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-- ################################################################################################# -- # << NEORV32 - Processor-Internal Instruction Cache >> # -- # ********************************************************************************************* # -- # Direct mapped (ICACHE_NUM_SETS = 1) or 2-way set-associative (ICACHE_NUM_SETS = 2). # -- # Least recently used replacement policy (if ICACHE_NUM_SETS > 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_icache is generic ( ICACHE_NUM_BLOCKS : natural; -- number of blocks (min 1), has to be a power of 2 ICACHE_BLOCK_SIZE : natural; -- block size in bytes (min 4), has to be a power of 2 ICACHE_NUM_SETS : natural -- associativity / number of sets (1=direct_mapped), has to be a power of 2 ); port ( -- global control -- clk_i : in std_ulogic; -- global clock, rising edge rstn_i : in std_ulogic; -- global reset, low-active, async clear_i : in std_ulogic; -- cache clear -- host controller interface -- host_addr_i : in std_ulogic_vector(data_width_c-1 downto 0); -- bus access address host_rdata_o : out std_ulogic_vector(data_width_c-1 downto 0); -- bus read data host_wdata_i : in std_ulogic_vector(data_width_c-1 downto 0); -- bus write data host_ben_i : in std_ulogic_vector(03 downto 0); -- byte enable host_we_i : in std_ulogic; -- write enable host_re_i : in std_ulogic; -- read enable host_ack_o : out std_ulogic; -- bus transfer acknowledge host_err_o : out std_ulogic; -- bus transfer error -- peripheral bus interface -- bus_addr_o : out std_ulogic_vector(data_width_c-1 downto 0); -- bus access address bus_rdata_i : in std_ulogic_vector(data_width_c-1 downto 0); -- bus read data bus_wdata_o : out std_ulogic_vector(data_width_c-1 downto 0); -- bus write data bus_ben_o : out std_ulogic_vector(03 downto 0); -- byte enable bus_we_o : out std_ulogic; -- write enable bus_re_o : out std_ulogic; -- read enable bus_ack_i : in std_ulogic; -- bus transfer acknowledge bus_err_i : in std_ulogic -- bus transfer error ); end neorv32_icache; architecture neorv32_icache_rtl of neorv32_icache is -- cache layout -- constant cache_offset_size_c : natural := index_size_f(ICACHE_BLOCK_SIZE/4); -- offset addresses full 32-bit words constant cache_index_size_c : natural := index_size_f(ICACHE_NUM_BLOCKS); constant cache_tag_size_c : natural := 32 - (cache_offset_size_c + cache_index_size_c + 2); -- 2 additonal bits for byte offset -- cache memory -- component neorv32_icache_memory generic ( ICACHE_NUM_BLOCKS : natural := 4; -- number of blocks (min 1), has to be a power of 2 ICACHE_BLOCK_SIZE : natural := 16; -- block size in bytes (min 4), has to be a power of 2 ICACHE_NUM_SETS : natural := 1 -- associativity; 0=direct-mapped, 1=2-way set-associative ); port ( -- global control -- clk_i : in std_ulogic; -- global clock, rising edge invalidate_i : in std_ulogic; -- invalidate whole cache -- host cache access (read-only) -- host_addr_i : in std_ulogic_vector(31 downto 0); -- access address host_re_i : in std_ulogic; -- read enable host_rdata_o : out std_ulogic_vector(31 downto 0); -- read data -- access status (1 cycle delay to access) -- hit_o : out std_ulogic; -- hit access -- ctrl cache access (write-only) -- ctrl_en_i : in std_ulogic; -- control interface enable ctrl_addr_i : in std_ulogic_vector(31 downto 0); -- access address ctrl_we_i : in std_ulogic; -- write enable (full-word) ctrl_wdata_i : in std_ulogic_vector(31 downto 0); -- write data ctrl_tag_we_i : in std_ulogic; -- write tag to selected block ctrl_valid_i : in std_ulogic; -- make selected block valid ctrl_invalid_i : in std_ulogic -- make selected block invalid ); end component; -- cache interface -- type cache_if_t is record clear : std_ulogic; -- cache clear -- host_addr : std_ulogic_vector(31 downto 0); -- cpu access address host_rdata : std_ulogic_vector(31 downto 0); -- cpu read data -- hit : std_ulogic; -- hit access -- ctrl_en : std_ulogic; -- control access enable ctrl_addr : std_ulogic_vector(31 downto 0); -- control access address ctrl_we : std_ulogic; -- control write enable ctrl_wdata : std_ulogic_vector(31 downto 0); -- control write data ctrl_tag_we : std_ulogic; -- control tag write enabled ctrl_valid_we : std_ulogic; -- control valid flag set ctrl_invalid_we : std_ulogic; -- control valid flag clear end record; signal cache : cache_if_t; -- control engine -- type ctrl_engine_state_t is (S_IDLE, S_CACHE_CLEAR, S_CACHE_CHECK, S_CACHE_MISS, S_BUS_DOWNLOAD_REQ, S_BUS_DOWNLOAD_GET, S_CACHE_RESYNC_0, S_CACHE_RESYNC_1, S_BUS_ERROR); type ctrl_t is record state : ctrl_engine_state_t; -- current state state_nxt : ctrl_engine_state_t; -- next state addr_reg : std_ulogic_vector(31 downto 0); -- address register for block download addr_reg_nxt : std_ulogic_vector(31 downto 0); -- re_buf : std_ulogic; -- read request buffer re_buf_nxt : std_ulogic; -- clear_buf : std_ulogic; -- clear request buffer clear_buf_nxt : std_ulogic; end record; signal ctrl : ctrl_t; begin -- Sanity Checks -------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- -- configuration -- assert not (is_power_of_two_f(ICACHE_NUM_BLOCKS) = false) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache number of blocks <ICACHE_NUM_BLOCKS> has to be a power of 2." severity error; assert not (is_power_of_two_f(ICACHE_BLOCK_SIZE) = false) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache block size <ICACHE_BLOCK_SIZE> has to be a power of 2." severity error; assert not ((is_power_of_two_f(ICACHE_NUM_SETS) = false)) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache associativity <ICACHE_NUM_SETS> has to be a power of 2." severity error; assert not (ICACHE_NUM_BLOCKS < 1) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache number of blocks <ICACHE_NUM_BLOCKS> has to be >= 1." severity error; assert not (ICACHE_BLOCK_SIZE < 4) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache block size <ICACHE_BLOCK_SIZE> has to be >= 4." severity error; assert not ((ICACHE_NUM_SETS = 0) or (ICACHE_NUM_SETS > 2)) report "NEORV32 PROCESSOR CONFIG ERROR! i-cache associativity <ICACHE_NUM_SETS> has to be 1 (direct-mapped) or 2 (2-way set-associative)." severity error; -- Control Engine FSM Sync ---------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- -- registers that REQUIRE a specific reset state -- ctrl_engine_fsm_sync_rst: process(rstn_i, clk_i) begin if (rstn_i = '0') then ctrl.state <= S_CACHE_CLEAR; ctrl.re_buf <= '0'; ctrl.clear_buf <= '0'; elsif rising_edge(clk_i) then ctrl.state <= ctrl.state_nxt; ctrl.re_buf <= ctrl.re_buf_nxt; ctrl.clear_buf <= ctrl.clear_buf_nxt; end if; end process ctrl_engine_fsm_sync_rst; -- registers that do not require a specific reset state -- ctrl_engine_fsm_sync: process(clk_i) begin if rising_edge(clk_i) then ctrl.addr_reg <= ctrl.addr_reg_nxt; end if; end process ctrl_engine_fsm_sync; -- Control Engine FSM Comb ---------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- ctrl_engine_fsm_comb: process(ctrl, cache, clear_i, host_addr_i, host_re_i, bus_rdata_i, bus_ack_i, bus_err_i) begin -- control defaults -- ctrl.state_nxt <= ctrl.state; ctrl.addr_reg_nxt <= ctrl.addr_reg; ctrl.re_buf_nxt <= ctrl.re_buf or host_re_i; ctrl.clear_buf_nxt <= ctrl.clear_buf or clear_i; -- buffer clear request from CPU -- cache defaults -- cache.clear <= '0'; cache.host_addr <= host_addr_i; cache.ctrl_en <= '0'; cache.ctrl_addr <= ctrl.addr_reg; cache.ctrl_we <= '0'; cache.ctrl_wdata <= bus_rdata_i; cache.ctrl_tag_we <= '0'; cache.ctrl_valid_we <= '0'; cache.ctrl_invalid_we <= '0'; -- host interface defaults -- host_ack_o <= '0'; host_err_o <= '0'; host_rdata_o <= cache.host_rdata; -- peripheral bus interface defaults -- bus_addr_o <= ctrl.addr_reg; bus_wdata_o <= (others => '0'); -- cache is read-only bus_ben_o <= (others => '0'); -- cache is read-only bus_we_o <= '0'; -- cache is read-only bus_re_o <= '0'; -- fsm -- case ctrl.state is when S_IDLE => -- wait for host access request or cache control operation -- ------------------------------------------------------------ if (ctrl.clear_buf = '1') then -- cache control operation? ctrl.state_nxt <= S_CACHE_CLEAR; elsif (host_re_i = '1') or (ctrl.re_buf = '1') then -- cache access ctrl.re_buf_nxt <= '0'; ctrl.state_nxt <= S_CACHE_CHECK; end if; when S_CACHE_CLEAR => -- invalidate all cache entries -- ------------------------------------------------------------ ctrl.clear_buf_nxt <= '0'; cache.clear <= '1'; ctrl.state_nxt <= S_IDLE; when S_CACHE_CHECK => -- finalize host access if cache hit -- ------------------------------------------------------------ if (cache.hit = '1') then -- cache HIT host_ack_o <= '1'; ctrl.state_nxt <= S_IDLE; else -- cache MISS ctrl.state_nxt <= S_CACHE_MISS; end if; when S_CACHE_MISS => -- -- ------------------------------------------------------------ -- compute block base address -- ctrl.addr_reg_nxt <= host_addr_i; ctrl.addr_reg_nxt((2+cache_offset_size_c)-1 downto 2) <= (others => '0'); -- block-aligned ctrl.addr_reg_nxt(1 downto 0) <= "00"; -- word-aligned -- ctrl.state_nxt <= S_BUS_DOWNLOAD_REQ; when S_BUS_DOWNLOAD_REQ => -- download new cache block: request new word -- ------------------------------------------------------------ cache.ctrl_en <= '1'; -- we are in cache control mode bus_re_o <= '1'; -- request new read transfer ctrl.state_nxt <= S_BUS_DOWNLOAD_GET; when S_BUS_DOWNLOAD_GET => -- download new cache block: wait for bus response -- ------------------------------------------------------------ cache.ctrl_en <= '1'; -- we are in cache control mode -- if (bus_err_i = '1') then -- bus error ctrl.state_nxt <= S_BUS_ERROR; elsif (bus_ack_i = '1') then -- ACK = write to cache and get next word cache.ctrl_we <= '1'; -- write to cache if (and_reduce_f(ctrl.addr_reg((2+cache_offset_size_c)-1 downto 2)) = '1') then -- block complete? cache.ctrl_tag_we <= '1'; -- current block is valid now cache.ctrl_valid_we <= '1'; -- write tag of current address ctrl.state_nxt <= S_CACHE_RESYNC_0; else -- get next word ctrl.addr_reg_nxt <= std_ulogic_vector(unsigned(ctrl.addr_reg) + 4); ctrl.state_nxt <= S_BUS_DOWNLOAD_REQ; end if; end if; when S_CACHE_RESYNC_0 => -- re-sync host/cache access: cache read-latency -- ------------------------------------------------------------ ctrl.state_nxt <= S_CACHE_RESYNC_1; when S_CACHE_RESYNC_1 => -- re-sync host/cache access: finalize CPU request -- ------------------------------------------------------------ host_ack_o <= '1'; ctrl.state_nxt <= S_IDLE; when S_BUS_ERROR => -- bus error during download -- ------------------------------------------------------------ host_err_o <= '1'; ctrl.state_nxt <= S_IDLE; when others => -- undefined -- ------------------------------------------------------------ ctrl.state_nxt <= S_IDLE; end case; end process ctrl_engine_fsm_comb; -- Cache Memory --------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- neorv32_icache_memory_inst: neorv32_icache_memory generic map ( ICACHE_NUM_BLOCKS => ICACHE_NUM_BLOCKS, -- number of blocks (min 1), has to be a power of 2 ICACHE_BLOCK_SIZE => ICACHE_BLOCK_SIZE, -- block size in bytes (min 4), has to be a power of 2 ICACHE_NUM_SETS => ICACHE_NUM_SETS -- associativity; 0=direct-mapped, 1=2-way set-associative ) port map ( -- global control -- clk_i => clk_i, -- global clock, rising edge invalidate_i => cache.clear, -- invalidate whole cache -- host cache access (read-only) -- host_addr_i => cache.host_addr, -- access address host_re_i => host_re_i, -- read enable host_rdata_o => cache.host_rdata, -- read data -- access status (1 cycle delay to access) -- hit_o => cache.hit, -- hit access -- ctrl cache access (write-only) -- ctrl_en_i => cache.ctrl_en, -- control interface enable ctrl_addr_i => cache.ctrl_addr, -- access address ctrl_we_i => cache.ctrl_we, -- write enable (full-word) ctrl_wdata_i => cache.ctrl_wdata, -- write data ctrl_tag_we_i => cache.ctrl_tag_we, -- write tag to selected block ctrl_valid_i => cache.ctrl_valid_we, -- make selected block valid ctrl_invalid_i => cache.ctrl_invalid_we -- make selected block invalid ); end neorv32_icache_rtl; -- ########################################################################################################################################### -- ########################################################################################################################################### -- ################################################################################################# -- # << NEORV32 - Cache Memory >> # -- # ********************************************************************************************* # -- # Direct mapped (ICACHE_NUM_SETS = 1) or 2-way set-associative (ICACHE_NUM_SETS = 2). # -- # Least recently used replacement policy (if ICACHE_NUM_SETS > 1). # -- # Read-only for host, write-only for control. All output signals have one cycle latency. # -- # # -- # Cache sets are mapped to individual memory components - no multi-dimensional memory arrays # -- # are used as some synthesis tools have problems to map these to actual BRAM primitives. # -- # ********************************************************************************************* # -- # BSD 3-Clause License # -- # # -- # Copyright (c) 2020, 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_icache_memory is generic ( ICACHE_NUM_BLOCKS : natural := 4; -- number of blocks (min 1), has to be a power of 2 ICACHE_BLOCK_SIZE : natural := 16; -- block size in bytes (min 4), has to be a power of 2 ICACHE_NUM_SETS : natural := 1 -- associativity; 1=direct-mapped, 2=2-way set-associative ); port ( -- global control -- clk_i : in std_ulogic; -- global clock, rising edge invalidate_i : in std_ulogic; -- invalidate whole cache -- host cache access (read-only) -- host_addr_i : in std_ulogic_vector(31 downto 0); -- access address host_re_i : in std_ulogic; -- read enable host_rdata_o : out std_ulogic_vector(31 downto 0); -- read data -- access status (1 cycle delay to access) -- hit_o : out std_ulogic; -- hit access -- ctrl cache access (write-only) -- ctrl_en_i : in std_ulogic; -- control interface enable ctrl_addr_i : in std_ulogic_vector(31 downto 0); -- access address ctrl_we_i : in std_ulogic; -- write enable (full-word) ctrl_wdata_i : in std_ulogic_vector(31 downto 0); -- write data ctrl_tag_we_i : in std_ulogic; -- write tag to selected block ctrl_valid_i : in std_ulogic; -- make selected block valid ctrl_invalid_i : in std_ulogic -- make selected block invalid ); end neorv32_icache_memory; architecture neorv32_icache_memory_rtl of neorv32_icache_memory is -- cache layout -- constant cache_offset_size_c : natural := index_size_f(ICACHE_BLOCK_SIZE/4); -- offset addresses full 32-bit words constant cache_index_size_c : natural := index_size_f(ICACHE_NUM_BLOCKS); constant cache_tag_size_c : natural := 32 - (cache_offset_size_c + cache_index_size_c + 2); -- 2 additonal bits for byte offset constant cache_entries_c : natural := ICACHE_NUM_BLOCKS * (ICACHE_BLOCK_SIZE/4); -- number of 32-bit entries (per set) -- status flag memory -- signal valid_flag_s0 : std_ulogic_vector(ICACHE_NUM_BLOCKS-1 downto 0); signal valid_flag_s1 : std_ulogic_vector(ICACHE_NUM_BLOCKS-1 downto 0); signal valid : std_ulogic_vector(1 downto 0); -- valid flag read data -- tag memory -- type tag_mem_t is array (0 to ICACHE_NUM_BLOCKS-1) of std_ulogic_vector(cache_tag_size_c-1 downto 0); signal tag_mem_s0 : tag_mem_t; signal tag_mem_s1 : tag_mem_t; type tag_rd_t is array (0 to 1) of std_ulogic_vector(cache_tag_size_c-1 downto 0); signal tag : tag_rd_t; -- tag read data -- access status -- signal hit : std_ulogic_vector(1 downto 0); -- access address decomposition -- type acc_addr_t is record tag : std_ulogic_vector(cache_tag_size_c-1 downto 0); index : std_ulogic_vector(cache_index_size_c-1 downto 0); offset : std_ulogic_vector(cache_offset_size_c-1 downto 0); end record; signal host_acc_addr, ctrl_acc_addr : acc_addr_t; -- cache data memory -- type cache_mem_t is array (0 to cache_entries_c-1) of std_ulogic_vector(31 downto 0); signal cache_data_memory_s0 : cache_mem_t; -- set 0 signal cache_data_memory_s1 : cache_mem_t; -- set 1 -- cache data memory access -- type cache_rdata_t is array (0 to 1) of std_ulogic_vector(31 downto 0); signal cache_rdata : cache_rdata_t; signal cache_index : std_ulogic_vector(cache_index_size_c-1 downto 0); signal cache_offset : std_ulogic_vector(cache_offset_size_c-1 downto 0); signal cache_addr : std_ulogic_vector((cache_index_size_c+cache_offset_size_c)-1 downto 0); -- index & offset signal cache_we : std_ulogic; -- write enable (full-word) signal set_select : std_ulogic; -- access history -- type history_t is record re_ff : std_ulogic; last_used_set : std_ulogic_vector(ICACHE_NUM_BLOCKS-1 downto 0); to_be_replaced : std_ulogic; end record; signal history : history_t; begin -- Access Address Decomposition ----------------------------------------------------------- -- ------------------------------------------------------------------------------------------- host_acc_addr.tag <= host_addr_i(31 downto 31-(cache_tag_size_c-1)); host_acc_addr.index <= host_addr_i(31-cache_tag_size_c downto 2+cache_offset_size_c); host_acc_addr.offset <= host_addr_i(2+(cache_offset_size_c-1) downto 2); -- discard byte offset ctrl_acc_addr.tag <= ctrl_addr_i(31 downto 31-(cache_tag_size_c-1)); ctrl_acc_addr.index <= ctrl_addr_i(31-cache_tag_size_c downto 2+cache_offset_size_c); ctrl_acc_addr.offset <= ctrl_addr_i(2+(cache_offset_size_c-1) downto 2); -- discard byte offset -- Cache Access History ------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- access_history: process(clk_i) begin if rising_edge(clk_i) then history.re_ff <= host_re_i; if (invalidate_i = '1') then -- invalidate whole cache history.last_used_set <= (others => '1'); elsif (history.re_ff = '1') and (or_reduce_f(hit) = '1') and (ctrl_en_i = '0') then -- store last accessed set that caused a hit history.last_used_set(to_integer(unsigned(cache_index))) <= not hit(0); end if; history.to_be_replaced <= history.last_used_set(to_integer(unsigned(cache_index))); end if; end process access_history; -- which set is going to be replaced? -> opposite of last used set = least recently used set -- set_select <= '0' when (ICACHE_NUM_SETS = 1) else (not history.to_be_replaced); -- Status flag memory --------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- status_memory: process(clk_i) begin if rising_edge(clk_i) then -- write access -- if (invalidate_i = '1') then -- invalidate whole cache valid_flag_s0 <= (others => '0'); valid_flag_s1 <= (others => '0'); elsif (ctrl_en_i = '1') then if (ctrl_invalid_i = '1') then -- make current block invalid if (set_select = '0') then valid_flag_s0(to_integer(unsigned(cache_index))) <= '0'; else valid_flag_s1(to_integer(unsigned(cache_index))) <= '0'; end if; elsif (ctrl_valid_i = '1') then -- make current block valid if (set_select = '0') then valid_flag_s0(to_integer(unsigned(cache_index))) <= '1'; else valid_flag_s1(to_integer(unsigned(cache_index))) <= '1'; end if; end if; end if; -- read access (sync) -- valid(0) <= valid_flag_s0(to_integer(unsigned(cache_index))); valid(1) <= valid_flag_s1(to_integer(unsigned(cache_index))); end if; end process status_memory; -- Tag memory ----------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- tag_memory: process(clk_i) begin if rising_edge(clk_i) then if (ctrl_en_i = '1') and (ctrl_tag_we_i = '1') then -- write access if (set_select = '0') then tag_mem_s0(to_integer(unsigned(cache_index))) <= ctrl_acc_addr.tag; else tag_mem_s1(to_integer(unsigned(cache_index))) <= ctrl_acc_addr.tag; end if; end if; tag(0) <= tag_mem_s0(to_integer(unsigned(cache_index))); tag(1) <= tag_mem_s1(to_integer(unsigned(cache_index))); end if; end process tag_memory; -- comparator -- comparator: process(host_acc_addr, tag, valid) begin hit <= (others => '0'); for i in 0 to ICACHE_NUM_SETS-1 loop if (host_acc_addr.tag = tag(i)) and (valid(i) = '1') then hit(i) <= '1'; end if; end loop; -- i end process comparator; -- global hit -- hit_o <= or_reduce_f(hit); -- Cache Data Memory ---------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- cache_mem_access: process(clk_i) begin if rising_edge(clk_i) then if (cache_we = '1') then -- write access from control (full-word) if (set_select = '0') or (ICACHE_NUM_SETS = 1) then cache_data_memory_s0(to_integer(unsigned(cache_addr))) <= ctrl_wdata_i; else cache_data_memory_s1(to_integer(unsigned(cache_addr))) <= ctrl_wdata_i; end if; end if; -- read access from host (full-word) -- cache_rdata(0) <= cache_data_memory_s0(to_integer(unsigned(cache_addr))); cache_rdata(1) <= cache_data_memory_s1(to_integer(unsigned(cache_addr))); end if; end process cache_mem_access; -- data output -- host_rdata_o <= cache_rdata(0) when (hit(0) = '1') or (ICACHE_NUM_SETS = 1) else cache_rdata(1); -- cache block ram access address -- cache_addr <= cache_index & cache_offset; -- cache access select -- cache_index <= host_acc_addr.index when (ctrl_en_i = '0') else ctrl_acc_addr.index; cache_offset <= host_acc_addr.offset when (ctrl_en_i = '0') else ctrl_acc_addr.offset; cache_we <= '0' when (ctrl_en_i = '0') else ctrl_we_i; end neorv32_icache_memory_rtl;
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