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(PacketPtr 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             bool success;
 164
 165             pkt->flags |= SNOOP_COMMIT;
 166             success = timingSnoop(pkt);
 167             assert(success);
 168
 169             if (pkt->flags & SATISFIED) {
 170                 //Cache-Cache transfer occuring
 171                 if (inRetry) {
 172                     retryList.front()->onRetryList(false);
 173                     retryList.pop_front();
 174                     inRetry = false;
 175                 }
 176                 occupyBus(pkt);
 177                 return true;
 178             }
 179             port = findPort(pkt->getAddr(), pkt->getSrc());
 180         } else {
 181             //Snoop didn't succeed
 182             DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 183             addToRetryList(pktPort);
 184             return false;
 185         }
 186     } else {
 187         assert(dest >= 0 && dest < interfaces.size());
 188         assert(dest != pkt->getSrc()); // catch infinite loops
 189         port = interfaces[dest];
 190     }
 191
 192     occupyBus(pkt);
 193
 194     if (port->sendTiming(pkt))  {
 195         // Packet was successfully sent. Return true.
 196         // Also take care of retries
 197         if (inRetry) {
 198             DPRINTF(Bus, "Remove retry from list %i\n", retryList.front());
 199             retryList.front()->onRetryList(false);
 200             retryList.pop_front();
 201             inRetry = false;
 202         }
 203         return true;
 204     }
 205
 206     // Packet not successfully sent. Leave or put it on the retry list.
 207     DPRINTF(Bus, "Adding a retry to RETRY list %i\n", pktPort);
 208     addToRetryList(pktPort);
 209     return false;
 210 }
 211
 212 void
 213 Bus::recvRetry(int id)
 214 {
 215     DPRINTF(Bus, "Received a retry\n");
 216     // If there's anything waiting, and the bus isn't busy...
 217     if (retryList.size() && curTick >= tickNextIdle) {
 218         //retryingPort = retryList.front();
 219         inRetry = true;
 220         DPRINTF(Bus, "Sending a retry\n");
 221         retryList.front()->sendRetry();
 222         // If inRetry is still true, sendTiming wasn't called
 223         if (inRetry)
 224         {
 225             retryList.front()->onRetryList(false);
 226             retryList.pop_front();
 227             inRetry = false;
 228
 229             //Bring tickNextIdle up to the present
 230             while (tickNextIdle < curTick)
 231                 tickNextIdle += clock;
 232
 233             //Burn a cycle for the missed grant.
 234             tickNextIdle += clock;
 235
 236             if (!busIdle.scheduled()) {
 237                 busIdle.schedule(tickNextIdle);
 238             } else {
 239                 busIdle.reschedule(tickNextIdle);
 240             }
 241         }
 242     }
 243 }
 244
 245 Port *
 246 Bus::findPort(Addr addr, int id)
 247 {
 248     /* An interval tree would be a better way to do this. --ali. */
 249     int dest_id = -1;
 250     int i = 0;
 251     bool found = false;
 252     AddrRangeIter iter;
 253
 254     while (i < portList.size() && !found)
 255     {
 256         if (portList[i].range == addr) {
 257             dest_id = portList[i].portId;
 258             found = true;
 259             DPRINTF(Bus, "  found addr %#llx on device %d\n", addr, dest_id);
 260         }
 261         i++;
 262     }
 263
 264     // Check if this matches the default range
 265     if (dest_id == -1) {
 266         for (iter = defaultRange.begin(); iter != defaultRange.end(); iter++) {
 267             if (*iter == addr) {
 268                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 269                 return defaultPort;
 270             }
 271         }
 272         panic("Unable to find destination for addr: %#llx", addr);
 273     }
 274
 275
 276     // we shouldn't be sending this back to where it came from
 277     assert(dest_id != id);
 278
 279     return interfaces[dest_id];
 280 }
 281
 282 std::vector<int>
 283 Bus::findSnoopPorts(Addr addr, int id)
 284 {
 285     int i = 0;
 286     AddrRangeIter iter;
 287     std::vector<int> ports;
 288
 289     while (i < portSnoopList.size())
 290     {
 291         if (portSnoopList[i].range == addr && portSnoopList[i].portId != id) {
 292             //Careful  to not overlap ranges
 293             //or snoop will be called more than once on the port
 294             ports.push_back(portSnoopList[i].portId);
 295 //            DPRINTF(Bus, "  found snoop addr %#llx on device%d\n", addr,
 296 //                    portSnoopList[i].portId);
 297         }
 298         i++;
 299     }
 300     return ports;
 301 }
 302
 303 Tick
 304 Bus::atomicSnoop(PacketPtr pkt)
 305 {
 306     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 307     Tick response_time = 0;
 308
 309     while (!ports.empty())
 310     {
 311         Tick response = interfaces[ports.back()]->sendAtomic(pkt);
 312         if (response) {
 313             assert(!response_time);  //Multiple responders
 314             response_time = response;
 315         }
 316         ports.pop_back();
 317     }
 318     return response_time;
 319 }
 320
 321 void
 322 Bus::functionalSnoop(PacketPtr pkt)
 323 {
 324     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 325
 326     while (!ports.empty() && pkt->result != Packet::Success)
 327     {
 328         interfaces[ports.back()]->sendFunctional(pkt);
 329         ports.pop_back();
 330     }
 331 }
 332
 333 bool
 334 Bus::timingSnoop(PacketPtr pkt)
 335 {
 336     std::vector<int> ports = findSnoopPorts(pkt->getAddr(), pkt->getSrc());
 337     bool success = true;
 338
 339     while (!ports.empty() && success)
 340     {
 341         success = interfaces[ports.back()]->sendTiming(pkt);
 342         ports.pop_back();
 343     }
 344
 345     return success;
 346 }
 347
 348
 349 /** Function called by the port when the bus is receiving a Atomic
 350  * transaction.*/
 351 Tick
 352 Bus::recvAtomic(PacketPtr pkt)
 353 {
 354     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 355             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 356     assert(pkt->getDest() == Packet::Broadcast);
 357     Tick snoopTime = atomicSnoop(pkt);
 358     if (snoopTime)
 359         return snoopTime;  //Snoop satisfies it
 360     else
 361         return findPort(pkt->getAddr(), pkt->getSrc())->sendAtomic(pkt);
 362 }
 363
 364 /** Function called by the port when the bus is receiving a Functional
 365  * transaction.*/
 366 void
 367 Bus::recvFunctional(PacketPtr pkt)
 368 {
 369     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 370             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 371     assert(pkt->getDest() == Packet::Broadcast);
 372     functionalSnoop(pkt);
 373
 374     // If the snooping found what we were looking for, we're done.
 375     if (pkt->result != Packet::Success)
 376         findPort(pkt->getAddr(), pkt->getSrc())->sendFunctional(pkt);
 377 }
 378
 379 /** Function called by the port when the bus is receiving a status change.*/
 380 void
 381 Bus::recvStatusChange(Port::Status status, int id)
 382 {
 383     AddrRangeList ranges;
 384     AddrRangeList snoops;
 385     int x;
 386     AddrRangeIter iter;
 387
 388     assert(status == Port::RangeChange &&
 389            "The other statuses need to be implemented.");
 390
 391     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 392
 393     if (id == defaultId) {
 394         defaultRange.clear();
 395         defaultPort->getPeerAddressRanges(ranges, snoops);
 396         assert(snoops.size() == 0);
 397         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 398             defaultRange.push_back(*iter);
 399             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 400                     iter->start, iter->end);
 401         }
 402     } else {
 403
 404         assert((id < interfaces.size() && id >= 0) || id == defaultId);
 405         Port *port = interfaces[id];
 406         std::vector<DevMap>::iterator portIter;
 407         std::vector<DevMap>::iterator snoopIter;
 408
 409         // Clean out any previously existent ids
 410         for (portIter = portList.begin(); portIter != portList.end(); ) {
 411             if (portIter->portId == id)
 412                 portIter = portList.erase(portIter);
 413             else
 414                 portIter++;
 415         }
 416
 417         for (snoopIter = portSnoopList.begin(); snoopIter != portSnoopList.end(); ) {
 418             if (snoopIter->portId == id)
 419                 snoopIter = portSnoopList.erase(snoopIter);
 420             else
 421                 snoopIter++;
 422         }
 423
 424         port->getPeerAddressRanges(ranges, snoops);
 425
 426         for(iter = snoops.begin(); iter != snoops.end(); iter++) {
 427             DevMap dm;
 428             dm.portId = id;
 429             dm.range = *iter;
 430
 431             DPRINTF(BusAddrRanges, "Adding snoop range %#llx - %#llx for id %d\n",
 432                     dm.range.start, dm.range.end, id);
 433             portSnoopList.push_back(dm);
 434         }
 435
 436         for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 437             DevMap dm;
 438             dm.portId = id;
 439             dm.range = *iter;
 440
 441             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 442                     dm.range.start, dm.range.end, id);
 443             portList.push_back(dm);
 444         }
 445     }
 446     DPRINTF(MMU, "port list has %d entries\n", portList.size());
 447
 448     // tell all our peers that our address range has changed.
 449     // Don't tell the device that caused this change, it already knows
 450     for (x = 0; x < interfaces.size(); x++)
 451         if (x != id)
 452             interfaces[x]->sendStatusChange(Port::RangeChange);
 453
 454     if (id != defaultId && defaultPort)
 455         defaultPort->sendStatusChange(Port::RangeChange);
 456 }
 457
 458 void
 459 Bus::addressRanges(AddrRangeList &resp, AddrRangeList &snoop, int id)
 460 {
 461     std::vector<DevMap>::iterator portIter;
 462     AddrRangeIter dflt_iter;
 463     bool subset;
 464
 465     resp.clear();
 466     snoop.clear();
 467
 468     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 469
 470     for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 471             dflt_iter++) {
 472         resp.push_back(*dflt_iter);
 473         DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",dflt_iter->start,
 474                 dflt_iter->end);
 475     }
 476     for (portIter = portList.begin(); portIter != portList.end(); portIter++) {
 477         subset = false;
 478         for (dflt_iter = defaultRange.begin(); dflt_iter != defaultRange.end();
 479                 dflt_iter++) {
 480             if ((portIter->range.start < dflt_iter->start &&
 481                 portIter->range.end >= dflt_iter->start) ||
 482                (portIter->range.start < dflt_iter->end &&
 483                 portIter->range.end >= dflt_iter->end))
 484                 fatal("Devices can not set ranges that itersect the default set\
 485                         but are not a subset of the default set.\n");
 486             if (portIter->range.start >= dflt_iter->start &&
 487                 portIter->range.end <= dflt_iter->end) {
 488                 subset = true;
 489                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 490                     portIter->range.start, portIter->range.end);
 491             }
 492         }
 493         if (portIter->portId != id && !subset) {
 494             resp.push_back(portIter->range);
 495             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 496                     portIter->range.start, portIter->range.end);
 497         }
 498     }
 499 }
 500
 501 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 502
 503     Param<int> bus_id;
 504     Param<int> clock;
 505     Param<int> width;
 506
 507 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 508
 509 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 510     INIT_PARAM(bus_id, "a globally unique bus id"),
 511     INIT_PARAM(clock, "bus clock speed"),
 512     INIT_PARAM(width, "width of the bus (bits)")
 513 END_INIT_SIM_OBJECT_PARAMS(Bus)
 514
 515 CREATE_SIM_OBJECT(Bus)
 516 {
 517     return new Bus(getInstanceName(), bus_id, clock, width);
 518 }
 519
 520 REGISTER_SIM_OBJECT("Bus", Bus)