From a38ae503ff3a88852bcf27cc8b56ff110595081b Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Thu, 10 Oct 2019 00:38:03 +1100
Subject: [PATCH] cache_ram: Add write-enables

They will be needed by the dcache

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 cache_ram.vhdl | 25 +++++++++++++++++++++++--
 icache.vhdl    |  1 +
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/cache_ram.vhdl b/cache_ram.vhdl
index e0ffd17..346c6fe 100644
--- a/cache_ram.vhdl
+++ b/cache_ram.vhdl
@@ -6,7 +6,8 @@ use ieee.math_real.all;
 entity cache_ram is
     generic(
 	ROW_BITS : integer := 16;
-	WIDTH    : integer := 64
+	WIDTH    : integer := 64;
+	TRACE    : boolean := false
 	);
 
     port(
@@ -15,6 +16,7 @@ entity cache_ram is
 	rd_addr : in  std_logic_vector(ROW_BITS - 1 downto 0);
 	rd_data : out std_logic_vector(WIDTH - 1 downto 0);
 	wr_en   : in  std_logic;
+	wr_sel  : in  std_logic_vector(WIDTH/8 - 1 downto 0);
 	wr_addr : in  std_logic_vector(ROW_BITS - 1 downto 0);
 	wr_data : in  std_logic_vector(WIDTH - 1 downto 0)
 	);
@@ -33,13 +35,32 @@ architecture rtl of cache_ram is
 
 begin
     process(clk)
+	variable lbit : integer range 0 to WIDTH - 1;
+	variable mbit : integer range 0 to WIDTH - 1;
+	variable widx : integer range 0 to SIZE - 1;
     begin
 	if rising_edge(clk) then
 	    if wr_en = '1' then
-		ram(to_integer(unsigned(wr_addr))) <= wr_data;
+		if TRACE then
+		    report "write a:" & to_hstring(wr_addr) &
+			" sel:" & to_hstring(wr_sel) &
+			" dat:" & to_hstring(wr_data);
+		end if;
+		for i in 0 to WIDTH/8-1 loop
+		    lbit := i * 8;
+		    mbit := lbit + 7;
+		    widx := to_integer(unsigned(wr_addr));
+		    if wr_sel(i) = '1' then
+			ram(widx)(mbit downto lbit) <= wr_data(mbit downto lbit);
+		    end if;
+		end loop;
 	    end if;
 	    if rd_en = '1' then
 		rd_data <= ram(to_integer(unsigned(rd_addr)));
+		if TRACE then
+		    report "read a:" & to_hstring(rd_addr) &
+			" dat:" & to_hstring(ram(to_integer(unsigned(rd_addr))));
+		end if;
 	    end if;
 	end if;
     end process;
diff --git a/icache.vhdl b/icache.vhdl
index 89e491e..804b648 100644
--- a/icache.vhdl
+++ b/icache.vhdl
@@ -290,6 +290,7 @@ begin
 		rd_addr => rd_addr,
 		rd_data => dout,
 		wr_en   => do_write,
+		wr_sel  => (others => '1'),
 		wr_addr => wr_addr,
 		wr_data => wishbone_in.dat
 		);