Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5248c657898c018bcd23ef77759fa1d6c690bdf4
Commit: 5248c657898c018bcd23ef77759fa1d6c690bdf4
Parent: 156864f806baa4e1aa6eabd28ac45ecc92b31315
Author: David Brownell <[EMAIL PROTECTED]>
AuthorDate: Mon Nov 12 17:59:10 2007 +0100
Committer: Russell King <[EMAIL PROTECTED]>
CommitDate: Sat Jan 26 15:00:31 2008 +0000
[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 <[EMAIL PROTECTED]>
Acked-by: Remy Bhmer <[EMAIL PROTECTED]>
Acked-by: Andrew Victor <[EMAIL PROTECTED]>
Signed-off-by: Russell King <[EMAIL PROTECTED]>
---
arch/arm/Kconfig | 1 +
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
-
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