[Bug 220326] New: Mismatch between the meanings of brightness and actual_brightness

[Bug 220326] New: Mismatch between the meanings of brightness and actual_brightness

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=220326

            Bug ID: 220326
           Summary: Mismatch between the meanings of brightness and
                    actual_brightness
           Product: Drivers
           Version: 2.5
          Hardware: AMD
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: kernvirt@gmail.com
        Regression: No

Amd ryzen 5 7520u (Mendocino)
/sys/class/backlight/amdgpu_bl1/type = raw
max_brightness = 255
Bug: The meaning of brightness does not match the meaning of actual_brightness
in /sys/class/backlight/amdgpu_bl1. For example, I set brightness 160 and
actual_brightness at this moment = 100, Also for example 80/25. In other words,
the higher the brightness level I set, the larger the adjustment step per
brightness percentage becomes of actual_brightness, for example 0-4% brightness
in kde = 0 in actual_brightness, While the difference between 40 and 45% is
already 11 units in actual_brightness. 
Tested kernels:6.13-6.15.5
Distro - debian/fedora/arch
I've tried:
-kernel parameters: acpi_backlight=video/vendor/native
amdgpu.backlight=0
-brightnessctl, acpilight 
-tty, DE
Everywhere the result is the same as I described above.

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[Bug 220326] Mismatch between the meanings of brightness and actual_brightness

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=220326

--- Comment #1 from Van (kernvirt@gmail.com) ---
Update: I'm tested debian trixie kernel 6.12 lts, and there they use amdgpu_bl0
instead bl1, and brightness = actual_brigtness, Fedora also uses amdgpu_bl1,
just like Arch, but the situation is better at the time of kernel 6.14
brightness 50 = actual_brightness 33, 103/73, but still I don't know how to get
normal behavior in Arch and Fedora on the upstream version of the kernel

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[Bug 220326] Mismatch between the meanings of brightness and actual_brightness

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=220326

--- Comment #2 from Van (kernvirt@gmail.com) ---
Update 2: I'm tested Ubuntu 25.04 with kernel 6.14, amdgpu_bl1, and brightness
works the same as on Debian with 6.12 lts, But for some reason on Fedora and
Arch with kernels 6.14 and 6.15.5 the brightness is non-linear, as I said
earlier, That is, the meaning of brightness does not match with the meaning of
actual brightness. 

Model of laptop: ASUS Vivobook go E1504FA

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[Bug 220326] Mismatch between the meanings of brightness and actual_brightness

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=220326

Artem S. Tashkinov (aros@gmx.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |ANSWERED

--- Comment #3 from Artem S. Tashkinov (aros@gmx.com) ---
Please report here after confirming it's an issue under 6.15.6:

https://gitlab.freedesktop.org/drm/amd/-/issues

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