src/sim/clocked_object.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2012-2013, 2015-2017, 2019-2020 ARM Limited
  * Copyright (c) 2013 Cornell University
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * 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
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Redistribution and use in source and binary forms, with or without
  * 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
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders 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.
  */

 /**
  * @file
  * ClockedObject declaration and implementation.
  */

 #ifndef __SIM_CLOCKED_OBJECT_HH__
 #define __SIM_CLOCKED_OBJECT_HH__


 #include "params/ClockedObject.hh"
 #include "sim/core.hh"
 #include "sim/clock_domain.hh"
 #include "sim/power_state.hh"
 #include "sim/sim_object.hh"

 namespace gem5
 {

 /**
  * Helper class for objects that need to be clocked. Clocked objects
  * typically inherit from this class. Objects that need SimObject
  * functionality as well should inherit from ClockedObject.
  */
 class Clocked
 {

   private:
     // the tick value of the next clock edge (>= curTick()) at the
     // time of the last call to update()
     mutable Tick tick;

     // The cycle counter value corresponding to the current value of
     // 'tick'
     mutable Cycles cycle;

     /**
      *  Align cycle and tick to the next clock edge if not already done. When
      *  complete, tick must be at least curTick().
      */
     void
     update() const
     {
         // both tick and cycle are up-to-date and we are done, note
         // that the >= is important as it captures cases where tick
         // has already passed curTick()
         if (tick >= curTick())
             return;

         // optimise for the common case and see if the tick should be
         // advanced by a single clock period
         tick += clockPeriod();
         ++cycle;

         // see if we are done at this point
         if (tick >= curTick())
             return;

         // if not, we have to recalculate the cycle and tick, we
         // perform the calculations in terms of relative cycles to
         // allow changes to the clock period in the future
         Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
         cycle += elapsedCycles;
         tick += elapsedCycles * clockPeriod();
     }

     /**
      * The clock domain this clocked object belongs to
      */
     ClockDomain &clockDomain;

   protected:

     /**
      * Create a clocked object and set the clock domain based on the
      * parameters.
      */
     Clocked(ClockDomain &clk_domain)
         : tick(0), cycle(0), clockDomain(clk_domain)
     {
         // Register with the clock domain, so that if the clock domain
         // frequency changes, we can update this object's tick.
         clockDomain.registerWithClockDomain(this);
     }

     Clocked(Clocked &) = delete;
     Clocked &operator=(Clocked &) = delete;

     /**
      * Virtual destructor due to inheritance.
      */
     virtual ~Clocked() { }

     /**
      * Reset the object's clock using the current global tick value. Likely
      * to be used only when the global clock is reset. Currently, this done
      * only when Ruby is done warming up the memory system.
      */
     void
     resetClock() const
     {
         Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
         cycle = elapsedCycles;
         tick = elapsedCycles * clockPeriod();
     }

     /**
      * A hook subclasses can implement so they can do any extra work that's
      * needed when the clock rate is changed.
      */
     virtual void clockPeriodUpdated() {}

   public:

     /**
      * Update the tick to the current tick.
      */
     void
     updateClockPeriod()
     {
         update();
         clockPeriodUpdated();
     }

     /**
      * Determine the tick when a cycle begins, by default the current one, but
      * the argument also enables the caller to determine a future cycle. When
      * curTick() is on a clock edge, the number of cycles in the parameter is
      * added to curTick() to be returned. When curTick() is not aligned to a
      * clock edge, the number of cycles in the parameter is added to the next
      * clock edge.
      *
      * @param cycles The number of cycles into the future
      *
      * @return The start tick when the requested clock edge occurs. Precisely,
      * this tick can be
      *     curTick() + [0, clockPeriod()) + clockPeriod() * cycles
      */
     Tick
     clockEdge(Cycles cycles=Cycles(0)) const
     {
         // align tick to the next clock edge
         update();

         // figure out when this future cycle is
         return tick + clockPeriod() * cycles;
     }

     /**
      * Determine the current cycle, corresponding to a tick aligned to
      * a clock edge.
      *
      * @return When curTick() is on a clock edge, return the Cycle corresponding
      * to that clock edge. When curTick() is not on a clock edge, return the
      * Cycle corresponding to the next clock edge.
      */
     Cycles
     curCycle() const
     {
         // align cycle to the next clock edge.
         update();

         return cycle;
     }

     /**
      * Based on the clock of the object, determine the start tick of the first
      * cycle that is at least one cycle in the future. When curTick() is at the
      * current cycle edge, this returns the next clock edge. When calling this
      * during the middle of a cycle, this returns 2 clock edges in the future.
      *
      * @return The start tick of the first cycle that is at least one cycle in
      * the future. Precisely, the returned tick can be in the range
      *     curTick() + [clockPeriod(), 2 * clockPeriod())
      */
     Tick nextCycle() const { return clockEdge(Cycles(1)); }

     uint64_t frequency() const { return sim_clock::Frequency / clockPeriod(); }

     Tick clockPeriod() const { return clockDomain.clockPeriod(); }

     double voltage() const { return clockDomain.voltage(); }

     Cycles
     ticksToCycles(Tick t) const
     {
         return Cycles(divCeil(t, clockPeriod()));
     }

     Tick cyclesToTicks(Cycles c) const { return clockPeriod() * c; }
 };

 /**
  * The ClockedObject class extends the SimObject with a clock and
  * accessor functions to relate ticks to the cycles of the object.
  */
 class ClockedObject : public SimObject, public Clocked
 {
   public:
     ClockedObject(const ClockedObjectParams &p);

     /** Parameters of ClockedObject */
     using Params = ClockedObjectParams;

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

     PowerState *powerState;
 };

 } // namespace gem5

 #endif //__SIM_CLOCKED_OBJECT_HH__
	/*
	* Copyright (c) 2012-2013, 2015-2017, 2019-2020 ARM Limited
	* Copyright (c) 2013 Cornell University
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* 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
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Redistribution and use in source and binary forms, with or without
	* 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
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders 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.
	*/

	/**
	* @file
	* ClockedObject declaration and implementation.
	*/

	#ifndef __SIM_CLOCKED_OBJECT_HH__
	#define __SIM_CLOCKED_OBJECT_HH__


	#include "params/ClockedObject.hh"
	#include "sim/core.hh"
	#include "sim/clock_domain.hh"
	#include "sim/power_state.hh"
	#include "sim/sim_object.hh"

	namespace gem5
	{

	/**
	* Helper class for objects that need to be clocked. Clocked objects
	* typically inherit from this class. Objects that need SimObject
	* functionality as well should inherit from ClockedObject.
	*/
	class Clocked
	{

	private:
	// the tick value of the next clock edge (>= curTick()) at the
	// time of the last call to update()
	mutable Tick tick;

	// The cycle counter value corresponding to the current value of
	// 'tick'
	mutable Cycles cycle;

	/**
	* Align cycle and tick to the next clock edge if not already done. When
	* complete, tick must be at least curTick().
	*/
	void
	update() const
	{
	// both tick and cycle are up-to-date and we are done, note
	// that the >= is important as it captures cases where tick
	// has already passed curTick()
	if (tick >= curTick())
	return;

	// optimise for the common case and see if the tick should be
	// advanced by a single clock period
	tick += clockPeriod();
	++cycle;

	// see if we are done at this point
	if (tick >= curTick())
	return;

	// if not, we have to recalculate the cycle and tick, we
	// perform the calculations in terms of relative cycles to
	// allow changes to the clock period in the future
	Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
	cycle += elapsedCycles;
	tick += elapsedCycles * clockPeriod();
	}

	/**
	* The clock domain this clocked object belongs to
	*/
	ClockDomain &clockDomain;

	protected:

	/**
	* Create a clocked object and set the clock domain based on the
	* parameters.
	*/
	Clocked(ClockDomain &clk_domain)
	: tick(0), cycle(0), clockDomain(clk_domain)
	{
	// Register with the clock domain, so that if the clock domain
	// frequency changes, we can update this object's tick.
	clockDomain.registerWithClockDomain(this);
	}

	Clocked(Clocked &) = delete;
	Clocked &operator=(Clocked &) = delete;

	/**
	* Virtual destructor due to inheritance.
	*/
	virtual ~Clocked() { }

	/**
	* Reset the object's clock using the current global tick value. Likely
	* to be used only when the global clock is reset. Currently, this done
	* only when Ruby is done warming up the memory system.
	*/
	void
	resetClock() const
	{
	Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
	cycle = elapsedCycles;
	tick = elapsedCycles * clockPeriod();
	}

	/**
	* A hook subclasses can implement so they can do any extra work that's
	* needed when the clock rate is changed.
	*/
	virtual void clockPeriodUpdated() {}

	public:

	/**
	* Update the tick to the current tick.
	*/
	void
	updateClockPeriod()
	{
	update();
	clockPeriodUpdated();
	}

	/**
	* Determine the tick when a cycle begins, by default the current one, but
	* the argument also enables the caller to determine a future cycle. When
	* curTick() is on a clock edge, the number of cycles in the parameter is
	* added to curTick() to be returned. When curTick() is not aligned to a
	* clock edge, the number of cycles in the parameter is added to the next
	* clock edge.
	*
	* @param cycles The number of cycles into the future
	*
	* @return The start tick when the requested clock edge occurs. Precisely,
	* this tick can be
	* curTick() + [0, clockPeriod()) + clockPeriod() * cycles
	*/
	Tick
	clockEdge(Cycles cycles=Cycles(0)) const
	{
	// align tick to the next clock edge
	update();

	// figure out when this future cycle is
	return tick + clockPeriod() * cycles;
	}

	/**
	* Determine the current cycle, corresponding to a tick aligned to
	* a clock edge.
	*
	* @return When curTick() is on a clock edge, return the Cycle corresponding
	* to that clock edge. When curTick() is not on a clock edge, return the
	* Cycle corresponding to the next clock edge.
	*/
	Cycles
	curCycle() const
	{
	// align cycle to the next clock edge.
	update();

	return cycle;
	}

	/**
	* Based on the clock of the object, determine the start tick of the first
	* cycle that is at least one cycle in the future. When curTick() is at the
	* current cycle edge, this returns the next clock edge. When calling this
	* during the middle of a cycle, this returns 2 clock edges in the future.
	*
	* @return The start tick of the first cycle that is at least one cycle in
	* the future. Precisely, the returned tick can be in the range
	* curTick() + [clockPeriod(), 2 * clockPeriod())
	*/
	Tick nextCycle() const { return clockEdge(Cycles(1)); }

	uint64_t frequency() const { return sim_clock::Frequency / clockPeriod(); }

	Tick clockPeriod() const { return clockDomain.clockPeriod(); }

	double voltage() const { return clockDomain.voltage(); }

	Cycles
	ticksToCycles(Tick t) const
	{
	return Cycles(divCeil(t, clockPeriod()));
	}

	Tick cyclesToTicks(Cycles c) const { return clockPeriod() * c; }
	};

	/**
	* The ClockedObject class extends the SimObject with a clock and
	* accessor functions to relate ticks to the cycles of the object.
	*/
	class ClockedObject : public SimObject, public Clocked
	{
	public:
	ClockedObject(const ClockedObjectParams &p);

	/** Parameters of ClockedObject */
	using Params = ClockedObjectParams;

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

	PowerState *powerState;
	};

	} // namespace gem5

	#endif //__SIM_CLOCKED_OBJECT_HH__