Bug 2217269

Summary:	Power saving option "Screen Blank" doesn't switch off the screen if connected using Display Port to HDMI cable
Product:	[Fedora] Fedora	Reporter:	Jan Obrátil <obrys82>
Component:	gnome-desktop	Assignee:	Orphan Owner <extras-orphan>
Status:	NEW ---	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	38	CC:	extras-orphan, fmuellner, gnome-sig, lmaly, mclasen, rhughes, rstrode
Target Milestone:	---	Keywords:	Desktop
Target Release:	---
Hardware:	x86_64
OS:	Linux
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Description Jan Obrátil 2023-06-25 18:44:04 UTC

My computer is AMD Ryzen 9 5900X, Radeon PRO WX 3100. I have two monitors connected. The primary connected using Display Port, and the secondary connected using Display Port to HDMI.
If the secondary monitor (connected using the reduction) is connected, the system cannot switch off monitors (all of them). If I disconnect the monitor connected using the reduction, the system switches off the monitor after the specified time of inactivity (the Blank Screen options in Power Saving Options).
I have replaced the cable (DP to HDMI) for DP to DP, and the displays started working as expected.
In Windows 10 system, the issue is not present. Other Linux distros seem to be affected too.

Reproducible: Always

Steps to Reproduce:
I'm not sure if other HW is affected. 
1. Connect the monitor using Display Port to the HDMI cable (Display Port in the Graphic Card, HDMI in a monitor).
2. In Fedora Workstation (version 38), in Power Saving Options, set Screen Blank to 1 minute.
3. Wait a minute. The monitor dims but not switches off.
Actual Results:  
The monitor is not switched off. It dims, but the backlight is still on.

Expected Results:  
The monitor switches off, no backlight.

Comment 1 Lucian Maly 2023-07-27 04:47:33 UTC

Hi, I have a similar issue on Red Hat Enterprise Linux release 9.2 (Plow), GNOME 40.4.0, Wayland.
I have two ports on my PC: DPort & HDMI. I tested both, using their native cables (HDMI to HDMI and DPort to DPort) with exactly the same settings (Screen Blank = 5 mins). Result is:
1) When monitor is connected via HDMI, after 5 minutes the monitor only dims
2) When monitor is connected via DPort, after 5 minutes the monitor goes into stand by mode and completely turns off

My HW:
PC: Micro Computer HK Tech Limited minisforum TH80
Memory: 32GB
Processor: 11th Gen Intel Core i7-11800H @ 2.30GHz × 16 
Graphics: Mesa Intel UHD Graphics (TGL GT1)
Disk: 1.5 TB
Monitor: Xiaomi Curved Gaming Monitor 34"

$ xset q                 
Keyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000000
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    off    02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:       off
    06: Suspend:     off    07: Mute:        off    08: Misc:        off
    09: Mail:        off    10: Charging:    off    11: Shift Lock:  off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  500    repeat rate:  33
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  2/1    threshold:  4
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  300    cycle:  300
Colors:
  default colormap:  0x40    BlackPixel:  0x0    WhitePixel:  0xffffff
Font Path:
  catalogue:/etc/X11/fontpath.d,built-ins
DPMS (Energy Star):
  Server does not have the DPMS Extension