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

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Date:   Tue, 15 Nov 2022 11:02:51 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de,
        Peng Fan <peng.fan@....com>, linux-kernel@...r.kernel.org,
        linux-imx@....com, kernel@...gutronix.de, festevam@...il.com,
        linux-arm-kernel@...ts.infradead.org
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.

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:

> +				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
> 
> 
>