Fix runtime PM handling of control messages by adding the required PM
counter operations.

Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

Cc: <sta...@vger.kernel.org>    # v2.6.27
Signed-off-by: Johan Hovold <jhov...@gmail.com>
---
 drivers/usb/class/cdc-acm.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 56419254ef75..2258827df084 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -122,13 +122,23 @@ static void acm_release_minor(struct acm *acm)
 static int acm_ctrl_msg(struct acm *acm, int request, int value,
                                                        void *buf, int len)
 {
-       int retval = usb_control_msg(acm->dev, usb_sndctrlpipe(acm->dev, 0),
+       int retval;
+
+       retval = usb_autopm_get_interface(acm->control);
+       if (retval)
+               return retval;
+
+       retval = usb_control_msg(acm->dev, usb_sndctrlpipe(acm->dev, 0),
                request, USB_RT_ACM, value,
                acm->control->altsetting[0].desc.bInterfaceNumber,
                buf, len, 5000);
+
        dev_dbg(&acm->control->dev,
                        "%s - rq 0x%02x, val %#x, len %#x, result %d\n",
                        __func__, request, value, len, retval);
+
+       usb_autopm_put_interface(acm->control);
+
        return retval < 0 ? retval : 0;
 }
 
-- 
1.8.5.5

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