[Samsung NP530U4E-K02PL] Cannot change backlight

[adam]

Option stopped working after upgrading to 15.10, full light all time (before with some hacking it was working, but still was lacking keeping the levels between reboots).

WORKAROUND: Add kernel parameter:
acpi_osi=

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: linux-image-4.2.0-18-generic 4.2.0-18.22
ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3
Uname: Linux 4.2.0-18-generic x86_64
ApportVersion: 2.19.1-0ubuntu4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ab 2051 F.... pulseaudio
CurrentDesktop: KDE
Date: Sat Nov 14 22:44:57 2015
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=33abcad5-3750-4855-b97b-2d5b0fb864ee
InstallationDate: Installed on 2013-10-24 (751 days ago)
InstallationMedia: Kubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: SAMSUNG ELECTRONICS CO., LTD. 530U4E/540U4E
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-18-generic root=UUID=f467e962-e87d-4a39-a861-79138b4809d1 ro quiet splash resume=/dev/sdb2 vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-4.2.0-18-generic N/A
 linux-backports-modules-4.2.0-18-generic N/A
 linux-firmware 1.149.2
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/05/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P07ACM.063.130905.dg
dmi.board.asset.tag: No Asset Tag
dmi.board.name: NP530U4E-K02PL
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: SEC_SW_REVISION_1234567890ABCD
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 9
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP07ACM.063.130905.dg:bd09/05/2013:svnSAMSUNGELECTRONICSCO.,LTD.:pn530U4E/540U4E:pvrP07ACM:rvnSAMSUNGELECTRONICSCO.,LTD.:rnNP530U4E-K02PL:rvrSEC_SW_REVISION_1234567890ABCD:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvrN/A:
dmi.product.name: 530U4E/540U4E
dmi.product.version: P07ACM
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

[Brad Figg (brad-figg)]

This change was made by a bot.

[adam (adamdd55)]

No change when using kernel parameter acpi_backlight=vendor

vendorbacklight:
intel_backlight

No change in brightness for
echo 8 > /sys/class/backlight/intel_backlight/brightness

[adam (adamdd55)]

Reboot with just kernel parameter video.use_bios_initial_backlight=0
- still cannot change the backlight with hotkeys nor brightness applet.

[adam (adamdd55)]

Reboot with just kernel parameter acpi_osi=
- backlight works!!!
I am in heaven with my linux again :)

[adam (adamdd55)]

Just to follow up - now the backlight is also keeping its level between reboots.

[penalvch (penalvch)]

adam, thank you for reporting this and helping make Ubuntu better.

Could you please undo your WORKAROUND and test the latest upstream kernel available from the very top line at the top of the page from http://kernel.ubuntu.com/~kernel-ppa/mainline/?C=N;O=D (the release names are irrelevant for testing, and please do not test the daily folder)? Install instructions are available at https://wiki.ubuntu.com/Kernel/MainlineBuilds . This will allow additional upstream developers to examine the issue.

If the latest kernel did not allow you to test to the issue (ex. you couldn't boot into the OS) please make a comment in your report about this, and continue to test the next most recent kernel version until you can test to the issue. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this issue is fixed in the mainline kernel, please add the following tags by clicking on the yellow circle with a black pencil icon, next to the word Tags, located at the bottom of the report description:
kernel-fixed-upstream
kernel-fixed-upstream-X.Y-rcZ

Where X, and Y are two numbers corresponding to the kernel version, and Z is one release candidate number if applicable.

If the mainline kernel does not fix the issue, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-X.Y-rcZ

Please note, an error to install the kernel does not fit the criteria of kernel-bug-exists-upstream.

Once testing of the latest upstream kernel is complete, please mark this report's Status as Confirmed. Please let us know your results.

Thank you for your understanding.

[adam (adamdd55)]

Mainline kernel doesn't fix this issue - tested with the same boot flags, only acpi_osi= is bringing backlight control back.
Tested with 4.3.0-040300-generic #201511020949

[adam (adamdd55)]

Let me know if you need any additional data/info from my side.

[penalvch (penalvch)]

adam, could you please test drm-intel-nightly and advise to the results?

[adam (adamdd55)]

I've got drm-intel-nightly from 2015-11-25 compiled and tested on this laptop
(due to a bug with cycle-dependency in LNET, you need to disable LNET and LUSTRE modules, than comment CLEAN in Makefile that has deb-pkg target, otherwise just follow instructions for https://wiki.ubuntu.com/Kernel/MainlineBuilds)

kernel: 4.4.0-rc2-custom

Backligh works only with acpi_osi=

Not sure if related, but there is a a warning while installing this deb kernel:
W: Possible missing firmware /lib/firmware/i915/skl_guc_ver4.bin for module i915

[penalvch (penalvch)]

adam, to clarify the Bug Description, were you able to change the backlight by default (i.e. no WORKAROUNDs) prior to upgrading?

[adam (adamdd55)]

I do not have an exact copy of my grub before update, I think I had some flags as a fix maybe year or 1.5y before but probably not acpi_osi= as I would not see any difference or problem later.

 I just tried fresh latest LTS 14.04.3 from usb and it doesn't work with default settings.

[penalvch (penalvch)]

adam, the issue you are reporting is an upstream one. Could you please report this problem following the instructions verbatim at https://wiki.ubuntu.com/Bugs/Upstream/kernel to the appropriate venue (TO Zhang Rui CC linux-acpi)?

Please provide a direct URL to your newly made report when it becomes available so that it may be tracked.

Thank you for your understanding.

[adam (adamdd55)]

Reported at kernel linux-acpi list with a bug report https://bugzilla.kernel.org/show_bug.cgi?id=108971