linux-kernel - Re: [PATCH v1] usb: typec: tcpm: Wait in SNK

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Message-ID: <e9b8ec9f-6790-3b83-2298-4032e169cea2@roeck-us.net>
Date:   Wed, 24 Nov 2021 14:50:10 -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 v1] usb: typec: tcpm: Wait in SNK_DEBOUNCED until
 disconnect

On 11/24/21 2:40 PM, Badhri Jagan Sridharan wrote:
> 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."
> 
> This change makes TCPM to wait in SNK_DEBOUNCED state until
> CC1 and CC2 pins is SNK.Open for at least tPDDebounce. Previously,
> TCPM resets the port if vbus is not present in PD_T_PS_SOURCE_ON.
> This causes TCPM to loop continuously when connected to a
> faulty power source that does not present vbus. Waiting in
> SNK_DEBOUNCED also ensures that TCPM is adherant to
> "4.5.2.2.4.2 Exiting from AttachWait.SNK State" requirements.
> 
> [ 6169.280751] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [ 6169.280759] state change TOGGLING -> SNK_ATTACH_WAIT [rev2 NONE_AMS]
> [ 6169.280771] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev2 NONE_AMS]
> [ 6169.282427] CC1: 0 -> 0, CC2: 5 -> 5 [state SNK_ATTACH_WAIT, polarity 0, connected]
> [ 6169.450825] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
> [ 6169.450834] pending state change SNK_DEBOUNCED -> PORT_RESET @ 480 ms [rev2 NONE_AMS]
> [ 6169.930892] state change SNK_DEBOUNCED -> PORT_RESET [delayed 480 ms]
> [ 6169.931296] disable vbus discharge ret:0
> [ 6169.931301] Setting usb_comm capable false
> [ 6169.932783] Setting voltage/current limit 0 mV 0 mA
> [ 6169.932802] polarity 0
> [ 6169.933706] Requesting mux state 0, usb-role 0, orientation 0
> [ 6169.936689] cc:=0
> [ 6169.936812] pending state change PORT_RESET -> PORT_RESET_WAIT_OFF @ 100 ms [rev2 NONE_AMS]
> [ 6169.937157] CC1: 0 -> 0, CC2: 5 -> 0 [state PORT_RESET, polarity 0, disconnected]
> [ 6170.036880] state change PORT_RESET -> PORT_RESET_WAIT_OFF [delayed 100 ms]
> [ 6170.036890] state change PORT_RESET_WAIT_OFF -> SNK_UNATTACHED [rev2 NONE_AMS]
> [ 6170.036896] Start toggling
> [ 6170.041412] CC1: 0 -> 0, CC2: 0 -> 0 [state TOGGLING, polarity 0, disconnected]
> [ 6170.042973] CC1: 0 -> 0, CC2: 0 -> 5 [state TOGGLING, polarity 0, connected]
> [ 6170.042976] state change TOGGLING -> SNK_ATTACH_WAIT [rev2 NONE_AMS]
> [ 6170.042981] pending state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED @ 170 ms [rev2 NONE_AMS]
> [ 6170.213014] state change SNK_ATTACH_WAIT -> SNK_DEBOUNCED [delayed 170 ms]
> [ 6170.213019] pending state change SNK_DEBOUNCED -> PORT_RESET @ 480 ms [rev2 NONE_AMS]
> [ 6170.693068] state change SNK_DEBOUNCED -> PORT_RESET [delayed 480 ms]
> [ 6170.693304] disable vbus discharge ret:0
> [ 6170.693308] Setting usb_comm capable false
> [ 6170.695193] Setting voltage/current limit 0 mV 0 mA
> [ 6170.695210] polarity 0
> [ 6170.695990] Requesting mux state 0, usb-role 0, orientation 0
> [ 6170.701896] cc:=0
> [ 6170.702181] pending state change PORT_RESET -> PORT_RESET_WAIT_OFF @ 100 ms [rev2 NONE_AMS]
> [ 6170.703343] CC1: 0 -> 0, CC2: 5 -> 0 [state PORT_RESET, polarity 0, disconnected]
> 
> Fixes: f0690a25a140b8 ("staging: typec: USB Type-C Port Manager (tcpm)")
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

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

> ---
>   drivers/usb/typec/tcpm/tcpm.c | 4 ----
>   1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 7f2f3ff1b391..6010b9901126 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -4110,11 +4110,7 @@ static void run_state_machine(struct tcpm_port *port)
>   				       tcpm_try_src(port) ? SRC_TRY
>   							  : SNK_ATTACHED,
>   				       0);
> -		else
> -			/* Wait for VBUS, but not forever */
> -			tcpm_set_state(port, PORT_RESET, PD_T_PS_SOURCE_ON);
>   		break;
> -
>   	case SRC_TRY:
>   		port->try_src_count++;
>   		tcpm_set_cc(port, tcpm_rp_cc(port));
>