linux-kernel - Re: [PATCH v2 3/3] USB: Disable LPM on WD19's Realtek Hub

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Date:   Fri, 10 Jan 2020 11:36:43 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        AceLan Kao <acelan.kao@...onical.com>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] USB: Disable LPM on WD19's Realtek Hub

On Fri, 10 Jan 2020, Kai-Heng Feng wrote:

> On Fri, Jan 10, 2020 at 11:40 PM Alan Stern <stern@...land.harvard.edu> wrote:
> >
> > On Fri, 10 Jan 2020, Kai-Heng Feng wrote:
> >
> > > Realtek Hub (0bda:0x0487) used in Dell Dock WD19 sometimes drops off the
> > > bus when bringing underlying ports from U3 to U0.
> > >
> > > Disabling LPM on the hub during setting link state is not enough, so
> > > let's disable LPM completely for this hub.
> > >
> > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > > ---
> > >  drivers/usb/core/quirks.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
> > > index 6b6413073584..2fb7c1602280 100644
> > > --- a/drivers/usb/core/quirks.c
> > > +++ b/drivers/usb/core/quirks.c
> > > @@ -371,6 +371,9 @@ static const struct usb_device_id usb_quirk_list[] = {
> > >       { USB_DEVICE(0x0b05, 0x17e0), .driver_info =
> > >                       USB_QUIRK_IGNORE_REMOTE_WAKEUP },
> > >
> > > +     /* Realtek hub in Dell WD19 (Type-C) */
> > > +     { USB_DEVICE(0x0bda, 0x0487), .driver_info = USB_QUIRK_NO_LPM },
> > > +
> > >       /* Action Semiconductor flash disk */
> > >       { USB_DEVICE(0x10d6, 0x2200), .driver_info =
> > >                       USB_QUIRK_STRING_FETCH_255 },
> > >
> >
> > This is a very partial patch.  There were four hunks in the original
> > version but there's only one hunk in V2.
> 
> Because the original approach is insufficient, it significantly
> reduced the fail rate but the issue is still there.
> USB_QUIRK_NO_LPM is used instead so no other parts are needed.

Oh, all right.  This change looks okay to me.  Has AceLan Kao tested 
it?

Alan Stern