[PATCH 155/270] USB: Enable LPM after a failed probe.

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Mon Nov 26 16:57:25 UTC 2012

3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.


From: Sarah Sharp <sarah.a.sharp at linux.intel.com>

commit d01f87c0ffa96cb44faa78710711eb6e974b891c upstream.

Before a driver is probed, we want to disable USB 3.0 Link Power
Management (LPM), in case the driver needs hub-initiated LPM disabled.
After the probe finishes, we want to attempt to re-enable LPM, order to
balance the LPM ref count.

When a probe fails (such as when libusual doesn't want to bind to a USB
3.0 mass storage device), make sure to balance the LPM ref counts by
re-enabling LPM.

This patch should be backported to kernels as old as 3.5, that contain
the commit 8306095fd2c1100e8244c09bf560f97aca5a311d "USB: Disable USB
3.0 LPM in critical sections."

Signed-off-by: Sarah Sharp <sarah.a.sharp at linux.intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 drivers/usb/core/driver.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index f536aeb..da33079 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -371,6 +371,10 @@ static int usb_probe_interface(struct device *dev)
 	intf->condition = USB_INTERFACE_UNBOUND;
+	/* If the LPM disable succeeded, balance the ref counts. */
+	if (!lpm_disable_error)
+		usb_unlocked_enable_lpm(udev);
 	/* Unbound interfaces are always runtime-PM-disabled and -suspended */
 	if (driver->supports_autosuspend)

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