axis: Add AXI stream multiplexer module and testbench

Signed-off-by: Alex Forencich <[email protected]>

README.md

@@ -39,6 +39,7 @@ To facilitate the dual-license model, contributions to the project can only be a
     *  Asynchronous FIFO
     *  Combined FIFO + width converter
     *  Combined async FIFO + width converter
+    *  Multiplexer
     *  Broadcaster
     *  COBS encoder
     *  COBS decoder

rtl/axis/taxi_axis_mux.sv

@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: CERN-OHL-S-2.0
+/*
+
+Copyright (c) 2014-2025 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+*/
+
+`resetall
+`timescale 1ns / 1ps
+`default_nettype none
+
+/*
+ * AXI4-Stream multiplexer
+ */
+module taxi_axis_mux #
+(
+    // Number of AXI stream inputs
+    parameter S_COUNT = 4
+)
+(
+    input  wire logic                        clk,
+    input  wire logic                        rst,
+
+
+    /*
+     * AXI4-Stream inputs (sinks)
+     */
+    taxi_axis_if.snk                         s_axis[S_COUNT],
+
+    /*
+     * AXI4-Stream output (source)
+     */
+    taxi_axis_if.src                         m_axis,
+
+    /*
+     * Control
+     */
+    input  wire logic                        enable,
+    input  wire logic [$clog2(S_COUNT)-1:0]  select
+);
+
+// extract parameters
+localparam DATA_W = s_axis.DATA_W;
+localparam logic KEEP_EN = s_axis.KEEP_EN && m_axis.KEEP_EN;
+localparam KEEP_W = s_axis.KEEP_W;
+localparam logic STRB_EN = s_axis.STRB_EN && m_axis.STRB_EN;
+localparam logic LAST_EN = s_axis.LAST_EN && m_axis.LAST_EN;
+localparam logic ID_EN = s_axis.ID_EN && m_axis.ID_EN;
+localparam ID_W = s_axis.ID_W;
+localparam logic DEST_EN = s_axis.DEST_EN && m_axis.DEST_EN;
+localparam DEST_W = s_axis.DEST_W;
+localparam logic USER_EN = s_axis.USER_EN && m_axis.USER_EN;
+localparam USER_W = s_axis.USER_W;
+
+// check configuration
+if (m_axis.DATA_W != DATA_W)
+    $fatal(0, "Error: Interface DATA_W parameter mismatch (instance %m)");
+
+if (KEEP_EN && m_axis.KEEP_W != KEEP_W)
+    $fatal(0, "Error: Interface KEEP_W parameter mismatch (instance %m)");
+
+parameter CL_S_COUNT = $clog2(S_COUNT);
+
+reg [CL_S_COUNT-1:0] select_reg = 2'd0, select_next;
+reg frame_reg = 1'b0, frame_next;
+
+reg [S_COUNT-1:0] s_axis_tready_reg = 0, s_axis_tready_next;
+
+// internal datapath
+reg  [DATA_W-1:0]  m_axis_tdata_int;
+reg  [KEEP_W-1:0]  m_axis_tkeep_int;
+reg  [KEEP_W-1:0]  m_axis_tstrb_int;
+reg                m_axis_tvalid_int;
+reg                m_axis_tready_int_reg = 1'b0;
+reg                m_axis_tlast_int;
+reg  [ID_W-1:0]    m_axis_tid_int;
+reg  [DEST_W-1:0]  m_axis_tdest_int;
+reg  [USER_W-1:0]  m_axis_tuser_int;
+wire               m_axis_tready_int_early;
+
+// unpack interface array
+wire [S_COUNT-1:0][DATA_W-1:0]  s_axis_tdata;
+wire [S_COUNT-1:0][KEEP_W-1:0]  s_axis_tkeep;
+wire [S_COUNT-1:0][KEEP_W-1:0]  s_axis_tstrb;
+wire [S_COUNT-1:0]              s_axis_tvalid;
+wire [S_COUNT-1:0]              s_axis_tready;
+wire [S_COUNT-1:0]              s_axis_tlast;
+wire [S_COUNT-1:0][ID_W-1:0]    s_axis_tid;
+wire [S_COUNT-1:0][DEST_W-1:0]  s_axis_tdest;
+wire [S_COUNT-1:0][USER_W-1:0]  s_axis_tuser;
+
+for (genvar n = 0; n < S_COUNT; n = n + 1) begin
+    assign s_axis_tdata[n] = s_axis[n].tdata;
+    assign s_axis_tkeep[n] = s_axis[n].tkeep;
+    assign s_axis_tstrb[n] = s_axis[n].tstrb;
+    assign s_axis_tvalid[n] = s_axis[n].tvalid;
+    assign s_axis[n].tready = s_axis_tready[n];
+    assign s_axis_tlast[n] = s_axis[n].tlast;
+    assign s_axis_tid[n] = s_axis[n].tid;
+    assign s_axis_tdest[n] = s_axis[n].tdest;
+    assign s_axis_tuser[n] = s_axis[n].tuser;
+end
+
+assign s_axis_tready = s_axis_tready_reg;
+
+// mux for incoming packet
+wire [DATA_W-1:0]  current_s_tdata  = s_axis_tdata[select_reg];
+wire [KEEP_W-1:0]  current_s_tkeep  = s_axis_tkeep[select_reg];
+wire [KEEP_W-1:0]  current_s_tstrb  = s_axis_tstrb[select_reg];
+wire               current_s_tvalid = s_axis_tvalid[select_reg];
+wire               current_s_tready = s_axis_tready[select_reg];
+wire               current_s_tlast  = s_axis_tlast[select_reg];
+wire [ID_W-1:0]    current_s_tid    = s_axis_tid[select_reg];
+wire [DEST_W-1:0]  current_s_tdest  = s_axis_tdest[select_reg];
+wire [USER_W-1:0]  current_s_tuser  = s_axis_tuser[select_reg];
+
+always_comb begin
+    select_next = select_reg;
+    frame_next = frame_reg;
+
+    s_axis_tready_next = 0;
+
+    if (current_s_tvalid & current_s_tready) begin
+        // end of frame detection
+        if (current_s_tlast) begin
+            frame_next = 1'b0;
+        end
+    end
+
+    if (!frame_reg && enable && s_axis_tvalid[select]) begin
+        // start of frame, grab select value
+        frame_next = 1'b1;
+        select_next = select;
+    end
+
+    // generate ready signal on selected port
+    s_axis_tready_next[select_next] = m_axis_tready_int_early && frame_next;
+
+    // pass through selected packet data
+    m_axis_tdata_int  = current_s_tdata;
+    m_axis_tkeep_int  = current_s_tkeep;
+    m_axis_tstrb_int  = current_s_tstrb;
+    m_axis_tvalid_int = current_s_tvalid && current_s_tready && frame_reg;
+    m_axis_tlast_int  = current_s_tlast;
+    m_axis_tid_int    = current_s_tid;
+    m_axis_tdest_int  = current_s_tdest;
+    m_axis_tuser_int  = current_s_tuser;
+end
+
+always_ff @(posedge clk) begin
+    select_reg <= select_next;
+    frame_reg <= frame_next;
+    s_axis_tready_reg <= s_axis_tready_next;
+
+    if (rst) begin
+        select_reg <= 0;
+        frame_reg <= 1'b0;
+        s_axis_tready_reg <= 0;
+    end
+end
+
+// output datapath logic
+reg [DATA_W-1:0]  m_axis_tdata_reg  = '0;
+reg [KEEP_W-1:0]  m_axis_tkeep_reg  = '0;
+reg [KEEP_W-1:0]  m_axis_tstrb_reg  = '0;
+reg               m_axis_tvalid_reg = 1'b0, m_axis_tvalid_next;
+reg               m_axis_tlast_reg  = 1'b0;
+reg [ID_W-1:0]    m_axis_tid_reg    = '0;
+reg [DEST_W-1:0]  m_axis_tdest_reg  = '0;
+reg [USER_W-1:0]  m_axis_tuser_reg  = '0;
+
+reg [DATA_W-1:0]  temp_m_axis_tdata_reg  = '0;
+reg [KEEP_W-1:0]  temp_m_axis_tkeep_reg  = '0;
+reg [KEEP_W-1:0]  temp_m_axis_tstrb_reg  = '0;
+reg               temp_m_axis_tvalid_reg = 1'b0, temp_m_axis_tvalid_next;
+reg               temp_m_axis_tlast_reg  = 1'b0;
+reg [ID_W-1:0]    temp_m_axis_tid_reg    = '0;
+reg [DEST_W-1:0]  temp_m_axis_tdest_reg  = '0;
+reg [USER_W-1:0]  temp_m_axis_tuser_reg  = '0;
+
+// datapath control
+reg store_axis_int_to_output;
+reg store_axis_int_to_temp;
+reg store_axis_temp_to_output;
+
+assign m_axis.tdata  = m_axis_tdata_reg;
+assign m_axis.tkeep  = KEEP_EN ? m_axis_tkeep_reg : '1;
+assign m_axis.tstrb  = STRB_EN ? m_axis_tstrb_reg : m_axis.tkeep;
+assign m_axis.tvalid = m_axis_tvalid_reg;
+assign m_axis.tlast  = m_axis_tlast_reg;
+assign m_axis.tid    = ID_EN   ? m_axis_tid_reg   : '0;
+assign m_axis.tdest  = DEST_EN ? m_axis_tdest_reg : '0;
+assign m_axis.tuser  = USER_EN ? m_axis_tuser_reg : '0;
+
+// enable ready input next cycle if output is ready or the temp reg will not be filled on the next cycle (output reg empty or no input)
+assign m_axis_tready_int_early = m_axis.tready || (!temp_m_axis_tvalid_reg && (!m_axis_tvalid_reg || !m_axis_tvalid_int));
+
+always_comb begin
+    // transfer sink ready state to source
+    m_axis_tvalid_next = m_axis_tvalid_reg;
+    temp_m_axis_tvalid_next = temp_m_axis_tvalid_reg;
+
+    store_axis_int_to_output = 1'b0;
+    store_axis_int_to_temp = 1'b0;
+    store_axis_temp_to_output = 1'b0;
+
+    if (m_axis_tready_int_reg) begin
+        // input is ready
+        if (m_axis.tready || !m_axis_tvalid_reg) begin
+            // output is ready or currently not valid, transfer data to output
+            m_axis_tvalid_next = m_axis_tvalid_int;
+            store_axis_int_to_output = 1'b1;
+        end else begin
+            // output is not ready, store input in temp
+            temp_m_axis_tvalid_next = m_axis_tvalid_int;
+            store_axis_int_to_temp = 1'b1;
+        end
+    end else if (m_axis.tready) begin
+        // input is not ready, but output is ready
+        m_axis_tvalid_next = temp_m_axis_tvalid_reg;
+        temp_m_axis_tvalid_next = 1'b0;
+        store_axis_temp_to_output = 1'b1;
+    end
+end
+
+always_ff @(posedge clk) begin
+    m_axis_tvalid_reg <= m_axis_tvalid_next;
+    m_axis_tready_int_reg <= m_axis_tready_int_early;
+    temp_m_axis_tvalid_reg <= temp_m_axis_tvalid_next;
+
+    // datapath
+    if (store_axis_int_to_output) begin
+        m_axis_tdata_reg <= m_axis_tdata_int;
+        m_axis_tkeep_reg <= m_axis_tkeep_int;
+        m_axis_tstrb_reg <= m_axis_tstrb_int;
+        m_axis_tlast_reg <= m_axis_tlast_int;
+        m_axis_tid_reg   <= m_axis_tid_int;
+        m_axis_tdest_reg <= m_axis_tdest_int;
+        m_axis_tuser_reg <= m_axis_tuser_int;
+    end else if (store_axis_temp_to_output) begin
+        m_axis_tdata_reg <= temp_m_axis_tdata_reg;
+        m_axis_tkeep_reg <= temp_m_axis_tkeep_reg;
+        m_axis_tstrb_reg <= temp_m_axis_tstrb_reg;
+        m_axis_tlast_reg <= temp_m_axis_tlast_reg;
+        m_axis_tid_reg   <= temp_m_axis_tid_reg;
+        m_axis_tdest_reg <= temp_m_axis_tdest_reg;
+        m_axis_tuser_reg <= temp_m_axis_tuser_reg;
+    end
+
+    if (store_axis_int_to_temp) begin
+        temp_m_axis_tdata_reg <= m_axis_tdata_int;
+        temp_m_axis_tkeep_reg <= m_axis_tkeep_int;
+        temp_m_axis_tstrb_reg <= m_axis_tstrb_int;
+        temp_m_axis_tlast_reg <= m_axis_tlast_int;
+        temp_m_axis_tid_reg   <= m_axis_tid_int;
+        temp_m_axis_tdest_reg <= m_axis_tdest_int;
+        temp_m_axis_tuser_reg <= m_axis_tuser_int;
+    end
+
+    if (rst) begin
+        m_axis_tvalid_reg <= 1'b0;
+        m_axis_tready_int_reg <= 1'b0;
+        temp_m_axis_tvalid_reg <= 1'b0;
+    end
+end
+
+endmodule
+
+`resetall

tb/axis/taxi_axis_mux/Makefile

@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: CERN-OHL-S-2.0
+#
+# Copyright (c) 2021-2025 FPGA Ninja, LLC
+#
+# Authors:
+# - Alex Forencich
+
+TOPLEVEL_LANG = verilog
+
+SIM ?= verilator
+WAVES ?= 0
+
+COCOTB_HDL_TIMEUNIT = 1ns
+COCOTB_HDL_TIMEPRECISION = 1ps
+
+DUT      = taxi_axis_mux
+COCOTB_TEST_MODULES = test_$(DUT)
+COCOTB_TOPLEVEL     = test_$(DUT)
+MODULE   = $(COCOTB_TEST_MODULES)
+TOPLEVEL = $(COCOTB_TOPLEVEL)
+VERILOG_SOURCES += $(COCOTB_TOPLEVEL).sv
+VERILOG_SOURCES += ../../../rtl/axis/$(DUT).sv
+VERILOG_SOURCES += ../../../rtl/axis/taxi_axis_if.sv
+
+# handle file list files
+process_f_file = $(call process_f_files,$(addprefix $(dir $1),$(shell cat $1)))
+process_f_files = $(foreach f,$1,$(if $(filter %.f,$f),$(call process_f_file,$f),$f))
+uniq_base = $(if $1,$(call uniq_base,$(foreach f,$1,$(if $(filter-out $(notdir $(lastword $1)),$(notdir $f)),$f,))) $(lastword $1))
+VERILOG_SOURCES := $(call uniq_base,$(call process_f_files,$(VERILOG_SOURCES)))
+
+# module parameters
+export PARAM_S_COUNT := 4
+export PARAM_DATA_W := 8
+export PARAM_KEEP_EN := $(shell expr $(PARAM_DATA_W) \> 8 )
+export PARAM_KEEP_W := $(shell expr \( $(PARAM_DATA_W) + 7 \) / 8 )
+export PARAM_STRB_EN := 0
+export PARAM_LAST_EN := 1
+export PARAM_ID_EN := 1
+export PARAM_ID_W := 8
+export PARAM_DEST_EN := 1
+export PARAM_DEST_W := 8
+export PARAM_USER_EN := 1
+export PARAM_USER_W := 1
+
+ifeq ($(SIM), icarus)
+	PLUSARGS += -fst
+
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-P $(COCOTB_TOPLEVEL).$(subst PARAM_,,$(v))=$($(v)))
+else ifeq ($(SIM), verilator)
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-G$(subst PARAM_,,$(v))=$($(v)))
+
+	ifeq ($(WAVES), 1)
+		COMPILE_ARGS += --trace-fst
+		VERILATOR_TRACE = 1
+	endif
+endif
+
+include $(shell cocotb-config --makefiles)/Makefile.sim