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
  54     // if_name ignored?  forced to be empty?
  55     int id = interfaces.size();
  56     BusPort *bp = new BusPort(csprintf("%s-p%d", name(), id), this, id);
  57     interfaces.push_back(bp);
  58     return bp;
  59 }
  60
  61 /** Get the ranges of anyone other buses that we are connected to. */
  62 void
  63 Bus::init()
  64 {
  65     std::vector<BusPort*>::iterator intIter;
  66
  67     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
  68         (*intIter)->sendStatusChange(Port::RangeChange);
  69 }
  70
  71 Bus::BusFreeEvent::BusFreeEvent(Bus *_bus) : Event(&mainEventQueue), bus(_bus)
  72 {}
  73
  74 void Bus::BusFreeEvent::process()
  75 {
  76     bus->recvRetry(-1);
  77 }
  78
  79 const char * Bus::BusFreeEvent::description()
  80 {
  81     return "bus became available";
  82 }
  83
  84 void Bus::occupyBus(PacketPtr pkt)
  85 {
  86     //Bring tickNextIdle up to the present tick
  87     //There is some potential ambiguity where a cycle starts, which might make
  88     //a difference when devices are acting right around a cycle boundary. Using
  89     //a < allows things which happen exactly on a cycle boundary to take up only
  90     //the following cycle. Anthing that happens later will have to "wait" for
  91     //the end of that cycle, and then start using the bus after that.
  92     while (tickNextIdle < curTick)
  93         tickNextIdle += clock;
  94
  95     // The packet will be sent. Figure out how long it occupies the bus, and
  96     // how much of that time is for the first "word", aka bus width.
  97     int numCycles = 0;
  98     // Requests need one cycle to send an address
  99     if (pkt->isRequest())
 100         numCycles++;
 101     else if (pkt->isResponse() || pkt->hasData()) {
 102         // If a packet has data, it needs ceil(size/width) cycles to send it
 103         // We're using the "adding instead of dividing" trick again here
 104         if (pkt->hasData()) {
 105             int dataSize = pkt->getSize();
 106             for (int transmitted = 0; transmitted < dataSize;
 107                     transmitted += width) {
 108                 numCycles++;
 109             }
 110         } else {
 111             // If the packet didn't have data, it must have been a response.
 112             // Those use the bus for one cycle to send their data.
 113             numCycles++;
 114         }
 115     }
 116
 117     // The first word will be delivered after the current tick, the delivery
 118     // of the address if any, and one bus cycle to deliver the data
 119     pkt->firstWordTime =
 120         tickNextIdle +
 121         pkt->isRequest() ? clock : 0 +
 122         clock;
 123
 124     //Advance it numCycles bus cycles.
 125     //XXX Should this use the repeated addition trick as well?
 126     tickNextIdle += (numCycles * clock);
 127     if (!busIdle.scheduled()) {
 128         busIdle.schedule(tickNextIdle);
 129     } else {
 130         busIdle.reschedule(tickNextIdle);
 131     }
 132     DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
 133             curTick, tickNextIdle);
 134
 135     // The bus will become idle once the current packet is delivered.
 136     pkt->finishTime = tickNextIdle;
 137 }
 138
 139 /** Function called by the port when the bus is receiving a Timing
 140  * transaction.*/
 141 bool
 142 Bus::recvTiming(PacketPtr pkt)
 143 {
 144     Port *port;
 145     DPRINTF(Bus, "recvTiming: packet src %d dest %d addr 0x%x cmd %s\n",
 146             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 147
 148     BusPort *pktPort;
 149     if (pkt->getSrc() == defaultId)
 150         pktPort = defaultPort;
 151     else pktPort = interfaces[pkt->getSrc()];
 152
 153     // If the bus is busy, or other devices are in line ahead of the current
 154     // one, put this device on the retry list.
 155     if (tickNextIdle > curTick ||
 156             (retryList.size() && (!inRetry || pktPort != retryList.front()))) {
 157         addToRetryList(pktPort);
 158         return false;
 159     }
 160
 161     short dest = pkt->getDest();
 162     if (dest == Packet::Broadcast) {
 163         if (timingSnoop(pkt)) {
 164             bool success;
 165
 166             pkt->flags |= SNOOP_COMMIT;
 167             success = timingSnoop(pkt);
 168             assert(success);
 169
 170             if (pkt->flags & SATISFIED) {
 171                 //Cache-Cache transfer occuring
 172                 if (inRetry) {
 173                     retryList.front()->onRetryList(false);
 174                     retryList.pop_front();
 175                     inRetry = false;
 176                 }
 177                 occupyBus(pkt);
 178                 return true;
 179             }
 180             port = findPort(pkt->getAddr(), pkt->getSrc());
 181         } else {
 182             //Snoop didn't succeed
 183             DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 184             addToRetryList(pktPort);
 185             return false;
 186         }
 187     } else {
 188         assert(dest >= 0 && dest < interfaces.size());
 189         assert(dest != pkt->getSrc()); // catch infinite loops
 190         port = interfaces[dest];
 191     }
 192
 193     occupyBus(pkt);
 194
 195     if (port->sendTiming(pkt))  {
 196         // Packet was successfully sent. Return true.
 197         // Also take care of retries
 198         if (inRetry) {
 199             DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
 200             retryList.front()->onRetryList(false);
 201             retryList.pop_front();
 202             inRetry = false;
 203         }
 204         return true;
 205     }
 206
 207     // Packet not successfully sent. Leave or put it on the retry list.
 208     DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 209     addToRetryList(pktPort);
 210     return false;
 211 }
 212
 213 void
 214 Bus::recvRetry(int id)
 215 {
 216     DPRINTF(Bus, "Received a retry\n");
 217     // If there's anything waiting, and the bus isn't busy...
 218     if (retryList.size() && curTick >= tickNextIdle) {
 219         //retryingPort = retryList.front();
 220         inRetry = true;
 221         DPRINTF(Bus, "Sending a retry\n");
 222         retryList.front()->sendRetry();
 223         // If inRetry is still true, sendTiming wasn't called
 224         if (inRetry)
 225         {
 226             retryList.front()->onRetryList(false);
 227             retryList.pop_front();
 228             inRetry = false;
 229
 230             //Bring tickNextIdle up to the present
 231             while (tickNextIdle < curTick)
 232                 tickNextIdle += clock;
 233
 234             //Burn a cycle for the missed grant.
 235             tickNextIdle += clock;
 236
 237             if (!busIdle.scheduled()) {
 238                 busIdle.schedule(tickNextIdle);
 239             } else {
 240                 busIdle.reschedule(tickNextIdle);
 241             }
 242         }
 243     }
 244     //If we weren't able to drain before, we might be able to now.
 245     if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle) {
 246         drainEvent->process();
 247         // Clear the drain event once we're done with it.
 248         drainEvent = NULL;
 249     }
 250 }
 251
 252 Port *
 253 Bus::findPort(Addr addr, int id)
 254 {
 255     /* An interval tree would be a better way to do this. --ali. */
 256     int dest_id = -1;
 257     int i = 0;
 258     bool found = false;
 259     AddrRangeIter iter;
 260
 261     while (i < portList.size() && !found)
 262     {
 263         if (portList[i].range == addr) {
 264             dest_id = portList[i].portId;
 265             found = true;
 266             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 267         }
 268         i++;
 269     }
 270
 271     // Check if this matches the default range
 272     if (dest_id == -1) {
 273         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 274             if (*iter == addr) {
 275                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 276                 return defaultPort;
 277             }
 278         }
 279
 280         if (responderSet) {
 281             panic("Unable to find destination for addr (user set default "
 282                   "responder): %#llx", addr);
 283         } else {
 284             DPRINTF(Bus, "Unable to find destination for addr: %#llx, will use "
 285                     "default port", addr);
 286
 287             return defaultPort;
 288         }
 289     }
 290
 291
 292     // we shouldn't be sending this back to where it came from
 293     assert(dest_id != id);
 294
 295     return interfaces[dest_id];
 296 }
 297
 298 std::vector<int>
 299 Bus::findSnoopPorts(Addr addr, int id)
 300 {
 301     int i = 0;
 302     AddrRangeIter iter;
 303     std::vector<int> ports;
 304
 305     while (i < portSnoopList.size())
 306     {
 307         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 308             //Careful  to not overlap ranges
 309             //or snoop will be called more than once on the port
 310             ports.push_back(portSnoopList[i].portId);
 311 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 312 //                    portSnoopList[i].portId);
 313         }
 314         i++;
 315     }
 316     return ports;
 317 }
 318
 319 Tick
 320 Bus::atomicSnoop(PacketPtr pkt)
 321 {
 322     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 323     Tick response_time = 0;
 324
 325     while (!ports.empty())
 326     {
 327         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 328         if (response) {
 329             assert(!response_time);  //Multiple responders
 330             response_time = response;
 331         }
 332         ports.pop_back();
 333     }
 334     return response_time;
 335 }
 336
 337 void
 338 Bus::functionalSnoop(PacketPtr pkt)
 339 {
 340     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 341
 342     while (!ports.empty() && pkt->result != Packet::Success)
 343     {
 344         interfaces[ports.back()]->sendFunctional(pkt);
 345         ports.pop_back();
 346     }
 347 }
 348
 349 bool
 350 Bus::timingSnoop(PacketPtr pkt)
 351 {
 352     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 353     bool success = true;
 354
 355     while (!ports.empty() && success)
 356     {
 357         success = interfaces[ports.back()]->sendTiming(pkt);
 358         ports.pop_back();
 359     }
 360
 361     return success;
 362 }
 363
 364
 365 /** Function called by the port when the bus is receiving a Atomic
 366  * transaction.*/
 367 Tick
 368 Bus::recvAtomic(PacketPtr pkt)
 369 {
 370     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 371             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 372     assert(pkt->getDest() == Packet::Broadcast);
 373
 374     // Assume one bus cycle in order to get through.  This may have
 375     // some clock skew issues yet again...
 376     pkt->finishTime = curTick + clock;
 377     Tick snoopTime = atomicSnoop(pkt);
 378     if (snoopTime)
 379         return snoopTime;  //Snoop satisfies it
 380     else
 381         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 382 }
 383
 384 /** Function called by the port when the bus is receiving a Functional
 385  * transaction.*/
 386 void
 387 Bus::recvFunctional(PacketPtr pkt)
 388 {
 389     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 390             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 391     assert(pkt->getDest() == Packet::Broadcast);
 392     functionalSnoop(pkt);
 393
 394     // If the snooping found what we were looking for, we're done.
 395     if (pkt->result != Packet::Success)
 396         findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 397 }
 398
 399 /** Function called by the port when the bus is receiving a status change.*/
 400 void
 401 Bus::recvStatusChange(Port::Status status, int id)
 402 {
 403     AddrRangeList ranges;
 404     AddrRangeList snoops;
 405     int x;
 406     AddrRangeIter iter;
 407
 408     assert(status == Port::RangeChange &&
 409            "The other statuses need to be implemented.");
 410
 411     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 412
 413     if (id == defaultId) {
 414         defaultRange.clear();
 415         // Only try to update these ranges if the user set a default responder.
 416         if (responderSet) {
 417             defaultPort->getPeerAddressRanges(ranges, snoops);
 418             assert(snoops.size() == 0);
 419             for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 420                 defaultRange.push_back(*iter);
 421                 DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 422                         iter->start, iter->end);
 423             }
 424         }
 425     } else {
 426
 427         assert((id < interfaces.size() && id >= 0) || id == defaultId);
 428         Port *port = interfaces[id];
 429         std::vector<DevMap>::iterator portIter;
 430         std::vector<DevMap>::iterator snoopIter;
 431
 432         // Clean out any previously existent ids
 433         for (portIter = portList.begin(); portIter != portList.end(); ) {
 434             if (portIter->portId == id)
 435                 portIter = portList.erase(portIter);
 436             else
 437                 portIter++;
 438         }
 439
 440         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 441             if (snoopIter->portId == id)
 442                 snoopIter = portSnoopList.erase(snoopIter);
 443             else
 444                 snoopIter++;
 445         }
 446
 447         port->getPeerAddressRanges(ranges, snoops);
 448
 449         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 450             DevMap dm;
 451             dm.portId = id;
 452             dm.range = *iter;
 453
 454             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 455                     dm.range.start, dm.range.end, id);
 456             portSnoopList.push_back(dm);
 457         }
 458
 459         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 460             DevMap dm;
 461             dm.portId = id;
 462             dm.range = *iter;
 463
 464             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 465                     dm.range.start, dm.range.end, id);
 466             portList.push_back(dm);
 467         }
 468     }
 469     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 470
 471     // tell all our peers that our address range has changed.
 472     // Don't tell the device that caused this change, it already knows
 473     for (x = 0; x < interfaces.size(); x++)
 474         if (x != id)
 475             interfaces[x]->sendStatusChange(Port::RangeChange);
 476
 477     if (id != defaultId && defaultPort)
 478         defaultPort->sendStatusChange(Port::RangeChange);
 479 }
 480
 481 void
 482 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 483 {
 484     std::vector<DevMap>::iterator portIter;
 485     AddrRangeIter dflt_iter;
 486     bool subset;
 487
 488     resp.clear();
 489     snoop.clear();
 490
 491     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 492
 493     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 494             dflt_iter++) {
 495         resp.push_back(*dflt_iter);
 496         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 497                 dflt_iter->end);
 498     }
 499     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 500         subset = false;
 501         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 502                 dflt_iter++) {
 503             if ((portIter->range.start < dflt_iter->start &&
 504                 portIter->range.end >= dflt_iter->start) ||
 505                (portIter->range.start < dflt_iter->end &&
 506                 portIter->range.end >= dflt_iter->end))
 507                 fatal("Devices can not set ranges that itersect the default set\
 508                         but are not a subset of the default set.\n");
 509             if (portIter->range.start >= dflt_iter->start &&
 510                 portIter->range.end <= dflt_iter->end) {
 511                 subset = true;
 512                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 513                     portIter->range.start, portIter->range.end);
 514             }
 515         }
 516         if (portIter->portId != id && !subset) {
 517             resp.push_back(portIter->range);
 518             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 519                     portIter->range.start, portIter->range.end);
 520         }
 521     }
 522 }
 523
 524 unsigned int
 525 Bus::drain(Event * de)
 526 {
 527     //We should check that we're not "doing" anything, and that noone is
 528     //waiting. We might be idle but have someone waiting if the device we
 529     //contacted for a retry didn't actually retry.
 530     if (curTick >= tickNextIdle && retryList.size() == 0) {
 531         return 0;
 532     } else {
 533         drainEvent = de;
 534         return 1;
 535     }
 536 }
 537
 538 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 539
 540     Param<int> bus_id;
 541     Param<int> clock;
 542     Param<int> width;
 543     Param<bool> responder_set;
 544
 545 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 546
 547 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 548     INIT_PARAM(bus_id, "a globally unique bus id"),
 549     INIT_PARAM(clock, "bus clock speed"),
 550     INIT_PARAM(width, "width of the bus (bits)"),
 551     INIT_PARAM(responder_set, "Is a default responder set by the user")
 552 END_INIT_SIM_OBJECT_PARAMS(Bus)
 553
 554 CREATE_SIM_OBJECT(Bus)
 555 {
 556     return new Bus(getInstanceName(), bus_id, clock, width, responder_set);
 557 }
 558
 559 REGISTER_SIM_OBJECT("Bus", Bus)