linux-kernel - Re: [PATCH v1] usb: typec: tcpm: Fix TDA 2.2.1.1 and TDA 2.2.1.2 failures

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Date:   Mon, 10 Aug 2020 18:51:10 -0700
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
Subject: Re: [PATCH v1] usb: typec: tcpm: Fix TDA 2.2.1.1 and TDA 2.2.1.2
 failures

On 8/10/20 6:11 PM, Badhri Jagan Sridharan wrote:
>>>From the spec:
> "7.1.5 Response to Hard Resets
> Hard Reset Signaling indicates a communication failure has occurred and
> the Source Shall stop driving VCONN, Shall remove Rp from the VCONN pin
> and Shall drive VBUS to vSafe0V as shown in Figure 7-9. The USB connection
> May reset during a Hard Reset since the VBUS voltage will be less than
> vSafe5V for an extended period of time. After establishing the vSafe0V
> voltage condition on VBUS, the Source Shall wait tSrcRecover before
> re-applying VCONN and restoring VBUS to vSafe5V. A Source Shall conform
> to the VCONN timing as specified in [USB Type-C 1.3]."
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 3ef37202ee37..e41c4e5d3c71 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -3372,13 +3372,19 @@ static void run_state_machine(struct tcpm_port *port)
>  			tcpm_set_state(port, SNK_HARD_RESET_SINK_OFF, 0);
>  		break;
>  	case SRC_HARD_RESET_VBUS_OFF:
> -		tcpm_set_vconn(port, true);
> +		/*
> +		 * 7.1.5 Response to Hard Resets
> +		 * Hard Reset Signaling indicates a communication failure has occurred and the
> +		 * Source Shall stop driving VCONN, Shall remove Rp from the VCONN pin and Shall
> +		 * drive VBUS to vSafe0V as shown in Figure 7-9.
> +		 */
> +		tcpm_set_vconn(port, false);
>  		tcpm_set_vbus(port, false);
>  		tcpm_set_roles(port, port->self_powered, TYPEC_SOURCE,
>  			       tcpm_data_role_for_source(port));
> -		tcpm_set_state(port, SRC_HARD_RESET_VBUS_ON, PD_T_SRC_RECOVER);

I am a bit concerned about this. If I understand correctly, it means that
we won't turn VBUS back on unless a SRC_HARD_RESET_VBUS_OFF PD event is received.
Is that correct ? What happens if that event is never received ?

Thanks,
Guenter

>  		break;
>  	case SRC_HARD_RESET_VBUS_ON:
> +		tcpm_set_vconn(port, true);
>  		tcpm_set_vbus(port, true);
>  		port->tcpc->set_pd_rx(port->tcpc, true);
>  		tcpm_set_attached_state(port, true);
> @@ -3944,7 +3950,11 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
>  		tcpm_set_state(port, SNK_HARD_RESET_WAIT_VBUS, 0);
>  		break;
>  	case SRC_HARD_RESET_VBUS_OFF:
> -		tcpm_set_state(port, SRC_HARD_RESET_VBUS_ON, 0);
> +		/*
> +		 * After establishing the vSafe0V voltage condition on VBUS, the Source Shall wait
> +		 * tSrcRecover before re-applying VCONN and restoring VBUS to vSafe5V.
> +		 */
> +		tcpm_set_state(port, SRC_HARD_RESET_VBUS_ON, PD_T_SRC_RECOVER);
>  		break;
>  	case HARD_RESET_SEND:
>  		break;
>