I'm seeing the same behavior on Fedora 32 beta (5.6.3-300.fc32.x86_64) on XPS 9300 w/ 1.0.7 firmware. I have not tried to downgrade firmware, but the machine was properly shutting down and rebooting previously.

Have you tried going to 1.0.6 and see what happens ?

You can downgrade then upgrade again using the fwupdmgr console tool.

I got the 1.0.6 and everything works fine so I'm a bit cautious about going 1.0.7

That version has been out for a month but I don't want shutdown troubles.

For a test I upgraded my firmware from 1.0.6 to 1.0.7

No shutdown nor sleep problems are observed

Using Ubuntu 18.04 LTS

kernel :

Linux asgard 5.0.0-1050-oem-osp1 #55-Ubuntu SMP Fri Apr 24 11:08:25 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

I did downgrade to 1.0.6 and the shutdown problem persisted (and should've updated this thread). I'm back up to 1.0.7 now. This could be something Fedora (fedora kernel) specific or some particular setting in firmware. I've not tried to narrow it down, as I rarely shutdown/reboot.

Linux monkfish 5.6.8-300.fc32.x86_64 #1 SMP Wed Apr 29 19:01:34 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Edit: add kernel ver

I noticed the exact same thing on my XPS 13 7390 2-in-1 (08B0).

Everything worked fine on my previous Latitude 7400 2-in-1.

Haven't been able to pin it on any kernel configuration setting, but also haven't looked into it much.

Do you have anything in the kernel log ? The last step of shutting down is to send an ACPI PowerOff to the hardware so it shuts down. We can start by comparing the Ubuntu kernel options. Then look into the /etc for anything related to this.

I started to dig into this today. Confirmed freeze on shutdown multiple times, even with 'poweroff -f'. Keyboard backlight stays lit, capslock does not toggle, with and without AC power.

I ran a dnf update before digging further and the issue seems to be resolved after the update! Kernel version bumped from 5.6.8 to 5.6.11.

So it appears that Fedora kernel 5.6.11-300.fc32.x86_64 does not exhibit the problem. I upgraded and tested 15 shutdowns and they all completed successfully.

The only thing that was shown on the screen was that the system was powering off but nothing in the logs indicated any problems.

That's great

To anyone encountering this, at this point it looks like a kernel regression in kernel 5.5.  This particular issue is popping up in Fedora because moves more rapidly to newer kernel versions.

The upstream kernel bug report is here: 

https://bugzilla.kernel.org/show_bug.cgi?id=206571

And you can find a Fedora specific bug report here:

https://bugzilla.redhat.com/show_bug.cgi?id=1834277

The commit that caused this problem is here:

https://github.com/torvalds/linux/commit/6c3a44ed3c553c324845744f30bcd1d3b07d61fd

Until the problem has been fixed in the upstream kernel and Fedora's kernel for a workaround you can turn off "VT-d" in BIOS setup.  This is not a permanent solution as by doing so you will turn off DMA attack mitigations such as those discussed in public vulnerabilities like Thunderspy.   The permanent solution will need to be discussed upstream.