# git rev-parse -q --verify 50d2a40f2caac5bb31627ee20039e74332bd0d8a^{commit}
50d2a40f2caac5bb31627ee20039e74332bd0d8a
already have revision, skipping fetch
# git checkout -q -f -B kisskb 50d2a40f2caac5bb31627ee20039e74332bd0d8a
# git clean -qxdf
# < git log -1
# commit 50d2a40f2caac5bb31627ee20039e74332bd0d8a
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Mon Jul 25 14:37:29 2022 +1000
# 
#     drm/amdgpu: Re-enable DCN for 64-bit powerpc
#     
#     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>
#     Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2100
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-ld --version
# < git log --format=%s --max-count=1 50d2a40f2caac5bb31627ee20039e74332bd0d8a
# < make -s -j 32 ARCH=s390 O=/kisskb/build/powerpc-fixes_s390-defconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-  defconfig
# Added to kconfig CONFIG_DEBUG_INFO_BTF=n
# Added to kconfig 
# < make -s -j 32 ARCH=s390 O=/kisskb/build/powerpc-fixes_s390-defconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-  help
# make -s -j 32 ARCH=s390 O=/kisskb/build/powerpc-fixes_s390-defconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-  olddefconfig
# make -s -j 32 ARCH=s390 O=/kisskb/build/powerpc-fixes_s390-defconfig_s390x-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.5.0-nolibc/s390-linux/bin/s390-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_s390-defconfig_s390x-gcc8
# Build took: 0:06:27.868052