src/mem/coherent_xbar.hh

   1 /*
   2  * Copyright (c) 2011-2014 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) 2002-2005 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: Ron Dreslinski
  41  *          Ali Saidi
  42  *          Andreas Hansson
  43  *          William Wang
  44  */
  45
  46 /**
  47  * @file
  48  * Declaration of a coherent crossbar.
  49  */
  50
  51 #ifndef __MEM_COHERENT_XBAR_HH__
  52 #define __MEM_COHERENT_XBAR_HH__
  53
  54 #include "mem/snoop_filter.hh"
  55 #include "mem/xbar.hh"
  56 #include "params/CoherentXBar.hh"
  57
  58 /**
  59  * A coherent crossbar connects a number of (potentially) snooping
  60  * masters and slaves, and routes the request and response packets
  61  * based on the address, and also forwards all requests to the
  62  * snoopers and deals with the snoop responses.
  63  *
  64  * The coherent crossbar can be used as a template for modelling QPI,
  65  * HyperTransport, ACE and coherent OCP buses, and is typically used
  66  * for the L1-to-L2 buses and as the main system interconnect.  @sa
  67  * \ref gem5MemorySystem "gem5 Memory System"
  68  */
  69 class CoherentXBar : public BaseXBar
  70 {
  71
  72   protected:
  73
  74     /**
  75      * Declare the layers of this crossbar, one vector for requests,
  76      * one for responses, and one for snoop responses
  77      */
  78     typedef Layer<SlavePort,MasterPort> ReqLayer;
  79     typedef Layer<MasterPort,SlavePort> RespLayer;
  80     typedef Layer<SlavePort,MasterPort> SnoopLayer;
  81     std::vector<ReqLayer*> reqLayers;
  82     std::vector<RespLayer*> respLayers;
  83     std::vector<SnoopLayer*> snoopLayers;
  84
  85     /**
  86      * Declaration of the coherent crossbar slave port type, one will
  87      * be instantiated for each of the master ports connecting to the
  88      * crossbar.
  89      */
  90     class CoherentXBarSlavePort : public SlavePort
  91     {
  92
  93       private:
  94
  95         /** A reference to the crossbar to which this port belongs. */
  96         CoherentXBar &xbar;
  97
  98       public:
  99
 100         CoherentXBarSlavePort(const std::string &_name,
 101                              CoherentXBar &_xbar, PortID _id)
 102             : SlavePort(_name, &_xbar, _id), xbar(_xbar)
 103         { }
 104
 105       protected:
 106
 107         /**
 108          * When receiving a timing request, pass it to the crossbar.
 109          */
 110         virtual bool recvTimingReq(PacketPtr pkt)
 111         { return xbar.recvTimingReq(pkt, id); }
 112
 113         /**
 114          * When receiving a timing snoop response, pass it to the crossbar.
 115          */
 116         virtual bool recvTimingSnoopResp(PacketPtr pkt)
 117         { return xbar.recvTimingSnoopResp(pkt, id); }
 118
 119         /**
 120          * When receiving an atomic request, pass it to the crossbar.
 121          */
 122         virtual Tick recvAtomic(PacketPtr pkt)
 123         { return xbar.recvAtomic(pkt, id); }
 124
 125         /**
 126          * When receiving a functional request, pass it to the crossbar.
 127          */
 128         virtual void recvFunctional(PacketPtr pkt)
 129         { xbar.recvFunctional(pkt, id); }
 130
 131         /**
 132          * When receiving a retry, pass it to the crossbar.
 133          */
 134         virtual void recvRetry()
 135         { panic("Crossbar slave ports should never retry.\n"); }
 136
 137         /**
 138          * Return the union of all adress ranges seen by this crossbar.
 139          */
 140         virtual AddrRangeList getAddrRanges() const
 141         { return xbar.getAddrRanges(); }
 142
 143     };
 144
 145     /**
 146      * Declaration of the coherent crossbar master port type, one will be
 147      * instantiated for each of the slave interfaces connecting to the
 148      * crossbar.
 149      */
 150     class CoherentXBarMasterPort : public MasterPort
 151     {
 152       private:
 153         /** A reference to the crossbar to which this port belongs. */
 154         CoherentXBar &xbar;
 155
 156       public:
 157
 158         CoherentXBarMasterPort(const std::string &_name,
 159                               CoherentXBar &_xbar, PortID _id)
 160             : MasterPort(_name, &_xbar, _id), xbar(_xbar)
 161         { }
 162
 163       protected:
 164
 165         /**
 166          * Determine if this port should be considered a snooper. For
 167          * a coherent crossbar master port this is always true.
 168          *
 169          * @return a boolean that is true if this port is snooping
 170          */
 171         virtual bool isSnooping() const
 172         { return true; }
 173
 174         /**
 175          * When receiving a timing response, pass it to the crossbar.
 176          */
 177         virtual bool recvTimingResp(PacketPtr pkt)
 178         { return xbar.recvTimingResp(pkt, id); }
 179
 180         /**
 181          * When receiving a timing snoop request, pass it to the crossbar.
 182          */
 183         virtual void recvTimingSnoopReq(PacketPtr pkt)
 184         { return xbar.recvTimingSnoopReq(pkt, id); }
 185
 186         /**
 187          * When receiving an atomic snoop request, pass it to the crossbar.
 188          */
 189         virtual Tick recvAtomicSnoop(PacketPtr pkt)
 190         { return xbar.recvAtomicSnoop(pkt, id); }
 191
 192         /**
 193          * When receiving a functional snoop request, pass it to the crossbar.
 194          */
 195         virtual void recvFunctionalSnoop(PacketPtr pkt)
 196         { xbar.recvFunctionalSnoop(pkt, id); }
 197
 198         /** When reciving a range change from the peer port (at id),
 199             pass it to the crossbar. */
 200         virtual void recvRangeChange()
 201         { xbar.recvRangeChange(id); }
 202
 203         /** When reciving a retry from the peer port (at id),
 204             pass it to the crossbar. */
 205         virtual void recvRetry()
 206         { xbar.recvRetry(id); }
 207
 208     };
 209
 210     /**
 211      * Internal class to bridge between an incoming snoop response
 212      * from a slave port and forwarding it through an outgoing slave
 213      * port. It is effectively a dangling master port.
 214      */
 215     class SnoopRespPort : public MasterPort
 216     {
 217
 218       private:
 219
 220         /** The port which we mirror internally. */
 221         SlavePort& slavePort;
 222
 223       public:
 224
 225         /**
 226          * Create a snoop response port that mirrors a given slave port.
 227          */
 228         SnoopRespPort(SlavePort& slave_port, CoherentXBar& _xbar) :
 229             MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
 230             slavePort(slave_port) { }
 231
 232         /**
 233          * Override the sending of retries and pass them on through
 234          * the mirrored slave port.
 235          */
 236         void sendRetry() {
 237             slavePort.sendRetry();
 238         }
 239
 240         /**
 241          * Provided as necessary.
 242          */
 243         void recvRetry() { panic("SnoopRespPort should never see retry\n"); }
 244
 245         /**
 246          * Provided as necessary.
 247          */
 248         bool recvTimingResp(PacketPtr pkt)
 249         {
 250             panic("SnoopRespPort should never see timing response\n");
 251             return false;
 252         }
 253
 254     };
 255
 256     std::vector<SnoopRespPort*> snoopRespPorts;
 257
 258     std::vector<SlavePort*> snoopPorts;
 259
 260     /**
 261      * Store the outstanding requests that we are expecting snoop
 262      * responses from so we can determine which snoop responses we
 263      * generated and which ones were merely forwarded.
 264      */
 265     m5::hash_set<RequestPtr> outstandingSnoop;
 266
 267     /**
 268      * Keep a pointer to the system to be allow to querying memory system
 269      * properties.
 270      */
 271     System *system;
 272
 273     /** A snoop filter that tracks cache line residency and can restrict the
 274       * broadcast needed for probes.  NULL denotes an absent filter. */
 275     SnoopFilter *snoopFilter;
 276
 277     /** Function called by the port when the crossbar is recieving a Timing
 278       request packet.*/
 279     bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
 280
 281     /** Function called by the port when the crossbar is recieving a Timing
 282       response packet.*/
 283     bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
 284
 285     /** Function called by the port when the crossbar is recieving a timing
 286         snoop request.*/
 287     void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
 288
 289     /** Function called by the port when the crossbar is recieving a timing
 290         snoop response.*/
 291     bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
 292
 293     /** Timing function called by port when it is once again able to process
 294      * requests. */
 295     void recvRetry(PortID master_port_id);
 296
 297     /**
 298      * Forward a timing packet to our snoopers, potentially excluding
 299      * one of the connected coherent masters to avoid sending a packet
 300      * back to where it came from.
 301      *
 302      * @param pkt Packet to forward
 303      * @param exclude_slave_port_id Id of slave port to exclude
 304      */
 305     void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
 306         forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
 307     }
 308
 309     /**
 310      * Forward a timing packet to a selected list of snoopers, potentially
 311      * excluding one of the connected coherent masters to avoid sending a packet
 312      * back to where it came from.
 313      *
 314      * @param pkt Packet to forward
 315      * @param exclude_slave_port_id Id of slave port to exclude
 316      * @param dests Vector of destination ports for the forwarded pkt
 317      */
 318     void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
 319                        const std::vector<SlavePort*>& dests);
 320
 321     /** Function called by the port when the crossbar is recieving a Atomic
 322       transaction.*/
 323     Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
 324
 325     /** Function called by the port when the crossbar is recieving an
 326         atomic snoop transaction.*/
 327     Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
 328
 329     /**
 330      * Forward an atomic packet to our snoopers, potentially excluding
 331      * one of the connected coherent masters to avoid sending a packet
 332      * back to where it came from.
 333      *
 334      * @param pkt Packet to forward
 335      * @param exclude_slave_port_id Id of slave port to exclude
 336      *
 337      * @return a pair containing the snoop response and snoop latency
 338      */
 339     std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
 340                                           PortID exclude_slave_port_id)
 341     {
 342         return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID, snoopPorts);
 343     }
 344
 345     /**
 346      * Forward an atomic packet to a selected list of snoopers, potentially
 347      * excluding one of the connected coherent masters to avoid sending a packet
 348      * back to where it came from.
 349      *
 350      * @param pkt Packet to forward
 351      * @param exclude_slave_port_id Id of slave port to exclude
 352      * @param source_master_port_id Id of the master port for snoops from below
 353      * @param dests Vector of destination ports for the forwarded pkt
 354      *
 355      * @return a pair containing the snoop response and snoop latency
 356      */
 357     std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
 358                                           PortID exclude_slave_port_id,
 359                                           PortID source_master_port_id,
 360                                           const std::vector<SlavePort*>& dests);
 361
 362     /** Function called by the port when the crossbar is recieving a Functional
 363         transaction.*/
 364     void recvFunctional(PacketPtr pkt, PortID slave_port_id);
 365
 366     /** Function called by the port when the crossbar is recieving a functional
 367         snoop transaction.*/
 368     void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
 369
 370     /**
 371      * Forward a functional packet to our snoopers, potentially
 372      * excluding one of the connected coherent masters to avoid
 373      * sending a packet back to where it came from.
 374      *
 375      * @param pkt Packet to forward
 376      * @param exclude_slave_port_id Id of slave port to exclude
 377      */
 378     void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
 379
 380     Stats::Scalar snoops;
 381     Stats::Distribution snoopFanout;
 382
 383   public:
 384
 385     virtual void init();
 386
 387     CoherentXBar(const CoherentXBarParams *p);
 388
 389     virtual ~CoherentXBar();
 390
 391     unsigned int drain(DrainManager *dm);
 392
 393     virtual void regStats();
 394 };
 395
 396 #endif //__MEM_COHERENT_XBAR_HH__