Timing analysis - long combinational path

Yes, this is the filter. Both multiply and accumulate happens in the FILTERING-state, along with truncation. In addition, there is a RAM holding the accumulated sum. Input-samples are not stored when coming in.

  o_coef_addr <= std_logic_vector(coef_addr_cnt);

  -- Accumulator RAM
  p_accRAM : process (clk) is
  begin
    if rising_edge(clk) then
      if (we_accRAM = '1') then
        accRAM_Re(to_integer(accRAM_addr_in)) <= accRAM_Re_in;
        accRAM_Im(to_integer(accRAM_addr_in)) <= accRAM_Im_in;
      end if;
      accRAM_Re_out <= accRAM_Re(to_integer(accRAM_addr_out));
      accRAM_Im_out <= accRAM_Im(to_integer(accRAM_addr_out));
    end if;
  end process p_accRAM;

  -- Sample input-samples and detect tvalid-flanks
  p_edge : process (clk) is
  begin
    if rising_edge(clk)  then
      sample_s1.tvalid <= i_sample.tvalid;
      sample_s1.tdata  <= i_sample.tdata;

      if (i_sample.tvalid = '1' and sample_s1.tvalid = '0') then
        sample_tvalid_posedge <= '1';
        sample_tvalid_negedge <= '0';
      elsif (i_sample.tvalid = '0' and sample_s1.tvalid = '1') then
        sample_tvalid_negedge <= '1';
        sample_tvalid_posedge <= '0';
      else
        sample_tvalid_posedge <= '0';
        sample_tvalid_negedge <= '0';
      end if;
    end if;
  end process p_edge;