt = AcpiQuery("APIC");
    if (Madt == NULL) {
        KeKnot(KNOT_MISC, "lapic: could not obtain MADT\n");
    }

    Mcb = &Kpcr->Mcb;
    Mcb->LapicBase = PMA_TO_VMA((UPTR)Madt->LapicAddr);
    Mcb->HasX2Apic = LapicHasX2Apic();

    /* Enable the Local APIC */
    LapicEnable();
}