src/mem/bridge.hh

   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
  50 class 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->result != Packet::Nacked)
  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 event"; }
 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                                             AddrRangeList &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__