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Date: Thu, 20 Aug 2020 10:55:57 +0300
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Badhri Jagan Sridharan <badhri@...gle.com>
Cc: Guenter Roeck <linux@...ck-us.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] usb: typec: tcpm: Fix Fix source hard reset response
for TDA 2.3.1.1 and TDA 2.3.1.2 failures
On Mon, Aug 17, 2020 at 11:46:01AM -0700, Badhri Jagan Sridharan wrote:
> The patch addresses the compliance test failures while running TDA
> 2.3.1.1 and TDA 2.3.1.2 of the "PD Communications Engine USB PD
> Compliance MOI" test plan published in https://www.usb.org/usbc.
> For a product to be Type-C compliant, it's expected that these tests
> are run on usb.org certified Type-C compliance tester as mentioned in
> https://www.usb.org/usbc.
>
> While the purpose of TDA 2.3.1.1 and TDA 2.3.1.2 is to verify that
> the static and dynamic electrical capabilities of a Source meet the
> requirements for each PDO offered, while doing so, the tests also
> monitor that the timing of the VBUS waveform versus the messages meets
> the requirements for Hard Reset defined in PROT-PROC-HR-TSTR as
> mentioned in step 11 of TDA.2.3.1.1 and step 15 of TDA.2.3.1.2.
>
> TDB.2.2.13.1: PROT-PROC-HR-TSTR Procedure and Checks for Tester
> Originated Hard Reset
> Purpose: To perform the appropriate protocol checks relating to any
> circumstance in which the Hard Reset signal is sent by the Tester.
>
> UUT is behaving as source:
> The Tester sends a Hard Reset signal.
> 1. Check VBUS stays within present valid voltage range for
> tPSHardReset min (25ms) after last bit of Hard Reset signal.
> [PROT_PROC_HR_TSTR_1]
> 2. Check that VBUS starts to fall below present valid voltage range by
> tPSHardReset max (35ms). [PROT_PROC_HR_TSTR_2]
> 3. Check that VBUS reaches vSafe0V within tSafe0v max (650 ms).
> [PROT_PROC_HR_TSTR_3]
> 4. Check that VBUS starts rising to vSafe5V after a delay of
> tSrcRecover (0.66s - 1s) from reaching vSafe0V. [PROT_PROC_HR_TSTR_4]
> 5. Check that VBUS reaches vSafe5V within tSrcTurnOn max (275ms) of
> rising above vSafe0v max (0.8V). [PROT_PROC_HR_TSTR_5] Power Delivery
> Compliance Plan 139 6. Check that Source Capabilities are finished
> sending within tFirstSourceCap max (250ms) of VBUS reaching vSafe5v
> min. [PROT_PROC_HR_TSTR_6].
>
> This is in line with 7.1.5 Response to Hard Resets of the USB Power
> Delivery Specification Revision 3.0, Version 1.2,
> "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]."
>
> With the above guidelines from the spec in mind, TCPM does not turn
> off VCONN while entering SRC_HARD_RESET_VBUS_OFF. The patch makes TCPM
> turn off VCONN while entering SRC_HARD_RESET_VBUS_OFF and turn it back
> on while entering SRC_HARD_RESET_VBUS_ON along with vbus instead of
> having VCONN on through hardreset.
>
> Also, the spec clearly states that "After establishing the vSafe0V
> voltage condition on VBUS", the Source Shall wait tSrcRecover before
> re-applying VCONN and restoring VBUS to vSafe5V.
> TCPM does not conform to this requirement. If the TCPC driver calls
> tcpm_vbus_change with vbus off signal, TCPM right away enters
> SRC_HARD_RESET_VBUS_ON without waiting for tSrcRecover.
> For TCPC's which are buggy/does not call tcpm_vbus_change, TCPM
> assumes that the vsafe0v is instantaneous as TCPM only waits
> tSrcRecover instead of waiting for tSafe0v + tSrcRecover.
> This patch also fixes this behavior by making sure that TCPM waits for
> tSrcRecover before transitioning into SRC_HARD_RESET_VBUS_ON when
> tcpm_vbus_change is called by TCPC.
> When TCPC does not call tcpm_vbus_change, TCPM assumes the worst case
> i.e. tSafe0v + tSrcRecover before transitioning into
> SRC_HARD_RESET_VBUS_ON.
>
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
> Changes since V1 (Guenter's suggestion):
> - Bound SRC_HARD_RESET_VBUS_ON to accommodate tcpc drivers which doesn't
> update the vbus status.
>
> Changes since V2:
> - Reviewed-by: Guenter Roeck <linux@...ck-us.net>
>
> Changes since V3:
> - Fixed compliance test numbers and updated commit description and made
> in more elaborate to address Heikki's suggestion.
> ---
> 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;
> --
> 2.28.0.236.gb10cc79966-goog
--
heikki
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