bridge.cc revision 4918:3214e3694fb2 
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 "params/Bridge.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        DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
212        delete buf;
213    }
214
215
216    if (pkt->isRequest() && !pkt->wasNacked()) {
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        sendEvent.schedule(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    // Ugly! @todo When multilevel coherence works this will be removed
247    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
248            !pkt->wasNacked()) {
249        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
250                            Packet::Broadcast);
251        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
252        sendFunctional(funcPkt);
253        pkt->cmd = MemCmd::WriteReq;
254        delete funcPkt;
255    }
256
257    DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
258            buf->origSrc, pkt->getDest(), pkt->getAddr());
259
260    bool wasReq = pkt->isRequest();
261    bool wasNacked = pkt->wasNacked();
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 (!wasNacked) {
279            if (wasReq)
280                --queuedRequests;
281            else
282                --outstandingResponses;
283        }
284
285        // If there are more packets to send, schedule event to try again.
286        if (!sendQueue.empty()) {
287            buf = sendQueue.front();
288            DPRINTF(BusBridge, "Scheduling next send\n");
289            sendEvent.schedule(std::max(buf->ready, curTick + 1));
290        }
291    } else {
292        DPRINTF(BusBridge, "  unsuccessful\n");
293        inRetry = true;
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        sendEvent.schedule(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    // fix partial atomic writes... similar to the timing code that does the
317    // same... will be removed once our code gets this right
318    if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite) {
319
320        PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
321                         Packet::Broadcast);
322        funcPkt->dataStatic(pkt->getPtr<uint8_t>());
323        otherPort->sendFunctional(funcPkt);
324        delete funcPkt;
325        pkt->cmd = MemCmd::WriteReq;
326    }
327    return delay + otherPort->sendAtomic(pkt);
328}
329
330/** Function called by the port when the bus is receiving a Functional
331 * transaction.*/
332void
333Bridge::BridgePort::recvFunctional(PacketPtr pkt)
334{
335    std::list<PacketBuffer*>::iterator i;
336
337    for (i = sendQueue.begin();  i != sendQueue.end(); ++i) {
338        if (pkt->checkFunctional((*i)->pkt))
339            return;
340    }
341
342    // fall through if pkt still not satisfied
343    otherPort->sendFunctional(pkt);
344}
345
346/** Function called by the port when the bus is receiving a status change.*/
347void
348Bridge::BridgePort::recvStatusChange(Port::Status status)
349{
350    otherPort->sendStatusChange(status);
351}
352
353void
354Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
355                                           bool &snoop)
356{
357    otherPort->getPeerAddressRanges(resp, snoop);
358    // we don't allow snooping across bridges
359    snoop = false;
360}
361
362Bridge *
363BridgeParams::create()
364{
365    return new Bridge(this);
366}
367