kernel-ark/Documentation/devicetree/bindings/display/panel/panel-common.yaml

# SPDX-License-Identifier: GPL-2.0
%YAML 1.2
---
$id: http://devicetree.org/schemas/display/panel/panel-common.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Common Properties for Display Panels

maintainers:
  - Thierry Reding <thierry.reding@gmail.com>
  - Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

description: |
  This document defines device tree properties common to several classes of
  display panels. It doesn't constitue a device tree binding specification by
  itself but is meant to be referenced by device tree bindings.

  When referenced from panel device tree bindings the properties defined in this
  document are defined as follows. The panel device tree bindings are
  responsible for defining whether each property is required or optional.  

properties:
  # Descriptive Properties
  width-mm:
    description:
      Specifies the width of the physical area where images are displayed. This
      property is expressed in millimeters and rounded to the closest unit.

  height-mm:
    description:
      Specifies the height of the physical area where images are displayed. This
      property is expressed in millimeters and rounded to the closest unit.

  label:
    description: |
      The label property specifies a symbolic name for the panel as a
      string suitable for use by humans. It typically contains a name inscribed
      on the system (e.g. as an affixed label) or specified in the system's
      documentation (e.g. in the user's manual).

      If no such name exists, and unless the property is mandatory according to
      device tree bindings, it shall rather be omitted than constructed of
      non-descriptive information. For instance an LCD panel in a system that
      contains a single panel shall not be labelled "LCD" if that name is not
      inscribed on the system or used in a descriptive fashion in system
      documentation.      

  rotation:
    description:
      Display rotation in degrees counter clockwise (0,90,180,270)
    $ref: /schemas/types.yaml#/definitions/uint32
    enum: [0, 90, 180, 270]

  # Display Timings
  panel-timing:
    description:
      Most display panels are restricted to a single resolution and
      require specific display timings. The panel-timing subnode expresses those
      timings.
    $ref: panel-timing.yaml#

  display-timings:
    description:
      Some display panels support several resolutions with different timings.
      The display-timings bindings supports specifying several timings and
      optionally specifying which is the native mode.
    $ref: display-timings.yaml#

  # Connectivity
  port:
    $ref: /schemas/graph.yaml#/properties/port

  ddc-i2c-bus:
    $ref: /schemas/types.yaml#/definitions/phandle
    description:
      Some panels expose EDID information through an I2C-compatible
      bus such as DDC2 or E-DDC. For such panels the ddc-i2c-bus contains a
      phandle to the system I2C controller connected to that bus.

  no-hpd:
    type: boolean
    description:
      This panel is supposed to communicate that it's ready via HPD
      (hot plug detect) signal, but the signal isn't hooked up so we should
      hardcode the max delay from the panel spec when powering up the panel.

  hpd-gpios:
    maxItems: 1
    description:
      If Hot Plug Detect (HPD) is connected to a GPIO in the system rather
      than a dedicated HPD pin the pin can be specified here.

  # Control I/Os

  # Many display panels can be controlled through pins driven by GPIOs. The nature
  # and timing of those control signals are device-specific and left for panel
  # device tree bindings to specify. The following GPIO specifiers can however be
  # used for panels that implement compatible control signals.

  enable-gpios:
    maxItems: 1
    description: |
      Specifier for a GPIO connected to the panel enable control signal. The
      enable signal is active high and enables operation of the panel. This
      property can also be used for panels implementing an active low power down
      signal, which is a negated version of the enable signal. Active low enable
      signals (or active high power down signals) can be supported by inverting
      the GPIO specifier polarity flag.

      Note that the enable signal control panel operation only and must not be
      confused with a backlight enable signal.      

  reset-gpios:
    maxItems: 1
    description:
      Specifier for a GPIO connected to the panel reset control signal.
      The reset signal is active low and resets the panel internal logic
      while active. Active high reset signals can be supported by inverting the
      GPIO specifier polarity flag.

  te-gpios:
    maxItems: 1
    description:
      GPIO spec for the tearing effect synchronization signal.
      The tearing effect signal is active high. Active low signals can be
      supported by inverting the GPIO specifier polarity flag.

  # Power
  power-supply:
    description:
      Display panels require power to be supplied. While several panels need
      more than one power supply with panel-specific constraints governing the
      order and timings of the power supplies, in many cases a single power
      supply is sufficient, either because the panel has a single power rail, or
      because all its power rails can be driven by the same supply. In that case
      the power-supply property specifies the supply powering the panel as a
      phandle to a regulator.

  # Backlight

  # Most display panels include a backlight. Some of them also include a backlight
  # controller exposed through a control bus such as I2C or DSI. Others expose
  # backlight control through GPIO, PWM or other signals connected to an external
  # backlight controller.

  backlight:
    $ref: /schemas/types.yaml#/definitions/phandle
    description:
      For panels whose backlight is controlled by an external backlight
      controller, this property contains a phandle that references the
      controller.

dependencies:
  width-mm: [ height-mm ]
  height-mm: [ width-mm ]

additionalProperties: true

...