linux-kernel - Re: [PATCH v3] powerpc/boot: Don't always pass -mcpu=powerpc when building 32-bit uImage

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Date:   Sun, 28 Aug 2022 17:39:25 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Pali Rohár <pali@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Joel Stanley <joel@....id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] powerpc/boot: Don't always pass -mcpu=powerpc when
 building 32-bit uImage



Le 28/08/2022 à 19:33, Christophe Leroy a écrit :
> 
> 
> Le 28/08/2022 à 11:56, Pali Rohár a écrit :
>> When CONFIG_TARGET_CPU is specified then pass its value to the compiler
>> -mcpu option. This fixes following build 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
> 
> corenet64_smp_defconfig :
> 
>    BOOTAS  arch/powerpc/boot/crt0.o
> powerpc64-linux-gcc: error: missing argument to '-mcpu='
> make[1]: *** [arch/powerpc/boot/Makefile:237 : arch/powerpc/boot/crt0.o] 
> Erreur 1
> make: *** [arch/powerpc/Makefile:253 : uImage] Erreur 2
> 
> 

Seems like in fact, E5500_CPU and E6500_CPU are not taken into account 
in CONFIG_TARGET_CPU, and get special treatment directly in 
arch/powerpc/Makefile.

This goes unnoticed because of CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += 
$(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))

I think we need to fix that prior to your patch.

> Christophe
> 
> 
>>
>> 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@...r.kernel.org # 446cda1b21d9 ("powerpc/32: Don't always 
>> pass -mcpu=powerpc to the compiler")
>> Signed-off-by: Pali Rohár <pali@...nel.org>
>> ---
>>   arch/powerpc/boot/Makefile | 14 ++++++++++----
>>   1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
>> index a9cd2ea4a861..1957a3de7a1c 100644
>> --- a/arch/powerpc/boot/Makefile
>> +++ b/arch/powerpc/boot/Makefile
>> @@ -38,13 +38,19 @@ BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes 
>> -Wno-trigraphs \
>>            $(LINUXINCLUDE)
>>   ifdef CONFIG_PPC64_BOOT_WRAPPER
>> -ifdef CONFIG_CPU_LITTLE_ENDIAN
>> -BOOTCFLAGS    += -m64 -mcpu=powerpc64le
>> +BOOTCFLAGS    += -m64
>>   else
>> -BOOTCFLAGS    += -m64 -mcpu=powerpc64
>> +BOOTCFLAGS    += -m32
>>   endif
>> +
>> +ifdef CONFIG_TARGET_CPU_BOOL
>> +BOOTCFLAGS    += -mcpu=$(CONFIG_TARGET_CPU)
>> +else ifdef CONFIG_PPC64_BOOT_WRAPPER
>> +ifdef CONFIG_CPU_LITTLE_ENDIAN
>> +BOOTCFLAGS    += -mcpu=powerpc64le
>>   else
>> -BOOTCFLAGS    += -m32 -mcpu=powerpc
>> +BOOTCFLAGS    += -mcpu=powerpc64
>> +endif
>>   endif
>>   BOOTCFLAGS    += -isystem $(shell $(BOOTCC) -print-file-name=include)