bridge.cc revision 5283 
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),
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 && !port->getPeer()->isDefaultPort())
82        panic("bridge side %s already connected to %s.",
83                if_name, port->getPeer()->name());
84    return port;
85}
86
87
88void
89Bridge::init()
90{
91    // Make sure that both sides are connected to.
92    if (portA.getPeer() == NULL || portB.getPeer() == NULL)
93        fatal("Both ports of bus bridge are not connected to a bus.\n");
94
95    if (portA.peerBlockSize() != portB.peerBlockSize())
96        fatal("Busses don't have the same block size... Not supported.\n");
97}
98
99bool
100Bridge::BridgePort::respQueueFull()
101{
102    assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
103    return outstandingResponses >= respQueueLimit;
104}
105
106bool
107Bridge::BridgePort::reqQueueFull()
108{
109    assert(queuedRequests >= 0 && queuedRequests <= reqQueueLimit);
110    return queuedRequests >= reqQueueLimit;
111}
112
113/** Function called by the port when the bus is receiving a Timing
114 * transaction.*/
115bool
116Bridge::BridgePort::recvTiming(PacketPtr pkt)
117{
118    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
119                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
120
121    DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
122                    sendQueue.size(), queuedRequests, outstandingResponses);
123    DPRINTF(BusBridge, "Remote queue size: %d outreq: %d outresp: %d\n",
124                    otherPort->sendQueue.size(), otherPort->queuedRequests,
125                    otherPort->outstandingResponses);
126
127    if (pkt->isRequest() && otherPort->reqQueueFull()) {
128        DPRINTF(BusBridge, "Remote queue full, nacking\n");
129        nackRequest(pkt);
130        return true;
131    }
132
133    if (pkt->needsResponse())
134        if (respQueueFull()) {
135            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
136            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
137                    sendQueue.size(), queuedRequests, outstandingResponses);
138            nackRequest(pkt);
139            return true;
140        } else {
141            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
142            ++outstandingResponses;
143        }
144
145    otherPort->queueForSendTiming(pkt);
146
147    return true;
148}
149
150void
151Bridge::BridgePort::nackRequest(PacketPtr pkt)
152{
153    // Nack the packet
154    pkt->makeTimingResponse();
155    pkt->setNacked();
156
157    //put it on the list to send
158    Tick readyTime = curTick + nackDelay;
159    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
160
161    // nothing on the list, add it and we're done
162    if (sendQueue.empty()) {
163        assert(!sendEvent.scheduled());
164        sendEvent.schedule(readyTime);
165        sendQueue.push_back(buf);
166        return;
167    }
168
169    assert(sendEvent.scheduled() || inRetry);
170
171    // does it go at the end?
172    if (readyTime >= sendQueue.back()->ready) {
173        sendQueue.push_back(buf);
174        return;
175    }
176
177    // ok, somewhere in the middle, fun
178    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
179    std::list<PacketBuffer*>::iterator end = sendQueue.end();
180    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
181    bool done = false;
182
183    while (i != end && !done) {
184        if (readyTime < (*i)->ready) {
185            if (i == begin)
186                sendEvent.reschedule(readyTime);
187            sendQueue.insert(i,buf);
188            done = true;
189        }
190        i++;
191    }
192    assert(done);
193}
194
195
196void
197Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
198{
199    if (pkt->isResponse()) {
200        // This is a response for a request we forwarded earlier.  The
201        // corresponding PacketBuffer should be stored in the packet's
202        // senderState field.
203
204        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
205        assert(buf != NULL);
206        // set up new packet dest & senderState based on values saved
207        // from original request
208        buf->fixResponse(pkt);
209
210        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
211        delete buf;
212    }
213
214
215    if (pkt->isRequest()) {
216        ++queuedRequests;
217    }
218
219
220
221    Tick readyTime = curTick + delay;
222    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
223
224    // If we're about to put this packet at the head of the queue, we
225    // need to schedule an event to do the transmit.  Otherwise there
226    // should already be an event scheduled for sending the head
227    // packet.
228    if (sendQueue.empty()) {
229        sendEvent.schedule(readyTime);
230    }
231    sendQueue.push_back(buf);
232}
233
234void
235Bridge::BridgePort::trySend()
236{
237    assert(!sendQueue.empty());
238
239    PacketBuffer *buf = sendQueue.front();
240
241    assert(buf->ready <= curTick);
242
243    PacketPtr pkt = buf->pkt;
244
245    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
246            buf->origSrc, pkt->getDest(), pkt->getAddr());
247
248    bool wasReq = pkt->isRequest();
249    bool was_nacked_here = buf->nackedHere;
250
251    // If the send was successful, make sure sender state was set to NULL
252    // otherwise we could get a NACK back of a packet that didn't expect a
253    // response and we would try to use freed memory.
254
255    Packet::SenderState *old_sender_state = pkt->senderState;
256    if (pkt->isRequest() && !buf->expectResponse)
257        pkt->senderState = NULL;
258
259    if (sendTiming(pkt)) {
260        // send successful
261        sendQueue.pop_front();
262        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
263
264        if (buf->expectResponse) {
265            // Must wait for response
266            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
267                    outstandingResponses);
268        } else {
269            // no response expected... deallocate packet buffer now.
270            DPRINTF(BusBridge, "  successful: no response expected\n");
271            delete buf;
272        }
273
274        if (wasReq)
275            --queuedRequests;
276        else if (!was_nacked_here)
277            --outstandingResponses;
278
279        // If there are more packets to send, schedule event to try again.
280        if (!sendQueue.empty()) {
281            buf = sendQueue.front();
282            DPRINTF(BusBridge, "Scheduling next send\n");
283            sendEvent.schedule(std::max(buf->ready, curTick + 1));
284        }
285    } else {
286        DPRINTF(BusBridge, "  unsuccessful\n");
287        pkt->senderState = old_sender_state;
288        inRetry = true;
289    }
290
291    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
292                    sendQueue.size(), queuedRequests, outstandingResponses);
293}
294
295
296void
297Bridge::BridgePort::recvRetry()
298{
299    inRetry = false;
300    Tick nextReady = sendQueue.front()->ready;
301    if (nextReady <= curTick)
302        trySend();
303    else
304        sendEvent.schedule(nextReady);
305}
306
307/** Function called by the port when the bus is receiving a Atomic
308 * transaction.*/
309Tick
310Bridge::BridgePort::recvAtomic(PacketPtr pkt)
311{
312    return delay + otherPort->sendAtomic(pkt);
313}
314
315/** Function called by the port when the bus is receiving a Functional
316 * transaction.*/
317void
318Bridge::BridgePort::recvFunctional(PacketPtr pkt)
319{
320    std::list<PacketBuffer*>::iterator i;
321
322    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
323        if (pkt->checkFunctional((*i)->pkt))
324            return;
325    }
326
327    // fall through if pkt still not satisfied
328    otherPort->sendFunctional(pkt);
329}
330
331/** Function called by the port when the bus is receiving a status change.*/
332void
333Bridge::BridgePort::recvStatusChange(Port::Status status)
334{
335    otherPort->sendStatusChange(status);
336}
337
338void
339Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
340                                           bool &snoop)
341{
342    otherPort->getPeerAddressRanges(resp, snoop);
343    FilterRangeList(filterRanges, resp);
344    // we don't allow snooping across bridges
345    snoop = false;
346}
347
348Bridge *
349BridgeParams::create()
350{
351    return new Bridge(this);
352}
353