linux-kernel - Re: [PATCH 2/8] arm64: dts: imx8mm-kontron: Make sure SOC and DRAM supply voltages are correct

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Message-ID: <20211015035122.GE22881@dragon>
Date:   Fri, 15 Oct 2021 11:51:27 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Frieder Schrempf <frieder.schrempf@...tron.de>
Cc:     Frieder Schrempf <frieder@...s.de>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH 2/8] arm64: dts: imx8mm-kontron: Make sure SOC and DRAM
 supply voltages are correct

On Tue, Oct 05, 2021 at 03:10:14PM +0200, Frieder Schrempf wrote:
> On 05.10.21 08:53, Shawn Guo wrote:
> > On Thu, Sep 30, 2021 at 05:56:25PM +0200, Frieder Schrempf wrote:
> >> From: Frieder Schrempf <frieder.schrempf@...tron.de>
> >>
> >> VDD_SOC should be 800 mV in suspend and 850 mV in run mode. VDD_DRAM
> >> should be 950 mV for DDR clock frequencies of 1.5 GHz.
> >>
> >> This information is taken from the datasheet and the uboot-imx code.
> > 
> > I'm wondering where the existing settings were coming from?
> 
> Good question, but I can't really retrace now how I actually determined
> the values back then. Seems like I had failed to validate them properly.

Please update commit log with these background info.

Shawn

> 
> > 
> >>
> >> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
> >> ---
> >>  arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi | 6 ++++--
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> >> index 03b3516abd64..b12fb7ce6686 100644
> >> --- a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> >> +++ b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
> >> @@ -92,10 +92,12 @@ regulators {
> >>  			reg_vdd_soc: BUCK1 {
> >>  				regulator-name = "buck1";
> >>  				regulator-min-microvolt = <800000>;
> >> -				regulator-max-microvolt = <900000>;
> >> +				regulator-max-microvolt = <850000>;
> >>  				regulator-boot-on;
> >>  				regulator-always-on;
> >>  				regulator-ramp-delay = <3125>;
> >> +				nxp,dvs-run-voltage = <850000>;
> >> +				nxp,dvs-standby-voltage = <800000>;
> >>  			};
> >>  
> >>  			reg_vdd_arm: BUCK2 {
> >> @@ -111,7 +113,7 @@ reg_vdd_arm: BUCK2 {
> >>  			reg_vdd_dram: BUCK3 {
> >>  				regulator-name = "buck3";
> >>  				regulator-min-microvolt = <850000>;
> >> -				regulator-max-microvolt = <900000>;
> >> +				regulator-max-microvolt = <950000>;
> >>  				regulator-boot-on;
> >>  				regulator-always-on;
> >>  			};
> >> -- 
> >> 2.33.0
> >>