/**
 ******************************************************************************
 *
 * @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
 * @defgroup   PIOS_IRQ IRQ Setup Functions
 * @{
 * 
 *****************************************************************************/
/* 
 * 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
 */


/* 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;


/**
* 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;
}