On Tue, Mar 24, 2026 at 10:30:12AM +0000, Andrei Kuchynski wrote:
> In the current implementation, if a cable's alternate mode enter operation
> is not supported, the tbt->plug[TYPEC_PLUG_SOP_P] pointer is cleared by the
> time tbt_enter_mode() is called. This prevents the driver from identifying
> the cable's VDO.
> 
> As a result, the Thunderbolt connection falls back to the default
> TBT_CABLE_USB3_PASSIVE speed, even if the cable supports higher speeds.
> To ensure the correct VDO value is used during mode entry, calculate and
> store the enter_vdo earlier during the initialization phase in tbt_ready().
> 
> Cc: stable@vger.kernel.org
> Fixes: 100e25738659 ("usb: typec: Add driver for Thunderbolt 3 Alternate Mode")
> Tested-by: Madhu M <madhu.m@intel.corp-partner.google.com>
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
> Changes in V2:
> - Marked as a Fix
> 
>  drivers/usb/typec/altmodes/thunderbolt.c | 44 ++++++++++++------------
>  1 file changed, 22 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/usb/typec/altmodes/thunderbolt.c b/drivers/usb/typec/altmodes/thunderbolt.c
> index c4c5da6154da9..32250b94262a9 100644
> --- a/drivers/usb/typec/altmodes/thunderbolt.c
> +++ b/drivers/usb/typec/altmodes/thunderbolt.c
> @@ -39,28 +39,7 @@ static bool tbt_ready(struct typec_altmode *alt);
>  
>  static int tbt_enter_mode(struct tbt_altmode *tbt)
>  {
> -	struct typec_altmode *plug = tbt->plug[TYPEC_PLUG_SOP_P];
> -	u32 vdo;
> -
> -	vdo = tbt->alt->vdo & (TBT_VENDOR_SPECIFIC_B0 | TBT_VENDOR_SPECIFIC_B1);
> -	vdo |= tbt->alt->vdo & TBT_INTEL_SPECIFIC_B0;
> -	vdo |= TBT_MODE;
> -
> -	if (plug) {
> -		if (typec_cable_is_active(tbt->cable))
> -			vdo |= TBT_ENTER_MODE_ACTIVE_CABLE;
> -
> -		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_SPEED(plug->vdo));
> -		vdo |= plug->vdo & TBT_CABLE_ROUNDED;
> -		vdo |= plug->vdo & TBT_CABLE_OPTICAL;
> -		vdo |= plug->vdo & TBT_CABLE_RETIMER;
> -		vdo |= plug->vdo & TBT_CABLE_LINK_TRAINING;
> -	} else {
> -		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_USB3_PASSIVE);
> -	}
> -
> -	tbt->enter_vdo = vdo;
> -	return typec_altmode_enter(tbt->alt, &vdo);
> +	return typec_altmode_enter(tbt->alt, &tbt->enter_vdo);
>  }
>  
>  static void tbt_altmode_work(struct work_struct *work)
> @@ -337,6 +316,7 @@ static bool tbt_ready(struct typec_altmode *alt)
>  {
>  	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
>  	struct typec_altmode *plug;
> +	u32 vdo;
>  
>  	if (tbt->cable)
>  		return true;
> @@ -364,6 +344,26 @@ static bool tbt_ready(struct typec_altmode *alt)
>  		tbt->plug[i] = plug;
>  	}
>  
> +	vdo = tbt->alt->vdo & (TBT_VENDOR_SPECIFIC_B0 | TBT_VENDOR_SPECIFIC_B1);
> +	vdo |= tbt->alt->vdo & TBT_INTEL_SPECIFIC_B0;
> +	vdo |= TBT_MODE;
> +	plug = tbt->plug[TYPEC_PLUG_SOP_P];
> +
> +	if (plug) {
> +		if (typec_cable_is_active(tbt->cable))
> +			vdo |= TBT_ENTER_MODE_ACTIVE_CABLE;
> +
> +		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_SPEED(plug->vdo));
> +		vdo |= plug->vdo & TBT_CABLE_ROUNDED;
> +		vdo |= plug->vdo & TBT_CABLE_OPTICAL;
> +		vdo |= plug->vdo & TBT_CABLE_RETIMER;
> +		vdo |= plug->vdo & TBT_CABLE_LINK_TRAINING;
> +	} else {
> +		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_USB3_PASSIVE);
> +	}
> +
> +	tbt->enter_vdo = vdo;
> +
>  	return true;
>  }
>  
> -- 
> 2.53.0.983.g0bb29b3bc5-goog
> 
>