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** Changed in: linux (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1854413
Title:
Backlight adjustments shows OSD but does not change anything on
Samsung OLED panel
Status in linux package in Ubuntu:
Confirmed
Bug description:
When running Ubuntu with linux-image-5.3.0-23-generic, mainline
5.3.13, or latest 5.4+ my Lenovo ThinkPad P1 Gen 2 with a Samsung OLED
panel is unable to change the backlight brightness. The buttons
trigger the on-screen display and move the bar but the actual display
brightness does not change. With the kernel option
i915.enable_dpcd_backlight=1 it does make the backlight change but
erratically. For example moving through the range you get stuff like
off, medium bright, dim, bright, medium, off. This does work in
Ubuntu linux-image-4.15.0-1059-oem. It seems the following commits in
particular make the difference.
UBUNTU: SAUCE: i915: intel_dp_aux_backlight: Fix max backlight calculations
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-oem/+git/eoan/commit/?h=oem&id=ff39163c455f31005e2709a2006a7605b3d8a05f
UBUNTU: SAUCE: drm/i915: customize DPCD brightness control for specific panel
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-oem/+git/eoan/commit/?h=oem&id=cf7286b44a6e27967f5ed134c4492dd17bde118a
It has been explained to me that these OEM changes are unlikely to be
directly ported into -generic images but it seems relevant to document
the issue. I ported the above commits to the latest linux mainline
kernel and am running that (other than while reporting this issue).
This was in part because >= 5.3.12 fixes another issue with this
hardware where the screen remains black after a resume
(https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1854177). I
have filed https://bugzilla.kernel.org/show_bug.cgi?id=205699.
https://github.com/altendky/linux/commit/395eb4b85f6a0f85061c0598247727de0d9316f6
https://github.com/altendky/linux/commit/c2dc38e6aadf3d979bea83e382a1b119574df7af
Built with:
git clean -fdx && cp /boot/config-5.3.0-23-generic .config && yes '' |
make oldconfig && make clean && make -j `getconf _NPROCESSORS_ONLN`
deb-pkg LOCALVERSION=-altendky-backlight
Note that the use of DEVICE_ID_ANY is likely bad and the correct ID
for this panel should be identified. I wanted to first confirm it
worked before bothering to figure out which ID was needed there and
how to get it.
I have naively ported these patches. While I have done embedded C for
years and some hardware design... I am not familiar with Linux kernel
development nor any details of controlling this hardware.
ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: linux-image-5.3.0-23-generic 5.3.0-23.25
ProcVersionSignature: Ubuntu 5.3.0-23.25-generic 5.3.7
Uname: Linux 5.3.0-23-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: altendky 1381 F.... pulseaudio
CurrentDesktop: KDE
Date: Thu Nov 28 21:24:12 2019
InstallationDate: Installed on 2019-11-26 (2 days ago)
InstallationMedia: Kubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
MachineType: LENOVO 20QTCTO1WW
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.3.0-23-generic
root=/dev/mapper/lvm_group-root ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-5.3.0-23-generic N/A
linux-backports-modules-5.3.0-23-generic N/A
linux-firmware 1.183.2
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/17/2019
dmi.bios.vendor: LENOVO
dmi.bios.version: N2OET40W (1.27 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20QTCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: SDK0T08861 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias:
dmi:bvnLENOVO:bvrN2OET40W(1.27):bd10/17/2019:svnLENOVO:pn20QTCTO1WW:pvrThinkPadP1Gen2:rvnLENOVO:rn20QTCTO1WW:rvrSDK0T08861WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad P1 Gen 2
dmi.product.name: 20QTCTO1WW
dmi.product.sku: LENOVO_MT_20QT_BU_Think_FM_ThinkPad P1 Gen 2
dmi.product.version: ThinkPad P1 Gen 2
dmi.sys.vendor: LENOVO
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