bridge.cc revision 4626 
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->result !=
125            Packet::Nacked) {
126        DPRINTF(BusBridge, "Remote queue full, nacking\n");
127        nackRequest(pkt);
128        return true;
129    }
130
131    if (pkt->needsResponse() && pkt->result != Packet::Nacked)
132        if (respQueueFull()) {
133            DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
134            DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
135                    sendQueue.size(), queuedRequests, outstandingResponses);
136            nackRequest(pkt);
137            return true;
138        } else {
139            DPRINTF(BusBridge, "Request Needs response, reserving space\n");
140            ++outstandingResponses;
141        }
142
143    otherPort->queueForSendTiming(pkt);
144
145    return true;
146}
147
148void
149Bridge::BridgePort::nackRequest(PacketPtr pkt)
150{
151    // Nack the packet
152    pkt->result = Packet::Nacked;
153    pkt->setDest(pkt->getSrc());
154
155    //put it on the list to send
156    Tick readyTime = curTick + nackDelay;
157    PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
158
159    // nothing on the list, add it and we're done
160    if (sendQueue.empty()) {
161        assert(!sendEvent.scheduled());
162        sendEvent.schedule(readyTime);
163        sendQueue.push_back(buf);
164        return;
165    }
166
167    assert(sendEvent.scheduled() || inRetry);
168
169    // does it go at the end?
170    if (readyTime >= sendQueue.back()->ready) {
171        sendQueue.push_back(buf);
172        return;
173    }
174
175    // ok, somewhere in the middle, fun
176    std::list<PacketBuffer*>::iterator i = sendQueue.begin();
177    std::list<PacketBuffer*>::iterator end = sendQueue.end();
178    std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
179    bool done = false;
180
181    while (i != end && !done) {
182        if (readyTime < (*i)->ready) {
183            if (i == begin)
184                sendEvent.reschedule(readyTime);
185            sendQueue.insert(i,buf);
186            done = true;
187        }
188        i++;
189    }
190    assert(done);
191}
192
193
194void
195Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
196{
197    if (pkt->isResponse() || pkt->result == Packet::Nacked) {
198        // This is a response for a request we forwarded earlier.  The
199        // corresponding PacketBuffer should be stored in the packet's
200        // senderState field.
201        PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
202        assert(buf != NULL);
203        // set up new packet dest & senderState based on values saved
204        // from original request
205        buf->fixResponse(pkt);
206
207        // Check if this packet was expecting a response and it's a nacked
208        // packet, in which case we will never being seeing it
209        if (buf->expectResponse && pkt->result == Packet::Nacked)
210            --outstandingResponses;
211
212
213        DPRINTF(BusBridge, "restoring  sender state: %#X, from packet buffer: %#X\n",
214                        pkt->senderState, buf);
215        DPRINTF(BusBridge, "  is response, new dest %d\n", pkt->getDest());
216        delete buf;
217    }
218
219
220    if (pkt->isRequest() && pkt->result != Packet::Nacked) {
221        ++queuedRequests;
222    }
223
224
225
226    Tick readyTime = curTick + delay;
227    PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
228    DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
229            buf->origSenderState, buf);
230
231    // If we're about to put this packet at the head of the queue, we
232    // need to schedule an event to do the transmit.  Otherwise there
233    // should already be an event scheduled for sending the head
234    // packet.
235    if (sendQueue.empty()) {
236        sendEvent.schedule(readyTime);
237    }
238    sendQueue.push_back(buf);
239}
240
241void
242Bridge::BridgePort::trySend()
243{
244    assert(!sendQueue.empty());
245
246    PacketBuffer *buf = sendQueue.front();
247
248    assert(buf->ready <= curTick);
249
250    PacketPtr pkt = buf->pkt;
251
252    // Ugly! @todo When multilevel coherence works this will be removed
253    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
254            pkt->result != Packet::Nacked) {
255        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
256                            Packet::Broadcast);
257        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
258        sendFunctional(funcPkt);
259        pkt->cmd = MemCmd::WriteReq;
260        delete funcPkt;
261    }
262
263    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
264            buf->origSrc, pkt->getDest(), pkt->getAddr());
265
266    bool wasReq = pkt->isRequest();
267    bool wasNacked = pkt->result == Packet::Nacked;
268
269    if (sendTiming(pkt)) {
270        // send successful
271        sendQueue.pop_front();
272        buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
273
274        if (buf->expectResponse) {
275            // Must wait for response
276            DPRINTF(BusBridge, "  successful: awaiting response (%d)\n",
277                    outstandingResponses);
278        } else {
279            // no response expected... deallocate packet buffer now.
280            DPRINTF(BusBridge, "  successful: no response expected\n");
281            delete buf;
282        }
283
284        if (!wasNacked) {
285            if (wasReq)
286                --queuedRequests;
287            else
288                --outstandingResponses;
289        }
290
291        // If there are more packets to send, schedule event to try again.
292        if (!sendQueue.empty()) {
293            buf = sendQueue.front();
294            DPRINTF(BusBridge, "Scheduling next send\n");
295            sendEvent.schedule(std::max(buf->ready, curTick + 1));
296        }
297    } else {
298        DPRINTF(BusBridge, "  unsuccessful\n");
299        inRetry = true;
300    }
301    DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
302                    sendQueue.size(), queuedRequests, outstandingResponses);
303}
304
305
306void
307Bridge::BridgePort::recvRetry()
308{
309    inRetry = false;
310    Tick nextReady = sendQueue.front()->ready;
311    if (nextReady <= curTick)
312        trySend();
313    else
314        sendEvent.schedule(nextReady);
315}
316
317/** Function called by the port when the bus is receiving a Atomic
318 * transaction.*/
319Tick
320Bridge::BridgePort::recvAtomic(PacketPtr pkt)
321{
322    // fix partial atomic writes... similar to the timing code that does the
323    // same... will be removed once our code gets this right
324    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite) {
325
326        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
327                         Packet::Broadcast);
328        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
329        otherPort->sendFunctional(funcPkt);
330        delete funcPkt;
331        pkt->cmd = MemCmd::WriteReq;
332    }
333    return delay + otherPort->sendAtomic(pkt);
334}
335
336/** Function called by the port when the bus is receiving a Functional
337 * transaction.*/
338void
339Bridge::BridgePort::recvFunctional(PacketPtr pkt)
340{
341    std::list<PacketBuffer*>::iterator i;
342
343    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
344        if (pkt->checkFunctional((*i)->pkt))
345            return;
346    }
347
348    // fall through if pkt still not satisfied
349    otherPort->sendFunctional(pkt);
350}
351
352/** Function called by the port when the bus is receiving a status change.*/
353void
354Bridge::BridgePort::recvStatusChange(Port::Status status)
355{
356    otherPort->sendStatusChange(status);
357}
358
359void
360Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
361                                           bool &snoop)
362{
363    otherPort->getPeerAddressRanges(resp, snoop);
364}
365
366BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
367
368   Param<int> req_size_a;
369   Param<int> req_size_b;
370   Param<int> resp_size_a;
371   Param<int> resp_size_b;
372   Param<Tick> delay;
373   Param<Tick> nack_delay;
374   Param<bool> write_ack;
375   Param<bool> fix_partial_write_a;
376   Param<bool> fix_partial_write_b;
377
378END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
379
380BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
381
382    INIT_PARAM(req_size_a, "The size of the queue for requests coming into side a"),
383    INIT_PARAM(req_size_b, "The size of the queue for requests coming into side b"),
384    INIT_PARAM(resp_size_a, "The size of the queue for responses coming into side a"),
385    INIT_PARAM(resp_size_b, "The size of the queue for responses coming into side b"),
386    INIT_PARAM(delay, "The miminum delay to cross this bridge"),
387    INIT_PARAM(nack_delay, "The minimum delay to nack a packet"),
388    INIT_PARAM(write_ack, "Acknowledge any writes that are received."),
389    INIT_PARAM(fix_partial_write_a, "Fixup any partial block writes that are received"),
390    INIT_PARAM(fix_partial_write_b, "Fixup any partial block writes that are received")
391
392END_INIT_SIM_OBJECT_PARAMS(Bridge)
393
394CREATE_SIM_OBJECT(Bridge)
395{
396    Bridge::Params *p = new Bridge::Params;
397    p->name = getInstanceName();
398    p->req_size_a = req_size_a;
399    p->req_size_b = req_size_b;
400    p->resp_size_a = resp_size_a;
401    p->resp_size_b = resp_size_b;
402    p->delay = delay;
403    p->nack_delay = nack_delay;
404    p->write_ack = write_ack;
405    p->fix_partial_write_a = fix_partial_write_a;
406    p->fix_partial_write_b = fix_partial_write_b;
407    return new Bridge(p);
408}
409
410REGISTER_SIM_OBJECT("Bridge", Bridge)
411
412
413