linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: sc7280: Add PCIe and PHY related nodes

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Message-ID: <CAE-0n50k9z0ZFqP_pOmQjp0s3NCSKYHTmHvZ5rxLb3MzqgavrA@mail.gmail.com>
Date:   Fri, 4 Jun 2021 21:43:43 +0000
From:   Stephen Boyd <swboyd@...omium.org>
To:     Prasad Malisetty <pmaliset@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        mgautam@...eaurora.org, dianders@...omium.org, mka@...omium.org
Subject: Re: [PATCH 2/3] arm64: dts: qcom: sc7280: Add PCIe and PHY related nodes

Quoting Prasad Malisetty (2021-05-21 02:57:00)
> On 2021-05-08 01:36, Stephen Boyd wrote:
> > Quoting Prasad Malisetty (2021-05-07 03:17:27)
> >> Add PCIe controller and PHY nodes for sc7280 SOC.
> >>
> >> Signed-off-by: Prasad Malisetty <pmaliset@...eaurora.org>
> >> ---
> >>  arch/arm64/boot/dts/qcom/sc7280.dtsi | 138
> >> +++++++++++++++++++++++++++++++++++
> >>  1 file changed, 138 insertions(+)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> >> b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> >> index 2cc4785..a9f25fc1 100644
> >> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> >> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> >> @@ -12,6 +12,7 @@
> >>  #include <dt-bindings/power/qcom-aoss-qmp.h>
> >>  #include <dt-bindings/power/qcom-rpmpd.h>
> >>  #include <dt-bindings/soc/qcom,rpmh-rsc.h>
> >> +#include <dt-bindings/gpio/gpio.h>
> >>
> >>  / {
> >>         interrupt-parent = <&intc>;
> >> @@ -316,6 +317,118 @@
> >>                         };
> >>                 };
> >>
> > [...]
> >> +
> >> +               pcie1_phy: phy@...e000 {
> >> +                       compatible =
> >> "qcom,sm8250-qmp-gen3x2-pcie-phy";
> >> +                       reg = <0 0x01c0e000 0 0x1c0>;
> >> +                       #address-cells = <2>;
> >> +                       #size-cells = <2>;
> >> +                       ranges;
> >> +                       clocks = <&gcc GCC_PCIE_1_AUX_CLK>,
> >> +                                <&gcc GCC_PCIE_1_CFG_AHB_CLK>,
> >> +                                <&gcc GCC_PCIE_CLKREF_EN>,
> >> +                                <&gcc GCC_PCIE1_PHY_RCHNG_CLK>;
> >> +                       clock-names = "aux", "cfg_ahb", "ref",
> >> "refgen";
> >> +
> >> +                       resets = <&gcc GCC_PCIE_1_PHY_BCR>;
> >> +                       reset-names = "phy";
> >> +
> >> +                       assigned-clocks = <&gcc
> >> GCC_PCIE1_PHY_RCHNG_CLK>;
> >> +                       assigned-clock-rates = <100000000>;
> >> +
> >> +                       status = "disabled";
> >
> > I think the style is to put status disabled close to the compatible?
>
> Generally I have added status disabled in end as like many nodes. just
> curious to ask is there any specific reason to put close to compatible.

It's really up to qcom maintainers, which I am not.

> >> +                               };
> >> +
> >> +                               reset-n {
> >> +                                       pins = "gpio2";
> >> +                                       function = "gpio";
> >> +
> >> +                                       drive-strength = <16>;
> >> +                                       output-low;
> >> +                                       bias-disable;
> >> +                               };
> >> +
> >> +                               wake-n {
> >> +                                       pins = "gpio3";
> >> +                                       function = "gpio";
> >> +
> >> +                                       drive-strength = <2>;
> >> +                                       bias-pull-up;
> >> +                               };
> >
> > These last two nodes with the pull-up and drive-strength settings
> > should
> > be in the board files, like the idp one, instead of here in the SoC
> > file. That way board designers can take the SoC and connect the pcie to
> > an external device using these pins and set the configuration they want
> > on these pins, or choose not to connect them to the SoC at all and use
> > those pins for something else.
> >
> > In addition, it looks like the reset could be a reset-gpios property
> > instead of an output-low config.
> >
> we are using reset property as perst gpio in pcie node.

Ok, perst-gpios should be fine. Presumably perst-gpios should be in the
board and not in the SoC because of what I wrote up above.