gem5/src/sim/power_state.hh

/*
 * Copyright (c) 2015-2017, 2020 ARM Limited
 * All rights reserved
 *
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 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
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 * modified or unmodified, in source code or in binary form.
 *
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 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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/**
 * @file
 * PowerState declaration and implementation.
 */

#ifndef __SIM_POWER_STATE_HH__
#define __SIM_POWER_STATE_HH__

#include <set>
#include <vector>

#include "base/callback.hh"
#include "base/statistics.hh"
#include "enums/PwrState.hh"
#include "params/PowerState.hh"
#include "sim/sim_object.hh"

namespace gem5
{

class PowerDomain;

/**
 * Helper class for objects that have power states. This class provides the
 * basic functionality to change between power states.
 */
class PowerState : public SimObject
{
  public:
    PowerState(const PowerStateParams &p);

    /** Parameters of PowerState object */
    PARAMS(PowerState);

    virtual void addFollower(PowerState* pwr_obj) {};
    void setControlledDomain(PowerDomain* pwr_dom);

    void serialize(CheckpointOut &cp) const override;
    void unserialize(CheckpointIn &cp) override;

    /**
     * Change the power state of this object to the power state p
     */
    void set(enums::PwrState p);


    inline enums::PwrState get() const
    {
        return _currState;
    }

    inline std::string getName() const
    {
        return enums::PwrStateStrings[_currState];
    }

    /** Returns the percentage residency for each power state */
    std::vector<double> getWeights() const;

    /**
     * Record stats values like state residency by computing the time
     * difference from previous update. Also, updates the previous evaluation
     * tick once all stats are recorded.
     * Usually called on power state change and stats dump callback.
     */
    void computeStats();

    /**
     * Change the power state of this object to a power state equal to OR more
     * performant than p. Returns the power state the object actually went to.
     */
    enums::PwrState matchPwrState(enums::PwrState p);

    /**
     * Return the power states this object can be in
     */
    std::set<enums::PwrState> getPossibleStates() const
    {
        return possibleStates;
    }

  protected:

    /** To keep track of the current power state */
    enums::PwrState _currState;

    /** The possible power states this object can be in */
    std::set<enums::PwrState> possibleStates;

    /** Last tick the power stats were calculated */
    Tick prvEvalTick = 0;

    /**
     * The power domain that this power state leads, nullptr if it
     * doesn't lead any.
     */
    PowerDomain* controlledDomain = nullptr;

    struct PowerStateStats : public statistics::Group
    {
        PowerStateStats(PowerState &ps);

        void regStats() override;
        void preDumpStats() override;

        PowerState &powerState;

        statistics::Scalar numTransitions;
        statistics::Scalar numPwrMatchStateTransitions;
        statistics::Distribution ticksClkGated;
        /** Tracks the time spent in each of the power states */
        statistics::Vector pwrStateResidencyTicks;
    } stats;
};

} // namespace gem5

#endif //__SIM_POWER_STATE_HH__