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I have a dell thunderbolt usb-C dock, and it only appears to work on boot. I have a display, keyboard and mouse plugged in.

If I boot with the thunderbolt plugged, all is well, but if I hotplug, I get display flicker and then nothing.

I'm using kernel 4.13.0-41 on ubuntu 16.4

udevadm monitor sees it:

KERNEL[477.988798] change   /devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0003:00/power_supply/AC (power_supply)
UDEV  [477.997665] change   /devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0003:00/power_supply/AC (power_supply)
KERNEL[478.005687] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV  [478.006458] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[484.516809] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
UDEV  [484.517543] change   /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0 (power_supply)
KERNEL[487.952109] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-6 (drm)
KERNEL[487.952169] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [487.953432] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-6 (drm)
UDEV  [487.953966] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[487.954831] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [487.955564] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[487.958190] add      /devices/pci0000:00/0000:00:02.0/i2c-21/i2c-dev/i2c-21 (i2c-dev)
KERNEL[487.958204] add      /devices/pci0000:00/0000:00:02.0/i2c-21 (i2c)
KERNEL[487.958233] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-7 (drm)
KERNEL[487.958250] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[487.958272] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-8 (drm)
KERNEL[487.958287] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[487.958301] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [487.958931] add      /devices/pci0000:00/0000:00:02.0/i2c-21/i2c-dev/i2c-21 (i2c-dev)
UDEV  [487.959240] add      /devices/pci0000:00/0000:00:02.0/i2c-21 (i2c)
UDEV  [487.960662] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-7 (drm)
UDEV  [487.961160] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [487.962009] add      /devices/pci0000:00/0000:00:02.0/drm/card1/card1-DP-8 (drm)
UDEV  [487.962378] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [487.962715] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[489.087740] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [489.088473] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
KERNEL[490.251883] change   /devices/pci0000:00/0000:00:02.0/drm/card1/card1-eDP-1/intel_backlight (backlight)
UDEV  [490.252773] change   /devices/pci0000:00/0000:00:02.0/drm/card1/card1-eDP-1/intel_backlight (backlight)
KERNEL[499.164089] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)
UDEV  [499.164857] change   /devices/pci0000:00/0000:00:02.0/drm/card1 (drm)

And the mouse and keyboard show up properly in lsusb, but they aren't useable.

modprobe thunderbolt returns nothing and makes no change.

It looks like USB-C hotplug support was backported from RHEL into the mainline kernel quite a while ago - so I don't think that's the issue, I have no idea what else could be causing it. Any ideas as to why I can't use these devices, even though they come up, only when they're hotplugged?

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