In this change: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2815ef7fe4d43072b9eda448d04fbc184f2aa513 Runtime PM was turned on by default for the XHCI controller that's part of the Alpine Ridge thunderbolt controller. The ASUS Maximus VIII Impact motherboard, which I have, is a funny beast, which uses an Alpine Ridge (0x1578 specifically) chip but with Thunderbolt disabled, and running in some mode where it only does USB 3.1 and nothing else. The USB controller is always visible and none of the Thunderbolt control mechanisms are exposed, I believe (but I've not looked through the ACPI, and probably wouldn't recognise anything even if I did). (They did this weird configuration because apparently they couldn't run the wiring in a thunderbolt compliant way.) After this change is active, the USB controller appears as normal and the root hub is detected but if I plug a USB device in, nothing gets detected. If I have a device plugged in at boot, that devices is detected but once unplugged, it can't be plugged in again. So whatever mechanism is being used to detect a plugged in device is going to sleep and not waking up or otherwise working. I've confirmed that manually disabling runtime PM makes things work again. I've put together a trivial patch to skip applying the new quirk if the subsystem vendor/device IDs are detected on the USB controller (although note that the values appear made up (subsystem_vendor: 0x2222, subsystem_device: 0x1111). I'll attach it shortly, after I do a full test.
Created attachment 280193 [details] Patch to skip quirk based on subsystem match
On Sun, Dec 30, 2018 at 01:29:16AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=202095 > > Bug ID: 202095 > Summary: Default runtime PM for Alpine Ridge USB Controller > breaks usage on Asus Maximus VIII Impact Motherboard > Product: Drivers > Version: 2.5 > Kernel Version: 4.20 All USB bugs should be sent to the linux-usb@vger.kernel.org mailing list, and not entered into bugzilla. Please bring this issue up there, if it is still a problem in the latest kernel release.