Re: [PATCH RESEND 3/4] ARM: dts: imx6ul: phycore: Change USB LDO voltage for usb compliance

[Shawn Guo <shawnguo@kernel.org>]

On Mon, Jan 31, 2022 at 09:05:25AM +0100, Andrej Picej wrote:
> From: Yunus Bas <y.bas@phytec.de>
> 
> According to the NXP usb compliance reference, the USB data lines for
> Full/Low speed are connected to the ARM USB LDO, which is set to
> minimum-voltage = 2.6V and maximum-voltage = 3.4 V. When the regulator
> is deactivated, the data lines are defaulty driven with 2.6V, which is
> not USB Full-Speed compliant. To be compliant, we need to activate the
> USB LDO regulator and set it to the value of 3V, which is the specified
> value in the USB specification.
> 
> Signed-off-by: Yunus Bas <y.bas@phytec.de>
> Signed-off-by: Andrej Picej <andrej.picej@norik.com>
> ---
>  arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi b/arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi
> index 3cddc68917a0..2e03be3d43ec 100644
> --- a/arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi
> +++ b/arch/arm/boot/dts/imx6ul-phytec-phycore-som.dtsi
> @@ -83,6 +83,11 @@ eeprom@52 {
>  	};
>  };
>  
> +&reg_3p0 {
> +	regulator-min-microvolt = <3000000>;
> +	regulator-always-on;

Rather than setting it always-on, shouldn't the consumer of the
regulator turn it on/off as needed?

Shawn

> +};
> +
>  &snvs_poweroff {
>  	status = "okay";
>  };
> -- 
> 2.25.1
>