[PATCH 4.20 028/117] USB: serial: ftdi_sio: fix GPIO not working in autosuspend

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Karoly Pados <pados@xxxxxxxx>

commit a8eda9fa1bd84065b75bfa81bf675a7af9055478 upstream.

There is a bug in the current GPIO code for ftdi_sio: it failed to take USB
autosuspend into account. If the device is in autosuspend, calls to
usb_control_msg() fail with -EHOSTUNREACH. Because the standard value for
autosuspend timeout is usually 2-5 seconds, this made it almost impossible
to use the GPIOs on machines that have USB autosuspend enabled. This patch
fixes the issue by acquiring a PM lock on the device for the duration of
the USB transfers. Tested on an FT231X device.

Signed-off-by: Karoly Pados <pados@xxxxxxxx>
[ johan: simplify code somewhat ]
Fixes: ba93cc7da896 ("USB: serial: ftdi_sio: implement GPIO support for FT-X devices")
Cc: stable <stable@xxxxxxxxxxxxxxx>	# 4.20
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/serial/ftdi_sio.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1783,6 +1783,10 @@ static int ftdi_set_bitmode(struct usb_s
 	int result;
 	u16 val;
 
+	result = usb_autopm_get_interface(serial->interface);
+	if (result)
+		return result;
+
 	val = (mode << 8) | (priv->gpio_output << 4) | priv->gpio_value;
 	result = usb_control_msg(serial->dev,
 				 usb_sndctrlpipe(serial->dev, 0),
@@ -1795,6 +1799,8 @@ static int ftdi_set_bitmode(struct usb_s
 			val, result);
 	}
 
+	usb_autopm_put_interface(serial->interface);
+
 	return result;
 }
 
@@ -1846,9 +1852,15 @@ static int ftdi_read_cbus_pins(struct us
 	unsigned char *buf;
 	int result;
 
+	result = usb_autopm_get_interface(serial->interface);
+	if (result)
+		return result;
+
 	buf = kmalloc(1, GFP_KERNEL);
-	if (!buf)
+	if (!buf) {
+		usb_autopm_put_interface(serial->interface);
 		return -ENOMEM;
+	}
 
 	result = usb_control_msg(serial->dev,
 				 usb_rcvctrlpipe(serial->dev, 0),
@@ -1863,6 +1875,7 @@ static int ftdi_read_cbus_pins(struct us
 	}
 
 	kfree(buf);
+	usb_autopm_put_interface(serial->interface);
 
 	return result;
 }