linux-kernel - Re: [PATCH] usb: typec: tcpm: skip checking port->send

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Date:   Tue, 21 Nov 2023 06:47:42 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Guan-Yu Lin <guanyulin@...gle.com>,
        heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        badhri@...gle.com, kyletso@...gle.com, albertccwang@...gle.com
Subject: Re: [PATCH] usb: typec: tcpm: skip checking port->send_discover in
 PD3.0

On 11/16/23 00:32, Guan-Yu Lin wrote:
> The original Collison Avoidance mechanism, port->send_discover, avoids
> the conflict when port partners start AMS almost the same time. However,
> this mechanism is replaced by SINK_TX_OK and SINK_TX_NG. Skip the check
> in PD3.0 to avoid the deadlock when source is requesting DR_SWAP where
> sink is requesting DISCOVER_IDENTITY.
> 
> Signed-off-by: Guan-Yu Lin <guanyulin@...gle.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/usb/typec/tcpm/tcpm.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 058d5b853b57..ff3c171a3a75 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -2847,7 +2847,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>   					   PD_MSG_CTRL_NOT_SUPP,
>   					   NONE_AMS);
>   		} else {
> -			if (port->send_discover) {
> +			if (port->send_discover && port->negotiated_rev < PD_REV30) {
>   				tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
>   				break;
>   			}
> @@ -2863,7 +2863,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>   					   PD_MSG_CTRL_NOT_SUPP,
>   					   NONE_AMS);
>   		} else {
> -			if (port->send_discover) {
> +			if (port->send_discover && port->negotiated_rev < PD_REV30) {
>   				tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
>   				break;
>   			}
> @@ -2872,7 +2872,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>   		}
>   		break;
>   	case PD_CTRL_VCONN_SWAP:
> -		if (port->send_discover) {
> +		if (port->send_discover && port->negotiated_rev < PD_REV30) {
>   			tcpm_queue_message(port, PD_MSG_CTRL_WAIT);
>   			break;
>   		}