Re: [PATCH v4 13/15] drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT

[Guenter Roeck]

On 5/24/24 06:18, Alex Deucher wrote:
> On Fri, May 24, 2024 at 9:17 AM Alex Deucher <alexdeucher@xxxxxxxxx> wrote:
> > On Fri, May 24, 2024 at 5:16 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > > Hi,
> > >
> > > On Fri, Mar 29, 2024 at 12:18:28AM -0700, Samuel Holland wrote:
> > > > Now that all previously-supported architectures select
> > > > ARCH_HAS_KERNEL_FPU_SUPPORT, this code can depend on that symbol instead
> > > > of the existing list of architectures. It can also take advantage of the
> > > > common kernel-mode FPU API and method of adjusting CFLAGS.
> > > >
> > > > Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
> > > > Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> > > > Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> > >
> > > With this patch in the mainline kernel, I get the following build error
> > > when trying to build powerpc:ppc32_allmodconfig.
> > >
> > > powerpc64-linux-ld: drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o uses hard float, drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_helpers.o uses soft float
> > > powerpc64-linux-ld: failed to merge target specific data of file drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o
> > >
> > > [ repeated many times ]
> > >
> > > The problem is no longer seen after reverting this patch.
> >
> > Should be fixed with this patch:
> > https://gitlab.freedesktop.org/agd5f/linux/-/commit/5f56be33f33dd1d50b9433f842c879a20dc00f5b
> > Will pull it into my -fixes branch.
>
> Nevermind, this is something else.

mdgpu_dm_helpers.o is built with -msoft-float, display_mode_lib.o is built
with -mhard-float.

-msoft-float is from

arch/powerpc/Makefile:KBUILD_CFLAGS     += $(CC_FLAGS_NO_FPU)

-mhard-float is from

drivers/gpu/drm/amd/display/dc/dml/Makefile:dml_ccflags := $(CC_FLAGS_FPU)
drivers/gpu/drm/amd/display/dc/dml/Makefile:dml_rcflags := $(CC_FLAGS_NO_FPU)
drivers/gpu/drm/amd/display/dc/dml2/Makefile:dml2_ccflags := $(CC_FLAGS_FPU)
drivers/gpu/drm/amd/display/dc/dml2/Makefile:dml2_rcflags := $(CC_FLAGS_NO_FPU)

Unfortunately I have no idea know how to resolve this.

Guenter