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| author | David Brownell <david-b@pacbell.net> | 2007-11-12 17:59:10 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2008-01-26 15:00:31 +0000 |
| commit | 5248c657898c018bcd23ef77759fa1d6c690bdf4 (patch) | |
| tree | 48204e22be9aa73f5e8dba4ed79df6517a1f7b21 | |
| parent | 156864f806baa4e1aa6eabd28ac45ecc92b31315 (diff) | |
| download | op-kernel-dev-5248c657898c018bcd23ef77759fa1d6c690bdf4.zip op-kernel-dev-5248c657898c018bcd23ef77759fa1d6c690bdf4.tar.gz | |
[ARM] 4646/1: AT91: configurable HZ, default to 128
This makes HZ configurable on AT91, following the model used on OMAP.
It defaults to a power of two on AT91rm9200 chips, avoiding rounding
errors which come from dividing a 32 KiHz clock to generate scheduler
irqs; and uses 100 on AT91sam926x chips, using MCK/16 (multi-MHZ).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Remy Bhmer <linux@bohmer.net>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
| -rw-r--r-- | arch/arm/Kconfig | 1 | ||||
| -rw-r--r-- | arch/arm/mach-at91/Kconfig | 16 |
2 files changed, 17 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index a04f507..93e40b6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -657,6 +657,7 @@ config HZ default 128 if ARCH_L7200 default 200 if ARCH_EBSA110 || ARCH_S3C2410 default OMAP_32K_TIMER_HZ if ARCH_OMAP && OMAP_32K_TIMER + default AT91_TIMER_HZ if ARCH_AT91 default 100 config AEABI diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig index 05a9f8a..214733e 100644 --- a/arch/arm/mach-at91/Kconfig +++ b/arch/arm/mach-at91/Kconfig @@ -219,6 +219,22 @@ config AT91_PROGRAMMABLE_CLOCKS Select this if you need to program one or more of the PCK0..PCK3 programmable clock outputs. +config AT91_TIMER_HZ + int "Kernel HZ (jiffies per second)" + range 32 1024 + depends on ARCH_AT91 + default "128" if ARCH_AT91RM9200 + default "100" + help + On AT91rm9200 chips where you're using a system clock derived + from the 32768 Hz hardware clock, this tick rate should divide + it exactly: use a power-of-two value, such as 128 or 256, to + reduce timing errors caused by rounding. + + On AT91sam926x chips, or otherwise when using a higher precision + system clock (of at least several MHz), rounding is less of a + problem so it can be safer to use a decimal values like 100. + endmenu endif |
