I noticed that upstream v5.4.18 allowed me to adjust my screen
brightness while Ubuntu-5.4-5.4.0-14.17 does not, which indicates an
Ubuntu SAUCE patch as the culprit. I bisected between the two kernels
and this was the result:
$ git bisect good
3269788061d24e316633165608259de1c110b801 is the first bad commit
commit 3269788061d24e316633165608259de1c110b801
Author: AceLan Kao <acelan....@canonical.com>
Date: Thu Dec 12 17:07:44 2019 +0800
USUNTU: SAUCE: drm/i915: Force DPCD backlight mode on Dell Precision
4K sku
BugLink: https://bugs.launchpad.net/bugs/1856134
This platform using DPCD aux to control backlight,
so adding the first 3 OUI bytes to the quirk.
Signed-off-by: AceLan Kao <acelan....@canonical.com>
Signed-off-by: Seth Forshee <seth.fors...@canonical.com>
:040000 040000 5eb20635c698b49ae34aece26e3ee9f24631ca72
0a3389d202d1306745004ff8837731f2ceda317e M drivers
I'm no expert in this area but it looks to me like that commit is being
too generic and a more specific device_id is needed to target that Dell
device.
Here's the information on my panel:
$ edid-decode /sys/class/drm/card0-eDP-1/edid
edid-decode (hex):
00 ff ff ff ff ff ff 00 26 cf 7f 05 00 00 00 00
00 1b 01 04 a5 1f 11 78 0a 1d 39 a7 50 47 97 27
13 4f 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 60 6d 80 c8 70 38 14 40 18 30
a5 00 35 ae 10 00 00 19 00 00 00 fe 00 4d 31 34
30 4e 56 46 37 20 52 30 20 0a 00 00 00 03 00 04
30 ff 05 3c 9d 2b 14 39 9d 00 00 00 00 00 00 03
00 06 18 ff 0f 3c 3b 2a 0b 39 3b 01 01 00 00 ad
----------------
EDID version: 1.4
Manufacturer: IVO Model 1407 Serial Number 0
Made in year 2017
Digital display
8 bits per primary color channel
DisplayPort interface
Maximum image size: 31 cm x 17 cm
Gamma: 2.20
Supported color formats: RGB 4:4:4, YCrCb 4:4:4
First detailed timing includes the native pixel format and preferred refresh
rate
Color Characteristics
Red: 0.6523, 0.3134
Green: 0.2802, 0.5908
Blue: 0.1523, 0.0771
White: 0.3105, 0.3291
Established Timings I & II: none
Standard Timings: none
Detailed mode: Clock 280.000 MHz, 309 mm x 174 mm
1920 1944 1992 2120 ( 24 48 128)
1080 1090 1095 1100 ( 10 5 5)
-hsync -vsync
VertFreq: 120.069 Hz, HorFreq: 132.075 kHz
Alphanumeric Data String: M140NVF7 R0
Manufacturer-Specified Display Descriptor (0x03): 00 03 00 04 30 ff 05 3c 9d 2b
14 39 9d 00 00 00 ....0..<.+.9....
Manufacturer-Specified Display Descriptor (0x03): 00 03 00 06 18 ff 0f 3c 3b 2a
0b 39 3b 01 01 00 .......<;*.9;...
Checksum: 0xad
** Changed in: linux-5.4 (Ubuntu Focal)
Assignee: (unassigned) => AceLan Kao (acelankao)
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You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-5.4 in Ubuntu.
https://bugs.launchpad.net/bugs/1861521
Title:
[FOCAL][REGRESSION] Intel Gen 9 brightness cannot be controlled
Status in linux-5.4 package in Ubuntu:
Confirmed
Status in linux-5.4 source package in Focal:
Confirmed
Bug description:
After upgrading from Eoan (5.3.0-29.31) to Focal (5.4.0-12.15), I no
longer have the ability to control the backlight brightness on my HP
EliteBook 840 G5. When pressing the brightness hotkeys, the on-screen
indicator pops up and shows that the brightness setting is being
changed but the actual screen brightness is stuck on the lowest
setting.
This laptop has a built-in privacy screen. If I activate the privacy
screen (fn-f2), then the actual screen brightness goes to the maximum
setting and then I am able to dim and brighten the backlight as long
as the privacy screen functionality is turned on.
This is a regression from Eoan's 5.3.0-29.31 kernel where I was able
to control the brightness with and without the privacy screen
functionality being turned on.
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-12-generic 5.4.0-12.15
ProcVersionSignature: Ubuntu 5.4.0-12.15-generic 5.4.8
Uname: Linux 5.4.0-12-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Fri Jan 31 11:42:16 2020
InstallationDate: Installed on 2019-06-24 (221 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: linux-signed-5.4
UpgradeStatus: Upgraded to focal on 2020-01-28 (3 days ago)
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https://bugs.launchpad.net/ubuntu/+source/linux-5.4/+bug/1861521/+subscriptions
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