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+//
+// Copyright 2021 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+// Module: chdr_convert_down
+//
+// Description:
+//
+// Takes a CHDR packet data stream that was generated using a CHDR width
+// (I_CHDR_W) that is wider than the current bus width (DATA_W) and reformats
+// the packet stream to use the CHDR_W equal to that of the current bus width
+// (DATA_W). It does not resize the bus, but rather only changes the CHDR_W
+// of the encoded packets.
+//
+// Packets with different CHDR width have a different maximum number of
+// metadata bytes. This module repacks the the metadata into the new word
+// size, little-endian ordered. If there is too much metadata for the smaller
+// DATA_W packet, then the excess metadata will be discarded.
+//
+// Parameters:
+//
+// I_CHDR_W : CHDR_W for the input data stream on i_chdr. Must be larger than
+// DATA_W.
+// DATA_W : Width of the data bus, and the new CHDR_W for the output data
+// stream on o_chdr.
+// PIPELINE : Indicates whether to add pipeline stages to the input and/or
+// output. This can be: "NONE", "IN", "OUT", or "INOUT".
+
+`default_nettype none
+
+
+module chdr_convert_down #(
+ parameter I_CHDR_W = 512,
+ parameter DATA_W = 64,
+ parameter PIPELINE = "NONE"
+) (
+ input wire clk,
+ input wire rst,
+
+ // Input
+ input wire [DATA_W-1:0] i_chdr_tdata,
+ input wire i_chdr_tlast,
+ input wire i_chdr_tvalid,
+ output wire i_chdr_tready,
+
+ // Output
+ output wire [DATA_W-1:0] o_chdr_tdata,
+ output wire o_chdr_tlast,
+ output wire o_chdr_tvalid,
+ input wire o_chdr_tready
+);
+
+ `include "../core/rfnoc_chdr_utils.vh"
+ `include "../core/rfnoc_chdr_internal_utils.vh"
+
+ // Calculate ceiling(N/D)
+ `define DIV_CEIL(N,D) (((N)+(D)-1)/(D))
+
+
+ //---------------------------------------------------------------------------
+ // Check Parameters
+ //---------------------------------------------------------------------------
+
+ generate
+ if (!(
+ // Must be reducing the CHDR width
+ (I_CHDR_W > DATA_W) &&
+ // CHDR widths must be valid (at least 64 and powers of 2)
+ (I_CHDR_W >= 64) &&
+ (DATA_W >= 64) &&
+ (2**$clog2(I_CHDR_W) == I_CHDR_W) &&
+ (2**$clog2(DATA_W) == DATA_W) &&
+ // I_CHDR_W must be a multiple of DATA_W
+ (I_CHDR_W % DATA_W == 0)
+ )) begin : gen_error
+ ERROR__Invalid_CHDR_or_data_width_parameters();
+ end
+ endgenerate
+
+
+ //---------------------------------------------------------------------------
+ // Input Register
+ //---------------------------------------------------------------------------
+
+ wire [DATA_W-1:0] i_pipe_tdata;
+ wire i_pipe_tlast;
+ wire i_pipe_tvalid;
+ reg i_pipe_tready;
+
+ if (PIPELINE == "IN" || PIPELINE == "INOUT") begin : gen_in_pipeline
+ // Add a pipeline stage
+ axi_fifo_flop2 #(
+ .WIDTH (1 + DATA_W)
+ ) axi_fifo_flop2_i (
+ .clk (clk),
+ .reset (rst),
+ .clear (1'b0),
+ .i_tdata ({i_chdr_tlast, i_chdr_tdata}),
+ .i_tvalid (i_chdr_tvalid),
+ .i_tready (i_chdr_tready),
+ .o_tdata ({i_pipe_tlast, i_pipe_tdata}),
+ .o_tvalid (i_pipe_tvalid),
+ .o_tready (i_pipe_tready),
+ .space (),
+ .occupied ()
+ );
+ end else begin : gen_no_in_pipeline
+ assign i_pipe_tdata = i_chdr_tdata;
+ assign i_pipe_tlast = i_chdr_tlast;
+ assign i_pipe_tvalid = i_chdr_tvalid;
+ assign i_chdr_tready = i_pipe_tready;
+ end
+
+
+ //---------------------------------------------------------------------------
+ // Downsize State Machine
+ //---------------------------------------------------------------------------
+ //
+ // This state machine does the translation from the larger CHDR_W to the
+ // smaller CHDR_W by updating the header and dropping empty words.
+ //
+ //---------------------------------------------------------------------------
+
+ // States
+ localparam [2:0] ST_HDR = 3'd0; // CHDR header
+ localparam [2:0] ST_TS = 3'd1; // CHDR timestamp
+ localparam [2:0] ST_HDR_DROP = 3'd2; // CHDR header, drop unused words
+ localparam [2:0] ST_MDATA = 3'd3; // CHDR metadata words
+ localparam [2:0] ST_MDATA_DROP = 3'd4; // CHDR metadata, drop unused words
+ localparam [2:0] ST_PYLD = 3'd5; // CHDR payload words
+ localparam [2:0] ST_PYLD_DROP = 3'd6; // CHDR payload, drop unused words
+ localparam [2:0] ST_MGMT_PYLD = 3'd7; // CHDR management payload words
+
+ reg [2:0] state = ST_HDR;
+
+ // Determine the number of bits needed to represent the new number of
+ // metadata words, which might be bigger than the allowed value of 31.
+ localparam NUM_MDATA_W = $clog2(31*I_CHDR_W/DATA_W + 1);
+
+ // Number of output words per input word
+ localparam NUM_WORDS = I_CHDR_W/DATA_W;
+
+ // Determine the number of bits needed to represent a counter to track which
+ // CHDR words are valid and which are unused and need to be dropped.
+ localparam COUNT_W = $clog2(NUM_WORDS);
+
+ // Determine the maximum number DATA_W-sized payload words. The maximum
+ // packet size is 2**16-1 bytes, then subtract one word for the smallest
+ // possible header and convert that to a number of whole CHDR words.
+ localparam NUM_PYLD_WORDS = `DIV_CEIL((2**16-1) - (DATA_W/8), DATA_W/8);
+
+ // Determine the number of bits needed to represent a counter to track which
+ // O_DATA_W payload word we are processing.
+ localparam PYLD_COUNT_W = $clog2(NUM_PYLD_WORDS + 1);
+
+ // Header info we need to save
+ reg [ NUM_MDATA_W-1:0] i_num_mdata_reg; // Input packet NumMData in terms of DATA_W words
+ reg [ 4:0] o_num_mdata_reg; // Output packet NumMData to keep
+ reg [ 2:0] pkt_type_reg; // Packet type
+ reg [PYLD_COUNT_W-1:0] pyld_len_reg; // Packet payload length in DATA_W words
+ reg [PYLD_COUNT_W-1:0] mgmt_pyld_len_reg; // Management payload length in DATA_W words
+
+ // Counters (number of DATA_W sized words processed on the input)
+ reg [ NUM_MDATA_W-1:0] mdata_count;
+ reg [PYLD_COUNT_W-1:0] pyld_count;
+ reg [ COUNT_W-1:0] word_count; // Zero based (starts at 0)
+
+ // Shortcuts for CHDR header info
+ wire [ 2:0] pkt_type = chdr_get_pkt_type(i_pipe_tdata[63:0]);
+ wire [15:0] pyld_len_bytes = chdr_calc_payload_length(I_CHDR_W, i_pipe_tdata[63:0]);
+
+ // Calculate the payload length in DATA_W words
+ wire [PYLD_COUNT_W-1:0] pyld_len = `DIV_CEIL(pyld_len_bytes, DATA_W/8);
+
+ // Calculate the payload length of a management packet in words (management
+ // packets have the same number of payload words, regardless of CHDR width).
+ wire [PYLD_COUNT_W-1:0] mgmt_pyld_len =
+ `DIV_CEIL(chdr_calc_payload_length(I_CHDR_W, i_pipe_tdata), I_CHDR_W/8);
+
+ // Calculate NumMData from input packet in terms of DATA_W words
+ wire [NUM_MDATA_W-1:0] i_num_mdata =
+ chdr_get_num_mdata(i_pipe_tdata[63:0]) * (I_CHDR_W/DATA_W);
+ // Calculate NumMData for output packet (limit to max of 31)
+ wire [4:0] o_num_mdata = (i_num_mdata <= 31) ? i_num_mdata : 31;
+
+ // Generate packet headers with updated NumMData and Length fields
+ reg [DATA_W-1:0] new_header;
+ always @(*) begin
+ new_header = i_pipe_tdata;
+ // Update NumMData
+ new_header[63:0] = chdr_set_num_mdata(new_header, o_num_mdata);
+ // Update packet length
+ new_header[63:0] = chdr_update_length(DATA_W, new_header,
+ (pkt_type == CHDR_PKT_TYPE_MGMT) ? mgmt_pyld_len * (DATA_W/8) : pyld_len_bytes);
+ end
+
+ reg [DATA_W-1:0] new_mgmt_header;
+ always @(*) begin
+ // Update the CHDRWidth field in the management header.
+ new_mgmt_header = i_pipe_tdata;
+ new_mgmt_header[63:0] =
+ chdr_mgmt_set_chdr_w(i_pipe_tdata[63:0], chdr_w_to_enum(DATA_W));
+ end
+
+
+ always @(posedge clk) begin
+ if (rst) begin
+ state <= ST_HDR;
+ mdata_count <= 'bX;
+ pyld_count <= 'bX;
+ word_count <= 'bX;
+ pkt_type_reg <= 'bX;
+ pyld_len_reg <= 'bX;
+ mgmt_pyld_len_reg <= 'bX;
+ i_num_mdata_reg <= 'bX;
+ o_num_mdata_reg <= 'bX;
+ end else if (i_pipe_tvalid & i_pipe_tready) begin
+ // Default assignment
+ word_count <= word_count + 1;
+
+ case (state)
+
+ // ST_HDR: CHDR Header
+ ST_HDR: begin
+ mdata_count <= 1; // The first metadata word will be word 1
+ pyld_count <= 1; // The first payload word will be word 1
+ word_count <= 1; // Word 0 is the current word (header)
+ pkt_type_reg <= pkt_type;
+ pyld_len_reg <= pyld_len;
+ mgmt_pyld_len_reg <= mgmt_pyld_len;
+ // Save number of DATA_W words of mdata we expect
+ i_num_mdata_reg <= i_num_mdata;
+ // Save the number of DATA_W words of mdata we can keep
+ o_num_mdata_reg <= o_num_mdata;
+ if (DATA_W == 64) begin
+ if (pkt_type == CHDR_PKT_TYPE_DATA_TS) begin
+ // Next word must be the timestamp
+ state <= ST_TS;
+ end else begin
+ // Next word(s) must be empty, so drop it
+ state <= ST_HDR_DROP;
+ end
+ end else begin
+ // DATA_W >= 128. We should have received the header word and
+ // timestamp (if present) this clock cycle. Since I_CHDR_W >
+ // DATA_W, there must be extra words with the header that we need
+ // to drop.
+ state <= ST_HDR_DROP;
+ end
+ end
+
+ // ST_TS: Timestamp (DATA_W == 64 only)
+ ST_TS: begin
+ if (I_CHDR_W > 128) begin
+ state <= ST_HDR_DROP;
+ end else if (o_num_mdata_reg != 0) begin
+ state <= ST_MDATA;
+ end else begin
+ state <= ST_PYLD;
+ end
+ end
+
+ // ST_HDR_DROP: CHDR header, drop unused words
+ ST_HDR_DROP: begin
+ if (word_count == NUM_WORDS-1) begin
+ if (o_num_mdata_reg != 0) begin
+ state <= ST_MDATA;
+ end else if(pkt_type_reg == CHDR_PKT_TYPE_MGMT) begin
+ state <= ST_MGMT_PYLD;
+ end else begin
+ state <= ST_PYLD;
+ end
+ end
+ end
+
+ // ST_MDATA: Metadata words
+ ST_MDATA: begin
+ mdata_count <= mdata_count + 1;
+ if (mdata_count == o_num_mdata_reg) begin
+ if (mdata_count < i_num_mdata_reg) begin
+ // There are more MDATA words to deal with than we can fit, so we
+ // need to drop the rest.
+ state <= ST_MDATA_DROP;
+ end else if (pkt_type_reg == CHDR_PKT_TYPE_MGMT) begin
+ state <= ST_MGMT_PYLD;
+ end else begin
+ state <= ST_PYLD;
+ end
+ end
+ end
+
+ // ST_MDATA_DROP: Drop excess metadata words
+ ST_MDATA_DROP: begin
+ mdata_count <= mdata_count + 1;
+ if (mdata_count == i_num_mdata_reg) begin
+ if (pkt_type_reg == CHDR_PKT_TYPE_MGMT) begin
+ state <= ST_MGMT_PYLD;
+ end else begin
+ state <= ST_PYLD;
+ end
+ end
+ end
+
+ // ST_PYLD: Payload words
+ ST_PYLD: begin
+ pyld_count <= pyld_count + 1;
+ if (i_pipe_tlast) begin
+ state <= ST_HDR;
+ end else if (pyld_count == pyld_len_reg) begin
+ state <= ST_PYLD_DROP;
+ end
+ end
+
+ // ST_PYLD_DROP: Payload, drop unused words
+ ST_PYLD_DROP: begin
+ // The input packet may have had empty words at the end if the
+ // payload didn't fill the last CHDR word. We remove those here.
+ if (i_pipe_tlast) begin
+ state <= ST_HDR;
+ end
+ end
+
+ // ST_MGMT_PYLD: Management words
+ ST_MGMT_PYLD: begin
+ // Management packets are different from other packet types in that
+ // the payload is not serialized. In the new DATA_W, we'll have empty
+ // words we need to discard. When word_count is zero, that's when we
+ // have a valid word. For all other counts, we want to discard words.
+ if (word_count == 0) begin
+ pyld_count <= pyld_count + 1;
+ end
+ if (i_pipe_tlast) begin
+ state <= ST_HDR;
+ end
+ end
+
+ endcase
+ end
+ end
+
+
+ //-----------------------------
+ // State machine output logic
+ //-----------------------------
+
+ reg [DATA_W-1:0] o_pipe_tdata;
+ reg o_pipe_tlast;
+ reg o_pipe_tvalid;
+ wire o_pipe_tready;
+
+ always @(*) begin
+ case (state)
+ ST_HDR : begin
+ o_pipe_tdata = new_header;
+ o_pipe_tlast = i_pipe_tlast;
+ o_pipe_tvalid = i_pipe_tvalid;
+ i_pipe_tready = o_pipe_tready;
+ end
+ ST_TS : begin
+ o_pipe_tdata = i_pipe_tdata;
+ o_pipe_tlast = i_pipe_tlast;
+ o_pipe_tvalid = i_pipe_tvalid;
+ i_pipe_tready = o_pipe_tready;
+ end
+ ST_HDR_DROP : begin
+ o_pipe_tdata = { DATA_W {1'bX} };
+ o_pipe_tlast = 1'bX;
+ o_pipe_tvalid = 1'b0;
+ i_pipe_tready = 1'b1;
+ end
+ ST_MDATA : begin
+ o_pipe_tdata = i_pipe_tdata;
+ o_pipe_tlast = i_pipe_tlast;
+ o_pipe_tvalid = i_pipe_tvalid;
+ i_pipe_tready = o_pipe_tready;
+ end
+ ST_MDATA_DROP : begin
+ o_pipe_tdata = { DATA_W {1'bX} };
+ o_pipe_tlast = 1'bX;
+ o_pipe_tvalid = 1'b0;
+ i_pipe_tready = 1'b1;
+ end
+ ST_PYLD : begin
+ o_pipe_tdata = i_pipe_tdata;
+ o_pipe_tlast = (pyld_count == pyld_len_reg);
+ o_pipe_tvalid = i_pipe_tvalid;
+ i_pipe_tready = o_pipe_tready;
+ end
+ ST_PYLD_DROP : begin
+ o_pipe_tdata = { DATA_W {1'bX} };
+ o_pipe_tlast = 1'bX;
+ o_pipe_tvalid = 1'b0;
+ i_pipe_tready = 1'b1;
+ end
+ ST_MGMT_PYLD : begin
+ if (word_count == 0) begin
+ o_pipe_tdata = (pyld_count == 1) ? new_mgmt_header : i_pipe_tdata;
+ o_pipe_tlast = (pyld_count == mgmt_pyld_len_reg);
+ o_pipe_tvalid = i_pipe_tvalid;
+ i_pipe_tready = o_pipe_tready;
+ end else begin
+ // Drop unused management payload words
+ o_pipe_tdata = { DATA_W {1'bX} };
+ o_pipe_tlast = 1'bX;
+ o_pipe_tvalid = 1'b0;
+ i_pipe_tready = 1'b1;
+ end
+ end
+ default : begin
+ o_pipe_tdata = { DATA_W {1'bX} };
+ o_pipe_tlast = 1'bX;
+ o_pipe_tvalid = 1'bX;
+ i_pipe_tready = 1'bX;
+ end
+ endcase
+ end
+
+
+ //---------------------------------------------------------------------------
+ // Output Register
+ //---------------------------------------------------------------------------
+
+ if (PIPELINE == "OUT" || PIPELINE == "INOUT") begin : gen_out_pipeline
+ // Add a pipeline stage
+ axi_fifo_flop2 #(
+ .WIDTH (1 + DATA_W)
+ ) axi_fifo_flop2_i (
+ .clk (clk),
+ .reset (rst),
+ .clear (1'b0),
+ .i_tdata ({ o_pipe_tlast, o_pipe_tdata }),
+ .i_tvalid (o_pipe_tvalid),
+ .i_tready (o_pipe_tready),
+ .o_tdata ({ o_chdr_tlast, o_chdr_tdata }),
+ .o_tvalid (o_chdr_tvalid),
+ .o_tready (o_chdr_tready),
+ .space (),
+ .occupied ()
+ );
+ end else begin : gen_no_out_pipeline
+ assign o_chdr_tdata = o_pipe_tdata;
+ assign o_chdr_tlast = o_pipe_tlast;
+ assign o_chdr_tvalid = o_pipe_tvalid;
+ assign o_pipe_tready = o_chdr_tready;
+ end
+
+endmodule
+
+
+`default_nettype wire
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