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ARM: OMAP2+: Get rid of custom OMAP_32K_TIMER_HZ 

The timekeeping doesn't depend on HZ value in presence of fine grained
clocksource and hence there should not be any time drift because of HZ
value which was chosen to be divisor of 32768.

OMAP has been using HZ = 128 value to avoid any time drift issues
because of 32768 HZ clock. But with various measurements performed
with HZ = 100, no time drift is observed and it also proves the
point about HZ not having impact on time keeping on OMAP.

Very informative thread on this topic is here:
	https://lkml.org/lkml/2013/1/29/435

Special thanks to John Stulz, Arnd Bergmann and Russell King for their
valuable suggestions.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Tony Lindgren <tony@atomide.com>

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This commit is contained in:
Santosh Shilimkar 2013-01-31 21:02:00 +05:30 committed by Tony Lindgren
parent 14e067c1a5
commit 8f0de0d62f
3 changed files with 0 additions and 18 deletions
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1
arch/arm/Kconfig
View File

@ -1650,7 +1650,6 @@ config HZ
int
default 200 if ARCH_EBSA110 || ARCH_S3C24XX || ARCH_S5P64X0 || \
ARCH_S5PV210 || ARCH_EXYNOS4
default OMAP_32K_TIMER_HZ if ARCH_OMAP && OMAP_32K_TIMER
default AT91_TIMER_HZ if ARCH_AT91
default SHMOBILE_TIMER_HZ if ARCH_SHMOBILE
default 100

9
arch/arm/plat-omap/Kconfig
View File

@ -177,15 +177,6 @@ config OMAP3_L2_AUX_SECURE_SERVICE_SET_ID
help
PPA routine service ID for setting L2 auxiliary control register.
config OMAP_32K_TIMER_HZ
int "Kernel internal timer frequency for 32KHz timer"
range 32 1024
depends on OMAP_32K_TIMER
default "128"
help
Kernel internal timer frequency should be a divisor of 32768,
such as 64 or 128.
config OMAP_DM_TIMER
bool "Use dual-mode timer"
depends on ARCH_OMAP16XX || ARCH_OMAP2PLUS

8
arch/arm/plat-omap/include/plat/timex.h
View File

@ -28,14 +28,6 @@
#if !defined(__ASM_ARCH_OMAP_TIMEX_H)
#define __ASM_ARCH_OMAP_TIMEX_H
/*
* OMAP 32KHz timer updates time one jiffie at a time from a secondary timer,
* and that's why the CLOCK_TICK_RATE is not 32768.
*/
#ifdef CONFIG_OMAP_32K_TIMER
#define CLOCK_TICK_RATE (CONFIG_OMAP_32K_TIMER_HZ)
#else
#define CLOCK_TICK_RATE (HZ * 100000UL)
#endif
#endif /* __ASM_ARCH_OMAP_TIMEX_H */