linux-kernel - Re: [PATCH 1/3] arm64: dts: qcom: sdm630: fix UART1 pin bias

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Date:   Fri, 30 Sep 2022 13:19:24 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Rob Clark <robdclark@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH 1/3] arm64: dts: qcom: sdm630: fix UART1 pin bias

Hi,

On Fri, Sep 30, 2022 at 11:22 AM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> There is no "bias-no-pull" property.  Assume intentions were disabling
> bias.
>
> Fixes: b190fb010664 ("arm64: dts: qcom: sdm630: Add sdm630 dts file")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>
> ---
>
> Not tested on hardware.
> ---
>  arch/arm64/boot/dts/qcom/sdm630.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

This does change behavior and has the potential to break someone.
Thus, without a bug report or someone to give a tested-by I'm at least
moderately worried about this going to stable@

I would also note that convention on Qualcomm SoCs that I've worked on
was that bias shouldn't be specified in the SoC dtsi file and should
be left to board files. This is talked a bit about in a previous email
thread [1].

That being said, it does look like this was the intention of the
original commit, so thus:

Reviewed-by: Douglas Anderson <dianders@...omium.org>

[1] https://lore.kernel.org/lkml/CAD=FV=VUL4GmjaibAMhKNdpEso_Hg_R=XeMaqah1LSj_9-Ce4Q@mail.gmail.com/