On Mon, Dec 20, 2021 at 11:19:03AM +0100, Filip Žaludek wrote:

  Yes, you are right! Such gadget hardware is without hw flow control.
  I am using serial line only to capture console logs. I've tested
  both commands also with sw flow control ixon, ixoff with similar
  results.

The FTDI and PL2303 chips typically support automatic hardware flow
control, but you need to make sure the signals are wired up.

  Hopefully somebody sitting on scarce big iron with both usb port and
  serial port with proper hw flow control from this list gets
  attracted to kindly re-test.

No need to retest anything. Just enable hardware flow control otherwise
there cannot be any guarantees.

Interesting part for me is that only serial to usb direction is
failing..

But in this case, it looks like your test script is just broken. You
kill the consumer before it has read all the data:

	uart_send__cat()
	{
	    cat < "$1" > /tmp/d16 &
	    RX_PID=$!
	    cat /tmp/d16_0 > "$2"
	    stty sane                           # better results
	    kill $RX_PID
	    wait $RX_PID
	    uart_info "$3"
	}

	...

	stty -F /dev/$SER 115200 raw -echo
	stty -F /dev/$USB 115200 raw -echo

	while true
	do
	    uart_send__cat /dev/$SER /dev/$USB "u->s"
	    uart_send__cat /dev/$USB /dev/$SER "s->u"
	done

Johan