linux-kernel - Re: [PATCH v3 13/14] arm64: dts: qcom: sc7280: Add the CPU compatible to the soc@0 node

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Message-ID: <Yf2f8Az5v1TtlAjd@builder.lan>
Date:   Fri, 4 Feb 2022 15:51:44 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     pmaliset@...eaurora.org, mka@...omium.org,
        quic_rjendra@...cinc.com,
        Shaik Sajida Bhanu <sbhanu@...eaurora.org>,
        kgodara@...eaurora.org, konrad.dybcio@...ainline.org,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        sibis@...eaurora.org, swboyd@...omium.org,
        Andy Gross <agross@...nel.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 v3 13/14] arm64: dts: qcom: sc7280: Add the CPU
 compatible to the soc@0 node

On Wed 02 Feb 15:23 CST 2022, Douglas Anderson wrote:

> We'd like to start including the CPU name as the compatible under the
> "soc" node so that we can get rid of it from the top-level compatible
> string.
> 
> Suggested-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> Probably needs a .yaml file somewhere?
> 
> Changes in v3:
> - ("sc7280: Add the CPU compatible to the soc@0 node") new for v3.
> 
>  arch/arm64/boot/dts/qcom/sc7280.dtsi | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> index 618ae0407cd6..2bfc919d4018 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> @@ -573,7 +573,7 @@ soc: soc@0 {
>  		#size-cells = <2>;
>  		ranges = <0 0 0 0 0x10 0>;
>  		dma-ranges = <0 0 0 0 0x10 0>;
> -		compatible = "simple-bus";
> +		compatible = "qcom,sc7280", "simple-bus";

To me this implies that /soc represents the sc7280, but as noted earlier
I don't think that's accurate. E.g. if this node represents the sc7280,
why are the cpus described outside this node?

Further more, if we look at the reg nodes on this bus it's clear that
this is some mmio bus, which per the ranges has 36 bit address width.
But not all buses in the sc7280 has 36 bit address width, so it's not
inconceivable that one would actually have to split /soc into more than
one entity with different dma-ranges. Perhaps not today, but I don't
like the precedence it sets.

Regards,
Bjorn

>  
>  		gcc: clock-controller@...000 {
>  			compatible = "qcom,gcc-sc7280";
> -- 
> 2.35.0.rc2.247.g8bbb082509-goog
>