Re: Monitor switched off after resume from hibernation

[Joe <joe@jretrading.com>]

On Sat, 07 Jan 2017 08:18:51 +0100
solitone <solitone@mail.com> wrote:

> On Friday, January 6, 2017 9:52:13 PM CET David Wright wrote:
> > in your terminal, you'll probably find that
> > $ echo $DISPLAY
> > will give you :0 (locally) or localhost:10.0 (if you ssh into
> > another computer). So your terminal's xset command will be
> > happy without -display as it's got $DISPLAY instead.
> > [...]
> > I'm assuming that a systemd command that suddenly pops up from
> > nowhere will not have a suitable value for $DISPLAY.  
> 
> OK, I see.
> 
> I've ssh'd into the computer with the screen issue, and done some
> additional tests. I can switch off and on the monitor from ssh with
> the following commands ($DISPLAY is not set in shh):
> 
> $ xset -display :0 dpms force off
> $ xset -display :0 dpms force on
> 
> So, I turn the monitor off, hibernate, and resume, and I get the
> usual black screen. The system is up and running, as I can ssh into
> it. From ssh I give:
> 
> $ xset -display :0 dpms force on
> 
> but nothing happen. Even if I try:
> 
> $ xset -display :0 dpms force off
> $ xset -display :0 dpms force on
> 
> nothing happens either.
> 
> So the behaviour I have from ssh is similar to what I get from a
> systemd script. The system is apparently up and running, but I can't
> turn the monitor on, neither from systemd, nor from ssh. Funny thing!
> 

Is the screen truly off? If you look at it from unusual angles, can you
see any faint sign of the correct display?

I gave up trying suspend and hibernate on any Linux, as none of them
seem to work correctly. One effect I did see sometimes was that the
screen backlight was off, but the display was being operated correctly
and I could see, from some angles, the right screen material. I
couldn't find any way to turn on the backlight in this situation.

-- 
Joe