[PATCH] amdgpu: re-enable DCN for ppc64le
Michael Ellerman
michael at ellerman.id.au
Fri Jul 22 22:32:06 AEST 2022
Hi Dan,
[ Cc += linuxppc-dev ]
Dan Horák <dan at danny.cz> 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.
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?
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
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