serial_link.cc revision 11321
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
60SerialLink::SerialLinkSlavePort::SerialLinkSlavePort(const std::string& _name,
61                                         SerialLink& _serial_link,
62                                         SerialLinkMasterPort& _masterPort,
63                                         Cycles _delay, int _resp_limit,
64                                         const std::vector<AddrRange>&
65                                         _ranges)
66    : SlavePort(_name, &_serial_link), serial_link(_serial_link),
67      masterPort(_masterPort), delay(_delay),
68      ranges(_ranges.begin(), _ranges.end()),
69      outstandingResponses(0), retryReq(false),
70      respQueueLimit(_resp_limit), sendEvent(*this)
71{
72}
73
74SerialLink::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)
81{
82}
83
84SerialLink::SerialLink(SerialLinkParams *p)
85    : MemObject(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{
92}
93
94BaseMasterPort&
95SerialLink::getMasterPort(const std::string &if_name, PortID idx)
96{
97    if (if_name == "master")
98        return masterPort;
99    else
100        // pass it along to our super class
101        return MemObject::getMasterPort(if_name, idx);
102}
103
104BaseSlavePort&
105SerialLink::getSlavePort(const std::string &if_name, PortID idx)
106{
107    if (if_name == "slave")
108        return slavePort;
109    else
110        // pass it along to our super class
111        return MemObject::getSlavePort(if_name, idx);
112}
113
114void
115SerialLink::init()
116{
117    // make sure both sides are connected and have the same block size
118    if (!slavePort.isConnected() || !masterPort.isConnected())
119        fatal("Both ports of a serial_link must be connected.\n");
120
121    // notify the master side  of our address ranges
122    slavePort.sendRangeChange();
123}
124
125bool
126SerialLink::SerialLinkSlavePort::respQueueFull() const
127{
128    return outstandingResponses == respQueueLimit;
129}
130
131bool
132SerialLink::SerialLinkMasterPort::reqQueueFull() const
133{
134    return transmitList.size() == reqQueueLimit;
135}
136
137bool
138SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt)
139{
140    // all checks are done when the request is accepted on the slave
141    // side, so we are guaranteed to have space for the response
142    DPRINTF(SerialLink, "recvTimingResp: %s addr 0x%x\n",
143            pkt->cmdString(), pkt->getAddr());
144
145    DPRINTF(SerialLink, "Request queue size: %d\n", transmitList.size());
146
147    // @todo: We need to pay for this and not just zero it out
148    pkt->headerDelay = pkt->payloadDelay = 0;
149
150    // This is similar to what happens for the request packets:
151    // The serializer will start serialization as soon as it receives the
152    // first flit, but the deserializer (at the host side in this case), will
153    // have to wait to receive the whole packet. So we only account for the
154    // deserialization latency.
155    Cycles cycles = delay;
156    cycles += Cycles(divCeil(pkt->getSize() * 8, serial_link.num_lanes));
157    Tick t = serial_link.clockEdge(cycles);
158
159    //@todo: If the processor sends two uncached requests towards HMC and the
160    // second one is smaller than the first one. It may happen that the second
161    // one crosses this link faster than the first one (because the packet
162    // waits in the link based on its size). This can reorder the received
163    // response.
164    slavePort.schedTimingResp(pkt, t);
165
166    return true;
167}
168
169bool
170SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt)
171{
172    DPRINTF(SerialLink, "recvTimingReq: %s addr 0x%x\n",
173            pkt->cmdString(), pkt->getAddr());
174
175    // we should not see a timing request if we are already in a retry
176    assert(!retryReq);
177
178    DPRINTF(SerialLink, "Response queue size: %d outresp: %d\n",
179            transmitList.size(), outstandingResponses);
180
181    // if the request queue is full then there is no hope
182    if (masterPort.reqQueueFull()) {
183        DPRINTF(SerialLink, "Request queue full\n");
184        retryReq = true;
185    } else if ( !retryReq ) {
186        // look at the response queue if we expect to see a response
187        bool expects_response = pkt->needsResponse() &&
188            !pkt->cacheResponding();
189        if (expects_response) {
190            if (respQueueFull()) {
191                DPRINTF(SerialLink, "Response queue full\n");
192                retryReq = true;
193            } else {
194                // ok to send the request with space for the response
195                DPRINTF(SerialLink, "Reserving space for response\n");
196                assert(outstandingResponses != respQueueLimit);
197                ++outstandingResponses;
198
199                // no need to set retryReq to false as this is already the
200                // case
201            }
202        }
203
204        if (!retryReq) {
205            // @todo: We need to pay for this and not just zero it out
206            pkt->headerDelay = pkt->payloadDelay = 0;
207
208            // We assume that the serializer component at the transmitter side
209            // does not need to receive the whole packet to start the
210            // serialization (this assumption is consistent with the HMC
211            // standard). But the deserializer waits for the complete packet
212            // to check its integrity first. So everytime a packet crosses a
213            // serial link, we should account for its deserialization latency
214            // only.
215            Cycles cycles = delay;
216            cycles += Cycles(divCeil(pkt->getSize() * 8,
217                serial_link.num_lanes));
218            Tick t = serial_link.clockEdge(cycles);
219
220            //@todo: If the processor sends two uncached requests towards HMC
221            // and the second one is smaller than the first one. It may happen
222            // that the second one crosses this link faster than the first one
223            // (because the packet waits in the link based on its size).
224            // This can reorder the received response.
225            masterPort.schedTimingReq(pkt, t);
226        }
227    }
228
229    // remember that we are now stalling a packet and that we have to
230    // tell the sending master to retry once space becomes available,
231    // we make no distinction whether the stalling is due to the
232    // request queue or response queue being full
233    return !retryReq;
234}
235
236void
237SerialLink::SerialLinkSlavePort::retryStalledReq()
238{
239    if (retryReq) {
240        DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
241        retryReq = false;
242        sendRetryReq();
243    }
244}
245
246void
247SerialLink::SerialLinkMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
248{
249    // If we're about to put this packet at the head of the queue, we
250    // need to schedule an event to do the transmit.  Otherwise there
251    // should already be an event scheduled for sending the head
252    // packet.
253    if (transmitList.empty()) {
254        serial_link.schedule(sendEvent, when);
255    }
256
257    assert(transmitList.size() != reqQueueLimit);
258
259    transmitList.emplace_back(DeferredPacket(pkt, when));
260}
261
262
263void
264SerialLink::SerialLinkSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
265{
266    // If we're about to put this packet at the head of the queue, we
267    // need to schedule an event to do the transmit.  Otherwise there
268    // should already be an event scheduled for sending the head
269    // packet.
270    if (transmitList.empty()) {
271        serial_link.schedule(sendEvent, when);
272    }
273
274    transmitList.emplace_back(DeferredPacket(pkt, when));
275}
276
277void
278SerialLink::SerialLinkMasterPort::trySendTiming()
279{
280    assert(!transmitList.empty());
281
282    DeferredPacket req = transmitList.front();
283
284    assert(req.tick <= curTick());
285
286    PacketPtr pkt = req.pkt;
287
288    DPRINTF(SerialLink, "trySend request addr 0x%x, queue size %d\n",
289            pkt->getAddr(), transmitList.size());
290
291    if (sendTimingReq(pkt)) {
292        // send successful
293        transmitList.pop_front();
294
295        DPRINTF(SerialLink, "trySend request successful\n");
296
297        // If there are more packets to send, schedule event to try again.
298        if (!transmitList.empty()) {
299            DeferredPacket next_req = transmitList.front();
300            DPRINTF(SerialLink, "Scheduling next send\n");
301
302            // Make sure bandwidth limitation is met
303            Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
304                serial_link.num_lanes));
305            Tick t = serial_link.clockEdge(cycles);
306            serial_link.schedule(sendEvent, std::max(next_req.tick, t));
307        }
308
309        // if we have stalled a request due to a full request queue,
310        // then send a retry at this point, also note that if the
311        // request we stalled was waiting for the response queue
312        // rather than the request queue we might stall it again
313        slavePort.retryStalledReq();
314    }
315
316    // if the send failed, then we try again once we receive a retry,
317    // and therefore there is no need to take any action
318}
319
320void
321SerialLink::SerialLinkSlavePort::trySendTiming()
322{
323    assert(!transmitList.empty());
324
325    DeferredPacket resp = transmitList.front();
326
327    assert(resp.tick <= curTick());
328
329    PacketPtr pkt = resp.pkt;
330
331    DPRINTF(SerialLink, "trySend response addr 0x%x, outstanding %d\n",
332            pkt->getAddr(), outstandingResponses);
333
334    if (sendTimingResp(pkt)) {
335        // send successful
336        transmitList.pop_front();
337        DPRINTF(SerialLink, "trySend response successful\n");
338
339        assert(outstandingResponses != 0);
340        --outstandingResponses;
341
342        // If there are more packets to send, schedule event to try again.
343        if (!transmitList.empty()) {
344            DeferredPacket next_resp = transmitList.front();
345            DPRINTF(SerialLink, "Scheduling next send\n");
346
347            // Make sure bandwidth limitation is met
348            Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
349                serial_link.num_lanes));
350            Tick t = serial_link.clockEdge(cycles);
351            serial_link.schedule(sendEvent, std::max(next_resp.tick, t));
352        }
353
354        // if there is space in the request queue and we were stalling
355        // a request, it will definitely be possible to accept it now
356        // since there is guaranteed space in the response queue
357        if (!masterPort.reqQueueFull() && retryReq) {
358            DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
359            retryReq = false;
360            sendRetryReq();
361        }
362    }
363
364    // if the send failed, then we try again once we receive a retry,
365    // and therefore there is no need to take any action
366}
367
368void
369SerialLink::SerialLinkMasterPort::recvReqRetry()
370{
371    trySendTiming();
372}
373
374void
375SerialLink::SerialLinkSlavePort::recvRespRetry()
376{
377    trySendTiming();
378}
379
380Tick
381SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt)
382{
383    return delay * serial_link.clockPeriod() + masterPort.sendAtomic(pkt);
384}
385
386void
387SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt)
388{
389    pkt->pushLabel(name());
390
391    // check the response queue
392    for (auto i = transmitList.begin();  i != transmitList.end(); ++i) {
393        if (pkt->checkFunctional((*i).pkt)) {
394            pkt->makeResponse();
395            return;
396        }
397    }
398
399    // also check the master port's request queue
400    if (masterPort.checkFunctional(pkt)) {
401        return;
402    }
403
404    pkt->popLabel();
405
406    // fall through if pkt still not satisfied
407    masterPort.sendFunctional(pkt);
408}
409
410bool
411SerialLink::SerialLinkMasterPort::checkFunctional(PacketPtr pkt)
412{
413    bool found = false;
414    auto i = transmitList.begin();
415
416    while (i != transmitList.end() && !found) {
417        if (pkt->checkFunctional((*i).pkt)) {
418            pkt->makeResponse();
419            found = true;
420        }
421        ++i;
422    }
423
424    return found;
425}
426
427AddrRangeList
428SerialLink::SerialLinkSlavePort::getAddrRanges() const
429{
430    return ranges;
431}
432
433SerialLink *
434SerialLinkParams::create()
435{
436    return new SerialLink(this);
437}
438