Issue:
Soft power options like Shutdown and Reboot are not working.
System hang/lockup after any of shutdown/reboot commands.

Precondition:
Ubuntu Desktop OS (20.4.3) and Linux kernel 5.16
No display, Headless mode with UART shell
Boot to OS
Perform soft reboot / shutdown

Other observations:
Inherited the new 5.16 kernel by building on my own using default defconfig.
5.15 kernel working good and dont see this issue, reverted and checked in same board.
Strange case is, when we do the same with power buttons on the board, it working good.

Does this a regression and anyone faced this? using nomodeset in grub is solving the issue.


[ 246.489981] systemd-shutdown[1]: All loop devices detached.
[ 246.510717] systemd-shutdown[1]: Detaching DM devices.
[ 246.516184] systemd-shutdown[1]: All DM devices detached.
[ 246.521882] systemd-shutdown[1]: All filesystems, swaps, loop devices and DM devices detached.
[ 246.544269] systemd-shutdown[1]: Syncing filesystems and block devices.
[ 246.551020] systemd-shutdown[1]: Rebooting.
[ 246.555537] kvm: exiting hardware virtualization

AFAIK nomodeset is for graphics. Since you don't have graphics, why don't you make that permanent?