linux-kernel - Re: [PATCH RESEND] ARM: dts: sun8i: r40: open the regulator aldo1

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Message-ID: <20231221103906.1830ef94@donnerap.manchester.arm.com>
Date: Thu, 21 Dec 2023 10:39:06 +0000
From: Andre Przywara <andre.przywara@....com>
To: fuyao <fuyao@...erm.com>
Cc: fuyao <fuyao1697@....com>, Rob Herring <robh+dt@...nel.org>, Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley
 <conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
 <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, Alexandre
 TORGUE <alexandre.torgue@...com>, Enric Balletbo i Serra
 <eballetbo@...il.com>, Baruch Siach <baruch@...s.co.il>, Paul Barker
 <paul.barker@...cloud.com>, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] ARM: dts: sun8i: r40: open the regulator aldo1

On Thu, 21 Dec 2023 10:20:49 +0800
fuyao <fuyao@...erm.com> wrote:

Hi,

thanks for the reply!

> On Wed, Dec 20, 2023 at 03:04:00PM +0000, Andre Przywara wrote:
> > On Wed, 20 Dec 2023 16:18:43 +0800
> > fuyao <fuyao1697@....com> wrote:
> > 
> > Hi,
> >   
> > > the aldo1 is connect regulator pin which power the TV.  
> > 
> > What do you mean with that? That ALDO1 is connected to VCC-TVOUT and/or
> > VCC-TVIN on the R40 SoC?  
> 
> The ALDO1 is connected to VCC-TVOUT on the R40 Soc.

Ah, thanks for the confirmation.

> > > The USB core use TV ref as reference Voltage.  
> > 
> > The USB core in the SoC? So pin VCC-USB, which requires 3.3V, the same
> > voltage as the TV pins?
> > Which means this doesn't really have much to do with TV, it's just that
> > USB and also "TV" are supplied by ALDO1?  
> 
> The internal USB PHY requires a reference voltage. It seems that in
> order to save costs, the reference voltage of the TVOUT module is used.

Do you mean a USB *reference* voltage that is separate from the USB PHY
power supply voltage, so pin VCC-USB on the SoC? And that it is internally
connected to some TV-OUT related circuits? So that would apply to all
devices using the R40 SoC then?

Or is it simply that the SoC pins VCC-TVOUT and VCC-USB are connected
together, on this SoM?
Do you have access to some schematic? I couldn't find one online easily,
so cannot check this myself.

Thanks,
Andre

> > > Signed-off-by: fuyao <fuyao1697@....com>
> > > ---
> > >  arch/arm/boot/dts/allwinner/sun8i-r40-feta40i.dtsi | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/arch/arm/boot/dts/allwinner/sun8i-r40-feta40i.dtsi b/arch/arm/boot/dts/allwinner/sun8i-r40-feta40i.dtsi
> > > index 9f39b5a2bb35..8906170461df 100644
> > > --- a/arch/arm/boot/dts/allwinner/sun8i-r40-feta40i.dtsi
> > > +++ b/arch/arm/boot/dts/allwinner/sun8i-r40-feta40i.dtsi
> > > @@ -42,6 +42,13 @@ &pio {
> > >  	vcc-pg-supply = <&reg_dldo1>;
> > >  };
> > >  
> > > +&reg_aldo1 {
> > > +	regulator-always-on;  
> > 
> > So did USB never work before, with the DT as in mainline?
> >   
> 
> The USB can work, but is unstable. Occasionally disconnected because of
> the D+/D- electrical characteristics.
> 
> > For always-on regulators it would be good to see some rationale why this
> > cannot be referenced by its consumer. If it is really supplying the USB
> > core, that would be a reason, because we don't have a good way of
> > describing this.
> >   
> > > +	regulator-min-microvolt = <3300000>;
> > > +	regulator-max-microvolt = <3300000>;
> > > +	regulator-name = "vcc-aldo1";  
> > 
> > Regulators should be named after their users, so use something like:
> > 	regulator-name = "vcc-3v3-tv-usb";
> >   
> 
> thanks.
> 
> > That then also serves as documentation of why this is always on.
> > 
> > Cheers,
> > Andre
> >   
> > > +};
> > > +
> > >  &reg_aldo2 {
> > >  	regulator-always-on;
> > >  	regulator-min-microvolt = <1800000>;  
> >   
>