2025-10-11 6:58 AM
This is the current implementation of the `panel_lvds_backlight`, i'm trying to implement the pwn brightness control for this.
{
/* https://github.com/STMicroelectronics/linux/blob/f01241fb/arch/arm64/boot/dts/st/stm32mp257f-ev1.dts */
....
	panel_lvds_backlight: panel-lvds-backlight {
		compatible = "gpio-backlight";
		gpios = <&gpioi 5 GPIO_ACTIVE_HIGH>;
		default-on;
		default-brightness-level = <1>;
		status = "okay";
	};
....
}
/dts-v1/;
/plugin/;
#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/input/input.h>
#include <dt-bindings/pinctrl/stm32-pinfunc.h> /* This is required by fragment@3 for pinctrl */
/ {
    compatible = "st,stm32mp257f-ev1";
    /* Modify panel timing clock frequency */
    fragment@0 {
        target = <&panel_lvds>;
        __overlay__ {
            panel-timing {
                clock-frequency = <54000000>;
            };
        };
    };
    /* Replace GPIO backlight with PWM backlight */
    fragment@1 {
        target = <&panel_lvds_backlight>;
        __overlay__ {
            /* Delete old GPIO backlight properties */
            /delete-property/ gpios;
            /delete-property/ default-on;
            /* Change compatible and add PWM properties */
            compatible = "pwm-backlight";
            pwms = <&pwm5 1 1000000 0>;
            brightness-levels = <0 16 22 30 40 55 75 102 138 188 255>;
            default-brightness-level = <10>;
            status = "okay";
        };
    };
    /* Configure PWM5 CH2 pins (active state) */
    fragment@2 {
        target = <&pinctrl>;
        __overlay__ {
            pwm5_ch2_pins_a: pwm5-ch2-0 {
                pins {
                    pinmux = <STM32_PINMUX('I', 5, AF9)>; /* TIM5_CH2 - AF9 - pinctrl-stm32mp257.c */
                    bias-pull-down;
                    drive-push-pull;
                    slew-rate = <0>;
                };
            };
            pwm5_ch2_sleep_pins_a: pwm5-ch2-sleep-0 {
                pins {
                    pinmux = <STM32_PINMUX('I', 5, ANALOG)>; /* TIM5_CH2 */
                };
            };
        };
    };
    /* Enable timers5 and PWM5 */
    fragment@3 {
        target = <&timers5>;
        __overlay__ {
            status = "okay";
            pwm5: pwm {
                compatible = "st,stm32mp25-pwm";
                pinctrl-0 = <&pwm5_ch2_pins_a>;
                pinctrl-1 = <&pwm5_ch2_sleep_pins_a>;
                pinctrl-names = "default", "sleep";
                status = "okay";
            };
        };
    };
};
I implemented this dt overlay and i'm sure that this overlay is successfully applied during the boot but im getting deffered probing error in this dt overlay example.
root@stm32mp25-eval-e3-e4-2e:~# [   27.055167] weston[1619]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set
[   27.625314] platform 48060000.lvds: deferred probe pending
[   27.625369] platform panel-lvds-backlight: deferred probe pending
[   27.631789] platform panel-lvds: deferred probe pending
[   27.636838] platform 48010000.display-controller: deferred probe pending
[   27.643680] stm32mp_pm_domain power-domain-d1: sync_state() pending due to 48010000.display-controller
[   27.652958] stm32mp_pm_domain power-domain-d1: sync_state() pending due to 48060000.lvds
[   31.974569] vddio3: disabling
[   31.974653] vddio4: disabling
[   31.974910] vdda18adc: disabling
[   31.978162] vddcore: disabling
[   31.994557] v1v8: disabling
 
Can anyone help me debug and solve this issue. i'm pretty sure about what i'm doing here, i referred the pwm-back-light implemented in stm32mp257f-dk.dts. apart from using DT overlay i even tried applying patch with same implementation as above shared overlay, end up having same kernel log again.
Hoping for a quick reply, thanks in advance.
2025-10-14 12:14 AM
Hello @Erwan SZYMANSKI and @PatrickF ,
I am also facing the same issue, Can anyone help us on this above query ?
2025-10-20 9:11 PM
Hi @Erwan SZYMANSKI and @PatrickF
I have been waiting for the reply since a week now, can anyone help me with getting solution for this issue.
Thank in advance.
2025-10-23 2:25 AM
Hi @Vijay_V2225 ,
Sorry if the ST Community has not yet brought you the hoped solution, but ST cannot commit any delay in answer on this channel.
Your issue looks very specific, and you might probably get a better support using OLS support channel Home
Olivier
