linux-kernel - RE: [PATCH V5 07/12] arm64: dts: imx8mn-evk: update vdd

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Message-ID: <DU0PR04MB941725DCB67C215999733C6688079@DU0PR04MB9417.eurprd04.prod.outlook.com>
Date:   Wed, 16 Nov 2022 15:47:01 +0000
From:   Peng Fan <peng.fan@....com>
To:     Marco Felsch <m.felsch@...gutronix.de>
CC:     "Peng Fan (OSS)" <peng.fan@....nxp.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH V5 07/12] arm64: dts: imx8mn-evk: update vdd_soc dvs
 voltage

> Subject: Re: [PATCH V5 07/12] arm64: dts: imx8mn-evk: update vdd_soc dvs
> voltage
> 
> On 22-11-16, Peng Fan wrote:
> > > Subject: Re: [PATCH V5 07/12] arm64: dts: imx8mn-evk: update vdd_soc
> > > dvs voltage
> > >
> > > Hi Peng,
> > >
> > > On 22-11-15, Peng Fan (OSS) wrote:
> > > > From: Peng Fan <peng.fan@....com>
> > > >
> > > > Per schematic, BUCK1 is for VDD_SOC&DRAM&PU_0V9. The
> > > > nxp,dvs-run-voltage and nxp,dvs-standby-voltage need set for
> > > > BUCK1, not
> > > BUCK2.
> > > > BUCK2 is for A53, which is handled by DVFS, so no need dvs property.
> > > >
> > > > Signed-off-by: Peng Fan <peng.fan@....com>
> > > > ---
> > > >  arch/arm64/boot/dts/freescale/imx8mn-evk.dts | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/boot/dts/freescale/imx8mn-evk.dts
> > > > b/arch/arm64/boot/dts/freescale/imx8mn-evk.dts
> > > > index 4eb467df5ba7..a5a7d74ec1d5 100644
> > > > --- a/arch/arm64/boot/dts/freescale/imx8mn-evk.dts
> > > > +++ b/arch/arm64/boot/dts/freescale/imx8mn-evk.dts
> > > > @@ -47,6 +47,8 @@ buck1: BUCK1{
> > > >  				regulator-boot-on;
> > > >  				regulator-always-on;
> > > >  				regulator-ramp-delay = <3125>;
> > > > +				nxp,dvs-run-voltage = <950000>;
> > >
> > > One last question on this. According the schematic the max should be
> > > 0.88/0.945V and you are going to set it to 0.950V.
> >
> > No, my schematic shows the TYP voltage is 0.85/0.95V.
> 
> I have the Rev.A2 i.MX8MNano DDR4 SoM schematic and TYP is listed as
> 0.8/0.9V. Is this different for different ram configurations?
[Peng Fan] 

It maybe DDR4 board support 2400MTS, LPDDR4 board support 3200MTS,
but I am not sure.

Regards,
Peng.

 Sorry for asking
> but the i.MX8MNano LPDDR4 schematic is not available.
> 
> > > According the driver the nxp,dvs-run-voltage is just the same as the
> > > normal regulator voltage. So I would suggest to just use the
> > > nxp,dvs-standby- voltage property to enable the DVS feature since
> > > the run voltage is already handled by the
> > > regulator-min-microvolt/regulator-max-microvolt. So it would be just:
> > It should be fine to not set nxp,dvs-run-voltage, because bootloader
> > already set that.
> 
> Okay, so leave the voltage as it is right now and just add the nxp,dvs-
> standby-voltage seems fine :)
> 
> Regards,
>   Marco
> 
> >
> > Thanks,
> > Peng.
> > >
> > > > +				nxp,dvs-standby-voltage = <750000>;
> > >
> > > Regards,
> > >   Marco
> > >
> > > >  			};
> > > >
> > > >  			buck2: BUCK2 {
> > > > @@ -56,8 +58,6 @@ buck2: BUCK2 {
> > > >  				regulator-boot-on;
> > > >  				regulator-always-on;
> > > >  				regulator-ramp-delay = <3125>;
> > > > -				nxp,dvs-run-voltage = <950000>;
> > > > -				nxp,dvs-standby-voltage = <850000>;
> > > >  			};
> > > >
> > > >  			buck4: BUCK4{
> > > > --
> > > > 2.37.1
> > > >
> > > >
> > > >
> >