1/*
2 * Copyright (c) 2012,2015,2018 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 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ali Saidi
41 *          Andreas Hansson
42 */
43
44#include "mem/packet_queue.hh"
45
46#include "base/trace.hh"
47#include "debug/Drain.hh"
48#include "debug/PacketQueue.hh"
49
50PacketQueue::PacketQueue(EventManager& _em, const std::string& _label,
51                         const std::string& _sendEventName,
52                         bool force_order,
53                         bool disable_sanity_check)
54    : em(_em), sendEvent([this]{ processSendEvent(); }, _sendEventName),
55      _disableSanityCheck(disable_sanity_check),
56      forceOrder(force_order),
57      label(_label), waitingOnRetry(false)
58{
59}
60
61PacketQueue::~PacketQueue()
62{
63}
64
65void
66PacketQueue::retry()
67{
68    DPRINTF(PacketQueue, "Queue %s received retry\n", name());
69    assert(waitingOnRetry);
70    waitingOnRetry = false;
71    sendDeferredPacket();
72}
73
74bool
75PacketQueue::checkConflict(const PacketPtr pkt, const int blk_size) const
76{
77    // caller is responsible for ensuring that all packets have the
78    // same alignment
79    for (const auto& p : transmitList) {
80        if (p.pkt->matchBlockAddr(pkt, blk_size))
81            return true;
82    }
83    return false;
84}
85
86bool
87PacketQueue::trySatisfyFunctional(PacketPtr pkt)
88{
89    pkt->pushLabel(label);
90
91    auto i = transmitList.begin();
92    bool found = false;
93
94    while (!found && i != transmitList.end()) {
95        // If the buffered packet contains data, and it overlaps the
96        // current packet, then update data
97        found = pkt->trySatisfyFunctional(i->pkt);
98        ++i;
99    }
100
101    pkt->popLabel();
102
103    return found;
104}
105
106void
107PacketQueue::schedSendTiming(PacketPtr pkt, Tick when)
108{
109    DPRINTF(PacketQueue, "%s for %s address %x size %d when %lu ord: %i\n",
110            __func__, pkt->cmdString(), pkt->getAddr(), pkt->getSize(), when,
111            forceOrder);
112
113    // we can still send a packet before the end of this tick
114    assert(when >= curTick());
115
116    // express snoops should never be queued
117    assert(!pkt->isExpressSnoop());
118
119    // add a very basic sanity check on the port to ensure the
120    // invisible buffer is not growing beyond reasonable limits
121    if (!_disableSanityCheck && transmitList.size() > 100) {
122        panic("Packet queue %s has grown beyond 100 packets\n",
123              name());
124    }
125
126    // we should either have an outstanding retry, or a send event
127    // scheduled, but there is an unfortunate corner case where the
128    // x86 page-table walker and timing CPU send out a new request as
129    // part of the receiving of a response (called by
130    // PacketQueue::sendDeferredPacket), in which we end up calling
131    // ourselves again before we had a chance to update waitingOnRetry
132    // assert(waitingOnRetry || sendEvent.scheduled());
133
134    // this belongs in the middle somewhere, so search from the end to
135    // order by tick; however, if forceOrder is set, also make sure
136    // not to re-order in front of some existing packet with the same
137    // address
138    auto it = transmitList.end();
139    while (it != transmitList.begin()) {
140        --it;
141        if ((forceOrder && it->pkt->matchAddr(pkt)) || it->tick <= when) {
142            // emplace inserts the element before the position pointed to by
143            // the iterator, so advance it one step
144            transmitList.emplace(++it, when, pkt);
145            return;
146        }
147    }
148    // either the packet list is empty or this has to be inserted
149    // before every other packet
150    transmitList.emplace_front(when, pkt);
151    schedSendEvent(when);
152}
153
154void
155PacketQueue::schedSendEvent(Tick when)
156{
157    // if we are waiting on a retry just hold off
158    if (waitingOnRetry) {
159        DPRINTF(PacketQueue, "Not scheduling send as waiting for retry\n");
160        assert(!sendEvent.scheduled());
161        return;
162    }
163
164    if (when != MaxTick) {
165        // we cannot go back in time, and to be consistent we stick to
166        // one tick in the future
167        when = std::max(when, curTick() + 1);
168        // @todo Revisit the +1
169
170        if (!sendEvent.scheduled()) {
171            em.schedule(&sendEvent, when);
172        } else if (when < sendEvent.when()) {
173            // if the new time is earlier than when the event
174            // currently is scheduled, move it forward
175            em.reschedule(&sendEvent, when);
176        }
177    } else {
178        // we get a MaxTick when there is no more to send, so if we're
179        // draining, we may be done at this point
180        if (drainState() == DrainState::Draining &&
181            transmitList.empty() && !sendEvent.scheduled()) {
182
183            DPRINTF(Drain, "PacketQueue done draining,"
184                    "processing drain event\n");
185            signalDrainDone();
186        }
187    }
188}
189
190void
191PacketQueue::sendDeferredPacket()
192{
193    // sanity checks
194    assert(!waitingOnRetry);
195    assert(deferredPacketReady());
196
197    DeferredPacket dp = transmitList.front();
198
199    // take the packet of the list before sending it, as sending of
200    // the packet in some cases causes a new packet to be enqueued
201    // (most notaly when responding to the timing CPU, leading to a
202    // new request hitting in the L1 icache, leading to a new
203    // response)
204    transmitList.pop_front();
205
206    // use the appropriate implementation of sendTiming based on the
207    // type of queue
208    waitingOnRetry = !sendTiming(dp.pkt);
209
210    // if we succeeded and are not waiting for a retry, schedule the
211    // next send
212    if (!waitingOnRetry) {
213        schedSendEvent(deferredPacketReadyTime());
214    } else {
215        // put the packet back at the front of the list
216        transmitList.emplace_front(dp);
217    }
218}
219
220void
221PacketQueue::processSendEvent()
222{
223    assert(!waitingOnRetry);
224    sendDeferredPacket();
225}
226
227DrainState
228PacketQueue::drain()
229{
230    if (transmitList.empty()) {
231        return DrainState::Drained;
232    } else {
233        DPRINTF(Drain, "PacketQueue not drained\n");
234        return DrainState::Draining;
235    }
236}
237
238ReqPacketQueue::ReqPacketQueue(EventManager& _em, MasterPort& _masterPort,
239                               const std::string _label)
240    : PacketQueue(_em, _label, name(_masterPort, _label)),
241      masterPort(_masterPort)
242{
243}
244
245bool
246ReqPacketQueue::sendTiming(PacketPtr pkt)
247{
248    return masterPort.sendTimingReq(pkt);
249}
250
251SnoopRespPacketQueue::SnoopRespPacketQueue(EventManager& _em,
252                                           MasterPort& _masterPort,
253                                           bool force_order,
254                                           const std::string _label)
255    : PacketQueue(_em, _label, name(_masterPort, _label), force_order),
256      masterPort(_masterPort)
257{
258}
259
260bool
261SnoopRespPacketQueue::sendTiming(PacketPtr pkt)
262{
263    return masterPort.sendTimingSnoopResp(pkt);
264}
265
266RespPacketQueue::RespPacketQueue(EventManager& _em, SlavePort& _slavePort,
267                                 bool force_order,
268                                 const std::string _label)
269    : PacketQueue(_em, _label, name(_slavePort, _label), force_order),
270      slavePort(_slavePort)
271{
272}
273
274bool
275RespPacketQueue::sendTiming(PacketPtr pkt)
276{
277    return slavePort.sendTimingResp(pkt);
278}
279