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Projet_SETI_RISC-V/neorv32/rtl/core/neorv32_icache.vhd

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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) 2023, 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
miss_o : out std_ulogic; -- cache miss
-- host controller interface --
host_addr_i : in std_ulogic_vector(31 downto 0); -- bus access address
host_rdata_o : out std_ulogic_vector(31 downto 0); -- bus read data
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_cached_o : out std_ulogic; -- set if cached (!) access in progress
bus_addr_o : out std_ulogic_vector(31 downto 0); -- bus access address
bus_rdata_i : in std_ulogic_vector(31 downto 0); -- bus read data
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; 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
host_rstat_o : out std_ulogic; -- read status
-- 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_wstat_i : in std_ulogic; -- write status
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
host_rstat : std_ulogic; -- cpu read status
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_wstat : std_ulogic; -- control write status
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);
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 ----------------------------------------------------------------
-- -------------------------------------------------------------------------------------------
ctrl_engine_fsm_sync: process(rstn_i, clk_i)
begin
if (rstn_i = '0') then
ctrl.state <= S_CACHE_CLEAR; -- to reset cache information memory, which does not have an explicit reset
ctrl.re_buf <= '0';
ctrl.clear_buf <= '0';
ctrl.addr_reg <= (others => '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;
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_wstat <= bus_err_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_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
if (cache.host_rstat = '1') then -- data word from cache marked as faulty?
host_err_o <= '1';
else
host_ack_o <= '1';
end if;
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_ack_i = '1') or (bus_err_i = '1') then -- ACK or ERROR = 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
-- ------------------------------------------------------------
if (cache.host_rstat = '1') then -- data word from cache marked as faulty?
host_err_o <= '1';
else
host_ack_o <= '1';
end if;
ctrl.state_nxt <= S_IDLE;
when others => -- undefined
-- ------------------------------------------------------------
ctrl.state_nxt <= S_IDLE;
end case;
end process ctrl_engine_fsm_comb;
-- signal cache miss to CPU --
miss_o <= '1' when (ctrl.state = S_CACHE_MISS) else '0';
-- cache access in progress --
bus_cached_o <= '1' when (ctrl.state = S_BUS_DOWNLOAD_REQ) or (ctrl.state = S_BUS_DOWNLOAD_GET) else '0';
-- 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
host_rstat_o => cache.host_rstat, -- read status
-- 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_wstat_i => cache.ctrl_wstat, -- write status
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) 2022, 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
host_rstat_o : out std_ulogic; -- read status
-- 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_wstat_i : in std_ulogic; -- write status
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 additional 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 (32-bit data + 1-bit status) --
type cache_mem_t is array (0 to cache_entries_c-1) of std_ulogic_vector(31+1 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+1 downto 0);
signal cache_rd : 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 <= '1' when (or_reduce_f(hit) = '1') else '0';
-- 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_wstat_i & ctrl_wdata_i;
else
cache_data_memory_s1(to_integer(unsigned(cache_addr))) <= ctrl_wstat_i & ctrl_wdata_i;
end if;
end if;
-- read access from host (full-word) --
cache_rd(0) <= cache_data_memory_s0(to_integer(unsigned(cache_addr)));
cache_rd(1) <= cache_data_memory_s1(to_integer(unsigned(cache_addr)));
end if;
end process cache_mem_access;
-- data output --
host_rdata_o <= cache_rd(0)(31 downto 0) when (hit(0) = '1') or (ICACHE_NUM_SETS = 1) else cache_rd(1)(31 downto 0);
host_rstat_o <= cache_rd(0)(32) when (hit(0) = '1') or (ICACHE_NUM_SETS = 1) else cache_rd(1)(32);
-- 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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