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

////                                                              ////

////  Xilinx DDR2 controller Wishbone Interface                   ////

////                                                              ////

////  Description                                                 ////

////  Simple interface to the Xilinx MIG generated DDR2 controller////

////                                                              ////

////  To Do:                                                      ////

////   Increase usage of cache BRAM to maximum (currently only    ////

////   256 bytes out of about 8192)                               ////

////   Make this a Wishbone B3 registered feedback burst friendly ////

////   server.                                                    ////

////                                                              ////

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

////      - Julius Baxter, julius.baxter@orsoc.se                 ////

////                                                              ////

////                                                              ////

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

////                                                              ////

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

////                                                              ////

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

/*

 * The controller is design to stream lots of data out at the DDR2 controller's

 * rate. All we implement here is enough to do the simplest accesses into a

 * small cache, which eases the domain crossing headaches.

 *

 * This was originally written to handle a DDR2 part which is doing burst length

 * of 4 as a minimum via a databus which is 64-bits wide.

 *

 * This means the smallest accesses is 4*64=256-bits or 32-bytes.

 *

 * We are bridging to a 32-bit wide system bus, so this means we must handle

 * accesses in 8-word lots.

 *

 * A simple cache mechanism has been implemented, meaning we check if the cached

 * data has been written to, and therefore needs writing back to the main memory

 * before any other access can occur.

 *

 * Cache memory:

 * The cache memory is a core-generated module, instantiating something out

 * of the XilinxCoreLib. The reason is because an arrangement or RAMB36s with

 * different sized A and B data in/out ports can't be instantiated directly

 * for some reason.

 * What we have is side A with 32-bits, and side B with 128-bits wide.

 *

 * TODO:

 * This only supports 8-words for now but can easily be expanded, although

 * multiple way/associativity caching will require some extra work to handle

 * multiple cached addresses.

 *

 * But it should be easy enough to make this thing cache as much as its RAMB

 * resources allow (4-RAMB16s becuase due to the 128-bit DDR2-side interface)

 * which is about 8Kbyte.

 *

 * Multi-cycle paths:

 * Write:

 * To indicate that a writeback is occuring, a system-bus domain (wishbone, in

 * this case) signal is set, and then sampled in the controller domain whenever

 * a system-bus domain clock edge is detected. This register is "do_writeback"

 * and then the controller domain register "ddr2_write_done" is asserted when

 * the data has been written out of the RAMs and into the controller's fifos.

 * "ddr2_write_done" is then sampled by the system-bus domain and "do_writeback"

 * So there are paths between:

 * ( register -> (sampled by) -> register )

 * wb_clk:do_writeback -> ddr2_clk:do_writeback_ddr2_shifter

 * wb_clk:do_writeback -> ddr2_clk:ddr2_write_done

 * ddr2_clk:ddr2_write_done -> wb_clk:do_writeback

 *

 * Read:

 * The only signal crossing we have here is the one indicating the read data

 * has arrived into the cache RAM from the controller. The controller domain

 * register "ddr2_read_done" is set, and sampled in the system-bus domain by the

 * logic controlling the "do_readfrom" register. "ddr2_read_done" is cleared

 * when the controller domain sees that "do_readfrom" has been de-asserted.

 * So there are paths between:

 * ( register -> (sampled by) -> register )

 * ddr2_clk:ddr2_read_done -> wb_clk:do_readfrom

 * wb_clk:do_readfrom -> ddr2_clk:ddr2_read_done

 *

 */

module xilinx_ddr2_if (

    input [31:0]       wb_adr_i,

    input              wb_stb_i,

    input              wb_cyc_i,

    input              wb_we_i,

    input [3:0]        wb_sel_i,

    input [31:0]       wb_dat_i,

    output [31:0]      wb_dat_o,

    output reg         wb_ack_o,

    output [12:0]      ddr2_a,

    output [1:0]       ddr2_ba,

    output             ddr2_ras_n,

    output             ddr2_cas_n,

    output             ddr2_we_n,

    output [1:0]       ddr2_cs_n,

    output [1:0]       ddr2_odt,

    output [1:0]       ddr2_cke,

    output [7:0]       ddr2_dm,

    inout [63:0]       ddr2_dq,

    inout [7:0]        ddr2_dqs,

    inout [7:0]        ddr2_dqs_n,

    output [1:0]       ddr2_ck,

    output [1:0]       ddr2_ck_n,

    input              ddr2_if_clk,

    input              ddr2_if_rst,

    input              idly_clk_200,

    input              wb_clk,

    input              wb_rst);

`include "xilinx_ddr2_params.v"

   wire                ddr2_clk; // DDR2 iface domain clock.

   wire                ddr2_rst; // reset from the ddr2 module

   wire                wb_req;

   reg                 wb_req_r;

   reg                 wb_ack_o_r;

   wire                wb_req_new;

   reg                 wb_req_new_r;

   reg                 wb_req_addr_hit;

   reg                 cached_addr_valid;

   reg [31:6]          cached_addr;

   wire                cache_hit;

   reg                 cache_dirty;

   reg [2:0]            wb_req_cache_word_addr;

   wire                wb_cache_en;

   reg                 do_writeback, do_writeback_r;

   wire                do_writeback_start, do_writeback_finished;

   wire                doing_writeback;

   reg                 do_readfrom, do_readfrom_r;

   wire                do_readfrom_start, do_readfrom_finished;

   wire                doing_readfrom;

   // Domain crossing logic

   reg                 wb_clk_r;

   reg                 wb_clk_in_ddr2_clk;

   reg                 wb_clk_in_ddr2_clk_r;

   wire                wb_clk_edge;

   reg [2:0]            ddr2_clk_phase;

   // Sample when clk phase is 0

   reg [7:0]            do_writeback_ddr2_shifter;

   reg [7:0]            do_writeback_ddr2_shifter_r;

   reg                 do_writeback_ddr2_fifo_we;

   reg                 ddr2_write_done;

   // Currently, ddr2-side of cache is address is a single bit

   reg [1:0]            ddr2_cache_addr;

   wire [127:0]        ddr2_cache_data_o;

   reg                 rd_data_valid_r;

   reg                 ddr2_read_done;

   // DDR2 MIG interface wires

   wire                app_af_afull;

   wire                app_wdf_afull;

   wire                app_wdf_wren;

   wire                app_af_wren;

   wire [30:0]          app_af_addr;

   wire [2:0]           app_af_cmd;

   wire [(APPDATA_WIDTH)-1:0] app_wdf_data;

   wire [(APPDATA_WIDTH/8)-1:0] app_wdf_mask_data;

   wire                         rd_data_valid;

   wire [(APPDATA_WIDTH)-1:0]    rd_data_fifo_out;

   wire                         phy_init_done;

   assign cache_hit = (cached_addr ==  wb_adr_i[31:6]) & cached_addr_valid;

   // Wishbone request detection

   assign wb_req = wb_stb_i & wb_cyc_i & phy_init_done;

   always @(posedge wb_clk)

     wb_req_r <= wb_req;

   assign wb_req_new = wb_req & !wb_req_r;

   always @(posedge wb_clk)

     wb_req_new_r <= wb_req_new;

   // Register whether it's a hit or not

   // As more lines are added, add them to this check.

   always @(posedge wb_clk)

     if (wb_rst)

       wb_req_addr_hit <= 0;

     else

       wb_req_addr_hit <= wb_req & cache_hit & cached_addr_valid;

   always @(posedge wb_clk)

     if (wb_rst)

       wb_ack_o <= 0;

     else

       wb_ack_o <= wb_req_addr_hit & !wb_ack_o & !wb_ack_o_r;

   always @(posedge wb_clk)

     wb_ack_o_r <= wb_ack_o;

   // Address valid logic

   always @(posedge wb_clk)

     if (wb_rst)

       cached_addr_valid <= 0;

     else if (do_readfrom_finished)

       cached_addr_valid <= 1;

     else if ( do_writeback_finished ) // Data written back, cache not valid

       cached_addr_valid <= 0;

     else if (wb_req & !cache_hit & cached_addr_valid & !cache_dirty)

       // Invalidate cache so a readfrom begins

       cached_addr_valid <= 0;

   // Address cacheing

   always @(posedge wb_clk)

     if (wb_rst)

       cached_addr <= 0;

     else if (do_readfrom_start)

       cached_addr <= wb_adr_i[31:6];

   // Cache dirty signal

   always @(posedge wb_clk)

     if (wb_rst)

       cache_dirty <= 0;

     else if (wb_req & wb_we_i & wb_req_addr_hit & wb_ack_o)

       cache_dirty <= 1;

     else if (!cached_addr_valid & cache_dirty)

       cache_dirty <= 0;

   // Wishbone side of cache enable. Important!

   // 1. Enable on first access, if it's not a write

   // 2. Enable if we've just refreshed the cache

   // 3. Enable on ACK'ing for a write

   assign wb_cache_en = (wb_req_new & !wb_we_i) | do_readfrom_finished |

                        (wb_req_addr_hit & wb_stb_i & !wb_we_i & !wb_ack_o) |

                        (wb_ack_o & wb_we_i);

   // Writeback detect logic

   always @(posedge wb_clk)

     if (wb_rst)

       do_writeback <= 0;

     else if (ddr2_write_done) // DDR2 domain signal

       do_writeback <= 0;

     else if (wb_req & !cache_hit & cached_addr_valid & !doing_writeback & cache_dirty)

       do_writeback <= 1;

   always @(posedge wb_clk)

     do_writeback_r <= do_writeback;

   assign do_writeback_start = do_writeback & !do_writeback_r;

   assign do_writeback_finished = !do_writeback & do_writeback_r;

   assign doing_writeback = do_writeback | do_writeback_r;

   // DDR2 Read detect logic

   always @(posedge wb_clk)

     if (wb_rst)

       do_readfrom <= 0;

     else if (ddr2_read_done) // DDR2 domain signal

       do_readfrom <= 0;

     else if (wb_req & !cache_hit & !cached_addr_valid & !doing_readfrom & !cache_dirty)

       do_readfrom <= 1;

   always @(posedge wb_clk)

     do_readfrom_r <= do_readfrom;

   assign do_readfrom_start = do_readfrom & !do_readfrom_r;

   assign do_readfrom_finished = !do_readfrom & do_readfrom_r;

   assign doing_readfrom = do_readfrom | do_readfrom_r;

   // Address fifo signals

   assign app_af_wren = (do_writeback_finished | do_readfrom_start);

   assign app_af_cmd[0] = do_readfrom_start; // 1 - read, 0 - write

   assign app_af_cmd[2:1] = 0;

   assign app_af_addr = do_readfrom_start ?  {2'd0, wb_adr_i[31:6],3'd0} :

                        {2'd0,cached_addr,3'd0};

   assign app_wdf_wren = do_writeback_ddr2_fifo_we;

   assign app_wdf_data = ddr2_cache_data_o;

   assign app_wdf_mask_data = 0;

   always @(posedge wb_clk) if (wb_rst) wb_clk_r <= 0; else wb_clk_r <= ~wb_clk_r;

   always @(posedge ddr2_clk) wb_clk_in_ddr2_clk <= wb_clk_r;

   always @(posedge ddr2_clk) wb_clk_in_ddr2_clk_r <= wb_clk_in_ddr2_clk;

   assign wb_clk_edge = wb_clk_in_ddr2_clk & !wb_clk_in_ddr2_clk_r;

   always @(posedge ddr2_clk)

     if (ddr2_rst)

       ddr2_clk_phase <= 0;

     else if (wb_clk_edge)

       ddr2_clk_phase <= 0;

     else

       ddr2_clk_phase <= ddr2_clk_phase + 1;

   always @(posedge ddr2_clk)

     do_writeback_ddr2_fifo_we <= (do_writeback_ddr2_shifter_r[0]) |

                                  (do_writeback_ddr2_shifter_r[2]) |

                                  (do_writeback_ddr2_shifter_r[4]) |

                                  (do_writeback_ddr2_shifter_r[6]);

   // Kick off counting when we see that the wb_clk domain is

   // doing a writeback.

   always @(posedge ddr2_clk)

     if (ddr2_rst)

       do_writeback_ddr2_shifter <= 4'h0;

     else if  (|do_writeback_ddr2_shifter)

       do_writeback_ddr2_shifter <= {do_writeback_ddr2_shifter[6:0], 1'b0};

     else if (!(|ddr2_clk_phase) & do_writeback & !ddr2_write_done) // sample WB domain

       do_writeback_ddr2_shifter <= 1;

   always @(posedge ddr2_clk)

     do_writeback_ddr2_shifter_r <= do_writeback_ddr2_shifter;

   always @(posedge ddr2_clk)

     if (ddr2_rst)

       ddr2_write_done <= 0;

     else if (do_writeback_ddr2_shifter[7])

       ddr2_write_done <= 1;

     else if ((!(|ddr2_clk_phase)) & !do_writeback) // sample WB domain

       ddr2_write_done <= 0;

   always @(posedge ddr2_clk)

     if (ddr2_rst)

       ddr2_cache_addr <= 0;

     else if (rd_data_valid | do_writeback_ddr2_fifo_we)

       ddr2_cache_addr <= ddr2_cache_addr + 1;

   always @(posedge ddr2_clk)

     rd_data_valid_r <= rd_data_valid;

   // Read done signaling to WB domain

   always @(posedge ddr2_clk)

     if (ddr2_rst)

       ddr2_read_done <= 0;

     else if (!rd_data_valid & rd_data_valid_r) // Detect read data valid falling edge

       ddr2_read_done <= 1;

     else if (!(|ddr2_clk_phase) & !do_readfrom) // Read WB domain

       ddr2_read_done <= 0;

   wire [3:0]                    wb_cache_adr;

   assign wb_cache_adr = wb_adr_i[5:2];

   wire [3:0]                    wb_cache_sel_we;

   assign wb_cache_sel_we = {4{wb_we_i}} & wb_sel_i;

   wire                         ddr2_cache_en;

   wire [15:0]                   ddr2_cache_we;

   assign ddr2_cache_en = rd_data_valid | (|do_writeback_ddr2_shifter);

   assign ddr2_cache_we = {16{rd_data_valid}};

   // Xilinx Coregen true dual-port RAMB array.

   // Wishbone side : 32-bit

   // DDR2 side : 128-bit

   xilinx_ddr2_if_cache cache_mem0

     (

      // Wishbone side

      .clka(wb_clk),

      .ena(wb_cache_en),

      .wea(wb_cache_sel_we),

      .addra({8'd0,wb_cache_adr}),

      .dina(wb_dat_i),

      .douta(wb_dat_o),

      // DDR2 controller side

      .clkb(ddr2_clk),

      .enb(ddr2_cache_en),

      .web(ddr2_cache_we),

      .addrb({8'd0,ddr2_cache_addr}),

      .dinb(rd_data_fifo_out),

      .doutb(ddr2_cache_data_o));

   ddr2_mig #

     (

      .BANK_WIDTH            (BANK_WIDTH),

      .CKE_WIDTH             (CKE_WIDTH),

      .CLK_WIDTH             (CLK_WIDTH),

      .COL_WIDTH             (COL_WIDTH),

      .CS_NUM                (CS_NUM),

      .CS_WIDTH              (CS_WIDTH),

      .CS_BITS               (CS_BITS),

      .DM_WIDTH              (DM_WIDTH),

      .DQ_WIDTH              (DQ_WIDTH),

      .DQ_PER_DQS            (DQ_PER_DQS),

      .DQ_BITS               (DQ_BITS),

      .DQS_WIDTH             (DQS_WIDTH),

      .DQS_BITS              (DQS_BITS),

      .HIGH_PERFORMANCE_MODE (HIGH_PERFORMANCE_MODE),

      .ODT_WIDTH             (ODT_WIDTH),

      .ROW_WIDTH             (ROW_WIDTH),

      .APPDATA_WIDTH         (APPDATA_WIDTH),

      .ADDITIVE_LAT          (ADDITIVE_LAT),

      .BURST_LEN             (BURST_LEN),

      .BURST_TYPE            (BURST_TYPE),

      .CAS_LAT               (CAS_LAT),

      .ECC_ENABLE            (ECC_ENABLE),

      .MULTI_BANK_EN         (MULTI_BANK_EN),

      .ODT_TYPE              (ODT_TYPE),

      .REDUCE_DRV            (REDUCE_DRV),

      .REG_ENABLE            (REG_ENABLE),

      .TREFI_NS              (TREFI_NS),

      .TRAS                  (TRAS),

      .TRCD                  (TRCD),

      .TRFC                  (TRFC),

      .TRP                   (TRP),

      .TRTP                  (TRTP),

      .TWR                   (TWR),

      .TWTR                  (TWTR),

      .SIM_ONLY              (SIM_ONLY),

      .RST_ACT_LOW           (RST_ACT_LOW),

      .CLK_TYPE              (CLK_TYPE),

      .DLL_FREQ_MODE         (DLL_FREQ_MODE),

      .CLK_PERIOD            (CLK_PERIOD)

      )

   ddr2_mig0

     (

      .sys_clk           (ddr2_if_clk),

      .idly_clk_200      (idly_clk_200),

      .sys_rst_n         (ddr2_if_rst), // Act. high, sync. to ddr2_if_clk

      .ddr2_ras_n        (ddr2_ras_n),

      .ddr2_cas_n        (ddr2_cas_n),

      .ddr2_we_n         (ddr2_we_n),

      .ddr2_cs_n         (ddr2_cs_n),

      .ddr2_cke          (ddr2_cke),

      .ddr2_odt          (ddr2_odt),

      .ddr2_dm           (ddr2_dm),

      .ddr2_dq           (ddr2_dq),

      .ddr2_dqs          (ddr2_dqs),

      .ddr2_dqs_n        (ddr2_dqs_n),

      .ddr2_ck           (ddr2_ck),

      .ddr2_ck_n         (ddr2_ck_n),

      .ddr2_ba           (ddr2_ba),

      .ddr2_a            (ddr2_a),

      .clk0_tb           (ddr2_clk),

      .rst0_tb           (ddr2_rst),

      .usr_clk           (wb_clk),

      .app_af_afull      (app_af_afull),

      .app_wdf_afull     (app_wdf_afull),

      .rd_data_valid     (rd_data_valid),

      .rd_data_fifo_out  (rd_data_fifo_out),

      .app_af_wren       (app_af_wren),

      .app_af_cmd        (app_af_cmd),

      .app_af_addr       (app_af_addr),

      .app_wdf_wren      (app_wdf_wren),

      .app_wdf_data      (app_wdf_data),

      .app_wdf_mask_data (app_wdf_mask_data),

      .phy_init_done     (phy_init_done)

      );

endmodule // ml501_ddr2_if

// Local Variables:

// verilog-library-directories:("." "ddr2_mig")

// verilog-library-extensions:(".v" ".h")

// End: