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[130.180.211.218]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a1f5a2ce36sm16710394f8f.71.2025.05.13.07.52.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 May 2025 07:52:38 -0700 (PDT) Date: Tue, 13 May 2025 16:52:36 +0200 From: Daniel Lezcano To: John Stultz Cc: Will McVicker , Catalin Marinas , Will Deacon , Peter Griffin , =?iso-8859-1?Q?Andr=E9?= Draszik , Tudor Ambarus , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Alim Akhtar , Thomas Gleixner , Saravana Kannan , Krzysztof Kozlowski , Donghoon Yu , Hosung Kim , kernel-team@android.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Youngmin Nam , linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v2 6/7] clocksource/drivers/exynos_mct: Add module support Message-ID: References: <20250402233407.2452429-1-willmcvicker@google.com> <20250402233407.2452429-7-willmcvicker@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Apr 15, 2025 at 05:48:41PM -0700, John Stultz wrote: > On Tue, Apr 15, 2025 at 9:50 AM Daniel Lezcano > wrote: > > On Wed, Apr 02, 2025 at 04:33:57PM -0700, Will McVicker wrote: > > > From: Donghoon Yu > > > > > > On Arm64 platforms the Exynos MCT driver can be built as a module. On > > > boot (and even after boot) the arch_timer is used as the clocksource and > > > tick timer. Once the MCT driver is loaded, it can be used as the wakeup > > > source for the arch_timer. > > > > From a previous thread where there is no answer: > > > > https://lore.kernel.org/all/c1e8abec-680c-451d-b5df-f687291aa413@linaro.org/ > > > > I don't feel comfortable with changing the clocksource / clockevent drivers to > > a module for the reasons explained in the aforementionned thread. > > I wasn't CC'ed on that, but to address a few of your points: > > > I have some concerns about this kind of changes: > > > > * the core code may not be prepared for that, so loading / unloading > > the modules with active timers may result into some issues > > That's a fair concern, but permanent modules (which are loaded but not > unloaded) shouldn't suffer this issue. I recognize having modules be > fully unloadable is generally cleaner and preferred, but I also see > the benefit of allowing permanent modules to be one-way loaded so a > generic/distro kernel shared between lots of different platforms > doesn't need to be bloated with drivers that aren't used everywhere. > Obviously any single driver doesn't make a huge difference, but all > the small drivers together does add up. Perhaps using module_platform_driver_probe() should do the trick with some scripts updated for my git hooks to check module_platform_driver() is not used. [ ... ] -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog