[Dell Latitude E6440] Unable to adjust brightness on Precise

[Po-Hsu Lin]

CID: 201306-13688 Dell Latitude E6440

Backlight control does not work on Precise (3.2.0-56):
1. Hotkey event was not detected.
2. No scroll bar in brightness applet.
3. No entries in /sys/class/backlight.

Steps:
1. Install 12.04.1 + update
2. Try to adjust the brightness by hotkeys
3. Try to adjust the brightness by the brightness applet

Expected result:
Brightness could be adjusted.

Actual result:
Hotkeys are not responding, no scroll bar in brightness applet.

Debugging information:
$ ls /sys/class/backlight > backlight
(Nothing)

$ dmesg | grep 'ACPI: Video'
(Nothing)

$ cat /proc/version
Linux version 3.2.0-56-generic (buildd@roseapple) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #86-Ubuntu SMP Wed Oct 23 09:20:45 UTC 2013

Boot with "acpi_backlight=vendor" kernel parameter
The hotkey could change the indicator level, and the scroll bar would appear in brightness applet.
However, the brightness still cannot be altered.

$ ls /sys/class/backlight/
dell_backlight

Boot with "video.use_bios_initial_backlight=0" kernel parameter
It behaves like without adding any other parameter.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-56-generic 3.2.0-56.86
ProcVersionSignature: Ubuntu 3.2.0-56.86-generic 3.2.51
Uname: Linux 3.2.0-56-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 1: PCH [HDA Intel PCH], device 0: ALC292 Analog [ALC292 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 1: PCH [HDA Intel PCH], device 0: ALC292 Analog [ALC292 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: ubuntu 1566 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf7d34000 irq 43'
   Mixer name : 'Generic 0000 ID 0'
   Components : 'HDA:00000000,80860101,00100000'
   Controls : 0
   Simple ctrls : 0
Card0.Amixer.values:

Card1.Amixer.info:
 Card hw:1 'PCH'/'HDA Intel PCH at 0xf7d30000 irq 43'
   Mixer name : 'Realtek ALC292'
   Components : 'HDA:10ec0292,102805bd,00100001'
   Controls : 19
   Simple ctrls : 10
Date: Wed Nov 13 03:16:25 2013
HibernationDevice: RESUME=UUID=aeb30de4-c85d-4d93-874d-8f06ce1303b2
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
MachineType: Dell Inc. Latitude E6440
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-56-generic root=UUID=3cde48ea-3225-4afa-b02b-584a672a94e4 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-56-generic N/A
 linux-backports-modules-3.2.0-56-generic N/A
 linux-firmware 1.79.7
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/03/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: X23
dmi.board.name: 02P3T1
dmi.board.vendor: Dell Inc.
dmi.board.version: X03
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrX23:bd07/03/2013:svnDellInc.:pnLatitudeE6440:pvr01:rvnDellInc.:rn02P3T1:rvrX03:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6440
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.

[Brad Figg (brad-figg)]

This change was made by a bot.

[Anthony Wong (anthonywong)]

The closest enablement bug that I can find is bug 1180284, but it says the hotkeys doesn't work only _sometimes_, and from the bug description it looks like a BIOS bug to me, which we should have found this issue during enablement.

[Po-Hsu Lin (cypressyew)]

There's one ACPI related bug on 3.8 kernel, bug 1249978

According to Keng-Yu, this bug is related to brightness control through ACPI

[Alex Hung (alexhung)]

@a16g,

I agree with what you said. We should check whether any workaround added during the enablement and ask s/w engineer not to add workaround unless schedule will slip or BIOS won't fix.

[Alex Hung (alexhung)]

Tested Ubuntu 12.04.03 (kernel 3.8) and brightness hotkey works fine. I am going to verify https://bugs.launchpad.net/ubuntu/+source/linux-lts-raring/+bug/1249978/comments/2 on kernel 3.2 and to backport if it is the fix.

[Alex Hung (alexhung)]

I tested patch @ #11, and brightness does not work. I also used the drivrs/acpi/video.c in kernel 3.5, and brightness does not work either.

I executed "lsmod | grep 915" and found this Haswell system does not have i915 running. The brightness may not be working for more than one reason - including kernel 3.2 does not support Haswell, which is supported in Kernel 3.5.