Colibri IMX8QXP DSI to HDMI not working

Technical Support
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1

Hello All,

We are trying to evaluate the dsi hdmi apdater on a colibri unit but no display come out at all. We have followed the instructions online and modified overlay.txt to:

fdt_overlays=colibri-imx8x_dsihdmi_overlay.dtbo

Hardware we used:

  1. Colibri IMX8QXP 2GB WB IT
  2. Carrier Board: Iris 2.0
  3. Colibri DSI-HDMI Adapter Ver 1.1
  4. Colibri HDMI Adapter Ver 1.0
    we daisy chained the Dsi-hdmi adapter with the Hdmi adapter from the X2 port of the colibri imx8x.

OS we are using is the reference multimedia image from toradex:

Linux colibri-imx8x-07021654 5.4.161-5.6.0+git.0f0011824921 #1 SMP PREEMPT

To be more specifics:

cat /etc/issue

TDX Wayland with XWayland 5.6.0+build.18 (dunfell) \n \l
Colibri-iMX8X_Reference-Multimedia-Image

We have tried different display but no luck. The display resolution we have used are 1920*1080.

So far we have seen:
In the /sys/class/drm/card0-HDMI-A-1, the status is Disconnected
when query the Lt8912 by using dmseg | grep -i lt8912, nothing is returned.

Any ideas where we should look at for troubleshooting?

Thanks,
Warren

Update

We managed to get one monitor 19201080 working. However, we are trying to connect to a 7 inch 10801920 potrait screen and could not get it to work. No Lt8912 event in dmesg log.

2

Hi @warrenlee,

First of all, welcome to our community! Feel free to ask us any questions that you might have.

All of these displays you’ve mentioned were in portrait mode? None of them worked?

Could you please share the model of your display? Or send the datasheet for us?

About the events in the dmesg log, I tried here to boot up my iMX8X without any display and I couldn’t see any errors logs too, so I suspected that this is normal, you won’t see any logs from LT8912.

Best Regards,
Hiago.

3

Thanks for the reply Hiago!

For the display we are using is:
https://focuslcds.com/product/7-0-tft-display-capacitive-tp-e70rd-i-hs500-c/

All the datasheet is listed within this url under documentation sections. I have also attached here for reference:
E70RD-I-HS500-C_Spec.pdf (3.7 MB)

To answer your questions:

All of these displays you’ve mentioned were in portrait mode? None of them worked?
We have tested with one normal landscape monitor with 1920*1080 and it worked. But none of the portrait screen we used works. The portrait specs is the datasheet attached above.

4

Hi @warrenlee,

Thanks for the info!

In this case, you can go to /etc/xdg/weston/weston.ini and add the output mode to match your resolution. Also, you could edit the transform parameter to rotate your screen.
I’m not sure if it will be enough to only edit this parameter, can you test editing this file and check if that works?
Here is the reference: Display Output, Resolution and Timings (Linux) | Toradex Developer Center

Best regards,
Hiago.

5

Hi,

We have tried the weston.ini before and I don’t think it work.

Not sure if this information help, we do have an IMX6S and use the hdmi socket work out of the box and it works with that portrait screen. We have tried same weston.ini on those those two boards too, but the imx8x with the dsi-hdmi adapter could not show up any display.

Warren

6

I think this issue could be related to this topic

LCD (HDMI) doesn’t display - Technical Support - Toradex Community

Our thoughts is that the Panel we were using does not provide all the EDID information. We want to following this example but not sure how we could apply those to the device tree.

http://git.toradex.com/cgit/linux-toradex.git/diff/Documentation/devicetree/bindings/display/bridge/lontium,lt8912.txt?h=colibri&id=331ac1cf6e09d90e7d9ab39445bc8812ff33f178

Could you provide guidance on how to modify the device tree overlay to apply those changes.

Thanks

7

Hi @warrenlee,

I was looking through the datasheet here and apparently, as you said, your display does not support EDID, so indeed you’ll need to hardcode the display timings. Do you have them? I couldn’t find it in the datasheet that you sent me.

Also, I found very good documentation in the Linux Kernel about the timings and configurations that you can enable in your device tree: display-timing.txt « panel « display « bindings « devicetree « Documentation - linux-toradex.git - Linux kernel for Apalis, Colibri and Verdin modules

You can check this article on how to create a device tree overlay: Device Tree Overlays (Linux) | Toradex Developer Center

For your problem, you will need to edit the lt8912_hdmi node.
I wrote this example of a device-tree overlay for you:

/dts-v1/;
/plugin/;
/ {
	compatible = "toradex,colibri-imx8x";
};

&lt8912_hdmi {
	status = "okay";
   
     display-timings {

		native-mode = <&timing0>;

		timing0: 1080p24 {
			/* 1920x1080p24 */
			clock-frequency = <52000000>;
			hactive = <1920>;
			vactive = <1080>;
			hfront-porch = <25>;
			hback-porch = <25>;
			hsync-len = <25>;
			vback-porch = <2>;
			vfront-porch = <2>;
			vsync-len = <2>;
			hsync-active = <1>;
		};
	};
};

You can name this file whatever you think it’s better, compile it, and add it to your module.

Of course, this is only an example that I extracted from the document that I sent you. You’ll need to check your display datasheet and add the necessary configurations.

Best Regards,
Hiago.

8

Thanks for the reply and help!

I have tried modify the the device tree file like suggested but unfortunately couldn’t get it working. However, I managed to force the video mode in kernel command and get it displaying by setting
video = HDMI-A-1:1200x1920@60. Only issue right now is there is a small offset on top of the screen.

I think the DSI to HDMI converter does not support non standard resolution naturally. We have tried different 1200x1920 screen with proper EDID(ver. 1.3) and none of them could work without forcing video mode on it.

We are looking to hook up directly to a MIPI based display(MIPI to MIPI). Could you point me to some documentations or examples on how to achieve this, if possible?

Thanks again for the help.

Warren

9

Hi @warrenlee,

Sorry for the delay.

Unfortunately, I couldn’t find any documentation about MIPI to MIPI in our documentation.
There is this guide from NXP called i.MX Linux Reference Manual, you might find something useful in that. Other than that, I couldn’t find other relevant documentation.

Best Regards,
Hiago.