Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752272AbcKRH5r (ORCPT ); Fri, 18 Nov 2016 02:57:47 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36147 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751971AbcKRH5p (ORCPT ); Fri, 18 Nov 2016 02:57:45 -0500 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] ARM: Drop fixed 200 Hz timer requirement from Samsung platforms From: Kukjin Kim X-Mailer: iPhone Mail (14B100) In-Reply-To: <1479453418-25314-1-git-send-email-krzk@kernel.org> Date: Fri, 18 Nov 2016 16:57:40 +0900 Cc: Russell King , Kukjin Kim , Javier Martinez Canillas , linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Ben Dooks , Lee Jones , Arnd Bergmann , Marek Szyprowski , Bartlomiej Zolnierkiewicz , Sylwester Nawrocki , Tomasz Figa Content-Transfer-Encoding: 7bit Message-Id: References: <1479453418-25314-1-git-send-email-krzk@kernel.org> To: Krzysztof Kozlowski Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 63 2016. 11. 18. 16:16 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 enabled. > > 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. > > Exynos uses its own MCT or arch timer and can work with all HZ values. > Older platforms use newer Samsung PWM timer driver which should handle > down to 100 Hz. > > 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 > [Dropping 200_HZ from S3C/S5P suggested by Arnd] > Reported-by: Arnd Bergmann > Signed-off-by: Krzysztof Kozlowski > Cc: Kukjin Kim Acked-by: Kukjin Kim > Tested-by: Javier Martinez Canillas > > --- > > Tested on Exynos5422 and Exynos5800 (by Javier). It would be > appreciated if anyone could test it on S3C24xx or S5PV210. > > Changes since v1: > 1. Add Javier's tested-by. > 2. Drop HZ_FIXED also from ARCH_S5PV210 and ARCH_S3C24XX after Arnd > suggestions and analysis. > --- > arch/arm/Kconfig | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index b5d529fdffab..ced2e08a9d08 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1496,8 +1496,7 @@ source kernel/Kconfig.preempt > > config HZ_FIXED > int > - default 200 if ARCH_EBSA110 || ARCH_S3C24XX || \ > - ARCH_S5PV210 || ARCH_EXYNOS4 > + default 200 if ARCH_EBSA110 > default 128 if SOC_AT91RM9200 > default 0 > > -- > 2.7.4 >