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Date: Thu, 17 Nov 2016 12:40:41 -0300 From: Javier Martinez Canillas <javier@....samsung.com> To: Krzysztof Kozlowski <krzk@...nel.org>, Russell King <linux@...linux.org.uk>, Kukjin Kim <kgene@...nel.org>, linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Ben Dooks <ben.dooks@...ethink.co.uk>, Lee Jones <lee.jones@...aro.org>, Arnd Bergmann <arnd@...db.de>, Marek Szyprowski <m.szyprowski@...sung.com>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>, Sylwester Nawrocki <s.nawrocki@...sung.com>, Tomasz Figa <tomasz.figa@...il.com> Subject: Re: [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms Hello Krzysztof, On 11/14/2016 03:27 PM, Krzysztof Kozlowski wrote: > All Samsung platforms, including the Exynos, are selecting HZ_FIXED with > 200 Hz. Unfortunately in case of multiplatform image this affects also > other platforms when Exynos is selected. > > This looks like an very old legacy code, dating back to initial > upstreaming of S3C24xx. Probably it was required for s3c24xx timer > driver, which was removed in commit ad38bdd15d5b ("ARM: SAMSUNG: Remove > unused plat-samsung/time.c"). > > Since then, this fixed 200 Hz spread everywhere, including out-of-tree > Samsung kernels (SoC vendor's and Tizen's). I believe this choice > was rather an effect of coincidence instead of conscious choice. In > fact Exynos can work with different timers. > > Few perf mem and sched tests on Odroid XU3 board (Exynos5422, 4x Cortex > A7, 4x Cortex A15) show no regressions when switching from 200 Hz to > other values. > > Reported-by: Lee Jones <lee.jones@...aro.org> > Reported-by: Arnd Bergmann <arnd@...db.de> > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org> > > --- > > Testing on other Exynos platforms would be appreciated. I tested this patch on an Exynos5800 Peach Pi Chromebook with different HZ values (100/200/250/300/500/1000), and found no issues. Tested-by: Javier Martinez Canillas <javier@....samsung.com> Best regards, -- Javier Martinez Canillas Open Source Group Samsung Research America
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