src/mem/bus.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 /**
  32  * @file
  33  * Definition of a bus object.
  34  */
  35
  36
  37 #include "base/misc.hh"
  38 #include "base/trace.hh"
  39 #include "mem/bus.hh"
  40 #include "sim/builder.hh"
  41
  42 Port *
  43 Bus::getPort(const std::string &if_name, int idx)
  44 {
  45     if (if_name == "default")
  46         if (defaultPort == NULL) {
  47             defaultPort = new BusPort(csprintf("%s-default",name()), this,
  48                     defaultId);
  49             return defaultPort;
  50         } else
  51             fatal("Default port already set\n");
  52
  53     // if_name ignored?  forced to be empty?
  54     int id = interfaces.size();
  55     BusPort *bp = new BusPort(csprintf("%s-p%d", name(), id), this, id);
  56     interfaces.push_back(bp);
  57     return bp;
  58 }
  59
  60 /** Get the ranges of anyone other buses that we are connected to. */
  61 void
  62 Bus::init()
  63 {
  64     std::vector<BusPort*>::iterator intIter;
  65
  66     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
  67         (*intIter)->sendStatusChange(Port::RangeChange);
  68 }
  69
  70 Bus::BusFreeEvent::BusFreeEvent(Bus *_bus) : Event(&mainEventQueue), bus(_bus)
  71 {}
  72
  73 void Bus::BusFreeEvent::process()
  74 {
  75     bus->recvRetry(-1);
  76 }
  77
  78 const char * Bus::BusFreeEvent::description()
  79 {
  80     return "bus became available";
  81 }
  82
  83 void Bus::occupyBus(PacketPtr pkt)
  84 {
  85     //Bring tickNextIdle up to the present tick
  86     //There is some potential ambiguity where a cycle starts, which might make
  87     //a difference when devices are acting right around a cycle boundary. Using
  88     //a < allows things which happen exactly on a cycle boundary to take up only
  89     //the following cycle. Anthing that happens later will have to "wait" for
  90     //the end of that cycle, and then start using the bus after that.
  91     while (tickNextIdle < curTick)
  92         tickNextIdle += clock;
  93
  94     // The packet will be sent. Figure out how long it occupies the bus, and
  95     // how much of that time is for the first "word", aka bus width.
  96     int numCycles = 0;
  97     // Requests need one cycle to send an address
  98     if (pkt->isRequest())
  99         numCycles++;
 100     else if (pkt->isResponse() || pkt->hasData()) {
 101         // If a packet has data, it needs ceil(size/width) cycles to send it
 102         // We're using the "adding instead of dividing" trick again here
 103         if (pkt->hasData()) {
 104             int dataSize = pkt->getSize();
 105             for (int transmitted = 0; transmitted < dataSize;
 106                     transmitted += width) {
 107                 numCycles++;
 108             }
 109         } else {
 110             // If the packet didn't have data, it must have been a response.
 111             // Those use the bus for one cycle to send their data.
 112             numCycles++;
 113         }
 114     }
 115
 116     // The first word will be delivered after the current tick, the delivery
 117     // of the address if any, and one bus cycle to deliver the data
 118     pkt->firstWordTime =
 119         tickNextIdle +
 120         pkt->isRequest() ? clock : 0 +
 121         clock;
 122
 123     //Advance it numCycles bus cycles.
 124     //XXX Should this use the repeated addition trick as well?
 125     tickNextIdle += (numCycles * clock);
 126     if (!busIdle.scheduled()) {
 127         busIdle.schedule(tickNextIdle);
 128     } else {
 129         busIdle.reschedule(tickNextIdle);
 130     }
 131     DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
 132             curTick, tickNextIdle);
 133
 134     // The bus will become idle once the current packet is delivered.
 135     pkt->finishTime = tickNextIdle;
 136 }
 137
 138 /** Function called by the port when the bus is receiving a Timing
 139  * transaction.*/
 140 bool
 141 Bus::recvTiming(Packet *pkt)
 142 {
 143     Port *port;
 144     DPRINTF(Bus, "recvTiming: packet src %d dest %d addr 0x%x cmd %s\n",
 145             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 146
 147     BusPort *pktPort = interfaces[pkt->getSrc()];
 148
 149     // If the bus is busy, or other devices are in line ahead of the current
 150     // one, put this device on the retry list.
 151     if (tickNextIdle > curTick ||
 152             (retryList.size() && (!inRetry || pktPort != retryList.front()))) {
 153         addToRetryList(pktPort);
 154         return false;
 155     }
 156
 157     short dest = pkt->getDest();
 158     if (dest == Packet::Broadcast) {
 159         if (timingSnoop(pkt)) {
 160             pkt->flags |= SNOOP_COMMIT;
 161             bool success = timingSnoop(pkt);
 162             assert(success);
 163             if (pkt->flags & SATISFIED) {
 164                 //Cache-Cache transfer occuring
 165                 if (inRetry) {
 166                     retryList.front()->onRetryList(false);
 167                     retryList.pop_front();
 168                     inRetry = false;
 169                 }
 170                 occupyBus(pkt);
 171                 return true;
 172             }
 173             port = findPort(pkt->getAddr(), pkt->getSrc());
 174         } else {
 175             //Snoop didn't succeed
 176             addToRetryList(pktPort);
 177             return false;
 178         }
 179     } else {
 180         assert(dest >= 0 && dest < interfaces.size());
 181         assert(dest != pkt->getSrc()); // catch infinite loops
 182         port = interfaces[dest];
 183     }
 184
 185     occupyBus(pkt);
 186
 187     if (port->sendTiming(pkt))  {
 188         // Packet was successfully sent. Return true.
 189         // Also take care of retries
 190         if (inRetry) {
 191             DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
 192             retryList.front()->onRetryList(false);
 193             retryList.pop_front();
 194             inRetry = false;
 195         }
 196         return true;
 197     }
 198
 199     // Packet not successfully sent. Leave or put it on the retry list.
 200     DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 201     addToRetryList(pktPort);
 202     return false;
 203 }
 204
 205 void
 206 Bus::recvRetry(int id)
 207 {
 208     DPRINTF(Bus, "Received a retry\n");
 209     // If there's anything waiting, and the bus isn't busy...
 210     if (retryList.size() && curTick >= tickNextIdle) {
 211         //retryingPort = retryList.front();
 212         inRetry = true;
 213         DPRINTF(Bus, "Sending a retry\n");
 214         retryList.front()->sendRetry();
 215         // If inRetry is still true, sendTiming wasn't called
 216         if (inRetry)
 217         {
 218             retryList.front()->onRetryList(false);
 219             retryList.pop_front();
 220             inRetry = false;
 221
 222             //Bring tickNextIdle up to the present
 223             while (tickNextIdle < curTick)
 224                 tickNextIdle += clock;
 225
 226             //Burn a cycle for the missed grant.
 227             tickNextIdle += clock;
 228
 229             if (!busIdle.scheduled()) {
 230                 busIdle.schedule(tickNextIdle);
 231             } else {
 232                 busIdle.reschedule(tickNextIdle);
 233             }
 234         }
 235     }
 236 }
 237
 238 Port *
 239 Bus::findPort(Addr addr, int id)
 240 {
 241     /* An interval tree would be a better way to do this. --ali. */
 242     int dest_id = -1;
 243     int i = 0;
 244     bool found = false;
 245     AddrRangeIter iter;
 246
 247     while (i < portList.size() && !found)
 248     {
 249         if (portList[i].range == addr) {
 250             dest_id = portList[i].portId;
 251             found = true;
 252             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 253         }
 254         i++;
 255     }
 256
 257     // Check if this matches the default range
 258     if (dest_id == -1) {
 259         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 260             if (*iter == addr) {
 261                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 262                 return defaultPort;
 263             }
 264         }
 265         panic("Unable to find destination for addr: %#llx", addr);
 266     }
 267
 268
 269     // we shouldn't be sending this back to where it came from
 270     assert(dest_id != id);
 271
 272     return interfaces[dest_id];
 273 }
 274
 275 std::vector<int>
 276 Bus::findSnoopPorts(Addr addr, int id)
 277 {
 278     int i = 0;
 279     AddrRangeIter iter;
 280     std::vector<int> ports;
 281
 282     while (i < portSnoopList.size())
 283     {
 284         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 285             //Careful  to not overlap ranges
 286             //or snoop will be called more than once on the port
 287             ports.push_back(portSnoopList[i].portId);
 288 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 289 //                    portSnoopList[i].portId);
 290         }
 291         i++;
 292     }
 293     return ports;
 294 }
 295
 296 Tick
 297 Bus::atomicSnoop(Packet *pkt)
 298 {
 299     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 300     Tick response_time = 0;
 301
 302     while (!ports.empty())
 303     {
 304         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 305         if (response) {
 306             assert(!response_time);  //Multiple responders
 307             response_time = response;
 308         }
 309         ports.pop_back();
 310     }
 311     return response_time;
 312 }
 313
 314 void
 315 Bus::functionalSnoop(Packet *pkt)
 316 {
 317     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 318
 319     while (!ports.empty())
 320     {
 321         interfaces[ports.back()]->sendFunctional(pkt);
 322         ports.pop_back();
 323     }
 324 }
 325
 326 bool
 327 Bus::timingSnoop(Packet *pkt)
 328 {
 329     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 330     bool success = true;
 331
 332     while (!ports.empty() && success)
 333     {
 334         success = interfaces[ports.back()]->sendTiming(pkt);
 335         ports.pop_back();
 336     }
 337
 338     return success;
 339 }
 340
 341
 342 /** Function called by the port when the bus is receiving a Atomic
 343  * transaction.*/
 344 Tick
 345 Bus::recvAtomic(Packet *pkt)
 346 {
 347     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 348             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 349     assert(pkt->getDest() == Packet::Broadcast);
 350     Tick snoopTime = atomicSnoop(pkt);
 351     if (snoopTime)
 352         return snoopTime;  //Snoop satisfies it
 353     else
 354         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 355 }
 356
 357 /** Function called by the port when the bus is receiving a Functional
 358  * transaction.*/
 359 void
 360 Bus::recvFunctional(Packet *pkt)
 361 {
 362     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 363             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 364     assert(pkt->getDest() == Packet::Broadcast);
 365     functionalSnoop(pkt);
 366     findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 367 }
 368
 369 /** Function called by the port when the bus is receiving a status change.*/
 370 void
 371 Bus::recvStatusChange(Port::Status status, int id)
 372 {
 373     AddrRangeList ranges;
 374     AddrRangeList snoops;
 375     int x;
 376     AddrRangeIter iter;
 377
 378     assert(status == Port::RangeChange &&
 379            "The other statuses need to be implemented.");
 380
 381     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 382
 383     if (id == defaultId) {
 384         defaultRange.clear();
 385         defaultPort->getPeerAddressRanges(ranges, snoops);
 386         assert(snoops.size() == 0);
 387         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 388             defaultRange.push_back(*iter);
 389             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 390                     iter->start, iter->end);
 391         }
 392     } else {
 393
 394         assert((id < interfaces.size() && id >= 0) || id == -1);
 395         Port *port = interfaces[id];
 396         std::vector<DevMap>::iterator portIter;
 397         std::vector<DevMap>::iterator snoopIter;
 398
 399         // Clean out any previously existent ids
 400         for (portIter = portList.begin(); portIter != portList.end(); ) {
 401             if (portIter->portId == id)
 402                 portIter = portList.erase(portIter);
 403             else
 404                 portIter++;
 405         }
 406
 407         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 408             if (snoopIter->portId == id)
 409                 snoopIter = portSnoopList.erase(snoopIter);
 410             else
 411                 snoopIter++;
 412         }
 413
 414         port->getPeerAddressRanges(ranges, snoops);
 415
 416         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 417             DevMap dm;
 418             dm.portId = id;
 419             dm.range = *iter;
 420
 421             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 422                     dm.range.start, dm.range.end, id);
 423             portSnoopList.push_back(dm);
 424         }
 425
 426         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 427             DevMap dm;
 428             dm.portId = id;
 429             dm.range = *iter;
 430
 431             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 432                     dm.range.start, dm.range.end, id);
 433             portList.push_back(dm);
 434         }
 435     }
 436     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 437
 438     // tell all our peers that our address range has changed.
 439     // Don't tell the device that caused this change, it already knows
 440     for (x = 0; x < interfaces.size(); x++)
 441         if (x != id)
 442             interfaces[x]->sendStatusChange(Port::RangeChange);
 443
 444     if (id != defaultId && defaultPort)
 445         defaultPort->sendStatusChange(Port::RangeChange);
 446 }
 447
 448 void
 449 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 450 {
 451     std::vector<DevMap>::iterator portIter;
 452     AddrRangeIter dflt_iter;
 453     bool subset;
 454
 455     resp.clear();
 456     snoop.clear();
 457
 458     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 459
 460     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 461             dflt_iter++) {
 462         resp.push_back(*dflt_iter);
 463         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 464                 dflt_iter->end);
 465     }
 466     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 467         subset = false;
 468         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 469                 dflt_iter++) {
 470             if ((portIter->range.start < dflt_iter->start &&
 471                 portIter->range.end >= dflt_iter->start) ||
 472                (portIter->range.start < dflt_iter->end &&
 473                 portIter->range.end >= dflt_iter->end))
 474                 fatal("Devices can not set ranges that itersect the default set\
 475                         but are not a subset of the default set.\n");
 476             if (portIter->range.start >= dflt_iter->start &&
 477                 portIter->range.end <= dflt_iter->end) {
 478                 subset = true;
 479                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 480                     portIter->range.start, portIter->range.end);
 481             }
 482         }
 483         if (portIter->portId != id && !subset) {
 484             resp.push_back(portIter->range);
 485             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 486                     portIter->range.start, portIter->range.end);
 487         }
 488     }
 489 }
 490
 491 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 492
 493     Param<int> bus_id;
 494     Param<int> clock;
 495     Param<int> width;
 496
 497 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 498
 499 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 500     INIT_PARAM(bus_id, "a globally unique bus id"),
 501     INIT_PARAM(clock, "bus clock speed"),
 502     INIT_PARAM(width, "width of the bus (bits)")
 503 END_INIT_SIM_OBJECT_PARAMS(Bus)
 504
 505 CREATE_SIM_OBJECT(Bus)
 506 {
 507     return new Bus(getInstanceName(), bus_id, clock, width);
 508 }
 509
 510 REGISTER_SIM_OBJECT("Bus", Bus)