Echo on screen image

in 10% of system startups I noticed an echo in the image

the echo can already be seen in the kernel splash screen stage
and all the time until restart

My platform iris 2.0 , imx8x + lvds display

Have you tried another cable or/and monitor?

I tested different LCD panel on LVDS and test another monitor !

Images in my first post are from LCD on LVDS

IRIS 2.0 has VGA output on DVI , now in attachmend I send image from DVI-VGA out image when I have “echo” on LVDS
the picture on VGA is more broken !
dmesg_ok.txt (30.9 KB)
dmesg_echo.txt (30.8 KB)

Hi @MariusM ,

Could you please share more information about you setup?

  • Which Colibri iMX8 version are you using?
  • From your dmesg we see that you are using Linux version 5.4.161-5.6.0-devel+git.e395d949e46b
  • Can you please check the overlays that you have active (/boot/overlays.txt)?
  • Which display are you using (model and version)?

Best regards,

Looks like LCD parametres like pixel clock, sync signal polarity etc doesn’t exactly match your display spec.

Colibri iMX8 PN: 00381003 Colibri iMX8 QuadXPlus 2GB Wi-Fi / Bluetooth IT
Carrier board: PN: 01352000 Iris Carrier Board V2.0A
BSP version: TDX Wayland with XWayland 5.6.0-devel-20220201194419+build.0 (dunfell)
Kernel: Linux colibri-imx8x-06948283 5.4.161-5.6.0-devel+git.e395d949e46b
Application: Qt + 3D in OpenGLES
Normal mode: Qt application display on screen connected over LVDS to IRIS

Display AA070MC01 Mitsubishi

fdt_overlays=colibri-imx8x_parallel-rgb-lvds_overlay.dtbo colibri-imx8x_atmel-mxt-connector_overlay.dtbo display-edt7_overlay.dtbo

Hi @MariusM !

Comparing the datasheet and the overlay that you are using (display-edt7_overlay.dtbo), seems like they are not compatible.

Let’s take a look at the timing diagram of your display

From this, seems like all the blanking time (front porch + back porch + sync) must be either before or after the active time for both vertical and horizontal time.

And the overlay for Toradex’s EDT7 display has blanking time for both before and after active time.
Reference: device-trees/display-edt7_overlay.dts at fdac8d2e0269f6d735d5b69d7975bd2c23a81438 · toradex/device-trees · GitHub

Could you please try both settings:

  • back porches to zero,
  • front porches and sync to zero

Best regards,

Thanks for the suggestions.
I am watching the screen!
Echo does not appear!

Hi @MariusM !

Great that it worked for you!

Could you please share the working device tree, so it can serve as a guide for others?

Best regards,

I’m still investigating the problem!

Hi @MariusM !

Do you have any news related to this issue?

Best regards,