Introduce real_addr_t and addr_to_real()

This moves REAL_ADDR_BITS out of the caches and defines a real_addr_t
type for a real address, along with a addr_to_real() conversion helper.

It makes the vhdl a bit more readable

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

common.vhdl

@@ -156,6 +156,12 @@ package common is
     constant FPSCR_NI     : integer := 63 - 61;
     constant FPSCR_RN     : integer := 63 - 63;
 
+    -- Real addresses
+    -- REAL_ADDR_BITS is the number of real address bits that we store
+    constant REAL_ADDR_BITS : positive := 56;
+    subtype real_addr_t is std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+    function addr_to_real(addr: std_ulogic_vector(63 downto 0)) return real_addr_t;
+
     -- Used for tracking instruction completion and pending register writes
     constant TAG_COUNT : positive := 4;
     constant TAG_NUMBER_BITS : natural := log2(TAG_COUNT);
@@ -779,4 +785,9 @@ package body common is
     begin
         return tag1.valid = '1' and tag2.valid = '1' and tag1.tag = tag2.tag;
     end;
+
+    function addr_to_real(addr: std_ulogic_vector(63 downto 0)) return real_addr_t is
+    begin
+        return addr(real_addr_t'range);
+    end;
 end common;

dcache.vhdl

@@ -67,8 +67,6 @@ architecture rtl of dcache is
 
     -- Bit fields counts in the address
 
-    -- REAL_ADDR_BITS is the number of real address bits that we store
-    constant REAL_ADDR_BITS : positive := 56;
     -- ROW_BITS is the number of bits to select a row 
     constant ROW_BITS      : natural := log2(BRAM_ROWS);
     -- ROW_LINEBITS is the number of bits to select a row within a line
@@ -289,7 +287,7 @@ architecture rtl of dcache is
         op        : op_t;
         valid     : std_ulogic;
         dcbz      : std_ulogic;
-        real_addr : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+        real_addr : real_addr_t;
         data      : std_ulogic_vector(63 downto 0);
         byte_sel  : std_ulogic_vector(7 downto 0);
         hit_way   : way_t;
@@ -412,7 +410,7 @@ architecture rtl of dcache is
     signal tlb_hit : std_ulogic;
     signal tlb_hit_way : tlb_way_t;
     signal pte : tlb_pte_t;
-    signal ra : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+    signal ra : real_addr_t;
     signal valid_ra : std_ulogic;
     signal perm_attr : perm_attr_t;
     signal rc_ok : std_ulogic;
@@ -803,7 +801,7 @@ begin
 
     -- Cache tag RAM second read port, for snooping
     cache_tag_read_2 : process(clk)
-        variable addr : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+        variable addr : real_addr_t;
     begin
         if rising_edge(clk) then
             addr := (others => '0');
@@ -830,7 +828,7 @@ begin
         variable s_hit       : std_ulogic;
         variable s_tag       : cache_tag_t;
         variable s_pte       : tlb_pte_t;
-        variable s_ra        : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+        variable s_ra        : real_addr_t;
         variable hit_set     : std_ulogic_vector(TLB_NUM_WAYS - 1 downto 0);
         variable hit_way_set : hit_way_set_t;
         variable rel_matches : std_ulogic_vector(TLB_NUM_WAYS - 1 downto 0);

icache.vhdl

@@ -46,8 +46,6 @@ entity icache is
         TLB_SIZE : positive := 64;
         -- L1 ITLB log_2(page_size)
         TLB_LG_PGSZ : positive := 12;
-        -- Number of real address bits that we store
-        REAL_ADDR_BITS : positive := 56;
         -- Non-zero to enable log data collection
         LOG_LENGTH : natural := 0
         );
@@ -210,7 +208,7 @@ architecture rtl of icache is
     signal req_laddr   : std_ulogic_vector(63 downto 0);
 
     signal tlb_req_index : tlb_index_t;
-    signal real_addr     : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+    signal real_addr     : real_addr_t;
     signal ra_valid      : std_ulogic;
     signal priv_fault    : std_ulogic;
     signal access_ok     : std_ulogic;
@@ -468,7 +466,7 @@ begin
             end if;
             eaa_priv <= pte(3);
         else
-            real_addr <= i_in.nia(REAL_ADDR_BITS - 1 downto 0);
+            real_addr <= addr_to_real(i_in.nia);
             ra_valid <= '1';
             eaa_priv <= '1';
         end if;
@@ -627,7 +625,7 @@ begin
     icache_miss : process(clk)
 	variable tagset    : cache_tags_set_t;
         variable tag       : cache_tag_t;
-        variable snoop_addr : std_ulogic_vector(REAL_ADDR_BITS - 1 downto 0);
+        variable snoop_addr : real_addr_t;
         variable snoop_tag : cache_tag_t;
         variable snoop_cache_tags : cache_tags_set_t;
     begin