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#1 2023-01-12 16:55:23

NWhisper
Member
Registered: 2009-04-24
Posts: 11

Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

When iMac Mid 2011 boots on kernel versions 6.1.4.arch1-1 and 6.1.5.arch1-1, /sys/class/backlight/radeon_bl0 is missing.
On kernel version 6.1.3.arch1-1 and below everything works normally.

# cat /proc/cmdline
initrd=\intel-ucode.img initrd=\initramfs-linux.img root=UUID=379486b8-e105-46b5-b271-224baff9597c rw quiet acpi_backlight=vendor
# lshw -class display
  *-display
       description: VGA compatible controller
       product: Whistler [Radeon HD 6730M/6770M/7690M XT]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:01:00.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=radeon latency=0
       resources: irq:28 memory:90000000-9fffffff memory:a8800000-a881ffff ioport:2000(size=256) memory:a8820000-a883ffff

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#2 2023-01-12 17:12:54

V1del
Forum Moderator
Registered: 2012-10-16
Posts: 18,209

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

What happens if you remove the acpi_backlight=vendor parameter? I remember reading some kernel devs post about potentially breaking the parameter due to rewritting the backlight handling, though I'd find it weird that an intentional change in this space would be introduced in a minor release.

FWIW logs of 6.1.6 mention

commit 9c152189a7e85dac1f759d6ba95f877af91ccf8c
Author: Mario Limonciello <mario.limonciello@amd.com>
Date:   Thu Dec 8 10:42:07 2022 -0600

    ACPI: video: Don't enable fallback path for creating ACPI backlight by default
    
    [ Upstream commit 5aa9d943e9b6bf6e6023645cbe7ce7d5ed84baf4 ]
    
    The ACPI video detection code has a module parameter
    `register_backlight_delay` which is currently configured to 8 seconds.
    This means that if after 8 seconds of booting no native driver has created
    a backlight device then the code will attempt to make an ACPI video
    backlight device.
    
    This was intended as a safety mechanism with the backlight overhaul that
    occurred in kernel 6.1, but as it doesn't appear necesssary set it to be
    disabled by default.
    
    Suggested-by: Hans de Goede <hdegoede@redhat.com>
    Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
    Reviewed-by: Hans de Goede <hdegoede@redhat.com>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@>

maybe try setting that parameter to 8 again.

Last edited by V1del (2023-01-12 17:16:45)

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#3 2023-01-12 18:01:20

NWhisper
Member
Registered: 2009-04-24
Posts: 11

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

V1del wrote:

What happens if you remove the acpi_backlight=vendor parameter? I remember reading some kernel devs post about potentially breaking the parameter due to rewritting the backlight handling, though I'd find it weird that an intentional change in this space would be introduced in a minor release.

On the iMac mid 2011 backlight has always worked only with acpi_backlight=vendor. If it is removed or changed to another value, backlight stops working. This happens on kernel version 6.1.3.arch1-1 or below. On kernel versions 6.1.[45].arch1-1 backlight does not work with any setting of the acpi_backlight parameter, including if it is removed... sad

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#4 2023-01-12 21:14:32

rod.maccallum
Member
Registered: 2023-01-12
Posts: 1

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

I posted this to your bug submission... might not have been the proper place!

What happens if you boot with the option acpi_backlight=native? This fixed this same issue for me on a 2012 MacBook Pro with intel graphics. I found the fix at:  https://bugzilla.kernel.org/show_bug.cgi?id=216904

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#5 2023-01-12 21:36:13

loqs
Member
Registered: 2014-03-06
Posts: 15,629

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

rod.maccallum wrote:

What happens if you boot with the option acpi_backlight=native? This fixed this same issue for me on a 2012 MacBook Pro with intel graphics.

That matches https://bugs.archlinux.org/task/77056

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#6 2023-01-13 06:34:10

NWhisper
Member
Registered: 2009-04-24
Posts: 11

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

rod.maccallum wrote:

What happens if you boot with the option acpi_backlight=native? This fixed this same issue for me on a 2012 MacBook Pro with intel graphics. I found the fix at:  https://bugzilla.kernel.org/show_bug.cgi?id=216904

Thanks guys! Replacing acpi_backlight=vendor -> native restores proper backlight operation.

Apparently, when I was testing before writing the forum post, I made a mistake.

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#7 2023-01-13 16:47:55

vacant
Member
From: downstairs
Registered: 2004-11-05
Posts: 811

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

rod.maccallum wrote:

What happens if you boot with the option acpi_backlight=native?

Thanks, that option also fixed my old Acer 5742Z laptop with an Intel graphics chip. Now I have a /sys/classes/backlight/intel_backlight.

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#8 2023-01-16 23:21:50

cyanara
Member
Registered: 2022-10-30
Posts: 5

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

I'm still facing this issue on my Lenovo Ideapad 3, backlight control broke on kernel version 6.1.4-arch1-1 and I can confirm it's still broken on 6.1.6-arch1-1.

I have an AMD Ryzen 5 5500U with Radeon Graphics and was using the kernel parameter acpi_backlight=video (my brightness control buttons don't work with the other options).
This worked fine up to kernel version 6.1.3, but is now broken since 6.1.4. Changing the parameter to vendor, native or removing it does not solve the issue for me.

Sadly I was only able to fix it by downgrading to 6.1.3.

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#9 2023-01-17 14:10:54

loqs
Member
Registered: 2014-03-06
Posts: 15,629

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

@cyanara are there any entries in /sys/class/backlight/ under 6.1.6 with any of the different acpi_backlight= values?

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#10 2023-01-17 18:00:51

cyanara
Member
Registered: 2022-10-30
Posts: 5

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

loqs wrote:

@cyanara are there any entries in /sys/class/backlight/ under 6.1.6 with any of the different acpi_backlight= values?

Yes, and they change depending on the values.

Using video:   There's an acpi_video0 entry, the brightness buttons don't work and writing to acpi_video0/brightness does nothing.
Using vendor:   There's an ideapad entry, the brightness buttons don't work and writing to ideapad/brightness does nothing.
Using native or without parameter:   There's an amdgpu_bl0 entry, brightness buttons don't work, but writing to amdgpu_bl0/brightness does change the brightness.

On kernel version 6.1.3 and using acpi_backlight=video, there would be two entries (acpi_video0 and amdgpu_bl0) and everything would work.
I guess my only issue is that something made the brightness buttons stop working on 6.1.4+

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#11 2023-01-17 18:08:29

loqs
Member
Registered: 2014-03-06
Posts: 15,629

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

I would suggest trying linux-mainline 6.2-rc4 available from miffe's Unofficial user repositories.
If that still has the issue I can build you the latest 6.1 with the relevant commits reverted and see if that resolves the issue.  If so you can then report it upstream.

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#12 2023-01-17 20:24:27

cyanara
Member
Registered: 2022-10-30
Posts: 5

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

So, I just installed and tested 6.2.0-rc4-1-mainline and it does in fact have the same issue.

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#14 2023-01-17 22:44:23

cyanara
Member
Registered: 2022-10-30
Posts: 5

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

@loqs thank you!
I just tested it and the brightness control buttons are working again, reverting those commits really solves the issue.
So I guess I'm supposed to report this problem upstream now, right? How can do I do that?

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#15 2023-01-17 23:07:44

loqs
Member
Registered: 2014-03-06
Posts: 15,629

Re: Radeon backlight does not work on kernel versions 6.1.4.arch1-1 and 6.

Might already be as https://bugzilla.kernel.org/show_bug.cgi?id=216904 although there are some differences in your symptoms.
I would use that bug report to document 6.1.6 and 6.2-rc4 the brightness buttons are no longer functional.

Last edited by loqs (2023-01-17 23:08:03)

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