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

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Message-ID: <aa61fc51-c6ea-2ad9-42c6-c62b280ab034@csgroup.eu>
Date:   Wed, 7 Dec 2022 13:39:18 +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 26/11/2022 à 17:30, Pali Rohár a écrit :
> On Wednesday 02 November 2022 14:05:35 Christophe Leroy wrote:
>> 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.
> 
> Ok, Did you have a time to look at it?

I just sent a patch for it.

Christophe