src/sim/clock_domain.cc

/*
 * Copyright (c) 2013-2014, 2019 ARM Limited
 * Copyright (c) 2013 Cornell University
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#include "sim/clock_domain.hh"

#include <algorithm>
#include <functional>

#include "base/logging.hh"
#include "base/trace.hh"
#include "debug/ClockDomain.hh"
#include "params/ClockDomain.hh"
#include "params/DerivedClockDomain.hh"
#include "params/SrcClockDomain.hh"
#include "sim/clocked_object.hh"
#include "sim/serialize.hh"
#include "sim/voltage_domain.hh"

namespace gem5
{

ClockDomain::ClockDomainStats::ClockDomainStats(ClockDomain &cd)
    : statistics::Group(&cd),
    ADD_STAT(clock, statistics::units::Tick::get(), "Clock period in ticks")
{
    // Expose the current clock period as a stat for observability in
    // the dumps
    clock.scalar(cd._clockPeriod);
}

ClockDomain::ClockDomain(const Params &p, VoltageDomain *voltage_domain)
    : SimObject(p),
      _clockPeriod(0),
      _voltageDomain(voltage_domain),
      stats(*this)
{
}

double
ClockDomain::voltage() const
{
    return _voltageDomain->voltage();
}

SrcClockDomain::SrcClockDomain(const Params &p) :
    ClockDomain(p, p.voltage_domain),
    freqOpPoints(p.clock),
    _domainID(p.domain_id),
    _perfLevel(p.init_perf_level)
{
    VoltageDomain *vdom = p.voltage_domain;

    fatal_if(freqOpPoints.empty(), "DVFS: Empty set of frequencies for "\
             "domain %d %s\n", _domainID, name());

    fatal_if(!vdom, "DVFS: Empty voltage domain specified for "\
             "domain %d %s\n", _domainID, name());

    fatal_if((vdom->numVoltages() > 1) &&
             (vdom->numVoltages() != freqOpPoints.size()),
             "DVFS: Number of frequency and voltage scaling points do "\
             "not match: %d:%d ID: %d %s.\n", vdom->numVoltages(),
             freqOpPoints.size(), _domainID, name());

    // Frequency (& voltage) points should be declared in descending order,
    // NOTE: Frequency is inverted to ticks, so checking for ascending ticks
    fatal_if(!std::is_sorted(freqOpPoints.begin(), freqOpPoints.end()),
             "DVFS: Frequency operation points not in descending order for "\
             "domain with ID %d\n", _domainID);

    fatal_if(_perfLevel >= freqOpPoints.size(), "DVFS: Initial DVFS point %d "\
             "is outside of list for Domain ID: %d\n", _perfLevel, _domainID);

    clockPeriod(freqOpPoints[_perfLevel]);

    vdom->registerSrcClockDom(this);
}

void
SrcClockDomain::clockPeriod(Tick clock_period)
{
    if (clock_period == 0) {
        fatal("%s has a clock period of zero\n", name());
    }

    // Align all members to the current tick
    for (auto m = members.begin(); m != members.end(); ++m) {
        (*m)->updateClockPeriod();
    }

    _clockPeriod = clock_period;

    DPRINTF(ClockDomain,
            "Setting clock period to %d ticks for source clock %s\n",
            _clockPeriod, name());

    // inform any derived clocks they need to updated their period
    for (auto c = children.begin(); c != children.end(); ++c) {
        (*c)->updateClockPeriod();
    }
}

void
SrcClockDomain::perfLevel(PerfLevel perf_level)
{
    assert(validPerfLevel(perf_level));

    if (perf_level == _perfLevel) {
        // Silently ignore identical overwrites
        return;
    }

    DPRINTF(ClockDomain, "DVFS: Switching performance level of domain %s "\
            "(id: %d) from  %d to %d\n", name(), domainID(), _perfLevel,
            perf_level);

    _perfLevel = perf_level;

    signalPerfLevelUpdate();
}

void SrcClockDomain::signalPerfLevelUpdate()
{
    // Signal the voltage domain that we have changed our perf level so that the
    // voltage domain can recompute its performance level
    voltageDomain()->sanitiseVoltages();

    // Integrated switching of the actual clock value, too
    clockPeriod(clkPeriodAtPerfLevel());
}

void
SrcClockDomain::serialize(CheckpointOut &cp) const
{
    SERIALIZE_SCALAR(_perfLevel);
    ClockDomain::serialize(cp);
}

void
SrcClockDomain::unserialize(CheckpointIn &cp)
{
    ClockDomain::unserialize(cp);
    UNSERIALIZE_SCALAR(_perfLevel);
}

void
SrcClockDomain::startup()
{
    // Perform proper clock update when all related components have been
    // created (i.e. after unserialization / object creation)
    signalPerfLevelUpdate();
}

DerivedClockDomain::DerivedClockDomain(const Params &p) :
    ClockDomain(p, p.clk_domain->voltageDomain()),
    parent(*p.clk_domain),
    clockDivider(p.clk_divider)
{
    // Ensure that clock divider setting works as frequency divider and never
    // work as frequency multiplier
    if (clockDivider < 1) {
       fatal("Clock divider param cannot be less than 1");
    }

    // let the parent keep track of this derived domain so that it can
    // propagate changes
    parent.addDerivedDomain(this);

    // update our clock period based on the parents clock
    updateClockPeriod();
}

void
DerivedClockDomain::updateClockPeriod()
{
    // Align all members to the current tick
    for (auto m = members.begin(); m != members.end(); ++m) {
        (*m)->updateClockPeriod();
    }

    // recalculate the clock period, relying on the fact that changes
    // propagate downwards in the tree
    _clockPeriod = parent.clockPeriod() * clockDivider;

    DPRINTF(ClockDomain,
            "Setting clock period to %d ticks for derived clock %s\n",
            _clockPeriod, name());

    // inform any derived clocks
    for (auto c = children.begin(); c != children.end(); ++c) {
        (*c)->updateClockPeriod();
    }
}

} // namespace gem5