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 "params/Bridge.hh"
  49 #include "sim/eventq.hh"
  50
  51 class 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->result != Packet::Nacked)
  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 event"; }
 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__