Re: [PATCH v2 1/3] dt-bindings: display: add bindings for MIPI DBI compatible SPI panels

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Noralf,

On Tue, Feb 08, 2022 at 01:16:44PM +0100, Noralf Trønnes wrote:
> Den 08.02.2022 00.20, skrev Rob Herring:
> > On Thu, Jan 27, 2022 at 10:37:22AM +0100, Maxime Ripard wrote:
> >> Hi,
> >>
> >> On Tue, Jan 25, 2022 at 06:56:58PM +0100, Noralf Trønnes wrote:
> >>> Add binding for MIPI DBI compatible SPI panels.
> >>>
> >>> 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@xxxxxxxxxxx>
> >>> ---
> >>>  .../display/panel/panel-mipi-dbi-spi.yaml     | 59 +++++++++++++++++++
> >>>  1 file changed, 59 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..b7cbeea0f8aa
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
> >>> @@ -0,0 +1,59 @@
> >>> +# SPDX-License-Identifier: GPL-2.0-only
> >>> +%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 Panels Device Tree Bindings
> >>> +
> >>> +maintainers:
> >>> +  - Noralf Trønnes <noralf@xxxxxxxxxxx>
> >>> +
> >>> +description:
> >>> +  This binding is for display panels using a MIPI DBI controller
> >>> +  in SPI mode.
> >>> +
> >>> +allOf:
> >>> +  - $ref: panel-common.yaml#
> >>> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> >>> +
> >>> +properties:
> >>> +  compatible:
> >>> +    const: panel-mipi-dbi-spi
> >>
> >> You need contains here, otherwise it will error out if you have two compatibles.
> > 
> > Shouldn't it always have 2?
> > 
> > Either way, this has to be split up between a common, shareable schema 
> > and specific, complete schema(s). Like this:
> > 
> > - A schema for everything common (that allows additional properties)
> > 
> > - A schema for 'panel-mipi-dbi-spi' referencing the common schema plus 
> >   'unevaluatedProperties: false'
> > 
> > - Schemas for panels with their own additional properties (regulators, 
> >   GPIOs, etc.)
> > 
> > LVDS was restructured like this IIRC.
>
> The whole point of this exercise is to avoid the need for controller
> specific bindings.

I'm not sure to follow you here, nothing that either Rob or I discussed
would require a controller specific binding.

It would require a controller compatible, but the binding itself can
just mandate a controller compatible in addition to the
panel-mipi-dbi-spi compatible, without enforcing anything wrt the
compatible itself.

And the driver will just match panel-mipi-dbi-spi so there won't be any
driver change either?

In essence, it would be similar to the bindings of panel-lvds or the
AT24 EEPROM binding: you have two compatibles, but the driver is generic
and will just infer its behaviour based on the DT properties (and in our
case will load a firmware based on the specific compatible).

Wouldn't that work?

> This binding will cover all specifics about these
> controllers except for one thing and that is the controller
> configuration. Each controller has its own configuration commands. These
> commands will be loaded as a firmware file based on the compatible and
> applied by the driver.
> 
> So this binding, the panel-common and spi-peripheral-props covers
> everything except for the controller configuration.
> 
> Here's a copy of the DBI spec: https://www.docin.com/p-219732497.html
> 
> This is my current version of the binding:
> 
> # 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@xxxxxxxxxxx>
> 
> 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
> 
>   write-only:
>     type: boolean
>     description:
>       Controller is not readable (ie. MISO is not wired up).
> 
>   dc-gpios:
>     maxItems: 1
>     description: |
>       Controller data/command selection (D/CX) in 4-line SPI mode.
>       If not set, the controller is in 3-line SPI mode.
> 
> required:
>   - compatible
>   - reg
>   - panel-timing
> 
> unevaluatedProperties: false
> 
> examples:
>   - |
>     #include <dt-bindings/gpio/gpio.h>
> 
>     spi {
>             #address-cells = <1>;
>             #size-cells = <0>;
> 
>             display@0{
>                     compatible = "sainsmart18", "panel-dbi-spi";
>                     reg = <0>;
>                     spi-max-frequency = <40000000>;
> 
>                     dc-gpios = <&gpio 24 GPIO_ACTIVE_HIGH>;
>                     reset-gpios = <&gpio 25 GPIO_ACTIVE_HIGH>;
>                     write-only;
> 
>                     backlight = <&backlight>;
> 
>                     width-mm = <35>;
>                     height-mm = <28>;
> 
>                     panel-timing {
>                         hactive = <160>;
>                         vactive = <128>;
>                         hback-porch = <0>;
>                         vback-porch = <0>;
> 
>                         clock-frequency = <0>;
>                         hfront-porch = <0>;
>                         hsync-len = <0>;
>                         vfront-porch = <0>;
>                         vsync-len = <0>;
>                     };
>             };
>     };
> 
> ...

Yep, this looks good to me

Maxime

Attachment: signature.asc
Description: PGP signature


[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]


  Powered by Linux