'Property power-supply for an external pwm-backlight IC

I have this LCD panel:

enter image description here

LED panel's backlight is driven by the MIC2297 chip which takes two signals:

  • BRT - PWM signal for setting brightness of the LCD's background LEDs.
  • BL_EN that - gpio signal that enables or disables the LCD's background LEDs.

MIC2297 is powered from the +12V.

Now I connected this display to the Beaglebone Black's (BBB's) expansion connector and I am already running Linux on the BBB's microcontroller AM335x.

In order to enable the backlight I have to properly define it in the device tree i.e. .dts file. Currently I managed to set this up:

backlightt: backlight {
    compatible = "pwm-backlight";
    pwms = <&ehrpwm1 0 500000000>;
    power-supply <>; // ???
    enable-gpios = <&gpio2 3 0>;
    brightness-levels = <0 4 8 16 32 64 128 255>;
    default-brightness-level = <7>;
};

What I don't understand is the property power-supply. How can I know which regulator to use? My devicce uses external 12V! This is really confusing! Why do we even have to specify the regulator?

beagleboneblackdevice-tree


Solution 1:[1]

I found solution...

PWM backlight requires a property "power-supply" that points to some regulator inside the AM335x. This regulator is used to set the output voltage of the PWM - so we don't need to put any kind of voltage regulator between an AM335x and the backlight IC (which might only support 1.5V PWM input on some mobile devices). This is actually really useful.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 71GA

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