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// ========== Copyright Header Begin ==========================================

// 

// OpenSPARC T1 Processor File: sparc_ifu_milfsm.v

// Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.

// DO NOT ALTER OR REMOVE COPYRIGHT NOTICES.

// 

// The above named program is free software; you can redistribute it and/or

// modify it under the terms of the GNU General Public

// License version 2 as published by the Free Software Foundation.

// 

// The above named program is distributed in the hope that it will be 

// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

// General Public License for more details.

// 

// You should have received a copy of the GNU General Public

// License along with this work; if not, write to the Free Software

// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.

// 

// ========== Copyright Header End ============================================

////////////////////////////////////////////////////////////////////////

/*

//  Module Name: sparc_ifu_ifqdp

//  Description:

//  The IFQ is the icache fill queue.  This communicates between the

//  IFU and the outside world.  It handles icache misses and

//  invalidate requests from the crossbar.

*/

////////////////////////////////////////////////////////////////////////

// Global header file includes

////////////////////////////////////////////////////////////////////////

`include "ifu.h"

//`define MILFSM_NULL   4'b0000

//`define MILFSM_WAIT   4'b1000

//`define MILFSM_REQ    4'b1100

//`define MILFSM_FILL0  4'b1001

//`define MILFSM_FILL1  4'b1011

//`define MIL_V  3

//`define MIL_R  2

//`define MIL_A  1

//`define MIL_F  0

module sparc_ifu_milfsm(/*AUTOARG*/

   // Outputs

   so, fsm_ifc_errreq, fsm_ifc_wrt_tir, fsm_ifc_comp_valid,

   fsm_ifc_mil_valid, fsm_ifc_mil_cancel, fsm_ifc_thr_ready,

   fsm_ifc_pred_rdy, fsm_ifc_pcxreq, fsm_ifc_addrbit4_i2,

   fsm_ifc_milchld, fsm_ifc_milstate,

   // Inputs

   ifc_fsm_can_thisthr, ifc_fsm_fill_thisthr_i2,

   ifc_fsm_wr_complete_f, ifqadv_i2, ifd_ifc_4bpkt_i2,

   fcl_ifq_thr_s1, ifc_fsm_imiss_thisthr_s, ifc_fsm_milhit_s,

   ifc_fsm_hiton_thismil_s, ifc_fsm_pcxaccept_thisthr,

   ifc_fsm_miladdr4, clk, se, si, reset, ifc_fsm_err_thisthr

   );

   input       ifc_fsm_can_thisthr,

                     ifc_fsm_fill_thisthr_i2;

   input       ifc_fsm_wr_complete_f;

   input       ifqadv_i2;

   input       ifd_ifc_4bpkt_i2;

   input [1:0] fcl_ifq_thr_s1;

   input       ifc_fsm_imiss_thisthr_s;

   input       ifc_fsm_milhit_s;

         input       ifc_fsm_hiton_thismil_s,

               ifc_fsm_pcxaccept_thisthr;

   input       ifc_fsm_miladdr4;

   input       clk,

               se,

               si,

               reset;

   input       ifc_fsm_err_thisthr;

   output      so;

   output      fsm_ifc_errreq;

   output      fsm_ifc_wrt_tir;

   output      fsm_ifc_comp_valid,

                     fsm_ifc_mil_valid,

               fsm_ifc_mil_cancel,

                     fsm_ifc_thr_ready;

   output      fsm_ifc_pred_rdy,

                     fsm_ifc_pcxreq,

                     fsm_ifc_addrbit4_i2;

   output [2:0] fsm_ifc_milchld;

   output [3:0] fsm_ifc_milstate;

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

// Declarations

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

   // local variables

   reg [3:0]     next_state;

   wire [3:0]    milstate;

   wire [2:0]   local_milchld;

   wire         milchld_valid;

   wire   fill_this16b;

   wire         cancel_mil,

                      cancel_next;

   wire         err_pending,

                      err_pending_next;

   wire         valid_d1,

                valid_i2;

   wire [2:0]    next_milchld;

   // Missed Instruction List State Machine

   // 3   - valid

   // 2   - req

   // 1   - addr for fill fill (1/0)

   // 0   - fill

   //

   // 2   - child valid

   // 1:0 - child thr ptr

   //

   always @(/*AUTOSENSE*/err_pending or ifc_fsm_err_thisthr

            or ifc_fsm_fill_thisthr_i2 or ifc_fsm_imiss_thisthr_s

            or ifc_fsm_milhit_s or ifc_fsm_pcxaccept_thisthr

            or ifc_fsm_wr_complete_f or ifd_ifc_4bpkt_i2 or ifqadv_i2

            or milstate)

     begin

              case (milstate)  //  synopsys parallel_case

                4'b0000: // null

                  begin

                     //ic_wrreq_i2 = 1'b0;             

                     //  orphan_chld = 1'b0;

               next_state[1:0] = 2'b0;

               if (ifc_fsm_err_thisthr | ifc_fsm_imiss_thisthr_s)

                             begin

                                next_state[`MIL_V] = 1'b1;

                                if (ifc_fsm_milhit_s & ~ifc_fsm_err_thisthr)

                                  next_state[`MIL_R] = 1'b0;  // MILFSM_WAIT

                                else

                                  next_state[`MIL_R] = 1'b1;  // MILFSM_REQ;

                             end

                     else

                             next_state = milstate;

                  end // case: begin...

                4'b1100:  // req

                  begin

                     // ic_wrreq_i2 = 1'b0;             

                     // if canthr=1, the request will not be sent out in this cycle.

               if ((ifc_fsm_pcxaccept_thisthr) &

                   ~(ifc_fsm_err_thisthr | err_pending))

                 // two requests are made when there is an error.

                 // one, with errbit=1 gets back in invalidate response, 

                 // the other, with errbit=0, gets the regular ifill 

                 // return

                             begin

                                // we invalidate the icache on detecting an error

                                // only if this wasn't an MIL hit as well.  If it

                                // was an MIL we would have gone to the wait state

                                // already and it is too late to invalidate the cache

                                next_state = `MILFSM_WAIT;

                    //              orphan_chld = 1'b0;             

                             end

//                   else if ((cancel_mil | ifc_fsm_can_thisthr) & 

//                        ~milchld_valid & ~ifc_fsm_hiton_thismil_s)

//                           begin

//                              next_state = `MILFSM_NULL;

//                           end

                     else

                             begin

                                next_state = milstate;

                    //              orphan_chld = 1'b0;

                             end

                  end // case: 4'b1100

                4'b1000: // wait

                  begin

               //              orphan_chld = 1'b0;

                     if (ifc_fsm_fill_thisthr_i2)

                             begin

                                // ic_wrreq_i2 = 1'b1;

                    if (ifd_ifc_4bpkt_i2 & ifqadv_i2) // 4B ifill from IOB

                      // don't want to advance too quickly and get fasle compl

                      next_state = `MILFSM_NULL;

                    else if (~ifd_ifc_4bpkt_i2)

                                  next_state = `MILFSM_FILL0;

                    else

                      next_state = milstate;

                             end

                     else

                             begin

                                next_state = milstate;

                                //ic_wrreq_i2 = 1'b0;               

                             end

                  end // case: 4'b1000

                4'b1001: // fill0

                  begin

               //              orphan_chld = 1'b0;

               if (ifc_fsm_wr_complete_f)

                             begin

                                next_state = `MILFSM_FILL1;

                                //ic_wrreq_i2 = 1'b1;

                             end

                     else

                             begin

                                next_state = milstate;

                                //ic_wrreq_i2 = 1'b1;

                             end

                  end // case: 4'b1001

                4'b1011: // fill1

                  // Do we really need this state??  yes, to start thr

                  begin

               //              orphan_chld = 1'b0;                  

                     if (ifc_fsm_wr_complete_f)

                             begin

                                //ic_wrreq_i2 = 1'b0;               

                    //              if (delay_mil | ifc_fsm_imiss_thisthr_s)

                    //                next_state = `MILFSM_REQ;

                    //              else

                                next_state = `MILFSM_NULL;

                             end

                     else

                             begin

                                //ic_wrreq_i2 = 1'b1;

                                next_state = milstate;

                             end // else: !if(ifc_fsm_wr_complete_f)

                  end // case: 4'b10001

                default:

                  begin

               // synopsys translate_off

                     // 0in <fire -message "MILSTATE, Error: SPARC/IFU/MILFSM: unknown state!"

`ifdef DEFINE_0IN

`else

               if ($time > (4* `CMP_CLK_PERIOD))

                 begin

                                `ifdef MODELSIM

                                          $display ("MILSTATE",

                            "Error: SPARC/IFU/MILFSM: unknown state! %b\n",milstate);

                                `else

                          $error ("MILSTATE",

                            "Error: SPARC/IFU/MILFSM: unknown state! %b\n",milstate);

                                `endif

                 end

`endif

               // synopsys translate_on               

                     next_state = milstate;

                     //ic_wrreq_i2 = 1'b0;                  

               //              orphan_chld = 1'b0;      

                  end // case: default

              endcase // casex(milstate)

     end // always @ (...

   // MIL state reg

   dffr_s #(4) milst_reg(.din  (next_state[3:0]),

                                   .q    (milstate[3:0]),

                                   .clk  (clk),

                                   .rst  (reset),

                                   .se   (se), .si(), .so());

   // Cancel - Delay state machine

   // -- not used anymore

   // C D

   // 0 0  - null

   // 1 0  - current thread cancelled but pending from L2

   // 1 1  - one ifill pending from L2, current thread will be sent

   //        out after that.

//   assign cancel_next = (ifc_fsm_can_thisthr | 

//                                         cancel_mil) & next_state[`MIL_V];    // reset wins

   assign cancel_next = (ifc_fsm_can_thisthr | cancel_mil) &

                          (milstate[`MIL_V] | ifc_fsm_imiss_thisthr_s |

                           ifc_fsm_err_thisthr);    // reset wins

   dffr_s #(1) can_ff(.din  (cancel_next),

                                .q    (cancel_mil),

                                .clk  (clk),

                                .rst  (reset),

                                .se   (se), .si(), .so());

   // track if we need to send out an error request

   assign err_pending_next = (ifc_fsm_err_thisthr &

                              (milstate[`MIL_R] | ~milstate[`MIL_V]) |

//                            err_pending & next_state[`MIL_V]) &       

                        err_pending & milstate[`MIL_V]) &

                              ~ifc_fsm_pcxaccept_thisthr;

                         // & ~ifc_fsm_can_thisthr;

   dffr_s #(1) err_ff(.din (err_pending_next),

                                .q   (err_pending),

                                .clk (clk),

                                .rst (reset), .se(se), .si(), .so());

   assign fsm_ifc_errreq = err_pending;

   // Track secondary hits

   assign next_milchld[2] = ifc_fsm_hiton_thismil_s |    // hit on MIL by

                                                             // someone else

                                    fsm_ifc_milchld[2] & milstate[`MIL_V]; // reset

   assign next_milchld[1:0] = ifc_fsm_hiton_thismil_s ? fcl_ifq_thr_s1 :

                                                                          fsm_ifc_milchld[1:0];

   dffr_s #(3) milchld_reg(.din  (next_milchld),

                                     .clk  (clk),

                                     .rst  (reset),

                                     .q    (local_milchld),

                                     .se   (se), .si(), .so());

   assign fsm_ifc_milchld[2] = local_milchld[2] & milstate[`MIL_V];

   assign fsm_ifc_milchld[1:0] = local_milchld[1:0];

   assign milchld_valid = local_milchld[2] & milstate[`MIL_V];

//   assign fsm_ifc_addrbit4_i2 = milstate[`MIL_F];

   assign fsm_ifc_addrbit4_i2 = milstate[`MIL_F] & milstate[`MIL_V] &

                                (milstate[`MIL_A] | ifc_fsm_wr_complete_f);

   // determine if we want to fill from the first pkt or second pkt

   assign fill_this16b = ~(milstate[`MIL_F] ^ ifc_fsm_miladdr4) |

                            ifd_ifc_4bpkt_i2;

   // write to thread inst reg (TIR)

//   assign fsm_ifc_wrt_tir =  (next_state[`MIL_F]) & ~cancel_mil & 

//                           ifc_fsm_fill_thisthr_i2;

   assign fsm_ifc_wrt_tir =  (milstate[`MIL_V] & ~milstate[`MIL_R]) &

                                                 ~(cancel_mil | ifc_fsm_can_thisthr) &

                               ifc_fsm_fill_thisthr_i2 &

                               fill_this16b;

   // write to Icache 

//   assign fsm_ifc_wrreq_i2 = ic_wrreq_i2;

   assign valid_i2 = milstate[`MIL_V] & ~fsm_ifc_thr_ready;

   dff_s vld_ff(.din (valid_i2),

                    .q   (valid_d1),

                    .clk (clk),

                    .se  (se), .si(), .so());

   // signal thread completion

   assign fsm_ifc_thr_ready = milstate[`MIL_V] & milstate[`MIL_F] &

                              milstate[`MIL_A] & ifc_fsm_wr_complete_f |

                              ~milstate[`MIL_V] & valid_d1;

   // predict ready assuming 2nd ifill happens in the next cycle

   assign fsm_ifc_pred_rdy =  milstate[`MIL_V] & milstate[`MIL_F] &

                              (ifc_fsm_wr_complete_f |

                               milstate[`MIL_A]); //  & ifc_fsm_fill_thisthr_i2

   // set compare valid for mil hit signal

   assign fsm_ifc_comp_valid = milstate[`MIL_V] &     // valid entry

                                     ~milstate[`MIL_F] &    // not f0 or f1

                               ~milchld_valid;        // no chld already

   assign fsm_ifc_mil_valid = milstate[`MIL_V];

   assign fsm_ifc_mil_cancel = cancel_mil;

   // In the request state or if we need to send an error invalidate, 

   // ask for bus from LSU. 

//   assign fsm_ifc_pcxreq = (milstate[`MIL_V] & milstate[`MIL_R] |

//                          err_pending | ifc_fsm_err_thisthr) & 

//                         ~ifc_fsm_pcxaccept_thisthr & 

//                            (milchld_valid | ~cancel_mil);

//   assign fsm_ifc_pcxreq = (milstate[`MIL_V] & milstate[`MIL_R] & 

//                                ~ifc_fsm_pcxaccept_thisthr & 

//                            (milchld_valid | ~cancel_mil));

   // removed pcx_accept from critical path

   assign fsm_ifc_pcxreq = milstate[`MIL_V] & milstate[`MIL_R];

   assign fsm_ifc_milstate = milstate;

endmodule