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From:   Kyle Tso <kyletso@google.com>
Date:   Tue, 15 Jun 2021 00:55:09 +0800
Message-ID: <CAGZ6i=37OKFC6TPuhzHxAFPxrCqgybF9R_3gwA22JoJUCYAzug@mail.gmail.com>
Subject: Re: [PATCH] usb: typec: tcpm: Relax disconnect threshold during power negotiation
To:     Badhri Jagan Sridharan <badhri@google.com>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        USB <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Jun 15, 2021 at 12:52 AM Badhri Jagan Sridharan
<badhri@google.com> wrote:
>
> Hi Kyle,
>
> The change doesn't seem to handle the cases where the partner does not
> accept the request i.e.
>        "case PD_CTRL_REJECT:
>         case PD_CTRL_WAIT:
>         case PD_CTRL_NOT_SUPP:"
> We should fall back to the disconnect threshold based on the
> previously negotiated voltage levels in those cases.
>
> Regards,
> Badhri
>
>
> On Sun, Jun 13, 2021 at 8:13 AM Kyle Tso <kyletso@google.com> 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 disconnect threshold for Sink after receiving Accept
> > Message to ensure the relaxed setting is enabled before the voltage
> > collapse. And 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@google.com>
> > Signed-off-by: Kyle Tso <kyletso@google.com>
> > ---
> >  drivers/usb/typec/tcpm/tcpm.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 0db685d5d9c0..9f3f37da71b6 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -2646,6 +2646,8 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> >                 switch (port->state) {
> >                 case SNK_NEGOTIATE_CAPABILITIES:
> >                         port->pps_data.active = false;
> > +                       /* Voltage is going to be at new level. Relax the threshold here. */
> > +                       tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> >                         tcpm_set_state(port, SNK_TRANSITION_SINK, 0);
> >                         break;
> >                 case SNK_NEGOTIATE_PPS_CAPABILITIES:
> > @@ -2656,6 +2658,8 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
> >                         port->req_supply_voltage = port->pps_data.req_out_volt;
> >                         port->req_current_limit = port->pps_data.req_op_curr;
> >                         power_supply_changed(port->psy);
> > +                       /* Voltage is going to be at new level. Relax the threshold here. */
> > +                       tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, 0);
> >                         tcpm_set_state(port, SNK_TRANSITION_SINK, 0);
> >                         break;

Yes, Badhri you are right.

And it's still too late for PPS power negotiation. The Source begins
to lower it's Vbus level just after Accept Message.
I will send patch v2 to fix these problems.

thanks,
Kyle

> >                 case SOFT_RESET_SEND:
> > --
> > 2.32.0.272.g935e593368-goog
> >