[PATCH] USB: serial: ftdi_sio: Fix serial port stall after resume

[Helge Deller]

With a 4-port serial USB HUB with FT232BM chips the serial ports stop
working after a software suspend/resume cycle.
Rewriting the latency timer during the resume phase fixes it.

Cc: sta...@vger.kernel.org
Signed-off-by: Helge Deller <del...@gmx.de>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 9823bb424abd..8ee6cf6215c1 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1092,6 +1092,7 @@ static u32 ftdi_232bm_baud_base_to_divisor(int baud, int 
base);
 static u32 ftdi_232bm_baud_to_divisor(int baud);
 static u32 ftdi_2232h_baud_base_to_divisor(int baud, int base);
 static u32 ftdi_2232h_baud_to_divisor(int baud);
+static int ftdi_reset_resume(struct usb_serial *serial);

 static struct usb_serial_driver ftdi_sio_device = {
        .driver = {
@@ -1122,6 +1123,7 @@ static struct usb_serial_driver ftdi_sio_device = {
        .set_termios =          ftdi_set_termios,
        .break_ctl =            ftdi_break_ctl,
        .tx_empty =             ftdi_tx_empty,
+       .reset_resume =         ftdi_reset_resume,
 };

 static struct usb_serial_driver * const serial_drivers[] = {
@@ -2379,6 +2381,16 @@ static int ftdi_stmclite_probe(struct usb_serial *serial)
        return 0;
 }

+static int ftdi_reset_resume(struct usb_serial *serial)
+{
+       struct usb_serial_port *port = serial->port[0];
+
+       if (tty_port_initialized(&port->port))
+               write_latency_timer(port);
+
+       return usb_serial_generic_resume(serial);
+}
+
 static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
        struct ftdi_private *priv = usb_get_serial_port_data(port);