path: root/nuttx/arch/mips/src/common/up_idle.c

/****************************************************************************
 *  arch/mips/src/common/up_idle.c
 *
 *   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <nuttx/arch.h>
#include "up_internal.h"

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

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

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

/****************************************************************************
 * 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

  /* This would be an appropriate place to put some MCU-specific logic to
   * sleep in a reduced power mode until an interrupt occurs to save power
   */

  /* This is a kludge that I still don't understand.  The call to kmm_trysemaphore()
   * in the os_start.c IDLE loop seems necessary for the good health of the IDLE
   * loop.  When the work queue is enabled, this logic is removed from the IDLE
   * loop and it appears that we are somehow left idling with interrupts non-
   * functional. The following should be no-op, it just disables then re-enables
   * interrupts.  But it fixes the problem and will stay here until I understand
   * the problem/fix better.
   *
   * And no, the contents of the CP0 status register are not incorrect.  But for
   * some reason the status register needs to be re-written again on this thread
   * for it to take effect.  This might be a PIC32-only issue?
   */

#ifdef CONFIG_SCHED_WORKQUEUE
  irqstate_t flags = irqsave();
  irqrestore(flags);
#endif
#endif
}