[PATCH] drm/amdgpu: Always align dumb buffer at PAGE_SIZE

[Marek Olšák]

The kernel could report the true alignment from the ioctl instead of 0.

Marek

On Fri, Sep 23, 2022 at 1:31 AM Christian König <christian.koenig at amd.com>
wrote:

> Am 23.09.22 um 07:28 schrieb lepton:
> > On Thu, Sep 22, 2022 at 10:14 PM Christian König
> > <christian.koenig at amd.com> wrote:
> >> Am 23.09.22 um 01:04 schrieb Lepton Wu:
> >>> Since size has been aligned to PAGE_SIZE already, just align it
> >>> to PAGE_SIZE so later the buffer can be used as a texture in mesa
> >>> after
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcgit.freedesktop.org%2Fmesa%2Fmesa%2Fcommit%2F%3Fid%3Df7a4051b8&data=05%7C01%7Cchristian.koenig%40amd.com%7C645f6878a7bd487588b708da9d246c4c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637995077041120091%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=NMEAl8TByDLQFWW1d%2FaJfiGrXc4mpwL5dxNH0M0QH84%3D&reserved=0
> >>> Otherwise, si_texture_create_object will fail at line
> >>> "buf->alignment < tex->surface.alignment"
> >> I don't think that those Mesa checks are a good idea in the first place.
> >>
> >> The alignment value is often specified as zero when it doesn't matter
> >> because the minimum alignment can never be less than the page size.
> > Are you suggesting to change those mesa checks?
>
> Yes, the minimum alignment of allocations is always 4096 because that's
> the page size of the GPU.
>
> > While that can be
> > done, I still think a kernel side "fix" is still
> > useful since it doesn't hurt while can fix issues for some versions of
> mesa.
>
> No, we have tons of places where we don't specify and alignment for
> buffers because it never mattered. I certainly don't want to fix all of
> those.
>
> Regards,
> Christian.
>
> >> Christian.
> >>
> >>> Signed-off-by: Lepton Wu <ytht.net at gmail.com>
> >>> ---
> >>>    drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 2 +-
> >>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >>> index 8ef31d687ef3b..8dca0c920d3ce 100644
> >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> >>> @@ -928,7 +928,7 @@ int amdgpu_mode_dumb_create(struct drm_file
> *file_priv,
> >>>        args->size = ALIGN(args->size, PAGE_SIZE);
> >>>        domain = amdgpu_bo_get_preferred_domain(adev,
> >>>                                amdgpu_display_supported_domains(adev,
> flags));
> >>> -     r = amdgpu_gem_object_create(adev, args->size, 0, domain, flags,
> >>> +     r = amdgpu_gem_object_create(adev, args->size, PAGE_SIZE,
> domain, flags,
> >>>                                     ttm_bo_type_device, NULL, &gobj);
> >>>        if (r)
> >>>                return -ENOMEM;
>
>
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