2016. 11. 18. 16:16 Krzysztof Kozlowski <[email protected]> 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 <[email protected]> > [Dropping 200_HZ from S3C/S5P suggested by Arnd] > Reported-by: Arnd Bergmann <[email protected]> > Signed-off-by: Krzysztof Kozlowski <[email protected]> > Cc: Kukjin Kim <[email protected]>
Acked-by: Kukjin Kim <[email protected]> > Tested-by: Javier Martinez Canillas <[email protected]> > > --- > > 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 >
