Document that the device line-status register doesn't tell when the transmitter shift register has emptied and that this is why the one-character drain delay is needed. Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> --- drivers/usb/serial/io_ti.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c index 75325c2b295e..17720670e06c 100644 --- a/drivers/usb/serial/io_ti.c +++ b/drivers/usb/serial/io_ti.c @@ -2590,6 +2590,10 @@ static int edge_port_probe(struct usb_serial_port *port) if (ret) goto err; + /* + * The LSR does not tell when the transmitter shift register has + * emptied so add a one-character drain delay. + */ port->port.drain_delay = 1; return 0; -- 2.26.3
