[Bug 203439] New: amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[Bug 203439] New: amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

            Bug ID: 203439
           Summary: amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is
                    too high
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: spaz16@wp.pl
        Regression: No

I have Huawei Matebook D 14 with AMD Ryzen 2500U.

Since kernel 5.0.x the minimum brightness level is too high. It is not possible
to dim the display as much as on previous kernel version. Kernel 4.20 also
allows to disable the backlight on level 0.

Value of "0" in "/sys/class/backlight/amdgpu_bl0/brightness" currently doesn't
disable backlight as in previous version. Value of "1" means the screen is dim,
but not as much as in kernel 4.20. Sometimes the screen is still too bright
even on level 0 in kernel 5.0.

Since commit 206bbafe00dcacccf40e6f09e624329ec124201b I can see the define:
> #define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12

Maybe it should be defined to "0" to restore the old behavior? (I haven't
tested yet)

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

--- Comment #1 from Błażej Szczygieł (spaz16@wp.pl) ---
*** Bug 203427 has been marked as a duplicate of this bug. ***

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

Nicholas Kazlauskas (nicholas.kazlauskas@amd.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nicholas.kazlauskas@amd.com

--- Comment #2 from Nicholas Kazlauskas (nicholas.kazlauskas@amd.com) ---
At some point we started reading the ACPI backlight caps to respect the actual
backlight range for the panel. We map the backlight level specified by the user
from 0-255 to that range.

In the case where the caps aren't valid we use a default minimum brightness
that's non-zero since some panels will flash when the backlight level goes to
zero.

While I don't know offhand the reasoning for 12 specifically I also don't think
we'll be dropping it back down to zero.

Wouldn't DPMS off give you what you want in this case?

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

--- Comment #3 from Błażej Szczygieł (spaz16@wp.pl) ---
Thank you for the reply!

In bright room you can quickly disable the backlight (set it to 0) using the
Fn+F1 keys. You can save power and the display content doesn't disturb you, but
you can still notice that computer is working (the screen content can be still
visible). It is more convenient than DPMS, especially if you have duplicated
screen with HDMI and you don't want to reconfigure anything, just you want to
quickly disable the backlight.

Moreover, the current minimum backlight level is too bright for very dark room.
Sometimes I need to set to value of "2" or even "1" in kernel 4.20. Since
kernel 5.0 it is not possible and I'm not feeling convenient with too bright
display.

On Huawei Matebook D 14 the display doesn't flicker at all even on brightness
level 1 on kernel 4.20 (no PWM). Maybe it is a good idea to blacklist or
whitelist some devices? Or maybe it is a good idea to add an additional kernel
parameter to restore the old behavior and unlock all possible backlight levels
for more advanced users?

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

acomagu@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |acomagu@gmail.com

--- Comment #4 from acomagu@gmail.com ---
I also need this fix.

As Błażej Szczygieł says, the minimum backlight level is too bright at night
for me. That's why I'm staying at 4.19 instead of 5.x.

I hope anyone considers better strategy like based on such device list.

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

--- Comment #5 from acomagu@gmail.com ---
I forgot to mention about my device. I'm using HP Envy 13 x360(ag0000).

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[Bug 203439] amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203439

Anish Sapkota (sapkotaanish000@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sapkotaanish000@gmail.com

--- Comment #6 from Anish Sapkota (sapkotaanish000@gmail.com) ---
I am still facing this problem in Acer Aspire 5.
Are there any updates to it?

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