linux-kernel - Re: [PATCH v2] powerpc: make ALTIVEC select PPC

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Message-ID: <d2821589-0205-cd80-ef81-050d396f8cc1@infradead.org>
Date:   Wed, 21 Apr 2021 13:59:27 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org
Cc:     kernel test robot <lkp@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org,
        Segher Boessenkool <segher@...nel.crashing.org>
Subject: Re: [PATCH v2] powerpc: make ALTIVEC select PPC_FPU

On 4/20/21 10:19 PM, Christophe Leroy wrote:
> 
> 
> Le 21/04/2021 à 04:56, Randy Dunlap a écrit :
>> On a kernel config with ALTIVEC=y and PPC_FPU not set/enabled,
>> there are build errors:
>>
>> drivers/cpufreq/pmac32-cpufreq.c:262:2: error: implicit declaration of function 'enable_kernel_fp' [-Werror,-Wimplicit-function-declaration]
>>             enable_kernel_fp();
>> ../arch/powerpc/lib/sstep.c: In function 'do_vec_load':
>> ../arch/powerpc/lib/sstep.c:637:3: error: implicit declaration of function 'put_vr' [-Werror=implicit-function-declaration]
>>    637 |   put_vr(rn, &u.v);
>>        |   ^~~~~~
>> ../arch/powerpc/lib/sstep.c: In function 'do_vec_store':
>> ../arch/powerpc/lib/sstep.c:660:3: error: implicit declaration of function 'get_vr'; did you mean 'get_oc'? [-Werror=implicit-function-declaration]
>>    660 |   get_vr(rn, &u.v);
>>        |   ^~~~~~
>>
>> In theory ALTIVEC is independent of PPC_FPU but in practice nobody
>> is going to build such a machine, so make ALTIVEC require PPC_FPU
>> by selecting it.
>>
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Reported-by: kernel test robot <lkp@...el.com>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: linuxppc-dev@...ts.ozlabs.org
>> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
>> Cc: Segher Boessenkool <segher@...nel.crashing.org>
>> Cc: lkp@...el.com
>> ---
>> v2: change ALTIVEC depends on PPC_FPU to select (Christophe and Michael)
>>
>>   arch/powerpc/platforms/86xx/Kconfig    |    1 +
>>   arch/powerpc/platforms/Kconfig.cputype |    2 ++
>>   2 files changed, 3 insertions(+)
>>
>> --- linux-next-20210416.orig/arch/powerpc/platforms/86xx/Kconfig
>> +++ linux-next-20210416/arch/powerpc/platforms/86xx/Kconfig
>> @@ -4,6 +4,7 @@ menuconfig PPC_86xx
>>       bool "86xx-based boards"
>>       depends on PPC_BOOK3S_32
>>       select FSL_SOC
>> +    select PPC_FPU
> 
> Now that ALTIVEC selects PPC_FPU by itself, I don't think you need that.
> 
>>       select ALTIVEC
>>       help
>>         The Freescale E600 SoCs have 74xx cores.
>> --- linux-next-20210416.orig/arch/powerpc/platforms/Kconfig.cputype
>> +++ linux-next-20210416/arch/powerpc/platforms/Kconfig.cputype
>> @@ -186,6 +186,7 @@ config E300C3_CPU
>>   config G4_CPU
>>       bool "G4 (74xx)"
>>       depends on PPC_BOOK3S_32
>> +    select PPC_FPU
> 
> Same

Of course. v3 coming up.
Thanks.

>>       select ALTIVEC
>>     endchoice
>> @@ -310,6 +311,7 @@ config PHYS_64BIT
>>   config ALTIVEC
>>       bool "AltiVec Support"
>>       depends on PPC_BOOK3S_32 || PPC_BOOK3S_64 || (PPC_E500MC && PPC64)
>> +    select PPC_FPU
>>       help
>>         This option enables kernel support for the Altivec extensions to the
>>         PowerPC processor. The kernel currently supports saving and restoring
>>


-- 
~Randy