On 8/11/20 12:39 PM, Badhri Jagan Sridharan wrote: > On Tue, Aug 11, 2020 at 11:45 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >> >> On Tue, Aug 11, 2020 at 11:24:07AM -0700, Badhri Jagan Sridharan wrote: >>> On Mon, Aug 10, 2020 at 6:51 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >>>> >>>> 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@xxxxxxxxxx> >>>>> --- >>>>> 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 >>> >>> The term PD event is a little ambiguous to me. Trying to summarize the workflow. >>> Lower level tcpc driver would have to call tcpm_vbus_change which >>> would in-turn trigger TCPM_VBUS_EVENT >>> and queries port->tcpc->get_vbus to get the vbus status. It is not >>> really a PD protocol driven event hence the >>> confusion. >>> >>> "What happens if that event is never received ?" >>> Yeah TCPM would be in SRC_HARD_RESET_VBUS_OFF till the tcpc calls the >>> tcpm_vbus_change. >>> Do you suspect that existing tcpc would not have the capability to >>> monitor vbus status while sourcing and call tcpm_vbus_change? >>> >> That, or the driver might be buggy, or the hardware does't signal a status >> update, or the update gets lost. I think we should have some backup, >> to trigger if the event is not received in a reasonable amout of time. >> I don't know if the specification has some kind of maximum limit. If >> not, we should still have something >> >> Thanks, >> Guenter > > Got it ! The specification actually has a bound for vbus off. > tSafe0V - Time to reach vSafe0V max - 650ms. (PD_T_SAFE_0V). > So I will bound it to that. > Excellent. Thanks a lot for looking into this! Guenter >>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). > > Thanks, > Badhri > >> >>> Thanks, >>> Badhri >>> >>> >>>>> 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; >>>>> >>>>
