1/*
2 * Copyright (c) 2011-2013 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 * Copyright (c) 2015 The University of Bologna
16 * All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions are
20 * met: redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer;
22 * redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution;
25 * neither the name of the copyright holders nor the names of its
26 * contributors may be used to endorse or promote products derived from
27 * this software without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40 *
41 * Authors: Ali Saidi
42 * Steve Reinhardt
43 * Andreas Hansson
44 * Erfan Azarkhish
45 */
46
47/**
48 * @file
49 * Implementation of the SerialLink Class, modeling Hybrid-Memory-Cube's
50 * serial interface.
51 */
52
53#include "mem/serial_link.hh"
54
55#include "base/trace.hh"
56#include "debug/SerialLink.hh"
57#include "params/SerialLink.hh"
58
59
59SerialLink::SerialLinkSlavePort::SerialLinkSlavePort(const std::string& _name,
60 SerialLink& _serial_link,
61 SerialLinkMasterPort& _masterPort,
62 Cycles _delay, int _resp_limit,
63 const std::vector<AddrRange>&
64 _ranges)
65 : SlavePort(_name, &_serial_link), serial_link(_serial_link),
66 masterPort(_masterPort), delay(_delay),
67 ranges(_ranges.begin(), _ranges.end()),
68 outstandingResponses(0), retryReq(false),
69 respQueueLimit(_resp_limit), sendEvent(*this)
70{
71}
72
73SerialLink::SerialLinkMasterPort::SerialLinkMasterPort(const std::string&
74 _name, SerialLink& _serial_link,
75 SerialLinkSlavePort& _slavePort,
76 Cycles _delay, int _req_limit)
77 : MasterPort(_name, &_serial_link), serial_link(_serial_link),
78 slavePort(_slavePort), delay(_delay), reqQueueLimit(_req_limit),
79 sendEvent(*this)
80{
81}
82
83SerialLink::SerialLink(SerialLinkParams *p)
84 : MemObject(p),
85 slavePort(p->name + ".slave", *this, masterPort,
86 ticksToCycles(p->delay), p->resp_size, p->ranges),
87 masterPort(p->name + ".master", *this, slavePort,
88 ticksToCycles(p->delay), p->req_size),
89 num_lanes(p->num_lanes),
90 link_speed(p->link_speed)
91
92{
93}
94
95BaseMasterPort&
96SerialLink::getMasterPort(const std::string &if_name, PortID idx)
97{
98 if (if_name == "master")
99 return masterPort;
100 else
101 // pass it along to our super class
102 return MemObject::getMasterPort(if_name, idx);
103}
104
105BaseSlavePort&
106SerialLink::getSlavePort(const std::string &if_name, PortID idx)
107{
108 if (if_name == "slave")
109 return slavePort;
110 else
111 // pass it along to our super class
112 return MemObject::getSlavePort(if_name, idx);
113}
114
115void
116SerialLink::init()
117{
118 // make sure both sides are connected and have the same block size
119 if (!slavePort.isConnected() || !masterPort.isConnected())
120 fatal("Both ports of a serial_link must be connected.\n");
121
122 // notify the master side of our address ranges
123 slavePort.sendRangeChange();
124}
125
126bool
127SerialLink::SerialLinkSlavePort::respQueueFull() const
128{
129 return outstandingResponses == respQueueLimit;
130}
131
132bool
133SerialLink::SerialLinkMasterPort::reqQueueFull() const
134{
135 return transmitList.size() == reqQueueLimit;
136}
137
138bool
139SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt)
140{
141 // all checks are done when the request is accepted on the slave
142 // side, so we are guaranteed to have space for the response
143 DPRINTF(SerialLink, "recvTimingResp: %s addr 0x%x\n",
144 pkt->cmdString(), pkt->getAddr());
145
146 DPRINTF(SerialLink, "Request queue size: %d\n", transmitList.size());
147
148 // @todo: We need to pay for this and not just zero it out
149 pkt->headerDelay = pkt->payloadDelay = 0;
150
151 // This is similar to what happens for the request packets:
152 // The serializer will start serialization as soon as it receives the
153 // first flit, but the deserializer (at the host side in this case), will
154 // have to wait to receive the whole packet. So we only account for the
155 // deserialization latency.
156 Cycles cycles = delay;
157 cycles += Cycles(divCeil(pkt->getSize() * 8, serial_link.num_lanes
158 * serial_link.link_speed));
159 Tick t = serial_link.clockEdge(cycles);
160
161 //@todo: If the processor sends two uncached requests towards HMC and the
162 // second one is smaller than the first one. It may happen that the second
163 // one crosses this link faster than the first one (because the packet
164 // waits in the link based on its size). This can reorder the received
165 // response.
166 slavePort.schedTimingResp(pkt, t);
167
168 return true;
169}
170
171bool
172SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt)
173{
174 DPRINTF(SerialLink, "recvTimingReq: %s addr 0x%x\n",
175 pkt->cmdString(), pkt->getAddr());
176
177 // we should not see a timing request if we are already in a retry
178 assert(!retryReq);
179
180 DPRINTF(SerialLink, "Response queue size: %d outresp: %d\n",
181 transmitList.size(), outstandingResponses);
182
183 // if the request queue is full then there is no hope
184 if (masterPort.reqQueueFull()) {
185 DPRINTF(SerialLink, "Request queue full\n");
186 retryReq = true;
187 } else if ( !retryReq ) {
188 // look at the response queue if we expect to see a response
189 bool expects_response = pkt->needsResponse() &&
190 !pkt->cacheResponding();
191 if (expects_response) {
192 if (respQueueFull()) {
193 DPRINTF(SerialLink, "Response queue full\n");
194 retryReq = true;
195 } else {
196 // ok to send the request with space for the response
197 DPRINTF(SerialLink, "Reserving space for response\n");
198 assert(outstandingResponses != respQueueLimit);
199 ++outstandingResponses;
200
201 // no need to set retryReq to false as this is already the
202 // case
203 }
204 }
205
206 if (!retryReq) {
207 // @todo: We need to pay for this and not just zero it out
208 pkt->headerDelay = pkt->payloadDelay = 0;
209
210 // We assume that the serializer component at the transmitter side
211 // does not need to receive the whole packet to start the
212 // serialization (this assumption is consistent with the HMC
213 // standard). But the deserializer waits for the complete packet
214 // to check its integrity first. So everytime a packet crosses a
215 // serial link, we should account for its deserialization latency
216 // only.
217 Cycles cycles = delay;
218 cycles += Cycles(divCeil(pkt->getSize() * 8,
219 serial_link.num_lanes * serial_link.link_speed));
220 Tick t = serial_link.clockEdge(cycles);
221
222 //@todo: If the processor sends two uncached requests towards HMC
223 // and the second one is smaller than the first one. It may happen
224 // that the second one crosses this link faster than the first one
225 // (because the packet waits in the link based on its size).
226 // This can reorder the received response.
227 masterPort.schedTimingReq(pkt, t);
228 }
229 }
230
231 // remember that we are now stalling a packet and that we have to
232 // tell the sending master to retry once space becomes available,
233 // we make no distinction whether the stalling is due to the
234 // request queue or response queue being full
235 return !retryReq;
236}
237
238void
239SerialLink::SerialLinkSlavePort::retryStalledReq()
240{
241 if (retryReq) {
242 DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
243 retryReq = false;
244 sendRetryReq();
245 }
246}
247
248void
249SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
250{
251 // If we're about to put this packet at the head of the queue, we
252 // need to schedule an event to do the transmit. Otherwise there
253 // should already be an event scheduled for sending the head
254 // packet.
255 if (transmitList.empty()) {
256 serial_link.schedule(sendEvent, when);
257 }
258
259 assert(transmitList.size() != reqQueueLimit);
260
261 transmitList.emplace_back(DeferredPacket(pkt, when));
262}
263
264
265void
266SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
267{
268 // If we're about to put this packet at the head of the queue, we
269 // need to schedule an event to do the transmit. Otherwise there
270 // should already be an event scheduled for sending the head
271 // packet.
272 if (transmitList.empty()) {
273 serial_link.schedule(sendEvent, when);
274 }
275
276 transmitList.emplace_back(DeferredPacket(pkt, when));
277}
278
279void
280SerialLink::SerialLinkMasterPort::trySendTiming()
281{
282 assert(!transmitList.empty());
283
284 DeferredPacket req = transmitList.front();
285
286 assert(req.tick <= curTick());
287
288 PacketPtr pkt = req.pkt;
289
290 DPRINTF(SerialLink, "trySend request addr 0x%x, queue size %d\n",
291 pkt->getAddr(), transmitList.size());
292
293 if (sendTimingReq(pkt)) {
294 // send successful
295 transmitList.pop_front();
296
297 DPRINTF(SerialLink, "trySend request successful\n");
298
299 // If there are more packets to send, schedule event to try again.
300 if (!transmitList.empty()) {
301 DeferredPacket next_req = transmitList.front();
302 DPRINTF(SerialLink, "Scheduling next send\n");
303
304 // Make sure bandwidth limitation is met
305 Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
306 serial_link.num_lanes * serial_link.link_speed));
307 Tick t = serial_link.clockEdge(cycles);
308 serial_link.schedule(sendEvent, std::max(next_req.tick, t));
309 }
310
311 // if we have stalled a request due to a full request queue,
312 // then send a retry at this point, also note that if the
313 // request we stalled was waiting for the response queue
314 // rather than the request queue we might stall it again
315 slavePort.retryStalledReq();
316 }
317
318 // if the send failed, then we try again once we receive a retry,
319 // and therefore there is no need to take any action
320}
321
322void
323SerialLink::SerialLinkSlavePort::trySendTiming()
324{
325 assert(!transmitList.empty());
326
327 DeferredPacket resp = transmitList.front();
328
329 assert(resp.tick <= curTick());
330
331 PacketPtr pkt = resp.pkt;
332
333 DPRINTF(SerialLink, "trySend response addr 0x%x, outstanding %d\n",
334 pkt->getAddr(), outstandingResponses);
335
336 if (sendTimingResp(pkt)) {
337 // send successful
338 transmitList.pop_front();
339 DPRINTF(SerialLink, "trySend response successful\n");
340
341 assert(outstandingResponses != 0);
342 --outstandingResponses;
343
344 // If there are more packets to send, schedule event to try again.
345 if (!transmitList.empty()) {
346 DeferredPacket next_resp = transmitList.front();
347 DPRINTF(SerialLink, "Scheduling next send\n");
348
349 // Make sure bandwidth limitation is met
350 Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
351 serial_link.num_lanes * serial_link.link_speed));
352 Tick t = serial_link.clockEdge(cycles);
353 serial_link.schedule(sendEvent, std::max(next_resp.tick, t));
354 }
355
356 // if there is space in the request queue and we were stalling
357 // a request, it will definitely be possible to accept it now
358 // since there is guaranteed space in the response queue
359 if (!masterPort.reqQueueFull() && retryReq) {
360 DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
361 retryReq = false;
362 sendRetryReq();
363 }
364 }
365
366 // if the send failed, then we try again once we receive a retry,
367 // and therefore there is no need to take any action
368}
369
370void
371SerialLink::SerialLinkMasterPort::recvReqRetry()
372{
373 trySendTiming();
374}
375
376void
377SerialLink::SerialLinkSlavePort::recvRespRetry()
378{
379 trySendTiming();
380}
381
382Tick
383SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt)
384{
385 return delay * serial_link.clockPeriod() + masterPort.sendAtomic(pkt);
386}
387
388void
389SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt)
390{
391 pkt->pushLabel(name());
392
393 // check the response queue
394 for (auto i = transmitList.begin(); i != transmitList.end(); ++i) {
395 if (pkt->checkFunctional((*i).pkt)) {
396 pkt->makeResponse();
397 return;
398 }
399 }
400
401 // also check the master port's request queue
402 if (masterPort.checkFunctional(pkt)) {
403 return;
404 }
405
406 pkt->popLabel();
407
408 // fall through if pkt still not satisfied
409 masterPort.sendFunctional(pkt);
410}
411
412bool
413SerialLink::SerialLinkMasterPort::checkFunctional(PacketPtr pkt)
414{
415 bool found = false;
416 auto i = transmitList.begin();
417
418 while (i != transmitList.end() && !found) {
419 if (pkt->checkFunctional((*i).pkt)) {
420 pkt->makeResponse();
421 found = true;
422 }
423 ++i;
424 }
425
426 return found;
427}
428
429AddrRangeList
430SerialLink::SerialLinkSlavePort::getAddrRanges() const
431{
432 return ranges;
433}
434
435SerialLink *
436SerialLinkParams::create()
437{
438 return new SerialLink(this);
439}