[3.11.y.z extended stable] Patch "USB: cdc-acm: fix runtime PM imbalance at shutdown" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c093b250e5de9627e97f1de62f2f06daa3a1d56a Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold at gmail.com>
Date: Mon, 26 May 2014 19:23:45 +0200
Subject: 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 at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/class/cdc-acm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 83a19ae3c31c..a72b7f1f6e17 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -575,12 +575,13 @@ 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 (;;) {
@@ -598,7 +599,8 @@ 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);
 }
--
1.9.1