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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b08366c74dsm171510225ad.62.2026.03.23.21.21.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2026 21:21:28 -0700 (PDT) Message-ID: Date: Tue, 24 Mar 2026 14:21:12 +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 v6 39/40] arm_mpam: Quirk CMN-650's CSU NRDY behaviour To: Ben Horgan Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, james.morse@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev, zengheng4@huawei.com, linux-doc@vger.kernel.org References: <20260313144617.3420416-1-ben.horgan@arm.com> <20260313144617.3420416-40-ben.horgan@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20260313144617.3420416-40-ben.horgan@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/14/26 12:46 AM, Ben Horgan wrote: > From: James Morse > > CMN-650 is afflicted with an erratum where the CSU NRDY bit never clears. > This tells us the monitor never finishes scanning the cache. The erratum > document says to wait the maximum time, then ignore the field. > > Add a flag to indicate whether this is the final attempt to read the > counter, and when this quirk is applied, ignore the NRDY field. > > This means accesses to this counter will always retry, even if the counter > was previously programmed to the same values. > > The counter value is not expected to be stable, it drifts up and down with > each allocation and eviction. The CSU register provides the value for a > point in time. > > Reviewed-by: Zeng Heng > Signed-off-by: James Morse > Signed-off-by: Ben Horgan > --- > Changes since v3: > parentheses in macro > --- > Documentation/arch/arm64/silicon-errata.rst | 3 +++ > drivers/resctrl/mpam_devices.c | 12 ++++++++++++ > drivers/resctrl/mpam_internal.h | 6 ++++++ > 3 files changed, 21 insertions(+) > Reviewed-by: Gavin Shan