[Lenovo V480] Unable to control the brightness from Max - Min

[Po-Hsu Lin]

CID: 201204-10924 Lenovo V480

With the Brightness applet, the brightness level on this system cannot be adjusted from Max (let's say, level 11) to Min (level 1).
The brightness level will goes down and up, which behaves like 11-10-9-8-7-6-5-4-3-4-5

Steps:
1. Install 12.04.3 + update (3.8.0-33), boot to desktop
2. Adjust the screen brightness by the Brightness and Lock applet, clicking the leftmost part of the scroll bar to change the brightness stepwise
3. Click and drag the slider to adjust the brightness

Expected result:
- Brightness could be adjusted smoothly.

Actual result:
1. Brightness cannot go down to the lowest level, it behaves like 11-10-9-8-7-6-5-4-3-4-5
2. When you drag and move the slider, the backlight will flash between Max and the indicated level.

Debugging information:
$ ls /sys/class/backlight
acpi_video0@ intel_backlight@

$ dmesg | grep 'ACPI: Video'
[ 7.104361] ACPI: Video Device [PEGP] (multi-head: no rom: yes post: no)
[ 7.107524] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no)

$ cat /proc/version
Linux version 3.8.0-33-generic (buildd@toyol) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #48~precise1-Ubuntu SMP Thu Oct 24 16:28:06 UTC 2013

Note: the hotkey is probably affected by bug 1248442, but it will cause the same result when it's working.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.8.0-33-generic 3.8.0-33.48~precise1
ProcVersionSignature: Ubuntu 3.8.0-33.48~precise1-generic 3.8.13.11
Uname: Linux 3.8.0-33-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.8.0-33-generic.
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: ALC269VC Analog [ALC269VC Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ubuntu 1776 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xf3610000 irq 47'
   Mixer name : 'Intel PantherPoint HDMI'
   Components : 'HDA:10ec0269,17aa5002,00100202 HDA:80862806,80860101,00100000'
   Controls : 29
   Simple ctrls : 11
Card29.Amixer.info:
 Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw unknown'
   Mixer name : 'ThinkPad EC (unknown)'
   Components : ''
   Controls : 1
   Simple ctrls : 1
Card29.Amixer.values:
 Simple mixer control 'Console',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Tue Nov 26 01:10:44 2013
HibernationDevice: RESUME=UUID=0a4cd402-c938-4cc7-a55d-6230c539e25d
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
MachineType: LENOVO 814TD01
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB:
 0 inteldrmfb
 1 nouveaufb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-33-generic root=UUID=6a396d09-0ad3-41a0-9d7d-18446b177e9d ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.8.0-33-generic N/A
 linux-backports-modules-3.8.0-33-generic N/A
 linux-firmware 1.79.7
SourcePackage: linux-lts-raring
StagingDrivers: keucr
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/10/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: H5ET73WW(1.16)
dmi.board.asset.tag: Not Available
dmi.board.name: 814TD01
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrH5ET73WW(1.16):bd04/10/2013:svnLENOVO:pn814TD01:pvrLenovoV480:rvnLENOVO:rn814TD01:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 814TD01
dmi.product.version: Lenovo V480
dmi.sys.vendor: LENOVO

[Po-Hsu Lin (cypressyew)]

after adding "acpi_backlight=vendor" to grub

the hotkey works fine, but the brightness level indicator won't pop-out
and the Brightness applet become not working at all, brightness won't change when you try to adjust it.

Debuggung information:
$ ls /sys/class/backlight
intel_backlight thinkpad_screen

# ls -la /sys/class/backlight/intel_backlight
lrwxrwxrwx 1 root root 0 Nov 26 04:54 /sys/class/backlight/intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight

Brightness will change to very low with
echo 8 > /sys/class/backlight/intel_backlight/brightness

[Po-Hsu Lin (cypressyew)]

after adding "video.use_bios_initial_backlight=0" to grub

It behaves like what I described in the bug description

[Po-Hsu Lin (cypressyew)]

With the proprietary driver (nvidia-319-updates) installed, the problem still exist,
and it behaves like without the proprietary driver.

[Alex Hung (alexhung)]

It seems the _BCM is broken (_BCM is called when writing to /sys/class/backlight/acpi_video0/brightness).

We will need BIOS to fix it (if it is still possible).

[Anthony Wong (anthonywong)]

As this is BIOS issue, we can't really fix it. According to Lenovo website http://support.lenovo.com/en_US/research/hints-or-tips/detail.page?DocID=HT073558, the latest BIOS is 1.16, which is the same as what we are using now.

[Po-Hsu Lin (cypressyew)]

This issue still exist in 12.04.4 with nouveau/nvidia-331-update

[Po-Hsu Lin (cypressyew)]

More update with the open source driver:
Trusty 3.13.0-65 - brightness would change with hotkey and the applet, but it's not changing in the expected order.
Trusty 3.16.0-50 - brightness control works with applet, but hotkey event is not detected (nothing from showkey command)
Trusty 3.19.0-30 - brightness control with applet and hotkey works as expected.