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

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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 bridge is receiving a range change.*/
342void
343Bridge::BridgePort::recvRangeChange()
344{
345 otherPort->sendRangeChange();
346}
347
348AddrRangeList
349Bridge::BridgePort::getAddrRanges()
350{
351 AddrRangeList ranges = otherPort->getPeer()->getAddrRanges();
352 FilterRangeList(filterRanges, ranges);
353 return ranges;
354}
355
356Bridge *
357BridgeParams::create()
358{
359 return new Bridge(this);
360}