src/mem/bridge.cc

   1
   2 /*
   3  * Copyright (c) 2006 The Regents of The University of Michigan
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions are
   8  * met: redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer;
  10  * redistributions in binary form must reproduce the above copyright
  11  * notice, this list of conditions and the following disclaimer in the
  12  * documentation and/or other materials provided with the distribution;
  13  * neither the name of the copyright holders nor the names of its
  14  * contributors may be used to endorse or promote products derived from
  15  * this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  20  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  21  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  22  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  23  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  27  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  *
  29  * Authors: Ali Saidi
  30  *          Steve Reinhardt
  31  */
  32
  33 /**
  34  * @file
  35  * Definition of a simple bus bridge without buffering.
  36  */
  37
  38 #include <algorithm>
  39
  40 #include "base/trace.hh"
  41 #include "mem/bridge.hh"
  42 #include "sim/builder.hh"
  43
  44 Bridge::BridgePort::BridgePort(const std::string &_name,
  45                                Bridge *_bridge, BridgePort *_otherPort,
  46                                int _delay, int _queueLimit)
  47     : Port(_name), bridge(_bridge), otherPort(_otherPort),
  48       delay(_delay), outstandingResponses(0),
  49       queueLimit(_queueLimit), sendEvent(this)
  50 {
  51 }
  52
  53 Bridge::Bridge(const std::string &n, int qsa, int qsb,
  54                Tick _delay, int write_ack)
  55     : MemObject(n),
  56       portA(n + "-portA", this, &portB, _delay, qsa),
  57       portB(n + "-portB", this, &portA, _delay, qsa),
  58       ackWrites(write_ack)
  59 {
  60 }
  61
  62 Port *
  63 Bridge::getPort(const std::string &if_name, int idx)
  64 {
  65     BridgePort *port;
  66
  67     if (if_name == "side_a")
  68         port = &portA;
  69     else if (if_name == "side_b")
  70         port = &portB;
  71     else
  72         return NULL;
  73
  74     if (port->getPeer() != NULL)
  75         panic("bridge side %s already connected to.", if_name);
  76     return port;
  77 }
  78
  79
  80 void
  81 Bridge::init()
  82 {
  83     // Make sure that both sides are connected to.
  84     if (portA.getPeer() == NULL || portB.getPeer() == NULL)
  85         panic("Both ports of bus bridge are not connected to a bus.\n");
  86 }
  87
  88
  89 /** Function called by the port when the bus is receiving a Timing
  90  * transaction.*/
  91 bool
  92 Bridge::BridgePort::recvTiming(PacketPtr pkt)
  93 {
  94     if (pkt->flags & SNOOP_COMMIT) {
  95         DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
  96                 pkt->getSrc(), pkt->getDest(), pkt->getAddr());
  97
  98         return otherPort->queueForSendTiming(pkt);
  99     }
 100     else {
 101         // Else it's just a snoop, properly return if we are blocking
 102         return !queueFull();
 103     }
 104 }
 105
 106
 107 bool
 108 Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
 109 {
 110     if (queueFull())
 111         return false;
 112
 113    if (pkt->isResponse()) {
 114         // This is a response for a request we forwarded earlier.  The
 115         // corresponding PacketBuffer should be stored in the packet's
 116         // senderState field.
 117         PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
 118         assert(buf != NULL);
 119         // set up new packet dest & senderState based on values saved
 120         // from original request
 121         buf->fixResponse(pkt);
 122         DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
 123                         pkt->senderState, buf);
 124         DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
 125         delete buf;
 126     }
 127
 128     Tick readyTime = curTick + delay;
 129     PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
 130     DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
 131             buf->origSenderState, buf);
 132
 133     // If we're about to put this packet at the head of the queue, we
 134     // need to schedule an event to do the transmit.  Otherwise there
 135     // should already be an event scheduled for sending the head
 136     // packet.
 137     if (sendQueue.empty()) {
 138         sendEvent.schedule(readyTime);
 139     }
 140
 141     sendQueue.push_back(buf);
 142
 143     return true;
 144 }
 145
 146 void
 147 Bridge::BridgePort::trySend()
 148 {
 149     assert(!sendQueue.empty());
 150
 151     bool was_full = queueFull();
 152
 153     PacketBuffer *buf = sendQueue.front();
 154
 155     assert(buf->ready <= curTick);
 156
 157     PacketPtr pkt = buf->pkt;
 158
 159     DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
 160             buf->origSrc, pkt->getDest(), pkt->getAddr());
 161
 162     pkt->flags &= ~SNOOP_COMMIT; //CLear it if it was set
 163     if (sendTiming(pkt)) {
 164         // send successful
 165         sendQueue.pop_front();
 166         buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
 167
 168         if (buf->expectResponse) {
 169             // Must wait for response.  We just need to count outstanding
 170             // responses (in case we want to cap them); PacketBuffer
 171             // pointer will be recovered on response.
 172             ++outstandingResponses;
 173             DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
 174                     outstandingResponses);
 175         } else {
 176             // no response expected... deallocate packet buffer now.
 177             DPRINTF(BusBridge, "  successful: no response expected\n");
 178             delete buf;
 179         }
 180
 181         // If there are more packets to send, schedule event to try again.
 182         if (!sendQueue.empty()) {
 183             buf = sendQueue.front();
 184             sendEvent.schedule(std::max(buf->ready, curTick + 1));
 185         }
 186         // Let things start sending again
 187         if (was_full) {
 188           DPRINTF(BusBridge, "Queue was full, sending retry\n");
 189           otherPort->sendRetry();
 190         }
 191
 192     } else {
 193         DPRINTF(BusBridge, "  unsuccessful\n");
 194     }
 195 }
 196
 197
 198 void
 199 Bridge::BridgePort::recvRetry()
 200 {
 201     trySend();
 202 }
 203
 204 /** Function called by the port when the bus is receiving a Atomic
 205  * transaction.*/
 206 Tick
 207 Bridge::BridgePort::recvAtomic(PacketPtr pkt)
 208 {
 209     return otherPort->sendAtomic(pkt) + delay;
 210 }
 211
 212 /** Function called by the port when the bus is receiving a Functional
 213  * transaction.*/
 214 void
 215 Bridge::BridgePort::recvFunctional(PacketPtr pkt)
 216 {
 217     std::list<PacketBuffer*>::iterator i;
 218     bool pktContinue = true;
 219
 220     for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
 221         if (pkt->intersect((*i)->pkt)) {
 222             pktContinue &= fixPacket(pkt, (*i)->pkt);
 223         }
 224     }
 225
 226     if (pktContinue) {
 227         otherPort->sendFunctional(pkt);
 228     }
 229 }
 230
 231 /** Function called by the port when the bus is receiving a status change.*/
 232 void
 233 Bridge::BridgePort::recvStatusChange(Port::Status status)
 234 {
 235     otherPort->sendStatusChange(status);
 236 }
 237
 238 void
 239 Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
 240                                            AddrRangeList &snoop)
 241 {
 242     otherPort->getPeerAddressRanges(resp, snoop);
 243 }
 244
 245 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
 246
 247    Param<int> queue_size_a;
 248    Param<int> queue_size_b;
 249    Param<Tick> delay;
 250    Param<bool> write_ack;
 251
 252 END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
 253
 254 BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
 255
 256     INIT_PARAM(queue_size_a, "The size of the queue for data coming into side a"),
 257     INIT_PARAM(queue_size_b, "The size of the queue for data coming into side b"),
 258     INIT_PARAM(delay, "The miminum delay to cross this bridge"),
 259     INIT_PARAM(write_ack, "Acknowledge any writes that are received.")
 260
 261 END_INIT_SIM_OBJECT_PARAMS(Bridge)
 262
 263 CREATE_SIM_OBJECT(Bridge)
 264 {
 265     return new Bridge(getInstanceName(), queue_size_a, queue_size_b, delay,
 266             write_ack);
 267 }
 268
 269 REGISTER_SIM_OBJECT("Bridge", Bridge)