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 #include <algorithm>
  37 #include <limits>
  38
  39 #include "base/misc.hh"
  40 #include "base/trace.hh"
  41 #include "mem/bus.hh"
  42 #include "sim/builder.hh"
  43
  44 Port *
  45 Bus::getPort(const std::string &if_name, int idx)
  46 {
  47     if (if_name == "default") {
  48         if (defaultPort == NULL) {
  49             defaultPort = new BusPort(csprintf("%s-default",name()), this,
  50                                       defaultId);
  51             cachedBlockSizeValid = false;
  52             return defaultPort;
  53         } else
  54             fatal("Default port already set\n");
  55     }
  56     int id;
  57     if (if_name == "functional") {
  58         if (!funcPort) {
  59             id = maxId++;
  60             funcPort = new BusPort(csprintf("%s-p%d-func", name(), id), this, id);
  61             funcPortId = id;
  62             interfaces[id] = funcPort;
  63         }
  64         return funcPort;
  65     }
  66
  67     // if_name ignored?  forced to be empty?
  68     id = maxId++;
  69     assert(maxId < std::numeric_limits<typeof(maxId)>::max());
  70     BusPort *bp = new BusPort(csprintf("%s-p%d", name(), id), this, id);
  71     interfaces[id] = bp;
  72     cachedBlockSizeValid = false;
  73     return bp;
  74 }
  75
  76 void
  77 Bus::deletePortRefs(Port *p)
  78 {
  79
  80     BusPort *bp =  dynamic_cast<BusPort*>(p);
  81     if (bp == NULL)
  82         panic("Couldn't convert Port* to BusPort*\n");
  83     // If this is our one functional port
  84     if (funcPort == bp)
  85         return;
  86     interfaces.erase(bp->getId());
  87     delete bp;
  88 }
  89
  90 /** Get the ranges of anyone other buses that we are connected to. */
  91 void
  92 Bus::init()
  93 {
  94     m5::hash_map<short,BusPort*>::iterator intIter;
  95
  96     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
  97         intIter->second->sendStatusChange(Port::RangeChange);
  98 }
  99
 100 Bus::BusFreeEvent::BusFreeEvent(Bus *_bus) : Event(&mainEventQueue), bus(_bus)
 101 {}
 102
 103 void Bus::BusFreeEvent::process()
 104 {
 105     bus->recvRetry(-1);
 106 }
 107
 108 const char * Bus::BusFreeEvent::description()
 109 {
 110     return "bus became available";
 111 }
 112
 113 void Bus::occupyBus(PacketPtr pkt)
 114 {
 115     //Bring tickNextIdle up to the present tick
 116     //There is some potential ambiguity where a cycle starts, which might make
 117     //a difference when devices are acting right around a cycle boundary. Using
 118     //a < allows things which happen exactly on a cycle boundary to take up
 119     //only the following cycle. Anything that happens later will have to "wait"
 120     //for the end of that cycle, and then start using the bus after that.
 121     if (tickNextIdle < curTick) {
 122         tickNextIdle = curTick;
 123         if (tickNextIdle % clock != 0)
 124             tickNextIdle = curTick - (curTick % clock) + clock;
 125     }
 126
 127     // The packet will be sent. Figure out how long it occupies the bus, and
 128     // how much of that time is for the first "word", aka bus width.
 129     int numCycles = 0;
 130     // Requests need one cycle to send an address
 131     if (pkt->isRequest())
 132         numCycles++;
 133     else if (pkt->isResponse() || pkt->hasData()) {
 134         // If a packet has data, it needs ceil(size/width) cycles to send it
 135         // We're using the "adding instead of dividing" trick again here
 136         if (pkt->hasData()) {
 137             int dataSize = pkt->getSize();
 138             numCycles += dataSize/width;
 139             if (dataSize % width)
 140                 numCycles++;
 141         } else {
 142             // If the packet didn't have data, it must have been a response.
 143             // Those use the bus for one cycle to send their data.
 144             numCycles++;
 145         }
 146     }
 147
 148     // The first word will be delivered after the current tick, the delivery
 149     // of the address if any, and one bus cycle to deliver the data
 150     pkt->firstWordTime =
 151         tickNextIdle +
 152         pkt->isRequest() ? clock : 0 +
 153         clock;
 154
 155     //Advance it numCycles bus cycles.
 156     //XXX Should this use the repeated addition trick as well?
 157     tickNextIdle += (numCycles * clock);
 158     if (!busIdle.scheduled()) {
 159         busIdle.schedule(tickNextIdle);
 160     } else {
 161         busIdle.reschedule(tickNextIdle);
 162     }
 163     DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
 164             curTick, tickNextIdle);
 165
 166     // The bus will become idle once the current packet is delivered.
 167     pkt->finishTime = tickNextIdle;
 168 }
 169
 170 /** Function called by the port when the bus is receiving a Timing
 171  * transaction.*/
 172 bool
 173 Bus::recvTiming(PacketPtr pkt)
 174 {
 175     int port_id;
 176     DPRINTF(Bus, "recvTiming: packet src %d dest %d addr 0x%x cmd %s\n",
 177             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 178
 179     BusPort *pktPort;
 180     if (pkt->getSrc() == defaultId)
 181         pktPort = defaultPort;
 182     else pktPort = interfaces[pkt->getSrc()];
 183
 184     // If the bus is busy, or other devices are in line ahead of the current
 185     // one, put this device on the retry list.
 186     if (tickNextIdle > curTick ||
 187         (retryList.size() && (!inRetry || pktPort != retryList.front())))
 188     {
 189         addToRetryList(pktPort);
 190         DPRINTF(Bus, "recvTiming: Bus is busy, returning false\n");
 191         return false;
 192     }
 193
 194     short dest = pkt->getDest();
 195
 196     // Make sure to clear the snoop commit flag so it doesn't think an
 197     // access has been handled twice.
 198     if (dest == Packet::Broadcast) {
 199         port_id = findPort(pkt->getAddr());
 200         timingSnoop(pkt, interfaces[port_id]);
 201
 202         if (pkt->memInhibitAsserted()) {
 203             //Cache-Cache transfer occuring
 204             if (inRetry) {
 205                 retryList.front()->onRetryList(false);
 206                 retryList.pop_front();
 207                 inRetry = false;
 208             }
 209             occupyBus(pkt);
 210             DPRINTF(Bus, "recvTiming: Packet sucessfully sent\n");
 211             return true;
 212         }
 213     } else {
 214         assert(dest >= 0 && dest < maxId);
 215         assert(dest != pkt->getSrc()); // catch infinite loops
 216         port_id = dest;
 217     }
 218
 219     occupyBus(pkt);
 220
 221     if (port_id != pkt->getSrc()) {
 222         if (interfaces[port_id]->sendTiming(pkt))  {
 223             // Packet was successfully sent. Return true.
 224             // Also take care of retries
 225             if (inRetry) {
 226                 DPRINTF(Bus, "Remove retry from list %d\n",
 227                         retryList.front()->getId());
 228                 retryList.front()->onRetryList(false);
 229                 retryList.pop_front();
 230                 inRetry = false;
 231             }
 232             return true;
 233         }
 234
 235         // Packet not successfully sent. Leave or put it on the retry list.
 236         DPRINTF(Bus, "Adding2 a retry to RETRY list %d\n",
 237                 pktPort->getId());
 238         addToRetryList(pktPort);
 239         return false;
 240     }
 241     else {
 242         //Forwarding up from responder, just return true;
 243         DPRINTF(Bus, "recvTiming: can we be here?\n");
 244         return true;
 245     }
 246 }
 247
 248 void
 249 Bus::recvRetry(int id)
 250 {
 251     // If there's anything waiting, and the bus isn't busy...
 252     if (retryList.size() && curTick >= tickNextIdle) {
 253         //retryingPort = retryList.front();
 254         inRetry = true;
 255         DPRINTF(Bus, "Sending a retry to %s\n", retryList.front()->getPeer()->name());
 256         retryList.front()->sendRetry();
 257         // If inRetry is still true, sendTiming wasn't called
 258         if (inRetry)
 259         {
 260             retryList.front()->onRetryList(false);
 261             retryList.pop_front();
 262             inRetry = false;
 263
 264             //Bring tickNextIdle up to the present
 265             while (tickNextIdle < curTick)
 266                 tickNextIdle += clock;
 267
 268             //Burn a cycle for the missed grant.
 269             tickNextIdle += clock;
 270
 271             busIdle.reschedule(tickNextIdle, true);
 272         }
 273     }
 274     //If we weren't able to drain before, we might be able to now.
 275     if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle) {
 276         drainEvent->process();
 277         // Clear the drain event once we're done with it.
 278         drainEvent = NULL;
 279     }
 280 }
 281
 282 int
 283 Bus::findPort(Addr addr)
 284 {
 285     /* An interval tree would be a better way to do this. --ali. */
 286     int dest_id = -1;
 287
 288     PortIter i = portMap.find(RangeSize(addr,1));
 289     if (i != portMap.end())
 290         dest_id = i->second;
 291
 292     // Check if this matches the default range
 293     if (dest_id == -1) {
 294         for (AddrRangeIter iter = defaultRange.begin();
 295              iter != defaultRange.end(); iter++) {
 296             if (*iter == addr) {
 297                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 298                 return defaultId;
 299             }
 300         }
 301
 302         if (responderSet) {
 303             panic("Unable to find destination for addr (user set default "
 304                   "responder): %#llx", addr);
 305         } else {
 306             DPRINTF(Bus, "Unable to find destination for addr: %#llx, will use "
 307                     "default port", addr);
 308
 309             return defaultId;
 310         }
 311     }
 312
 313     return dest_id;
 314 }
 315
 316 void
 317 Bus::functionalSnoop(PacketPtr pkt, Port *responder)
 318 {
 319     // The packet may be changed by another bus on snoops, restore the
 320     // id after each
 321     int src_id = pkt->getSrc();
 322
 323     assert(pkt->isRequest()); // hasn't already been satisfied
 324
 325     for (SnoopIter s_iter = snoopPorts.begin();
 326          s_iter != snoopPorts.end();
 327          s_iter++) {
 328         BusPort *p = *s_iter;
 329         if (p != responder && p->getId() != src_id) {
 330             p->sendFunctional(pkt);
 331         }
 332         if (pkt->isResponse()) {
 333             break;
 334         }
 335         pkt->setSrc(src_id);
 336     }
 337 }
 338
 339 bool
 340 Bus::timingSnoop(PacketPtr pkt, Port* responder)
 341 {
 342     for (SnoopIter s_iter = snoopPorts.begin();
 343          s_iter != snoopPorts.end();
 344          s_iter++) {
 345         BusPort *p = *s_iter;
 346         if (p != responder && p->getId() != pkt->getSrc()) {
 347             bool success = p->sendTiming(pkt);
 348             if (!success)
 349                 return false;
 350         }
 351     }
 352
 353     return true;
 354 }
 355
 356
 357 /** Function called by the port when the bus is receiving a Atomic
 358  * transaction.*/
 359 Tick
 360 Bus::recvAtomic(PacketPtr pkt)
 361 {
 362     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 363             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 364     assert(pkt->getDest() == Packet::Broadcast);
 365     assert(pkt->isRequest());
 366
 367     // Variables for recording original command and snoop response (if
 368     // any)... if a snooper respondes, we will need to restore
 369     // original command so that additional snoops can take place
 370     // properly
 371     MemCmd orig_cmd = pkt->cmd;
 372     MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
 373     Tick snoop_response_latency = 0;
 374     int orig_src = pkt->getSrc();
 375
 376     int target_port_id = findPort(pkt->getAddr());
 377     Port *target_port = interfaces[target_port_id];
 378
 379     SnoopIter s_end = snoopPorts.end();
 380     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
 381         BusPort *p = *s_iter;
 382         // same port should not have both target addresses and snooping
 383         assert(p != target_port);
 384         if (p->getId() != pkt->getSrc()) {
 385             Tick latency = p->sendAtomic(pkt);
 386             if (pkt->isResponse()) {
 387                 // response from snoop agent
 388                 assert(pkt->cmd != orig_cmd);
 389                 assert(pkt->memInhibitAsserted());
 390                 // should only happen once
 391                 assert(snoop_response_cmd == MemCmd::InvalidCmd);
 392                 // save response state
 393                 snoop_response_cmd = pkt->cmd;
 394                 snoop_response_latency = latency;
 395                 // restore original packet state for remaining snoopers
 396                 pkt->cmd = orig_cmd;
 397                 pkt->setSrc(orig_src);
 398                 pkt->setDest(Packet::Broadcast);
 399             }
 400         }
 401     }
 402
 403     Tick response_latency = 0;
 404
 405     // we can get requests sent up from the memory side of the bus for
 406     // snooping... don't send them back down!
 407     if (target_port_id != pkt->getSrc()) {
 408         response_latency = target_port->sendAtomic(pkt);
 409     }
 410
 411     // if we got a response from a snooper, restore it here
 412     if (snoop_response_cmd != MemCmd::InvalidCmd) {
 413         // no one else should have responded
 414         assert(!pkt->isResponse());
 415         assert(pkt->cmd == orig_cmd);
 416         pkt->cmd = snoop_response_cmd;
 417         response_latency = snoop_response_latency;
 418     }
 419
 420     // why do we have this packet field and the return value both???
 421     pkt->finishTime = curTick + response_latency;
 422     return response_latency;
 423 }
 424
 425 /** Function called by the port when the bus is receiving a Functional
 426  * transaction.*/
 427 void
 428 Bus::recvFunctional(PacketPtr pkt)
 429 {
 430     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 431             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 432     assert(pkt->getDest() == Packet::Broadcast);
 433
 434     int port_id = findPort(pkt->getAddr());
 435     Port *port = interfaces[port_id];
 436     functionalSnoop(pkt, port);
 437
 438     // If the snooping hasn't found what we were looking for, keep going.
 439     if (!pkt->isResponse() && port_id != pkt->getSrc()) {
 440         port->sendFunctional(pkt);
 441     }
 442 }
 443
 444 /** Function called by the port when the bus is receiving a status change.*/
 445 void
 446 Bus::recvStatusChange(Port::Status status, int id)
 447 {
 448     AddrRangeList ranges;
 449     bool snoops;
 450     AddrRangeIter iter;
 451
 452     assert(status == Port::RangeChange &&
 453            "The other statuses need to be implemented.");
 454
 455     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 456
 457     if (id == defaultId) {
 458         defaultRange.clear();
 459         // Only try to update these ranges if the user set a default responder.
 460         if (responderSet) {
 461             defaultPort->getPeerAddressRanges(ranges, snoops);
 462             assert(snoops == false);
 463             for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 464                 defaultRange.push_back(*iter);
 465                 DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 466                         iter->start, iter->end);
 467             }
 468         }
 469     } else {
 470
 471         assert((id < maxId && id >= 0) || id == defaultId);
 472         BusPort *port = interfaces[id];
 473
 474         // Clean out any previously existent ids
 475         for (PortIter portIter = portMap.begin();
 476              portIter != portMap.end(); ) {
 477             if (portIter->second == id)
 478                 portMap.erase(portIter++);
 479             else
 480                 portIter++;
 481         }
 482
 483         for (SnoopIter s_iter = snoopPorts.begin();
 484              s_iter != snoopPorts.end(); ) {
 485             if ((*s_iter)->getId() == id)
 486                 s_iter = snoopPorts.erase(s_iter);
 487             else
 488                 s_iter++;
 489         }
 490
 491         port->getPeerAddressRanges(ranges, snoops);
 492
 493         if (snoops) {
 494             DPRINTF(BusAddrRanges, "Adding id %d to snoop list\n", id);
 495             snoopPorts.push_back(port);
 496         }
 497
 498         for (iter = ranges.begin(); iter != ranges.end(); iter++) {
 499             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 500                     iter->start, iter->end, id);
 501             if (portMap.insert(*iter, id) == portMap.end())
 502                 panic("Two devices with same range\n");
 503
 504         }
 505     }
 506     DPRINTF(MMU, "port list has %d entries\n", portMap.size());
 507
 508     // tell all our peers that our address range has changed.
 509     // Don't tell the device that caused this change, it already knows
 510     m5::hash_map<short,BusPort*>::iterator intIter;
 511
 512     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
 513         if (intIter->first != id && intIter->first != funcPortId)
 514             intIter->second->sendStatusChange(Port::RangeChange);
 515
 516     if (id != defaultId && defaultPort)
 517         defaultPort->sendStatusChange(Port::RangeChange);
 518 }
 519
 520 void
 521 Bus::addressRanges(AddrRangeList &resp, bool &snoop, int id)
 522 {
 523     resp.clear();
 524     snoop = false;
 525
 526     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 527
 528     for (AddrRangeIter dflt_iter = defaultRange.begin();
 529          dflt_iter != defaultRange.end(); dflt_iter++) {
 530         resp.push_back(*dflt_iter);
 531         DPRINTF(BusAddrRanges, "  -- Dflt: %#llx : %#llx\n",dflt_iter->start,
 532                 dflt_iter->end);
 533     }
 534     for (PortIter portIter = portMap.begin();
 535          portIter != portMap.end(); portIter++) {
 536         bool subset = false;
 537         for (AddrRangeIter dflt_iter = defaultRange.begin();
 538              dflt_iter != defaultRange.end(); dflt_iter++) {
 539             if ((portIter->first.start < dflt_iter->start &&
 540                 portIter->first.end >= dflt_iter->start) ||
 541                (portIter->first.start < dflt_iter->end &&
 542                 portIter->first.end >= dflt_iter->end))
 543                 fatal("Devices can not set ranges that itersect the default set\
 544                         but are not a subset of the default set.\n");
 545             if (portIter->first.start >= dflt_iter->start &&
 546                 portIter->first.end <= dflt_iter->end) {
 547                 subset = true;
 548                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 549                     portIter->first.start, portIter->first.end);
 550             }
 551         }
 552         if (portIter->second != id && !subset) {
 553             resp.push_back(portIter->first);
 554             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 555                     portIter->first.start, portIter->first.end);
 556         }
 557     }
 558
 559     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != snoopPorts.end();
 560          s_iter++) {
 561         if ((*s_iter)->getId() != id) {
 562             snoop = true;
 563             break;
 564         }
 565     }
 566 }
 567
 568 int
 569 Bus::findBlockSize(int id)
 570 {
 571     if (cachedBlockSizeValid)
 572         return cachedBlockSize;
 573
 574     int max_bs = -1;
 575
 576     for (PortIter portIter = portMap.begin();
 577          portIter != portMap.end(); portIter++) {
 578         int tmp_bs = interfaces[portIter->second]->peerBlockSize();
 579         if (tmp_bs > max_bs)
 580             max_bs = tmp_bs;
 581     }
 582     for (SnoopIter s_iter = snoopPorts.begin();
 583          s_iter != snoopPorts.end(); s_iter++) {
 584         int tmp_bs = (*s_iter)->peerBlockSize();
 585         if (tmp_bs > max_bs)
 586             max_bs = tmp_bs;
 587     }
 588     if (max_bs <= 0)
 589         max_bs = defaultBlockSize;
 590
 591     if (max_bs != 64)
 592         warn_once("Blocksize found to not be 64... hmm... probably not.\n");
 593     cachedBlockSize = max_bs;
 594     cachedBlockSizeValid = true;
 595     return max_bs;
 596 }
 597
 598
 599 unsigned int
 600 Bus::drain(Event * de)
 601 {
 602     //We should check that we're not "doing" anything, and that noone is
 603     //waiting. We might be idle but have someone waiting if the device we
 604     //contacted for a retry didn't actually retry.
 605     if (curTick >= tickNextIdle && retryList.size() == 0) {
 606         return 0;
 607     } else {
 608         drainEvent = de;
 609         return 1;
 610     }
 611 }
 612
 613 void
 614 Bus::startup()
 615 {
 616     if (tickNextIdle < curTick)
 617         tickNextIdle = (curTick / clock) * clock + clock;
 618 }
 619
 620 BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bus)
 621
 622     Param<int> bus_id;
 623     Param<int> clock;
 624     Param<int> width;
 625     Param<bool> responder_set;
 626     Param<int> block_size;
 627
 628 END_DECLARE_SIM_OBJECT_PARAMS(Bus)
 629
 630 BEGIN_INIT_SIM_OBJECT_PARAMS(Bus)
 631     INIT_PARAM(bus_id, "a globally unique bus id"),
 632     INIT_PARAM(clock, "bus clock speed"),
 633     INIT_PARAM(width, "width of the bus (bits)"),
 634     INIT_PARAM(responder_set, "Is a default responder set by the user"),
 635     INIT_PARAM(block_size, "Default blocksize if no device has one")
 636 END_INIT_SIM_OBJECT_PARAMS(Bus)
 637
 638 CREATE_SIM_OBJECT(Bus)
 639 {
 640     return new Bus(getInstanceName(), bus_id, clock, width, responder_set,
 641             block_size);
 642 }
 643
 644 REGISTER_SIM_OBJECT("Bus", Bus)