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

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Message-ID: <20221116094900.52tbr2o3z4hvaw4z@pengutronix.de>
Date:   Wed, 16 Nov 2022 10:49:00 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Peng Fan <peng.fan@....com>
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

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? 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
> > >
> > >
> > >
>