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