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

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Date:   Thu, 6 Apr 2023 09:28:32 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     Will Deacon <will@...nel.org>
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

Hello Will,

On 3/27/23 14:17, Will Deacon wrote:
> 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.

I am not sure I see where the static inline function should be added.
Do you prefer to have function like the following in
include/linux/cacheinfo.h ?

static inline bool use_arch_cache_info(unsigned int cpu)
{
#if defined(CONFIG_ARM64)
	return true;
#else
	return false;
#endif
}

Regards,
Pierre

> 
> Will