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         //If we weren't able to drain before, we might be able to now.
 244         if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle)
 245             drainEvent->process();
 246     }
 247 }
 248
 249 Port *
 250 Bus::findPort(Addr addr, int id)
 251 {
 252     /* An interval tree would be a better way to do this. --ali. */
 253     int dest_id = -1;
 254     int i = 0;
 255     bool found = false;
 256     AddrRangeIter iter;
 257
 258     while (i < portList.size() && !found)
 259     {
 260         if (portList[i].range == addr) {
 261             dest_id = portList[i].portId;
 262             found = true;
 263             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 264         }
 265         i++;
 266     }
 267
 268     // Check if this matches the default range
 269     if (dest_id == -1) {
 270         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 271             if (*iter == addr) {
 272                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 273                 return defaultPort;
 274             }
 275         }
 276
 277         if (responderSet) {
 278             panic("Unable to find destination for addr (user set default "
 279                   "responder): %#llx", addr);
 280         } else {
 281             DPRINTF(Bus, "Unable to find destination for addr: %#llx, will use "
 282                     "default port", addr);
 283
 284             return defaultPort;
 285         }
 286     }
 287
 288
 289     // we shouldn't be sending this back to where it came from
 290     assert(dest_id != id);
 291
 292     return interfaces[dest_id];
 293 }
 294
 295 std::vector<int>
 296 Bus::findSnoopPorts(Addr addr, int id)
 297 {
 298     int i = 0;
 299     AddrRangeIter iter;
 300     std::vector<int> ports;
 301
 302     while (i < portSnoopList.size())
 303     {
 304         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 305             //Careful  to not overlap ranges
 306             //or snoop will be called more than once on the port
 307             ports.push_back(portSnoopList[i].portId);
 308 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 309 //                    portSnoopList[i].portId);
 310         }
 311         i++;
 312     }
 313     return ports;
 314 }
 315
 316 Tick
 317 Bus::atomicSnoop(PacketPtr pkt)
 318 {
 319     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 320     Tick response_time = 0;
 321
 322     while (!ports.empty())
 323     {
 324         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 325         if (response) {
 326             assert(!response_time);  //Multiple responders
 327             response_time = response;
 328         }
 329         ports.pop_back();
 330     }
 331     return response_time;
 332 }
 333
 334 void
 335 Bus::functionalSnoop(PacketPtr pkt)
 336 {
 337     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 338
 339     while (!ports.empty() && pkt->result != Packet::Success)
 340     {
 341         interfaces[ports.back()]->sendFunctional(pkt);
 342         ports.pop_back();
 343     }
 344 }
 345
 346 bool
 347 Bus::timingSnoop(PacketPtr pkt)
 348 {
 349     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 350     bool success = true;
 351
 352     while (!ports.empty() && success)
 353     {
 354         success = interfaces[ports.back()]->sendTiming(pkt);
 355         ports.pop_back();
 356     }
 357
 358     return success;
 359 }
 360
 361
 362 /** Function called by the port when the bus is receiving a Atomic
 363  * transaction.*/
 364 Tick
 365 Bus::recvAtomic(PacketPtr pkt)
 366 {
 367     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 368             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 369     assert(pkt->getDest() == Packet::Broadcast);
 370     Tick snoopTime = atomicSnoop(pkt);
 371     if (snoopTime)
 372         return snoopTime;  //Snoop satisfies it
 373     else
 374         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 375 }
 376
 377 /** Function called by the port when the bus is receiving a Functional
 378  * transaction.*/
 379 void
 380 Bus::recvFunctional(PacketPtr pkt)
 381 {
 382     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 383             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 384     assert(pkt->getDest() == Packet::Broadcast);
 385     functionalSnoop(pkt);
 386
 387     // If the snooping found what we were looking for, we're done.
 388     if (pkt->result != Packet::Success)
 389         findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 390 }
 391
 392 /** Function called by the port when the bus is receiving a status change.*/
 393 void
 394 Bus::recvStatusChange(Port::Status status, int id)
 395 {
 396     AddrRangeList ranges;
 397     AddrRangeList snoops;
 398     int x;
 399     AddrRangeIter iter;
 400
 401     assert(status == Port::RangeChange &&
 402            "The other statuses need to be implemented.");
 403
 404     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 405
 406     if (id == defaultId) {
 407         defaultRange.clear();
 408         // Only try to update these ranges if the user set a default responder.
 409         if (responderSet) {
 410             defaultPort->getPeerAddressRanges(ranges, snoops);
 411             assert(snoops.size() == 0);
 412             for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 413                 defaultRange.push_back(*iter);
 414                 DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 415                         iter->start, iter->end);
 416             }
 417         }
 418     } else {
 419
 420         assert((id < interfaces.size() && id >= 0) || id == defaultId);
 421         Port *port = interfaces[id];
 422         std::vector<DevMap>::iterator portIter;
 423         std::vector<DevMap>::iterator snoopIter;
 424
 425         // Clean out any previously existent ids
 426         for (portIter = portList.begin(); portIter != portList.end(); ) {
 427             if (portIter->portId == id)
 428                 portIter = portList.erase(portIter);
 429             else
 430                 portIter++;
 431         }
 432
 433         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 434             if (snoopIter->portId == id)
 435                 snoopIter = portSnoopList.erase(snoopIter);
 436             else
 437                 snoopIter++;
 438         }
 439
 440         port->getPeerAddressRanges(ranges, snoops);
 441
 442         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 443             DevMap dm;
 444             dm.portId = id;
 445             dm.range = *iter;
 446
 447             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 448                     dm.range.start, dm.range.end, id);
 449             portSnoopList.push_back(dm);
 450         }
 451
 452         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 453             DevMap dm;
 454             dm.portId = id;
 455             dm.range = *iter;
 456
 457             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 458                     dm.range.start, dm.range.end, id);
 459             portList.push_back(dm);
 460         }
 461     }
 462     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 463
 464     // tell all our peers that our address range has changed.
 465     // Don't tell the device that caused this change, it already knows
 466     for (x = 0; x < interfaces.size(); x++)
 467         if (x != id)
 468             interfaces[x]->sendStatusChange(Port::RangeChange);
 469
 470     if (id != defaultId && defaultPort)
 471         defaultPort->sendStatusChange(Port::RangeChange);
 472 }
 473
 474 void
 475 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 476 {
 477     std::vector<DevMap>::iterator portIter;
 478     AddrRangeIter dflt_iter;
 479     bool subset;
 480
 481     resp.clear();
 482     snoop.clear();
 483
 484     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 485
 486     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 487             dflt_iter++) {
 488         resp.push_back(*dflt_iter);
 489         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 490                 dflt_iter->end);
 491     }
 492     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 493         subset = false;
 494         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 495                 dflt_iter++) {
 496             if ((portIter->range.start < dflt_iter->start &&
 497                 portIter->range.end >= dflt_iter->start) ||
 498                (portIter->range.start < dflt_iter->end &&
 499                 portIter->range.end >= dflt_iter->end))
 500                 fatal("Devices can not set ranges that itersect the default set\
 501                         but are not a subset of the default set.\n");
 502             if (portIter->range.start >= dflt_iter->start &&
 503                 portIter->range.end <= dflt_iter->end) {
 504                 subset = true;
 505                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 506                     portIter->range.start, portIter->range.end);
 507             }
 508         }
 509         if (portIter->portId != id && !subset) {
 510             resp.push_back(portIter->range);
 511             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 512                     portIter->range.start, portIter->range.end);
 513         }
 514     }
 515 }
 516
 517 unsigned int
 518 Bus::drain(Event * de)
 519 {
 520     //We should check that we're not "doing" anything, and that noone is
 521     //waiting. We might be idle but have someone waiting if the device we
 522     //contacted for a retry didn't actually retry.
 523     if (curTick >= tickNextIdle && retryList.size() == 0) {
 524         drainEvent = de;
 525         return 1;
 526     } else {
 527         return 0;
 528     }
 529 }
 530
 531 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 532
 533     Param<int> bus_id;
 534     Param<int> clock;
 535     Param<int> width;
 536     Param<bool> responder_set;
 537
 538 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 539
 540 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 541     INIT_PARAM(bus_id, "a globally unique bus id"),
 542     INIT_PARAM(clock, "bus clock speed"),
 543     INIT_PARAM(width, "width of the bus (bits)"),
 544     INIT_PARAM(responder_set, "Is a default responder set by the user")
 545 END_INIT_SIM_OBJECT_PARAMS(Bus)
 546
 547 CREATE_SIM_OBJECT(Bus)
 548 {
 549     return new Bus(getInstanceName(), bus_id, clock, width, responder_set);
 550 }
 551
 552 REGISTER_SIM_OBJECT("Bus", Bus)