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Commit 8f0de0d6 authored by Santosh Shilimkar's avatar Santosh Shilimkar Committed by Tony Lindgren
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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: default avatarSantosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: default avatarLokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
parent 14e067c1

arch/arm/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/arm/plat-omap/Kconfig

+0 −9
Original line number Diff line number Diff line
@@ -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

arch/arm/plat-omap/include/plat/timex.h

+0 −8
Original line number Diff line number Diff line
@@ -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 */