linux-kernel - Re: [RFC PATCH 1/6] dt-bindings: display: imx: Add EPDC

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Message-ID: <36445c86-036e-0942-a9a4-919595886c67@canonical.com>
Date:   Thu, 17 Feb 2022 10:21:15 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Andreas Kemnade <andreas@...nade.info>, p.zabel@...gutronix.de,
        airlied@...ux.ie, daniel@...ll.ch, robh+dt@...nel.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, alistair@...stair23.me,
        samuel@...lland.org, josua.mayer@....eu,
        letux-kernel@...nphoenux.org
Subject: Re: [RFC PATCH 1/6] dt-bindings: display: imx: Add EPDC

On 06/02/2022 09:00, Andreas Kemnade wrote:
> Add a binding for the Electrophoretic Display Controller found at least
> in the i.MX6.
> The timing subnode is directly here to avoid having display parameters
> spread all over the plate.
> 
> Supplies are organized the same way as in the fbdev driver in the
> NXP/Freescale kernel forks. The regulators used for that purpose,
> like the TPS65185, the SY7636A and MAX17135 have typically a single bit to
> start a bunch of regulators of higher or negative voltage with a
> well-defined timing. VCOM can be handled separately, but can also be
> incorporated into that single bit.
> 
> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> ---
>  .../bindings/display/imx/fsl,mxc-epdc.yaml    | 159 ++++++++++++++++++
>  1 file changed, 159 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/imx/fsl,mxc-epdc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/imx/fsl,mxc-epdc.yaml b/Documentation/devicetree/bindings/display/imx/fsl,mxc-epdc.yaml
> new file mode 100644
> index 000000000000..7e0795cc3f70
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/imx/fsl,mxc-epdc.yaml
> @@ -0,0 +1,159 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/imx/fsl,mxc-epdc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Freescale i.MX6 EPDC
> +
> +maintainers:
> +  - Andreas Kemnade <andreas@...nade.info>
> +
> +description: |
> +  The EPDC is a controller for handling electronic paper displays found in
> +  i.MX6 SoCs.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - fsl,imx6sl-epdc
> +      - fsl,imx6sll-epdc
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: Bus clock
> +      - description: Pixel clock
> +
> +  clock-names:
> +    items:
> +      - const: axi
> +      - const: pix
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  vscan-holdoff:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1

Except what Rob already said, all these are not arrays, so maxItems is
not appropriate. You can define minimum/maximum values instead.

> +
> +  sdoed-width:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  sdoed-delay:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  sdoez-width:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  sdoez-delay:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  gdclk-hp-offs:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  gdsp-offs:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  gdoe-offs:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  gdclk-offs:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  num-ce:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maxItems: 1
> +
> +  timing:
> +    $ref: /display/panel/panel-timing.yaml#
> +
> +  DISPLAY-supply:
> +    description:
> +      A couple of +/- voltages automatically powered on in a defintive order

Typo, definitive?

> +
> +  VCOM-supply:
> +    description: compensation voltage
> +
> +  V3P3-supply:

All of supplies names - lowercase.

> +    description: V3P3 supply
> +
> +  epd-thermal-zone:
> +    description:
> +      Zone to get temperature of the EPD from, practically ambient temperature.

Is it a phandle?

> +
> +
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +  - interrupts
> +  - vscan-holdoff
> +  - sdoed-width
> +  - sdoed-delay
> +  - sdoez-width
> +  - sdoez-delay
> +  - gdclk-hp-offs
> +  - gdsp-offs
> +  - gdoe-offs
> +  - gdclk-offs
> +  - num-ce
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/clock/imx6sl-clock.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    epdc: epdc@...4000 {

Generic node name, e.g. display-controller

> +        compatible = "fsl,imx6sl-epdc";
> +        reg = <0x020f4000 0x4000>;
> +        interrupts = <0 97 IRQ_TYPE_LEVEL_HIGH>;

s/0/GIC_SPI/

> +        clocks = <&clks IMX6SL_CLK_EPDC_AXI>, <&clks IMX6SL_CLK_EPDC_PIX>;
> +        clock-names = "axi", "pix";
> +


Best regards,
Krzysztof