Comment 24 for bug 1437492

I am seeing this same issue on two separate Z87 boards from Asus on Gentoo. It looks like the culprit is the Asmedia USB 3 controller, at least from my end.

Cutting power to the system and powering on allows the init sequence to complete normally. Upon reboot or regular power on, the device with ID 174c:2074 ASMedia Technology Inc. fails to load throwing the unable to enumerate USB device message in dmesg.

I started noticing this problem when I switched to a 4.0 kernel on Gentoo. Subscribing to follow up on this issue.