From be640317a1d0b9cf42fedb2debc2887a7cfa38de Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Mon, 18 Jul 2022 23:44:18 +1000 Subject: powerpc/64s: Disable stack variable initialisation for prom_init With GCC 12 allmodconfig prom_init fails to build: Error: External symbol 'memset' referenced from prom_init.c make[2]: *** [arch/powerpc/kernel/Makefile:204: arch/powerpc/kernel/prom_init_check] Error 1 The allmodconfig build enables KASAN, so all calls to memset in prom_init should be converted to __memset by the #ifdefs in asm/string.h, because prom_init must use the non-KASAN instrumented versions. The build failure happens because there's a call to memset that hasn't been caught by the pre-processor and converted to __memset. Typically that's because it's a memset generated by the compiler itself, and that is the case here. With GCC 12, allmodconfig enables CONFIG_INIT_STACK_ALL_PATTERN, which causes the compiler to emit memset calls to initialise on-stack variables with a pattern. Because prom_init is non-user-facing boot-time only code, as a workaround just disable stack variable initialisation to unbreak the build. Reported-by: Sudip Mukherjee Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220718134418.354114-1-mpe@ellerman.id.au --- arch/powerpc/kernel/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index f91f0f29a566..c8cf924bf9c0 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -20,6 +20,7 @@ CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom_init.o += -fno-stack-protector CFLAGS_prom_init.o += -DDISABLE_BRANCH_PROFILING CFLAGS_prom_init.o += -ffreestanding +CFLAGS_prom_init.o += $(call cc-option, -ftrivial-auto-var-init=uninitialized) ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code -- cgit From c653c591789b3acfa4bf6ae45d5af4f330e50a91 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Mon, 25 Jul 2022 14:37:29 +1000 Subject: drm/amdgpu: Re-enable DCN for 64-bit powerpc MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Alex Deucher Reviewed-by: Dan Horák Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2100 Link: https://lore.kernel.org/r/20220725123918.1903255-1-mpe@ellerman.id.au --- arch/powerpc/Kconfig | 4 ++++ drivers/gpu/drm/amd/display/Kconfig | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 7aa12e88c580..287cc2d4a4b3 100644 --- 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 index 0ba0598eba20..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 && !(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 -- cgit