linux-kernel - Re: [PATCH v2 1/2] ARM: dts: imx6qp-sabresd: Enable PCIe support

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Date:   Sun, 13 Feb 2022 12:32:00 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     l.stach@...gutronix.de, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de, linux-imx@....com
Subject: Re: [PATCH v2 1/2] ARM: dts: imx6qp-sabresd: Enable PCIe support

On Fri, Feb 11, 2022 at 03:32:58PM +0800, Richard Zhu wrote:
> In the i.MX6QP sabresd board(sch-28857) design, one external oscillator
> is used as the PCIe reference clock source by the endpoint device.
> 
> If RC uses this oscillator as reference clock too, PLL6(ENET PLL) would
> has to be in bypass mode, and ENET clocks would be messed up.
> 
> To keep things simple, let RC use the internal PLL as reference clock
> and always enable the external oscillator for endpoint device on
> i.MX6QP sabresd board.
> 
> NOTE: This reference clock setup is used to pass the GEN2 TX compliance
> tests, and isn't recommended as a setup in the end-user design.

I do not quite follow.  The commit log is all talking about external
oscillator reference clock, while code is playing 'vgen3' regulator.

Shawn

> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  arch/arm/boot/dts/imx6qp-sabresd.dts | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/boot/dts/imx6qp-sabresd.dts b/arch/arm/boot/dts/imx6qp-sabresd.dts
> index 480e73183f6b..083cf90bcab5 100644
> --- a/arch/arm/boot/dts/imx6qp-sabresd.dts
> +++ b/arch/arm/boot/dts/imx6qp-sabresd.dts
> @@ -50,8 +50,14 @@ MX6QDL_PAD_SD3_DAT7__SD3_DATA7		0x17059
>  	};
>  };
>  
> +&vgen3_reg {
> +	regulator-min-microvolt = <1800000>;
> +	regulator-max-microvolt = <3300000>;
> +	regulator-always-on;
> +};
> +
>  &pcie {
> -	status = "disabled";
> +	status = "okay";
>  };
>  
>  &sata {
> -- 
> 2.25.1
>