HDMI display resolution cannot be set

Technical Support
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1

I’ve been using Torizon OS 7.1.0+build.4 on Verdin iMX8M-Plus with an external HDMI display.
The resolution I need is 1920x1080@60Hz (16:9) and so I use the following lines in weston.ini

[output]
# you must uncomment the "name” line and provide the name of the output interface being customized, otherwise, changes will not apply
name=HDMI-A-1
# uncomment line below to set an output resolution. Run for example 'cat /sys/class/drm/card1-HDMI-A-1/modes' to list the available modes.
mode=1920x1080@60 16:9

I think that mode should force the resolution of the display to the given value.
Everything works fine with some different displays.
But I have another display that has strange/wrong EDID data.
Based on these EDID, 1920x1080 is not listed as one of the supported resolution.
But in reality it’s supported.
I see that when Torizon OS boots, it sets the resolution to 1020x768 (that is listed in the EDID of the display).
I’ve already asked thte manufacturer of the display that EDID should be fixed.
In the meanwhile, is there a way to “force” the resolution to 1920x1080 (even if this is not listed in the EDID)?

Thanks

2

Hi, I’m the Toradex AI Assistant. The Toradex Support team will follow up with you shortly!

Did you like my answer?

:+1: :-1:

Hello!

For the Verdin iMX8M Plus, you have two options for configuring HDMI:

  1. Native HDMI Interface: This can be set up using the device tree overlay verdin-imx8mp_hdmi_overlay.dtbo. You can find more details on configuring displays with Torizon in the Toradex documentation and a list of available overlays here.

  2. DSI to HDMI Adapter: This setup uses the overlay verdin-imx8mp_dsi-to-hdmi_overlay.dtbo. The same documentation links provide guidance on this configuration.

Both overlays support a default resolution of 1920x1080. If you need to force a resolution not listed in the EDID, here are some steps you can take:

  • First, confirm which overlay you are currently using.
  • Ensure that the overlay is correctly enabled in your system.

If you need further assistance with EDID override options, I can provide a general approach to handling EDID issues or focus on the documented overlay configurations. Please let me know how you would like to proceed.

Best regards,
Toradex AI Assistant

3

I use Native HDMI Interface, but in the overlay there is no setting of a specific resolution.

Please, suggest me a general approach to handling EDID issues (if you can).

4

Hello @vix,

You can try to force a specific resolution to be valid.
This is done via a kernel argument:

sudo fw_setenv tdxargs video=HDMI-A-1:1920x1080

This does not always works, as the available resolutions are limited.

Another alternative would be to load an external edid firmware.
This approach has some limitations which I outlined in the following post: Inject custom edid - #10 by bruno.tx

Best Regards,
Bruno

5

Hi @bruno.tx

can I do this with torizoncore-builder?

6

Hello @vix,

It depends on the approach.
In this context, with TorizonCore Builder, you can:

  • Add kernel arguments
  • Add custom services

With TorizonCore Builder, you cannot:

  • Modify the initramfs

Best Regards,
Bruno

7

Using tcb to set a kernel argument worked for me.

8

Hello @vix,

Thanks for the update, it is good to know it worked.

Best Regards,
Bruno

9

Hi @bruno.tx
one thing that I’ve just noticed is that the frequency is not honored by the kernel setting.
I set 60 Hz but I gei 148.5Hz.
Do you know why?

10

Hello @vix,

How are you checking this frequency?

148.5 looks like a valid frequency, in MHz, for the pixel clock.
Maybe you are looking at the pixel clock and not the refresh rate of the screen.

Best Regards,
Bruno

11

You’re right.
I see the weston log and I did a mistake:

weston-imx8-1      | [11:50:48.615] Output HDMI-A-1 (crtc 33) video modes:
weston-imx8-1      |                1920x1080@60.0, preferred, 148.5 MHz
weston-imx8-1      |                1920x1080@60.0, 148.5 MHz
weston-imx8-1      |                1920x1080@60.0 16:9, current, 148.5 MHz

60 fps (or 60 Hz) is the refresh rate.
148.5 is in MHz, not in Hz. And so it’s a pixel clock.

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