[PATCH 1/4] arm64: dts: imx8mp: Describe VDD_ARM run and standby voltage for DH i.MX8M Plus DHCOM SoM

[Marek Vasut]

On 9/7/23 17:45, Marco Felsch wrote:
> Hi Marek,

Hi,

> On 23-08-31, Marek Vasut wrote:
>> Describe VDD_ARM (BUCK2) run and standby voltage in DT.
>>
>> Signed-off-by: Marek Vasut <marex at denx.de>
>> ---
>> Cc: Conor Dooley <conor+dt at kernel.org>
>> Cc: Fabio Estevam <festevam at gmail.com>
>> Cc: Frieder Schrempf <frieder.schrempf at kontron.de>
>> Cc: Geert Uytterhoeven <geert+renesas at glider.be>
>> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt at linaro.org>
>> Cc: Magnus Damm <magnus.damm at gmail.com>
>> Cc: Marek Vasut <marex at denx.de>
>> Cc: NXP Linux Team <linux-imx at nxp.com>
>> Cc: Peng Fan <peng.fan at nxp.com>
>> Cc: Pengutronix Kernel Team <kernel at pengutronix.de>
>> Cc: Rob Herring <robh+dt at kernel.org>
>> Cc: Sascha Hauer <s.hauer at pengutronix.de>
>> Cc: Shawn Guo <shawnguo at kernel.org>
>> Cc: devicetree at vger.kernel.org
>> Cc: linux-arm-kernel at lists.infradead.org
>> ---
>>   arch/arm64/boot/dts/freescale/imx8mp-dhcom-som.dtsi | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-dhcom-som.dtsi b/arch/arm64/boot/dts/freescale/imx8mp-dhcom-som.dtsi
>> index cb1953d14aa90..1644b56c3953d 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mp-dhcom-som.dtsi
>> +++ b/arch/arm64/boot/dts/freescale/imx8mp-dhcom-som.dtsi
>> @@ -293,6 +293,8 @@ buck1: BUCK1 {	/* VDD_SOC (dual-phase with BUCK3) */
>>   			};
>>   
>>   			buck2: BUCK2 {	/* VDD_ARM */
>> +				nxp,dvs-run-voltage = <950000>;
> 
> Why do we need to set the "nxp,dvs-run-voltage"? If I read the driver
> correctly, then nxp,dvs-run-voltage and regulator-min/max-microvolt are
> touching the same register.

My understanding is that the nxp,dvs-run-voltage selects the default 
regulator voltage which is configured early on once the regulator is 
detected in DT (see of_parse_cb callback in the PCA9450 regulator 
driver) and may be higher than regulator-min-microvolt, while later on 
DVFS can adjust the regulator in range of regulator-min-microvolt to 
regulator-max-microvolt .

>> +				nxp,dvs-standby-voltage = <850000>;
>>   				regulator-min-microvolt = <850000>;
>>   				regulator-max-microvolt = <1000000>;

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