bridge.cc revision 4433 
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
35 * Definition of a simple bus bridge without buffering.
36 */
37
38#include <algorithm>
39
40#include "base/trace.hh"
41#include "mem/bridge.hh"
42#include "sim/builder.hh"
43
44Bridge::BridgePort::BridgePort(const std::string &_name,
45                               Bridge *_bridge, BridgePort *_otherPort,
46                               int _delay, int _queueLimit,
47                               bool fix_partial_write)
48    : Port(_name), bridge(_bridge), otherPort(_otherPort),
49      delay(_delay), fixPartialWrite(fix_partial_write),
50      outstandingResponses(0), queuedRequests(0),
51      queueLimit(_queueLimit), sendEvent(this)
52{
53}
54
55Bridge::Bridge(const std::string &n, int qsa, int qsb,
56               Tick _delay, int write_ack, bool fix_partial_write_a,
57               bool fix_partial_write_b)
58    : MemObject(n),
59      portA(n + "-portA", this, &portB, _delay, qsa, fix_partial_write_a),
60      portB(n + "-portB", this, &portA, _delay, qsa, fix_partial_write_b),
61      ackWrites(write_ack)
62{
63    if (ackWrites)
64        panic("No support for acknowledging writes\n");
65}
66
67Port *
68Bridge::getPort(const std::string &if_name, int idx)
69{
70    BridgePort *port;
71
72    if (if_name == "side_a")
73        port = &portA;
74    else if (if_name == "side_b")
75        port = &portB;
76    else
77        return NULL;
78
79    if (port->getPeer() != NULL)
80        panic("bridge side %s already connected to.", if_name);
81    return port;
82}
83
84
85void
86Bridge::init()
87{
88    // Make sure that both sides are connected to.
89    if (portA.getPeer() == NULL || portB.getPeer() == NULL)
90        fatal("Both ports of bus bridge are not connected to a bus.\n");
91
92    if (portA.peerBlockSize() != portB.peerBlockSize())
93        fatal("Busses don't have the same block size... Not supported.\n");
94}
95
96bool
97Bridge::BridgePort::queueFull()
98{
99    // use >= here because sendQueue could get larger because of
100    // nacks getting inserted
101    return queuedRequests + outstandingResponses >= queueLimit;
102}
103
104/** Function called by the port when the bus is receiving a Timing
105 * transaction.*/
106bool
107Bridge::BridgePort::recvTiming(PacketPtr pkt)
108{
109    if (!(pkt->flags & SNOOP_COMMIT))
110        return true;
111
112
113    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
114                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
115
116    if (pkt->isRequest() && otherPort->queueFull()) {
117        DPRINTF(BusBridge, "Remote queue full, nacking\n");
118        nackRequest(pkt);
119        return true;
120    }
121
122    if (pkt->needsResponse() && pkt->result != Packet::Nacked)
123        if (queueFull()) {
124            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
125            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
126                    sendQueue.size(), queuedRequests, outstandingResponses);
127            nackRequest(pkt);
128            return true;
129        } else {
130            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
131            ++outstandingResponses;
132        }
133
134    otherPort->queueForSendTiming(pkt);
135
136    return true;
137}
138
139void
140Bridge::BridgePort::nackRequest(PacketPtr pkt)
141{
142    // Nack the packet
143    pkt->result = Packet::Nacked;
144    pkt->setDest(pkt->getSrc());
145
146    //put it on the list to send
147    Tick readyTime = curTick + delay;
148    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
149    if (sendQueue.empty()) {
150        sendEvent.schedule(readyTime);
151    }
152    sendQueue.push_back(buf);
153}
154
155
156void
157Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
158{
159   if (pkt->isResponse() || pkt->result == Packet::Nacked) {
160        // This is a response for a request we forwarded earlier.  The
161        // corresponding PacketBuffer should be stored in the packet's
162        // senderState field.
163        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
164        assert(buf != NULL);
165        // set up new packet dest & senderState based on values saved
166        // from original request
167        buf->fixResponse(pkt);
168
169        // Check if this packet was expecting a response (this is either it or
170        // its a nacked packet and we won't be seeing that response)
171        if (buf->expectResponse)
172            --outstandingResponses;
173
174
175        DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
176                        pkt->senderState, buf);
177        DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
178        delete buf;
179    }
180
181    Tick readyTime = curTick + delay;
182    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
183    DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
184            buf->origSenderState, buf);
185
186    // If we're about to put this packet at the head of the queue, we
187    // need to schedule an event to do the transmit.  Otherwise there
188    // should already be an event scheduled for sending the head
189    // packet.
190    if (sendQueue.empty()) {
191        sendEvent.schedule(readyTime);
192    }
193    ++queuedRequests;
194    sendQueue.push_back(buf);
195}
196
197void
198Bridge::BridgePort::trySend()
199{
200    assert(!sendQueue.empty());
201
202    bool was_full = queueFull();
203    int pbs = peerBlockSize();
204
205    PacketBuffer *buf = sendQueue.front();
206
207    assert(buf->ready <= curTick);
208
209    PacketPtr pkt = buf->pkt;
210
211    pkt->flags &= ~SNOOP_COMMIT; //CLear it if it was set
212
213    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
214            pkt->result != Packet::Nacked && pkt->getOffset(pbs) &&
215            pkt->getSize() != pbs) {
216        buf->partialWriteFix(this);
217        pkt = buf->pkt;
218    }
219
220    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
221            buf->origSrc, pkt->getDest(), pkt->getAddr());
222
223
224    if (sendTiming(pkt)) {
225        // send successful
226        sendQueue.pop_front();
227        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
228
229        if (buf->expectResponse) {
230            // Must wait for response
231            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
232                    outstandingResponses);
233        } else {
234            // no response expected... deallocate packet buffer now.
235            DPRINTF(BusBridge, "  successful: no response expected\n");
236            delete buf;
237        }
238
239        if (!buf->nacked)
240                --queuedRequests;
241
242        // If there are more packets to send, schedule event to try again.
243        if (!sendQueue.empty()) {
244            buf = sendQueue.front();
245            DPRINTF(BusBridge, "Scheduling next send\n");
246            sendEvent.schedule(std::max(buf->ready, curTick + 1));
247        }
248        // Let things start sending again
249        if (was_full && !queueFull()) {
250          DPRINTF(BusBridge, "Queue was full, sending retry\n");
251          otherPort->sendRetry();
252        }
253
254    } else {
255        DPRINTF(BusBridge, "  unsuccessful\n");
256        buf->undoPartialWriteFix();
257    }
258    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
259                    sendQueue.size(), queuedRequests, outstandingResponses);
260}
261
262
263void
264Bridge::BridgePort::recvRetry()
265{
266    trySend();
267}
268
269/** Function called by the port when the bus is receiving a Atomic
270 * transaction.*/
271Tick
272Bridge::BridgePort::recvAtomic(PacketPtr pkt)
273{
274    return otherPort->sendAtomic(pkt) + delay;
275}
276
277/** Function called by the port when the bus is receiving a Functional
278 * transaction.*/
279void
280Bridge::BridgePort::recvFunctional(PacketPtr pkt)
281{
282    std::list<PacketBuffer*>::iterator i;
283    bool pktContinue = true;
284
285    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
286        if (pkt->intersect((*i)->pkt)) {
287            pktContinue &= fixPacket(pkt, (*i)->pkt);
288        }
289    }
290
291    if (pktContinue) {
292        otherPort->sendFunctional(pkt);
293    }
294}
295
296/** Function called by the port when the bus is receiving a status change.*/
297void
298Bridge::BridgePort::recvStatusChange(Port::Status status)
299{
300    otherPort->sendStatusChange(status);
301}
302
303void
304Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
305                                           AddrRangeList &snoop)
306{
307    otherPort->getPeerAddressRanges(resp, snoop);
308}
309
310BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
311
312   Param<int> queue_size_a;
313   Param<int> queue_size_b;
314   Param<Tick> delay;
315   Param<bool> write_ack;
316   Param<bool> fix_partial_write_a;
317   Param<bool> fix_partial_write_b;
318
319END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
320
321BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
322
323    INIT_PARAM(queue_size_a, "The size of the queue for data coming into side a"),
324    INIT_PARAM(queue_size_b, "The size of the queue for data coming into side b"),
325    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
326    INIT_PARAM(write_ack, "Acknowledge any writes that are received."),
327    INIT_PARAM(fix_partial_write_a, "Fixup any partial block writes that are received"),
328    INIT_PARAM(fix_partial_write_b, "Fixup any partial block writes that are received")
329
330END_INIT_SIM_OBJECT_PARAMS(Bridge)
331
332CREATE_SIM_OBJECT(Bridge)
333{
334    return new Bridge(getInstanceName(), queue_size_a, queue_size_b, delay,
335            write_ack, fix_partial_write_a, fix_partial_write_b);
336}
337
338REGISTER_SIM_OBJECT("Bridge", Bridge)
339
340