linux-kernel - Re: [PATCH 1/2] arm64: dts: qcom: sm8550-qrd: add PCIe0

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Message-ID: <CAA8EJpq0x=H_SirdOwwhuiU7b1GPhP6-3xgR9PTQ_b2HYinMzQ@mail.gmail.com>
Date:   Tue, 16 May 2023 20:15:16 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.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 1/2] arm64: dts: qcom: sm8550-qrd: add PCIe0

On Tue, 16 May 2023 at 19:43, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 16/05/2023 18:39, Dmitry Baryshkov wrote:
> > On Tue, 16 May 2023 at 16:30, Krzysztof Kozlowski
> > <krzysztof.kozlowski@...aro.org> wrote:
> >>
> >> Add PCIe0 nodes used with WCN7851 device.  The PCIe1 is not connected,
> >> thus skip pcie_1_phy_aux_clk input clock to GCC.
> >>
> >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> >> ---
> >>  arch/arm64/boot/dts/qcom/sm8550-qrd.dts | 32 +++++++++++++++++++++++++
> >>  1 file changed, 32 insertions(+)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/sm8550-qrd.dts b/arch/arm64/boot/dts/qcom/sm8550-qrd.dts
> >> index ccc58e6b45bd..e7a2bc5d788b 100644
> >> --- a/arch/arm64/boot/dts/qcom/sm8550-qrd.dts
> >> +++ b/arch/arm64/boot/dts/qcom/sm8550-qrd.dts
> >> @@ -385,6 +385,38 @@ vreg_l3g_1p2: ldo3 {
> >>         };
> >>  };
> >>
> >> +&gcc {
> >> +       clocks = <&bi_tcxo_div2>, <&sleep_clk>,
> >> +                <&pcie0_phy>,
> >> +                <&pcie1_phy>,
> >> +                <0>,
> >> +                <&ufs_mem_phy 0>,
> >> +                <&ufs_mem_phy 1>,
> >> +                <&ufs_mem_phy 2>,
> >> +                <&usb_dp_qmpphy QMP_USB43DP_USB3_PIPE_CLK>;
> >> +};
> >
> > Is there any reason to disable the PCIe1 PHY AUX clock here? I mean,
> > the PCIe1 is still enabled in the hardware.
>
> I was thinking about this. The AUX clock seems to be an external clock,
> although I could not find it in schematics. I assume that on QRD8550 it
> could be missing, if it is really external. OTOH, downstream DTS did not
> seem to care...

I might be completely wrong here, but I think that AUX clock is yet
another clock provided by the PHY to the GCC, which we were just
ignoring for now. For example, for sm8450 we have <0> there. I don't
see it as an external clock, so I think it is internal to the SoC.

-- 
With best wishes
Dmitry