tport.cc revision 4874 
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
33void
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;
45        }
46    }
47}
48
49void
50SimpleTimingPort::recvFunctional(PacketPtr pkt)
51{
52    checkFunctional(pkt);
53
54    // Just do an atomic access and throw away the returned latency
55    if (!pkt->isResponse())
56        recvAtomic(pkt);
57}
58
59bool
60SimpleTimingPort::recvTiming(PacketPtr pkt)
61{
62    // If the device is only a slave, it should only be sending
63    // responses, which should never get nacked.  There used to be
64    // code to hanldle nacks here, but I'm pretty sure it didn't work
65    // correctly with the drain code, so that would need to be fixed
66    // if we ever added it back.
67    assert(pkt->isRequest());
68
69    if (pkt->memInhibitAsserted()) {
70        // snooper will supply based on copy of packet
71        // still target's responsibility to delete packet
72        delete pkt->req;
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->req;
87        delete pkt;
88    }
89
90    return true;
91}
92
93
94void
95SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
96{
97    assert(when > curTick);
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 and this is not the head, so event should
107    // already be scheduled
108    assert(waitingOnRetry ||
109           (sendEvent->scheduled() && sendEvent->when() <= when));
110
111    // list is non-empty & this belongs at the end
112    if (when >= transmitList.back().tick) {
113        transmitList.push_back(DeferredPacket(when, pkt));
114        return;
115    }
116
117    // this belongs in the middle somewhere
118    DeferredPacketIterator i = transmitList.begin();
119    i++; // already checked for insertion at front
120    DeferredPacketIterator end = transmitList.end();
121
122    for (; i != end; ++i) {
123        if (when < i->tick) {
124            transmitList.insert(i, DeferredPacket(when, pkt));
125            return;
126        }
127    }
128    assert(false); // should never get here
129}
130
131
132void
133SimpleTimingPort::sendDeferredPacket()
134{
135    assert(deferredPacketReady());
136    // take packet off list here; if recvTiming() on the other side
137    // calls sendTiming() back on us (like SimpleTimingCpu does), then
138    // we get confused by having a non-active packet on transmitList
139    DeferredPacket dp = transmitList.front();
140    transmitList.pop_front();
141    bool success = sendTiming(dp.pkt);
142
143    if (success) {
144        if (!transmitList.empty() && !sendEvent->scheduled()) {
145            Tick time = transmitList.front().tick;
146            sendEvent->schedule(time <= curTick ? curTick+1 : time);
147        }
148
149        if (transmitList.empty() && drainEvent) {
150            drainEvent->process();
151            drainEvent = NULL;
152        }
153    } else {
154        // Unsuccessful, need to put back on transmitList.  Callee
155        // should not have messed with it (since it didn't accept that
156        // packet), so we can just push it back on the front.
157        assert(!sendEvent->scheduled());
158        transmitList.push_front(dp);
159    }
160
161    waitingOnRetry = !success;
162
163    if (waitingOnRetry) {
164        DPRINTF(Bus, "Send failed, waiting on retry\n");
165    }
166}
167
168
169void
170SimpleTimingPort::recvRetry()
171{
172    DPRINTF(Bus, "Received retry\n");
173    assert(waitingOnRetry);
174    sendDeferredPacket();
175}
176
177
178void
179SimpleTimingPort::processSendEvent()
180{
181    assert(!waitingOnRetry);
182    sendDeferredPacket();
183}
184
185
186unsigned int
187SimpleTimingPort::drain(Event *de)
188{
189    if (transmitList.size() == 0)
190        return 0;
191    drainEvent = de;
192    return 1;
193}
194