linux-kernel - Re: [PATCH] arm64: dts: qcom: ipq6018: add #power-domain-cells for gcc node

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Date: Thu, 4 Jan 2024 12:30:57 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Fenglin Wu <quic_fenglinw@...cinc.com>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>, quic_tdas@...cinc.com, 
	quic_aiquny@...cinc.com, kernel@...cinc.com, Andy Gross <agross@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: ipq6018: add #power-domain-cells for
 gcc node

On Thu, 4 Jan 2024 at 12:27, Fenglin Wu <quic_fenglinw@...cinc.com> wrote:
>
>
>
> On 1/4/2024 6:16 PM, Konrad Dybcio wrote:
> > On 4.01.2024 11:13, Fenglin Wu wrote:
> >>
> >>
> >> On 1/4/2024 5:53 PM, Dmitry Baryshkov wrote:
> >>> On Thu, 4 Jan 2024 at 10:06, Fenglin Wu via B4 Relay
> >>> <devnull+quic_fenglinw.quicinc.com@...nel.org> wrote:
> >>>>
> >>>> From: Fenglin Wu <quic_fenglinw@...cinc.com>
> >>>>
> >>>> Property '#power-domain-cells' is required as per defined in qcom,gcc.yaml
> >>>> so add it for ipq6018 gcc device node to eliminate following warning in
> >>>> dtbs_check:
> >>>>
> >>>> arch/arm64/boot/dts/qcom/ipq6018-cp01-c1.dtb: gcc@...0000:
> >>>>           '#power-domain-cells' is a required property
> >>>> from schema $id: http://devicetree.org/schemas/clock/qcom,gcc-ipq6018.yaml#
> >>>
> >>> But ipq6018 doesn't implement GDSC support. So for the sake of fixing
> >>> the warning you are adding a bogus property.
> >>>
> >> I agree. However, there are also some gcc drivers not implementing GDSC support but the bindings are adding '#power-domain-cells' in the DT example, such as: qcom,gcc-apq8064.yaml, qcom,gcc-ipq4019.yaml, qcom,gcc-ipq6018.yaml, qcom,gcc-ipq8064.yaml, qcom,gcc-msm8660.yaml.
> >>
> >> Actually I thought that maybe we should do a clean up by removing '#power-domain-cells' out of the qcom,gcc.yaml binding and only adding it into individual qcom,gcc-xxx.yaml for the driver which has implemented GDSC support. I checked this with Taniya offline, but she prefers only fixing it in ipq6018.dtsi as it doesn't hurt anything by adding the property, and she expects the GDSC support should be existing in most of qcom,gcc drivers especially the newer Qcom chipsets.
> >
> > Before we start changing anything, we should assess whether these
> > platforms actually have GDSCs within this clock controller block,
> > even if they are (currently) not described in the clk driver.
> >
> I would assume '#power-domain-cells' is only required for drivers which
> register GDSC as power-domain device, for drivers that only configure
> GDSC during probe or for platforms have GDSC but not register them as
> power-domain device, making '#power-domain-cells' as a required property
> doesn't help anything but just generating more dtbs check warnings.

If there is a hardware GDSC, it should be registered in software
unless there is a good reason to do otherwise.


-- 
With best wishes
Dmitry