Subversion Repositories neorv32

-- #################################################################################################

-- # << NEORV32 - Stream Link Interface (SLINK) >>                                                 #

-- # ********************************************************************************************* #

-- # Up to 8 input (RX) and up to 8 output (TX) stream links are supported. Each link provides an  #

-- # internal FIFO for buffering. Each stream direction provides a global interrupt to indicate    #

-- # that a RX link has received new data or that a TX link has finished sending data              #

-- # (if FIFO_DEPTH = 1) OR if RX/TX link FIFO has become half full (if FIFO_DEPTH > 1).           #

-- # ********************************************************************************************* #

-- # BSD 3-Clause License                                                                          #

-- #                                                                                               #

-- # Copyright (c) 2021, Stephan Nolting. All rights reserved.                                     #

-- #                                                                                               #

-- # Redistribution and use in source and binary forms, with or without modification, are          #

-- # permitted provided that the following conditions are met:                                     #

-- #                                                                                               #

-- # 1. Redistributions of source code must retain the above copyright notice, this list of        #

-- #    conditions and the following disclaimer.                                                   #

-- #                                                                                               #

-- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of     #

-- #    conditions and the following disclaimer in the documentation and/or other materials        #

-- #    provided with the distribution.                                                            #

-- #                                                                                               #

-- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #

-- #    endorse or promote products derived from this software without specific prior written      #

-- #    permission.                                                                                #

-- #                                                                                               #

-- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #

-- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #

-- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #

-- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #

-- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #

-- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #

-- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING     #

-- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #

-- # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #

-- # ********************************************************************************************* #

-- # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

-- #################################################################################################

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

library neorv32;

use neorv32.neorv32_package.all;

entity neorv32_slink is

  generic (

    SLINK_NUM_TX  : natural; -- number of TX links (0..8)

    SLINK_NUM_RX  : natural; -- number of TX links (0..8)

    SLINK_TX_FIFO : natural; -- TX fifo depth, has to be a power of two

    SLINK_RX_FIFO : natural  -- RX fifo depth, has to be a power of two

  );

  port (

    -- host access --

    clk_i          : in  std_ulogic; -- global clock line

    addr_i         : in  std_ulogic_vector(31 downto 0); -- address

    rden_i         : in  std_ulogic; -- read enable

    wren_i         : in  std_ulogic; -- write enable

    data_i         : in  std_ulogic_vector(31 downto 0); -- data in

    data_o         : out std_ulogic_vector(31 downto 0); -- data out

    ack_o          : out std_ulogic; -- transfer acknowledge

    -- interrupt --

    irq_tx_o       : out std_ulogic; -- transmission done

    irq_rx_o       : out std_ulogic; -- data received

    -- TX stream interfaces --

    slink_tx_dat_o : out sdata_8x32_t; -- output data

    slink_tx_val_o : out std_ulogic_vector(7 downto 0); -- valid output

    slink_tx_rdy_i : in  std_ulogic_vector(7 downto 0); -- ready to send

    -- RX stream interfaces --

    slink_rx_dat_i : in  sdata_8x32_t; -- input data

    slink_rx_val_i : in  std_ulogic_vector(7 downto 0); -- valid input

    slink_rx_rdy_o : out std_ulogic_vector(7 downto 0)  -- ready to receive

  );

end neorv32_slink;

architecture neorv32_slink_rtl of neorv32_slink is

  -- IO space: module base address --

  constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit

  constant lo_abb_c : natural := index_size_f(slink_size_c); -- low address boundary bit

  -- control register bits --

  constant ctrl_rx_num_lsb_c  : natural :=  0; -- r/-: number of implemented RX links

  constant ctrl_rx_num_msb_c  : natural :=  3;

  --

  constant ctrl_tx_num_lsb_c  : natural :=  4; -- r/-: number of implemented TX links

  constant ctrl_tx_num_msb_c  : natural :=  7;

  --

  constant ctrl_rx_size_lsb_c : natural :=  8; -- r/-: log2(RX FIFO size)

  constant ctrl_rx_size_msb_c : natural := 11;

  --

  constant ctrl_tx_size_lsb_c : natural := 12; -- r/-: log2(TX FIFO size)

  constant ctrl_tx_size_msb_c : natural := 15;

  --

  constant ctrl_en_c          : natural := 31; -- r/w: global enable

  -- interrupt configuration register bits --

  constant irq_rx_en_lsb_c   : natural :=  0; -- r/w: enable RX interrupt for link 0..7

  constant irq_rx_en_msb_c   : natural :=  7;

  --

  constant irq_rx_mode_lsb_c : natural :=  8; -- r/w: RX IRQ mode: 0=FIFO at least half-full; 1=FIFO not empty

  constant irq_rx_mode_msb_c : natural := 15;

  --

  constant irq_tx_en_lsb_c   : natural := 16; -- r/w: enable TX interrupt for link 0..7

  constant irq_tx_en_msb_c   : natural := 23;

  --

  constant irq_tx_mode_lsb_c : natural := 24; -- r/w: TX IRQ mode: 0=FIFO less than half-full; 1=FIFO not full

  constant irq_tx_mode_msb_c : natural := 31;

  -- status register bits --

  constant status_rx_avail_lsb_c : natural :=  0; -- r/-: set if RX link 0..7 FIFO is NOT empty

  constant status_rx_avail_msb_c : natural :=  7;

  --

  constant status_tx_free_lsb_c  : natural :=  8; -- r/-: set if TX link 0..7 FIFO is NOT full

  constant status_tx_free_msb_c  : natural := 15;

  --

  constant status_rx_half_lsb_c  : natural := 16; -- r/-: set if RX link 0..7 FIFO fill-level is >= half-full

  constant status_rx_half_msb_c  : natural := 23;

  --

  constant status_tx_half_lsb_c  : natural := 24; -- r/-: set if TX link 0..7 FIFO fill-level is > half-full

  constant status_tx_half_msb_c  : natural := 31;

  -- bus access control --

  signal ack_read  : std_ulogic;

  signal ack_write : std_ulogic;

  signal acc_en    : std_ulogic;

  signal addr      : std_ulogic_vector(31 downto 0);

  signal wren      : std_ulogic; -- word write enable

  signal rden      : std_ulogic; -- read enable

  -- control register --

  signal enable : std_ulogic; -- global enable

  -- IRQ configuration register --

  signal irq_rx_en   : std_ulogic_vector(7 downto 0);

  signal irq_rx_mode : std_ulogic_vector(7 downto 0);

  signal irq_tx_en   : std_ulogic_vector(7 downto 0);

  signal irq_tx_mode : std_ulogic_vector(7 downto 0);

  -- stream link fifo interface --

  type fifo_data_t is array (0 to 7) of std_ulogic_vector(31 downto 0);

  signal rx_fifo_rdata : fifo_data_t;

  signal fifo_clear    : std_ulogic;

  signal link_sel      : std_ulogic_vector(7 downto 0);

  signal tx_fifo_we    : std_ulogic_vector(7 downto 0);

  signal rx_fifo_re    : std_ulogic_vector(7 downto 0);

  signal rx_fifo_avail : std_ulogic_vector(7 downto 0);

  signal tx_fifo_free  : std_ulogic_vector(7 downto 0);

  signal rx_fifo_half  : std_ulogic_vector(7 downto 0);

  signal tx_fifo_half  : std_ulogic_vector(7 downto 0);

  -- interrupt generator --

  type detect_t is array (0 to 7) of std_ulogic_vector(1 downto 0);

  type irq_t is record

    pending : std_ulogic; -- pending interrupt request

    detect  : detect_t; -- rising-edge detector

    trigger : std_ulogic_vector(7 downto 0);

    set     : std_ulogic_vector(7 downto 0);

    clr     : std_ulogic;

  end record;

  signal rx_irq, tx_irq : irq_t;

begin

  -- Sanity Checks --------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  assert not (is_power_of_two_f(SLINK_TX_FIFO) = false) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_TX_FIFO> has to be a power of two." severity error;

  assert not (SLINK_TX_FIFO > 2**15) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_TX_FIFO> has to be 1..32768." severity error;

  --

  assert not (is_power_of_two_f(SLINK_RX_FIFO) = false) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_RX_FIFO> has to be a power of two." severity error;

  assert not (SLINK_RX_FIFO > 2**15) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_RX_FIFO> has to be 1..32768." severity error;

  --

  assert not (SLINK_NUM_RX > 8) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_NUM_RX> has to be 0..8." severity error;

  assert not (SLINK_NUM_TX > 8) report "NEORV32 PROCESSOR CONFIG ERROR: SLINK <SLINK_NUM_TX> has to be 0..8." severity error;

  --

  assert false report "NEORV32 PROCESSOR CONFIG NOTE: Implementing " & integer'image(SLINK_NUM_RX) & " RX and " &

  integer'image(SLINK_NUM_TX) & " TX stream links." severity note;

  -- Access Control -------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = slink_base_c(hi_abb_c downto lo_abb_c)) else '0';

  addr   <= slink_base_c(31 downto lo_abb_c) & addr_i(lo_abb_c-1 downto 2) & "00"; -- word aligned

  wren   <= acc_en and wren_i;

  rden   <= acc_en and rden_i;

  -- Read/Write Access ----------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  rw_access: process(clk_i)

  begin

    if rising_edge(clk_i) then

      -- write access --

      ack_write <= '0';

      if (wren = '1') then

        if (addr(5) = '0') then -- control/status/irq

          if (addr(4 downto 3) = "00") then -- control register

            enable <= data_i(ctrl_en_c);

          end if;

          if (addr(4 downto 3) = "01") then -- IRQ configuration register

            for i in 0 to SLINK_NUM_RX-1 loop

              irq_rx_en(i)   <= data_i(i + irq_rx_en_lsb_c);

              irq_rx_mode(i) <= data_i(i + irq_rx_mode_lsb_c);

            end loop;

            for i in 0 to SLINK_NUM_TX-1 loop

              irq_tx_en(i)   <= data_i(i + irq_tx_en_lsb_c);

              irq_tx_mode(i) <= data_i(i + irq_tx_mode_lsb_c);

            end loop;

          end if;

          ack_write <= '1';

        else -- TX links

          ack_write <= or_reduce_f(link_sel and tx_fifo_free);

        end if;

      end if;

      -- read access --

      data_o   <= (others => '0');

      ack_read <= '0';

      if (rden = '1') then

        if (addr(5) = '0') then -- control/status registers

          ack_read <= '1';

          case addr(4 downto 3) is

            when "00" => -- control register

              data_o(ctrl_rx_num_msb_c  downto ctrl_rx_num_lsb_c)  <= std_ulogic_vector(to_unsigned(SLINK_NUM_RX, 4));

              data_o(ctrl_tx_num_msb_c  downto ctrl_tx_num_lsb_c)  <= std_ulogic_vector(to_unsigned(SLINK_NUM_TX, 4));

              data_o(ctrl_rx_size_msb_c downto ctrl_rx_size_lsb_c) <= std_ulogic_vector(to_unsigned(index_size_f(SLINK_RX_FIFO), 4));

              data_o(ctrl_tx_size_msb_c downto ctrl_tx_size_lsb_c) <= std_ulogic_vector(to_unsigned(index_size_f(SLINK_TX_FIFO), 4));

              data_o(ctrl_en_c)                                    <= enable;

            when "01" => -- IRQ configuration register

              for i in 0 to SLINK_NUM_RX-1 loop

                data_o(irq_rx_en_lsb_c   + i) <= irq_rx_en(i);

                data_o(irq_rx_mode_lsb_c + i) <= irq_rx_mode(i) or bool_to_ulogic_f(boolean(SLINK_RX_FIFO = 1)); -- tie to one if SLINK_RX_FIFO is 1

              end loop;

              for i in 0 to SLINK_NUM_TX-1 loop

                data_o(irq_tx_en_lsb_c   + i) <= irq_tx_en(i);

                data_o(irq_tx_mode_lsb_c + i) <= irq_tx_mode(i) or bool_to_ulogic_f(boolean(SLINK_TX_FIFO = 1)); -- tie to one if SLINK_TX_FIFO is 1

              end loop;

            when "10" | "11" => -- fifo status register

              data_o(status_rx_avail_msb_c downto status_rx_avail_lsb_c) <= rx_fifo_avail;

              data_o(status_tx_free_msb_c  downto status_tx_free_lsb_c)  <= tx_fifo_free;

              data_o(status_rx_half_msb_c  downto status_rx_half_lsb_c)  <= rx_fifo_half;

              data_o(status_tx_half_msb_c  downto status_tx_half_lsb_c)  <= tx_fifo_half;

            when others =>

              data_o <= (others => '0');

          end case;

        else -- RX links

          data_o   <= rx_fifo_rdata(to_integer(unsigned(addr(4 downto 2))));

          ack_read <= or_reduce_f(link_sel and rx_fifo_avail);

        end if;

      end if;

    end if;

  end process rw_access;

  -- bus access acknowledge --

  ack_o <= ack_write or ack_read;

  -- link fifo reset (sync) --

  fifo_clear <= not enable;

  -- Interrupt Generator --------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  irq_type: process(irq_rx_mode, rx_fifo_avail, rx_fifo_half,

                    irq_tx_mode, tx_fifo_free,  tx_fifo_half)

  begin

    -- RX interrupt --

    rx_irq.trigger <= (others => '0');

    for i in 0 to SLINK_NUM_RX-1 loop

      if (SLINK_RX_FIFO = 1) then

        rx_irq.trigger(i) <= rx_fifo_avail(i); -- fire if any RX_FIFO is not empty

      else

        if (irq_rx_mode(i) = '0') then -- fire if any RX_FIFO is at least half-full

          rx_irq.trigger(i) <= rx_fifo_half(i);

        else -- fire if any RX_FIFO is not empty (= data available)

          rx_irq.trigger(i) <= rx_fifo_avail(i);

        end if;

      end if;

    end loop;

    -- TX interrupt --

    tx_irq.trigger <= (others => '0');

    for i in 0 to SLINK_NUM_TX-1 loop

      if (SLINK_TX_FIFO = 1) then

        tx_irq.trigger(i) <= tx_fifo_free(i); -- fire if any TX_FIFO is not full

      else

        if (irq_tx_mode(i) = '0') then -- fire if any TX_FIFO is less than half-full

          tx_irq.trigger(i) <= not tx_fifo_half(i);

        else -- fire if any TX_FIFO is not full (= free buffer space available)

          tx_irq.trigger(i) <= tx_fifo_free(i);

        end if;

      end if;

    end loop;

  end process irq_type;

  -- interrupt trigger --

  irq_trigger_sync: process(clk_i)

  begin

    if rising_edge(clk_i) then

      -- RX --

      rx_irq.detect <= (others => (others => '0')); -- default

      if (enable = '1') then

        for i in 0 to SLINK_NUM_RX-1 loop

          rx_irq.detect(i) <= rx_irq.detect(i)(0) & rx_irq.trigger(i);

        end loop;

      end if;

      -- TX --

      tx_irq.detect <= (others => (others => '0')); -- default

      if (enable = '1') then

        for i in 0 to SLINK_NUM_TX-1 loop

          tx_irq.detect(i) <= tx_irq.detect(i)(0) & tx_irq.trigger(i);

        end loop;

      end if;

    end if;

  end process irq_trigger_sync;

  -- interrupt trigger --

  irq_trigger_comb: process(rx_irq, irq_rx_en, tx_irq, irq_tx_en)

  begin

    -- RX --

    rx_irq.set <= (others => '0');

    for i in 0 to SLINK_NUM_RX-1 loop

      if (rx_irq.detect(i) = "01") and (irq_rx_en(i) = '1') then -- rising-edge

        rx_irq.set(i) <= '1';

      end if;

    end loop;

    -- TX --

    tx_irq.set <= (others => '0');

    for i in 0 to SLINK_NUM_TX-1 loop

      if (tx_irq.detect(i) = "01") and (irq_tx_en(i) = '1') then -- rising-edge

        tx_irq.set(i) <= '1';

      end if;

    end loop;

  end process irq_trigger_comb;

  -- interrupt arbiter --

  irq_generator: process(clk_i)

  begin

    if rising_edge(clk_i) then

      if (enable = '0') then

        rx_irq.pending <= '0';

        tx_irq.pending <= '0';

      else

        -- RX --

        if (or_reduce_f(rx_irq.set) = '1') then

          rx_irq.pending <= '1';

        elsif (rx_irq.clr = '1') then

          rx_irq.pending <= '0';

        end if;

        -- TX --

        if (or_reduce_f(tx_irq.set) = '1') then

          tx_irq.pending <= '1';

        elsif (tx_irq.clr = '1') then

          tx_irq.pending <= '0';

        end if;

      end if;

    end if;

  end process irq_generator;

  -- IRQ requests to CPU --

  irq_rx_o <= rx_irq.pending;

  irq_tx_o <= tx_irq.pending;

  -- IRQ acknowledge --

  rx_irq.clr <= '1' when ((rden = '1') and (addr(5) = '1')) or ((wren = '1') and (addr(5 downto 3) = "000")) else '0'; -- read from data FIFO OR write to control register

  tx_irq.clr <= '1' when ((wren = '1') and (addr(5) = '1')) or ((wren = '1') and (addr(5 downto 3) = "000")) else '0'; -- write to data FIFO  OR write to control register

  -- Link Select ----------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  link_select: process(addr)

  begin

    case addr(5 downto 2) is -- MSB = data fifo access at all?

      when "1000" => link_sel <= "00000001";

      when "1001" => link_sel <= "00000010";

      when "1010" => link_sel <= "00000100";

      when "1011" => link_sel <= "00001000";

      when "1100" => link_sel <= "00010000";

      when "1101" => link_sel <= "00100000";

      when "1110" => link_sel <= "01000000";

      when "1111" => link_sel <= "10000000";

      when others => link_sel <= "00000000";

    end case;

  end process link_select;

  fifo_access_gen:

  for i in 0 to 7 generate

    tx_fifo_we(i) <= link_sel(i) and wren;

    rx_fifo_re(i) <= link_sel(i) and rden;

  end generate;

  -- TX Link FIFOs --------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  transmit_fifo_gen:

  for i in 0 to SLINK_NUM_TX-1 generate

    transmit_fifo_inst: neorv32_fifo

    generic map (

      FIFO_DEPTH => SLINK_TX_FIFO, -- number of fifo entries; has to be a power of two; min 1

      FIFO_WIDTH => 32,            -- size of data elements in fifo

      FIFO_RSYNC => false,         -- async read

      FIFO_SAFE  => true           -- safe access

    )

    port map (

      -- control --

      clk_i   => clk_i,             -- clock, rising edge

      rstn_i  => '1',               -- async reset, low-active

      clear_i => fifo_clear,        -- sync reset, high-active

      level_o => open,              -- fill level

      half_o  => tx_fifo_half(i),   -- FIFO is at least half full

      -- write port --

      wdata_i => data_i,            -- write data

      we_i    => tx_fifo_we(i),     -- write enable

      free_o  => tx_fifo_free(i),   -- at least one entry is free when set

      -- read port --

      re_i    => slink_tx_rdy_i(i), -- read enable

      rdata_o => slink_tx_dat_o(i), -- read data

      avail_o => slink_tx_val_o(i)  -- data available when set

    );

  end generate;

  -- terminate unimplemented links --

  transmit_fifo_gen_terminate:

  for i in SLINK_NUM_TX to 7 generate

    tx_fifo_free(i)   <= '0';

    slink_tx_dat_o(i) <= (others => '0');

    slink_tx_val_o(i) <= '0';

    tx_fifo_half(i)   <= '0';

  end generate;

  -- RX Link FIFOs --------------------------------------------------------------------------

  -- -------------------------------------------------------------------------------------------

  receive_fifo_gen:

  for i in 0 to SLINK_NUM_RX-1 generate

    receive_fifo_inst: neorv32_fifo

    generic map (

      FIFO_DEPTH => SLINK_RX_FIFO, -- number of fifo entries; has to be a power of two; min 1

      FIFO_WIDTH => 32,            -- size of data elements in fifo

      FIFO_RSYNC => false,         -- async read

      FIFO_SAFE  => true           -- safe access

    )

    port map (

      -- control --

      clk_i   => clk_i,             -- clock, rising edge

      rstn_i  => '1',               -- async reset, low-active

      clear_i => fifo_clear,        -- sync reset, high-active

      level_o => open,              -- fill level

      half_o  => rx_fifo_half(i),   -- FIFO is at least half full

      -- write port --

      wdata_i => slink_rx_dat_i(i), -- write data

      we_i    => slink_rx_val_i(i), -- write enable

      free_o  => slink_rx_rdy_o(i), -- at least one entry is free when set

      -- read port --

      re_i    => rx_fifo_re(i),     -- read enable

      rdata_o => rx_fifo_rdata(i),  -- read data

      avail_o => rx_fifo_avail(i)   -- data available when set

    );

  end generate;

  -- terminate unimplemented links --

  receive_fifo_gen_terminate:

  for i in SLINK_NUM_RX to 7 generate

    rx_fifo_avail(i)  <= '0';

    slink_rx_rdy_o(i) <= '0';

    rx_fifo_rdata(i)  <= (others => '0');

    rx_fifo_half(i)   <= '0';

  end generate;

end neorv32_slink_rtl;