soc: Add DRAM address decoding

Still not attached to any board

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

core_tb.vhdl

@@ -14,6 +14,10 @@ architecture behave of core_tb is
 
 	-- testbench signals
 	constant clk_period : time := 10 ns;
+
+        -- Dummy DRAM
+	signal wb_dram_in : wishbone_master_out;
+	signal wb_dram_out : wishbone_slave_out;
 begin
 
     soc0: entity work.soc
@@ -28,6 +32,8 @@ begin
 	    system_clk => clk,
 	    uart0_rxd => '0',
 	    uart0_txd => open,
+	    wb_dram_in => wb_dram_in,
+	    wb_dram_out => wb_dram_out,
 	    alt_reset => '0'
 	    );
 
@@ -48,4 +54,10 @@ begin
     end process;
 
     jtag: entity work.sim_jtag;
+
+    -- Dummy DRAM
+    wb_dram_out.ack <= wb_dram_in.cyc and wb_dram_in.stb;
+    wb_dram_out.dat <= x"FFFFFFFFFFFFFFFF";
+    wb_dram_out.stall <= wb_dram_in.cyc and not wb_dram_out.ack;
+
 end;

fpga/toplevel.vhdl

@@ -30,6 +30,10 @@ architecture behaviour of toplevel is
     signal system_clk : std_ulogic;
     signal system_clk_locked : std_ulogic;
 
+    -- Dummy DRAM
+    signal wb_dram_in : wishbone_master_out;
+    signal wb_dram_out : wishbone_slave_out;
+
 begin
 
     reset_controller: entity work.soc_reset
@@ -73,4 +77,9 @@ begin
 	    uart0_rxd         => uart0_rxd
 	    );
 
+    -- Dummy DRAM
+    wb_dram_out.ack <= wb_dram_in.cyc and wb_dram_in.stb;
+    wb_dram_out.dat <= x"FFFFFFFFFFFFFFFF";
+    wb_dram_out.stall <= wb_dram_in.cyc and not wb_dram_out.ack;
+
 end architecture behaviour;

soc.vhdl

@@ -10,24 +10,39 @@ use work.common.all;
 use work.wishbone_types.all;
 
 
--- 0x00000000: Main memory (1 MB)
+-- Memory map:
--- 0xc0002000: UART0 (for host communication)
+--
+-- 0x00000000: Block RAM
+-- 0x40000000: DRAM (when present)
+-- 0xc0002000: UART0
 -- 0xc0004000: XICS ICP
+-- 0xf0000000: Block RAM (aliased & repeated)
+-- 0xffff0000: DRAM init code (if any)
+
 entity soc is
     generic (
 	MEMORY_SIZE   : positive;
 	RAM_INIT_FILE : string;
 	RESET_LOW     : boolean;
 	SIM           : boolean;
-	DISABLE_FLATTEN_CORE : boolean := false
+	DISABLE_FLATTEN_CORE : boolean := false;
+	HAS_DRAM      : boolean  := false
 	);
     port(
 	rst          : in  std_ulogic;
 	system_clk   : in  std_ulogic;
 
+	-- DRAM controller signals
+	wb_dram_in   : out wishbone_master_out;
+	wb_dram_out  : in wishbone_slave_out;
+	wb_dram_csr  : out std_ulogic;
+	wb_dram_init : out std_ulogic;
+
 	-- UART0 signals:
 	uart0_txd    : out std_ulogic;
 	uart0_rxd    : in  std_ulogic;
+
+	-- DRAM controller signals
 	alt_reset    : in std_ulogic
 	);
 end entity soc;
@@ -130,26 +145,36 @@ begin
 	    );
 
     -- Wishbone slaves address decoder & mux
-    slave_intercon: process(wb_master_out, wb_bram_out, wb_uart0_out)
+    slave_intercon: process(wb_master_out, wb_bram_out, wb_uart0_out, wb_dram_out)
 	-- Selected slave
-	type slave_type is (SLAVE_UART_0,
+	type slave_type is (SLAVE_UART,
-			    SLAVE_MEMORY,
+			    SLAVE_BRAM,
+			    SLAVE_DRAM,
+			    SLAVE_DRAM_INIT,
+			    SLAVE_DRAM_CSR,
 			    SLAVE_ICP_0,
 			    SLAVE_NONE);
 	variable slave : slave_type;
     begin
 	-- Simple address decoder.
 	slave := SLAVE_NONE;
-	if wb_master_out.adr(31 downto 24) = x"00" then
+	-- Simple address decoder. Ignore top bits to save silicon for now
-	    slave := SLAVE_MEMORY;
+	slave := SLAVE_NONE;
-	elsif wb_master_out.adr(31 downto 24) = x"c0" then
+	if    std_match(wb_master_out.adr, x"0-------") then
-	    if wb_master_out.adr(23 downto 12) = x"002" then
+	    slave := SLAVE_BRAM;
-		slave := SLAVE_UART_0;
+	elsif std_match(wb_master_out.adr, x"FFFF----") then
-	    end if;
+	    slave := SLAVE_DRAM_INIT;
-	    if wb_master_out.adr(23 downto 12) = x"004" then
+	elsif std_match(wb_master_out.adr, x"F-------") then
+	    slave := SLAVE_BRAM;
+	elsif std_match(wb_master_out.adr, x"4-------") and HAS_DRAM then
+	    slave := SLAVE_DRAM;
+	elsif std_match(wb_master_out.adr, x"C0002---") then
+	    slave := SLAVE_UART;
+	elsif std_match(wb_master_out.adr, x"C01-----") then
+	    slave := SLAVE_DRAM_CSR;
+	elsif std_match(wb_master_out.adr, x"C0004---") then
 	    slave := SLAVE_ICP_0;
 	end if;
-	end if;
 
 	-- Wishbone muxing. Defaults:
 	wb_bram_in <= wb_master_out;
@@ -162,11 +187,27 @@ begin
 	wb_xics0_in.adr <= (others => '0');
 	wb_xics0_in.adr(7 downto 0) <= wb_master_out.adr(7 downto 0);
 	wb_xics0_in.cyc  <= '0';
+
+	wb_dram_in <= wb_master_out;
+	wb_dram_in.cyc <= '0';
+	wb_dram_csr <= '0';
+	wb_dram_init <= '0';
 	case slave is
-	when SLAVE_MEMORY =>
+	when SLAVE_BRAM =>
 	    wb_bram_in.cyc <= wb_master_out.cyc;
 	    wb_master_in <= wb_bram_out;
-	when SLAVE_UART_0 =>
+	when SLAVE_DRAM =>
+	    wb_dram_in.cyc <= wb_master_out.cyc;
+	    wb_master_in <= wb_dram_out;
+	when SLAVE_DRAM_INIT =>
+	    wb_dram_in.cyc <= wb_master_out.cyc;
+	    wb_master_in <= wb_dram_out;
+	    wb_dram_init <= '1';
+	when SLAVE_DRAM_CSR =>
+	    wb_dram_in.cyc <= wb_master_out.cyc;
+	    wb_master_in <= wb_dram_out;
+	    wb_dram_csr <= '1';
+	when SLAVE_UART =>
 	    wb_uart0_in.cyc <= wb_master_out.cyc;
 	    wb_master_in <= wb_uart0_out;
 	when SLAVE_ICP_0 =>