pid/zone.cpp - openbmc/phosphor-pid-control - Gitiles

 /**
  * Copyright 2017 Google Inc.
  *
  * Licensed 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.
  */

 /* Configuration. */
 #include "zone.hpp"

 #include "conf.hpp"
 #include "pid/controller.hpp"
 #include "pid/ec/pid.hpp"
 #include "pid/fancontroller.hpp"
 #include "pid/stepwisecontroller.hpp"
 #include "pid/thermalcontroller.hpp"
 #include "pid/tuning.hpp"

 #include <algorithm>
 #include <chrono>
 #include <cstring>
 #include <fstream>
 #include <iostream>
 #include <memory>
 #include <sstream>
 #include <string>

 using tstamp = std::chrono::high_resolution_clock::time_point;
 using namespace std::literals::chrono_literals;

 // Enforces minimum duration between events
 // Rreturns true if event should be allowed, false if disallowed
 bool allowThrottle(const tstamp& now, const std::chrono::seconds& pace)
 {
     static tstamp then;
     static bool first = true;

     if (first)
     {
         // Special case initialization
         then = now;
         first = false;

         // Initialization, always allow
         return true;
     }

     auto elapsed = now - then;
     if (elapsed < pace)
     {
         // Too soon since last time, disallow
         return false;
     }

     // It has been long enough, allow
     then = now;
     return true;
 }

 namespace pid_control
 {

 double DbusPidZone::getMaxSetPointRequest(void) const
 {
     return _maximumSetPoint;
 }

 bool DbusPidZone::getManualMode(void) const
 {
     return _manualMode;
 }

 void DbusPidZone::setManualMode(bool mode)
 {
     _manualMode = mode;

     // If returning to automatic mode, need to restore PWM from PID loop
     if (!mode)
     {
         _redundantWrite = true;
     }
 }

 bool DbusPidZone::getFailSafeMode(void) const
 {
     // If any keys are present at least one sensor is in fail safe mode.
     return !_failSafeSensors.empty();
 }

 int64_t DbusPidZone::getZoneID(void) const
 {
     return _zoneId;
 }

 void DbusPidZone::addSetPoint(double setPoint, const std::string& name)
 {
     _SetPoints.push_back(setPoint);
     /*
      * if there are multiple thermal controllers with the same
      * value, pick the first one in the iterator
      */
     if (_maximumSetPoint < setPoint)
     {
         _maximumSetPoint = setPoint;
         _maximumSetPointName = name;
     }
 }

 void DbusPidZone::addRPMCeiling(double ceiling)
 {
     _RPMCeilings.push_back(ceiling);
 }

 void DbusPidZone::clearRPMCeilings(void)
 {
     _RPMCeilings.clear();
 }

 void DbusPidZone::clearSetPoints(void)
 {
     _SetPoints.clear();
     _maximumSetPoint = 0;
 }

 double DbusPidZone::getFailSafePercent(void) const
 {
     return _failSafePercent;
 }

 double DbusPidZone::getMinThermalSetPoint(void) const
 {
     return _minThermalOutputSetPt;
 }

 uint64_t DbusPidZone::getCycleIntervalTime(void) const
 {
     return _cycleTime.cycleIntervalTimeMS;
 }

 uint64_t DbusPidZone::getUpdateThermalsCycle(void) const
 {
     return _cycleTime.updateThermalsTimeMS;
 }

 void DbusPidZone::addFanPID(std::unique_ptr<Controller> pid)
 {
     _fans.push_back(std::move(pid));
 }

 void DbusPidZone::addThermalPID(std::unique_ptr<Controller> pid)
 {
     _thermals.push_back(std::move(pid));
 }

 double DbusPidZone::getCachedValue(const std::string& name)
 {
     return _cachedValuesByName.at(name).scaled;
 }

 ValueCacheEntry DbusPidZone::getCachedValues(const std::string& name)
 {
     return _cachedValuesByName.at(name);
 }

 void DbusPidZone::setOutputCache(std::string_view name,
                                  const ValueCacheEntry& values)
 {
     _cachedFanOutputs[std::string{name}] = values;
 }

 void DbusPidZone::addFanInput(const std::string& fan)
 {
     _fanInputs.push_back(fan);
 }

 void DbusPidZone::addThermalInput(const std::string& therm)
 {
     _thermalInputs.push_back(therm);
 }

 // Updates desired RPM setpoint from optional text file
 // Returns true if rpmValue updated, false if left unchanged
 static bool fileParseRpm(const std::string& fileName, double& rpmValue)
 {
     static constexpr std::chrono::seconds throttlePace{3};

     std::string errText;

     try
     {
         std::ifstream ifs;
         ifs.open(fileName);
         if (ifs)
         {
             int value;
             ifs >> value;

             if (value <= 0)
             {
                 errText = "File content could not be parsed to a number";
             }
             else if (value <= 100)
             {
                 errText = "File must contain RPM value, not PWM value";
             }
             else
             {
                 rpmValue = static_cast<double>(value);
                 return true;
             }
         }
     }
     catch (const std::exception& e)
     {
         errText = "Exception: ";
         errText += e.what();
     }

     // The file is optional, intentionally not an error if file not found
     if (!(errText.empty()))
     {
         tstamp now = std::chrono::high_resolution_clock::now();
         if (allowThrottle(now, throttlePace))
         {
             std::cerr << "Unable to read from '" << fileName << "': " << errText
                       << "\n";
         }
     }

     return false;
 }

 void DbusPidZone::determineMaxSetPointRequest(void)
 {
     std::vector<double>::iterator result;
     double minThermalThreshold = getMinThermalSetPoint();

     if (_RPMCeilings.size() > 0)
     {
         result = std::min_element(_RPMCeilings.begin(), _RPMCeilings.end());
         // if Max set point is larger than the lowest ceiling, reset to lowest
         // ceiling.
         if (*result < _maximumSetPoint)
         {
             _maximumSetPoint = *result;
             // When using lowest ceiling, controller name is ceiling.
             _maximumSetPointName = "Ceiling";
         }
     }

     /*
      * If the maximum RPM setpoint output is below the minimum RPM
      * setpoint, set it to the minimum.
      */
     if (minThermalThreshold >= _maximumSetPoint)
     {
         _maximumSetPoint = minThermalThreshold;
         _maximumSetPointName = "";
     }
     else if (_maximumSetPointName.compare(_maximumSetPointNamePrev))
     {
         std::cerr << "PID Zone " << _zoneId << " max SetPoint "
                   << _maximumSetPoint << " requested by "
                   << _maximumSetPointName;
         for (const auto& sensor : _failSafeSensors)
         {
             if (sensor.find("Fan") == std::string::npos)
             {
                 std::cerr << " " << sensor;
             }
         }
         std::cerr << "\n";
         _maximumSetPointNamePrev.assign(_maximumSetPointName);
     }
     if (tuningEnabled)
     {
         /*
          * We received no setpoints from thermal sensors.
          * This is a case experienced during tuning where they only specify
          * fan sensors and one large fan PID for all the fans.
          */
         static constexpr auto setpointpath = "/etc/thermal.d/setpoint";

         fileParseRpm(setpointpath, _maximumSetPoint);

         // Allow per-zone setpoint files to override overall setpoint file
         std::ostringstream zoneSuffix;
         zoneSuffix << ".zone" << _zoneId;
         std::string zoneSetpointPath = setpointpath + zoneSuffix.str();

         fileParseRpm(zoneSetpointPath, _maximumSetPoint);
     }
     return;
 }

 void DbusPidZone::initializeLog(void)
 {
     /* Print header for log file:
      * epoch_ms,setpt,fan1,fan1_raw,fan1_pwm,fan1_pwm_raw,fan2,fan2_raw,fan2_pwm,fan2_pwm_raw,fanN,fanN_raw,fanN_pwm,fanN_pwm_raw,sensor1,sensor1_raw,sensor2,sensor2_raw,sensorN,sensorN_raw,failsafe
      */

     _log << "epoch_ms,setpt,requester";

     for (const auto& f : _fanInputs)
     {
         _log << "," << f << "," << f << "_raw";
         _log << "," << f << "_pwm," << f << "_pwm_raw";
     }
     for (const auto& t : _thermalInputs)
     {
         _log << "," << t << "," << t << "_raw";
     }

     _log << ",failsafe";
     _log << std::endl;
 }

 void DbusPidZone::writeLog(const std::string& value)
 {
     _log << value;
 }

 /*
  * TODO(venture) This is effectively updating the cache and should check if the
  * values they're using to update it are new or old, or whatnot.  For instance,
  * if we haven't heard from the host in X time we need to detect this failure.
  *
  * I haven't decided if the Sensor should have a lastUpdated method or whether
  * that should be for the ReadInterface or etc...
  */

 /**
  * We want the PID loop to run with values cached, so this will get all the
  * fan tachs for the loop.
  */
 void DbusPidZone::updateFanTelemetry(void)
 {
     /* TODO(venture): Should I just make _log point to /dev/null when logging
      * is disabled?  I think it's a waste to try and log things even if the
      * data is just being dropped though.
      */
     tstamp now = std::chrono::high_resolution_clock::now();
     if (loggingEnabled)
     {
         _log << std::chrono::duration_cast<std::chrono::milliseconds>(
                     now.time_since_epoch())
                     .count();
         _log << "," << _maximumSetPoint;
         _log << "," << _maximumSetPointName;
     }

     for (const auto& f : _fanInputs)
     {
         auto sensor = _mgr.getSensor(f);
         ReadReturn r = sensor->read();
         _cachedValuesByName[f] = {r.value, r.unscaled};
         int64_t timeout = sensor->getTimeout();
         tstamp then = r.updated;

         auto duration =
             std::chrono::duration_cast<std::chrono::seconds>(now - then)
                 .count();
         auto period = std::chrono::seconds(timeout).count();
         /*
          * TODO(venture): We should check when these were last read.
          * However, these are the fans, so if I'm not getting updated values
          * for them... what should I do?
          */
         if (loggingEnabled)
         {
             const auto& v = _cachedValuesByName[f];
             _log << "," << v.scaled << "," << v.unscaled;
             const auto& p = _cachedFanOutputs[f];
             _log << "," << p.scaled << "," << p.unscaled;
         }

         if (debugEnabled)
         {
             std::cerr << f << " fan sensor reading: " << r.value << "\n";
         }

         // check if fan fail.
         if (sensor->getFailed())
         {
             _failSafeSensors.insert(f);
             if (debugEnabled)
             {
                 std::cerr << f << " fan sensor get failed\n";
             }
         }
         else if (timeout != 0 && duration >= period)
         {
             _failSafeSensors.insert(f);
             if (debugEnabled)
             {
                 std::cerr << f << " fan sensor timeout\n";
             }
         }
         else
         {
             // Check if it's in there: remove it.
             auto kt = _failSafeSensors.find(f);
             if (kt != _failSafeSensors.end())
             {
                 if (debugEnabled)
                 {
                     std::cerr << f << " is erased from failsafe sensor set\n";
                 }
                 _failSafeSensors.erase(kt);
             }
         }
     }

     if (loggingEnabled)
     {
         for (const auto& t : _thermalInputs)
         {
             const auto& v = _cachedValuesByName[t];
             _log << "," << v.scaled << "," << v.unscaled;
         }
     }

     return;
 }

 void DbusPidZone::updateSensors(void)
 {
     using namespace std::chrono;
     /* margin and temp are stored as temp */
     tstamp now = high_resolution_clock::now();

     for (const auto& t : _thermalInputs)
     {
         auto sensor = _mgr.getSensor(t);
         ReadReturn r = sensor->read();
         int64_t timeout = sensor->getTimeout();

         _cachedValuesByName[t] = {r.value, r.unscaled};
         tstamp then = r.updated;

         auto duration = duration_cast<std::chrono::seconds>(now - then).count();
         auto period = std::chrono::seconds(timeout).count();

         if (debugEnabled)
         {
             std::cerr << t << " temperature sensor reading: " << r.value
                       << "\n";
         }

         if (sensor->getFailed())
         {
             _failSafeSensors.insert(t);
             if (debugEnabled)
             {
                 std::cerr << t << " temperature sensor get failed\n";
             }
         }
         else if (timeout != 0 && duration >= period)
         {
             // std::cerr << "Entering fail safe mode.\n";
             _failSafeSensors.insert(t);
             if (debugEnabled)
             {
                 std::cerr << t << " temperature sensor get timeout\n";
             }
         }
         else
         {
             // Check if it's in there: remove it.
             auto kt = _failSafeSensors.find(t);
             if (kt != _failSafeSensors.end())
             {
                 if (debugEnabled)
                 {
                     std::cerr << t << " is erased from failsafe sensor set\n";
                 }
                 _failSafeSensors.erase(kt);
             }
         }
     }

     return;
 }

 void DbusPidZone::initializeCache(void)
 {
     auto nan = std::numeric_limits<double>::quiet_NaN();

     for (const auto& f : _fanInputs)
     {
         _cachedValuesByName[f] = {nan, nan};
         _cachedFanOutputs[f] = {nan, nan};

         // Start all fans in fail-safe mode.
         _failSafeSensors.insert(f);
     }

     for (const auto& t : _thermalInputs)
     {
         _cachedValuesByName[t] = {nan, nan};

         // Start all sensors in fail-safe mode.
         _failSafeSensors.insert(t);
     }
 }

 void DbusPidZone::dumpCache(void)
 {
     std::cerr << "Cache values now: \n";
     for (const auto& [name, value] : _cachedValuesByName)
     {
         std::cerr << name << ": " << value.scaled << " " << value.unscaled
                   << "\n";
     }

     std::cerr << "Fan outputs now: \n";
     for (const auto& [name, value] : _cachedFanOutputs)
     {
         std::cerr << name << ": " << value.scaled << " " << value.unscaled
                   << "\n";
     }
 }

 void DbusPidZone::processFans(void)
 {
     for (auto& p : _fans)
     {
         p->process();
     }

     if (_redundantWrite)
     {
         // This is only needed once
         _redundantWrite = false;
     }
 }

 void DbusPidZone::processThermals(void)
 {
     for (auto& p : _thermals)
     {
         p->process();
     }
 }

 Sensor* DbusPidZone::getSensor(const std::string& name)
 {
     return _mgr.getSensor(name);
 }

 bool DbusPidZone::getRedundantWrite(void) const
 {
     return _redundantWrite;
 }

 bool DbusPidZone::manual(bool value)
 {
     std::cerr << "manual: " << value << std::endl;
     setManualMode(value);
     return ModeObject::manual(value);
 }

 bool DbusPidZone::failSafe() const
 {
     return getFailSafeMode();
 }

 } // namespace pid_control
	/**
	* Copyright 2017 Google Inc.
	*
	* Licensed 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.
	*/

	/* Configuration. */
	#include "zone.hpp"

	#include "conf.hpp"
	#include "pid/controller.hpp"
	#include "pid/ec/pid.hpp"
	#include "pid/fancontroller.hpp"
	#include "pid/stepwisecontroller.hpp"
	#include "pid/thermalcontroller.hpp"
	#include "pid/tuning.hpp"

	#include <algorithm>
	#include <chrono>
	#include <cstring>
	#include <fstream>
	#include <iostream>
	#include <memory>
	#include <sstream>
	#include <string>

	using tstamp = std::chrono::high_resolution_clock::time_point;
	using namespace std::literals::chrono_literals;

	// Enforces minimum duration between events
	// Rreturns true if event should be allowed, false if disallowed
	bool allowThrottle(const tstamp& now, const std::chrono::seconds& pace)
	{
	static tstamp then;
	static bool first = true;

	if (first)
	{
	// Special case initialization
	then = now;
	first = false;

	// Initialization, always allow
	return true;
	}

	auto elapsed = now - then;
	if (elapsed < pace)
	{
	// Too soon since last time, disallow
	return false;
	}

	// It has been long enough, allow
	then = now;
	return true;
	}

	namespace pid_control
	{

	double DbusPidZone::getMaxSetPointRequest(void) const
	{
	return _maximumSetPoint;
	}

	bool DbusPidZone::getManualMode(void) const
	{
	return _manualMode;
	}

	void DbusPidZone::setManualMode(bool mode)
	{
	_manualMode = mode;

	// If returning to automatic mode, need to restore PWM from PID loop
	if (!mode)
	{
	_redundantWrite = true;
	}
	}

	bool DbusPidZone::getFailSafeMode(void) const
	{
	// If any keys are present at least one sensor is in fail safe mode.
	return !_failSafeSensors.empty();
	}

	int64_t DbusPidZone::getZoneID(void) const
	{
	return _zoneId;
	}

	void DbusPidZone::addSetPoint(double setPoint, const std::string& name)
	{
	_SetPoints.push_back(setPoint);
	/*
	* if there are multiple thermal controllers with the same
	* value, pick the first one in the iterator
	*/
	if (_maximumSetPoint < setPoint)
	{
	_maximumSetPoint = setPoint;
	_maximumSetPointName = name;
	}
	}

	void DbusPidZone::addRPMCeiling(double ceiling)
	{
	_RPMCeilings.push_back(ceiling);
	}

	void DbusPidZone::clearRPMCeilings(void)
	{
	_RPMCeilings.clear();
	}

	void DbusPidZone::clearSetPoints(void)
	{
	_SetPoints.clear();
	_maximumSetPoint = 0;
	}

	double DbusPidZone::getFailSafePercent(void) const
	{
	return _failSafePercent;
	}

	double DbusPidZone::getMinThermalSetPoint(void) const
	{
	return _minThermalOutputSetPt;
	}

	uint64_t DbusPidZone::getCycleIntervalTime(void) const
	{
	return _cycleTime.cycleIntervalTimeMS;
	}

	uint64_t DbusPidZone::getUpdateThermalsCycle(void) const
	{
	return _cycleTime.updateThermalsTimeMS;
	}

	void DbusPidZone::addFanPID(std::unique_ptr<Controller> pid)
	{
	_fans.push_back(std::move(pid));
	}

	void DbusPidZone::addThermalPID(std::unique_ptr<Controller> pid)
	{
	_thermals.push_back(std::move(pid));
	}

	double DbusPidZone::getCachedValue(const std::string& name)
	{
	return _cachedValuesByName.at(name).scaled;
	}

	ValueCacheEntry DbusPidZone::getCachedValues(const std::string& name)
	{
	return _cachedValuesByName.at(name);
	}

	void DbusPidZone::setOutputCache(std::string_view name,
	const ValueCacheEntry& values)
	{
	_cachedFanOutputs[std::string{name}] = values;
	}

	void DbusPidZone::addFanInput(const std::string& fan)
	{
	_fanInputs.push_back(fan);
	}

	void DbusPidZone::addThermalInput(const std::string& therm)
	{
	_thermalInputs.push_back(therm);
	}

	// Updates desired RPM setpoint from optional text file
	// Returns true if rpmValue updated, false if left unchanged
	static bool fileParseRpm(const std::string& fileName, double& rpmValue)
	{
	static constexpr std::chrono::seconds throttlePace{3};

	std::string errText;

	try
	{
	std::ifstream ifs;
	ifs.open(fileName);
	if (ifs)
	{
	int value;
	ifs >> value;

	if (value <= 0)
	{
	errText = "File content could not be parsed to a number";
	}
	else if (value <= 100)
	{
	errText = "File must contain RPM value, not PWM value";
	}
	else
	{
	rpmValue = static_cast<double>(value);
	return true;
	}
	}
	}
	catch (const std::exception& e)
	{
	errText = "Exception: ";
	errText += e.what();
	}

	// The file is optional, intentionally not an error if file not found
	if (!(errText.empty()))
	{
	tstamp now = std::chrono::high_resolution_clock::now();
	if (allowThrottle(now, throttlePace))
	{
	std::cerr << "Unable to read from '" << fileName << "': " << errText
	<< "\n";
	}
	}

	return false;
	}

	void DbusPidZone::determineMaxSetPointRequest(void)
	{
	std::vector<double>::iterator result;
	double minThermalThreshold = getMinThermalSetPoint();

	if (_RPMCeilings.size() > 0)
	{
	result = std::min_element(_RPMCeilings.begin(), _RPMCeilings.end());
	// if Max set point is larger than the lowest ceiling, reset to lowest
	// ceiling.
	if (*result < _maximumSetPoint)
	{
	_maximumSetPoint = *result;
	// When using lowest ceiling, controller name is ceiling.
	_maximumSetPointName = "Ceiling";
	}
	}

	/*
	* If the maximum RPM setpoint output is below the minimum RPM
	* setpoint, set it to the minimum.
	*/
	if (minThermalThreshold >= _maximumSetPoint)
	{
	_maximumSetPoint = minThermalThreshold;
	_maximumSetPointName = "";
	}
	else if (_maximumSetPointName.compare(_maximumSetPointNamePrev))
	{
	std::cerr << "PID Zone " << _zoneId << " max SetPoint "
	<< _maximumSetPoint << " requested by "
	<< _maximumSetPointName;
	for (const auto& sensor : _failSafeSensors)
	{
	if (sensor.find("Fan") == std::string::npos)
	{
	std::cerr << " " << sensor;
	}
	}
	std::cerr << "\n";
	_maximumSetPointNamePrev.assign(_maximumSetPointName);
	}
	if (tuningEnabled)
	{
	/*
	* We received no setpoints from thermal sensors.
	* This is a case experienced during tuning where they only specify
	* fan sensors and one large fan PID for all the fans.
	*/
	static constexpr auto setpointpath = "/etc/thermal.d/setpoint";

	fileParseRpm(setpointpath, _maximumSetPoint);

	// Allow per-zone setpoint files to override overall setpoint file
	std::ostringstream zoneSuffix;
	zoneSuffix << ".zone" << _zoneId;
	std::string zoneSetpointPath = setpointpath + zoneSuffix.str();

	fileParseRpm(zoneSetpointPath, _maximumSetPoint);
	}
	return;
	}

	void DbusPidZone::initializeLog(void)
	{
	/* Print header for log file:
	* epoch_ms,setpt,fan1,fan1_raw,fan1_pwm,fan1_pwm_raw,fan2,fan2_raw,fan2_pwm,fan2_pwm_raw,fanN,fanN_raw,fanN_pwm,fanN_pwm_raw,sensor1,sensor1_raw,sensor2,sensor2_raw,sensorN,sensorN_raw,failsafe
	*/

	_log << "epoch_ms,setpt,requester";

	for (const auto& f : _fanInputs)
	{
	_log << "," << f << "," << f << "_raw";
	_log << "," << f << "_pwm," << f << "_pwm_raw";
	}
	for (const auto& t : _thermalInputs)
	{
	_log << "," << t << "," << t << "_raw";
	}

	_log << ",failsafe";
	_log << std::endl;
	}

	void DbusPidZone::writeLog(const std::string& value)
	{
	_log << value;
	}

	/*
	* TODO(venture) This is effectively updating the cache and should check if the
	* values they're using to update it are new or old, or whatnot. For instance,
	* if we haven't heard from the host in X time we need to detect this failure.
	*
	* I haven't decided if the Sensor should have a lastUpdated method or whether
	* that should be for the ReadInterface or etc...
	*/

	/**
	* We want the PID loop to run with values cached, so this will get all the
	* fan tachs for the loop.
	*/
	void DbusPidZone::updateFanTelemetry(void)
	{
	/* TODO(venture): Should I just make _log point to /dev/null when logging
	* is disabled? I think it's a waste to try and log things even if the
	* data is just being dropped though.
	*/
	tstamp now = std::chrono::high_resolution_clock::now();
	if (loggingEnabled)
	{
	_log << std::chrono::duration_cast<std::chrono::milliseconds>(
	now.time_since_epoch())
	.count();
	_log << "," << _maximumSetPoint;
	_log << "," << _maximumSetPointName;
	}

	for (const auto& f : _fanInputs)
	{
	auto sensor = _mgr.getSensor(f);
	ReadReturn r = sensor->read();
	_cachedValuesByName[f] = {r.value, r.unscaled};
	int64_t timeout = sensor->getTimeout();
	tstamp then = r.updated;

	auto duration =
	std::chrono::duration_cast<std::chrono::seconds>(now - then)
	.count();
	auto period = std::chrono::seconds(timeout).count();
	/*
	* TODO(venture): We should check when these were last read.
	* However, these are the fans, so if I'm not getting updated values
	* for them... what should I do?
	*/
	if (loggingEnabled)
	{
	const auto& v = _cachedValuesByName[f];
	_log << "," << v.scaled << "," << v.unscaled;
	const auto& p = _cachedFanOutputs[f];
	_log << "," << p.scaled << "," << p.unscaled;
	}

	if (debugEnabled)
	{
	std::cerr << f << " fan sensor reading: " << r.value << "\n";
	}

	// check if fan fail.
	if (sensor->getFailed())
	{
	_failSafeSensors.insert(f);
	if (debugEnabled)
	{
	std::cerr << f << " fan sensor get failed\n";
	}
	}
	else if (timeout != 0 && duration >= period)
	{
	_failSafeSensors.insert(f);
	if (debugEnabled)
	{
	std::cerr << f << " fan sensor timeout\n";
	}
	}
	else
	{
	// Check if it's in there: remove it.
	auto kt = _failSafeSensors.find(f);
	if (kt != _failSafeSensors.end())
	{
	if (debugEnabled)
	{
	std::cerr << f << " is erased from failsafe sensor set\n";
	}
	_failSafeSensors.erase(kt);
	}
	}
	}

	if (loggingEnabled)
	{
	for (const auto& t : _thermalInputs)
	{
	const auto& v = _cachedValuesByName[t];
	_log << "," << v.scaled << "," << v.unscaled;
	}
	}

	return;
	}

	void DbusPidZone::updateSensors(void)
	{
	using namespace std::chrono;
	/* margin and temp are stored as temp */
	tstamp now = high_resolution_clock::now();

	for (const auto& t : _thermalInputs)
	{
	auto sensor = _mgr.getSensor(t);
	ReadReturn r = sensor->read();
	int64_t timeout = sensor->getTimeout();

	_cachedValuesByName[t] = {r.value, r.unscaled};
	tstamp then = r.updated;

	auto duration = duration_cast<std::chrono::seconds>(now - then).count();
	auto period = std::chrono::seconds(timeout).count();

	if (debugEnabled)
	{
	std::cerr << t << " temperature sensor reading: " << r.value
	<< "\n";
	}

	if (sensor->getFailed())
	{
	_failSafeSensors.insert(t);
	if (debugEnabled)
	{
	std::cerr << t << " temperature sensor get failed\n";
	}
	}
	else if (timeout != 0 && duration >= period)
	{
	// std::cerr << "Entering fail safe mode.\n";
	_failSafeSensors.insert(t);
	if (debugEnabled)
	{
	std::cerr << t << " temperature sensor get timeout\n";
	}
	}
	else
	{
	// Check if it's in there: remove it.
	auto kt = _failSafeSensors.find(t);
	if (kt != _failSafeSensors.end())
	{
	if (debugEnabled)
	{
	std::cerr << t << " is erased from failsafe sensor set\n";
	}
	_failSafeSensors.erase(kt);
	}
	}
	}

	return;
	}

	void DbusPidZone::initializeCache(void)
	{
	auto nan = std::numeric_limits<double>::quiet_NaN();

	for (const auto& f : _fanInputs)
	{
	_cachedValuesByName[f] = {nan, nan};
	_cachedFanOutputs[f] = {nan, nan};

	// Start all fans in fail-safe mode.
	_failSafeSensors.insert(f);
	}

	for (const auto& t : _thermalInputs)
	{
	_cachedValuesByName[t] = {nan, nan};

	// Start all sensors in fail-safe mode.
	_failSafeSensors.insert(t);
	}
	}

	void DbusPidZone::dumpCache(void)
	{
	std::cerr << "Cache values now: \n";
	for (const auto& [name, value] : _cachedValuesByName)
	{
	std::cerr << name << ": " << value.scaled << " " << value.unscaled
	<< "\n";
	}

	std::cerr << "Fan outputs now: \n";
	for (const auto& [name, value] : _cachedFanOutputs)
	{
	std::cerr << name << ": " << value.scaled << " " << value.unscaled
	<< "\n";
	}
	}

	void DbusPidZone::processFans(void)
	{
	for (auto& p : _fans)
	{
	p->process();
	}

	if (_redundantWrite)
	{
	// This is only needed once
	_redundantWrite = false;
	}
	}

	void DbusPidZone::processThermals(void)
	{
	for (auto& p : _thermals)
	{
	p->process();
	}
	}

	Sensor* DbusPidZone::getSensor(const std::string& name)
	{
	return _mgr.getSensor(name);
	}

	bool DbusPidZone::getRedundantWrite(void) const
	{
	return _redundantWrite;
	}

	bool DbusPidZone::manual(bool value)
	{
	std::cerr << "manual: " << value << std::endl;
	setManualMode(value);
	return ModeObject::manual(value);
	}

	bool DbusPidZone::failSafe() const
	{
	return getFailSafeMode();
	}

	} // namespace pid_control