tport.cc revision 5606 
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
33bool
34SimpleTimingPort::checkFunctional(PacketPtr pkt)
35{
36    DeferredPacketIterator i = transmitList.begin();
37    DeferredPacketIterator end = transmitList.end();
38
39    for (; i != end; ++i) {
40        PacketPtr target = i->pkt;
41        // If the target contains data, and it overlaps the
42        // probed request, need to update data
43        if (pkt->checkFunctional(target)) {
44            return true;
45        }
46    }
47
48    return false;
49}
50
51void
52SimpleTimingPort::recvFunctional(PacketPtr pkt)
53{
54    if (!checkFunctional(pkt)) {
55        // Just do an atomic access and throw away the returned latency
56        recvAtomic(pkt);
57    }
58}
59
60bool
61SimpleTimingPort::recvTiming(PacketPtr pkt)
62{
63    // If the device is only a slave, it should only be sending
64    // responses, which should never get nacked.  There used to be
65    // code to hanldle nacks here, but I'm pretty sure it didn't work
66    // correctly with the drain code, so that would need to be fixed
67    // if we ever added it back.
68    assert(pkt->isRequest());
69
70    if (pkt->memInhibitAsserted()) {
71        // snooper will supply based on copy of packet
72        // still target's responsibility to delete packet
73        delete pkt;
74        return true;
75    }
76
77    bool needsResponse = pkt->needsResponse();
78    Tick latency = recvAtomic(pkt);
79    // turn packet around to go back to requester if response expected
80    if (needsResponse) {
81        // recvAtomic() should already have turned packet into
82        // atomic response
83        assert(pkt->isResponse());
84        schedSendTiming(pkt, curTick + latency);
85    } else {
86        delete pkt;
87    }
88
89    return true;
90}
91
92
93void
94SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
95{
96    assert(when > curTick);
97    assert(when < curTick + Clock::Int::ms);
98
99    // Nothing is on the list: add it and schedule an event
100    if (transmitList.empty() || when < transmitList.front().tick) {
101        transmitList.push_front(DeferredPacket(when, pkt));
102        schedSendEvent(when);
103        return;
104    }
105
106    // list is non-empty & this belongs at the end
107    if (when >= transmitList.back().tick) {
108        transmitList.push_back(DeferredPacket(when, pkt));
109        return;
110    }
111
112    // this belongs in the middle somewhere
113    DeferredPacketIterator i = transmitList.begin();
114    i++; // already checked for insertion at front
115    DeferredPacketIterator end = transmitList.end();
116
117    for (; i != end; ++i) {
118        if (when < i->tick) {
119            transmitList.insert(i, DeferredPacket(when, pkt));
120            return;
121        }
122    }
123    assert(false); // should never get here
124}
125
126
127void
128SimpleTimingPort::sendDeferredPacket()
129{
130    assert(deferredPacketReady());
131    // take packet off list here; if recvTiming() on the other side
132    // calls sendTiming() back on us (like SimpleTimingCpu does), then
133    // we get confused by having a non-active packet on transmitList
134    DeferredPacket dp = transmitList.front();
135    transmitList.pop_front();
136    bool success = sendTiming(dp.pkt);
137
138    if (success) {
139        if (!transmitList.empty() && !sendEvent->scheduled()) {
140            Tick time = transmitList.front().tick;
141            schedule(sendEvent, time <= curTick ? curTick+1 : time);
142        }
143
144        if (transmitList.empty() && drainEvent) {
145            drainEvent->process();
146            drainEvent = NULL;
147        }
148    } else {
149        // Unsuccessful, need to put back on transmitList.  Callee
150        // should not have messed with it (since it didn't accept that
151        // packet), so we can just push it back on the front.
152        assert(!sendEvent->scheduled());
153        transmitList.push_front(dp);
154    }
155
156    waitingOnRetry = !success;
157
158    if (waitingOnRetry) {
159        DPRINTF(Bus, "Send failed, waiting on retry\n");
160    }
161}
162
163
164void
165SimpleTimingPort::recvRetry()
166{
167    DPRINTF(Bus, "Received retry\n");
168    assert(waitingOnRetry);
169    sendDeferredPacket();
170}
171
172
173void
174SimpleTimingPort::processSendEvent()
175{
176    assert(!waitingOnRetry);
177    sendDeferredPacket();
178}
179
180
181unsigned int
182SimpleTimingPort::drain(Event *de)
183{
184    if (transmitList.size() == 0)
185        return 0;
186    drainEvent = de;
187    return 1;
188}
189