linux-kernel - Re: [PATCH v2,1/5] powerpc: 85xx: make FSL_85XX_CACHE

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Message-ID: <4800a04c-e26e-9832-c91f-04b12660282b@c-s.fr>
Date:   Wed, 15 Apr 2020 18:26:01 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Wang Wenhu <wenhu.wang@...o.com>, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, oss@...error.net,
        linuxppc-dev@...ts.ozlabs.org
Cc:     kernel@...o.com, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2,1/5] powerpc: 85xx: make FSL_85XX_CACHE_SRAM
 configurable



Le 15/04/2020 à 17:24, Wang Wenhu a écrit :
> Enable FSL_85XX_CACHE_SRAM selection. On e500 platforms, the cache
> could be configured and used as a piece of SRAM which is hignly
> friendly for some user level application performances.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Scott Wood <oss@...error.net>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Wang Wenhu <wenhu.wang@...o.com>
> ---
> Changes since v1:
>   * None
> ---
>   arch/powerpc/platforms/85xx/Kconfig    | 2 +-
>   arch/powerpc/platforms/Kconfig.cputype | 5 +++--
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/85xx/Kconfig b/arch/powerpc/platforms/85xx/Kconfig
> index fa3d29dcb57e..6debb4f1b9cc 100644
> --- a/arch/powerpc/platforms/85xx/Kconfig
> +++ b/arch/powerpc/platforms/85xx/Kconfig
> @@ -17,7 +17,7 @@ if FSL_SOC_BOOKE
>   if PPC32
>   
>   config FSL_85XX_CACHE_SRAM
> -	bool
> +	bool "Freescale 85xx Cache-Sram"
>   	select PPC_LIB_RHEAP
>   	help
>   	  When selected, this option enables cache-sram support
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index 0c3c1902135c..1921e9a573e8 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -1,6 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   config PPC32
> -	bool
> +	bool "32-bit kernel"

Why make that user selectable ?

Either a kernel is 64-bit or it is 32-bit. So having PPC64 user 
selectable is all we need.

And what is the link between this change and the description in the log ?

>   	default y if !PPC64
>   	select KASAN_VMALLOC if KASAN && MODULES
>   
> @@ -15,6 +15,7 @@ config PPC_BOOK3S_32
>   	bool
>   
>   menu "Processor support"
> +

Why adding this space ?

>   choice
>   	prompt "Processor Type"
>   	depends on PPC32
> @@ -211,9 +212,9 @@ config PPC_BOOK3E
>   	depends on PPC_BOOK3E_64
>   
>   config E500
> +	bool "e500 Support"
>   	select FSL_EMB_PERFMON
>   	select PPC_FSL_BOOK3E
> -	bool

Why make this user-selectable ? This is already selected by the 
processors requiring it, ie 8500, e5500 and e6500.

Is there any other case where we need E500 ?

And again, what's the link between this change and the description in 
the log ?


>   
>   config PPC_E500MC
>   	bool "e500mc Support"
> 

Christophe