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

[Michel Dänzer]

On 29.10.2015 04:03, Alex Deucher wrote:
> 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.

Both patches are

Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>


Apologies for the regression, and thanks for the fixes Alex!


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer