linux-kernel - Re: [PATCH 1/2] dt-bindings: leds: backlight: Add Awinic AW99706 backlight

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Message-ID: <CAK6c68gqHMR-FpH3MY9E_9R+V0J75V9zOii=x81e+bRcnBYOig@mail.gmail.com>
Date: Mon, 27 Oct 2025 14:58:51 +0800
From: Junjie Cao <caojunjie650@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Lee Jones <lee@...nel.org>, Daniel Thompson <danielt@...nel.org>, 
	Jingoo Han <jingoohan1@...il.com>, Pavel Machek <pavel@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Helge Deller <deller@....de>, 
	dri-devel@...ts.freedesktop.org, linux-leds@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: leds: backlight: Add Awinic AW99706 backlight

On Sun, Oct 26, 2025 at 9:48 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 26/10/2025 13:39, Junjie Cao wrote:
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  enable-gpios:
> > +    description: GPIO to use to enable/disable the backlight (HWEN pin).
> > +    maxItems: 1
> > +
> > +  awinic,dim-mode:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: >
> > +      Select dimming mode of the device.
> > +        0 = Bypass mode.
> > +        1 = DC mode.
> > +        2 = MIX mode.
> > +        3 = MIX-26k.
> > +    enum: [0, 1, 2, 3]
> > +    default: 1
> > +
> > +  awinic,sw-freq:
>
> Please use proper units, see:
> https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml
> and other examples
>
> Same everywhere else.
>

ACK

>
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Boost switching frequency in kHz.
> > +    enum: [300, 400, 500, 600, 660, 750, 850, 1000, 1200, 1330, 1500, 1700]
> > +    default: 750
> > +
> > +  awinic,sw-ilmt:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Switching current limitation in mA.
> > +    enum: [1500, 2000, 2500, 3000]
> > +    default: 3000
> > +
> > +  awinic,iled-max:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Maximum LED current setting in uA.
> > +    minimum: 5000
> > +    maximum: 50000
> > +    multipleOf: 500
> > +    default: 20000
> > +
> > +  awinic,uvlo-thres:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: UVLO(Under Voltage Lock Out) in mV.
> > +    enum: [2200, 5000]
> > +    default: 2200
> > +
> > +  awinic,fade-time:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Fade In/Out Time(per step) in us.
> > +    enum: [8, 16, 32, 64, 128, 256, 512, 1024]
>
> Why would this be fixed setting? This really looks like runtime, drop.
>

Yes, it is fixed. I am quoting this from the datasheet.
AW99706B provides Fade in/out mode to transform backlight from one brightness
to another or turn on/off backlight with a fixed slope. Writing 0b00 into
RAMP_CTR (CFG 0x06) to enter Fade in/out mode, and the the slope of current
transition can be set in FADE_TIME (CFG 0x06).

> > +    default: 16
> > +
> > +  awinic,slope-time:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Slope time in ms.
>
> Slope of what?
>

Ramp time in slope mode, it is retained from downstream drivers, it will
be more clear in the next version.

> > +    enum: [8, 24, 48, 96, 200, 300, 400, 500]
> > +    default: 300
> > +
> > +  awinic,ramp-ctl:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: >
> > +      Select ramp control and filter of the device.
> > +        0 = Fade in/fade out.
> > +        1 = Light filter.
> > +        2 = Medium filter.
> > +        3 = Heavy filter.
> > +    enum: [0, 1, 2, 3]
> > +    default: 2
> > +
> > +  awinic,brt-mode:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: >
> > +      Select brightness control of the device.
> > +        0 = PWM.
> > +        1 = IIC.
> > +        2 = IIC x PWM.
> > +        3 = IIC x PWM(P-ramp).
> > +    enum: [0, 1, 2, 3]
> > +    default: 1
> > +
> > +  awinic,onoff-time:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: Turn on/off time(per step) in ns.
> > +    enum: [250, 500, 1000, 2000, 4000, 8000, 16000]
>
> Not a DT property.
>

It is mandatory in the downstream driver, I keep it.

The following is the description about it,

If the value in ONOFF_CTR(CFG 0x08 [4:3]) is 0b00, the turning on/off ramp of
AW99706B is soft start and fast end. In this mode, the ramp time can be
programmed by ONOFF_TIME (CFG 0x08 [2:0]).

> > +    default: 2000
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - enable-gpios
> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        aw99706@76 {
> > +            compatible = "awinic,aw99706";
> > +            reg = <0x76>;
> > +            enable-gpios = <&tlmm 88 GPIO_ACTIVE_HIGH>;
>
> Where are other properties from common.yaml? Looks like you re-invented
> some parts.
>

Sorry, I forgot it, when writing the bindings, I used ktz8866.yaml as a
template. I  should have dropped the common.yaml. This driver does
not require other properties in common.yaml.

Regards,
Junjie