linux-kernel - Re: [PATCH v1 1/5] powerpc/64: Set default CPU in Kconfig

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Message-ID: <20221220201353.xhzdzmh5n2jwtv5w@pali>
Date:   Tue, 20 Dec 2022 21:13:53 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>, jbglaw@...-owl.de,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 1/5] powerpc/64: Set default CPU in Kconfig

On Monday 19 December 2022 19:45:56 Christophe Leroy wrote:
> Since 0069f3d14e7a ("powerpc/64e: Tie PPC_BOOK3E_64 to PPC_E500MC"), the
> only possible BOOK3E/64 are E500, so no need of a default CPU over the
> E5500.
> 
> When the user selects book3e, they must have an e500 compatible
> compiler, and it won't work anymore with the default -mcpu=power64, see
> commit d6b551b8f90c ("powerpc/64e: Fix build failure with GCC 12
> (unrecognized opcode: `wrteei')").
> 
> For book3s/64, replace GENERIC_CPU by POWERPC64_CPU to match the PPC32
> POWERPC_CPU, and set a default mpcu value in Kconfig directly.
> 
> When a user selects a particular CPU, they must ensure the compiler has
> the requested capability. Therefore, remove hidden fallback, instead
> offer user the possibility to say they want to use the toolchain
> default.
> 
> It also fixes the non existing E5500_CPU which is a leftover of
> commit d6b551b8f90c ("powerpc/64e: Fix build failure with GCC 12
> (unrecognized opcode: `wrteei')")
> 
> Fixes: d6b551b8f90c ("powerpc/64e: Fix build failure with GCC 12 (unrecognized opcode: `wrteei')")
> Reported-by: Pali Rohár <pali@...nel.org>
> Tested-by: Pali Rohár <pali@...nel.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>

Acked-by: Pali Rohár <pali@...nel.org>

> ---
>  arch/powerpc/Makefile                  | 22 +++++-----------------
>  arch/powerpc/platforms/Kconfig.cputype | 12 +++++++-----
>  2 files changed, 12 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index dc4cbf0a5ca9..bf5f0a998273 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -146,19 +146,6 @@ CFLAGS-$(CONFIG_PPC32)	+= $(call cc-option, $(MULTIPLEWORD))
>  
>  CFLAGS-$(CONFIG_PPC32)	+= $(call cc-option,-mno-readonly-in-sdata)
>  
> -ifdef CONFIG_PPC_BOOK3S_64
> -ifdef CONFIG_CPU_LITTLE_ENDIAN
> -CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power8
> -else
> -CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power4
> -endif
> -CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power10,	\
> -				  $(call cc-option,-mtune=power9,	\
> -				  $(call cc-option,-mtune=power8)))
> -else ifdef CONFIG_PPC_BOOK3E_64
> -CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=powerpc64
> -endif
> -
>  ifdef CONFIG_FUNCTION_TRACER
>  CC_FLAGS_FTRACE := -pg
>  ifdef CONFIG_MPROFILE_KERNEL
> @@ -166,11 +153,12 @@ CC_FLAGS_FTRACE += -mprofile-kernel
>  endif
>  endif
>  
> -CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
> -AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
> +CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU)
> +AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU)
>  
> -CFLAGS-$(CONFIG_E5500_CPU) += $(call cc-option,-mcpu=e500mc64,-mcpu=powerpc64)
> -CFLAGS-$(CONFIG_E6500_CPU) += $(call cc-option,-mcpu=e6500,$(E5500_CPU))
> +CFLAGS-$(CONFIG_POWERPC64_CPU) += $(call cc-option,-mtune=power10,	\
> +				  $(call cc-option,-mtune=power9,	\
> +				  $(call cc-option,-mtune=power8)))
>  
>  asinstr := $(call as-instr,lis 9$(comma)foo@...h,-DHAVE_AS_ATHIGH=1)
>  
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index 9563336e3348..31cea2eeb59e 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -118,19 +118,18 @@ endchoice
>  
>  choice
>  	prompt "CPU selection"
> -	default GENERIC_CPU
>  	help
>  	  This will create a kernel which is optimised for a particular CPU.
>  	  The resulting kernel may not run on other CPUs, so use this with care.
>  
>  	  If unsure, select Generic.
>  
> -config GENERIC_CPU
> +config POWERPC64_CPU
>  	bool "Generic (POWER5 and PowerPC 970 and above)"
>  	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
>  	select PPC_64S_HASH_MMU
>  
> -config GENERIC_CPU
> +config POWERPC64_CPU
>  	bool "Generic (POWER8 and above)"
>  	depends on PPC_BOOK3S_64 && CPU_LITTLE_ENDIAN
>  	select ARCH_HAS_FAST_MULTIPLIER
> @@ -233,13 +232,12 @@ config E500MC_CPU
>  
>  config TOOLCHAIN_DEFAULT_CPU
>  	bool "Rely on the toolchain's implicit default CPU"
> -	depends on PPC32
>  
>  endchoice
>  
>  config TARGET_CPU_BOOL
>  	bool
> -	default !GENERIC_CPU && !TOOLCHAIN_DEFAULT_CPU
> +	default !TOOLCHAIN_DEFAULT_CPU
>  
>  config TARGET_CPU
>  	string
> @@ -251,6 +249,10 @@ config TARGET_CPU
>  	default "power8" if POWER8_CPU
>  	default "power9" if POWER9_CPU
>  	default "power10" if POWER10_CPU
> +	default "e500mc64" if E5500_CPU
> +	default "e6500" if E6500_CPU
> +	default "power4" if POWERPC64_CPU && !CPU_LITTLE_ENDIAN
> +	default "power8" if POWERPC64_CPU && CPU_LITTLE_ENDIAN
>  	default "405" if 405_CPU
>  	default "440" if 440_CPU
>  	default "464" if 464_CPU
> -- 
> 2.38.1
>