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

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Date:   Sat, 1 Oct 2022 11:57:55 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Doug Anderson <dianders@...omium.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

On 30/09/2022 22:19, Doug Anderson wrote:
> 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@

Indeed. I can drop Cc-stable, but AUTOSEL can still pick it up because
of Fixes tag. Fixes tag is here important to indicate we are having a
bug before.

> 
> 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].

Uh, that makes a lot of sense. It is almost always a property of a board.

> 
> That being said, it does look like this was the intention of the
> original commit, so thus:
> 
> Reviewed-by: Douglas Anderson <dianders@...omium.org>

Thanks.

I can also drop the property entirely to match existing behavior (not
the intention).

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

Best regards,
Krzysztof