m15 R7, TB dock issues, ensure hybrid graphics is enabled in bios

Just figured I'd post a PSA for anyone running into this issue, since I found an ancient thread elsewheres about people having this issue - 

we had some users report to us that their docking stations (Dell WD22TB4's) had stopped working properly on their Alienware m15 R7 laptops. Sure enough, lots of problems presenting - after much troubleshooting and updating of firmware and drivers and such, we discovered that the docks would work only if connected at initial power on, and wouldn't work after the fact if not.

The culprit:  hybrid graphics had to be on in the bios in order for the dock to work like normal. Enabled it in bios, downloaded the latest intel & nvidia driver from support.dell,  clean installs, and after a reboot the dock started to work like one would expect.

Cheers,