From: Alan Stern <stern@rowland.harvard.edu>

Date: Tue, 1 Aug 2017 10:41:56 -0400

Subject: [PATCH] USB: Check for dropped connection before switching to full

 speed

References: bnc#1060662

Patch-mainline: v4.12.8

Git-commit: 94c43b9897abf4ea366ed4dba027494e080c7050

commit 94c43b9897abf4ea366ed4dba027494e080c7050 upstream.

Some buggy USB disk adapters disconnect and reconnect multiple times

during the enumeration procedure.  This may lead to a device

connecting at full speed instead of high speed, because when the USB

stack sees that a device isn't able to enumerate at high speed, it

tries to hand the connection over to a full-speed companion

controller.

The logic for doing this is careful to check that the device is still

connected.  But this check is inadequate if the device disconnects and

reconnects before the check is done.  The symptom is that a device

works, but much more slowly than it is capable of operating.

The situation was made worse recently by commit 22547c4cc4fe ("usb:

hub: Wait for connection to be reestablished after port reset"), which

increases the delay following a reset before a disconnect is

recognized, thus giving the device more time to reconnect.

This patch makes the check more robust.  If the device was

disconnected at any time during enumeration, we will now skip the

full-speed handover.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

Reported-and-tested-by: Zdenek Kabelac <zkabelac@redhat.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 drivers/usb/core/hub.c | 10 ++++++----

 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c

index b8bb20d7acdb..0881a3e8131c 100644

--- a/drivers/usb/core/hub.c

+++ b/drivers/usb/core/hub.c

@@ -4730,7 +4730,8 @@ hub_power_remaining(struct usb_hub *hub)

 static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,

 		u16 portchange)

 {

-	int status, i;

+	int status = -ENODEV;

+	int i;

 	unsigned unit_load;

 	struct usb_device *hdev = hub->hdev;

 	struct usb_hcd *hcd = bus_to_hcd(hdev->bus);

@@ -4934,9 +4935,10 @@ loop:

 done:

 	hub_port_disable(hub, port1, 1);

-	if (hcd->driver->relinquish_port && !hub->hdev->parent)

-		hcd->driver->relinquish_port(hcd, port1);

-

+	if (hcd->driver->relinquish_port && !hub->hdev->parent) {

+		if (status != -ENOTCONN && status != -ENODEV)

+			hcd->driver->relinquish_port(hcd, port1);

+	}

 }

 /* Handle physical or logical connection change events.

-- 

2.14.2