Dell P2715Q Monitor does not wake up after sleep (off, standby, or suspend)

Alex Deucher alexdeucher at
Fri Aug 11 19:15:03 UTC 2017

On Fri, Aug 11, 2017 at 3:08 PM, Greg Gorsuch <thewatchman at> wrote:
> Your description sounds about right. Since I do see a message ("Entering
> energy saver mode") come up on the monitor when I move the mouse as I
> mentioned before, this does suggest it has been awakened and becomes
> unrigistered at this point and sees no input anymore (hence the message).
> All the windows are already moved to the other monitor at this point and the
> screen saver seems like it has more or less died (though it does prompt for
> the password and allows me to log in).
> I did what you asked, but it didn't really give any useful info since it
> normally takes a while for the monitor to fail to come back up (maybe 5 or
> 10 minutes after I lock the screen even with the sleep time as 1 minutes or
> so).  I kind of already generated the info you may be seeking in my original
> post.
> I am wondering if there is some way to just "lock" the setup so that the
> monitor is always there if it is a registration problem, or change things so
> the monitor is not unrigestering itself.

Does the monitor have an option to disable input polling?  Some
monitors rotate through their inputs when they are not getting a
signal to see if one attaches so they can automatically switch to that
input.  This often confuses drivers because the input switching on the
monitor often triggers a hotplug event which looks like the display
has been disconnected to the driver since the monitor has switched to
another input.


> On Thu, Aug 10, 2017 at 9:55 AM, Thomas L├╝bking <thomas.luebking at>
> wrote:
>> On Wed, Aug 09, 2017 at 11:39:06AM -0400, Greg Gorsuch wrote:
>>> Where are the sleep logistics handled? Is it with the X server, the
>>> drivers, the Linux Kernel, or somewhere else? Is it possible to capture
>>> the
>>> communications on Windows 10 to identify how it is being handled. I don't
>>> get the feeling it should be that complex to fix or at least implement a
>>> work around since xrander is able to bring the monitor back online.
>> It sounds like when you go dpms off, the monitor unregisters and when
>> you go dpms on, the monitor re-registers.
>> Then some semi-smart randr daemon kicks in and adjusts the layout, but
>> does not so when the monitor comes back.
>> Try to log the setup in the various modes:
>> xset dpms force standby; sleep 10; xrandr --current > ~/randr.standby;
>> xset dpms force suspend; sleep 10; xrandr --current > ~/randr.suspend;
>> xset dpms force off; sleep 10; xrandr --current > ~/; xset
>> dpms force on
>> Also try the behavior on a "naked" X11 server (no desktop session, only
>> an xterm) to see whether some client or the server adjusts the randr
>> setup.
>> Cheers,
>> Thomas
> --
> Greg Gorsuch
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