From 4b8e07951ff53e702bd5d6d21450b17152d124d7 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Mon, 12 Apr 2021 11:38:13 +0200 Subject: USB: serial: io_ti: document reason for drain delay 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. Reviewed-by: Greg Kroah-Hartman Signed-off-by: Johan Hovold --- drivers/usb/serial/io_ti.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/usb/serial') 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; -- cgit v1.2.3