RE: [PATCH v2 5/8] usb: typec: Use Thunderbolt 3 cable discover mode VDO in Enter_USB message

Patel, Utkarsh H
2020-11-17T23:28:47Z

Hi Heikki,

> -----Original Message-----
> From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Sent: Tuesday, November 17, 2020 4:10 AM
> To: Patel, Utkarsh H <utkarsh.h.patel@intel.com>
> Cc: linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org;
> pmalani@chromium.org; enric.balletbo@collabora.com; Mani, Rajmohan
> <rajmohan.mani@intel.com>; Shaikh, Azhar <azhar.shaikh@intel.com>
> Subject: Re: [PATCH v2 5/8] usb: typec: Use Thunderbolt 3 cable discover
> mode VDO in Enter_USB message
>
> On Fri, Nov 13, 2020 at 12:25:00PM -0800, Utkarsh Patel wrote:
> > USB4 also uses same cable properties as Thunderbolt 3 so use
> > Thunderbolt 3 cable discover mode VDO to fill details such as active
> > cable plug link training and cable rounded support.
>
> I'm sorry, but I think that has to be explained better. We only need the
> Thunderbolt 3 properties when we create the USB4 connection with
> Thunderbolt 3 cables. With USB4 cables that information is simply not
> available. Claiming that USB4 uses the same properties in general is not true.

Ack. I will change the commit message.

>
> > Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > Signed-off-by: Utkarsh Patel <utkarsh.h.patel@intel.com>
> > --
> > Changes in v2:
> > - No change.
> > --
> > ---
> > include/linux/usb/typec.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> > index 6be558045942..d91e09d9d91c 100644
> > --- a/include/linux/usb/typec.h
> > +++ b/include/linux/usb/typec.h
> > @@ -75,6 +75,7 @@ enum typec_orientation {
> > /*
> > * struct enter_usb_data - Enter_USB Message details
> > * @eudo: Enter_USB Data Object
> > + * @tbt_cable_vdo: TBT3 Cable Discover Mode Response
> > * @active_link_training: Active Cable Plug Link Training
> > *
> > * @active_link_training is a flag that should be set with
> > uni-directional SBRX
>
> Please also explain the same here with a short comment. So basically, if the
> USB4 connection is created using TBT3 cable, then we need to supply also the
> TBT3 Cable VDO as part of this data. But if USB4 cable is used, then that
> member should not be filled at all.

Ack.

>
> > @@ -83,6 +84,7 @@ enum typec_orientation {
> > */
> > struct enter_usb_data {
> > u32 eudo;
> > + u32 tbt_cable_vdo;
> > unsigned char active_link_training:1;
> > };
>
> thanks,
>
> --
> Heikki

Sincerely,
Utkarsh Patel.