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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
),
70 sendEvent([this]{ trySendTiming(); }, _name
)
74 SerialLink::SerialLinkMasterPort::SerialLinkMasterPort(const std::string
&
75 _name
, SerialLink
& _serial_link
,
76 SerialLinkSlavePort
& _slavePort
,
77 Cycles _delay
, int _req_limit
)
78 : MasterPort(_name
, &_serial_link
), serial_link(_serial_link
),
79 slavePort(_slavePort
), delay(_delay
), reqQueueLimit(_req_limit
),
80 sendEvent([this]{ trySendTiming(); }, _name
)
84 SerialLink::SerialLink(SerialLinkParams
*p
)
86 slavePort(p
->name
+ ".slave", *this, masterPort
,
87 ticksToCycles(p
->delay
), p
->resp_size
, p
->ranges
),
88 masterPort(p
->name
+ ".master", *this, slavePort
,
89 ticksToCycles(p
->delay
), p
->req_size
),
90 num_lanes(p
->num_lanes
),
91 link_speed(p
->link_speed
)
97 SerialLink::getMasterPort(const std::string
&if_name
, PortID idx
)
99 if (if_name
== "master")
102 // pass it along to our super class
103 return MemObject::getMasterPort(if_name
, idx
);
107 SerialLink::getSlavePort(const std::string
&if_name
, PortID idx
)
109 if (if_name
== "slave")
112 // pass it along to our super class
113 return MemObject::getSlavePort(if_name
, idx
);
119 // make sure both sides are connected and have the same block size
120 if (!slavePort
.isConnected() || !masterPort
.isConnected())
121 fatal("Both ports of a serial_link must be connected.\n");
123 // notify the master side of our address ranges
124 slavePort
.sendRangeChange();
128 SerialLink::SerialLinkSlavePort::respQueueFull() const
130 return outstandingResponses
== respQueueLimit
;
134 SerialLink::SerialLinkMasterPort::reqQueueFull() const
136 return transmitList
.size() == reqQueueLimit
;
140 SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt
)
142 // all checks are done when the request is accepted on the slave
143 // side, so we are guaranteed to have space for the response
144 DPRINTF(SerialLink
, "recvTimingResp: %s addr 0x%x\n",
145 pkt
->cmdString(), pkt
->getAddr());
147 DPRINTF(SerialLink
, "Request queue size: %d\n", transmitList
.size());
149 // @todo: We need to pay for this and not just zero it out
150 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
152 // This is similar to what happens for the request packets:
153 // The serializer will start serialization as soon as it receives the
154 // first flit, but the deserializer (at the host side in this case), will
155 // have to wait to receive the whole packet. So we only account for the
156 // deserialization latency.
157 Cycles cycles
= delay
;
158 cycles
+= Cycles(divCeil(pkt
->getSize() * 8, serial_link
.num_lanes
159 * serial_link
.link_speed
));
160 Tick t
= serial_link
.clockEdge(cycles
);
162 //@todo: If the processor sends two uncached requests towards HMC and the
163 // second one is smaller than the first one. It may happen that the second
164 // one crosses this link faster than the first one (because the packet
165 // waits in the link based on its size). This can reorder the received
167 slavePort
.schedTimingResp(pkt
, t
);
173 SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt
)
175 DPRINTF(SerialLink
, "recvTimingReq: %s addr 0x%x\n",
176 pkt
->cmdString(), pkt
->getAddr());
178 // we should not see a timing request if we are already in a retry
181 DPRINTF(SerialLink
, "Response queue size: %d outresp: %d\n",
182 transmitList
.size(), outstandingResponses
);
184 // if the request queue is full then there is no hope
185 if (masterPort
.reqQueueFull()) {
186 DPRINTF(SerialLink
, "Request queue full\n");
188 } else if ( !retryReq
) {
189 // look at the response queue if we expect to see a response
190 bool expects_response
= pkt
->needsResponse() &&
191 !pkt
->cacheResponding();
192 if (expects_response
) {
193 if (respQueueFull()) {
194 DPRINTF(SerialLink
, "Response queue full\n");
197 // ok to send the request with space for the response
198 DPRINTF(SerialLink
, "Reserving space for response\n");
199 assert(outstandingResponses
!= respQueueLimit
);
200 ++outstandingResponses
;
202 // no need to set retryReq to false as this is already the
208 // @todo: We need to pay for this and not just zero it out
209 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
211 // We assume that the serializer component at the transmitter side
212 // does not need to receive the whole packet to start the
213 // serialization (this assumption is consistent with the HMC
214 // standard). But the deserializer waits for the complete packet
215 // to check its integrity first. So everytime a packet crosses a
216 // serial link, we should account for its deserialization latency
218 Cycles cycles
= delay
;
219 cycles
+= Cycles(divCeil(pkt
->getSize() * 8,
220 serial_link
.num_lanes
* serial_link
.link_speed
));
221 Tick t
= serial_link
.clockEdge(cycles
);
223 //@todo: If the processor sends two uncached requests towards HMC
224 // and the second one is smaller than the first one. It may happen
225 // that the second one crosses this link faster than the first one
226 // (because the packet waits in the link based on its size).
227 // This can reorder the received response.
228 masterPort
.schedTimingReq(pkt
, t
);
232 // remember that we are now stalling a packet and that we have to
233 // tell the sending master to retry once space becomes available,
234 // we make no distinction whether the stalling is due to the
235 // request queue or response queue being full
240 SerialLink::SerialLinkSlavePort::retryStalledReq()
243 DPRINTF(SerialLink
, "Request waiting for retry, now retrying\n");
250 SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt
, Tick when
)
252 // If we're about to put this packet at the head of the queue, we
253 // need to schedule an event to do the transmit. Otherwise there
254 // should already be an event scheduled for sending the head
256 if (transmitList
.empty()) {
257 serial_link
.schedule(sendEvent
, when
);
260 assert(transmitList
.size() != reqQueueLimit
);
262 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
267 SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt
, Tick when
)
269 // If we're about to put this packet at the head of the queue, we
270 // need to schedule an event to do the transmit. Otherwise there
271 // should already be an event scheduled for sending the head
273 if (transmitList
.empty()) {
274 serial_link
.schedule(sendEvent
, when
);
277 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
281 SerialLink::SerialLinkMasterPort::trySendTiming()
283 assert(!transmitList
.empty());
285 DeferredPacket req
= transmitList
.front();
287 assert(req
.tick
<= curTick());
289 PacketPtr pkt
= req
.pkt
;
291 DPRINTF(SerialLink
, "trySend request addr 0x%x, queue size %d\n",
292 pkt
->getAddr(), transmitList
.size());
294 if (sendTimingReq(pkt
)) {
296 transmitList
.pop_front();
298 DPRINTF(SerialLink
, "trySend request successful\n");
300 // If there are more packets to send, schedule event to try again.
301 if (!transmitList
.empty()) {
302 DeferredPacket next_req
= transmitList
.front();
303 DPRINTF(SerialLink
, "Scheduling next send\n");
305 // Make sure bandwidth limitation is met
306 Cycles cycles
= Cycles(divCeil(pkt
->getSize() * 8,
307 serial_link
.num_lanes
* serial_link
.link_speed
));
308 Tick t
= serial_link
.clockEdge(cycles
);
309 serial_link
.schedule(sendEvent
, std::max(next_req
.tick
, t
));
312 // if we have stalled a request due to a full request queue,
313 // then send a retry at this point, also note that if the
314 // request we stalled was waiting for the response queue
315 // rather than the request queue we might stall it again
316 slavePort
.retryStalledReq();
319 // if the send failed, then we try again once we receive a retry,
320 // and therefore there is no need to take any action
324 SerialLink::SerialLinkSlavePort::trySendTiming()
326 assert(!transmitList
.empty());
328 DeferredPacket resp
= transmitList
.front();
330 assert(resp
.tick
<= curTick());
332 PacketPtr pkt
= resp
.pkt
;
334 DPRINTF(SerialLink
, "trySend response addr 0x%x, outstanding %d\n",
335 pkt
->getAddr(), outstandingResponses
);
337 if (sendTimingResp(pkt
)) {
339 transmitList
.pop_front();
340 DPRINTF(SerialLink
, "trySend response successful\n");
342 assert(outstandingResponses
!= 0);
343 --outstandingResponses
;
345 // If there are more packets to send, schedule event to try again.
346 if (!transmitList
.empty()) {
347 DeferredPacket next_resp
= transmitList
.front();
348 DPRINTF(SerialLink
, "Scheduling next send\n");
350 // Make sure bandwidth limitation is met
351 Cycles cycles
= Cycles(divCeil(pkt
->getSize() * 8,
352 serial_link
.num_lanes
* serial_link
.link_speed
));
353 Tick t
= serial_link
.clockEdge(cycles
);
354 serial_link
.schedule(sendEvent
, std::max(next_resp
.tick
, t
));
357 // if there is space in the request queue and we were stalling
358 // a request, it will definitely be possible to accept it now
359 // since there is guaranteed space in the response queue
360 if (!masterPort
.reqQueueFull() && retryReq
) {
361 DPRINTF(SerialLink
, "Request waiting for retry, now retrying\n");
367 // if the send failed, then we try again once we receive a retry,
368 // and therefore there is no need to take any action
372 SerialLink::SerialLinkMasterPort::recvReqRetry()
378 SerialLink::SerialLinkSlavePort::recvRespRetry()
384 SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt
)
386 return delay
* serial_link
.clockPeriod() + masterPort
.sendAtomic(pkt
);
390 SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt
)
392 pkt
->pushLabel(name());
394 // check the response queue
395 for (auto i
= transmitList
.begin(); i
!= transmitList
.end(); ++i
) {
396 if (pkt
->trySatisfyFunctional((*i
).pkt
)) {
402 // also check the master port's request queue
403 if (masterPort
.trySatisfyFunctional(pkt
)) {
409 // fall through if pkt still not satisfied
410 masterPort
.sendFunctional(pkt
);
414 SerialLink::SerialLinkMasterPort::trySatisfyFunctional(PacketPtr pkt
)
417 auto i
= transmitList
.begin();
419 while (i
!= transmitList
.end() && !found
) {
420 if (pkt
->trySatisfyFunctional((*i
).pkt
)) {
431 SerialLink::SerialLinkSlavePort::getAddrRanges() const
437 SerialLinkParams::create()
439 return new SerialLink(this);