1/*
2 * Copyright (c) 2011-2013, 2015 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2006 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Ali Saidi
41 * Steve Reinhardt
42 * Andreas Hansson
43 */
44
45/**
46 * @file
47 * Implementation of a memory-mapped bridge that connects a master
48 * and a slave through a request and response queue.
49 */
50
51#include "base/trace.hh"
52#include "debug/Bridge.hh"
53#include "mem/bridge.hh"
54#include "params/Bridge.hh"
55
56Bridge::BridgeSlavePort::BridgeSlavePort(const std::string& _name,
57 Bridge& _bridge,
58 BridgeMasterPort& _masterPort,
59 Cycles _delay, int _resp_limit,
60 std::vector<AddrRange> _ranges)
61 : SlavePort(_name, &_bridge), bridge(_bridge), masterPort(_masterPort),
62 delay(_delay), ranges(_ranges.begin(), _ranges.end()),
63 outstandingResponses(0), retryReq(false),
64 respQueueLimit(_resp_limit), sendEvent(*this)
65{
66}
67
68Bridge::BridgeMasterPort::BridgeMasterPort(const std::string& _name,
69 Bridge& _bridge,
70 BridgeSlavePort& _slavePort,
71 Cycles _delay, int _req_limit)
72 : MasterPort(_name, &_bridge), bridge(_bridge), slavePort(_slavePort),
73 delay(_delay), reqQueueLimit(_req_limit), sendEvent(*this)
74{
75}
76
77Bridge::Bridge(Params *p)
78 : MemObject(p),
79 slavePort(p->name + ".slave", *this, masterPort,
80 ticksToCycles(p->delay), p->resp_size, p->ranges),
81 masterPort(p->name + ".master", *this, slavePort,
82 ticksToCycles(p->delay), p->req_size)
83{
84}
85
86BaseMasterPort&
87Bridge::getMasterPort(const std::string &if_name, PortID idx)
88{
89 if (if_name == "master")
90 return masterPort;
91 else
92 // pass it along to our super class
93 return MemObject::getMasterPort(if_name, idx);
94}
95
96BaseSlavePort&
97Bridge::getSlavePort(const std::string &if_name, PortID idx)
98{
99 if (if_name == "slave")
100 return slavePort;
101 else
102 // pass it along to our super class
103 return MemObject::getSlavePort(if_name, idx);
104}
105
106void
107Bridge::init()
108{
109 // make sure both sides are connected and have the same block size
110 if (!slavePort.isConnected() || !masterPort.isConnected())
111 fatal("Both ports of a bridge must be connected.\n");
112
113 // notify the master side of our address ranges
114 slavePort.sendRangeChange();
115}
116
117bool
118Bridge::BridgeSlavePort::respQueueFull() const
119{
120 return outstandingResponses == respQueueLimit;
121}
122
123bool
124Bridge::BridgeMasterPort::reqQueueFull() const
125{
126 return transmitList.size() == reqQueueLimit;
127}
128
129bool
130Bridge::BridgeMasterPort::recvTimingResp(PacketPtr pkt)
131{
132 // all checks are done when the request is accepted on the slave
133 // side, so we are guaranteed to have space for the response
134 DPRINTF(Bridge, "recvTimingResp: %s addr 0x%x\n",
135 pkt->cmdString(), pkt->getAddr());
136
137 DPRINTF(Bridge, "Request queue size: %d\n", transmitList.size());
138
139 // technically the packet only reaches us after the header delay,
140 // and typically we also need to deserialise any payload (unless
141 // the two sides of the bridge are synchronous)
142 Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
143 pkt->headerDelay = pkt->payloadDelay = 0;
144
145 slavePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
146 receive_delay);
147
148 return true;
149}
150
151bool
152Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
153{
154 DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
155 pkt->cmdString(), pkt->getAddr());
156
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159
160 // we should not get a new request after committing to retry the
161 // current one, but unfortunately the CPU violates this rule, so
162 // simply ignore it for now
163 if (retryReq)
164 return false;
165
166 DPRINTF(Bridge, "Response queue size: %d outresp: %d\n",
167 transmitList.size(), outstandingResponses);
168
169 // if the request queue is full then there is no hope
170 if (masterPort.reqQueueFull()) {
171 DPRINTF(Bridge, "Request queue full\n");
172 retryReq = true;
173 } else {
174 // look at the response queue if we expect to see a response
175 bool expects_response = pkt->needsResponse();
176 if (expects_response) {
177 if (respQueueFull()) {
178 DPRINTF(Bridge, "Response queue full\n");
179 retryReq = true;
180 } else {
181 // ok to send the request with space for the response
182 DPRINTF(Bridge, "Reserving space for response\n");
183 assert(outstandingResponses != respQueueLimit);
184 ++outstandingResponses;
185
186 // no need to set retryReq to false as this is already the
187 // case
188 }
189 }
190
191 if (!retryReq) {
192 // technically the packet only reaches us after the header
193 // delay, and typically we also need to deserialise any
194 // payload (unless the two sides of the bridge are
195 // synchronous)
196 Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
197 pkt->headerDelay = pkt->payloadDelay = 0;
198
199 masterPort.schedTimingReq(pkt, bridge.clockEdge(delay) +
200 receive_delay);
201 }
202 }
203
204 // remember that we are now stalling a packet and that we have to
205 // tell the sending master to retry once space becomes available,
206 // we make no distinction whether the stalling is due to the
207 // request queue or response queue being full
208 return !retryReq;
209}
210
211void
212Bridge::BridgeSlavePort::retryStalledReq()
213{
214 if (retryReq) {
215 DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
216 retryReq = false;
217 sendRetryReq();
218 }
219}
220
221void
222Bridge::BridgeMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
223{
224 // If we're about to put this packet at the head of the queue, we
225 // need to schedule an event to do the transmit. Otherwise there
226 // should already be an event scheduled for sending the head
227 // packet.
228 if (transmitList.empty()) {
229 bridge.schedule(sendEvent, when);
230 }
231
232 assert(transmitList.size() != reqQueueLimit);
233
234 transmitList.emplace_back(pkt, when);
235}
236
237
238void
239Bridge::BridgeSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
240{
241 // If we're about to put this packet at the head of the queue, we
242 // need to schedule an event to do the transmit. Otherwise there
243 // should already be an event scheduled for sending the head
244 // packet.
245 if (transmitList.empty()) {
246 bridge.schedule(sendEvent, when);
247 }
248
249 transmitList.emplace_back(pkt, when);
250}
251
252void
253Bridge::BridgeMasterPort::trySendTiming()
254{
255 assert(!transmitList.empty());
256
257 DeferredPacket req = transmitList.front();
258
259 assert(req.tick <= curTick());
260
261 PacketPtr pkt = req.pkt;
262
263 DPRINTF(Bridge, "trySend request addr 0x%x, queue size %d\n",
264 pkt->getAddr(), transmitList.size());
265
266 if (sendTimingReq(pkt)) {
267 // send successful
268 transmitList.pop_front();
269 DPRINTF(Bridge, "trySend request successful\n");
270
271 // If there are more packets to send, schedule event to try again.
272 if (!transmitList.empty()) {
273 DeferredPacket next_req = transmitList.front();
274 DPRINTF(Bridge, "Scheduling next send\n");
275 bridge.schedule(sendEvent, std::max(next_req.tick,
276 bridge.clockEdge()));
277 }
278
279 // if we have stalled a request due to a full request queue,
280 // then send a retry at this point, also note that if the
281 // request we stalled was waiting for the response queue
282 // rather than the request queue we might stall it again
283 slavePort.retryStalledReq();
284 }
285
286 // if the send failed, then we try again once we receive a retry,
287 // and therefore there is no need to take any action
288}
289
290void
291Bridge::BridgeSlavePort::trySendTiming()
292{
293 assert(!transmitList.empty());
294
295 DeferredPacket resp = transmitList.front();
296
297 assert(resp.tick <= curTick());
298
299 PacketPtr pkt = resp.pkt;
300
301 DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
302 pkt->getAddr(), outstandingResponses);
303
304 if (sendTimingResp(pkt)) {
305 // send successful
306 transmitList.pop_front();
307 DPRINTF(Bridge, "trySend response successful\n");
308
309 assert(outstandingResponses != 0);
310 --outstandingResponses;
311
312 // If there are more packets to send, schedule event to try again.
313 if (!transmitList.empty()) {
314 DeferredPacket next_resp = transmitList.front();
315 DPRINTF(Bridge, "Scheduling next send\n");
316 bridge.schedule(sendEvent, std::max(next_resp.tick,
317 bridge.clockEdge()));
318 }
319
320 // if there is space in the request queue and we were stalling
321 // a request, it will definitely be possible to accept it now
322 // since there is guaranteed space in the response queue
323 if (!masterPort.reqQueueFull() && retryReq) {
324 DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
325 retryReq = false;
326 sendRetryReq();
327 }
328 }
329
330 // if the send failed, then we try again once we receive a retry,
331 // and therefore there is no need to take any action
332}
333
334void
335Bridge::BridgeMasterPort::recvReqRetry()
336{
337 trySendTiming();
338}
339
340void
341Bridge::BridgeSlavePort::recvRespRetry()
342{
343 trySendTiming();
344}
345
346Tick
347Bridge::BridgeSlavePort::recvAtomic(PacketPtr pkt)
348{
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