arch/arm/src/lpc17xx_40xx/lpc17_40_idle.c

/****************************************************************************
 * arch/arm/src/lpc17xx_40xx/lpc17_40_idle.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <arch/board/board.h>
#include <nuttx/config.h>

#include <nuttx/arch.h>
#include <nuttx/board.h>

#include "arm_internal.h"
#include "lpc17_40_gpdma.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Does the board support an IDLE LED to indicate that the board is in the
 * IDLE state?
 */

#if defined(CONFIG_ARCH_LEDS) && defined(LED_IDLE)
#  define BEGIN_IDLE() board_autoled_on(LED_IDLE)
#  define END_IDLE()   board_autoled_off(LED_IDLE)
#else
#  define BEGIN_IDLE()
#  define END_IDLE()
#endif

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_idle
 *
 * Description:
 *   up_idle() is the logic that will be executed when there is no other
 *   ready-to-run task.  This is processor idle time and will continue until
 *   some interrupt occurs to cause a context switch from the idle task.
 *
 *   Processing in this state may be processor-specific. e.g., this is where
 *   power management operations might be performed.
 *
 ****************************************************************************/

void up_idle(void)
{
#if defined(CONFIG_SUPPRESS_INTERRUPTS) || defined(CONFIG_SUPPRESS_TIMER_INTS)
  /* If the system is idle and there are no timer interrupts, then process
   * "fake" timer interrupts. Hopefully, something will wake up.
   */

  nxsched_process_timer();
#else

/* If the g_dma_inprogress is zero, then there is no DMA in progress.  This
 * value is needed in the IDLE loop to determine if the IDLE loop should
 * go into lower power power consumption modes.  According to the LPC17xx
 * User Manual: "The DMA controller can continue to work in Sleep mode, and
 * has access to the peripheral SRAMs and all peripheral registers. The
 * flash memory and the Main SRAM are not available in Sleep mode, they are
 * disabled in order to save power."
 */

#ifdef CONFIG_LPC17_40_GPDMA
  if (g_dma_inprogress == 0)
#endif
    {
      /* Sleep until an interrupt occurs in order to save power */

      BEGIN_IDLE();
      asm("WFI");
      END_IDLE();
    }
#endif
}