cdc_fifo_gray: Fix SpyGlass CDC Lint issues (#262)

* Refactor Source side CDC for lint compliance

* Port fix to cdc_fifo_gray_clearable

* Fixup

---------

Co-authored-by: moritz <[email protected]>

Author: MoritzScherer

src/cdc_fifo_gray.sv

@@ -187,15 +187,17 @@ module cdc_fifo_gray_src #(
   localparam int PtrWidth = LOG_DEPTH+1;
   localparam logic [PtrWidth-1:0] PtrFull = (1 << LOG_DEPTH);
 
-  T [2**LOG_DEPTH-1:0] data_q;
+  T [2**LOG_DEPTH-1:0] data_q, data_d;
   logic [PtrWidth-1:0] wptr_q, wptr_d, wptr_bin, wptr_next, rptr, rptr_bin;
 
   // Data FIFO.
   assign async_data_o = data_q;
-  for (genvar i = 0; i < 2**LOG_DEPTH; i++) begin : gen_word
-    `FFLNR(data_q[i], src_data_i,
-          src_valid_i & src_ready_o & (wptr_bin[LOG_DEPTH-1:0] == i), src_clk_i)
+
+  always_comb begin
+    data_d                          = data_q;
+    data_d[wptr_bin[LOG_DEPTH-1:0]] = src_data_i;
   end
+  `FFLARN(data_q, data_d, src_valid_i & src_ready_o, '0, src_clk_i, src_rst_ni)
 
   // Read pointer.
   for (genvar i = 0; i < PtrWidth; i++) begin : gen_sync

src/cdc_fifo_gray_clearable.sv

@@ -285,15 +285,16 @@ module cdc_fifo_gray_src_clearable #(
   localparam int PtrWidth = LOG_DEPTH+1;
   localparam logic [PtrWidth-1:0] PtrFull = (1 << LOG_DEPTH);
 
-  T [2**LOG_DEPTH-1:0] data_q;
+  T [2**LOG_DEPTH-1:0] data_q, data_d;
   logic [PtrWidth-1:0] wptr_q, wptr_d, wptr_bin, wptr_next, rptr, rptr_bin;
 
   // Data FIFO.
   assign async_data_o = data_q;
-  for (genvar i = 0; i < 2**LOG_DEPTH; i++) begin : gen_word
-    `FFLNR(data_q[i], src_data_i,
-          src_valid_i & src_ready_o & (wptr_bin[LOG_DEPTH-1:0] == i), src_clk_i)
+  always_comb begin
+    data_d                          = data_q;
+    data_d[wptr_bin[LOG_DEPTH-1:0]] = src_data_i;
   end
+  `FFLARN(data_q, data_d, src_valid_i & src_ready_o, '0, src_clk_i, src_rst_ni)
 
   // Read pointer.
   for (genvar i = 0; i < PtrWidth; i++) begin : gen_sync