/***************************************************************************
 * Copyright (c) 2026 Eclipse ThreadX contributors
 *
 * This program and the accompanying materials are made available under the
 * terms of the MIT License which is available at
 * https://opensource.org/licenses/MIT.
 *
 * AI Disclosure: This file was largely AI-generated by Claude Code (Opus 5.5).
 * The AI-generated portions may be considered public domain (CC0-1.0)
 * and not subject to the project's licence. The human contributor has
 * reviewed and verified that the code is correct.
 *
 * SPDX-License-Identifier: MIT and CC0-1.0
 **************************************************************************/

/* PLIC driver for Erbium, machine-mode context of the current hart.  */

#include "plic.h"
#include <stddef.h>

static irq_callback callbacks[MAX_CALLBACK_NUM];

/* Source 0 is reserved and the six sources fit in the first enable word.  */
static int plic_source_valid(int irqno)
{
    return (irqno > 0) && (irqno < MAX_CALLBACK_NUM);
}

void plic_irq_enable(int irqno)
{
    volatile uint32_t *reg = (volatile uint32_t *)PLIC_MENABLE(riscv_get_core());
    int intr_enable;

    if (!plic_source_valid(irqno))
        return;

    intr_enable = riscv_mintr_save();
    *reg = *reg | (1u << (unsigned int)irqno);
    riscv_mintr_restore(intr_enable);
}

void plic_irq_disable(int irqno)
{
    volatile uint32_t *reg = (volatile uint32_t *)PLIC_MENABLE(riscv_get_core());
    int intr_enable;

    if (!plic_source_valid(irqno))
        return;

    intr_enable = riscv_mintr_save();
    *reg = *reg & ~(1u << (unsigned int)irqno);
    riscv_mintr_restore(intr_enable);
}

int plic_register_callback(int irqno, irq_callback callback)
{
    if (!plic_source_valid(irqno))
        return -1;
    callbacks[irqno] = callback;
    return 0;
}

int plic_unregister_callback(int irqno)
{
    return plic_register_callback(irqno, NULL);
}

int plic_init(void)
{
    uintptr_t hart = riscv_get_core();

    for (int i = 0; i < MAX_CALLBACK_NUM; i++)
        callbacks[i] = NULL;

    /* Do not depend on the reset state or on a prior boot stage: start
       with every source disabled for this context.  Drivers enable their
       own sources.  */
    *(volatile uint32_t *)PLIC_MENABLE(hart) = 0;

    /* The values the silicon hardwires; see plic.h.  */
    *(volatile uint32_t *)PLIC_MTHRESHOLD(hart) = 0;
    for (int i = 1; i <= PLIC_NUM_SOURCES; i++)
        *(volatile uint32_t *)PLIC_PRIORITY(i) = 1;

    return 0;
}

int plic_claim(void)
{
    return (int)(*(volatile uint32_t *)PLIC_MCLAIM(riscv_get_core()));
}

void plic_complete(int irqno)
{
    *(volatile uint32_t *)PLIC_MCOMPLETE(riscv_get_core()) = (uint32_t)irqno;
}

int plic_irq_intr(void)
{
    int ret = -1;
    int irqno = plic_claim();

    /* Nothing pending: another context claimed it first.  */
    if (irqno == 0)
        return 0;

    if (!plic_source_valid(irqno))
    {
        plic_complete(irqno);
        return -1;
    }

    if (callbacks[irqno] != NULL)
        ret = (callbacks[irqno])(irqno);

    plic_complete(irqno);
    return ret;
}