ACK/Cmnt: [SRU][B][PATCH 1/1] usb: handle warm-reset port requests on hub resume

[Stefan Bader]

On 27.07.20 01:24, Matthew Ruffell wrote:
> From: Jan-Marek Glogowski <glogow at fbihome.de>
> 
> BugLink: https://bugs.launchpad.net/bugs/1859873
> 
> On plug-in of my USB-C device, its USB_SS_PORT_LS_SS_INACTIVE
> link state bit is set. Greping all the kernel for this bit shows
> that the port status requests a warm-reset this way.
> 
> This just happens, if its the only device on the root hub, the hub
> therefore resumes and the HCDs status_urb isn't yet available.
> If a warm-reset request is detected, this sets the hubs event_bits,
> which will prevent any auto-suspend and allows the hubs workqueue
> to warm-reset the port later in port_event.
> 
> Signed-off-by: Jan-Marek Glogowski <glogow at fbihome.de>
> Acked-by: Alan Stern <stern at rowland.harvard.edu>
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> (cherry picked from commit 4fdc1790e6a9ef22399c6bc6e63b80f4609f3b7e)
> Signed-off-by: Matthew Ruffell <matthew.ruffell at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---

Ack for Bionic. For Eoan, the question is whether this would be useful. Eoan is
EOL since Jul-17. The won't be a generic update there. We still have a few
special projects that are on 5.3 but quickly being replaced and not sure whether
those are using hw which benefits from the change.

-Stefan

>  drivers/usb/core/hub.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index b99602789ca2..7a27237f6b67 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -107,6 +107,8 @@ EXPORT_SYMBOL_GPL(ehci_cf_port_reset_rwsem);
>  static void hub_release(struct kref *kref);
>  static int usb_reset_and_verify_device(struct usb_device *udev);
>  static int hub_port_disable(struct usb_hub *hub, int port1, int set_state);
> +static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
> +		u16 portstatus);
>  
>  static inline char *portspeed(struct usb_hub *hub, int portstatus)
>  {
> @@ -1117,6 +1119,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>  						   USB_PORT_FEAT_ENABLE);
>  		}
>  
> +		/* Make sure a warm-reset request is handled by port_event */
> +		if (type == HUB_RESUME &&
> +		    hub_port_warm_reset_required(hub, port1, portstatus))
> +			set_bit(port1, hub->event_bits);
> +
>  		/*
>  		 * Add debounce if USB3 link is in polling/link training state.
>  		 * Link will automatically transition to Enabled state after
> 


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