[Bug 107446] Monitor on 2nd DisplayPort is not initialized

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107446

--- Comment #19 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
(In reply to Cedric M from comment #18)
> Created attachment 143122 [details]
> dmesg of 5.0.0 drm-tip failing to wake up external monitor, failing once
> when forcing mode with xrandr, then succeeding the second time
> 
> This dmesg log shows the following sequence:
> 
> 1. locking gnome-shell, which puts the monitors in standby mode
> 
> 2. after a while, returning to the laptop and resuming work : the external
> monitor tries to wake up but fails and returns to sleep

The log shows we correctly resume the display:
[ 3200.652687] [drm:intel_enable_pipe [i915]] enabling pipe B

Then the display magically disappears:
[ 3200.724984] [drm:intel_encoder_hotplug [i915]] [CONNECTOR:75:DP-1] status
updated from connected to disconnected

Then (presumably) userspace responds by turning it off:
[ 3201.164373] [drm:intel_disable_pipe [i915]] disabling pipe B

And almost immediately the display magically reappears:
[ 3202.240649] [drm:intel_encoder_hotplug [i915]] [CONNECTOR:75:DP-1] status
updated from disconnected to connected

> 
> 3. after a couple of minutes : forcing mode with xrandr : external monitor
> tries to wake up, but this time it fails and returns to sleep... again

And the same sequence repeats after you manually try to turn the display back
on. So looks like a broken display of some sort. I presme it would work just
fine if userspace didn't respond to the bogus hpd by turning the display off.
Also I'm not sure why userspace isn't turning the display back on after it
reappears.

> 
> 4. after a couple of minutes : trying to force mode with xrandr a 2nd time :
> this time it succeeds

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