linux-kernel - Re: [PATCH] powerpc: e500: Fix compilation with gcc e500 compiler

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Message-ID: <8D562851-304F-4153-9194-426CC22B7FF2@ellerman.id.au>
Date:   Mon, 04 Jul 2022 20:23:29 +1000
From:   Michael Ellerman <michael@...erman.id.au>
To:     Pali Rohár <pali@...nel.org>
CC:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: e500: Fix compilation with gcc e500 compiler



On 2 July 2022 7:44:05 pm AEST, "Pali Rohár" <pali@...nel.org> wrote:
>On Tuesday 24 May 2022 11:39:39 Pali Rohár wrote:
>> gcc e500 compiler does not support -mcpu=powerpc option. When it is
>> specified then gcc throws compile error:
>> 
>>   gcc: error: unrecognized argument in option ‘-mcpu=powerpc’
>>   gcc: note: valid arguments to ‘-mcpu=’ are: 8540 8548 native
>> 
>> So do not set -mcpu=powerpc option when CONFIG_E500 is set. Correct option
>> -mcpu=8540 for CONFIG_E500 is set few lines below in that Makefile.
>> 
>> Signed-off-by: Pali Rohár <pali@...nel.org>
>> Cc: stable@...r.kernel.org
>
>Michael, do you have any objections about this patch?

I don't particularly like it :)

>From the discussion with Segher, it sounds like this is a problem with a specific build of gcc that you're using, not a general problem with gcc built with e500 support.

Keying it off CONFIG_E500 means it will fix your problem, but not anyone else who has a different non-e500 compiler that also doesn't support -mcpu=powerpc (for whatever reason).

So I wonder if a better fix is to use cc-option when setting -mcpu=powerpc.

cheers