vhdl: reorganize receive FSM to avoid ghdl issues

https://github.com/ghdl/ghdl/issues/2077
https://github.com/ghdl/ghdl/issues/2078

vhdl/splink.vhdl

@@ -22,61 +22,125 @@ entity splink is
 end entity;
 
 architecture a of splink is
-	signal driver_out : std_logic;
-
 	constant BITS_PER_LED: natural := 24;
 	subtype color_t is std_logic_vector(BITS_PER_LED-1 downto 0);
-	type strand_store_t is array(0 to MAX_STRAND_LEN) of color_t;
-	signal strand_store: strand_store_t;
 
-	signal led_addr : std_logic_vector(7 downto 0);
-	signal current_color : color_t;
+	type led_data_t is record
+		addr : std_logic_vector(7 downto 0);
+		current_color : color_t;
+
+		was_written : std_logic;
+	end record;
+
+	type led_data_arr_t is array(0 to NUM_STRANDS-1) of led_data_t;
+	signal led_data_arr : led_data_arr_t;
+
+	signal active_strand: natural range 0 to NUM_STRANDS-1;
+	signal num_pixels: natural range 1 to MAX_STRAND_LEN;
+	signal frame_number: unsigned(31 downto 0);
+	signal pixels_received: natural range 0 to MAX_STRAND_LEN-1;
+
+	type receive_state_t is (FRAME_NUM, STRAND_NUM, DATA, DROP);
+	signal receive_state : receive_state_t;
 begin
-	ws2812_inst: entity work.ws2812
-		generic map (
-			NUM_LEDS => MAX_STRAND_LEN,
-			COLOR_ORDER => "GRB",
-			T_CLK => 12.5 ns,
+	driver_gen: for i in 0 to NUM_STRANDS-1 generate
+		ws2812_inst: entity work.ws2812
+			generic map (
+				NUM_LEDS => MAX_STRAND_LEN,
+				COLOR_ORDER => "GRB",
+				T_CLK => 12.5 ns,
 
-			T0H => 0.35 us,
-			T0L => 0.8 us,
-			T1H => 0.7 us,
-			T1L => 0.6 us,
+				T0H => 0.35 us,
+				T0L => 0.8 us,
+				T1H => 0.7 us,
+				T1L => 0.6 us,
 
-			T_RES => 80 us
-		)
-		port map (
-			n_reset => not reset,
-			clk     => clk,
+				T_RES => 80 us
+			)
+			port map (
+				n_reset => not reset,
+				clk     => clk,
 
-			led_addr => led_addr,
+				led_addr => led_data_arr(i).addr,
 
-			led_red   => current_color(7 downto 0),
-			led_green => current_color(15 downto 8),
-			led_blue  => current_color(23 downto 16),
+				led_red   => led_data_arr(i).current_color(23 downto 16),
+				led_green => led_data_arr(i).current_color(15 downto 8),
+				led_blue  => led_data_arr(i).current_color(7 downto 0),
 
-			dout => driver_out
-		);
+				dout => drivers(i)
+			);
 
-	-- https://github.com/YosysHQ/yosys/issues/3360
-	drivers <= (19 => driver_out, others => '0');
+		writer: process(clk)
+			type strand_store_t is array(0 to MAX_STRAND_LEN-1) of color_t;
+			variable strand_store: strand_store_t;
+		begin
+			if rising_edge(clk) then
+				led_data_arr(i).current_color <= strand_store(to_integer(unsigned(led_data_arr(i).addr)));
 
-	writer: process(clk)
-		variable store_counter: natural range 0 to MAX_STRAND_LEN-1;
+				if udp_valid = '1' and receive_state = DATA and active_strand = i then
+					strand_store(pixels_received) := udp_data(23 downto 0);
+
+					if pixels_received = num_pixels - 1 and udp_last = '1' then
+						led_data_arr(i).was_written <= '1';
+					end if;
+				end if;
+
+				if frame_done then
+					led_data_arr(i).was_written <= '0';
+				end if;
+			end if;
+		end process;
+	end generate;
+
+	process(led_data_arr)
+	begin
+		frame_done <= '1';
+
+		for i in 0 to NUM_STRANDS-1 loop
+			if not led_data_arr(i).was_written then
+				frame_done <= '0';
+			end if;
+		end loop;
+	end process;
+
+	fsm: process(clk)
 	begin
 		if rising_edge(clk) then
-			frame_done <= '0';
-			current_color <= strand_store(to_integer(unsigned(led_addr)));
-
-			if udp_valid then
-				strand_store(store_counter) <= udp_data(23 downto 0);
-
+			if reset then
+				receive_state <= STRAND_NUM;
+			elsif udp_valid then
 				if udp_last then
-					frame_done <= '1';
-					store_counter := 0;
-				elsif store_counter /= MAX_STRAND_LEN-1 then
-					store_counter := store_counter + 1;
+					-- always resynchronize to start of packet
+					receive_state <= STRAND_NUM;
 				end if;
+
+				case receive_state is
+					when STRAND_NUM =>
+						-- TODO udp_length, range check with MAX_STRAND_LEN
+						num_pixels <= MAX_STRAND_LEN;
+
+						-- FIXME bounds check
+						active_strand <= to_integer(unsigned(udp_data));
+
+						receive_state <= FRAME_NUM;
+
+					when FRAME_NUM =>
+						frame_number <= unsigned(udp_data);
+
+						pixels_received <= 0;
+						receive_state <= DATA;
+
+					when DATA =>
+						if pixels_received /= num_pixels - 1 then
+							pixels_received <= pixels_received + 1;
+						elsif not udp_last then
+							-- packet too long
+							receive_state <= DROP;
+						end if;
+
+					when DROP =>
+						-- wait until udp_last
+				end case;
 			end if;
 		end if;
 	end process;