Re: [PATCH v2 2/2] ARM: dts: renesas: r9a06g032-rzn1d400-eb: enable GPIOs on CN12

Hi Wolfram,

On Tue, 11 Aug 2026 at 03:51, Wolfram Sang
<[email protected]> wrote:
> > > +       pins_gpio2b: pins-gpio2b {
> >
> > pins-cn12?
>
> Okay.
>
> > > +               pinmux = <RZN1_PINMUX(164, RZN1_FUNC_GPIO)>,
> > > +                        <RZN1_PINMUX(165, RZN1_FUNC_GPIO)>,
> > > +                        <RZN1_PINMUX(166, RZN1_FUNC_GPIO)>,
> > > +                        <RZN1_PINMUX(167, RZN1_FUNC_GPIO)>,
> > > +                        <RZN1_PINMUX(168, RZN1_FUNC_GPIO)>,
> > > +                        <RZN1_PINMUX(169, RZN1_FUNC_GPIO)>;
> > > +               drive-strength = <6>;
> > > +               bias-disable;
> >
> > These pins don't have any external pull-ups, so disabling bias will
> > make them pick-up random EM noise when left unconnected.
>
> Can fix, but is this bad? I'd assume the connected pins will handle it.
> And if not, the DT needs to be adapted to that use case. Otherwise, a
> default pull-up needs to be disabled for another use case.

Currently, nothing is connected to these pins. Unconnected CMOS
inputs must never be left floating, as that can cause oscillations
and increased power consumption.

Default I/O configuration is "2’b01: Pull up (default value)" for bias.

While at it, why did you lower drive strength from the "2’b10: 8 mA
(default value)" 6 mA?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds