Re: [PATCH 2/5] usb: typec: ps883x: Return -EOPNOTSUPP for USB4 when parade,disable-usb4 is set

[Dr. David Alan Gilbert]

* Jens Glathe via B4 Relay (devnull+jens.glathe.oldschoolsolutions.biz@xxxxxxxxxx) wrote:
> From: Jens Glathe <jens.glathe@xxxxxxxxxxxxxxxxxxxxxx>
> 
> On Qualcomm X1E80100 platforms using the Parade PS883x retimer (like
> Lenovo ThinkPad T14s Gen6), hotplugging USB4-capable docks such as the
> Lenovo 40B0 results in working USB but no DisplayPort output on the
> dock's HDMI/DP ports.
> 
> When the dock negotiates USB4, the retimer receives TYPEC_MODE_USB4
> and forwards it via typec_mux_set(). The qmp_combo PHY then selects
> QMPPHY_MODE_USB3_ONLY because no classic DP altmode SVID is present in
> the state, leaving the DP transmitter and AUX channel disabled.
> 
> Add a DT property "parade,disable-usb4" that, when present, makes the
> PS883x driver reject USB4 modes as not supported. DP altmode
> configuration is still applied if negotiated, so both USB and
> DisplayPort continue to work.
> 
> This is a temporary workaround until proper USB4 DP tunneling support
> is available in the X1E USB4 controller and qmp_combo PHY stack.
> 
> Link: https://patch.msgid.link/20260312101431.2375709-1-krishna.kurapati@xxxxxxxxxxxxxxxx
> Assisted-by: Grok(xAI):4.3
> Signed-off-by: Jens Glathe <jens.glathe@xxxxxxxxxxxxxxxxxxxxxx>

Tested-by: Dr. David Alan Gilbert <dave@xxxxxxxxxxx>
  On zenbook a14 with the following patches and a TB cable

> ---
>  drivers/usb/typec/mux/ps883x.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/typec/mux/ps883x.c b/drivers/usb/typec/mux/ps883x.c
> index 64e0a61b776a1..3fa26ce01a9c9 100644
> --- a/drivers/usb/typec/mux/ps883x.c
> +++ b/drivers/usb/typec/mux/ps883x.c
> @@ -62,6 +62,7 @@ struct ps883x_retimer {
>  
>  	enum typec_orientation orientation;
>  	bool in_reset;
> +	bool disable_usb4;
>  };
>  
>  static int ps883x_enable_vregs(struct ps883x_retimer *retimer)
> @@ -249,6 +250,13 @@ static int ps883x_set(struct ps883x_retimer *retimer, struct typec_retimer_state
>  			cfg0 |= CONN_STATUS_0_USB_3_1_CONNECTED;
>  			break;
>  		case TYPEC_MODE_USB4:
> +			if (retimer->disable_usb4) {
> +				dev_info(&retimer->client->dev,
> +					 "USB4 disabled via DT property, rejecting USB4 mode\n");
> +				return -EOPNOTSUPP;
> +			}
> +
> +			/* Normal USB4 handling */
>  			eudo_data = state->data;
>  
>  			cfg2 |= CONN_STATUS_2_USB4_CONNECTED;
> @@ -378,6 +386,8 @@ static int ps883x_retimer_probe(struct i2c_client *client)
>  
>  	retimer->client = client;
>  
> +	retimer->disable_usb4 = device_property_read_bool(dev, "parade,disable-usb4");
> +
>  	mutex_init(&retimer->lock);
>  
>  	retimer->regmap = devm_regmap_init_i2c(client, &ps883x_retimer_regmap);
> 
> -- 
> 2.53.0
> 
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
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