The three-character drain delay was added by commit f1175daa5312 ("USB:
ti_usb_3410_5052: kill custom closing_wait") when removing the custom
closing-wait implementation, which used a fixed 20 ms poll period and
drain delay.
This was likely a bit too conservative as a one-character timeout (e.g.
33 ms at 300 bps) should be enough to compensate for the lack of a
transmitter empty bit in the TUSB5052 line-status register.
Signed-off-by: Johan Hovold <jo...@kernel.org>
---
drivers/usb/serial/ti_usb_3410_5052.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/serial/ti_usb_3410_5052.c
b/drivers/usb/serial/ti_usb_3410_5052.c
index 03839289d6c0..8ed64115987f 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -610,7 +610,11 @@ static int ti_port_probe(struct usb_serial_port *port)
usb_set_serial_port_data(port, tport);
- port->port.drain_delay = 3;
+ /*
+ * The TUSB5052 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
