pios_irq.c

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/* 
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 3 of the License, or 
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
 * for more details.
 * 
 * You should have received a copy of the GNU General Public License along 
 * with this program; if not, see <http://www.gnu.org/licenses/>
 */

/* Project Includes */
#include "pios.h"

/* Private Function Prototypes */

/* Local Variables */
/* The nesting counter ensures, that interrupts won't be enabled so long nested functions disable them */
static uint32_t nested_ctr;

/* Stored priority level before IRQ has been disabled (important for co-existence with vPortEnterCritical) */
static uint32_t prev_primask;

int32_t PIOS_IRQ_Disable(void)
{
        /* XXX TODO: This is racy */
        /* Get current priority if nested level == 0 */
        if (!nested_ctr) {
                __asm volatile ("   mrs %0, primask\n":"=r" (prev_primask)
                    );
        }

        /* Disable interrupts */
        __asm volatile ("     mov r0, #1     \n" "     msr primask, r0\n":::"r0");

        ++nested_ctr;

        /* No error */
        return 0;
}

int32_t PIOS_IRQ_Enable(void)
{
        /* Check for nesting error */
        if (nested_ctr == 0) {
                /* Nesting error */
                return -1;
        }

        /* Decrease nesting level */
        --nested_ctr;

        /* Set back previous priority once nested level reached 0 again */
        if (nested_ctr == 0) {
                __asm volatile ("   msr primask, %0\n"::"r" (prev_primask)
                    );
        }

        /* No error */
        return 0;
}

bool PIOS_IRQ_InISR(void)
{
        return (__get_IPSR() & 0xff) != 0;
}