// The MIT License

 

 // Copyright (c) 2009 Massachusetts Institute of Technology

 

 // Permission is hereby granted, free of charge, to any person obtaining a copy

 // of this software and associated documentation files (the "Software"), to deal

 // in the Software without restriction, including without limitation the rights

 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 // copies of the Software, and to permit persons to whom the Software is

 // furnished to do so, subject to the following conditions:

 

 // The above copyright notice and this permission notice shall be included in

 // all copies or substantial portions of the Software.

 

 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 // THE SOFTWARE.

 

 import Connectable::*;

 import GetPut::*;

 import ClientServer::*;

 import RegFile::*;

 import FIFO::*;

 import FIFOF::*;

 import RWire::*;

 

 import BFIFO::*;

 import MemTypes::*;

 import ProcTypes::*;

 import Trace::*;

 

 interface ICacheStats;

   interface Get#(Stat) num_accesses;

   interface Get#(Stat) num_misses;

   interface Get#(Stat) num_evictions;

 endinterface

 

 interface ICache#( type req_t, type resp_t );

 

   // Interface from processor to cache

   interface Server#(req_t,resp_t) proc_server;

 

   // Interface from cache to main memory

   interface Client#(MainMemReq,MainMemResp) mmem_client;

 

   // Interface for enabling/disabling statistics

   interface Put#(Bool) statsEn_put;

 

   // Interface for collecting statistics

   interface ICacheStats stats;

 

 endinterface

 

 //----------------------------------------------------------------------

 // Cache Types

 //----------------------------------------------------------------------

 

 typedef 10 CacheLineIndexSz;

 typedef 20 CacheLineTagSz;

 typedef 32 CacheLineSz;

 

 typedef Bit#(CacheLineIndexSz) CacheLineIndex;

 typedef Bit#(CacheLineTagSz)   CacheLineTag;

 typedef Bit#(CacheLineSz)      CacheLine;

 

 typedef enum 

 { 

   Init,

   Access, 

   Evict, 

   RefillReq, 

   RefillResp 

 } 

 CacheStage 

 deriving (Eq,Bits);

 

 //----------------------------------------------------------------------

 // Helper functions

 //----------------------------------------------------------------------

 

 function Bit#(AddrSz) getAddr( InstReq req );

 

   Bit#(AddrSz) addr = ?;

   case ( req ) matches

     tagged LoadReq  .ld : addr = ld.addr;

     tagged StoreReq .st : addr = st.addr;

   endcase

 

   return addr;

 

 endfunction

 

 function CacheLineIndex getCacheLineIndex( InstReq req );

   Bit#(AddrSz) addr = getAddr(req);

   Bit#(CacheLineIndexSz) index = truncate( addr >> 2 );

   return index;

 endfunction

 

 function CacheLineTag getCacheLineTag( InstReq req );

   Bit#(AddrSz)         addr = getAddr(req);

   Bit#(CacheLineTagSz) tag  = truncate( addr >> fromInteger(valueOf(CacheLineIndexSz)) >> 2 );

   return tag;

 endfunction

 

 function Bit#(AddrSz) getCacheLineAddr( InstReq req );

   Bit#(AddrSz) addr = getAddr(req);

   return ((addr >> 2) << 2);

 endfunction

 

 //----------------------------------------------------------------------

 // Main module

 //----------------------------------------------------------------------

 

 (* doc = "synthesis attribute ram_style mkInstCache distributed;" *)

 (* synthesize *)

 module mkInstCache( ICache#(InstReq,InstResp) );

 

   //-----------------------------------------------------------

   // State

 

   Reg#(CacheStage) stage <- mkReg(Init);

 

   RegFile#(CacheLineIndex,Maybe#(CacheLineTag)) cacheTagRam  <- mkRegFileFull();

   RegFile#(CacheLineIndex,CacheLine)            cacheDataRam <- mkRegFileFull();

 

   FIFO#(InstReq)   reqQ  <- mkFIFO();

   FIFOF#(InstResp) respQ <- mkBFIFOF1();

 

   FIFO#(MainMemReq)  mainMemReqQ  <- mkBFIFO1();

   FIFO#(MainMemResp) mainMemRespQ <- mkFIFO();

 

   Reg#(CacheLineIndex) initCounter <- mkReg(1);

 

   // Statistics state

 

   Reg#(Bool)     statsEn        <- mkReg(False);

 

   Reg#(Stat) numAccesses <- mkReg(0);

   Reg#(Stat) numMisses <- mkReg(0);

   Reg#(Stat) numEvictions <- mkReg(0);

 

   //-----------------------------------------------------------

   // Name some wires

 

   let req              = reqQ.first();

   let reqIndex         = getCacheLineIndex(req);

   let reqTag           = getCacheLineTag(req);

   let reqCacheLineAddr = getCacheLineAddr(req);

   let refill           = mainMemRespQ.first();

 

   //-----------------------------------------------------------

   // Initialize

 

   rule init ( stage == Init );

     traceTiny("mkInstCacheBlocking", "stage","i");

     initCounter <= initCounter + 1;

     cacheTagRam.upd(initCounter,Invalid);

     if ( initCounter == 0 )

       stage <= Access;

   endrule

 

   //-----------------------------------------------------------

   // Cache access rule

 

   rule access ( (stage == Access) && respQ.notFull() );

 

     // Statistics

 

     if ( statsEn )

       numAccesses <= numAccesses + 1;

   

     // Check tag and valid bit to see if this is a hit or a miss

 

     Maybe#(CacheLineTag) cacheLineTag = cacheTagRam.sub(reqIndex);

   

     // Handle cache hits ...

 

     if ( isValid(cacheLineTag) && ( unJust(cacheLineTag) == reqTag ) )

      begin

        traceTiny("mkInstCacheBlocking", "hitMiss","h");

        reqQ.deq();

 

        case ( req ) matches

           

          tagged LoadReq .ld :

 	  respQ.enq( LoadResp { tag  : ld.tag, data : cacheDataRam.sub(reqIndex) } );

 

          tagged StoreReq .st :

           $display( " RTL-ERROR : %m : Stores are not allowed on the inst port!" );

        

        endcase

 

      end

 

     // Handle cache misses - since lines in instruction cache are

     // never dirty we can always immediately issue a refill request

     

     else 

      begin

        traceTiny("mkInstCacheBlocking", "hitMiss","m");

        if ( statsEn )

          numMisses <= numMisses + 1;

        if ( statsEn )

          if ( isJust(cacheLineTag) )

            numEvictions <= numEvictions + 1;

 

        MainMemReq rfReq

         = LoadReq { tag  : 0,

 	            addr : reqCacheLineAddr };

 

        mainMemReqQ.enq(rfReq);

        stage <= RefillResp;    

      end

 

   endrule

 

   //-----------------------------------------------------------

   // Refill response rule

   

    rule refillResp ( stage == RefillResp );

     traceTiny("mkInstCacheBlocking", "stage","R");

     traceTiny("mkInstCacheBlocking", "refill",refill);

 

     // Write the new data into the cache and update the tag

 

     mainMemRespQ.deq();

     case ( mainMemRespQ.first() ) matches

 

       tagged LoadResp .ld :

        begin

 	 cacheTagRam.upd(reqIndex,Valid(reqTag));

 	 cacheDataRam.upd(reqIndex,ld.data);	

        end

        

       tagged StoreResp .st :

 	noAction;

      

     endcase

 

     stage <= Access;

   endrule

 

   //-----------------------------------------------------------

   // Methods

 

   interface Client mmem_client;

     interface Get request  = fifoToGet(mainMemReqQ);

     interface Put response = fifoToPut(mainMemRespQ);

   endinterface

 

   interface Server proc_server;

     interface Put request  = tracePut("mkInstCacheBlocking", "reqTiny",toPut(reqQ));

     interface Get response = traceGet("mkInstCacheBlocking", "respTiny",toGet(respQ));

   endinterface

 

   interface Put statsEn_put = toPut(asReg(statsEn));

 

   interface ICacheStats stats;

     interface Get num_accesses = toGet(asReg(numAccesses));

     interface Get num_misses = toGet(asReg(numMisses));

     interface Get num_evictions = toGet(asReg(numEvictions));

   endinterface

 

 endmodule