usb hub driver bug in overcurrent handling?

[Alan Stern <stern@rowland.harvard.edu>]

On Fri, 13 Jul 2018, Bin Liu wrote:

> Hi,
> 
> I got a report saying that when overcurrent happens in one of the hub
> downstream ports, USB_PORT_STAT_OVERCURRENT is not set in portstatus,
> instead USB_PORT_STAT_C_OVERCURRENT is set in portchange, then the
> overcurrent condition is not handled in hub_event().
> 
> The following patch solves the issue.
> 
> t a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 442be7f312f6..118557acc74b 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1144,7 +1144,8 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>                          * check for a new connection
>                          */
>                         if (udev || (portstatus & USB_PORT_STAT_CONNECTION) ||
> -                           (portstatus & USB_PORT_STAT_OVERCURRENT))
> +                           (portstatus & USB_PORT_STAT_OVERCURRENT) ||
> +                           (portchange & USB_PORT_STAT_C_OVERCURRENT))
>                                 set_bit(port1, hub->change_bits);
>  
>                 } else if (portstatus & USB_PORT_STAT_ENABLE) {

Please also update the immediately preceding comment.

> The usb2.0 spec section 11.12.5 states
>     "If a hub has per-port power switching and per-port current limiting, an
>      over-current on one port may still cause the power on another port to
>      fall below specific minimums. In this case, the affected port is placed
>      in the Power-Off state and C_PORT_OVER_CURRENT is set for the port, but
>      PORT_OVER_CURRENT is not set."
> 
> So is the patch above a proper fix? or something else might be missing?

It certainly seems like a reasonable thing to do.  If you say it fixes 
the problem, we can add it in.

Alan Stern
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