RE: [PATCH v2 2/3] arm64: dts: exynos: ExynosAutov920: Add regulators for the USB

[pritam.sutar]

Hi Krzysztof,

> -----Original Message-----
> From: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
> Sent: Thursday, January 22, 2026 7:04 PM
> To: Pritam Manohar Sutar <pritam.sutar@xxxxxxxxxxx>; robh@xxxxxxxxxx;
> krzk+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx; alim.akhtar@xxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> samsung-soc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> rosa.pila@xxxxxxxxxxx; dev.tailor@xxxxxxxxxxx;
> faraz.ata@xxxxxxxxxxx; muhammed.ali@xxxxxxxxxxx;
> selvarasu.g@xxxxxxxxxxx
> Subject: Re: [PATCH v2 2/3] arm64: dts: exynos: ExynosAutov920: Add
> regulators for the USB
> 
> On 22/01/2026 14:07, Pritam Manohar Sutar wrote:
> > Add dummy regulator for USB and PHY supplies.
> >
> > Add vbus regulator that is enabled by GPIO pin.
> >
> > Signed-off-by: Pritam Manohar Sutar <pritam.sutar@xxxxxxxxxxx>
> > ---
> >  .../boot/dts/exynos/exynosautov920-sadk.dts   | 139
> ++++++++++++++++++
> >  1 file changed, 139 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/exynos/exynosautov920-sadk.dts
> > b/arch/arm64/boot/dts/exynos/exynosautov920-sadk.dts
> > index a397f068ed53..f90f7704597c 100644
> > --- a/arch/arm64/boot/dts/exynos/exynosautov920-sadk.dts
> > +++ b/arch/arm64/boot/dts/exynos/exynosautov920-sadk.dts
> > @@ -52,6 +52,76 @@ memory@80000000 {
> >  		      <0x8 0x80000000 0x1 0xfba00000>,
> >  		      <0xa 0x00000000 0x2 0x00000000>;
> >  	};
> > +
> > +	/* TODO: Remove this once PMIC is implemented  */
> > +	dummy_regulator: regulator-0 {
> > +		 compatible = "regulator-fixed";
> > +		 regulator-name = "dummy_regulator";
> > +	};
> > +
> > +	usbdrd31_dwc3_vbus: usbdrd31_dwc3-vbus {
> 
> Please use name for all fixed regulators which matches current format
> recommendation: 'regulator-[0-9]v[0-9]'
> 
> https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/
> Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
> 
> None of the regulators are called like you wrote. Really NONE.
> 

Thank you for the references. Will bring changes for regulator's name 
and labels as 
			
-       usbdrd31_dwc3_vbus: usbdrd31_dwc3-vbus {
+       reg_usbdrd31_dwc3_vbus: regulator-1 {

> Also, carefully follow DTS coding style.
> 

Sorry for that. Checking the code and will update in next 
patchset version (v3).

> > +	       compatible = "regulator-fixed";
> > +	       regulator-name = "usbdrd31_dwc3-vbus";
> > +	       regulator-min-microvolt = <5000000>;
> > +	       regulator-max-microvolt = <5000000>;
> > +	       enable-active-high;
> > +	       regulator-always-on;
> > +	       gpio = <&gpp2 0 GPIO_ACTIVE_HIGH>;
> > +	};
> > +
> > +	/* Use gpio for enabling vbus regulator */
> > +	usb_phy0: usb-phy0 {
> 
> usb-phy-0
> 
> > +		compatible = "usb-nop-xceiv";
> > +		vbus-supply = <&usbdrd31_dwc3_vbus>;
> 
> That's pretty incomplete. Why do you need such node - just to toggle
> regulator?
> 

There is no external controller to detect or switch the USB modes 
automatically rather it is switched using userspace control 
(sysfs attributes) for this SoC.  GPIO pins are required to enable 
vbus regulators. Existing phy-generic and fixed regulator are used to 
avoid making any USB driver changes for the same purpose and it is 
referenced from below -
				
https://lore.kernel.org/r/20230825215445.28309-3-semen.protsenko@xxxxxxxxxx
a12af1c20751340ab6e449a5ef78b37d31123aca: ARM64: dts: marvell: armada-3720-db: Add phy for USB3
		
> > +	};
> 
> ...
> 
> > +&usbdrd20_phy2 {
> > +	dvdd-supply = <&dummy_regulator>;
> > +	vdd18-supply = <&dummy_regulator>;
> > +	vdd33-supply = <&dummy_regulator>;
> > +};
> > +
> > +&usbdrd20_dwc3_2 {
> > +	maximum-speed = "high-speed";
> > +	usb-phy = <&usb_phy3>;
> > +};
> > +
> > +&usbdrd20_2 {
> > +	vdd10-supply = <&dummy_regulator>;
> > +	vdd33-supply = <&dummy_regulator>;
> > +};
> 
> That's a bit too much of dummies. This is heavily incomplete. You need to
> bring back the PMIC first.
> 

Presently, relying on USB LDOs being enabled by the bootloader in this
automotive SoC. However, we understand the concern and it is added in case 
if anyone wants to use implemented PMIC in future. For now, would like 
to proceed with the dummy regulators to enable the required USB features. 
Dummy regulators are clearly marked so that they will be replaced once 
the PMIC driver is fully up.

> 
> Best regards,
> Krzysztof

Thank you,

Regards,
Pritam