| Laurent Pinchart | 14da3ed | 2016-11-16 05:41:56 +0200 | [diff] [blame] | 1 | Common Properties for Display Panel |
| 2 | =================================== |
| 3 | |
| 4 | This document defines device tree properties common to several classes of |
| 5 | display panels. It doesn't constitue a device tree binding specification by |
| 6 | itself but is meant to be referenced by device tree bindings. |
| 7 | |
| 8 | When referenced from panel device tree bindings the properties defined in this |
| 9 | document are defined as follows. The panel device tree bindings are |
| 10 | responsible for defining whether each property is required or optional. |
| 11 | |
| 12 | |
| 13 | Descriptive Properties |
| 14 | ---------------------- |
| 15 | |
| 16 | - width-mm, |
| 17 | - height-mm: The width-mm and height-mm specify the width and height of the |
| 18 | physical area where images are displayed. These properties are expressed in |
| 19 | millimeters and rounded to the closest unit. |
| 20 | |
| 21 | - label: The label property specifies a symbolic name for the panel as a |
| 22 | string suitable for use by humans. It typically contains a name inscribed on |
| 23 | the system (e.g. as an affixed label) or specified in the system's |
| 24 | documentation (e.g. in the user's manual). |
| 25 | |
| 26 | If no such name exists, and unless the property is mandatory according to |
| 27 | device tree bindings, it shall rather be omitted than constructed of |
| 28 | non-descriptive information. For instance an LCD panel in a system that |
| 29 | contains a single panel shall not be labelled "LCD" if that name is not |
| 30 | inscribed on the system or used in a descriptive fashion in system |
| 31 | documentation. |
| 32 | |
| 33 | |
| 34 | Display Timings |
| 35 | --------------- |
| 36 | |
| 37 | - panel-timing: Most display panels are restricted to a single resolution and |
| 38 | require specific display timings. The panel-timing subnode expresses those |
| 39 | timings as specified in the timing subnode section of the display timing |
| 40 | bindings defined in |
| Geert Uytterhoeven | f130307 | 2018-04-25 09:49:38 +0200 | [diff] [blame^] | 41 | Documentation/devicetree/bindings/display/panel/display-timing.txt. |
| Laurent Pinchart | 14da3ed | 2016-11-16 05:41:56 +0200 | [diff] [blame] | 42 | |
| 43 | |
| 44 | Connectivity |
| 45 | ------------ |
| 46 | |
| 47 | - ports: Panels receive video data through one or multiple connections. While |
| 48 | the nature of those connections is specific to the panel type, the |
| 49 | connectivity is expressed in a standard fashion using ports as specified in |
| 50 | the device graph bindings defined in |
| 51 | Documentation/devicetree/bindings/graph.txt. |
| 52 | |
| 53 | - ddc-i2c-bus: Some panels expose EDID information through an I2C-compatible |
| 54 | bus such as DDC2 or E-DDC. For such panels the ddc-i2c-bus contains a |
| 55 | phandle to the system I2C controller connected to that bus. |
| 56 | |
| 57 | |
| 58 | Control I/Os |
| 59 | ------------ |
| 60 | |
| 61 | Many display panels can be controlled through pins driven by GPIOs. The nature |
| 62 | and timing of those control signals are device-specific and left for panel |
| 63 | device tree bindings to specify. The following GPIO specifiers can however be |
| 64 | used for panels that implement compatible control signals. |
| 65 | |
| 66 | - enable-gpios: Specifier for a GPIO connected to the panel enable control |
| 67 | signal. The enable signal is active high and enables operation of the panel. |
| 68 | This property can also be used for panels implementing an active low power |
| 69 | down signal, which is a negated version of the enable signal. Active low |
| 70 | enable signals (or active high power down signals) can be supported by |
| 71 | inverting the GPIO specifier polarity flag. |
| 72 | |
| 73 | Note that the enable signal control panel operation only and must not be |
| 74 | confused with a backlight enable signal. |
| 75 | |
| 76 | - reset-gpios: Specifier for a GPIO coonnected to the panel reset control |
| 77 | signal. The reset signal is active low and resets the panel internal logic |
| 78 | while active. Active high reset signals can be supported by inverting the |
| 79 | GPIO specifier polarity flag. |
| 80 | |
| Maxime Ripard | 2e7e2eb | 2017-12-21 12:02:27 +0100 | [diff] [blame] | 81 | Power |
| 82 | ----- |
| 83 | |
| 84 | - power-supply: display panels require power to be supplied. While several |
| 85 | panels need more than one power supply with panel-specific constraints |
| 86 | governing the order and timings of the power supplies, in many cases a single |
| 87 | power supply is sufficient, either because the panel has a single power rail, |
| 88 | or because all its power rails can be driven by the same supply. In that case |
| 89 | the power-supply property specifies the supply powering the panel as a phandle |
| 90 | to a regulator. |
| Laurent Pinchart | 14da3ed | 2016-11-16 05:41:56 +0200 | [diff] [blame] | 91 | |
| 92 | Backlight |
| 93 | --------- |
| 94 | |
| 95 | Most display panels include a backlight. Some of them also include a backlight |
| 96 | controller exposed through a control bus such as I2C or DSI. Others expose |
| 97 | backlight control through GPIO, PWM or other signals connected to an external |
| 98 | backlight controller. |
| 99 | |
| 100 | - backlight: For panels whose backlight is controlled by an external backlight |
| 101 | controller, this property contains a phandle that references the controller. |