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

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Message-ID: <DB3PR0402MB391621D12FF3B43490505C7CF5EC0@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date:   Mon, 24 Feb 2020 02:01:50 +0000
From:   Anson Huang <anson.huang@....com>
To:     Shawn Guo <shawnguo@...nel.org>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Abel Vesa <abel.vesa@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] arm64: dts: imx8mn-ddr4-evk: Adjust 1.2GHz OPP voltage to
 OD mode

Hi, Shawn

> 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?

Yes, you are correct, for now, it is NOT related to board, I will do the change
in .dtsi in V2.

Anson