bridge.cc revision 5606:6da7a58b0bc8 
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(_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.isConnected() || !portB.isConnected())
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
146    otherPort->queueForSendTiming(pkt);
147
148    return true;
149}
150
151void
152Bridge::BridgePort::nackRequest(PacketPtr pkt)
153{
154    // Nack the packet
155    pkt->makeTimingResponse();
156    pkt->setNacked();
157
158    //put it on the list to send
159    Tick readyTime = curTick + nackDelay;
160    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
161
162    // nothing on the list, add it and we're done
163    if (sendQueue.empty()) {
164        assert(!sendEvent.scheduled());
165        schedule(sendEvent, readyTime);
166        sendQueue.push_back(buf);
167        return;
168    }
169
170    assert(sendEvent.scheduled() || inRetry);
171
172    // does it go at the end?
173    if (readyTime >= sendQueue.back()->ready) {
174        sendQueue.push_back(buf);
175        return;
176    }
177
178    // ok, somewhere in the middle, fun
179    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
180    std::list<PacketBuffer*>::iterator end = sendQueue.end();
181    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
182    bool done = false;
183
184    while (i != end && !done) {
185        if (readyTime < (*i)->ready) {
186            if (i == begin)
187                reschedule(sendEvent, readyTime);
188            sendQueue.insert(i,buf);
189            done = true;
190        }
191        i++;
192    }
193    assert(done);
194}
195
196
197void
198Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
199{
200    if (pkt->isResponse()) {
201        // This is a response for a request we forwarded earlier.  The
202        // corresponding PacketBuffer should be stored in the packet's
203        // senderState field.
204
205        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
206        assert(buf != NULL);
207        // set up new packet dest & senderState based on values saved
208        // from original request
209        buf->fixResponse(pkt);
210
211        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
212        delete buf;
213    }
214
215
216    if (pkt->isRequest()) {
217        ++queuedRequests;
218    }
219
220
221
222    Tick readyTime = curTick + delay;
223    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
224
225    // If we're about to put this packet at the head of the queue, we
226    // need to schedule an event to do the transmit.  Otherwise there
227    // should already be an event scheduled for sending the head
228    // packet.
229    if (sendQueue.empty()) {
230        schedule(sendEvent, readyTime);
231    }
232    sendQueue.push_back(buf);
233}
234
235void
236Bridge::BridgePort::trySend()
237{
238    assert(!sendQueue.empty());
239
240    PacketBuffer *buf = sendQueue.front();
241
242    assert(buf->ready <= curTick);
243
244    PacketPtr pkt = buf->pkt;
245
246    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
247            buf->origSrc, pkt->getDest(), pkt->getAddr());
248
249    bool wasReq = pkt->isRequest();
250    bool was_nacked_here = buf->nackedHere;
251
252    // If the send was successful, make sure sender state was set to NULL
253    // otherwise we could get a NACK back of a packet that didn't expect a
254    // response and we would try to use freed memory.
255
256    Packet::SenderState *old_sender_state = pkt->senderState;
257    if (pkt->isRequest() && !buf->expectResponse)
258        pkt->senderState = NULL;
259
260    if (sendTiming(pkt)) {
261        // send successful
262        sendQueue.pop_front();
263        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
264
265        if (buf->expectResponse) {
266            // Must wait for response
267            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
268                    outstandingResponses);
269        } else {
270            // no response expected... deallocate packet buffer now.
271            DPRINTF(BusBridge, "  successful: no response expected\n");
272            delete buf;
273        }
274
275        if (wasReq)
276            --queuedRequests;
277        else if (!was_nacked_here)
278            --outstandingResponses;
279
280        // If there are more packets to send, schedule event to try again.
281        if (!sendQueue.empty()) {
282            buf = sendQueue.front();
283            DPRINTF(BusBridge, "Scheduling next send\n");
284            schedule(sendEvent, std::max(buf->ready, curTick + 1));
285        }
286    } else {
287        DPRINTF(BusBridge, "  unsuccessful\n");
288        pkt->senderState = old_sender_state;
289        inRetry = true;
290    }
291
292    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
293                    sendQueue.size(), queuedRequests, outstandingResponses);
294}
295
296
297void
298Bridge::BridgePort::recvRetry()
299{
300    inRetry = false;
301    Tick nextReady = sendQueue.front()->ready;
302    if (nextReady <= curTick)
303        trySend();
304    else
305        schedule(sendEvent, nextReady);
306}
307
308/** Function called by the port when the bus is receiving a Atomic
309 * transaction.*/
310Tick
311Bridge::BridgePort::recvAtomic(PacketPtr pkt)
312{
313    return delay + otherPort->sendAtomic(pkt);
314}
315
316/** Function called by the port when the bus is receiving a Functional
317 * transaction.*/
318void
319Bridge::BridgePort::recvFunctional(PacketPtr pkt)
320{
321    std::list<PacketBuffer*>::iterator i;
322
323    pkt->pushLabel(name());
324
325    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
326        if (pkt->checkFunctional((*i)->pkt))
327            return;
328    }
329
330    pkt->popLabel();
331
332    // fall through if pkt still not satisfied
333    otherPort->sendFunctional(pkt);
334}
335
336/** Function called by the port when the bus is receiving a status change.*/
337void
338Bridge::BridgePort::recvStatusChange(Port::Status status)
339{
340    otherPort->sendStatusChange(status);
341}
342
343void
344Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
345                                           bool &snoop)
346{
347    otherPort->getPeerAddressRanges(resp, snoop);
348    FilterRangeList(filterRanges, resp);
349    // we don't allow snooping across bridges
350    snoop = false;
351}
352
353Bridge *
354BridgeParams::create()
355{
356    return new Bridge(this);
357}
358