PWM problems

Chip Platform Rockchip
1

Type: Self-Compiled Firmware
SDK Package Name: rk356x_linux_release_v1.3.0b_20221213
Modification Content: LVDS with PWM configuration
Log: no log.zip

I have a custom board based on RK3568jq.
I made Linux minimal image using Yocto:
https://wiki.t-firefly.com/en/Fi … e/manual_yocto.html
I added PWM control and it works fine using next command:echo 100 > /sys/class/backlight/backlight/brightness

but as i can see using oscilloscope , the frequency of PWM signal is about 40 seconds instead of 20 kHz !

my dtsi-file modifications:
rk3568-firefly-roc-pc.dtsi

backlight:backlight {
status = “okay”;
compatible = “pwm-backlight”;
pwms = <&pwm4 0 50000 0>;
…
}

lvds_panel: lvds-panel {
compatible = “simple-panel”;
status = “okay”;
backlight = <&backlight>;
…
}

what im doing wrong about frequency?
The third paramenter 50000 is frequency in nanoseconds ?

pwms = <&pwm4 0 50000 0>;

tchip_askquestions
no log.zip (22 Bytes)

2

The 50000 is means 50000ns.
If you need to set the maximum clock frequency, please use ‘echo 255 > /sys/class/backlight/backlight/brightness’.

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