On Debian forky, the new Extended Dynamic Range feature is always on, no matter if it's checked or not in the display settings. This setting keeps messing with the brightness of the display through the kernel backlight interface and it's extremely annoying. The result is steppy brightness on an AMD laptop that's abrupt, jarring and doesn't even syncronize with what is happening on the display. This is a totally useless feature that should have never had any time wasted on it. If the user wants HDR, they go buy an HDR display which works correctly and doesn't try to be clever by manipulating the very laggy backlight driver. What's worse is the bug forces this awful feature ON. It can't be disabled. Epic fail. Please respond with a way to disable this featue manually so it can't mess with the backlight. If I have to disable all backlight control by keeping Plasma's hands off it and adjust the display manually through /sys/class/backlight myself, so be it until this bug is fixed.
Update: On this laptop, the issue only occurs when running on battery.
What you're describing isn't related to EDR in any way. Stop being so rude, or your bug reports will be completely ignored in the future. *** This bug has been marked as a duplicate of bug 495545 ***
Now that you described the actual problem in bug 495545, maybe you can provide some information about it. 1. What hardware do you have? 2. Attach the output of drm_info and kscreen-doctor -o 3. Does it also happen on a new user account? 4. Does adding amdgpu.abmlevel=0 to your kernel command line change anything?
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Sorry about the delay in getting back on this. Thanks for the suggestion about changing amdgpu.abmlevel. That fixed the problem, so it seems the amdgpu driver is the culprit: the graphics driver is dynamically changing the backlight based on what's on-screen. This surprise must be due to a kernel update that just happened to coincide with the Plasma update introducing EDR because modinfo shows the default for abmlevel being -1. I didn't notice this behavior before. It seems like this is a bad thing to have enabled with any kind of dynamic range feature as it could mess with accuracy.