Commit 7ff799af authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman

USB: Check for dropped connection before switching to full speed

commit 94c43b98 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 22547c4c ("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: default avatarAlan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: default avatarZdenek Kabelac <zkabelac@redhat.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c45923eb
...@@ -4730,7 +4730,8 @@ hub_power_remaining(struct usb_hub *hub) ...@@ -4730,7 +4730,8 @@ hub_power_remaining(struct usb_hub *hub)
static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus, static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
u16 portchange) u16 portchange)
{ {
int status, i; int status = -ENODEV;
int i;
unsigned unit_load; unsigned unit_load;
struct usb_device *hdev = hub->hdev; struct usb_device *hdev = hub->hdev;
struct usb_hcd *hcd = bus_to_hcd(hdev->bus); struct usb_hcd *hcd = bus_to_hcd(hdev->bus);
...@@ -4934,9 +4935,10 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus, ...@@ -4934,9 +4935,10 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
done: done:
hub_port_disable(hub, port1, 1); hub_port_disable(hub, port1, 1);
if (hcd->driver->relinquish_port && !hub->hdev->parent) if (hcd->driver->relinquish_port && !hub->hdev->parent) {
hcd->driver->relinquish_port(hcd, port1); if (status != -ENOTCONN && status != -ENODEV)
hcd->driver->relinquish_port(hcd, port1);
}
} }
/* Handle physical or logical connection change events. /* Handle physical or logical connection change events.
......
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