linux-kernel - Re: [PATCH 6/6] arm64: tegra: Add support for PCIe endpoint mode in P2972-0000 platform

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Date:   Fri, 22 Nov 2019 14:25:33 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Vidya Sagar <vidyas@...dia.com>
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com, robh+dt@...nel.org,
        jonathanh@...dia.com, andrew.murray@....com, kishon@...com,
        gustavo.pimentel@...opsys.com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH 6/6] arm64: tegra: Add support for PCIe endpoint mode in
 P2972-0000 platform

On Fri, Nov 22, 2019 at 04:15:05PM +0530, Vidya Sagar wrote:
> Add endpoint mode support for PCIe C5 controller in P2972-0000 platform
> with information about supplies, PHY, PERST GPIO and GPIO that controls
> PCIe reference clock coming from the host system.
> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> ---
>  .../boot/dts/nvidia/tegra194-p2972-0000.dts   | 29 +++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts b/arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts
> index 7eb64b816e08..58c3a9677bc8 100644
> --- a/arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts
> +++ b/arch/arm64/boot/dts/nvidia/tegra194-p2972-0000.dts
> @@ -43,6 +43,19 @@
>  
>  		gpio@...0000 {
>  			status = "okay";
> +			/*
> +			 * Change the below node's status to 'okay' when
> +			 * PCIe C5 controller is enabled to operate in endpoint
> +			 * to allow REFCLK from the host system to flow into
> +			 * the controller.
> +			 */
> +			pex-refclk-sel-high {
> +				gpio-hog;
> +				output-high;
> +				gpios = <TEGRA194_AON_GPIO(AA, 5) 0>;
> +				label = "pex_refclk_sel_high";
> +				status = "disabled";
> +			};

Why don't we put this into the PCIe controller's node as a reference to
that GPIO? Seems like the controller would know exactly when this pin
needs to go high or low, so why does it have to be a hog?

Thierry

>  		};
>  
>  		pwm@...0000 {
> @@ -144,6 +157,22 @@
>  			    "p2u-5", "p2u-6", "p2u-7";
>  	};
>  
> +	pcie_ep@...a0000 {
> +		status = "disabled";
> +
> +		vddio-pex-ctl-supply = <&vdd_1v8ao>;
> +
> +		nvidia,pex-rst-gpio = <&gpio TEGRA194_MAIN_GPIO(GG, 1)
> +					GPIO_ACTIVE_LOW>;
> +
> +		phys = <&p2u_nvhs_0>, <&p2u_nvhs_1>, <&p2u_nvhs_2>,
> +		       <&p2u_nvhs_3>, <&p2u_nvhs_4>, <&p2u_nvhs_5>,
> +		       <&p2u_nvhs_6>, <&p2u_nvhs_7>;
> +
> +		phy-names = "p2u-0", "p2u-1", "p2u-2", "p2u-3", "p2u-4",
> +			    "p2u-5", "p2u-6", "p2u-7";
> +	};
> +
>  	fan: fan {
>  		compatible = "pwm-fan";
>  		pwms = <&pwm4 0 45334>;
> -- 
> 2.17.1
> 

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