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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's DC FSM                                             ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://opencores.org/project,or1k                           ////
////                                                              ////
////  Description                                                 ////
////  Data cache state machine                                    ////
////                                                              ////
////  To Do:                                                      ////
////   - Test error during line read or write                     ////
////                                                              ////
////  Author(s):                                                  ////
////      - Damjan Lampret, lampret@opencores.org                 ////
////      - Julius Baxter, julius@opencores.org                   ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2000, 2010 Authors and OPENCORES.ORG           ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source 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 Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// $Log: or1200_dc_fsm.v,v $
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Minor update: 
// Bugs fixed. 
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
`define OR1200_DCFSM_IDLE       3'd0
`define OR1200_DCFSM_CLOADSTORE 3'd1
`define OR1200_DCFSM_LOOP2      3'd2
`define OR1200_DCFSM_LOOP3      3'd3
`define OR1200_DCFSM_LOOP4      3'd4
`define OR1200_DCFSM_FLUSH5     3'd5
`define OR1200_DCFSM_INV6       3'd6
`define OR1200_DCFSM_WAITSPRCS7 3'd7
 
 
 
//
// Data cache FSM for cache line of 16 bytes (4x singleword)
//
 
module or1200_dc_fsm
  (
   // Clock and reset
   clk, rst,
 
   // Internal i/f to top level DC
   dc_en, dcqmem_cycstb_i, dcqmem_ci_i, dcqmem_we_i, dcqmem_sel_i,
   tagcomp_miss, biudata_valid, biudata_error, lsu_addr,
   dcram_we, biu_read, biu_write, biu_do_sel, dcram_di_sel, first_hit_ack,
   first_miss_ack, first_miss_err, burst, tag_we, tag_valid, dc_addr,
   dc_no_writethrough, tag_dirty, dirty, tag, tag_v, dc_block_flush,
   dc_block_writeback, spr_dat_i, mtspr_dc_done, spr_cswe
   );
 
   //
   // I/O
   //
   input                                clk;
   input                                rst;
   input                                dc_en;
   input                                dcqmem_cycstb_i;
   input                                dcqmem_ci_i;
   input                                dcqmem_we_i;
   input [3:0]                           dcqmem_sel_i;
   input                                tagcomp_miss;
   input                                biudata_valid;
   input                                biudata_error;
   input [31:0]                  lsu_addr;
   output [3:0]                  dcram_we;
   output                               biu_read;
   output                               biu_write;
   output                               dcram_di_sel;
   output                               biu_do_sel;
   output                               first_hit_ack;
   output                               first_miss_ack;
   output                               first_miss_err;
   output                               burst;
   output                               tag_we;
   output                               tag_valid;
   output [31:0]                         dc_addr;
   input                                dc_no_writethrough;
   output                               tag_dirty;
   input                                dirty;
   input [`OR1200_DCTAG_W-2:0]           tag;
   input                                tag_v;
   input                                dc_block_flush;
   input                                dc_block_writeback;
   input [31:0]                  spr_dat_i;
   output                               mtspr_dc_done;
   input                                spr_cswe;
 
 
   //
   // Internal wires and regs
   //
   reg [31:0]                            addr_r;
   reg [2:0]                             state;
   reg [2:0]                             cnt;
   reg                                  hitmiss_eval;
   reg                                  store;
   reg                                  load;
   reg                                  cache_inhibit;
   reg                                  cache_miss;
   reg                                  cache_dirty_needs_writeback;
   reg                                  did_early_load_ack;
   reg                                  cache_spr_block_flush;
   reg                                  cache_spr_block_writeback;
   reg                                  cache_wb;
   wire                                 load_hit_ack;
   wire                                 load_miss_ack;
   wire                                 load_inhibit_ack;
   wire                                 store_hit_ack;
   wire                                 store_hit_writethrough_ack;
   wire                                 store_miss_writethrough_ack;
   wire                                 store_inhibit_ack;
   wire                                 store_miss_ack;
   wire                                 dcram_we_after_line_load;
   wire                                 dcram_we_during_line_load;
   wire                                 tagram_we_end_of_loadstore_loop;
   wire                                 tagram_dirty_bit_set;
   wire                                 writethrough;
   wire                                 cache_inhibit_with_eval;
   wire [1:0]                            next_addr_word;
 
   //
   // Cache inhibit
   //
 
   // Indicates whether cache is inhibited, during hitmiss_eval and after
   assign cache_inhibit_with_eval = (hitmiss_eval & dcqmem_ci_i) |
                                    (!hitmiss_eval & cache_inhibit);
 
   //
   // Generate of DCRAM write enables
   //
 
   // WE when non-writethrough, and had to wait for a line to load.
   assign dcram_we_after_line_load = (state == `OR1200_DCFSM_LOOP3) &
                                    dcqmem_we_i & !cache_dirty_needs_writeback &
                                     !did_early_load_ack;
 
   // WE when receiving the data cache line
   assign dcram_we_during_line_load = (state == `OR1200_DCFSM_LOOP2) & load &
                                      biudata_valid;
 
   assign dcram_we =(// Write when hit - make sure it is only when hit - could
                     // maybe be doing write through and don't want to corrupt
                     // cache lines corresponding to the writethrough addr_r.
                     ({4{store_hit_ack | store_hit_writethrough_ack}} |
                     // Write after load of line
                     {4{dcram_we_after_line_load}}) &
                     dcqmem_sel_i                ) |
                    // Write during load
                    {4{dcram_we_during_line_load}};
 
   //
   // Tag RAM signals
   //
 
   // WE to tag RAM when we finish loading a line.
   assign tagram_we_end_of_loadstore_loop = ((state==`OR1200_DCFSM_LOOP2) &
                                             biudata_valid & !(|cnt));
 
`ifndef OR1200_DC_WRITETHROUGH
   // No writethrough, so mark a line dirty whenever we write to it
   assign tagram_dirty_bit_set = store_hit_ack | store_miss_ack;
 
   // Generate done signal for MTSPR instructions that may block execution
   assign mtspr_dc_done = // Either DC disabled or we're not selected, or
                          !dc_en | !spr_cswe |
                          // Requested address not valid or writeback and !dirty
                          ((state==`OR1200_DCFSM_FLUSH5) &
                           (!tag_v | (cache_spr_block_writeback & !dirty))) |
                          // Writeback or flush is finished
                          ((state==`OR1200_DCFSM_LOOP3) &
                           (cache_spr_block_flush | cache_spr_block_writeback))|
                          // Invalidate of clean line finished
                          ((state==`OR1200_DCFSM_INV6) & cache_spr_block_flush);
 
 
`else
 `ifdef OR1200_DC_NOSTACKWRITETHROUGH
   // For dirty bit setting when having writethrough but not for stack
   assign tagram_dirty_bit_set = store_hit_ack | store_miss_ack;
 `else
   // Lines will never be dirty if always writethrough
   assign tagram_dirty_bit_set = 0;
 `endif
 
   assign mtspr_dc_done = 1'b1;
 
`endif
 
   assign tag_dirty = tagram_dirty_bit_set;
 
   // WE to tag RAM
   assign tag_we = tagram_we_end_of_loadstore_loop |
                    tagram_dirty_bit_set | (state == `OR1200_DCFSM_INV6);
 
 
   // Valid bit
   // Set valid when end of line load, or marking dirty (is still valid)
   assign tag_valid = ( tagram_we_end_of_loadstore_loop &
                        (load | (store & cache_spr_block_writeback)) ) |
                      tagram_dirty_bit_set;
 
 
 
   //
   // BIU read and write
   //
 
   assign biu_read = // Bus read request when:
                     // 1) Have a miss and not dirty or a load with inhibit
                     ((state == `OR1200_DCFSM_CLOADSTORE) &
                      (((hitmiss_eval & tagcomp_miss & !dirty &
                         !(store & writethrough)) |
                        (load & cache_inhibit_with_eval)) & dcqmem_cycstb_i)) |
                     // 2) In the loop and loading
                     ((state == `OR1200_DCFSM_LOOP2) & load);
 
 
   assign biu_write = // Bus write request when:
                      // 1) Have a miss and dirty or store with inhibit
                      ((state == `OR1200_DCFSM_CLOADSTORE) &
                       (((hitmiss_eval & tagcomp_miss & dirty) |
                         (store & writethrough)) |
                        (store & cache_inhibit_with_eval)) & dcqmem_cycstb_i) |
                      // 2) In the loop and storing
                      ((state == `OR1200_DCFSM_LOOP2) & store);
 
   //
   // Select for data to actual cache RAM (from LSU or BIU)
   //
   // Data to DCRAM - from external bus when loading (from IU when store)
   assign dcram_di_sel = load;
   // Data to external bus - always from IU except in case of bursting back
   //                        the line to memory. (1 selects DCRAM)
   assign biu_do_sel = (state == `OR1200_DCFSM_LOOP2) & store;
 
   // 2-bit wire for calculating next word of burst write
   assign next_addr_word = addr_r[3:2] + 1;
 
   // Address to cache RAM (tag address also derived from this)   
   assign dc_addr =
                   // First check if we've got a block flush or WB op
                   ((dc_block_flush & !cache_spr_block_flush) |
                   (dc_block_writeback & !cache_spr_block_writeback)) ?
                   spr_dat_i :
                   (state==`OR1200_DCFSM_FLUSH5) ? addr_r:
                    // If no SPR action, then always put out address from LSU
                    (state==`OR1200_DCFSM_IDLE | hitmiss_eval) ? lsu_addr :
                    // Next, if in writeback loop, when ACKed must immediately
                    // output next word address (the RAM address takes a cycle
                    // to increment, but it's needed immediately for burst)
                    // otherwise, output our registered address.
                    (state==`OR1200_DCFSM_LOOP2 & biudata_valid & store ) ?
                    {addr_r[31:4], next_addr_word, 2'b00} : addr_r;
 
`ifdef OR1200_DC_WRITETHROUGH
 `ifdef OR1200_DC_NOSTACKWRITETHROUGH
   assign writethrough = !dc_no_writethrough;
 `else
   assign writethrough = 1;
 `endif
`else
   assign writethrough = 0;
`endif
 
   //
   // ACK generation for LSU
   //
 
   // ACK for when it's a cache hit
   assign first_hit_ack = load_hit_ack | store_hit_ack |
                          store_hit_writethrough_ack |
                          store_miss_writethrough_ack |
                          store_inhibit_ack | store_miss_ack ;
 
   // ACK for when it's a cache miss - load only, is used in MUX for data back
   //                                  LSU straight off external data bus. In
   //                                  this was is also used for cache inhibit
   //                                  loads.
   assign first_miss_ack = load_miss_ack | load_inhibit_ack;
 
   // ACK cache hit on load
   assign load_hit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                         hitmiss_eval & !tagcomp_miss & !dcqmem_ci_i & load;
 
   // ACK cache hit on store, no writethrough
   assign store_hit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                          hitmiss_eval  & !tagcomp_miss & !dcqmem_ci_i &
                          store & !writethrough;
 
   // ACK cache hit on store with writethrough
   assign store_hit_writethrough_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                                       !cache_miss & !cache_inhibit &
                                       store & writethrough & biudata_valid;
 
   // ACK cache miss on store with writethrough
   assign store_miss_writethrough_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                                        cache_miss & !cache_inhibit &
                                        store & writethrough & biudata_valid;
 
   // ACK store when cacheinhibit
   assign store_inhibit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                              store & cache_inhibit & biudata_valid;
 
 
   // Get the _early_ ack on first ACK back from wishbone during load only
   // Condition is that we're in the loop - that it's the first ack we get (can
   // tell from value of cnt), and we're loading a line to read from it (not
   // loading to write to it, in the case of a write without writethrough.)
   assign load_miss_ack =  ((state== `OR1200_DCFSM_LOOP2) & load &
                             (cnt==`OR1200_DCLS-1) & biudata_valid &
                            !(dcqmem_we_i & !writethrough));
 
   assign load_inhibit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
                             load & cache_inhibit & biudata_valid;
 
   // This will be case of write through disabled, and had to load a line.
   assign store_miss_ack = dcram_we_after_line_load;
 
   assign first_miss_err = biudata_error & dcqmem_cycstb_i;
 
   // Signal burst when in the load/store loop. We will always try to burst.
   assign burst = (state == `OR1200_DCFSM_LOOP2);
 
   //
   // Main DC FSM
   //
   always @(posedge clk or `OR1200_RST_EVENT rst) begin
      if (rst == `OR1200_RST_VALUE) begin
         state <=  `OR1200_DCFSM_IDLE;
         addr_r <=  32'b0;
         hitmiss_eval <=  1'b0;
         store <=  1'b0;
         load <=  1'b0;
         cnt <=  3'b000;
         cache_miss <=  1'b0;
         cache_dirty_needs_writeback <= 1'b0;
         cache_inhibit <=  1'b0;
         did_early_load_ack <= 1'b0;
         cache_spr_block_flush <= 1'b0;
         cache_spr_block_writeback <= 1'b0;
      end
      else
        case (state)    // synopsys parallel_case
 
          `OR1200_DCFSM_IDLE : begin
             if (dc_en & (dc_block_flush | dc_block_writeback))
               begin
                  cache_spr_block_flush <= dc_block_flush;
                  cache_spr_block_writeback <= dc_block_writeback;
                  hitmiss_eval <= 1'b1;
                  state <= `OR1200_DCFSM_FLUSH5;
                  addr_r <=  spr_dat_i;
               end
             else if (dc_en & dcqmem_cycstb_i)
               begin
                  state <= `OR1200_DCFSM_CLOADSTORE;
                  hitmiss_eval <=  1'b1;
                  store <=  dcqmem_we_i;
                  load <=  !dcqmem_we_i;
               end
 
 
          end // case: `OR1200_DCFSM_IDLE
 
          `OR1200_DCFSM_CLOADSTORE: begin
             hitmiss_eval <=  1'b0;
             if (hitmiss_eval) begin
                cache_inhibit <=  dcqmem_ci_i; // Check for cache inhibit here
                cache_miss <=  tagcomp_miss;
                cache_dirty_needs_writeback <= dirty;
                addr_r <=  lsu_addr;
             end
 
             // Evaluate any cache line load/stores in first cycle:
                             //
             if (hitmiss_eval & tagcomp_miss & !(store & writethrough) &
                 !dcqmem_ci_i)
               begin
                  // Miss - first either:
                  //  1) write back dirty line 
                  if (dirty) begin
                     // Address for writeback
                     addr_r <=  {tag, lsu_addr[`OR1200_DCINDXH:2],2'd0};
                     load <= 1'b0;
                     store <= 1'b1;
`ifdef OR1200_VERBOSE
                     $display("%t: dcache miss and dirty", $time);
`endif
                  end
                  //  2) load requested line
                  else begin
                     addr_r <=  lsu_addr;
                     load <= 1'b1;
                     store <= 1'b0;
                  end // else: !if(dirty)
                  state <= `OR1200_DCFSM_LOOP2;
                  // Set the counter for the burst accesses
                  cnt <=  `OR1200_DCLS-1;
               end
             else if (// Strobe goes low
                      !dcqmem_cycstb_i |
                      // Cycle finishes
                      (!hitmiss_eval & (biudata_valid | biudata_error)) |
                      // Cache hit in first cycle....
                      (hitmiss_eval & !tagcomp_miss & !dcqmem_ci_i &
                      // .. and you're not doing a writethrough store..
                      !(store & writethrough))) begin
                state <=  `OR1200_DCFSM_IDLE;
                load <=  1'b0;
                store <= 1'b0;
                cache_inhibit <= 1'b0;
                cache_dirty_needs_writeback <= 1'b0;
             end
          end // case: `OR1200_DCFSM_CLOADSTORE   
 
          `OR1200_DCFSM_LOOP2 : begin // loop/abort          
             if (!dc_en| biudata_error) begin
                state <=  `OR1200_DCFSM_IDLE;
                load <=  1'b0;
                store <= 1'b0;
                cnt <= 1'b0;
             end
             if (biudata_valid & (|cnt)) begin
                cnt <=  cnt - 1'b1;
                addr_r[3:2] <=  addr_r[3:2] + 1'b1;
             end
             else if (biudata_valid & !(|cnt)) begin
                state <= `OR1200_DCFSM_LOOP3;
                addr_r <=  lsu_addr;
                load <= 1'b0;
                store <= 1'b0;
             end
 
             // Track if we did an early ack during a load
             if (load_miss_ack)
               did_early_load_ack <= 1'b1;
 
 
          end // case: `OR1200_DCFSM_LOOP2
 
          `OR1200_DCFSM_LOOP3: begin // figure out next step
             if (cache_dirty_needs_writeback) begin
                // Just did store of the dirty line so now load new one
                load <= 1'b1;
                // Set the counter for the burst accesses
                cnt <=  `OR1200_DCLS-1;
                // Address of line to be loaded
                addr_r <=  lsu_addr;
                cache_dirty_needs_writeback <= 1'b0;
                state <= `OR1200_DCFSM_LOOP2;
             end // if (cache_dirty_needs_writeback)
             else if (cache_spr_block_flush | cache_spr_block_writeback) begin
                // Just wrote back the line to memory, we're finished.
                cache_spr_block_flush <= 1'b0;
                cache_spr_block_writeback <= 1'b0;
                state <= `OR1200_DCFSM_WAITSPRCS7;
             end
             else begin
                // Just loaded a new line, finish up
                did_early_load_ack <= 1'b0;
                state <= `OR1200_DCFSM_LOOP4;
             end
          end // case: `OR1200_DCFSM_LOOP3
 
          `OR1200_DCFSM_LOOP4: begin
             state <=  `OR1200_DCFSM_IDLE;
          end
 
          `OR1200_DCFSM_FLUSH5: begin
             hitmiss_eval <= 1'b0;
             if (hitmiss_eval & !tag_v)
               begin
                  // Not even cached, just ignore
                  cache_spr_block_flush <= 1'b0;
                  cache_spr_block_writeback <= 1'b0;
                  state <=  `OR1200_DCFSM_WAITSPRCS7;
               end
             else if (hitmiss_eval & tag_v)
               begin
                  // Tag is valid - what do we do?
                  if ((cache_spr_block_flush | cache_spr_block_writeback) &
                      dirty) begin
                     // Need to writeback
                     // Address for writeback (spr_dat_i has already changed so
                     // use line number from addr_r)
                     addr_r <=  {tag, addr_r[`OR1200_DCINDXH:2],2'd0};
                     load <= 1'b0;
                     store <= 1'b1;
`ifdef OR1200_VERBOSE
                     $display("%t: block flush: dirty block", $time);
`endif
                     state <= `OR1200_DCFSM_LOOP2;
                     // Set the counter for the burst accesses
                     cnt <=  `OR1200_DCLS-1;
                  end
                  else if (cache_spr_block_flush & !dirty)
                    begin
                       // Line not dirty, just need to invalidate
                       state <=  `OR1200_DCFSM_INV6;
                    end // else: !if(dirty)
                  else if (cache_spr_block_writeback & !dirty)
                    begin
                       // Nothing to do - line is valid but not dirty
                       cache_spr_block_writeback <= 1'b0;
                       state <=  `OR1200_DCFSM_WAITSPRCS7;
                    end
          end // if (hitmiss_eval & tag_v)
          end
          `OR1200_DCFSM_INV6: begin
             cache_spr_block_flush <= 1'b0;
             // Wait until SPR CS goes low before going back to idle
             if (!spr_cswe)
               state <=  `OR1200_DCFSM_IDLE;
          end
          `OR1200_DCFSM_WAITSPRCS7: begin
             // Wait until SPR CS goes low before going back to idle
             if (!spr_cswe)
               state <=  `OR1200_DCFSM_IDLE;
          end
 
        endcase // case (state)
 
   end // always @ (posedge clk or `OR1200_RST_EVENT rst)
 
 
endmodule

Line No.	Rev	Author	Line
1	10	unneback	`//////////////////////////////////////////////////////////////////////`
2			`//// ////`
3			`//// OR1200's DC FSM ////`
4			`//// ////`
5			`//// This file is part of the OpenRISC 1200 project ////`
6	258	julius	`//// http://opencores.org/project,or1k ////`
7	10	unneback	`//// ////`
8			`//// Description ////`
9			`//// Data cache state machine ////`
10			`//// ////`
11			`//// To Do: ////`
12	258	julius	`//// - Test error during line read or write ////`
13	10	unneback	`//// ////`
14			`//// Author(s): ////`
15			`//// - Damjan Lampret, lampret@opencores.org ////`
16	258	julius	`//// - Julius Baxter, julius@opencores.org ////`
17	10	unneback	`//// ////`
18			`//////////////////////////////////////////////////////////////////////`
19			`//// ////`
20	258	julius	`//// Copyright (C) 2000, 2010 Authors and OPENCORES.ORG ////`
21	10	unneback	`//// ////`
22			`//// This source file may be used and distributed without ////`
23			`//// restriction provided that this copyright statement is not ////`
24			`//// removed from the file and that any derivative work contains ////`
25			`//// the original copyright notice and the associated disclaimer. ////`
26			`//// ////`
27			`//// This source file is free software; you can redistribute it ////`
28			`//// and/or modify it under the terms of the GNU Lesser General ////`
29			`//// Public License as published by the Free Software Foundation; ////`
30			`//// either version 2.1 of the License, or (at your option) any ////`
31			`//// later version. ////`
32			`//// ////`
33			`//// This source is distributed in the hope that it will be ////`
34			`//// useful, but WITHOUT ANY WARRANTY; without even the implied ////`
35			`//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////`
36			`//// PURPOSE. See the GNU Lesser General Public License for more ////`
37			`//// details. ////`
38			`//// ////`
39			`//// You should have received a copy of the GNU Lesser General ////`
40			`//// Public License along with this source; if not, download it ////`
41			`//// from http://www.opencores.org/lgpl.shtml ////`
42			`//// ////`
43			`//////////////////////////////////////////////////////////////////////`
44			`//`
45	141	marcus.erl	`// $Log: or1200_dc_fsm.v,v $`
46			`// Revision 2.0 2010/06/30 11:00:00 ORSoC`
47			`// Minor update:`
48			`// Bugs fixed.`
49			`//`
50	10	unneback
51			`// synopsys translate_off`
52			`include "timescale.v"
53			`// synopsys translate_on`
54			`include "or1200_defines.v"
55
56			`define OR1200_DCFSM_IDLE 3'd0
57	258	julius	`define OR1200_DCFSM_CLOADSTORE 3'd1
58			`define OR1200_DCFSM_LOOP2 3'd2
59			`define OR1200_DCFSM_LOOP3 3'd3
60			`define OR1200_DCFSM_LOOP4 3'd4
61			`define OR1200_DCFSM_FLUSH5 3'd5
62			`define OR1200_DCFSM_INV6 3'd6
63			`define OR1200_DCFSM_WAITSPRCS7 3'd7
64	10	unneback
65	258	julius
66
67	10	unneback	`//`
68			`// Data cache FSM for cache line of 16 bytes (4x singleword)`
69			`//`
70
71	258	julius	`module or1200_dc_fsm`
72			`(`
73			`// Clock and reset`
74			`clk, rst,`
75
76			`// Internal i/f to top level DC`
77			`dc_en, dcqmem_cycstb_i, dcqmem_ci_i, dcqmem_we_i, dcqmem_sel_i,`
78			`tagcomp_miss, biudata_valid, biudata_error, lsu_addr,`
79			`dcram_we, biu_read, biu_write, biu_do_sel, dcram_di_sel, first_hit_ack,`
80			`first_miss_ack, first_miss_err, burst, tag_we, tag_valid, dc_addr,`
81			`dc_no_writethrough, tag_dirty, dirty, tag, tag_v, dc_block_flush,`
82			`dc_block_writeback, spr_dat_i, mtspr_dc_done, spr_cswe`
83			`);`
84	10	unneback
85	258	julius	`//`
86			`// I/O`
87			`//`
88			`input clk;`
89			`input rst;`
90			`input dc_en;`
91			`input dcqmem_cycstb_i;`
92			`input dcqmem_ci_i;`
93			`input dcqmem_we_i;`
94			`input [3:0] dcqmem_sel_i;`
95			`input tagcomp_miss;`
96			`input biudata_valid;`
97			`input biudata_error;`
98			`input [31:0] lsu_addr;`
99			`output [3:0] dcram_we;`
100			`output biu_read;`
101			`output biu_write;`
102			`output dcram_di_sel;`
103			`output biu_do_sel;`
104			`output first_hit_ack;`
105			`output first_miss_ack;`
106			`output first_miss_err;`
107			`output burst;`
108			`output tag_we;`
109			`output tag_valid;`
110			`output [31:0] dc_addr;`
111			`input dc_no_writethrough;`
112			`output tag_dirty;`
113			`input dirty;`
114			input [`OR1200_DCTAG_W-2:0] tag;
115			`input tag_v;`
116			`input dc_block_flush;`
117			`input dc_block_writeback;`
118			`input [31:0] spr_dat_i;`
119			`output mtspr_dc_done;`
120			`input spr_cswe;`
121
122
123			`//`
124			`// Internal wires and regs`
125			`//`
126			`reg [31:0] addr_r;`
127			`reg [2:0] state;`
128			`reg [2:0] cnt;`
129			`reg hitmiss_eval;`
130			`reg store;`
131			`reg load;`
132			`reg cache_inhibit;`
133			`reg cache_miss;`
134			`reg cache_dirty_needs_writeback;`
135			`reg did_early_load_ack;`
136			`reg cache_spr_block_flush;`
137			`reg cache_spr_block_writeback;`
138			`reg cache_wb;`
139			`wire load_hit_ack;`
140			`wire load_miss_ack;`
141			`wire load_inhibit_ack;`
142			`wire store_hit_ack;`
143			`wire store_hit_writethrough_ack;`
144			`wire store_miss_writethrough_ack;`
145			`wire store_inhibit_ack;`
146			`wire store_miss_ack;`
147			`wire dcram_we_after_line_load;`
148			`wire dcram_we_during_line_load;`
149			`wire tagram_we_end_of_loadstore_loop;`
150			`wire tagram_dirty_bit_set;`
151			`wire writethrough;`
152			`wire cache_inhibit_with_eval;`
153			`wire [1:0] next_addr_word;`
154	10	unneback
155	258	julius	`//`
156			`// Cache inhibit`
157			`//`
158
159			`// Indicates whether cache is inhibited, during hitmiss_eval and after`
160			`assign cache_inhibit_with_eval = (hitmiss_eval & dcqmem_ci_i) \|`
161			`(!hitmiss_eval & cache_inhibit);`
162
163			`//`
164			`// Generate of DCRAM write enables`
165			`//`
166	10	unneback
167	258	julius	`// WE when non-writethrough, and had to wait for a line to load.`
168			assign dcram_we_after_line_load = (state == `OR1200_DCFSM_LOOP3) &
169			`dcqmem_we_i & !cache_dirty_needs_writeback &`
170			`!did_early_load_ack;`
171	10	unneback
172	258	julius	`// WE when receiving the data cache line`
173			assign dcram_we_during_line_load = (state == `OR1200_DCFSM_LOOP2) & load &
174			`biudata_valid;`
175
176			`assign dcram_we =(// Write when hit - make sure it is only when hit - could`
177			`// maybe be doing write through and don't want to corrupt`
178			`// cache lines corresponding to the writethrough addr_r.`
179			`({4{store_hit_ack \| store_hit_writethrough_ack}} \|`
180			`// Write after load of line`
181			`{4{dcram_we_after_line_load}}) &`
182			`dcqmem_sel_i ) \|`
183			`// Write during load`
184			`{4{dcram_we_during_line_load}};`
185	10	unneback
186	258	julius	`//`
187			`// Tag RAM signals`
188			`//`
189
190			`// WE to tag RAM when we finish loading a line.`
191			assign tagram_we_end_of_loadstore_loop = ((state==`OR1200_DCFSM_LOOP2) &
192			`biudata_valid & !(\|cnt));`
193
194			`ifndef OR1200_DC_WRITETHROUGH
195			`// No writethrough, so mark a line dirty whenever we write to it`
196			`assign tagram_dirty_bit_set = store_hit_ack \| store_miss_ack;`
197	10	unneback
198	258	julius	`// Generate done signal for MTSPR instructions that may block execution`
199			`assign mtspr_dc_done = // Either DC disabled or we're not selected, or`
200			`!dc_en \| !spr_cswe \|`
201			`// Requested address not valid or writeback and !dirty`
202			((state==`OR1200_DCFSM_FLUSH5) &
203			`(!tag_v \| (cache_spr_block_writeback & !dirty))) \|`
204			`// Writeback or flush is finished`
205			((state==`OR1200_DCFSM_LOOP3) &
206			`(cache_spr_block_flush \| cache_spr_block_writeback))\|`
207			`// Invalidate of clean line finished`
208			((state==`OR1200_DCFSM_INV6) & cache_spr_block_flush);
209
210
211			`else
212			`ifdef OR1200_DC_NOSTACKWRITETHROUGH
213			`// For dirty bit setting when having writethrough but not for stack`
214			`assign tagram_dirty_bit_set = store_hit_ack \| store_miss_ack;`
215			`else
216			`// Lines will never be dirty if always writethrough`
217			`assign tagram_dirty_bit_set = 0;`
218			`endif
219
220			`assign mtspr_dc_done = 1'b1;`
221
222			`endif
223	10	unneback
224	258	julius	`assign tag_dirty = tagram_dirty_bit_set;`
225
226			`// WE to tag RAM`
227			`assign tag_we = tagram_we_end_of_loadstore_loop \|`
228			tagram_dirty_bit_set \| (state == `OR1200_DCFSM_INV6);
229
230	10	unneback
231	258	julius	`// Valid bit`
232			`// Set valid when end of line load, or marking dirty (is still valid)`
233			`assign tag_valid = ( tagram_we_end_of_loadstore_loop &`
234			`(load \| (store & cache_spr_block_writeback)) ) \|`
235			`tagram_dirty_bit_set;`
236	10	unneback
237	258	julius
238
239			`//`
240			`// BIU read and write`
241			`//`
242
243			`assign biu_read = // Bus read request when:`
244			`// 1) Have a miss and not dirty or a load with inhibit`
245			((state == `OR1200_DCFSM_CLOADSTORE) &
246			`(((hitmiss_eval & tagcomp_miss & !dirty &`
247			`!(store & writethrough)) \|`
248			`(load & cache_inhibit_with_eval)) & dcqmem_cycstb_i)) \|`
249			`// 2) In the loop and loading`
250			((state == `OR1200_DCFSM_LOOP2) & load);
251
252
253			`assign biu_write = // Bus write request when:`
254			`// 1) Have a miss and dirty or store with inhibit`
255			((state == `OR1200_DCFSM_CLOADSTORE) &
256			`(((hitmiss_eval & tagcomp_miss & dirty) \|`
257			`(store & writethrough)) \|`
258			`(store & cache_inhibit_with_eval)) & dcqmem_cycstb_i) \|`
259			`// 2) In the loop and storing`
260			((state == `OR1200_DCFSM_LOOP2) & store);
261
262			`//`
263			`// Select for data to actual cache RAM (from LSU or BIU)`
264			`//`
265			`// Data to DCRAM - from external bus when loading (from IU when store)`
266			`assign dcram_di_sel = load;`
267			`// Data to external bus - always from IU except in case of bursting back`
268			`// the line to memory. (1 selects DCRAM)`
269			assign biu_do_sel = (state == `OR1200_DCFSM_LOOP2) & store;
270
271			`// 2-bit wire for calculating next word of burst write`
272			`assign next_addr_word = addr_r[3:2] + 1;`
273
274			`// Address to cache RAM (tag address also derived from this)`
275			`assign dc_addr =`
276			`// First check if we've got a block flush or WB op`
277			`((dc_block_flush & !cache_spr_block_flush) \|`
278			`(dc_block_writeback & !cache_spr_block_writeback)) ?`
279			`spr_dat_i :`
280			(state==`OR1200_DCFSM_FLUSH5) ? addr_r:
281			`// If no SPR action, then always put out address from LSU`
282			(state==`OR1200_DCFSM_IDLE \| hitmiss_eval) ? lsu_addr :
283			`// Next, if in writeback loop, when ACKed must immediately`
284			`// output next word address (the RAM address takes a cycle`
285			`// to increment, but it's needed immediately for burst)`
286			`// otherwise, output our registered address.`
287			(state==`OR1200_DCFSM_LOOP2 & biudata_valid & store ) ?
288			`{addr_r[31:4], next_addr_word, 2'b00} : addr_r;`
289
290			`ifdef OR1200_DC_WRITETHROUGH
291			`ifdef OR1200_DC_NOSTACKWRITETHROUGH
292			`assign writethrough = !dc_no_writethrough;`
293			`else
294			`assign writethrough = 1;`
295			`endif
296			`else
297			`assign writethrough = 0;`
298			`endif
299
300			`//`
301			`// ACK generation for LSU`
302			`//`
303
304			`// ACK for when it's a cache hit`
305			`assign first_hit_ack = load_hit_ack \| store_hit_ack \|`
306			`store_hit_writethrough_ack \|`
307			`store_miss_writethrough_ack \|`
308			`store_inhibit_ack \| store_miss_ack ;`
309
310			`// ACK for when it's a cache miss - load only, is used in MUX for data back`
311			`// LSU straight off external data bus. In`
312			`// this was is also used for cache inhibit`
313			`// loads.`
314			`assign first_miss_ack = load_miss_ack \| load_inhibit_ack;`
315
316			`// ACK cache hit on load`
317			assign load_hit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
318			`hitmiss_eval & !tagcomp_miss & !dcqmem_ci_i & load;`
319
320			`// ACK cache hit on store, no writethrough`
321			assign store_hit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
322			`hitmiss_eval & !tagcomp_miss & !dcqmem_ci_i &`
323			`store & !writethrough;`
324
325			`// ACK cache hit on store with writethrough`
326			assign store_hit_writethrough_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
327			`!cache_miss & !cache_inhibit &`
328			`store & writethrough & biudata_valid;`
329
330			`// ACK cache miss on store with writethrough`
331			assign store_miss_writethrough_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
332			`cache_miss & !cache_inhibit &`
333			`store & writethrough & biudata_valid;`
334
335			`// ACK store when cacheinhibit`
336			assign store_inhibit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
337			`store & cache_inhibit & biudata_valid;`
338
339
340			`// Get the _early_ ack on first ACK back from wishbone during load only`
341			`// Condition is that we're in the loop - that it's the first ack we get (can`
342			`// tell from value of cnt), and we're loading a line to read from it (not`
343			`// loading to write to it, in the case of a write without writethrough.)`
344			assign load_miss_ack = ((state== `OR1200_DCFSM_LOOP2) & load &
345			(cnt==`OR1200_DCLS-1) & biudata_valid &
346			`!(dcqmem_we_i & !writethrough));`
347
348			assign load_inhibit_ack = (state == `OR1200_DCFSM_CLOADSTORE) &
349			`load & cache_inhibit & biudata_valid;`
350
351			`// This will be case of write through disabled, and had to load a line.`
352			`assign store_miss_ack = dcram_we_after_line_load;`
353
354			`assign first_miss_err = biudata_error & dcqmem_cycstb_i;`
355
356			`// Signal burst when in the load/store loop. We will always try to burst.`
357			assign burst = (state == `OR1200_DCFSM_LOOP2);
358
359			`//`
360			`// Main DC FSM`
361			`//`
362	358	julius	always @(posedge clk or `OR1200_RST_EVENT rst) begin
363			if (rst == `OR1200_RST_VALUE) begin
364	258	julius	state <= `OR1200_DCFSM_IDLE;
365			`addr_r <= 32'b0;`
366			`hitmiss_eval <= 1'b0;`
367			`store <= 1'b0;`
368			`load <= 1'b0;`
369			`cnt <= 3'b000;`
370			`cache_miss <= 1'b0;`
371			`cache_dirty_needs_writeback <= 1'b0;`
372			`cache_inhibit <= 1'b0;`
373			`did_early_load_ack <= 1'b0;`
374			`cache_spr_block_flush <= 1'b0;`
375			`cache_spr_block_writeback <= 1'b0;`
376			`end`
377			`else`
378	10	unneback	`case (state) // synopsys parallel_case`
379	258	julius
380			`OR1200_DCFSM_IDLE : begin
381			`if (dc_en & (dc_block_flush \| dc_block_writeback))`
382			`begin`
383			`cache_spr_block_flush <= dc_block_flush;`
384			`cache_spr_block_writeback <= dc_block_writeback;`
385			`hitmiss_eval <= 1'b1;`
386			state <= `OR1200_DCFSM_FLUSH5;
387			`addr_r <= spr_dat_i;`
388			`end`
389			`else if (dc_en & dcqmem_cycstb_i)`
390			`begin`
391			state <= `OR1200_DCFSM_CLOADSTORE;
392			`hitmiss_eval <= 1'b1;`
393			`store <= dcqmem_we_i;`
394			`load <= !dcqmem_we_i;`
395			`end`
396
397
398			end // case: `OR1200_DCFSM_IDLE
399
400			`OR1200_DCFSM_CLOADSTORE: begin
401			`hitmiss_eval <= 1'b0;`
402			`if (hitmiss_eval) begin`
403			`cache_inhibit <= dcqmem_ci_i; // Check for cache inhibit here`
404			`cache_miss <= tagcomp_miss;`
405			`cache_dirty_needs_writeback <= dirty;`
406			`addr_r <= lsu_addr;`
407			`end`
408
409			`// Evaluate any cache line load/stores in first cycle:`
410			`//`
411			`if (hitmiss_eval & tagcomp_miss & !(store & writethrough) &`
412			`!dcqmem_ci_i)`
413			`begin`
414			`// Miss - first either:`
415			`// 1) write back dirty line`
416			`if (dirty) begin`
417			`// Address for writeback`
418			addr_r <= {tag, lsu_addr[`OR1200_DCINDXH:2],2'd0};
419			`load <= 1'b0;`
420			`store <= 1'b1;`
421			`ifdef OR1200_VERBOSE
422			`$display("%t: dcache miss and dirty", $time);`
423	10	unneback	`endif
424	258	julius	`end`
425			`// 2) load requested line`
426			`else begin`
427			`addr_r <= lsu_addr;`
428			`load <= 1'b1;`
429			`store <= 1'b0;`
430			`end // else: !if(dirty)`
431			state <= `OR1200_DCFSM_LOOP2;
432			`// Set the counter for the burst accesses`
433			cnt <= `OR1200_DCLS-1;
434			`end`
435			`else if (// Strobe goes low`
436			`!dcqmem_cycstb_i \|`
437			`// Cycle finishes`
438			`(!hitmiss_eval & (biudata_valid \| biudata_error)) \|`
439			`// Cache hit in first cycle....`
440			`(hitmiss_eval & !tagcomp_miss & !dcqmem_ci_i &`
441			`// .. and you're not doing a writethrough store..`
442			`!(store & writethrough))) begin`
443			state <= `OR1200_DCFSM_IDLE;
444			`load <= 1'b0;`
445			`store <= 1'b0;`
446			`cache_inhibit <= 1'b0;`
447			`cache_dirty_needs_writeback <= 1'b0;`
448			`end`
449			end // case: `OR1200_DCFSM_CLOADSTORE
450
451			`OR1200_DCFSM_LOOP2 : begin // loop/abort
452			`if (!dc_en\| biudata_error) begin`
453			state <= `OR1200_DCFSM_IDLE;
454			`load <= 1'b0;`
455			`store <= 1'b0;`
456			`cnt <= 1'b0;`
457			`end`
458			`if (biudata_valid & (\|cnt)) begin`
459			`cnt <= cnt - 1'b1;`
460			`addr_r[3:2] <= addr_r[3:2] + 1'b1;`
461			`end`
462			`else if (biudata_valid & !(\|cnt)) begin`
463			state <= `OR1200_DCFSM_LOOP3;
464			`addr_r <= lsu_addr;`
465			`load <= 1'b0;`
466			`store <= 1'b0;`
467			`end`
468
469			`// Track if we did an early ack during a load`
470			`if (load_miss_ack)`
471			`did_early_load_ack <= 1'b1;`
472
473
474			end // case: `OR1200_DCFSM_LOOP2
475
476			`OR1200_DCFSM_LOOP3: begin // figure out next step
477			`if (cache_dirty_needs_writeback) begin`
478			`// Just did store of the dirty line so now load new one`
479			`load <= 1'b1;`
480			`// Set the counter for the burst accesses`
481			cnt <= `OR1200_DCLS-1;
482			`// Address of line to be loaded`
483			`addr_r <= lsu_addr;`
484			`cache_dirty_needs_writeback <= 1'b0;`
485			state <= `OR1200_DCFSM_LOOP2;
486			`end // if (cache_dirty_needs_writeback)`
487			`else if (cache_spr_block_flush \| cache_spr_block_writeback) begin`
488			`// Just wrote back the line to memory, we're finished.`
489			`cache_spr_block_flush <= 1'b0;`
490			`cache_spr_block_writeback <= 1'b0;`
491			state <= `OR1200_DCFSM_WAITSPRCS7;
492			`end`
493			`else begin`
494			`// Just loaded a new line, finish up`
495			`did_early_load_ack <= 1'b0;`
496			state <= `OR1200_DCFSM_LOOP4;
497			`end`
498			end // case: `OR1200_DCFSM_LOOP3
499
500			`OR1200_DCFSM_LOOP4: begin

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