Re: [PATCH v3 1/3] dt-bindings: display: add bindings for MIPI DBI compatible SPI panels

["Noralf Trønnes" <noralf@tronnes.org>]

Den 11.02.2022 14.27, skrev Maxime Ripard:
> On Fri, Feb 11, 2022 at 02:04:32PM +0100, Noralf Trønnes wrote:
>> Add binding for MIPI DBI compatible SPI panels.
>>
>> v3:
>> - Move properties to Device Tree (Maxime)
>> - Use contains for compatible (Maxime)
>> - Add backlight property to example
>> - Flesh out description
>>
>> v2:
>> - Fix path for panel-common.yaml
>> - Use unevaluatedProperties
>> - Drop properties which are in the allOf section
>> - Drop model property (Rob)
>>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> ---
>>  .../display/panel/panel-mipi-dbi-spi.yaml     | 124 ++++++++++++++++++
>>  1 file changed, 124 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml b/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
>> new file mode 100644
>> index 000000000000..4d017a36ad4d
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
>> @@ -0,0 +1,124 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/panel/panel-mipi-dbi-spi.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: MIPI DBI SPI Panel
>> +
>> +maintainers:
>> +  - Noralf Trønnes <noralf@tronnes.org>
>> +
>> +description: |
>> +  This binding is for display panels using a MIPI DBI compatible controller
>> +  in SPI mode.
>> +
>> +  The MIPI Alliance Standard for Display Bus Interface defines the electrical
>> +  and logical interfaces for display controllers historically used in mobile
>> +  phones. The standard defines 4 display architecture types and this binding is
>> +  for type 1 which has full frame memory. There are 3 interface types in the
>> +  standard and type C is the serial interface.
>> +
>> +  The standard defines the following interface signals for type C:
>> +  - Power:
>> +    - Vdd: Power supply for display module
>> +    - Vddi: Logic level supply for interface signals
>> +    Combined into one in this binding called: power-supply
>> +  - Interface:
>> +    - CSx: Chip select
>> +    - SCL: Serial clock
>> +    - Dout: Serial out
>> +    - Din: Serial in
>> +    - SDA: Bidrectional in/out
>> +    - D/CX: Data/command selection, high=data, low=command
>> +      Called dc-gpios in this binding.
>> +    - RESX: Reset when low
>> +      Called reset-gpios in this binding.
>> +
>> +  The type C interface has 3 options:
>> +
>> +    - Option 1: 9-bit mode and D/CX as the 9th bit
>> +      |              Command              |  the next command or following data  |
>> +      |<0><D7><D6><D5><D4><D3><D2><D1><D0>|<D/CX><D7><D6><D5><D4><D3><D2><D1><D0>|
>> +
>> +    - Option 2: 16-bit mode and D/CX as a 9th bit
>> +      |              Command or data                              |
>> +      |<X><X><X><X><X><X><X><D/CX><D7><D6><D5><D4><D3><D2><D1><D0>|
>> +
>> +    - Option 3: 8-bit mode and D/CX as a separate interface line
>> +      |        Command or data         |
>> +      |<D7><D6><D5><D4><D3><D2><D1><D0>|
>> +
>> +  The panel resolution is specified using the panel-timing node properties
>> +  hactive (width) and vactive (height). The other mandatory panel-timing
>> +  properties should be set to zero except clock-frequency which can be
>> +  optionally set to inform about the actual pixel clock frequency.
>> +
>> +  If the panel is wired to the controller at an offset specify this using
>> +  hback-porch (x-offset) and vback-porch (y-offset).
>> +
>> +allOf:
>> +  - $ref: panel-common.yaml#
>> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
>> +
>> +properties:
>> +  compatible:
>> +    contains:
>> +      const: panel-dbi-spi
> 
> This could be further improved by using
> 
> properties:
>   compatible:
>     items:
>       - {} # Panel Specific Compatible
>       - const: panel-dbi-spi
> 
> To make it obvious we expect two compatible, and what the first one should be.
> 

Ok.

I see that for some reason I've dropped the mipi infix here in the
compatible and in the example. I'll fix that and make it
panel-mipi-dbi-spi in the next version.

Noralf.

> Once fixed,
> 
> Acked-by: Maxime Ripard <maxime@cerno.tech>
> 
> Maxime