Created attachment 298155 [details]
dmesg

I believe this bug is very similar if not the same to https://bugzilla.kernel.org/show_bug.cgi?id=103211.

I have managed to work around it and have the computer power off by using the two setpci commands from comment 298 in bug report 103211 in a systemd shutdown script placed in /lib/systemd/system-shutdown.

#!/bin/sh

case $1 in
	poweroff)
	setpci -s1c.0 0x20.l=0xf011f001
	setpci -s1c.0 0x24.l=0xf031f021
	;;
esac

Without the script the computer will just hang at shutdown. It also will not suspend properly. It looks like it does, but then it will not wake up and I have to hard power it down by holding the power button for 10 seconds before I can turn it back on again.

I am attaching the output of dmesg, lspci, dmidecode and /proc/iomem and /proc/ioports to aid in possibly extending the quirk fix from the previous bug report. Hopefully the issue is similar enough that it will be a quick fix.

I do believe I am running the latest BIOS (427.140.8.0.0 06/13/2021) which I believe was installed when I installed Big Sur.