linux-kernel - Re: [PATCH 13/14] dt-bindings: backlight: Add Mediatek MT6370 backlight binding documentation

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Date:   Wed, 1 Jun 2022 09:34:54 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     ChiaEn Wu <peterwu.pub@...il.com>, lee.jones@...aro.org,
        daniel.thompson@...aro.org, jingoohan1@...il.com, pavel@....cz,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        matthias.bgg@...il.com, sre@...nel.org, chunfeng.yun@...iatek.com,
        gregkh@...uxfoundation.org, jic23@...nel.org, lars@...afoo.de,
        lgirdwood@...il.com, broonie@...nel.org, linux@...ck-us.net,
        heikki.krogerus@...ux.intel.com, deller@....de
Cc:     cy_huang@...htek.com, alice_chen@...htek.com,
        chiaen_wu@...htek.com, dri-devel@...ts.freedesktop.org,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 13/14] dt-bindings: backlight: Add Mediatek MT6370
 backlight binding documentation

On 31/05/2022 12:28, ChiaEn Wu wrote:
> From: ChiYuan Huang <cy_huang@...htek.com>
> 
> Add mt6370 backlight binding documentation.
> 
> Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> ---
>  .../backlight/mediatek,mt6370-backlight.yaml  | 110 ++++++++++++++++++
>  1 file changed, 110 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/mediatek,mt6370-backlight.yaml
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/mediatek,mt6370-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/mediatek,mt6370-backlight.yaml
> new file mode 100644
> index 000000000000..81d72ed44be4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/mediatek,mt6370-backlight.yaml
> @@ -0,0 +1,110 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/mediatek,mt6370-backlight.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Mediatek MT6370 Backlight
> +
> +maintainers:
> +  - ChiaEn Wu <chiaen_wu@...htek.com>
> +
> +description: |
> +  MT6370 is a highly-integrated smart power management IC, which includes a
> +  single cell Li-Ion/Li-Polymer switching battery charger, a USB Type-C &
> +  Power Delivery (PD) controller, dual flash LED current sources, a RGB LED
> +  driver, a backlight WLED driver, a display bias driver and a general LDO for
> +  portable devices.

Do not repeat entire device description, but describe only this part.
Your other pieces of MFD were doing it correctly, so why here it is
different?

> +
> +  For the LCD backlight, it can provide 4 channel WLED driving capability.
> +  Each channel driving current is up to 30mA
> +
> +allOf:
> +  - $ref: common.yaml#
> +
> +properties:
> +  compatible:
> +    const: mediatek,mt6370-backlight
> +
> +  default-brightness:
> +    minimum: 0
> +    maximum: 2048
> +
> +  max-brightness:
> +    minimum: 0
> +    maximum: 2048
> +
> +  enable-gpios:
> +    description: External backlight 'enable' pin
> +    maxItems: 1
> +
> +  mediatek,bled-pwm-enable:
> +    description: |
> +      Enable external PWM input for backlight dimming
> +    type: boolean
> +
> +  mediatek,bled-pwm-hys-enable:
> +    description: |
> +      Enable the backlight input-hysteresis for PWM mode
> +    type: boolean
> +
> +  mediatek,bled-pwm-hys-sel:
> +    $ref: /schemas/types.yaml#/definitions/uint8
> +    enum: [0, 1, 2, 3]
> +    description: |
> +      Backlight PWM hysteresis input level selection.
> +      value mapping:
> +        - 0: 1bit
> +        - 1: 2bit
> +        - 2: 4bit
> +        - 3: 6bit

Please explain what is this input level and what is the meaning of
6bit... In any case you cannot have values mapping, but instead you
should use the logical values (so 1, 2, 4, and 6).

If "sel" is shortcut of "selection" please drop it.

> +
> +  mediatek,bled-ovp-shutdown:
> +    description: |
> +      Enable the backlight shutdown when OVP level triggered
> +    type: boolean
> +
> +  mediatek,bled-ovp-level-sel:
> +    $ref: /schemas/types.yaml#/definitions/uint8
> +    enum: [0, 1, 2, 3]
> +    description: |
> +      Backlight OVP level selection.
> +      value mapping:
> +        - 0: 17V
> +        - 1: 21V
> +        - 2: 25V
> +        - 3: 29V

Logical values in microvolts. Name it according to unit suffices and
drop any useless parts of property name like "level selection". It is
simply - mediatek,bled-ovp-microvolt.

> +
> +  mediatek,bled-ocp-shutdown:
> +    description: |
> +      Enable the backlight shutdown when OCP level triggerred.
> +    type: boolean
> +
> +  mediatek,bled-ocp-level-sel:
> +    $ref: /schemas/types.yaml#/definitions/uint8
> +    enum: [0, 1, 2, 3]
> +    description: |
> +      Backlight OC level selection.
> +      value mapping:
> +        - 0: 900mA
> +        - 1: 1200mA
> +        - 2: 1500mA
> +        - 3: 1800mA

Same comments.

> +
> +  mediatek,bled-channel-use:
> +    $ref: /schemas/types.yaml#/definitions/uint8
> +    description: |
> +      Backlight LED channel to be used.
> +      Each bit mapping to:
> +        - 0: CH4
> +        - 1: CH3
> +        - 2: CH2
> +        - 3: CH1> +    minimum: 1
> +    maximum: 15
> +
> +required:
> +  - compatible
> +  - mediatek,bled-channel-use
> +
> +additionalProperties: false


Best regards,
Krzysztof