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authorAlan Stern <stern@rowland.harvard.edu>2017-08-01 10:41:56 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-10 11:50:54 -0700
commit94c43b9897abf4ea366ed4dba027494e080c7050 (patch)
tree3f7abf5250dc1e956d69d0ef98ecacf8469ee069
parente788787ef4f9c24aafefc480a8da5f92b914e5e6 (diff)
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USB: Check for dropped connection before switching to full speed
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> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/core/hub.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 6e6797d145dd..822f8c50e423 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4725,7 +4725,8 @@ 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);
@@ -4929,9 +4930,10 @@ 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.