bridge.cc revision 4870 
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 _nack_delay, int _req_limit,
47                               int _resp_limit, bool fix_partial_write)
48    : Port(_name), bridge(_bridge), otherPort(_otherPort),
49      delay(_delay), nackDelay(_nack_delay), fixPartialWrite(fix_partial_write),
50      outstandingResponses(0), queuedRequests(0), inRetry(false),
51      reqQueueLimit(_req_limit), respQueueLimit(_resp_limit), sendEvent(this)
52{
53}
54
55Bridge::Bridge(Params *p)
56    : MemObject(p->name),
57      portA(p->name + "-portA", this, &portB, p->delay, p->nack_delay,
58              p->req_size_a, p->resp_size_a, p->fix_partial_write_a),
59      portB(p->name + "-portB", this, &portA, p->delay, p->nack_delay,
60              p->req_size_b, p->resp_size_b, p->fix_partial_write_b),
61      ackWrites(p->write_ack), _params(p)
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::respQueueFull()
98{
99    assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
100    return outstandingResponses >= respQueueLimit;
101}
102
103bool
104Bridge::BridgePort::reqQueueFull()
105{
106    assert(queuedRequests >= 0 && queuedRequests <= reqQueueLimit);
107    return queuedRequests >= reqQueueLimit;
108}
109
110/** Function called by the port when the bus is receiving a Timing
111 * transaction.*/
112bool
113Bridge::BridgePort::recvTiming(PacketPtr pkt)
114{
115    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
116                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
117
118    DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
119                    sendQueue.size(), queuedRequests, outstandingResponses);
120    DPRINTF(BusBridge, "Remove queue size: %d outreq: %d outresp: %d\n",
121                    otherPort->sendQueue.size(), otherPort->queuedRequests,
122                    otherPort->outstandingResponses);
123
124    if (pkt->isRequest() && otherPort->reqQueueFull() && !pkt->wasNacked()) {
125        DPRINTF(BusBridge, "Remote queue full, nacking\n");
126        nackRequest(pkt);
127        return true;
128    }
129
130    if (pkt->needsResponse() && !pkt->wasNacked())
131        if (respQueueFull()) {
132            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
133            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
134                    sendQueue.size(), queuedRequests, outstandingResponses);
135            nackRequest(pkt);
136            return true;
137        } else {
138            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
139            ++outstandingResponses;
140        }
141
142    otherPort->queueForSendTiming(pkt);
143
144    return true;
145}
146
147void
148Bridge::BridgePort::nackRequest(PacketPtr pkt)
149{
150    // Nack the packet
151    pkt->setNacked();
152    pkt->setDest(pkt->getSrc());
153
154    //put it on the list to send
155    Tick readyTime = curTick + nackDelay;
156    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
157
158    // nothing on the list, add it and we're done
159    if (sendQueue.empty()) {
160        assert(!sendEvent.scheduled());
161        sendEvent.schedule(readyTime);
162        sendQueue.push_back(buf);
163        return;
164    }
165
166    assert(sendEvent.scheduled() || inRetry);
167
168    // does it go at the end?
169    if (readyTime >= sendQueue.back()->ready) {
170        sendQueue.push_back(buf);
171        return;
172    }
173
174    // ok, somewhere in the middle, fun
175    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
176    std::list<PacketBuffer*>::iterator end = sendQueue.end();
177    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
178    bool done = false;
179
180    while (i != end && !done) {
181        if (readyTime < (*i)->ready) {
182            if (i == begin)
183                sendEvent.reschedule(readyTime);
184            sendQueue.insert(i,buf);
185            done = true;
186        }
187        i++;
188    }
189    assert(done);
190}
191
192
193void
194Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
195{
196    if (pkt->isResponse() || pkt->wasNacked()) {
197        // This is a response for a request we forwarded earlier.  The
198        // corresponding PacketBuffer should be stored in the packet's
199        // senderState field.
200        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
201        assert(buf != NULL);
202        // set up new packet dest & senderState based on values saved
203        // from original request
204        buf->fixResponse(pkt);
205
206        // Check if this packet was expecting a response and it's a nacked
207        // packet, in which case we will never being seeing it
208        if (buf->expectResponse && pkt->wasNacked())
209            --outstandingResponses;
210
211
212        DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
213                        pkt->senderState, buf);
214        DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
215        delete buf;
216    }
217
218
219    if (pkt->isRequest() && !pkt->wasNacked()) {
220        ++queuedRequests;
221    }
222
223
224
225    Tick readyTime = curTick + delay;
226    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
227    DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
228            buf->origSenderState, buf);
229
230    // If we're about to put this packet at the head of the queue, we
231    // need to schedule an event to do the transmit.  Otherwise there
232    // should already be an event scheduled for sending the head
233    // packet.
234    if (sendQueue.empty()) {
235        sendEvent.schedule(readyTime);
236    }
237    sendQueue.push_back(buf);
238}
239
240void
241Bridge::BridgePort::trySend()
242{
243    assert(!sendQueue.empty());
244
245    PacketBuffer *buf = sendQueue.front();
246
247    assert(buf->ready <= curTick);
248
249    PacketPtr pkt = buf->pkt;
250
251    // Ugly! @todo When multilevel coherence works this will be removed
252    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
253            !pkt->wasNacked()) {
254        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
255                            Packet::Broadcast);
256        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
257        sendFunctional(funcPkt);
258        pkt->cmd = MemCmd::WriteReq;
259        delete funcPkt;
260    }
261
262    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
263            buf->origSrc, pkt->getDest(), pkt->getAddr());
264
265    bool wasReq = pkt->isRequest();
266    bool wasNacked = pkt->wasNacked();
267
268    if (sendTiming(pkt)) {
269        // send successful
270        sendQueue.pop_front();
271        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
272
273        if (buf->expectResponse) {
274            // Must wait for response
275            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
276                    outstandingResponses);
277        } else {
278            // no response expected... deallocate packet buffer now.
279            DPRINTF(BusBridge, "  successful: no response expected\n");
280            delete buf;
281        }
282
283        if (!wasNacked) {
284            if (wasReq)
285                --queuedRequests;
286            else
287                --outstandingResponses;
288        }
289
290        // If there are more packets to send, schedule event to try again.
291        if (!sendQueue.empty()) {
292            buf = sendQueue.front();
293            DPRINTF(BusBridge, "Scheduling next send\n");
294            sendEvent.schedule(std::max(buf->ready, curTick + 1));
295        }
296    } else {
297        DPRINTF(BusBridge, "  unsuccessful\n");
298        inRetry = true;
299    }
300    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
301                    sendQueue.size(), queuedRequests, outstandingResponses);
302}
303
304
305void
306Bridge::BridgePort::recvRetry()
307{
308    inRetry = false;
309    Tick nextReady = sendQueue.front()->ready;
310    if (nextReady <= curTick)
311        trySend();
312    else
313        sendEvent.schedule(nextReady);
314}
315
316/** Function called by the port when the bus is receiving a Atomic
317 * transaction.*/
318Tick
319Bridge::BridgePort::recvAtomic(PacketPtr pkt)
320{
321    // fix partial atomic writes... similar to the timing code that does the
322    // same... will be removed once our code gets this right
323    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite) {
324
325        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
326                         Packet::Broadcast);
327        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
328        otherPort->sendFunctional(funcPkt);
329        delete funcPkt;
330        pkt->cmd = MemCmd::WriteReq;
331    }
332    return delay + otherPort->sendAtomic(pkt);
333}
334
335/** Function called by the port when the bus is receiving a Functional
336 * transaction.*/
337void
338Bridge::BridgePort::recvFunctional(PacketPtr pkt)
339{
340    std::list<PacketBuffer*>::iterator i;
341
342    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
343        if (pkt->checkFunctional((*i)->pkt))
344            return;
345    }
346
347    // fall through if pkt still not satisfied
348    otherPort->sendFunctional(pkt);
349}
350
351/** Function called by the port when the bus is receiving a status change.*/
352void
353Bridge::BridgePort::recvStatusChange(Port::Status status)
354{
355    otherPort->sendStatusChange(status);
356}
357
358void
359Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
360                                           bool &snoop)
361{
362    otherPort->getPeerAddressRanges(resp, snoop);
363}
364
365BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
366
367   Param<int> req_size_a;
368   Param<int> req_size_b;
369   Param<int> resp_size_a;
370   Param<int> resp_size_b;
371   Param<Tick> delay;
372   Param<Tick> nack_delay;
373   Param<bool> write_ack;
374   Param<bool> fix_partial_write_a;
375   Param<bool> fix_partial_write_b;
376
377END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
378
379BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
380
381    INIT_PARAM(req_size_a, "The size of the queue for requests coming into side a"),
382    INIT_PARAM(req_size_b, "The size of the queue for requests coming into side b"),
383    INIT_PARAM(resp_size_a, "The size of the queue for responses coming into side a"),
384    INIT_PARAM(resp_size_b, "The size of the queue for responses coming into side b"),
385    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
386    INIT_PARAM(nack_delay, "The minimum delay to nack a packet"),
387    INIT_PARAM(write_ack, "Acknowledge any writes that are received."),
388    INIT_PARAM(fix_partial_write_a, "Fixup any partial block writes that are received"),
389    INIT_PARAM(fix_partial_write_b, "Fixup any partial block writes that are received")
390
391END_INIT_SIM_OBJECT_PARAMS(Bridge)
392
393CREATE_SIM_OBJECT(Bridge)
394{
395    Bridge::Params *p = new Bridge::Params;
396    p->name = getInstanceName();
397    p->req_size_a = req_size_a;
398    p->req_size_b = req_size_b;
399    p->resp_size_a = resp_size_a;
400    p->resp_size_b = resp_size_b;
401    p->delay = delay;
402    p->nack_delay = nack_delay;
403    p->write_ack = write_ack;
404    p->fix_partial_write_a = fix_partial_write_a;
405    p->fix_partial_write_b = fix_partial_write_b;
406    return new Bridge(p);
407}
408
409REGISTER_SIM_OBJECT("Bridge", Bridge)
410
411
412