axis_mii_tx: Add reset

Yosys doesn't optimize FSMs without resets. Add one so ours gets
optimized.

Signed-off-by: Sean Anderson <seanga2@gmail.com>

rtl/axis_mii_tx.v

@@ -18,7 +18,7 @@
  */
 
 module axis_mii_tx (
-	input clk,
+	input clk, rst,
 
 	/* MII */
 	output reg mii_tx_ce,
@@ -155,17 +155,13 @@ module axis_mii_tx (
 	wire [7:0] buf_data;
 	wire buf_err, buf_valid, buf_last;
 	reg buf_ready, buf_ready_next, replay, replay_next, done, done_next;
-	initial begin
-		buf_ready = 0;
-		done = 0;
-		replay = 0;
-	end
 
 	axis_replay_buffer #(
 		.DATA_WIDTH(9),
 		.BUF_SIZE(DATA_EARLY_BYTES)
 	) replay_buffer (
 		.clk(clk),
+		.rst(rst),
 		.s_axis_data({ axis_data, axis_err }),
 		.s_axis_valid(axis_valid),
 		.s_axis_ready(axis_ready),
@@ -188,24 +184,6 @@ module axis_mii_tx (
 	reg transmit_ok_next, gave_up_next, late_collision_next;
 	reg underflow_next;
 
-	initial begin
-		mii_tx_counter = MII_100_RATIO;
-		mii_tx_ce = 0;
-		mii_tx_ce_next = 0;
-		mii_tx_ce_next_next = 0;
-		mii_tx_en = 0;
-		mii_txd = 0;
-		odd = 0;
-		state = IPG_EARLY;
-		state_counter = IPG_EARLY_BYTES - 1;
-		retries = MAX_RETRIES - 1;
-		lfsr = 10'h3ff;
-		transmit_ok = 0;
-		gave_up = 0;
-		late_collision = 0;
-		underflow = 0;
-	end
-
 	always @(*) begin
 		mii_tx_ce_next_next_next = 0;
 		mii_tx_counter_next = mii_tx_counter - 1;
@@ -503,30 +481,51 @@ module axis_mii_tx (
 		endcase
 	end
 
-	always @(posedge clk) begin
+	always @(posedge clk, posedge rst) begin
-		mii_tx_ce <= mii_tx_ce_next;
+		if (rst) begin
-		mii_tx_ce_next <= mii_tx_ce_next_next;
+			mii_tx_counter <= MII_100_RATIO;
-		mii_tx_ce_next_next <= mii_tx_ce_next_next_next;
+			mii_tx_ce <= 0;
-		mii_tx_counter <= mii_tx_counter_next;
+			mii_tx_ce_next <= 0;
-		mii_tx_en <= mii_tx_en_next;
+			mii_tx_ce_next_next <= 0;
-		mii_txd <= odd_next ? data_next[7:4] : data_next[3:0];
+			mii_tx_en <= 0;
-		do_crc <= do_crc_next;
+			mii_txd <= 0;
-		odd <= odd_next;
+			odd <= 0;
-		state <= state_next;
+			state <= IPG_EARLY;
-		state_counter <= state_counter_next;
+			state_counter <= IPG_EARLY_BYTES - 1;
-		buf_ready <= buf_ready_next;
+			retries <= MAX_RETRIES - 1;
-		data <= data_next;
+			lfsr <= 10'h3ff;
-		replay <= replay_next;
+			transmit_ok <= 0;
-		done <= done_next;
+			gave_up <= 0;
-		retries <= retries_next;
+			late_collision <= 0;
-		backoff <= backoff_next;
+			underflow <= 0;
-		lfsr <= lfsr_next;
+			buf_ready <= 0;
-		crc_state <= crc_state_next;
+			done <= 0;
-		collision <= collision_next;
+			replay <= 0;
-		transmit_ok <= transmit_ok_next;
+		end else begin
-		gave_up <= gave_up_next;
+			mii_tx_ce <= mii_tx_ce_next;
-		late_collision <= late_collision_next;
+			mii_tx_ce_next <= mii_tx_ce_next_next;
-		underflow <= underflow_next;
+			mii_tx_ce_next_next <= mii_tx_ce_next_next_next;
+			mii_tx_counter <= mii_tx_counter_next;
+			mii_tx_en <= mii_tx_en_next;
+			mii_txd <= odd_next ? data_next[7:4] : data_next[3:0];
+			do_crc <= do_crc_next;
+			odd <= odd_next;
+			state <= state_next;
+			state_counter <= state_counter_next;
+			buf_ready <= buf_ready_next;
+			data <= data_next;
+			replay <= replay_next;
+			done <= done_next;
+			retries <= retries_next;
+			backoff <= backoff_next;
+			lfsr <= lfsr_next;
+			crc_state <= crc_state_next;
+			collision <= collision_next;
+			transmit_ok <= transmit_ok_next;
+			gave_up <= gave_up_next;
+			late_collision <= late_collision_next;
+			underflow <= underflow_next;
+		end
 	end
 
 `ifndef SYNTHESIS

rtl/axis_replay_buffer.v

@@ -25,7 +25,7 @@
 `include "common.vh"
 
 module axis_replay_buffer (
-	input clk,
+	input clk, rst,
 
 	/* AXI Stream slave */
 	input [DATA_WIDTH - 1:0] s_axis_data,
@@ -72,19 +72,6 @@ module axis_replay_buffer (
 	reg last, last_next;
 	reg full, full_next, empty, replayable_next, we, re;
 
-	initial begin
-		m_ptr = 0;
-		s_ptr = 0;
-		last = 0;
-		replayable = 1;
-		s_axis_valid_last = 0;
-		s_axis_last_last = 0;
-		s_axis_ready = 1;
-		m_axis_valid = 0;
-		m_axis_last = 0;
-		sent_last = 0;
-	end
-
 	always @(*) begin
 		we = 0;
 		s_ptr_next = s_ptr;
@@ -157,19 +144,34 @@ module axis_replay_buffer (
 			buffer[s_ptr[BUF_WIDTH - 1:0]] <= { s_axis_data_last };
 		if (re)
 			{ m_axis_data } <= buffer[m_ptr[BUF_WIDTH - 1:0]];
+	end
 
-		s_axis_data_last <= s_axis_data;
+	always @(posedge clk, posedge rst) begin
-		s_axis_valid_last <= s_axis_valid;
+		if (rst) begin
-		s_axis_last_last <= s_axis_last;
+			m_ptr <= 0;
-		s_axis_ready <= s_axis_ready_next;
+			s_ptr <= 0;
-		m_axis_last <= m_axis_last_next;
+			last <= 0;
-		m_axis_valid <= m_axis_valid_next;
+			replayable <= 1;
-		sent_last <= sent_last_next;
+			s_axis_valid_last <= 0;
-		m_ptr <= m_ptr_next;
+			s_axis_last_last <= 0;
-		s_ptr <= s_ptr_next;
+			s_axis_ready <= 1;
-		last <= last_next;
+			m_axis_valid <= 0;
-		last_ptr <= last_ptr_next;
+			m_axis_last <= 0;
-		replayable <= replayable_next;
+			sent_last <= 0;
+		end else begin
+			s_axis_data_last <= s_axis_data;
+			s_axis_valid_last <= s_axis_valid;
+			s_axis_last_last <= s_axis_last;
+			s_axis_ready <= s_axis_ready_next;
+			m_axis_last <= m_axis_last_next;
+			m_axis_valid <= m_axis_valid_next;
+			sent_last <= sent_last_next;
+			m_ptr <= m_ptr_next;
+			s_ptr <= s_ptr_next;
+			last <= last_next;
+			last_ptr <= last_ptr_next;
+			replayable <= replayable_next;
+		end
 	end
 
 `ifndef SYNTHESIS

tb/axis_mii_tx.py

@@ -21,13 +21,16 @@ import os
 skip_slow = not os.environ.get('RUN_SLOW', False)
 
 async def init(mac):
+    mac.rst.value = 1
     mac.mii_col.value = 0
     mac.mii_crs.value = 0
     mac.axis_valid.value = 0
     mac.axis_err.value = 0
     mac.short_backoff.value = 1
     await Timer(1)
+    mac.rst.value = 0
     await cocotb.start(Clock(mac.clk, 8, units='ns').start())
+    await FallingEdge(mac.clk)
 
 def send_packet(mac, packet, ratio=1):
     return axis_replay_buffer.send_packet({

tb/axis_replay_buffer.py

@@ -34,6 +34,7 @@ async def send_packet(signals, packet, ratio=1):
 
 @timeout(30, 'us')
 async def test_replay(buf, in_ratio, out_ratio):
+    buf.rst.value = 1
     buf.s_axis_valid.value = 0
     buf.s_axis_last.value = 0
     buf.m_axis_ready.value = 1
@@ -41,6 +42,7 @@ async def test_replay(buf, in_ratio, out_ratio):
     buf.done.value = 0
 
     await Timer(1)
+    buf.rst.value = 0
     await cocotb.start(Clock(buf.clk, 8, units='ns').start())
     await FallingEdge(buf.clk)
     await cocotb.start(ClockEnable(buf.clk, buf.m_axis_ready, out_ratio))