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    Subject[PATCH 5.15 221/244] powerpc/32: Dont always pass -mcpu=powerpc to the compiler
    Date
    From: Christophe Leroy <christophe.leroy@csgroup.eu>

    [ Upstream commit 446cda1b21d9a6b3697fe399c6a3a00ff4a285f5 ]

    Since commit 4bf4f42a2feb ("powerpc/kbuild: Set default generic
    machine type for 32-bit compile"), when building a 32 bits kernel
    with a bi-arch version of GCC, or when building a book3s/32 kernel,
    the option -mcpu=powerpc is passed to GCC at all time, relying on it
    being eventually overriden by a subsequent -mcpu=xxxx.

    But when building the same kernel with a 32 bits only version of GCC,
    that is not done, relying on gcc being built with the expected default
    CPU.

    This logic has two problems. First, it is a bit fragile to rely on
    whether the GCC version is bi-arch or not, because today we can have
    bi-arch versions of GCC configured with a 32 bits default. Second,
    there are some versions of GCC which don't support -mcpu=powerpc,
    for instance for e500 SPE-only versions.

    So, stop relying on this approximative logic and allow the user to
    decide whether he/she wants to use the toolchain's default CPU or if
    he/she wants to set one, and allow only possible CPUs based on the
    selected target.

    Reported-by: Pali Rohár <pali@kernel.org>
    Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    Tested-by: Pali Rohár <pali@kernel.org>
    Reviewed-by: Arnd Bergmann <arnd@arndb.de>
    Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/d4df724691351531bf46d685d654689e5dfa0d74.1657549153.git.christophe.leroy@csgroup.eu
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/Makefile | 26 +-------------------------
    arch/powerpc/platforms/Kconfig.cputype | 21 ++++++++++++++++++---
    2 files changed, 19 insertions(+), 28 deletions(-)

    diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
    index 72610e2d6176..2bb0fe9b2058 100644
    --- a/arch/powerpc/Makefile
    +++ b/arch/powerpc/Makefile
    @@ -17,23 +17,6 @@ HAS_BIARCH := $(call cc-option-yn, -m32)
    # Set default 32 bits cross compilers for vdso and boot wrapper
    CROSS32_COMPILE ?=

    -ifeq ($(HAS_BIARCH),y)
    -ifeq ($(CROSS32_COMPILE),)
    -ifdef CONFIG_PPC32
    -# These options will be overridden by any -mcpu option that the CPU
    -# or platform code sets later on the command line, but they are needed
    -# to set a sane 32-bit cpu target for the 64-bit cross compiler which
    -# may default to the wrong ISA.
    -KBUILD_CFLAGS += -mcpu=powerpc
    -KBUILD_AFLAGS += -mcpu=powerpc
    -endif
    -endif
    -endif
    -
    -ifdef CONFIG_PPC_BOOK3S_32
    -KBUILD_CFLAGS += -mcpu=powerpc
    -endif
    -
    # If we're on a ppc/ppc64/ppc64le machine use that defconfig, otherwise just use
    # ppc64_defconfig because we have nothing better to go on.
    uname := $(shell uname -m)
    @@ -185,6 +168,7 @@ endif
    endif

    CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
    +AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))

    # Altivec option not allowed with e500mc64 in GCC.
    ifdef CONFIG_ALTIVEC
    @@ -195,14 +179,6 @@ endif
    CFLAGS-$(CONFIG_E5500_CPU) += $(E5500_CPU)
    CFLAGS-$(CONFIG_E6500_CPU) += $(call cc-option,-mcpu=e6500,$(E5500_CPU))

    -ifdef CONFIG_PPC32
    -ifdef CONFIG_PPC_E500MC
    -CFLAGS-y += $(call cc-option,-mcpu=e500mc,-mcpu=powerpc)
    -else
    -CFLAGS-$(CONFIG_E500) += $(call cc-option,-mcpu=8540 -msoft-float,-mcpu=powerpc)
    -endif
    -endif
    -
    asinstr := $(call as-instr,lis 9$(comma)foo@high,-DHAVE_AS_ATHIGH=1)

    KBUILD_CPPFLAGS += -I $(srctree)/arch/$(ARCH) $(asinstr)
    diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
    index 81f8c9634832..1b1e67ff9d21 100644
    --- a/arch/powerpc/platforms/Kconfig.cputype
    +++ b/arch/powerpc/platforms/Kconfig.cputype
    @@ -137,9 +137,9 @@ config GENERIC_CPU
    depends on PPC64 && CPU_LITTLE_ENDIAN
    select ARCH_HAS_FAST_MULTIPLIER

    -config GENERIC_CPU
    +config POWERPC_CPU
    bool "Generic 32 bits powerpc"
    - depends on PPC32 && !PPC_8xx
    + depends on PPC32 && !PPC_8xx && !PPC_85xx

    config CELL_CPU
    bool "Cell Broadband Engine"
    @@ -193,11 +193,23 @@ config G4_CPU
    depends on PPC_BOOK3S_32
    select ALTIVEC

    +config E500_CPU
    + bool "e500 (8540)"
    + depends on PPC_85xx && !PPC_E500MC
    +
    +config E500MC_CPU
    + bool "e500mc"
    + depends on PPC_85xx && PPC_E500MC
    +
    +config TOOLCHAIN_DEFAULT_CPU
    + bool "Rely on the toolchain's implicit default CPU"
    + depends on PPC32
    +
    endchoice

    config TARGET_CPU_BOOL
    bool
    - default !GENERIC_CPU
    + default !GENERIC_CPU && !TOOLCHAIN_DEFAULT_CPU

    config TARGET_CPU
    string
    @@ -212,6 +224,9 @@ config TARGET_CPU
    default "e300c2" if E300C2_CPU
    default "e300c3" if E300C3_CPU
    default "G4" if G4_CPU
    + default "8540" if E500_CPU
    + default "e500mc" if E500MC_CPU
    + default "powerpc" if POWERPC_CPU

    config PPC_BOOK3S
    def_bool y
    --
    2.35.1


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