Bug 488935

Summary:	Adjusting Power Profile Affects Display Colours
Product:	[Plasma] plasmashell	Reporter:	Eamonn Rea <eamonnrea>
Component:	Power and Battery widget	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	kde, me, natalie_clarius, nate
Priority:	NOR
Version First Reported In:	6.1.0
Target Milestone:	1.0
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Eamonn Rea 2024-06-21 22:39:28 UTC

SUMMARY
I couldn't find much information on this so I assume it is a specific bug and perhaps not intended, but if it is intended and I am being silly, feel free to close!

When changing the CPU power profile in the Power Management widget, the display colours change. They will become much more washed out at Powersave, but look normal at Balanced and Performance (the display seems brighter at Performance, but that's it).

I am aware that some systems allow you to toggle a display power profile and a CPU power profile, but I have not seen them grouped together. I also don't recall this happening on an old laptop I had where I changed the CPU performance governor manually. It also does not happen on my Desktop PC, or if it does, it is not noticeable. But this may be specific to a laptop power profile - or this laptop's power profile, as I could not see information online about this behaviour.

The closest I could think of is that the power profile affects how much power the screen could be getting? But even on other devices where you can set a TDP limit, such as the Steam Deck, the screen colours are never affected in this way.

I am using a Framework 16 laptop.

This could very well be intended behaviour, but I couldn't find information about changing the Power Profile affecting display colours. This problem could also be an OS configuration issue and not something on the KDE side.

I noticed this because I was keeping my laptop in Power Save, and when I opened some YouTube videos, the video quality was noticeably poor (like poor exposure or something).

STEPS TO REPRODUCE
1. Adjust Performance Profile from a higher value to a lower value (naming and options may be different depending on the CPU)
2. Display colours will become washed out.
3. Turn the Performance Profile back up.
4. The colours will look normal.

OBSERVED RESULT
Display colours become washed out when turning the Power Profile down.

EXPECTED RESULT
Power profile should not impact the screen, or if it is intended, there should be an option to tweak this (perhaps a separate option under Displays for this?)

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 6.9.5 Linux Zen
KDE Plasma Version: 6.1.0
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.1

ADDITIONAL INFORMATION
I did not notice if this happened on Plasma 6.0.5.

Comment 1 Nate Graham 2024-06-25 20:55:24 UTC

Tthere's a 99.99% chance this is actually a hardware/firmeware bug, or even intentional behavior.

The way power profiles work is that they trigger vendor-specific functionality supplied by the firmware. This firmware can do whatever the vendor wants is to to. I think it's not at all unrealistic for the vendor to do things like force down the refresh rate or maximum screen brightness, disable HDR, etc.

As to whether or not these behaviors are desirable, ehh... you'll have to take that up with the hardware vendor!

Comment 2 Eamonn Rea 2024-06-25 21:35:58 UTC

Alright then, thanks! I'll take this up with Framework. The only thing that changes with the screen are the colours.

Comment 3 Eamonn Rea 2024-09-01 03:58:38 UTC

Just as a follow-up in case someone else stumbles across this, this is indeed related to AMD firmware, as per the Power Profiles Daemon Readme (https://gitlab.freedesktop.org/upower/power-profiles-daemon#panel-power-savings):

> Laptops with integrated Radeon graphics have a dedicated hardware function
> to decrease panel power consumption in exchange for color accuracy. This
> function is used when the system is on battery and the user has selected
> the "balanced" or "power-saver" profiles.

Although colour accuracy doesn't seem to be affected for me outside of "Power Saver".

The Readme also has instructions for how to disable this.