[Bug 203905] New: amdgpu:actual_brightness has unreal/wrong value

[Bug 203905] New: amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

            Bug ID: 203905
           Summary: amdgpu:actual_brightness has unreal/wrong value
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.1.9
          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: bjo@nord-west.org
        Regression: No

Radeon R5/R6/R7 Graphics in a Thinkpad A275 has wrong values on
actual_brightness of amdgpu_bl0. While max_brightness is 255 and it can be set
to 255, actual_brightness reports a 5 digit number like 12470. As a result,
tools which want to change the brightness related to actual_brightness fail, as
brightness does not accept any 5 digit number,

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #1 from Michel Dänzer (michel@daenzer.net) ---
Please attach the output of dmesg.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #2 from Bjoern Franke (bjo@nord-west.org) ---
Created attachment 283299
  --> https://bugzilla.kernel.org/attachment.cgi?id=283299&action=edit
dmesg

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #3 from Lukáš Krejčí (lskrejci@gmail.com) ---
Commit 262485a50fd4 ("drm/amd/display: Expand dc to use 16.16 bit backlight")
changed the value that is returned for `actual_brightness`:

-static unsigned int dce_abm_get_current_backlight_8_bit(struct abm *abm)
+static unsigned int dce_abm_get_current_backlight(struct abm *abm)
 {
    struct dce_abm *abm_dce = TO_DCE_ABM(abm);
    unsigned int backlight = REG_READ(BL1_PWM_CURRENT_ABM_LEVEL);

-   return (backlight >> 8);
+   /* return backlight in hardware format which is unsigned 17 bits, with
+    * 1 bit integer and 16 bit fractional
+    */
+   return backlight;
 }


I could not find anything official about the range of `actual_brightness`, only
the following blog says that is has to be in range of `brightness`:
https://nikula.org/~jani/backlight/#index3h3

I guess amdgpu_dm_backlight_get_brightness() could be changed to bring the
`actual_brightness` value in range of `brightness` again since it returns the
value of `brightness` in the error path anyway.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Sandor Ecker (esanya@freemail.hu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |esanya@freemail.hu

--- Comment #4 from Sandor Ecker (esanya@freemail.hu) ---
Hi,

I have the same Issue.

I have written a bug report to this:

https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-amdgpu/+bug/1861925

Maybe that is not the correct place...

Is any news regarding the problem?

Thx,
Regards,
Sandor

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #5 from Sandor Ecker (esanya@freemail.hu) ---
Would it be possible to set max_brightness to 2^16-1 ?

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #6 from Sandor Ecker (esanya@freemail.hu) ---
So it seems that the 16 bit actual_brightness is not a bug, but a feature... :)

https://github.com/torvalds/linux/commit/262485a50fd4532a8d71165190adc7a0a19bcc9e#diff-b496037255b7766a782d3f3711b50db8

So my question now:
-why are the max_brightness and brightness values in 8bit range?

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #7 from Sandor Ecker (esanya@freemail.hu) ---
I have upgraded to 5.6.rc1:

uname -a
Linux Aspire-A315-41 5.6.0-050600rc1-generic #202002092032 SMP Mon Feb 10
01:36:50 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux


I have seen that the code has log messages like:

DC_LOG_BACKLIGHT("New Backlight level: %d (0x%X)\n",
                        backlight_pwm_u16_16, backlight_pwm_u16_16);

I have set the kernel log by

echo "8" > /proc/sys/kernel/printk
cat /proc/sys/kernel/printk
8       4       1       7

but I can't see any logmessage with "New Backlight" in the output of the
commands:

grep -i "new backli" /var/log/*
dmesg |grep -i "back"

Maybe it does not reach that line of code? Or the log should be visible
somewhere else... ? 

Can somebody help...?

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Flo Bock (flo@dontshoot.at) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |flo@dontshoot.at

--- Comment #8 from Flo Bock (flo@dontshoot.at) ---
With recent systemd changes, the 16 bit values in actual_brightness break
saving and restoring the backlight values using AMDGPU. According to a closed
issue on Github, Lennart Poettering sees this as a kernel issue[1]. Is there
any good reason for actual_brightness to be 16bit, whereas both max_brightness
and brightness are 8bit?

[1]: https://github.com/systemd/systemd/issues/16600

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Kunal Bhat (kunal.bhat2001@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kunal.bhat2001@gmail.com

--- Comment #9 from Kunal Bhat (kunal.bhat2001@gmail.com) ---
(In reply to Flo Bock from comment #8)
> With recent systemd changes, the 16 bit values in actual_brightness break
> saving and restoring the backlight values using AMDGPU. According to a
> closed issue on Github, Lennart Poettering sees this as a kernel issue[1].
> Is there any good reason for actual_brightness to be 16bit, whereas both
> max_brightness and brightness are 8bit?
> 
> [1]: https://github.com/systemd/systemd/issues/16600



I believe it's there to provide a higher range of precision for the backlight.
Not sure why they never extended the range for max_brightness. 

The systemd devs are adamant that this is a driver issue, and aren't ready to
implement a work around for it. 
I believe this is the open issue with the discussions right now:
https://github.com/systemd/systemd/issues/16630

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #10 from Alexander Monakov (amonakov@gmail.com) ---
Proposed patch:
https://lore.kernel.org/lkml/20200803200218.2167-1-amonakov@ispras.ru/

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #11 from Alexander Monakov (amonakov@gmail.com) ---
v2 patch:
https://lore.kernel.org/lkml/20200804201313.6464-1-amonakov@ispras.ru/

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

rugk (jml86khakons@opayq.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jml86khakons@opayq.com

--- Comment #12 from rugk (jml86khakons@opayq.com) ---
(Backlink only) Same issue reported on
https://discussion.fedoraproject.org/t/amd-amdgpu-bl0-backlight-not-restored/20445?u=rugk

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

shanmukhateja@gmail.com (shanmukhateja@gmail.com) changed:

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

--- Comment #13 from shanmukhateja@gmail.com (shanmukhateja@gmail.com) ---
I have built a workaround for this issue by forking systemd-backlight for the
time-being. It has been tested on my ASUS TUF FX505DT with Ryzen 3550H.

https://github.com/shanmukhateja/systemd/tree/fix-amdgpu-backlight

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #14 from Xia Mu (mu.xia.77@gmail.com) ---
The bug should be fixed in 5.9.0-0.rc3. I tested it on my laptop with AMD Ryzen
7 PRO 4750U CPU with Renoir GPU.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

John Shand (jshand2013@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jshand2013@gmail.com

--- Comment #15 from John Shand (jshand2013@gmail.com) ---
i have had this problem as well.  was recently working well with kernel 5.8.7. 
i then install ucode-amd and then grub-mkconfig -o /boot/grub/grub.cfg to set
the changes.  grub automatically made the new code image work with initramfs
and then, backlight went back to about 20% or 255.

would this have anything to do with amd's ucode image??

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #16 from John Shand (jshand2013@gmail.com) ---
Created attachment 292417
  --> https://bugzilla.kernel.org/attachment.cgi?id=292417&action=edit
Dmesg 8-9-2020

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #17 from John Shand (jshand2013@gmail.com) ---
Created attachment 292419
  --> https://bugzilla.kernel.org/attachment.cgi?id=292419&action=edit
Journalctl 8-9-2020

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Germán Ríos González (german.rios.gonzalez@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |german.rios.gonzalez@gmail.
                   |                            |com

--- Comment #18 from Germán Ríos González (german.rios.gonzalez@gmail.com) ---
(In reply to Xia Mu from comment #14)
> The bug should be fixed in 5.9.0-0.rc3. I tested it on my laptop with AMD
> Ryzen 7 PRO 4750U CPU with Renoir GPU.

I'm actually using 5.9.9-200.fc33.x86_64 and the problem it's still there

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

kurmikon@libero.it changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kurmikon@libero.it

--- Comment #19 from kurmikon@libero.it ---
I confirm that the bug is not fixed in 5.9.12.

https://github.com/systemd/systemd/issues/17826

As Poettering pointed out, actual_brightness is read-only and reports the
brightness currently in effect, while brightness is writable and reports the
value set by userspace.

Not only the actual brightness is in a different range that breaks systemd
backlight restoring service at startup, but on my device its value is also
fixed on the same value while it should reflect the correct level on brightness
changes.

Brightness at the maximum:
/sys/class/backlight/amdgpu_bl0/actual_brightness > 249
/sys/class/backlight/amdgpu_bl0/brightness > 255
/sys/class/backlight/amdgpu_bl0/max_brightness > 255

Brightness at the minimum:
/sys/class/backlight/amdgpu_bl0/actual_brightness > 249
/sys/class/backlight/amdgpu_bl0/brightness > 2
/sys/class/backlight/amdgpu_bl0/max_brightness > 255

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Antony J.R (antonyjr000@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |antonyjr000@gmail.com

--- Comment #20 from Antony J.R (antonyjr000@gmail.com) ---
I can confirm that the bug is still not fixed even in 5.11-rc6 (the latest
kernel at the time of writing).

I can't control brightness also.

I have a AMD Ryzen 7 4800H APU which has Renoir Graphics.

The brightness control only works with Fedora Workstation 32 with Linux Kernel
5.6.6 but with 5.11-rc6 brightness control does not work at all.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Paulo Nascimento (paulo.ulusu@googlemail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |paulo.ulusu@googlemail.com

--- Comment #21 from Paulo Nascimento (paulo.ulusu@googlemail.com) ---
I confirm that the bug is not fixed in kenel 5.11-rc3

max brightness:
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/actual_brightness
311
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/brightness
255
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/max_brightness
255

min brightness:
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/actual_brightness
311
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/brightness
0
[pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/max_brightness
255

My laptop has an amd ryzen 5 4600h with renoir igpu and nvidia dgpu. 
Tests are done with renoir igpu:

[pn@pn-legion backlight]$ inxi -G
Graphics:  Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver: nouveau
v: kernel 
           Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu v:
kernel 
           Device-3: Chicony Integrated Camera type: USB driver: uvcvideo 
           Display: x11 server: X.Org 1.20.10 driver: loaded:
amdgpu,ati,modesetting,nouveau resolution: 1920x1080~120Hz 
           OpenGL: renderer: AMD RENOIR (DRM 3.40.0 5.11.0-1-MANJARO LLVM
11.0.1) v: 4.6 Mesa 20.3.3

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #22 from Antony J.R (antonyjr000@gmail.com) ---
A workaround for this is done by the OpenSUSE folks, Please see
https://bugzilla.opensuse.org/show_bug.cgi?id=1180749

The only distro which fixes this is OpenSUSE. This is because there is a
bug in the mainline kernel and kernel devs are not responding to us for
some reason(maybe file a new issue???).

The problem is that the kernel uses aux for backlight control but our
systems don't support backlight control via aux. So disabling aux
completely from amdgpu kernel module can give us backlight control for the
iGPU. I've tested it and it works just find.

Regards,
Antony J.R

On Mon, Feb 8, 2021 at 3:47 AM <bugzilla-daemon@bugzilla.kernel.org> wrote:

> https://bugzilla.kernel.org/show_bug.cgi?id=203905
>
> Paulo Nascimento (paulo.ulusu@googlemail.com) changed:
>
>            What    |Removed                     |Added
>
> ----------------------------------------------------------------------------
>                  CC|                            |
> paulo.ulusu@googlemail.com
>
> --- Comment #21 from Paulo Nascimento (paulo.ulusu@googlemail.com) ---
> I confirm that the bug is not fixed in kenel 5.11-rc3
>
> max brightness:
> [pn@pn-legion backlight]$ cat
> /sys/class/backlight/amdgpu_bl1/actual_brightness
> 311
> [pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/brightness
> 255
> [pn@pn-legion backlight]$ cat
> /sys/class/backlight/amdgpu_bl1/max_brightness
> 255
>
> min brightness:
> [pn@pn-legion backlight]$ cat
> /sys/class/backlight/amdgpu_bl1/actual_brightness
> 311
> [pn@pn-legion backlight]$ cat /sys/class/backlight/amdgpu_bl1/brightness
> 0
> [pn@pn-legion backlight]$ cat
> /sys/class/backlight/amdgpu_bl1/max_brightness
> 255
>
> My laptop has an amd ryzen 5 4600h with renoir igpu and nvidia dgpu.
> Tests are done with renoir igpu:
>
> [pn@pn-legion backlight]$ inxi -G
> Graphics:  Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver:
> nouveau
> v: kernel
>            Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver:
> amdgpu v:
> kernel
>            Device-3: Chicony Integrated Camera type: USB driver: uvcvideo
>            Display: x11 server: X.Org 1.20.10 driver: loaded:
> amdgpu,ati,modesetting,nouveau resolution: 1920x1080~120Hz
>            OpenGL: renderer: AMD RENOIR (DRM 3.40.0 5.11.0-1-MANJARO LLVM
> 11.0.1) v: 4.6 Mesa 20.3.3
>
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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

m11.1l1.f64@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |m11.1l1.f64@gmail.com

--- Comment #23 from m11.1l1.f64@gmail.com ---
There's a workaround here



I hope it helps :)



simply write this into `/etc/systemd/system/backlight-fix.service`:

```
[Unit]
Description=Dummy service for attempting to start the problematic amdgpu_bl0
service

[Service]
Type=simple
ExecStart=systemctl start systemd-backlight@backlight:amdgpu_bl0

[Install]
WantedBy=multi-user.target
```

And then `sudo systemctl enable --now backlight-fix.service`

Bingo!!

The problem is gone

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #24 from m11.1l1.f64@gmail.com ---
Related to the previous post:

https://www.linux.org/threads/failed-to-start-load-save-screen-backlight-brightness-of-amdgpu_bl1.31998/#post-113058

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #25 from m11.1l1.f64@gmail.com ---
I found another workaround and it's easier than EVER and it's done via
mkinitcpio😁


First, what's mkinitcpio(https://wiki.archlinux.org/index.php/Mkinitcpio)?



The initial ramdisk is in essence a very small environment (early userspace)
which loads various kernel modules and sets up necessary things before handing
over control to init. This makes it possible to have, for example, encrypted
root file systems and root file systems on a software RAID array. mkinitcpio
allows for easy extension with custom hooks, has autodetection at runtime, and
many other features.

So go ahead and edit with `sudo nano /etc/mkinitcpio.conf`


Then add the "amdgpu" in the modules section like this:


`MODULES=(amdgpu)`


After that, simply run `sudo mkinitcpio -P` so that it regenerates mkinitcpio
for all kernels


This solved my issue, I hope it works for others too :)_

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #26 from Paulo Nascimento (paulo.ulusu@googlemail.com) ---
laptop: Lenovo Legion 5, amd ryzen 5 4600h
Graphics:  Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver: nouveau
           Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu
Kernel 5.11.6-1
Manjaro 21.1

I have tried all suggested workarounds:
- systemctl start systemd-backlight@backlight:amdgpu_bl0

- mkinitcpio with MODULES=(amdgpu)

- acpi_backlight=vendor

- acpi_backlight=video

- /usr/lib/systemd/systemd-backlight save backlight:amdgpu_bl0
  /usr/lib/systemd/systemd-backlight load backlight:amdgpu_bl0

Even echo 10 >/sys/class/backlight/amdgpu_bl0/brightness doesn't change the
brightness.

Any suggestions?

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #27 from kurmikon@libero.it ---
For me the only workaround to avoid this bug is disabling systemd backlight
restoration. Then use brillo and enable a specific service to restore the
brightness at startup.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #28 from Antony J.R (antonyjr000@gmail.com) ---
(In reply to Paulo Nascimento from comment #26)
> laptop: Lenovo Legion 5, amd ryzen 5 4600h
> Graphics:  Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver:
> nouveau
>            Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu
> Kernel 5.11.6-1
> Manjaro 21.1
> 
> I have tried all suggested workarounds:
> - systemctl start systemd-backlight@backlight:amdgpu_bl0
> 
> - mkinitcpio with MODULES=(amdgpu)
> 
> - acpi_backlight=vendor
> 
> - acpi_backlight=video
> 
> - /usr/lib/systemd/systemd-backlight save backlight:amdgpu_bl0
>   /usr/lib/systemd/systemd-backlight load backlight:amdgpu_bl0
> 
> Even echo 10 >/sys/class/backlight/amdgpu_bl0/brightness doesn't change the
> brightness.
> 
> Any suggestions?

Please read the entire thread here ->
https://bugzilla.opensuse.org/show_bug.cgi?id=1180749

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

Filip Hejsek (filip.hejsek@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |filip.hejsek@gmail.com

--- Comment #29 from Filip Hejsek (filip.hejsek@gmail.com) ---
All the workarounds posted here are for a different bug:
https://bugzilla.kernel.org/show_bug.cgi?id=210263

There are three different problems:
- setting brightness doesn't work before showing something on display (the bug
linked above)
- actual_brightness has wrong range (this bug)
- kernel uses aux for backlight control on systems that don't support it

For the third problem, there is a patch in
https://bugzilla.opensuse.org/show_bug.cgi?id=1180749, and it seems to be
merged already. However, because there is no way yet to detect that aux
backlight doesn't work, the workaround has to be enabled with
amdgpu.aux_backlight=0 (assuming you have a kernel with the patch).

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #30 from Paulo Nascimento (paulo.ulusu@googlemail.com) ---
laptop: Lenovo Legion 5, amd ryzen 5 4600h
Graphics:  Device-1: NVIDIA TU116M [GeForce GTX 1660 Ti Mobile] driver: nouveau
           Device-2: Advanced Micro Devices [AMD/ATI] Renoir driver: amdgpu
Kernel: 5.12.0-1-MANJARO x86_64

I have loaded kernel 5.12 and enabled the patch with amdgpu.backlight=0. The
brightness controls Fn+F5/F6 works as well as the controls in KDE panel.

There are still the error messages at boot and shutdown though.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #31 from Paulo Nascimento (paulo.ulusu@googlemail.com) ---
Error messages are:
Mai 03 23:01:37 pn-legion systemd-backlight[861]: Failed to get backlight or
LED device 'backlight:acpi_video1': No such device
Mai 03 23:01:37 pn-legion systemd-backlight[862]: amdgpu_bl1: Failed to write
system 'brightness' attribute: No such device or address
Mai 03 23:01:37 pn-legion systemd[1]: Failed to start Load/Save Screen
Backlight Brightness of backlight:acpi_video1.

I think it has to do with the NVIDIA device.

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #32 from Filip Hejsek (filip.hejsek@gmail.com) ---
The acpi_video error seems to be
https://github.com/systemd/systemd/issues/15329 - first the ACPI driver creates
acpi_video1 device, then amdgpu removes it in favor of amdgpu_bl1, but systemd
still tries to set brightness on the removed device (which fails). You can
remove the error by masking `systemd-backlight@backlight:acpi_video1.service`.

The amdgpu_bl1 error is probably the bug i linked earlier -
https://bugzilla.kernel.org/show_bug.cgi?id=210263. Do you have silent boot? If
yes, you need to print something to console before setting backlight during
boot. You can use the workaround i posted here:
https://bbs.archlinux.org/viewtopic.php?pid=1971198#p1971198. If you use my
workaround, make sure to remove other workarounds you may have applied for that
error (like another service that runs systemctl start
systemd-backlight@backlight:amdgpu_bl0).

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[Bug 203905] amdgpu:actual_brightness has unreal/wrong value

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https://bugzilla.kernel.org/show_bug.cgi?id=203905

--- Comment #33 from Filip Hejsek (filip.hejsek@gmail.com) ---
Forgot to mention: since your AMD GPU has number 1 (not 0), you need to replace
acpi_video0 with acpi_video1 in my workaround.

(To others: sorry for the email spam)

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