Re: [PATCH] drm/amdgpu: shut up #warning for compile testing

[Michel DÃnzer]

On 02/02/17 12:59 AM, Arnd Bergmann wrote:
> My randconfig tests on linux-next showed a newly introduced warning:
> 
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c: In function 'amdgpu_bo_create_restricted':
> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c:377:2: error: #warning Please enable CONFIG_MTRR and CONFIG_X86_PAT for better performance thanks to write-combining [-Werror=cpp]
> 
> Generally speaking, warnings about bad kernel configuration are not particularly
> helpful. We could enforce the selection of X86_PAT through Kconfig, so the driver
> cannot even be used unless it is enabled,

Making AMDGPU depend on X86_PAT would be wrong I think, and any fancier
Kconfig solution might be overkill.


> or we could just rely on the runtime warning that is also there.

That might make sense, since the runtime warning is only triggered when
the lack of PAT actually makes a difference.

OTOH the people running the kernel aren't always the same people
building it, so the downside is that this would potentially delay
getting X86_PAT enabled.


> In this version, I'm making the warning conditional on CONFIG_COMPILE_TEST, which
> shuts it up for me, but not people that may actually want to run the kernel
> as a compromize.

This is fine with me as well.


Whichever way we end up going for this, it should be applied to the
radeon driver as well.


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