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incubator-nuttx/drivers/power/pm/activity_governor.c

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/****************************************************************************
* drivers/power/pm/activity_governor.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 <nuttx/config.h>
#include <stdint.h>
#include <assert.h>
#include <sys/types.h>
#include <stdlib.h>
#include <nuttx/power/pm.h>
#include <nuttx/wqueue.h>
#include <nuttx/irq.h>
#include "pm.h"
#ifdef CONFIG_PM_GOVERNOR_ACTIVITY
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define PM_TIMER_GAP (TIME_SLICE_TICKS * 2)
/* Convert the time slice interval into system clock ticks.
*
* CONFIG_PM_SLICEMS provides the duration of one time slice in milliseconds.
* CLOCKS_PER_SEC provides the number of timer ticks in one second.
*
* slice ticks = (CONFIG_PM_SLICEMS msec / 1000 msec/sec) /
* (CLOCKS_PER_SEC ticks/sec)
*/
#define TIME_SLICE_TICKS ((CONFIG_PM_GOVERNOR_SLICEMS * CLOCKS_PER_SEC) / 1000)
/****************************************************************************
* Private Type Declarations
****************************************************************************/
struct pm_domain_state_s
{
/* recommended - The recommended state based on the governor policy
* mndex - The index to the next slot in the memory[] array to use.
* mcnt - A tiny counter used only at start up. The actual algorithm
* cannot be applied until CONFIG_PM_GOVERNOR_MEMORY
* samples have been collected.
*/
uint8_t recommended;
uint8_t mndx;
uint8_t mcnt;
/* accum - The accumulated counts in this time interval */
int16_t accum;
#if CONFIG_PM_GOVERNOR_MEMORY > 1
/* This is the averaging "memory." 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_GOVERNOR_MEMORY provides the memory for the algorithm.
* Default: 2
* CONFIG_PM_COEFn provides weight for each sample. Default: 1
*/
int16_t memory[CONFIG_PM_GOVERNOR_MEMORY - 1];
#endif
/* stime - The time (in ticks) at the start of the current time slice */
clock_t stime;
/* btime - The time (in ticks) at the start of the current state */
clock_t btime;
/* Timer to decrease state */
struct wdog_s wdog;
};
struct pm_activity_governor_s
{
/* Threshold time slice count to enter the next low power consdumption
* state. Indexing is next state 0:IDLE, 1: STANDBY, 2: SLEEP.
*/
const uint32_t pmcount[3];
/* Threshold activity values to enter into the next lower power consumption
* state. Indexing is next state 0:IDLE, 1:STANDBY, 2:SLEEP.
*/
const int32_t pmenterthresh[3];
/* Threshold activity values to leave the current low power consdumption
* state. Indexing is current state 0:IDLE, 1: STANDBY, 2: SLEEP.
*/
const int32_t pmexitthresh[3];
/* CONFIG_PM_GOVERNOR_MEMORY is the total number of time slices (including
* the current time slice). The history of previous values is then
* CONFIG_PM_GOVERNOR_MEMORY-1.
*/
#if CONFIG_PM_GOVERNOR_MEMORY > 1
const int16_t pmcoeffs[CONFIG_PM_GOVERNOR_MEMORY - 1];
#endif
struct pm_domain_state_s domain_states[CONFIG_PM_NDOMAINS];
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static void governor_initialize(void);
static void governor_statechanged(int domain, enum pm_state_e newstate);
static enum pm_state_e governor_checkstate(int domain);
static void governor_activity(int domain, int count);
static void governor_timer(int domain);
static void governor_update(int domain, int16_t accum);
/****************************************************************************
* Private Data
****************************************************************************/
struct pm_activity_governor_s g_pm_activity_governor =
{
{
CONFIG_PM_GOVERNOR_IDLEENTER_COUNT,
CONFIG_PM_GOVERNOR_STANDBYENTER_COUNT,
CONFIG_PM_GOVERNOR_SLEEPENTER_COUNT
},
{
CONFIG_PM_GOVERNOR_IDLEENTER_THRESH,
CONFIG_PM_GOVERNOR_STANDBYENTER_THRESH,
CONFIG_PM_GOVERNOR_SLEEPENTER_THRESH
},
{
CONFIG_PM_GOVERNOR_IDLEEXIT_THRESH,
CONFIG_PM_GOVERNOR_STANDBYEXIT_THRESH,
CONFIG_PM_GOVERNOR_SLEEPEXIT_THRESH
},
#if CONFIG_PM_GOVERNOR_MEMORY > 1
{
CONFIG_PM_GOVERNOR_COEF1
#if CONFIG_PM_GOVERNOR_MEMORY > 2
, CONFIG_PM_GOVERNOR_COEF2
#endif
#if CONFIG_PM_GOVERNOR_MEMORY > 3
, CONFIG_PM_GOVERNOR_COEF3
#endif
#if CONFIG_PM_GOVERNOR_MEMORY > 4
, CONFIG_PM_GOVERNOR_COEF4
#endif
#if CONFIG_PM_GOVERNOR_MEMORY > 5
, CONFIG_PM_GOVERNOR_COEF5
#endif
#if CONFIG_PM_GOVERNOR_MEMORY > 6
# warning "This logic needs to be extended"
#endif
}
#endif
};
static const struct pm_governor_s g_pmgovernor =
{
governor_initialize, /* initialize */
NULL, /* deinitialize */
governor_statechanged, /* statechanged */
governor_checkstate, /* checkstate */
governor_activity, /* activity */
NULL /* priv */
};
/****************************************************************************
* Private Functions
****************************************************************************/
static void governor_initialize(void)
{
FAR struct pm_domain_state_s *pdomstate;
int i;
for (i = 0; i < CONFIG_PM_NDOMAINS; i++)
{
pdomstate = &g_pm_activity_governor.domain_states[i];
pdomstate->stime = clock_systime_ticks();
pdomstate->btime = clock_systime_ticks();
}
}
static void governor_activity(int domain, int count)
{
FAR struct pm_domain_state_s *pdomstate;
clock_t now, elapsed;
uint32_t accum;
irqstate_t flags;
/* Get a convenience pointer to minimize all of the indexing */
DEBUGASSERT(domain >= 0 && domain < CONFIG_PM_NDOMAINS);
pdomstate = &g_pm_activity_governor.domain_states[domain];
/* Just increment the activity count in the current time slice. The
* priority is simply the number of counts that are added.
*/
if (count > 0)
{
/* Add the activity count to the accumulated counts. */
flags = pm_domain_lock(domain);
accum = (uint32_t)pdomstate->accum + count;
/* Make sure that we do not overflow the underlying representation */
if (accum > INT16_MAX)
{
accum = INT16_MAX;
}
/* Save the updated count */
pdomstate->accum = (int16_t)accum;
/* 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_systime_ticks();
elapsed = now - pdomstate->stime;
if (elapsed >= TIME_SLICE_TICKS)
{
int16_t tmp;
/* Sample the count, reset the time and count, and assess the PM
* state. This is an atomic operation because interrupts are
* still disabled.
*/
tmp = pdomstate->accum;
pdomstate->stime = now;
pdomstate->accum = 0;
governor_update(domain, tmp);
}
pm_domain_unlock(domain, flags);
}
}
/****************************************************************************
* Name: governor_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:
* domain - The PM domain associated with the accumulator
* 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.
*
****************************************************************************/
static void governor_update(int domain, int16_t accum)
{
FAR struct pm_domain_state_s *pdomstate;
uint8_t state;
int32_t y;
int index;
#if CONFIG_PM_GOVERNOR_MEMORY > 1
int32_t denom;
int i = 0;
int j;
#endif
/* Get a convenience pointer to minimize all of the indexing */
DEBUGASSERT(domain >= 0 && domain < CONFIG_PM_NDOMAINS);
pdomstate = &g_pm_activity_governor.domain_states[domain];
state = g_pmglobals.domain[domain].state;
#if CONFIG_PM_GOVERNOR_MEMORY > 1
/* We won't bother to do anything until we have accumulated
* CONFIG_PM_GOVERNOR_MEMORY-1 samples.
*/
if (pdomstate->mcnt < CONFIG_PM_GOVERNOR_MEMORY - 1)
{
index = pdomstate->mcnt++;
pdomstate->memory[index] = accum;
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_GOVERNOR_MEMORY:
* provides the memory for the algorithm. Default: 2
* CONFIG_PM_GOVERNOR_COEFn:
* provides weight for each sample. Default: 1
*
* First, calculate Y = An*X
*/
y = CONFIG_PM_GOVERNOR_COEFN * accum;
denom = CONFIG_PM_GOVERNOR_COEFN;
/* Then calculate Y += SUM(Ai*Yi), i = 1..n-1. The oldest sample will
* reside at the domain's mndx (and this is the value that we will
* overwrite with the new value).
*/
for (j = pdomstate->mndx; i < CONFIG_PM_GOVERNOR_MEMORY - 1; i++, j++)
{
if (j >= CONFIG_PM_GOVERNOR_MEMORY - 1)
{
j = 0;
}
y += g_pm_activity_governor.pmcoeffs[i] * pdomstate->memory[j];
denom += g_pm_activity_governor.pmcoeffs[i];
}
/* Compute and save the new activity value */
y /= denom;
index = pdomstate->mndx++;
pdomstate->memory[index] = y;
if (pdomstate->mndx >= CONFIG_PM_GOVERNOR_MEMORY - 1)
{
pdomstate->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 (state > PM_NORMAL)
{
/* Get the table index for the current state (which will be the
* current state minus one)
*/
index = state - 1;
/* Has the threshold to return to normal power consumption state been
* exceeded?
*/
if (y > g_pm_activity_governor.pmexitthresh[index])
{
/* Yes... reset the count and recommend the normal state. */
pdomstate->btime = clock_systime_ticks();
pdomstate->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 (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 = state;
nextstate = state + 1;
/* Has the threshold to enter the next lower power consumption state
* been exceeded?
*/
if (y > g_pm_activity_governor.pmenterthresh[index])
{
/* No... reset the count and recommend the current state */
pdomstate->btime = clock_systime_ticks();
pdomstate->recommended = state;
}
/* Yes.. have we already recommended this state? If so, do nothing */
else if (pdomstate->recommended < nextstate)
{
/* No.. calculate the count. Has it passed the count required
* for a state transition?
*/
if (clock_systime_ticks() - pdomstate->btime >=
g_pm_activity_governor.pmcount[index] * TIME_SLICE_TICKS)
{
/* Yes, recommend the new state and set up for the next
* transition.
*/
pdomstate->btime = clock_systime_ticks();
pdomstate->recommended = nextstate;
}
}
}
}
static enum pm_state_e governor_checkstate(int domain)
{
FAR struct pm_domain_state_s *pdomstate;
FAR struct pm_domain_s *pdom;
clock_t now, elapsed;
irqstate_t flags;
int index;
/* Get a convenience pointer to minimize all of the indexing */
pdomstate = &g_pm_activity_governor.domain_states[domain];
pdom = &g_pmglobals.domain[domain];
/* 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 governor_activity().
*/
flags = pm_domain_lock(domain);
/* 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_systime_ticks();
elapsed = now - pdomstate->stime;
if (elapsed >= 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 = pdomstate->accum;
pdomstate->stime = now;
pdomstate->accum = 0;
governor_update(domain, accum);
}
/* Consider the possible power state lock here */
for (index = 0; index < pdomstate->recommended; index++)
{
if (!dq_empty(&pdom->wakelock[index]))
{
pdomstate->recommended = index;
break;
}
}
pm_domain_unlock(domain, flags);
return pdomstate->recommended;
}
static void governor_statechanged(int domain, enum pm_state_e newstate)
{
if (newstate != PM_RESTORE)
{
/* Start PM timer to decrease PM state */
governor_timer(domain);
}
}
static void governor_timer_cb(wdparm_t arg)
{
pm_auto_updatestate((int)arg);
}
/****************************************************************************
* Name: governor_timer
*
* Description:
* This internal function is called to start one timer to decrease power
* state level.
*
* Input Parameters:
* domain - The PM domain associated with the accumulator
*
* Returned Value:
* None.
*
****************************************************************************/
static void governor_timer(int domain)
{
FAR struct pm_domain_state_s *pdomstate;
FAR struct pm_domain_s *pdom;
uint8_t state;
static const int pmtick[3] =
{
TIME_SLICE_TICKS * CONFIG_PM_GOVERNOR_IDLEENTER_COUNT,
TIME_SLICE_TICKS * CONFIG_PM_GOVERNOR_STANDBYENTER_COUNT,
TIME_SLICE_TICKS * CONFIG_PM_GOVERNOR_SLEEPENTER_COUNT
};
pdom = &g_pmglobals.domain[domain];
pdomstate = &g_pm_activity_governor.domain_states[domain];
state = pdom->state;
if (state < PM_SLEEP && dq_empty(&pdom->wakelock[state]))
{
sclock_t delay = pmtick[state] +
pdomstate->btime -
clock_systime_ticks();
sclock_t left = wd_gettime(&pdomstate->wdog);
if (delay <= 0)
{
delay = 1;
}
if (!WDOG_ISACTIVE(&pdomstate->wdog) ||
abs(delay - left) > PM_TIMER_GAP)
{
wd_start(&pdomstate->wdog, delay, governor_timer_cb,
(wdparm_t)domain);
}
}
else
{
wd_cancel(&pdomstate->wdog);
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
FAR const struct pm_governor_s *pm_activity_governor_initialize(void)
{
return &g_pmgovernor;
}
#endif /* CONFIG_PM_GOVERNOR_ACTIVITY */
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