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ARM: OMAP2+: Get rid of custom OMAP_32K_TIMER_HZ

PATCH New Santosh Shilimkar 4 participants 4 messages Jan 31, 2013 – Feb 3, 2013

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Santosh Shilimkar

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#0 lore raw

PATCH 1/1 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 <[email protected]>
Cc Russell King <[email protected]>
Cc John Stultz <[email protected]>
Cc Tony Lindgren <[email protected]>
Signed-off-by Santosh Shilimkar <[email protected]>
Tested-by Lokesh Vutla <[email protected]>
---
 arch/arm/Kconfig                        |    1 -
 arch/arm/plat-omap/Kconfig              |    9 ---------
 arch/arm/plat-omap/include/plat/timex.h |    8 --------
 3 files changed, 18 deletions(-)
arch/arm/Kconfig +0 -1
index b35b27f..5493164 100644
@@ -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
arch/arm/plat-omap/Kconfig +0 -9
index 67c859c..ce66eb9 100644
@@ -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
arch/arm/plat-omap/include/plat/timex.h +0 -8
index 6d35767..e27d2da 100644
@@ -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 */
Signature · 1 line
1.7.9.5
#1 lore raw

PATCH 1/1 ARM: OMAP2+: Get rid of custom OMAP_32K_TIMER_HZ

Quoted 12 lines · 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
Quoted 7 lines

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

Cc Arnd Bergmann <[email protected]>
Cc Russell King <[email protected]>
Cc John Stultz <[email protected]>
Cc Tony Lindgren <[email protected]>
Acked-by Arnd Bergmann <[email protected]>

Thanks so much for looking into this!

#2 lore raw

PATCH 1/1 ARM: OMAP2+: Get rid of custom OMAP_32K_TIMER_HZ

Quoted 16 lines · Arnd Bergmann
Quoted 15 lines · 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.

Quoted 8 lines
Quoted 4 lines
Cc Arnd Bergmann <[email protected]>
Cc Russell King <[email protected]>
Cc John Stultz <[email protected]>
Cc Tony Lindgren <[email protected]>
Acked-by Arnd Bergmann <[email protected]>

Thanks so much for looking into this!

Great thanks for checking it Santosh! Applying into omap-for-v3.9/soc.

Tony

#3 lore raw

PATCH 1/1 ARM: OMAP2+: Get rid of custom OMAP_32K_TIMER_HZ

In reply to Santosh Shilimkar
Quoted 8 lines · Santosh Shilimkar

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!

Quoted 11 lines

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 <[email protected]>
Cc Russell King <[email protected]>
Cc John Stultz <[email protected]>
Cc Tony Lindgren <[email protected]>

If it still not too late:

Acked-by Igor Grinberg <[email protected]>
Quoted 61 lines
Signed-off-by Santosh Shilimkar <[email protected]>
Tested-by Lokesh Vutla <[email protected]>
---
 arch/arm/Kconfig                        |    1 -
 arch/arm/plat-omap/Kconfig              |    9 ---------
 arch/arm/plat-omap/include/plat/timex.h |    8 --------
 3 files changed, 18 deletions(-)
arch/arm/Kconfig +0 -1
index b35b27f..5493164 100644
@@ -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
arch/arm/plat-omap/Kconfig +0 -9
index 67c859c..ce66eb9 100644
@@ -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
arch/arm/plat-omap/include/plat/timex.h +0 -8
index 6d35767..e27d2da 100644
@@ -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 */
Signature · 2 lines
Regards,
Igor.