Re: FreeBSD/X11: Howto revive DisplayPort?

One of HP 840 G5's docking station's DPs is connected to a VGA KVM
switch via a DP to VGA connector. Confirmed, this is an issue.

The VGA KVM switch is also connected to my employer's HP 840 G9, also
via a DP to VGA connector. No problems there. Though that machine uses
the newer Thunderbolt docking station. Given that it's a newer machine
with a newer docking station I think the comparison only goes so far.

Whether this is a FreeBSD or a UEFI BIOS problem isn't quite understood
by me. When booting the FreeBSD machine and if the KVM is not switched
to the FreeBSD machine, the text mode console will have the wrong
geometry. Even in single user the login prompt is far below the bottom
of the monitor.

But once XDM has started it assumes a graphic geometry that fits the
laptop's screen, not the external monitor. I have a script that
disables the LVDS when the VGA is connected.

I suspect that this problem will require more tinkering (not by myself)
to better understand it. There are too many variables to say it's a
single issue.

Another issue is, X segfaults on occasion on this machine. The segfault
always occurs when firefox is active. The screen goes blank as
drm-66-kmod (I think) is corrupted. (This happens maybe once or twice
a month, not enough to pull me away from other projects.) Are you
talking about this or the first issue above?


-- 
Cheers,
Cy Schubert <Cy.Schubert@cschubert.com>
FreeBSD UNIX:  <cy@FreeBSD.org>   Web:  https://FreeBSD.org
NTP:           <cy@nwtime.org>    Web:  https://nwtime.org

			e**(i*pi)+1=0


On Thu, 27 Nov 2025 06:31:34 +0100
FreeBSD User <freebsd@walstatt-de.de> wrote:

> On Wed, 26 Nov 2025 22:31:20 +0100
> Lars Tunkrans <drsnx60@gmail.com> wrote:
> 
> > HI
> > 
> >     Yes I  have  same experience.
> > 
> >     I beleive its because the  DDC/ EDID   info sent from screen over  
> > the  connection cable
> >     is  lost  if  the  KVM  and screen is not connected to the computer 
> > at start up.
> >      If I make sure that  the screen is attached to  the computer when 
> > the computer powers up
> >       a  Usable resoultion/timing is selected by the graphics card.
> > 
> >    Regards.  
> 
> Exactly.
> this behaviour is observed by myself on FreeBSD, Linux or Windows, on the contrary, seems
> to have a solution to reestablish a DP connection, so it might be possible on FreeBSD
> also (but is somehow by default disabled, I hope).
> 
> Having for computer attached to one KVM, three of them are FBSD boxes and one is a Linux
> based commercial product provided by my employer leaves me with trouble when powering up
> all machines.
> 
> Kind regards,
> 
> oh
> 
> > 
> > 
> > Den 2025-11-26 kl. 16:37, skrev FreeBSD User:  
> > > Using FreeBSD CURREN and FreeBSD STABLE/15.
> > > Also, most systems are attached to a KVM switch, connected via DP.
> > >
> > > Hosts booting all UEFI.
> > >
> > > On hosts using X11/xdm GUI, switching forth and back to the output/host I want to use
> > > DP does obviously not "lose" DP output, so after graphics has been initialized I'm
> > > able to see the GUI.
> > >
> > > The situation is completely different with plain consoles, provided by FreeBSD's
> > > EFI/UEFI simple framebuffer device driver. Working on the console on one host,
> > > switching to another host, working there and trying to switch back leaves me with no
> > > output anymore! I see this behaviour with different types of KVM switches I have at
> > > hand.
> > >
> > > Can this behaviour be changed, even with no X11?
> > >
> > > Thanks in advance and wishes,
> > >
> > > O. Hartmann
> > >    
> 
>