"No signal" reported by monitor after turning the monitor off and then back on

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I use HP ZBook 15 Gen 2 laptop with a BenQ 4K monitor connected through HP Advanced Docking Station 2012. DisplayPort cable. The OS is Ubuntu 20.04 with latest updates.

My normal mode of operation is that the lid on the laptop is closed and I only use the external 4K monitor with external keyboard and mouse. I never open the lid. I power the computer through the docking station power button and shut it down through software.

The problem I have is that if I turn off power on the 4K monitor and then turn it on I get "No signal" message from the monitor and of course nothing gets displayed.

I could live with that easily, however, the same thing happens after a few hours of not touching the computer, typically overnight. The next day there is "No signal" reported by the monitor. I believe that the mechanism of this mode of failure must be the same. The only way I am able to recover gracefully from this situation is to login to the laptop remotely through ssh and initiate reboot - (shutdown -r now).

I have Settings -> Privacy -> Screen Lock set up as follows:

  • Blank Screen Delay - Never,
  • Automatic Screen Lock - Off,
  • Lock Screen on Suspend - Off,
  • Show Notifications on Lock Screen - On,

I have Settings -> Power -> Power Settings set up as follows:

  • Blank Screen - Never,

I have Settings -> Power -> Suspend and Power Button setup as follows:

  • Automatic Suspend - Off,
  • Power Button Action - Power Off,

How can I prevent this loss of image on the monitor after turning it off and then on from happening with the "No signal" reported by the monitor.

Here is the output from xrand(1) edited for brevity:

screen 0: minimum 320 x 200, current 3840 x 2160, maximum 16384 x 16384

DP-1 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 708mm x 399mm
   3840x2160     60.00*+  59.97    30.00

DP-2 disconnected (normal left inverted right x axis y axis)

DP-3 disconnected (normal left inverted right x axis y axis)

eDP-1-1 connected (normal left inverted right x axis y axis)
   1920x1080     60.01 +  59.97    59.96    59.93    40.01

VGA-1-1 disconnected (normal left inverted right x axis y axis)
  1920x1080 (0x62) 266.500MHz +HSync -VSync DoubleScan
        h: width  1920 start 1944 end 1960 total 2000 skew    0 clock 133.25KHz
        v: height 1080 start 1081 end 1084 total 1111           clock  59.97Hz

I understand that:

  • DP-1 is the first DisplayPort on the docking station - the 4K monitor connects here.

  • DP-2 is the second DisplayPort on the docking station - unused

  • DP-3 is the DisplayPort on the laptop - unused

  • eDP-1-1 is the DisplayPort for the internal screen of the laptop

  • VGA-1-1 is the VGA port on the laptop - unused

Your assistance will be appreciated.


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