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

commit 5292afa657d0e790b7479ad8eef9450c1e040b3d upstream.

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>
(cherry picked from commit 4421a014e97c6669db6eb8600ce83d29e5484842)

Change-Id: I9038def962389acfca7f6a583e719d15f0f8d758
Signed-off-by: Neil Patel <neilp@nvidia.com>
Reviewed-on: http://git-master/r/553907
GVS: Gerrit_Virtual_Submit
Reviewed-by: Steve Lin <stlin@nvidia.com>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 6c313b1f274ab46682fafc270a0921596bdf7a9f..dc7ed4c6a022dfbf4224fede46e01b44d40739a5 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -649,12 +649,13 @@ static void acm_port_shutdown(struct tty_port *port)
 {
        struct acm *acm = container_of(port, struct acm, port);
        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);
                usb_kill_urb(acm->ctrlurb);
                for (i = 0; i < ACM_NW; i++)
@@ -662,7 +663,8 @@ 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);
 }