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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::getPort(const std::string
&if_name
, PortID idx
)
99 if (if_name
== "master")
101 else if (if_name
== "slave")
104 // pass it along to our super class
105 return MemObject::getPort(if_name
, idx
);
111 // make sure both sides are connected and have the same block size
112 if (!slavePort
.isConnected() || !masterPort
.isConnected())
113 fatal("Both ports of a serial_link must be connected.\n");
115 // notify the master side of our address ranges
116 slavePort
.sendRangeChange();
120 SerialLink::SerialLinkSlavePort::respQueueFull() const
122 return outstandingResponses
== respQueueLimit
;
126 SerialLink::SerialLinkMasterPort::reqQueueFull() const
128 return transmitList
.size() == reqQueueLimit
;
132 SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt
)
134 // all checks are done when the request is accepted on the slave
135 // side, so we are guaranteed to have space for the response
136 DPRINTF(SerialLink
, "recvTimingResp: %s addr 0x%x\n",
137 pkt
->cmdString(), pkt
->getAddr());
139 DPRINTF(SerialLink
, "Request queue size: %d\n", transmitList
.size());
141 // @todo: We need to pay for this and not just zero it out
142 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
144 // This is similar to what happens for the request packets:
145 // The serializer will start serialization as soon as it receives the
146 // first flit, but the deserializer (at the host side in this case), will
147 // have to wait to receive the whole packet. So we only account for the
148 // deserialization latency.
149 Cycles cycles
= delay
;
150 cycles
+= Cycles(divCeil(pkt
->getSize() * 8, serial_link
.num_lanes
151 * serial_link
.link_speed
));
152 Tick t
= serial_link
.clockEdge(cycles
);
154 //@todo: If the processor sends two uncached requests towards HMC and the
155 // second one is smaller than the first one. It may happen that the second
156 // one crosses this link faster than the first one (because the packet
157 // waits in the link based on its size). This can reorder the received
159 slavePort
.schedTimingResp(pkt
, t
);
165 SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt
)
167 DPRINTF(SerialLink
, "recvTimingReq: %s addr 0x%x\n",
168 pkt
->cmdString(), pkt
->getAddr());
170 // we should not see a timing request if we are already in a retry
173 DPRINTF(SerialLink
, "Response queue size: %d outresp: %d\n",
174 transmitList
.size(), outstandingResponses
);
176 // if the request queue is full then there is no hope
177 if (masterPort
.reqQueueFull()) {
178 DPRINTF(SerialLink
, "Request queue full\n");
180 } else if ( !retryReq
) {
181 // look at the response queue if we expect to see a response
182 bool expects_response
= pkt
->needsResponse() &&
183 !pkt
->cacheResponding();
184 if (expects_response
) {
185 if (respQueueFull()) {
186 DPRINTF(SerialLink
, "Response queue full\n");
189 // ok to send the request with space for the response
190 DPRINTF(SerialLink
, "Reserving space for response\n");
191 assert(outstandingResponses
!= respQueueLimit
);
192 ++outstandingResponses
;
194 // no need to set retryReq to false as this is already the
200 // @todo: We need to pay for this and not just zero it out
201 pkt
->headerDelay
= pkt
->payloadDelay
= 0;
203 // We assume that the serializer component at the transmitter side
204 // does not need to receive the whole packet to start the
205 // serialization (this assumption is consistent with the HMC
206 // standard). But the deserializer waits for the complete packet
207 // to check its integrity first. So everytime a packet crosses a
208 // serial link, we should account for its deserialization latency
210 Cycles cycles
= delay
;
211 cycles
+= Cycles(divCeil(pkt
->getSize() * 8,
212 serial_link
.num_lanes
* serial_link
.link_speed
));
213 Tick t
= serial_link
.clockEdge(cycles
);
215 //@todo: If the processor sends two uncached requests towards HMC
216 // and the second one is smaller than the first one. It may happen
217 // that the second one crosses this link faster than the first one
218 // (because the packet waits in the link based on its size).
219 // This can reorder the received response.
220 masterPort
.schedTimingReq(pkt
, t
);
224 // remember that we are now stalling a packet and that we have to
225 // tell the sending master to retry once space becomes available,
226 // we make no distinction whether the stalling is due to the
227 // request queue or response queue being full
232 SerialLink::SerialLinkSlavePort::retryStalledReq()
235 DPRINTF(SerialLink
, "Request waiting for retry, now retrying\n");
242 SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt
, Tick when
)
244 // If we're about to put this packet at the head of the queue, we
245 // need to schedule an event to do the transmit. Otherwise there
246 // should already be an event scheduled for sending the head
248 if (transmitList
.empty()) {
249 serial_link
.schedule(sendEvent
, when
);
252 assert(transmitList
.size() != reqQueueLimit
);
254 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
259 SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt
, Tick when
)
261 // If we're about to put this packet at the head of the queue, we
262 // need to schedule an event to do the transmit. Otherwise there
263 // should already be an event scheduled for sending the head
265 if (transmitList
.empty()) {
266 serial_link
.schedule(sendEvent
, when
);
269 transmitList
.emplace_back(DeferredPacket(pkt
, when
));
273 SerialLink::SerialLinkMasterPort::trySendTiming()
275 assert(!transmitList
.empty());
277 DeferredPacket req
= transmitList
.front();
279 assert(req
.tick
<= curTick());
281 PacketPtr pkt
= req
.pkt
;
283 DPRINTF(SerialLink
, "trySend request addr 0x%x, queue size %d\n",
284 pkt
->getAddr(), transmitList
.size());
286 if (sendTimingReq(pkt
)) {
288 transmitList
.pop_front();
290 DPRINTF(SerialLink
, "trySend request successful\n");
292 // If there are more packets to send, schedule event to try again.
293 if (!transmitList
.empty()) {
294 DeferredPacket next_req
= transmitList
.front();
295 DPRINTF(SerialLink
, "Scheduling next send\n");
297 // Make sure bandwidth limitation is met
298 Cycles cycles
= Cycles(divCeil(pkt
->getSize() * 8,
299 serial_link
.num_lanes
* serial_link
.link_speed
));
300 Tick t
= serial_link
.clockEdge(cycles
);
301 serial_link
.schedule(sendEvent
, std::max(next_req
.tick
, t
));
304 // if we have stalled a request due to a full request queue,
305 // then send a retry at this point, also note that if the
306 // request we stalled was waiting for the response queue
307 // rather than the request queue we might stall it again
308 slavePort
.retryStalledReq();
311 // if the send failed, then we try again once we receive a retry,
312 // and therefore there is no need to take any action
316 SerialLink::SerialLinkSlavePort::trySendTiming()
318 assert(!transmitList
.empty());
320 DeferredPacket resp
= transmitList
.front();
322 assert(resp
.tick
<= curTick());
324 PacketPtr pkt
= resp
.pkt
;
326 DPRINTF(SerialLink
, "trySend response addr 0x%x, outstanding %d\n",
327 pkt
->getAddr(), outstandingResponses
);
329 if (sendTimingResp(pkt
)) {
331 transmitList
.pop_front();
332 DPRINTF(SerialLink
, "trySend response successful\n");
334 assert(outstandingResponses
!= 0);
335 --outstandingResponses
;
337 // If there are more packets to send, schedule event to try again.
338 if (!transmitList
.empty()) {
339 DeferredPacket next_resp
= transmitList
.front();
340 DPRINTF(SerialLink
, "Scheduling next send\n");
342 // Make sure bandwidth limitation is met
343 Cycles cycles
= Cycles(divCeil(pkt
->getSize() * 8,
344 serial_link
.num_lanes
* serial_link
.link_speed
));
345 Tick t
= serial_link
.clockEdge(cycles
);
346 serial_link
.schedule(sendEvent
, std::max(next_resp
.tick
, t
));
349 // if there is space in the request queue and we were stalling
350 // a request, it will definitely be possible to accept it now
351 // since there is guaranteed space in the response queue
352 if (!masterPort
.reqQueueFull() && retryReq
) {
353 DPRINTF(SerialLink
, "Request waiting for retry, now retrying\n");
359 // if the send failed, then we try again once we receive a retry,
360 // and therefore there is no need to take any action
364 SerialLink::SerialLinkMasterPort::recvReqRetry()
370 SerialLink::SerialLinkSlavePort::recvRespRetry()
376 SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt
)
378 return delay
* serial_link
.clockPeriod() + masterPort
.sendAtomic(pkt
);
382 SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt
)
384 pkt
->pushLabel(name());
386 // check the response queue
387 for (auto i
= transmitList
.begin(); i
!= transmitList
.end(); ++i
) {
388 if (pkt
->trySatisfyFunctional((*i
).pkt
)) {
394 // also check the master port's request queue
395 if (masterPort
.trySatisfyFunctional(pkt
)) {
401 // fall through if pkt still not satisfied
402 masterPort
.sendFunctional(pkt
);
406 SerialLink::SerialLinkMasterPort::trySatisfyFunctional(PacketPtr pkt
)
409 auto i
= transmitList
.begin();
411 while (i
!= transmitList
.end() && !found
) {
412 if (pkt
->trySatisfyFunctional((*i
).pkt
)) {
423 SerialLink::SerialLinkSlavePort::getAddrRanges() const
429 SerialLinkParams::create()
431 return new SerialLink(this);