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

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Date:   Tue, 13 Nov 2018 15:55:33 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Dennis Wassenberg <dennis.wassenberg@...unet.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: Re: [PATCH] usb: core: Fix hub port connection events lost

On 13.11.2018 15:40, Dennis Wassenberg wrote:
> 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);
>   
>   			/*
> 

Acked-by: Mathias Nyman <mathias.nyman@...ux.intel.com>