linux-kernel - Re: [PATCH] arm64: dts: qcom: sdm845: add missing power-controller compatible

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Date:   Tue, 21 Dec 2021 08:46:28 +0000
From:   David Heidelberg <david@...t.cz>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
CC:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        ~okias/devicetree@...ts.sr.ht, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sdm845: add missing power-controller compatible

It's more about how documentation is written. Documentation expect "specific compatible", "generic compatible" in that order. Of course it can be changed to allow also  only specific compatible.

Also this syntax ensure that older kernel (without implemented device compatible/support) will try to work when new dts is used. Kernel can fallback to generic one compatible and code and device will still work, if the driver is generic enough to provide at least some basic support without knowing which exact device is handled.

If I missed some reason to use it, I guess Rob will correct me :)

David


-------- Původní zpráva --------
Odesílatel: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Odesláno: 21. prosince 2021 6:58:45 UTC
Komu: David Heidelberg <david@...t.cz>
Kopie: Andy Gross <agross@...nel.org>, Bjorn Andersson <bjorn.andersson@...aro.org>, Rob Herring <robh+dt@...nel.org>, ~okias/devicetree@...ts.sr.ht, linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Předmět: Re: [PATCH] arm64: dts: qcom: sdm845: add missing power-controller compatible

On Mon, Dec 20, 2021 at 10:14:43PM +0100, David Heidelberg wrote:
> dt-schema expect to have fallback compatible, which is now in-place.
> 
> Fixes warning generated by `make qcom/sdm845-oneplus-fajita.dtb`:
> arch/arm64/boot/dts/qcom/sdm845-oneplus-fajita.dt.yaml: power-controller@...0000: compatible: ['qcom,sdm845-aoss-qmp'] is too short
>         From schema: Documentation/devicetree/bindings/soc/qcom/qcom,aoss-qmp.yaml
> 
> Signed-off-by: David Heidelberg <david@...t.cz>
> ---
>  arch/arm64/boot/dts/qcom/sdm845.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> index 92ab4513a08b..dbdb4243499c 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> @@ -4619,7 +4619,7 @@ aoss_reset: reset-controller@...0000 {
>  		};
>  
>  		aoss_qmp: power-controller@...0000 {
> -			compatible = "qcom,sdm845-aoss-qmp";
> +			compatible = "qcom,sdm845-aoss-qmp", "qcom,aoss-qmp";

"qcom,sdm845-aoss-qmp" compatible is supported by the driver. So ideally we
don't need a fallback here.

Is this something for DT backwards compatibility?

Thanks,
Mani

>  			reg = <0 0x0c300000 0 0x100000>;
>  			interrupts = <GIC_SPI 389 IRQ_TYPE_EDGE_RISING>;
>  			mboxes = <&apss_shared 0>;
> -- 
> 2.34.1
>