Skylake graphics regression: projector failure with 4.8-rc3

[James Bottomley]

On Fri, 2016-08-26 at 09:10 -0400, James Bottomley wrote:
> We seem to have an xrandr regression with skylake now.  What's
> happening is that I can get output on to a projector, but the system 
> is losing video when I change the xrandr sessions (like going from a 
> --above b to a --same-as b).  The main screen goes blank, which is
> basically a reboot situation.  Unfortunately, I can't seem to get the
> logs out of systemd to see if there was a dump to dmesg (the system 
> was definitely responding).
> 
> I fell back to 4.6.2 which worked perfectly, so this is definitely 
> some sort of regression.  I'll be able to debug more fully when I get 
> back home from the Linux Security Summit.

Sorry, ignore the logs: they're from a previous bug; as I said I'll try
to gather logs when I get back to a more controlled environment over
the weekend.

James