On Fri, 22 Jul 2022 22:32:06 +1000 Michael Ellerman <michael@xxxxxxxxxxxxxx> wrote: > Hi Dan, > > [ Cc += linuxppc-dev ] > > Dan Horák <dan@xxxxxxxx> writes: > > Commit d11219ad53dc disabled the DCN driver for all platforms that > > define PPC64 due long build issues during "make allmodconfig" using > > cross-compilation. Cross-compilation defaults to the ppc64_defconfig > > and thus big-endian toolchain configuration. The ppc64le platform uses a > > different ABI and doesn't suffer from the build issues. > > Unfortunately it's a bit messier than that. yes, seems it is :-) > The build error occurs when the compiler is built to use a 64-bit long > double type. > > The ppc64le ABI document says that long double should be 128-bits, but > there are ppc64le compilers out there that are configured to use 64-bit > long double, notably the kernel.org crosstool compilers. > > So just testing for CPU_LITTLE_ENDIAN means we'll still get build errors > on those compilers. > > But I think we can detect the long double size and key off that. Can you > test the patch below works for you? yes, it does work, meaning it defines AMD_DC_DCN on Fedora/ppc64le (and build is OK) Dan > > cheers > > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 7aa12e88c580..e9f8cd50af99 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -281,6 +281,9 @@ config PPC > # Please keep this list sorted alphabetically. > # > > +config PCC_LONG_DOUBLE_128 > + def_bool $(success,test "$(shell,echo __LONG_DOUBLE_128__ | $(CC) -E -P -)" = 1) > + > config PPC_BARRIER_NOSPEC > bool > default y > diff --git a/drivers/gpu/drm/amd/display/Kconfig b/drivers/gpu/drm/amd/display/Kconfig > index b4029c0d5d8c..ec6771e87e73 100644 > --- a/drivers/gpu/drm/amd/display/Kconfig > +++ b/drivers/gpu/drm/amd/display/Kconfig > @@ -6,7 +6,7 @@ config DRM_AMD_DC > bool "AMD DC - Enable new display engine" > default y > select SND_HDA_COMPONENT if SND_HDA_CORE > - select DRM_AMD_DC_DCN if (X86 || PPC64) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) > + select DRM_AMD_DC_DCN if (X86 || PPC_LONG_DOUBLE_128) && !(KCOV_INSTRUMENT_ALL && KCOV_ENABLE_COMPARISONS) > help > Choose this option if you want to use the new display engine > support for AMDGPU. This adds required support for Vega and
