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 "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     // technically the packet only reaches us after the header delay,
 140     // and typically we also need to deserialise any payload (unless
 141     // the two sides of the bridge are synchronous)
 142     Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
 143     pkt->headerDelay = pkt->payloadDelay = 0;
 144
 145     slavePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
 146                               receive_delay);
 147
 148     return true;
 149 }
 150
 151 bool
 152 Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
 153 {
 154     DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
 155             pkt->cmdString(), pkt->getAddr());
 156
 157     // if a cache is responding, sink the packet without further
 158     // action, also discard any packet that is not a read or a write
 159     if (pkt->cacheResponding() ||
 160         !(pkt->isWrite() || pkt->isRead())) {
 161         assert(!pkt->needsResponse());
 162         pendingDelete.reset(pkt);
 163         return true;
 164     }
 165
 166     // we should not get a new request after committing to retry the
 167     // current one, but unfortunately the CPU violates this rule, so
 168     // simply ignore it for now
 169     if (retryReq)
 170         return false;
 171
 172     DPRINTF(Bridge, "Response queue size: %d outresp: %d\n",
 173             transmitList.size(), outstandingResponses);
 174
 175     // if the request queue is full then there is no hope
 176     if (masterPort.reqQueueFull()) {
 177         DPRINTF(Bridge, "Request queue full\n");
 178         retryReq = true;
 179     } else {
 180         // look at the response queue if we expect to see a response
 181         bool expects_response = pkt->needsResponse();
 182         if (expects_response) {
 183             if (respQueueFull()) {
 184                 DPRINTF(Bridge, "Response queue full\n");
 185                 retryReq = true;
 186             } else {
 187                 // ok to send the request with space for the response
 188                 DPRINTF(Bridge, "Reserving space for response\n");
 189                 assert(outstandingResponses != respQueueLimit);
 190                 ++outstandingResponses;
 191
 192                 // no need to set retryReq to false as this is already the
 193                 // case
 194             }
 195         }
 196
 197         if (!retryReq) {
 198             // technically the packet only reaches us after the header
 199             // delay, and typically we also need to deserialise any
 200             // payload (unless the two sides of the bridge are
 201             // synchronous)
 202             Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
 203             pkt->headerDelay = pkt->payloadDelay = 0;
 204
 205             masterPort.schedTimingReq(pkt, bridge.clockEdge(delay) +
 206                                       receive_delay);
 207         }
 208     }
 209
 210     // remember that we are now stalling a packet and that we have to
 211     // tell the sending master to retry once space becomes available,
 212     // we make no distinction whether the stalling is due to the
 213     // request queue or response queue being full
 214     return !retryReq;
 215 }
 216
 217 void
 218 Bridge::BridgeSlavePort::retryStalledReq()
 219 {
 220     if (retryReq) {
 221         DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 222         retryReq = false;
 223         sendRetryReq();
 224     }
 225 }
 226
 227 void
 228 Bridge::BridgeMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
 229 {
 230     // If we're about to put this packet at the head of the queue, we
 231     // need to schedule an event to do the transmit.  Otherwise there
 232     // should already be an event scheduled for sending the head
 233     // packet.
 234     if (transmitList.empty()) {
 235         bridge.schedule(sendEvent, when);
 236     }
 237
 238     assert(transmitList.size() != reqQueueLimit);
 239
 240     transmitList.emplace_back(pkt, when);
 241 }
 242
 243
 244 void
 245 Bridge::BridgeSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
 246 {
 247     // If we're about to put this packet at the head of the queue, we
 248     // need to schedule an event to do the transmit.  Otherwise there
 249     // should already be an event scheduled for sending the head
 250     // packet.
 251     if (transmitList.empty()) {
 252         bridge.schedule(sendEvent, when);
 253     }
 254
 255     transmitList.emplace_back(pkt, when);
 256 }
 257
 258 void
 259 Bridge::BridgeMasterPort::trySendTiming()
 260 {
 261     assert(!transmitList.empty());
 262
 263     DeferredPacket req = transmitList.front();
 264
 265     assert(req.tick <= curTick());
 266
 267     PacketPtr pkt = req.pkt;
 268
 269     DPRINTF(Bridge, "trySend request addr 0x%x, queue size %d\n",
 270             pkt->getAddr(), transmitList.size());
 271
 272     if (sendTimingReq(pkt)) {
 273         // send successful
 274         transmitList.pop_front();
 275         DPRINTF(Bridge, "trySend request successful\n");
 276
 277         // If there are more packets to send, schedule event to try again.
 278         if (!transmitList.empty()) {
 279             DeferredPacket next_req = transmitList.front();
 280             DPRINTF(Bridge, "Scheduling next send\n");
 281             bridge.schedule(sendEvent, std::max(next_req.tick,
 282                                                 bridge.clockEdge()));
 283         }
 284
 285         // if we have stalled a request due to a full request queue,
 286         // then send a retry at this point, also note that if the
 287         // request we stalled was waiting for the response queue
 288         // rather than the request queue we might stall it again
 289         slavePort.retryStalledReq();
 290     }
 291
 292     // if the send failed, then we try again once we receive a retry,
 293     // and therefore there is no need to take any action
 294 }
 295
 296 void
 297 Bridge::BridgeSlavePort::trySendTiming()
 298 {
 299     assert(!transmitList.empty());
 300
 301     DeferredPacket resp = transmitList.front();
 302
 303     assert(resp.tick <= curTick());
 304
 305     PacketPtr pkt = resp.pkt;
 306
 307     DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
 308             pkt->getAddr(), outstandingResponses);
 309
 310     if (sendTimingResp(pkt)) {
 311         // send successful
 312         transmitList.pop_front();
 313         DPRINTF(Bridge, "trySend response successful\n");
 314
 315         assert(outstandingResponses != 0);
 316         --outstandingResponses;
 317
 318         // If there are more packets to send, schedule event to try again.
 319         if (!transmitList.empty()) {
 320             DeferredPacket next_resp = transmitList.front();
 321             DPRINTF(Bridge, "Scheduling next send\n");
 322             bridge.schedule(sendEvent, std::max(next_resp.tick,
 323                                                 bridge.clockEdge()));
 324         }
 325
 326         // if there is space in the request queue and we were stalling
 327         // a request, it will definitely be possible to accept it now
 328         // since there is guaranteed space in the response queue
 329         if (!masterPort.reqQueueFull() && retryReq) {
 330             DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
 331             retryReq = false;
 332             sendRetryReq();
 333         }
 334     }
 335
 336     // if the send failed, then we try again once we receive a retry,
 337     // and therefore there is no need to take any action
 338 }
 339
 340 void
 341 Bridge::BridgeMasterPort::recvReqRetry()
 342 {
 343     trySendTiming();
 344 }
 345
 346 void
 347 Bridge::BridgeSlavePort::recvRespRetry()
 348 {
 349     trySendTiming();
 350 }
 351
 352 Tick
 353 Bridge::BridgeSlavePort::recvAtomic(PacketPtr pkt)
 354 {
 355     return delay * bridge.clockPeriod() + masterPort.sendAtomic(pkt);
 356 }
 357
 358 void
 359 Bridge::BridgeSlavePort::recvFunctional(PacketPtr pkt)
 360 {
 361     pkt->pushLabel(name());
 362
 363     // check the response queue
 364     for (auto i = transmitList.begin();  i != transmitList.end(); ++i) {
 365         if (pkt->checkFunctional((*i).pkt)) {
 366             pkt->makeResponse();
 367             return;
 368         }
 369     }
 370
 371     // also check the master port's request queue
 372     if (masterPort.checkFunctional(pkt)) {
 373         return;
 374     }
 375
 376     pkt->popLabel();
 377
 378     // fall through if pkt still not satisfied
 379     masterPort.sendFunctional(pkt);
 380 }
 381
 382 bool
 383 Bridge::BridgeMasterPort::checkFunctional(PacketPtr pkt)
 384 {
 385     bool found = false;
 386     auto i = transmitList.begin();
 387
 388     while (i != transmitList.end() && !found) {
 389         if (pkt->checkFunctional((*i).pkt)) {
 390             pkt->makeResponse();
 391             found = true;
 392         }
 393         ++i;
 394     }
 395
 396     return found;
 397 }
 398
 399 AddrRangeList
 400 Bridge::BridgeSlavePort::getAddrRanges() const
 401 {
 402     return ranges;
 403 }
 404
 405 Bridge *
 406 BridgeParams::create()
 407 {
 408     return new Bridge(this);
 409 }