linux-kernel - Re: [PATCH v2 1/2] usb: typec: tcpm: Do not disconnect while receiving VBUS off

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Date:   Tue, 25 Jan 2022 19:34:03 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kyle Tso <kyletso@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] usb: typec: tcpm: Do not disconnect while
 receiving VBUS off

On 1/25/22 18:00, Badhri Jagan Sridharan wrote:
> With some chargers, vbus might momentarily raise above VSAFE5V and fall
> back to 0V before tcpm gets to read port->tcpc->get_vbus. This will
> report a VBUS off event causing TCPM to transition to SNK_UNATTACHED
> where it should be waiting in either SNK_ATTACH_WAIT or SNK_DEBOUNCED
> state. This patch makes TCPM avoid vbus off 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: f0690a25a140b8 ("staging: typec: USB Type-C Port Manager (tcpm)")
> Cc: stable@...r.kernel.org
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

Why did you drop the Reviewed-by/Acked-by tags ?

Guenter

> ---
> Changes since v1:
> - Fix typos stated by Guenter Roeck.
> ---
>   drivers/usb/typec/tcpm/tcpm.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 59d4fa2443f2..3bf79f52bd34 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -5156,7 +5156,8 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
>   	case SNK_TRYWAIT_DEBOUNCE:
>   		break;
>   	case SNK_ATTACH_WAIT:
> -		tcpm_set_state(port, SNK_UNATTACHED, 0);
> +	case SNK_DEBOUNCED:
> +		/* Do nothing, as TCPM is still waiting for vbus to reach VSAFE5V to connect */
>   		break;
>   
>   	case SNK_NEGOTIATE_CAPABILITIES: