linux-kernel - Re: [PATCH v2 1/7] arm64: dts: qcom: sm8450: add spmi node

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Date:   Thu, 29 Dec 2022 10:12:49 -0600
From:   Bjorn Andersson <andersson@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, agross@...nel.org,
        marijn.suijten@...ainline.org, Vinod Koul <vkoul@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] arm64: dts: qcom: sm8450: add spmi node

On Thu, Dec 29, 2022 at 11:57:58AM +0100, Krzysztof Kozlowski wrote:
> On 29/12/2022 11:45, Konrad Dybcio wrote:
> > 
> > 
> > On 29.12.2022 11:42, Krzysztof Kozlowski wrote:
> >> On 29/12/2022 11:32, Konrad Dybcio wrote:
> >>> From: Vinod Koul <vkoul@...nel.org>
> >>>
> >>> Add the spmi bus as found in the SM8450 SoC
> >>>
> >>> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> >>> Reviewed-by: Konrad Dybcio <konrad.dybcio@...ainline.org>
> >>> [Konrad: 0x0 -> 0, move #cells down, make reg-names a vertical list]
> >>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> >>> ---
> >>> v1 -> v2:
> >>> No changes
> >>>
> >>>  arch/arm64/boot/dts/qcom/sm8450.dtsi | 22 ++++++++++++++++++++++
> >>>  1 file changed, 22 insertions(+)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> >>> index 570475040d95..b9b59c5223eb 100644
> >>> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> >>> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> >>> @@ -2715,6 +2715,28 @@ aoss_qmp: power-controller@...0000 {
> >>>  			#clock-cells = <0>;
> >>>  		};
> >>>  
> >>> +		spmi_bus: spmi@...d000 {
> >>
> >> Hmm looks different than reg.
> >>
> >>> +			compatible = "qcom,spmi-pmic-arb";
> >>> +			reg = <0 0x0c400000 0 0x00003000>,
> >>> +			      <0 0x0c500000 0 0x00400000>,
> >>> +			      <0 0x0c440000 0 0x00080000>,
> >>> +			      <0 0x0c4c0000 0 0x00010000>,
> >>> +			      <0 0x0c42d000 0 0x00010000>;
> >> x
> > Hm, my guess would be that Vinod chose to put the "cnfg" reg
> > instead of "core" in the unit address, as 8450 has 2 SPMI bus
> > hosts and they both share the core reg, so it would have been
> > impossible to have two spmi@...e nodes..
> 
> Eh? SM8450 has 2 SPMI hosts both using 0x0c400000? How does that work?
> Usually address can be mapped only once.
> 

The SPMI controller does something like multi-master. The driver expects
the same region to be mapped multiple times and qcom,channel is used to
select which one each instance should operate on.

Regards,
Bjorn

> Where is the second SPMI? I cannot find it in linux-next.
> 
> 
> Best regards,
> Krzysztof
>