Re: [PATCH] drm/amdgpu: drop the long-double-128 powerpc check/hack

[Michael Ellerman <mpe@ellerman.id.au>]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 31/03/2023 à 12:53, Michael Ellerman a écrit :
>> "Daniel Kolesa" <daniel@octaforge.org> writes:
>>> 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.
>> ...
>>> 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