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

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Date:   Sat, 26 Nov 2022 17:30:44 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
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

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?