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

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Jun 20, 2022 at 05:51:04PM -0400, Alex Deucher wrote:
> On Sat, Jun 18, 2022 at 7:27 PM Guenter Roeck <linux@roeck-us.net> 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@ellerman.id.au>
> > Cc: Daniel Axtens <dja@axtens.net>
> > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > ---
> >  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
> 
> This stuff was all moved as part of the FP rework in:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=26f4712aedbdf4b9f5e3888a50a2a4b130ee4a9b
> @Siqueira, Rodrigo
> , @Melissa Wen, @Dhillon, Jasdeep  can you take a look to understand
> why this is necessary?  If we add back the PPC flags, I think we need
> to add back the x86 ones as well.
> 

For my part I have no idea. All I can see is that powerpc:allmodconfig
builds fail with the above errors. I have not seen any build errors with
other architectures.

Guenter

> Alex
> 
> > +
> >  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)
> > --
> > 2.35.1
> >