[Bug 105051] New: Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[Bug 105051] New: Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

            Bug ID: 105051
           Summary: Radeon sets max_brightness to -1, breaking GNOME
                    backlight control on Macbook Pro mid-2015 11,5
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.2.1
          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: tim.sammut@gmail.com
        Regression: No

Created attachment 188601
  --> https://bugzilla.kernel.org/attachment.cgi?id=188601&action=edit
dmesg output

The radeon driver appears to be setting an incorrect value of -1 for
max_brightness in 
/sys/devices/pnp0/00:03/backlight/gmux_backlight/max_brightness. This computer
is a Macbook Pro Retina mid-2015 model 11,5 without any video or acpi related
kernel command line options.

This prevents GNOME from correctly managing the backlight. You can see this
using the following commands:

$ cat /sys/devices/pnp0/00:03/backlight/gmux_backlight/max_brightness
-1

$ /usr/libexec/gsd-backlight-helper --get-max-brightness
Could not get the maximum value of the backlight: got invalid backlight value
from /sys/devices/pnp0/00:03/backlight/gmux_backlight/max_brightness

$ sudo /usr/libexec/gsd-backlight-helper --set-brightness 500
Could not get the maximum value of the backlight: got invalid backlight value
from /sys/devices/pnp0/00:03/backlight/gmux_backlight/max_brightness


This looks to be the same issue reported into the RedHat bugzilla at:

https://bugzilla.redhat.com/show_bug.cgi?id=1263387

I've attached the dmesg from my machine.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

Alex Deucher <alexdeucher@gmail.com> changed:

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

--- Comment #1 from Alex Deucher <alexdeucher@gmail.com> ---
Radeon hardware supports 256 levels of brightness (0-255).  The backlight
integer property max_brightness is thus set to RADEON_MAX_BL_LEVEL (0xff).  It
sounds like GNOME is misinterpreting the value.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

Robert Abraham <robert.abraham86@googlemail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |robert.abraham86@googlemail
                   |                            |.com

--- Comment #2 from Robert Abraham <robert.abraham86@googlemail.com> ---
I have a similar problem. gmux_backlight/max_brightness is set to -1.
But i also have a radeon_bl entry in /sys/class/backlight which has the correct
values.
But no matter which value i echo into /sys/class/backlight/radeon_bl/brightness
i am on max brightness, except i echo 0. in this case the backlight turns off.

so i can only choose between backlight off or on max brightness.
it works perfectly fine on 4.0.x kernel though.

i will happily provide any information you need.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #3 from Alex Deucher <alexdeucher@gmail.com> ---
(In reply to Robert Abraham from comment #2)
> 
> it works perfectly fine on 4.0.x kernel though.

The radeon backlight code hasn't really changed since it was added so
presumably something else did.  Can you bisect?  Since this is a mac, it's
possible the GPU driver does not actually control the backlight.  Everything is
a one off on macs.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #4 from Tim Sammut <tim.sammut@gmail.com> ---
(In reply to Alex Deucher from comment #1)
> Radeon hardware supports 256 levels of brightness (0-255).  The backlight
> integer property max_brightness is thus set to RADEON_MAX_BL_LEVEL (0xff). 
> It sounds like GNOME is misinterpreting the value.

Hi Alex, thanks. I don't think is a GNOME issue. This is via /sys and you can
see the max_brightness = -1 here:

$ for F in /sys/class/backlight/*/{type,max_brightness}; do echo $F: $(cat $F);
done | sort
/sys/class/backlight/gmux_backlight/max_brightness: -1
/sys/class/backlight/gmux_backlight/type: platform
/sys/class/backlight/radeon_bl0/max_brightness: 255
/sys/class/backlight/radeon_bl0/type: raw

Manually adjusting the brightness via `echo $level >
/sys/class/backlight/gmux_backlight/brightness` works, but GNOME control of
brightness and the on-screen display do not. 


> The radeon backlight code hasn't really changed since it was added so
> presumably something else did.  Can you bisect?  Since this is a mac,
> it's possible the GPU driver does not actually control the backlight.
> Everything is a one off on macs.

Yeah, but probably not for 3+ weeks... sorry.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #5 from Tim Sammut <tim.sammut@gmail.com> ---
(In reply to Robert Abraham from comment #2)
> But i also have a radeon_bl entry in /sys/class/backlight which has the
> correct values.
> But no matter which value i echo into
> /sys/class/backlight/radeon_bl/brightness i am on max brightness, except i
> echo 0. in this case the backlight turns off.
> 
> so i can only choose between backlight off or on max brightness.
> it works perfectly fine on 4.0.x kernel though.

Just for the record, this is precise how my machine behaves as well.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #6 from Robert Abraham <robert.abraham86@googlemail.com> ---
commit 
4eebd5a4e72697aac25a8a57d3f888a9d5f80370

breaks the backlight for me.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #7 from Alex Deucher <alexdeucher@gmail.com> ---
Perhaps the radeon driver should just not attempt to register a backlight
interface on Macs since they seem to use the gmux for backlight control.  Some
one with more knowledge of mac hw should probably comment on how they should be
handled.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #8 from Michel Dänzer <michel@daenzer.net> ---
(In reply to Robert Abraham from comment #6)
> commit 
> 4eebd5a4e72697aac25a8a57d3f888a9d5f80370
> 
> breaks the backlight for me.

That's an apple-gmux change, not a radeon driver change. Please reassign the
component of this bug report accordingly.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #9 from Tim Sammut <tim.sammut@gmail.com> ---
(In reply to Michel Dänzer from comment #8)
> 
> That's an apple-gmux change, not a radeon driver change. Please reassign the
> component of this bug report accordingly.

Thanks, I'd be happy to, but I don't see where to but it and looking at other
apple_gmux bugs seem scattered. Help!?

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #10 from Michel Dänzer <michel@daenzer.net> ---
It may be easier to contact the apple-gmux developers via e-mail. The
scripts/get_maintainer.pl script should be useful for that.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

Tim Sammut <tim.sammut@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Video(DRI - non Intel)      |Platform_x86

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #11 from Tim Sammut <tim.sammut@gmail.com> ---
(In reply to Robert Abraham from comment #6)
> commit 
> 4eebd5a4e72697aac25a8a57d3f888a9d5f80370
> 
> breaks the backlight for me.

Yep, me too. Reverting that change against a 4.2.1 kernel completely fixes the
issues. Brightness adjusts and OSD appears.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #12 from Tim Sammut <tim.sammut@gmail.com> ---
(In reply to Michel Dänzer from comment #8)
> 
> That's an apple-gmux change, not a radeon driver change. Please reassign the
> component of this bug report accordingly.

Hi. I changed the component based on the output of scripts/get_maintainer.pl,
but I do not appear to be able to reassign the bug. 

Is anyone watching this bug able to reassign it?

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #13 from Alex Deucher <alexdeucher@gmail.com> ---
Only the original filer or an admin can change it as far as I know.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

Felipe Ortiz <fortizc@gmail.com> changed:

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

--- Comment #14 from Felipe Ortiz <fortizc@gmail.com> ---
I can confirm the problem with 4eebd5a4e72697aac25a8a57d3f888a9d5f80370. I have
a MPB 11,5 with AMD/Intel graphics. I recompile the module (a previous version
of 4eebd5a4e72697aac25a8a57d3f888a9d5f80370) and brightness adjusts is working
again.

I see two problems: 

1) If someone uses gpu-switch (https://github.com/0xbb/gpu-switch) with this
bug screen seem not work, after severals reboots (with different kernels) I can
access a terminal and execute gpu-switch -d and then screen seems work again.

2) If you use a Intel card (swiched with gpu-switch) the OSD (activated with
functions keys) is so slow and chromium have the same problem (temporary fix is
deactivate chromium hw acceleration) is this a intel driver bug?

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

--- Comment #15 from Darren Hart <dvhart@infradead.org> ---
Thanks for reporting, we're following up on the platform-drivers-x86 mailing
list.

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[Bug 105051] Radeon sets max_brightness to -1, breaking GNOME backlight control on Macbook Pro mid-2015 11,5

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=105051

Darren Hart <dvhart@infradead.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|drivers_video-dri@kernel-bu |drivers_platform_x86@kernel
                   |gs.osdl.org                 |-bugs.osdl.org

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