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 "mem/tport.hh"
  32
  33 using namespace std;
  34
  35 SimpleTimingPort::SimpleTimingPort(string pname, MemObject *_owner)
  36     : Port(pname, _owner), sendEvent(0), drainEvent(NULL),
  37       waitingOnRetry(false)
  38 {
  39     sendEvent =  new EventWrapper<SimpleTimingPort,
  40         &SimpleTimingPort::processSendEvent>(this);
  41 }
  42
  43 SimpleTimingPort::~SimpleTimingPort()
  44 {
  45     delete sendEvent;
  46 }
  47
  48 bool
  49 SimpleTimingPort::checkFunctional(PacketPtr pkt)
  50 {
  51     DeferredPacketIterator i = transmitList.begin();
  52     DeferredPacketIterator end = transmitList.end();
  53
  54     for (; i != end; ++i) {
  55         PacketPtr target = i->pkt;
  56         // If the target contains data, and it overlaps the
  57         // probed request, need to update data
  58         if (pkt->checkFunctional(target)) {
  59             return true;
  60         }
  61     }
  62
  63     return false;
  64 }
  65
  66 void
  67 SimpleTimingPort::recvFunctional(PacketPtr pkt)
  68 {
  69     if (!checkFunctional(pkt)) {
  70         // Just do an atomic access and throw away the returned latency
  71         recvAtomic(pkt);
  72     }
  73 }
  74
  75 bool
  76 SimpleTimingPort::recvTiming(PacketPtr pkt)
  77 {
  78     // If the device is only a slave, it should only be sending
  79     // responses, which should never get nacked.  There used to be
  80     // code to hanldle nacks here, but I'm pretty sure it didn't work
  81     // correctly with the drain code, so that would need to be fixed
  82     // if we ever added it back.
  83
  84     if (pkt->memInhibitAsserted()) {
  85         // snooper will supply based on copy of packet
  86         // still target's responsibility to delete packet
  87         delete pkt;
  88         return true;
  89     }
  90
  91     bool needsResponse = pkt->needsResponse();
  92     Tick latency = recvAtomic(pkt);
  93     // turn packet around to go back to requester if response expected
  94     if (needsResponse) {
  95         // recvAtomic() should already have turned packet into
  96         // atomic response
  97         assert(pkt->isResponse());
  98         schedSendTiming(pkt, curTick + latency);
  99     } else {
 100         delete pkt;
 101     }
 102
 103     return true;
 104 }
 105
 106
 107 void
 108 SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
 109 {
 110     assert(when > curTick);
 111     assert(when < curTick + Clock::Int::ms);
 112
 113     // Nothing is on the list: add it and schedule an event
 114     if (transmitList.empty() || when < transmitList.front().tick) {
 115         transmitList.push_front(DeferredPacket(when, pkt));
 116         schedSendEvent(when);
 117         return;
 118     }
 119
 120     // list is non-empty & this belongs at the end
 121     if (when >= transmitList.back().tick) {
 122         transmitList.push_back(DeferredPacket(when, pkt));
 123         return;
 124     }
 125
 126     // this belongs in the middle somewhere
 127     DeferredPacketIterator i = transmitList.begin();
 128     i++; // already checked for insertion at front
 129     DeferredPacketIterator end = transmitList.end();
 130
 131     for (; i != end; ++i) {
 132         if (when < i->tick) {
 133             transmitList.insert(i, DeferredPacket(when, pkt));
 134             return;
 135         }
 136     }
 137     assert(false); // should never get here
 138 }
 139
 140
 141 void
 142 SimpleTimingPort::sendDeferredPacket()
 143 {
 144     assert(deferredPacketReady());
 145     // take packet off list here; if recvTiming() on the other side
 146     // calls sendTiming() back on us (like SimpleTimingCpu does), then
 147     // we get confused by having a non-active packet on transmitList
 148     DeferredPacket dp = transmitList.front();
 149     transmitList.pop_front();
 150     bool success = sendTiming(dp.pkt);
 151
 152     if (success) {
 153         if (!transmitList.empty() && !sendEvent->scheduled()) {
 154             Tick time = transmitList.front().tick;
 155             schedule(sendEvent, time <= curTick ? curTick+1 : time);
 156         }
 157
 158         if (transmitList.empty() && drainEvent) {
 159             drainEvent->process();
 160             drainEvent = NULL;
 161         }
 162     } else {
 163         // Unsuccessful, need to put back on transmitList.  Callee
 164         // should not have messed with it (since it didn't accept that
 165         // packet), so we can just push it back on the front.
 166         assert(!sendEvent->scheduled());
 167         transmitList.push_front(dp);
 168     }
 169
 170     waitingOnRetry = !success;
 171
 172     if (waitingOnRetry) {
 173         DPRINTF(Bus, "Send failed, waiting on retry\n");
 174     }
 175 }
 176
 177
 178 void
 179 SimpleTimingPort::recvRetry()
 180 {
 181     DPRINTF(Bus, "Received retry\n");
 182     assert(waitingOnRetry);
 183     sendDeferredPacket();
 184 }
 185
 186
 187 void
 188 SimpleTimingPort::processSendEvent()
 189 {
 190     assert(!waitingOnRetry);
 191     sendDeferredPacket();
 192 }
 193
 194
 195 unsigned int
 196 SimpleTimingPort::drain(Event *de)
 197 {
 198     if (transmitList.size() == 0)
 199         return 0;
 200     drainEvent = de;
 201     return 1;
 202 }