From: Johan Hovold <johan@kernel.org>
Date: Mon, 12 Apr 2021 09:38:13 +0000 (+0200)
Subject: USB: serial: io_ti: document reason for drain delay
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4b8e07951ff53e702bd5d6d21450b17152d124d7;p=linux.git

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 <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 75325c2b295e4..17720670e06c2 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;