bridge.hh revision 9128:6921ec2e77c4 
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#include <queue>
56#include <string>
57
58#include "base/types.hh"
59#include "mem/mem_object.hh"
60#include "mem/packet.hh"
61#include "mem/port.hh"
62#include "params/Bridge.hh"
63#include "sim/eventq.hh"
64
65/**
66 * A bridge is used to interface two different busses (or in general a
67 * memory-mapped master and slave), with buffering for requests and
68 * responses. The bridge has a fixed delay for packets passing through
69 * it and responds to a fixed set of address ranges.
70 *
71 * The bridge comprises a slave port and a master port, that buffer
72 * outgoing responses and requests respectively. Buffer space is
73 * reserved when a request arrives, also reserving response space
74 * before forwarding the request. An incoming request is always
75 * accepted (recvTiming returns true), but is potentially NACKed if
76 * there is no request space or response space.
77 */
78class Bridge : public MemObject
79{
80  protected:
81
82    /**
83     * A bridge request state stores packets along with their sender
84     * state and original source. It has enough information to also
85     * restore the response once it comes back to the bridge.
86     */
87    class RequestState : public Packet::SenderState
88    {
89
90      public:
91
92        Packet::SenderState *origSenderState;
93        PortID origSrc;
94
95        RequestState(PacketPtr _pkt)
96            : origSenderState(_pkt->senderState),
97              origSrc(_pkt->getSrc())
98        { }
99
100        void fixResponse(PacketPtr pkt)
101        {
102            assert(pkt->senderState == this);
103            pkt->setDest(origSrc);
104            pkt->senderState = origSenderState;
105        }
106    };
107
108    /**
109     * A deferred request stores a packet along with its scheduled
110     * transmission time, and whether we can expect to see a response
111     * or not.
112     */
113    class DeferredRequest
114    {
115
116      public:
117
118        Tick ready;
119        PacketPtr pkt;
120        bool expectResponse;
121
122        DeferredRequest(PacketPtr _pkt, Tick t)
123            : ready(t), pkt(_pkt), expectResponse(_pkt->needsResponse())
124        { }
125    };
126
127    /**
128     * A deferred response stores a packet along with its scheduled
129     * transmission time. It also contains information of whether the
130     * bridge NACKed the packet to be able to correctly maintain
131     * counters of outstanding responses.
132     */
133    class DeferredResponse {
134
135      public:
136
137        Tick ready;
138        PacketPtr pkt;
139        bool nackedHere;
140
141        DeferredResponse(PacketPtr _pkt, Tick t, bool nack = false)
142            : ready(t), pkt(_pkt), nackedHere(nack)
143        { }
144    };
145
146    // Forward declaration to allow the slave port to have a pointer
147    class BridgeMasterPort;
148
149    /**
150     * The port on the side that receives requests and sends
151     * responses. The slave port has a set of address ranges that it
152     * is responsible for. The slave port also has a buffer for the
153     * responses not yet sent.
154     */
155    class BridgeSlavePort : public SlavePort
156    {
157
158      private:
159
160        /** A pointer to the bridge to which this port belongs. */
161        Bridge *bridge;
162
163        /**
164         * Master port on the other side of the bridge
165         * (connected to the other bus).
166         */
167        BridgeMasterPort& masterPort;
168
169        /** Minimum request delay though this bridge. */
170        Tick delay;
171
172        /** Min delay to respond with a nack. */
173        Tick nackDelay;
174
175        /** Address ranges to pass through the bridge */
176        AddrRangeList ranges;
177
178        /**
179         * Response packet queue. Response packets are held in this
180         * queue for a specified delay to model the processing delay
181         * of the bridge.
182         */
183        std::list<DeferredResponse> responseQueue;
184
185        /** Counter to track the outstanding responses. */
186        unsigned int outstandingResponses;
187
188        /** If we're waiting for a retry to happen. */
189        bool inRetry;
190
191        /** Max queue size for reserved responses. */
192        unsigned int respQueueLimit;
193
194        /**
195         * Is this side blocked from accepting new response packets.
196         *
197         * @return true if the reserved space has reached the set limit
198         */
199        bool respQueueFull();
200
201        /**
202         * Turn the request packet into a NACK response and put it in
203         * the response queue and schedule its transmission.
204         *
205         * @param pkt the request packet to NACK
206         */
207        void nackRequest(PacketPtr pkt);
208
209        /**
210         * Handle send event, scheduled when the packet at the head of
211         * the response queue is ready to transmit (for timing
212         * accesses only).
213         */
214        void trySend();
215
216        /** Send event for the response queue. */
217        EventWrapper<BridgeSlavePort, &BridgeSlavePort::trySend> sendEvent;
218
219      public:
220
221        /**
222         * Constructor for the BridgeSlavePort.
223         *
224         * @param _name the port name including the owner
225         * @param _bridge the structural owner
226         * @param _masterPort the master port on the other side of the bridge
227         * @param _delay the delay from seeing a response to sending it
228         * @param _nack_delay the delay from a NACK to sending the response
229         * @param _resp_limit the size of the response queue
230         * @param _ranges a number of address ranges to forward
231         */
232        BridgeSlavePort(const std::string &_name, Bridge *_bridge,
233                        BridgeMasterPort& _masterPort, int _delay,
234                        int _nack_delay, int _resp_limit,
235                        std::vector<Range<Addr> > _ranges);
236
237        /**
238         * Queue a response packet to be sent out later and also schedule
239         * a send if necessary.
240         *
241         * @param pkt a response to send out after a delay
242         */
243        void queueForSendTiming(PacketPtr pkt);
244
245      protected:
246
247        /** When receiving a timing request from the peer port,
248            pass it to the bridge. */
249        virtual bool recvTimingReq(PacketPtr pkt);
250
251        /** When receiving a retry request from the peer port,
252            pass it to the bridge. */
253        virtual void recvRetry();
254
255        /** When receiving a Atomic requestfrom the peer port,
256            pass it to the bridge. */
257        virtual Tick recvAtomic(PacketPtr pkt);
258
259        /** When receiving a Functional request from the peer port,
260            pass it to the bridge. */
261        virtual void recvFunctional(PacketPtr pkt);
262
263        /** When receiving a address range request the peer port,
264            pass it to the bridge. */
265        virtual AddrRangeList getAddrRanges() const;
266    };
267
268
269    /**
270     * Port on the side that forwards requests and receives
271     * responses. The master port has a buffer for the requests not
272     * yet sent.
273     */
274    class BridgeMasterPort : public MasterPort
275    {
276
277      private:
278
279        /** A pointer to the bridge to which this port belongs. */
280        Bridge* bridge;
281
282        /**
283         * Pointer to the slave port on the other side of the bridge
284         * (connected to the other bus).
285         */
286        BridgeSlavePort& slavePort;
287
288        /** Minimum delay though this bridge. */
289        Tick delay;
290
291        /**
292         * Request packet queue. Request packets are held in this
293         * queue for a specified delay to model the processing delay
294         * of the bridge.
295         */
296        std::list<DeferredRequest> requestQueue;
297
298        /** If we're waiting for a retry to happen. */
299        bool inRetry;
300
301        /** Max queue size for request packets */
302        unsigned int reqQueueLimit;
303
304        /**
305         * Handle send event, scheduled when the packet at the head of
306         * the outbound queue is ready to transmit (for timing
307         * accesses only).
308         */
309        void trySend();
310
311        /** Send event for the request queue. */
312        EventWrapper<BridgeMasterPort, &BridgeMasterPort::trySend> sendEvent;
313
314      public:
315
316        /**
317         * Constructor for the BridgeMasterPort.
318         *
319         * @param _name the port name including the owner
320         * @param _bridge the structural owner
321         * @param _slavePort the slave port on the other side of the bridge
322         * @param _delay the delay from seeing a request to sending it
323         * @param _req_limit the size of the request queue
324         */
325        BridgeMasterPort(const std::string &_name, Bridge *_bridge,
326                         BridgeSlavePort& _slavePort, int _delay,
327                         int _req_limit);
328
329        /**
330         * Is this side blocked from accepting new request packets.
331         *
332         * @return true if the occupied space has reached the set limit
333         */
334        bool reqQueueFull();
335
336        /**
337         * Queue a request packet to be sent out later and also schedule
338         * a send if necessary.
339         *
340         * @param pkt a request to send out after a delay
341         */
342        void queueForSendTiming(PacketPtr pkt);
343
344        /**
345         * Check a functional request against the packets in our
346         * request queue.
347         *
348         * @param pkt packet to check against
349         *
350         * @return true if we find a match
351         */
352        bool checkFunctional(PacketPtr pkt);
353
354      protected:
355
356        /** When receiving a timing request from the peer port,
357            pass it to the bridge. */
358        virtual bool recvTimingResp(PacketPtr pkt);
359
360        /** When receiving a retry request from the peer port,
361            pass it to the bridge. */
362        virtual void recvRetry();
363    };
364
365    /** Slave port of the bridge. */
366    BridgeSlavePort slavePort;
367
368    /** Master port of the bridge. */
369    BridgeMasterPort masterPort;
370
371    /** If this bridge should acknowledge writes. */
372    bool ackWrites;
373
374  public:
375    typedef BridgeParams Params;
376
377  protected:
378    Params *_params;
379
380  public:
381    const Params *params() const { return _params; }
382
383    virtual MasterPort& getMasterPort(const std::string& if_name,
384                                      int idx = -1);
385    virtual SlavePort& getSlavePort(const std::string& if_name, int idx = -1);
386
387    virtual void init();
388
389    Bridge(Params *p);
390};
391
392#endif //__MEM_BUS_HH__
393