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

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Message-ID: <d49c5905-ff68-00e9-ddaf-d60d5e5ebe65@csgroup.eu>
Date:   Sun, 28 Aug 2022 17:43:53 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Pali Rohár <pali@...nel.org>
CC:     Michael Ellerman <mpe@...erman.id.au>,
        Joel Stanley <joel@....id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "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 19:41, Pali Rohár a écrit :
> On Sunday 28 August 2022 17:39:25 Christophe Leroy wrote:
>> 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.
> 
> It looks like that CONFIG_TARGET_CPU is broken.
> 
>    $ make ARCH=powerpc corenet64_smp_defconfig CROSS_COMPILE=powerpc64-linux-gnu-
>    ...
>    # configuration written to .config
> 
>    $ grep CONFIG_TARGET_CPU .config
>    CONFIG_TARGET_CPU_BOOL=y
> 
> CONFIG_TARGET_CPU_BOOL is set but CONFIG_TARGET_CPU not!

Yes, because there is no default value for E5500_CPU and E6500_CPU. We 
need to add one for each.

> 
>>> 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)