linux-kernel - Re: [PATCH] arm64: dts: qcom: qcs404-evb: Set vdd

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Date:   Wed, 16 Oct 2019 13:44:01 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Niklas Cassel <niklas.cassel@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: qcs404-evb: Set vdd_apc regulator in
 high power mode

On 14-10-19, 14:09, Niklas Cassel wrote:
> vdd_apc is the regulator that supplies the main CPU cluster.
> 
> At sudden CPU load changes, we have noticed invalid page faults on
> addresses with all bits shifted, as well as on addresses with individual
> bits flipped.
> 
> By putting the vdd_apc regulator in high power mode, the voltage drops
> during sudden load changes will be less severe, and we have not been able
> to reproduce the invalid page faults with the regulator in this mode.

Reviewed-by: Vinod Koul <vkoul@...nel.org>

This seems a good bug fix, maybe CC stable?

> 
> Signed-off-by: Niklas Cassel <niklas.cassel@...aro.org>
> Suggested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>  arch/arm64/boot/dts/qcom/qcs404-evb.dtsi | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/qcs404-evb.dtsi b/arch/arm64/boot/dts/qcom/qcs404-evb.dtsi
> index 501a7330dbc8..522d3ef72df5 100644
> --- a/arch/arm64/boot/dts/qcom/qcs404-evb.dtsi
> +++ b/arch/arm64/boot/dts/qcom/qcs404-evb.dtsi
> @@ -73,6 +73,7 @@
>  		regulator-always-on;
>  		regulator-boot-on;
>  		regulator-name = "vdd_apc";
> +		regulator-initial-mode = <1>;
>  		regulator-min-microvolt = <1048000>;
>  		regulator-max-microvolt = <1384000>;
>  	};
> -- 
> 2.21.0

-- 
~Vinod