packet_queue.cc revision 8708 
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 "debug/Bus.hh"
32#include "mem/mem_object.hh"
33#include "mem/tport.hh"
34
35using namespace std;
36
37SimpleTimingPort::SimpleTimingPort(string pname, MemObject *_owner)
38    : Port(pname, _owner), sendEvent(NULL), drainEvent(NULL),
39      waitingOnRetry(false)
40{
41    sendEvent =  new EventWrapper<SimpleTimingPort,
42        &SimpleTimingPort::processSendEvent>(this);
43}
44
45SimpleTimingPort::~SimpleTimingPort()
46{
47    delete sendEvent;
48}
49
50bool
51SimpleTimingPort::checkFunctional(PacketPtr pkt)
52{
53    DeferredPacketIterator i = transmitList.begin();
54    DeferredPacketIterator end = transmitList.end();
55
56    for (; i != end; ++i) {
57        PacketPtr target = i->pkt;
58        // If the target contains data, and it overlaps the
59        // probed request, need to update data
60        if (pkt->checkFunctional(target)) {
61            return true;
62        }
63    }
64
65    return false;
66}
67
68void
69SimpleTimingPort::recvFunctional(PacketPtr pkt)
70{
71    if (!checkFunctional(pkt)) {
72        // Just do an atomic access and throw away the returned latency
73        recvAtomic(pkt);
74    }
75}
76
77bool
78SimpleTimingPort::recvTiming(PacketPtr pkt)
79{
80    // If the device is only a slave, it should only be sending
81    // responses, which should never get nacked.  There used to be
82    // code to hanldle nacks here, but I'm pretty sure it didn't work
83    // correctly with the drain code, so that would need to be fixed
84    // if we ever added it back.
85
86    if (pkt->memInhibitAsserted()) {
87        // snooper will supply based on copy of packet
88        // still target's responsibility to delete packet
89        delete pkt;
90        return true;
91    }
92
93    bool needsResponse = pkt->needsResponse();
94    Tick latency = recvAtomic(pkt);
95    // turn packet around to go back to requester if response expected
96    if (needsResponse) {
97        // recvAtomic() should already have turned packet into
98        // atomic response
99        assert(pkt->isResponse());
100        schedSendTiming(pkt, curTick() + latency);
101    } else {
102        delete pkt;
103    }
104
105    return true;
106}
107
108void
109SimpleTimingPort::schedSendEvent(Tick when)
110{
111    if (waitingOnRetry) {
112        assert(!sendEvent->scheduled());
113        return;
114    }
115
116    if (!sendEvent->scheduled()) {
117        owner->schedule(sendEvent, when);
118    } else if (sendEvent->when() > when) {
119        owner->reschedule(sendEvent, when);
120    }
121}
122
123void
124SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
125{
126    assert(when > curTick());
127    assert(when < curTick() + SimClock::Int::ms);
128
129    // Nothing is on the list: add it and schedule an event
130    if (transmitList.empty() || when < transmitList.front().tick) {
131        transmitList.push_front(DeferredPacket(when, pkt));
132        schedSendEvent(when);
133        return;
134    }
135
136    // list is non-empty & this belongs at the end
137    if (when >= transmitList.back().tick) {
138        transmitList.push_back(DeferredPacket(when, pkt));
139        return;
140    }
141
142    // this belongs in the middle somewhere
143    DeferredPacketIterator i = transmitList.begin();
144    i++; // already checked for insertion at front
145    DeferredPacketIterator end = transmitList.end();
146
147    for (; i != end; ++i) {
148        if (when < i->tick) {
149            transmitList.insert(i, DeferredPacket(when, pkt));
150            return;
151        }
152    }
153    assert(false); // should never get here
154}
155
156
157void
158SimpleTimingPort::sendDeferredPacket()
159{
160    assert(deferredPacketReady());
161    // take packet off list here; if recvTiming() on the other side
162    // calls sendTiming() back on us (like SimpleTimingCpu does), then
163    // we get confused by having a non-active packet on transmitList
164    DeferredPacket dp = transmitList.front();
165    transmitList.pop_front();
166    bool success = sendTiming(dp.pkt);
167
168    if (success) {
169        if (!transmitList.empty() && !sendEvent->scheduled()) {
170            Tick time = transmitList.front().tick;
171            owner->schedule(sendEvent, time <= curTick() ? curTick()+1 : time);
172        }
173
174        if (transmitList.empty() && drainEvent && !sendEvent->scheduled()) {
175            drainEvent->process();
176            drainEvent = NULL;
177        }
178    } else {
179        // Unsuccessful, need to put back on transmitList.  Callee
180        // should not have messed with it (since it didn't accept that
181        // packet), so we can just push it back on the front.
182        assert(!sendEvent->scheduled());
183        transmitList.push_front(dp);
184    }
185
186    waitingOnRetry = !success;
187
188    if (waitingOnRetry) {
189        DPRINTF(Bus, "Send failed, waiting on retry\n");
190    }
191}
192
193
194void
195SimpleTimingPort::recvRetry()
196{
197    DPRINTF(Bus, "Received retry\n");
198    assert(waitingOnRetry);
199    sendDeferredPacket();
200}
201
202
203void
204SimpleTimingPort::processSendEvent()
205{
206    assert(!waitingOnRetry);
207    sendDeferredPacket();
208}
209
210
211unsigned int
212SimpleTimingPort::drain(Event *de)
213{
214    if (transmitList.size() == 0 && !sendEvent->scheduled())
215        return 0;
216    drainEvent = de;
217    return 1;
218}
219