linux-kernel - [PATCH] usb: core: Fix hub port connection events lost

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Date:   Tue, 13 Nov 2018 14:40:34 +0100
From:   Dennis Wassenberg <dennis.wassenberg@...unet.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...el.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
CC:     Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        "Kuppuswamy Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Bin Liu <b-liu@...com>,
        Maxim Moseychuk <franchesko.salias.hudro.pedros@...il.com>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Dominik Bozek <dominikx.bozek@...el.com>,
        USB list <linux-usb@...r.kernel.org>,
        "Kernel development list" <linux-kernel@...r.kernel.org>
Subject: [PATCH] usb: core: Fix hub port connection events lost

This will clear the USB_PORT_FEAT_C_CONNECTION bit in case of a hub port reset
only if a device is was attached to the hub port before resetting the hub port.

Using a Lenovo T480s attached to the ultra dock it was not possible to detect
some usb-c devices at the dock usb-c ports because the hub_port_reset code
will clear the USB_PORT_FEAT_C_CONNECTION bit after the actual hub port reset.
Using this device combo the USB_PORT_FEAT_C_CONNECTION bit was set between the
actual hub port reset and the clear of the USB_PORT_FEAT_C_CONNECTION bit.
This ends up with clearing the USB_PORT_FEAT_C_CONNECTION bit after the
new device was attached such that it was not detected.

This patch will not clear the USB_PORT_FEAT_C_CONNECTION bit if there is
currently no device attached to the port before the hub port reset.
This will avoid clearing the connection bit for new attached devices.

Signed-off-by: Dennis Wassenberg <dennis.wassenberg@...unet.com>
---
 drivers/usb/core/hub.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c6077d582d29..2731fad6f659 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2849,7 +2849,9 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
 					USB_PORT_FEAT_C_BH_PORT_RESET);
 			usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_PORT_LINK_STATE);
-			usb_clear_port_feature(hub->hdev, port1,
+
+			if (udev)
+				usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_CONNECTION);

 			/*
-- 
2.17.1