src/mem/bridge.hh

   1 /*
   2  * Copyright (c) 2011 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/fast_alloc.hh"
  59 #include "base/types.hh"
  60 #include "mem/mem_object.hh"
  61 #include "mem/packet.hh"
  62 #include "mem/port.hh"
  63 #include "params/Bridge.hh"
  64 #include "sim/eventq.hh"
  65
  66 /**
  67  * A bridge is used to interface two different busses (or in general a
  68  * memory-mapped master and slave), with buffering for requests and
  69  * responses. The bridge has a fixed delay for packets passing through
  70  * it and responds to a fixed set of address ranges.
  71  *
  72  * The bridge comprises a slave port and a master port, that buffer
  73  * outgoing responses and requests respectively. Buffer space is
  74  * reserved when a request arrives, also reserving response space
  75  * before forwarding the request. An incoming request is always
  76  * accepted (recvTiming returns true), but is potentially NACKed if
  77  * there is no request space or response space.
  78  */
  79 class Bridge : public MemObject
  80 {
  81   protected:
  82
  83     /**
  84      * A packet buffer stores packets along with their sender state
  85      * and scheduled time for transmission.
  86      */
  87     class PacketBuffer : public Packet::SenderState, public FastAlloc {
  88
  89       public:
  90         Tick ready;
  91         PacketPtr pkt;
  92         bool nackedHere;
  93         Packet::SenderState *origSenderState;
  94         short origSrc;
  95         bool expectResponse;
  96
  97         PacketBuffer(PacketPtr _pkt, Tick t, bool nack = false)
  98             : ready(t), pkt(_pkt), nackedHere(nack),
  99               origSenderState(_pkt->senderState),
 100               origSrc(nack ? _pkt->getDest() : _pkt->getSrc() ),
 101               expectResponse(_pkt->needsResponse() && !nack)
 102
 103         {
 104             if (!pkt->isResponse() && !nack)
 105                 pkt->senderState = this;
 106         }
 107
 108         void fixResponse(PacketPtr pkt)
 109         {
 110             assert(pkt->senderState == this);
 111             pkt->setDest(origSrc);
 112             pkt->senderState = origSenderState;
 113         }
 114     };
 115
 116     // Forward declaration to allow the slave port to have a pointer
 117     class BridgeMasterPort;
 118
 119     /**
 120      * The port on the side that receives requests and sends
 121      * responses. The slave port has a set of address ranges that it
 122      * is responsible for. The slave port also has a buffer for the
 123      * responses not yet sent.
 124      */
 125     class BridgeSlavePort : public Port
 126     {
 127
 128       private:
 129
 130         /** A pointer to the bridge to which this port belongs. */
 131         Bridge *bridge;
 132
 133         /**
 134          * Pointer to the master port on the other side of the bridge
 135          * (connected to the other bus).
 136          */
 137         BridgeMasterPort* masterPort;
 138
 139         /** Minimum request delay though this bridge. */
 140         Tick delay;
 141
 142         /** Min delay to respond with a nack. */
 143         Tick nackDelay;
 144
 145         /** Address ranges to pass through the bridge */
 146         AddrRangeList ranges;
 147
 148         /**
 149          * Response packet queue. Response packets are held in this
 150          * queue for a specified delay to model the processing delay
 151          * of the bridge.
 152          */
 153         std::list<PacketBuffer*> responseQueue;
 154
 155         /** Counter to track the outstanding responses. */
 156         unsigned int outstandingResponses;
 157
 158         /** If we're waiting for a retry to happen. */
 159         bool inRetry;
 160
 161         /** Max queue size for reserved responses. */
 162         unsigned int respQueueLimit;
 163
 164         /**
 165          * Is this side blocked from accepting new response packets.
 166          *
 167          * @return true if the reserved space has reached the set limit
 168          */
 169         bool respQueueFull();
 170
 171         /**
 172          * Turn the request packet into a NACK response and put it in
 173          * the response queue and schedule its transmission.
 174          *
 175          * @param pkt the request packet to NACK
 176          */
 177         void nackRequest(PacketPtr pkt);
 178
 179         /**
 180          * Handle send event, scheduled when the packet at the head of
 181          * the response queue is ready to transmit (for timing
 182          * accesses only).
 183          */
 184         void trySend();
 185
 186         /**
 187          * Private class for scheduling sending of responses from the
 188          * response queue.
 189          */
 190         class SendEvent : public Event
 191         {
 192             BridgeSlavePort *port;
 193
 194           public:
 195             SendEvent(BridgeSlavePort *p) : port(p) {}
 196             virtual void process() { port->trySend(); }
 197             virtual const char *description() const { return "bridge send"; }
 198         };
 199
 200         /** Send event for the response queue. */
 201         SendEvent sendEvent;
 202
 203       public:
 204
 205         /**
 206          * Constructor for the BridgeSlavePort.
 207          *
 208          * @param _name the port name including the owner
 209          * @param _bridge the structural owner
 210          * @param _masterPort the master port on the other side of the bridge
 211          * @param _delay the delay from seeing a response to sending it
 212          * @param _nack_delay the delay from a NACK to sending the response
 213          * @param _resp_limit the size of the response queue
 214          * @param _ranges a number of address ranges to forward
 215          */
 216         BridgeSlavePort(const std::string &_name, Bridge *_bridge,
 217                         BridgeMasterPort* _masterPort, int _delay,
 218                         int _nack_delay, int _resp_limit,
 219                         std::vector<Range<Addr> > _ranges);
 220
 221         /**
 222          * Queue a response packet to be sent out later and also schedule
 223          * a send if necessary.
 224          *
 225          * @param pkt a response to send out after a delay
 226          */
 227         void queueForSendTiming(PacketPtr pkt);
 228
 229       protected:
 230
 231         /** When receiving a timing request from the peer port,
 232             pass it to the bridge. */
 233         virtual bool recvTiming(PacketPtr pkt);
 234
 235         /** When receiving a retry request from the peer port,
 236             pass it to the bridge. */
 237         virtual void recvRetry();
 238
 239         /** When receiving a Atomic requestfrom the peer port,
 240             pass it to the bridge. */
 241         virtual Tick recvAtomic(PacketPtr pkt);
 242
 243         /** When receiving a Functional request from the peer port,
 244             pass it to the bridge. */
 245         virtual void recvFunctional(PacketPtr pkt);
 246
 247         /**
 248          * When receiving a range change on the slave side do nothing.
 249          */
 250         virtual void recvRangeChange();
 251
 252         /** When receiving a address range request the peer port,
 253             pass it to the bridge. */
 254         virtual AddrRangeList getAddrRanges();
 255     };
 256
 257
 258     /**
 259      * Port on the side that forwards requests and receives
 260      * responses. The master port has a buffer for the requests not
 261      * yet sent.
 262      */
 263     class BridgeMasterPort : public Port
 264     {
 265
 266       private:
 267
 268         /** A pointer to the bridge to which this port belongs. */
 269         Bridge* bridge;
 270
 271         /**
 272          * Pointer to the slave port on the other side of the bridge
 273          * (connected to the other bus).
 274          */
 275         BridgeSlavePort* slavePort;
 276
 277         /** Minimum delay though this bridge. */
 278         Tick delay;
 279
 280         /**
 281          * Request packet queue. Request packets are held in this
 282          * queue for a specified delay to model the processing delay
 283          * of the bridge.
 284          */
 285         std::list<PacketBuffer*> requestQueue;
 286
 287         /** If we're waiting for a retry to happen. */
 288         bool inRetry;
 289
 290         /** Max queue size for request packets */
 291         unsigned int reqQueueLimit;
 292
 293         /**
 294          * Handle send event, scheduled when the packet at the head of
 295          * the outbound queue is ready to transmit (for timing
 296          * accesses only).
 297          */
 298         void trySend();
 299
 300         /**
 301          * Private class for scheduling sending of requests from the
 302          * request queue.
 303          */
 304         class SendEvent : public Event
 305         {
 306             BridgeMasterPort *port;
 307
 308           public:
 309             SendEvent(BridgeMasterPort *p) : port(p) {}
 310             virtual void process() { port->trySend(); }
 311             virtual const char *description() const { return "bridge send"; }
 312         };
 313
 314         /** Send event for the request queue. */
 315         SendEvent sendEvent;
 316
 317       public:
 318
 319         /**
 320          * Constructor for the BridgeMasterPort.
 321          *
 322          * @param _name the port name including the owner
 323          * @param _bridge the structural owner
 324          * @param _slavePort the slave port on the other side of the bridge
 325          * @param _delay the delay from seeing a request to sending it
 326          * @param _req_limit the size of the request queue
 327          */
 328         BridgeMasterPort(const std::string &_name, Bridge *_bridge,
 329                          BridgeSlavePort* _slavePort, int _delay,
 330                          int _req_limit);
 331
 332         /**
 333          * Is this side blocked from accepting new request packets.
 334          *
 335          * @return true if the occupied space has reached the set limit
 336          */
 337         bool reqQueueFull();
 338
 339         /**
 340          * Queue a request packet to be sent out later and also schedule
 341          * a send if necessary.
 342          *
 343          * @param pkt a request to send out after a delay
 344          */
 345         void queueForSendTiming(PacketPtr pkt);
 346
 347         /**
 348          * Check a functional request against the packets in our
 349          * request queue.
 350          *
 351          * @param pkt packet to check against
 352          *
 353          * @return true if we find a match
 354          */
 355         bool checkFunctional(PacketPtr pkt);
 356
 357       protected:
 358
 359         /** When receiving a timing request from the peer port,
 360             pass it to the bridge. */
 361         virtual bool recvTiming(PacketPtr pkt);
 362
 363         /** When receiving a retry request from the peer port,
 364             pass it to the bridge. */
 365         virtual void recvRetry();
 366
 367         /** When receiving a Atomic requestfrom the peer port,
 368             pass it to the bridge. */
 369         virtual Tick recvAtomic(PacketPtr pkt);
 370
 371         /** When receiving a Functional request from the peer port,
 372             pass it to the bridge. */
 373         virtual void recvFunctional(PacketPtr pkt);
 374
 375         /**
 376          * When receiving a range change, pass it through the bridge.
 377          */
 378         virtual void recvRangeChange();
 379     };
 380
 381     /** Slave port of the bridge. */
 382     BridgeSlavePort slavePort;
 383
 384     /** Master port of the bridge. */
 385     BridgeMasterPort masterPort;
 386
 387     /** If this bridge should acknowledge writes. */
 388     bool ackWrites;
 389
 390   public:
 391     typedef BridgeParams Params;
 392
 393   protected:
 394     Params *_params;
 395
 396   public:
 397     const Params *params() const { return _params; }
 398
 399     /** A function used to return the port associated with this bus object. */
 400     virtual Port *getPort(const std::string &if_name, int idx = -1);
 401
 402     virtual void init();
 403
 404     Bridge(Params *p);
 405 };
 406
 407 #endif //__MEM_BUS_HH__