1/*
2 * Copyright (c) 2011-2015 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2006 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ali Saidi
41 * Andreas Hansson
42 * William Wang
43 */
44
45/**
46 * @file
47 * Definition of a crossbar object.
48 */
49
50#include "base/misc.hh"
51#include "base/trace.hh"
52#include "debug/AddrRanges.hh"
53#include "debug/CoherentXBar.hh"
54#include "mem/coherent_xbar.hh"
55#include "sim/system.hh"
56
57CoherentXBar::CoherentXBar(const CoherentXBarParams *p)
58 : BaseXBar(p), system(p->system), snoopFilter(p->snoop_filter),
59 snoopResponseLatency(p->snoop_response_latency)
60{
61 // create the ports based on the size of the master and slave
62 // vector ports, and the presence of the default port, the ports
63 // are enumerated starting from zero
64 for (int i = 0; i < p->port_master_connection_count; ++i) {
65 std::string portName = csprintf("%s.master[%d]", name(), i);
66 MasterPort* bp = new CoherentXBarMasterPort(portName, *this, i);
67 masterPorts.push_back(bp);
68 reqLayers.push_back(new ReqLayer(*bp, *this,
69 csprintf(".reqLayer%d", i)));
70 snoopLayers.push_back(new SnoopRespLayer(*bp, *this,
71 csprintf(".snoopLayer%d", i)));
72 }
73
74 // see if we have a default slave device connected and if so add
75 // our corresponding master port
76 if (p->port_default_connection_count) {
77 defaultPortID = masterPorts.size();
78 std::string portName = name() + ".default";
79 MasterPort* bp = new CoherentXBarMasterPort(portName, *this,
80 defaultPortID);
81 masterPorts.push_back(bp);
82 reqLayers.push_back(new ReqLayer(*bp, *this, csprintf(".reqLayer%d",
83 defaultPortID)));
84 snoopLayers.push_back(new SnoopRespLayer(*bp, *this,
85 csprintf(".snoopLayer%d",
86 defaultPortID)));
87 }
88
89 // create the slave ports, once again starting at zero
90 for (int i = 0; i < p->port_slave_connection_count; ++i) {
91 std::string portName = csprintf("%s.slave[%d]", name(), i);
92 SlavePort* bp = new CoherentXBarSlavePort(portName, *this, i);
93 slavePorts.push_back(bp);
94 respLayers.push_back(new RespLayer(*bp, *this,
95 csprintf(".respLayer%d", i)));
96 snoopRespPorts.push_back(new SnoopRespPort(*bp, *this));
97 }
98
99 if (snoopFilter)
100 snoopFilter->setSlavePorts(slavePorts);
101
102 clearPortCache();
103}
104
105CoherentXBar::~CoherentXBar()
106{
107 for (auto l: reqLayers)
108 delete l;
109 for (auto l: respLayers)
110 delete l;
111 for (auto l: snoopLayers)
112 delete l;
113 for (auto p: snoopRespPorts)
114 delete p;
115}
116
117void
118CoherentXBar::init()
119{
120 // the base class is responsible for determining the block size
121 BaseXBar::init();
122
123 // iterate over our slave ports and determine which of our
124 // neighbouring master ports are snooping and add them as snoopers
125 for (const auto& p: slavePorts) {
126 // check if the connected master port is snooping
127 if (p->isSnooping()) {
128 DPRINTF(AddrRanges, "Adding snooping master %s\n",
129 p->getMasterPort().name());
130 snoopPorts.push_back(p);
131 }
132 }
133
134 if (snoopPorts.empty())
135 warn("CoherentXBar %s has no snooping ports attached!\n", name());
136}
137
138bool
139CoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
140{
141 // determine the source port based on the id
142 SlavePort *src_port = slavePorts[slave_port_id];
143
144 // remember if the packet is an express snoop
145 bool is_express_snoop = pkt->isExpressSnoop();
146 bool is_inhibited = pkt->memInhibitAsserted();
147 // for normal requests, going downstream, the express snoop flag
148 // and the inhibited flag should always be the same
149 assert(is_express_snoop == is_inhibited);
150
151 // determine the destination based on the address
152 PortID master_port_id = findPort(pkt->getAddr());
153
154 // test if the crossbar should be considered occupied for the current
155 // port, and exclude express snoops from the check
156 if (!is_express_snoop && !reqLayers[master_port_id]->tryTiming(src_port)) {
157 DPRINTF(CoherentXBar, "recvTimingReq: src %s %s 0x%x BUSY\n",
158 src_port->name(), pkt->cmdString(), pkt->getAddr());
159 return false;
160 }
161
162 DPRINTF(CoherentXBar, "recvTimingReq: src %s %s expr %d 0x%x\n",
163 src_port->name(), pkt->cmdString(), is_express_snoop,
164 pkt->getAddr());
165
166 // store size and command as they might be modified when
167 // forwarding the packet
168 unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0;
169 unsigned int pkt_cmd = pkt->cmdToIndex();
170
171 // store the old header delay so we can restore it if needed
172 Tick old_header_delay = pkt->headerDelay;
173
174 // a request sees the frontend and forward latency
175 Tick xbar_delay = (frontendLatency + forwardLatency) * clockPeriod();
176
177 // set the packet header and payload delay
178 calcPacketTiming(pkt, xbar_delay);
179
180 // determine how long to be crossbar layer is busy
181 Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay;
182
183 if (!system->bypassCaches()) {
184 // the packet is a memory-mapped request and should be
185 // broadcasted to our snoopers but the source
186 if (snoopFilter) {
187 // check with the snoop filter where to forward this packet
188 auto sf_res = snoopFilter->lookupRequest(pkt, *src_port);
189 // If SnoopFilter is enabled, the total time required by a packet
190 // to be delivered through the xbar has to be charged also with
191 // to lookup latency of the snoop filter (sf_res.second).
192 pkt->headerDelay += sf_res.second * clockPeriod();
193 packetFinishTime += sf_res.second * clockPeriod();
194 DPRINTF(CoherentXBar, "recvTimingReq: src %s %s 0x%x"\
195 " SF size: %i lat: %i\n", src_port->name(),
196 pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),
197 sf_res.second);
198 forwardTiming(pkt, slave_port_id, sf_res.first);
199 } else {
200 forwardTiming(pkt, slave_port_id);
201 }
202 }
203
204 // remember if the packet will generate a snoop response
205 const bool expect_snoop_resp = !is_inhibited && pkt->memInhibitAsserted();
206 const bool expect_response = pkt->needsResponse() &&
207 !pkt->memInhibitAsserted();
208
209 // Note: Cannot create a copy of the full packet, here.
210 MemCmd orig_cmd(pkt->cmd);
211
212 // since it is a normal request, attempt to send the packet
213 bool success = masterPorts[master_port_id]->sendTimingReq(pkt);
214
215 if (snoopFilter && !system->bypassCaches()) {
216 // The packet may already be overwritten by the sendTimingReq function.
217 // The snoop filter needs to see the original request *and* the return
218 // status of the send operation, so we need to recreate the original
219 // request. Atomic mode does not have the issue, as there the send
220 // operation and the response happen instantaneously and don't need two
221 // phase tracking.
222 MemCmd tmp_cmd(pkt->cmd);
223 pkt->cmd = orig_cmd;
224 // Let the snoop filter know about the success of the send operation
225 snoopFilter->updateRequest(pkt, *src_port, !success);
226 pkt->cmd = tmp_cmd;
227 }
228
229 // check if we were successful in sending the packet onwards
230 if (!success) {
231 // express snoops and inhibited packets should never be forced
232 // to retry
233 assert(!is_express_snoop);
234 assert(!pkt->memInhibitAsserted());
235
236 // restore the header delay
237 pkt->headerDelay = old_header_delay;
238
239 DPRINTF(CoherentXBar, "recvTimingReq: src %s %s 0x%x RETRY\n",
240 src_port->name(), pkt->cmdString(), pkt->getAddr());
241
242 // update the layer state and schedule an idle event
243 reqLayers[master_port_id]->failedTiming(src_port,
244 clockEdge(Cycles(1)));
245 } else {
246 // express snoops currently bypass the crossbar state entirely
247 if (!is_express_snoop) {
248 // if this particular request will generate a snoop
249 // response
250 if (expect_snoop_resp) {
251 // we should never have an exsiting request outstanding
252 assert(outstandingSnoop.find(pkt->req) ==
253 outstandingSnoop.end());
254 outstandingSnoop.insert(pkt->req);
255
256 // basic sanity check on the outstanding snoops
257 panic_if(outstandingSnoop.size() > 512,
258 "Outstanding snoop requests exceeded 512\n");
259 }
260
261 // remember where to route the normal response to
262 if (expect_response || expect_snoop_resp) {
263 assert(routeTo.find(pkt->req) == routeTo.end());
264 routeTo[pkt->req] = slave_port_id;
265
266 panic_if(routeTo.size() > 512,
267 "Routing table exceeds 512 packets\n");
268 }
269
270 // update the layer state and schedule an idle event
271 reqLayers[master_port_id]->succeededTiming(packetFinishTime);
272 }
273
274 // stats updates only consider packets that were successfully sent
275 pktCount[slave_port_id][master_port_id]++;
276 pktSize[slave_port_id][master_port_id] += pkt_size;
277 transDist[pkt_cmd]++;
278
279 if (is_express_snoop)
280 snoops++;
281 }
282
283 return success;
284}
285
286bool
287CoherentXBar::recvTimingResp(PacketPtr pkt, PortID master_port_id)
288{
289 // determine the source port based on the id
290 MasterPort *src_port = masterPorts[master_port_id];
291
292 // determine the destination
293 const auto route_lookup = routeTo.find(pkt->req);
294 assert(route_lookup != routeTo.end());
295 const PortID slave_port_id = route_lookup->second;
296 assert(slave_port_id != InvalidPortID);
297 assert(slave_port_id < respLayers.size());
298
299 // test if the crossbar should be considered occupied for the
300 // current port
301 if (!respLayers[slave_port_id]->tryTiming(src_port)) {
302 DPRINTF(CoherentXBar, "recvTimingResp: src %s %s 0x%x BUSY\n",
303 src_port->name(), pkt->cmdString(), pkt->getAddr());
304 return false;
305 }
306
307 DPRINTF(CoherentXBar, "recvTimingResp: src %s %s 0x%x\n",
308 src_port->name(), pkt->cmdString(), pkt->getAddr());
309
310 // store size and command as they might be modified when
311 // forwarding the packet
312 unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0;
313 unsigned int pkt_cmd = pkt->cmdToIndex();
314
315 // a response sees the response latency
316 Tick xbar_delay = responseLatency * clockPeriod();
317
318 // set the packet header and payload delay
319 calcPacketTiming(pkt, xbar_delay);
320
321 // determine how long to be crossbar layer is busy
322 Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay;
323
324 if (snoopFilter && !system->bypassCaches()) {
325 // let the snoop filter inspect the response and update its state
326 snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]);
327 }
328
329 // send the packet through the destination slave port
330 bool success M5_VAR_USED = slavePorts[slave_port_id]->sendTimingResp(pkt);
331
332 // currently it is illegal to block responses... can lead to
333 // deadlock
334 assert(success);
335
336 // remove the request from the routing table
337 routeTo.erase(route_lookup);
338
339 respLayers[slave_port_id]->succeededTiming(packetFinishTime);
340
341 // stats updates
342 pktCount[slave_port_id][master_port_id]++;
343 pktSize[slave_port_id][master_port_id] += pkt_size;
344 transDist[pkt_cmd]++;
345
346 return true;
347}
348
349void
350CoherentXBar::recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id)
351{
352 DPRINTF(CoherentXBar, "recvTimingSnoopReq: src %s %s 0x%x\n",
353 masterPorts[master_port_id]->name(), pkt->cmdString(),
354 pkt->getAddr());
355
356 // update stats here as we know the forwarding will succeed
357 transDist[pkt->cmdToIndex()]++;
358 snoops++;
359
360 // we should only see express snoops from caches
361 assert(pkt->isExpressSnoop());
362
363 // remeber if the packet is inhibited so we can see if it changes
364 const bool is_inhibited = pkt->memInhibitAsserted();
365
366 if (snoopFilter) {
367 // let the Snoop Filter work its magic and guide probing
368 auto sf_res = snoopFilter->lookupSnoop(pkt);
369 // No timing here: packetFinishTime += sf_res.second * clockPeriod();
370 DPRINTF(CoherentXBar, "recvTimingSnoopReq: src %s %s 0x%x"\
371 " SF size: %i lat: %i\n", masterPorts[master_port_id]->name(),
372 pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),
373 sf_res.second);
374
375 // forward to all snoopers
376 forwardTiming(pkt, InvalidPortID, sf_res.first);
377 } else {
378 forwardTiming(pkt, InvalidPortID);
379 }
380
381 // if we can expect a response, remember how to route it
382 if (!is_inhibited && pkt->memInhibitAsserted()) {
383 assert(routeTo.find(pkt->req) == routeTo.end());
384 routeTo[pkt->req] = master_port_id;
385 }
386
387 // a snoop request came from a connected slave device (one of
388 // our master ports), and if it is not coming from the slave
389 // device responsible for the address range something is
390 // wrong, hence there is nothing further to do as the packet
391 // would be going back to where it came from
392 assert(master_port_id == findPort(pkt->getAddr()));
393}
394
395bool
396CoherentXBar::recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id)
397{
398 // determine the source port based on the id
399 SlavePort* src_port = slavePorts[slave_port_id];
400
401 // get the destination
402 const auto route_lookup = routeTo.find(pkt->req);
403 assert(route_lookup != routeTo.end());
404 const PortID dest_port_id = route_lookup->second;
405 assert(dest_port_id != InvalidPortID);
406
407 // determine if the response is from a snoop request we
408 // created as the result of a normal request (in which case it
409 // should be in the outstandingSnoop), or if we merely forwarded
410 // someone else's snoop request
411 const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
412 outstandingSnoop.end();
413
414 // test if the crossbar should be considered occupied for the
415 // current port, note that the check is bypassed if the response
416 // is being passed on as a normal response since this is occupying
417 // the response layer rather than the snoop response layer
418 if (forwardAsSnoop) {
419 assert(dest_port_id < snoopLayers.size());
420 if (!snoopLayers[dest_port_id]->tryTiming(src_port)) {
421 DPRINTF(CoherentXBar, "recvTimingSnoopResp: src %s %s 0x%x BUSY\n",
422 src_port->name(), pkt->cmdString(), pkt->getAddr());
423 return false;
424 }
425 } else {
426 // get the master port that mirrors this slave port internally
427 MasterPort* snoop_port = snoopRespPorts[slave_port_id];
428 assert(dest_port_id < respLayers.size());
429 if (!respLayers[dest_port_id]->tryTiming(snoop_port)) {
430 DPRINTF(CoherentXBar, "recvTimingSnoopResp: src %s %s 0x%x BUSY\n",
431 snoop_port->name(), pkt->cmdString(), pkt->getAddr());
432 return false;
433 }
434 }
435
436 DPRINTF(CoherentXBar, "recvTimingSnoopResp: src %s %s 0x%x\n",
437 src_port->name(), pkt->cmdString(), pkt->getAddr());
438
439 // store size and command as they might be modified when
440 // forwarding the packet
441 unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0;
442 unsigned int pkt_cmd = pkt->cmdToIndex();
443
444 // responses are never express snoops
445 assert(!pkt->isExpressSnoop());
446
447 // a snoop response sees the snoop response latency, and if it is
448 // forwarded as a normal response, the response latency
449 Tick xbar_delay =
450 (forwardAsSnoop ? snoopResponseLatency : responseLatency) *
451 clockPeriod();
452
453 // set the packet header and payload delay
454 calcPacketTiming(pkt, xbar_delay);
455
456 // determine how long to be crossbar layer is busy
457 Tick packetFinishTime = clockEdge(Cycles(1)) + pkt->payloadDelay;
458
459 // forward it either as a snoop response or a normal response
460 if (forwardAsSnoop) {
461 // this is a snoop response to a snoop request we forwarded,
462 // e.g. coming from the L1 and going to the L2, and it should
463 // be forwarded as a snoop response
464
465 if (snoopFilter) {
466 // update the probe filter so that it can properly track the line
467 snoopFilter->updateSnoopForward(pkt, *slavePorts[slave_port_id],
468 *masterPorts[dest_port_id]);
469 }
470
471 bool success M5_VAR_USED =
472 masterPorts[dest_port_id]->sendTimingSnoopResp(pkt);
473 pktCount[slave_port_id][dest_port_id]++;
474 pktSize[slave_port_id][dest_port_id] += pkt_size;
475 assert(success);
476
477 snoopLayers[dest_port_id]->succeededTiming(packetFinishTime);
478 } else {
479 // we got a snoop response on one of our slave ports,
480 // i.e. from a coherent master connected to the crossbar, and
481 // since we created the snoop request as part of recvTiming,
482 // this should now be a normal response again
483 outstandingSnoop.erase(pkt->req);
484
485 // this is a snoop response from a coherent master, hence it
486 // should never go back to where the snoop response came from,
487 // but instead to where the original request came from
488 assert(slave_port_id != dest_port_id);
489
490 if (snoopFilter) {
491 // update the probe filter so that it can properly track the line
492 snoopFilter->updateSnoopResponse(pkt, *slavePorts[slave_port_id],
493 *slavePorts[dest_port_id]);
494 }
495
496 DPRINTF(CoherentXBar, "recvTimingSnoopResp: src %s %s 0x%x"\
497 " FWD RESP\n", src_port->name(), pkt->cmdString(),
498 pkt->getAddr());
499
500 // as a normal response, it should go back to a master through
501 // one of our slave ports, at this point we are ignoring the
502 // fact that the response layer could be busy and do not touch
503 // its state
504 bool success M5_VAR_USED =
505 slavePorts[dest_port_id]->sendTimingResp(pkt);
506
507 // @todo Put the response in an internal FIFO and pass it on
508 // to the response layer from there
509
510 // currently it is illegal to block responses... can lead
511 // to deadlock
512 assert(success);
513
514 respLayers[dest_port_id]->succeededTiming(packetFinishTime);
515 }
516
517 // remove the request from the routing table
518 routeTo.erase(route_lookup);
519
520 // stats updates
521 transDist[pkt_cmd]++;
522 snoops++;
523
524 return true;
525}
526
527
528void
529CoherentXBar::forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
530 const std::vector<SlavePort*>& dests)
531{
532 DPRINTF(CoherentXBar, "%s for %s address %x size %d\n", __func__,
533 pkt->cmdString(), pkt->getAddr(), pkt->getSize());
534
535 // snoops should only happen if the system isn't bypassing caches
536 assert(!system->bypassCaches());
537
538 unsigned fanout = 0;
539
540 for (const auto& p: dests) {
541 // we could have gotten this request from a snooping master
542 // (corresponding to our own slave port that is also in
543 // snoopPorts) and should not send it back to where it came
544 // from
545 if (exclude_slave_port_id == InvalidPortID ||
546 p->getId() != exclude_slave_port_id) {
547 // cache is not allowed to refuse snoop
548 p->sendTimingSnoopReq(pkt);
549 fanout++;
550 }
551 }
552
553 // Stats for fanout of this forward operation
554 snoopFanout.sample(fanout);
555}
556
557void
558CoherentXBar::recvReqRetry(PortID master_port_id)
559{
560 // responses and snoop responses never block on forwarding them,
561 // so the retry will always be coming from a port to which we
562 // tried to forward a request
563 reqLayers[master_port_id]->recvRetry();
564}
565
566Tick
567CoherentXBar::recvAtomic(PacketPtr pkt, PortID slave_port_id)
568{
569 DPRINTF(CoherentXBar, "recvAtomic: packet src %s addr 0x%x cmd %s\n",
570 slavePorts[slave_port_id]->name(), pkt->getAddr(),
571 pkt->cmdString());
572
573 unsigned int pkt_size = pkt->hasData() ? pkt->getSize() : 0;
574 unsigned int pkt_cmd = pkt->cmdToIndex();
575
576 MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
577 Tick snoop_response_latency = 0;
578
579 if (!system->bypassCaches()) {
580 // forward to all snoopers but the source
581 std::pair<MemCmd, Tick> snoop_result;
582 if (snoopFilter) {
583 // check with the snoop filter where to forward this packet
584 auto sf_res =
585 snoopFilter->lookupRequest(pkt, *slavePorts[slave_port_id]);
586 snoop_response_latency += sf_res.second * clockPeriod();
587 DPRINTF(CoherentXBar, "%s: src %s %s 0x%x"\
588 " SF size: %i lat: %i\n", __func__,
589 slavePorts[slave_port_id]->name(), pkt->cmdString(),
590 pkt->getAddr(), sf_res.first.size(), sf_res.second);
591 snoop_result = forwardAtomic(pkt, slave_port_id, InvalidPortID,
592 sf_res.first);
593 } else {
594 snoop_result = forwardAtomic(pkt, slave_port_id);
595 }
596 snoop_response_cmd = snoop_result.first;
597 snoop_response_latency += snoop_result.second;
598 }
599
600 // even if we had a snoop response, we must continue and also
601 // perform the actual request at the destination
602 PortID master_port_id = findPort(pkt->getAddr());
603
604 // stats updates for the request
605 pktCount[slave_port_id][master_port_id]++;
606 pktSize[slave_port_id][master_port_id] += pkt_size;
607 transDist[pkt_cmd]++;
608
609 // forward the request to the appropriate destination
610 Tick response_latency = masterPorts[master_port_id]->sendAtomic(pkt);
611
612 // Lower levels have replied, tell the snoop filter
613 if (snoopFilter && !system->bypassCaches() && pkt->isResponse()) {
614 snoopFilter->updateResponse(pkt, *slavePorts[slave_port_id]);
615 }
616
617 // if we got a response from a snooper, restore it here
618 if (snoop_response_cmd != MemCmd::InvalidCmd) {
619 // no one else should have responded
620 assert(!pkt->isResponse());
621 pkt->cmd = snoop_response_cmd;
622 response_latency = snoop_response_latency;
623 }
624
625 // add the response data
626 if (pkt->isResponse()) {
627 pkt_size = pkt->hasData() ? pkt->getSize() : 0;
628 pkt_cmd = pkt->cmdToIndex();
629
630 // stats updates
631 pktCount[slave_port_id][master_port_id]++;
632 pktSize[slave_port_id][master_port_id] += pkt_size;
633 transDist[pkt_cmd]++;
634 }
635
636 // @todo: Not setting header time
637 pkt->payloadDelay = response_latency;
638 return response_latency;
639}
640
641Tick
642CoherentXBar::recvAtomicSnoop(PacketPtr pkt, PortID master_port_id)
643{
644 DPRINTF(CoherentXBar, "recvAtomicSnoop: packet src %s addr 0x%x cmd %s\n",
645 masterPorts[master_port_id]->name(), pkt->getAddr(),
646 pkt->cmdString());
647
648 // add the request snoop data
649 snoops++;
650
651 // forward to all snoopers
652 std::pair<MemCmd, Tick> snoop_result;
653 Tick snoop_response_latency = 0;
654 if (snoopFilter) {
655 auto sf_res = snoopFilter->lookupSnoop(pkt);
656 snoop_response_latency += sf_res.second * clockPeriod();
657 DPRINTF(CoherentXBar, "%s: src %s %s 0x%x SF size: %i lat: %i\n",
658 __func__, masterPorts[master_port_id]->name(), pkt->cmdString(),
659 pkt->getAddr(), sf_res.first.size(), sf_res.second);
660 snoop_result = forwardAtomic(pkt, InvalidPortID, master_port_id,
661 sf_res.first);
662 } else {
663 snoop_result = forwardAtomic(pkt, InvalidPortID);
664 }
665 MemCmd snoop_response_cmd = snoop_result.first;
666 snoop_response_latency += snoop_result.second;
667
668 if (snoop_response_cmd != MemCmd::InvalidCmd)
669 pkt->cmd = snoop_response_cmd;
670
671 // add the response snoop data
672 if (pkt->isResponse()) {
673 snoops++;
674 }
675
676 // @todo: Not setting header time
677 pkt->payloadDelay = snoop_response_latency;
678 return snoop_response_latency;
679}
680
681std::pair<MemCmd, Tick>
682CoherentXBar::forwardAtomic(PacketPtr pkt, PortID exclude_slave_port_id,
683 PortID source_master_port_id,
684 const std::vector<SlavePort*>& dests)
685{
686 // the packet may be changed on snoops, record the original
687 // command to enable us to restore it between snoops so that
688 // additional snoops can take place properly
689 MemCmd orig_cmd = pkt->cmd;
690 MemCmd snoop_response_cmd = MemCmd::InvalidCmd;
691 Tick snoop_response_latency = 0;
692
693 // snoops should only happen if the system isn't bypassing caches
694 assert(!system->bypassCaches());
695
696 unsigned fanout = 0;
697
698 for (const auto& p: dests) {
699 // we could have gotten this request from a snooping master
700 // (corresponding to our own slave port that is also in
701 // snoopPorts) and should not send it back to where it came
702 // from
703 if (exclude_slave_port_id != InvalidPortID &&
704 p->getId() == exclude_slave_port_id)
705 continue;
706
707 Tick latency = p->sendAtomicSnoop(pkt);
708 fanout++;
709
710 // in contrast to a functional access, we have to keep on
711 // going as all snoopers must be updated even if we get a
712 // response
713 if (!pkt->isResponse())
714 continue;
715
716 // response from snoop agent
717 assert(pkt->cmd != orig_cmd);
718 assert(pkt->memInhibitAsserted());
719 // should only happen once
720 assert(snoop_response_cmd == MemCmd::InvalidCmd);
721 // save response state
722 snoop_response_cmd = pkt->cmd;
723 snoop_response_latency = latency;
724
725 if (snoopFilter) {
726 // Handle responses by the snoopers and differentiate between
727 // responses to requests from above and snoops from below
728 if (source_master_port_id != InvalidPortID) {
729 // Getting a response for a snoop from below
730 assert(exclude_slave_port_id == InvalidPortID);
731 snoopFilter->updateSnoopForward(pkt, *p,
732 *masterPorts[source_master_port_id]);
733 } else {
734 // Getting a response for a request from above
735 assert(source_master_port_id == InvalidPortID);
736 snoopFilter->updateSnoopResponse(pkt, *p,
737 *slavePorts[exclude_slave_port_id]);
738 }
739 }
740 // restore original packet state for remaining snoopers
741 pkt->cmd = orig_cmd;
742 }
743
744 // Stats for fanout
745 snoopFanout.sample(fanout);
746
747 // the packet is restored as part of the loop and any potential
748 // snoop response is part of the returned pair
749 return std::make_pair(snoop_response_cmd, snoop_response_latency);
750}
751
752void
753CoherentXBar::recvFunctional(PacketPtr pkt, PortID slave_port_id)
754{
755 if (!pkt->isPrint()) {
756 // don't do DPRINTFs on PrintReq as it clutters up the output
757 DPRINTF(CoherentXBar,
758 "recvFunctional: packet src %s addr 0x%x cmd %s\n",
759 slavePorts[slave_port_id]->name(), pkt->getAddr(),
760 pkt->cmdString());
761 }
762
763 if (!system->bypassCaches()) {
764 // forward to all snoopers but the source
765 forwardFunctional(pkt, slave_port_id);
766 }
767
768 // there is no need to continue if the snooping has found what we
769 // were looking for and the packet is already a response
770 if (!pkt->isResponse()) {
771 PortID dest_id = findPort(pkt->getAddr());
772
773 masterPorts[dest_id]->sendFunctional(pkt);
774 }
775}
776
777void
778CoherentXBar::recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id)
779{
780 if (!pkt->isPrint()) {
781 // don't do DPRINTFs on PrintReq as it clutters up the output
782 DPRINTF(CoherentXBar,
783 "recvFunctionalSnoop: packet src %s addr 0x%x cmd %s\n",
784 masterPorts[master_port_id]->name(), pkt->getAddr(),
785 pkt->cmdString());
786 }
787
788 // forward to all snoopers
789 forwardFunctional(pkt, InvalidPortID);
790}
791
792void
793CoherentXBar::forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id)
794{
795 // snoops should only happen if the system isn't bypassing caches
796 assert(!system->bypassCaches());
797
798 for (const auto& p: snoopPorts) {
799 // we could have gotten this request from a snooping master
800 // (corresponding to our own slave port that is also in
801 // snoopPorts) and should not send it back to where it came
802 // from
803 if (exclude_slave_port_id == InvalidPortID ||
804 p->getId() != exclude_slave_port_id)
805 p->sendFunctionalSnoop(pkt);
806
807 // if we get a response we are done
808 if (pkt->isResponse()) {
809 break;
810 }
811 }
812}
813
814unsigned int
815CoherentXBar::drain(DrainManager *dm)
816{
817 // sum up the individual layers
818 unsigned int total = 0;
819 for (auto l: reqLayers)
820 total += l->drain(dm);
821 for (auto l: respLayers)
822 total += l->drain(dm);
823 for (auto l: snoopLayers)
824 total += l->drain(dm);
825 return total;
826}
827
828void
829CoherentXBar::regStats()
830{
831 // register the stats of the base class and our layers
832 BaseXBar::regStats();
833 for (auto l: reqLayers)
834 l->regStats();
835 for (auto l: respLayers)
836 l->regStats();
837 for (auto l: snoopLayers)
838 l->regStats();
839
840 snoops
841 .name(name() + ".snoops")
842 .desc("Total snoops (count)")
843 ;
844
845 snoopFanout
846 .init(0, snoopPorts.size(), 1)
847 .name(name() + ".snoop_fanout")
848 .desc("Request fanout histogram")
849 ;
850}
851
852CoherentXBar *
853CoherentXBarParams::create()
854{
855 return new CoherentXBar(this);
856}