bridge.hh revision 4873:b135f6e6adfe 
1/*
2 * Copyright (c) 2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Ali Saidi
29 *          Steve Reinhardt
30 */
31
32/**
33 * @file
34 * Declaration of a simple bus bridge object with no buffering
35 */
36
37#ifndef __MEM_BRIDGE_HH__
38#define __MEM_BRIDGE_HH__
39
40#include <string>
41#include <list>
42#include <inttypes.h>
43#include <queue>
44
45#include "mem/mem_object.hh"
46#include "mem/packet.hh"
47#include "mem/port.hh"
48#include "sim/eventq.hh"
49
50class Bridge : public MemObject
51{
52  protected:
53    /** Declaration of the buses port type, one will be instantiated for each
54        of the interfaces connecting to the bus. */
55    class BridgePort : public Port
56    {
57        /** A pointer to the bridge to which this port belongs. */
58        Bridge *bridge;
59
60        /**
61         * Pointer to the port on the other side of the bridge
62         * (connected to the other bus).
63         */
64        BridgePort *otherPort;
65
66        /** Minimum delay though this bridge. */
67        Tick delay;
68
69        /** Min delay to respond to a nack. */
70        Tick nackDelay;
71
72        bool fixPartialWrite;
73
74        class PacketBuffer : public Packet::SenderState {
75
76          public:
77            Tick ready;
78            PacketPtr pkt;
79            Packet::SenderState *origSenderState;
80            short origSrc;
81            bool expectResponse;
82
83            PacketBuffer(PacketPtr _pkt, Tick t, bool nack = false)
84                : ready(t), pkt(_pkt),
85                  origSenderState(_pkt->senderState), origSrc(_pkt->getSrc()),
86                  expectResponse(_pkt->needsResponse() && !nack)
87
88            {
89                if (!pkt->isResponse() && !nack && !pkt->wasNacked())
90                    pkt->senderState = this;
91            }
92
93            void fixResponse(PacketPtr pkt)
94            {
95                assert(pkt->senderState == this);
96                pkt->setDest(origSrc);
97                pkt->senderState = origSenderState;
98            }
99        };
100
101        /**
102         * Outbound packet queue.  Packets are held in this queue for a
103         * specified delay to model the processing delay of the
104         * bridge.
105         */
106        std::list<PacketBuffer*> sendQueue;
107
108        int outstandingResponses;
109        int queuedRequests;
110
111        /** If we're waiting for a retry to happen.*/
112        bool inRetry;
113
114        /** Max queue size for outbound packets */
115        int reqQueueLimit;
116
117        /** Max queue size for reserved responses. */
118        int respQueueLimit;
119
120        /**
121         * Is this side blocked from accepting outbound packets?
122         */
123        bool respQueueFull();
124        bool reqQueueFull();
125
126        void queueForSendTiming(PacketPtr pkt);
127
128        void finishSend(PacketBuffer *buf);
129
130        void nackRequest(PacketPtr pkt);
131
132        /**
133         * Handle send event, scheduled when the packet at the head of
134         * the outbound queue is ready to transmit (for timing
135         * accesses only).
136         */
137        void trySend();
138
139        class SendEvent : public Event
140        {
141            BridgePort *port;
142
143          public:
144            SendEvent(BridgePort *p)
145                : Event(&mainEventQueue), port(p) {}
146
147            virtual void process() { port->trySend(); }
148
149            virtual const char *description() { return "bridge send"; }
150        };
151
152        SendEvent sendEvent;
153
154      public:
155        /** Constructor for the BusPort.*/
156        BridgePort(const std::string &_name, Bridge *_bridge,
157                BridgePort *_otherPort, int _delay, int _nack_delay,
158                int _req_limit, int _resp_limit, bool fix_partial_write);
159
160      protected:
161
162        /** When receiving a timing request from the peer port,
163            pass it to the bridge. */
164        virtual bool recvTiming(PacketPtr pkt);
165
166        /** When receiving a retry request from the peer port,
167            pass it to the bridge. */
168        virtual void recvRetry();
169
170        /** When receiving a Atomic requestfrom the peer port,
171            pass it to the bridge. */
172        virtual Tick recvAtomic(PacketPtr pkt);
173
174        /** When receiving a Functional request from the peer port,
175            pass it to the bridge. */
176        virtual void recvFunctional(PacketPtr pkt);
177
178        /** When receiving a status changefrom the peer port,
179            pass it to the bridge. */
180        virtual void recvStatusChange(Status status);
181
182        /** When receiving a address range request the peer port,
183            pass it to the bridge. */
184        virtual void getDeviceAddressRanges(AddrRangeList &resp,
185                                            bool &snoop);
186    };
187
188    BridgePort portA, portB;
189
190    /** If this bridge should acknowledge writes. */
191    bool ackWrites;
192
193  public:
194    struct Params
195    {
196        std::string name;
197        int req_size_a;
198        int req_size_b;
199        int resp_size_a;
200        int resp_size_b;
201        Tick delay;
202        Tick nack_delay;
203        bool write_ack;
204        bool fix_partial_write_a;
205        bool fix_partial_write_b;
206    };
207
208  protected:
209    Params *_params;
210
211  public:
212    const Params *params() const { return _params; }
213
214    /** A function used to return the port associated with this bus object. */
215    virtual Port *getPort(const std::string &if_name, int idx = -1);
216
217    virtual void init();
218
219    Bridge(Params *p);
220};
221
222#endif //__MEM_BUS_HH__
223