Re: [PATCH v3] usb: typec: tcpm: Relax disconnect threshold during power negotiation

[Badhri Jagan Sridharan]

On Wed, Jun 16, 2021 at 6:42 AM Heikki Krogerus
<heikki.krogerus@xxxxxxxxxxxxxxx> wrote:
>
> On Wed, Jun 16, 2021 at 05:01:02PM +0800, Kyle Tso wrote:
> > If the voltage is being decreased in power negotiation, the Source will
> > set the power supply to operate at the new voltage level before sending
> > PS_RDY. Relax the threshold before sending Request Message so that it
> > will not race with Source which begins to adjust the voltage right after
> > it sends Accept Message (PPS) or tSrcTransition (25~35ms) after it sends
> > Accept Message (non-PPS).
> >
> > The real threshold will be set after Sink receives PS_RDY Message.
> >
> > Fixes: f321a02caebd ("usb: typec: tcpm: Implement enabling Auto Discharge disconnect support")
> > Cc: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> > Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
>
> Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Reviewed-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
>
> > ---
> > Changes in v3:
> > - move the timing of setting threshold for Fixed RDO as I did for PPS in
> >   v2, i.e. move it to tcpm_pd_send_request.
> > - add Cc: tag for Badhri
> > - update the commit message for the above changes
> >
> > Changes in v2:
> > - move the timing of setting threshold up to "before sending Request"
> >   for PPS power negotiation so that it won't race with the Source.
> > - PPS: if it fails to send the Request, fallback to previous threshold
> > - PPS: if the Source doesn't respond Accept, fallback to previous
> >   threshold
> > - update the commit message for above changes
> >
> >  drivers/usb/typec/tcpm/tcpm.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 197556038ba4..b1d310ab84c4 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -2604,6 +2604,11 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> >                       } else {
> >                               next_state = SNK_WAIT_CAPABILITIES;
> >                       }
> > +
> > +                     /* Threshold was relaxed before sending Request. Restore it back. */
> > +                     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > +                                                            port->pps_data.active,
> > +                                                            port->supply_voltage);
> >                       tcpm_set_state(port, next_state, 0);
> >                       break;
> >               case SNK_NEGOTIATE_PPS_CAPABILITIES:
> > @@ -2617,6 +2622,11 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> >                           port->send_discover)
> >                               port->vdm_sm_running = true;
> >
> > +                     /* Threshold was relaxed before sending Request. Restore it back. */
> > +                     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > +                                                            port->pps_data.active,
> > +                                                            port->supply_voltage);
> > +
> >                       tcpm_set_state(port, SNK_READY, 0);
> >                       break;
> >               case DR_SWAP_SEND:
> > @@ -3336,6 +3346,12 @@ static int tcpm_pd_send_request(struct tcpm_port *port)
> >       if (ret < 0)
> >               return ret;
> >
> > +     /*
> > +      * Relax the threshold as voltage will be adjusted after Accept Message plus tSrcTransition.
> > +      * It is safer to modify the threshold here.
> > +      */
> > +     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> > +
> >       memset(&msg, 0, sizeof(msg));
> >       msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
> >                                 port->pwr_role,
> > @@ -3433,6 +3449,9 @@ static int tcpm_pd_send_pps_request(struct tcpm_port *port)
> >       if (ret < 0)
> >               return ret;
> >
> > +     /* Relax the threshold as voltage will be adjusted right after Accept Message. */
> > +     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> > +
> >       memset(&msg, 0, sizeof(msg));
> >       msg.header = PD_HEADER_LE(PD_DATA_REQUEST,
> >                                 port->pwr_role,
> > @@ -4196,6 +4215,10 @@ static void run_state_machine(struct tcpm_port *port)
> >               port->hard_reset_count = 0;
> >               ret = tcpm_pd_send_request(port);
> >               if (ret < 0) {
> > +                     /* Restore back to the original state */
> > +                     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > +                                                            port->pps_data.active,
> > +                                                            port->supply_voltage);
> >                       /* Let the Source send capabilities again. */
> >                       tcpm_set_state(port, SNK_WAIT_CAPABILITIES, 0);
> >               } else {
> > @@ -4206,6 +4229,10 @@ static void run_state_machine(struct tcpm_port *port)
> >       case SNK_NEGOTIATE_PPS_CAPABILITIES:
> >               ret = tcpm_pd_send_pps_request(port);
> >               if (ret < 0) {
> > +                     /* Restore back to the original state */
> > +                     tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_PD,
> > +                                                            port->pps_data.active,
> > +                                                            port->supply_voltage);
> >                       port->pps_status = ret;
> >                       /*
> >                        * If this was called due to updates to sink
> > --
> > 2.32.0.272.g935e593368-goog
>
> --
> heikki