bridge.cc revision 4739:9f8edf47aeca 
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    if (!(pkt->flags & SNOOP_COMMIT))
116        return true;
117
118
119    DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
120                pkt->getSrc(), pkt->getDest(), pkt->getAddr());
121
122    DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
123                    sendQueue.size(), queuedRequests, outstandingResponses);
124    DPRINTF(BusBridge, "Remove queue size: %d outreq: %d outresp: %d\n",
125                    otherPort->sendQueue.size(), otherPort->queuedRequests,
126                    otherPort->outstandingResponses);
127
128    if (pkt->isRequest() && otherPort->reqQueueFull() && pkt->result !=
129            Packet::Nacked) {
130        DPRINTF(BusBridge, "Remote queue full, nacking\n");
131        nackRequest(pkt);
132        return true;
133    }
134
135    if (pkt->needsResponse() && pkt->result != Packet::Nacked)
136        if (respQueueFull()) {
137            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
138            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
139                    sendQueue.size(), queuedRequests, outstandingResponses);
140            nackRequest(pkt);
141            return true;
142        } else {
143            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
144            ++outstandingResponses;
145        }
146
147    otherPort->queueForSendTiming(pkt);
148
149    return true;
150}
151
152void
153Bridge::BridgePort::nackRequest(PacketPtr pkt)
154{
155    // Nack the packet
156    pkt->result = Packet::Nacked;
157    pkt->setDest(pkt->getSrc());
158
159    //put it on the list to send
160    Tick readyTime = curTick + nackDelay;
161    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
162
163    // nothing on the list, add it and we're done
164    if (sendQueue.empty()) {
165        assert(!sendEvent.scheduled());
166        sendEvent.schedule(readyTime);
167        sendQueue.push_back(buf);
168        return;
169    }
170
171    assert(sendEvent.scheduled() || inRetry);
172
173    // does it go at the end?
174    if (readyTime >= sendQueue.back()->ready) {
175        sendQueue.push_back(buf);
176        return;
177    }
178
179    // ok, somewhere in the middle, fun
180    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
181    std::list<PacketBuffer*>::iterator end = sendQueue.end();
182    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
183    bool done = false;
184
185    while (i != end && !done) {
186        if (readyTime < (*i)->ready) {
187            if (i == begin)
188                sendEvent.reschedule(readyTime);
189            sendQueue.insert(i,buf);
190            done = true;
191        }
192        i++;
193    }
194    assert(done);
195}
196
197
198void
199Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
200{
201    if (pkt->isResponse() || pkt->result == Packet::Nacked) {
202        // This is a response for a request we forwarded earlier.  The
203        // corresponding PacketBuffer should be stored in the packet's
204        // senderState field.
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        // Check if this packet was expecting a response and it's a nacked
212        // packet, in which case we will never being seeing it
213        if (buf->expectResponse && pkt->result == Packet::Nacked)
214            --outstandingResponses;
215
216        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
217        delete buf;
218    }
219
220
221    if (pkt->isRequest() && pkt->result != Packet::Nacked) {
222        ++queuedRequests;
223    }
224
225
226
227    Tick readyTime = curTick + delay;
228    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
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    pkt->flags &= ~SNOOP_COMMIT; //CLear it if it was set
252
253    // Ugly! @todo When multilevel coherence works this will be removed
254    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
255            pkt->result != Packet::Nacked) {
256        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
257                            Packet::Broadcast);
258        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
259        sendFunctional(funcPkt);
260        pkt->cmd = MemCmd::WriteReq;
261        delete funcPkt;
262    }
263
264    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
265            buf->origSrc, pkt->getDest(), pkt->getAddr());
266
267    bool wasReq = pkt->isRequest();
268    bool wasNacked = pkt->result == Packet::Nacked;
269
270    if (sendTiming(pkt)) {
271        // send successful
272        sendQueue.pop_front();
273        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
274
275        if (buf->expectResponse) {
276            // Must wait for response
277            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
278                    outstandingResponses);
279        } else {
280            // no response expected... deallocate packet buffer now.
281            DPRINTF(BusBridge, "  successful: no response expected\n");
282            delete buf;
283        }
284
285        if (!wasNacked) {
286            if (wasReq)
287                --queuedRequests;
288            else
289                --outstandingResponses;
290        }
291
292        // If there are more packets to send, schedule event to try again.
293        if (!sendQueue.empty()) {
294            buf = sendQueue.front();
295            DPRINTF(BusBridge, "Scheduling next send\n");
296            sendEvent.schedule(std::max(buf->ready, curTick + 1));
297        }
298    } else {
299        DPRINTF(BusBridge, "  unsuccessful\n");
300        inRetry = true;
301    }
302    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
303                    sendQueue.size(), queuedRequests, outstandingResponses);
304}
305
306
307void
308Bridge::BridgePort::recvRetry()
309{
310    inRetry = false;
311    Tick nextReady = sendQueue.front()->ready;
312    if (nextReady <= curTick)
313        trySend();
314    else
315        sendEvent.schedule(nextReady);
316}
317
318/** Function called by the port when the bus is receiving a Atomic
319 * transaction.*/
320Tick
321Bridge::BridgePort::recvAtomic(PacketPtr pkt)
322{
323    // fix partial atomic writes... similar to the timing code that does the
324    // same... will be removed once our code gets this right
325    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite) {
326
327        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
328                         Packet::Broadcast);
329        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
330        otherPort->sendFunctional(funcPkt);
331        delete funcPkt;
332        pkt->cmd = MemCmd::WriteReq;
333    }
334    return delay + otherPort->sendAtomic(pkt);
335}
336
337/** Function called by the port when the bus is receiving a Functional
338 * transaction.*/
339void
340Bridge::BridgePort::recvFunctional(PacketPtr pkt)
341{
342    std::list<PacketBuffer*>::iterator i;
343    bool pktContinue = true;
344
345    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
346        if (pkt->intersect((*i)->pkt)) {
347            pktContinue &= fixPacket(pkt, (*i)->pkt);
348        }
349    }
350
351    if (pktContinue) {
352        otherPort->sendFunctional(pkt);
353    }
354}
355
356/** Function called by the port when the bus is receiving a status change.*/
357void
358Bridge::BridgePort::recvStatusChange(Port::Status status)
359{
360    otherPort->sendStatusChange(status);
361}
362
363void
364Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
365                                           bool &snoop)
366{
367    otherPort->getPeerAddressRanges(resp, snoop);
368}
369
370BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
371
372   Param<int> req_size_a;
373   Param<int> req_size_b;
374   Param<int> resp_size_a;
375   Param<int> resp_size_b;
376   Param<Tick> delay;
377   Param<Tick> nack_delay;
378   Param<bool> write_ack;
379   Param<bool> fix_partial_write_a;
380   Param<bool> fix_partial_write_b;
381
382END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
383
384BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
385
386    INIT_PARAM(req_size_a, "The size of the queue for requests coming into side a"),
387    INIT_PARAM(req_size_b, "The size of the queue for requests coming into side b"),
388    INIT_PARAM(resp_size_a, "The size of the queue for responses coming into side a"),
389    INIT_PARAM(resp_size_b, "The size of the queue for responses coming into side b"),
390    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
391    INIT_PARAM(nack_delay, "The minimum delay to nack a packet"),
392    INIT_PARAM(write_ack, "Acknowledge any writes that are received."),
393    INIT_PARAM(fix_partial_write_a, "Fixup any partial block writes that are received"),
394    INIT_PARAM(fix_partial_write_b, "Fixup any partial block writes that are received")
395
396END_INIT_SIM_OBJECT_PARAMS(Bridge)
397
398CREATE_SIM_OBJECT(Bridge)
399{
400    Bridge::Params *p = new Bridge::Params;
401    p->name = getInstanceName();
402    p->req_size_a = req_size_a;
403    p->req_size_b = req_size_b;
404    p->resp_size_a = resp_size_a;
405    p->resp_size_b = resp_size_b;
406    p->delay = delay;
407    p->nack_delay = nack_delay;
408    p->write_ack = write_ack;
409    p->fix_partial_write_a = fix_partial_write_a;
410    p->fix_partial_write_b = fix_partial_write_b;
411    return new Bridge(p);
412}
413
414REGISTER_SIM_OBJECT("Bridge", Bridge)
415
416
417