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

Alex Deucher alexdeucher at gmail.com
Wed Oct 28 12:03:44 PDT 2015


On Wed, Oct 28, 2015 at 3:11 AM, Michel Dänzer <michel at daenzer.net> wrote:
> On 28.10.2015 01:43, Alex Deucher wrote:
>> 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?
>
> My only doubt about this patch is: Should we also fall back to the old
> beahviour in the !(rdev->mode_info.firmware_flags &
> ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU) case?

Theoretically, it's not necessary, but I guess better safe than sorry.
Updated patches attached.

Alex
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