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

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Commit d11219ad53dc ("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 d11219ad53dc 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: d11219ad53dc ("amdgpu: disable powerpc support for the newer display engine")
Fixes: 16a9dea110a6 ("amdgpu: Enable initial DCN support on POWER")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Dan Horák <dan@danny.cz>
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2100
Link: https://lore.kernel.org/r/20220725123918.1903255-1-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2022-07-25 14:37:29 +10:00
parent 3c69a99b62
commit c653c59178
2 changed files with 5 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/Kconfig
View File

@ -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

2
drivers/gpu/drm/amd/display/Kconfig
View File

@ -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