linux-kernel - Re: [PATCH v2] dt-bindings: display: panel: add panel-mipi-dsi-bringup

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Message-ID: <CAPY8ntCkZB3K2LoLcBseDcg=qNrOvZbYaCdiyNcR4R2Oo3sLoA@mail.gmail.com>
Date:   Wed, 17 May 2023 11:25:34 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Paulo Pavačić <pavacic.p@...il.com>
Cc:     krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        neil.armstrong@...aro.org, sam@...nborg.org, airlied@...il.com,
        robh+dt@...nel.org, daniel@...ll.ch, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2] dt-bindings: display: panel: add panel-mipi-dsi-bringup

Hi Paulo

On Tue, 16 May 2023 at 14:09, Paulo Pavačić <pavacic.p@...il.com> wrote:
>
> Add dt-bindings documentation for panel-mipi-dsi-bringup which currently
> supports fannal,c3004 panel. Also added fannal to vendor-prefixes.
>
> v2 changelog:
>   - revised driver title, now describes purpose
>   - revised description, now describes hw
>   - revised maintainers, now has only 1 mail
>   - removed diacritics from commit/commit author
>   - properties/compatible is now enum
>   - compatible using only lowercase
>   - revised dts example
>   - modified MAINTAINERS in this commit (instead of driver commit)
>   - dt_bindings_check checked yml
>   - checkpatch warning fixed
>
> Signed-off-by: Paulo Pavacic <pavacic.p@...il.com>
> ---
>  .../display/panel/panel-mipi-dsi-bringup.yaml | 54 +++++++++++++++++++
>  .../devicetree/bindings/vendor-prefixes.yaml  |  2 +
>  MAINTAINERS                                   |  6 +++
>  3 files changed, 62 insertions(+)
>  create mode 100644
> Documentation/devicetree/bindings/display/panel/panel-mipi-dsi-bringup.yaml
>
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-mipi-dsi-bringup.yaml
> b/Documentation/devicetree/bindings/display/panel/panel-mipi-dsi-bringup.yaml
> new file mode 100644
> index 000000000000..c9e2b545657e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-mipi-dsi-bringup.yaml
> @@ -0,0 +1,54 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/panel-mipi-dsi-bringup.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: MIPI DSI Bringup Panel Porting Bindings
> +
> +description: |
> +  MIPI DSI Bringup Panel porting bindings to be used for a collection of panels
> +  from different manufacturers which don't require backlight control from the
> +  driver and have a single reset pin which is required to be passed as an
> +  argument.

Don't we already have support for DSI displays that only need a single
reset pin via panel-simple? [1]

The bit that confuses me is that the driver patch [2] is using DSI DCS
commands to configure the panel - that differs from this dt binding
description of the panel only needing a reset pin.

Potentially there is gain in having a template DSI panel driver
available for reference, but this driver/binding appears to be trying
to act as a generic thing.

  Dave

[1] https://elixir.bootlin.com/linux/v6.3.2/source/drivers/gpu/drm/panel/panel-simple.c#L4605
[2] https://lists.freedesktop.org/archives/dri-devel/2023-May/404775.html


> +
> +maintainers:
> +  - Paulo Pavacic <pavacic.p@...il.com>
> +
> +allOf:
> +  - $ref: panel-common.yaml#
> +
> +properties:
> +
> +  compatible:
> +    enum:
> +      # compatible must be listed in alphabetical order, ordered by compatible.
> +      # The description in the comment is mandatory for each compatible.
> +
> +        # Fannal 480x800 panel
> +      - fannal,c3004
> +
> +  reg: true
> +  reset-gpios: true
> +
> +required:
> +  - compatible
> +  - reg
> +  - reset-gpios
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    //example on IMX8MM where GPIO pin 9 is used as a reset pin
> +    mipi_dsi@...10000 {
> +        panel@0 {
> +            compatible = "fannal,c3004";
> +            reg = <0>;
> +            pinctrl-0 = <&pinctrl_mipi_dsi_rst>;
> +            pinctrl-names = "default";
> +            reset-gpios = <&gpio1 9 GPIO_ACTIVE_LOW>;
> +        };
> +    };
> +...
> diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml
> b/Documentation/devicetree/bindings/vendor-prefixes.yaml
> index 82d39ab0231b..f962750f630a 100644
> --- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
> +++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
> @@ -462,6 +462,8 @@ patternProperties:
>      description: Facebook
>    "^fairphone,.*":
>      description: Fairphone B.V.
> +  "^fannal,.*":
> +    description: Fannal Electronics Co., Ltd
>    "^faraday,.*":
>      description: Faraday Technology Corporation
>    "^fastrax,.*":
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e0ad886d3163..46f988ee60bd 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6566,6 +6566,12 @@ T:    git git://anongit.freedesktop.org/drm/drm-misc
>  F:    Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
>  F:    drivers/gpu/drm/tiny/panel-mipi-dbi.c
>
> +DRM DRIVER FOR MIPI DSI BRINGUP
> +M:    Paulo Pavacic <pavacic.p@...il.com>
> +S:    Maintained
> +C:    mipi-dsi-bringup:matrix.org
> +F:    Documentation/devicetree/bindings/display/panel/panel-mipi-dsi-bringup.yaml
> +
>  DRM DRIVER FOR MSM ADRENO GPU
>  M:    Rob Clark <robdclark@...il.com>
>  M:    Abhinav Kumar <quic_abhinavk@...cinc.com>
> --
> 2.40.1
>