how to avoid this warning?

In your code you have tyhe following stuctures

assign flg_oc_2 = flg_oc_1;

always @ (posedge out_feed or posedge flg_oc_2)

begin

if (out_feed)

begin

flg_block_drive_1 <= 1'b0;

end

else if (flg_oc_2)

begin

flg_block_drive_1 <= 1'b1;

end

end

You may be assuming that flg_oc_2 is just a strobe but in fact the coding style infers a clock!

The above code will infer a FlipFlop for flg_block_drive_1 with flg_oc_2 as a clock input.

So the warning is correct.

Hope this helps