linux-kernel - Re: [PATCH] usb: typec: tcpm: Relax disconnect threshold during power negotiation

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Message-ID: <CAPTae5JHHYO=y7279pFcHrt1oD3HHU8m3qkdb1vmNkbf6rLpqA@mail.gmail.com>
Date:   Mon, 14 Jun 2021 09:51:31 -0700
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     Kyle Tso <kyletso@...gle.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: typec: tcpm: Relax disconnect threshold during power negotiation

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@...gle.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@...gle.com>
> Signed-off-by: Kyle Tso <kyletso@...gle.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;
>                 case SOFT_RESET_SEND:
> --
> 2.32.0.272.g935e593368-goog
>