linux-kernel - Re: [PATCH v2 2/4] dt-bindings: pinctrl: qcom,tlmm-common: document i2c pull property

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Message-ID: <CACRpkdZtkHCkfUAcezSJvmei=HOezK6oyx+4C5kBrEtU+vAB-g@mail.gmail.com>
Date:   Thu, 24 Nov 2022 14:11:32 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Abel Vesa <abel.vesa@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v2 2/4] dt-bindings: pinctrl: qcom,tlmm-common: document
 i2c pull property

On Wed, Nov 23, 2022 at 4:20 PM Abel Vesa <abel.vesa@...aro.org> wrote:

> From: Neil Armstrong <neil.armstrong@...aro.org>
>
> Document the new i2c_pull property introduced for SM8550 setting
> an I2C specific pull mode on I2C able pins.
>
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
(...)
> +      qcom,i2c-pull:
> +        type: boolean
> +        description: enable bias pull feature designed for I2C on pin

But what is this?

I2C buses are usually just plain old bias-high-impedance, high-z
or open drain, wire-or or whatever you want to call it.

But now there is some special i2c mode, huh?

The description is pretty much "it is what it is"... can we have
some explanation about what this means electrically speaking
and why you cannot use bias-high-impedance?

Yours,
Linus Walleij