linux-kernel - Re: [PATCH] arm64: dts: imx8mn-ddr4-evk: Adjust 1.2GHz OPP voltage to OD mode

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Message-ID: <20200224014759.GB27688@dragon>
Date:   Mon, 24 Feb 2020 09:48:00 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Anson Huang <Anson.Huang@....com>
Cc:     robh+dt@...nel.org, mark.rutland@....com, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, abel.vesa@....com,
        leonard.crestez@....com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Linux-imx@....com
Subject: Re: [PATCH] arm64: dts: imx8mn-ddr4-evk: Adjust 1.2GHz OPP voltage
 to OD mode

On Tue, Feb 18, 2020 at 09:52:32AM +0800, Anson Huang wrote:
> According to latest datasheet Rev.0, 10/2019, there is restriction
> as below:
> 
> "If VDD_SOC/GPU/DDR = 0.95V, then VDD_ARM must be >= 0.95V."
> 
> As by default SoC is running at OD mode(VDD_SOC = 0.95V), so
> VDD_ARM 1.2GHz OPP's voltage should be increased to 0.95V.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>
> ---
>  arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts b/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> index 2497eeb..7a61a1a 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mn-ddr4-evk.dts
> @@ -13,6 +13,12 @@
>  	compatible = "fsl,imx8mn-ddr4-evk", "fsl,imx8mn";
>  };
>  
> +&a53_opp_table {
> +	opp-1200000000 {
> +		opp-microvolt = <950000>;
> +	};
> +};
> +

The restriction applies to SoC rather than a particular board, right?
If so, the change should be made in imx8mn.dtsi?

Shawn

>  &A53_0 {
>  	cpu-supply = <&buck2_reg>;
>  };
> -- 
> 2.7.4
>