linux-kernel - Re: [PATCH v1 2/2] usb: typec: tcpm: Do not disconnect when receiving VSAFE0V

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Date:   Tue, 25 Jan 2022 11:02:25 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kyle Tso <kyletso@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v1 2/2] usb: typec: tcpm: Do not disconnect when
 receiving VSAFE0V

On Fri, Jan 21, 2022 at 05:55:20PM -0800, Badhri Jagan Sridharan wrote:
> With some chargers, vbus might momentarily raise above VSAFE5V and fall
> back to 0V causing VSAFE0V to be triggered. This will
> will report a VBUS off event causing TCPM to transition to
> SNK_UNATTACHED state where it should be waiting in either SNK_ATTACH_WAIT
> or SNK_DEBOUNCED state. This patch makes TCPM avoid VSAFE0V events
> while in SNK_ATTACH_WAIT or SNK_DEBOUNCED state.
> 
> Stub from the spec:
>     "4.5.2.2.4.2 Exiting from AttachWait.SNK State
>     A Sink shall transition to Unattached.SNK when the state of both
>     the CC1 and CC2 pins is SNK.Open for at least tPDDebounce.
>     A DRP shall transition to Unattached.SRC when the state of both
>     the CC1 and CC2 pins is SNK.Open for at least tPDDebounce."
> 
> [23.194131] CC1: 0 -> 0, CC2: 0 -> 5 [state SNK_UNATTACHED, polarity 0, connected]
> [23.201777] state change SNK_UNATTACHED -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> [23.209949] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev3 NONE_AMS]
> [23.300579] VBUS off
> [23.300668] state change SNK_ATTACH_WAIT -> SNK_UNATTACHED [rev3 NONE_AMS]
> [23.301014] VBUS VSAFE0V
> [23.301111] Start toggling
> 
> Fixes: 28b43d3d746b8 ("usb: typec: tcpm: Introduce vsafe0v for vbus")
> Cc: stable@...r.kernel.org
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/usb/typec/tcpm/tcpm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index b8afe3d8c882..5fce795b69c7 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -5264,6 +5264,10 @@ static void _tcpm_pd_vbus_vsafe0v(struct tcpm_port *port)
>  	case PR_SWAP_SNK_SRC_SOURCE_ON:
>  		/* Do nothing, vsafe0v is expected during transition */
>  		break;
> +	case SNK_ATTACH_WAIT:
> +	case SNK_DEBOUNCED:
> +		/*Do nothing, still waiting for VSAFE5V for connect */
> +		break;
>  	default:
>  		if (port->pwr_role == TYPEC_SINK && port->auto_vbus_discharge_enabled)
>  			tcpm_set_state(port, SNK_UNATTACHED, 0);
> -- 
> 2.35.0.rc0.227.g00780c9af4-goog

-- 
heikki