Re: [PATCH] drm/amd/display: Add missing hard-float compile flags for PPC64 builds

[Rodrigo Siqueira Jordao <Rodrigo.Siqueira@xxxxxxx>]

On 2022-06-18 19:27, Guenter Roeck wrote:
> ppc:allmodconfig builds fail with the following error.
>
> powerpc64-linux-ld:
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o
> 		uses hard float,
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dcn31/dcn31_resource.o
> 		uses soft float
> powerpc64-linux-ld:
> 	failed to merge target specific data of file
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dcn31/dcn31_resource.o
> powerpc64-linux-ld:
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o
> 		uses hard float,
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dcn315/dcn315_resource.o
> 		uses soft float
> powerpc64-linux-ld:
> 	failed to merge target specific data of
> 	file drivers/gpu/drm/amd/amdgpu/../display/dc/dcn315/dcn315_resource.o
> powerpc64-linux-ld:
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o
> 		uses hard float,
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dcn316/dcn316_resource.o
> 		uses soft float
> powerpc64-linux-ld:
> 	failed to merge target specific data of file
> 	drivers/gpu/drm/amd/amdgpu/../display/dc/dcn316/dcn316_resource.o
>
> The problem was introduced with commit 41b7a347bf14 ("powerpc: Book3S
> 64-bit outline-only KASAN support") which adds support for KASAN. This
> commit in turn enables DRM_AMD_DC_DCN because KCOV_INSTRUMENT_ALL and
> KCOV_ENABLE_COMPARISONS are no longer enabled. As result, new files are
> compiled which lack the selection of hard-float.
>
> Fixes: 41b7a347bf14 ("powerpc: Book3S 64-bit outline-only KASAN support")
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Daniel Axtens <dja@xxxxxxxxxx>
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
>   drivers/gpu/drm/amd/display/dc/dcn31/Makefile  | 4 ++++
>   drivers/gpu/drm/amd/display/dc/dcn315/Makefile | 4 ++++
>   drivers/gpu/drm/amd/display/dc/dcn316/Makefile | 4 ++++
>   3 files changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn31/Makefile b/drivers/gpu/drm/amd/display/dc/dcn31/Makefile
> index ec041e3cda30..74be02114ae4 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn31/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn31/Makefile
> @@ -15,6 +15,10 @@ DCN31 = dcn31_resource.o dcn31_hubbub.o dcn31_hwseq.o dcn31_init.o dcn31_hubp.o
>   	dcn31_apg.o dcn31_hpo_dp_stream_encoder.o dcn31_hpo_dp_link_encoder.o \
>   	dcn31_afmt.o dcn31_vpg.o
>   
> +ifdef CONFIG_PPC64
> +CFLAGS_$(AMDDALPATH)/dc/dcn31/dcn31_resource.o := -mhard-float -maltivec
> +endif
> +
>   AMD_DAL_DCN31 = $(addprefix $(AMDDALPATH)/dc/dcn31/,$(DCN31))
>   
>   AMD_DISPLAY_FILES += $(AMD_DAL_DCN31)
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn315/Makefile b/drivers/gpu/drm/amd/display/dc/dcn315/Makefile
> index 59381d24800b..1395c1ced8c5 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn315/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn315/Makefile
> @@ -25,6 +25,10 @@
>   
>   DCN315 = dcn315_resource.o
>   
> +ifdef CONFIG_PPC64
> +CFLAGS_$(AMDDALPATH)/dc/dcn315/dcn315_resource.o := -mhard-float -maltivec
> +endif
> +
>   AMD_DAL_DCN315 = $(addprefix $(AMDDALPATH)/dc/dcn315/,$(DCN315))
>   
>   AMD_DISPLAY_FILES += $(AMD_DAL_DCN315)
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn316/Makefile b/drivers/gpu/drm/amd/display/dc/dcn316/Makefile
> index 819d44a9439b..c3d2dd78f1e2 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn316/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn316/Makefile
> @@ -25,6 +25,10 @@
>   
>   DCN316 = dcn316_resource.o
>   
> +ifdef CONFIG_PPC64
> +CFLAGS_$(AMDDALPATH)/dc/dcn316/dcn316_resource.o := -mhard-float -maltivec
> +endif
> +
>   AMD_DAL_DCN316 = $(addprefix $(AMDDALPATH)/dc/dcn316/,$(DCN316))
>   
>   AMD_DISPLAY_FILES += $(AMD_DAL_DCN316)

Hi,

I don't want to re-introduce those FPU flags for DCN31/DCN314/DCN316 
since we fully isolate FPU operations for those ASICs inside the DML 
folder. Notice that we have the PPC64 in the DML Makefile:

https://gitlab.freedesktop.org/agd5f/linux/-/blob/amd-staging-drm-next/drivers/gpu/drm/amd/display/dc/dml/Makefile

Could you share what you see without your patch in the 
amd-staging-drm-next? Also:
* Are you using cross-compilation? If so, could you share your setup?
* Which GCC/Clang version are you using?

Thanks
Siqueira