bridge.hh revision 4918:3214e3694fb2 
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 "params/Bridge.hh"
49#include "sim/eventq.hh"
50
51class Bridge : public MemObject
52{
53  protected:
54    /** Declaration of the buses port type, one will be instantiated for each
55        of the interfaces connecting to the bus. */
56    class BridgePort : public Port
57    {
58        /** A pointer to the bridge to which this port belongs. */
59        Bridge *bridge;
60
61        /**
62         * Pointer to the port on the other side of the bridge
63         * (connected to the other bus).
64         */
65        BridgePort *otherPort;
66
67        /** Minimum delay though this bridge. */
68        Tick delay;
69
70        /** Min delay to respond to a nack. */
71        Tick nackDelay;
72
73        bool fixPartialWrite;
74
75        class PacketBuffer : public Packet::SenderState {
76
77          public:
78            Tick ready;
79            PacketPtr pkt;
80            Packet::SenderState *origSenderState;
81            short origSrc;
82            bool expectResponse;
83
84            PacketBuffer(PacketPtr _pkt, Tick t, bool nack = false)
85                : ready(t), pkt(_pkt),
86                  origSenderState(_pkt->senderState), origSrc(_pkt->getSrc()),
87                  expectResponse(_pkt->needsResponse() && !nack)
88
89            {
90                if (!pkt->isResponse() && !nack && !pkt->wasNacked())
91                    pkt->senderState = this;
92            }
93
94            void fixResponse(PacketPtr pkt)
95            {
96                assert(pkt->senderState == this);
97                pkt->setDest(origSrc);
98                pkt->senderState = origSenderState;
99            }
100        };
101
102        /**
103         * Outbound packet queue.  Packets are held in this queue for a
104         * specified delay to model the processing delay of the
105         * bridge.
106         */
107        std::list<PacketBuffer*> sendQueue;
108
109        int outstandingResponses;
110        int queuedRequests;
111
112        /** If we're waiting for a retry to happen.*/
113        bool inRetry;
114
115        /** Max queue size for outbound packets */
116        int reqQueueLimit;
117
118        /** Max queue size for reserved responses. */
119        int respQueueLimit;
120
121        /**
122         * Is this side blocked from accepting outbound packets?
123         */
124        bool respQueueFull();
125        bool reqQueueFull();
126
127        void queueForSendTiming(PacketPtr pkt);
128
129        void finishSend(PacketBuffer *buf);
130
131        void nackRequest(PacketPtr pkt);
132
133        /**
134         * Handle send event, scheduled when the packet at the head of
135         * the outbound queue is ready to transmit (for timing
136         * accesses only).
137         */
138        void trySend();
139
140        class SendEvent : public Event
141        {
142            BridgePort *port;
143
144          public:
145            SendEvent(BridgePort *p)
146                : Event(&mainEventQueue), port(p) {}
147
148            virtual void process() { port->trySend(); }
149
150            virtual const char *description() { return "bridge send"; }
151        };
152
153        SendEvent sendEvent;
154
155      public:
156        /** Constructor for the BusPort.*/
157        BridgePort(const std::string &_name, Bridge *_bridge,
158                BridgePort *_otherPort, int _delay, int _nack_delay,
159                int _req_limit, int _resp_limit, bool fix_partial_write);
160
161      protected:
162
163        /** When receiving a timing request from the peer port,
164            pass it to the bridge. */
165        virtual bool recvTiming(PacketPtr pkt);
166
167        /** When receiving a retry request from the peer port,
168            pass it to the bridge. */
169        virtual void recvRetry();
170
171        /** When receiving a Atomic requestfrom the peer port,
172            pass it to the bridge. */
173        virtual Tick recvAtomic(PacketPtr pkt);
174
175        /** When receiving a Functional request from the peer port,
176            pass it to the bridge. */
177        virtual void recvFunctional(PacketPtr pkt);
178
179        /** When receiving a status changefrom the peer port,
180            pass it to the bridge. */
181        virtual void recvStatusChange(Status status);
182
183        /** When receiving a address range request the peer port,
184            pass it to the bridge. */
185        virtual void getDeviceAddressRanges(AddrRangeList &resp,
186                                            bool &snoop);
187    };
188
189    BridgePort portA, portB;
190
191    /** If this bridge should acknowledge writes. */
192    bool ackWrites;
193
194  public:
195    typedef BridgeParams Params;
196
197  protected:
198    Params *_params;
199
200  public:
201    const Params *params() const { return _params; }
202
203    /** A function used to return the port associated with this bus object. */
204    virtual Port *getPort(const std::string &if_name, int idx = -1);
205
206    virtual void init();
207
208    Bridge(Params *p);
209};
210
211#endif //__MEM_BUS_HH__
212