Backlight doesn't work with latest Maverick kernel

[marcio]

Hey nanders,
thanks for the tip on the power management! I was also able to stop the flickering by deselecting the 'dim display when idle' option. This actually means that samsung-backlight and power management are conflicting? if so, is there a way to fix this (I mean permanently, apart from deselecting the option, which works fine anyway)? thanks a lot to all the savy persons out there.

[Mawh]

The checkbox "dim display when idle" was never checked on my computer. :/

Maybe it is resolved just because something has changed in the settings, regardless of what it is ? Honestly I don't have the skill to deal with that.. come on, skilled people, give us some help !

[ignasigarcia]

On my NP150 this brightness blinking will also prevent the screen from going to sleep. If I enter in a terminal the command sleep 1; xset s activate to put the screen to sleep I can reproduce the blinking and the screen backlight does not turn off.

Yesterday I restarted my netbook and everything worked fine (no blinking, samsung-backlight driver loaded and working). Today I restarted and the blinking is back. I'm trying now to find out why yesterday it was working fine.

Ignacio

[ignasigarcia]

This is curious, if brightness level is set to minimum, i.e. cat /sys/class/backlight/samsung/brightness equals 0, then the blinking won't occur and the screen will sleep ok.

CAn anyone confirm this on their unit?

Ignacio

[ignasigarcia]

I've been able to figure out why yesterday the problem was gone, and therefore, I found a way to prevent this problem from happening. I've tried this with success on Fortunato's kernel as well as with 2.6.37 available at mainline kernel's ppa.

I've tried this with my NP150. Note that this is not a FIX, but a WORKAROUND.

The first step is to have the /etc/default/grub following line modified as stated at the beginning of this topic:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor intel_idle.max_cstate=0"

Then run:

sudo update-grub; sudo update-initramfs -u

Second, blacklist your samsung-backlight module, so it won't be loaded at bootup. To do so, edit /etc/modprobe.d/blacklist.conf and add the following text to the end of it:

samsung-backlight

And third, edit /etc/rc.local and paste the next command one line before the "exit 0" statement that you'll find at the end of the file:

modprobe samsung-backlight

By doing so, you're loading the samsunbg-backlight module after all the other drivers are loaded. I don't know why, but by doing so the problem's gone here.

Reboot

That's it. I hope it works for you too.

Ignacio

[gradatz]

The workaround by ignasigarcia also works on my N220.

I have just two notes to add:

1) To be precise, it should be blacklist samsung-backlight in /etc/modprobe.d/blacklist.conf (at least this is the syntax for all other modules listed there)

and
2) For some reason changing the brightness does not work with the login screen, but only after having logged in successfully: If I use the brightness keys at the login screen, the On Screen Notification Area pops up, but the brightness is not changed at all. Strange, isn't it?

[ignasigarcia]

The workaround by ignasigarcia also works on my N220.

I have just two notes to add:

1) To be precise, it should be blacklist samsung-backlight in /etc/modprobe.d/blacklist.conf (at least this is the syntax for all other modules listed there)

Yes, you're right... My mistake.

and
2) For some reason changing the brightness does not work with the login screen, but only after having logged in successfully: If I use the brightness keys at the login screen, the On Screen Notification Area pops up, but the brightness is not changed at all. Strange, isn't it?

Yes. In my netbook I have autologin enabled, so I missed that completely.

OTOH, I have also realized that sometimes the blinking still occurs, often after a restore from suspend. Maybe if I unloaded the samsung-backlight module before suspend... I'll check it out.

Ignacio

[ignasigarcia]

I can confirm that if I tell Ubuntu to unload the module before suspend and reload it after restore the blinking occuring sometimes after restoring is gone.

To do so, edit (or create) a file called /etc/pm/config.d/unload_modules

that file must contain a variable declaration and a list of modules separated by empty spaces that we want to unload before suspend. In our case you need to have at least this:

SUSPEND_MODULES="samsung-backlight"

Reboot.

Regards,

Ignacio

[Drake]

I filed another bug (forgot to tell you).
http://code.google.com/p/easy-slow-down ... etail?id=7

[gradatz]

Drake, are you sure this is the right forum related to your bug report?

[Drake]

Uh, I am pretty sure that this is even the right THREAD.
If you read the whole thread and the related previous bug report and you are still wondering about my post... well, I will be ready for your complaints.

[spino]

I can confirm that if I tell Ubuntu to unload the module before suspend and reload it after restore the blinking occuring sometimes after restoring is gone.

To do so, edit (or create) a file called /etc/pm/config.d/unload_modules

that file must contain a variable declaration and a list of modules separated by empty spaces that we want to unload before suspend. In our case you need to have at least this:

SUSPEND_MODULES="samsung-backlight"

Reboot.

Regards,

Ignacio

hi ignacio, thanks for the great insight. i'm writing to report one minor annoyance i get now - though most of the times this workaround is good: after the screen goes in idle state brightness (ie minimum) it doesnt awake back - i have to revert to normal brightness manually.

one more note, today after 4 days of intense use, once and only once the bug stroke back. no idea what set it off though.

hope they fix this because it was working as a charme before

[.dawn]

hey guys,
i use a n220 marvel plus with ubuntu 10.10 and have the same problems.
i tried ignasigarcia tutorial but that didnt work for me. my brightness at startup is set so lvl 0, so i have to edit manually /sys/class/backlight/samsung/brightness and set to lvl 7. also sometimes the notebook doesnt wake up from hibernation...
anyone can help me? it would mean a lot to me if i could at startup have brightness-lvl 7. (and not to open console everytime at first) and anyone know sth about voria updating the packages for 10.10?

greetings

[spino]

i see there's a new kernel out. is the new kernel fixing this? anybody tried it yet?

[spino]

Uh, I am pretty sure that this is even the right THREAD.
If you read the whole thread and the related previous bug report and you are still wondering about my post... well, I will be ready for your complaints.

hi drake,
i see that in the thread where you filed the bug there's a new version of easy-slow-down-manager (0.13.7) that solved your problems. can you confirm that? i installed it and tried the additional option samsung_backlight.use_sabi=0 with no results (i get a "option not supported" at boot). any news?

thanks