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 void
  34 SimpleTimingPort::checkFunctional(PacketPtr pkt)
  35 {
  36     DeferredPacketIterator i = transmitList.begin();
  37     DeferredPacketIterator end = transmitList.end();
  38
  39     for (; i != end; ++i) {
  40         PacketPtr target = i->pkt;
  41         // If the target contains data, and it overlaps the
  42         // probed request, need to update data
  43         if (target->intersect(pkt)) {
  44             if (!fixPacket(pkt, target)) {
  45                 // fixPacket returns true for continue, false for done
  46                 return;
  47             }
  48         }
  49     }
  50 }
  51
  52 void
  53 SimpleTimingPort::recvFunctional(PacketPtr pkt)
  54 {
  55     checkFunctional(pkt);
  56
  57     // Just do an atomic access and throw away the returned latency
  58     if (pkt->result != Packet::Success)
  59         recvAtomic(pkt);
  60 }
  61
  62 bool
  63 SimpleTimingPort::recvTiming(PacketPtr pkt)
  64 {
  65     // If the device is only a slave, it should only be sending
  66     // responses, which should never get nacked.  There used to be
  67     // code to hanldle nacks here, but I'm pretty sure it didn't work
  68     // correctly with the drain code, so that would need to be fixed
  69     // if we ever added it back.
  70     assert(pkt->isRequest());
  71     assert(pkt->result == Packet::Unknown);
  72     bool needsResponse = pkt->needsResponse();
  73     Tick latency = recvAtomic(pkt);
  74     // turn packet around to go back to requester if response expected
  75     if (needsResponse) {
  76         // recvAtomic() should already have turned packet into atomic response
  77         assert(pkt->isResponse());
  78         pkt->convertAtomicToTimingResponse();
  79         schedSendTiming(pkt, curTick + latency);
  80     } else {
  81         delete pkt->req;
  82         delete pkt;
  83     }
  84     return true;
  85 }
  86
  87
  88 void
  89 SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
  90 {
  91     assert(when > curTick);
  92
  93     // Nothing is on the list: add it and schedule an event
  94     if (transmitList.empty() || when < transmitList.front().tick) {
  95         transmitList.push_front(DeferredPacket(when, pkt));
  96         schedSendEvent(when);
  97         return;
  98     }
  99
 100     // list is non-empty and this is not the head, so event should
 101     // already be scheduled
 102     assert(waitingOnRetry ||
 103            (sendEvent->scheduled() && sendEvent->when() <= when));
 104
 105     // list is non-empty & this belongs at the end
 106     if (when >= transmitList.back().tick) {
 107         transmitList.push_back(DeferredPacket(when, pkt));
 108         return;
 109     }
 110
 111     // this belongs in the middle somewhere
 112     DeferredPacketIterator i = transmitList.begin();
 113     i++; // already checked for insertion at front
 114     DeferredPacketIterator end = transmitList.end();
 115
 116     for (; i != end; ++i) {
 117         if (when < i->tick) {
 118             transmitList.insert(i, DeferredPacket(when, pkt));
 119             return;
 120         }
 121     }
 122     assert(false); // should never get here
 123 }
 124
 125
 126 void
 127 SimpleTimingPort::sendDeferredPacket()
 128 {
 129     assert(deferredPacketReady());
 130     bool success = sendTiming(transmitList.front().pkt);
 131
 132     if (success) {
 133         //send successful, remove packet
 134         transmitList.pop_front();
 135         if (!transmitList.empty()) {
 136             Tick time = transmitList.front().tick;
 137             sendEvent->schedule(time <= curTick ? curTick+1 : time);
 138         }
 139
 140         if (transmitList.empty() && drainEvent) {
 141             drainEvent->process();
 142             drainEvent = NULL;
 143         }
 144     }
 145
 146     waitingOnRetry = !success;
 147
 148     if (waitingOnRetry) {
 149         DPRINTF(Bus, "Send failed, waiting on retry\n");
 150     }
 151 }
 152
 153
 154 void
 155 SimpleTimingPort::recvRetry()
 156 {
 157     DPRINTF(Bus, "Received retry\n");
 158     assert(waitingOnRetry);
 159     sendDeferredPacket();
 160 }
 161
 162
 163 void
 164 SimpleTimingPort::processSendEvent()
 165 {
 166     assert(!waitingOnRetry);
 167     sendDeferredPacket();
 168 }
 169
 170
 171 unsigned int
 172 SimpleTimingPort::drain(Event *de)
 173 {
 174     if (transmitList.size() == 0)
 175         return 0;
 176     drainEvent = de;
 177     return 1;
 178 }