microwatt/fpga/top-arty.vhdl

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

library unisim;
use unisim.vcomponents.all;

library work;
use work.wishbone_types.all;

entity toplevel is
    generic (
        MEMORY_SIZE        : integer  := 16384;
        RAM_INIT_FILE      : string   := "firmware.hex";
        RESET_LOW          : boolean  := true;
        CLK_FREQUENCY      : positive := 100000000;
        USE_LITEDRAM       : boolean  := false;
        NO_BRAM            : boolean  := false;
        DISABLE_FLATTEN_CORE : boolean := false;
        SCLK_STARTUPE2     : boolean := false;
        SPI_FLASH_OFFSET   : integer := 4194304;
        SPI_FLASH_DEF_CKDV : natural := 1;
        SPI_FLASH_DEF_QUAD : boolean := true;
        LOG_LENGTH         : natural := 512
        );
    port(
        ext_clk   : in  std_ulogic;
        ext_rst   : in  std_ulogic;

        -- UART0 signals:
        uart_main_tx : out std_ulogic;
        uart_main_rx : in  std_ulogic;

        -- LEDs
        led0_b  : out std_ulogic;
        led0_g  : out std_ulogic;
        led0_r  : out std_ulogic;

        -- SPI
        spi_flash_cs_n   : out std_ulogic;
        spi_flash_clk    : out std_ulogic;
        spi_flash_mosi   : inout std_ulogic;
        spi_flash_miso   : inout std_ulogic;
        spi_flash_wp_n   : inout std_ulogic;
        spi_flash_hold_n : inout std_ulogic;

        -- DRAM wires
        ddram_a       : out std_ulogic_vector(13 downto 0);
        ddram_ba      : out std_ulogic_vector(2 downto 0);
        ddram_ras_n   : out std_ulogic;
        ddram_cas_n   : out std_ulogic;
        ddram_we_n    : out std_ulogic;
        ddram_cs_n    : out std_ulogic;
        ddram_dm      : out std_ulogic_vector(1 downto 0);
        ddram_dq      : inout std_ulogic_vector(15 downto 0);
        ddram_dqs_p   : inout std_ulogic_vector(1 downto 0);
        ddram_dqs_n   : inout std_ulogic_vector(1 downto 0);
        ddram_clk_p   : out std_ulogic;
        ddram_clk_n   : out std_ulogic;
        ddram_cke     : out std_ulogic;
        ddram_odt     : out std_ulogic;
        ddram_reset_n : out std_ulogic
        );
end entity toplevel;

architecture behaviour of toplevel is

    -- Reset signals:
    signal soc_rst : std_ulogic;
    signal pll_rst : std_ulogic;

    -- Internal clock signals:
    signal system_clk : std_ulogic;
    signal system_clk_locked : std_ulogic;

    -- DRAM main data wishbone connection
    signal wb_dram_in       : wishbone_master_out;
    signal wb_dram_out      : wishbone_slave_out;

    -- DRAM control wishbone connection
    signal wb_dram_ctrl_in  : wb_io_master_out;
    signal wb_dram_ctrl_out : wb_io_slave_out;
    signal wb_dram_is_csr   : std_ulogic;
    signal wb_dram_is_init  : std_ulogic;

    -- Control/status
    signal core_alt_reset : std_ulogic;

    -- Status LED
    signal led0_b_pwm : std_ulogic;
    signal led0_r_pwm : std_ulogic;
    signal led0_g_pwm : std_ulogic;

    -- Dumb PWM for the LEDs, those RGB LEDs are too bright otherwise
    signal pwm_counter  : std_ulogic_vector(8 downto 0);

    -- SPI flash
    signal spi_sck     : std_ulogic;
    signal spi_cs_n    : std_ulogic;
    signal spi_sdat_o  : std_ulogic_vector(3 downto 0);
    signal spi_sdat_oe : std_ulogic_vector(3 downto 0);
    signal spi_sdat_i  : std_ulogic_vector(3 downto 0);

    -- Fixup various memory sizes based on generics
    function get_bram_size return natural is
    begin
        if USE_LITEDRAM and NO_BRAM then
            return 0;
        else
            return MEMORY_SIZE;
        end if;
    end function;

    function get_payload_size return natural is
    begin
        if USE_LITEDRAM and NO_BRAM then
            return MEMORY_SIZE;
        else
            return 0;
        end if;
    end function;
    
    constant BRAM_SIZE    : natural := get_bram_size;
    constant PAYLOAD_SIZE : natural := get_payload_size;
begin

    -- Main SoC
    soc0: entity work.soc
        generic map(
            MEMORY_SIZE        => BRAM_SIZE,
            RAM_INIT_FILE      => RAM_INIT_FILE,
            RESET_LOW          => RESET_LOW,
            SIM                => false,
            CLK_FREQ           => CLK_FREQUENCY,
            HAS_DRAM           => USE_LITEDRAM,
            DRAM_SIZE          => 256 * 1024 * 1024,
            DRAM_INIT_SIZE     => PAYLOAD_SIZE,
            DISABLE_FLATTEN_CORE => DISABLE_FLATTEN_CORE,
            HAS_SPI_FLASH      => true,
            SPI_FLASH_DLINES   => 4,
            SPI_FLASH_OFFSET   => SPI_FLASH_OFFSET,
            SPI_FLASH_DEF_CKDV => SPI_FLASH_DEF_CKDV,
            SPI_FLASH_DEF_QUAD => SPI_FLASH_DEF_QUAD,
            LOG_LENGTH         => LOG_LENGTH
            )
        port map (
            -- System signals
            system_clk        => system_clk,
            rst               => soc_rst,

            -- UART signals
            uart0_txd         => uart_main_tx,
            uart0_rxd         => uart_main_rx,

            -- SPI signals
            spi_flash_sck     => spi_sck,
            spi_flash_cs_n    => spi_cs_n,
            spi_flash_sdat_o  => spi_sdat_o,
            spi_flash_sdat_oe => spi_sdat_oe,
            spi_flash_sdat_i  => spi_sdat_i,

            -- DRAM wishbone
            wb_dram_in        => wb_dram_in,
            wb_dram_out       => wb_dram_out,
            wb_dram_ctrl_in   => wb_dram_ctrl_in,
            wb_dram_ctrl_out  => wb_dram_ctrl_out,
            wb_dram_is_csr    => wb_dram_is_csr,
            wb_dram_is_init   => wb_dram_is_init,
            alt_reset         => core_alt_reset
            );

    -- SPI Flash
    --
    -- Note: Unlike many other boards, the SPI flash on the Arty has
    -- an actual pin to generate the clock and doesn't require to use
    -- the STARTUPE2 primitive.
    --
    spi_flash_cs_n   <= spi_cs_n;
    spi_flash_mosi   <= spi_sdat_o(0) when spi_sdat_oe(0) = '1' else 'Z';
    spi_flash_miso   <= spi_sdat_o(1) when spi_sdat_oe(1) = '1' else 'Z';
    spi_flash_wp_n   <= spi_sdat_o(2) when spi_sdat_oe(2) = '1' else 'Z';
    spi_flash_hold_n <= spi_sdat_o(3) when spi_sdat_oe(3) = '1' else 'Z';
    spi_sdat_i(0)    <= spi_flash_mosi;
    spi_sdat_i(1)    <= spi_flash_miso;
    spi_sdat_i(2)    <= spi_flash_wp_n;
    spi_sdat_i(3)    <= spi_flash_hold_n;

    spi_sclk_startupe2: if SCLK_STARTUPE2 generate
        spi_flash_clk    <= 'Z';

        STARTUPE2_INST: STARTUPE2
            port map (
                CLK => '0',
                GSR => '0',
                GTS => '0',
                KEYCLEARB => '0',
                PACK => '0',
                USRCCLKO => spi_sck,
                USRCCLKTS => '0',
                USRDONEO => '1',
                USRDONETS => '0'
                );
    end generate;

    spi_direct_sclk: if not SCLK_STARTUPE2 generate
        spi_flash_clk    <= spi_sck;
    end generate;

    nodram: if not USE_LITEDRAM generate
        signal ddram_clk_dummy : std_ulogic;
    begin
        reset_controller: entity work.soc_reset
            generic map(
                RESET_LOW => RESET_LOW
                )
            port map(
                ext_clk => ext_clk,
                pll_clk => system_clk,
                pll_locked_in => system_clk_locked,
                ext_rst_in => ext_rst,
                pll_rst_out => pll_rst,
                rst_out => soc_rst
                );

        clkgen: entity work.clock_generator
            generic map(
                CLK_INPUT_HZ => 100000000,
                CLK_OUTPUT_HZ => CLK_FREQUENCY
                )
            port map(
                ext_clk => ext_clk,
                pll_rst_in => pll_rst,
                pll_clk_out => system_clk,
                pll_locked_out => system_clk_locked
                );

        led0_b_pwm <= '1';
        led0_r_pwm <= '1';
        led0_g_pwm <= '0';
        core_alt_reset <= '0';

        -- Vivado barfs on those differential signals if left
        -- unconnected. So instanciate a diff. buffer and feed
        -- it a constant '0'.
        dummy_dram_clk: OBUFDS
            port map (
                O => ddram_clk_p,
                OB => ddram_clk_n,
                I => ddram_clk_dummy
                );
        ddram_clk_dummy <= '0';

    end generate;

    has_dram: if USE_LITEDRAM generate
        signal dram_init_done  : std_ulogic;
        signal dram_init_error : std_ulogic;
        signal dram_sys_rst    : std_ulogic;
    begin

        -- Eventually dig out the frequency from the generator
        -- but for now, assert it's 100Mhz
        assert CLK_FREQUENCY = 100000000;

        reset_controller: entity work.soc_reset
            generic map(
                RESET_LOW => RESET_LOW,
                PLL_RESET_BITS => 18,
                SOC_RESET_BITS => 1
                )
            port map(
                ext_clk => ext_clk,
                pll_clk => system_clk,
                pll_locked_in => '1',
                ext_rst_in => ext_rst,
                pll_rst_out => pll_rst,
                rst_out => open
                );

        dram: entity work.litedram_wrapper
            generic map(
                DRAM_ABITS => 24,
                DRAM_ALINES => 14,
                PAYLOAD_FILE => RAM_INIT_FILE,
                PAYLOAD_SIZE => PAYLOAD_SIZE
                )
            port map(
                clk_in          => ext_clk,
                rst             => pll_rst,
                system_clk      => system_clk,
                system_reset    => soc_rst,
                core_alt_reset  => core_alt_reset,
                pll_locked      => system_clk_locked,

                wb_in           => wb_dram_in,
                wb_out          => wb_dram_out,
                wb_ctrl_in      => wb_dram_ctrl_in,
                wb_ctrl_out     => wb_dram_ctrl_out,
                wb_ctrl_is_csr  => wb_dram_is_csr,
                wb_ctrl_is_init => wb_dram_is_init,

                init_done       => dram_init_done,
                init_error      => dram_init_error,

                ddram_a         => ddram_a,
                ddram_ba        => ddram_ba,
                ddram_ras_n     => ddram_ras_n,
                ddram_cas_n     => ddram_cas_n,
                ddram_we_n      => ddram_we_n,
                ddram_cs_n      => ddram_cs_n,
                ddram_dm        => ddram_dm,
                ddram_dq        => ddram_dq,
                ddram_dqs_p     => ddram_dqs_p,
                ddram_dqs_n     => ddram_dqs_n,
                ddram_clk_p     => ddram_clk_p,
                ddram_clk_n     => ddram_clk_n,
                ddram_cke       => ddram_cke,
                ddram_odt       => ddram_odt,
                ddram_reset_n   => ddram_reset_n
                );

        led0_b_pwm <= not dram_init_done;
        led0_r_pwm <= dram_init_error;
        led0_g_pwm <= dram_init_done and not dram_init_error;

    end generate;

    leds_pwm : process(system_clk)
    begin
        if rising_edge(system_clk) then
            pwm_counter <= std_ulogic_vector(signed(pwm_counter) + 1);
            if pwm_counter(8 downto 4) = "00000" then
                led0_b <= led0_b_pwm;
                led0_r <= led0_r_pwm;
                led0_g <= led0_g_pwm;
            else
                led0_b <= '0';
                led0_r <= '0';
                led0_g <= '0';
            end if;
        end if;
    end process;

end architecture behaviour;