Bug 507456

Summary: Powerdevil slows down login due to timeout with dccutil execution
Product: [Plasma] plasmashell Reporter: Mauro <calimauro>
Component: Power management & brightnessAssignee: Plasma Bugs List <plasma-bugs-null>
Status: NEEDSINFO WAITINGFORINFO    
Severity: normal CC: Endxcher, kdedev, nate
Priority: NOR Keywords: regression
Version First Reported In: 6.3.4   
Target Milestone: 1.0   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description Mauro 2025-07-24 18:50:33 UTC 
SUMMARY


STEPS TO REPRODUCE
1. Login to your account
2. Experience super slow login
3. After looking in the logs what's the issue, powerdevil seems to take long time to start due to timeout with dccutil execution


OBSERVED RESULT
Login after password successful takes around 15seconds to get to the fully functional desktop
Result of the command $ time systemctl --user restart plasma-powerdevil.service
real    0m12,568s
user    0m0,000s
sys     0m0,004s

EXPECTED RESULT
Login in 2 seconds

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Kubuntu 25.04
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.3

ADDITIONAL INFORMATION
Summary
KDE Powerdevil service takes 13+ seconds to start instead of <1 second, causing significant login delays after a recent libddcutil upgrade in Kubuntu 25.04.
Environment

OS: Kubuntu 25.04 (Plucky Pufferfish)
KDE Plasma: 6.3.4
Powerdevil: 4:6.3.4-0ubuntu1
libddcutil: 2.2.0-1 (upgraded from libddcutil4 1.4.1-1build2)
Hardware: AMD Ryzen 9 5900X, AMD RX 6700 XT (16GB VRAM)
Monitors: 2x ASUS ROG displays via DisplayPort

ASUS ROG PG278QR (2016, Week 43)
ASUS ROG PG279Q (2016, Week 2)



Timeline of Issue

October 7, 2024: Initial installation with libddcutil4 1.4.1 - working normally
July 6, 2025: libddcutil4 removed during system update - problems began
July 22, 2025: Investigation revealed the regression

Problem Description
After the July 6, 2025 update that removed libddcutil4 and later installation of libddcutil5 2.2.0-1, powerdevil consistently takes 13+ seconds to initialize, causing significant delays during login.

Root Cause Analysis
Powerdevil service logs show libddcutil spending excessive time communicating with monitors via DDC/CI:

jui 22 08:20:53 mauro-amd org_kde_powerdevil[2723]: Starting libddcutil. library built Feb 22 2025 at 15:37:45
jui 22 08:20:53 mauro-amd org_kde_powerdevil[2723]: Initializing libddcutil.  ddcutil version: 2.2.0-dev
jui 22 08:20:55 mauro-amd org_kde_powerdevil[2723]: busno=9, sleep-multiplier= 2,00, Testing for unsupported feature 0xdd returned Error_Info[DDCRC_RETRIES
jui 22 08:20:55 mauro-amd org_kde_powerdevil[2723]: Turning off dynamic sleep and retrying
jui 22 08:20:56 mauro-amd org_kde_powerdevil[2723]: busno=9, sleep-multiplier = 1,00, Retesting for unsupported feature 0xdd
[...pattern repeats for ~13 seconds across bus 9 and 10...]
jui 22 08:21:06 mauro-amd org_kde_powerdevil[2723]: Library initialization complete.

Performance Comparison
DDC/CI detection times:

HDMI connection: 1.6 seconds (normal)
DisplayPort connection: 6.7+ seconds (problematic)

Manual ddcutil testing:
$ ddcutil detect --sleep-multiplier 0.3 --disable-dynamic-sleep
Display 1
  I2C bus:  /dev/i2c-9
  DRM connector: card1-DP-1
  Model: ROG PG278QR
  [Completes in ~3 seconds]

Display 2  
  I2C bus:  /dev/i2c-10
  DRM connector: card1-DP-2
  Model: ROG PG279Q
  [Completes in ~3 seconds]

System Logs Evidence
Package change history:
$ grep "ddcutil" /var/log/dpkg.log*
/var/log/dpkg.log:2025-07-06 09:10:36 remove libddcutil4:amd64 1.4.1-1build2 <none>
/var/log/dpkg.log:2025-07-06 09:10:36 status not-installed libddcutil4:amd64 <none>
/var/log/dpkg.log:2025-07-22 09:55:26 install ddcutil:amd64 <none> 2.2.0-1

Current package versions:
$ dpkg -l | grep -E "(ddcutil|powerdevil)"
ii  ddcutil                    2.2.0-1                amd64        Control monitor settings
ii  libddcutil5:amd64          2.2.0-1                amd64        Control monitor settings - shared library  
ii  libpowerdevilcore2:amd64   4:6.3.4-0ubuntu1       amd64        shared library for KDE power management
ii  powerdevil                 4:6.3.4-0ubuntu1       amd64        KDE power management service for Plasma

I/O errors in system logs:
jui 22 10:35:17 mauro-amd fwupd[7971]: failed to add device card1-DP-1/drm_dp_aux0: failed to read device firmware header: failed to write 7 bytes to 14: Erreur d'entree/sortie
jui 22 10:35:17 mauro-amd fwupd[7971]: failed to add device card1-DP-2/drm_dp_aux1: failed to read device firmware header: failed to write 7 bytes to 14: Erreur d'entree/sortie

Analysis and Evidence

Hardware is not the issue: Identical symptoms appearing simultaneously on two different monitor models with different manufacturing dates is statistically improbable
DisplayPort vs HDMI: DDC/CI works significantly faster on HDMI than DisplayPort for the same monitors
Regression timing: Problem correlates precisely with libddcutil4 → libddcutil5 upgrade
Version evidence: libddcutil5 2.2.0-1 is a development version (2.2.0-dev) with apparent regressions

Attempted Solutions
The following configuration attempts had no effect on powerdevil startup time:

Environment variables: POWERDEVIL_NO_DDC=1, DDCUTIL_SLEEP_MULTIPLIER=0.3
ddcutil configuration files: /etc/ddcutil/ddcutilrc with optimized parameters
Systemd service overrides: Custom environment variables in service configuration
Wrapper scripts: Custom powerdevil executable wrapper with environment settings


Reproduction Steps

Install Kubuntu 25.04 with libddcutil5 2.2.0-1
Connect multiple DisplayPort monitors (eventually older models from 2016-2017)
Observe powerdevil startup time: time systemctl --user restart plasma-powerdevil.service
Compare with HDMI connection on same monitors


Significant user experience degradation during login (13+ second delays)
No workaround available through configuration
Comment 1 Mauro 2025-07-24 19:09:00 UTC 
I forgot to mention that all controls on the 2 screens works flawlessly and without lag, color temperature from the KDE Plasma settings, brightness from the taskbar widget, ...
Everything is applied on the flight and i can see it in the OSD menus of the 2 screens.
Comment 2 Endxcher 2025-07-28 00:01:32 UTC 
I’ve been experiencing the same issue repeatedly in the past. However, after the latest system update (with ddcutil still at version 2.2.0-1), this problem no longer seems to reproduce on my Arch Linux laptop. Perhaps this issue is also related to other packages?

Below is the package update log.

[2025-07-27T14:36:29+0800] [ALPM] upgraded alsa-card-profiles (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded libpipewire (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded lib32-libpipewire (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded pipewire (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded lib32-pipewire (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded libdeflate (1.23-1 -> 1.24-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded libdovi (3.3.1-1 -> 3.3.2-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded libnvme (1.14-1 -> 1.15-1)
[2025-07-27T14:36:29+0800] [ALPM] upgraded linux-cachyos (6.15.7-2 -> 6.15.8-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded linux-cachyos-headers (6.15.7-2 -> 6.15.8-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded luajit (2.1.1748459687-1 -> 2.1.1753364724-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded pipewire-audio (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded pipewire-session-manager (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded pipewire-jack (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded pipewire-pulse (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded pulse-native-provider (1:1.4.6-1 -> 1:1.4.7-1)
[2025-07-27T14:36:30+0800] [ALPM] upgraded qt6-base (6.9.1-4 -> 6.9.1-5)
[2025-07-27T14:36:31+0800] [ALPM] upgraded telegram-desktop (5.16.4-1 -> 5.16.6-1)

[2025-07-25T20:25:50+0800] [ALPM] upgraded bash (5.3.0-1 -> 5.3.3-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded ca-certificates-mozilla (3.113.1-1 -> 3.114-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded fastfetch (2.48.0-1 -> 2.48.1-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded nspr (4.36-1 -> 4.37-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded nss (3.113.1-1 -> 3.114-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded pixman (0.46.2-1 -> 0.46.4-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded libopenmpt (0.8.1-1 -> 0.8.2-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded firefox (140.0.4-1 -> 141.0-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded firefox-i18n-zh-cn (140.0.4-1 -> 141.0-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded gettext (0.25.1-1 -> 0.26-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded hmcl (3.6.14-2 -> 3.6.15-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded less (1:668-1 -> 1:679-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded lib32-glibc (2.41+r48+g5cb575ca9a3d-1 -> 2.41+r65+ge7c419a29575-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded lib32-libx11 (1.8.12-1 -> 1.8.12-2)
[2025-07-25T20:25:51+0800] [ALPM] upgraded lib32-llvm-libs (1:20.1.6-1 -> 1:20.1.8-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded lib32-nspr (4.36-1 -> 4.37-1)
[2025-07-25T20:25:51+0800] [ALPM] upgraded lib32-nss (3.113.1-1 -> 3.114-1)
[2025-07-25T20:25:52+0800] [ALPM] upgraded linux-cachyos (6.15.7-1 -> 6.15.7-2)
[2025-07-25T20:25:53+0800] [ALPM] upgraded linux-cachyos-headers (6.15.7-1 -> 6.15.7-2)
[2025-07-25T20:25:53+0800] [ALPM] upgraded nodejs (24.4.1-1 -> 24.4.1-2)
[2025-07-25T20:25:53+0800] [ALPM] upgraded npm (11.4.2-1 -> 11.5.1-1)
[2025-07-25T20:25:53+0800] [ALPM] upgraded opencv (4.12.0-1 -> 4.12.0-2)
[2025-07-25T20:25:53+0800] [ALPM] upgraded phonon-qt6 (4.12.0-4 -> 4.12.0-5)
[2025-07-25T20:25:53+0800] [ALPM] upgraded qt6-declarative (6.9.1-1 -> 6.9.1-2)
[2025-07-25T20:25:54+0800] [ALPM] upgraded qt6-webengine (6.9.1-1 -> 6.9.1-2)
[2025-07-25T20:25:54+0800] [ALPM] upgraded tevent (1:0.16.2-1 -> 1:0.17.0-1)
[2025-07-25T20:25:54+0800] [ALPM] upgraded yt-dlp (2025.06.30-1 -> 2025.07.21-1)

There is some information.

Operating System: Arch Linux 
WM: KWin (Wayland)
KDE Plasma Version: 6.4.3
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.15.8-1-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 12 × 12th Gen Intel® Core™ i5-12450H
Graphics Processor: Intel® Graphics
Display (CMN162B): 1920x1200 @ 60 Hz (as 1536x960) in 16" [Built-in]
Manufacturer: LENOVO
System Version: XiaoXin 16 IAH8
ddcutil version: 2.2.0-1
powerdevil version: 6.4.3-1
Comment 3 Mauro 2025-07-28 09:39:54 UTC 
Here is my current  report
=== SYSTEM INFO ===
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 25.04
Release:        25.04
Codename:       plucky

KDE Plasma: 6.3.4
Qt: 5.15.15
Kernel: 6.14.0-24-generic

=== PACKAGE VERSIONS ===
ddcutil: 2.2.0-1
gstreamer1.0-pipewire:amd64: 1.2.7-1ubuntu5.1
kdeplasma-addons-data: 4:6.3.4-0ubuntu1
libddcutil5:amd64: 2.2.0-1
libegl-mesa0:amd64: 25.0.7-0ubuntu0.25.04.1
libegl-mesa0:i386: 25.0.7-0ubuntu0.25.04.1
libgl1-mesa-dri:amd64: 25.0.7-0ubuntu0.25.04.1
libgl1-mesa-dri:i386: 25.0.7-0ubuntu0.25.04.1
libglu1-mesa:amd64: 9.0.2-1.1build1
libglu1-mesa-dev:amd64: 9.0.2-1.1build1
libglx-mesa0:amd64: 25.0.7-0ubuntu0.25.04.1
libglx-mesa0:i386: 25.0.7-0ubuntu0.25.04.1
libkpipewire-data: 6.3.4-0ubuntu1
libkpipewire6:amd64: 6.3.4-0ubuntu1
libkpipewiredmabuf6:amd64: 6.3.4-0ubuntu1
libkpipewirerecord6:amd64: 6.3.4-0ubuntu1
libpipewire-0.3-0t64:amd64: 1.2.7-1ubuntu5.1
libpipewire-0.3-common: 1.2.7-1ubuntu5.1
libpipewire-0.3-modules:amd64: 1.2.7-1ubuntu5.1
libplasma-geolocation-interface6:amd64: 4:6.3.4-0ubuntu1
libplasma5support-data: 4:6.3.4-0ubuntu1
libplasma5support6:amd64: 4:6.3.4-0ubuntu1
libplasma6:amd64: 6.3.4-0ubuntu1
libplasmaactivities6:amd64: 6.3.4-0ubuntu1
libplasmaactivitiesstats1:amd64: 6.3.4-0ubuntu1
libplasmaquick6:amd64: 6.3.4-0ubuntu1
libpowerdevilcore2:amd64: 4:6.3.4-0ubuntu1
libreoffice-plasma: 4:25.2.4-0ubuntu0.25.04.1
mesa-libgallium:amd64: 25.0.7-0ubuntu0.25.04.1
mesa-libgallium:i386: 25.0.7-0ubuntu0.25.04.1
mesa-utils: 9.0.0-2
mesa-utils-bin:amd64: 9.0.0-2
mesa-va-drivers:amd64: 25.0.7-0ubuntu0.25.04.1
mesa-va-drivers:i386: 25.0.7-0ubuntu0.25.04.1
mesa-vdpau-drivers:amd64: 25.0.7-0ubuntu0.25.04.1
mesa-vdpau-drivers:i386: 25.0.7-0ubuntu0.25.04.1
mesa-vulkan-drivers:amd64: 25.0.7-0ubuntu0.25.04.1
mesa-vulkan-drivers:i386: 25.0.7-0ubuntu0.25.04.1
pipewire:amd64: 1.2.7-1ubuntu5.1
pipewire-bin: 1.2.7-1ubuntu5.1
pipewire-pulse: 1.2.7-1ubuntu5.1
plasma-activities-bin: 6.3.4-0ubuntu1
plasma-browser-integration: 6.3.4-0ubuntu1
plasma-calendar-addons:amd64: 4:6.3.4-0ubuntu1
plasma-dataengines-addons:amd64: 4:6.3.4-0ubuntu1
plasma-desktop: 4:6.3.4-0ubuntu1
plasma-desktop-data: 4:6.3.4-0ubuntu1
plasma-desktoptheme: 6.3.4-0ubuntu1
plasma-discover: 6.3.4-0ubuntu1
plasma-discover-backend-flatpak: 6.3.4-0ubuntu1
plasma-discover-backend-fwupd: 6.3.4-0ubuntu1
plasma-discover-backend-snap: 6.3.4-0ubuntu1
plasma-discover-common: 6.3.4-0ubuntu1
plasma-discover-notifier: 6.3.4-0ubuntu1
plasma-disks: 6.3.4-0ubuntu1
plasma-distro-release-notifier: 20241226-0ubuntu2
plasma-firewall: 6.3.4-0ubuntu1
plasma-integration: 6.3.4-0ubuntu1
plasma-nm: 4:6.3.4-0ubuntu1
plasma-pa: 4:6.3.4-0ubuntu1
plasma-systemmonitor: 6.3.4-0ubuntu1
plasma-theme-oxygen: 4:6.3.4-0ubuntu1
plasma-thunderbolt: 6.3.4-0ubuntu1
plasma-vault: 6.3.4-0ubuntu1
plasma-wallpapers-addons:amd64: 4:6.3.4-0ubuntu1
plasma-welcome: 6.3.4-0ubuntu1
plasma-widgets-addons: 4:6.3.4-0ubuntu1
plasma-workspace: 4:6.3.4-0ubuntu2
plasma-workspace-data: 4:6.3.4-0ubuntu2
plasma-workspace-wallpapers: 4:6.3.4-0ubuntu1
plasma5-integration: 6.3.4-0ubuntu1
powerdevil: 4:6.3.4-0ubuntu1
powerdevil-data: 4:6.3.4-0ubuntu1
qml6-module-org-kde-pipewire:amd64: 6.3.4-0ubuntu1
qml6-module-org-kde-plasma-plasma5support:amd64: 4:6.3.4-0ubuntu1


Could it be that dccutil 2.2.0-1 isn 't working well with my PowerDevil 6.3.4 version ?? I don't know.
Comment 4 Mauro 2025-08-29 11:18:56 UTC 
Any news on this issue ?
Comment 5 Nate Graham 2025-09-17 16:54:59 UTC 
Can you upgrade to Plasma 6.4.5 and ddcutil 2.2.1 and try again? There have been some fixed in those versions.
Comment 6 Mauro 2025-09-18 10:20:04 UTC 
I need to look on how to deploy these version on my Kubuntu 25.04 as this doesn't seem to be delivered by the current update channel, i am still with Plasma 6.3.4 and ddcutil 2.2.0-dev.
Comment 7 Bug Janitor Service 2025-10-03 03:46:28 UTC 
🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!