Fix plru_tb to use the new plrufn and take out the old plru.vhdl

This reworks (and simplifies) plru_tb to use the new plrufn module
instead of the old (and now unused) plru module.

The latter is now removed completely.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Makefile

@@ -68,7 +68,7 @@ all: $(all)
 $(shell scripts/make_version.sh git.vhdl)
 
 core_files = decode_types.vhdl common.vhdl wishbone_types.vhdl fetch1.vhdl \
-	utils.vhdl plru.vhdl plrufn.vhdl cache_ram.vhdl icache.vhdl \
+	utils.vhdl plrufn.vhdl cache_ram.vhdl icache.vhdl \
 	predecode.vhdl decode1.vhdl helpers.vhdl insn_helpers.vhdl \
 	control.vhdl decode2.vhdl register_file.vhdl \
 	cr_file.vhdl crhelpers.vhdl ppc_fx_insns.vhdl rotator.vhdl \

microwatt.core

@@ -33,7 +33,6 @@ filesets:
       - insn_helpers.vhdl
       - core.vhdl
       - icache.vhdl
-      - plru.vhdl
       - plrufn.vhdl
       - cache_ram.vhdl
       - core_debug.vhdl

plru.vhdl

@@ -1,86 +0,0 @@
-library ieee;
-use ieee.std_logic_1164.all;
-use ieee.numeric_std.all;
-use ieee.math_real.all;
-
-entity plru is
-    generic (
-        BITS : positive := 2
-        )
-        ;
-    port (
-        clk    : in std_ulogic;
-        rst    : in std_ulogic;
-
-        acc    : in std_ulogic_vector(BITS-1 downto 0);
-        acc_en : in std_ulogic;
-        lru    : out std_ulogic_vector(BITS-1 downto 0)
-        );
-end entity plru;
-
-architecture rtl of plru is
-    -- Each level of the tree (from leaf to root) has half the number of nodes
-    -- of the previous level. So for a 2^N bits LRU, we have a level of N/2 bits
-    -- one of N/4 bits etc.. down to 1. This gives us 2^N-1 nodes. Ie, 2 bits
-    -- LRU has 3 nodes (2 + 1), 4 bits LRU has 15 nodes (8 + 4 + 2 + 1) etc...
-    constant count : positive := 2 ** BITS - 1;
-    subtype node_t is integer range 0 to count - 1;
-    type tree_t is array(node_t) of std_ulogic;
-
-    signal tree: tree_t;
-begin
-
-    -- XXX Check if we can turn that into a little ROM instead that
-    -- takes the tree bit vector and returns the LRU. See if it's better
-    -- in term of FPGA resource usage...
-    get_lru: process(tree)
-        variable node : node_t;
-        variable abit : std_ulogic;
-    begin
-        node := 0;
-        for i in 0 to BITS-1 loop
---          report "GET: i:" & integer'image(i) & " node:" & integer'image(node) & " val:" & std_ulogic'image(tree(node));
-            abit := tree(node);
-            lru(BITS-1-i) <= abit;
-            if i /= BITS-1 then
-                node := node * 2;
-                if abit = '1' then
-                    node := node + 2;
-                else
-                    node := node + 1;
-                end if;
-            end if;
-        end loop;
-    end process;
-
-    update_lru: process(clk)
-        variable node : node_t;
-        variable abit : std_ulogic;
-    begin
-        if rising_edge(clk) then
-            if rst = '1' then
-                tree <= (others => '0');
-            elsif acc_en = '1' then
-                node := 0;
-                for i in 0 to BITS-1 loop
-                    abit := acc(BITS-1-i);
-                    tree(node) <= not abit;
---                  report "UPD: i:" & integer'image(i) & " node:" & integer'image(node) & " val" & std_ulogic'image(not abit);
-                    if i /= BITS-1 then
-                        node := node * 2;
-                        if abit = '1' then
-                            node := node + 2;
-                        else
-                            node := node + 1;
-                        end if;
-                    end if;
-                end loop;
-            end if;
-        end if;
---        if falling_edge(clk) then
---            if acc_en = '1' then
---                report "UPD: tree:" & to_string(tree);
---            end if;
---        end if;
-    end process;
-end;

plru_tb.vhdl

@@ -3,6 +3,7 @@ context vunit_lib.vunit_context;
 
 library ieee;
 use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
 
 library work;
 use work.common.all;
@@ -17,22 +18,25 @@ architecture behave of plru_tb is
     signal rst          : std_ulogic;
 
     constant clk_period : time := 10 ns;
+    constant plru_bits  : integer := 3;
 
-    signal acc_en : std_ulogic;
+    subtype plru_val_t  is std_ulogic_vector(plru_bits - 1 downto 0);
-    signal acc : std_ulogic_vector(2 downto 0);
+    subtype plru_tree_t is std_ulogic_vector(2 ** plru_bits - 2 downto 0);
-    signal lru : std_ulogic_vector(2 downto 0);
+    signal do_update : std_ulogic := '0';
+    signal acc : plru_val_t;
+    signal lru : plru_val_t;
+    signal state : plru_tree_t;
+    signal state_upd : plru_tree_t;
 
 begin
-    plru0: entity work.plru
+    plrufn0: entity work.plrufn
         generic map(
-            BITS => 3
+            BITS => plru_bits
             )
         port map(
-            clk => clk,
-            rst => rst,
-
             acc => acc,
-            acc_en => acc_en,
+            tree_in => state,
+            tree_out => state_upd,
             lru => lru
             );
 
@@ -52,7 +56,26 @@ begin
         wait;
     end process;
 
-    stim: process
+    plru_process: process(clk)
+    begin
+        if rising_edge(clk) then
+            if rst = '1' then
+                state <= (others => '0');
+            elsif do_update = '1' then
+                state <= state_upd;
+            end if;
+        end if;
+    end process;
+
+    stim_process: process
+        procedure test_access(acc_val: integer; expected: integer) is
+        begin
+            acc <= std_ulogic_vector(to_unsigned(acc_val, acc'length));
+            do_update <= '1';
+            wait for clk_period;
+            info("accessed " & integer'image(acc_val) & " LRU=" & to_hstring(lru));
+            check_equal(lru, expected, result("LRU ACC=" & integer'image(acc_val)));
+        end procedure;
     begin
         test_runner_setup(runner, runner_cfg);
 
@@ -61,66 +84,31 @@ begin
         info("reset state:" & to_hstring(lru));
         check_equal(lru, 0, result("LRU "));
 
-        info("accessing 1:");
+        test_access(1, 4);
-        acc <= "001";
+        test_access(2, 4);
-        acc_en <= '1';
+        test_access(7, 0);
-        wait for clk_period;
+        test_access(4, 0);
-        info("lru:" & to_hstring(lru));
+        test_access(3, 6);
-        check_equal(lru, 4, result("LRU"));
+        test_access(5, 0);
-
+        test_access(3, 6);
-        info("accessing 2:");
+        test_access(5, 0);
-        acc <= "010";
+        test_access(6, 0);
-        wait for clk_period;
+        test_access(0, 4);
-        info("lru:" & to_hstring(lru));
+        test_access(1, 4);
-        check_equal(lru, 4, result("LRU"));
+        test_access(2, 4);
-
+        test_access(3, 4);
-        info("accessing 7:");
+        test_access(4, 0);
-        acc <= "111";
+        test_access(5, 0);
-        wait for clk_period;
+        test_access(6, 0);
-        info("lru:" & to_hstring(lru));
+        test_access(7, 0);
-        check_equal(lru, 0, result("LRU"));
+        test_access(6, 0);
-
+        test_access(5, 0);
-        info("accessing 4:");
+        test_access(4, 0);
-        acc <= "100";
+        test_access(3, 7);
-        wait for clk_period;
+        test_access(2, 7);
-        info("lru:" & to_hstring(lru));
+        test_access(1, 7);
-        check_equal(lru, 0, result("LRU"));
+        test_access(0, 7);
 
-        info("accessing 3:");
-        acc <= "011";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 6, result("LRU"));
-
-        info("accessing 5:");
-        acc <= "101";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 0, result("LRU"));
-
-        info("accessing 3:");
-        acc <= "011";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 6, result("LRU"));
-
-        info("accessing 5:");
-        acc <= "101";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 0, result("LRU"));
-
-        info("accessing 6:");
-        acc <= "110";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 0, result("LRU"));
-
-        info("accessing 0:");
-        acc <= "000";
-        wait for clk_period;
-        info("lru:" & to_hstring(lru));
-        check_equal(lru, 4, result("LRU"));
 
         wait for clk_period;
         wait for clk_period;