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/*
* 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__