linux-kernel - Re: [PATCH 1/6] dt-bindings: display: Document NewVision NV3052C DT node

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Date:   Mon, 27 Jul 2020 21:10:52 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Noralf Trønnes <noralf@...nnes.org>,
        od@...c.me, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] dt-bindings: display: Document NewVision NV3052C DT
 node

Hi Paul.

On Mon, Jul 27, 2020 at 06:46:08PM +0200, Paul Cercueil wrote:
> Add documentation for the Device Tree node for LCD panels based on the
> NewVision NV3052C controller.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>

Very happy to see work on RG-350 :-)
Some feedback below.

	Sam

> ---
>  .../display/panel/newvision,nv3052c.yaml      | 69 +++++++++++++++++++
>  1 file changed, 69 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/panel/newvision,nv3052c.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/newvision,nv3052c.yaml b/Documentation/devicetree/bindings/display/panel/newvision,nv3052c.yaml
> new file mode 100644
> index 000000000000..751a28800fc2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/newvision,nv3052c.yaml
> @@ -0,0 +1,69 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/newvision,nv3052c.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: NewVision NV3052C TFT LCD panel driver with SPI control bus
> +
> +maintainers:
> +  - Paul Cercueil <paul@...pouillou.net>
> +
> +description: |
> +  This is a driver for 320x240 TFT panels,
The binding describes the HW, not the driver. So please re-phrase this
part.

This datasheet: https://www.phoenixdisplay.com/wp-content/uploads/2019/05/NV3052C-Datasheet-V0.2.pdf
tells that the driver supports additional resoltions.
I guess the 320x240 resolution is limited to the leadtek panel.

> +  accepting a variety of input
> +  streams that get adapted and scaled to the panel. The panel output has
> +  960 TFT source driver pins and 240 TFT gate driver pins, VCOM, VCOML and
> +  VCOMH outputs.
> +
> +  The panel must obey the rules for a SPI slave device as specified in
> +  spi/spi-controller.yaml
> +
> +allOf:
> +  - $ref: panel-common.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +        - leadtek,ltk035c5444t-spi
> +
> +      - const: newvision,nv3052c
> +
> +  reg:
> +    maxItems: 1
> +
> +  reset-gpios: true
> +  port: true
> +
> +required:
> +  - compatible
> +  - reg
> +
> +unevaluatedProperties: false
> +
Do the panel need any power?
I had expected to see a power-supply node as mandatory.

> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    spi {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      display@0 {
> +        compatible = "leadtek,ltk035c5444t-spi", "newvision,nv3052c";
> +        reg = <0>;
> +
> +        spi-max-frequency = <15000000>;
> +        spi-3wire;
> +        reset-gpios = <&gpe 2 GPIO_ACTIVE_LOW>;


> +        backlight = <&backlight>;
> +        power-supply = <&vcc>;
These would fail later due to "unevaluatedProperties: false".
Add them above like
  backlight: true
  power-supply: true

as done for reset-gpios for example.

> +
> +        port {
> +          panel_input: endpoint {
> +              remote-endpoint = <&panel_output>;
> +          };
> +        };
> +      };
> +    };
Personally I prefer 4 space indent. But there is no fixed rule (yet)
what to use.

> +
> +...
> -- 
> 2.27.0