Hi,
I’m encountering a problem on an Apalis IMX8QM 4GB IT v1.1E. This is a problem I haven’t seen before and it’s unclear whether it’s an issue with the new imx8 rev, driver bug, or a board defect.
It only occurs (randomly) when the HDMI is connected during boot.
It seems that roughly on half of the time the OS boots properly and everything works. The other half of the time, the HDMI monitor remains completely blank, the serial console hangs at login, and the card reboots itself after 30 seconds.
I set my kernel loglevel to DEBUG and captured this diff - a failed boot is on the left and a successful boot on the right. Notably the s-mhdp-imx 56268000.hdmi: lane-mapping 0x93 message is missing from the failed boot.
There are no messages visible in the console when the card resets itself, but I am wondering if the watchdog is noticing that the HDMI lane failed to map?
Any suggestions would be appreciated.
Model: Toradex Apalis iMX8 QuadMax 4GB IT V1.1E, Serial# 15489780
BuildInfo:
- SCFW 0d54291f, SECO-FW d63fdb21, IMX-MKIMAGE 8947fea3, ATF 835a8f6
- U-Boot 2020.04-5.3.0-devel+git.2e5818d88ee0
Linux version 5.4.115-5.3.0-devel+git.64dbf17bb33e
Torizon: 5.3.0-devel
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Hello!
Thank you for providing the detailed information, including the kernel versions and the diff logs. Based on your description and the captured logs, this intermittent HDMI issue during boot is a known problem with older kernel and BSP versions on the Apalis iMX8QM.
Key observations:
- The missing
s-mhdp-imx 56268000.hdmi: lane-mapping 0x93 in failed boots suggests the HDMI hardware is not being successfully initialized.
- The 30-second reboot and console hang are consistent with a watchdog timeout, which can be triggered when the system detects a failure in critical early initialization routines like HDMI.
Your current software stack:
- U-Boot 2020.04 and Linux 5.4.115 as part of Torizon 5.3.0-devel, using an older BSP.
Suggestions:
-
Upgrade to a Newer BSP/Torizon Version:
The issue you’re facing has been improved in later BSP releases. Both BSP 6.8.0 (Yocto Kirkstone, Linux 5.15) and BSP 7.1.0 (Yocto Scarthgap, Linux 6.6) deliver significant stability improvements, including in HDMI and display subsystem initialization.
See the Toradex Embedded Linux Release Matrix for current versions.
-
Hardware Compatibility Checks:
Although unlikely, sometimes HDMI issues can also stem from specific cable or monitor combinations. Try different HDMI cables and monitors to eliminate compatibility edge cases.
-
Enable Extended Serial Logging:
Keep the serial console attached during boot, and capture the complete boot logs at high loglevel (DEBUG). This can reveal suppressed warnings or failures in the HDMI initialization sequence.
-
Watchdog Reset Root Cause:
The pattern (blank HDMI, console hang, 30s reboot) aligns with systemd failing to initialize critical targets due to display subsystem lock-up, triggering the hardware watchdog. Upgrading your BSP greatly helps with such intermittent system-level failures.
Next Steps:
- Consider upgrading to BSP 6.8.0 or 7.1.0, and test if the HDMI issue persists.
- Capture and review fresh serial logs, especially if problems remain post-upgrade.
If you hit issues specific to your hardware revision on newer BSPs, please share the updated logs and version details for further troubleshooting.
Best regards,
Toradex AI Assistant.
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Are you using a Toradex-built Torizon image, or have you made custom modifications to the Linux kernel?
A similar issue was resolved in Torizon 5.2.0.
Have you tried using one of our latest Torizon releases (7.x)?
HAR-9336 Thanks, I’m working on updating my custom 5.3.0 build to the 7.x line and will close this if it fixes it.
