bridge.cc revision 2665:a124942bacb8 
1
2/*
3 * Copyright (c) 2006 The Regents of The University of Michigan
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer;
10 * redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution;
13 * neither the name of the copyright holders nor the names of its
14 * contributors may be used to endorse or promote products derived from
15 * this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * Authors: Ali Saidi
30 *          Steve Reinhardt
31 */
32
33/**
34 * @file Definition of a simple bus bridge without buffering.
35 */
36
37#include <algorithm>
38
39#include "base/trace.hh"
40#include "mem/bridge.hh"
41#include "sim/builder.hh"
42
43Bridge::BridgePort::BridgePort(const std::string &_name,
44                               Bridge *_bridge, BridgePort *_otherPort,
45                               int _delay, int _queueLimit)
46    : Port(_name), bridge(_bridge), otherPort(_otherPort),
47      delay(_delay), outstandingResponses(0),
48      queueLimit(_queueLimit), sendEvent(this)
49{
50}
51
52Bridge::Bridge(const std::string &n, int qsa, int qsb,
53               Tick _delay, int write_ack)
54    : MemObject(n),
55      portA(n + "-portA", this, &portB, _delay, qsa),
56      portB(n + "-portB", this, &portA, _delay, qsa),
57      ackWrites(write_ack)
58{
59}
60
61Port *
62Bridge::getPort(const std::string &if_name)
63{
64    BridgePort *port;
65
66    if (if_name == "side_a")
67        port = &portA;
68    else if (if_name == "side_b")
69        port = &portB;
70    else
71        return NULL;
72
73    if (port->getPeer() != NULL)
74        panic("bridge side %s already connected to.", if_name);
75    return port;
76}
77
78
79void
80Bridge::init()
81{
82    // Make sure that both sides are connected to.
83    if (portA.getPeer() == NULL || portB.getPeer() == NULL)
84        panic("Both ports of bus bridge are not connected to a bus.\n");
85}
86
87
88/** Function called by the port when the bus is receiving a Timing
89 * transaction.*/
90bool
91Bridge::BridgePort::recvTiming(Packet *pkt)
92{
93    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
94            pkt->getSrc(), pkt->getDest(), pkt->getAddr());
95
96    return otherPort->queueForSendTiming(pkt);
97}
98
99
100bool
101Bridge::BridgePort::queueForSendTiming(Packet *pkt)
102{
103    if (queueFull())
104        return false;
105
106   if (pkt->isResponse()) {
107        // This is a response for a request we forwarded earlier.  The
108        // corresponding PacketBuffer should be stored in the packet's
109        // senderState field.
110        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
111        assert(buf != NULL);
112        // set up new packet dest & senderState based on values saved
113        // from original request
114        buf->fixResponse(pkt);
115        DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
116                        pkt->senderState, buf);
117        DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
118        delete buf;
119    }
120
121    Tick readyTime = curTick + delay;
122    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
123    DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
124            buf->origSenderState, buf);
125
126    // If we're about to put this packet at the head of the queue, we
127    // need to schedule an event to do the transmit.  Otherwise there
128    // should already be an event scheduled for sending the head
129    // packet.
130    if (sendQueue.empty()) {
131        sendEvent.schedule(readyTime);
132    }
133
134    sendQueue.push_back(buf);
135
136    return true;
137}
138
139void
140Bridge::BridgePort::trySend()
141{
142    assert(!sendQueue.empty());
143
144    bool was_full = queueFull();
145
146    PacketBuffer *buf = sendQueue.front();
147
148    assert(buf->ready <= curTick);
149
150    Packet *pkt = buf->pkt;
151
152    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
153            buf->origSrc, pkt->getDest(), pkt->getAddr());
154
155    if (sendTiming(pkt)) {
156        // send successful
157        sendQueue.pop_front();
158        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
159
160        if (buf->expectResponse) {
161            // Must wait for response.  We just need to count outstanding
162            // responses (in case we want to cap them); PacketBuffer
163            // pointer will be recovered on response.
164            ++outstandingResponses;
165            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
166                    outstandingResponses);
167        } else {
168            // no response expected... deallocate packet buffer now.
169            DPRINTF(BusBridge, "  successful: no response expected\n");
170            delete buf;
171        }
172
173        // If there are more packets to send, schedule event to try again.
174        if (!sendQueue.empty()) {
175            buf = sendQueue.front();
176            sendEvent.schedule(std::max(buf->ready, curTick + 1));
177        }
178        // Let things start sending again
179        if (was_full) {
180          DPRINTF(BusBridge, "Queue was full, sending retry\n");
181          otherPort->sendRetry();
182        }
183
184    } else {
185        DPRINTF(BusBridge, "  unsuccessful\n");
186    }
187}
188
189
190void
191Bridge::BridgePort::recvRetry()
192{
193    trySend();
194}
195
196/** Function called by the port when the bus is receiving a Atomic
197 * transaction.*/
198Tick
199Bridge::BridgePort::recvAtomic(Packet *pkt)
200{
201    return otherPort->sendAtomic(pkt) + delay;
202}
203
204/** Function called by the port when the bus is receiving a Functional
205 * transaction.*/
206void
207Bridge::BridgePort::recvFunctional(Packet *pkt)
208{
209    std::list<PacketBuffer*>::iterator i;
210    bool pktContinue = true;
211
212    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
213        if (pkt->intersect((*i)->pkt)) {
214            pktContinue &= fixPacket(pkt, (*i)->pkt);
215        }
216    }
217
218    if (pktContinue) {
219        otherPort->sendFunctional(pkt);
220    }
221}
222
223/** Function called by the port when the bus is receiving a status change.*/
224void
225Bridge::BridgePort::recvStatusChange(Port::Status status)
226{
227    otherPort->sendStatusChange(status);
228}
229
230void
231Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
232                                           AddrRangeList &snoop)
233{
234    otherPort->getPeerAddressRanges(resp, snoop);
235}
236
237BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
238
239   Param<int> queue_size_a;
240   Param<int> queue_size_b;
241   Param<Tick> delay;
242   Param<bool> write_ack;
243
244END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
245
246BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
247
248    INIT_PARAM(queue_size_a, "The size of the queue for data coming into side a"),
249    INIT_PARAM(queue_size_b, "The size of the queue for data coming into side b"),
250    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
251    INIT_PARAM(write_ack, "Acknowledge any writes that are received.")
252
253END_INIT_SIM_OBJECT_PARAMS(Bridge)
254
255CREATE_SIM_OBJECT(Bridge)
256{
257    return new Bridge(getInstanceName(), queue_size_a, queue_size_b, delay,
258            write_ack);
259}
260
261REGISTER_SIM_OBJECT("Bridge", Bridge)
262