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

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Message-ID: <c29b2b0c-2b0c-f79c-9de5-58a67edd5c87@linaro.org>
Date:   Sat, 17 Jun 2023 19:42:29 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     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,
        Maximilian Weigand <mweigand@...igand.net>
Subject: Re: [PATCH 2/3] dt-bindings: backlight: lm3630a: add entries to
 control boost frequency

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).

Best regards,
Krzysztof