[Bug 85924] [hsw DP-to-DVI] DP hot plug fails if booted without Monitor Attached

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=85924

--- Comment #4 from Zoran Stojsavljevic <zoran.stojsavljevic at intel.com> ---
Hello Jani,

Let me summarize some ideas and my thoughts here.

It seems that on headless booting vBIOS, using mode 50h (assuming this mode is
set), waits for some synch signals it sent to monitor if HW I/F (DP, eDP, HDMI,
DVI, VGA) present. The timer is set. Once timer expires, vBIOS concludes that
monitor is NOT present, then it disables host/monitor synch protocol and
continues booting. If vBIOS does not detect any HW I/F, it automatically
disables host/monitor synch protocol, then continues booting.

So, while booting kernel, GFX driver in its init function should retest HW
presense, and regardless enable host/monitor synch protocol again, or to make
sure that monitor hot plug works, not to take blindly any vBIOS assumptions.

My best guess.

Thank you,
Zoran

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