flip_done timed out / attached crtc is active, but connector isn't

I'm running Linus' tip (as of yesterday, 0f4498cef9f5c) and I'm pretty sure this is a result of some of the i915 commits made in 09d78dde88 as it's just started showing up.

There is no bug report; but I've got an i7-1065G7 (IceLake).

I'd suspended with my external monitor (USB-C DP AltMode) attached. When I'd resumed without the monitor attached, I'd essentially gotten a screen lockup and the following splats in dmesg (I'll put those in the next entry, it's fairly sizeable). I could Ctrl-Alt-F1 to get a login screen (after some delay) but the X window never came back stayed frozen and had to S/U/B to recover.

Let me know if you need more info.