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

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

[Arnd Bergmann]

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

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.

Fixes: a2e2f29970aa ("drm/amdgpu: Bring bo creation in line with radeon driver (v2)")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index d1aa291b2638..da3a53a39d0b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -374,8 +374,10 @@ int amdgpu_bo_create_restricted(struct amdgpu_device *adev,
 	 * See https://bugs.freedesktop.org/show_bug.cgi?id=88758
 	 */
 
+#ifndef CONFIG_COMPILE_TEST
 #warning Please enable CONFIG_MTRR and CONFIG_X86_PAT for better performance \
 	 thanks to write-combining
+#endif
 
 	if (bo->flags & AMDGPU_GEM_CREATE_CPU_GTT_USWC)
 		DRM_INFO_ONCE("Please enable CONFIG_MTRR and CONFIG_X86_PAT for "
-- 
2.9.0

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

[Michel Dänzer]

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

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

[Christian König]

Am 02.02.2017 um 07:09 schrieb Michel Dänzer:
> [SNIP]
> 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.

And exactly for this reason I would rather like to keep the warning.

Regards,
Christian.

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

[Michel Dänzer]

On 02/02/17 06:36 PM, Christian König wrote:
> Am 02.02.2017 um 07:09 schrieb Michel Dänzer:
>> [SNIP]
>> 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.
> 
> And exactly for this reason I would rather like to keep the warning.

Right, so let's take the patch as is:

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


Arnd, can you make the corresponding patch for radeon as well? Otherwise
I can probably do it next week.


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

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

[Alex Deucher]

On Fri, Feb 3, 2017 at 5:15 AM, Michel Dänzer <michel@daenzer.net> wrote:
> On 02/02/17 06:36 PM, Christian König wrote:
>> Am 02.02.2017 um 07:09 schrieb Michel Dänzer:
>>> [SNIP]
>>> 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.
>>
>> And exactly for this reason I would rather like to keep the warning.
>
> Right, so let's take the patch as is:
>
> Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
>

Applied.  thanks!

Alex

>
> Arnd, can you make the corresponding patch for radeon as well? Otherwise
> I can probably do it next week.
>
>
> --
> Earthling Michel Dänzer               |               http://www.amd.com
> Libre software enthusiast             |             Mesa and X developer
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