linux-kernel - Re: [PATCH 2/3] dt-bindings: backlight: lm3630a: add entries to control boost frequency

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Message-ID: <5d2eb5af-b674-751b-1583-e048fbf8c3a5@mweigand.net>
Date:   Sat, 17 Jun 2023 20:15:29 +0200
From:   Maximilian Weigand <mweigand@...igand.net>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Heiko Stübner <heiko@...ech.de>,
        Maximilian Weigand <mweigand2017@...il.com>,
        Lee Jones <lee@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Helge Deller <deller@....de>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH 2/3] dt-bindings: backlight: lm3630a: add entries to
 control boost frequency

Hi,

On 17.06.23 19:42, Krzysztof Kozlowski wrote:
> On 17/06/2023 18:34, Heiko Stübner wrote:
>> Am Samstag, 17. Juni 2023, 12:12:17 CEST schrieb Krzysztof Kozlowski:
>>> On 14/06/2023 21:08, Maximilian Weigand wrote:
>>>> From: Maximilian Weigand <mweigand@...igand.net>
>>>>
>>>> Add 'ti,boost_use_1mhz' to switch between 500 kHz and 1 MHz boost
>>>> converter switching frequency, and add 'ti,boost_frequency_shift' to
>>>> activate a frequency shift to 560 kHz or 1.12 MHz, respectively.
>>>>
>>>> Signed-off-by: Maximilian Weigand <mweigand@...igand.net>
>>>> ---
>>>>  .../bindings/leds/backlight/lm3630a-backlight.yaml           | 12 ++++++++++++
>>>>  1 file changed, 12 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml
>>>> index 3c9b4054ed9a..ef7ea0ad2d25 100644
>>>> --- a/Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml
>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml
>>>> @@ -33,6 +33,18 @@ properties:
>>>>      description: GPIO to use to enable/disable the backlight (HWEN pin).
>>>>      maxItems: 1
>>>>  
>>>> +  ti,boost_use_1mhz:
>>>
>>> No underscores in property names.
>>>
>>>> +    description: |
>>>
>>> Do not need '|' unless you need to preserve formatting.
>>>
>>>> +      If present, change the boost converter switching frequency from the
>>>> +      default 500 kHz to 1 MHz. Refer to data sheet for hardware requirements.
>>>> +    type: boolean
>>>> +
>>>> +  ti,boost_frequency_shift:
>>>> +    description: |
>>>> +      If present, change boost converter switching frequency from 500 kHz to
>>>> +      560 kHz or from 1 Mhz to 1.12 Mhz, respectively.
>>>
>>> So just make it a property choosing the frequency, not bools, with
>>> proper unit suffix.
>>
>> i.e.
>> ti,boost-frequency-hz = <x>;
>> with x being 500000, 560000, 1000000, 1120000
>>
>> with the driver failing when the frequency is not achievable
>> with the two knobs of 1mhz and shift.
> 
> Yeah, with a default value (500000, I guess).

Thanks for the feedback, this is quite obviously the better solution! I
will rework the submission accordingly.

Best regards

Maximilian