/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2022 Damien P. George
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <assert.h>
#include "pendsv.h"
#include "RP2040.h"

static pendsv_dispatch_t pendsv_dispatch_table[PENDSV_DISPATCH_NUM_SLOTS];
static int pendsv_lock;

void pendsv_suspend(void) {
    pendsv_lock++;
}

void pendsv_resume(void) {
    pendsv_lock--;
    assert(pendsv_lock >= 0);
    // Run pendsv if needed.  Find an entry with a dispatch and call pendsv dispatch
    // with it.  If pendsv runs it will service all slots.
    int count = PENDSV_DISPATCH_NUM_SLOTS;
    while (count--) {
        if (pendsv_dispatch_table[count]) {
            pendsv_schedule_dispatch(count, pendsv_dispatch_table[count]);
            break;
        }
    }
}

void pendsv_schedule_dispatch(size_t slot, pendsv_dispatch_t f) {
    assert(pendsv_lock >= 0);
    pendsv_dispatch_table[slot] = f;
    if (pendsv_lock == 0) {
        SCB->ICSR = SCB_ICSR_PENDSVSET_Msk;
    }
}

// PendSV interrupt handler to perform background processing.
void PendSV_Handler(void) {
    assert(pendsv_lock == 0);
    for (size_t i = 0; i < PENDSV_DISPATCH_NUM_SLOTS; ++i) {
        if (pendsv_dispatch_table[i] != NULL) {
            pendsv_dispatch_t f = pendsv_dispatch_table[i];
            pendsv_dispatch_table[i] = NULL;
            f();
        }
    }
}