linux-kernel - Re: [PATCH v3 1/3] ARM: dts: rockchip: veyron: Remove 0 point from brightness-levels

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Date:   Wed, 28 Oct 2020 14:55:51 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Alexandru Stan <amstan@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>, Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 1/3] ARM: dts: rockchip: veyron: Remove 0 point from
 brightness-levels

On Wed, Oct 21, 2020 at 10:04:43PM -0700, Alexandru Stan wrote:
> The extra 0 only adds one point in the userspace visible range,
> so this change is almost a noop with the current driver behavior.
> 
> We don't need the 0% point, userspace seems to handle this just fine
> because it uses the bl_power property to turn off the display.
> 
> Furthermore after adding "backlight: pwm_bl: Fix interpolation" patch,
> the backlight interpolation will work a little differently. So we need
> to preemptively remove the 0-3 segment since otherwise we would have a
> 252 long interpolation that would slowly go between 0 and 3, looking
> really bad in userspace. So it's almost a noop/cleanup now, but it will
> be required in the future.
> 
> Signed-off-by: Alexandru Stan <amstan@...omium.org>

Acked-by: Daniel Thompson <daniel.thompson@...aro.org>


> ---
> 
>  arch/arm/boot/dts/rk3288-veyron-jaq.dts    | 2 +-
>  arch/arm/boot/dts/rk3288-veyron-minnie.dts | 2 +-
>  arch/arm/boot/dts/rk3288-veyron-tiger.dts  | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/rk3288-veyron-jaq.dts b/arch/arm/boot/dts/rk3288-veyron-jaq.dts
> index af77ab20586d..4a148cf1defc 100644
> --- a/arch/arm/boot/dts/rk3288-veyron-jaq.dts
> +++ b/arch/arm/boot/dts/rk3288-veyron-jaq.dts
> @@ -20,7 +20,7 @@ / {
>  
>  &backlight {
>  	/* Jaq panel PWM must be >= 3%, so start non-zero brightness at 8 */
> -	brightness-levels = <0 8 255>;
> +	brightness-levels = <8 255>;
>  	num-interpolated-steps = <247>;
>  };
>  
> diff --git a/arch/arm/boot/dts/rk3288-veyron-minnie.dts b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
> index f8b69e0a16a0..82fc6fba9999 100644
> --- a/arch/arm/boot/dts/rk3288-veyron-minnie.dts
> +++ b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
> @@ -39,7 +39,7 @@ volum_up {
>  
>  &backlight {
>  	/* Minnie panel PWM must be >= 1%, so start non-zero brightness at 3 */
> -	brightness-levels = <0 3 255>;
> +	brightness-levels = <3 255>;
>  	num-interpolated-steps = <252>;
>  };
>  
> diff --git a/arch/arm/boot/dts/rk3288-veyron-tiger.dts b/arch/arm/boot/dts/rk3288-veyron-tiger.dts
> index 069f0c2c1fdf..52a84cbe7a90 100644
> --- a/arch/arm/boot/dts/rk3288-veyron-tiger.dts
> +++ b/arch/arm/boot/dts/rk3288-veyron-tiger.dts
> @@ -23,7 +23,7 @@ / {
>  
>  &backlight {
>  	/* Tiger panel PWM must be >= 1%, so start non-zero brightness at 3 */
> -	brightness-levels = <0 3 255>;
> +	brightness-levels = <3 255>;
>  	num-interpolated-steps = <252>;
>  };
>  
> -- 
> 2.28.0