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nuttx/drivers/power/pm_update.c

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/****************************************************************************
* drivers/power/pm_update.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
* 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 <nuttx/config.h>
#include <assert.h>
#include <nuttx/power/pm.h>
#include <nuttx/wqueue.h>
#include "pm.h"
#ifdef CONFIG_PM
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/* CONFIG_PM_MEMORY is the total number of time slices (including the current
* time slice. The histor or previous values is then CONFIG_PM_MEMORY-1.
*/
#if CONFIG_PM_MEMORY > 1
static const int16_t g_pmcoeffs[CONFIG_PM_MEMORY-1] =
{
CONFIG_PM_COEF1
#if CONFIG_PM_MEMORY > 2
, CONFIG_PM_COEF2
#endif
#if CONFIG_PM_MEMORY > 3
, CONFIG_PM_COEF3
#endif
#if CONFIG_PM_MEMORY > 4
, CONFIG_PM_COEF4
#endif
#if CONFIG_PM_MEMORY > 5
, CONFIG_PM_COEF5
#endif
#if CONFIG_PM_MEMORY > 6
# warning "This logic needs to be extended"
#endif
};
#endif
/* Threshold activity values to enter into the next lower power consumption
* state. Indexing is next state 0:IDLE, 1:STANDBY, 2:SLEEP.
*/
static const int16_t g_pmenterthresh[3] =
{
CONFIG_PM_IDLEENTER_THRESH,
CONFIG_PM_STANDBYENTER_THRESH,
CONFIG_PM_SLEEPENTER_THRESH
};
/* Threshold activity values to leave the current low power consdumption
* state. Indexing is current state 0:IDLE, 1: STANDBY, 2: SLEEP.
*/
static const int16_t g_pmexitthresh[3] =
{
CONFIG_PM_IDLEEXIT_THRESH,
CONFIG_PM_STANDBYEXIT_THRESH,
CONFIG_PM_SLEEPEXIT_THRESH
};
/* Threshold time slice count to enter the next low power consdumption
* state. Indexing is next state 0:IDLE, 1: STANDBY, 2: SLEEP.
*/
static const uint16_t g_pmcount[3] =
{
CONFIG_PM_IDLEENTER_COUNT,
CONFIG_PM_STANDBYENTER_COUNT,
CONFIG_PM_SLEEPENTER_COUNT
};
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: pm_worker
*
* Description:
* This worker function is queue at the end of a time slice in order to
* update driver activity metrics and recommended states.
*
* Input Parameters:
* arg - The value of the activity accumulator at the end of the time
* slice.
*
* Returned Value:
* None.
*
* Assumptions:
* This function runs on the worker thread.
*
****************************************************************************/
void pm_worker(FAR void *arg)
{
int16_t accum = (int16_t)((intptr_t)arg);
int32_t Y;
int index;
#if CONFIG_PM_MEMORY > 1
int32_t denom;
int i, j;
/* We won't bother to do anything until we have accumulated
* CONFIG_PM_MEMORY-1 samples.
*/
if (g_pmglobals.mcnt < CONFIG_PM_MEMORY-1)
{
g_pmglobals.memory[g_pmglobals.mcnt] = accum;
g_pmglobals.mcnt++;
return;
}
/* The averaging algorithm is simply: Y = (An*X + SUM(Ai*Yi))/SUM(Aj), where
* i = 1..n-1 and j= 1..n, n is the length of the "memory", Ai is the
* weight applied to each value, and X is the current activity.
*
* CONFIG_PM_MEMORY provides the memory for the algorithm. Default: 2
* CONFIG_PM_COEFn provides weight for each sample. Default: 1
*
* First, calclate Y = An*X
*/
Y = CONFIG_PM_COEFN * accum;
denom = CONFIG_PM_COEFN;
/* Then calculate Y += SUM(Ai*Yi), i = 1..n-1. The oldest sample will
* reside at g_pmglobals.mndx (and this is the value that we will overwrite
* with the new value).
*/
for (i = 0, j = g_pmglobals.mndx; i < CONFIG_PM_MEMORY-1; i++, j++)
{
if (j >= CONFIG_PM_MEMORY-1)
{
j = 0;
}
Y += g_pmcoeffs[i] * g_pmglobals.memory[j];
denom += g_pmcoeffs[i];
}
/* Compute and save the new activity value */
Y /= denom;
g_pmglobals.memory[g_pmglobals.mndx] = Y;
g_pmglobals.mndx++;
if (g_pmglobals.mndx >= CONFIG_PM_MEMORY-1)
{
g_pmglobals.mndx = 0;
}
#else
/* No smoothing */
Y = accum;
#endif
/* First check if increased activity should cause us to return to the
* normal operating state. This would be unlikely for the lowest power
* consumption states because the CPU is probably asleep. However this
* probably does apply for the IDLE state.
*/
if (g_pmglobals.state > PM_NORMAL)
{
/* Get the table index for the current state (which will be the
* current state minus one)
*/
index = g_pmglobals.state - 1;
/* Has the threshold to return to normal power consumption state been
* exceeded?
*/
if (Y > g_pmexitthresh[index])
{
/* Yes... reset the count and recommend the normal state. */
g_pmglobals.thrcnt = 0;
g_pmglobals.recommended = PM_NORMAL;
return;
}
}
/* Now, compare this new activity level to the thresholds and counts for
* the next lower power consumption state. If we are already in the SLEEP
* state, then there is nothing more to be done (in fact, I would be
* surprised to be executing!).
*/
if (g_pmglobals.state < PM_SLEEP)
{
unsigned int nextstate;
/* Get the next state and the table index for the next state (which will
* be the current state)
*/
index = g_pmglobals.state;
nextstate = g_pmglobals.state + 1;
/* Has the threshold to enter the next lower power consumption state
* been exceeded?
*/
if (Y > g_pmenterthresh[index])
{
/* No... reset the count and recommend the current state */
g_pmglobals.thrcnt = 0;
g_pmglobals.recommended = g_pmglobals.state;
}
/* Yes.. have we already recommended this state? If so, do nothing */
else if (g_pmglobals.recommended < nextstate)
{
/* No.. increment the count. Has it passed the count required
* for a state transition?
*/
if (++g_pmglobals.thrcnt >= g_pmcount[index])
{
/* Yes, recommend the new state and set up for the next
* transition.
*/
g_pmglobals.thrcnt = 0;
g_pmglobals.recommended = nextstate;
}
}
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pm_update
*
* Description:
* This internal function is called at the end of a time slice in order to
* update driver activity metrics and recommended states.
*
* Input Parameters:
* accum - The value of the activity accumulator at the end of the time
* slice.
*
* Returned Value:
* None.
*
* Assumptions:
* This function may be called from a driver, perhaps even at the interrupt
* level. It may also be called from the IDLE loop at the lowest possible
* priority level. To reconcile these various conditions, all work is
* performed on the worker thread at a user-selectable priority. This will
* also serialize all of the updates and eliminate any need for additional
* protection.
*
****************************************************************************/
void pm_update(int16_t accum)
{
/* The work will be performed on the worker thread */
DEBUGASSERT(g_pmglobals.work.worker == NULL);
(void)work_queue(HPWORK, &g_pmglobals.work, pm_worker,
(FAR void *)((intptr_t)accum), 0);
}
#endif /* CONFIG_PM */
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