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[175.34.62.5]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23de42b01dbsm36977215ad.85.2025.07.10.21.42.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Jul 2025 21:42:40 -0700 (PDT) Message-ID: <5147e48d-2376-4b0c-adff-b8663e56f152@redhat.com> Date: Fri, 11 Jul 2025 14:42:34 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] cacheinfo: Add arch hook to compress CPU h/w id into 32 bits for cache-id To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , sudeep.holla@arm.com, Rob Herring , Ben Horgan , Jonathan Cameron , Catalin Marinas , WillDeaconwill@kernel.org References: <20250704173826.13025-1-james.morse@arm.com> <20250704173826.13025-3-james.morse@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20250704173826.13025-3-james.morse@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/5/25 3:38 AM, James Morse wrote: > Filesystems like resctrl use the cache-id exposed via sysfs to identify > groups of CPUs. The value is also used for PCIe cache steering tags. On > DT platforms cache-id is not something that is described in the > device-tree, but instead generated from the smallest CPU h/w id of the > CPUs associated with that cache. > > CPU h/w ids may be larger than 32 bits. > > Add a hook to allow architectures to compress the value from the devicetree > into 32 bits. Returning the same value is always safe as cache_of_set_id() > will stop if a value larger than 32 bits is seen. > > For example, on arm64 the value is the MPIDR affinity register, which only > has 32 bits of affinity data, but spread accross the 64 bit field. An > arch-specific bit swizzle gives a 32 bit value. > > Signed-off-by: James Morse > Reviewed-by: Jonathan Cameron > --- > drivers/base/cacheinfo.c | 5 +++++ > 1 file changed, 5 insertions(+) > Reviewed-by: Gavin Shan