Refactor and comment

Author: LarsAsplund

vunit/vhdl/verification_components/src/axi_stream_master.vhd

@@ -114,24 +114,30 @@ begin
 
       procedure drive_policy(signal s : out std_logic_vector; policy : inactive_bus_policy_t) is
       begin
-        if policy = 'X' then
-          s <= (s'range => 'X');
-        elsif policy = '0' then
-          s <= (s'range => '0');
-        elsif policy = '1' then
-          s <= (s'range => '1');
-        end if;
+        case policy is
+          when 'X' =>
+            s <= (s'range => 'X');
+          when '0' =>
+            s <= (s'range => '0');
+          when '1' =>
+            s <= (s'range => '1');
+          when hold =>
+            null;
+        end case;
       end;
 
       procedure drive_policy(signal s : out std_logic; policy : inactive_bus_policy_t) is
       begin
-        if policy = 'X' then
-          s <= 'X';
-        elsif policy = '0' then
-          s <= '0';
-        elsif policy = '1' then
-          s <= '1';
-        end if;
+        case policy is
+          when 'X' =>
+            s <= 'X';
+          when '0' =>
+            s <= '0';
+          when '1' =>
+            s <= '1';
+          when hold =>
+            null;
+        end case;
       end;
 
     begin

vunit/vhdl/verification_components/src/axi_stream_pkg.vhd

@@ -36,6 +36,7 @@ package axi_stream_pkg is
   type axi_stream_signal_t is (tdata, tlast, tkeep, tstrb, tid, tdest, tuser, all_signals);
   type inactive_axi_stream_policy_t is array (tdata to tuser) of inactive_bus_policy_t;
 
+  -- The standard protocol checker requires tuser to be a known value when the reset is released
   constant default_axi_stream_policy : inactive_axi_stream_policy_t := (tuser => '0', others => 'X');
   constant all_0_policy : inactive_axi_stream_policy_t := (others => '0');
   constant all_1_policy : inactive_axi_stream_policy_t := (others => '1');
@@ -464,6 +465,8 @@ package body axi_stream_pkg is
   impure function to_integer_vector_ptr(stall_config : stall_config_t) return integer_vector_ptr_t is
     variable result : integer_vector_ptr_t := new_integer_vector_ptr(3);
   begin
+    -- Since values are in the 0 - 1 range, we can have the full resolution of the mantissa fit within
+    -- an integer if reals are implemented as single-precision floats.
     set(result, 0, integer(stall_config.stall_probability * (2.0 ** 23)));
     set(result, 1, stall_config.min_stall_cycles);
     set(result, 2, stall_config.max_stall_cycles);