Description of problem:

I've got the following setup:
-- Lenovo T470;
-- Ultra Dock (mechanical docking station);
-- an external monitor connected to the dock's HDMI output.

When I try to start the computer with the lid closed, the GRUB menu displays fine on the external monitor. Then the screen turns black and the monitor indicates it doesn't receive an HDMI signal anymore.

At that point, if I open the laptop's lid, I can see the Fedora logo on the laptop's screen, and it just stays there forever.

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Version-Release number of selected component (if applicable):

Fedora 27 fresh install (I don't know which component is concerned)

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How reproducible:

Always

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Steps to Reproduce:
1. Get a Lenovo T470, and install Fedora 27
2. Put the laptop on a Ultra Dock
3. Make sure the lid is closed
4. Connect an HDMI monitor to the dock
5. Turn on the computer using the dock's power button

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Actual results:

The external monitor turns black, the system seems to freeze during the boot process.

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Expected results:

The computer should boot, using the external monitor as only display.


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Additional info:

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