[topgen] Avoid adding a comma after the last parameter in the list

The previous code added a comma after a parameter unless this was the
last parameter of the module and this was the last module in the list.
This works fine unless the last module in the list doesn't happen to
have any parameters.

In that situation, you got something like

     ...
      parameter int unsigned RvCoreIbexDmExceptionAddr =
          tl_main_pkg::ADDR_SPACE_RV_DM__MEM + dm::ExceptionAddress[31:0],
      parameter bit RvCoreIbexPipeLine = 0,
      // parameters for mbx0
      // parameters for mbx1
      // parameters for mbx2
    ) (
     ...

which is a syntax error (the parser sees something like "a, b, )").

Tweak the logic slightly so that we add a comma unless this is the
last parameter in the module and this is the last module *with
parameters* in the list

The diagnosis and main work was done by Robert Schilling. I just
tweaked the code to make it a bit easier for me to follow.

Signed-off-by: Rupert Swarbrick <[email protected]>
Co-authored-by: Robert Schilling <[email protected]>

util/topgen/lib.py

@@ -244,6 +244,14 @@ def get_pad_list(padstr):
     return pads
 
 
+def idx_of_last_module_with_params(top):
+    last = -1
+    for idx, module in enumerate(top["module"]):
+        if len(module["param_list"]):
+            last = idx
+    return last
+
+
 # Template functions
 def ljust(x, width):
     return "{:<{width}}".format(x, width=width)

util/topgen/templates/toplevel.sv.tpl

@@ -37,6 +37,8 @@ for m in top['memory']:
   if m['type'] == 'rom':
     has_toplevel_rom = True
 
+last_modidx_with_params = lib.idx_of_last_module_with_params(top)
+
 %>\
 `include "prim_assert.sv"
 
@@ -59,12 +61,15 @@ module top_${top["name"]} #(
 
     p_lhs = f'{p_type_word}{p_exp["name_top"]}'
     p_rhs = p_exp['default']
+
+    params_follow = not loop.last or loop.parent.index < last_modidx_with_params
+    comma_char = ',' if params_follow else ''
 %>\
     % if 12 + len(p_lhs) + 3 + len(p_rhs) + 1 < 100:
-  parameter ${p_lhs} = ${p_rhs}${"" if loop.parent.last & loop.last else ","}
+  parameter ${p_lhs} = ${p_rhs}${comma_char}
     % else:
   parameter ${p_lhs} =
-      ${p_rhs}${"" if loop.parent.last & loop.last else ","}
+      ${p_rhs}${comma_char}
     % endif
   % endfor
 % endfor