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Date:   Mon, 11 Jul 2022 13:11:08 +0200
From:   Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
To:     Jacopo Mondi <jacopo@jmondi.org>
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: <20220711111108.GA66765@tom-ThinkPad-T14s-Gen-2i>
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 <20220711093659.mf7i4uqtrejtfong@uno.localdomain>
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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.

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?

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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