linux-kernel - Re: [PATCH] usb: typec: tcpm: Stay in SNK_TRY_WAIT_DEBOUNCE_CHECK

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Message-ID: <20201125141731.GC97010@roeck-us.net>
Date:   Wed, 25 Nov 2020 06:17:31 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: tcpm: Stay in
 SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS till Rp is seen

On Tue, Nov 24, 2020 at 05:48:04PM -0800, Badhri Jagan Sridharan wrote:
> TD.4.7.3. Try SNK DRP Connect Try.SRC DRP fails. The compliance
> tester mimics being a Try.SRC USB-C port.
> The failure is due to TCPM exiting SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS
> when VBUS is not present eventhough when SNK.Rp is seen. Exit to
> SRC_TRYWAIT from SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS only when SNK.Rp
> is not seen for PD_T_TRY_CC_DEBOUNCE.
> 
> From the spec:
> The port shall then transition to Attached.SNK when the SNK.Rp state
> is detected on exactly one of the CC1 or CC2 pins for at least
> tTryCCDebounce and VBUS is detected. Alternatively, the port shall
> transition to TryWait.SRC if SNK.Rp state is not detected for
> tTryCCDebounce.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>

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

> ---
>  drivers/usb/typec/tcpm/tcpm.c | 18 +++++++++++++-----
>  include/linux/usb/pd.h        |  1 +
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 4aac0efdb720..b2cffa00d737 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -3124,15 +3124,13 @@ static void run_state_machine(struct tcpm_port *port)
>  		break;
>  	case SNK_TRY_WAIT_DEBOUNCE:
>  		tcpm_set_state(port, SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS,
> -			       PD_T_PD_DEBOUNCE);
> +			       PD_T_TRY_CC_DEBOUNCE);
>  		break;
>  	case SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS:
> -		if (port->vbus_present && tcpm_port_is_sink(port)) {
> +		if (port->vbus_present && tcpm_port_is_sink(port))
>  			tcpm_set_state(port, SNK_ATTACHED, 0);
> -		} else {
> -			tcpm_set_state(port, SRC_TRYWAIT, 0);
> +		else
>  			port->max_wait = 0;
> -		}
>  		break;
>  	case SRC_TRYWAIT:
>  		tcpm_set_cc(port, tcpm_rp_cc(port));
> @@ -4053,6 +4051,12 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
>  		if (!tcpm_port_is_sink(port))
>  			tcpm_set_state(port, SNK_TRYWAIT_DEBOUNCE, 0);
>  		break;
> +	case SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS:
> +		if (!tcpm_port_is_sink(port))
> +			tcpm_set_state(port, SRC_TRYWAIT, PD_T_TRY_CC_DEBOUNCE);
> +		else
> +			tcpm_set_state(port, SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS, 0);
> +		break;
>  	case SNK_TRYWAIT:
>  		/* Do nothing, waiting for tCCDebounce */
>  		break;
> @@ -4139,6 +4143,10 @@ static void _tcpm_pd_vbus_on(struct tcpm_port *port)
>  	case SNK_TRYWAIT_DEBOUNCE:
>  		/* Do nothing, waiting for Rp */
>  		break;
> +	case SNK_TRY_WAIT_DEBOUNCE_CHECK_VBUS:
> +		if (port->vbus_present && tcpm_port_is_sink(port))
> +			tcpm_set_state(port, SNK_ATTACHED, 0);
> +		break;
>  	case SRC_TRY_WAIT:
>  	case SRC_TRY_DEBOUNCE:
>  		/* Do nothing, waiting for sink detection */
> diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
> index 3a805e2ecbc9..63a66dd5d832 100644
> --- a/include/linux/usb/pd.h
> +++ b/include/linux/usb/pd.h
> @@ -484,6 +484,7 @@ static inline unsigned int rdo_max_power(u32 rdo)
>  
>  #define PD_T_CC_DEBOUNCE	200	/* 100 - 200 ms */
>  #define PD_T_PD_DEBOUNCE	20	/* 10 - 20 ms */
> +#define PD_T_TRY_CC_DEBOUNCE	15	/* 10 - 20 ms */
>  
>  #define PD_N_CAPS_COUNT		(PD_T_NO_RESPONSE / PD_T_SEND_SOURCE_CAP)
>  #define PD_N_HARD_RESET_COUNT	2
> -- 
> 2.29.2.454.gaff20da3a2-goog
>