From 0770fd4405e3042364470cca75520cfbf2ac4bef Mon Sep 17 00:00:00 2001
From: Wade Fife <wade.fife@ettus.com>
Date: Fri, 24 May 2024 14:18:01 -0500
Subject: [PATCH] fpga: lib: Add axis_sideband_tuser

Original-commit: 1549f95dc5c06d006499c30560184338c17a389e
---
 lib/axi/Makefile.srcs         |   1 +
 lib/axi/axis_sideband_tuser.v | 124 ++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 lib/axi/axis_sideband_tuser.v

diff --git a/lib/axi/Makefile.srcs b/lib/axi/Makefile.srcs
index e940a15..a9d45a6 100644
--- a/lib/axi/Makefile.srcs
+++ b/lib/axi/Makefile.srcs
@@ -38,4 +38,5 @@ axis_combine.v \
 axis_packetize.v \
 axis_pkt_throttle.sv \
 axis_data_if_packetize.v \
+axis_sideband_tuser.v \
 ))
diff --git a/lib/axi/axis_sideband_tuser.v b/lib/axi/axis_sideband_tuser.v
new file mode 100644
index 0000000..ed01345
--- /dev/null
+++ b/lib/axi/axis_sideband_tuser.v
@@ -0,0 +1,124 @@
+//
+// Copyright 2023 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+// Module: axis_sideband_tuser
+//
+// Description:
+//
+//   AXI stream buses often lack a pass-through tuser signal.
+//   This block uses a FIFO to implement that functionality.
+//   The FIFO can store a tuser entry for every bus transaction or
+//   it can operate in packet mode where the tuser signal is assumed
+//   to be constant during an entire packet to save resources.
+//
+//   NOTE: For buses / modules that consume a vector of samples (i.e. FFT block),
+//         the FIFO size must be deep enough for the entire vector or a deadlock
+//         can occur.
+//
+// Parameters:
+//
+//   WIDTH                : Width to tuser signal
+//   FIFO_SIZE_LOG2       : Log2 size of FIFO
+//   PACKET_MODE          : 0: Store tuser on every bus transaction
+//                          1: Replicate tuser from first word in a packet
+//                          2: Replicate tuser from last word in a packet, useful when tuser is EOB
+//
+
+`default_nettype none
+
+module axis_sideband_tuser
+#(
+  parameter WIDTH                 = 32,
+  parameter USER_WIDTH            = 1,
+  parameter FIFO_SIZE_LOG2        = 5,
+  parameter PACKET_MODE           = 1
+)(
+  // Clock/Reset
+  input  wire                  clk,
+  input  wire                  reset,
+
+  // Toplevel AXI stream buses with tuser
+  input  wire [WIDTH-1:0]      s_axis_tdata,
+  input  wire [USER_WIDTH-1:0] s_axis_tuser,
+  input  wire                  s_axis_tlast,
+  input  wire                  s_axis_tvalid,
+  output wire                  s_axis_tready,
+  output wire [WIDTH-1:0]      m_axis_tdata,
+  output wire [USER_WIDTH-1:0] m_axis_tuser,
+  output wire                  m_axis_tlast,
+  output wire                  m_axis_tvalid,
+  input  wire                  m_axis_tready,
+
+  // AXI stream buses to module / bus without tuser
+  output wire [WIDTH-1:0]      m_axis_mod_tdata,
+  output wire                  m_axis_mod_tlast,
+  output wire                  m_axis_mod_tvalid,
+  input  wire                  m_axis_mod_tready,
+  input  wire [WIDTH-1:0]      s_axis_mod_tdata,
+  input  wire                  s_axis_mod_tlast,
+  input  wire                  s_axis_mod_tvalid,
+  output wire                  s_axis_mod_tready
+);
+
+  wire [USER_WIDTH-1:0] fifo_in_tdata;
+  wire                  fifo_in_tvalid;
+  wire                  fifo_in_tready;
+  wire [USER_WIDTH-1:0] fifo_out_tdata;
+  wire                  fifo_out_tvalid;
+  wire                  fifo_out_tready;
+
+  axi_fifo #(
+    .WIDTH    (USER_WIDTH),
+    .SIZE     (FIFO_SIZE_LOG2))
+  axi_fifo_tuser (
+    .clk      (clk),
+    .reset    (reset),
+    .clear    (1'b0),
+    .i_tdata  (fifo_in_tdata),
+    .i_tvalid (fifo_in_tvalid),
+    .i_tready (fifo_in_tready),
+    .o_tdata  (fifo_out_tdata),
+    .o_tvalid (fifo_out_tvalid),
+    .o_tready (fifo_out_tready),
+    .space    (),
+    .occupied ()
+  );
+
+  reg first_word = 1'b1;
+  always @(posedge clk) begin
+    if (s_axis_tvalid & s_axis_tready) begin
+      first_word <= s_axis_tlast;
+    end
+    if (reset) begin
+      first_word <= 1'b1;
+    end
+  end
+
+  assign fifo_in_tdata      = s_axis_tuser;
+  assign fifo_in_tvalid     = m_axis_mod_tready & s_axis_tvalid &
+                              (PACKET_MODE == 0 ? 1'b1         :
+                               PACKET_MODE == 1 ? first_word   :
+                               PACKET_MODE == 2 ? s_axis_tlast :
+                               /* else */         1'b1);
+  assign fifo_out_tready    = m_axis_tready & s_axis_mod_tvalid &
+                              (PACKET_MODE == 0 ? 1'b1             :
+                               PACKET_MODE == 1 ? s_axis_mod_tlast :
+                               PACKET_MODE == 2 ? s_axis_mod_tlast :
+                               /* else */         1'b1);
+
+  assign s_axis_tready     = fifo_in_tready & m_axis_mod_tready;
+  assign m_axis_mod_tdata  = s_axis_tdata;
+  assign m_axis_mod_tlast  = s_axis_tlast;
+  assign m_axis_mod_tvalid = fifo_in_tready & s_axis_tvalid;
+
+  assign s_axis_mod_tready = m_axis_tready & fifo_out_tvalid;
+  assign m_axis_tdata      = s_axis_mod_tdata;
+  assign m_axis_tuser      = fifo_out_tdata;
+  assign m_axis_tlast      = s_axis_mod_tlast;
+  assign m_axis_tvalid     = s_axis_mod_tvalid & fifo_out_tvalid;
+
+endmodule
+
+`default_nettype wire