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[35.247.103.198]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2297866efb5sm921995ad.201.2025.04.02.15.39.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Apr 2025 15:39:49 -0700 (PDT) Date: Wed, 2 Apr 2025 15:39:45 -0700 From: William McVicker To: Youngmin Nam Cc: John Stultz , Catalin Marinas , Will Deacon , Peter Griffin , =?iso-8859-1?Q?Andr=E9?= Draszik , Tudor Ambarus , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Alim Akhtar , Daniel Lezcano , Thomas Gleixner , Saravana Kannan , Krzysztof Kozlowski , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org, tigersoundkim@gmail.com Subject: Re: [PATCH v1 3/6] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu Message-ID: References: <20250331230034.806124-1-willmcvicker@google.com> <20250331230034.806124-4-willmcvicker@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250402_153951_092829_747D0C06 X-CRM114-Status: GOOD ( 26.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 04/02/2025, Youngmin Nam wrote: > On Tue, Apr 01, 2025 at 09:36:19AM -0700, William McVicker wrote: > > On 03/31/2025, John Stultz wrote: > > > On Mon, Mar 31, 2025 at 4:00 PM 'Will McVicker' via kernel-team > > > wrote: > > > > > > > > From: Hosung Kim > > > > > > > > The MCT local timers can be used as a per-cpu event timer. To prevent > > > > > > Can be used, or are used? If it's an option, is this change important > > > in both cases? > > > > > > > the timer interrupts from migrating to other CPUs, set the flag > > > > IRQF_PERCPU. > > > > > > Might be work expanding this a bit to clarify why the interrupts > > > migrating to other cpus is undesired. > > > > Let me dig into this further to figure out if the IP has a limitation where the > > interrupts need to be handled by the CPU the timer was triggered on or if this > > is just an optimization. > > > > Any chance you know this @Youngmin? > > > > Thanks, > > Will > > > > Hi Will. > > Yes. In downstream, we’ve been using MCT as the clock event timer instead of the ARM timer. > Setting this flag allows each CPU to handle its own clock events, such as scheduling interrupts. Thanks for the explanation! I'll integrate this into the commit text. Regards, Will > > > > > > > > Signed-off-by: Hosung Kim > > > > [Original commit from https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16] > > > > Signed-off-by: Will McVicker > > > > > > thanks! > > > -john > > > >