netdev - RE: [PATCH v2] r8152: disable RX aggregation on Dell TB16 dock

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Date:   Thu, 18 Jan 2018 17:06:34 +0000
From:   <Mario.Limonciello@...l.com>
To:     <kai.heng.feng@...onical.com>, <davem@...emloft.net>
CC:     <hayeswang@...ltek.com>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <nic_swsd@...ltek.com>
Subject: RE: [PATCH v2] r8152: disable RX aggregation on Dell TB16 dock

> -----Original Message-----
> From: Kai Heng Feng [mailto:kai.heng.feng@...onical.com]
> Sent: Thursday, January 18, 2018 10:57 AM
> To: David Miller <davem@...emloft.net>
> Cc: Hayes Wang <hayeswang@...ltek.com>; gregkh@...uxfoundation.org; linux-
> usb@...r.kernel.org; netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> Limonciello, Mario <Mario_Limonciello@...l.com>; nic_swsd@...ltek.com
> Subject: Re: [PATCH v2] r8152: disable RX aggregation on Dell TB16 dock
> 
> 
> 
> > On 18 Jan 2018, at 10:50 PM, David Miller <davem@...emloft.net> wrote:
> >
> > From: Hayes Wang <hayeswang@...ltek.com>
> > Date: Thu, 18 Jan 2018 03:04:08 +0000
> >
> >> [...]
> >>>> r8153 on Dell TB15/16 dock corrupts rx packets.
> >>>>
> >>>> This change is suggested by Realtek. They guess that the XHCI
> >>>> controller doesn't have enough buffer, and their guesswork is correct,
> >>>> once the RX aggregation gets disabled, the issue is gone.
> >>>>
> >>>> ASMedia is currently working on a real sulotion for this issue.
> >>>>
> >>>> Dell and ODM confirm the bcdDevice and iSerialNumber is unique for TB16.
> >>>>
> >>>> Note that TB15 has different bcdDevice and iSerialNumber, which are
> >>>> not unique values. If you still have TB15, please contact Dell to
> >>>> replace it with TB16.
> >>
> >> Excuse me. I don't understand why this patch is for specific USB nic rather than
> xHCI.
> >> It seems to make the specific USB nic working and the other ones keeping error.
> >
> > Well, are we sure that the device being in the TB16 dock doesn't
> > contribute to the issue as well?

Previous version of this patch checked the parent device to ensure it was in TB16.
I believe there was negative feedback to that approach, which prompted the discussion
to check bcdDevice and iSerialNumber with all vendors involved.

If it's still desirable to analyze parentage tree, I suppose bcdDevice, iSerialNumber
and parent's USB device VID/PID can be analyzed  all at the same time.

> 
> This is what vendors concluded for now. The very same NIC on WD15 doesn’t
> have the issue.

And just so it's extra clear to everyone on this list - WD15 has different bcdDevice
iSerialNumber, and doesn't connect to ASMedia host controller.