LVDS Display Troubleshooting

[NPal.2]

Hi all,

I am trying to bring a LVDS display up. Display: BOE EV121WXM-N10-1850. Datasheet: Link

Driving MPU : STM32MP1. I am using VisionSoM STM32MP1 based evaluation Kit. Link

The firmware changes required to make the device up are part of git: Link

I have made following changes in the dts files to support display:

kernel/stm32mp157a-visionsom-rgb-emmc-mx.dts and u-boot/stm32mp157a-visionsom-rgb-emmc-mx.dts has following changes :

    panel {
 
        compatible = "boe,ev121wxmn10", "simple-panel";
 
        backlight = <&backlight>;
 
        port {
 
            panel_in: endpoint {
 
                remote-endpoint = <&ltdc_out_rgb>;
 
            };
 
        };
 
    };

In case u-boot/stm32mp157a-visionsom-rgb-emmc-mx-u-boot.dtsi

    panel {
 
                display-timings {
 
                        timing0: timing0 {
 
                                clock-frequency = <74250000>;
 
                                hactive = <1280>;
 
                                vactive = <800>;
 
                                hfront-porch = <48>;
 
                                hback-porch = <80>;
 
                                hsync-len = <32>;
 
                                vback-porch = <15>;
 
                                vfront-porch = <3>;
 
                                vsync-len = <5>;
 
                                hsync-active = <0>;
 
                                vsync-active = <0>;
 
                                de-active = <0>;
 
                                pixelclk-active = <1>;
 
                        };
 
                };
 
    };

Here i have added panel settings to support the above display. Now the port which i have out on the board is RGB. I have used RGB to LVDS converter DS90C385A. Since I am trying to drive LVDS display.

The issue i am facing is that , I am unable to drive the display. Nothing is coming up.

Queries:

1. The settings which i have made , are those correct ?
2. What additional changes I might need to make , if i am missing any?
3. What can be potential failure points in this ?
4. What is the correct way to drive LVDS display? Is this correct way to do this ?

[PatrickF · Accepted solution]

Hi,

I'm not specialist, maybe asking Somlabs could be useful for support on their DT.

Probably missing some &ltdc node modifications to define that the panel is connected to it.

Example with external si9022 RGB2HDMI transceiver could be helpful : https://wiki.st.com/stm32mpu/wiki/LTDC_device_tree_configuration

Regards,

[NPal.2]

Thanks @PatrickF​ for the response , will take a look into it.