src/mem/bridge.cc

   1 /*
   2  * Copyright (c) 2011-2013 ARM Limited
   3  * All rights reserved
   4  *
   5  * The license below extends only to copyright in the software and shall
   6  * not be construed as granting a license to any other intellectual
   7  * property including but not limited to intellectual property relating
   8  * to a hardware implementation of the functionality of the software
   9  * licensed hereunder.  You may use the software subject to the license
  10  * terms below provided that you ensure that this notice is replicated
  11  * unmodified and in its entirety in all distributions of the software,
  12  * modified or unmodified, in source code or in binary form.
  13  *
  14  * Copyright (c) 2006 The Regents of The University of Michigan
  15  * All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions are
  19  * met: redistributions of source code must retain the above copyright
  20  * notice, this list of conditions and the following disclaimer;
  21  * redistributions in binary form must reproduce the above copyright
  22  * notice, this list of conditions and the following disclaimer in the
  23  * documentation and/or other materials provided with the distribution;
  24  * neither the name of the copyright holders nor the names of its
  25  * contributors may be used to endorse or promote products derived from
  26  * this software without specific prior written permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  29  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  30  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  31  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  32  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  33  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  34  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  35  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  *
  40  * Authors: Ali Saidi
  41  *          Steve Reinhardt
  42  *          Andreas Hansson
  43  */
  44
  45 /**
  46  * @file
  47  * Implementation of a memory-mapped bridge that connects a master
  48  * and a slave through a request and response queue.
  49  */
  50
  51 #include "base/trace.hh"
  52 #include "debug/Bridge.hh"
  53 #include "mem/bridge.hh"
  54 #include "params/Bridge.hh"
  55
  56 Bridge::BridgeSlavePort::BridgeSlavePort(const std::string& _name,
  57                                          Bridge& _bridge,
  58                                          BridgeMasterPort& _masterPort,
  59                                          Cycles _delay, int _resp_limit,
  60                                          std::vector<AddrRange> _ranges)
  61     : SlavePort(_name, &_bridge), bridge(_bridge), masterPort(_masterPort),
  62       delay(_delay), ranges(_ranges.begin(), _ranges.end()),
  63       outstandingResponses(0), retryReq(false),
  64       respQueueLimit(_resp_limit), sendEvent(*this)
  65 {
  66 }
  67
  68 Bridge::BridgeMasterPort::BridgeMasterPort(const std::string& _name,
  69                                            Bridge& _bridge,
  70                                            BridgeSlavePort& _slavePort,
  71                                            Cycles _delay, int _req_limit)
  72     : MasterPort(_name, &_bridge), bridge(_bridge), slavePort(_slavePort),
  73       delay(_delay), reqQueueLimit(_req_limit), sendEvent(*this)
  74 {
  75 }
  76
  77 Bridge::Bridge(Params *p)
  78     : MemObject(p),
  79       slavePort(p->name + ".slave", *this, masterPort,
  80                 ticksToCycles(p->delay), p->resp_size, p->ranges),
  81       masterPort(p->name + ".master", *this, slavePort,
  82                  ticksToCycles(p->delay), p->req_size)
  83 {
  84 }
  85
  86 BaseMasterPort&
  87 Bridge::getMasterPort(const std::string &if_name, PortID idx)
  88 {
  89     if (if_name == "master")
  90         return masterPort;
  91     else
  92         // pass it along to our super class
  93         return MemObject::getMasterPort(if_name, idx);
  94 }
  95
  96 BaseSlavePort&
  97 Bridge::getSlavePort(const std::string &if_name, PortID idx)
  98 {
  99     if (if_name == "slave")
 100         return slavePort;
 101     else
 102         // pass it along to our super class
 103         return MemObject::getSlavePort(if_name, idx);
 104 }
 105
 106 void
 107 Bridge::init()
 108 {
 109     // make sure both sides are connected and have the same block size
 110     if (!slavePort.isConnected() || !masterPort.isConnected())
 111         fatal("Both ports of a bridge must be connected.\n");
 112
 113     // notify the master side  of our address ranges
 114     slavePort.sendRangeChange();
 115 }
 116
 117 bool
 118 Bridge::BridgeSlavePort::respQueueFull() const
 119 {
 120     return outstandingResponses == respQueueLimit;
 121 }
 122
 123 bool
 124 Bridge::BridgeMasterPort::reqQueueFull() const
 125 {
 126     return transmitList.size() == reqQueueLimit;
 127 }
 128
 129 bool
 130 Bridge::BridgeMasterPort::recvTimingResp(PacketPtr pkt)
 131 {
 132     // all checks are done when the request is accepted on the slave
 133     // side, so we are guaranteed to have space for the response
 134     DPRINTF(Bridge, "recvTimingResp: %s addr 0x%x\n",
 135             pkt->cmdString(), pkt->getAddr());
 136
 137     DPRINTF(Bridge, "Request queue size: %d\n", transmitList.size());
 138
 139     // @todo: We need to pay for this and not just zero it out
 140     pkt->headerDelay = pkt->payloadDelay = 0;
 141
 142     slavePort.schedTimingResp(pkt, bridge.clockEdge(delay));
 143
 144     return true;
 145 }
 146
 147 bool
 148 Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
 149 {
 150     DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
 151             pkt->cmdString(), pkt->getAddr());
 152
 153     // we should not see a timing request if we are already in a retry
 154     assert(!retryReq);
 155
 156     DPRINTF(Bridge, "Response queue size: %d outresp: %d\n",
 157             transmitList.size(), outstandingResponses);
 158
 159     // if the request queue is full then there is no hope
 160     if (masterPort.reqQueueFull()) {
 161         DPRINTF(Bridge, "Request queue full\n");
 162         retryReq = true;
 163     } else {
 164         // look at the response queue if we expect to see a response
 165         bool expects_response = pkt->needsResponse() &&
 166             !pkt->memInhibitAsserted();
 167         if (expects_response) {
 168             if (respQueueFull()) {
 169                 DPRINTF(Bridge, "Response queue full\n");
 170                 retryReq = true;
 171             } else {
 172                 // ok to send the request with space for the response
 173                 DPRINTF(Bridge, "Reserving space for response\n");
 174                 assert(outstandingResponses != respQueueLimit);
 175                 ++outstandingResponses;
 176
 177                 // no need to set retryReq to false as this is already the
 178                 // case
 179             }
 180         }
 181
 182         if (!retryReq) {
 183             // @todo: We need to pay for this and not just zero it out
 184             pkt->headerDelay = pkt->payloadDelay = 0;
 185
 186             masterPort.schedTimingReq(pkt, bridge.clockEdge(delay));
 187         }
 188     }
 189
 190     // remember that we are now stalling a packet and that we have to
 191     // tell the sending master to retry once space becomes available,
 192     // we make no distinction whether the stalling is due to the
 193     // request queue or response queue being full
 194     return !retryReq;
 195 }
 196
 197 void
 198 Bridge::BridgeSlavePort::retryStalledReq()
 199 {
 200     if (retryReq) {
 201         DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 202         retryReq = false;
 203         sendRetryReq();
 204     }
 205 }
 206
 207 void
 208 Bridge::BridgeMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
 209 {
 210     // If we're about to put this packet at the head of the queue, we
 211     // need to schedule an event to do the transmit.  Otherwise there
 212     // should already be an event scheduled for sending the head
 213     // packet.
 214     if (transmitList.empty()) {
 215         bridge.schedule(sendEvent, when);
 216     }
 217
 218     assert(transmitList.size() != reqQueueLimit);
 219
 220     transmitList.emplace_back(pkt, when);
 221 }
 222
 223
 224 void
 225 Bridge::BridgeSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
 226 {
 227     // If we're about to put this packet at the head of the queue, we
 228     // need to schedule an event to do the transmit.  Otherwise there
 229     // should already be an event scheduled for sending the head
 230     // packet.
 231     if (transmitList.empty()) {
 232         bridge.schedule(sendEvent, when);
 233     }
 234
 235     transmitList.emplace_back(pkt, when);
 236 }
 237
 238 void
 239 Bridge::BridgeMasterPort::trySendTiming()
 240 {
 241     assert(!transmitList.empty());
 242
 243     DeferredPacket req = transmitList.front();
 244
 245     assert(req.tick <= curTick());
 246
 247     PacketPtr pkt = req.pkt;
 248
 249     DPRINTF(Bridge, "trySend request addr 0x%x, queue size %d\n",
 250             pkt->getAddr(), transmitList.size());
 251
 252     if (sendTimingReq(pkt)) {
 253         // send successful
 254         transmitList.pop_front();
 255         DPRINTF(Bridge, "trySend request successful\n");
 256
 257         // If there are more packets to send, schedule event to try again.
 258         if (!transmitList.empty()) {
 259             DeferredPacket next_req = transmitList.front();
 260             DPRINTF(Bridge, "Scheduling next send\n");
 261             bridge.schedule(sendEvent, std::max(next_req.tick,
 262                                                 bridge.clockEdge()));
 263         }
 264
 265         // if we have stalled a request due to a full request queue,
 266         // then send a retry at this point, also note that if the
 267         // request we stalled was waiting for the response queue
 268         // rather than the request queue we might stall it again
 269         slavePort.retryStalledReq();
 270     }
 271
 272     // if the send failed, then we try again once we receive a retry,
 273     // and therefore there is no need to take any action
 274 }
 275
 276 void
 277 Bridge::BridgeSlavePort::trySendTiming()
 278 {
 279     assert(!transmitList.empty());
 280
 281     DeferredPacket resp = transmitList.front();
 282
 283     assert(resp.tick <= curTick());
 284
 285     PacketPtr pkt = resp.pkt;
 286
 287     DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
 288             pkt->getAddr(), outstandingResponses);
 289
 290     if (sendTimingResp(pkt)) {
 291         // send successful
 292         transmitList.pop_front();
 293         DPRINTF(Bridge, "trySend response successful\n");
 294
 295         assert(outstandingResponses != 0);
 296         --outstandingResponses;
 297
 298         // If there are more packets to send, schedule event to try again.
 299         if (!transmitList.empty()) {
 300             DeferredPacket next_resp = transmitList.front();
 301             DPRINTF(Bridge, "Scheduling next send\n");
 302             bridge.schedule(sendEvent, std::max(next_resp.tick,
 303                                                 bridge.clockEdge()));
 304         }
 305
 306         // if there is space in the request queue and we were stalling
 307         // a request, it will definitely be possible to accept it now
 308         // since there is guaranteed space in the response queue
 309         if (!masterPort.reqQueueFull() && retryReq) {
 310             DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 311             retryReq = false;
 312             sendRetryReq();
 313         }
 314     }
 315
 316     // if the send failed, then we try again once we receive a retry,
 317     // and therefore there is no need to take any action
 318 }
 319
 320 void
 321 Bridge::BridgeMasterPort::recvReqRetry()
 322 {
 323     trySendTiming();
 324 }
 325
 326 void
 327 Bridge::BridgeSlavePort::recvRespRetry()
 328 {
 329     trySendTiming();
 330 }
 331
 332 Tick
 333 Bridge::BridgeSlavePort::recvAtomic(PacketPtr pkt)
 334 {
 335     return delay * bridge.clockPeriod() + masterPort.sendAtomic(pkt);
 336 }
 337
 338 void
 339 Bridge::BridgeSlavePort::recvFunctional(PacketPtr pkt)
 340 {
 341     pkt->pushLabel(name());
 342
 343     // check the response queue
 344     for (auto i = transmitList.begin();  i != transmitList.end(); ++i) {
 345         if (pkt->checkFunctional((*i).pkt)) {
 346             pkt->makeResponse();
 347             return;
 348         }
 349     }
 350
 351     // also check the master port's request queue
 352     if (masterPort.checkFunctional(pkt)) {
 353         return;
 354     }
 355
 356     pkt->popLabel();
 357
 358     // fall through if pkt still not satisfied
 359     masterPort.sendFunctional(pkt);
 360 }
 361
 362 bool
 363 Bridge::BridgeMasterPort::checkFunctional(PacketPtr pkt)
 364 {
 365     bool found = false;
 366     auto i = transmitList.begin();
 367
 368     while(i != transmitList.end() && !found) {
 369         if (pkt->checkFunctional((*i).pkt)) {
 370             pkt->makeResponse();
 371             found = true;
 372         }
 373         ++i;
 374     }
 375
 376     return found;
 377 }
 378
 379 AddrRangeList
 380 Bridge::BridgeSlavePort::getAddrRanges() const
 381 {
 382     return ranges;
 383 }
 384
 385 Bridge *
 386 BridgeParams::create()
 387 {
 388     return new Bridge(this);
 389 }