On Monday 11 July 2022 16:19:30 Christophe Leroy wrote:

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.

Hello! Exactly same issue is still in file arch/powerpc/boot/Makefile:

  ifdef CONFIG_PPC64_BOOT_WRAPPER
  ifdef CONFIG_CPU_LITTLE_ENDIAN
  BOOTCFLAGS	+= -m64 -mcpu=powerpc64le
  else
  BOOTCFLAGS	+= -m64 -mcpu=powerpc64
  endif
  else
  BOOTCFLAGS	+= -m32 -mcpu=powerpc
  endif

It cause compile error:

  make ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnuspe- mpc85xx_smp_defconfig uImage
  ...
    BOOTAS  arch/powerpc/boot/crt0.o
  powerpc-linux-gnuspe-gcc: error: unrecognized argument in option ‘-mcpu=powerpc’
  powerpc-linux-gnuspe-gcc: note: valid arguments to ‘-mcpu=’ are: 8540 8548 native
  make[1]: *** [arch/powerpc/boot/Makefile:231: arch/powerpc/boot/crt0.o] Error 1

Reported-by: Pali Rohár <pali@kernel.org>
Tested-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: Segher Boessenkool <redacted>
Signed-off-by: Christophe Leroy <redacted>
---
 arch/powerpc/Makefile                  | 26 +-------------------------
 arch/powerpc/platforms/Kconfig.cputype | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 28 deletions(-)