USB: cdc-acm: fix runtime PM imbalance at shutdown

Make sure only to decrement the PM counters if they were actually
incremented.

Note that the USB PM counter, but not necessarily the driver core PM
counter, is reset when the interface is unbound.

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

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index eddeba61a88c87adfe9bdd777993532c253f59cd..6bbd203f18611449b8df1db38579ed6ded79b4b7 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -590,12 +590,13 @@ static void acm_port_shutdown(struct tty_port *port)
        struct urb *urb;
        struct acm_wb *wb;
        int i;
+       int pm_err;
 
        dev_dbg(&acm->control->dev, "%s\n", __func__);
 
        mutex_lock(&acm->mutex);
        if (!acm->disconnected) {
-               usb_autopm_get_interface(acm->control);
+               pm_err = usb_autopm_get_interface(acm->control);
                acm_set_control(acm, acm->ctrlout = 0);
 
                for (;;) {
@@ -613,7 +614,8 @@ static void acm_port_shutdown(struct tty_port *port)
                for (i = 0; i < acm->rx_buflimit; i++)
                        usb_kill_urb(acm->read_urbs[i]);
                acm->control->needs_remote_wakeup = 0;
-               usb_autopm_put_interface(acm->control);
+               if (!pm_err)
+                       usb_autopm_put_interface(acm->control);
        }
        mutex_unlock(&acm->mutex);
 }