packet_queue.cc revision 7823 
1/*
2 * Copyright (c) 2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Ali Saidi
29 */
30
31#include "mem/tport.hh"
32
33using namespace std;
34
35SimpleTimingPort::SimpleTimingPort(string pname, MemObject *_owner)
36    : Port(pname, _owner), sendEvent(0), drainEvent(NULL),
37      waitingOnRetry(false)
38{
39    sendEvent =  new EventWrapper<SimpleTimingPort,
40        &SimpleTimingPort::processSendEvent>(this);
41}
42
43SimpleTimingPort::~SimpleTimingPort()
44{
45    delete sendEvent;
46}
47
48bool
49SimpleTimingPort::checkFunctional(PacketPtr pkt)
50{
51    DeferredPacketIterator i = transmitList.begin();
52    DeferredPacketIterator end = transmitList.end();
53
54    for (; i != end; ++i) {
55        PacketPtr target = i->pkt;
56        // If the target contains data, and it overlaps the
57        // probed request, need to update data
58        if (pkt->checkFunctional(target)) {
59            return true;
60        }
61    }
62
63    return false;
64}
65
66void
67SimpleTimingPort::recvFunctional(PacketPtr pkt)
68{
69    if (!checkFunctional(pkt)) {
70        // Just do an atomic access and throw away the returned latency
71        recvAtomic(pkt);
72    }
73}
74
75bool
76SimpleTimingPort::recvTiming(PacketPtr pkt)
77{
78    // If the device is only a slave, it should only be sending
79    // responses, which should never get nacked.  There used to be
80    // code to hanldle nacks here, but I'm pretty sure it didn't work
81    // correctly with the drain code, so that would need to be fixed
82    // if we ever added it back.
83
84    if (pkt->memInhibitAsserted()) {
85        // snooper will supply based on copy of packet
86        // still target's responsibility to delete packet
87        delete pkt;
88        return true;
89    }
90
91    bool needsResponse = pkt->needsResponse();
92    Tick latency = recvAtomic(pkt);
93    // turn packet around to go back to requester if response expected
94    if (needsResponse) {
95        // recvAtomic() should already have turned packet into
96        // atomic response
97        assert(pkt->isResponse());
98        schedSendTiming(pkt, curTick() + latency);
99    } else {
100        delete pkt;
101    }
102
103    return true;
104}
105
106
107void
108SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
109{
110    assert(when > curTick());
111    assert(when < curTick() + SimClock::Int::ms);
112
113    // Nothing is on the list: add it and schedule an event
114    if (transmitList.empty() || when < transmitList.front().tick) {
115        transmitList.push_front(DeferredPacket(when, pkt));
116        schedSendEvent(when);
117        return;
118    }
119
120    // list is non-empty & this belongs at the end
121    if (when >= transmitList.back().tick) {
122        transmitList.push_back(DeferredPacket(when, pkt));
123        return;
124    }
125
126    // this belongs in the middle somewhere
127    DeferredPacketIterator i = transmitList.begin();
128    i++; // already checked for insertion at front
129    DeferredPacketIterator end = transmitList.end();
130
131    for (; i != end; ++i) {
132        if (when < i->tick) {
133            transmitList.insert(i, DeferredPacket(when, pkt));
134            return;
135        }
136    }
137    assert(false); // should never get here
138}
139
140
141void
142SimpleTimingPort::sendDeferredPacket()
143{
144    assert(deferredPacketReady());
145    // take packet off list here; if recvTiming() on the other side
146    // calls sendTiming() back on us (like SimpleTimingCpu does), then
147    // we get confused by having a non-active packet on transmitList
148    DeferredPacket dp = transmitList.front();
149    transmitList.pop_front();
150    bool success = sendTiming(dp.pkt);
151
152    if (success) {
153        if (!transmitList.empty() && !sendEvent->scheduled()) {
154            Tick time = transmitList.front().tick;
155            schedule(sendEvent, time <= curTick() ? curTick()+1 : time);
156        }
157
158        if (transmitList.empty() && drainEvent && !sendEvent->scheduled()) {
159            drainEvent->process();
160            drainEvent = NULL;
161        }
162    } else {
163        // Unsuccessful, need to put back on transmitList.  Callee
164        // should not have messed with it (since it didn't accept that
165        // packet), so we can just push it back on the front.
166        assert(!sendEvent->scheduled());
167        transmitList.push_front(dp);
168    }
169
170    waitingOnRetry = !success;
171
172    if (waitingOnRetry) {
173        DPRINTF(Bus, "Send failed, waiting on retry\n");
174    }
175}
176
177
178void
179SimpleTimingPort::recvRetry()
180{
181    DPRINTF(Bus, "Received retry\n");
182    assert(waitingOnRetry);
183    sendDeferredPacket();
184}
185
186
187void
188SimpleTimingPort::processSendEvent()
189{
190    assert(!waitingOnRetry);
191    sendDeferredPacket();
192}
193
194
195unsigned int
196SimpleTimingPort::drain(Event *de)
197{
198    if (transmitList.size() == 0 && !sendEvent->scheduled())
199        return 0;
200    drainEvent = de;
201    return 1;
202}
203