[SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

s79to-norm · 2025-09-04 19:40:24

Solved using this upstream bug report:
https://gitlab.freedesktop.org/drm/amd/-/issues/4556

Please don’t get confused by my report below. If you’re experiencing brightness or gamma issues at low brightness levels, refer to the link above or one of the resources shared by other members below.

Notice for newcomers:
If a kernel parameter doesn’t seem to work.First, check whether it is actually being applied at boot. If you’ve created any custom boot entries remember that they won’t automatically pick the changes made in /etc/default/grub (or wherever your bootloader’s main configuration file is).Custom entries need to be updated manually to include the new parameter.

Hello! so Im facing this issue where no matter what i do i cant set Amd Adaptive Backlight Management (ABM) to the value i want currently on 6.16.4-arch1-1 kernel it defaults to -1 and i dont like it it changes the gamma and brightness just like night shift on low brightness levels from 8% and below till it gets so red i cant see anything even in a completely dark room and no keyboard backlight is on
so i tried adding a kernel parameter in "/etc/default/grub" : amdgpu.abmlevel=0, also tried editing power-profiles-daemon's ExecStart by adding --block-action=amdgpu_panel_power in the override.conf and the actual config file of power-profiles-daemon just to make sure the issue wasn't that and i also created a module parameter in /etc/modprobe.d/amd-abm-level.conf as : options amdgpu abmlevel=0. I have tried everything i know to disable the override of the value setting it to -1 by default to one of the values i wish to use and it is usually 0 but nothing seems to work. At first i thought this is a kde plasma issue so i switched to another DE and the issue is still there so i changed the booted kernel to LTS and then to Linux-g14 custom kernel cuz im on an asus laptop with amd ryzen 9 8945HS and i found that neither kernels had this issue i can set it however i want and it defaults to 0. after i have searched this issue on the net i saw that this issue was happening before some recorded it in 2024 some in 2023 so i guess this was an ongoing issue but for some reason it only started showing in this new kernel update. So does anyone know how can i solve this issue.

Edit: even after mysteriously got changed to 0 i really dont know what i did, The low brightness acts like nightshift persists i really dont know what is going on i uninstalled power-profiles-daemon disabled all nvidia/control services for the graphics switch and all including asusctl supergfxd switcheroo-control .... uninstalled the other DE i tested this issue on and i cant seem to solve the issue it's just that switching the kernel is the only solution i have tho it kinda seems like this issue is solved by that BUT no i dont want to use my system like i used to on windows if i find a workaround i call it a life not a day. I want to know what is the issue and how to really solve it not workaround it so please someone help.

Last edited by s79to-norm (2025-09-06 22:13:17)

loqs · 2025-09-04 20:14:05

Have you looked at Debugging Kernel regressions? Let me know if you need any help with the bisection.

s79to-norm · 2025-09-04 20:30:23

i will do that and get back to you.

Last edited by s79to-norm (2025-09-04 20:30:47)

seth · 2025-09-04 20:43:08

Is the regression strictly between 6.16.3 and 6.16.4?
https://github.com/gregkh/linux/commit/ … f0de5db399
https://github.com/gregkh/linux/commit/ … 85f50bbc66

x-ref into more recent amdgpu backlight shenanigans, https://bbs.archlinux.org/viewtopic.php … 3#p2259493

s79to-norm · 2025-09-05 16:07:12

seth wrote:

Is the regression strictly between 6.16.3 and 6.16.4?
https://github.com/gregkh/linux/commit/ … f0de5db399
https://github.com/gregkh/linux/commit/ … 85f50bbc66

loqs wrote:

Have you looked at Debugging Kernel regressions? Let me know if you need any help with the bisection.

Thank you guys for your help ! it took me nearly a day to figure out were the regression first started tho i was 100% sure it was between 6.16.3 and 6.16.4 somehow i marked all git bisects as bad LOL then i took extra steps for no reason starting the bisect process from 6.16.0 all the way to 6.16.4 just to find it in 6.16.3 LOL. However, this was the most fun troubleshooting i have ever done also it was my first time for everything i have dealt with in this troubleshooting so it took me sometime to read and learn what happens in each step of git bisect ...... so at last i found the issue started from this :

7133d48b9b06750d0c593926c4302285f50bbc66 is the first bad commit
commit 7133d48b9b06750d0c593926c4302285f50bbc66
Author: Mario Limonciello <mario.limonciello@amd.com>
Date: Sun Jul 20 23:39:41 2025 -0500
drm/amd/display: Revert "drm/amd/display: Fix AMDGPU_MAX_BL_LEVEL value"

commit 8e6a18cbf3ee2c1e3d0afd8d3debd0ba8738ad0c upstream.

This reverts commit 66abb996999de0d440a02583a6e70c2c24deab45.
This broke custom brightness curves but it wasn't obvious because
of other related changes. Custom brightness curves are always
from a 0-255 input signal. The correct fix was to fix the default
value which was done by [1].

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4412
Link: https://lore.kernel.org/amd-gfx/0f094c4 … f4a61fdaf2
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 6ec8a5cbec751625133461600d0d4950ffd3a214)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

Great now what ? do i report this as a bug and who will i report this to or what exactly should i do after i knew where the issue started from.

seth · 2025-09-05 16:29:51

Did you confirm this is the only offender by reverting only it?
=> Comment at https://gitlab.freedesktop.org/drm/amd/-/issues/4412 but since this seems deliberate, do you actually just run last months hot button issue?

https://bbs.archlinux.org/viewtopic.php … 4#p2248154 - add "amdgpu.dcdebugmask=0x40000" to the https://wiki.archlinux.org/title/Kernel_parameters
Does that get you the desired behavior as well?

s79to-norm · 2025-09-06 01:00:46

seth wrote:

Did you confirm this is the only offender by reverting only it?
=> Comment at https://gitlab.freedesktop.org/drm/amd/-/issues/4412 but since this seems deliberate, do you actually just run last months hot button issue?
https://bbs.archlinux.org/viewtopic.php … 4#p2248154 - add "amdgpu.dcdebugmask=0x40000" to the https://wiki.archlinux.org/title/Kernel_parameters
Does that get you the desired behavior as well?

I confirmed that reverting commit 7133d48b9b06750d0c593926c4302285f50bbc66 on top of 6.16.4 resolves the regression. This confirms that the revert of the AMDGPU_MAX_BL_LEVEL that is supposed to be a "revert" of a previous commit is the cause of the issue. so Mario Limonciello tried to solve an issue solved it then created and issue someone complained on https://gitlab.freedesktop.org/drm/amd/-/issues/4412 so he made a revert to only make another issue for other people. And no my issue is completely different from what some people complained about my issue is that for some reason in linux 6.16.4 after that commit made in 6.16.3 the brightness level under 8% just turns the gamma into night shift style meaning the color temperature turning more red and red till 0% i can't see anything on the screen the brightness is at the lowest possible level possibly with white points reduced and a gamma that's so red you cant see anything no matter how dark the room your in and since i have an OLED SCREEN that means the pixels can literally be turned off to reach true black if the screen brightness is at that low level with white points reduces and a gamma that's extremely red you are pitch from a turned off screen. Now at first i thought it has to do with amd ABM since it's normal value is 0 and on the newest kernel it was -1 but somehow it got back to 0 after multiple reboots and changes but this issue of the brightness persisted and then after doing a kernel bisect i knew the exact point where the issue started from and i even went far to build the rc version of linux-6.17.0 kernel finding that it's still there it started in 6.16.3 and it is going all the way to 6.17 and if this didn't get solved now i think it will continue to all the next versions of the kernel leading to the need of a self maintained patched kernel so that every time a new version releases i need to revert that commit and continue using the kernel but if they change something else that needs to communicate with the bugged version Im literally wasted i don't know nothing about programming. Also i have tried the kernel parameter : amdgpu.dcdebugmask=0x40000 it does not help i don't get my desired behavior. Again ! Im still asking for further support on this issue because i don't know what to do Im currently running the kernel version 6.16.3 before that commit and i also noticed the issue happening in linux lts 6.12.44-1-lts but not as annoying it just changes the gamma to something close to 3000K only on the 0% brightness level which is pretty weird but not annoying.

seth · 2025-09-06 08:57:17

https://en.wikipedia.org/wiki/Paragraph
https://en.wikipedia.org/wiki/Punctuation

seth wrote:

Comment at https://gitlab.freedesktop.org/drm/amd/-/issues/4412

loqs · 2025-09-06 13:50:45

seth wrote:

Comment at https://gitlab.freedesktop.org/drm/amd/-/issues/4412

There is also now https://gitlab.freedesktop.org/drm/amd/-/issues/4556.

seth · 2025-09-06 14:56:57

OP on the upsrteam bug wrote:

I tried booting with amdgpu.dcdebugmask=0x40000 and it completely fixed the red gamma/brightness issue.

@s79to-norm, after trying to add that, what's the output of "systool -vm amdgpu"?

s79to-norm · 2025-09-06 21:52:20

seth wrote:

https://en.wikipedia.org/wiki/Paragraph
https://en.wikipedia.org/wiki/Punctuation
Comment at https://gitlab.freedesktop.org/drm/amd/-/issues/4412

loqs wrote:

There is also now https://gitlab.freedesktop.org/drm/amd/-/issues/4556.

Thank you for your help and assistance. I’ve also found that using the kernel parameter

amdgpu.dcdebugmask=0x40000

works as expected. My mistake was assuming that adding the parameter in /etc/default/grub and updating GRUB would be enough, while forgetting that I had created a custom boot entry and hadn’t updated it manually. That’s why it seemed like the parameter wasn’t working after reboot.

@seth — apologies for not being clear in my earlier post and for the poor punctuation. I’ll make sure to write more carefully in future posts.

I also found this upstream bug report very helpful: AMDGPU issue #4556

LeonCS · 2025-09-14 22:32:55

Yesterday, this also happened to me after a pacman -Syu. And adding kernel parameter [amdgpu.dcdebugmask=0x40000] to my /etc/default/grub also fixed this for me. Thank you.
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#1 2025-09-04 19:40:24

[SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#2 2025-09-04 20:14:05

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#3 2025-09-04 20:30:23

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#4 2025-09-04 20:43:08

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#5 2025-09-05 16:07:12

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#6 2025-09-05 16:29:51

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#7 2025-09-06 01:00:46

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#8 2025-09-06 08:57:17

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#9 2025-09-06 13:50:45

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#10 2025-09-06 14:56:57

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#11 2025-09-06 21:52:20

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

#12 2025-09-14 22:32:55

Re: [SOLVED] AMDGPU:Brightness/Gamma Not Working Properly In Kernel 6.16.4

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