Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] drm/amdgpu: Re-enable DCN for 64-bit powerpc | Date | Tue, 26 Jul 2022 10:56:07 +1000 |
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Linus Torvalds <torvalds@linux-foundation.org> writes: > On Mon, Jul 25, 2022 at 5:39 AM Michael Ellerman <mpe@ellerman.id.au> wrote: >> >> Further digging shows that the build failures only occur with compilers >> that default to 64-bit long double. > > Where the heck do we have 'long double' things anywhere in the kernel?
There's one or two uses, but not in any code that's relevant to this issue AFAICS.
> I tried to grep for it, and failed miserably. I found some constants > that would qualify, but they were in the v4l colorspaces-details.rst > doc file. > > Strange.
It doesn't seem to matter if you use long double or not. It's just that if the long double size is 64-bits the linker refuses to link a mixture of soft/hard-float objects.
The 64-bit ABI says long double is 128-bits, so the compilers that are using 64-bit long double are either not built correctly, or we are not passing the correct flags to them.
There's an -mlong-double-128 flag which we can pass at build time which seems to do the right thing, I will probably add that to the kernel CFLAGS, but I want that to get a bit more testing.
cheers
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