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

////                                                              ////

////  OR1200's Instruction MMU top level                          ////

////                                                              ////

////  This file is part of the OpenRISC 1200 project              ////

////  http://www.opencores.org/project,or1k                       ////

////                                                              ////

////  Description                                                 ////

////  Instantiation of all IMMU blocks.                           ////

////                                                              ////

////  To Do:                                                      ////

////   - cache inhibit                                            ////

////                                                              ////

////  Author(s):                                                  ////

////      - Damjan Lampret, lampret@opencores.org                 ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2000 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                     ////

////                                                              ////

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

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "or1200_defines.v"

//

// Insn MMU

//

module or1200_immu_top(

        // Rst and clk

        clk, rst,

        // CPU i/f

        ic_en, immu_en, supv, icpu_adr_i, icpu_cycstb_i,

        icpu_adr_o, icpu_tag_o, icpu_rty_o, icpu_err_o,

        // SR Interface

        boot_adr_sel_i,

        // SPR access

        spr_cs, spr_write, spr_addr, spr_dat_i, spr_dat_o,

`ifdef OR1200_BIST

        // RAM BIST

        mbist_si_i, mbist_so_o, mbist_ctrl_i,

`endif

        // QMEM i/f

        qmemimmu_rty_i, qmemimmu_err_i, qmemimmu_tag_i, qmemimmu_adr_o, qmemimmu_cycstb_o, qmemimmu_ci_o

);

parameter dw = `OR1200_OPERAND_WIDTH;

parameter aw = `OR1200_OPERAND_WIDTH;

parameter boot_adr = `OR1200_BOOT_ADR;

//

// I/O

//

//

// Clock and reset

//

input                           clk;

input                           rst;

//

// CPU I/F

//

input                           ic_en;

input                           immu_en;

input                           supv;

input   [aw-1:0]         icpu_adr_i;

input                           icpu_cycstb_i;

output  [aw-1:0]         icpu_adr_o;

output  [3:0]                    icpu_tag_o;

output                          icpu_rty_o;

output                          icpu_err_o;

//

// SR Interface

//

input                           boot_adr_sel_i;

//

// SPR access

//

input                           spr_cs;

input                           spr_write;

input   [aw-1:0]         spr_addr;

input   [31:0]                   spr_dat_i;

output  [31:0]                   spr_dat_o;

`ifdef OR1200_BIST

//

// RAM BIST

//

input mbist_si_i;

input [`OR1200_MBIST_CTRL_WIDTH - 1:0] mbist_ctrl_i;

output mbist_so_o;

`endif

//

// IC I/F

//

input                           qmemimmu_rty_i;

input                           qmemimmu_err_i;

input   [3:0]                    qmemimmu_tag_i;

output  [aw-1:0]         qmemimmu_adr_o;

output                          qmemimmu_cycstb_o;

output                          qmemimmu_ci_o;

//

// Internal wires and regs

//

wire                            itlb_spr_access;

wire    [31:`OR1200_IMMU_PS]    itlb_ppn;

wire                            itlb_hit;

wire                            itlb_uxe;

wire                            itlb_sxe;

wire    [31:0]                   itlb_dat_o;

wire                            itlb_en;

wire                            itlb_ci;

wire                            itlb_done;

wire                            fault;

wire                            miss;

wire                            page_cross;

reg     [31:0]                   icpu_adr_default;

reg                             icpu_adr_select;

reg             [31:0]           icpu_adr_o;

reg     [31:`OR1200_IMMU_PS]    icpu_vpn_r;

`ifdef OR1200_NO_IMMU

`else

reg                             itlb_en_r;

reg                             dis_spr_access_frst_clk;

reg                             dis_spr_access_scnd_clk;

`endif

//

// Implemented bits inside match and translate registers

//

// itlbwYmrX: vpn 31-10  v 0

// itlbwYtrX: ppn 31-10  uxe 7  sxe 6

//

// itlb memory width:

// 19 bits for ppn

// 13 bits for vpn

// 1 bit for valid

// 2 bits for protection

// 1 bit for cache inhibit

//

// icpu_adr_o

//

`ifdef OR1200_REGISTERED_OUTPUTS

wire    [31:0]                   icpu_adr_boot = boot_adr;

always @(`OR1200_RST_EVENT rst or posedge clk)

        // default value 

        if (rst == `OR1200_RST_VALUE) begin

                // select async. value due to reset state

                icpu_adr_default <=  32'h0000_0100;

                icpu_adr_select  <=  1'b1;

        end

        // selected value (different from default) is written 

        // into FF after reset state

        else if (icpu_adr_select) begin

                // dynamic value can only be assigned to FF out of reset!

                icpu_adr_default <=  icpu_adr_boot;

                // select FF value 

                icpu_adr_select  <=  1'b0;

        end

        else begin

                icpu_adr_default <=  icpu_adr_i;

        end

// select async. value for boot address after reset - PC jumps to the address 

// selected after boot! 

   //assign icpu_adr_boot = {(boot_adr_sel_i ? `OR1200_EXCEPT_EPH1_P : 

   // `OR1200_EXCEPT_EPH0_P), 12'h100} ;

always @(icpu_adr_boot or icpu_adr_default or icpu_adr_select)

        if (icpu_adr_select)

                // async. value is selected due to reset state 

                icpu_adr_o = icpu_adr_boot ;

        else

                // FF value is selected 2nd clock after reset state 

                icpu_adr_o = icpu_adr_default ;

`else

Unsupported !!!

`endif

//

// Page cross

//

// Asserted when CPU address crosses page boundary. Most of the time it is zero.

//

assign page_cross = icpu_adr_i[31:`OR1200_IMMU_PS] != icpu_vpn_r;

//

// Register icpu_adr_i's VPN for use when IMMU is not enabled but PPN is expected to come

// one clock cycle after offset part.

//

always @(posedge clk or `OR1200_RST_EVENT rst)

        if (rst == `OR1200_RST_VALUE)

                icpu_vpn_r <=  {32-`OR1200_IMMU_PS{1'b0}};

        else

                icpu_vpn_r <=  icpu_adr_i[31:`OR1200_IMMU_PS];

`ifdef OR1200_NO_IMMU

//

// Put all outputs in inactive state

//

assign spr_dat_o = 32'h00000000;

assign qmemimmu_adr_o = icpu_adr_i;

assign icpu_tag_o = qmemimmu_tag_i;

assign qmemimmu_cycstb_o = icpu_cycstb_i & ~page_cross;

assign icpu_rty_o = qmemimmu_rty_i;

assign icpu_err_o = qmemimmu_err_i;

assign qmemimmu_ci_o = `OR1200_IMMU_CI;

`ifdef OR1200_BIST

assign mbist_so_o = mbist_si_i;

`endif

`else

//

// ITLB SPR access

//

// 1200 - 12FF  itlbmr w0

// 1200 - 123F  itlbmr w0 [63:0]

//

// 1300 - 13FF  itlbtr w0

// 1300 - 133F  itlbtr w0 [63:0]

//

assign itlb_spr_access = spr_cs & ~dis_spr_access_scnd_clk;

//

// Disable ITLB SPR access

//

// This flops are used to mask ITLB miss/fault exception

// during first & second clock cycles of accessing ITLB SPR. In

// subsequent clock cycles it is assumed that ITLB SPR

// access was accomplished and that normal instruction fetching

// can proceed.

//

// spr_cs sets dis_spr_access_frst_clk and icpu_rty_o clears it.

// dis_spr_access_frst_clk  sets dis_spr_access_scnd_clk and 

// icpu_rty_o clears it.

//

always @(posedge clk or `OR1200_RST_EVENT rst)

        if (rst == `OR1200_RST_VALUE)

                dis_spr_access_frst_clk  <=  1'b0;

        else if (!icpu_rty_o)

                dis_spr_access_frst_clk  <=  1'b0;

        else if (spr_cs)

                dis_spr_access_frst_clk  <=  1'b1;

always @(posedge clk or `OR1200_RST_EVENT rst)

        if (rst == `OR1200_RST_VALUE)

                dis_spr_access_scnd_clk  <=  1'b0;

        else if (!icpu_rty_o)

                dis_spr_access_scnd_clk  <=  1'b0;

        else if (dis_spr_access_frst_clk)

                dis_spr_access_scnd_clk  <=  1'b1;

//

// Tags:

//

// OR1200_ITAG_TE - TLB miss Exception

// OR1200_ITAG_PE - Page fault Exception

//

assign icpu_tag_o = miss ? `OR1200_ITAG_TE : fault ? `OR1200_ITAG_PE : qmemimmu_tag_i;

//

// icpu_rty_o

//

// assign icpu_rty_o = !icpu_err_o & qmemimmu_rty_i;

//assign icpu_rty_o = qmemimmu_rty_i | itlb_spr_access & immu_en;

assign icpu_rty_o = qmemimmu_rty_i;

//

// icpu_err_o

//

assign icpu_err_o = miss | fault | qmemimmu_err_i;

//

// Assert itlb_en_r after one clock cycle and when there is no

// ITLB SPR access

//

always @(posedge clk or `OR1200_RST_EVENT rst)

        if (rst == `OR1200_RST_VALUE)

                itlb_en_r <=  1'b0;

        else

                itlb_en_r <=  itlb_en & ~itlb_spr_access;

//

// ITLB lookup successful

//

assign itlb_done = itlb_en_r & ~page_cross;

//

// Cut transfer when access (mtspr/mfspr) to/from ITLB occure or if something goes 

// wrong with translation. If IC is disabled, use delayed signals.

//

// assign qmemimmu_cycstb_o = (!ic_en & immu_en) ? ~(miss | fault) & icpu_cycstb_i & ~page_cross : (miss | fault) ? 1'b0 : icpu_cycstb_i & ~page_cross; // DL

//assign qmemimmu_cycstb_o = immu_en ? ~(miss | fault) & icpu_cycstb_i & ~page_cross & itlb_done : icpu_cycstb_i & ~page_cross;

assign qmemimmu_cycstb_o = immu_en ? ~(miss | fault) & icpu_cycstb_i & ~page_cross & itlb_done & ~itlb_spr_access : icpu_cycstb_i & ~page_cross;

//

// Cache Inhibit

//

// Cache inhibit is not really needed for instruction memory subsystem.

// If we would doq it, we would doq it like this.

// assign qmemimmu_ci_o = immu_en ? itlb_done & itlb_ci : `OR1200_IMMU_CI;

// However this causes an async combinatorial loop so we stick to

// no cache inhibit.

//assign qmemimmu_ci_o = `OR1200_IMMU_CI;

// Cache inhibit without an async combinatorial loop 

assign qmemimmu_ci_o = immu_en ? itlb_ci : `OR1200_IMMU_CI;

//

// Physical address is either translated virtual address or

// simply equal when IMMU is disabled

//

//assign qmemimmu_adr_o = itlb_done ? {itlb_ppn, icpu_adr_i[`OR1200_IMMU_PS-1:0]} : {icpu_vpn_r, icpu_adr_i[`OR1200_IMMU_PS-1:0]}; // DL: immu_en

assign qmemimmu_adr_o = immu_en & itlb_done ? {itlb_ppn, icpu_adr_i[`OR1200_IMMU_PS-1:2], 2'h0} : {icpu_vpn_r, icpu_adr_i[`OR1200_IMMU_PS-1:2], 2'h0};

reg     [31:0]                  spr_dat_reg;

//

// Output to SPRS unit

//

// spr_dat_o is registered on the 1st clock of spr read 

// so itlb can continue with process during execution of mfspr.

always @(posedge clk or `OR1200_RST_EVENT rst)

        if (rst == `OR1200_RST_VALUE)

                spr_dat_reg <=  32'h0000_0000;

        else if (spr_cs & !dis_spr_access_scnd_clk)

                spr_dat_reg <=  itlb_dat_o;

assign spr_dat_o = itlb_spr_access ? itlb_dat_o : spr_dat_reg;

//

// Page fault exception logic

//

assign fault = itlb_done &

                        (  (!supv & !itlb_uxe)          // Execute in user mode not enabled

                        || (supv & !itlb_sxe));         // Execute in supv mode not enabled

//

// TLB Miss exception logic

//

assign miss = itlb_done & !itlb_hit;

//

// ITLB Enable

//

assign itlb_en = immu_en & icpu_cycstb_i;

//

// Instantiation of ITLB

//

or1200_immu_tlb or1200_immu_tlb(

        // Rst and clk

        .clk(clk),

        .rst(rst),

        // I/F for translation

        .tlb_en(itlb_en),

        .vaddr(icpu_adr_i),

        .hit(itlb_hit),

        .ppn(itlb_ppn),

        .uxe(itlb_uxe),

        .sxe(itlb_sxe),

        .ci(itlb_ci),

`ifdef OR1200_BIST

        // RAM BIST

        .mbist_si_i(mbist_si_i),

        .mbist_so_o(mbist_so_o),

        .mbist_ctrl_i(mbist_ctrl_i),

`endif

        // SPR access

        .spr_cs(itlb_spr_access),

        .spr_write(spr_write),

        .spr_addr(spr_addr),

        .spr_dat_i(spr_dat_i),

        .spr_dat_o(itlb_dat_o)

);

`endif

endmodule