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

[Thomas Lübking]

On Sat, Aug 12, 2017 at 02:28:03PM -0400, Greg Gorsuch wrote:
>Actually, I was looking at the output from the xrander -q I posted in my
>first e-mail. It does show the display as connected still

or "again" - the only explanation I see for the DPMS (?) induced change.

>I have tried udevadm monitor and do not see any events.

Not even when you actually unplug the device???

>a rule  UBSYSTEM=="drm", ACTION=="change",
>RUN+="/usr/local/bin/fix_dell_monitor.sh",
>but it doesn't seem like that ever gets executed.

Hard to say. Typical pitfall is that xrandr needs to be run for the
current XAuthority and Display (iow. as you user and with some
environment set) - not as root. Try to "echo foo > /tmp/bar" to check
whether it's called.
Also do not forget to reload the rules.

>Where is the logic for deactivating monitors and waking up from sleep
>actually handled?

*Shrug*
The hardware triggers an interrupt, the kernel/module sends a udev event
and "some™" userspace process acts accordingly (or not)

I'd try with a pure X11 server first and foremost to see whether some
supersophisticated DE daemon makes a bad choice. (Ie. launch only the
server and an xterm)

The nvidia blob actually has an "UseHotplugEvents" device option, but
that won't work w/ DP (because hotplug events are mandatory for this
connection)

Cheers,
Thomas