linux-kernel - Re: [PATCH v3 3/4] ARM: dts: imx6qdl-colibri: backlight pwm: Simplify inverted backlight

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Message-ID: <CAOMZO5Au5_=0enWpfQBOK6_62r_5iL4m-pd93Px-NUO9dXb5-w@mail.gmail.com>
Date:   Fri, 13 May 2022 07:53:23 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Max Krummenacher <max.oss.09@...il.com>
Cc:     Max Krummenacher <max.krummenacher@...adex.com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] ARM: dts: imx6qdl-colibri: backlight pwm: Simplify
 inverted backlight

Hi Max,

On Fri, May 13, 2022 at 7:27 AM Max Krummenacher <max.oss.09@...il.com> wrote:
>
> From: Max Krummenacher <max.krummenacher@...adex.com>
>
> Set #pwm-cells to the default 3 to gain access to the parameter
> which allows inverting the PWM signal. This is useful to specify
> a backlight which has its highest brightness at 0.
>
> With the change to use the PWM with inverted polarity the PWM signal
> is inverted to how it was before this patch.
> This changes the meaning of the values in the brightness-levels
> property. I.e. the duty-cycle changes from x/255 to (255-x)/255.
> Keeping the brightness-levels will then have a big brightness
> jump from 0 to 127 duty cycle, the other 6 steps will then be
> barely noticeable.
>
> Change the brightness-levels to provide the same brightness-levels
> as before.
>
> Signed-off-by: Max Krummenacher <max.krummenacher@...adex.com>

Thanks for the rework:

Reviewed-by: Fabio Estevam <festevam@...il.com>