/****************************************************************************
* drivers/power/pm_checkstate.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
* 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
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* 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 <nuttx/config.h>
#include <nuttx/power/pm.h>
#include <nuttx/clock.h>
#include <arch/irq.h>
#include "pm_internal.h"
#ifdef CONFIG_PM
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pm_checkstate
*
* Description:
* This function is called from the MCU-specific IDLE loop to monitor the
* the power management conditions. This function returns the "recommended"
* power management state based on the PM configuration and activity
* reported in the last sampling periods. The power management state is
* not automatically changed, however. The IDLE loop must call
* pm_changestate() in order to make the state change.
*
* These two steps are separated because the plaform-specific IDLE loop may
* have additional situational information that is not available to the
* the PM sub-system. For example, the IDLE loop may know that the
* battery charge level is very low and may force lower power states
* even if there is activity.
*
* NOTE: That these two steps are separated in time and, hence, the IDLE
* loop could be suspended for a long period of time between calling
* pm_checkstate() and pm_changestate(). The IDLE loop may need to make
* these calls atomic by either disabling interrupts until the state change
* is completed.
*
* Input Parameters:
* None
*
* Returned Value:
* The recommended power management state.
*
****************************************************************************/
enum pm_state_e pm_checkstate(void)
{
uint32_t now;
irqstate_t flags;
/* Check for the end of the current time slice. This must be performed
* with interrupts disabled so that it does not conflict with the similar
* logic in pm_activity().
*/
flags = irqsave();
/* Check the elapsed time. In periods of low activity, time slicing is
* controlled by IDLE loop polling; in periods of higher activity, time
* slicing is controlled by driver activity. In either case, the duration
* of the time slice is only approximate; during times of heavy activity,
* time slices may be become longer and the activity level may be over-
* estimated.
*/
now = clock_systimer();
if (now - g_pmglobals.stime >= TIME_SLICE_TICKS)
{
int16_t accum;
/* Sample the count, reset the time and count, and assess the PM
* state. This is an atomic operation because interrupts are
* still disabled.
*/
accum = g_pmglobals.accum;
g_pmglobals.stime = now;
g_pmglobals.accum = 0;
/* Reassessing the PM state may require some computation. However,
* the work will actually be performed on a worker thread at a user-
* controlled priority.
*/
(void)pm_update(accum);
}
irqrestore(flags);
/* Return the recommended state. Assuming that we are called from the
* IDLE thread at the lowest priority level, any updates scheduled on the
* worker thread above should have already been peformed and the recommended
* state should be current:
*/
return g_pmglobals.recommended;
}
#endif /* CONFIG_PM */
