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SubjectRe: [PATCH v2] powerpc/boot: Don't always pass -mcpu=powerpc when building 32-bit uImage
On Saturday 27 August 2022 18:32:42 Christophe Leroy wrote:
> Le 27/08/2022 à 19:36, Pali Rohár a écrit :
> > On Saturday 27 August 2022 17:31:10 Christophe Leroy wrote:
> >> Le 27/08/2022 à 15:39, Pali Rohár a écrit :
> >>> For 32-bit uImage try to use CONFIG_TARGET_CPU option for -mcpu. This fixes
> >>> following compiler error when building kernel with powerpc e500 SPE capable
> >>> cross compilers:
> >>>
> >>> 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
> >>>
> >>> For 64-bit uImage and 64-bit kernels with 32-bit uImage wrapper there is no
> >>> change.
> >>>
> >>> Similar change was already introduced for the main powerpc Makefile in
> >>> commit 446cda1b21d9 ("powerpc/32: Don't always pass -mcpu=powerpc to the
> >>> compiler").
> >>>
> >>> Fixes: 40a75584e526 ("powerpc/boot: Build wrapper for an appropriate CPU")
> >>> Cc: stable@vger.kernel.org
> >>> Signed-off-by: Pali Rohár <pali@kernel.org>
> >>> ---
> >>> arch/powerpc/boot/Makefile | 8 ++++++++
> >>> 1 file changed, 8 insertions(+)
> >>>
> >>> diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
> >>> index a9cd2ea4a861..f56a5f90a5d8 100644
> >>> --- a/arch/powerpc/boot/Makefile
> >>> +++ b/arch/powerpc/boot/Makefile
> >>> @@ -44,8 +44,16 @@ else
> >>> BOOTCFLAGS += -m64 -mcpu=powerpc64
> >>> endif
> >>> else
> >>> +ifdef CONFIG_PPC32
> >>> +ifdef CONFIG_TARGET_CPU_BOOL
> >>> +BOOTCFLAGS += -m32 -mcpu=$(CONFIG_TARGET_CPU)
> >>> +else
> >>> +BOOTCFLAGS += -m32 -mcpu=powerpc
> >>
> >> You can't do that. You get here only if user has selected
> >> TOOLCHAIN_DEFAULT_CPU, in which case you don't want to for -mcpu=powerpc.
> >
> > So do I understand it correctly that in this branch I should omit -mcpu=powerpc?
>
> Correct.

Ok, I will fix it in v3.

> >
> >> -mcpu=powerpc is set when user selects CONFIG_POWERPC_CPU, in which case
> >> CONFIG_TARGET_CPU_BOOL is set as well.
> >>
> >>> +endif
> >>> +else
> >>> BOOTCFLAGS += -m32 -mcpu=powerpc
> >>
> >> Same, for PPC64 I think you don't want that either, unless the
> >> CONFIG_GENERIC_CPU has been selected in which case
> >> CONFIG_TARGET_CPU_BOOL is not set.
> >>
> >> When CONFIG_TARGET_CPU_BOOL is set for PPC64 you also want
> >> -mcpu=$(CONFIG_TARGET_CPU)
> >
> > I understand that this branch is called for PPC64 build with 32-bit
> > uImage wrapper. So in this case should not be used TARGET_CPU as it
> > would be 64-bit and not 32-bit as requited for 32-bit uImage wrapper.
>
> Why ?
>
> -mcpu=e6500 -m32 works as far as I can see.

Hm... I did not know that. Ok, if you want I will put it into
-m32 -mcpu=$(CONFIG_TARGET_CPU) branch too.

> >
> > Anyway, in this change I'm touching only PPC32 build, so all PPC64 stay
> > as it was before.
> >
> >>> endif
> >>> +endif
> >>>
> >>> BOOTCFLAGS += -isystem $(shell $(BOOTCC) -print-file-name=include)
> >>>

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