linux-kernel - Re: [PATCH v4 2/3] arm64: dts: qcom: sc7180: revert "arm64: dts: qcom: sc7180: Avoid glitching SPI CS at bootup on trogdor"

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Date:   Wed, 26 Oct 2022 16:01:50 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] arm64: dts: qcom: sc7180: revert "arm64: dts:
 qcom: sc7180: Avoid glitching SPI CS at bootup on trogdor"

Quoting Krzysztof Kozlowski (2022-10-20 15:51:34)
> This reverts commit e440e30e26dd6b0424002ad0ddcbbcea783efd85 because it
> is not a reliable way of fixing SPI CS glitch and it depends on specific
> Linux kernel pin controller driver behavior.
>
> This behavior of kernel driver was changed in commit b991f8c3622c
> ("pinctrl: core: Handling pinmux and pinconf separately") thus
> effectively the DTS fix stopped being effective.
>
> Proper solution for the glitching SPI chip select must be implemented in
> the drivers, not via ordering of entries in DTS, and is already
> introduced in commit d21f4b7ffc22 ("pinctrl: qcom: Avoid glitching lines
> when we first mux to output").
>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Tested-by: Douglas Anderson <dianders@...omium.org>
>
> ---

Reviewed-by: Stephen Boyd <swboyd@...omium.org>