//======================================================================
//
// keywrap.v
// --------
// Top level wrapper for the KEY WRAP core.
//
//
// Author: Joachim Strombergson
// Copyright (c) 2018, NORDUnet A/S
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// - Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the
//   documentation and/or other materials provided with the distribution.
//
// - Neither the name of the NORDUnet nor the names of its contributors may
//   be used to endorse or promote products derived from this software
//   without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//======================================================================

module keywrap(
               // Clock and reset.
               input wire           clk,
               input wire           reset_n,

               // Control.
               input wire           cs,
               input wire           we,

               // Data ports.
               input wire  [7 : 0]  address,
               input wire  [31 : 0] write_data,
               output wire [31 : 0] read_data,
               output wire          error
              );


  //----------------------------------------------------------------
  // Internal constant and parameter definitions.
  //----------------------------------------------------------------
  localparam ADDR_NAME0       = 8'h00;
  localparam ADDR_NAME1       = 8'h01;
  localparam ADDR_VERSION     = 8'h02;

  localparam ADDR_CTRL        = 8'h08;
  localparam CTRL_INIT_BIT    = 0;
  localparam CTRL_NEXT_BIT    = 1;

  localparam ADDR_STATUS      = 8'h09;
  localparam STATUS_READY_BIT = 0;
  localparam STATUS_VALID_BIT = 1;

  localparam ADDR_CONFIG      = 8'h0a;
  localparam CTRL_ENCDEC_BIT  = 0;
  localparam CTRL_KEYLEN_BIT  = 1;

  localparam ADDR_RLEN        = 8'h0c;
  localparam ADDR_A_LSB       = 8'h0e;
  localparam ADDR_A_MSB       = 8'h0f;

  localparam ADDR_KEY0        = 8'h10;
  localparam ADDR_KEY7        = 8'h17;

  localparam ADDR_WRITE_DATA  = 8'h20;

  localparam ADDR_READ_DATA   = 8'h30;

  localparam CORE_NAME0       = 32'h6b657920; // "key "
  localparam CORE_NAME1       = 32'h77726170; // "wrap"
  localparam CORE_VERSION     = 32'h302e3230; // "0.20"


  //----------------------------------------------------------------
  // Registers including update variables and write enable.
  //----------------------------------------------------------------
  reg init_reg;
  reg init_new;

  reg next_reg;
  reg next_new;

  reg encdec_reg;
  reg keylen_reg;
  reg config_we;

  reg api_cs_reg;
  reg api_cs_new;

  reg api_we_reg;
  reg api_we_new;

  reg [12 : 0] rlen_reg;
  reg          rlen_we;

  reg [31 : 0] a0_reg;
  reg          a0_we;

  reg [31 : 0] a1_reg;
  reg          a1_we;

  reg [31 : 0] key_reg [0 : 7];
  reg          key_we;

  reg valid_reg;
  reg ready_reg;


  //----------------------------------------------------------------
  // Wires.
  //----------------------------------------------------------------
  reg [31 : 0]   tmp_read_data;
  reg            tmp_error;

  wire           core_ready;
  wire           core_valid;
  wire [255 : 0] core_key;
  wire [31 : 0]  core_api_rd_data;
  wire [63 : 0]  core_a_result;


  //----------------------------------------------------------------
  // Concurrent connectivity for ports etc.
  //----------------------------------------------------------------
  assign read_data = tmp_read_data;
  assign error     = tmp_error;

  assign core_key = {key_reg[0], key_reg[1], key_reg[2], key_reg[3],
                     key_reg[4], key_reg[5], key_reg[6], key_reg[7]};


  //----------------------------------------------------------------
  // core instantiation.
  //----------------------------------------------------------------
  keywrap_core core(
                    .clk(clk),
                    .reset_n(reset_n),

                    .init(init_reg),
                    .next(next_reg),
                    .encdec(encdec_reg),

                    .ready(core_ready),
                    .valid(core_valid),

                    .rlen(rlen_reg),

                    .key(core_key),
                    .keylen(keylen_reg),

                    .a_init({a1_reg, a0_reg}),
                    .a_result(core_a_result),

                    .api_cs(api_cs_reg),
                    .api_we(api_we_reg),
                    .api_wr_data(write_data),
                    .api_rd_data(core_api_rd_data)
                   );


  //----------------------------------------------------------------
  // reg_update
  //----------------------------------------------------------------
  always @ (posedge clk or negedge reset_n)
    begin : reg_update
      integer i;

      if (!reset_n)
        begin
          for (i = 0 ; i < 8 ; i = i + 1)
            key_reg[i] <= 32'h0;

          init_reg   <= 1'h0;
          next_reg   <= 1'h0;
          encdec_reg <= 1'h0;
          keylen_reg <= 1'h0;
          rlen_reg   <= 13'h0;
          valid_reg  <= 1'h0;
          ready_reg  <= 1'h0;
          api_cs_reg <= 1'h0;
          api_we_reg <= 1'h0;
          a0_reg     <= 32'h0;
          a1_reg     <= 32'h0;
        end
      else
        begin
          ready_reg  <= core_ready;
          valid_reg  <= core_valid;
          init_reg   <= init_new;
          next_reg   <= next_new;
          api_cs_reg <= api_cs_new;
          api_we_reg <= api_we_new;

          if (config_we)
            begin
              encdec_reg <= write_data[CTRL_ENCDEC_BIT];
              keylen_reg <= write_data[CTRL_KEYLEN_BIT];
            end

          if (rlen_we)
            rlen_reg <= write_data[12 : 0];

          if (a0_we)
            a0_reg <= write_data;

          if (a1_we)
            a1_reg <= write_data;

          if (key_we)
            key_reg[address[2 : 0]] <= write_data;
        end
    end // reg_update


  //----------------------------------------------------------------
  // api
  //
  // The interface command decoding logic.
  //----------------------------------------------------------------
  always @*
    begin : api
      init_new      = 1'h0;
      next_new      = 1'h0;
      config_we     = 1'h0;
      rlen_we       = 1'h0;
      key_we        = 1'h0;
      api_cs_new    = 1'h0;
      api_we_new    = 1'h0;
      a0_we         = 1'h1;
      a1_we         = 1'h1;
      tmp_read_data = 32'h0;
      tmp_error     = 1'h0;

      if (cs)
        begin
          if (we)
            begin
              if (address == ADDR_CTRL)
                begin
                  init_new = write_data[CTRL_INIT_BIT];
                  next_new = write_data[CTRL_NEXT_BIT];
                end

              if (address == ADDR_CONFIG)
                config_we = 1'h1;

              if (address == ADDR_RLEN)
                config_we = 1'h1;

              if (address == ADDR_A_LSB)
                a0_we = 1'h1;

              if (address == ADDR_A_MSB)
                a1_we = 1'h1;

              if ((address >= ADDR_KEY0) && (address <= ADDR_KEY7))
                key_we = 1'h1;

              if (address == ADDR_WRITE_DATA)
                begin
                  api_cs_new = 1'h1;
                  api_we_new = 1'h1;
                end
            end // if (we)

          else
            begin
              case (address)
                ADDR_NAME0:   tmp_read_data = CORE_NAME0;
                ADDR_NAME1:   tmp_read_data = CORE_NAME1;
                ADDR_VERSION: tmp_read_data = CORE_VERSION;
                ADDR_CTRL:    tmp_read_data = {28'h0, keylen_reg, encdec_reg, next_reg, init_reg};
                ADDR_STATUS:  tmp_read_data = {30'h0, valid_reg, ready_reg};

                default:
                  begin
                  end
              endcase // case (address)

              if (address == ADDR_A_LSB)
                tmp_read_data = core_a_result[31 : 0];

              if (address == ADDR_A_MSB)
                tmp_read_data = core_a_result[63 : 32];

              if (address == ADDR_READ_DATA)
                begin
                  api_cs_new    = 1'h1;
                  tmp_read_data = core_api_rd_data;
                end
            end
        end
    end // addr_decoder
endmodule // keywrap

//======================================================================
// EOF keywrap.v
//======================================================================