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Date:   Mon, 11 Jul 2022 14:36:29 +0200
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Cc:     linuxfancy@googlegroups.com, linux-amarula@amarulasolutions.com,
        quentin.schulz@theobroma-systems.com,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Daniel Scally <djrscally@gmail.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 5/6] media: dt-bindings: ov5693: document YAML binding
Message-ID: <20220711123629.xcknkluu3wwokoz3@uno.localdomain>
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Hi Tommaso

On Mon, Jul 11, 2022 at 01:11:08PM +0200, Tommaso Merciai wrote:
> Hi Jacopo,
> Thanks for your review.
>
> On Mon, Jul 11, 2022 at 11:36:59AM +0200, Jacopo Mondi wrote:
> > Hi Tommaso, Krzysztof,
> >
> >    This has been reviewed by Krzysztof already, so I guess it's fine,
> > but let me ask anyway
> >
> > On Thu, Jun 30, 2022 at 03:48:34PM +0200, Tommaso Merciai wrote:
> > > Add documentation of device tree in YAML schema for the OV5693
> > > CMOS image sensor from Omnivision
> > >
> > > Signed-off-by: Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
> > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> > > ---
> > > Changes since v1:
> > >  - Fix allOf position as suggested by Krzysztof
> > >  - Remove port description as suggested by Krzysztof
> > >  - Fix EOF as suggested by Krzysztof
> > >
> > > Changes since v2:
> > >  - Fix commit body as suggested by Krzysztof
> > >
> > > Changes since v3:
> > >  - Add reviewed-by tags, suggested by Jacopo, Krzysztof
> > >
> > > Changes since v4:
> > >  - Remove wrong Sakari reviewed-by tag, suggested by Krzysztof, Sakari
> > >
> > >  .../bindings/media/i2c/ovti,ov5693.yaml       | 106 ++++++++++++++++++
> > >  MAINTAINERS                                   |   1 +
> > >  2 files changed, 107 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/media/i2c/ovti,ov5693.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/i2c/ovti,ov5693.yaml b/Documentation/devicetree/bindings/media/i2c/ovti,ov5693.yaml
> > > new file mode 100644
> > > index 000000000000..b83c9fc04023
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/media/i2c/ovti,ov5693.yaml
> > > @@ -0,0 +1,106 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +# Copyright (c) 2022 Amarulasolutions
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/media/i2c/ovti,ov5693.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Omnivision OV5693 CMOS Sensor
> > > +
> > > +maintainers:
> > > +  - Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
> > > +
> > > +description: |
> > > +  The Omnivision OV5693 is a high performance, 1/4-inch, 5 megapixel, CMOS
> > > +  image sensor that delivers 2592x1944 at 30fps. It provides full-frame,
> > > +  sub-sampled, and windowed 10-bit MIPI images in various formats via the
> > > +  Serial Camera Control Bus (SCCB) interface.
> > > +
> > > +  OV5693 is controlled via I2C and two-wire Serial Camera Control Bus (SCCB).
> > > +  The sensor output is available via CSI-2 serial data output (up to 2-lane).
> > > +
> > > +allOf:
> > > +  - $ref: /schemas/media/video-interface-devices.yaml#
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: ovti,ov5693
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  clocks:
> > > +    description:
> > > +      System input clock (aka XVCLK). From 6 to 27 MHz.
> > > +    maxItems: 1
> > > +
> > > +  dovdd-supply:
> > > +    description:
> > > +      Digital I/O voltage supply, 1.8V.
> > > +
> > > +  avdd-supply:
> > > +    description:
> > > +      Analog voltage supply, 2.8V.
> > > +
> > > +  dvdd-supply:
> > > +    description:
> > > +      Digital core voltage supply, 1.2V.
> > > +
> > > +  reset-gpios:
> > > +    description:
> > > +      The phandle and specifier for the GPIO that controls sensor reset.
> > > +      This corresponds to the hardware pin XSHUTDN which is physically
> > > +      active low.
> > > +    maxItems: 1
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - clocks
> > > +  - dovdd-supply
> > > +  - avdd-supply
> > > +  - dvdd-supply
> >
> > Should supplies be made mandatory ? Sensors are often powered by fixed
> > rails. Do we want DTS writers to create "fixed-regulators" for all of
> > them ? The fact the regulator framework creates dummies if there's no
> > entry in .dts for a regulator makes me think it's fine to have them
> > optional, but I understand how Linux works should not be an indication
> > of how a bindings should look like.
>
> You are right, this depends on hw design and yes in many cases sensors are
> powered by fixed rails.
> But let me say, I see some design in wich I have to handle these signals and
> in fact are mandatory.

It's fine if you have to handle them, my question is it if it should
be -mandatory- to specify them

>
> I check also in others binding's doc like:
>
>  - Documentation/devicetree/bindings/media/i2c/ovti,ov5640.yaml
>  - Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
>  - Documentation/devicetree/bindings/media/i2c/ovti,ov8865.yaml
>  ...
>
> These keep this information.
>
> Anyway, You suggest to drop off:
>
>  - dovdd-supply
>  - avdd-supply
>  - dvdd-supply
>
> From required properties, right?

Yes, I wonder if they should be required. As usual there's a
bunch of different styles in media/i2c/ and it's not always easy to
distinguish which ones are actually intended from the ones which are
instead the result of copying the existing.


>
> Tommmaso
>
> >
> > > +  - port
> > > +
> > > +unevaluatedProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/clock/px30-cru.h>
> > > +    #include <dt-bindings/gpio/gpio.h>
> > > +    #include <dt-bindings/pinctrl/rockchip.h>
> > > +
> > > +    i2c {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        ov5693: camera@36 {
> > > +            compatible = "ovti,ov5693";
> > > +            reg = <0x36>;
> > > +
> > > +            reset-gpios = <&gpio2 RK_PB1 GPIO_ACTIVE_LOW>;
> > > +            pinctrl-names = "default";
> > > +            pinctrl-0 = <&cif_clkout_m0>;
> > > +
> > > +            clocks = <&cru SCLK_CIF_OUT>;
> > > +            assigned-clocks = <&cru SCLK_CIF_OUT>;
> > > +            assigned-clock-rates = <19200000>;
> > > +
> > > +            avdd-supply = <&vcc_1v8>;
> > > +            dvdd-supply = <&vcc_1v2>;
> > > +            dovdd-supply = <&vcc_2v8>;
> > > +
> > > +            rotation = <90>;
> > > +            orientation = <0>;
> > > +
> > > +            port {
> > > +                ucam_out: endpoint {
> > > +                    remote-endpoint = <&mipi_in_ucam>;
> > > +                    data-lanes = <1 2>;
> > > +                    link-frequencies = /bits/ 64 <450000000>;
> > > +                };
> > > +            };
> > > +        };
> > > +    };
> > > +
> > > +...
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index 1fc9ead83d2a..844307cb20c4 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -14719,6 +14719,7 @@ M:	Daniel Scally <djrscally@gmail.com>
> > >  L:	linux-media@vger.kernel.org
> > >  S:	Maintained
> > >  T:	git git://linuxtv.org/media_tree.git
> > > +F:	Documentation/devicetree/bindings/media/i2c/ovti,ov5693.yaml
> > >  F:	drivers/media/i2c/ov5693.c
> > >
> > >  OMNIVISION OV5695 SENSOR DRIVER
> > > --
> > > 2.25.1
> > >
>
> --
> Tommaso Merciai
> Embedded Linux Engineer
> tommaso.merciai@amarulasolutions.com
> __________________________________
>
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> Via Le Canevare 30, 31100 Treviso, Veneto, IT
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