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->isResponse())
  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
  72     if (pkt->memInhibitAsserted()) {
  73         // snooper will supply based on copy of packet
  74         // still target's responsibility to delete packet
  75         delete pkt->req;
  76         delete pkt;
  77         return true;
  78     }
  79
  80     bool needsResponse = pkt->needsResponse();
  81     Tick latency = recvAtomic(pkt);
  82     // turn packet around to go back to requester if response expected
  83     if (needsResponse) {
  84         // recvAtomic() should already have turned packet into
  85         // atomic response
  86         assert(pkt->isResponse());
  87         schedSendTiming(pkt, curTick + latency);
  88     } else {
  89         delete pkt->req;
  90         delete pkt;
  91     }
  92
  93     return true;
  94 }
  95
  96
  97 void
  98 SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
  99 {
 100     assert(when > curTick);
 101
 102     // Nothing is on the list: add it and schedule an event
 103     if (transmitList.empty() || when < transmitList.front().tick) {
 104         transmitList.push_front(DeferredPacket(when, pkt));
 105         schedSendEvent(when);
 106         return;
 107     }
 108
 109     // list is non-empty and this is not the head, so event should
 110     // already be scheduled
 111     assert(waitingOnRetry ||
 112            (sendEvent->scheduled() && sendEvent->when() <= when));
 113
 114     // list is non-empty & this belongs at the end
 115     if (when >= transmitList.back().tick) {
 116         transmitList.push_back(DeferredPacket(when, pkt));
 117         return;
 118     }
 119
 120     // this belongs in the middle somewhere
 121     DeferredPacketIterator i = transmitList.begin();
 122     i++; // already checked for insertion at front
 123     DeferredPacketIterator end = transmitList.end();
 124
 125     for (; i != end; ++i) {
 126         if (when < i->tick) {
 127             transmitList.insert(i, DeferredPacket(when, pkt));
 128             return;
 129         }
 130     }
 131     assert(false); // should never get here
 132 }
 133
 134
 135 void
 136 SimpleTimingPort::sendDeferredPacket()
 137 {
 138     assert(deferredPacketReady());
 139     // take packet off list here; if recvTiming() on the other side
 140     // calls sendTiming() back on us (like SimpleTimingCpu does), then
 141     // we get confused by having a non-active packet on transmitList
 142     DeferredPacket dp = transmitList.front();
 143     transmitList.pop_front();
 144     bool success = sendTiming(dp.pkt);
 145
 146     if (success) {
 147         if (!transmitList.empty() && !sendEvent->scheduled()) {
 148             Tick time = transmitList.front().tick;
 149             sendEvent->schedule(time <= curTick ? curTick+1 : time);
 150         }
 151
 152         if (transmitList.empty() && drainEvent) {
 153             drainEvent->process();
 154             drainEvent = NULL;
 155         }
 156     } else {
 157         // Unsuccessful, need to put back on transmitList.  Callee
 158         // should not have messed with it (since it didn't accept that
 159         // packet), so we can just push it back on the front.
 160         assert(!sendEvent->scheduled());
 161         transmitList.push_front(dp);
 162     }
 163
 164     waitingOnRetry = !success;
 165
 166     if (waitingOnRetry) {
 167         DPRINTF(Bus, "Send failed, waiting on retry\n");
 168     }
 169 }
 170
 171
 172 void
 173 SimpleTimingPort::recvRetry()
 174 {
 175     DPRINTF(Bus, "Received retry\n");
 176     assert(waitingOnRetry);
 177     sendDeferredPacket();
 178 }
 179
 180
 181 void
 182 SimpleTimingPort::processSendEvent()
 183 {
 184     assert(!waitingOnRetry);
 185     sendDeferredPacket();
 186 }
 187
 188
 189 unsigned int
 190 SimpleTimingPort::drain(Event *de)
 191 {
 192     if (transmitList.size() == 0)
 193         return 0;
 194     drainEvent = de;
 195     return 1;
 196 }