ONFI nand on Arria10

I want to implement an ONFI NAND flash in asynchronous and synchronous mode on Arria 10.

For synchronous mode, I use phylite module.

But i would like to use the NAND flash in both mode (asynchronous and synchronous), I create a phylite component for synchronous and I add a register to read the data coming from NAND flash component in asynchronous because in asynchronous, dqs signal is not driven. Quartus generates an error ("Source also drive out to other destination than the buffer").

My logic:

inout [7:0] data,

inout dqs

phylite phylite_inst(

.ref_clk(clk),

.reset_n(rstn),

.interface_locked(/*OPEN*/),

.group_0_data_io(data),

.group_0_strobe_io(dqs)

);

always @(posedge clk) begin

data_in_asynchronous <= data;

end

Do you any idea to resolve my issue?

Thank in advance.