linux-kernel - Re: [PATCH] usb: typec: tcpm: support sink port for debounce

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Date: Tue, 12 Mar 2024 13:07:59 +0200
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Michael Wu <michael@...winnertech.com>
Cc: gregkh@...uxfoundation.org, linux@...ck-us.net, badhri@...gle.com,
	kyletso@...gle.com, frank.wang@...k-chips.com, rdbabiera@...gle.com,
	xu.yang_2@....com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: support sink port for debounce

On Tue, Mar 12, 2024 at 09:13:00AM +0800, Michael Wu wrote:
> When both CC1 and CC2 pins are simultaneously pulled up, it often leads
> to the double Rp to Vbus cable being stuck in the SNK_ATTACH_WAIT state.
> And the state machine fails to transition to the SNK_ATTACHED state.
> 
> Therefore, it is recommended to focus on transitioning the sink port to
> the SNK_DEBOUNCED state instead. By doing so, the desired outcome can be
> achieved more effectively.

Recommended by whom (or what)?

> [  134.525750] VBUS on
> [  134.713240] CC1: 0 -> 3, CC2: 0 -> 3 [state TOGGLING, polarity 0, connected]
> [  134.713249] state change TOGGLING -> SNK_ATTACH_WAIT [rev3 NONE_AMS]
> 
> Signed-off-by: Michael Wu <michael@...winnertech.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 0965972310275..9228dbd78bf2b 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4197,6 +4197,8 @@ static void run_state_machine(struct tcpm_port *port)
>  		else if (tcpm_port_is_disconnected(port))
>  			tcpm_set_state(port, SNK_UNATTACHED,
>  				       PD_T_PD_DEBOUNCE);
> +		else if (tcpm_port_is_sink(port))
> +			tcpm_set_state(port, SNK_DEBOUNCED, 0);
>  		break;
>  	case SNK_DEBOUNCED:
>  		if (tcpm_port_is_disconnected(port))
> -- 
> 2.29.0

-- 
heikki