Re: [PATCH v2] usb: typec: tcpm: advance vdm_discovery_state on Discover Identity Not_Supported

[Heikki Krogerus]

+RD

On Wed, Sep 16, 2026 at 12:39:57PM +0800, Xu Yang wrote:
> From: Xu Yang <xu.yang_2@xxxxxxx>
> 
> Commit Fixes: 205dc9cb39f5 ("usb: typec: tcpm: implement retry mechanism
> for Discover Identity VDMs") advances vdm_discovery_state to
> VDM_DISCOVERY_COMPLETE when a CMDT_RSP_NAK is received, but it does not
> advance the state when a non-modal port returns PD_CTRL_NOT_SUPP.
> 
> This can re-arm another vdm_discovery_work if the port is going to
> respond with PD_CTRL_NOT_SUPP to the partner.
> 
>   tcpm_pd_handle_msg(port, PD_MSG_CTRL_NOT_SUPP, NONE_AMS);
>     tcpm_queue_message();
>       mod_tcpm_delayed_work();
>         tcpm_state_machine_work()
>           tcpm_send_queued_message()  -> send PD_MSG_CTRL_NOT_SUPP
>           run_state_machine()
>             case SRC_READY:
>             case SNK_READY:
>               mod_vdm_discovery_delayed_work(port, 0);
> 
> If both the port and its partner do not support modal operation, they
> will send DISCOVER_IDENTITY to each other infinitely.
> 
> Advance vdm_discovery_state to VDM_DISCOVERY_COMPLETE in this path as
> well. In particular, update the state to VDM_DISCOVERY_COMPLETE if it comes
> from the port partner, and to VDM_DISCOVERY_CABLE_IDENT if it comes from a
> cable.
> 
> Fixes: 205dc9cb39f5 ("usb: typec: tcpm: implement retry mechanism for Discover Identity VDMs")
> Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>
> 
> ---
> Changes in v2:
>  - cover a cable returns PD_CTRL_NOT_SUPP case reported by sashiko
>  - kick off vdm_discovery work to continue working
>  - correct previous wrong fix commit id
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 2d6b14aa2085..5cea820e00c4 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -3891,6 +3891,16 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>  		case SRC_READY:
>  		case SNK_READY:
>  			if (port->vdm_state > VDM_STATE_READY) {
> +				if (port->ams == DISCOVER_IDENTITY) {
> +					if (rx_sop_type == TCPC_TX_SOP) {
> +						tcpm_update_vdm_discovery_state(port,
> +								VDM_DISCOVERY_COMPLETE);
> +					} else if (rx_sop_type == TCPC_TX_SOP_PRIME) {
> +						tcpm_update_vdm_discovery_state(port,
> +								VDM_DISCOVERY_CABLE_IDENT);
> +						mod_vdm_discovery_delayed_work(port, 0);
> +					}
> +				}
>  				port->vdm_state = VDM_STATE_DONE;
>  				if (tcpm_vdm_ams(port))
>  					tcpm_ams_finish(port);
> -- 
> 2.34.1

-- 
heikki