No backlight since linux-4.2.4 - drivers/gpu/drm/radeon/atombios_encoders.c

[Alex Deucher]

On Tue, Oct 27, 2015 at 12:23 PM, Michael Burian <michael.burian at sbg.at> wrote:
> On 10/27/15 16:10, Alex Deucher wrote:
>
>>
>> It would appear that your system does not use the gpu backlight
>> controller.  Either it's lying or messing with the GPU backlight
>> controller causes some bad interaction with whatever does control it.
>> Does the attached radeon patch help?  I'm also attaching an amdgpu
>> patch for reference in case the same problem appears on amdgpu.
>>
>
> no, still no backlight when applied against current current mainline
>
> 858e904bd71dd0057a548d6785d94ce5ec4aeabd (Merge tag 'iommu-fixes-v4.3-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu)
>

I see the problem.  We don't enable native backlight control on older
asics like yours by default.  Does the attached patch help?

Alex
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