linux-kernel - Re: [PATCH 1/7] arm64: dts: qcom: sc8280xp: remove GCC from CX power domain

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Date:   Sat, 31 Dec 2022 00:41:01 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] arm64: dts: qcom: sc8280xp: remove GCC from CX power
 domain



On 30.12.2022 17:00, Krzysztof Kozlowski wrote:
> Bindings do not allow power-domain property in GCC clock controller and
> documentation does not indicate that GCC is part of VDD_CX.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> Maybe the bindings should be fixed? Maybe this was added as workaround?
> Anyway looking at documentation I do not see such relation, except
> downstream vdd_cx-supply (which is the same as in other SoCs and we do
> not represent it in upstream).
Some clocks scale with _CX, which is annotated on downstream with vdd-levels.
We take care of that by using opp tables in consumer drivers. Usually if
power-domains is added to a clock controller, it means that at least one of
the clocks needs the power domain to be on (which.. should be true for CX
if the ARM part runs anyway, no?), as for example VDD_MX/VDD_GFX may not be
on at boot and trying to enable such clocks would result in a big kaboom..

TL;DR: if nothing exploded, it's fine to remove it

Konrad
> ---
>  arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> index 1d1420c8720c..d14663c9f34c 100644
> --- a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> @@ -799,7 +799,6 @@ gcc: clock-controller@...000 {
>  				 <&pcie4_phy>,
>  				 <0>,
>  				 <0>;
> -			power-domains = <&rpmhpd SC8280XP_CX>;
>  		};
>  
>  		ipcc: mailbox@...000 {