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 "params/Bus.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     clearBusCache();
  88     delete bp;
  89 }
  90
  91 /** Get the ranges of anyone other buses that we are connected to. */
  92 void
  93 Bus::init()
  94 {
  95     m5::hash_map<short,BusPort*>::iterator intIter;
  96
  97     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
  98         intIter->second->sendStatusChange(Port::RangeChange);
  99 }
 100
 101 Bus::BusFreeEvent::BusFreeEvent(Bus *_bus) : Event(&mainEventQueue), bus(_bus)
 102 {}
 103
 104 void Bus::BusFreeEvent::process()
 105 {
 106     bus->recvRetry(-1);
 107 }
 108
 109 const char * Bus::BusFreeEvent::description()
 110 {
 111     return "bus became available";
 112 }
 113
 114 void Bus::occupyBus(PacketPtr pkt)
 115 {
 116     //Bring tickNextIdle up to the present tick
 117     //There is some potential ambiguity where a cycle starts, which might make
 118     //a difference when devices are acting right around a cycle boundary. Using
 119     //a < allows things which happen exactly on a cycle boundary to take up
 120     //only the following cycle. Anything that happens later will have to "wait"
 121     //for the end of that cycle, and then start using the bus after that.
 122     if (tickNextIdle < curTick) {
 123         tickNextIdle = curTick;
 124         if (tickNextIdle % clock != 0)
 125             tickNextIdle = curTick - (curTick % clock) + clock;
 126     }
 127
 128     // The packet will be sent. Figure out how long it occupies the bus, and
 129     // how much of that time is for the first "word", aka bus width.
 130     int numCycles = 0;
 131     // Requests need one cycle to send an address
 132     if (pkt->isRequest())
 133         numCycles++;
 134     else if (pkt->isResponse() || pkt->hasData()) {
 135         // If a packet has data, it needs ceil(size/width) cycles to send it
 136         // We're using the "adding instead of dividing" trick again here
 137         if (pkt->hasData()) {
 138             int dataSize = pkt->getSize();
 139             numCycles += dataSize/width;
 140             if (dataSize % width)
 141                 numCycles++;
 142         } else {
 143             // If the packet didn't have data, it must have been a response.
 144             // Those use the bus for one cycle to send their data.
 145             numCycles++;
 146         }
 147     }
 148
 149     // The first word will be delivered after the current tick, the delivery
 150     // of the address if any, and one bus cycle to deliver the data
 151     pkt->firstWordTime =
 152         tickNextIdle +
 153         pkt->isRequest() ? clock : 0 +
 154         clock;
 155
 156     //Advance it numCycles bus cycles.
 157     //XXX Should this use the repeated addition trick as well?
 158     tickNextIdle += (numCycles * clock);
 159     if (!busIdle.scheduled()) {
 160         busIdle.schedule(tickNextIdle);
 161     } else {
 162         busIdle.reschedule(tickNextIdle);
 163     }
 164     DPRINTF(Bus, "The bus is now occupied from tick %d to %d\n",
 165             curTick, tickNextIdle);
 166
 167     // The bus will become idle once the current packet is delivered.
 168     pkt->finishTime = tickNextIdle;
 169 }
 170
 171 /** Function called by the port when the bus is receiving a Timing
 172  * transaction.*/
 173 bool
 174 Bus::recvTiming(PacketPtr pkt)
 175 {
 176     short src = pkt->getSrc();
 177     DPRINTF(Bus, "recvTiming: packet src %d dest %d addr 0x%x cmd %s\n",
 178             src, pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 179
 180     BusPort *src_port;
 181     if (src == defaultId)
 182         src_port = defaultPort;
 183     else {
 184         src_port = checkBusCache(src);
 185         if (src_port == NULL) {
 186             src_port = interfaces[src];
 187             updateBusCache(src, src_port);
 188         }
 189     }
 190
 191     // If the bus is busy, or other devices are in line ahead of the current
 192     // one, put this device on the retry list.
 193     if (!pkt->isExpressSnoop() &&
 194         (tickNextIdle > curTick ||
 195          (retryList.size() && (!inRetry || src_port != retryList.front()))))
 196     {
 197         addToRetryList(src_port);
 198         DPRINTF(Bus, "recvTiming: Bus is busy, returning false\n");
 199         return false;
 200     }
 201
 202     if (!pkt->isExpressSnoop()) {
 203         occupyBus(pkt);
 204     }
 205
 206     short dest = pkt->getDest();
 207     int dest_port_id;
 208     Port *dest_port;
 209
 210     if (dest == Packet::Broadcast) {
 211         dest_port_id = findPort(pkt->getAddr());
 212         dest_port = (dest_port_id == defaultId) ?
 213             defaultPort : interfaces[dest_port_id];
 214         SnoopIter s_end = snoopPorts.end();
 215         for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
 216             BusPort *p = *s_iter;
 217             if (p != dest_port && p != src_port) {
 218                 // cache is not allowed to refuse snoop
 219                 bool success M5_VAR_USED = p->sendTiming(pkt);
 220                 assert(success);
 221             }
 222         }
 223     } else {
 224         assert(dest >= 0 && dest < maxId);
 225         assert(dest != src); // catch infinite loops
 226         dest_port_id = dest;
 227         if (dest_port_id == defaultId)
 228             dest_port = defaultPort;
 229         else {
 230             dest_port = checkBusCache(dest);
 231             if (dest_port == NULL) {
 232                 dest_port = interfaces[dest_port_id];
 233             // updateBusCache(dest_port_id, dest_port);
 234             }
 235         }
 236         dest_port = (dest_port_id == defaultId) ?
 237             defaultPort : interfaces[dest_port_id];
 238     }
 239
 240     if (dest_port_id == src) {
 241         // Must be forwarded snoop up from below...
 242         assert(dest == Packet::Broadcast);
 243     } else {
 244         // send to actual target
 245         if (!dest_port->sendTiming(pkt))  {
 246             // Packet not successfully sent. Leave or put it on the retry list.
 247             // illegal to block responses... can lead to deadlock
 248             assert(!pkt->isResponse());
 249             DPRINTF(Bus, "Adding2 a retry to RETRY list %d\n", src);
 250             addToRetryList(src_port);
 251             return false;
 252         }
 253         // send OK, fall through
 254     }
 255
 256     // Packet was successfully sent.
 257     // Also take care of retries
 258     if (inRetry) {
 259         DPRINTF(Bus, "Remove retry from list %d\n", src);
 260         retryList.front()->onRetryList(false);
 261         retryList.pop_front();
 262         inRetry = false;
 263     }
 264     return true;
 265 }
 266
 267 void
 268 Bus::recvRetry(int id)
 269 {
 270     // If there's anything waiting, and the bus isn't busy...
 271     if (retryList.size() && curTick >= tickNextIdle) {
 272         //retryingPort = retryList.front();
 273         inRetry = true;
 274         DPRINTF(Bus, "Sending a retry to %s\n", retryList.front()->getPeer()->name());
 275         retryList.front()->sendRetry();
 276         // If inRetry is still true, sendTiming wasn't called
 277         if (inRetry)
 278         {
 279             retryList.front()->onRetryList(false);
 280             retryList.pop_front();
 281             inRetry = false;
 282
 283             //Bring tickNextIdle up to the present
 284             while (tickNextIdle < curTick)
 285                 tickNextIdle += clock;
 286
 287             //Burn a cycle for the missed grant.
 288             tickNextIdle += clock;
 289
 290             busIdle.reschedule(tickNextIdle, true);
 291         }
 292     }
 293     //If we weren't able to drain before, we might be able to now.
 294     if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle) {
 295         drainEvent->process();
 296         // Clear the drain event once we're done with it.
 297         drainEvent = NULL;
 298     }
 299 }
 300
 301 int
 302 Bus::findPort(Addr addr)
 303 {
 304     /* An interval tree would be a better way to do this. --ali. */
 305     int dest_id = -1;
 306
 307     dest_id = checkPortCache(addr);
 308     if (dest_id == -1) {
 309         PortIter i = portMap.find(RangeSize(addr,1));
 310         if (i != portMap.end())
 311           dest_id = i->second;
 312         updatePortCache(dest_id, i->first.start, i->first.end);
 313     }
 314
 315     // Check if this matches the default range
 316     if (dest_id == -1) {
 317         AddrRangeIter a_end = defaultRange.end();
 318         for (AddrRangeIter i = defaultRange.begin(); i != a_end; i++) {
 319             if (*i == addr) {
 320                 DPRINTF(Bus, "  found addr %#llx on default\n", addr);
 321                 return defaultId;
 322             }
 323         }
 324
 325         if (responderSet) {
 326             panic("Unable to find destination for addr (user set default "
 327                   "responder): %#llx", addr);
 328         } else {
 329             DPRINTF(Bus, "Unable to find destination for addr: %#llx, will use "
 330                     "default port", addr);
 331
 332             return defaultId;
 333         }
 334     }
 335
 336     return dest_id;
 337 }
 338
 339
 340 /** Function called by the port when the bus is receiving a Atomic
 341  * transaction.*/
 342 Tick
 343 Bus::recvAtomic(PacketPtr pkt)
 344 {
 345     DPRINTF(Bus, "recvAtomic: packet src %d dest %d addr 0x%x cmd %s\n",
 346             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 347     assert(pkt->getDest() == Packet::Broadcast);
 348     assert(pkt->isRequest());
 349
 350     // Variables for recording original command and snoop response (if
 351     // any)... if a snooper respondes, we will need to restore
 352     // original command so that additional snoops can take place
 353     // properly
 354     MemCmd orig_cmd = pkt->cmd;
 355     MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
 356     Tick snoop_response_latency = 0;
 357     int orig_src = pkt->getSrc();
 358
 359     int target_port_id = findPort(pkt->getAddr());
 360     BusPort *target_port;
 361     if (target_port_id == defaultId)
 362         target_port = defaultPort;
 363     else {
 364       target_port = checkBusCache(target_port_id);
 365       if (target_port == NULL) {
 366           target_port = interfaces[target_port_id];
 367           updateBusCache(target_port_id, target_port);
 368       }
 369     }
 370
 371     SnoopIter s_end = snoopPorts.end();
 372     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
 373         BusPort *p = *s_iter;
 374         // same port should not have both target addresses and snooping
 375         assert(p != target_port);
 376         if (p->getId() != pkt->getSrc()) {
 377             Tick latency = p->sendAtomic(pkt);
 378             if (pkt->isResponse()) {
 379                 // response from snoop agent
 380                 assert(pkt->cmd != orig_cmd);
 381                 assert(pkt->memInhibitAsserted());
 382                 // should only happen once
 383                 assert(snoop_response_cmd == MemCmd::InvalidCmd);
 384                 // save response state
 385                 snoop_response_cmd = pkt->cmd;
 386                 snoop_response_latency = latency;
 387                 // restore original packet state for remaining snoopers
 388                 pkt->cmd = orig_cmd;
 389                 pkt->setSrc(orig_src);
 390                 pkt->setDest(Packet::Broadcast);
 391             }
 392         }
 393     }
 394
 395     Tick response_latency = 0;
 396
 397     // we can get requests sent up from the memory side of the bus for
 398     // snooping... don't send them back down!
 399     if (target_port_id != pkt->getSrc()) {
 400         response_latency = target_port->sendAtomic(pkt);
 401     }
 402
 403     // if we got a response from a snooper, restore it here
 404     if (snoop_response_cmd != MemCmd::InvalidCmd) {
 405         // no one else should have responded
 406         assert(!pkt->isResponse());
 407         assert(pkt->cmd == orig_cmd);
 408         pkt->cmd = snoop_response_cmd;
 409         response_latency = snoop_response_latency;
 410     }
 411
 412     // why do we have this packet field and the return value both???
 413     pkt->finishTime = curTick + response_latency;
 414     return response_latency;
 415 }
 416
 417 /** Function called by the port when the bus is receiving a Functional
 418  * transaction.*/
 419 void
 420 Bus::recvFunctional(PacketPtr pkt)
 421 {
 422     DPRINTF(Bus, "recvFunctional: packet src %d dest %d addr 0x%x cmd %s\n",
 423             pkt->getSrc(), pkt->getDest(), pkt->getAddr(), pkt->cmdString());
 424     assert(pkt->getDest() == Packet::Broadcast);
 425
 426     int port_id = findPort(pkt->getAddr());
 427     Port *port = (port_id == defaultId) ? defaultPort : interfaces[port_id];
 428     // The packet may be changed by another bus on snoops, restore the
 429     // id after each
 430     int src_id = pkt->getSrc();
 431
 432     assert(pkt->isRequest()); // hasn't already been satisfied
 433
 434     SnoopIter s_end = snoopPorts.end();
 435     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
 436         BusPort *p = *s_iter;
 437         if (p != port && p->getId() != src_id) {
 438             p->sendFunctional(pkt);
 439         }
 440         if (pkt->isResponse()) {
 441             break;
 442         }
 443         pkt->setSrc(src_id);
 444     }
 445
 446     // If the snooping hasn't found what we were looking for, keep going.
 447     if (!pkt->isResponse() && port_id != pkt->getSrc()) {
 448         port->sendFunctional(pkt);
 449     }
 450 }
 451
 452 /** Function called by the port when the bus is receiving a status change.*/
 453 void
 454 Bus::recvStatusChange(Port::Status status, int id)
 455 {
 456     AddrRangeList ranges;
 457     bool snoops;
 458     AddrRangeIter iter;
 459
 460     if (inRecvStatusChange.count(id))
 461         return;
 462     inRecvStatusChange.insert(id);
 463
 464     assert(status == Port::RangeChange &&
 465            "The other statuses need to be implemented.");
 466
 467     DPRINTF(BusAddrRanges, "received RangeChange from device id %d\n", id);
 468
 469     clearPortCache();
 470     if (id == defaultId) {
 471         defaultRange.clear();
 472         // Only try to update these ranges if the user set a default responder.
 473         if (responderSet) {
 474             defaultPort->getPeerAddressRanges(ranges, snoops);
 475             assert(snoops == false);
 476             for(iter = ranges.begin(); iter != ranges.end(); iter++) {
 477                 defaultRange.push_back(*iter);
 478                 DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for default range\n",
 479                         iter->start, iter->end);
 480             }
 481         }
 482     } else {
 483
 484         assert((id < maxId && id >= 0) || id == defaultId);
 485         BusPort *port = interfaces[id];
 486
 487         // Clean out any previously existent ids
 488         for (PortIter portIter = portMap.begin();
 489              portIter != portMap.end(); ) {
 490             if (portIter->second == id)
 491                 portMap.erase(portIter++);
 492             else
 493                 portIter++;
 494         }
 495
 496         for (SnoopIter s_iter = snoopPorts.begin();
 497              s_iter != snoopPorts.end(); ) {
 498             if ((*s_iter)->getId() == id)
 499                 s_iter = snoopPorts.erase(s_iter);
 500             else
 501                 s_iter++;
 502         }
 503
 504         port->getPeerAddressRanges(ranges, snoops);
 505
 506         if (snoops) {
 507             DPRINTF(BusAddrRanges, "Adding id %d to snoop list\n", id);
 508             snoopPorts.push_back(port);
 509         }
 510
 511         for (iter = ranges.begin(); iter != ranges.end(); iter++) {
 512             DPRINTF(BusAddrRanges, "Adding range %#llx - %#llx for id %d\n",
 513                     iter->start, iter->end, id);
 514             if (portMap.insert(*iter, id) == portMap.end())
 515                 panic("Two devices with same range\n");
 516
 517         }
 518     }
 519     DPRINTF(MMU, "port list has %d entries\n", portMap.size());
 520
 521     // tell all our peers that our address range has changed.
 522     // Don't tell the device that caused this change, it already knows
 523     m5::hash_map<short,BusPort*>::iterator intIter;
 524
 525     for (intIter = interfaces.begin(); intIter != interfaces.end(); intIter++)
 526         if (intIter->first != id && intIter->first != funcPortId)
 527             intIter->second->sendStatusChange(Port::RangeChange);
 528
 529     if (id != defaultId && defaultPort)
 530         defaultPort->sendStatusChange(Port::RangeChange);
 531     inRecvStatusChange.erase(id);
 532 }
 533
 534 void
 535 Bus::addressRanges(AddrRangeList &resp, bool &snoop, int id)
 536 {
 537     resp.clear();
 538     snoop = false;
 539
 540     DPRINTF(BusAddrRanges, "received address range request, returning:\n");
 541
 542     for (AddrRangeIter dflt_iter = defaultRange.begin();
 543          dflt_iter != defaultRange.end(); dflt_iter++) {
 544         resp.push_back(*dflt_iter);
 545         DPRINTF(BusAddrRanges, "  -- Dflt: %#llx : %#llx\n",dflt_iter->start,
 546                 dflt_iter->end);
 547     }
 548     for (PortIter portIter = portMap.begin();
 549          portIter != portMap.end(); portIter++) {
 550         bool subset = false;
 551         for (AddrRangeIter dflt_iter = defaultRange.begin();
 552              dflt_iter != defaultRange.end(); dflt_iter++) {
 553             if ((portIter->first.start < dflt_iter->start &&
 554                 portIter->first.end >= dflt_iter->start) ||
 555                (portIter->first.start < dflt_iter->end &&
 556                 portIter->first.end >= dflt_iter->end))
 557                 fatal("Devices can not set ranges that itersect the default set\
 558                         but are not a subset of the default set.\n");
 559             if (portIter->first.start >= dflt_iter->start &&
 560                 portIter->first.end <= dflt_iter->end) {
 561                 subset = true;
 562                 DPRINTF(BusAddrRanges, "  -- %#llx : %#llx is a SUBSET\n",
 563                     portIter->first.start, portIter->first.end);
 564             }
 565         }
 566         if (portIter->second != id && !subset) {
 567             resp.push_back(portIter->first);
 568             DPRINTF(BusAddrRanges, "  -- %#llx : %#llx\n",
 569                     portIter->first.start, portIter->first.end);
 570         }
 571     }
 572
 573     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != snoopPorts.end();
 574          s_iter++) {
 575         if ((*s_iter)->getId() != id) {
 576             snoop = true;
 577             break;
 578         }
 579     }
 580 }
 581
 582 int
 583 Bus::findBlockSize(int id)
 584 {
 585     if (cachedBlockSizeValid)
 586         return cachedBlockSize;
 587
 588     int max_bs = -1;
 589
 590     PortIter p_end = portMap.end();
 591     for (PortIter p_iter = portMap.begin(); p_iter != p_end; p_iter++) {
 592         int tmp_bs = interfaces[p_iter->second]->peerBlockSize();
 593         if (tmp_bs > max_bs)
 594             max_bs = tmp_bs;
 595     }
 596     SnoopIter s_end = snoopPorts.end();
 597     for (SnoopIter s_iter = snoopPorts.begin(); s_iter != s_end; s_iter++) {
 598         int tmp_bs = (*s_iter)->peerBlockSize();
 599         if (tmp_bs > max_bs)
 600             max_bs = tmp_bs;
 601     }
 602     if (max_bs <= 0)
 603         max_bs = defaultBlockSize;
 604
 605     if (max_bs != 64)
 606         warn_once("Blocksize found to not be 64... hmm... probably not.\n");
 607     cachedBlockSize = max_bs;
 608     cachedBlockSizeValid = true;
 609     return max_bs;
 610 }
 611
 612
 613 unsigned int
 614 Bus::drain(Event * de)
 615 {
 616     //We should check that we're not "doing" anything, and that noone is
 617     //waiting. We might be idle but have someone waiting if the device we
 618     //contacted for a retry didn't actually retry.
 619     if (curTick >= tickNextIdle && retryList.size() == 0) {
 620         return 0;
 621     } else {
 622         drainEvent = de;
 623         return 1;
 624     }
 625 }
 626
 627 void
 628 Bus::startup()
 629 {
 630     if (tickNextIdle < curTick)
 631         tickNextIdle = (curTick / clock) * clock + clock;
 632 }
 633
 634 Bus *
 635 BusParams::create()
 636 {
 637     return new Bus(name, bus_id, clock, width, responder_set, block_size);
 638 }