text: /****************************************************************************
   *  arch/arm/src/stm32f0/stm32f0_idle.c
   *
   *   Copyright (C) 2017 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *           Alan Carvalho de Assis <acassis@gmail.com>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name NuttX nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <arch/board/board.h>
  #include <nuttx/config.h>
  
  #include <nuttx/arch.h>
  
  #include "up_internal.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
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: up_idle
   *
   * Description:
   *   up_idle() is the logic that will be executed when their 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.
     */
  
    sched_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_STM32F0_GPDMA
    if (g_dma_inprogress == 0)
  #endif
      {
        /* Sleep until an interrupt occurs in order to save power */
  
        BEGIN_IDLE();
        asm("WFI");
        END_IDLE();
      }
  #endif
  }
  