bridge.cc revision 8709:d7358736ac70 
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 "debug/BusBridge.hh"
43#include "mem/bridge.hh"
44#include "params/Bridge.hh"
45
46Bridge::BridgePort::BridgePort(const std::string &_name,
47                               Bridge *_bridge, BridgePort *_otherPort,
48                               int _delay, int _nack_delay, int _req_limit,
49                               int _resp_limit,
50                               std::vector<Range<Addr> > filter_ranges)
51    : Port(_name, _bridge), bridge(_bridge), otherPort(_otherPort),
52      delay(_delay), nackDelay(_nack_delay), filterRanges(filter_ranges),
53      outstandingResponses(0), queuedRequests(0), inRetry(false),
54      reqQueueLimit(_req_limit), respQueueLimit(_resp_limit), sendEvent(this)
55{
56}
57
58Bridge::Bridge(Params *p)
59    : MemObject(p),
60      portA(p->name + "-portA", this, &portB, p->delay, p->nack_delay,
61              p->req_size_a, p->resp_size_a, p->filter_ranges_a),
62      portB(p->name + "-portB", this, &portA, p->delay, p->nack_delay,
63              p->req_size_b, p->resp_size_b, p->filter_ranges_b),
64      ackWrites(p->write_ack), _params(p)
65{
66    if (ackWrites)
67        panic("No support for acknowledging writes\n");
68}
69
70Port *
71Bridge::getPort(const std::string &if_name, int idx)
72{
73    BridgePort *port;
74
75    if (if_name == "side_a")
76        port = &portA;
77    else if (if_name == "side_b")
78        port = &portB;
79    else
80        return NULL;
81
82    if (port->getPeer() != NULL)
83        panic("bridge side %s already connected to %s.",
84                if_name, port->getPeer()->name());
85    return port;
86}
87
88
89void
90Bridge::init()
91{
92    // Make sure that both sides are connected to.
93    if (!portA.isConnected() || !portB.isConnected())
94        fatal("Both ports of bus bridge are not connected to a bus.\n");
95
96    if (portA.peerBlockSize() != portB.peerBlockSize())
97        fatal("port A size %d, port B size %d \n " \
98              "Busses don't have the same block size... Not supported.\n",
99              portA.peerBlockSize(), portB.peerBlockSize());
100}
101
102bool
103Bridge::BridgePort::respQueueFull()
104{
105    assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
106    return outstandingResponses >= respQueueLimit;
107}
108
109bool
110Bridge::BridgePort::reqQueueFull()
111{
112    assert(queuedRequests >= 0 && queuedRequests <= reqQueueLimit);
113    return queuedRequests >= reqQueueLimit;
114}
115
116/** Function called by the port when the bus is receiving a Timing
117 * transaction.*/
118bool
119Bridge::BridgePort::recvTiming(PacketPtr pkt)
120{
121    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
122                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
123
124    DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
125                    sendQueue.size(), queuedRequests, outstandingResponses);
126    DPRINTF(BusBridge, "Remote queue size: %d outreq: %d outresp: %d\n",
127                    otherPort->sendQueue.size(), otherPort->queuedRequests,
128                    otherPort->outstandingResponses);
129
130    if (pkt->isRequest() && otherPort->reqQueueFull()) {
131        DPRINTF(BusBridge, "Remote queue full, nacking\n");
132        nackRequest(pkt);
133        return true;
134    }
135
136    if (pkt->needsResponse()) {
137        if (respQueueFull()) {
138            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
139            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
140                    sendQueue.size(), queuedRequests, outstandingResponses);
141            nackRequest(pkt);
142            return true;
143        } else {
144            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
145            ++outstandingResponses;
146        }
147    }
148
149    otherPort->queueForSendTiming(pkt);
150
151    return true;
152}
153
154void
155Bridge::BridgePort::nackRequest(PacketPtr pkt)
156{
157    // Nack the packet
158    pkt->makeTimingResponse();
159    pkt->setNacked();
160
161    //put it on the list to send
162    Tick readyTime = curTick() + nackDelay;
163    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
164
165    // nothing on the list, add it and we're done
166    if (sendQueue.empty()) {
167        assert(!sendEvent.scheduled());
168        bridge->schedule(sendEvent, readyTime);
169        sendQueue.push_back(buf);
170        return;
171    }
172
173    assert(sendEvent.scheduled() || inRetry);
174
175    // does it go at the end?
176    if (readyTime >= sendQueue.back()->ready) {
177        sendQueue.push_back(buf);
178        return;
179    }
180
181    // ok, somewhere in the middle, fun
182    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
183    std::list<PacketBuffer*>::iterator end = sendQueue.end();
184    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
185    bool done = false;
186
187    while (i != end && !done) {
188        if (readyTime < (*i)->ready) {
189            if (i == begin)
190                bridge->reschedule(sendEvent, readyTime);
191            sendQueue.insert(i,buf);
192            done = true;
193        }
194        i++;
195    }
196    assert(done);
197}
198
199
200void
201Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
202{
203    if (pkt->isResponse()) {
204        // This is a response for a request we forwarded earlier.  The
205        // corresponding PacketBuffer should be stored in the packet's
206        // senderState field.
207
208        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
209        assert(buf != NULL);
210        // set up new packet dest & senderState based on values saved
211        // from original request
212        buf->fixResponse(pkt);
213
214        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
215        delete buf;
216    }
217
218
219    if (pkt->isRequest()) {
220        ++queuedRequests;
221    }
222
223
224
225    Tick readyTime = curTick() + delay;
226    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
227
228    // If we're about to put this packet at the head of the queue, we
229    // need to schedule an event to do the transmit.  Otherwise there
230    // should already be an event scheduled for sending the head
231    // packet.
232    if (sendQueue.empty()) {
233        bridge->schedule(sendEvent, readyTime);
234    }
235    sendQueue.push_back(buf);
236}
237
238void
239Bridge::BridgePort::trySend()
240{
241    assert(!sendQueue.empty());
242
243    PacketBuffer *buf = sendQueue.front();
244
245    assert(buf->ready <= curTick());
246
247    PacketPtr pkt = buf->pkt;
248
249    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
250            buf->origSrc, pkt->getDest(), pkt->getAddr());
251
252    bool wasReq = pkt->isRequest();
253    bool was_nacked_here = buf->nackedHere;
254
255    // If the send was successful, make sure sender state was set to NULL
256    // otherwise we could get a NACK back of a packet that didn't expect a
257    // response and we would try to use freed memory.
258
259    Packet::SenderState *old_sender_state = pkt->senderState;
260    if (pkt->isRequest() && !buf->expectResponse)
261        pkt->senderState = NULL;
262
263    if (sendTiming(pkt)) {
264        // send successful
265        sendQueue.pop_front();
266        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
267
268        if (buf->expectResponse) {
269            // Must wait for response
270            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
271                    outstandingResponses);
272        } else {
273            // no response expected... deallocate packet buffer now.
274            DPRINTF(BusBridge, "  successful: no response expected\n");
275            delete buf;
276        }
277
278        if (wasReq)
279            --queuedRequests;
280        else if (!was_nacked_here)
281            --outstandingResponses;
282
283        // If there are more packets to send, schedule event to try again.
284        if (!sendQueue.empty()) {
285            buf = sendQueue.front();
286            DPRINTF(BusBridge, "Scheduling next send\n");
287            bridge->schedule(sendEvent, std::max(buf->ready, curTick() + 1));
288        }
289    } else {
290        DPRINTF(BusBridge, "  unsuccessful\n");
291        pkt->senderState = old_sender_state;
292        inRetry = true;
293    }
294
295    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
296                    sendQueue.size(), queuedRequests, outstandingResponses);
297}
298
299
300void
301Bridge::BridgePort::recvRetry()
302{
303    inRetry = false;
304    Tick nextReady = sendQueue.front()->ready;
305    if (nextReady <= curTick())
306        trySend();
307    else
308        bridge->schedule(sendEvent, nextReady);
309}
310
311/** Function called by the port when the bus is receiving a Atomic
312 * transaction.*/
313Tick
314Bridge::BridgePort::recvAtomic(PacketPtr pkt)
315{
316    return delay + otherPort->sendAtomic(pkt);
317}
318
319/** Function called by the port when the bus is receiving a Functional
320 * transaction.*/
321void
322Bridge::BridgePort::recvFunctional(PacketPtr pkt)
323{
324    std::list<PacketBuffer*>::iterator i;
325
326    pkt->pushLabel(name());
327
328    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
329        if (pkt->checkFunctional((*i)->pkt)) {
330            pkt->makeResponse();
331            return;
332        }
333    }
334
335    pkt->popLabel();
336
337    // fall through if pkt still not satisfied
338    otherPort->sendFunctional(pkt);
339}
340
341/** Function called by the port when the bus is receiving a status change.*/
342void
343Bridge::BridgePort::recvStatusChange(Port::Status status)
344{
345    otherPort->sendStatusChange(status);
346}
347
348void
349Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
350                                           bool &snoop)
351{
352    otherPort->getPeerAddressRanges(resp, snoop);
353    FilterRangeList(filterRanges, resp);
354    // we don't allow snooping across bridges
355    snoop = false;
356}
357
358Bridge *
359BridgeParams::create()
360{
361    return new Bridge(this);
362}
363