/**
 ******************************************************************************
 * @addtogroup PIOS PIOS Core hardware abstraction layer
 * @{
 * @addtogroup PIOS_IRQ IRQ Setup Functions
 * @brief STM32 Hardware code to enable and disable interrupts
 * @{
 *
 * @file       pios_irq.c
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 *              Parts by Thorsten Klose (tk@midibox.org) (tk@midibox.org)
 * @brief      IRQ Enable/Disable routines
 * @see        The GNU Public License (GPL) Version 3
 *
 *****************************************************************************/
/*
 * 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, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "pios.h"

#ifdef PIOS_INCLUDE_IRQ

/* 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;

/**
 * Disables all interrupts (nested)
 * \return < 0 On errors
 */
int32_t PIOS_IRQ_Disable(void)
{
    /* 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;
}

/**
 * Enables all interrupts (nested)
 * \return < 0 on errors
 * \return -1 on nesting errors (PIOS_IRQ_Disable() hasn't been called before)
 */
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;
}

#endif /* PIOS_INCLUDE_IRQ */

/**
 * @}
 * @}
 */