//
// Copyright 2016 Ettus Research
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: LGPL-3.0-or-later
//
// Converts strobed sample data from radio frontend to the AXI-Stream bus
// Outputs an error packet if an overrun, late timed command, or empty command fifo error occurs.

// HALT brings RX to an idle state as quickly as possible if RX is running
// without running the risk of leaving a packet fragment in downstream FIFO's.
// HALT also flushes all remaining pending commands in the commmand FIFO.

module rx_control_gen3 #(
  parameter SR_RX_CTRL_COMMAND = 0,     // Command FIFO
  parameter SR_RX_CTRL_TIME_HI = 1,     // Command execute time (high word)
  parameter SR_RX_CTRL_TIME_LO = 2,     // Command execute time (low word)
  parameter SR_RX_CTRL_HALT = 3,        // Halt command -> return to idle state
  parameter SR_RX_CTRL_MAXLEN = 4,      // Packet length
  parameter SR_RX_CTRL_CLEAR_CMDS = 5,   // Clear command FIFO
  parameter SR_RX_CTRL_OUTPUT_FORMAT = 6,  // Output format (use timestamps)
  parameter WIDTH = 32            // Can be 32 or 64
)(
  input clk, input reset,
  input clear, // Resets state machine and clear output FIFO.
  input [63:0] vita_time, input [31:0] sid, input [31:0] resp_sid,
  input set_stb, input [7:0] set_addr, input [31:0] set_data,
  // Data packets
  output [WIDTH-1:0] rx_tdata, output rx_tlast, output rx_tvalid, input rx_tready, output [127:0] rx_tuser,
  // Error packets, Note: Currently unused as error packets must come inline with data.
  output reg [63:0] resp_tdata, output reg [127:0] resp_tuser, output reg resp_tlast, output reg resp_tvalid, input resp_tready,
  // From radio frontend
  output run, input [WIDTH-1:0] sample, input strobe
);

  reg [31:0] error;
  reg [WIDTH-1:0] rx_reg_tdata;
  reg rx_reg_tlast, rx_reg_tvalid;
  wire rx_reg_tready;
  reg [127:0] rx_reg_tuser, error_tuser;

  wire overflow = rx_reg_tvalid & ~rx_reg_tready;
  reg [63:0] overflow_time;

  wire [31:0] command_i;
  wire [63:0] time_i;
  wire store_command;

  wire send_imm, chain, reload, stop;
  wire [27:0] numlines;
  wire [63:0] rcvtime;
  wire use_timestamps;

  wire now, early, late;
  wire command_valid;
  reg command_ready;

  reg chain_sav, reload_sav;
  reg clear_halt;
  reg halt;
  wire set_halt;
  wire [15:0] maxlen;
  wire eob;
  reg [63:0] start_time;
  wire clear_cmds;

  setting_reg #(.my_addr(SR_RX_CTRL_COMMAND)) sr_cmd (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(command_i),.changed());

  setting_reg #(.my_addr(SR_RX_CTRL_TIME_HI)) sr_time_h (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(time_i[63:32]),.changed());

  setting_reg #(.my_addr(SR_RX_CTRL_TIME_LO)) sr_time_l (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(time_i[31:0]),.changed(store_command));

  setting_reg #(.my_addr(SR_RX_CTRL_HALT)) sr_rx_halt (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(),.changed(set_halt));

  // use (maxlen >> 1) for 2 samples per cycle
  setting_reg #(.my_addr(SR_RX_CTRL_MAXLEN), .width(16)) sr_maxlen (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(maxlen),.changed());

  setting_reg #(.my_addr(SR_RX_CTRL_CLEAR_CMDS)) sr_clear_cmds (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(),.changed(clear_cmds));

  setting_reg #(.my_addr(SR_RX_CTRL_OUTPUT_FORMAT), .width(1), .at_reset(1'b1)) sr_output_format (
    .clk(clk),.rst(reset),.strobe(set_stb),.addr(set_addr),
    .in(set_data),.out(use_timestamps),.changed());

  always @(posedge clk)
    if (reset | clear | clear_halt | clear_cmds)
      halt <= 1'b0;
    else
      halt <= set_halt;

  axi_fifo_short #(.WIDTH(96)) commandfifo (
    .clk(clk),.reset(reset),.clear(clear | clear_halt | clear_cmds),
    .i_tdata({command_i,time_i}), .i_tvalid(store_command), .i_tready(),
    .o_tdata({send_imm,chain,reload,stop,numlines,rcvtime}),
    .o_tvalid(command_valid), .o_tready(command_ready),
    .occupied(), .space() );

  time_compare time_compare (
    .clk(clk), .reset(reset),
    .time_now(vita_time), .trigger_time(rcvtime), .now(now), .early(early), .late(late), .too_early());

  // State machine states
  localparam IBS_IDLE                = 0;
  localparam IBS_RUNNING             = 1;
  localparam IBS_ERR_WAIT_FOR_READY  = 2;
  localparam IBS_ERR_SEND_PKT        = 3;

  // Error codes
  localparam ERR_OVERRUN      = 32'd8;
  localparam ERR_BROKENCHAIN  = 32'd4;
  localparam ERR_LATECMD      = 32'd2;

  reg [2:0] ibs_state;
  reg [27:0] lines_left, repeat_lines;
  reg [15:0] lines_left_pkt;

  reg [11:0] seqnum_cnt;
  wire [11:0] next_seqnum = (rx_reg_tlast & rx_reg_tready & rx_reg_tvalid & (rx_reg_tuser[127:126] != 2'b11)) ? seqnum_cnt + 1'b1 : seqnum_cnt;
  always @(posedge clk) begin
    if (reset | clear | clear_halt) begin
      seqnum_cnt <= 'd0;
    end else begin
      seqnum_cnt <= next_seqnum;
    end
  end

  wire [127:0] error_header = {2'b11,           1'b1, 1'b1, next_seqnum,                  16'h24, resp_sid, overflow_time};
  wire [127:0] rx_header    = {2'b00, use_timestamps,  eob, next_seqnum, 16'h0 /* len ignored */,      sid, start_time};

  always @(posedge clk) begin
    if (reset | clear) begin
      ibs_state      <= IBS_IDLE;
      lines_left     <= 'd0;
      lines_left_pkt <= 'd0;
      repeat_lines   <= 'd0;
      start_time     <= 'd0;
      chain_sav      <= 1'b0;
      reload_sav     <= 1'b0;
      clear_halt     <= 1'b0;
      rx_reg_tdata   <= 'd0;
      rx_reg_tlast   <= 1'b0;
      rx_reg_tvalid  <= 1'b0;
      rx_reg_tuser   <= 'd0;
      resp_tdata     <= 'd0;
      resp_tlast     <= 1'b0;
      resp_tvalid    <= 1'b0;
      resp_tuser     <= 'd0;
      command_ready  <= 1'b0;
    end else begin
      case (ibs_state)
        IBS_IDLE : begin
          rx_reg_tlast   <= 1'b0;
          rx_reg_tvalid  <= 1'b0;
          command_ready  <= 1'b0;
          clear_halt     <= 1'b0; // Incase we got here through a HALT.
          if (command_valid & rx_reg_tready) begin
            // There is a valid command to pop from FIFO
            if (stop) begin
              // Stop bit set in this command, go idle.
              command_ready <= 1'b1;
              ibs_state     <= IBS_IDLE;
            end else if (late & ~send_imm) begin
              // Got this command later than its execution time.
              command_ready <= 1'b1;
              error         <= ERR_LATECMD;
              ibs_state     <= IBS_ERR_WAIT_FOR_READY;
            end else if (now | send_imm) begin
              // Either its time to run this command or it should run immediately without a time.
              command_ready  <= 1'b1;
              lines_left     <= numlines;
              repeat_lines   <= numlines;
              chain_sav      <= chain;
              reload_sav     <= reload;
              lines_left_pkt <= WIDTH == 64 ? (maxlen >> 1) : maxlen;
              ibs_state      <= IBS_RUNNING;
            end
          end
        end

        IBS_RUNNING : begin
          command_ready <= 1'b0;
          if (strobe) begin
            rx_reg_tvalid <= 1'b1;
            rx_reg_tlast  <= eob | (lines_left_pkt == 1);
            rx_reg_tuser  <= rx_header;
            rx_reg_tdata  <= sample;
            if (lines_left_pkt == 1) begin
              lines_left_pkt <= WIDTH == 64 ? (maxlen >> 1) : maxlen;
            end else begin
              lines_left_pkt <= lines_left_pkt - 1;
            end
            if (lines_left_pkt == (WIDTH == 64 ? (maxlen >> 1) : maxlen)) begin
              start_time <= vita_time;
            end
            if (lines_left == 1) begin
              if (halt) begin // Provide Halt mechanism used to bring RX into known IDLE state at re-initialization.
                ibs_state <= IBS_IDLE;
                clear_halt <= 1'b1;
              end else if (chain_sav) begin // If chain_sav is true then execute the next command now this one finished.
                if (command_valid) begin
                  command_ready <= 1'b1;
                  lines_left    <= numlines;
                  repeat_lines  <= numlines;
                  chain_sav     <= chain;
                  reload_sav    <= reload;
                  if (stop) begin // If the new command includes stop then go idle.
                    ibs_state <= IBS_IDLE;
                  end
                end else if (reload_sav) begin // There is no new command to pop from FIFO so re-run previous command.
                  lines_left <= repeat_lines;
                end else begin // Chain has been broken, no commands left in FIFO and reload not set.
                  error         <= ERR_BROKENCHAIN;
                  ibs_state     <= IBS_ERR_WAIT_FOR_READY;
                end
              end else begin // Chain is not true, so don't look for new command, instead go idle.
                ibs_state <= IBS_IDLE;
              end
            end else begin // Still counting down lines in current command.
              lines_left <= lines_left - 28'd1;
            end
          end else begin
            rx_reg_tvalid <= 1'b0;  // Sample consumed, drop tvalid
          end
          // Overflow condition -- can occur regardless of strobe state
          if (overflow) begin
            rx_reg_tvalid  <= 1'b1;      // Send final sample
            rx_reg_tlast   <= 1'b1;      // ... and end packet
            rx_reg_tuser   <= rx_header; // Update tuser with EOB set
            error          <= ERR_OVERRUN;
            ibs_state      <= IBS_ERR_WAIT_FOR_READY;
            overflow_time  <= vita_time;
          end
        end

        // Wait for output to be ready
        IBS_ERR_WAIT_FOR_READY : begin
          command_ready  <= 1'b0;
          if (rx_reg_tready) begin
            rx_reg_tvalid <= 1'b1;
            rx_reg_tlast  <= 1'b0;
            rx_reg_tdata  <= {WIDTH/32{error}};
            rx_reg_tuser  <= error_header;
            ibs_state     <= IBS_ERR_SEND_PKT;
          end
        end

        IBS_ERR_SEND_PKT : begin
          command_ready <= 1'b0;
          if (rx_reg_tready) begin
            rx_reg_tvalid <= 1'b1;
            rx_reg_tlast  <= 1'b1;
            rx_reg_tdata  <= 'd0;
            if (rx_reg_tlast) begin
              rx_reg_tvalid <= 1'b0;
              rx_reg_tlast  <= 1'b0;
              ibs_state     <= IBS_IDLE;
            end
          end
        end

        default : ibs_state <= IBS_IDLE;
      endcase
    end
  end

  assign run = (ibs_state == IBS_RUNNING);

  assign eob = ((lines_left == 1) & ( !chain_sav | (command_valid & stop) | (!command_valid & !reload_sav) | halt)) | overflow;

  // Register output
  axi_fifo_flop2 #(.WIDTH(129+WIDTH))
  axi_fifo_flop2 (
    .clk(clk), .reset(reset), .clear(clear),
    .i_tdata({rx_reg_tlast, rx_reg_tdata, rx_reg_tuser}), .i_tvalid(rx_reg_tvalid), .i_tready(rx_reg_tready),
    .o_tdata({rx_tlast, rx_tdata, rx_tuser}), .o_tvalid(rx_tvalid), .o_tready(rx_tready),
    .space(), .occupied());

endmodule