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

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Message-ID: <00398948-d06c-3894-5be3-acb6cc09ff6b@csgroup.eu>
Date:   Wed, 2 Nov 2022 14:05:35 +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 01/11/2022 à 23:12, Pali Rohár a écrit :
> On Sunday 09 October 2022 13:06:52 Pali Rohár wrote:
>> On Monday 29 August 2022 10:54:51 Pali Rohár wrote:
>>> On Sunday 28 August 2022 17:43:53 Christophe Leroy wrote:
>>>> 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.
>>>
>>> I see... Will you prepare this fixup for your previous patch?
>>>
>>> And I think that following construct
>>>
>>>    $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
>>>
>>> should be changed just to
>>>
>>>    -mcpu=$(CONFIG_TARGET_CPU)
>>>
>>> Because if user specified that want build for specific target CPU, it
>>> should not be silently ignored.
>>
>> Christophe, should I do something in this area?
> 
> Christophe, any input from your side?

Hi, sorry I was on holiday until today. I'll try to have a look in the 
coming days.