Created attachment 121492 [details]
dmesg 4.4.1

Whenever my screen try and go into standby, they get switched back on directly, and the windows of my second screen are moved to my first screen.

This worked fine with 4.3.X kernels. On an earlier run of this kernel, I also got an Error about an atomic update failure. I will try and see if it pops back up again.

Excuse me as my post was a little hasty. I'm running skylake.

xorg-x11-drv-intel-2.99.917-16.20150729.fc23.x86_64
mesa-dri-drivers-11.1.0-2.20151218.fc23.x86_64

I also noticed the 4.3.5 kernel only works if I set i915.disable_power_well=0. If I remove it, the screen go into standby, but won't wake up again.
Much like the bug I reported https://bugs.freedesktop.org/show_bug.cgi?id=92926 there.
I will attach a dmesg from a 4.3.5 kernel without power_well setting, which went into standby and didn't wake up, and a dmesg from a 4.3.5 kernel with power_well, which works as expected.

Created attachment 121497 [details]
dmesg 4.3.5 without i915.disable_power_well=0 - crashing

Created attachment 121498 [details]
dmesg 4.3.5 with disable_power_well - working

Please try v4.6-rc5 or later.

Seems to be working fine now. Do you need a dmesg anyway?

Thank you very much!

(In reply to Norbert Varzariu from comment #7)
> Seems to be working fine now. Do you need a dmesg anyway?
> 
> Thank you very much!

Great, thanks for testing! No need for the dmesg.

OK, the quirks are back. It worked for about a month now with 4.6.0-rc6, rc7 and the final release, but since yesterday the quirks are back. 
When the screen try and go into standby, they get switched right back on again. Also, sometimes the windows from my second screen all are moved to the first screen.

Please let me know what information you need or what steps I can take to help resolve this once and for all, hopefully.

OK, even more weird: 
- with former working 4.3.5 kernel I get complete lockups when the screens have been in standby for a while:
May 25 14:15:29 desktop kernel: [drm:check_wm_state [i915]] *ERROR* mismatch in DDB state pipe B plane 1 (expected (0,0), found (446,884))
May 25 14:15:29 desktop kernel: [drm:check_wm_state [i915]] *ERROR* mismatch in DDB state pipe B cursor (expected (0,0), found (884,892))

- with kernels 4.6-rc6 and later, which used to work kind of fine until just a couple of days ago, it now fails consistently to go into standby.

- standby with those kernels as well as the latest fedora kernel works in GDM when not logged in, but not after login.

4.6.0 works if only one screen is connected, I just noticed when I switched off my second screen from its power button.

And it suddenly started working again today, out of the blue. 4.6.0.

(In reply to Norbert Varzariu from comment #12)
> And it suddenly started working again today, out of the blue. 4.6.0.

Okay, we've also fixed a bunch of skl stuff for v4.7 and v4.8-rc. Please reopen if the problem comes back.