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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        mihai.caraman@freescale.com
Cc:     Nathan Chancellor <natechancellor@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Arnd Bergmann <arnd@kernel.org>,
        Brian Cain <bcain@codeaurora.org>,
        =?utf-8?B?RsSBbmctcnXDrCBTw7JuZw==?= <maskray@google.com>,
        kernel test robot <lkp@intel.com>, kbuild-all@lists.01.org,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: Error: invalid switch -me200
In-Reply-To: <14e9ce2b-1a83-5353-44c7-b0709796c70e@csgroup.eu>
References: <202011131146.g8dPLQDD-lkp@intel.com> <CAFP8O3LpSmxVnjHfQAN455k1ZRg3PbgZYhWr030evCq1T10k=Q@mail.gmail.com> <20201113190824.GA1477315@ubuntu-m3-large-x86> <CAKwvOdkEtTQhDRFRV_d66FyhQBe536vRbOW=fQjesiHz3dfeBA@mail.gmail.com> <20201113200444.GA1496675@ubuntu-m3-large-x86> <CAKwvOdkBSGPaKmQY1nERVe4_n19Q=MUtuwdond=FJAAF9N9Zhg@mail.gmail.com> <20201114002037.GW2672@gate.crashing.org> <14e9ce2b-1a83-5353-44c7-b0709796c70e@csgroup.eu>
Date:   Mon, 16 Nov 2020 17:06:21 +1100
Message-ID: <87h7pp4yzm.fsf@mpe.ellerman.id.au>
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Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 14/11/2020 =C3=A0 01:20, Segher Boessenkool a =C3=A9crit=C2=A0:
>> On Fri, Nov 13, 2020 at 12:14:18PM -0800, Nick Desaulniers wrote:
>>>>>> Error: invalid switch -me200
>>>>>> Error: unrecognized option -me200
>>>>>
>>>>> 251 cpu-as-$(CONFIG_E200)   +=3D -Wa,-me200
>>>>>
>>>>> Are those all broken configs, or is Kconfig messed up such that
>>>>> randconfig can select these when it should not?
>>>>
>>>> Hmmm, looks like this flag does not exist in mainline binutils? There =
is
>>>> a thread in 2010 about this that Segher commented on:
>>>>
>>>> https://lore.kernel.org/linuxppc-dev/9859E645-954D-4D07-8003-FFCD2391A=
B6E@kernel.crashing.org/
>>>>
>>>> Guess this config should be eliminated?
>>=20
>> The help text for this config options says that e200 is used in 55xx,
>> and there *is* an -me5500 GAS flag (which probably does this same
>> thing, too).  But is any of this tested, or useful, or wanted?
>>=20
>> Maybe Christophe knows, cc:ed.
>>=20
>
> I don't have much clue on this.

Me either.

> But I see on wikipedia that e5500 is a 64 bits powerpc (https://en.wikipe=
dia.org/wiki/PowerPC_e5500)
>
> What I see is that NXP seems to provide a GCC version that includes aditi=
onnal cpu (e200z0 e200z2=20
> e200z3 e200z4 e200z6 e200z7):
>
> valid arguments to '-mcpu=3D' are: 401 403 405 405fp 440 440fp 464 464fp =
476 476fp 505 601 602 603=20
> 603e 604 604e 620 630 740 7400 7450 750 801 821 823 8540 8548 860 970 G3 =
G4 G5 a2 cell e200z0 e200z2=20
> e200z3 e200z4 e200z6 e200z7 e300c2 e300c3 e500mc e500mc64 e5500 e6500 ec6=
03e native power3 power4=20
> power5 power5+ power6 power6x power7 power8 powerpc powerpc64 powerpc64le=
 rs64 titan "
>
> https://community.nxp.com/t5/MPC5xxx/GCC-generating-not-implemented-instr=
uctions/m-p/845049
>
> Apparently based on binutils 2.28
>
> https://www.nxp.com/docs/en/release-note/S32DS-POWER-v1-2-RN.pdf
>
> But that's not exactly -me200 though.
>
> Now, I can't see any defconfig that selects CONFIG_E200, so is that worth=
 keeping it in the kernel=20
> at all ?

There was a commit in 2014 that suggests it worked at least to some
extent then:

  3477e71d5319 ("powerpc/booke: Restrict SPE exception handlers to e200/e50=
0 cores")


Presumably there was a non-upstream toolchain where it was supported?

AFAICS the kernel builds OK with just the cpu-as modification removed:

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index a4d56f0a41d9..16b8336f91dd 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -248,7 +248,6 @@ KBUILD_CFLAGS               +=3D $(call cc-option,-mno-=
string)
 cpu-as-$(CONFIG_40x)           +=3D -Wa,-m405
 cpu-as-$(CONFIG_44x)           +=3D -Wa,-m440
 cpu-as-$(CONFIG_ALTIVEC)       +=3D $(call as-option,-Wa$(comma)-maltivec)
-cpu-as-$(CONFIG_E200)          +=3D -Wa,-me200
 cpu-as-$(CONFIG_E500)          +=3D -Wa,-me500

 # When using '-many -mpower4' gas will first try and find a matching power4


So that seems like the obvious fix for now.

I tried booting the resulting kernel in qemu, but I get:

  $ qemu-system-ppc -M none -cpu e200 -kernel build\~/vmlinux
  Error: Trying to register SPR 574 (23e) twice !


Which is not related AFAIK and indicates the qemu support is broken.

Unless we hear from someone that they're using mainline on an e200 then
it seems like it's a candidate for removal.

cheers