Screen flickering when not at full brightness

Grosskopf · 2018-10-29 20:06:45

Hi, I have an Acer Aspire E5-571G highly modified, the Ram is upgraded, the VGA Port fell of (it just broke off someday) and now during the complete replacement of the Case to a plywood Case my Screen was damaged a tiny bit, so i replaced it with an IPS LED Full HD Display from Touch and Screen that should have been compatible with a higher resolution than my 1366*768 screen. It works fine during bootup but as soon as the backlight goes below 100% it starts to flicker weird, i can lower the brightness over xrandr and i had no such problem with the old screen.
when the Brightness over system is close to 0 it flickers less often, closer to the middle constantly and closer to 100% less often again, the refreshrate of the screen is weirdly at 60,02 Hz and since it is an i915 processor i tried adjusting the Backlight with intel-gpu-tools to 60 Hz wich works for 100% backlight but again doesn't let me adjust my brightness, does anyone have an idea what the Problem might be or have an idea how i can lower my Backlight intensity in alternative ways? My software is up to date with testing activated and driverwise this Optimus setup has a Bumblebee config using i915 driver and nvidia driver.
Thanks in advance,
G. Großkopf

ewaller · 2018-10-29 20:30:07

What settings do you have for your backlight frequency? If you can control it, and if it is asynchronous to the LCD panel frequency, you generally want the frequencies far apart and such that their ratios do not have a lot of common factors. If the ratios are such that they are close to 1:1 or 2:1 or 3:2, etc... they will visually beat. 75:60 would be a bit better choice (That turns into 15:12 which is 5:4). I really prefer larger backlight frequencies measures in the hundreds of Hertz better..

Grosskopf · 2018-10-29 21:31:03

i'm following this guide: http://devbraindom.blogspot.com/2013/03 … intel.html and i have no idea what i'm doing, the read gives me 0x00000018 and i just tried random values between 60 and 700, the LCD panel refreshrate seem to be 120.04 at the highest if that is the value i can set for the screen in the gnome settings menu. i just set that register mentioned there to 0x30d030d wich is what it gave me for 240 hz and it now doesn't flicker visibly at any brightness setting but the colors are a bit off, that's not too much of an issue but would be nice to be able to fix sometime, installing intelpwm-udev made it constantly flicker so hard, i had to uninstall that again, setting it to 150 wich i think is this 5:4 value for my 120hz refresh rate if i'm correct makes it constantly flicker too

edit: oh, with a really low brightness setting it seems to disable backlight for 1-2 seconds every 4 minutes completely

Last edited by Grosskopf (2018-10-29 21:56:47)

Grosskopf · 2018-11-05 00:30:43

i fixed it, well i'm happy with this hack:
installed the intelpwm_udev thing and set the period to 030d since those are the last 4 digits of the 30d030d that worked kinda so far
The specs for my screen seem from the datasheet to also show that a backlight frequency between 200 and 1000 is possible so i could have just gone testing wildly in this range whenever i want to test more i'll just uninstall it again, and fix it to a new frequency
Even though intelpwm_udev makes it flicker forever from installation point i shouldn't have thrown it off my laptop again as it simply forces the laptop to adjust to the config whenever anything with backlight happens, so after configuring it i'll never have to again look at a flickering screen trying to find the terminal and executing this damn intel reg write maybe i'll figure out more correctly how this LP156WF6-SPP2 screen likes to be adressed but for the time being i'm happy with this hack

Arch Linux

#1 2018-10-29 20:06:45

Screen flickering when not at full brightness

#2 2018-10-29 20:30:07

Re: Screen flickering when not at full brightness

#3 2018-10-29 21:31:03

Re: Screen flickering when not at full brightness

#4 2018-11-05 00:30:43

Re: Screen flickering when not at full brightness

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