src/mem/cache/coherence/uni_coherence.hh

   1 /*
   2  * Copyright (c) 2003-2005 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: Erik Hallnor
  29  */
  30
  31 #ifndef __UNI_COHERENCE_HH__
  32 #define __UNI_COHERENCE_HH__
  33
  34 #include "base/trace.hh"
  35 #include "base/misc.hh"
  36 #include "mem/cache/cache_blk.hh"
  37 #include "mem/cache/miss/mshr_queue.hh"
  38 #include "mem/packet.hh"
  39
  40 class BaseCache;
  41
  42 class UniCoherence
  43 {
  44   protected:
  45     /** Buffers to hold forwarded invalidates. */
  46     MSHRQueue cshrs;
  47     /** Pointer to the parent cache. */
  48     BaseCache *cache;
  49
  50   public:
  51     /**
  52      * Construct and initialize this coherence policy.
  53      */
  54     UniCoherence();
  55
  56     /**
  57      * Set the pointer to the parent cache.
  58      * @param _cache The parent cache.
  59      */
  60     void setCache(BaseCache *_cache)
  61     {
  62         cache = _cache;
  63     }
  64
  65     /**
  66      * Register statistics.
  67      * @param name The name to prepend to stat descriptions.
  68      */
  69     void regStats(const std::string &name)
  70     {
  71     }
  72
  73     /**
  74      * Return Read.
  75      * @param cmd The request's command.
  76      * @param state The current state of the cache block.
  77      * @return The proper bus command, as determined by the protocol.
  78      * @todo Make changes so writebacks don't get here.
  79      */
  80     Packet::Command getBusCmd(Packet::Command &cmd, CacheBlk::State state)
  81     {
  82         if (cmd == Packet::HardPFReq && state)
  83             warn("Trying to issue a prefetch to a block we already have\n");
  84         if (cmd == Packet::Writeback)
  85             return Packet::Writeback;
  86         return Packet::ReadReq;
  87     }
  88
  89     /**
  90      * Just return readable and writeable.
  91      * @param pkt The bus response.
  92      * @param current The current block state.
  93      * @return The new state.
  94      */
  95     CacheBlk::State getNewState(Packet * &pkt, CacheBlk::State current)
  96     {
  97         if (pkt->senderState) //Blocking Buffers don't get mshrs
  98         {
  99             if (((MSHR *)(pkt->senderState))->originalCmd == Packet::HardPFReq) {
 100                 DPRINTF(HWPrefetch, "Marking a hardware prefetch as such in the state\n");
 101                 return BlkHWPrefetched | BlkValid | BlkWritable;
 102             }
 103             else {
 104                 return BlkValid | BlkWritable;
 105             }
 106         }
 107         //@todo What about prefetching with blocking buffers
 108         else
 109             return BlkValid | BlkWritable;
 110     }
 111     /**
 112      * Return outstanding invalidate to forward.
 113      * @return The next invalidate to forward to lower levels of cache.
 114      */
 115     Packet * getPacket();
 116
 117     /**
 118      * Handle snooped bus requests.
 119      * @param pkt The snooped bus request.
 120      * @param blk The cache block corresponding to the request, if any.
 121      * @param mshr The MSHR corresponding to the request, if any.
 122      * @param new_state The new coherence state of the block.
 123      * @return True if the request should be satisfied locally.
 124      */
 125     bool handleBusRequest(Packet * &pkt, CacheBlk *blk, MSHR *mshr,
 126                           CacheBlk::State &new_state);
 127
 128     /**
 129      * Return true if this coherence policy can handle fast cache writes.
 130      */
 131     bool allowFastWrites() { return true; }
 132
 133     bool hasProtocol() { return false; }
 134 };
 135
 136 #endif //__UNI_COHERENCE_HH__