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Subject[PATCH] USB: serial: ftdi_sio: Fix GPIO not working in autosuspend
Date
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@pados.hu>
---
Please consider backporting to 4.20.x, otherwise the GPIO driver is not
really usable for anybody with USB autosuspend enabled (eg. many laptops),
at least not without manual configuration.

drivers/usb/serial/ftdi_sio.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 1ab2a6191013..01813dce37f2 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1783,6 +1783,13 @@ static int ftdi_set_bitmode(struct usb_serial_port *port, u8 mode)
int result;
u16 val;

+ result = usb_autopm_get_interface(port->serial->interface);
+ if (result) {
+ dev_err(&port->serial->interface->dev,
+ "Failed to wake device from autosuspend.\n");
+ 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 +1802,8 @@ static int ftdi_set_bitmode(struct usb_serial_port *port, u8 mode)
val, result);
}

+ usb_autopm_put_interface(port->serial->interface);
+
return result;
}

@@ -1846,9 +1855,18 @@ static int ftdi_read_cbus_pins(struct usb_serial_port *port)
unsigned char *buf;
int result;

+ result = usb_autopm_get_interface(port->serial->interface);
+ if (result) {
+ dev_err(&port->serial->interface->dev,
+ "Failed to wake device from autosuspend.\n");
+ return result;
+ }
+
buf = kmalloc(1, GFP_KERNEL);
- if (!buf)
+ if (!buf) {
+ usb_autopm_put_interface(port->serial->interface);
return -ENOMEM;
+ }

result = usb_control_msg(serial->dev,
usb_rcvctrlpipe(serial->dev, 0),
@@ -1863,6 +1881,7 @@ static int ftdi_read_cbus_pins(struct usb_serial_port *port)
}

kfree(buf);
+ usb_autopm_put_interface(port->serial->interface);

return result;
}
--
2.20.1
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