I found the repo (git://people.freedesktop.org/~agd5f/linux and the
drm-next-4.12-wip branch with the commit already applied), so I built that for
testing but didn't have any luck. The primary GPU LEDs were stuck on maximum,
the second was a single blue LED (as before), and I lost signal multiple times
when trying to log in through my display manager.

Probably some unrelated regression is affecting that branch, preventing my
testing of your revised patch.