bridge.cc revision 4965:ad0e792a5c78 
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/range_ops.hh"
41#include "base/trace.hh"
42#include "mem/bridge.hh"
43#include "params/Bridge.hh"
44
45Bridge::BridgePort::BridgePort(const std::string &_name,
46                               Bridge *_bridge, BridgePort *_otherPort,
47                               int _delay, int _nack_delay, int _req_limit,
48                               int _resp_limit,
49                               std::vector<Range<Addr> > filter_ranges)
50    : Port(_name), bridge(_bridge), otherPort(_otherPort),
51      delay(_delay), nackDelay(_nack_delay), filterRanges(filter_ranges),
52      outstandingResponses(0), queuedRequests(0), inRetry(false),
53      reqQueueLimit(_req_limit), respQueueLimit(_resp_limit), sendEvent(this)
54{
55}
56
57Bridge::Bridge(Params *p)
58    : MemObject(p->name),
59      portA(p->name + "-portA", this, &portB, p->delay, p->nack_delay,
60              p->req_size_a, p->resp_size_a, p->filter_ranges_a),
61      portB(p->name + "-portB", this, &portA, p->delay, p->nack_delay,
62              p->req_size_b, p->resp_size_b, p->filter_ranges_b),
63      ackWrites(p->write_ack), _params(p)
64{
65    if (ackWrites)
66        panic("No support for acknowledging writes\n");
67}
68
69Port *
70Bridge::getPort(const std::string &if_name, int idx)
71{
72    BridgePort *port;
73
74    if (if_name == "side_a")
75        port = &portA;
76    else if (if_name == "side_b")
77        port = &portB;
78    else
79        return NULL;
80
81    if (port->getPeer() != NULL)
82        panic("bridge side %s already connected to.", if_name);
83    return port;
84}
85
86
87void
88Bridge::init()
89{
90    // Make sure that both sides are connected to.
91    if (portA.getPeer() == NULL || portB.getPeer() == NULL)
92        fatal("Both ports of bus bridge are not connected to a bus.\n");
93
94    if (portA.peerBlockSize() != portB.peerBlockSize())
95        fatal("Busses don't have the same block size... Not supported.\n");
96}
97
98bool
99Bridge::BridgePort::respQueueFull()
100{
101    assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
102    return outstandingResponses >= respQueueLimit;
103}
104
105bool
106Bridge::BridgePort::reqQueueFull()
107{
108    assert(queuedRequests >= 0 && queuedRequests <= reqQueueLimit);
109    return queuedRequests >= reqQueueLimit;
110}
111
112/** Function called by the port when the bus is receiving a Timing
113 * transaction.*/
114bool
115Bridge::BridgePort::recvTiming(PacketPtr pkt)
116{
117    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
118                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
119
120    DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
121                    sendQueue.size(), queuedRequests, outstandingResponses);
122    DPRINTF(BusBridge, "Remove queue size: %d outreq: %d outresp: %d\n",
123                    otherPort->sendQueue.size(), otherPort->queuedRequests,
124                    otherPort->outstandingResponses);
125
126    if (pkt->isRequest() && otherPort->reqQueueFull() && !pkt->wasNacked()) {
127        DPRINTF(BusBridge, "Remote queue full, nacking\n");
128        nackRequest(pkt);
129        return true;
130    }
131
132    if (pkt->needsResponse() && !pkt->wasNacked())
133        if (respQueueFull()) {
134            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
135            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
136                    sendQueue.size(), queuedRequests, outstandingResponses);
137            nackRequest(pkt);
138            return true;
139        } else {
140            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
141            ++outstandingResponses;
142        }
143
144    otherPort->queueForSendTiming(pkt);
145
146    return true;
147}
148
149void
150Bridge::BridgePort::nackRequest(PacketPtr pkt)
151{
152    // Nack the packet
153    pkt->setNacked();
154    pkt->setDest(pkt->getSrc());
155
156    //put it on the list to send
157    Tick readyTime = curTick + nackDelay;
158    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
159
160    // nothing on the list, add it and we're done
161    if (sendQueue.empty()) {
162        assert(!sendEvent.scheduled());
163        sendEvent.schedule(readyTime);
164        sendQueue.push_back(buf);
165        return;
166    }
167
168    assert(sendEvent.scheduled() || inRetry);
169
170    // does it go at the end?
171    if (readyTime >= sendQueue.back()->ready) {
172        sendQueue.push_back(buf);
173        return;
174    }
175
176    // ok, somewhere in the middle, fun
177    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
178    std::list<PacketBuffer*>::iterator end = sendQueue.end();
179    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
180    bool done = false;
181
182    while (i != end && !done) {
183        if (readyTime < (*i)->ready) {
184            if (i == begin)
185                sendEvent.reschedule(readyTime);
186            sendQueue.insert(i,buf);
187            done = true;
188        }
189        i++;
190    }
191    assert(done);
192}
193
194
195void
196Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
197{
198    if (pkt->isResponse() || pkt->wasNacked()) {
199        // This is a response for a request we forwarded earlier.  The
200        // corresponding PacketBuffer should be stored in the packet's
201        // senderState field.
202        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
203        assert(buf != NULL);
204        // set up new packet dest & senderState based on values saved
205        // from original request
206        buf->fixResponse(pkt);
207
208        // Check if this packet was expecting a response and it's a nacked
209        // packet, in which case we will never being seeing it
210        if (buf->expectResponse && pkt->wasNacked())
211            --outstandingResponses;
212
213        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
214        delete buf;
215    }
216
217
218    if (pkt->isRequest() && !pkt->wasNacked()) {
219        ++queuedRequests;
220    }
221
222
223
224    Tick readyTime = curTick + delay;
225    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
226
227    // If we're about to put this packet at the head of the queue, we
228    // need to schedule an event to do the transmit.  Otherwise there
229    // should already be an event scheduled for sending the head
230    // packet.
231    if (sendQueue.empty()) {
232        sendEvent.schedule(readyTime);
233    }
234    sendQueue.push_back(buf);
235}
236
237void
238Bridge::BridgePort::trySend()
239{
240    assert(!sendQueue.empty());
241
242    PacketBuffer *buf = sendQueue.front();
243
244    assert(buf->ready <= curTick);
245
246    PacketPtr pkt = buf->pkt;
247
248    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
249            buf->origSrc, pkt->getDest(), pkt->getAddr());
250
251    bool wasReq = pkt->isRequest();
252    bool wasNacked = pkt->wasNacked();
253
254    if (sendTiming(pkt)) {
255        // send successful
256        sendQueue.pop_front();
257        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
258
259        if (buf->expectResponse) {
260            // Must wait for response
261            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
262                    outstandingResponses);
263        } else {
264            // no response expected... deallocate packet buffer now.
265            DPRINTF(BusBridge, "  successful: no response expected\n");
266            delete buf;
267        }
268
269        if (!wasNacked) {
270            if (wasReq)
271                --queuedRequests;
272            else
273                --outstandingResponses;
274        }
275
276        // If there are more packets to send, schedule event to try again.
277        if (!sendQueue.empty()) {
278            buf = sendQueue.front();
279            DPRINTF(BusBridge, "Scheduling next send\n");
280            sendEvent.schedule(std::max(buf->ready, curTick + 1));
281        }
282    } else {
283        DPRINTF(BusBridge, "  unsuccessful\n");
284        inRetry = true;
285    }
286    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
287                    sendQueue.size(), queuedRequests, outstandingResponses);
288}
289
290
291void
292Bridge::BridgePort::recvRetry()
293{
294    inRetry = false;
295    Tick nextReady = sendQueue.front()->ready;
296    if (nextReady <= curTick)
297        trySend();
298    else
299        sendEvent.schedule(nextReady);
300}
301
302/** Function called by the port when the bus is receiving a Atomic
303 * transaction.*/
304Tick
305Bridge::BridgePort::recvAtomic(PacketPtr pkt)
306{
307    return delay + otherPort->sendAtomic(pkt);
308}
309
310/** Function called by the port when the bus is receiving a Functional
311 * transaction.*/
312void
313Bridge::BridgePort::recvFunctional(PacketPtr pkt)
314{
315    std::list<PacketBuffer*>::iterator i;
316
317    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
318        if (pkt->checkFunctional((*i)->pkt))
319            return;
320    }
321
322    // fall through if pkt still not satisfied
323    otherPort->sendFunctional(pkt);
324}
325
326/** Function called by the port when the bus is receiving a status change.*/
327void
328Bridge::BridgePort::recvStatusChange(Port::Status status)
329{
330    otherPort->sendStatusChange(status);
331}
332
333void
334Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
335                                           bool &snoop)
336{
337    otherPort->getPeerAddressRanges(resp, snoop);
338    FilterRangeList(filterRanges, resp);
339    // we don't allow snooping across bridges
340    snoop = false;
341}
342
343Bridge *
344BridgeParams::create()
345{
346    return new Bridge(this);
347}
348