linux-kernel - Re: [PATCH 1/3] dt-bindings: display: convert Atmel's HLCDC to DT schema

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Date: Wed, 10 Jan 2024 11:39:53 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Dharma Balasubiramani <dharma.b@...rochip.com>, sam@...nborg.org,
 bbrezillon@...nel.org, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
 claudiu.beznea@...on.dev, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, lee@...nel.org, thierry.reding@...il.com,
 u.kleine-koenig@...gutronix.de, linux-pwm@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: display: convert Atmel's HLCDC to DT
 schema

On 10/01/2024 11:25, Dharma Balasubiramani wrote:
> Convert the existing DT binding to DT schema of the Atmel's HLCDC display
> controller.
> 
> Signed-off-by: Dharma Balasubiramani <dharma.b@...rochip.com>
> ---
>  .../display/atmel/atmel,hlcdc-dc.yaml         | 133 ++++++++++++++++++
>  .../bindings/display/atmel/hlcdc-dc.txt       |  75 ----------
>  2 files changed, 133 insertions(+), 75 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/display/atmel/atmel,hlcdc-dc.yaml
>  delete mode 100644 Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
> 
> diff --git a/Documentation/devicetree/bindings/display/atmel/atmel,hlcdc-dc.yaml b/Documentation/devicetree/bindings/display/atmel/atmel,hlcdc-dc.yaml
> new file mode 100644
> index 000000000000..49ef28646c48
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/atmel/atmel,hlcdc-dc.yaml
> @@ -0,0 +1,133 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright (C) 2024 Microchip Technology, Inc. and its subsidiaries

What about original copyrights from TXT file? Although conversion is
quite independent, I could imagine some lawyer would call it a
derivative work of original TXT.

If you decide to add explicit copyrights (which anyway I do not
understand why), then please make it signed off by some of your lawyers
to be sure that you really claim that, in respect of other people
copyrights.

> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/atmel/atmel,hlcdc-dc.yaml#

Filename like compatible.

> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Atmel's HLCDC (High LCD Controller) DRM driver

Driver as Linux driver? Not suitable for bindings, so please drop.

> +
> +maintainers:
> +  - Nicolas Ferre <nicolas.ferre@...rochip.com>
> +  - Alexandre Belloni <alexandre.belloni@...tlin.com>
> +  - Claudiu Beznea <claudiu.beznea@...on.dev>
> +
> +description: |
> +  Device-Tree bindings for Atmel's HLCDC DRM driver. The Atmel HLCDC Display

Drop entire first sentence and instead describe hardware.

> +  Controller is a subdevice of the HLCDC MFD device.
> +  # See ../../mfd/atmel,hlcdc.yaml for more details.

Full paths please.

> +
> +properties:
> +  compatible:
> +    const: atmel,hlcdc-display-controller
> +
> +  pinctrl-names:
> +    const: default
> +
> +  pinctrl-0: true

Why do you need these two? Are they really required?

> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +  port@0:
> +    $ref: /schemas/graph.yaml#/$defs/port-base
> +    unevaluatedProperties: false
> +    description:
> +      Output endpoint of the controller, connecting the LCD panel signals.
> +
> +    properties:
> +      '#address-cells':
> +        const: 1
> +
> +      '#size-cells':
> +        const: 0
> +
> +      reg:
> +        maxItems: 1
> +
> +      endpoint:
> +        $ref: /schemas/graph.yaml#/$defs/endpoint-base

Hm, why do you reference endpoint-base? This looks oddly different than
all other bindings for such devices, so please explain why.

> +        unevaluatedProperties: false
> +        description:
> +          Endpoint connecting the LCD panel signals.
> +
> +        properties:
> +          bus-width:
> +            description: |
> +              Any endpoint grandchild node may specify a desired video interface according to
> +              ../../media/video-interfaces.yaml, specifically "bus-width" whose recognized

Drop redundant information. Don't you miss some $ref?


> +              values are <12>, <16>, <18> and <24>, and override any output mode selection
> +              heuristic, forcing "rgb444","rgb565", "rgb666" and "rgb888" respectively.
> +            enum: [ 12, 16, 18, 24 ]
> +
> +additionalProperties: false

This goes after required:

> +
> +required:
> +  - '#address-cells'
> +  - '#size-cells'
> +  - compatible
> +  - pinctrl-names
> +  - pinctrl-0
> +  - port@0
> +
> +examples:
> +  - |
> +    #include <dt-bindings/clock/at91.h>
> +    #include <dt-bindings/dma/at91.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    //Example 1

Drop

> +    hlcdc: hlcdc@...30000 {

Node names should be generic. See also an explanation and list of
examples (not exhaustive) in DT specification:
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation


> +      compatible = "atmel,sama5d3-hlcdc";
> +      reg = <0xf0030000 0x2000>;
> +      interrupts = <36 IRQ_TYPE_LEVEL_HIGH 0>;
> +      clocks = <&lcdc_clk>, <&lcdck>, <&clk32k>;
> +      clock-names = "periph_clk","sys_clk", "slow_clk";

This part does not look related... If this is part of other device,
usually it is enough to have just one complete example.

Also, fix coding style - space after ,

> +
> +      hlcdc-display-controller {
> +        compatible = "atmel,hlcdc-display-controller";
> +        pinctrl-names = "default";
> +        pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb888>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        port@0 {
> +          #address-cells = <1>;
> +          #size-cells = <0>;
> +          reg = <0>;
> +
> +          hlcdc_panel_output: endpoint@0 {
> +            reg = <0>;
> +            remote-endpoint = <&panel_input>;
> +          };
> +        };
> +      };
> +
> +      hlcdc_pwm: hlcdc-pwm {
> +        compatible = "atmel,hlcdc-pwm";

How is this related?

> +        pinctrl-names = "default";
> +        pinctrl-0 = <&pinctrl_lcd_pwm>;
> +        #pwm-cells = <3>;
> +      };
> +    };
> +  - |
> +    //Example 2 With a video interface override to force rgb565
> +    hlcdc-display-controller {
> +      pinctrl-names = "default";
> +      pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb565>;

And how is this? Where is the compatible? Maybe just drop second
example, what are the differences?

Are you sure your Microchip folks reviewed it before?

Best regards,
Krzysztof