How to add LVDS Display

Technical Support
,
1

I am using Verdin IMX8MP with mallow carrier board, so far I can’t make LVDS work. Could you please point out what I did wrong?

Here is what I did:

  1. create dts file:
    our LVDS maker has a timing table:
    (1) Timing Specifications:
    image
    image986×389 56.6 KB

My .dts file:
/dts-v1/;
/plugin/;

/ {
compatible = “toradex, verdin_imx8mp”;
fragment@0 {
target-path=“/panel-lvds”;
overlay {
status=“okay”;
data-mapping = “jeida-18”;
width-mm = <345>;
height-mm = <194>;

            panel-timing {
                    clock-frequency = <35700000>; 

                    hactive = <800>;
                    vactive = <480>;

                    // Horizontal timing
                    hfront-porch = <60>; 
                    hsync-len = <32>;   
                    hback-porch = <70>;  

                    vfront-porch = <8>;  
                    vsync-len = <5>;     
                    vback-porch = <35>;                

                    hsync-active = <0>;
                    vsync-active = <0>;
                    pixelclk-active = <0>;
            };
    };
};

};

Question: is this dts file correct?

  1. covert dts to dtbo: I use “dtc -I dts -O dtb -o my_overlay.dtbo my_overlay.dts”, then I transferred my_overlay.dtbo file to Verdin’s /sysroot/boot/ostree/torizon-xxxxxxx/dtb/overlay/, and modified overlay.txt: dt_overlays=my_overlay.dtbo
    Question: Device Tree Compiler (DTC) Tool on Build Device Tree Overlays from Source Code | Toradex Developer Center didn’t work for me: make failed.
    I managed to get a dtc, but maybe not correct.

After reboot, no display in my LVDS display. Please let me know the correct way for adding LVDS display.

Thanks.

2

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Hello,

To address the issues with adding an LVDS display to your Verdin iMX8MP setup, let’s break down the process and verify each step:

1. Device Tree Source (DTS) File

Your DTS file snippet seems to be on the right track, specifying the LVDS panel parameters. However, ensure that the compatible property matches exactly what is expected for the Verdin iMX8MP in the Linux kernel source you are using. The target-path should also correctly point to the node in the device tree where the LVDS display configuration is to be applied. This often requires a detailed review of the existing device tree structure to ensure the overlay applies correctly.

2. Converting DTS to DTBO

The command you used to convert the DTS file to a DTBO is correct. However, the issue with make failing suggests there might be a problem with your environment setup or with the DTS file itself. Ensure that your DTS file is free of syntax errors and that you have the necessary dependencies installed for compiling device tree overlays.

3. Applying the Overlay

Placing the DTBO file in the correct directory and modifying overlay.txt is a crucial step. However, ensure that the path to the DTBO file in overlay.txt is correct and that the filename matches exactly. It’s also important to verify that your TorizonCore version supports dynamic device tree overlays and that this feature is enabled.

Troubleshooting Steps:

  1. Verify Compatibility: Ensure that the compatible property in your DTS file matches your hardware and kernel version.
  2. Check the Device Tree Structure: Use tools like dtc to decompile the existing device tree blob (DTB) and verify that your overlay’s target-path correctly points to the intended node.
  3. Error Checking: Look for syntax errors or warnings when compiling your DTS file. These can often provide clues to the problem.
  4. Kernel Logs: After applying the overlay and rebooting, check the kernel log (dmesg) for any messages related to the display or LVDS interface. This can provide insights into what might be going wrong.
  5. Display Configuration: Ensure that any necessary kernel drivers for your LVDS display are enabled and correctly configured. This might involve additional kernel configuration or module parameters.

If after these steps your LVDS display still does not work, it may be necessary to review the entire device tree and kernel configuration to

Please, also check if these links can help you solve your problem:

Azurewave AW-CM276NF Wi-Fi & Bluetooth module | Toradex Developer Center.

3

Not exactly.

  • The overlay { node is not suitable here. Please check this article for details.
  • You haven’t included backlight and ports control node. Please check this file for example.

This thread may be also useful.

Regarding the issue with the Device Tree Compiler (DTC) tool, please describe in detail the steps you have taken. Include the system output for each step, highlighting the failed one.

4

Thanks alex.tx
I tried a few different dts files, so far all didnot work. and each time I have to re-install the easy installer.

My last file was:

/dts-v1/;
/plugin/;

/ {
compatible = “toradex,verdin-imx8mp”;
};

&panel_lvds {
status=“okay”;
data-mapping = “jeida-18”;
width-mm = <345>;
height-mm = <194>;

    panel-timing {
            clock-frequency = <35700000>;

            hactive = <800>;
            vactive = <480>;

            hfront-porch = <60>;
            hsync-len = <32>;
            hback-porch = <70>;

            vfront-porch = <8>;
            vsync-len = <5>;
            vback-porch = <35>;

            hsync-active = <0>;
            vsync-active = <0>;
            pixelclk-active = <0>;
  };

};

&adma_pwm {
status = “okay”;
};

&backlight {
status = “okay”;
};

&display_lcdif {
status = “okay”;
};

&panel_dpi {
status = “okay”;
};

Is this file Ok?,

Thanks.

5

No it’s not.
You haven’t included backlight and ports control node. Please check these DTS files for example 1, 2.