linux-kernel - Re: [PATCH v2 6/8] platform/chrome: cros_ec_typec: Use Thunderbolt 3 cable discover mode VDO in USB4 mode

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Date:   Tue, 17 Nov 2020 14:10:59 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Utkarsh Patel <utkarsh.h.patel@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        pmalani@...omium.org, enric.balletbo@...labora.com,
        rajmohan.mani@...el.com, azhar.shaikh@...el.com
Subject: Re: [PATCH v2 6/8] platform/chrome: cros_ec_typec: Use Thunderbolt 3
 cable discover mode VDO in USB4 mode

On Fri, Nov 13, 2020 at 12:25:01PM -0800, Utkarsh Patel wrote:
> Configure Thunderbolt3/USB4 cable generation value by filing Thunderbolt 3
> cable discover mode VDO to support rounded and non-rounded Thunderbolt3/
> USB4 cables.
> While we are here use Thunderbolt 3 cable discover mode VDO to fill active
> cable plug link training value.
> 
> Suggested-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Signed-off-by: Utkarsh Patel <utkarsh.h.patel@...el.com>

FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> --
> Changes in v2:
> - No change.
> --
> ---
>  drivers/platform/chrome/cros_ec_typec.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index 8111ed1fc574..b7416e82c3b3 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -514,8 +514,18 @@ static int cros_typec_enable_usb4(struct cros_typec_data *typec,
>  	else if (pd_ctrl->control_flags & USB_PD_CTRL_ACTIVE_CABLE)
>  		data.eudo |= EUDO_CABLE_TYPE_RE_TIMER << EUDO_CABLE_TYPE_SHIFT;
>  
> -	data.active_link_training = !!(pd_ctrl->control_flags &
> -				       USB_PD_CTRL_ACTIVE_LINK_UNIDIR);
> +	/*
> +	 * This driver does not have access to the identity information or
> +	 * capabilities of the cable, so we don't know is it a real USB4 or
> +	 * TBT3 cable. Therefore pretending that it's always TBT3 cable by
> +	 * filling the TBT3 Cable VDO.
> +	 */
> +	data.tbt_cable_vdo = TBT_MODE;
> +
> +	if (pd_ctrl->control_flags & USB_PD_CTRL_ACTIVE_LINK_UNIDIR)
> +		data.tbt_cable_vdo |= TBT_CABLE_LINK_TRAINING;
> +
> +	data.tbt_cable_vdo |= TBT_SET_CABLE_ROUNDED(pd_ctrl->cable_gen);
>  
>  	port->state.alt = NULL;
>  	port->state.data = &data;
> -- 
> 2.17.1

-- 
heikki