src/mem/tport.cc

   1 /*
   2  * Copyright (c) 2006 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Ali Saidi
  29  */
  30
  31 #include "debug/Bus.hh"
  32 #include "mem/mem_object.hh"
  33 #include "mem/tport.hh"
  34
  35 using namespace std;
  36
  37 SimpleTimingPort::SimpleTimingPort(string pname, MemObject *_owner)
  38     : Port(pname, _owner), sendEvent(NULL), drainEvent(NULL),
  39       waitingOnRetry(false)
  40 {
  41     sendEvent =  new EventWrapper<SimpleTimingPort,
  42         &SimpleTimingPort::processSendEvent>(this);
  43 }
  44
  45 SimpleTimingPort::~SimpleTimingPort()
  46 {
  47     delete sendEvent;
  48 }
  49
  50 bool
  51 SimpleTimingPort::checkFunctional(PacketPtr pkt)
  52 {
  53     DeferredPacketIterator i = transmitList.begin();
  54     DeferredPacketIterator end = transmitList.end();
  55
  56     for (; i != end; ++i) {
  57         PacketPtr target = i->pkt;
  58         // If the target contains data, and it overlaps the
  59         // probed request, need to update data
  60         if (pkt->checkFunctional(target)) {
  61             return true;
  62         }
  63     }
  64
  65     return false;
  66 }
  67
  68 void
  69 SimpleTimingPort::recvFunctional(PacketPtr pkt)
  70 {
  71     if (!checkFunctional(pkt)) {
  72         // Just do an atomic access and throw away the returned latency
  73         recvAtomic(pkt);
  74     }
  75 }
  76
  77 bool
  78 SimpleTimingPort::recvTiming(PacketPtr pkt)
  79 {
  80     // If the device is only a slave, it should only be sending
  81     // responses, which should never get nacked.  There used to be
  82     // code to hanldle nacks here, but I'm pretty sure it didn't work
  83     // correctly with the drain code, so that would need to be fixed
  84     // if we ever added it back.
  85
  86     if (pkt->memInhibitAsserted()) {
  87         // snooper will supply based on copy of packet
  88         // still target's responsibility to delete packet
  89         delete pkt;
  90         return true;
  91     }
  92
  93     bool needsResponse = pkt->needsResponse();
  94     Tick latency = recvAtomic(pkt);
  95     // turn packet around to go back to requester if response expected
  96     if (needsResponse) {
  97         // recvAtomic() should already have turned packet into
  98         // atomic response
  99         assert(pkt->isResponse());
 100         schedSendTiming(pkt, curTick() + latency);
 101     } else {
 102         delete pkt;
 103     }
 104
 105     return true;
 106 }
 107
 108 void
 109 SimpleTimingPort::schedSendEvent(Tick when)
 110 {
 111     if (waitingOnRetry) {
 112         assert(!sendEvent->scheduled());
 113         return;
 114     }
 115
 116     if (!sendEvent->scheduled()) {
 117         owner->schedule(sendEvent, when);
 118     } else if (sendEvent->when() > when) {
 119         owner->reschedule(sendEvent, when);
 120     }
 121 }
 122
 123 void
 124 SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
 125 {
 126     assert(when > curTick());
 127     assert(when < curTick() + SimClock::Int::ms);
 128
 129     // Nothing is on the list: add it and schedule an event
 130     if (transmitList.empty() || when < transmitList.front().tick) {
 131         transmitList.push_front(DeferredPacket(when, pkt));
 132         schedSendEvent(when);
 133         return;
 134     }
 135
 136     // list is non-empty & this belongs at the end
 137     if (when >= transmitList.back().tick) {
 138         transmitList.push_back(DeferredPacket(when, pkt));
 139         return;
 140     }
 141
 142     // this belongs in the middle somewhere
 143     DeferredPacketIterator i = transmitList.begin();
 144     i++; // already checked for insertion at front
 145     DeferredPacketIterator end = transmitList.end();
 146
 147     for (; i != end; ++i) {
 148         if (when < i->tick) {
 149             transmitList.insert(i, DeferredPacket(when, pkt));
 150             return;
 151         }
 152     }
 153     assert(false); // should never get here
 154 }
 155
 156
 157 void
 158 SimpleTimingPort::sendDeferredPacket()
 159 {
 160     assert(deferredPacketReady());
 161     // take packet off list here; if recvTiming() on the other side
 162     // calls sendTiming() back on us (like SimpleTimingCpu does), then
 163     // we get confused by having a non-active packet on transmitList
 164     DeferredPacket dp = transmitList.front();
 165     transmitList.pop_front();
 166     bool success = sendTiming(dp.pkt);
 167
 168     if (success) {
 169         if (!transmitList.empty() && !sendEvent->scheduled()) {
 170             Tick time = transmitList.front().tick;
 171             owner->schedule(sendEvent, time <= curTick() ? curTick()+1 : time);
 172         }
 173
 174         if (transmitList.empty() && drainEvent && !sendEvent->scheduled()) {
 175             drainEvent->process();
 176             drainEvent = NULL;
 177         }
 178     } else {
 179         // Unsuccessful, need to put back on transmitList.  Callee
 180         // should not have messed with it (since it didn't accept that
 181         // packet), so we can just push it back on the front.
 182         assert(!sendEvent->scheduled());
 183         transmitList.push_front(dp);
 184     }
 185
 186     waitingOnRetry = !success;
 187
 188     if (waitingOnRetry) {
 189         DPRINTF(Bus, "Send failed, waiting on retry\n");
 190     }
 191 }
 192
 193
 194 void
 195 SimpleTimingPort::recvRetry()
 196 {
 197     DPRINTF(Bus, "Received retry\n");
 198     assert(waitingOnRetry);
 199     sendDeferredPacket();
 200 }
 201
 202
 203 void
 204 SimpleTimingPort::processSendEvent()
 205 {
 206     assert(!waitingOnRetry);
 207     sendDeferredPacket();
 208 }
 209
 210
 211 unsigned int
 212 SimpleTimingPort::drain(Event *de)
 213 {
 214     if (transmitList.size() == 0 && !sendEvent->scheduled())
 215         return 0;
 216     drainEvent = de;
 217     return 1;
 218 }