linux-kernel - Re: [PATCH] powerpc: unify two CONFIG_POWERPC64

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Message-ID: <6205828d-34ef-445d-8117-71a5269dc22f@csgroup.eu>
Date: Sat, 7 Jun 2025 13:47:15 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Masahiro Yamada <masahiroy@...nel.org>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Naveen N Rao <naveen@...nel.org>, linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: unify two CONFIG_POWERPC64_CPU entries in the
 same choice block



Le 07/06/2025 à 12:13, Masahiro Yamada a écrit :
> There are two CONFIG_POWERPC64_CPU entries in the "CPU selection"
> choice block.
> 
> I guess the intent is to display a different prompt depending on
> CPU_LITTLE_ENDIAN: "Generic (POWER5 and PowerPC 970 and above)" for big
> endian, and "Generic (POWER8 and above)" for little endian.
> 
> I stumbled on this tricky use case, and worked around it on Kconfig with
> commit 4d46b5b623e0 ("kconfig: fix infinite loop in sym_calc_choice()").
> However, I doubt that supporting multiple entries with the same symbol
> in a choice block is worth the complexity - this is the only such case
> in the kernel tree.
> 
> This commit merges the two entries. Once this cleanup is accepted in
> the powerpc subsystem, I will proceed to refactor the Kconfig parser.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

> ---
> 
>   arch/powerpc/platforms/Kconfig.cputype | 13 ++++---------
>   1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index 613b383ed8b3..7b527d18aa5e 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -122,16 +122,11 @@ choice
>   	  If unsure, select Generic.
>   
>   config POWERPC64_CPU
> -	bool "Generic (POWER5 and PowerPC 970 and above)"
> -	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
> +	bool "Generic 64 bits powerpc"
> +	depends on PPC_BOOK3S_64
> +	select ARCH_HAS_FAST_MULTIPLIER if CPU_LITTLE_ENDIAN
>   	select PPC_64S_HASH_MMU
> -
> -config POWERPC64_CPU
> -	bool "Generic (POWER8 and above)"
> -	depends on PPC_BOOK3S_64 && CPU_LITTLE_ENDIAN
> -	select ARCH_HAS_FAST_MULTIPLIER
> -	select PPC_64S_HASH_MMU
> -	select PPC_HAS_LBARX_LHARX
> +	select PPC_HAS_LBARX_LHARX if CPU_LITTLE_ENDIAN
>   
>   config POWERPC_CPU
>   	bool "Generic 32 bits powerpc"