Subversion Repositories mpmc8

`timescale 1ns / 1ps

// ============================================================================

//        __

//   \\__/ o\    (C) 2015-2022  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch@finitron.ca

//       ||

//

// BSD 3-Clause License

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// modification, are permitted provided that the following conditions are met:

//

// 1. Redistributions of source code must retain the above copyright notice, this

//    list of conditions and the following disclaimer.

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// ============================================================================

//

import mpmc10_pkg::*;

module mpmc10_addr_resv_man(rst, clk, state,

        adr0, adr1, adr2, adr3, adr4, adr5, adr6, adr7,

        sr0, sr1, sr2, sr3, sr4, sr5, sr6, sr7,

        wch, we, wadr, cr, ch1_taghit,

        resv_ch, resv_adr, rack);

parameter NAR = 2;

input rst;

input clk;

input mpmc10_state_t state;

input [31:0] adr0;

input [31:0] adr1;

input [31:0] adr2;

input [31:0] adr3;

input [31:0] adr4;

input [31:0] adr5;

input [31:0] adr6;

input [31:0] adr7;

input sr0;

input sr1;

input sr2;

input sr3;

input sr4;

input sr5;

input sr6;

input sr7;

input [3:0] wch;

input cr;

input we;

input [31:0] wadr;

input ch1_taghit;

output reg [3:0] resv_ch [0:NAR-1];

output reg [31:0] resv_adr [0:NAR-1];

output reg [7:0] rack;  // reservation acknowledged

reg [19:0] resv_to_cnt;

wire [3:0] enc;

wire [7:0] srr = {sr7,sr6,sr5,sr4,sr3,sr2,sr1,sr0};

wire [31:0] adr [0:7];

assign adr[0] = adr0;

assign adr[1] = adr1;

assign adr[2] = adr2;

assign adr[3] = adr3;

assign adr[4] = adr4;

assign adr[5] = adr5;

assign adr[6] = adr6;

assign adr[7] = adr7;

roundRobin urr1

(

        .rst(rst),

        .clk(clk),

        .ce(1'b1),

        .req(srr),

        .lock(8'h00),

        .sel(),

        .sel_enc(enc)

);

// For address reservation below

reg [7:0] match;

always @(posedge clk)

if (rst)

        match <= 8'h00;

else begin

        if (match >= NAR)

                match <= 8'h00;

        else

                match <= match + 8'd1;

end

always_comb

        rack = ~srr | srr[enc];

// Managing address reservations

integer n7;

always_ff @(posedge clk)

if (rst) begin

        resv_to_cnt <= 20'd0;

        for (n7 = 0; n7 < NAR; n7 = n7 + 1)

                resv_ch[n7] <= 4'hF;

end

else begin

        resv_to_cnt <= resv_to_cnt + 20'd1;

        for (n7 = 0; n7 < 8; n7 = n7 + 1)

                if (enc==n7 && |srr)

                        reserve_adr({1'b0,n7[2:0]},adr[n7]);

        if (state==IDLE) begin

                if (we) begin

            if (cr) begin

                for (n7 = 0; n7 < NAR; n7 = n7 + 1)

                if ((resv_ch[n7]==wch) && (resv_adr[n7][31:4]==wadr[31:4]))

            resv_ch[n7] <= 4'hF;

            end

                end

        end

end

integer empty_resv;

function resv_held;

input [3:0] ch;

input [31:0] adr;

integer n8;

begin

        resv_held = 1'b0;

        for (n8 = 0; n8 < NAR; n8 = n8 + 1)

                if (resv_ch[n8]==ch && resv_adr[n8][31:5]==adr[31:5])

                        resv_held = 1'b1;

end

endfunction

// Find an empty reservation bucket

integer n9;

always_comb

begin

        empty_resv <= -1;

        for (n9 = 0; n9 < NAR; n9 = n9 + 1)

                if (resv_ch[n9]==4'hF)

                        empty_resv <= n9;

end

// Two reservation buckets are allowed for. There are two (or more) CPU's in the

// system and as long as they are not trying to control the same resource (the

// same semaphore) then they should be able to set a reservation. Ideally there

// could be more reservation buckets available, but it starts to be a lot of

// hardware.

task reserve_adr;

input [3:0] ch;

input [31:0] adr;

begin

        // Ignore an attempt to reserve an address that's already reserved. The LWAR

        // instruction is usually called in a loop and we don't want it to use up

        // all address reservations.

        if (!resv_held(ch,adr)) begin

                if (empty_resv >= 0) begin

                        resv_ch[empty_resv] <= ch;

                        resv_adr[empty_resv] <= adr;

                end

                // Here there were no free reservation buckets, so toss one of the

                // old reservations out.

                else begin

                        resv_ch[match] <= ch;

                        resv_adr[match] <= adr;

                end

        end

end

endtask

endmodule