bridge.hh revision 9542:683991c46ac8 
1/*
2 * Copyright (c) 2011-2012 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 * Declaration of a memory-mapped bus bridge that connects a master
48 * and a slave through a request and response queue.
49 */
50
51#ifndef __MEM_BRIDGE_HH__
52#define __MEM_BRIDGE_HH__
53
54#include <list>
55
56#include "base/types.hh"
57#include "mem/mem_object.hh"
58#include "params/Bridge.hh"
59
60/**
61 * A bridge is used to interface two different busses (or in general a
62 * memory-mapped master and slave), with buffering for requests and
63 * responses. The bridge has a fixed delay for packets passing through
64 * it and responds to a fixed set of address ranges.
65 *
66 * The bridge comprises a slave port and a master port, that buffer
67 * outgoing responses and requests respectively. Buffer space is
68 * reserved when a request arrives, also reserving response space
69 * before forwarding the request. If there is no space present, then
70 * the bridge will delay accepting the packet until space becomes
71 * available.
72 */
73class Bridge : public MemObject
74{
75  protected:
76
77    /**
78     * A bridge request state stores packets along with their sender
79     * state and original source. It has enough information to also
80     * restore the response once it comes back to the bridge.
81     */
82    class RequestState : public Packet::SenderState
83    {
84
85      public:
86
87        PortID origSrc;
88
89        RequestState(PortID orig_src) : origSrc(orig_src)
90        { }
91
92    };
93
94    /**
95     * A deferred packet stores a packet along with its scheduled
96     * transmission time
97     */
98    class DeferredPacket
99    {
100
101      public:
102
103        Tick tick;
104        PacketPtr pkt;
105
106        DeferredPacket(PacketPtr _pkt, Tick _tick) : tick(_tick), pkt(_pkt)
107        { }
108    };
109
110    // Forward declaration to allow the slave port to have a pointer
111    class BridgeMasterPort;
112
113    /**
114     * The port on the side that receives requests and sends
115     * responses. The slave port has a set of address ranges that it
116     * is responsible for. The slave port also has a buffer for the
117     * responses not yet sent.
118     */
119    class BridgeSlavePort : public SlavePort
120    {
121
122      private:
123
124        /** The bridge to which this port belongs. */
125        Bridge& bridge;
126
127        /**
128         * Master port on the other side of the bridge (connected to
129         * the other bus).
130         */
131        BridgeMasterPort& masterPort;
132
133        /** Minimum request delay though this bridge. */
134        Cycles delay;
135
136        /** Address ranges to pass through the bridge */
137        AddrRangeList ranges;
138
139        /**
140         * Response packet queue. Response packets are held in this
141         * queue for a specified delay to model the processing delay
142         * of the bridge.
143         */
144        std::list<DeferredPacket> transmitList;
145
146        /** Counter to track the outstanding responses. */
147        unsigned int outstandingResponses;
148
149        /** If we should send a retry when space becomes available. */
150        bool retryReq;
151
152        /** Max queue size for reserved responses. */
153        unsigned int respQueueLimit;
154
155        /**
156         * Is this side blocked from accepting new response packets.
157         *
158         * @return true if the reserved space has reached the set limit
159         */
160        bool respQueueFull();
161
162        /**
163         * Handle send event, scheduled when the packet at the head of
164         * the response queue is ready to transmit (for timing
165         * accesses only).
166         */
167        void trySendTiming();
168
169        /** Send event for the response queue. */
170        EventWrapper<BridgeSlavePort,
171                     &BridgeSlavePort::trySendTiming> sendEvent;
172
173      public:
174
175        /**
176         * Constructor for the BridgeSlavePort.
177         *
178         * @param _name the port name including the owner
179         * @param _bridge the structural owner
180         * @param _masterPort the master port on the other side of the bridge
181         * @param _delay the delay in cycles from receiving to sending
182         * @param _resp_limit the size of the response queue
183         * @param _ranges a number of address ranges to forward
184         */
185        BridgeSlavePort(const std::string& _name, Bridge& _bridge,
186                        BridgeMasterPort& _masterPort, Cycles _delay,
187                        int _resp_limit, std::vector<AddrRange> _ranges);
188
189        /**
190         * Queue a response packet to be sent out later and also schedule
191         * a send if necessary.
192         *
193         * @param pkt a response to send out after a delay
194         * @param when tick when response packet should be sent
195         */
196        void schedTimingResp(PacketPtr pkt, Tick when);
197
198        /**
199         * Retry any stalled request that we have failed to accept at
200         * an earlier point in time. This call will do nothing if no
201         * request is waiting.
202         */
203        void retryStalledReq();
204
205      protected:
206
207        /** When receiving a timing request from the peer port,
208            pass it to the bridge. */
209        bool recvTimingReq(PacketPtr pkt);
210
211        /** When receiving a retry request from the peer port,
212            pass it to the bridge. */
213        void recvRetry();
214
215        /** When receiving a Atomic requestfrom the peer port,
216            pass it to the bridge. */
217        Tick recvAtomic(PacketPtr pkt);
218
219        /** When receiving a Functional request from the peer port,
220            pass it to the bridge. */
221        void recvFunctional(PacketPtr pkt);
222
223        /** When receiving a address range request the peer port,
224            pass it to the bridge. */
225        AddrRangeList getAddrRanges() const;
226    };
227
228
229    /**
230     * Port on the side that forwards requests and receives
231     * responses. The master port has a buffer for the requests not
232     * yet sent.
233     */
234    class BridgeMasterPort : public MasterPort
235    {
236
237      private:
238
239        /** The bridge to which this port belongs. */
240        Bridge& bridge;
241
242        /**
243         * The slave port on the other side of the bridge (connected
244         * to the other bus).
245         */
246        BridgeSlavePort& slavePort;
247
248        /** Minimum delay though this bridge. */
249        Cycles delay;
250
251        /**
252         * Request packet queue. Request packets are held in this
253         * queue for a specified delay to model the processing delay
254         * of the bridge.
255         */
256        std::list<DeferredPacket> transmitList;
257
258        /** Max queue size for request packets */
259        unsigned int reqQueueLimit;
260
261        /**
262         * Handle send event, scheduled when the packet at the head of
263         * the outbound queue is ready to transmit (for timing
264         * accesses only).
265         */
266        void trySendTiming();
267
268        /** Send event for the request queue. */
269        EventWrapper<BridgeMasterPort,
270                     &BridgeMasterPort::trySendTiming> sendEvent;
271
272      public:
273
274        /**
275         * Constructor for the BridgeMasterPort.
276         *
277         * @param _name the port name including the owner
278         * @param _bridge the structural owner
279         * @param _slavePort the slave port on the other side of the bridge
280         * @param _delay the delay in cycles from receiving to sending
281         * @param _req_limit the size of the request queue
282         */
283        BridgeMasterPort(const std::string& _name, Bridge& _bridge,
284                         BridgeSlavePort& _slavePort, Cycles _delay,
285                         int _req_limit);
286
287        /**
288         * Is this side blocked from accepting new request packets.
289         *
290         * @return true if the occupied space has reached the set limit
291         */
292        bool reqQueueFull();
293
294        /**
295         * Queue a request packet to be sent out later and also schedule
296         * a send if necessary.
297         *
298         * @param pkt a request to send out after a delay
299         * @param when tick when response packet should be sent
300         */
301        void schedTimingReq(PacketPtr pkt, Tick when);
302
303        /**
304         * Check a functional request against the packets in our
305         * request queue.
306         *
307         * @param pkt packet to check against
308         *
309         * @return true if we find a match
310         */
311        bool checkFunctional(PacketPtr pkt);
312
313      protected:
314
315        /** When receiving a timing request from the peer port,
316            pass it to the bridge. */
317        bool recvTimingResp(PacketPtr pkt);
318
319        /** When receiving a retry request from the peer port,
320            pass it to the bridge. */
321        void recvRetry();
322    };
323
324    /** Slave port of the bridge. */
325    BridgeSlavePort slavePort;
326
327    /** Master port of the bridge. */
328    BridgeMasterPort masterPort;
329
330  public:
331
332    virtual BaseMasterPort& getMasterPort(const std::string& if_name,
333                                          PortID idx = InvalidPortID);
334    virtual BaseSlavePort& getSlavePort(const std::string& if_name,
335                                        PortID idx = InvalidPortID);
336
337    virtual void init();
338
339    typedef BridgeParams Params;
340
341    Bridge(Params *p);
342};
343
344#endif //__MEM_BUS_HH__
345