OutputUnit.cc

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/*
 * Copyright (c) 2020 Inria
 * Copyright (c) 2016 Georgia Institute of Technology
 * Copyright (c) 2008 Princeton University
 * All rights reserved.
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#include "mem/ruby/network/garnet2.0/OutputUnit.hh"

#include "debug/RubyNetwork.hh"
#include "mem/ruby/network/garnet2.0/Credit.hh"
#include "mem/ruby/network/garnet2.0/CreditLink.hh"
#include "mem/ruby/network/garnet2.0/Router.hh"
#include "mem/ruby/network/garnet2.0/flitBuffer.hh"

OutputUnit::OutputUnit(int id, PortDirection direction, Router *router)
  : Consumer(router), m_router(router), m_id(id), m_direction(direction),
    m_vc_per_vnet(m_router->get_vc_per_vnet())
{
    const int m_num_vcs = m_router->get_num_vcs();
    outVcState.reserve(m_num_vcs);
    for (int i = 0; i < m_num_vcs; i++) {
        outVcState.emplace_back(i, m_router->get_net_ptr());
    }
}

void
OutputUnit::decrement_credit(int out_vc)
{
    DPRINTF(RubyNetwork, "Router %d OutputUnit %d decrementing credit for "
            "outvc %d at time: %lld\n",
            m_router->get_id(), m_id, out_vc, m_router->curCycle());

    outVcState[out_vc].decrement_credit();
}

void
OutputUnit::increment_credit(int out_vc)
{
    DPRINTF(RubyNetwork, "Router %d OutputUnit %d incrementing credit for "
            "outvc %d at time: %lld\n",
            m_router->get_id(), m_id, out_vc, m_router->curCycle());

    outVcState[out_vc].increment_credit();
}

// Check if the output VC (i.e., input VC at next router)
// has free credits (i..e, buffer slots).
// This is tracked by OutVcState
bool
OutputUnit::has_credit(int out_vc)
{
    assert(outVcState[out_vc].isInState(ACTIVE_, m_router->curCycle()));
    return outVcState[out_vc].has_credit();
}


// Check if the output port (i.e., input port at next router) has free VCs.
bool
OutputUnit::has_free_vc(int vnet)
{
    int vc_base = vnet*m_vc_per_vnet;
    for (int vc = vc_base; vc < vc_base + m_vc_per_vnet; vc++) {
        if (is_vc_idle(vc, m_router->curCycle()))
            return true;
    }

    return false;
}

// Assign a free output VC to the winner of Switch Allocation
int
OutputUnit::select_free_vc(int vnet)
{
    int vc_base = vnet*m_vc_per_vnet;
    for (int vc = vc_base; vc < vc_base + m_vc_per_vnet; vc++) {
        if (is_vc_idle(vc, m_router->curCycle())) {
            outVcState[vc].setState(ACTIVE_, m_router->curCycle());
            return vc;
        }
    }

    return -1;
}

/*
 * The wakeup function of the OutputUnit reads the credit signal from the
 * downstream router for the output VC (i.e., input VC at downstream router).
 * It increments the credit count in the appropriate output VC state.
 * If the credit carries is_free_signal as true,
 * the output VC is marked IDLE.
 */

void
OutputUnit::wakeup()
{
    if (m_credit_link->isReady(m_router->curCycle())) {
        Credit *t_credit = (Credit*) m_credit_link->consumeLink();
        increment_credit(t_credit->get_vc());

        if (t_credit->is_free_signal())
            set_vc_state(IDLE_, t_credit->get_vc(), m_router->curCycle());

        delete t_credit;
    }
}

flitBuffer*
OutputUnit::getOutQueue()
{
    return &outBuffer;
}

void
OutputUnit::set_out_link(NetworkLink *link)
{
    m_out_link = link;
}

void
OutputUnit::set_credit_link(CreditLink *credit_link)
{
    m_credit_link = credit_link;
}

void
OutputUnit::insert_flit(flit *t_flit)
{
    outBuffer.insert(t_flit);
    m_out_link->scheduleEventAbsolute(m_router->clockEdge(Cycles(1)));
}

uint32_t
OutputUnit::functionalWrite(Packet *pkt)
{
    return outBuffer.functionalWrite(pkt);
}