No hdmi console output iMX8

Hello,

with the new Bsp (we tried 5.2 and 5.1) for the iMX8 we don’t see a linux terminal on the hdmi output (with bsp 3.0.3 it works) but only via serial connection, however if we choose the multimedia image we get a hdmi output. We get the gui displayed at the hdmi monitor but also no terminal output at start up or anything similar at startup.

any ideas?

Thank you for your help!

Dear @Flo ,

As mentioned in this developer article, tdx-reference-minimal-image is a minimal image without any GUI. GUI is only supported in the Multimedia image, like you already have discovered.

Best Regards,
Janani

Dear saijanani.tx,
what I meant is not a fancy graphical user interface, but a commandline style output. In older images you will see a terminal output at the monitor that is connected to the hdmi port. This ouput is similar to the serial output. You won’t see this output with the build “TDX Wayland with XWayland RT 5.2.0-devel-20210203113425”. With the named build the monitor stays dark.

Best Regards

Dear @Flo ,

I understand now. Could you send me the dmesg.txt?

Thanks, Janani.

Dear @saijanani.tx ,

thank you for your fast reply and your help!
this is the dmesg output: dmesg

Best Regards

Could you try a regular image without RT? Could you attach the full console boot output including U-Boot everything?

This is the serial output with the rt image: serial output rt it should be the the same version of the image that I named in my initial question. It probably does not have the same version of the Uboot because I already tried different uboot versions, all with the same result: no hdmi output.

This is the output with out the rt version: serial output without rt the version is slightly newer because I build it today. It shows the hdmi output with the minimal image the hdmi is working.

I hope it helps.
Thank you.

Hello,
is there any new information regarding this topic?

Hello @Flo,

Sorry, I thought the question was already answered. We only test and recommend non-RT images to our customers, and I see your HDMI is already working.

Is there a reason why you would want to use the RT image?

Best Regards,
Janani

Hello @saijanani.tx,

thank you for your fast reply, we want to use the IMX8 in a environment with high demands on timing behaviour and determinism for example sensors and algorithms that are very sensitive to delay and jitter.

Best Regards

Hello @saijanani.tx,
For our application we will of course take care of the real-time behavior but on the side of the Linux it would be nice if toradex would provide a rt version of the image with basic functionalities (graphical output, hardware interfaces). As toradex provides webinars on developing real-time systems with embedded Linux (Webinar On-Demand: Development of Real-Time Systems with Embedded Linux) with their products and in previous versions of the images (kernel 4.14) HDMI output already worked so we did not think that this would complicate our work with this product.

I also do not find any information that says that toradex RT images are not tested and not recommended. Real-Time Linux (Toradex) only says “Note: It may be advantageous to disable display/graphics related drivers - namely FB, DRM & Vivante drivers. Power management or CPU governing may also present issues.” but not that they won’t work as expected.

Best Regards, Florian

Hello @Flo ,

I understand your concern. But, as I said before, we only test the non-RT images. And I also did not say we don’t recommend RT images.
And I agree with you that, we could have been more explicit in the developer article.

However, as for as this issue is concerned, we will look into it and try to get back to you soon.

We appreciate your understanding and patience in this regard.

Best Regards,
Janani

Hello @Flo,

Thank you very much for your patience. In the meanwhile we have had time to look into the issue and come up with a solution.

The reason why the HDMI wasn’t working is because the FrameBuffers CONFIG_FRAMEBUFFER_CONSOLE have not been set in the kernel (intended). By enabling this, the HDMI output is working.

The new config file that has also been tested for HDMI can be found here:
https://share.toradex.com/sh6v090oavsxhgs (this link is valid for a week only).

Hope this helps!

Best Regards,
Janani

Hello @saijanani.tx,

thank you for your support! whats the best way to use this kernelconfig. I replaced build/tmp/work-shared/apalis-imx8/kernel-source/.config and build a new Kernel (Image.gz), I also build and installed the kernel modules. However that didn’t seem to work, hdmi is still not working.
thank you again for your help.

Best Regards, Flo

Hello @flo,

In order to replace the kernel config, you need to change it either by make menuconfig and then selecting the correct config file or place the option you want in the defconfig.

Perhaps, this Yocto article can be helpful:
https://www.yoctoproject.org/docs/1.6/dev-manual/dev-manual.html#modifying-the-kernel

Best Regards,
Janani

Hello @saijanani.tx

Thank You, I now have an hdmi output. I guess the problem I had was that I didn’t sync after I copied the new kernel and kernel modules. Thank you!

Best Regards, Flo

Hello @Flo ,

Ah, I see. But I am glad you could figure that out and that your HDMI is working.

Best Regards,
Janani.