Created attachment 187974 [details] Logs SUMMARY Powerdevil dims all displays to 30% prior to sleep and randomly fails to restore the dimming setting on secondary monitors when the system wakes. This occurs on around half of wakes. Waiting for the idle timer to trigger a dimming and then cancelling it with an input will restore brightness on all monitors. This is a desktop system with 3 monitors connected, all to the discreet graphics card. The primary monitor is an Alienware AW3423DW, the two secondaries are both Asus VG248QE. The Alienware has HDR enabled, the other two do not. STEPS TO REPRODUCE 1. In System Settings -> Power Management, ensure Dim automatically is on 2. Wait for the system to sleep 3. Wake the system and log in OBSERVED RESULT Around half of the time, secondary monitors will retain a 30% dimming setting. EXPECTED RESULT Dimming value should be restored to 100% across all monitors. SOFTWARE/OS VERSIONS Below is the output of kinfo. Unsure why the 4090 is listed twice, there is only one installed and I'd expect the second graphics processor to be the AMD integrated one. Operating System: Arch Linux KDE Plasma Version: 6.5.4 KDE Frameworks Version: 6.21.0 Qt Version: 6.10.1 Kernel Version: 6.18.2-arch2-1 (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 9800X3D 8-Core Processor Memory: 64 GiB of RAM (60.4 GiB usable) Graphics Processor 1: NVIDIA GeForce RTX 4090/PCIe/SSE2 Graphics Processor 2: NVIDIA GeForce RTX 4090/PCIe/SSE2 ADDITIONAL INFORMATION This bug has existed since at least plasma version 6.5.2 - the earliest version I tried powerdevil logs & kscreen-doctor output included in attachments
The symptoms seem related to bug 510483 - where the brightness is dimmed to 30% incorrectly It's possible that the brightness is changing by itself because of a crash in powerdevil. I also see traces in the logs you provided. e.g. Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: Traced function stack on entry to i2c_check_open_bus_alive() Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: Traced function stack 0x7fbf54008e40 for current thread [187478] Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: i2c_check_open_bus_alive Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: ddc_write_read_with_retry Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: ddc_get_nontable_vcp_value Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: read_unsupported_feature Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: check_how_unsupported_reported Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: ddc_initial_checks_by_dh Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: ddc_initial_checks_by_dref Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: dw_add_display_by_businfo Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: dw_hotplug_change_handler Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: process_screen_change_event Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: dw_watch_display_connections Can you please run this and see if there are coredumps for powerdevil? sudo coredumpctl --reverse Thanks.
(In reply to TraceyC from comment #1) > The symptoms seem related to bug 510483 - where the brightness is dimmed to > 30% incorrectly > > It's possible that the brightness is changing by itself because of a crash > in powerdevil. I also see traces in the logs you provided. e.g. > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: Traced function stack > on entry to i2c_check_open_bus_alive() > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: Traced function stack > 0x7fbf54008e40 for current thread [187478] > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > i2c_check_open_bus_alive > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > ddc_write_read_with_retry > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > ddc_get_nontable_vcp_value > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > read_unsupported_feature > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > check_how_unsupported_reported > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > ddc_initial_checks_by_dh > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > ddc_initial_checks_by_dref > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > dw_add_display_by_businfo > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > dw_hotplug_change_handler > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > process_screen_change_event > Dec 25 10:46:39 aj-desktop org_kde_powerdevil[1213]: > dw_watch_display_connections > > Can you please run this and see if there are coredumps for powerdevil? > > sudo coredumpctl --reverse > > Thanks. coredumpctl doesn't show any crashes related to powerdevil or anything else around times where the monitor brightness has failed to properly reset. I was able to find that running kscreen-doctor output.DP-4.dimming.100; kscreen-doctor output.DP-5.dimming.100 will restore the brightness without having to wait for the idle timer to dim the screens
Thanks for confirming. Those who are more knowledgeable will have to take it from here.
I can confirm this issue. For me, both displays of my desktop computer stay dimmed after waking the system up from sleep/standby. Using "kscreen-doctor output.DP-x.dimming.100 output.DP-x.dimming.100" as a workaround to undim works nicely. Also, might be related or not: when waking up the system via Wake-On-LAN, oftentimes the displays are turned on (backlight is clearly visible), but stay black. The bad thing about this is that this state persists until a key is pressed or the mouse is moved, i.e. the displays will never be sent back to sleep automatically (waited for over an hour to test, nothing ever happens). KDE Plasma Version: 6.5.5 KDE Frameworks Version: 6.22.0 Qt Version: 6.10.1 Kernel Version: 6.18.8 Graphics Platform: Wayland Processors: AMD Ryzen 7 5800X Graphics Processor: NVIDIA GeForce RTX 3060
Same here, except it only started after the update to Plasma 6.6.0. My workaround for now is: kscreen-doctor output.DP-1.dimming.100
I'm going to mark this confirmed, since a few people have the same bug (In reply to Fonic from comment #4) > Also, might be related or not: when waking up the system via Wake-On-LAN, > oftentimes the displays are turned on (backlight is clearly visible), but > stay black. That sounds like a different bug that needs a different report. If there isn't one for it already, feel free to create a new one. Thanks!
(In reply to TraceyC from comment #6) > (In reply to Fonic from comment #4) > > Also, might be related or not: when waking up the system via Wake-On-LAN, > > oftentimes the displays are turned on (backlight is clearly visible), but > > stay black. > > That sounds like a different bug that needs a different report. If there > isn't one for it already, feel free to create a new one. Thanks! After posting here, I discovered bug #511118, which seems to cover that very same issue.
Maybe Bug 516407?
This one is about software dimming, not DDC/CI brightness
I'm on the same boat and I noticed the "Dim automatically" is missing in Plasma 6.6.
Git commit be28578dbb750b64dd48a90b07d8225ff4de4d85 by Xaver Hugl, on behalf of Patryk Ludwikowski. Committed on 02/05/2026 at 00:27. Pushed by zamundaaa into branch 'master'. Fix screen brightness stuck at 30% after PowerDevil restart PowerDevil's KWinDisplayBrightness constructor was inheriting KWin's runtime dimming state at startup. If KWin was running with a stale dimming=0.3 from a previous PowerDevil session, the new instance would inherit and permanently apply that value, causing the screen to stay dimmed despite moving the brightness slider. The dimming multiplier is exclusively managed by PowerDevil's DimDisplay action and is not persisted to disk. On startup, DimDisplay::m_dimmed is always false, so there's no way to know if KWin's runtime dimming state is valid or stale. The correct approach is to always initialize to 1.0 (no dimming), and let DimDisplay set it when the idle timeout fires. Co-Authored-By: Claude Sonnet <noreply@anthropic.com> M +1 -1 daemon/controllers/kwinbrightness.cpp https://invent.kde.org/plasma/powerdevil/-/commit/be28578dbb750b64dd48a90b07d8225ff4de4d85
Git commit c939ca749913894f9e6973ddb8db5f6a82be3a0f by Xaver Hugl. Committed on 02/05/2026 at 11:36. Pushed by zamundaaa into branch 'Plasma/6.6'. Fix screen brightness stuck at 30% after PowerDevil restart PowerDevil's KWinDisplayBrightness constructor was inheriting KWin's runtime dimming state at startup. If KWin was running with a stale dimming=0.3 from a previous PowerDevil session, the new instance would inherit and permanently apply that value, causing the screen to stay dimmed despite moving the brightness slider. The dimming multiplier is exclusively managed by PowerDevil's DimDisplay action and is not persisted to disk. On startup, DimDisplay::m_dimmed is always false, so there's no way to know if KWin's runtime dimming state is valid or stale. The correct approach is to always initialize to 1.0 (no dimming), and let DimDisplay set it when the idle timeout fires. Co-Authored-By: Claude Sonnet <noreply@anthropic.com> (cherry picked from commit be28578dbb750b64dd48a90b07d8225ff4de4d85) Co-authored-by: Patryk Ludwikowski <patryk.ludwikowski.7@gmail.com> M +1 -1 daemon/controllers/kwinbrightness.cpp https://invent.kde.org/plasma/powerdevil/-/commit/c939ca749913894f9e6973ddb8db5f6a82be3a0f
Unfortunately I'm still seeing this after updating to 6.6.5. I did notice https://invent.kde.org/plasma/powerdevil/-/merge_requests/613 which hopefully contains a solution. Operating System: Arch Linux KDE Plasma Version: 6.6.5 KDE Frameworks Version: 6.26.0 Qt Version: 6.11.0 Kernel Version: 7.0.5-arch1-1 (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 9800X3D 8-Core Processor Memory: 64 GiB of RAM (60.4 GiB usable) Graphics Processor 1: NVIDIA GeForce RTX 4090 Graphics Processor 2: AMD Ryzen 7 9800X3D 8-Core Processor
I've been having this issue as well! I noticed that it mainly happens when my PC is left on and it goes to sleep automatically. Operating System: CachyOS Linux KDE Plasma Version: 6.6.5 KDE Frameworks Version: 6.26.0 Qt Version: 6.11.1 Kernel Version: 7.0.8-1-cachyos (64-bit) Graphics Platform: Wayland Processors: 32 × AMD Ryzen 9 3950X 16-Core Processor Memory: 32 GiB of RAM (31.2 GiB usable) Graphics Processor: NVIDIA GeForce RTX 4070
*** Bug 516631 has been marked as a duplicate of this bug. ***