Re: [PATCH] ARM: Drop fixed 200 Hz timer requirement from Exynos platforms

Arnd Bergmann
2016-11-17T14:33:36Z

On Monday, November 14, 2016 8:27:05 PM CET Krzysztof Kozlowski wrote:
> @@ -1497,7 +1497,7 @@ source kernel/Kconfig.preempt
> config HZ_FIXED
> int
> default 200 if ARCH_EBSA110 || ARCH_S3C24XX || \
> - ARCH_S5PV210 || ARCH_EXYNOS4
> + ARCH_S5PV210
> default 128 if SOC_AT91RM9200
> default 0

After further research, I've concluded that we should also drop the
settings for ARCH_S5PV210 and ARCH_S3C24XX here.

ARCH_S5PV210 behaves exactly like EXYNOS here, it has 32-bit timers
so there won't be any overflow with 100Hz.

For ARCH_S3C24XX, it the requirement was that HZ_100 could not
be used with the old arch/arm/plat-samsung/time.c code that would
overflow its 16-bit counter.
However, the new drivers/clocksource/samsung_pwm_timer.c configures
the clock divider to '50' instead of '6', so there is no longer
a 16-bit overflow before the 100Hz tick, it now overflows every
3.7ms for the typical 12MHz clock.

Arnd