On 2019-07-26 1:55 p.m., Christian König wrote:
> Am 26.07.19 um 10:54 schrieb Michel Dänzer:
>> On 2019-07-26 9:11 a.m., Christian König wrote:
>>> Am 25.07.19 um 16:24 schrieb Andrey Grodzovsky:
>>>> Move the logic to clear AMDGPU_GEM_CREATE_CPU_GTT_USWC in
>>>> amdgpu_bo_do_create into standalone helper so it can be reused
>>>> in other functions.
>>>>
>>>> v4:
>>>> Switch to return bool.
>>>>
>>>> v5: Fix typos.
>>>>
>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
>>>> ---
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 61
>>>> +++++++++++++++++-------------
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 2 +
>>>> 2 files changed, 37 insertions(+), 26 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> index 989b7b5..8702062 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> @@ -413,6 +413,40 @@ static bool amdgpu_bo_validate_size(struct
>>>> amdgpu_device *adev,
>>>> return false;
>>>> }
>>>> +bool amdgpu_bo_support_uswc(u64 bo_flags)
>>>> +{
>>>> +
>>>> +#ifdef CONFIG_X86_32
>>>> + /* XXX: Write-combined CPU mappings of GTT seem broken on 32-bit
>>>> + * See https://bugs.freedesktop.org/show_bug.cgi?id=84627
>>>> + */
>>>> + return false;
>>>> +#elif defined(CONFIG_X86) && !defined(CONFIG_X86_PAT)
>>>> + /* Don't try to enable write-combining when it can't work, or
>>>> things
>>>> + * may be slow
>>>> + * 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 "
>>>> + "better performance thanks to write-combining\n");
>>> I don't think this message belongs here.
>>>
>>> [...]
>>>> @@ -466,33 +500,8 @@ static int amdgpu_bo_do_create(struct
>>>> [...]
>>>> + if (!amdgpu_bo_support_uswc(bo->flags))
>>>> bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC;
>>> Rather here we should do "if (bo_flags & AMDGPU_GEM_CREATE_CPU_GTT_USWC
>>> && !amdgpu_bo_support_uswc())" and then clear the flag and also print
>>> the warning.
>> That would require duplicating the CONFIG_X86_PAT related logic here as
>> well, which is a bit ugly.
>
> Actually I would say we should drop this extra check and always emit a
> message that USWC is disabled for this platform.
>
> We now need it for more than just better performance and it should be
> explicitly noted that this is not available in the logs.
A log message which doesn't explain why it's disabled / how to enable it
would probably cause us user support pain.
--
Earthling Michel Dänzer | https://www.amd.com
Libre software enthusiast | Mesa and X developer
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