This was referenced in the whats new thread.
I am aware of an issue in recent kernel versions that causes reboots to hang. The issue has been narrowed down to a potential race issue when “unplugging” DPAA2 objects from the drivers and futher debugging will be done in the new year. In the mean time, if you experience reboot hang issues, you should switch to legacy network management mode
Workaround 1) is to switch to legacy management mode.
(This will make all the GbE interfaces appear as link up all the time, which may cause issues if your system does automatic network configuration)
To move into legacy network mode, enter these commands at the U-Boot prompt:
setenv gbemode legacy
setenv sfpmode legacy
saveenv
reset
Workaround 2)
This patch I used for debugging seems to make the issue go away. It’s NOT a fix, the extra logging just adds enough delay to avoid the deadlock/race condition.