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             DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 177             addToRetryList(pktPort);
 178             return false;
 179         }
 180     } else {
 181         assert(dest >= 0 && dest < interfaces.size());
 182         assert(dest != pkt->getSrc()); // catch infinite loops
 183         port = interfaces[dest];
 184     }
 185
 186     occupyBus(pkt);
 187
 188     if (port->sendTiming(pkt))  {
 189         // Packet was successfully sent. Return true.
 190         // Also take care of retries
 191         if (inRetry) {
 192             DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
 193             retryList.front()->onRetryList(false);
 194             retryList.pop_front();
 195             inRetry = false;
 196         }
 197         return true;
 198     }
 199
 200     // Packet not successfully sent. Leave or put it on the retry list.
 201     DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 202     addToRetryList(pktPort);
 203     return false;
 204 }
 205
 206 void
 207 Bus::recvRetry(int id)
 208 {
 209     DPRINTF(Bus, "Received a retry\n");
 210     // If there's anything waiting, and the bus isn't busy...
 211     if (retryList.size() && curTick >= tickNextIdle) {
 212         //retryingPort = retryList.front();
 213         inRetry = true;
 214         DPRINTF(Bus, "Sending a retry\n");
 215         retryList.front()->sendRetry();
 216         // If inRetry is still true, sendTiming wasn't called
 217         if (inRetry)
 218         {
 219             retryList.front()->onRetryList(false);
 220             retryList.pop_front();
 221             inRetry = false;
 222
 223             //Bring tickNextIdle up to the present
 224             while (tickNextIdle < curTick)
 225                 tickNextIdle += clock;
 226
 227             //Burn a cycle for the missed grant.
 228             tickNextIdle += clock;
 229
 230             if (!busIdle.scheduled()) {
 231                 busIdle.schedule(tickNextIdle);
 232             } else {
 233                 busIdle.reschedule(tickNextIdle);
 234             }
 235         }
 236     }
 237 }
 238
 239 Port *
 240 Bus::findPort(Addr addr, int id)
 241 {
 242     /* An interval tree would be a better way to do this. --ali. */
 243     int dest_id = -1;
 244     int i = 0;
 245     bool found = false;
 246     AddrRangeIter iter;
 247
 248     while (i < portList.size() && !found)
 249     {
 250         if (portList[i].range == addr) {
 251             dest_id = portList[i].portId;
 252             found = true;
 253             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 254         }
 255         i++;
 256     }
 257
 258     // Check if this matches the default range
 259     if (dest_id == -1) {
 260         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 261             if (*iter == addr) {
 262                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 263                 return defaultPort;
 264             }
 265         }
 266         panic("Unable to find destination for addr: %#llx", addr);
 267     }
 268
 269
 270     // we shouldn't be sending this back to where it came from
 271     assert(dest_id != id);
 272
 273     return interfaces[dest_id];
 274 }
 275
 276 std::vector<int>
 277 Bus::findSnoopPorts(Addr addr, int id)
 278 {
 279     int i = 0;
 280     AddrRangeIter iter;
 281     std::vector<int> ports;
 282
 283     while (i < portSnoopList.size())
 284     {
 285         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 286             //Careful  to not overlap ranges
 287             //or snoop will be called more than once on the port
 288             ports.push_back(portSnoopList[i].portId);
 289 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 290 //                    portSnoopList[i].portId);
 291         }
 292         i++;
 293     }
 294     return ports;
 295 }
 296
 297 Tick
 298 Bus::atomicSnoop(Packet *pkt)
 299 {
 300     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 301     Tick response_time = 0;
 302
 303     while (!ports.empty())
 304     {
 305         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 306         if (response) {
 307             assert(!response_time);  //Multiple responders
 308             response_time = response;
 309         }
 310         ports.pop_back();
 311     }
 312     return response_time;
 313 }
 314
 315 void
 316 Bus::functionalSnoop(Packet *pkt)
 317 {
 318     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 319
 320     while (!ports.empty())
 321     {
 322         interfaces[ports.back()]->sendFunctional(pkt);
 323         ports.pop_back();
 324     }
 325 }
 326
 327 bool
 328 Bus::timingSnoop(Packet *pkt)
 329 {
 330     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 331     bool success = true;
 332
 333     while (!ports.empty() && success)
 334     {
 335         success = interfaces[ports.back()]->sendTiming(pkt);
 336         ports.pop_back();
 337     }
 338
 339     return success;
 340 }
 341
 342
 343 /** Function called by the port when the bus is receiving a Atomic
 344  * transaction.*/
 345 Tick
 346 Bus::recvAtomic(Packet *pkt)
 347 {
 348     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 349             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 350     assert(pkt->getDest() == Packet::Broadcast);
 351     Tick snoopTime = atomicSnoop(pkt);
 352     if (snoopTime)
 353         return snoopTime;  //Snoop satisfies it
 354     else
 355         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 356 }
 357
 358 /** Function called by the port when the bus is receiving a Functional
 359  * transaction.*/
 360 void
 361 Bus::recvFunctional(Packet *pkt)
 362 {
 363     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 364             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 365     assert(pkt->getDest() == Packet::Broadcast);
 366     functionalSnoop(pkt);
 367     findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 368 }
 369
 370 /** Function called by the port when the bus is receiving a status change.*/
 371 void
 372 Bus::recvStatusChange(Port::Status status, int id)
 373 {
 374     AddrRangeList ranges;
 375     AddrRangeList snoops;
 376     int x;
 377     AddrRangeIter iter;
 378
 379     assert(status == Port::RangeChange &&
 380            "The other statuses need to be implemented.");
 381
 382     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 383
 384     if (id == defaultId) {
 385         defaultRange.clear();
 386         defaultPort->getPeerAddressRanges(ranges, snoops);
 387         assert(snoops.size() == 0);
 388         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 389             defaultRange.push_back(*iter);
 390             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 391                     iter->start, iter->end);
 392         }
 393     } else {
 394
 395         assert((id < interfaces.size() && id >= 0) || id == -1);
 396         Port *port = interfaces[id];
 397         std::vector<DevMap>::iterator portIter;
 398         std::vector<DevMap>::iterator snoopIter;
 399
 400         // Clean out any previously existent ids
 401         for (portIter = portList.begin(); portIter != portList.end(); ) {
 402             if (portIter->portId == id)
 403                 portIter = portList.erase(portIter);
 404             else
 405                 portIter++;
 406         }
 407
 408         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 409             if (snoopIter->portId == id)
 410                 snoopIter = portSnoopList.erase(snoopIter);
 411             else
 412                 snoopIter++;
 413         }
 414
 415         port->getPeerAddressRanges(ranges, snoops);
 416
 417         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 418             DevMap dm;
 419             dm.portId = id;
 420             dm.range = *iter;
 421
 422             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 423                     dm.range.start, dm.range.end, id);
 424             portSnoopList.push_back(dm);
 425         }
 426
 427         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 428             DevMap dm;
 429             dm.portId = id;
 430             dm.range = *iter;
 431
 432             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 433                     dm.range.start, dm.range.end, id);
 434             portList.push_back(dm);
 435         }
 436     }
 437     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 438
 439     // tell all our peers that our address range has changed.
 440     // Don't tell the device that caused this change, it already knows
 441     for (x = 0; x < interfaces.size(); x++)
 442         if (x != id)
 443             interfaces[x]->sendStatusChange(Port::RangeChange);
 444
 445     if (id != defaultId && defaultPort)
 446         defaultPort->sendStatusChange(Port::RangeChange);
 447 }
 448
 449 void
 450 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 451 {
 452     std::vector<DevMap>::iterator portIter;
 453     AddrRangeIter dflt_iter;
 454     bool subset;
 455
 456     resp.clear();
 457     snoop.clear();
 458
 459     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 460
 461     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 462             dflt_iter++) {
 463         resp.push_back(*dflt_iter);
 464         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 465                 dflt_iter->end);
 466     }
 467     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 468         subset = false;
 469         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 470                 dflt_iter++) {
 471             if ((portIter->range.start < dflt_iter->start &&
 472                 portIter->range.end >= dflt_iter->start) ||
 473                (portIter->range.start < dflt_iter->end &&
 474                 portIter->range.end >= dflt_iter->end))
 475                 fatal("Devices can not set ranges that itersect the default set\
 476                         but are not a subset of the default set.\n");
 477             if (portIter->range.start >= dflt_iter->start &&
 478                 portIter->range.end <= dflt_iter->end) {
 479                 subset = true;
 480                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 481                     portIter->range.start, portIter->range.end);
 482             }
 483         }
 484         if (portIter->portId != id && !subset) {
 485             resp.push_back(portIter->range);
 486             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 487                     portIter->range.start, portIter->range.end);
 488         }
 489     }
 490 }
 491
 492 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 493
 494     Param<int> bus_id;
 495     Param<int> clock;
 496     Param<int> width;
 497
 498 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 499
 500 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 501     INIT_PARAM(bus_id, "a globally unique bus id"),
 502     INIT_PARAM(clock, "bus clock speed"),
 503     INIT_PARAM(width, "width of the bus (bits)")
 504 END_INIT_SIM_OBJECT_PARAMS(Bus)
 505
 506 CREATE_SIM_OBJECT(Bus)
 507 {
 508     return new Bus(getInstanceName(), bus_id, clock, width);
 509 }
 510
 511 REGISTER_SIM_OBJECT("Bus", Bus)