This d cache fsm is getting complex.

wally-pipelined/src/cache/ICacheCntrl.sv

@@ -413,6 +413,7 @@ module ICacheCntrl #(parameter BLOCKLEN = 256)
   assign NextFetchCount = FetchCount + 1'b1;
   
   // This part is confusing.
+  // *** Ross Thompson reduce the complexity. This is just dumb.
   // we need to remove the offset bits (PCPTrunkF).  Because the AHB interface is XLEN wide
   // we need to address on that number of bits so the PC is extended to the right by AHBByteLength with zeros.
   // fetch count is already aligned to AHBByteLength, but we need to extend back to the full address width with

wally-pipelined/src/cache/dcache.sv

@@ -27,103 +27,108 @@
 
 module dcache
   (input logic clk,
-   input logic 		       reset,
+   input logic		       reset,
-   input logic 		       StallM,
+   input logic		       StallM,
-   input logic 		       StallW,
+   input logic		       StallW,
-   input logic 		       FlushM,
+   input logic		       FlushM,
-   input logic 		       FlushW,
+   input logic		       FlushW,
 
    // cpu side
-   input logic [1:0] 	       MemRWM,
+   input logic [1:0]	       MemRWM,
-   input logic [2:0] 	       Funct3M,
+   input logic [2:0]	       Funct3M,
-   input logic [1:0] 	       AtomicM,
+   input logic [1:0]	       AtomicM,
    input logic [`PA_BITS-1:0]  MemAdrE, // virtual address, but we only use the lower 12 bits.
    input logic [`PA_BITS-1:0]  MemPAdrM, // physical address
 
    input logic [`XLEN-1:0]     WriteDataM,
    output logic [`XLEN-1:0]    ReadDataW,
-   output logic 	       DCacheStall,
+   output logic		       DCacheStall,
 
    // inputs from TLB and PMA/P
-   input logic 		       FaultM,
+   input logic		       FaultM,
-   input logic 		       DTLBMissM,
+   input logic		       DTLBMissM,
+   input logic		       UncachedM,
    // ahb side
    output logic [`PA_BITS-1:0] AHBPAdr, // to ahb
-   output logic 	       AHBRead,
+   output logic		       AHBRead,
-   output logic 	       AHBWrite,
+   output logic		       AHBWrite,
-   input logic 		       AHBAck, // from ahb
+   input logic		       AHBAck, // from ahb
    input logic [`XLEN-1:0]     HRDATA, // from ahb
    output logic [`XLEN-1:0]    HWDATA, // to ahb
-   output logic [2:0] 	       AHBSize
+   output logic [2:0]	       AHBSize
    );
 
-  localparam integer 	       BLOCKLEN = 256;
+  localparam integer	       BLOCKLEN = 256;
-  localparam integer 	       NUMLINES = 512;
+  localparam integer	       NUMLINES = 512;
-  localparam integer 	       NUMWAYS = 4;
+  localparam integer	       NUMWAYS = 4;
-  localparam integer 	       NUMREPL_BITS = 3;
+  localparam integer	       NUMREPL_BITS = 3;
 
-  localparam integer 	       BLOCKBYTELEN = BLOCKLEN/8;
+  localparam integer	       BLOCKBYTELEN = BLOCKLEN/8;
-  localparam integer 	       OFFSETLEN = $clog2(BLOCKBYTELEN);
+  localparam integer	       OFFSETLEN = $clog2(BLOCKBYTELEN);
-  localparam integer 	       INDEXLEN = $clog2(NUMLINES);
+  localparam integer	       INDEXLEN = $clog2(NUMLINES);
-  localparam integer 	       TAGLEN = `PA_BITS - OFFSETLEN - INDEXLEN;
+  localparam integer	       TAGLEN = `PA_BITS - OFFSETLEN - INDEXLEN;
-  localparam integer 	       WORDSPERLINE = BLOCKLEN/`XLEN;
+  localparam integer	       WORDSPERLINE = BLOCKLEN/`XLEN;
+  localparam integer	       LOGWPL = $clog2(WORDSPERLINE);
   
 
-  logic [1:0] 		       AdrSel;
+
-  logic [`PA_BITS-1:0] 	       MemPAdrW;
+  logic 		       SelAdrM;
-  logic [INDEXLEN-1:0] 	       SRAMAdr;
+  logic [`PA_BITS-1:0]	       MemPAdrW;
-  logic [NUMWAYS-1:0] 	       WriteEnable;
+  logic [INDEXLEN-1:0]	       SRAMAdr;
-  logic [NUMWAYS-1:0] 	       WriteWordEnable;  
+  logic [NUMWAYS-1:0]	       WriteEnable;
-  logic [BLOCKLEN-1:0] 	       SRAMWriteData;
+  logic [NUMWAYS-1:0]	       WriteWordEnable;
-  logic [TAGLEN-1:0] 	       WriteTag;
+  logic [BLOCKLEN-1:0]	       SRAMWriteData;
-  logic 		       SetValid, ClearValid;
+  logic			       SetValidM, ClearValidM, SetValidW, ClearValidW;
-  logic 		       SetDirty, ClearDirty;
+  logic			       SetDirtyM, ClearDirtyM, SetDirtyW, ClearDirtyW;
-  logic [BLOCKLEN-1:0] 	       ReadDataM, ReadDataMaskedM [NUMWAYS-1:0];
+  logic [BLOCKLEN-1:0]	       ReadDataM, ReadDataMaskedM [NUMWAYS-1:0];
-  logic [TAGLEN-1:0] 	       TagData [NUMWAYS-1:0];
+  logic [TAGLEN-1:0]	       TagData [NUMWAYS-1:0];
-  logic [NUMWAYS-1:0] 	       Valid, Dirty, WayHit;
+  logic [NUMWAYS-1:0]	       Valid, Dirty, WayHit;
-  logic 		       Hit;
+  logic			       CacheHit;
   logic [NUMREPL_BITS-1:0]     ReplacementBits, NewReplacement;
-  logic [BLOCKLEN-1:0] 	       ReadDataSelectWayM;
+  logic [BLOCKLEN-1:0]	       ReadDataSelectWayM;
-  logic [`XLEN-1:0] 	       ReadDataSelectWayXLEN [(WORDSPERLINE)-1:0];
+  logic [`XLEN-1:0]	       ReadDataSelectWayXLEN [(WORDSPERLINE)-1:0];
-  logic [`XLEN-1:0] 	       WordReadDataM, FinalReadDataM;
+  logic [`XLEN-1:0]	       WordReadDataM, FinalReadDataM;
-  logic [`XLEN-1:0] 	       WriteDataW, FinalWriteDataW;
+  logic [`XLEN-1:0]	       WriteDataW, FinalWriteDataW, FinalAMOWriteDataW;
-  logic [BLOCKLEN-1:0] 	       FinalWriteDataWordsW;
+  logic [BLOCKLEN-1:0]	       FinalWriteDataWordsW;
+  logic [LOGWPL:0] 	       FetchCount, NextFetchCount;
+  logic [NUMWAYS-1:0] 	       SRAMWordWriteEnableM, SRAMWordWriteEnableW;
+  logic [WORDSPERLINE-1:0]     SRAMWordEnable [NUMWAYS-1:0];
+  logic 		       SelMemWriteDataM, SelMemWriteDataW;
+  logic [2:0] 		       Funct3W;
+
+  logic 		       SRAMWordWriteEnableM, SRAMWordWriteEnableW;
+  logic 		       SRAMBlockWriteEnableM;
+  logic 		       SRAMWriteEnable;
+
+  logic 		       SaveSRAMRead;
+  logic [1:0] 		       AtomicW;
   
   
-  typedef enum 		       {STATE_READY,
-				STATE_MISS_FETCH_WDV,
-				STATE_MISS_FETCH_DONE,
-				STATE_MISS_WRITE_BACK,
-				STATE_MISS_READ_SRAM,
-				STATE_AMO_MISS_FETCH_WDV,
-				STATE_AMO_MISS_FETCH_DONE,
-				STATE_AMO_MISS_WRITE_BACK,
-				STATE_AMO_MISS_READ_SRAM,
-				STATE_AMO_MISS_UPDATE,
-				STATE_AMO_MISS_WRITE,
-				STATE_AMO_UPDATE,
-				STATE_AMO_WRITE,
-				STATE_SRAM_BUSY,
-				STATE_PTW_READY,
-				STATE_PTW_FETCH,
-				STATE_UNCACHED} statetype;
   
-  statetype CurrState, NextState;
   
 
+  // data path
+
   flopen #(`PA_BITS) MemPAdrWReg(.clk(clk),
 				 .en(~StallW),
 				 .d(MemPAdrM),
 				 .q(MemPAdrW));
 
-  mux3 #(INDEXLEN)
+  mux2 #(INDEXLEN)
   AdrSelMux(.d0(MemAdrE[INDEXLEN+OFFSET-1:OFFSET]),
 	    .d1(MemPAdrM[INDEXLEN+OFFSET-1:OFFSET]),
-	    .d2(MemPAdrW[INDEXLEN+OFFSET-1:OFFSET]),
+	    .s(SelAdrM),
-	    .s(AdrSel),
+	    .y(AdrMuxOut));
-	    .y(SRAMAdr));
 
-  genvar 		       way;
+
+  mux2 #(INDEXLEN)
+  SelAdrlMux2(.d0(AdrMuxOut),
+	      .d1(MemPAdrW[INDEXLEN+OFFSET-1:OFFSET]),
+	      .s(SRAMWordWriteEnableW),
+	      .y(SRAMAdr));
+  
+
+  genvar		       way;
   generate
     for(way = 0; way < NUMWAYS; way = way + 1) begin
       DCacheMem #(.NUMLINES(NUMLINES), .BLOCKLEN(BLOCKLEN), .TAGLEN(TAGLEN))
@@ -134,11 +139,11 @@ module dcache
 	     .WriteEnable(SRAMWriteEnable[way]),
 	     .WriteWordEnable(SRAMWordEnable[way]),
 	     .WriteData(SRAMWriteData),
-	     .WriteTag(WriteTag),
+	     .WriteTag(MemPAdrW[`PA_BITS-1:OFFSET+INDEXLEN]),
-	     .SetValid(SetValid),
+	     .SetValid(SetValidW),
-	     .ClearValid(ClearValid),
+	     .ClearValid(ClearValidW),
-	     .SetDirty(SetDirty),
+	     .SetDirty(SetDirtyW),
-	     .ClearDirty(ClearDirty),
+	     .ClearDirty(ClearDirtyW),
 	     .ReadData(ReadDataM[way]),
 	     .ReadTag(ReadTag[way]),
 	     .Valid(Valid[way]),
@@ -150,10 +155,13 @@ module dcache
 
   always_ff @(posedge clk, posedge reset) begin
     if (reset) ReplacementBits <= '0;
-    else if (WriteEnable) ReplacementBits[MemPAdrW[INDEXLEN+OFFSET-1:OFFSET]] <= NewReplacement;
+    else if (SRAMWriteEnable) ReplacementBits[MemPAdrW[INDEXLEN+OFFSET-1:OFFSET]] <= NewReplacement;
   end
 
-  assign Hit = |WayHit;
+  // *** TODO add replacement policy
+  assign NewReplacement = '0;
+
+  assign CacheHit = |WayHit;
   assign ReadDataSelectWayM = |ReadDataMaskedM; // second part of AO mux.
 
   // Convert the Read data bus ReadDataSelectWay into sets of XLEN so we can
@@ -184,12 +192,28 @@ module dcache
 			       .d(WriteDataM),
 			       .q(WriteDataW));
 
+  flopr #(3) Funct3WReg(.clk(clk),
+			.reset(reset),
+			.d(Funct3M),
+			.q(Funct3W));
+
   subwordwrite subwordwrite(.HRDATA(ReadDataW),
 			    .HADDRD(MemPAdrM[`XLEN/8-1:0]),
 			    .HSIZED(Funct3W),
 			    .HWDATAIN(WriteDataW),
 			    .HWDATA(FinalWriteDataW));
 
+  generate
+    if (`A_SUPPORTED) begin
+      logic [`XLEN-1:0] AMOResult;
+      amoalu amoalu(.srca(ReadDataW), .srcb(WriteDataW), .funct(Funct7W), .width(Funct3W), 
+                    .result(AMOResult));
+      mux2 #(`XLEN) wdmux(FinalWriteDataW, AMOResult, SelAMOWrite & AtomicW[1], FinalAMOWriteDataW);
+    end else
+      assign FinalAMOWriteDataW = FinalWriteDataW;
+  endgenerate
+  
+
   // register the fetch data from the next level of memory.
   generate
     for (index = 0; index < WORDSPERLINE; index++) begin:fetchbuffer
@@ -200,22 +224,205 @@ module dcache
     end
   endgenerate
 
+  flopenr #(LOGWPL+1) 
+  FetchCountReg(.clk(clk),
+		.reset(reset | CntReset),
+		.en(CntEn),
+		.d(NextFetchCount),
+		.q(FetchCount));
+
+  assign NextFetchCount = FetchCount + 1'b1;
+
+  assign AHBPAdr = (FetchCount << (`XLEN/8)) + MemPAdrM;
+  // remove later
+  assign AHBSize = 3'b000;
+  
+  
   // mux between the CPU's write and the cache fetch.
   generate
     for(index = 0; index < WORDSPERLINE; index++) begin
-      assign FinalWriteDataWordsW[((index+1)*`XLEN)-1 : (index*`XLEN)] = FinalWriteDataW;
+      assign FinalWriteDataWordsW[((index+1)*`XLEN)-1 : (index*`XLEN)] = FinalAMOWriteDataW;
     end
   endgenerate
 
   mux2 #(BLOCKLEN) WriteDataMux(.d0(FinalWriteDataWordsW),
 				.d1(DCacheMemWriteData),
-				.s(SelMemWriteData),
+				.s(SRAMBlockWriteEnableM),
 				.y(SRAMWriteData));
 
 
+  // control path *** eventually move to own module.
+
+  logic AnyCPUReqM;
+  logic FetchCountFlag;
+  logic PreCntEn;
+  logic CntEn;
+  logic CntReset;
   
   
+  typedef enum		       {STATE_READY,
+				STATE_READ_MISS_FETCH_WDV,
+				STATE_READ_MISS_FETCH_DONE,
+				STATE_READ_MISS_CHECK_EVICTED_DIRTY,
+				STATE_READ_MISS_WRITE_BACK_EVICTED_BLOCK,
+				STATE_READ_MISS_WRITE_CACHE_BLOCK,
+				STATE_READ_MISS_READ_WORD,
+				STATE_WRITE_MISS_FETCH_WDV,
+				STATE_WRITE_MISS_FETCH_DONE,
+				STATE_WRITE_MISS_CHECK_EVICTED_DIRTY,
+				STATE_WRITE_MISS_WRITE_BACK_EVICTED_BLOCK,
+				STATE_WRITE_MISS_WRITE_CACHE_BLOCK,
+				STATE_WRITE_MISS_WRITE_WORD,
+				STATE_AMO_MISS_FETCH_WDV,
+				STATE_AMO_MISS_FETCH_DONE,
+				STATE_AMO_MISS_CHECK_EVICTED_DIRTY,
+				STATE_AMO_MISS_WRITE_BACK_EVICTED_BLOCK,
+				STATE_AMO_MISS_WRITE_CACHE_BLOCK,
+				STATE_AMO_MISS_READ_WORD,
+				STATE_AMO_MISS_UPDATE_WORD,
+				STATE_AMO_MISS_WRITE_WORD,
+				STATE_AMO_UPDATE,
+				STATE_AMO_WRITE,
+				STATE_SRAM_BUSY,
+				STATE_PTW_READY,
+				STATE_PTW_MISS_FETCH_WDV,
+				STATE_PTW_MISS_FETCH_DONE,
+				STATE_PTW_MISS_CHECK_EVICTED_DIRTY,
+				STATE_PTW_MISS_WRITE_BACK_EVICTED_BLOCK,
+				STATE_PTW_MISS_WRITE_CACHE_BLOCK,
+				STATE_PTW_MISS_READ_SRAM,
+				STATE_UNCACHED_WDV,
+				STATE_UNCACHED_DONE} statetype;
+
+  statetype CurrState, NextState;
+
+  
+  localparam FetchCountThreshold = WORDSPERLINE - 1;
+  
+
+  assign AnyCPUReqM = |MemRWM | (|AtomicM);
+  assign FetchCountFlag = (FetchCount == FetchCountThreshold);
+
+  flopenr #(LOGWPL+1) 
+  FetchCountReg(.clk(clk),
+		.reset(reset | CntReset),
+		.en(CntEn),
+		.d(NextFetchCount),
+		.q(FetchCount));
+
+  assign NextFetchCount = FetchCount + 1'b1;
+
+  assign SRAMWriteEnable = SRAMBlockWriteEnableM | SRAMWordWriteEnableW;
+
+  flopr #(1+4+2)
+  SRAMWritePipeReg(.clk(clk),
+	      .reset(reset),
+	      .d({SRAMWordWriteEnableM, SetValidM, ClearValidM, SetDiryM, ClearDirtyM, AtomicM}),
+	      .q({SRAMWordWriteEnableW, SetValidW, ClearValidM, SetDiryM, ClearDirtyM, AtomicW}));
+  
+
+  // fsm state regs
+  flopenl #(.TYPE(statetype))
+  FSMReg(.clk(clk),
+	 .load(reset),
+	 .en(1'b1),
+	 .val(STATE_READY),
+	 .d(NextState),
+	 .q(CurrState));
+
+  // next state logic and some state ouputs.
+  always_comb begin
+    DCacheStall = 1'b0;
+    SelAdrM = 2'b00;
+    PreCntEn = 1'b0;
+    SetValidM = 1'b0;
+    ClearValidM = 1'b0;
+    SetDirtyM = 1'b0;    
+    ClearDirtyM = 1'b0;
+    SelMemWriteDataM = 1'b0;
+    SRAMWordWriteEnableM = 1'b0;
+    SRAMBlockWriteEnableM = 1'b0;
+    SaveSRAMRead = 1'b1;
+    CntReset = 1'b0;
+
+    case (CurrState)
+      STATE_READY: begin
+	// sram busy
+	if (AnyCPUReqM & SRAMWordWriteEnableW) begin
+	  NextState = STATE_BUSY;
+	  DCacheStall = 1'b1;
+	end
+	// TLB Miss	
+	else if(AnyCPUReqM & DTLBMissM) begin                      
+	  NextState = STATE_PTW_MISS_FETCH_WDV;
+	end
+	// amo hit
+	else if(|AtomicM & ~UncachedM & ~FSMReg & CacheHit & ~DTLBMissM) begin
+	  NextState = STATE_AMO_UPDATE;
+	  DCacheStall = 1'b1;
+	end
+	// read hit valid cached
+	else if(MemRWM[1] & ~UncachedM & ~FaultM & CacheHit & ~DTLBMissM) begin
+	  NextState = STATE_READY;
+	  DCacheStall = 1'b0;
+	end
+	// write hit valid cached
+	else if (MemRWM[0] & ~UncachedM & ~FaultM & CacheHit & ~DTLBMissM) begin
+	  NextState = STATE_READY;
+	  DCacheStall = 1'b0;
+	  SRAMWordWriteEnableM = 1'b1;
+	  SetDirtyM = 1'b1;
+	end
+	// read miss valid cached
+	else if(MemRWM[1] & ~UncachedM & ~FaultM & ~CacheHit & ~DTLBMissM) begin
+	  NextState = STATE_READ_MISS_FETCH_WDV;
+	  CntReset = 1'b1;
+	  DCacheStall = 1'b1;
+	end
+	// fault
+	else if(|MemRWM & FaultM & ~DTLBMissM) begin
+	  NextState = STATE_READY;
+	end
+      end
+      STATE_AMO_UPDATE: begin
+	NextState = STATE_AMO_WRITE;
+	SaveSRAMRead = 1'b1;
+	SRAMWordWriteEnableM = 1'b1; // pipelined 1 cycle
+      end
+      STATE_AMO_WRITE: begin
+	NextState = STATE_READY;
+	SelAMOWrite = 1'b1;
+      end
+
+      STATE_READ_MISS_FETCH_WDV: begin
+	DCacheStall = 1'b1;
+        PreCntEn = 1'b1;
+        if (FetchCountFlag & AHBAck) begin
+          NextState = STATE_READ_MISS_FETCH_DONE;
+        end else begin
+          NextState = STATE_READ_MISS_FETCH_WDV;
+        end
+      end
+
+      STATE_READ_MISS_FETCH_DONE: begin
+	DCacheStall = 1'b1;
+	NextState = STATE_READ_MISS_CHECK_EVICTED_DIRTY;
+      end
+
+      STATE_PTW_MISS_FETCH_WDV: begin
+	DCacheStall = 1'b1;
+	AdrSel = 2'b01;
+	if (FetchCountFlag & AHBAck) begin
+	  NextState = STATE_PTW_MISS_FETCH_DONE;
+	end else begin
+	  NextState = STATE_PTW_MISS_FETCH_WDV;
+	end
+      end
+      default: begin
+      end
+    endcase
+  end
+
+  assign CntEn = PreCntEn & AHBAck;
 
 endmodule; // dcache
-
-