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

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Message-ID: <7491264.lOV4Wx5bFT@diego>
Date:   Sat, 17 Jun 2023 18:34:28 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     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>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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

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.