Linux imx8mn device tree configuration for DSI to LVDS Bridge


I am building a system using Variscite SOM Nanos with the Yocto Linux distribution. I have gotten my hardware setup configured to drive a 4 channel LVDS display using their custom carrier board. The problem I am having is that the basic variscite device tree file to run the 7" 3 data channel LVDS display found in the imx8mn-var-som.dtsi file of the device tree consists of code that runs only a 3 channel LVDS display. I used the carrier board to solder an extra pair of headers to the last channel pair of the LVDS channel A block so that I could run the custom screen I am using, which is this one. I have changed the appropriate parameters to run the screen I am using, and have bitbaked the new image, but I still get pixelated screens on the 5" IPS display. To diagnose, I have hooked up the last two pairs of LVDS data lines to an oscilliscope, and when I do I get a horribly scrambled signal. All other LVDS lines I hook up to the oscilloscope are perfect except the last pair that I added. Im sure that the device tree needs to be configured properly to account for the extra pair of LVDS data lines that I am using, I just dont know how this is done. Is it done somewhere in the imx8mn-var-som.dtsi file? If it is, which part of the file I have attached below would I have to change to account for this? Any help would be greatly appreciated.
file_for_code_injection_of_screen (1).txt (1.9 KB)

Also if someone could explain what the variables <ti,width-mm> and <ti,height-mm> mean that would be greatly appreciated.

Thank you so much. I am happy to provide more information you shall need any:)

Hi jlind,

Well I would certainly like to help and in many case we at Toradex may in fact answer some questions that are generic and even not specific to our SoMs, but your question here seems like it very specific to Variscite and their offerings and for that reason we are not able to help.

We at Toradex make our own SoMs and I would be happy to discuss using one of ours for your project and provide support if you do have questions on it.

Best regards,


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Hey Michael,

Very much thanks for the reply. The questions is not particular to the variscite SOMs whatsoever just the device tree configuration for the lvds display bridge. Ive seen threads on here talking about similar things, but none that directly address what to do in the device tree when you add a fourth lvds data pairing. If you know of any guidance as to help that would be greatly appreciated:)

On a different note, variscite customer support is poor, and I wish that we had chosen a more reputable hardware supplier for our system like Toradex. I have heard great things about how you treat your customers, and I wish it was the same with varisicite. If you would be willing to help me here as much as you can, I would greatly appreciate it. I would also like to consider prototyping with toradex modules using the same Linux based yocto distribution on an iMX8MN if possible:)

Thank you mike.

  • jacob

Hi @jlind,

The flickering you’re seeing is probably due to timing errors in the device tree. For example, you can see our overlay here with some configurations for the Toradex display. You should have all the timings and configurations correctly based on the display datasheet.

There you need to place the size of your display, in mm.

Like Michael said, for more information you should reach out to Variscite support. If you use Toradex, I’ll be glad to dive into this problem and solve it with you.

Best Regards,

1 Like