src/mem/bridge.cc

   1 /*
   2  * Copyright (c) 2011-2013, 2015 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 "mem/bridge.hh"
  52
  53 #include "base/trace.hh"
  54 #include "debug/Bridge.hh"
  55 #include "params/Bridge.hh"
  56
  57 Bridge::BridgeSlavePort::BridgeSlavePort(const std::string& _name,
  58                                          Bridge& _bridge,
  59                                          BridgeMasterPort& _masterPort,
  60                                          Cycles _delay, int _resp_limit,
  61                                          std::vector<AddrRange> _ranges)
  62     : SlavePort(_name, &_bridge), bridge(_bridge), masterPort(_masterPort),
  63       delay(_delay), ranges(_ranges.begin(), _ranges.end()),
  64       outstandingResponses(0), retryReq(false), respQueueLimit(_resp_limit),
  65       sendEvent([this]{ trySendTiming(); }, _name)
  66 {
  67 }
  68
  69 Bridge::BridgeMasterPort::BridgeMasterPort(const std::string& _name,
  70                                            Bridge& _bridge,
  71                                            BridgeSlavePort& _slavePort,
  72                                            Cycles _delay, int _req_limit)
  73     : MasterPort(_name, &_bridge), bridge(_bridge), slavePort(_slavePort),
  74       delay(_delay), reqQueueLimit(_req_limit),
  75       sendEvent([this]{ trySendTiming(); }, _name)
  76 {
  77 }
  78
  79 Bridge::Bridge(Params *p)
  80     : MemObject(p),
  81       slavePort(p->name + ".slave", *this, masterPort,
  82                 ticksToCycles(p->delay), p->resp_size, p->ranges),
  83       masterPort(p->name + ".master", *this, slavePort,
  84                  ticksToCycles(p->delay), p->req_size)
  85 {
  86 }
  87
  88 Port &
  89 Bridge::getPort(const std::string &if_name, PortID idx)
  90 {
  91     if (if_name == "master")
  92         return masterPort;
  93     else if (if_name == "slave")
  94         return slavePort;
  95     else
  96         // pass it along to our super class
  97         return MemObject::getPort(if_name, idx);
  98 }
  99
 100 void
 101 Bridge::init()
 102 {
 103     // make sure both sides are connected and have the same block size
 104     if (!slavePort.isConnected() || !masterPort.isConnected())
 105         fatal("Both ports of a bridge must be connected.\n");
 106
 107     // notify the master side  of our address ranges
 108     slavePort.sendRangeChange();
 109 }
 110
 111 bool
 112 Bridge::BridgeSlavePort::respQueueFull() const
 113 {
 114     return outstandingResponses == respQueueLimit;
 115 }
 116
 117 bool
 118 Bridge::BridgeMasterPort::reqQueueFull() const
 119 {
 120     return transmitList.size() == reqQueueLimit;
 121 }
 122
 123 bool
 124 Bridge::BridgeMasterPort::recvTimingResp(PacketPtr pkt)
 125 {
 126     // all checks are done when the request is accepted on the slave
 127     // side, so we are guaranteed to have space for the response
 128     DPRINTF(Bridge, "recvTimingResp: %s addr 0x%x\n",
 129             pkt->cmdString(), pkt->getAddr());
 130
 131     DPRINTF(Bridge, "Request queue size: %d\n", transmitList.size());
 132
 133     // technically the packet only reaches us after the header delay,
 134     // and typically we also need to deserialise any payload (unless
 135     // the two sides of the bridge are synchronous)
 136     Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
 137     pkt->headerDelay = pkt->payloadDelay = 0;
 138
 139     slavePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
 140                               receive_delay);
 141
 142     return true;
 143 }
 144
 145 bool
 146 Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
 147 {
 148     DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
 149             pkt->cmdString(), pkt->getAddr());
 150
 151     panic_if(pkt->cacheResponding(), "Should not see packets where cache "
 152              "is responding");
 153
 154     // we should not get a new request after committing to retry the
 155     // current one, but unfortunately the CPU violates this rule, so
 156     // simply ignore it for now
 157     if (retryReq)
 158         return false;
 159
 160     DPRINTF(Bridge, "Response queue size: %d outresp: %d\n",
 161             transmitList.size(), outstandingResponses);
 162
 163     // if the request queue is full then there is no hope
 164     if (masterPort.reqQueueFull()) {
 165         DPRINTF(Bridge, "Request queue full\n");
 166         retryReq = true;
 167     } else {
 168         // look at the response queue if we expect to see a response
 169         bool expects_response = pkt->needsResponse();
 170         if (expects_response) {
 171             if (respQueueFull()) {
 172                 DPRINTF(Bridge, "Response queue full\n");
 173                 retryReq = true;
 174             } else {
 175                 // ok to send the request with space for the response
 176                 DPRINTF(Bridge, "Reserving space for response\n");
 177                 assert(outstandingResponses != respQueueLimit);
 178                 ++outstandingResponses;
 179
 180                 // no need to set retryReq to false as this is already the
 181                 // case
 182             }
 183         }
 184
 185         if (!retryReq) {
 186             // technically the packet only reaches us after the header
 187             // delay, and typically we also need to deserialise any
 188             // payload (unless the two sides of the bridge are
 189             // synchronous)
 190             Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
 191             pkt->headerDelay = pkt->payloadDelay = 0;
 192
 193             masterPort.schedTimingReq(pkt, bridge.clockEdge(delay) +
 194                                       receive_delay);
 195         }
 196     }
 197
 198     // remember that we are now stalling a packet and that we have to
 199     // tell the sending master to retry once space becomes available,
 200     // we make no distinction whether the stalling is due to the
 201     // request queue or response queue being full
 202     return !retryReq;
 203 }
 204
 205 void
 206 Bridge::BridgeSlavePort::retryStalledReq()
 207 {
 208     if (retryReq) {
 209         DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 210         retryReq = false;
 211         sendRetryReq();
 212     }
 213 }
 214
 215 void
 216 Bridge::BridgeMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
 217 {
 218     // If we're about to put this packet at the head of the queue, we
 219     // need to schedule an event to do the transmit.  Otherwise there
 220     // should already be an event scheduled for sending the head
 221     // packet.
 222     if (transmitList.empty()) {
 223         bridge.schedule(sendEvent, when);
 224     }
 225
 226     assert(transmitList.size() != reqQueueLimit);
 227
 228     transmitList.emplace_back(pkt, when);
 229 }
 230
 231
 232 void
 233 Bridge::BridgeSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
 234 {
 235     // If we're about to put this packet at the head of the queue, we
 236     // need to schedule an event to do the transmit.  Otherwise there
 237     // should already be an event scheduled for sending the head
 238     // packet.
 239     if (transmitList.empty()) {
 240         bridge.schedule(sendEvent, when);
 241     }
 242
 243     transmitList.emplace_back(pkt, when);
 244 }
 245
 246 void
 247 Bridge::BridgeMasterPort::trySendTiming()
 248 {
 249     assert(!transmitList.empty());
 250
 251     DeferredPacket req = transmitList.front();
 252
 253     assert(req.tick <= curTick());
 254
 255     PacketPtr pkt = req.pkt;
 256
 257     DPRINTF(Bridge, "trySend request addr 0x%x, queue size %d\n",
 258             pkt->getAddr(), transmitList.size());
 259
 260     if (sendTimingReq(pkt)) {
 261         // send successful
 262         transmitList.pop_front();
 263         DPRINTF(Bridge, "trySend request successful\n");
 264
 265         // If there are more packets to send, schedule event to try again.
 266         if (!transmitList.empty()) {
 267             DeferredPacket next_req = transmitList.front();
 268             DPRINTF(Bridge, "Scheduling next send\n");
 269             bridge.schedule(sendEvent, std::max(next_req.tick,
 270                                                 bridge.clockEdge()));
 271         }
 272
 273         // if we have stalled a request due to a full request queue,
 274         // then send a retry at this point, also note that if the
 275         // request we stalled was waiting for the response queue
 276         // rather than the request queue we might stall it again
 277         slavePort.retryStalledReq();
 278     }
 279
 280     // if the send failed, then we try again once we receive a retry,
 281     // and therefore there is no need to take any action
 282 }
 283
 284 void
 285 Bridge::BridgeSlavePort::trySendTiming()
 286 {
 287     assert(!transmitList.empty());
 288
 289     DeferredPacket resp = transmitList.front();
 290
 291     assert(resp.tick <= curTick());
 292
 293     PacketPtr pkt = resp.pkt;
 294
 295     DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
 296             pkt->getAddr(), outstandingResponses);
 297
 298     if (sendTimingResp(pkt)) {
 299         // send successful
 300         transmitList.pop_front();
 301         DPRINTF(Bridge, "trySend response successful\n");
 302
 303         assert(outstandingResponses != 0);
 304         --outstandingResponses;
 305
 306         // If there are more packets to send, schedule event to try again.
 307         if (!transmitList.empty()) {
 308             DeferredPacket next_resp = transmitList.front();
 309             DPRINTF(Bridge, "Scheduling next send\n");
 310             bridge.schedule(sendEvent, std::max(next_resp.tick,
 311                                                 bridge.clockEdge()));
 312         }
 313
 314         // if there is space in the request queue and we were stalling
 315         // a request, it will definitely be possible to accept it now
 316         // since there is guaranteed space in the response queue
 317         if (!masterPort.reqQueueFull() && retryReq) {
 318             DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 319             retryReq = false;
 320             sendRetryReq();
 321         }
 322     }
 323
 324     // if the send failed, then we try again once we receive a retry,
 325     // and therefore there is no need to take any action
 326 }
 327
 328 void
 329 Bridge::BridgeMasterPort::recvReqRetry()
 330 {
 331     trySendTiming();
 332 }
 333
 334 void
 335 Bridge::BridgeSlavePort::recvRespRetry()
 336 {
 337     trySendTiming();
 338 }
 339
 340 Tick
 341 Bridge::BridgeSlavePort::recvAtomic(PacketPtr pkt)
 342 {
 343     panic_if(pkt->cacheResponding(), "Should not see packets where cache "
 344              "is responding");
 345
 346     return delay * bridge.clockPeriod() + masterPort.sendAtomic(pkt);
 347 }
 348
 349 void
 350 Bridge::BridgeSlavePort::recvFunctional(PacketPtr pkt)
 351 {
 352     pkt->pushLabel(name());
 353
 354     // check the response queue
 355     for (auto i = transmitList.begin();  i != transmitList.end(); ++i) {
 356         if (pkt->trySatisfyFunctional((*i).pkt)) {
 357             pkt->makeResponse();
 358             return;
 359         }
 360     }
 361
 362     // also check the master port's request queue
 363     if (masterPort.trySatisfyFunctional(pkt)) {
 364         return;
 365     }
 366
 367     pkt->popLabel();
 368
 369     // fall through if pkt still not satisfied
 370     masterPort.sendFunctional(pkt);
 371 }
 372
 373 bool
 374 Bridge::BridgeMasterPort::trySatisfyFunctional(PacketPtr pkt)
 375 {
 376     bool found = false;
 377     auto i = transmitList.begin();
 378
 379     while (i != transmitList.end() && !found) {
 380         if (pkt->trySatisfyFunctional((*i).pkt)) {
 381             pkt->makeResponse();
 382             found = true;
 383         }
 384         ++i;
 385     }
 386
 387     return found;
 388 }
 389
 390 AddrRangeList
 391 Bridge::BridgeSlavePort::getAddrRanges() const
 392 {
 393     return ranges;
 394 }
 395
 396 Bridge *
 397 BridgeParams::create()
 398 {
 399     return new Bridge(this);
 400 }