RE: [PATCH] r8152: disable rx checksum offload on Dell TB dock

[<Mario.Limonciello@dell.com>]

> -----Original Message-----
> From: Kai Heng Feng [mailto:kai.heng.feng@canonical.com]
> Sent: Thursday, November 23, 2017 9:44 PM
> To: Greg KH <gregkh@linuxfoundation.org>
> Cc: David Miller <davem@davemloft.net>; hayeswang@realtek.co; linux-
> usb@vger.kernel.org; netdev@vger.kernel.org; LKML <linux-
> kernel@vger.kernel.org>; Limonciello, Mario <Mario_Limonciello@Dell.com>
> Subject: Re: [PATCH] r8152: disable rx checksum offload on Dell TB dock
> 
> 
> 
> > On 23 Nov 2017, at 5:24 PM, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Thu, Nov 23, 2017 at 04:53:41PM +0800, Kai Heng Feng wrote:
> >>
> >> What I want to do here is to finding this connection:
> >> Realtek r8153 <-> SMSC hub (USD ID: 0424:5537) <->
> >> ASMedia XHCI controller (PCI ID: 1b21:1142).
> >>
> >> Is there a safer way to do this?
> >
> > Nope!  You can't do that at all from within a USB driver, sorry.  As you
> > really should not care at all :)
> 
> Got it :)
> 
> The r8153 in Dell TB dock has version information, RTL_VER_05.
> We can use it to check for workaround, but many working RTL_VER_05 devices
> will also be affected.
> Do you think it’s an acceptable compromise?
> 
> >> I have a r8153 <-> USB 3.0 dongle which work just fine. I can’t find any
> >> information to differentiate them. Hence I want to use the connection to
> >> identify if r8153 is on a Dell TB dock.
> >
> > Are you sure there is nothing different in the version or release number
> > of the device?  'lsusb -v' shows the exact same information for both
> > devices?
> 
> Yes. I attached `lsusb -v` for r8153 on Dell TB dock, on a RJ45 <-> USB 3.0 dongle,
> and on a RJ45 <-> USB Type-C dongle.
> 
> >> Yes. From what I know, ASMedia is working on it, but not sure how long it
> >> will take. In the meantime, I’d like to workaround this issue for the users.
> >
> > Again, it's a host controller bug, it should be fixed there, don't try
> > to paper over the real issue in different individual drivers.
> >
> > I think I've seen various patches on the linux-usb list for this
> > controller already, have you tried them?
> 
> Yes. These patches are all in mainline Linux now.
> 
> >> Actually no.
> >> I just plugged r8153 dongle into the same hub, surprisingly the issue
> >> doesn’t happen in this scenario.
> >
> > Then something seems to be wrong with the device itself, as that would
> > be the same exact electrical/logical path, right?
> 
> I have no idea why externally plugged one doesn’t have this issue.
> Maybe it’s related how it’s wired inside the Dell TB dock...
> 
> Kai-Heng

This is quite surprising to me too.  The externally plugged in r8153 dongle,
was it connected over type C port or over type A port?  AFAIK Type C port is
actually Alpine ridge pass through port.  It is not connected to XHCI controller
or USB hub.