| Message ID | 1359646320-9086-1-git-send-email-santosh.shilimkar@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thursday 31 January 2013 21:02:00 Santosh Shilimkar wrote: > 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> Acked-by: Arnd Bergmann <arnd@arndb.de> Thanks so much for looking into this! -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
* Arnd Bergmann <arnd@arndb.de> [130131 07:41]: > On Thursday 31 January 2013 21:02:00 Santosh Shilimkar wrote: > > 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> > > Acked-by: Arnd Bergmann <arnd@arndb.de> > > Thanks so much for looking into this! Great thanks for checking it Santosh! Applying into omap-for-v3.9/soc. Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 01/31/13 17:32, Santosh Shilimkar wrote: > 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. Great! I had the same patch in my tree already for several months, but I was afraid to send it as I had no time to test it thoroughly. These kind of things are always scary to send without proper testing... Thank you very much for testing and sending this out! > > 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> If it still not too late: Acked-by: Igor Grinberg <grinberg@compulab.co.il> > > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> > Tested-by: Lokesh Vutla <lokeshvutla@ti.com> > --- > arch/arm/Kconfig | 1 - > arch/arm/plat-omap/Kconfig | 9 --------- > arch/arm/plat-omap/include/plat/timex.h | 8 -------- > 3 files changed, 18 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index b35b27f..5493164 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1648,7 +1648,6 @@ 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 > diff --git a/arch/arm/plat-omap/Kconfig b/arch/arm/plat-omap/Kconfig > index 67c859c..ce66eb9 100644 > --- a/arch/arm/plat-omap/Kconfig > +++ b/arch/arm/plat-omap/Kconfig > @@ -147,15 +147,6 @@ 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 > diff --git a/arch/arm/plat-omap/include/plat/timex.h b/arch/arm/plat-omap/include/plat/timex.h > index 6d35767..e27d2da 100644 > --- a/arch/arm/plat-omap/include/plat/timex.h > +++ b/arch/arm/plat-omap/include/plat/timex.h > @@ -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 */ >
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index b35b27f..5493164 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1648,7 +1648,6 @@ 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 diff --git a/arch/arm/plat-omap/Kconfig b/arch/arm/plat-omap/Kconfig index 67c859c..ce66eb9 100644 --- a/arch/arm/plat-omap/Kconfig +++ b/arch/arm/plat-omap/Kconfig @@ -147,15 +147,6 @@ 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 diff --git a/arch/arm/plat-omap/include/plat/timex.h b/arch/arm/plat-omap/include/plat/timex.h index 6d35767..e27d2da 100644 --- a/arch/arm/plat-omap/include/plat/timex.h +++ b/arch/arm/plat-omap/include/plat/timex.h @@ -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 */