Xilinx FPGAs: Eliminate Vivado critical warnings

This resolves various warnings and critical warnings from Vivado.

In particular, the asynchronous loops in the xilinx hardware RNG were
giving a lot of critical warnings, which proved to be difficult to
suppress, so this instead makes all the xilinx platforms use the
'nonrandom.vhdl' implementation, which always returns an error.

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

Author: paulusmack

countbits.vhdl

@@ -50,9 +50,11 @@ architecture behaviour of bit_counter is
 begin
     countzero_r: process(clk)
     begin
-        if rising_edge(clk) and stall = '0' then
-            inp_r <= inp;
-            sum_r <= sum;
+        if rising_edge(clk) then
+            if stall = '0' then
+                inp_r <= inp;
+                sum_r <= sum;
+            end if;
         end if;
     end process;
 

fetch1.vhdl

@@ -152,7 +152,7 @@ begin
         attribute ram_style of btc_memory : signal is "block";
 
         signal btc_valids : std_ulogic_vector(BTC_SIZE - 1 downto 0);
-        attribute ram_style of btc_valids : signal is "distributed";
+        -- attribute ram_style of btc_valids : signal is "distributed";
 
         signal btc_wr : std_ulogic;
         signal btc_wr_data : std_ulogic_vector(BTC_WIDTH - 1 downto 0);

fpga/arty_a7.xdc

@@ -171,15 +171,15 @@ set_property -dict { PACKAGE_PIN R15 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_po
 set_property -dict { PACKAGE_PIN P15 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io33 }];
 set_property -dict { PACKAGE_PIN R16 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io34 }];
 set_property -dict { PACKAGE_PIN N16 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io35 }];
-set_property -dict { PACKAGE_PIN N14 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io36 }];
-set_property -dict { PACKAGE_PIN U17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io37 }];
-set_property -dict { PACKAGE_PIN T18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io38 }];
-set_property -dict { PACKAGE_PIN R18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io39 }];
-set_property -dict { PACKAGE_PIN P18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io40 }];
-set_property -dict { PACKAGE_PIN N17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io41 }];
-set_property -dict { PACKAGE_PIN M17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io42 }]; # A
-set_property -dict { PACKAGE_PIN L18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io43 }]; # SCL
-set_property -dict { PACKAGE_PIN M18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io44 }]; # SDA
+#set_property -dict { PACKAGE_PIN N14 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io36 }];
+#set_property -dict { PACKAGE_PIN U17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io37 }];
+#set_property -dict { PACKAGE_PIN T18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io38 }];
+#set_property -dict { PACKAGE_PIN R18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io39 }];
+#set_property -dict { PACKAGE_PIN P18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io40 }];
+#set_property -dict { PACKAGE_PIN N17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io41 }];
+#set_property -dict { PACKAGE_PIN M17 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io42 }]; # A
+#set_property -dict { PACKAGE_PIN L18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io43 }]; # SCL
+#set_property -dict { PACKAGE_PIN M18 IOSTANDARD LVCMOS33 PULLDOWN TRUE } [get_ports { shield_io44 }]; # SDA
 #set_property -dict { PACKAGE_PIN C2  IOSTANDARD LVCMOS33 } [get_ports { shield_rst }];
 
 #set_property -dict { PACKAGE_PIN C1  IOSTANDARD LVCMOS33 } [get_ports { spi_hdr_ss }];

fpga/top-arty.vhdl

@@ -206,6 +206,9 @@ architecture behaviour of toplevel is
     signal ddram_clk_p_vec : std_logic_vector(0 downto 0);
     signal ddram_clk_n_vec : std_logic_vector(0 downto 0);
 
+    signal uart1_rxd : std_ulogic;
+    signal uart1_txd : std_ulogic;
+
     -- Fixup various memory sizes based on generics
     function get_bram_size return natural is
     begin
@@ -266,8 +269,8 @@ begin
             uart0_rxd         => uart_main_rx,
 
 	    -- UART1 signals
-	    --uart1_txd         => uart_pmod_tx,
-	    --uart1_rxd         => uart_pmod_rx,
+            uart1_txd         => uart1_txd,
+            uart1_rxd         => uart1_rxd,
 
             -- SPI signals
             spi_flash_sck     => spi_sck,
@@ -302,7 +305,7 @@ begin
             wishbone_dma_out     => wb_sddma_out
             );
 
-    --uart_pmod_rts_n <= '0';
+    uart1_txd <= '1';
 
     -- SPI Flash
     --
@@ -415,8 +418,9 @@ begin
                 );
 
         -- Generate SoC reset
-        soc_rst_gen: process(system_clk)
+        soc_rst_gen: process(system_clk, ext_rst_n)
         begin
+            -- XXX why does this need to be an asynchronous reset?
             if ext_rst_n = '0' then
                 soc_rst <= '1';
             elsif rising_edge(system_clk) then

icache.vhdl

@@ -403,12 +403,12 @@ begin
             variable snoop_addr : real_addr_t;
             variable next_raddr : real_addr_t;
         begin
-            replace_way := to_unsigned(0, WAY_BITS);
-            if NUM_WAYS > 1 then
-                -- Get victim way from plru
-                replace_way := plru_victim;
-            end if;
             if rising_edge(clk) then
+                replace_way := to_unsigned(0, WAY_BITS);
+                if NUM_WAYS > 1 then
+                    -- Get victim way from plru
+                    replace_way := plru_victim;
+                end if;
                 -- Read tags using NIA for next cycle
                 if flush_in = '1' or i_in.req = '0' or (stall_in = '0' and stall_out = '0') then
                     next_raddr := i_in.next_rpn & i_in.next_nia(MIN_LG_PGSZ - 1 downto 0);
@@ -649,6 +649,7 @@ begin
     begin
         if rising_edge(clk) then
             ev.icache_miss <= '0';
+            ev.itlb_miss_resolved <= '0';
             r.recv_valid <= '0';
 	    -- On reset, clear all valid bits to force misses
             if rst = '1' then

microwatt.core

@@ -62,14 +62,13 @@ filesets:
       - fpga/pp_soc_uart.vhd
       - fpga/pp_utilities.vhd
       - fpga/firmware.hex : {copyto : firmware.hex, file_type : user}
+      - nonrandom.vhdl
     file_type : vhdlSource-2008
 
   xilinx_specific:
     files:
       - xilinx-mult.vhdl : {file_type : vhdlSource-2008}
       - xilinx-mult-32s.vhdl : {file_type : vhdlSource-2008}
-      - fpga/fpga-random.vhdl : {file_type : vhdlSource-2008}
-      - fpga/fpga-random.xdc : {file_type : xdc}
 
   debug_xilinx:
     files:

xics.vhdl

@@ -386,15 +386,14 @@ begin
     reg_write: process(clk)
         variable be_in  : std_ulogic_vector(31 downto 0);
     begin
-        -- Byteswapped input
-        be_in := bswap(wb_in.dat);
-
         if rising_edge(clk) then
             if rst = '1' then
                 for i in 0 to SRC_NUM - 1 loop
                     xives(i) <= (pri => pri_masked);
                 end loop;
             elsif wb_valid = '1' and wb_in.we = '1' then
+                -- Byteswapped input
+                be_in := bswap(wb_in.dat);
                 if reg_is_xive then
                     -- TODO: When adding support for other bits, make sure to
                     -- properly implement wb_in.sel to allow partial writes.

xilinx-mult-32s.vhdl

@@ -286,9 +286,11 @@ begin
 
     process(clk)
     begin
-        if rising_edge(clk) and stall = '0' then
-            m_out.valid <= m_in.valid;
-            product_lo <= m01_p(5 downto 0) & m00_p(16 downto 0);
+        if rising_edge(clk) then
+            if stall = '0' then
+                m_out.valid <= m_in.valid;
+                product_lo <= m01_p(5 downto 0) & m00_p(16 downto 0);
+            end if;
         end if;
     end process;