/*

Copyright (c) 2015-2017 Alex Forencich

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

*/

// Language: Verilog 2001

`timescale 1ns / 1ps

/*
 * AXI4-Stream XGMII frame receiver (XGMII in, AXI out)
 */
module axis_xgmii_rx_32 #
(
    parameter DATA_WIDTH = 32,
    parameter KEEP_WIDTH = (DATA_WIDTH/8),
    parameter CTRL_WIDTH = (DATA_WIDTH/8),
    parameter PTP_TS_ENABLE = 0,
    parameter PTP_TS_WIDTH = 96,
    parameter USER_WIDTH = (PTP_TS_ENABLE ? PTP_TS_WIDTH : 0) + 1
)
(
    input  wire                     clk,
    input  wire                     rst,

    /*
     * XGMII input
     */
    input  wire [DATA_WIDTH-1:0]    xgmii_rxd,
    input  wire [CTRL_WIDTH-1:0]    xgmii_rxc,

    /*
     * AXI output
     */
    output wire [DATA_WIDTH-1:0]    m_axis_tdata,
    output wire [KEEP_WIDTH-1:0]    m_axis_tkeep,
    output wire                     m_axis_tvalid,
    output wire                     m_axis_tlast,
    output wire [USER_WIDTH-1:0]    m_axis_tuser,

    /*
     * PTP
     */
    input  wire [PTP_TS_WIDTH-1:0]  ptp_ts,

    /*
     * Status
     */
    output wire                     start_packet,
    output wire                     error_bad_frame,
    output wire                     error_bad_fcs
);

// bus width assertions
initial begin
    if (DATA_WIDTH != 32) begin
        $error("Error: Interface width must be 32");
        $finish;
    end

    if (KEEP_WIDTH * 8 != DATA_WIDTH || CTRL_WIDTH * 8 != DATA_WIDTH) begin
        $error("Error: Interface requires byte (8-bit) granularity");
        $finish;
    end
end

localparam [7:0]
    ETH_PRE = 8'h55,
    ETH_SFD = 8'hD5;

localparam [7:0]
    XGMII_IDLE = 8'h07,
    XGMII_START = 8'hfb,
    XGMII_TERM = 8'hfd,
    XGMII_ERROR = 8'hfe;

localparam [1:0]
    STATE_IDLE = 2'd0,
    STATE_PREAMBLE = 2'd1,
    STATE_PAYLOAD = 2'd2,
    STATE_LAST = 2'd3;

reg [1:0] state_reg = STATE_IDLE, state_next;

// datapath control signals
reg reset_crc;

reg [3:0] last_cycle_tkeep_reg = 4'd0, last_cycle_tkeep_next;

reg [DATA_WIDTH-1:0] xgmii_rxd_d0 = {DATA_WIDTH{1'b0}};
reg [DATA_WIDTH-1:0] xgmii_rxd_d1 = {DATA_WIDTH{1'b0}};
reg [DATA_WIDTH-1:0] xgmii_rxd_d2 = {DATA_WIDTH{1'b0}};

reg [CTRL_WIDTH-1:0] xgmii_rxc_d0 = {CTRL_WIDTH{1'b0}};
reg [CTRL_WIDTH-1:0] xgmii_rxc_d1 = {CTRL_WIDTH{1'b0}};
reg [CTRL_WIDTH-1:0] xgmii_rxc_d2 = {CTRL_WIDTH{1'b0}};

reg [DATA_WIDTH-1:0] m_axis_tdata_reg = {DATA_WIDTH{1'b0}}, m_axis_tdata_next;
reg [KEEP_WIDTH-1:0] m_axis_tkeep_reg = {KEEP_WIDTH{1'b0}}, m_axis_tkeep_next;
reg m_axis_tvalid_reg = 1'b0, m_axis_tvalid_next;
reg m_axis_tlast_reg = 1'b0, m_axis_tlast_next;
reg m_axis_tuser_reg = 1'b0, m_axis_tuser_next;

reg start_packet_reg = 1'b0, start_packet_next;
reg error_bad_frame_reg = 1'b0, error_bad_frame_next;
reg error_bad_fcs_reg = 1'b0, error_bad_fcs_next;

reg [PTP_TS_WIDTH-1:0] ptp_ts_reg = 0, ptp_ts_next;

reg [31:0] crc_state = 32'hFFFFFFFF;

wire [31:0] crc_next0;
wire [31:0] crc_next1;
wire [31:0] crc_next2;
wire [31:0] crc_next3;

wire crc_valid0 = crc_next0 == ~32'h2144df1c;
wire crc_valid1 = crc_next1 == ~32'h2144df1c;
wire crc_valid2 = crc_next2 == ~32'h2144df1c;
wire crc_valid3 = crc_next3 == ~32'h2144df1c;

reg crc_valid0_save = 1'b0;
reg crc_valid1_save = 1'b0;
reg crc_valid2_save = 1'b0;
reg crc_valid3_save = 1'b0;

assign m_axis_tdata = m_axis_tdata_reg;
assign m_axis_tkeep = m_axis_tkeep_reg;
assign m_axis_tvalid = m_axis_tvalid_reg;
assign m_axis_tlast = m_axis_tlast_reg;
assign m_axis_tuser = PTP_TS_ENABLE ? {ptp_ts_reg, m_axis_tuser_reg} : m_axis_tuser_reg;

assign start_packet = start_packet_reg;
assign error_bad_frame = error_bad_frame_reg;
assign error_bad_fcs = error_bad_fcs_reg;

wire last_cycle = state_reg == STATE_LAST;

lfsr #(
    .LFSR_WIDTH(32),
    .LFSR_POLY(32'h4c11db7),
    .LFSR_CONFIG("GALOIS"),
    .LFSR_FEED_FORWARD(0),
    .REVERSE(1),
    .DATA_WIDTH(8),
    .STYLE("AUTO")
)
eth_crc_8 (
    .data_in(xgmii_rxd_d0[7:0]),
    .state_in(crc_state),
    .data_out(),
    .state_out(crc_next0)
);

lfsr #(
    .LFSR_WIDTH(32),
    .LFSR_POLY(32'h4c11db7),
    .LFSR_CONFIG("GALOIS"),
    .LFSR_FEED_FORWARD(0),
    .REVERSE(1),
    .DATA_WIDTH(16),
    .STYLE("AUTO")
)
eth_crc_16 (
    .data_in(xgmii_rxd_d0[15:0]),
    .state_in(crc_state),
    .data_out(),
    .state_out(crc_next1)
);

lfsr #(
    .LFSR_WIDTH(32),
    .LFSR_POLY(32'h4c11db7),
    .LFSR_CONFIG("GALOIS"),
    .LFSR_FEED_FORWARD(0),
    .REVERSE(1),
    .DATA_WIDTH(24),
    .STYLE("AUTO")
)
eth_crc_24 (
    .data_in(xgmii_rxd_d0[23:0]),
    .state_in(crc_state),
    .data_out(),
    .state_out(crc_next2)
);

lfsr #(
    .LFSR_WIDTH(32),
    .LFSR_POLY(32'h4c11db7),
    .LFSR_CONFIG("GALOIS"),
    .LFSR_FEED_FORWARD(0),
    .REVERSE(1),
    .DATA_WIDTH(32),
    .STYLE("AUTO")
)
eth_crc_32 (
    .data_in(xgmii_rxd_d0[31:0]),
    .state_in(crc_state),
    .data_out(),
    .state_out(crc_next3)
);

// detect control characters
reg [3:0] detect_term = 4'd0;

reg [3:0] detect_term_save;

integer i;

// mask errors to within packet
reg [3:0] control_masked;
reg [3:0] tkeep_mask;

always @* begin
    casez (detect_term)
    4'b0000: begin
        control_masked = xgmii_rxc_d0;
        tkeep_mask = 4'b1111;
    end
    4'bzzz1: begin
        control_masked = 0;
        tkeep_mask = 4'b0000;   
    end
    4'bzz10: begin
        control_masked = xgmii_rxc_d0[0];
        tkeep_mask = 4'b0001;
    end
    4'bz100: begin
        control_masked = xgmii_rxc_d0[1:0];
        tkeep_mask = 4'b0011;
    end
    4'b1000: begin
        control_masked = xgmii_rxc_d0[2:0];
        tkeep_mask = 4'b0111;
    end
    default: begin
        control_masked = xgmii_rxc_d0;
        tkeep_mask = 4'b1111;
    end
    endcase
end

always @* begin
    state_next = STATE_IDLE;

    reset_crc = 1'b0;

    last_cycle_tkeep_next = last_cycle_tkeep_reg;

    m_axis_tdata_next = {DATA_WIDTH{1'b0}};
    m_axis_tkeep_next = {KEEP_WIDTH{1'b1}};
    m_axis_tvalid_next = 1'b0;
    m_axis_tlast_next = 1'b0;
    m_axis_tuser_next = 1'b0;

    start_packet_next = 1'b0;
    error_bad_frame_next = 1'b0;
    error_bad_fcs_next = 1'b0;

    ptp_ts_next = ptp_ts_reg;

    case (state_reg)
        STATE_IDLE: begin
            // idle state - wait for packet
            reset_crc = 1'b1;

            if (xgmii_rxc_d2[0] && xgmii_rxd_d2[7:0] == XGMII_START) begin
                // start condition
                if (control_masked) begin
                    // control or error characters in first data word
                    m_axis_tdata_next = {DATA_WIDTH{1'b0}};
                    m_axis_tkeep_next = 4'h1;
                    m_axis_tvalid_next = 1'b1;
                    m_axis_tlast_next = 1'b1;
                    m_axis_tuser_next = 1'b1;
                    error_bad_frame_next = 1'b1;
                    state_next = STATE_IDLE;
                end else begin
                    reset_crc = 1'b0;
                    state_next = STATE_PREAMBLE;
                end
            end else begin
                state_next = STATE_IDLE;
            end
        end
        STATE_PREAMBLE: begin
            // drop preamble
            ptp_ts_next = ptp_ts;
            start_packet_next = 1'b1;
            state_next = STATE_PAYLOAD;
        end
        STATE_PAYLOAD: begin
            // read payload
            m_axis_tdata_next = xgmii_rxd_d2;
            m_axis_tkeep_next = {KEEP_WIDTH{1'b1}};
            m_axis_tvalid_next = 1'b1;
            m_axis_tlast_next = 1'b0;
            m_axis_tuser_next = 1'b0;

            last_cycle_tkeep_next = tkeep_mask;

            if (control_masked) begin
                // control or error characters in packet
                m_axis_tlast_next = 1'b1;
                m_axis_tuser_next = 1'b1;
                error_bad_frame_next = 1'b1;
                reset_crc = 1'b1;
                state_next = STATE_IDLE;
            end else if (detect_term) begin
                if (detect_term[0]) begin
                    // end this cycle
                    reset_crc = 1'b1;
                    m_axis_tkeep_next = 4'b1111;
                    m_axis_tlast_next = 1'b1;
                    if (detect_term[0] && crc_valid3_save) begin
                        // CRC valid
                    end else begin
                        m_axis_tuser_next = 1'b1;
                        error_bad_frame_next = 1'b1;
                        error_bad_fcs_next = 1'b1;
                    end
                    state_next = STATE_IDLE;
                end else begin
                    // need extra cycle
                    state_next = STATE_LAST;
                end
            end else begin
                state_next = STATE_PAYLOAD;
            end
        end
        STATE_LAST: begin
            // last cycle of packet
            m_axis_tdata_next = xgmii_rxd_d2;
            m_axis_tkeep_next = last_cycle_tkeep_reg;
            m_axis_tvalid_next = 1'b1;
            m_axis_tlast_next = 1'b1;
            m_axis_tuser_next = 1'b0;

            reset_crc = 1'b1;

            if ((detect_term_save[1] && crc_valid0_save) ||
                (detect_term_save[2] && crc_valid1_save) ||
                (detect_term_save[3] && crc_valid2_save)) begin
                // CRC valid
            end else begin
                m_axis_tuser_next = 1'b1;
                error_bad_frame_next = 1'b1;
                error_bad_fcs_next = 1'b1;
            end

            state_next = STATE_IDLE;
        end
    endcase
end

always @(posedge clk) begin
    if (rst) begin
        state_reg <= STATE_IDLE;

        m_axis_tvalid_reg <= 1'b0;

        start_packet_reg <= 1'b0;
        error_bad_frame_reg <= 1'b0;
        error_bad_fcs_reg <= 1'b0;

        crc_state <= 32'hFFFFFFFF;

        xgmii_rxc_d0 <= {CTRL_WIDTH{1'b0}};
        xgmii_rxc_d1 <= {CTRL_WIDTH{1'b0}};
    end else begin
        state_reg <= state_next;

        m_axis_tvalid_reg <= m_axis_tvalid_next;

        start_packet_reg <= start_packet_next;
        error_bad_frame_reg <= error_bad_frame_next;
        error_bad_fcs_reg <= error_bad_fcs_next;

        xgmii_rxc_d0 <= xgmii_rxc;
        xgmii_rxc_d1 <= xgmii_rxc_d0;
        xgmii_rxc_d2 <= xgmii_rxc_d1;

        // datapath
        if (reset_crc) begin
            crc_state <= 32'hFFFFFFFF;
        end else begin
            crc_state <= crc_next3;
        end
    end

    m_axis_tdata_reg <= m_axis_tdata_next;
    m_axis_tkeep_reg <= m_axis_tkeep_next;
    m_axis_tlast_reg <= m_axis_tlast_next;
    m_axis_tuser_reg <= m_axis_tuser_next;

    ptp_ts_reg <= ptp_ts_next;

    last_cycle_tkeep_reg <= last_cycle_tkeep_next;

    for (i = 0; i < 4; i = i + 1) begin
        detect_term[i] <= xgmii_rxc[i] && (xgmii_rxd[i*8 +: 8] == XGMII_TERM);
    end

    detect_term_save <= detect_term;

    crc_valid0_save <= crc_valid0;
    crc_valid1_save <= crc_valid1;
    crc_valid2_save <= crc_valid2;
    crc_valid3_save <= crc_valid3;

    xgmii_rxd_d0 <= xgmii_rxd;
    xgmii_rxd_d1 <= xgmii_rxd_d0;
    xgmii_rxd_d2 <= xgmii_rxd_d1;
end

endmodule