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

Heikki Krogerus
2020-11-17T12:10:19Z

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.

> 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.

> @@ -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