linux-kernel - Re: [PATCH v1] tcpm: Avoid soft reset when partner does not support get

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Date:   Wed, 23 Aug 2023 06:25:00 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     gregkh@...uxfoundation.org, heikki.krogerus@...ux.intel.com,
        kyletso@...gle.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v1] tcpm: Avoid soft reset when partner does not support
 get_status

On Sun, Aug 20, 2023 at 04:44:48AM +0000, Badhri Jagan Sridharan wrote:
> When partner does not support get_status message, tcpm right now
> responds with soft reset message. This causes PD renegotiation to
> happen and resets PPS link. Avoid soft resetting the link when
> partner does not support get_status message to mitigate PPS resets.
> 
> [  208.926752] Setting voltage/current limit 9500 mV 2450 mA
> [  208.930407] set_auto_vbus_discharge_threshold mode:3 pps_active:y vbus:9500 ret:0
> [  208.930418] state change SNK_TRANSITION_SINK -> SNK_READY [rev3 POWER_NEGOTIATION]
> [  208.930455] AMS POWER_NEGOTIATION finished
> 
> // ALERT message from the Source
> [  213.948442] PD RX, header: 0x19a6 [1]
> [  213.948451] state change SNK_READY -> GET_STATUS_SEND [rev3 GETTING_SOURCE_SINK_STATUS]
> [  213.948457] PD TX, header: 0x492
> [  213.950402] PD TX complete, status: 0
> [  213.950427] pending state change GET_STATUS_SEND -> GET_STATUS_SEND_TIMEOUT @ 60 ms [rev3 GETTING_SOURCE_SINK_STATUS]
> 
> // NOT_SUPPORTED from the Source
> [  213.959954] PD RX, header: 0xbb0 [1]
> 
> // sink sends SOFT_RESET
> [  213.959958] state change GET_STATUS_SEND -> SNK_SOFT_RESET [rev3 GETTING_SOURCE_SINK_STATUS]
> [  213.959962] AMS GETTING_SOURCE_SINK_STATUS finished
> [  213.959964] AMS SOFT_RESET_AMS start
> [  213.959966] state change SNK_SOFT_RESET -> AMS_START [rev3 SOFT_RESET_AMS]
> [  213.959969] state change AMS_START -> SOFT_RESET_SEND [rev3 SOFT_RESET_AMS]
> 
> Cc: stable@...r.kernel.org
> Fixes: 8dea75e11380 ("usb: typec: tcpm: Protocol Error handling")
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

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

> ---
>  drivers/usb/typec/tcpm/tcpm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 5639b9a1e0bf..280ce1bd7b53 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -2753,6 +2753,13 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
>  			port->sink_cap_done = true;
>  			tcpm_set_state(port, ready_state(port), 0);
>  			break;
> +		/*
> +		 * Some port partners do not support GET_STATUS, avoid soft reset the link to
> +		 * prevent redundant power re-negotiation
> +		 */
> +		case GET_STATUS_SEND:
> +			tcpm_set_state(port, ready_state(port), 0);
> +			break;
>  		case SRC_READY:
>  		case SNK_READY:
>  			if (port->vdm_state > VDM_STATE_READY) {
> 
> base-commit: bbb9e06d2c6435af9c62074ad7048910eeb2e7bc
> -- 
> 2.42.0.rc1.204.g551eb34607-goog
>