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

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Message-ID: <CACRpkdZJaz9BEorQa7dTNkgTkwZjJNB-MWrpKFxHRgdsf3xJww@mail.gmail.com>
Date:   Fri, 25 Nov 2022 10:47:40 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     neil.armstrong@...aro.org
Cc:     Abel Vesa <abel.vesa@...aro.org>, 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>
Subject: Re: [PATCH v2 2/4] dt-bindings: pinctrl: qcom,tlmm-common: document
 i2c pull property

On Thu, Nov 24, 2022 at 2:24 PM Neil Armstrong
<neil.armstrong@...aro.org> wrote:
> On 24/11/2022 14:11, Linus Walleij wrote:
> > 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?
>
> I'll try to get some more info, but so far I only found what I wrote in the bindings.

Björn: can you see if you can get some clarity about the i2c
bias thing?

Yours,
Linus Walleij