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;
 148     if (pkt->getSrc() == defaultId)
 149         pktPort = defaultPort;
 150     else pktPort = interfaces[pkt->getSrc()];
 151
 152     // If the bus is busy, or other devices are in line ahead of the current
 153     // one, put this device on the retry list.
 154     if (tickNextIdle > curTick ||
 155             (retryList.size() && (!inRetry || pktPort != retryList.front()))) {
 156         addToRetryList(pktPort);
 157         return false;
 158     }
 159
 160     short dest = pkt->getDest();
 161     if (dest == Packet::Broadcast) {
 162         if (timingSnoop(pkt)) {
 163             pkt->flags |= SNOOP_COMMIT;
 164             bool success = timingSnoop(pkt);
 165             assert(success);
 166             if (pkt->flags & SATISFIED) {
 167                 //Cache-Cache transfer occuring
 168                 if (inRetry) {
 169                     retryList.front()->onRetryList(false);
 170                     retryList.pop_front();
 171                     inRetry = false;
 172                 }
 173                 occupyBus(pkt);
 174                 return true;
 175             }
 176             port = findPort(pkt->getAddr(), pkt->getSrc());
 177         } else {
 178             //Snoop didn't succeed
 179             DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 180             addToRetryList(pktPort);
 181             return false;
 182         }
 183     } else {
 184         assert(dest >= 0 && dest < interfaces.size());
 185         assert(dest != pkt->getSrc()); // catch infinite loops
 186         port = interfaces[dest];
 187     }
 188
 189     occupyBus(pkt);
 190
 191     if (port->sendTiming(pkt))  {
 192         // Packet was successfully sent. Return true.
 193         // Also take care of retries
 194         if (inRetry) {
 195             DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
 196             retryList.front()->onRetryList(false);
 197             retryList.pop_front();
 198             inRetry = false;
 199         }
 200         return true;
 201     }
 202
 203     // Packet not successfully sent. Leave or put it on the retry list.
 204     DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 205     addToRetryList(pktPort);
 206     return false;
 207 }
 208
 209 void
 210 Bus::recvRetry(int id)
 211 {
 212     DPRINTF(Bus, "Received a retry\n");
 213     // If there's anything waiting, and the bus isn't busy...
 214     if (retryList.size() && curTick >= tickNextIdle) {
 215         //retryingPort = retryList.front();
 216         inRetry = true;
 217         DPRINTF(Bus, "Sending a retry\n");
 218         retryList.front()->sendRetry();
 219         // If inRetry is still true, sendTiming wasn't called
 220         if (inRetry)
 221         {
 222             retryList.front()->onRetryList(false);
 223             retryList.pop_front();
 224             inRetry = false;
 225
 226             //Bring tickNextIdle up to the present
 227             while (tickNextIdle < curTick)
 228                 tickNextIdle += clock;
 229
 230             //Burn a cycle for the missed grant.
 231             tickNextIdle += clock;
 232
 233             if (!busIdle.scheduled()) {
 234                 busIdle.schedule(tickNextIdle);
 235             } else {
 236                 busIdle.reschedule(tickNextIdle);
 237             }
 238         }
 239     }
 240 }
 241
 242 Port *
 243 Bus::findPort(Addr addr, int id)
 244 {
 245     /* An interval tree would be a better way to do this. --ali. */
 246     int dest_id = -1;
 247     int i = 0;
 248     bool found = false;
 249     AddrRangeIter iter;
 250
 251     while (i < portList.size() && !found)
 252     {
 253         if (portList[i].range == addr) {
 254             dest_id = portList[i].portId;
 255             found = true;
 256             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 257         }
 258         i++;
 259     }
 260
 261     // Check if this matches the default range
 262     if (dest_id == -1) {
 263         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 264             if (*iter == addr) {
 265                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 266                 return defaultPort;
 267             }
 268         }
 269         panic("Unable to find destination for addr: %#llx", addr);
 270     }
 271
 272
 273     // we shouldn't be sending this back to where it came from
 274     assert(dest_id != id);
 275
 276     return interfaces[dest_id];
 277 }
 278
 279 std::vector<int>
 280 Bus::findSnoopPorts(Addr addr, int id)
 281 {
 282     int i = 0;
 283     AddrRangeIter iter;
 284     std::vector<int> ports;
 285
 286     while (i < portSnoopList.size())
 287     {
 288         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 289             //Careful  to not overlap ranges
 290             //or snoop will be called more than once on the port
 291             ports.push_back(portSnoopList[i].portId);
 292 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 293 //                    portSnoopList[i].portId);
 294         }
 295         i++;
 296     }
 297     return ports;
 298 }
 299
 300 Tick
 301 Bus::atomicSnoop(Packet *pkt)
 302 {
 303     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 304     Tick response_time = 0;
 305
 306     while (!ports.empty())
 307     {
 308         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 309         if (response) {
 310             assert(!response_time);  //Multiple responders
 311             response_time = response;
 312         }
 313         ports.pop_back();
 314     }
 315     return response_time;
 316 }
 317
 318 void
 319 Bus::functionalSnoop(Packet *pkt)
 320 {
 321     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 322
 323     while (!ports.empty() && pkt->result != Packet::Success)
 324     {
 325         interfaces[ports.back()]->sendFunctional(pkt);
 326         ports.pop_back();
 327     }
 328 }
 329
 330 bool
 331 Bus::timingSnoop(Packet *pkt)
 332 {
 333     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 334     bool success = true;
 335
 336     while (!ports.empty() && success)
 337     {
 338         success = interfaces[ports.back()]->sendTiming(pkt);
 339         ports.pop_back();
 340     }
 341
 342     return success;
 343 }
 344
 345
 346 /** Function called by the port when the bus is receiving a Atomic
 347  * transaction.*/
 348 Tick
 349 Bus::recvAtomic(Packet *pkt)
 350 {
 351     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 352             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 353     assert(pkt->getDest() == Packet::Broadcast);
 354     Tick snoopTime = atomicSnoop(pkt);
 355     if (snoopTime)
 356         return snoopTime;  //Snoop satisfies it
 357     else
 358         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 359 }
 360
 361 /** Function called by the port when the bus is receiving a Functional
 362  * transaction.*/
 363 void
 364 Bus::recvFunctional(Packet *pkt)
 365 {
 366     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 367             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 368     assert(pkt->getDest() == Packet::Broadcast);
 369     functionalSnoop(pkt);
 370
 371     // If the snooping found what we were looking for, we're done.
 372     if (pkt->result != Packet::Success)
 373         findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 374 }
 375
 376 /** Function called by the port when the bus is receiving a status change.*/
 377 void
 378 Bus::recvStatusChange(Port::Status status, int id)
 379 {
 380     AddrRangeList ranges;
 381     AddrRangeList snoops;
 382     int x;
 383     AddrRangeIter iter;
 384
 385     assert(status == Port::RangeChange &&
 386            "The other statuses need to be implemented.");
 387
 388     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 389
 390     if (id == defaultId) {
 391         defaultRange.clear();
 392         defaultPort->getPeerAddressRanges(ranges, snoops);
 393         assert(snoops.size() == 0);
 394         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 395             defaultRange.push_back(*iter);
 396             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 397                     iter->start, iter->end);
 398         }
 399     } else {
 400
 401         assert((id < interfaces.size() && id >= 0) || id == defaultId);
 402         Port *port = interfaces[id];
 403         std::vector<DevMap>::iterator portIter;
 404         std::vector<DevMap>::iterator snoopIter;
 405
 406         // Clean out any previously existent ids
 407         for (portIter = portList.begin(); portIter != portList.end(); ) {
 408             if (portIter->portId == id)
 409                 portIter = portList.erase(portIter);
 410             else
 411                 portIter++;
 412         }
 413
 414         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 415             if (snoopIter->portId == id)
 416                 snoopIter = portSnoopList.erase(snoopIter);
 417             else
 418                 snoopIter++;
 419         }
 420
 421         port->getPeerAddressRanges(ranges, snoops);
 422
 423         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 424             DevMap dm;
 425             dm.portId = id;
 426             dm.range = *iter;
 427
 428             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 429                     dm.range.start, dm.range.end, id);
 430             portSnoopList.push_back(dm);
 431         }
 432
 433         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 434             DevMap dm;
 435             dm.portId = id;
 436             dm.range = *iter;
 437
 438             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 439                     dm.range.start, dm.range.end, id);
 440             portList.push_back(dm);
 441         }
 442     }
 443     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 444
 445     // tell all our peers that our address range has changed.
 446     // Don't tell the device that caused this change, it already knows
 447     for (x = 0; x < interfaces.size(); x++)
 448         if (x != id)
 449             interfaces[x]->sendStatusChange(Port::RangeChange);
 450
 451     if (id != defaultId && defaultPort)
 452         defaultPort->sendStatusChange(Port::RangeChange);
 453 }
 454
 455 void
 456 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 457 {
 458     std::vector<DevMap>::iterator portIter;
 459     AddrRangeIter dflt_iter;
 460     bool subset;
 461
 462     resp.clear();
 463     snoop.clear();
 464
 465     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 466
 467     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 468             dflt_iter++) {
 469         resp.push_back(*dflt_iter);
 470         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 471                 dflt_iter->end);
 472     }
 473     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 474         subset = false;
 475         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 476                 dflt_iter++) {
 477             if ((portIter->range.start < dflt_iter->start &&
 478                 portIter->range.end >= dflt_iter->start) ||
 479                (portIter->range.start < dflt_iter->end &&
 480                 portIter->range.end >= dflt_iter->end))
 481                 fatal("Devices can not set ranges that itersect the default set\
 482                         but are not a subset of the default set.\n");
 483             if (portIter->range.start >= dflt_iter->start &&
 484                 portIter->range.end <= dflt_iter->end) {
 485                 subset = true;
 486                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 487                     portIter->range.start, portIter->range.end);
 488             }
 489         }
 490         if (portIter->portId != id && !subset) {
 491             resp.push_back(portIter->range);
 492             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 493                     portIter->range.start, portIter->range.end);
 494         }
 495     }
 496 }
 497
 498 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 499
 500     Param<int> bus_id;
 501     Param<int> clock;
 502     Param<int> width;
 503
 504 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 505
 506 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 507     INIT_PARAM(bus_id, "a globally unique bus id"),
 508     INIT_PARAM(clock, "bus clock speed"),
 509     INIT_PARAM(width, "width of the bus (bits)")
 510 END_INIT_SIM_OBJECT_PARAMS(Bus)
 511
 512 CREATE_SIM_OBJECT(Bus)
 513 {
 514     return new Bus(getInstanceName(), bus_id, clock, width);
 515 }
 516
 517 REGISTER_SIM_OBJECT("Bus", Bus)