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14 * Copyright (c) 2006 The Regents of The University of Michigan
15 * Copyright (c) 2015 The University of Bologna
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49 * Implementation of the SerialLink Class, modeling Hybrid-Memory-Cube's
53 #include "mem/serial_link.hh"
55 #include "base/trace.hh"
56 #include "debug/SerialLink.hh"
57 #include "params/SerialLink.hh"
59 SerialLink::SerialLinkSlavePort::SerialLinkSlavePort(const std::string
& _name
,
60 SerialLink
& _serial_link
,
61 SerialLinkMasterPort
& _masterPort
,
62 Cycles _delay
, int _resp_limit
,
63 const std::vector
<AddrRange
>&
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)
73 SerialLink::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
),
83 SerialLink::SerialLink(SerialLinkParams
*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
)
96 SerialLink::getMasterPort(const std::string
&if_name
, PortID idx
)
98 if (if_name
== "master")
101 // pass it along to our super class
102 return MemObject::getMasterPort(if_name
, idx
);
106 SerialLink::getSlavePort(const std::string
&if_name
, PortID idx
)
108 if (if_name
== "slave")
111 // pass it along to our super class
112 return MemObject::getSlavePort(if_name
, idx
);
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");
122 // notify the master side of our address ranges
123 slavePort
.sendRangeChange();
127 SerialLink::SerialLinkSlavePort::respQueueFull() const
129 return outstandingResponses
== respQueueLimit
;
133 SerialLink::SerialLinkMasterPort::reqQueueFull() const
135 return transmitList
.size() == reqQueueLimit
;
139 SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt
)
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());
146 DPRINTF(SerialLink
, "Request queue size: %d\n", transmitList
.size());
148 // @todo: We need to pay for this and not just zero it out
149 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
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
);
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
166 slavePort
.schedTimingResp(pkt
, t
);
172 SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt
)
174 DPRINTF(SerialLink
, "recvTimingReq: %s addr 0x%x\n",
175 pkt
->cmdString(), pkt
->getAddr());
177 // we should not see a timing request if we are already in a retry
180 DPRINTF(SerialLink
, "Response queue size: %d outresp: %d\n",
181 transmitList
.size(), outstandingResponses
);
183 // if the request queue is full then there is no hope
184 if (masterPort
.reqQueueFull()) {
185 DPRINTF(SerialLink
, "Request queue full\n");
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");
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
;
201 // no need to set retryReq to false as this is already the
207 // @todo: We need to pay for this and not just zero it out
208 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
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
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
);
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
);
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
239 SerialLink::SerialLinkSlavePort::retryStalledReq()
242 DPRINTF(SerialLink
, "Request waiting for retry, now retrying\n");
249 SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt
, Tick when
)
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
255 if (transmitList
.empty()) {
256 serial_link
.schedule(sendEvent
, when
);
259 assert(transmitList
.size() != reqQueueLimit
);
261 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
266 SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt
, Tick when
)
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
272 if (transmitList
.empty()) {
273 serial_link
.schedule(sendEvent
, when
);
276 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
280 SerialLink::SerialLinkMasterPort::trySendTiming()
282 assert(!transmitList
.empty());
284 DeferredPacket req
= transmitList
.front();
286 assert(req
.tick
<= curTick());
288 PacketPtr pkt
= req
.pkt
;
290 DPRINTF(SerialLink
, "trySend request addr 0x%x, queue size %d\n",
291 pkt
->getAddr(), transmitList
.size());
293 if (sendTimingReq(pkt
)) {
295 transmitList
.pop_front();
297 DPRINTF(SerialLink
, "trySend request successful\n");
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");
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
));
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();
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
323 SerialLink::SerialLinkSlavePort::trySendTiming()
325 assert(!transmitList
.empty());
327 DeferredPacket resp
= transmitList
.front();
329 assert(resp
.tick
<= curTick());
331 PacketPtr pkt
= resp
.pkt
;
333 DPRINTF(SerialLink
, "trySend response addr 0x%x, outstanding %d\n",
334 pkt
->getAddr(), outstandingResponses
);
336 if (sendTimingResp(pkt
)) {
338 transmitList
.pop_front();
339 DPRINTF(SerialLink
, "trySend response successful\n");
341 assert(outstandingResponses
!= 0);
342 --outstandingResponses
;
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");
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
));
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");
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
371 SerialLink::SerialLinkMasterPort::recvReqRetry()
377 SerialLink::SerialLinkSlavePort::recvRespRetry()
383 SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt
)
385 return delay
* serial_link
.clockPeriod() + masterPort
.sendAtomic(pkt
);
389 SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt
)
391 pkt
->pushLabel(name());
393 // check the response queue
394 for (auto i
= transmitList
.begin(); i
!= transmitList
.end(); ++i
) {
395 if (pkt
->checkFunctional((*i
).pkt
)) {
401 // also check the master port's request queue
402 if (masterPort
.checkFunctional(pkt
)) {
408 // fall through if pkt still not satisfied
409 masterPort
.sendFunctional(pkt
);
413 SerialLink::SerialLinkMasterPort::checkFunctional(PacketPtr pkt
)
416 auto i
= transmitList
.begin();
418 while (i
!= transmitList
.end() && !found
) {
419 if (pkt
->checkFunctional((*i
).pkt
)) {
430 SerialLink::SerialLinkSlavePort::getAddrRanges() const
436 SerialLinkParams::create()
438 return new SerialLink(this);