[FOCAL][REGRESSION] Intel Gen 9 brightness cannot be controlled

When the privacy screen functionality is enabled, I see the following warnings in the logs:

[188829.782403] hp_wmi: Unknown event_id - 20 - 0x46fe
[188834.848948] hp_wmi: Unknown event_id - 20 - 0x3c00
[188835.624987] hp_wmi: Unknown event_id - 20 - 0x4600

The first warning is when I press the privacy screen button (fn-f2). The second is when I press the brightness down button (fn-f3). The third is when I press the brightness up button (fn-f4).

I do not see similar warnings after the privacy screen functionality is turned off and I press the brightness up or down hotkeys.

I rebooted into Eoan's 5.3.0-29.31 kernel, with Focal's userspace, and verified that the screen brightness is still adjustable under that kernel. Additionally, it is worth noting that I saw the same "hp_wmi: Unknown event_id" warnings mentioned in comment 2 so they probably don't have anything to do with this bug.

I also am hitting this. This looks to be a gen 9 graphics problem, as sforshee with gen 10 graphics appears unaffected.

I'm on a Dell Inspiron 5540 with an i9-9880H

$ glxinfo | grep Device
Device: Mesa DRI Intel(R) UHD Graphics 630 (Coffeelake 3x8 GT2) (0x3e9b)

@tyhicks reported on #ubuntu-kernel his affected box was
Device: Mesa DRI Intel(R) UHD Graphics 620 (Kabylake GT2) (0x5917)

It appears that this might be limited to kaby and coffee lake generations of gpu.

Also I should have mentioned that 5.3.0-24-generic as a workaround also fixed it for me.

Another Gen 9 GPU that I have is not affected by this bug:

 $ glxinfo | grep Device
     Device: Mesa DRI Intel(R) HD Graphics 515 (Skylake GT2) (0x191e)
 $ cat /proc/version_signature
 Ubuntu 5.4.0-12.15-generic 5.4.8

I can increase and decrease the brightness without any issues.

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 <email address hidden>
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 <email address hidden>
    Signed-off-by: Seth Forshee <email address hidden>

: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

To provide further verification, I built Ubuntu-5.4-5.4.0-14.17 with a single patch on top that reverts commit 3269788061d2 ("USUNTU: SAUCE: drm/i915: Force DPCD backlight mode on Dell Precision 4K sku"). My screen brightness controls are working again and I can undock from my external monitor without having to forcibly reboot the system due to a blank screen on my built-in monitor (I guess my screen brightness is turned all the way down when I undock and I cannot adjust it).

I enabled the KMS debug messages in the drm module:

$ cat /etc/modprobe.d/drm-debug.conf
options drm debug=0x04
$ sudo update-initramfs -u -k $(uname -r) && sudo reboot
...

Unfortunately, it doesn't look like my device_id is set after the drm_dp_read_desc() in drm_dp_read_desc:

$ dmesg | grep -i OUI
[ 1.378026] [drm:drm_dp_read_desc [drm_kms_helper]] DP sink: OUI 38-ec-11 dev-ID HW-rev 0.0 SW-rev 0.0 quirks 0x0000

Hopefully the device_id is set for the Dell platform in bug #1856134 so that commit 3269788061d2 ("USUNTU: SAUCE: drm/i915: Force DPCD backlight mode on Dell Precision 4K sku") can be more specific to that device.

Note that the quirks in the debug output from comment #9 are 0x0000 because I've got still got commit 3269788061d2 ("USUNTU: SAUCE: drm/i915: Force DPCD backlight mode on Dell Precision 4K sku") reverted locally.

FWIW I'm seeing this on a XPS 13 9370 as well

cwayne@groot:~$ glxinfo |grep Device
    Device: Mesa Intel(R) UHD Graphics 620 (KBL GT2) (0x5917)

There is a new patchset switches to use EDID-based DP quirk to list those DPCD backlight panel.
I'll try verifying the new method and submit new SRU patches.
https://patchwork.kernel.org/cover/11376657/

BTW, before the new patch is ready, you can add a kernel cmdline to disable the DPCD backlight
   i915.enable_dpcd_backlight=0

Here is the test kernel and the patches I reverted/applied, could anyone helps me verify it.
This kernel fixes the Dell machine I have which uses the DPCD backlight, I hope this won't introduce regressions you've encountered.

https://people.canonical.com/~acelan/bugs/lp1861521/

This kernel fixes the issue on XPS 9370 at my hand.

On 2020-03-02 07:53:18, AceLan Kao wrote:
> Here is the test kernel and the patches I reverted/applied, could
> anyone helps me verify it.

I can confirm that the new kernel does _not_ regress brightness controls
on the machine that caused me to initially open this bug report.

Thanks!

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

verified fixed with proposed kernel on dell xps15 2-in-1.
Device: Mesa Intel(R) HD Graphics 630 (KBL GT2) (0x591b)

This bug was fixed in the package linux-oem-osp1 - 5.0.0-1043.48

---------------
linux-oem-osp1 (5.0.0-1043.48) bionic; urgency=medium

  * bionic/linux-oem-osp1: 5.0.0-1043.48 -proposed tracker (LP: #1867111)

  * All PS/2 ports on PS/2 Serial add-in bracket are not working after S3
    (LP: #1866734)
    - SAUCE: Input: i8042 - Fix the selftest retry logic

  * r8152 init may take up to 40 seconds at initialization with Dell WD19/WD19DC
    during hotplug (LP: #1864284)
    - UBUNTU SAUCE: r8151: check disconnect status after long sleep

  * Miscellaneous Ubuntu changes
    - [Config] Bump the GCC version

 -- Timo Aaltonen <email address hidden> Thu, 12 Mar 2020 11:14:40 +0200