linux-kernel - Re: [PATCH 3/3] cacheinfo: Add use_arch[|_cache]

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Date:   Mon, 27 Mar 2023 13:17:35 +0100
From:   Will Deacon <will@...nel.org>
To:     Pierre Gondois <pierre.gondois@....com>
Cc:     linux-kernel@...r.kernel.org, Radu Rendec <rrendec@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Akihiko Odaki <akihiko.odaki@...nix.com>,
        Gavin Shan <gshan@...hat.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] cacheinfo: Add use_arch[|_cache]_info field/function

On Mon, Mar 27, 2023 at 01:59:51PM +0200, Pierre Gondois wrote:
> The cache information can be extracted from either a Device
> Tree (DT), the PPTT ACPI table, or arch registers (clidr_el1
> for arm64).
> 
> The clidr_el1 register is used only if DT/ACPI information is not
> available. It does not states how caches are shared among CPUs.
> 
> Add a use_arch_cache_info field/function to identify when the
> DT/ACPI doesn't provide cache information. Use this information
> to assume L1 caches are privates and L2 and higher are shared among
> all CPUs.
> 
> Signed-off-by: Pierre Gondois <pierre.gondois@....com>
> ---
>  arch/arm64/kernel/cacheinfo.c |  5 +++++
>  drivers/base/cacheinfo.c      | 20 ++++++++++++++++++--
>  include/linux/cacheinfo.h     |  2 ++
>  3 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
> index c307f69e9b55..b6306cda0fa7 100644
> --- a/arch/arm64/kernel/cacheinfo.c
> +++ b/arch/arm64/kernel/cacheinfo.c
> @@ -96,3 +96,8 @@ int populate_cache_leaves(unsigned int cpu)
>  	}
>  	return 0;
>  }
> +
> +bool use_arch_cache_info(unsigned int cpu)
> +{
> +	return true;
> +}

It would be a lot nicer if this was a static inline function in a header
rather than a weak symbol.

Will