///////////////////////////////////////////
// cacheway
//
// Written: ross1728@gmail.com July 07, 2021
//          Implements the data, tag, valid, dirty, and replacement bits.
//
// Purpose: Storage and read/write access to data cache data, tag valid, dirty, and replacement.
// 
// A component of the Wally configurable RISC-V project.
// 
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// MIT LICENSE
// 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.
////////////////////////////////////////////////////////////////////////////////////////////////

`include "wally-config.vh"

module cacheway #(parameter NUMLINES=512, parameter LINELEN = 256, TAGLEN = 26,
				  parameter OFFSETLEN = 5, parameter INDEXLEN = 9, parameter DIRTY_BITS = 1) 
  (input logic 		       clk,
   input logic 						  reset,

   input logic [$clog2(NUMLINES)-1:0] RAdr,
   input logic [`PA_BITS-1:0] 		  PAdr,
   input logic 						  WriteEnable,
   input logic 						  VDWriteEnable, 
   input logic [LINELEN/`XLEN-1:0] 	  WriteWordEnable,
   input logic 						  TagWriteEnable,
   input logic [LINELEN-1:0] 		  WriteData,
   input logic 						  SetValid,
   input logic 						  ClearValid,
   input logic 						  SetDirty,
   input logic 						  ClearDirty,
   input logic 						  SelEvict,
   input logic 						  VictimWay,
   input logic 						  InvalidateAll,
   input logic 						  SelFlush,
   input logic 						  FlushWay,

   output logic [LINELEN-1:0] 		  ReadDataLineWayMasked,
   output logic 					  WayHit,
   output logic 					  VictimDirtyWay,
   output logic [TAGLEN-1:0] 		  VictimTagWay
   );

  logic [NUMLINES-1:0] 				  ValidBits;
  logic [NUMLINES-1:0] 				  DirtyBits;
  logic [LINELEN-1:0] 				  ReadDataLineWay;
  logic [TAGLEN-1:0] 				  ReadTag;
  logic 							  Valid;
  logic 							  Dirty;
  logic 							  SelectedWay;
  logic [TAGLEN-1:0] 				  VicDirtyWay;
  logic [TAGLEN-1:0] 				  FlushThisWay;

  logic [$clog2(NUMLINES)-1:0] 		  RAdrD;
  logic 							  SetValidD, ClearValidD;
  logic 							  SetDirtyD, ClearDirtyD;
  logic 							  WriteEnableD, VDWriteEnableD;
  
  /////////////////////////////////////////////////////////////////////////////////////////////
  // Data and Tag Arrays
  /////////////////////////////////////////////////////////////////////////////////////////////

  // Potential optimization: if byte write enables are available, could remove subwordwrites
/*  sram1rw #(.DEPTH(NUMLINES), .WIDTH(LINELEN)) CacheDataMem(
    .clk(clk), .Addr(RAdr),
    .ReadData(ReadDataLineWay), .WriteData(WriteData),
          .WriteEnable(WriteEnable & WriteWordEnable[words])); // *** */

  genvar 							  words;
  for(words = 0; words < LINELEN/`XLEN; words++) begin: word
    sram1rw #(.DEPTH(NUMLINES), .WIDTH(`XLEN))
    CacheDataMem(.clk(clk), .Addr(RAdr),
          .ReadData(ReadDataLineWay[(words+1)*`XLEN-1:words*`XLEN] ),
          .WriteData(WriteData[(words+1)*`XLEN-1:words*`XLEN]),
          .WriteEnable(WriteEnable & WriteWordEnable[words]));
  end

  sram1rw #(.DEPTH(NUMLINES), .WIDTH(TAGLEN)) CacheTagMem(.clk(clk),
		.Addr(RAdr), .ReadData(ReadTag),
	  .WriteData(PAdr[`PA_BITS-1:OFFSETLEN+INDEXLEN]), .WriteEnable(TagWriteEnable));

  assign WayHit = Valid & (ReadTag == PAdr[`PA_BITS-1:OFFSETLEN+INDEXLEN]);
  assign SelectedWay = SelFlush ? FlushWay : 
					   SelEvict ? VictimWay : WayHit;  
  assign ReadDataLineWayMasked = SelectedWay ? ReadDataLineWay : '0;  // first part of AO mux.

  assign VictimDirtyWay = SelFlush ? FlushWay & Dirty & Valid :
						  VictimWay & Dirty & Valid;

  assign VicDirtyWay = VictimWay ? ReadTag : '0;
  assign FlushThisWay = FlushWay ? ReadTag : '0;
  assign VictimTagWay = SelFlush ? FlushThisWay : VicDirtyWay;
  
  /////////////////////////////////////////////////////////////////////////////////////////////
  // Valid Bits
  /////////////////////////////////////////////////////////////////////////////////////////////
  
  always_ff @(posedge clk) begin // Valid bit array, 
    if (reset | InvalidateAll)                              ValidBits        <= #1 '0;
    else if (SetValidD   & (WriteEnableD | VDWriteEnableD)) ValidBits[RAdrD] <= #1 1'b1;
    else if (ClearValidD & (WriteEnableD | VDWriteEnableD)) ValidBits[RAdrD] <= #1 1'b0;
	end

/*  always_ff @(posedge clk) begin // pipeline register; helps timing ***Ross consider further
    RAdrD          <= #1 RAdr;
    SetValidD      <= #1 SetValid;
    ClearValidD    <= #1 ClearValid;    
    WriteEnableD   <= #1 WriteEnable;
    VDWriteEnableD <= #1 VDWriteEnable;
  end */
  flop #($clog2(NUMLINES)) RAdrDelayReg(clk, RAdr, RAdrD);
  flop #(4) ValidCtrlDelayReg(clk, {SetValid, ClearValid, WriteEnable, VDWriteEnable},
    {SetValidD, ClearValidD, WriteEnableD, VDWriteEnableD});
  assign Valid = ValidBits[RAdrD];

  /////////////////////////////////////////////////////////////////////////////////////////////
  // Dirty Bits
  /////////////////////////////////////////////////////////////////////////////////////////////

  // Dirty bits
  if (DIRTY_BITS) begin:dirty
    always_ff @(posedge clk) begin
      if (reset)                                              DirtyBits        <= #1 {NUMLINES{1'b0}};
      else if (SetDirtyD   & (WriteEnableD | VDWriteEnableD)) DirtyBits[RAdrD] <= #1 1'b1;
      else if (ClearDirtyD & (WriteEnableD | VDWriteEnableD)) DirtyBits[RAdrD] <= #1 1'b0;
    end
    flop #(2) DirtyCtlDelayReg(clk, {SetDirty, ClearDirty}, {SetDirtyD, ClearDirtyD});
/*    always_ff @(posedge clk) begin
      SetDirtyD <= SetDirty;
      ClearDirtyD <= ClearDirty;
    end */
    assign Dirty = DirtyBits[RAdrD];
  end else begin:dirty
    assign Dirty = 1'b0;
  end

  
endmodule // DCacheCacheWays