linux-kernel - Re: [PATCH 8/9] arm64: dts: mediatek: mt8183-kukui: Fix pull-down/up-adv values

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Message-ID: <CAGXv+5ECsP7_wbdcaAkWuD=RyJiJpPe4r60bhD5U8xUvEBzmXw@mail.gmail.com>
Date: Tue, 19 Aug 2025 13:27:50 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Julien Massot <julien.massot@...labora.com>, kernel@...labora.com, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Ikjoon Jang <ikjn@...omium.org>, 
	Enric Balletbo i Serra <eballetbo@...nel.org>, Weiyi Lu <weiyi.lu@...iatek.com>, 
	Eugen Hristev <eugen.hristev@...aro.org>, Liam Girdwood <lgirdwood@...il.com>, 
	Mark Brown <broonie@...nel.org>, Julien Massot <jmassot@...labora.com>, 
	Sean Wang <sean.wang@...nel.org>, linux-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	linux-sound@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH 8/9] arm64: dts: mediatek: mt8183-kukui: Fix
 pull-down/up-adv values

On Mon, Aug 18, 2025 at 11:22 PM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Wed, Aug 6, 2025 at 8:38 AM Chen-Yu Tsai <wenst@...omium.org> wrote:
> > On Fri, Aug 1, 2025 at 7:18 PM Julien Massot wrote
>
> > >                 pins-clk {
> > >                         pinmux = <PINMUX_GPIO124__FUNC_MSDC0_CLK>;
> > >                         drive-strength = <MTK_DRIVE_14mA>;
> > > -                       mediatek,pull-down-adv = <10>;
> > > +                       mediatek,pull-down-adv = <2>;
> >
> >         bias-pull-down = <MTK_PUPD_SET_R1R0_10>;
> >
> > and so on.
> >
> > ChenYu
>
> I agree with ChenYu, the more standardized properties are the better it is.
>
> All the custom properties makes sense for an engineer working with just
> that one SoC (like the SoC vendor...) but for field engineers who have
> to use different SoCs every day this is just a big mess for the mind.
>
> The standard properties are clear, concise and tell you exactly what
> they are about.
>
> The argument should be in Ohms though, according to the standard
> bindings, but maybe the value of MTK_PUPD_SET_R1R0_10 is
> something like that?

For reasons I can't recall clearly these are just placeholder values
that the driver then maps to the R1 and R0 settings. But at least they
use the standard properties.

The reason was either one of the following or both:

  a. not every group of pins had the same resistance values for R1 & R0
  b. there are no known precise values; the values depend on the process
     and batch


ChenYu