linux-kernel - Re: [PATCH] usb: hub: move resume delay at the head of all USB access functions

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Message-ID: <Pine.LNX.4.44L0.1912241021580.28718-100000@netrider.rowland.org>
Date:   Tue, 24 Dec 2019 10:23:12 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     AceLan Kao <acelan.kao@...onical.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Harry Pan <harry.pan@...el.com>,
        David Heinzelmann <heinzelmann.david@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Mathieu Malaterre <malat@...ian.org>,
        <linux-usb@...r.kernel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: hub: move resume delay at the head of all USB access
 functions

On Mon, 23 Dec 2019, AceLan Kao wrote:

> > > you'll encounter the below errors sometime.
> > > After the issue happens, have to re-plug the USB cable to recover.
> > >
> > > [ 837.483573] hub 2-3:1.0: hub_ext_port_status failed (err = -71)
> > > [ 837.490889] hub 2-3:1.0: hub_ext_port_status failed (err = -71)
> > > [ 837.506780] usb 2-3-port4: cannot disable (err = -71)
> >
> > You need to do a better job of figuring out why these errors occur.  It
> > is not connected to the resume delay; there must be a different reason.
> > Hint: This is the sort of error you would expect to see if the kernel
> > tried to resume a device while its parent hub was still suspended.
> Once this error shows, the USB port doesn't work until re-plug the cable.
> I have no idea what else I can do to this, do you have any idea that I
> could try?
> Thanks.

Maybe you can collect a usbmon trace showing what happens when the 
error occurs.  There's probably something going on that you aren't 
aware of.

Alan Stern