bridge.hh revision 13784:1941dc118243 
1/*
2 * Copyright (c) 2011-2013 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 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 <deque>
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 crossbars (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 deferred packet stores a packet along with its scheduled
79     * transmission time
80     */
81    class DeferredPacket
82    {
83
84      public:
85
86        const Tick tick;
87        const PacketPtr pkt;
88
89        DeferredPacket(PacketPtr _pkt, Tick _tick) : tick(_tick), pkt(_pkt)
90        { }
91    };
92
93    // Forward declaration to allow the slave port to have a pointer
94    class BridgeMasterPort;
95
96    /**
97     * The port on the side that receives requests and sends
98     * responses. The slave port has a set of address ranges that it
99     * is responsible for. The slave port also has a buffer for the
100     * responses not yet sent.
101     */
102    class BridgeSlavePort : public SlavePort
103    {
104
105      private:
106
107        /** The bridge to which this port belongs. */
108        Bridge& bridge;
109
110        /**
111         * Master port on the other side of the bridge.
112         */
113        BridgeMasterPort& masterPort;
114
115        /** Minimum request delay though this bridge. */
116        const Cycles delay;
117
118        /** Address ranges to pass through the bridge */
119        const AddrRangeList ranges;
120
121        /**
122         * Response packet queue. Response packets are held in this
123         * queue for a specified delay to model the processing delay
124         * of the bridge. We use a deque as we need to iterate over
125         * the items for functional accesses.
126         */
127        std::deque<DeferredPacket> transmitList;
128
129        /** Counter to track the outstanding responses. */
130        unsigned int outstandingResponses;
131
132        /** If we should send a retry when space becomes available. */
133        bool retryReq;
134
135        /** Max queue size for reserved responses. */
136        unsigned int respQueueLimit;
137
138        /**
139         * Upstream caches need this packet until true is returned, so
140         * hold it for deletion until a subsequent call
141         */
142        std::unique_ptr<Packet> pendingDelete;
143
144        /**
145         * Is this side blocked from accepting new response packets.
146         *
147         * @return true if the reserved space has reached the set limit
148         */
149        bool respQueueFull() const;
150
151        /**
152         * Handle send event, scheduled when the packet at the head of
153         * the response queue is ready to transmit (for timing
154         * accesses only).
155         */
156        void trySendTiming();
157
158        /** Send event for the response queue. */
159        EventFunctionWrapper sendEvent;
160
161      public:
162
163        /**
164         * Constructor for the BridgeSlavePort.
165         *
166         * @param _name the port name including the owner
167         * @param _bridge the structural owner
168         * @param _masterPort the master port on the other side of the bridge
169         * @param _delay the delay in cycles from receiving to sending
170         * @param _resp_limit the size of the response queue
171         * @param _ranges a number of address ranges to forward
172         */
173        BridgeSlavePort(const std::string& _name, Bridge& _bridge,
174                        BridgeMasterPort& _masterPort, Cycles _delay,
175                        int _resp_limit, std::vector<AddrRange> _ranges);
176
177        /**
178         * Queue a response packet to be sent out later and also schedule
179         * a send if necessary.
180         *
181         * @param pkt a response to send out after a delay
182         * @param when tick when response packet should be sent
183         */
184        void schedTimingResp(PacketPtr pkt, Tick when);
185
186        /**
187         * Retry any stalled request that we have failed to accept at
188         * an earlier point in time. This call will do nothing if no
189         * request is waiting.
190         */
191        void retryStalledReq();
192
193      protected:
194
195        /** When receiving a timing request from the peer port,
196            pass it to the bridge. */
197        bool recvTimingReq(PacketPtr pkt);
198
199        /** When receiving a retry request from the peer port,
200            pass it to the bridge. */
201        void recvRespRetry();
202
203        /** When receiving a Atomic requestfrom the peer port,
204            pass it to the bridge. */
205        Tick recvAtomic(PacketPtr pkt);
206
207        /** When receiving a Functional request from the peer port,
208            pass it to the bridge. */
209        void recvFunctional(PacketPtr pkt);
210
211        /** When receiving a address range request the peer port,
212            pass it to the bridge. */
213        AddrRangeList getAddrRanges() const;
214    };
215
216
217    /**
218     * Port on the side that forwards requests and receives
219     * responses. The master port has a buffer for the requests not
220     * yet sent.
221     */
222    class BridgeMasterPort : public MasterPort
223    {
224
225      private:
226
227        /** The bridge to which this port belongs. */
228        Bridge& bridge;
229
230        /**
231         * The slave port on the other side of the bridge.
232         */
233        BridgeSlavePort& slavePort;
234
235        /** Minimum delay though this bridge. */
236        const Cycles delay;
237
238        /**
239         * Request packet queue. Request packets are held in this
240         * queue for a specified delay to model the processing delay
241         * of the bridge.  We use a deque as we need to iterate over
242         * the items for functional accesses.
243         */
244        std::deque<DeferredPacket> transmitList;
245
246        /** Max queue size for request packets */
247        const unsigned int reqQueueLimit;
248
249        /**
250         * Handle send event, scheduled when the packet at the head of
251         * the outbound queue is ready to transmit (for timing
252         * accesses only).
253         */
254        void trySendTiming();
255
256        /** Send event for the request queue. */
257        EventFunctionWrapper sendEvent;
258
259      public:
260
261        /**
262         * Constructor for the BridgeMasterPort.
263         *
264         * @param _name the port name including the owner
265         * @param _bridge the structural owner
266         * @param _slavePort the slave port on the other side of the bridge
267         * @param _delay the delay in cycles from receiving to sending
268         * @param _req_limit the size of the request queue
269         */
270        BridgeMasterPort(const std::string& _name, Bridge& _bridge,
271                         BridgeSlavePort& _slavePort, Cycles _delay,
272                         int _req_limit);
273
274        /**
275         * Is this side blocked from accepting new request packets.
276         *
277         * @return true if the occupied space has reached the set limit
278         */
279        bool reqQueueFull() const;
280
281        /**
282         * Queue a request packet to be sent out later and also schedule
283         * a send if necessary.
284         *
285         * @param pkt a request to send out after a delay
286         * @param when tick when response packet should be sent
287         */
288        void schedTimingReq(PacketPtr pkt, Tick when);
289
290        /**
291         * Check a functional request against the packets in our
292         * request queue.
293         *
294         * @param pkt packet to check against
295         *
296         * @return true if we find a match
297         */
298        bool trySatisfyFunctional(PacketPtr pkt);
299
300      protected:
301
302        /** When receiving a timing request from the peer port,
303            pass it to the bridge. */
304        bool recvTimingResp(PacketPtr pkt);
305
306        /** When receiving a retry request from the peer port,
307            pass it to the bridge. */
308        void recvReqRetry();
309    };
310
311    /** Slave port of the bridge. */
312    BridgeSlavePort slavePort;
313
314    /** Master port of the bridge. */
315    BridgeMasterPort masterPort;
316
317  public:
318
319    Port &getPort(const std::string &if_name,
320                  PortID idx=InvalidPortID) override;
321
322    virtual void init();
323
324    typedef BridgeParams Params;
325
326    Bridge(Params *p);
327};
328
329#endif //__MEM_BRIDGE_HH__
330