2025-11-26 3:00 AM
Hi im working on stm32mp257f-ev1 and the "edt,etml0700z9ndha" display,
Im unable to decode the logic why the back-light enable gpio only gets high when there is a display connected in the lvds port, what logic is used to detect the lvds display connection.
Since i only see the display logs during boot only when there is a display connected, i need clarification regarding this from which driver this logic is implemented, and in the compatible string "edt,etml0700z9ndha" this is used but i found no driver with this compatible list.
If in case i want to use the RVT101HVLNWCA0 what driver should i use
and can i get a sample device tree for this display
panel_lvds: panel-lvds {
compatible = "edt,etml0700z9ndha", "panel-lvds";
enable-gpios = <&gpiog 15 GPIO_ACTIVE_HIGH>;
backlight = <&panel_lvds_backlight>;
power-supply = <&scmi_v3v3>;
default-on;
status = "okay";
width-mm = <156>;
height-mm = <92>;
data-mapping = "vesa-24";
panel-timing {
clock-frequency = <54000000>;
hactive = <1024>;
vactive = <600>;
hfront-porch = <150>;
hback-porch = <150>;
hsync-len = <21>;
vfront-porch = <24>;
vback-porch = <24>;
vsync-len = <21>;
};
port {
lvds_panel_in: endpoint {
remote-endpoint = <&lvds_out0>;
};
};
};
panel_lvds_backlight: panel-lvds-backlight {
compatible = "gpio-backlight";
gpios = <&gpioi 5 GPIO_ACTIVE_HIGH>;
default-on;
default-brightness-level = <1>;
status = "okay";
};
Solved! Go to Solution.
2026-01-16 4:41 AM
Hi @sanjaysb ,
Sorry to come late in this thread.
This is answer I could get from expert :
In U-Boot, we have a mechanism for detecting the presence of the panel (by querying the touchscreen ID via I2C). When a panel is detected in U-Boot, U-Boot disables the other display nodes (notably the HDMI link) and starts the kernel with the device tree it has modified. In U-Boot, the code related to autodetection is here:
https://github.com/STMicroelectronics/u-boot/blob/v2023.10-stm32mp/board/st/stm32mp2/stm32mp2.c
Hope it help
Olivier
2026-01-16 4:41 AM
Hi @sanjaysb ,
Sorry to come late in this thread.
This is answer I could get from expert :
In U-Boot, we have a mechanism for detecting the presence of the panel (by querying the touchscreen ID via I2C). When a panel is detected in U-Boot, U-Boot disables the other display nodes (notably the HDMI link) and starts the kernel with the device tree it has modified. In U-Boot, the code related to autodetection is here:
https://github.com/STMicroelectronics/u-boot/blob/v2023.10-stm32mp/board/st/stm32mp2/stm32mp2.c
Hope it help
Olivier
2026-01-16 4:47 AM
Thanks for the reply, i hope the only purpose of that hardcoded detection is to use lvds as default display interface when multiple display connectors are being used.