bridge.cc revision 2657:b119b774656b 
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
30/**
31 * @file Definition of a simple bus bridge without buffering.
32 */
33
34#include <algorithm>
35
36#include "base/trace.hh"
37#include "mem/bridge.hh"
38#include "sim/builder.hh"
39
40Bridge::BridgePort::BridgePort(const std::string &_name,
41                               Bridge *_bridge, BridgePort *_otherPort,
42                               int _delay, int _queueLimit)
43    : Port(_name), bridge(_bridge), otherPort(_otherPort),
44      delay(_delay), outstandingResponses(0),
45      queueLimit(_queueLimit), sendEvent(this)
46{
47}
48
49Bridge::Bridge(const std::string &n, int qsa, int qsb,
50               Tick _delay, int write_ack)
51    : MemObject(n),
52      portA(n + "-portA", this, &portB, _delay, qsa),
53      portB(n + "-portB", this, &portA, _delay, qsa),
54      ackWrites(write_ack)
55{
56}
57
58Port *
59Bridge::getPort(const std::string &if_name)
60{
61    BridgePort *port;
62
63    if (if_name == "side_a")
64        port = &portA;
65    else if (if_name == "side_b")
66        port = &portB;
67    else
68        return NULL;
69
70    if (port->getPeer() != NULL)
71        panic("bridge side %s already connected to.", if_name);
72    return port;
73}
74
75
76void
77Bridge::init()
78{
79    // Make sure that both sides are connected to.
80    if (portA.getPeer() == NULL || portB.getPeer() == NULL)
81        panic("Both ports of bus bridge are not connected to a bus.\n");
82}
83
84
85/** Function called by the port when the bus is receiving a Timing
86 * transaction.*/
87bool
88Bridge::BridgePort::recvTiming(Packet *pkt)
89{
90    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
91            pkt->getSrc(), pkt->getDest(), pkt->getAddr());
92
93    return otherPort->queueForSendTiming(pkt);
94}
95
96
97bool
98Bridge::BridgePort::queueForSendTiming(Packet *pkt)
99{
100    if (queueFull())
101        return false;
102
103   if (pkt->isResponse()) {
104        // This is a response for a request we forwarded earlier.  The
105        // corresponding PacketBuffer should be stored in the packet's
106        // senderState field.
107        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
108        assert(buf != NULL);
109        // set up new packet dest & senderState based on values saved
110        // from original request
111        buf->fixResponse(pkt);
112        DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
113                        pkt->senderState, buf);
114        DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
115        delete buf;
116    }
117
118    Tick readyTime = curTick + delay;
119    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
120    DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
121            buf->origSenderState, buf);
122
123    // If we're about to put this packet at the head of the queue, we
124    // need to schedule an event to do the transmit.  Otherwise there
125    // should already be an event scheduled for sending the head
126    // packet.
127    if (sendQueue.empty()) {
128        sendEvent.schedule(readyTime);
129    }
130
131    sendQueue.push_back(buf);
132
133    return true;
134}
135
136void
137Bridge::BridgePort::trySend()
138{
139    assert(!sendQueue.empty());
140
141    bool was_full = queueFull();
142
143    PacketBuffer *buf = sendQueue.front();
144
145    assert(buf->ready <= curTick);
146
147    Packet *pkt = buf->pkt;
148
149    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
150            buf->origSrc, pkt->getDest(), pkt->getAddr());
151
152    if (sendTiming(pkt)) {
153        // send successful
154        sendQueue.pop_front();
155        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
156
157        if (buf->expectResponse) {
158            // Must wait for response.  We just need to count outstanding
159            // responses (in case we want to cap them); PacketBuffer
160            // pointer will be recovered on response.
161            ++outstandingResponses;
162            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
163                    outstandingResponses);
164        } else {
165            // no response expected... deallocate packet buffer now.
166            DPRINTF(BusBridge, "  successful: no response expected\n");
167            delete buf;
168        }
169
170        // If there are more packets to send, schedule event to try again.
171        if (!sendQueue.empty()) {
172            buf = sendQueue.front();
173            sendEvent.schedule(std::max(buf->ready, curTick + 1));
174        }
175        // Let things start sending again
176        if (was_full) {
177          DPRINTF(BusBridge, "Queue was full, sending retry\n");
178          otherPort->sendRetry();
179        }
180
181    } else {
182        DPRINTF(BusBridge, "  unsuccessful\n");
183    }
184}
185
186
187void
188Bridge::BridgePort::recvRetry()
189{
190    trySend();
191}
192
193/** Function called by the port when the bus is receiving a Atomic
194 * transaction.*/
195Tick
196Bridge::BridgePort::recvAtomic(Packet *pkt)
197{
198    return otherPort->sendAtomic(pkt) + delay;
199}
200
201/** Function called by the port when the bus is receiving a Functional
202 * transaction.*/
203void
204Bridge::BridgePort::recvFunctional(Packet *pkt)
205{
206    std::list<PacketBuffer*>::iterator i;
207    bool pktContinue = true;
208
209    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
210        if (pkt->intersect((*i)->pkt)) {
211            pktContinue &= fixPacket(pkt, (*i)->pkt);
212        }
213    }
214
215    if (pktContinue) {
216        otherPort->sendFunctional(pkt);
217    }
218}
219
220/** Function called by the port when the bus is receiving a status change.*/
221void
222Bridge::BridgePort::recvStatusChange(Port::Status status)
223{
224    otherPort->sendStatusChange(status);
225}
226
227void
228Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
229                                           AddrRangeList &snoop)
230{
231    otherPort->getPeerAddressRanges(resp, snoop);
232}
233
234BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
235
236   Param<int> queue_size_a;
237   Param<int> queue_size_b;
238   Param<Tick> delay;
239   Param<bool> write_ack;
240
241END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
242
243BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
244
245    INIT_PARAM(queue_size_a, "The size of the queue for data coming into side a"),
246    INIT_PARAM(queue_size_b, "The size of the queue for data coming into side b"),
247    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
248    INIT_PARAM(write_ack, "Acknowledge any writes that are received.")
249
250END_INIT_SIM_OBJECT_PARAMS(Bridge)
251
252CREATE_SIM_OBJECT(Bridge)
253{
254    return new Bridge(getInstanceName(), queue_size_a, queue_size_b, delay,
255            write_ack);
256}
257
258REGISTER_SIM_OBJECT("Bridge", Bridge)
259