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Date:   Tue, 31 Mar 2020 17:12:53 +0200
From:   Marco Felsch <m.felsch@pengutronix.de>
To:     Robert Foss <robert.foss@linaro.org>
Cc:     Dongchun Zhu <dongchun.zhu@mediatek.com>,
        Fabio Estevam <festevam@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Tomasz Figa <tfiga@chromium.org>, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 1/3] media: dt-bindings: ov8856: Document YAML bindings
Message-ID: <20200331151253.q6ody3erhvsabznz@pengutronix.de>
References: <20200331133346.372517-1-robert.foss@linaro.org>
 <20200331133346.372517-2-robert.foss@linaro.org>
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Hi Robert,

On 20-03-31 15:33, Robert Foss wrote:
> From: Dongchun Zhu <dongchun.zhu@mediatek.com>
> 
> This patch adds documentation of device tree in YAML schema for the
> OV8856 CMOS image sensor.
> 
> Signed-off-by: Dongchun Zhu <dongchun.zhu@mediatek.com>
> Signed-off-by: Robert Foss <robert.foss@linaro.org>
> ---
> 
> - Changes since v5:
>   * Add assigned-clocks and assigned-clock-rates
>   * robher: dt-schema errors
> 
> - Changes since v4:
>   * Fabio: Change reset-gpio to GPIO_ACTIVE_LOW, explain in description
>   * Add clock-lanes property to example
>   * robher: Fix syntax error in devicetree example
> 
> - Changes since v3:
>   * robher: Fix syntax error
>   * robher: Removed maxItems
>   * Fixes yaml 'make dt-binding-check' errors
> 
> - Changes since v2:
>   Fixes comments from from Andy, Tomasz, Sakari, Rob.
>   * Convert text documentation to YAML schema.
> 
> - Changes since v1:
>   Fixes comments from Sakari, Tomasz
>   * Add clock-frequency and link-frequencies in DT
> 
>  .../devicetree/bindings/media/i2c/ov8856.yaml | 150 ++++++++++++++++++
>  MAINTAINERS                                   |   1 +
>  2 files changed, 151 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> new file mode 100644
> index 000000000000..beeddfbb8709
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> @@ -0,0 +1,150 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright (c) 2019 MediaTek Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/media/i2c/ov8856.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Omnivision OV8856 CMOS Sensor Device Tree Bindings
> +
> +maintainers:
> +  - Ben Kao <ben.kao@intel.com>
> +  - Dongchun Zhu <dongchun.zhu@mediatek.com>
> +
> +description: |-
> +  The Omnivision OV8856 is a high performance, 1/4-inch, 8 megapixel, CMOS
> +  image sensor that delivers 3264x2448 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. This chip is programmable
> +  through I2C and two-wire SCCB. The sensor output is available via CSI-2
> +  serial data output (up to 4-lane).
> +
> +properties:
> +  compatible:
> +    const: ovti,ov8856
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  clock-names:
> +    description:
> +      Input clock for the sensor.
> +    items:
> +      - const: xvclk
> +
> +  clock-frequency:
> +    description:
> +      Frequency of the xvclk clock in Hertz.

Why do we need this here?

> +  assigned-clocks:
> +    description:
> +      Input clock for the sensor.
> +
> +  assigned-clock-rates:
> +    description:
> +      Frequency of the xvclk clock in Hertz.

Also this isn't related to the chip. You need this because you are using
a qcom platform which provides the clock.

IMHO you only need to specify the clock. You can get the frequency with
the clk_get_rate() function.

> +  dovdd-supply:
> +    description:
> +      Definition of the regulator used as interface power supply.

Phandle to the interface power supply regulator?

> +
> +  avdd-supply:
> +    description:
> +      Definition of the regulator used as analog power supply.
> +
> +  dvdd-supply:
> +    description:
> +      Definition of the regulator used as digital power supply.
> +
> +  reset-gpios:
> +    description:
> +      The phandle and specifier for the GPIO that controls sensor reset.
> +      This corresponds to the hardware pin XSHUTDOWN which is physically
> +      active low.
> +
> +  port:
> +    type: object
> +    additionalProperties: false
> +    description:
> +      A node containing input and output port nodes with endpoint definitions
> +      as documented in
> +      Documentation/devicetree/bindings/media/video-interfaces.txt
> +
> +    properties:
> +      endpoint:
> +        type: object
> +
> +        properties:
> +          clock-lanes:
> +            maxItems: 1
> +
> +          data-lanes:
> +            maxItems: 1
> +
> +          remote-endpoint: true
> +
> +        required:
> +          - clock-lanes
> +          - data-lanes
> +          - remote-endpoint
> +
> +    required:
> +      - endpoint
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +  - clock-frequency
> +  - assigned-clocks
> +  - assigned-clock-rates
> +  - dovdd-supply
> +  - avdd-supply
> +  - dvdd-supply
> +  - reset-gpios
> +  - port
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/clock/qcom,camcc-sdm845.h>

IMHO we should avoid examples with hardware specific includes.

> +
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        ov8856: camera@10 {
> +            compatible = "ovti,ov8856";
> +            reg = <0x10>;
> +
> +            reset-gpios = <&pio 111 GPIO_ACTIVE_LOW>;
> +            pinctrl-names = "default";
> +            pinctrl-0 = <&clk_24m_cam>;
> +
> +            clocks = <&clock_camcc CAM_CC_MCLK0_CLK>;
> +            clock-names = "xvclk";
> +            clock-frequency = <19200000>;
> +            assigned-clocks = <&clock_camcc CAM_CC_MCLK0_CLK>;
> +            assigned-clock-rates = <19200000>;
> +
> +            avdd-supply = <&mt6358_vcama2_reg>;
> +            dvdd-supply = <&mt6358_vcamd_reg>;
> +            dovdd-supply = <&mt6358_vcamio_reg>;
> +
> +            port {
> +                wcam_out: endpoint {
> +                    remote-endpoint = <&mipi_in_wcam>;
> +                    clock-lanes = <0>;
> +                    data-lanes = <1 2 3 4>;
> +                    link-frequencies = /bits/ 64 <360000000 180000000>;

Should we add the link-frequencies as optional param?

Regards,
  Marco

> +                };
> +            };
> +        };
> +    };
> +...
> \ No newline at end of file
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a6fbdf354d34..0f99e863978a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12355,6 +12355,7 @@ L:	linux-media@vger.kernel.org
>  T:	git git://linuxtv.org/media_tree.git
>  S:	Maintained
>  F:	drivers/media/i2c/ov8856.c
> +F:	Documentation/devicetree/bindings/media/i2c/ov8856.yaml
>  
>  OMNIVISION OV9650 SENSOR DRIVER
>  M:	Sakari Ailus <sakari.ailus@linux.intel.com>
> -- 
> 2.25.1
> 
> 

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