Linux 4.11: Reported regressions as of Tuesday, 20176-03-14

[Christian König]

Am 15.03.2017 um 02:59 schrieb Michel Dänzer:
> [ Moving this sub-thread to the amd-gfx mailing list ]
>
> On 14/03/17 07:02 PM, Thorsten Leemhuis wrote:
>> Hi! Find below my first regression report for Linux 4.11. It lists 9
>> regressions I'm currently aware of.
> [...]
>
>> Desc: DRM BUG while initializing cape verde (2nd card)
>> Repo: 2017-03-13 https://bugzilla.kernel.org/show_bug.cgi?id=194867
>> Stat: n/a
>> Note: patch proposed by reporter
> I don't see any patch.
>
> Looks like the amdgpu driver has never fully initialized GDS support for
> SI family GPUs, and this now triggers the DRM_MM_BUG_ON which was added
> to drm_mm_init in 4.11.
>
> AMD folks, should this be addressed by fleshing out SI GDS support, or
> by completely disabling GDS initialization for SI?
Uff, good question. IIRC GDS was significantly different between SI and 
CIK in the hardware and requires pinned buffers on SI (userspace needs 
to know the physical address of the buffer).

So the current implementation most likely doesn't work as expected.

I would say disable it for now, but keep any existing code for at least 
one release. If nobody finds time to fix it properly (which is likely) 
we can throw away that and move on.

Christian.