Re: [PATCH] ARM: dts: r8a7742-iwg21d-q7-dbcm-ca: Add missing camera regulators

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Kieran,

On Fri, Oct 15, 2021 at 2:25 PM Kieran Bingham
<kieran.bingham@ideasonboard.com> wrote:
> Quoting Kieran Bingham (2021-10-15 13:17:27)
> > Quoting Geert Uytterhoeven (2021-10-14 15:44:12)
> > > make dtbs_check:
> > >
> > >     arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ca.dt.yaml: ov5640@3c: 'AVDD-supply' is a required property
> > >             From schema: Documentation/devicetree/bindings/media/i2c/ovti,ov5640.yaml
> > >     arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ca.dt.yaml: ov5640@3c: 'DVDD-supply' is a required property
> > >             From schema: Documentation/devicetree/bindings/media/i2c/ovti,ov5640.yaml
> > >     arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ca.dt.yaml: ov5640@3c: 'DOVDD-supply' is a required property
> > >             From schema: Documentation/devicetree/bindings/media/i2c/ovti,ov5640.yaml
> > >
> > > Fix this by describing the missing regulators.
> > >
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > > ---
> > > [PATCH v2 27/52] dt-bindings: media: Convert OV5640 binding to a schema
> > > https://lore.kernel.org/all/20210901091852.479202-28-maxime@cerno.tech/
> >
> > Given that the OV5640 datasheet explicitly states
> >
> >  "
> >  If 2.8V is used for I/O power, due to a high voltage drop at the
> >  internal DVDD regulator, there is a potential heat issue. Hence, for a
> >  2.8V power system, OmniVision recommends using an external DVDD source.
> >  Due to the higher power down current when using an external DVDD
> >  source, OmniVision strongly recommends cutting off all powers,
> >  including the external DVDD, when the sensor is not in use in the case
> >  of 2.8V I/O and external DVDD.
> >  "
> >
> > I was expecting these not to be fixed regulators. But having checked in
> > with you, I hear you've followed the schematics so that is what we have
> > to live with ;-)
> >
> >
> > Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

Thanks!

> > > --- a/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ca.dts
> > > +++ b/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ca.dts
> > > @@ -44,6 +44,22 @@ mclk_cam4: mclk-cam4 {
> > >                 #clock-cells = <0>;
> > >                 clock-frequency = <26000000>;
> > >         };
> > > +
> > > +       reg_1p8v: 1p8v {
> > > +               compatible = "regulator-fixed";
> > > +               regulator-name = "1P8V";
> > > +               regulator-min-microvolt = <1800000>;
> > > +               regulator-max-microvolt = <1800000>;
> > > +               regulator-always-on;
> > > +       };
> > > +
> > > +       reg_2p8v: 2p8v {
> > > +               compatible = "regulator-fixed";
> > > +               regulator-name = "2P8V";
> > > +               regulator-min-microvolt = <2800000>;
> > > +               regulator-max-microvolt = <2800000>;
> > > +               regulator-always-on;
> > > +       };
> > >  };
> > >
> > >  &avb {
> > > diff --git a/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ov5640-single.dtsi b/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ov5640-single.dtsi
> > > index 70c72ba4fe724a70..40cef0b1d1e6267f 100644
> > > --- a/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ov5640-single.dtsi
> > > +++ b/arch/arm/boot/dts/r8a7742-iwg21d-q7-dbcm-ov5640-single.dtsi
> > > @@ -17,6 +17,9 @@ ov5640@3c {
> > >                 reg = <0x3c>;
> > >                 clocks = <&MCLK_CAM>;
> > >                 clock-names = "xclk";
> > > +               AVDD-supply = <&reg_2p8v>;
> > > +               DOVDD-supply = <&reg_2p8v>;
> > > +               DVDD-supply = <&reg_1p8v>;
>
> I see in the bindings however that this DVDD is specified as 1.5v.
> I assume 1.8 is how the hardware is wired, and is within a tolerence
> range?
>
> The OV5640 datasheet does show
>  - VDD-A: Analog: 2.8v (AVDD)
>  - VDD-DA: Digital Core: 1.5v (DVDD)
>  - VDD-IO: Digital IO: 1.8v (DOVDD)
>
> (Brackets my interpretations)

That matches the part "digital inputs (typical conditions: AVDD =
2.8V, DVDD = 1.5V, DOVDD = 1.8V)" in Table 8-3 of the datasheet.

> Should DVDD be 1.5v?

I have used what's in the schematics I have.  Which matches the
part "internal DVDD short to DVDD, DVP output, AVDD = 2.8V, DOVDD =
2.8V" with footnote "using the internal DVDD regulator is strongly
recommended for minimum power down current" in Table 8-3, I guess.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds