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Troubleshooting • Re: Raspberry CM4 pwm-backlight duty cycle missing

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I've figured out that this seems to be the reason why it results in bl_power 4. Is there any option to get the Raspberry Pi PWM default enabled?

https://github.com/raspberrypi/linux/bl ... #L423-L424

This is the config in my overlay

Code:

    fragment@1 {        target = <&gpio>;        __overlay__ {            pwm_pins: pwm_pins {                brcm,pins = <12>;                brcm,function = <4>; // ALT0            };        };    };    fragment@2 {        target = <&pwm>;        frag1: __overlay__ {            pinctrl-names = "default";            pinctrl-0 = <&pwm_pins>;            assigned-clock-rates = <1000000>;            status = "okay";        };    };    fragment@3 {        target-path = "/";        __overlay__ {            rpi_backlight: rpi_backlight {                compatible = "pwm-backlight";                brightness-levels = <0 6 8 12 16 24 32 40 48 64 96 128 160 192 224 255>;                default-brightness-level = <6>;                pwms = <&pwm 0 200000 0>;                status = "okay";            };        };    };
Hi, were you able to get this resolved? I’m running into the same issue where bl_power ends up as 4, and I suspect it might be related to the same lines in the kernel source you linked. I'm also using a custom overlay with PWM for backlight control and trying to get the PWM output enabled by default. Would appreciate any insights or updates you might have on this!

Code:

/dts-v1/;/plugin/;/ {    compatible = "brcm,bcm2835";    fragment@0 {        target = <&gpio>;        __overlay__ {            pwm_pins: pwm_pins {                brcm,pins = <13>;                brcm,function = <4>; // ALT0                brcm,pull = <0>;            };        };    };    fragment@1 {        target = <&pwm>;        __overlay__ {            pinctrl-names = "default";            pinctrl-0 = <&pwm_pins>;            assigned-clock-rates = <100000000>;            status = "okay";        };    };    fragment@2 {        target-path = "/";        __overlay__ {            backlight_lvds: pwm13_backlight {                compatible = "pwm-backlight";                pwms = <&pwm 1 5000000 0>;                brightness-levels = <0 1000>;                num-interpolated-steps = <1000>;                default-brightness-level = <800>;                enable-gpios = <&gpio 26 0>;  // GPIO26 = backlight enable                post-pwm-on-delay-ms = <200>;                pwm-off-delay-ms = <200>;                status = "okay";            };        };    };};

Statistics: Posted by kirankarkada — Tue Jun 10, 2025 11:56 pm



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