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dt-bindings: display: convert display-timings to DT schema
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Add display-timings.yaml - that references panel-timings.yaml.
display-timings.yaml will be used for display bindings
when they are converted to meta-schema format.

For now the old display-timing.txt points to the new
display-timings.yaml - and all users are left as-is.

v2:
  - Updated native-mode description

v3:
  - Simpler "^timing" pattern (Rob)
  - timing node is of type object (Rob)
  - added display-timings to panel-common.yaml
  - added yaml document terminator "..."

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Cc: devicetree@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200216181513.28109-3-sam@ravnborg.org
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Sam Ravnborg committed Feb 29, 2020
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124 changes: 1 addition & 123 deletions Documentation/devicetree/bindings/display/panel/display-timing.txt
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display-timing bindings
=======================

display-timings node
--------------------

required properties:
- none

optional properties:
- native-mode: The native mode for the display, in case multiple modes are
provided. When omitted, assume the first node is the native.

timing subnode
--------------

required properties:
- hactive, vactive: display resolution
- hfront-porch, hback-porch, hsync-len: horizontal display timing parameters
in pixels
vfront-porch, vback-porch, vsync-len: vertical display timing parameters in
lines
- clock-frequency: display clock in Hz

optional properties:
- hsync-active: hsync pulse is active low/high/ignored
- vsync-active: vsync pulse is active low/high/ignored
- de-active: data-enable pulse is active low/high/ignored
- pixelclk-active: with
- active high = drive pixel data on rising edge/
sample data on falling edge
- active low = drive pixel data on falling edge/
sample data on rising edge
- ignored = ignored
- syncclk-active: with
- active high = drive sync on rising edge/
sample sync on falling edge of pixel
clock
- active low = drive sync on falling edge/
sample sync on rising edge of pixel
clock
- omitted = same configuration as pixelclk-active
- interlaced (bool): boolean to enable interlaced mode
- doublescan (bool): boolean to enable doublescan mode
- doubleclk (bool): boolean to enable doubleclock mode

All the optional properties that are not bool follow the following logic:
<1>: high active
<0>: low active
omitted: not used on hardware

There are different ways of describing the capabilities of a display. The
devicetree representation corresponds to the one commonly found in datasheets
for displays. If a display supports multiple signal timings, the native-mode
can be specified.

The parameters are defined as:

+----------+-------------------------------------+----------+-------+
| | ^ | | |
| | |vback_porch | | |
| | v | | |
+----------#######################################----------+-------+
| # ^ # | |
| # | # | |
| hback # | # hfront | hsync |
| porch # | hactive # porch | len |
|<-------->#<-------+--------------------------->#<-------->|<----->|
| # | # | |
| # |vactive # | |
| # | # | |
| # v # | |
+----------#######################################----------+-------+
| | ^ | | |
| | |vfront_porch | | |
| | v | | |
+----------+-------------------------------------+----------+-------+
| | ^ | | |
| | |vsync_len | | |
| | v | | |
+----------+-------------------------------------+----------+-------+

Note: In addition to being used as subnode(s) of display-timings, the timing
subnode may also be used on its own. This is appropriate if only one mode
need be conveyed. In this case, the node should be named 'panel-timing'.


Example:

display-timings {
native-mode = <&timing0>;
timing0: 1080p24 {
/* 1920x1080p24 */
clock-frequency = <52000000>;
hactive = <1920>;
vactive = <1080>;
hfront-porch = <25>;
hback-porch = <25>;
hsync-len = <25>;
vback-porch = <2>;
vfront-porch = <2>;
vsync-len = <2>;
hsync-active = <1>;
};
};

Every required property also supports the use of ranges, so the commonly used
datasheet description with minimum, typical and maximum values can be used.

Example:

timing1: timing {
/* 1920x1080p24 */
clock-frequency = <148500000>;
hactive = <1920>;
vactive = <1080>;
hsync-len = <0 44 60>;
hfront-porch = <80 88 95>;
hback-porch = <100 148 160>;
vfront-porch = <0 4 6>;
vback-porch = <0 36 50>;
vsync-len = <0 5 6>;
};
See display-timings.yaml in this directory.
77 changes: 77 additions & 0 deletions Documentation/devicetree/bindings/display/panel/display-timings.yaml
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# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/display/panel/display-timings.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: display timing bindings

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

description: |
A display panel may be able to handle several display timings,
with different resolutions.
The display-timings node makes it possible to specify the timing
and to specify the timing that is native for the display.
properties:
$nodename:
const: display-timings

native-mode:
$ref: /schemas/types.yaml#/definitions/phandle
description: |
The default display timing is the one specified as native-mode.
If no native-mode is specified then the first node is assumed the
native mode.
patternProperties:
"^timing":
type: object
allOf:
- $ref: panel-timing.yaml#

additionalProperties: false

examples:
- |+
/*
* Example that specifies panel timing using minimum, typical,
* maximum values as commonly used in datasheet description.
* timing1 is the native-mode.
*/
display-timings {
native-mode = <&timing1>;
timing0 {
/* 1920x1080p24 */
clock-frequency = <148500000>;
hactive = <1920>;
vactive = <1080>;
hsync-len = <0 44 60>;
hfront-porch = <80 88 95>;
hback-porch = <100 148 160>;
vfront-porch = <0 4 6>;
vback-porch = <0 36 50>;
vsync-len = <0 5 6>;
};
timing1 {
/* 1920x1080p24 */
clock-frequency = <52000000>;
hactive = <1920>;
vactive = <1080>;
hfront-porch = <25>;
hback-porch = <25>;
hsync-len = <0 25 25>;
vback-porch = <2>;
vfront-porch = <2>;
vsync-len = <2>;
hsync-active = <1>;
pixelclk-active = <1>;
};
};
...
8 changes: 8 additions & 0 deletions Documentation/devicetree/bindings/display/panel/panel-common.yaml
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allOf:
- $ref: panel-timing.yaml#

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

# Connectivity
port:
type: object
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