Need help with Dell D630 backlight, NVIDIA graphics chipset

jmetal88 · 2014-06-09 04:38:03

I posted a thread about this before, but I didn't get any replies so I kinda thought it'd be best to start over with a new thread. I never made any progress with the issue on my own, either.

Here's the situation. I use a Dell Latitude D630 with the NVIDIA graphics chipset (Quadro NVS 135M). A couple of years ago, it worked great on Archlinux with no hardware incompatibilities (at least that I can remember, apart from having a Broadcom wireless card that needed proprietary firmware). Then it broke and it took a while for me to get replacement parts and get it up and running again. Now it works exactly as it's supposed to in Windows, but in Archlinux I have no software control over the backlight. I would very much like to have my power management scheme dim the display while I'm on battery or after I haven't touched the computer for a period of time, but it absolutely does not work. I've tried a couple of other Linux distributions without luck as well.

I have tried setting the level manually through xbacklight and also through /sys/class/backlight/dell_backlight/brightness, and neither has any effect. I've tried various backlight-related kernel parameters for GRUB, but none of them helped. Here is the odd thing, though. When I use the brightness keys on my keyboard, the backlight behaves exactly the way it should! It also changes the value stored in /sys/class/backlight/dell_backlight/actual_brightness when I use the brightness keys, which is a value that does not change when I try changing the brightness in software. I've noticed a few people have D630s with Intel graphics chipsets that had similar issues, but their fixes don't seem to apply in my case.

Anyway, if anyone has any idea where I should be poking around to try and fix this, please, please let me know!

fungle · 2014-06-10 01:51:13

What power management scheme/software are you using?

jmetal88 · 2014-06-10 08:11:13

fungle wrote:

What power management scheme/software are you using?

Well, I'm using the power management utilities that come with KDE, but I'm pretty sure that's not where my problem is, considering I can't even get the backlight brightness to change from the command line using two different methods. That said, I have no idea why the keyboard controls *do* work. I'm pretty sure I remember a couple years back having trouble with the keyboard keys controlling my backlight brightness and having to add in stuff to fix that whereas the software control was already working, so I have no idea why the situation is suddenly reversed.

jmetal88 · 2014-06-10 09:14:46

I've also tried a couple of NVIDIA backlight modules from the AUR without any luck. I wanted to try the brightness adjustment tool that comes with nvclock, but it just has a segmentation fault every time I run it.

fungle · 2014-06-11 00:17:50

What nvidia graphic driver are you using? I have a Qaudro NVS 3100M using nouveau drivers and the corresponding acpi interface is /sys/class/backlight/acpi_video0/. So does the backlight not change when you go to battery? I have a Latitude E6410 so if i change the brightness while on battery using the brightness keys, it'll switch back to that same brightness if I go to battery next time. Does that not happen with you?

jmetal88 · 2014-06-11 05:50:00

It does seem to remember what level I have the backlight set when plugged in versus unplugged and changes accordingly. Actual ACPI events seem to behave exactly as they should (plugging/unplugging and adjusting the brightness with the keys on the keyboard affect the system in the way I'd expect). I just can't change the brightness by issuing commands or writing values to the interface (and therefore can't set power management to dim the display after a certain amount of time).

The /sys/class/backlight/acpi_video0/ interface does not exist on my system. All I have is /sys/class/backlight/dell_backlight/. Do you know a way I might be able to get the acpi_video0 interface to appear?

fungle · 2014-06-11 21:35:12

Well acpi_video0 is just a symlink to the pci device infterface in /sys. For me its

lrwxrwxrwx  1 root root 0 Jun  9 11:50 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0/

Looking through my journal log it seems the kernel is able to register the device instead of the nouveu drivers.

May 10 09:38:47 dell-latitudeE6410 kernel: nouveau  [     DRM] ACPI backlight interface available, not registering our own

Try looking through your logs and search for 'backlight' or the device number, in my case its '0000:01:00.0'.
You said you tried kernel options? Have you tried the ones mentioned in the wiki https://wiki.archlinux.org/index.php/Ba … ne_options
If what you say is true, and the backlight keys change the interface values, things should technically be working. So this command doesn't work?

sudo bash -c 'echo n > /sys/class/backlight/dell_backlight/brightness'

Where n is a number between 0 and max_brightness.
Truthfully this is beyong my own expertise. But I saw your thread had no replies so I decided to see if I could help at all.

jmetal88 · 2014-06-13 04:16:39

fungle wrote:

Well acpi_video0 is just a symlink to the pci device infterface in /sys. For me its
lrwxrwxrwx  1 root root 0 Jun  9 11:50 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0/
Looking through my journal log it seems the kernel is able to register the device instead of the nouveu drivers.
May 10 09:38:47 dell-latitudeE6410 kernel: nouveau  [     DRM] ACPI backlight interface available, not registering our own
Try looking through your logs and search for 'backlight' or the device number, in my case its '0000:01:00.0'.
You said you tried kernel options? Have you tried the ones mentioned in the wiki https://wiki.archlinux.org/index.php/Ba … ne_options
If what you say is true, and the backlight keys change the interface values, things should technically be working. So this command doesn't work?
sudo bash -c 'echo n > /sys/class/backlight/dell_backlight/brightness'
Where n is a number between 0 and max_brightness.
Truthfully this is beyong my own expertise. But I saw your thread had no replies so I decided to see if I could help at all.

That's fine, I appreciate you trying to talk me through it.

I'll check my logs in a bit, but no, echoing a number to /sys/class/backlight/dell_backlight/brightness does nothing. Using my keyboard keys does not affect the value in 'brightness' IIRC (I'm on Windows right now, but I'll confirm when I reboot to check the logs -- I think KDE might be changing the value in 'brightness', but I think it remained unchanged when I tried outside X), although the brightness of the backlight *does* change and the value in 'actual_brightness' changes accordingly.

Honestly, I wish I had a Latitude E series like yours. I almost upgraded to one when my D630 broke, but it was far, far cheaper to buy a new main board and base plastic for this computer. Something about the way the backlight is handled changed in the time while the computer was broken, though, and it frustrates me.

EDIT: Yeah, 'brightness' only changes when KDE moves the slider, but has no effect on the actual brightness of the screen. 'Actual_brightness' changes when I press the keys, as does the actual screen brightness, but 'brightness' is unaffected.

EDIT 2: I can't figure out where I should be looking in my logs. The logs in the 'journal' directory don't appear to be human-readable.

Last edited by jmetal88 (2014-06-13 04:42:39)

fungle · 2014-06-13 08:20:32

jmetal88 wrote:

EDIT 2: I can't figure out where I should be looking in my logs. The logs in the 'journal' directory don't appear to be human-readable.

journalctl -xb

will give you the logs from the most recent boot. Man journalctl if you wanna see more detailed options.

Arch Linux

#1 2014-06-09 04:38:03

Need help with Dell D630 backlight, NVIDIA graphics chipset

#2 2014-06-10 01:51:13

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#3 2014-06-10 08:11:13

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#4 2014-06-10 09:14:46

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#5 2014-06-11 00:17:50

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#6 2014-06-11 05:50:00

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#7 2014-06-11 21:35:12

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#8 2014-06-13 04:16:39

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

#9 2014-06-13 08:20:32

Re: Need help with Dell D630 backlight, NVIDIA graphics chipset

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