linux-kernel - Re: [PATCH v10 3/5] arm64: dts: qcom: sc7280: Add PCIe nodes for IDP board

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Date:   Mon, 4 Oct 2021 21:10:49 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Prasad Malisetty <pmaliset@...eaurora.org>, agross@...nel.org,
        bhelgaas@...gle.com, bjorn.andersson@...aro.org,
        lorenzo.pieralisi@....com, robh+dt@...nel.org, svarbanov@...sol.com
Cc:     devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        dianders@...omium.org, mka@...omium.org, vbadigan@...eaurora.org,
        sallenki@...eaurora.org, manivannan.sadhasivam@...aro.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v10 3/5] arm64: dts: qcom: sc7280: Add PCIe nodes for IDP board

Quoting Prasad Malisetty (2021-10-04 12:41:26)
> Enable PCIe controller and PHY for sc7280 IDP board.
> Add specific NVMe GPIO entries for SKU1 and SKU2 support.
>
> Signed-off-by: Prasad Malisetty <pmaliset@...eaurora.org>
> ---
>  arch/arm64/boot/dts/qcom/sc7280-idp.dts  |  8 +++++
>  arch/arm64/boot/dts/qcom/sc7280-idp.dtsi | 51 ++++++++++++++++++++++++++++++++
>  arch/arm64/boot/dts/qcom/sc7280-idp2.dts |  8 +++++
>  3 files changed, 67 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> index 272d5ca..b416f3d 100644
> --- a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> @@ -462,6 +491,28 @@
>  };
>
>  &tlmm {
> +       nvme_pwren_pin: nvme-pwren-pin {

pin is sort of redundant but OK. It would be simpler without the pin
postfix.

> +               function = "gpio";
> +               bias-pull-up;

Why is there a bias pull up on this enable pin? I'd expect to see a
bias-disable as this is an output pin and there's no need for a pull.

> +       };
> +
> +       pcie1_reset_n: pcie1-reset-n {
> +               pins = "gpio2";
> +               function = "gpio";
> +
> +               drive-strength = <16>;

Why such a strong drive strength?

> +               output-low;
> +               bias-disable;
> +       };
> +
> +       pcie1_wake_n: pcie1-wake-n {
> +               pins = "gpio3";
> +               function = "gpio";
> +
> +               drive-strength = <2>;
> +               bias-pull-up;
> +       };
> +
>         qup_uart7_sleep_cts: qup-uart7-sleep-cts {
>                 pins = "gpio28";
>                 function = "gpio";