Comment 81 for bug 1419355

@Michael Korn: No problem.

To summarize: there seems to be (at least) two groups of vendor/chipset combos here with a similar issue with xHCI controllers at power off time.

Asus and Lenovo have had it with Ivy Bridge/Panther Point chipsets. I attached a modified version of Marcus's patch to cover these.

The other group includes HP and Dell with the Lynxpoint chipsets. This is handled by a different set of conditions a few lines down from the Ivy Bridge case, so it might be worthwhile to have a separate patch for that.

I noticed that on my system at least, the reboot-after-powerdown behavior appears also when the system is shut down through a bootloader command (both rEFInd and GRUB). I would assume that the bootloaders mostly rely on firmware in USB matters, so it really looks like a BIOS issue. Just for fun, I'm seeing if I can replicate the workaround with an UEFI shell script (idea: unbind/unload the USB drivers, then manipulate PCI power state, then shutdown) but no success yet...