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 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}