how to setup simultaneous display (lvds + hdmi) for i.mx8m plus in linux os

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how to setup simultaneous display (lvds + hdmi) for i.mx8m plus in linux os

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Hello! Setting up simultaneous display output on both LVDS and HDMI with the Verdin iMX8M Plus under Linux is fully supported. Here’s a step-by-step guide to help you achieve this:

1. Enable Device Tree Overlays

You need to enable both the HDMI and LVDS overlays. On TorizonCore or Toradex Reference Images, do this by editing the overlays.txt file on the /boot partition:

# Backup the current overlays.txt (optional)
cp /boot/overlays.txt ~/overlays_backup.txt

# Add overlays for HDMI and LVDS
echo "fdt_overlays=verdin-imx8mp_hdmi_overlay.dtbo verdin-imx8mp_lvds_overlay.dtbo" > /boot/overlays.txt
sync
reboot

See more on display overlays

2. HDMI Output

  • HDMI uses automatic monitor detection (EDID/DDC), so usually no further configuration is needed.
  • If you want to force a specific resolution, edit your kernel command line (e.g., in U-Boot):
video=HDMI-A-1:1280x720

More on HDMI configuration

3. LVDS Display Setup

LVDS requires more specific configuration for timings and data-mapping according to your LCD panel. In your device tree overlay, make sure to set the fsl,data-mapping and fsl,data-width properties to match your display:

For example:

  • For an 18-bit JEIDA panel:
    fsl,data-mapping = "spwg"; fsl,data-width = <18>;
  • For a 24-bit VESA panel:
    fsl,data-mapping = "spwg"; fsl,data-width = <24>;
  • For a 24-bit JEIDA panel:
    fsl,data-mapping = "jeida"; fsl,data-width = <24>;

Full list of options and panel configuration

4. Verify Both Displays

After rebooting, check if both LVDS and HDMI displays are detected:

modetest -M imx-drm

This tool will list all connectors (HDMI-A-1, LVDS-1), their modes, and current configuration.

How to use modetest

5. Additional Tips

  • The i.MX 8M Plus can drive all three outputs (HDMI, LVDS, MIPI-DSI) at once, with certain performance limits (e.g., 2x 1080p60 + 1x 4kp30).
  • Use TorizonCore Builder or Yocto if you need to customize overlays or device trees further.

For more details and examples, please refer to the official Toradex Display Output documentation:

Best regards, Toradex AI Assistant.

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Hi @GeorgeChang

Have you tested this?