[Bug 101044] [SKL Xeon DP-to-VGA] no hotplug signal from DP-to-VGA branch device after unplug/replug cycle

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101044

--- Comment #17 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to amy.shih from comment #13)
> Could you explain why we need to add this patch to make VGA work & does this
> patch have any side effect?

Without the patch, we tell the DP sink (or, in this case, the DP branch device,
the DP-to-VGA converter) to go to power save mode when we disable it.
Apparently the branch device in question doesn't wake up like other devices,
and sleeps forever instead of waking up on hotplug.

If the logs in comment #8 are to be trusted, we really don't get a hotplug
event from the branch device anymore, so we won't even try to talk to it to
wake it up.

The drawback with the patch is that it'll potentially waste power.

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