Re: [Buildroot] [PATCH 2/9] arch/powerpc: Clarify generic CPUs

From: "Yann E. MORIN" <yann.morin.1998@free.fr>
To: Joel Stanley <joel@jms.id.au>
Cc: "Bernd Kuhls" <bernd.kuhls@t-online.de>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Cédric Le Goater" <clg@kaod.org>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	buildroot@buildroot.org, "Romain Naour" <romain.naour@gmail.com>
Subject: Re: [Buildroot] [PATCH 2/9] arch/powerpc: Clarify generic CPUs
Date: Fri, 29 Jul 2022 23:25:49 +0200	[thread overview]
Message-ID: <20220729212549.GF1554632@scaer> (raw)
In-Reply-To: <20220729000904.1295295-3-joel@jms.id.au>

Joel, All,

On 2022-07-29 09:38 +0930, Joel Stanley spake thusly:
> In the case where a specific CPU is not selected, set an appropriate
> gcc target for the architecture.

Sorry, I am not sure I understood this. Currently, there is always at
least one CPU variant that is available in the variant choice; it is
never empty.

So, how come we can have a situation where "a specific CPU is not
selected"?

> For clarity this introduces a BR2_generic_powerpc64 as a generic 64 bit
> CPU as this makes the it clearer when browsing menuconfig.
> 
> We can't have a generic ppc64le GCC, as attempting to configure glibc
> for powerpc64le fails:
> 
>  configure: error: ***  POWER8 or newer is required on powerpc64le.
>  __builtin_signbit is broken.  GCC 7.4 or newer is required to resolve
>  (PR83862). The compiler must support -mabi=ieeelongdouble and
>  -mlong-double-128 simultaneously.
> 
> Hence set Power8 as the default CPU for powerpc64le.

If the other CPUs are not valid for ppc64le, then they should not be
selectable, like is already dine e.g. for e5500 or e6500 (among others).
Currently, ppc64le allows:
    970
    power6
    power7
    power8

So, maybe all but power8 should be hidden?

Also, it looks like it should be a separate, previous patch in the
series.

Regards,
Yann E. MORIN.

> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
>  arch/Config.in.powerpc | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/Config.in.powerpc b/arch/Config.in.powerpc
> index ef0e85fec680..8d392bfde814 100644
> --- a/arch/Config.in.powerpc
> +++ b/arch/Config.in.powerpc
> @@ -9,12 +9,17 @@ config BR2_POWERPC_CPU_HAS_SPE
>  
>  choice
>  	prompt "Target Architecture Variant"
> -	default BR2_generic_powerpc
> +	default BR2_generic_powerpc if !BR2_ARCH_IS_64
> +	default BR2_generic_powerpc64 if BR2_ARCH_IS_64
> +	default BR2_powerpc_power8 if BR2_powerpc64le
>  	help
>  	  Specific CPU variant to use
>  config BR2_generic_powerpc
> -	bool "generic"
> -	# No C library supports this variant on ppc64le
> +	bool "generic (32 bit)"
> +	depends on !BR2_ARCH_IS_64
> +config BR2_generic_powerpc64
> +	bool "generic (64 bit)"
> +	depends on BR2_ARCH_IS_64
>  	depends on !BR2_powerpc64le
>  config BR2_powerpc_401
>  	bool "401"
> @@ -220,6 +225,8 @@ config BR2_GCC_TARGET_CPU
>  	default "power6"	if BR2_powerpc_power6
>  	default "power7"	if BR2_powerpc_power7
>  	default "power8"	if BR2_powerpc_power8
> +	default "powerpc64"	if BR2_generic_powerpc64
> +	default "powerpc"	if BR2_generic_powerpc
>  
>  config BR2_READELF_ARCH_NAME
>  	default "PowerPC"	if BR2_powerpc
> -- 
> 2.35.1
> 
> _______________________________________________
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> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot

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