drm/amdgpu: Re-enable DCN for 64-bit powerpc

Commit d11219a ("amdgpu: disable powerpc support for the newer display engine") disabled the DCN driver for all of powerpc due to unresolved build failures with some compilers. Further digging shows that the build failures only occur with compilers that default to 64-bit long double. Both the ppc64 and ppc64le ABIs define long double to be 128-bits, but there are compilers in the wild that default to 64-bits. The compilers provided by the major distros (Fedora, Ubuntu) default to 128-bits and are not affected by the build failure. There is a compiler flag to force 128-bit long double, which may be the correct long term fix, but as an interim fix only allow building the DCN driver if long double is 128-bits by default. The bisection in commit d11219a must have gone off the rails at some point, the build failure occurs all the way back to the original commit that enabled DCN support on powerpc, at least with some toolchains. Depends-on: d11219a ("amdgpu: disable powerpc support for the newer display engine") Fixes: 16a9dea ("amdgpu: Enable initial DCN support on POWER") Signed-off-by: Michael Ellerman <[email protected]> Acked-by: Alex Deucher <[email protected]> Reviewed-by: Dan Horák <[email protected]> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2100 Link: https://lore.kernel.org/r/[email protected]
niw · Jul 25, 2022 · c653c59 · c653c59
1 parent 3c69a99
commit c653c59
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diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
@@ -281,6 +281,10 @@ config PPC
 	# Please keep this list sorted alphabetically.
 	#
 
+config PPC_LONG_DOUBLE_128
+	depends on PPC64
+	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
@@ -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 && !(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