linux-kernel - Re: [PATCH v7 11/11] usb: typec: tcpci_maxim: Implemnent set_auto_vbus_discharge

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Date:   Fri, 18 Sep 2020 19:53:22 -0700
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 11/11] usb: typec: tcpci_maxim: Implemnent set_auto_vbus_discharge_threshold

On Fri, Sep 18, 2020 at 7:20 AM Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
>
> On Thu, Sep 17, 2020 at 03:18:56AM -0700, Badhri Jagan Sridharan wrote:
> > Programs VBUS_SINK_DISCONNECT_THRESHOLD based on the power_role,
> > voltage requested as sink, mode of operation.
> >
> > The programmed threshold is based on vSinkDisconnect and
> > vSinkDisconnectPD values.
> >
> > Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> > ---
> > Changes since v1:
> > - Changing patch version to v6 to fix version number confusion.
> >
> > Changes since v6:
> > - Rebase on usb-next.
> > ---
> >  drivers/usb/typec/tcpm/tcpci_maxim.c | 48 ++++++++++++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.c b/drivers/usb/typec/tcpm/tcpci_maxim.c
> > index 723d7dd38f75..8289b596d2ee 100644
> > --- a/drivers/usb/typec/tcpm/tcpci_maxim.c
> > +++ b/drivers/usb/typec/tcpm/tcpci_maxim.c
> > @@ -137,6 +137,52 @@ static void max_tcpci_init_regs(struct max_tcpci_chip *chip)
> >               return;
> >  }
> >
> > +static int max_tcpci_set_auto_vbus_discharge_threshold(struct tcpci *tcpci, struct tcpci_data *data,
> > +                                                    enum typec_role port_role,
> > +                                                    enum typec_pwr_opmode mode, bool pps_active,
> > +                                                    u32 requested_vbus_voltage_mv)
> > +{
> > +     struct max_tcpci_chip *chip = tdata_to_max_tcpci(data);
> > +     u32 threshold = 0;
> > +     u8 pwr_ctrl;
> > +
> > +     /*
> > +      * Indicates that vbus is going to go away due PR_SWAP, hard reset etc.
> > +      * Do not discharge vbus here.
> > +      */
> > +     if (requested_vbus_voltage_mv == 0)
> > +             goto write_thresh;
>
> I would assume that step is the same for every TCPC, no?
I agree so moved to tcpci.c code.
>
> > +     if (port_role == TYPEC_SINK) {
> > +             max_tcpci_read8(chip, TCPC_POWER_CTRL, &pwr_ctrl);
> > +             if (pwr_ctrl & TCPC_FAST_ROLE_SWAP_EN) {
> > +                     /* To prevent disconnect when the source is fast role swap is capable. */
> > +                     threshold = 3500;
> > +             } else if (mode == TYPEC_PWR_MODE_PD) {
> > +                     if (pps_active)
> > +                             threshold = (95 * requested_vbus_voltage_mv / 100) - 850;
> > +                     else
> > +                             threshold = (95 * requested_vbus_voltage_mv / 100) - 1250;
> > +             } else {
> > +                     /* 3.5V for non-pd sink */
> > +                     threshold = 3500;
> > +             }
> > +     } else {
> > +             /* 4V for source */
> > +             threshold = 4000;
> > +     }
> > +
> > +     threshold = threshold / TCPC_VBUS_SINK_DISCONNECT_THRESH_LSB;
> > +
> > +     if (threshold > TCPC_VBUS_SINK_DISCONNECT_THRESH_MAX) {
> > +             dev_err(chip->dev, "VBUS_SINK_DISCONNECT_THRESH out of range");
> > +             return -EINVAL;
> > +     }
> > +
> > +write_thresh:
> > +     return max_tcpci_write16(chip, TCPC_VBUS_SINK_DISCONNECT_THRESH, threshold);
>
> So couldn't tcpci.c write that register? This callback would then just
> calculate the value. I just want to avoid boilerplate.
Done !
>
> The threshold has type u32, but you still pass it to
> max_tcpci_write16(). Is that on purpose (doesn't the compiler
> complain)?
I didnt see any warnings ! I don't know why.
It wouldn't overflow though as TCPC_VBUS_SINK_DISCONNECT_THRESH_MAX
has a max value of 0x3ff. Have corrected it though and moved the code
to tcpci.c in v8.

Thanks,
Badhri

>
> thanks,
>
> --
> heikki