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Date:   Fri,  1 May 2020 15:21:23 +0200
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Alan Stern <>,
        Paul Zimmerman <>,
        Peter Chen <>
Subject: [PATCH 4.14 047/117] USB: hub: Fix handling of connect changes during sleep

From: Alan Stern <>

commit 9f952e26295d977dbfc6fedeaf8c4f112c818d37 upstream.

Commit 8099f58f1ecd ("USB: hub: Don't record a connect-change event
during reset-resume") wasn't very well conceived.  The problem it
tried to fix was that if a connect-change event occurred while the
system was asleep (such as a device disconnecting itself from the bus
when it is suspended and then reconnecting when it resumes)
requiring a reset-resume during the system wakeup transition, the hub
port's change_bit entry would remain set afterward.  This would cause
the hub driver to believe another connect-change event had occurred
after the reset-resume, which was wrong and would lead the driver to
send unnecessary requests to the device (which could interfere with a
firmware update).

The commit tried to fix this by not setting the change_bit during the
wakeup.  But this was the wrong thing to do; it means that when a
device is unplugged while the system is asleep, the hub driver doesn't
realize anything has happened: The change_bit flag which would tell it
to handle the disconnect event is clear.

The commit needs to be reverted and the problem fixed in a different
way.  Fortunately an alternative solution was noted in the commit's
Changelog: We can continue to set the change_bit entry in
hub_activate() but then clear it when a reset-resume occurs.  That way
the the hub driver will see the change_bit when a device is
disconnected but won't see it when the device is still present.

That's what this patch does.

Reported-and-tested-by: Peter Chen <>
Signed-off-by: Alan Stern <>
Fixes: 8099f58f1ecd ("USB: hub: Don't record a connect-change event during reset-resume")
Tested-by: Paul Zimmerman <>
CC: <>
Signed-off-by: Greg Kroah-Hartman <>

 drivers/usb/core/hub.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1195,6 +1195,11 @@ static void hub_activate(struct usb_hub
 #ifdef CONFIG_PM
 			udev->reset_resume = 1;
+			/* Don't set the change_bits when the device
+			 * was powered off.
+			 */
+			if (test_bit(port1, hub->power_bits))
+				set_bit(port1, hub->change_bits);
 		} else {
 			/* The power session is gone; tell hub_wq */
@@ -3008,6 +3013,15 @@ static int check_port_resume_type(struct
 		if (portchange & USB_PORT_STAT_C_ENABLE)
 			usb_clear_port_feature(hub->hdev, port1,
+		/*
+		 * Whatever made this reset-resume necessary may have
+		 * turned on the port1 bit in hub->change_bits.  But after
+		 * a successful reset-resume we want the bit to be clear;
+		 * if it was on it would indicate that something happened
+		 * following the reset-resume.
+		 */
+		clear_bit(port1, hub->change_bits);
 	return status;

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