Make LOG_LENGTH configurable per FPGA variant

This plumbs the LOG_LENGTH parameter (which controls how many entries
the core log RAM has) up to the top level so that it can be set on
the fusesoc command line and have different default values on
different FPGAs.

It now defaults to 512 entries generally and on the Artix-7 35 parts,
and 2048 on the larger Artix-7 FPGAs.  It can be set to 0 if desired.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

core.vhdl

@@ -11,7 +11,8 @@ entity core is
         SIM : boolean := false;
 	DISABLE_FLATTEN : boolean := false;
         EX1_BYPASS : boolean := true;
-	ALT_RESET_ADDRESS : std_ulogic_vector(63 downto 0) := (others => '0')
+	ALT_RESET_ADDRESS : std_ulogic_vector(63 downto 0) := (others => '0');
+        LOG_LENGTH : natural := 512
         );
     port (
         clk          : in std_ulogic;
@@ -372,6 +373,9 @@ begin
     log_data(139 downto 135) <= "00000";
 
     debug_0: entity work.core_debug
+        generic map (
+            LOG_LENGTH => LOG_LENGTH
+            )
 	port map (
 	    clk => clk,
 	    rst => rst_dbg,

core_debug.vhdl

@@ -9,7 +9,7 @@ use work.common.all;
 entity core_debug is
     generic (
         -- Length of log buffer
-        LOG_LENGTH : positive := 2048
+        LOG_LENGTH : natural := 512
         );
     port (
         clk          : in std_logic;
@@ -92,6 +92,8 @@ architecture behave of core_debug is
     constant DBG_CORE_LOG_ADDR       : std_ulogic_vector(3 downto 0) := "0110";
     constant DBG_CORE_LOG_DATA       : std_ulogic_vector(3 downto 0) := "0111";
 
+    constant LOG_INDEX_BITS : natural := log2(LOG_LENGTH);
+
     -- Some internal wires
     signal stat_reg : std_ulogic_vector(63 downto 0);
 
@@ -104,38 +106,12 @@ architecture behave of core_debug is
     signal do_gspr_rd   : std_ulogic;
     signal gspr_index   : gspr_index_t;
 
-    -- Logging RAM
-    constant LOG_INDEX_BITS : natural := log2(LOG_LENGTH);
-    subtype log_ptr_t is unsigned(LOG_INDEX_BITS - 1 downto 0);
-    type log_array_t is array(0 to LOG_LENGTH - 1) of std_ulogic_vector(255 downto 0);
-    signal log_array    : log_array_t;
-    signal log_rd_ptr   : log_ptr_t;
-    signal log_wr_ptr   : log_ptr_t;
-    signal log_toggle   : std_ulogic;
-    signal log_wr_enable : std_ulogic;
-    signal log_rd_ptr_latched : log_ptr_t;
-    signal log_rd       : std_ulogic_vector(255 downto 0);
-    signal log_dmi_addr : std_ulogic_vector(31 downto 0);
-    signal log_dmi_data : std_ulogic_vector(63 downto 0);
+    signal log_dmi_addr : std_ulogic_vector(31 downto 0) := (others => '0');
+    signal log_dmi_data : std_ulogic_vector(63 downto 0) := (others => '0');
     signal do_dmi_log_rd : std_ulogic;
-    signal log_dmi_reading : std_ulogic;
-    signal log_dmi_read_done : std_ulogic;
     signal dmi_read_log_data : std_ulogic;
     signal dmi_read_log_data_1 : std_ulogic;
 
-    function select_dword(data : std_ulogic_vector(255 downto 0);
-                          addr : std_ulogic_vector(31 downto 0)) return std_ulogic_vector is
-        variable firstbit : integer;
-    begin
-        firstbit := to_integer(unsigned(addr(1 downto 0))) * 64;
-        return data(firstbit + 63 downto firstbit);
-    end;
-
-    attribute ram_style : string;
-    attribute ram_style of log_array : signal is "block";
-    attribute ram_decomp : string;
-    attribute ram_decomp of log_array : signal is "power";
-
 begin
        -- Single cycle register accesses on DMI except for GSPR data
     dmi_ack <= dmi_req when dmi_addr /= DBG_CORE_GSPR_DATA
@@ -241,50 +217,86 @@ begin
     icache_rst <= do_icreset;
     terminated_out <= terminated;
 
-    -- Use MSB of read addresses to stop the logging
-    log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31));
-
-    log_ram: process(clk)
-    begin
-        if rising_edge(clk) then
-            if log_wr_enable = '1' then
-                log_array(to_integer(log_wr_ptr)) <= log_data;
-            end if;
-            log_rd <= log_array(to_integer(log_rd_ptr_latched));
-        end if;
-    end process;
-
+    -- Logging RAM
+    maybe_log: if LOG_LENGTH > 0 generate
+        subtype log_ptr_t is unsigned(LOG_INDEX_BITS - 1 downto 0);
+        type log_array_t is array(0 to LOG_LENGTH - 1) of std_ulogic_vector(255 downto 0);
+        signal log_array    : log_array_t;
+        signal log_rd_ptr   : log_ptr_t;
+        signal log_wr_ptr   : log_ptr_t;
+        signal log_toggle   : std_ulogic;
+        signal log_wr_enable : std_ulogic;
+        signal log_rd_ptr_latched : log_ptr_t;
+        signal log_rd       : std_ulogic_vector(255 downto 0);
+        signal log_dmi_reading : std_ulogic;
+        signal log_dmi_read_done : std_ulogic;
+
+        function select_dword(data : std_ulogic_vector(255 downto 0);
+                              addr : std_ulogic_vector(31 downto 0)) return std_ulogic_vector is
+            variable firstbit : integer;
+        begin
+            firstbit := to_integer(unsigned(addr(1 downto 0))) * 64;
+            return data(firstbit + 63 downto firstbit);
+        end;
+
+        attribute ram_style : string;
+        attribute ram_style of log_array : signal is "block";
+        attribute ram_decomp : string;
+        attribute ram_decomp of log_array : signal is "power";
 
-    log_buffer: process(clk)
-        variable b : integer;
-        variable data : std_ulogic_vector(255 downto 0);
     begin
-        if rising_edge(clk) then
-            if rst = '1' then
-                log_wr_ptr <= (others => '0');
-                log_toggle <= '0';
-            elsif log_wr_enable = '1' then
-                if log_wr_ptr = to_unsigned(LOG_LENGTH - 1, LOG_INDEX_BITS) then
-                    log_toggle <= not log_toggle;
+        -- Use MSB of read addresses to stop the logging
+        log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31));
+
+        log_ram: process(clk)
+        begin
+            if rising_edge(clk) then
+                if log_wr_enable = '1' then
+                    log_array(to_integer(log_wr_ptr)) <= log_data;
                 end if;
-                log_wr_ptr <= log_wr_ptr + 1;
-            end if;
-            if do_dmi_log_rd = '1' then
-                log_rd_ptr_latched <= unsigned(log_dmi_addr(LOG_INDEX_BITS + 1 downto 2));
-            else
-                log_rd_ptr_latched <= unsigned(log_read_addr(LOG_INDEX_BITS + 1 downto 2));
+                log_rd <= log_array(to_integer(log_rd_ptr_latched));
             end if;
-            if log_dmi_read_done = '1' then
-                log_dmi_data <= select_dword(log_rd, log_dmi_addr);
-            else
-                log_read_data <= select_dword(log_rd, log_read_addr);
+        end process;
+
+
+        log_buffer: process(clk)
+            variable b : integer;
+            variable data : std_ulogic_vector(255 downto 0);
+        begin
+            if rising_edge(clk) then
+                if rst = '1' then
+                    log_wr_ptr <= (others => '0');
+                    log_toggle <= '0';
+                elsif log_wr_enable = '1' then
+                    if log_wr_ptr = to_unsigned(LOG_LENGTH - 1, LOG_INDEX_BITS) then
+                        log_toggle <= not log_toggle;
+                    end if;
+                    log_wr_ptr <= log_wr_ptr + 1;
+                end if;
+                if do_dmi_log_rd = '1' then
+                    log_rd_ptr_latched <= unsigned(log_dmi_addr(LOG_INDEX_BITS + 1 downto 2));
+                else
+                    log_rd_ptr_latched <= unsigned(log_read_addr(LOG_INDEX_BITS + 1 downto 2));
+                end if;
+                if log_dmi_read_done = '1' then
+                    log_dmi_data <= select_dword(log_rd, log_dmi_addr);
+                else
+                    log_read_data <= select_dword(log_rd, log_read_addr);
+                end if;
+                log_dmi_read_done <= log_dmi_reading;
+                log_dmi_reading <= do_dmi_log_rd;
             end if;
-            log_dmi_read_done <= log_dmi_reading;
-            log_dmi_reading <= do_dmi_log_rd;
-        end if;
-    end process;
-    log_write_addr(LOG_INDEX_BITS - 1 downto 0) <= std_ulogic_vector(log_wr_ptr);
-    log_write_addr(LOG_INDEX_BITS) <= '1';
-    log_write_addr(31 downto LOG_INDEX_BITS + 1) <= (others => '0');
+        end process;
+        log_write_addr(LOG_INDEX_BITS - 1 downto 0) <= std_ulogic_vector(log_wr_ptr);
+        log_write_addr(LOG_INDEX_BITS) <= '1';
+        log_write_addr(31 downto LOG_INDEX_BITS + 1) <= (others => '0');
+    end generate;
+
+    no_log: if LOG_LENGTH = 0 generate
+    begin
+        log_read_data <= (others => '0');
+        log_write_addr <= x"00000001";
+    end generate;
+
 end behave;
 

fpga/top-arty.vhdl

@@ -20,7 +20,8 @@ entity toplevel is
         SCLK_STARTUPE2     : boolean := false;
         SPI_FLASH_OFFSET   : integer := 4194304;
         SPI_FLASH_DEF_CKDV : natural := 1;
-        SPI_FLASH_DEF_QUAD : boolean := true
+        SPI_FLASH_DEF_QUAD : boolean := true;
+        LOG_LENGTH         : natural := 512
         );
     port(
         ext_clk   : in  std_ulogic;
@@ -139,7 +140,8 @@ begin
             SPI_FLASH_DLINES   => 4,
             SPI_FLASH_OFFSET   => SPI_FLASH_OFFSET,
             SPI_FLASH_DEF_CKDV => SPI_FLASH_DEF_CKDV,
-            SPI_FLASH_DEF_QUAD => SPI_FLASH_DEF_QUAD
+            SPI_FLASH_DEF_QUAD => SPI_FLASH_DEF_QUAD,
+            LOG_LENGTH         => LOG_LENGTH
             )
         port map (
             -- System signals

microwatt.core

@@ -110,6 +110,7 @@ targets:
       - clk_input
       - clk_frequency
       - disable_flatten_core
+      - log_length=2048
     tools:
       vivado: {part : xc7a100tcsg324-1}
     toplevel : toplevel
@@ -124,6 +125,7 @@ targets:
       - clk_frequency
       - disable_flatten_core
       - spi_flash_offset=10485760
+      - log_length=2048
     tools:
       vivado: {part : xc7a200tsbg484-1}
     toplevel : toplevel
@@ -138,6 +140,7 @@ targets:
       - disable_flatten_core
       - no_bram
       - spi_flash_offset=10485760
+      - log_length=2048
     generate: [dram_nexys_video]
     tools:
       vivado: {part : xc7a200tsbg484-1}
@@ -153,6 +156,7 @@ targets:
       - clk_frequency
       - disable_flatten_core
       - spi_flash_offset=3145728
+      - log_length=512
     tools:
       vivado: {part : xc7a35ticsg324-1L}
     toplevel : toplevel
@@ -167,6 +171,7 @@ targets:
       - disable_flatten_core
       - no_bram
       - spi_flash_offset=3145728
+      - log_length=512
     generate: [dram_arty]
     tools:
       vivado: {part : xc7a35ticsg324-1L}
@@ -182,6 +187,7 @@ targets:
       - clk_frequency
       - disable_flatten_core
       - spi_flash_offset=4194304
+      - log_length=2048
     tools:
       vivado: {part : xc7a100ticsg324-1L}
     toplevel : toplevel
@@ -196,6 +202,7 @@ targets:
       - disable_flatten_core
       - no_bram
       - spi_flash_offset=4194304
+      - log_length=2048
     generate: [dram_arty]
     tools:
       vivado: {part : xc7a100ticsg324-1L}
@@ -211,6 +218,7 @@ targets:
       - clk_input=12000000
       - clk_frequency
       - disable_flatten_core
+      - log_length=512
     tools:
       vivado: {part : xc7a35tcpg236-1}
     toplevel : toplevel
@@ -281,3 +289,8 @@ parameters:
     datatype    : int
     description : Offset (in bytes) in the SPI flash of the code payload to run
     paramtype   : generic
+
+  log_length:
+    datatype    : int
+    description : Length of the core log buffer in entries (32 bytes each)
+    paramtype   : generic

soc.vhdl

@@ -41,7 +41,8 @@ entity soc is
         SPI_FLASH_DLINES   : positive := 1;
         SPI_FLASH_OFFSET   : integer := 0;
         SPI_FLASH_DEF_CKDV : natural := 2;
-        SPI_FLASH_DEF_QUAD : boolean := false
+        SPI_FLASH_DEF_QUAD : boolean := false;
+        LOG_LENGTH         : natural := 512
 	);
     port(
 	rst          : in  std_ulogic;
@@ -186,7 +187,8 @@ begin
 	generic map(
 	    SIM => SIM,
 	    DISABLE_FLATTEN => DISABLE_FLATTEN_CORE,
-	    ALT_RESET_ADDRESS => (23 downto 0 => '0', others => '1')
+	    ALT_RESET_ADDRESS => (23 downto 0 => '0', others => '1'),
+            LOG_LENGTH => LOG_LENGTH
 	    )
 	port map(
 	    clk => system_clk,