Comment 0 for bug 1621598

With 16.04 and an AsRock Fatal1ty Z170 motherboard, I cannot seem to connect USB3 devices to USB3 ports. They work if I plug them into a USB2 port. Also, USB2 devices work if plugged into a USB3 port.

I have read other descriptions of similar phenomena, but typically, USB3 does not work initially, but it is fixed by enabling the IOMMU setting in the BIOS. Unless I'm missing it, I don't seem to have such a setting. I do have "xhci handoff", and I have enabled that.

Excerpt from `lspci -k`:

    00:14.0 USB controller: Intel Corporation Sunrise Point-H USB 3.0 xHCI Controller (rev 31)
    Subsystem: ASRock Incorporation Sunrise Point-H USB 3.0 xHCI Controller
    Kernel driver in use: xhci_hcd

...and `dmesg | grep -e DMAR -e IOMMU`

'''
[ 0.000000] ACPI: DMAR 0x0000000087F59300 000070 (v01 INTEL SKL 00000001 INTL 00000001)
[ 0.101242] DMAR: Host address width 39
[ 0.101243] DMAR: DRHD base: 0x000000fed90000 flags: 0x1
[ 0.101248] DMAR: dmar0: reg_base_addr fed90000 ver 1:0 cap d2008c40660462 ecap f050da
[ 0.101249] DMAR: RMRR base: 0x00000087555000 end: 0x00000087574fff
[ 0.101250] DMAR-IR: IOAPIC id 2 under DRHD base 0xfed90000 IOMMU 0
[ 0.101251] DMAR-IR: HPET id 0 under DRHD base 0xfed90000
[ 0.101251] DMAR-IR: x2apic is disabled because BIOS sets x2apic opt out bit.
[ 0.101252] DMAR-IR: Use 'intremap=no_x2apic_optout' to override the BIOS setting.
[ 0.102531] DMAR-IR: Enabled IRQ remapping in xapic mode
[ 0.820995] AMD IOMMUv2 driver by Joerg Roedel <email address hidden>
[ 0.820996] AMD IOMMUv2 functionality not available on this system
'''

I have also tried adding `iommu=soft` or `iommu=pt` to my kernel command parameters, and this has not fixed the issue.

I have asked a question about this matter on AskUbuntu, but after two weeks, there has been no activity.

https://askubuntu.com/questions/815416/usb3-devices-not-working-when-plugged-into-usb3-port