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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Sat, 11 Jan 2020 00:46:13 +0800
Message-ID: <CAAd53p7aFKEgic+48EsN=vMjtoyDhVP7HkOMQic20-o9mAY0Ug@mail.gmail.com>
Subject: Re: [PATCH v2 3/3] USB: Disable LPM on WD19's Realtek Hub
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Mathias Nyman <mathias.nyman@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        AceLan Kao <acelan.kao@canonical.com>,
        USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Sat, Jan 11, 2020 at 12:36 AM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, 10 Jan 2020, Kai-Heng Feng wrote:
>
> > On Fri, Jan 10, 2020 at 11:40 PM Alan Stern <stern@rowland.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@canonical.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?

He didn't test it. I have physical access to the hardware and I've
thoroughly tested it.

Kai-Heng

>
> Alan Stern
>