On Tue, Jul 05, 2016 at 11:00:21AM +0800, AceLan Kao wrote: > These are logs from my machine. > > *** Before plug-in the USB key > > u@u-XPS-13-9xxx:~$ sudo lspci -vvvv -s 00:1c.0 > 00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1) (prog-if 00 > [Normal decode]) [...] > LnkSta: Speed 2.5GT/s, Width x0, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt- > SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surprise+ The link is down (DLActive-), but the root port is a hotplug port, so apparently with Alpine Ridge the controller is powered down if nothing is plugged in and this results in the controller being "unplugged" from the root port. This looks less fishy than I originally thought, it's just very different from the power management of pre Alpine Ridge controllers on Macs (which is the only thing I'm really familiar with), where the root port is not a hotplug port and the controller does not disappear from the system when powered down. (It's config space just becomes inaccessible.) Best regards, Lukas -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>