///////////////////////////////////////////
// lsu.sv
//
// Written: David_Harris@hmc.edu 9 January 2021
// Modified: 
//
// Purpose: Load/Store Unit 
//          Top level of the memory-stage core logic
//          Contains data cache, DTLB, subword read/write datapath, interface to external bus
// 
// 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 lsu (
   input logic              clk, reset,
   input logic              StallM, FlushM, StallW, FlushW,
   output logic             LSUStallM,
   // connected to cpu (controls)
   input logic [1:0]        MemRWM,
   input logic [2:0]        Funct3M,
   input logic [6:0]        Funct7M, 
   input logic [1:0]        AtomicM,
   input logic              TrapM,
   input logic              FlushDCacheM,
   output logic             CommittedM, 
   output logic             SquashSCW,
   output logic             DCacheMiss,
   output logic             DCacheAccess,
   // address and write data
   input logic [`XLEN-1:0]  IEUAdrE,
   (* mark_debug = "true" *)output logic [`XLEN-1:0] IEUAdrM,
   input logic [`XLEN-1:0]  WriteDataE, 
   output logic [`XLEN-1:0] ReadDataM,
   // cpu privilege
   input logic [1:0]        PrivilegeModeW,
   input logic              DTLBFlushM,
   // faults
   output logic             LoadPageFaultM, StoreAmoPageFaultM,
   output logic             LoadMisalignedFaultM, LoadAccessFaultM,
   // cpu hazard unit (trap)
   output logic             StoreAmoMisalignedFaultM, StoreAmoAccessFaultM,
            // connect to ahb
   (* mark_debug = "true" *)   output logic [`PA_BITS-1:0] LSUBusAdr,
   (* mark_debug = "true" *)   output logic LSUBusRead, 
   (* mark_debug = "true" *)   output logic LSUBusWrite,
   (* mark_debug = "true" *)   input logic LSUBusAck,
   (* mark_debug = "true" *)   input logic [`XLEN-1:0] LSUBusHRDATA,
   (* mark_debug = "true" *)   output logic [`XLEN-1:0] LSUBusHWDATA,
   (* mark_debug = "true" *)   output logic [2:0] LSUBusSize, 
            // page table walker
   input logic [`XLEN-1:0]  SATP_REGW, // from csr
   input logic              STATUS_MXR, STATUS_SUM, STATUS_MPRV,
   input logic [1:0]        STATUS_MPP,
   input logic [`XLEN-1:0]  PCF,
   input logic              ITLBMissF,
   input logic              InstrDAPageFaultF,
   output logic [`XLEN-1:0] PTE,
   output logic [1:0]       PageType,
   output logic             ITLBWriteF,
   input var                logic [7:0] PMPCFG_ARRAY_REGW[`PMP_ENTRIES-1:0],
   input var                logic [`XLEN-1:0] PMPADDR_ARRAY_REGW[`PMP_ENTRIES-1:0] // *** this one especially has a large note attached to it in pmpchecker.
  );

  logic [`XLEN+1:0]         IEUAdrExtM;
  logic [`PA_BITS-1:0]      LSUPAdrM;
  logic                     DTLBMissM;
  logic                     DTLBWriteM;
  logic [1:0]               LSURWM;
  logic [1:0]               PreLSURWM;
  logic [2:0]               LSUFunct3M;
  logic [6:0]               LSUFunct7M;
  logic [1:0]               LSUAtomicM;
  (* mark_debug = "true" *)  logic [`PA_BITS-1:0] 		   PreLSUPAdrM;
  logic [11:0]              PreLSUAdrE, LSUAdrE;  
  logic                     CPUBusy;
  logic                     DCacheStallM;
  logic                     CacheableM;
  logic                     SelHPTW;
  logic                     BusStall;
  logic                     InterlockStall;
  logic                     IgnoreRequestTLB, IgnoreRequestTrapM;
  logic                     BusCommittedM, DCacheCommittedM;
  logic                     LSUBusWriteCrit;
  logic                     DataDAPageFaultM;
  logic [`XLEN-1:0]         LSUWriteDataM;
  logic [(`XLEN-1)/8:0]     ByteMaskM;
  logic [`XLEN-1:0]         WriteDataM;
  
  // *** TO DO: Burst mode

  flopenrc #(`XLEN) AddressMReg(clk, reset, FlushM, ~StallM, IEUAdrE, IEUAdrM);
  flopenrc #(`XLEN) WriteDataMReg(clk, reset, FlushM, ~StallM, WriteDataE, WriteDataM);
  assign IEUAdrExtM = {2'b00, IEUAdrM}; 
  assign LSUStallM = DCacheStallM | InterlockStall | BusStall;

  /////////////////////////////////////////////////////////////////////////////////////////////
  // HPTW and Interlock FSM (only needed if VM supported)
  // MMU include PMP and is needed if any privileged supported
  /////////////////////////////////////////////////////////////////////////////////////////////

  if(`VIRTMEM_SUPPORTED) begin : VIRTMEM_SUPPORTED
    lsuvirtmem lsuvirtmem(.clk, .reset, .StallW, .MemRWM, .AtomicM, .ITLBMissF, .ITLBWriteF,
      .DTLBMissM, .DTLBWriteM, .InstrDAPageFaultF, .DataDAPageFaultM, 
      .TrapM, .DCacheStallM, .SATP_REGW, .PCF,
      .STATUS_MXR, .STATUS_SUM, .STATUS_MPRV, .STATUS_MPP, .PrivilegeModeW,
      .ReadDataM, .WriteDataM, .Funct3M, .LSUFunct3M, .Funct7M, .LSUFunct7M,
      .IEUAdrExtM, .PTE, .LSUWriteDataM, .PageType, .PreLSURWM, .LSUAtomicM, .IEUAdrE,
      .LSUAdrE, .PreLSUPAdrM, .CPUBusy, .InterlockStall, .SelHPTW,
      .IgnoreRequestTLB, .IgnoreRequestTrapM);
  end else begin
    assign {InterlockStall, SelHPTW, PTE, PageType, DTLBWriteM, ITLBWriteF, IgnoreRequestTLB} = '0;
    assign IgnoreRequestTrapM = TrapM; assign CPUBusy = StallW; assign PreLSURWM = MemRWM; 
    assign LSUAdrE = PreLSUAdrE; assign PreLSUAdrE = IEUAdrE[11:0]; 
    assign PreLSUPAdrM = IEUAdrExtM[`PA_BITS-1:0];
    assign LSUFunct3M = Funct3M;  assign LSUFunct7M = Funct7M; assign LSUAtomicM = AtomicM;
    assign LSUWriteDataM = WriteDataM;
   end

  // CommittedM tells the CPU's privilege unit the current instruction
  // in the memory stage is a memory operaton and that memory operation is either completed
  // or is partially executed. Partially completed memory operations need to prevent an interrupts.
  // There is not a clean way to restore back to a partial executed instruction.  CommiteedM will
  // delay the interrupt until the LSU is in a clean state.
  assign CommittedM = SelHPTW | DCacheCommittedM | BusCommittedM;

  // MMU and Misalignment fault logic required if privileged unit exists
  if(`ZICSR_SUPPORTED == 1) begin : dmmu
    logic DisableTranslation;
    assign DisableTranslation = SelHPTW | FlushDCacheM;
    mmu #(.TLB_ENTRIES(`DTLB_ENTRIES), .IMMU(0))
    dmmu(.clk, .reset, .SATP_REGW, .STATUS_MXR, .STATUS_SUM, .STATUS_MPRV, .STATUS_MPP,
      .PrivilegeModeW, .DisableTranslation,
      .PAdr(PreLSUPAdrM),
      .VAdr(IEUAdrM),
      .Size(LSUFunct3M[1:0]),
      .PTE,
      .PageTypeWriteVal(PageType),
      .TLBWrite(DTLBWriteM),
      .TLBFlush(DTLBFlushM),
      .PhysicalAddress(LSUPAdrM),
      .TLBMiss(DTLBMissM),
      .Cacheable(CacheableM), .Idempotent(), .AtomicAllowed(),
      .InstrAccessFaultF(), .LoadAccessFaultM, .StoreAmoAccessFaultM,
      .InstrPageFaultF(),.LoadPageFaultM, .StoreAmoPageFaultM,
      .LoadMisalignedFaultM, .StoreAmoMisalignedFaultM,   // *** these faults need to be supressed during hptw.
      .DAPageFault(DataDAPageFaultM),
         // *** should use LSURWM as this is includes the lr/sc squash. However this introduces a combo loop
         // from squash, depends on LSUPAdrM, depends on TLBHit, depends on these *AccessM inputs.
      .AtomicAccessM(|LSUAtomicM), .ExecuteAccessF(1'b0), 
      .WriteAccessM(PreLSURWM[0]), .ReadAccessM(PreLSURWM[1]),
      .PMPCFG_ARRAY_REGW, .PMPADDR_ARRAY_REGW);

  end else begin
    assign {DTLBMissM, LoadAccessFaultM, StoreAmoAccessFaultM, LoadMisalignedFaultM, StoreAmoMisalignedFaultM} = '0;
    assign {LoadPageFaultM, StoreAmoPageFaultM} = '0;
    assign LSUPAdrM = PreLSUPAdrM;
    assign CacheableM = '1;
  end
  
  /////////////////////////////////////////////////////////////////////////////////////////////
  //  Memory System
  //  Either Data Cache or Data Tightly Integrated Memory or just bus interface
  /////////////////////////////////////////////////////////////////////////////////////////////
  logic [`XLEN-1:0]    FinalAMOWriteDataM, FinalWriteDataM;
  logic [`XLEN-1:0]    ReadDataWordM;
  logic [`XLEN-1:0]    ReadDataWordMuxM;
  logic                IgnoreRequest;
  logic                SelUncachedAdr;
  assign IgnoreRequest = IgnoreRequestTLB | IgnoreRequestTrapM;
  
  if (`DMEM == `MEM_TIM) begin : dtim
    // *** directly instantiate RAM or ROM here.  Instantiate SRAM1P1RW.  
    // Merge SimpleRAM and SRAM1p1rw into one that is good for synthesis and RAM libraries and flops
    dtim dtim(.clk, .reset, .CPUBusy, .LSURWM, .IEUAdrM, .IEUAdrE, .TrapM, .FinalWriteDataM, 
              .ReadDataWordM, .BusStall, .LSUBusWrite,.LSUBusRead, .BusCommittedM,
              .DCacheStallM, .DCacheCommittedM, .ByteMaskM, .Cacheable(CacheableM),
              .DCacheMiss, .DCacheAccess);
  end 
  if (`DBUS) begin : bus  
    localparam           CACHE_ENABLED = `DMEM == `MEM_CACHE;
    localparam integer   WORDSPERLINE = (CACHE_ENABLED) ? `DCACHE_LINELENINBITS/`XLEN : 1;
    localparam integer   LINELEN = (CACHE_ENABLED) ? `DCACHE_LINELENINBITS : `XLEN;
    localparam integer   LOGWPL = (CACHE_ENABLED) ? $clog2(WORDSPERLINE) : 1;
    logic [LINELEN-1:0]  ReadDataLineM;
    logic [LINELEN-1:0]  DCacheBusWriteData;
    logic [`PA_BITS-1:0] DCacheBusAdr;
    logic                DCacheWriteLine;
    logic                DCacheFetchLine;
    logic                DCacheBusAck;
    logic                SelBus;
    logic [LOGWPL-1:0]   WordCount;
            
    busdp #(WORDSPERLINE, LINELEN, LOGWPL, CACHE_ENABLED) busdp(
      .clk, .reset,
      .LSUBusHRDATA, .LSUBusAck, .LSUBusWrite, .LSUBusRead, .LSUBusSize,
      .WordCount, .LSUBusWriteCrit,
      .LSUFunct3M, .LSUBusAdr, .DCacheBusAdr, .DCacheFetchLine,
      .DCacheWriteLine, .DCacheBusAck, .DCacheBusWriteData, .LSUPAdrM,
      .SelUncachedAdr, .IgnoreRequest, .LSURWM, .CPUBusy, .CacheableM,
      .BusStall, .BusCommittedM);

    mux2 #(`XLEN) UnCachedDataMux(.d0(ReadDataWordM), .d1(DCacheBusWriteData[`XLEN-1:0]),
      .s(SelUncachedAdr), .y(ReadDataWordMuxM));
    mux2 #(`XLEN) LsuBushwdataMux(.d0(ReadDataWordM), .d1(FinalWriteDataM),
      .s(SelUncachedAdr), .y(LSUBusHWDATA));
    
    if(CACHE_ENABLED) begin : dcache
      cache #(.LINELEN(`DCACHE_LINELENINBITS), .NUMLINES(`DCACHE_WAYSIZEINBYTES*8/LINELEN),
              .NUMWAYS(`DCACHE_NUMWAYS), .LOGWPL(LOGWPL), .WORDLEN(`XLEN), .MUXINTERVAL(`XLEN), .DCACHE(1)) dcache(
        .clk, .reset, .CPUBusy, .LSUBusWriteCrit, .RW(LSURWM), .Atomic(LSUAtomicM),
        .FlushCache(FlushDCacheM), .NextAdr(LSUAdrE), .PAdr(LSUPAdrM), 
        .ByteMask(ByteMaskM), .WordCount,
        .FinalWriteData(FinalWriteDataM), .Cacheable(CacheableM),
        .CacheStall(DCacheStallM), .CacheMiss(DCacheMiss), .CacheAccess(DCacheAccess),
        .IgnoreRequestTLB, .IgnoreRequestTrapM, .CacheCommitted(DCacheCommittedM), 
        .CacheBusAdr(DCacheBusAdr), .ReadDataWord(ReadDataWordM), 
        .CacheBusWriteData(DCacheBusWriteData), .CacheFetchLine(DCacheFetchLine), 
        .CacheWriteLine(DCacheWriteLine), .CacheBusAck(DCacheBusAck), .InvalidateCacheM(1'b0));

    end else begin : passthrough
      assign {ReadDataWordM, DCacheStallM, DCacheCommittedM, DCacheFetchLine, DCacheWriteLine} = '0;
      assign DCacheMiss = CacheableM; assign DCacheAccess = CacheableM;
    end
  end else begin: nobus // block: bus
    assign {LSUBusHWDATA, SelUncachedAdr} = '0; 
    assign ReadDataWordMuxM = ReadDataWordM;
  end

  subwordread subwordread(.ReadDataWordMuxM, .LSUPAdrM(LSUPAdrM[2:0]),
		.Funct3M(LSUFunct3M), .ReadDataM);

  /////////////////////////////////////////////////////////////////////////////////////////////
  // Atomic operations
  /////////////////////////////////////////////////////////////////////////////////////////////
  if (`A_SUPPORTED) begin:atomic
    atomic atomic(.clk, .reset, .FlushW, .CPUBusy, .ReadDataM, .LSUWriteDataM, .LSUPAdrM, 
      .LSUFunct7M, .LSUFunct3M, .LSUAtomicM, .PreLSURWM, .IgnoreRequest, 
      .FinalAMOWriteDataM, .SquashSCW, .LSURWM);
  end else begin:lrsc
    assign SquashSCW = 0; assign LSURWM = PreLSURWM; assign FinalAMOWriteDataM = LSUWriteDataM;
  end

  subwordwrite subwordwrite(.LSUPAdrM(LSUPAdrM[2:0]),
    .LSUFunct3M, .FinalAMOWriteDataM, .FinalWriteDataM, .ByteMaskM);

  
endmodule