N130 flickering backlight on startup

[Chris]

I have a Samsung N130 netbook and Ubuntu occasionally and erratically flickers the backlight brightness of my screen up and down, usually on startup and when it attempts to dim the screen on idle (even though, for some reason, this option isn't enabled). Along with this the notification area brightness overlay (which fades in when you adjust the brightness) goes nuts.

The problem is stopped by using the brightness hard-keys on my netbook.

Whilst this is a beta it's not healthy for the backlight - beta or not, OS code shouldn't be able to damage hardware.

Description: Ubuntu Natty (development branch)
Release: 11.04

All updates installed. Bug is present before and after update center is run.

[dmiranda (dmiranda)]

Same problem with a Samsung n220

[martinzul (pere-blay)]

Same problem here with a MSI Wind clone, backlight flickering and system kind of unresponsive untill i manage to click start button or some of the system tray icons, then flickering stops. It will start again if I try to set backlight brightness with laptop buttons, or when it attempts to dim the screen on idle.

Using Ubuntu Natty 11.04 beta 1 release for i386.

[Chris (moogleboi-deactivatedaccount)]

This is a serious problem.

I left my netbook, came back, the screen had been flickering erratically for about an hour.

I'm taking since this is prerelease software I can't hold Conical responsible for damage to my netbook backlight?

[Ivan (fairplay)]

I have the same problem on Samsung N130 both in Ubuntu and Arch with kernels >= 2.6.37

[Del (ctrlaltdelboy)]

I also the same problem, but with my Samsung N140 and I am running the Full Released version of 11.04

[Matt-sqsol (matt-sqsol)]

Agreed. This happens on my N130 as well - and only in Natty. Windows 7 is fine, and Maverick was fine. It did it in the prerelease when I tried it, and in the beta, and still in the release version. It's not nice.

[matejcik (matejcik)]

same here with MSI PR200

might be related to the fact that the laptop is sending brightness keys via two different event devices (apparently one is corresponding to keypresses and the other is videocard events). there is a long-standing bug about bad handling of hardware keys and related spam in system logs (see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/178860 )

[oiseau (artisaninformaticien)]

Same here on a samsung N150+

This is for me new to 11.04, i did use 10.10 with custom 2.6.37 kernel before and had not this serious problem.

[oiseau (artisaninformaticien)]

Also with 10.10 and regular kernel was not this problem; backlight Fn-keys never did nothing on 10.10 though, i had to rely on custom setpci script.

Maybe somebody knows how to disable backlight management in Xorg as a quick fix ?

[oiseau (artisaninformaticien)]

Quick fix:

for now i did add this line to /etc/modprobe.d/blacklist.conf :

blacklist samsung-backlight

you ca

[oiseau (artisaninformaticien)]

after reboot it seems to solve it. Backlight hotkeys don't work though, but you can try the attached script to adjust backlight when needed. This works on samsung N150+, don't know for others...

[Lars Heer (l-heer)]

If samsung-backlight causes the problem it should be related to https://launchpad.net/~voria/+archive/ppa

Maybe Fortunato has an idea on that prob...

[Lars Heer (l-heer)]

I added samsung-backlight to /etc/modprobe.d/blacklist.conf and rebooted.

Now flickering disappeared and backlight function keys are still working.

[Fortunato Ventre (voria)]

The situation with the brightness control is a complete mess at the moment and it's getting very annoying.
Unfortunately, I only have a Samsung NC10 and the brightness control here is working out-of-the-box, with no need to use the "samsung-backlight" kernel module, and I'm unable to investigate the problem further.

Anyway, from what I'm reading, each netbook model behaves differently, thus I've no clue on how to fix this permanently and for everyone.

Please try these steps:

- Completely remove "samsung-backlight", reboot, and check if brightness control works out-of-the-box for your model.
- If not, edit the file "/etc/default/grub" and add the option "acpi_backlight=vendor" to GRUB_CMDLINE_LINUX_DEFAULT,
  run update-grub and reboot, and check if brightness control works.
- If not, install "samsung-backlight", reboot and check if brightness control works.
- If it's not working yet, edit the file "/etc/modprobe.d/samsung-backlight.conf" and comment out the line starting with "options", then reboot.
- If up to this point it's not working yet, I'm sorry but I'm out of options. :(

Please report here the results in order to have a more complete picture of the situation.

[Fabz (fabz1)]

With the first three steps
     - remove 'samsung-backlight'
     - add the acpi_backlight
     - install 'samsung-backlight'
I got the brightness controll work fine on my N150, without any flickering when natty dim the screen on idle.

Thank you Fortunato.

[Lars Heer (l-heer)]

@Fortunato:

After half a day flickering began again and I did all steps Fabz did before.

Currently my n130 is running fine and function keys are working.

[matejcik (matejcik)]

@everyone,
your workaroundy solutions with samsung-backlight are all nice and cute, but please bear in mind that not only Samsungs are affected!

Laptops from MSI (PR200, Wind) have the same problem. Using acpi_backlight=vendor stops the flicker, but also disables any kind of backlight control, because the keys don't work by themselves and /sys/class/backlight structure is gone.
Interestingly, using acpi_backlight=vendor leads to a situation where keyboard doesn't send the backlight keycodes anymore, but /dev/input/event5 ("Video Bus") still sends the keypresses as it should. So it's a half-there half-gone solution.

see my more detailed report on opensuse bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=692441

[Robin Clark (robindtclark)]

Thank you Fortunato for your help so far.

I have a N130 running Natty 11.04, and have tried each step you mentioned in post #15. Unfortunately to no avail.

My screen flickers intermittently at the login screen on startup and during general use. There doesn't appear to be trigger, however when I use the Fn + up/down arrow that can sometimes cause it.

Please forgive I am very new to linux itself, but have searched on your forum http://vairo.com, and across the web for a solution. But have been unsuccessful so far.

If you could suggest a way I could take a step further in fixing this I would be grateful.

[JoshKopecek (joshkopecek)]

Same here, I'm running 11.04, on a Samsung N130.

Backlight flickers continuously on login (not login screen), until I fudge the backlight hotkeys.

I tried adding "acpi_backlight=vendor" to GRUB_CMDLINE_LINUX_DEFAULT, but no luck (although I'm running BURG), no luck.

The samsung-backlight package wasn't available on this system, so I'm guessing that's not interfering ;-)

What other packages control the backlight? And where are the config files?

[TimH1 (tim-h1)]

Samsung N130 installing 11.10 beta 1 - flicking occurs during the install process.

[Lars Heer (l-heer)]

Is it only a problem with the i915 driver?

Maybe the bug has to be renamed to: i915 flickering backlight on startup

[Carles Oriol (carlesoriol)]

On Samsung N130 flicking on 11.10 beta2.

[Lars Heer (l-heer)]

After reactivating the "deb http://ppa.launchpad.net/voria/ppa/ubuntu oneiric main" source and updated samsung backlight package... this problem got fixed for me in current 11.10 beta

Thanks again Fortunato...

[Renato Garcia (renatao-garcia)]

After I upgraded my Samsung N130 to 11.10, system became unusable because the flickering become much more frequently and pressing <Super> key would not stop it any more. So I installed samsung backlight from the voria PPA and it fixed the problem. Tks.

[simon james (sjames-vodamail)]

I have a Samsung N-130
I upgraded to 11.10 from 11.04. The flickering screen in 11.10 was worse than 11.04.

My Solution.

I installed :
Samsung Backlight & Samsung tools

The flickering persisted

I then added the following to the Grub Menu by editing /boot/grub/grub.cfg

noapic nolapic apci=off

So that the relevant line is as follows:
linux /boot/vmlinuz-3.0.0-12-generic root=UUID=108fc33a-18b8-410f-9991-a6bd4458f1ae ro quiet splash noapic nolapic apci=off vt.handoff=7

The flickering has stopped. And the special function keys now work.

[Matt Sturgeon (mattsturgeon)]

Related to Bug #810093??