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 bool
  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 true;
  45         }
  46     }
  47
  48     return false;
  49 }
  50
  51 void
  52 SimpleTimingPort::recvFunctional(PacketPtr pkt)
  53 {
  54     if (!checkFunctional(pkt)) {
  55         // Just do an atomic access and throw away the returned latency
  56         recvAtomic(pkt);
  57     }
  58 }
  59
  60 bool
  61 SimpleTimingPort::recvTiming(PacketPtr pkt)
  62 {
  63     // If the device is only a slave, it should only be sending
  64     // responses, which should never get nacked.  There used to be
  65     // code to hanldle nacks here, but I'm pretty sure it didn't work
  66     // correctly with the drain code, so that would need to be fixed
  67     // if we ever added it back.
  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;
  86     }
  87
  88     return true;
  89 }
  90
  91
  92 void
  93 SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
  94 {
  95     assert(when > curTick);
  96     assert(when < curTick + Clock::Int::ms);
  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 & 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     // take packet off list here; if recvTiming() on the other side
 131     // calls sendTiming() back on us (like SimpleTimingCpu does), then
 132     // we get confused by having a non-active packet on transmitList
 133     DeferredPacket dp = transmitList.front();
 134     transmitList.pop_front();
 135     bool success = sendTiming(dp.pkt);
 136
 137     if (success) {
 138         if (!transmitList.empty() && !sendEvent->scheduled()) {
 139             Tick time = transmitList.front().tick;
 140             schedule(sendEvent, time <= curTick ? curTick+1 : time);
 141         }
 142
 143         if (transmitList.empty() && drainEvent) {
 144             drainEvent->process();
 145             drainEvent = NULL;
 146         }
 147     } else {
 148         // Unsuccessful, need to put back on transmitList.  Callee
 149         // should not have messed with it (since it didn't accept that
 150         // packet), so we can just push it back on the front.
 151         assert(!sendEvent->scheduled());
 152         transmitList.push_front(dp);
 153     }
 154
 155     waitingOnRetry = !success;
 156
 157     if (waitingOnRetry) {
 158         DPRINTF(Bus, "Send failed, waiting on retry\n");
 159     }
 160 }
 161
 162
 163 void
 164 SimpleTimingPort::recvRetry()
 165 {
 166     DPRINTF(Bus, "Received retry\n");
 167     assert(waitingOnRetry);
 168     sendDeferredPacket();
 169 }
 170
 171
 172 void
 173 SimpleTimingPort::processSendEvent()
 174 {
 175     assert(!waitingOnRetry);
 176     sendDeferredPacket();
 177 }
 178
 179
 180 unsigned int
 181 SimpleTimingPort::drain(Event *de)
 182 {
 183     if (transmitList.size() == 0)
 184         return 0;
 185     drainEvent = de;
 186     return 1;
 187 }