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Date:   Tue, 11 Aug 2020 18:39:33 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Badhri Jagan Sridharan <badhri@google.com>
Cc:     Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] usb: typec: tcpm: Fix TDA 2.2.1.1 and TDA 2.2.1.2
 failures
Message-ID: <20200812013933.GA116439@roeck-us.net>
References: <20200811200228.433264-1-badhri@google.com>
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On Tue, Aug 11, 2020 at 01:02:28PM -0700, 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@google.com>

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

Guenter

> ---
> Changes since V1 (Guenter's suggestion):
> - Bound SRC_HARD_RESET_VBUS_ON to accommodate tcpc drivers which doesn't
>   update the vbus status.
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 3ef37202ee37..a48e3f90d196 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -3372,13 +3372,31 @@ 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);
> +		/*
> +		 * If tcpc fails to notify vbus off, TCPM will wait for PD_T_SAFE_0V +
> +		 * PD_T_SRC_RECOVER before turning vbus back on.
> +		 * From Table 7-12 Sequence Description for a Source Initiated Hard Reset:
> +		 * 4. Policy Engine waits tPSHardReset after sending Hard Reset Signaling and then
> +		 * tells the Device Policy Manager to instruct the power supply to perform a
> +		 * Hard Reset. The transition to vSafe0V Shall occur within tSafe0V (t2).
> +		 * 5. After tSrcRecover the Source applies power to VBUS in an attempt to
> +		 * re-establish communication with the Sink and resume USB Default Operation.
> +		 * The transition to vSafe5V Shall occur within tSrcTurnOn(t4).
> +		 */
> +		tcpm_set_state(port, SRC_HARD_RESET_VBUS_ON, PD_T_SAFE_0V + PD_T_SRC_RECOVER);
>  		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 +3962,11 @@ 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;