Re: [PATCH v2 05/15] dt-bindings: backlight: Add Mediatek MT6370 backlight

[ChiaEn Wu <peterwu.pub@gmail.com>]

Hi Krzysztof,

Thanks for your helpful feedback, I have some questions want to
confirm with you below.

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月17日 週五 清晨5:13寫道：
>
> On 13/06/2022 04:11, ChiaEn Wu wrote:
> > From: ChiYuan Huang <cy_huang@richtek.com>
> >
> > Add mt6370 backlight binding documentation.
> >
> > Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> > ---
> >  .../backlight/mediatek,mt6370-backlight.yaml  | 107 ++++++++++++++++++
> >  1 file changed, 107 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..25a05e607e83
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/leds/backlight/mediatek,mt6370-backlight.yaml
> > @@ -0,0 +1,107 @@
> > +# 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@richtek.com>
> > +
> > +description: |
> > +  This module is part of the MT6370 MFD device.
> > +  The MT6370 Backlight WLED driver supports up to a 29V output voltage for
> > +  4 channels of 8 series WLEDs. Each channel supports up to 30mA of current
> > +  capability with 2048 current steps (11 bits) in exponential or linear
> > +  mapping curves.
> > +
> > +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-input-bit:
> > +    $ref: /schemas/types.yaml#/definitions/uint8
> > +    enum: [0, 1, 2, 3]
> > +    description: |
> > +      The selection of the upper and lower bounds threshold of backlight
> > +      PWM resolution. If we choose selection 3 (6 bits), the variation of PWM
> > +      resolution needs over than 64 steps (2^6).
> > +      value mapping:
> > +        - 0: 1
> > +        - 1: 2
> > +        - 2: 4
> > +        - 3: 6
>
> Nope, I said last time:
> "In any case you cannot have values mapping"
>
> Please use proper real world value, not some register bits. The property
> name also needs fixing.

I so apologized for misunderstanding your meaning...
I try to modify it like below.
--------
mediatek,bled-pwm-hys-input-threshold-steps:
  $ref: /schemas/types.yaml#/definitions/uint8
  enum: [1, 4, 16, 64]
  description: |
    The selection of the upper and lower bounds threshold of backlight
    PWM resolution. If we choose selection 64, the variation of PWM
    resolution needs over 64 steps.
--------
If these changes meet your expectations, I will try to modify
"bled-ovp-microvolt" and "bled-ocp-microamp" in the same way.
Thank you so much.

>
> > +
> > +  mediatek,bled-ovp-shutdown:
> > +    description: |
> > +      Enable the backlight shutdown when OVP level triggered
> > +    type: boolean
> > +
> > +  mediatek,bled-ovp-microvolt:
> > +    enum: [0, 1, 2, 3]
> > +    description: |
> > +      Backlight OVP level selection.
> > +      value mapping:
> > +        - 0: 17000000
> > +        - 1: 21000000
> > +        - 2: 25000000
> > +        - 3: 29000000
>
> No. Please test your bindings.
>
> microvolt cannot be 1 mV. It's 21000000, not 1. No value mappings.
>
> > +
> > +  mediatek,bled-ocp-shutdown:
> > +    description: |
> > +      Enable the backlight shutdown when OCP level triggerred.
> > +    type: boolean
> > +
> > +  mediatek,bled-ocp-microamp:
> > +    enum: [0, 1, 2, 3]
> > +    description: |
> > +      Backlight OC level selection.
> > +      value mapping:
> > +        - 0: 900000
> > +        - 1: 1200000
> > +        - 2: 1500000
> > +        - 3: 1800000
>
> Nope.
>
> > +
> > +  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

Best regards,
ChiaEn Wu