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lampret |
//////////////////////////////////////////////////////////////////////
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//// ////
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//// OR1200's Freeze logic ////
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//// ////
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//// This file is part of the OpenRISC 1200 project ////
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//// http://www.opencores.org/cores/or1k/ ////
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//// ////
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//// Description ////
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//// Generates all freezes and stalls inside RISC ////
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//// ////
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//// To Do: ////
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//// - make it smaller and faster ////
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//// ////
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//// Author(s): ////
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//// - Damjan Lampret, lampret@opencores.org ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//// ////
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//// Copyright (C) 2000 Authors and OPENCORES.ORG ////
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//// ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer. ////
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//// ////
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//// This source file is free software; you can redistribute it ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// later version. ////
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//// ////
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//// This source is distributed in the hope that it will be ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// details. ////
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//// ////
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//// You should have received a copy of the GNU Lesser General ////
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//// Public License along with this source; if not, download it ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//
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// CVS Revision History
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//
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lampret |
// $Log: not supported by cvs2svn $
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// Revision 1.7 2001/10/14 13:12:09 lampret
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// MP3 version.
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//
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lampret |
// Revision 1.1.1.1 2001/10/06 10:18:36 igorm
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// no message
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//
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// Revision 1.2 2001/08/09 13:39:33 lampret
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// Major clean-up.
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//
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// Revision 1.1 2001/07/20 00:46:03 lampret
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// Development version of RTL. Libraries are missing.
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//
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//
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// synopsys translate_off
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`include "timescale.v"
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// synopsys translate_on
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`include "defines.v"
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`define NO_FREEZE 3'd0
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`define FREEZE_BYDC 3'd1
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`define FREEZE_BYMULTICYCLE 3'd2
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`define WAIT_LSU_TO_FINISH 3'd3
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`define WAIT_IC 3'd4
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//
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// Freeze logic (stalls CPU pipeline, ifetcher etc.)
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//
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module frz_logic(
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// Clock and reset
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clk, rst,
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// Internal i/f
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multicycle, except_flushpipe, lsu_stall, if_stall,
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dclsu_unstall, branch_stall, du_stall, mac_stall,
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force_dslot_fetch,
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if_freeze, id_freeze, ex_freeze, wb_freeze
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);
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//
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// I/O
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//
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input clk;
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input rst;
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input [`MULTICYCLE_WIDTH-1:0] multicycle;
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input except_flushpipe;
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input lsu_stall;
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input if_stall;
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input dclsu_unstall;
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input branch_stall;
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input force_dslot_fetch;
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input du_stall;
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input mac_stall;
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output if_freeze;
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output id_freeze;
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output ex_freeze;
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output wb_freeze;
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//
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// Internal wires and regs
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//
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reg multicycle_freeze;
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reg [2:0] state2;
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reg [2:0] multicycle_cnt;
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reg done_once;
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//
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// Pipeline freeze
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//
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// Rules how to create freeze signals:
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// 1. Not overwriting pipeline stages:
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// Frreze signals at the beginning of pipeline (such as if_freeze) can be asserted more
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// often than freeze signals at the of pipeline (such as wb_freeze). In other words, wb_freeze must never
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// be asserted when ex_freeze is not. ex_freeze must never be asserted when id_freeze is not etc.
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//
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// 2. Inserting NOPs in the middle of pipeline only if supported:
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// At this time, only ex_freeze (and wb_freeze) can be deassrted when id_freeze (and if_freeze) are asserted.
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// This way NOP is asserted from stage ID into EX stage.
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//
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assign if_freeze = id_freeze;
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assign id_freeze = (lsu_stall | (~dclsu_unstall & if_stall) | multicycle_freeze | force_dslot_fetch) & ~except_flushpipe | du_stall;
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assign ex_freeze = wb_freeze;
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assign wb_freeze = (lsu_stall | (~dclsu_unstall & if_stall) | multicycle_freeze) & ~except_flushpipe | du_stall | mac_stall;
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//
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// Freeze FSM2
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//
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always @(posedge clk or posedge rst) begin
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if (rst) begin
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state2 <= #1 `NO_FREEZE;
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multicycle_freeze <= #1 1'b1;
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multicycle_cnt <= #1 3'b0;
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done_once <= #1 1'b0;
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end
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else
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lampret |
case (state2) // synopsys parallel_case
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`NO_FREEZE :
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if (done_once && ex_freeze)
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done_once <= #1 1'b1;
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else if (multicycle) begin
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state2 <= #1 `FREEZE_BYMULTICYCLE;
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multicycle_freeze <= #1 1'b1;
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multicycle_cnt <= #1 multicycle - 'd1;
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done_once <= #1 1'b0;
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end
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else
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multicycle_freeze <= #1 1'b0;
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`FREEZE_BYMULTICYCLE :
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if (multicycle_cnt) begin
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multicycle_cnt <= #1 multicycle_cnt - 'd1;
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state2 <= #1 `FREEZE_BYMULTICYCLE;
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end
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else if (lsu_stall) begin
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state2 <= #1 `WAIT_LSU_TO_FINISH;
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multicycle_freeze <= #1 1'b0;
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end
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else if (if_stall) begin
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state2 <= #1 `NO_FREEZE;
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done_once <= #1 1'b1;
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multicycle_freeze <= #1 1'b0;
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end
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else begin
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state2 <= #1 `NO_FREEZE;
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multicycle_freeze <= #1 1'b0;
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end
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`WAIT_LSU_TO_FINISH:
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if (!lsu_stall && !(|multicycle)) begin
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state2 <= #1 `NO_FREEZE;
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end
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else if (!lsu_stall & (|multicycle)) begin
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state2 <= #1 `FREEZE_BYMULTICYCLE;
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multicycle_freeze <= #1 1'b1;
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multicycle_cnt <= #1 multicycle - 'd1;
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end
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endcase
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end
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endmodule
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