phy: rx: Introduce simple glitch filter

trashernet/trashernet_phy.vhd

@@ -37,9 +37,10 @@ begin
 
 	receiver : block
 		-- Signal conditioning
-		signal rx      : std_logic;
-		signal rx_last : std_logic;
-		signal rx_edge : std_logic;
+		signal rx             : std_logic;
+		signal rx_last        : std_logic;
+		signal rx_last_static : std_logic;
+		signal rx_edge        : std_logic;
 
 		-- Bit recovery
 		signal bit_value : std_logic;
@@ -61,11 +62,23 @@ begin
 				data_out => rx
 			);
 
-		-- Edge detector for RX
-		rx_last <= '0' when rst
-		           else rx when rising_edge(clk)
-		         ;
-		rx_edge <= rx_last xor rx;
+		-- Edge detector for RX (+glitch filter)
+		edgedet : process(clk, rst) is
+		begin
+			if rst then
+				rx_last        <= '0';
+				rx_last_static <= '0';
+				rx_edge        <= '0';
+
+			elsif rising_edge(clk) then
+				rx_edge <= '0';
+				if (rx_last = rx) then
+					rx_edge        <= rx_last_static xor rx;
+					rx_last_static <= rx;
+				end if;
+				rx_last <= rx;
+			end if;
+		end process edgedet;
 
 		demanchestizer : block
 			-- Transition detector