Christophe Leroy [off-list ref] writes:

Le 31/03/2023 à 12:53, Michael Ellerman a écrit :

quoted

"Daniel Kolesa" [off-list ref] writes:

quoted

Commit c653c591789b ("drm/amdgpu: Re-enable DCN for 64-bit powerpc")
introduced this check as a workaround for the driver not building
with toolchains that default to 64-bit long double.

...

quoted

In mainline, this work is now fully done, so this check is fully
redundant and does not do anything except preventing AMDGPU DC
from being built on systems such as those using musl libc. The
last piece of work to enable this was commit c92b7fe0d92a
("drm/amd/display: move remaining FPU code to dml folder")
and this has since been backported to 6.1 stable (in 6.1.7).

Relevant issue: https://gitlab.freedesktop.org/drm/amd/-/issues/2288

I looked to pick this up for 6.3 but was still seeing build errors with
some compilers. I assumed that was due to some fixes coming in
linux-next that I didn't have.

But applying the patch on v6.3-rc4 I still see build errors. This is
building allyesconfig with the kernel.org GCC 12.2.0 / binutils 2.39
toolchain:

   powerpc64le-linux-gnu-ld: drivers/gpu/drm/amd/display/dc/dml/display_mode_lib.o uses hard float, arch/powerpc/lib/test_emulate_step.o uses soft float
   powerpc64le-linux-gnu-ld: failed to merge target specific data of file drivers/gpu/drm/amd/display/dc/dml/display_mode_lib.o

etc.

All the conflicts are between test_emulate_step.o and some file in drivers/gpu/drm/amd/display/dc/dml.

So even with all the hard-float code isolated in the dml folder, we
still hit build errors, because allyesconfig wants to link those
hard-float using objects with soft-float objects from elsewhere in the
kernel.

It seems like the only workable fix is to force the kernel build to use
128-bit long double. I'll send a patch doing that.

Commit 78f0929884d4 ("powerpc/64: Always build with 128-bit long 
double") I guess ?

Yes.

Let's drop this patch from patchwork then.

Thanks.

cheers